GB1567041A

GB1567041A - Fuel injection system

Info

Publication number: GB1567041A
Application number: GB45147/76A
Authority: GB
Original assignee: Allied Chemical Corp
Current assignee: Honeywell International Inc
Priority date: 1975-11-06
Filing date: 1976-10-29
Publication date: 1980-05-08
Also published as: IT1071818B; FR2330869A1; DE2650657A1; CA1075987A

Description

(54) FUEL INJECTION SYSTEM (71) We, ALLIED CHEMICAL CORPORATION, a Corporation organized and existing under the laws of the State of New York of Columbia Road and Park Avenue, Morris Township, Morris County, New Jersey 07960, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a fuel metering and injection system for internal combustion engines.

Fuel injection systems, using injectors, can meter fuel to an engine much more precisely than a carburetor.. Early fuel mjection systems were directed to improving engine performance. More recently, fuel injection systems have been explored in an effort to reduce pollutants in the engine exhaust and to improve fuel economy.

In some early fuel injection systems, pulses were provided to all of the injector valves simultaneously. It was found that simultaneous injection limits the speed of response of the engine to changes in operating parameters. Other systems pro vlde separate electrical pulses, in timed relationship to one another, and to the operation of the engine, to activate each of the injector valves. For example, fully sequential fuel injection systems inject the fuel to the cylinders of an engine one cylinder at a time, usually in sequence with the firing order of the cylinders of the engine. Other recent fuel injection systems, instead of actuating the injectors singly, in sequence over the engine cycle, have arranged the injectors in groups of two or three according to firing order and staggered the firing of the injector groups over the engine cycle.

Prior art fuel injectors for fuel injection systems are typically located in the intake manifold and inject the fuel into the intake manifold, rather than into the cylinder head downstream from the intake manifold. As a result, not all the fuel passes quickly to the intake valve area to maximize heating action. As a result of their design, prior art fuel injector valves are typically too large to be located in the cylinder head.

According to the present invention there is provided a fuel injection system for use in combination with an internal combustion engine, the fuel injecting system comprising a plurality of fuel injectors to be selectively positioned in the engine; a source of fuel for the engine; a fuel supply conducting means disposed between the injectors and the source of fuel for conducting fuel under pressure from said source to the injectors; a low pressure pump for pumping fuel from the source of fuel to the supply conducting means; a pressure booster disposed in the supply conducting means between the pump and the injectors, the pump being adapted to pump fuel to the pressure booster at a low pressure which is less than the pressure applied by the pressure booster in use of the system but higher than the vapour pressure of the fuel in said source and the pressure booster comprising a variable volume chamber and means for urging the chamber into a condition of reduced volume so as to raise the pressure of fuel in the supply conducting means between the booster and the injectors to an elevated pressure higher than the pressure in the supply conducting means between the source of fuel and the booster and higher than the vapour pressure for fuel in the injectors, said urging means being adapted to reduce the volume of said chamber only by an amount that is substantially equivalent to the volume of fuel ejected by said injectors; and an electronic control computer for providing electrical injection pulses of predetermined length, at predetermined time intervals, for actuating the injectors.

A preferred form of valve for use in the injectors is claimed in our copending Divisional Patent Application No. 4008/79 (Serial No. 1567042) which claims an electromagnetically operated valve comprising a discharge structure, a sealing means for intermittently opening and closing the discharge structure; a fluid conduit for supplying fluid from a fluid inlet to the discharge structure; an electrical conductor for supplying an electrical signal to actuate the valve; an electromagnet circuit comprising: an armature, a pole having a downstream end, a housing, a coil, for magnetizing said electromagnetic circuit in response to said electrical signal, and a flux path, said armature being a disc having an upstream face, and being slidably disposed within said housing in a substantially close fitting relationship with the housing at a terminal end of the housing adjacent to and between the pole and the discharge structure for movement between an upstream position and a downstream position, said armature, said pole, and said housing co-operating to define a single series air gap in the flux path between the upstream face of the armature and the downstream end of the pole; a travel limiter disposed coaxially around the coil for limiting travel of the armature in its upstream direction towards the downstream end of the pole; said travel limiter maintaining a residual air gap between the upstream face of the disc and the downstream end of the pole; said residual gap forming part of the single series air gap and a biasing means disposed within the housing for biasing the armature to its downstream position.

In our copending Divisional Patent Application No. 4009/79 (Serial No.

1567043) we claim a preferred control computer for controlling the metering of fuel in a fuel injection system for an engine having a plurality of fuel injection means, an ignition system with primary and secondary circuits operative to generate a sequence of ignition pulses, an engine cycle time, a rotating output shaft, and at least one engine operating parameter sensor, said computer comprising: a plurality of independent computing channels each for operative coupling to at least one common engine operating parameter sensor and each adapted for operative coupling to at least one separate fuel injector means, each channel having a variable width pulse generator, each channel being available for operation for a time duration which is equal to more than 50% of an engine cycle in use of the computer, each channel being adapted to be operatively coupled to its separate injector means for substantially the entire cycle; and a common trigger means having a single input connection for connection from the primary of the ignition system and separate output connections to each of the computing channels operative sequentially, when the computer is in use controlling metering of fuel in an engine, to trigger each computing channel once per engine cycle during normal operation of the engine in timed relationship to the engine output rotation.

Description of the Accompanying Drawings Fig. 1 is a schematic diagram of the fuel injection system of the invention.

Fig. 2 is a schematic diagram of a portion of a cylinder head and an intake manifold of an engine showing the location of a fuel injector therein.

Fig. 3 is a cross-sectional view of a fuel injector, which is a component of a fuel injector system shown in Fig. 1.

Fig. 4 is an enlarged view of a downstream end of Fig. 3, showing the electromagnetically operated valve of the fuel injector.

Fig. 5 is a front elevational view of an upstream face of an armature which is a component of the valve shown in Fig. 4.

Fig. 6 is a cross-sectional view of Fig. 5 along the lines 6-6 in Fig. 5.

Fig. 7 is a front elevational view of a downstream face of the armature shown in Figs. 5 and 6.

Fig. 8 is a view of the nozzle shown at the downstream end of Fig. 4.

Fig. 9 is a view of a portion of Fig. 4.

Fig. 10 is an enlarged view of an upstream end of Fig. 3.

Fig. 11 is a cross-sectional view through a pressure booster, which is a component of the fuel injection system shown in Fig.

1.

Fig. 12 is a cross-sectional view through a sealed volume, fluid pressure wave or storage converter, which may be a component of the system shown in Fig. 1.

Fig. 13 is a plot of fluid pressure at an injector during an injection cycle, illustrating the operation of the pressure booster shown in Fig. 11.

Fig. 14 is a plot of piston stroke and displacement volume as a function of the angle of a cam which drives the pressure booster shown in Fig. 11, illustrating the operation of the pressure booster.

Fig. 15 is a plot of spring load versus deflection for the pressure booster shown in Fig. 11.

Fig. 16 is a schematic diagram of a por tion of the fuel injection system showing an electronic control computer, which is a component of the system shown in Fig. 1.

Fig. 17 is an electrical circuit diagram of a trigger circuit for a variable width pulse generator shown in Fig. 16.

Fig. 18 is a plot of waveforms occurring at various points in the circuitry of Fig. 17.

Fig. 19 is a schematic diagram of a por tion of the fuel injection system showing a start-up circuit, which may be a compo nent of the system shown in Fig. 1.

Fig. 20 is an electrical circuit diagram of a variable width pulse generator of the type used with the start-up circuit shown in Fig. 19.

Fig. 21 is a plot of voltages appearing at various points in the circuitry during oper ation of the engine.

Fig. 22 is a schematic diagram of a por tion of the fuel injection system showing a constant current drive circuit, which may be a component of the system shown in Fig. 1.

Fig. 23 is an electrical circuit diagram of the drive circuit shown in Fig. 22.

Fig. 24 is a plot of the characteristics of the transistor in the drive circuit output, illustrating the independence of output current from emitter resistance.

Fig. 25 is a schematic diagram of a pre ferred form of an electromagnetic pump means which is a component of the fuel injector system shown in Fig. 1ation 1.

Fig. 26 is a longitudinal section of the pump means shown in Fig. 25.

Fig. 27 is an electrical circuit diagram of the pump means of Fig. 25.

Fig. 28 is an electrical circuit diagram of a variable width pulse generation which is a component of the computer shown in Figs. 16 and 19.

Figs. 29A, 29B and 29C are electrical circuit diagrams of equivalent circuits of the pulse generator of Fig. 28, showing the circuit in three sequential modes.

Fig. 30 is a longitudinal section of an alternative pumps means.

Fig. 31 is a plot of percent charge enrichment and pulse width as a function of load for varying temperatures with prior art system.

Fig. 32 is a plot of percent enrichment as a function of load for the pulse generator of Fig. 28.

Fig. 33 is a plot of pulse width as a function of load for the pulse generator of Fig. 28.

Fig. 34 is a schematic diagram of a first embodiment of the pump control system which drives a positive displacement pump.

Fig. 35 is an electrical circuit diagram of the pump control circuitry of the embodi ment of Fig. 34.

Fig. 36 is a plot of wave forms occurring at particular points within the pump con trol system of Figs. 34 and 35 during a cycle engine after starting and below a crit ical speed.

Fig. 37 is a plot of wave forms occurring at particular points within the pump con trol system of Figs. 34 and 35 during an engine cycle after starting and above a crit ical speed.

Fig. 38 is a schematic diagram of an exhaust gas recirculation device.

Apparatus of the Injection System Referring to Figs. 1 and 2, a fuel injec tion system 2 (Fig. 1), is used in an internal combustion engine having a cylinder head 4 (Fig. 2) and a plurality of intake valves 6 (Fig. 2) in the cylinder head 4.

Referring to Fig. 1, the fuel injection system 2 includes: a plurality of injectors 10, a source of fuel 16, a fuel supply conducting means 8, a low pressure pump 18, and an electronic control computer 19, and a pressure booster 22. Referring to Fig. 2, the injectors 10 each have an electromagnetically-operated injector valve 11 and an injector conduit means 13. Preferably, each injector valve 11 is located entirely within the cylinder head 4 upstream of and adjacent to an upstream face of one or more of the intake valves 6 of the engine. In other embodiments, for example, in a siamese ported engine, one injector 10 may be used for two intake valves. The injector conduit means 13 extends from the injector valve 11 through the cylinder head 4 and through an intake manifold 15 to the exterior of the intake manifold 15.

Referring to Fig. 1, the source of fuel for the engine may be a known fuel tank 16, typically used in an automobile or truck. The supply conducting means 8 conducts fuel under pressure from the low pressure pumps 18 at the outlet from the fuel tank 16 to each of the injectors 10. In this embodiment, the supply conducting means 8 includes: a booster fuel line 30, a low pressure line fuel 17, a high pressure fuel line 21, and a plurality of branch lines or rails 14 leading to individual injectors 10. Low pressure line 17 is located between the pump 18 and the pressure booster 22. High pressure line 21 is located between the pressure booster 22 and the rails 14.The pressure booster 22 is disposed in the fuel supply conducting means 8 for raising and regulating the pressure of the fuel in the high pressure fuel line 21 and rails 14 between the pressure booster 22 and each of the injectors 10 to an elevated, substantially constant average pressure. Average pressure refers to the pressure of the fuel from cycle to cycle of the engine. The elevated pressure is higher than the pressure in the low pressure fuel line 17 between booster 22 and the low pressure pump 18. The elevated pressure is higher than a vapor pressure for the fuel in the injectors 10. The low pressure pump 18 pumps fuel from the fuel tank 16 through the low pressure line 17 at a rela tively low pressure, such as less than 10 psig, to the pressure booster 22.The low pressure is less than the elevated pressure applied by the pressure booster 22 to the fuel in the high pressure line 21, the rails 14 and the injectors 10. The low pressure is higher than a vapor pressure for the fuel in the fuel tank 16 and a vapor pressure for the fuel in low pressure line 17. The electronic computer 19 produces pulses of predetermined length, at predetermined time intervals, for opening the injectors 10. The computer 19 is an analog compu ter which has a plurality of separate com puting channels, one channel for one or more of the injectors 10.

Preferably, the fuel injection system 2 may also include a fluid storage converter means 42 and a plurality of fluid pressure wave converter means 43, 52, 54, 56 and 58. The fluid pressure wave converter means 43, 52, 54, 56 and 58 downstream of the pressure booster 22 function to maintain substantially constant instantaneous pressure in the supply conducting means 8 between the pressure booster 22 and the injectors 10. Instantaneous pres sure refers to the pressure of the fuel during an engine cycle. A preferable type of wave converter means is described in the specification of United States Patent No.

3,507,263. Preferably, fluid storage converter means 42 is located in the low pressure line 17. One fluid pressure wave converter means 43 is located in the high pressure line 21; and four fluid pressure wave converters 52, 54, 56 and 58 are located in the rails 14.

The injector valve typically supplies its fuel charge to an exterior side of an intake valve 6 in the engine. The fuel charge is admitted to the cylinder in timed relationship to the piston motion. The fuel is discharged from the injector 10, preferably in the form of a spray on the upstream surface of the engine intake valve 6 so that the fuel charge can be heated by contact with an area of the hot intake valve to a maximum degree before it is actually fed into the engine cylinder. This heating vaporizes the fuel droplets to improve the combustion process and thereby minimize pollution. If all of the injectors were fired simultaneously, once each cycle, this fuel heating time will vary for each cylinder, resulting in poor control of emission pollutants.The fuel injection system 2 has been arranged to maximize the heating action resulting from contact by an injected fuel charge with the intake valve area in order to partially vaporize the fuel charge and increase the speed of vaporization of the remainder of the fuel charge when it is drawn into the hot cylinder. The activation times of the injectors 10 have been arranged to maximize the time of contact of the injected fuel charge with the intake valve area in the cylinder head before opening of the intake valve. The precision of control of the injection volume is proportional to both the magnitude of the fluid pressure in the conduit feeding the injectors and the degree of regulation of the pressure. A high, regulated pressure is desirable. With relatively large engines, the injection systems require high flow rates of fuel.High pressure, high volume fluid pumps are inherently large and noisy.

Minimizing these disadvantages sharply increases the cost of the pump. In the prior art fuel injection systems, the conflict between cost and performance was typically simplified by lowering the pressure in the fuel injection system. Thus, previous fuel injection systems typically employed fluid pressures of about two atmospheres in the feed lines to the injectors although higher pressures would be desirable for increasing the precision of the injection process.

Previous fuel injection systems have also been deficient in the degree of regulation of the pressure provided to the injectors.

Since the fuel flow through the injector is proportional to the line pressure, variations in that pressure result in variations in volume of fuel injected into a cylinder.

The primary purpose of the fuel injection system is to improve the control of the volume of fluid fed to each cylinder over the relatively rough control obtained with conventional carburetion systems. Large variations in the fluid pressure to the injectors defeat the central purpose of the fuel injection system. In previous systems, the pressure regulation was adversely affected by line pressure drops which occurred each time an injector fired and instantaneously reduced the fluid volume of the injector. This produced a low pressure, or expansion wave, which travelled through the lines feeding the injectors, reducing the fluid pressure in the system.

Rapid and repeated firing of the injectors would induce a number of these low pressure waves, resulting in variations in the fluid pressure throughout the lines feeding the injectors.

The present fuel injection system 2 provides fuel under high relatively constant pressure to fuel injection valves 11 (Fig.

2). The injection valves 11 provide controlled intermittent bursts of fuel to the upstream faces of the intake valve 6 of the internal combustion engine. There is normally one fuel injector 10 provided for each of the cylinders of the internal combustion engine. Other embodiments, such as a siamese ported engine, may use one injector 10 for plurality of cylinders, such as one injector for every two cylinders.

The present invention will be explained by way of example with reference to an internal combustion engine of the Otto type having eight cylinders, typically used in automobiles in the United States. As a result, in this embodiment, there are eight fuel injectors 10, one for each of the eight cylinders of the internal combustion engine. However, other embodiments of the fuel injection system 2 may use a greater or lesser number of fuel injectors, depending upon the number of cylinders in the internal combustion engine for which the fuel injection system is used. For example, a four cylinder internal combustion engine would use four fuel injectors 10, one for each cylinder. A six cylinder internal combustion engine would use six fuel injectors 10, one for each of the cylinders.The quantity of fuel injected by the fuel injection valves 11 is a function of the pressure under which the fuel is supplied to the injection valves 11 and the length of time the injection valves 11 are open.

Fuel Injectors Referring to Fig. 3, each fuel injector 10 includes: a valve 11 operated electromagnetically by means of a solenoid, an upstream end 104, a downstream end 106, and a longitudinal axis. Referring to Figs.

3 and 4, the fuel injector 10 includes: a discharge means; a fuel conduit; an electrical conductor; an electromagnetic circuit; a biasing means; and a sealing means.

Preferably, the injector 10 also includes a travel limiter.

The discharge means, a metering nozzle 108, is located at the downstream end 106 of the injector 10 and has a longitudinally extending, centrally disposed orifice 110 parallel to, and preferably coincident with, the longitudinal axis of the injector 10 for delivering a fluid, such as fuel, i.e.

gasoline, to the engine. The nozzle 108 and orifice 110 have an upstream end and a downstream end. The fuel conduit 112 extends along the length of the fuel injector 10 for conducting fuel under pressure from a fuel inlet means 114 to the nozzle 108. The electrical conductor, such as an electrical wire 116, extends along the length of the injector 10 for supplying an electrical signal, i.e. an electrical pulse of predetermined duration at predetermined time intervals, to energize the electromagnetic circuit and actuate the injector 10. The electromagnetic circuit includes: an armature 118, a central first pole 120, and a coil 124 for magnetizing the electromagnetic circuit, and a flux path.

Referring to Figs. 5-7, the armature 118 has a downstream face 126 and an upstream face 128. Referring to Fig. 4, the armature 118 is disposed within the housing 122 and in slidable contact with the housing 122. The housing 122 is a combined, dual purpose, unitary housing and outer second pole made of a magnetizable material. The housing-outer pole 122 encloses the armature 118, travel limiter 123, coil 124 and center pole 120. The housing-outer pole 122 also forms part of the electromagnetic circuit. The armature 118 is disposed between the first pole 120 and the nozzle 108.The armature 118 is the sole moving component within the injector 10 and has an upstream position, a downstream position shown in Fig. 4, and predetermined, intermittent, unrestrained, free-floating, reciprocating motion parallel to the longitudinal axis of the injector 10 over a pre e ermined fixed travel distance 130 between the upstream position and the downstream position.

Referring to Fig. 9, a downstream end 132 of the travel limiter 123 limits movement of the armature 118 in an upstream direction toward its upstream position and toward a downstream end 136 of the first pole 120. The downstream end 132 of the travel limiting member 23, preferably made of a non-magnetizable material, defines a residual air gap 138 (exaggerated in scale in Fig. 9) in the flux path between the upstream face 128 of the armature 118 and the downstream end 136 of the first pole 120 when the upstream face 128 of the armature 118 is in its upstream position, that is, in contact with downstream end 132 of the travel limiter 123. There is a single air gap which is equal to the length of the residual air gap 138 plus the travel distance 130 of the armature 118, the significance of which will be described subsequently herein.Referring to Fig. 4, the biasing means, such as a spiral return spring 140, biases the armature 118 in its downstream position. The armature 118 is really a combined, dual purpose, unitary, armature 118-valve member. The armature 118 forms part of the electromagnetic circuit and part of an electromagnetically operated valve. In its downstream position (Fig. 4), at least a portion of the downstream face 126 of the armature 118 is in contact with the upstream face 142 of the nozzle 108.

The mass of the armature 118 has been minimized as much as possible. Referring to Figs. 5-7, the armature 118 is a disc made of a magnetic material and having a substantially circular outer circumference, cut-out sections 143 along at least one and preferably two portions of the outer circumference for allowing passage of fuel and, a major diameter 144 extending between opposing sides of the outer circumference. The armature diameter 144 approaches the dimension of an interior diameter of the housing 122. As a result, the circumference of the armature 118 has a close fitting, sliding contact with interior walls of the housing 122. The armature 118 has a thickness not exceeding one-half of the armature diameter 144 and prefer ably not exceeding one-quarter of the armature diameter 144.As a result, the armature 118 has relatively small dimensions and is light in weight, thereby allowing the armature 118 to be moved by a comparatively small force generated by the electromagnetic circuit, enabling the armature 118 to have a short time response, i.e., to be highly responsive to the electromagnetic circuit in quickly opening and closing the orifice 110.

Referring to Figs. 6-8, the sealing means for sealing the orifice 110 includes an annular ridge 146 disposed between the downstream face 126 of the armature 118 (Figs. 6 and 7) and the upstream face 142 (Fig. 8) of the nozzle 108. The annular ridge 146 has a circumference and a diameter which are slightly larger than the circumference and the diameter of the upstream end of the orifice 110 in order that the annular ridge 146 encircles the upstream end of the orifice 110. The annular ridge 146 preferably is disposed on the downstream face 126 of the armature 118.

In the alternative, the annular ridge 146 could be disposed on the upstream end 142 of the nozzle 108 surrounding the orifice 110. When the armature 118 is m its downstream closed position, the annu lar ridge 146 completely encircles a valve seat 147 on the upstream end of the orifice 110 and closes the orifice 110, pre venting fuel from entering the upstream end of the orifice 110.

The sealing means includes: the valve seat 147 and the annular ridge 146. There are annular outer lands 148 and a circular undercut portion 150 which are disposed between the downstream face 126 of the armature 118 and the upstream face 142 (Fig. 8) of the nozzle 108. Preferably, the valve seat 147 is on the upstream face 142 (Fig. 8) of the nozzle 108 surrounding the upstream end of the orifice 110. Preferably, the outer lands 148 are disposed on the downstream face 126 of the armature 118 and the undercut portion 150 is disposed on the upstream face 142 of the nozzle 108. The circumference of the outer lands 148 is substantially equal to the circumference of the undercut portion 150 so that the outer lands 148 mate with and fit into the undercut portion 150.Preferably, the outer lands 148 are disposed on the outer circumference of the downstream face 126 of the armature 118 and the undercut portion 150 is disposed on the outer circumference of the upstream face 142 of the nozzle 108. Alternatively, the outer lands 148 could be disposed on the outer circumference of the upstream face 142 of the nozzle 108 and the undercut portion 150 disposed on the outer circumference of the downstream face 126 of the armature 118.

The height of the annular ridge 146 is substantially equal to the height of the annular lands 148, in a direction parallel to the longitudinal axis of the injector 10.

When the armature 118 moves in a downstream direction to its downstream closed position, the annular ridge 146 makes contact with the upstream face 142 of the nozzle 108 before the outer lands 148 can make contact with the upstream face 142 of the nozzle 108, as a result of the undercut portion 150. This arrangement ensures an effective seal and closure of the orifice 110.

The travel limiter 123 maintains a residual air gap 138 between the upstream face of the armature 118 and the downstream end 136 of the first pole 120 when the armature 118 is in its upstream open position. The travel limiter 123 also prevents magnetic and fluid astiction between the upstream face 128 of the armature 118 and the flat surface at the downstream end 136 of the first pole 120. Such prevention of astiction allows the upstream face 128 of the armature 118 to be released from contact with the downstream end 132 of the travel limiter 123 easier and with less force than the upstream face 128 of the armature 118 could be released if it were in contact with the flat surface at the downstream end 136 of the first pole 120.

The travel limiter 123 is preferably a tubular member disposed coaxially around the coil 124.

Referring to Figs. 2, 3 and 8, a spray member 152 is preferably disposed in the orifice 110 for at least partially atomizing the fuel, and preferably completely atomizing the fuel, into a spray for delivery of the fuel in the form o a spray to the engine. Atomizing refers to breakup of the fuel into fine particles to accelerate evaporation of the fuel to facilitate mixing with air for improved combustion which reduces emission of pollutants from the engine, reduces fuel consumption and improves engine performance. Referring to Fig. 8, the spray member 152 has an interior bore 153 having a longitudinal axis. The orifice 110 also has a longitudinal axis.The longitudinal axis of the bore 153 is disposed at an angle 154 with reference to the longitudinal axis of the orifice 110 for achieving impact by the fuel against an interior wall of the orifice 110 after the fuel passes through the bore 153 of the spray member 152. Such impact produces atomization of the fuel into a spray. The angle 154 may be within the range from 5 to 80 , and preferably is within the range from 30 to 450. Alternatively, instead of a bore 153 extending at an angle to the orifice 110, the spray member 152 may use a helical bore. The helical bore could be arranged around the outer circumference of the spray member 152.Preferably, the breakup of the fuel flowing through the nozzle 108 into a spray is enhanced by a high velocity of the fuel, which in turn is enhanced by a high pressure maintained with the fuel injector 10. For example, the fuel may be supplied to the injector 10 under a pressure of about 100 pounds per square inch gauge.

In preferred embodiments using a spray member 152, the bore 153 becomes the operative orifice for the nozzle 108, rather than the orifice 110. In embodiments not using a spray member 152, the orifice 110 is the operative orifice and should be smaller in diameter than if a spray member 152 were used.

The significance of having a single air gap, as compared to prior art electromagnetic circuits which have commonly two or more air gaps, is that the efficiency and the force applied by the electromagnetic circuit to the armature 18 is markedly increased. For example, in U.S. Patent 3,412,718 there are multiple air gaps in the electromagnetic circuit, i.e., between inner pole 112 and flapper valve 126, and between the outer pole and the flapper vlave 126, with the result that the sum of the series of gaps is substantially equal to twice the travel distance of the flapper valve 126.Referring to Figs. 4 and 9, a typical line of flux in the flux path of the present electromagnetic circuit runs through the first pole 120, across the residual air gap 138, across the travel distance 130, through the armature 118, through the housing 122 which acts as a second pole of the electromagnetic circuit and back to the first pole 120. The amount of flux is inversely proportional to the air gap, as shown by the following known formula: Nx Ix 1.26 B=NxIx1.26 L where L is the length of the total series air gaps, that is, residual air gap 138 plus travel distance 130; B is the amount of flux, that is, the amount of flux lines per unit cross-sectional area; N is the number of turns in the coil; I is the amperage of electricity in the circuit; and 1.26 is a constant.Since there is only one air gap in the present construction rather than two or more air gaps as in prior art electromagnetic circuits, the amount of flux B in the present construction is approximately doubled. The amount of flux B is doubled because the total length of the series air gaps L is about alf or less than the length of the total series air gaps in prior art electromagnetic circuits. This is because the total length of the series air gaps L in the present invention is approximately equal to the travel distance 130 plus the residual air 138, rather than two or more times the travel distance as in prior art electromagnetic circuits.The force exerted by the electromagnetic circuit upon the armature 118 is proportion to the square of the amount of flux B, as shown by the following known formula: B2x A B2 x A where F is the electromagnetic force exerted (in dynes), B is the amount of flux, and A is the cross-sectional area of the air gap. As a result, the electromagnetic circuit of the present construction exerts significantly more force on the armature 18 than prior art electromagnetic circuits, approximately four times as much force; when all other variables are the same. Having once passed through the total series air gaps, the lines of force do not pass through the total series air gap a second time. There are no other air gaps in the electromagnetic circuit. For example, there is no gap between the armature 18 and the housing 122.There is only a close sliding fit between the outer circumference of the armature 18 and the interior wall of the housing 122. The total series air gap is between the downstream end 36 and the upstream face 128. The total series air gap is a single gap, having two components (the residual air gap 138 and the travel distance 130), not two or more separate gaps remote from one another. The significance of having the travel distance 130 plus the residual air gap 138 substantially equal to the length of the total series air gap is that the amount of flux is substantially increased, thereby increasing electromagnetic force F.

The nozzle 108 has a circular shape and a circumference dimensioned to fit within the housing 122. The coil 124 is disposed on a tubular bobbin 156 having flanges at each end. The first pole 120 is centrally and axially disposed within the bobbin 156. The first pole 120 has a flange at its upstream end in contact with the housing-outer pole 122. The flange has holes therethrough to allow passage of fuel. The bobbin 156 is centrally and axially disposed within the coil 124. The coil 124 is centrally and axially disposed within the travel limiter 123. The travel limiter 123 is a tubular member, centrally and axially disposed within the housing 122.

The electrical wire 116 is connected to the coil 124 by a first terminal 158 and a lead wire 160. The electrical wire 116 is insulated from the first pole by an insulator 161.

Referring to Figs. 3 and 4, the fuel conduit 112 is a tubular member connected to an upstream end of the housing 122 by an adapter 162. The fuel conduit 112 and the housing 122 are disposed parallel to the longitudinal axis of the injector 10. An "0" ring 163, is provided between the upstream end of the housing 122 and a downstream end of the adapter 162. The electrical wire 116 extends centrally and axially within the fuel conduit 112 along the length of the fuel conduit 112.

Referring to Fig. 3, a mounting means is provided around the fuel conduit 112 for mounting the fuel conduit 112 and the injector conduit means 13 to the engine, such as to the engine cylinder head 4 or to the intake manifold 15 of the engine and extending into the cylinder head 4, preferably in both cases with the valve 11 entirely within the cylinder head 4. The mounting means is located at the approximate middle portion of the fuel injector 10 and the fuel conduit 112 between the upstream end 4 and the downstream end 106 of the fuel injector 10. The mounting means includes: a sleeve 164, and adapter 166, and a male nut 168.

Referring to Figs. 3 and 10, the fuel inlet means 114 includes a fitting 170, an interior screen 172 disposed within the fitting 170 and a retaining ring 174 for holding the screen 172 within the fitting 170.

The screen 172 is intended to filter undesired particles from the fuel entering the inlet means 114. The screen 172 is not the main filtering device for fuel being supplied to the engine. The fitting 170 is attached to the upstream end of the fuel conduit 112, such as by welding.

A second terminal 176 is provided for connecting the electrical wire 116 to the fitting 170. The second terminal has a flange 178. A first non-compressible washer 180 and a first compressible washer 182 are disposed below the flange 178. A second non-compressible washer 184 and a second compressible washer 186 are disposed above the flange 178. The first compressible washer 182 is disposed between the flange 178 and the first noncompressible washer 180. The second non-compressible washer 184 is disposed between the second compressible washer 186 and the flange 178. The first and second non-compressible washers 180 and 184 may be made of a material such as nylon. The first and second compressible washers 182 and 186 may be made of a material such as rubber. The noncompressible washers 180 and 184 keep the second terminal 176 centered and prevent shorting of the electrical wire 116.

The compressible washers 182 and 186 allow crimping to achieve a tight mechanical seal to prevent leakage of the fuel.

In operation, the armature 118 is normally closed and opens only for short intervals of time. When the coil 124 of the electromagnetic circuit is energized, the armature 118 is moved from its downstream closed position (Fig. 4) to its upstream open position by the electromagnetic attraction of the coil 124. The armature 118 moves to its upstream open position in an upstream direction, indicated by arrow 188 in Fig. 4, against the force of the return spring 140 and against the flow of fuel into the fuel injector 10.

When the coil 124 is de-energized, the spring 140 pushes the armature 118 in a downstream direction, indicated by arrow 189 in Fig. 4, to its downstream closed position in which the armature 118 acts as a valve member closing the orifice 110 of the nozzle 108. In its upstream open position, the armature 118 moves away from the valve seat 147, thereby opening the nozzle 108 and allowing communication from the fuel injector 10 through the orifice 110 into the engine. The flow path of fuel passes from the fuel conduit 112 through an accumulation chamber 190, then through holes in the flange on the upstream end of the first pole 120, then around the outside of the travel limiter 123 where the return spring 140 is located, then through the cut-out sections 143 of the armature 118 and then through the orifice 110 when the orifice 110 is opened by the armature 118.

The disclosed electromagnetically operated valve achieves a high degree of responsiveness by: a design of the armature having a low mass, use of a travel limiter which prevents a problem of astiction, and an arrangement whereby the travel distance of the armature is substantially equal to a single air gap in the electromagnetic circuit rather than equal to two times the air gap. The electromagnetically operated valve achieves a more efficient electromagnetic circuit which can exert more force on the armature by having a single air gap, rather than two or more air gaps.The electromagnetically operated valve is durable, economical to manufacture, miniaturized in size, and highly responsive because it has only one moving part, a combined armature and valve member which forms part of the electromagnetic circuit, which also acts as a part of the valve to open and close the nozzle, and which has a disc shape. The electromagnetically operated valve, when used as a fuel injector in a fuel injection system for an internal combustion engine, achieves more complete combustion within the engine to reduce emission of pollutants, achieves reduced fuel consumption and achieves improved engine performance, by preferably delivering the fuel in the form of an atomized spray, rather than in the form of a liquid stream.

I Supply Referring to Fig. 1, fuel is provided to the fuel injection valves by a supply conducting means 8 which includes fuel rails 14. Fuel for feeding the rails 14 is derived from the fuel tank 16. The low pressure pump 18 is a pump which operates to feed the fuel from the fuel tank 16 through a one-way valve 220. The pump 18 is capable of pumping fuel at a vo umetric rate in excess of the engine requirements at maximum throttle opening. For a relatively large 8-cylinder engine this may be in excess of 25 gallons per hour. The outlet pressure of the pump 18 may be substantially lower than the 25-40 pounds per square inch provided by fuel pumps for typical injection fuel systems of the prior art. In a preferred embodiment of the present invention, a 5-10 pound per square inch outlet pressure will suffice.This pressure need not be well regulated and may vary with engine speed. Accordingly, the pump 18, described in detail subsequently, can be substantially simpler and lower m cost than fuel pumps used with previous injection systems.

Pressure Booster Referring to Fig. 1, the fuel pressure booster, generally indicated at 22, receives fuel passed through a one-way valve 220 from pump 18. The booster 22 is schematically illustrated in Fig. 1 and includes: a piston 224 movable within a cylinder 226 and biased by a spring 228. The spring 228 biases the piston 224 in a direction which moves the piston 224 to contract the volume of the cylinder 226 in communication with the fuel line 30. This increases the fluid pressure in the booster line 30, the high pressure fuel line 21 and the rails 14 to an elevated pressure. The elevated pressure is higher than the pressure in the low pressure fuel line 17 between the one-way valve 220 and the pump 18. The elevated pressure is higher than a vapor pressure for the fuel in the injectors 10. Preferably, the elevated pressure is above four atmospheres.More preferably, the elevated pressure is between five atmospheres and ten atmospheres. Most preferably, the pressure is between six atmospheres and eight atmospheres. A typical example of such an elevated pressure is 100 pounds per square inch gauge.

The one-way valve 220 prevents this increase in pressure from forcing a reverse flow to the pump 18.

A reset mechanism 232 is schematically illustrated in Fig. 1 as being connected to the piston 224 to periodically move the piston 224 against the bias of the spring 228 to enlarge the volume of the cylinder 226 in communication with booster line 30. This lowers the pressure in booster line 30 and allows momentary flow from the pump 18 through the one-way valve 220.

A second one-way valve 234 is connected downstream of the booster 22.

When the piston 224 moves under the bias of the spring 228 to contract the volume of the cylinder 226, the valve 234 allows the resulting high or elevated pressure to communicate with fuel line 21 that connects to the fuel rails 14, thus imposing this higher pressure on the rails 14. When the reset mechanism 232 withdraws the piston 224 against the force of the spring 238, allowing the pump 18 to force fuel into the low pressure fuel line 17, the one-way valve 234 prevents back-flow in the high pressure fuel line 21 toward the pressure booster 22 and thus in combination with fluid pressure wave converter 43 maintains the high fluid pressure in the rails 14. Optionally, the far ends of the rails 14 are connected together by a fuel line 38 to form a closed circuit. A constant bleed one-way valve 240 connects the fuel line 38 to the fuel tank 16 via a valve 74 and conduit 72.

Fig. 11 illustrates a unitary device incorporating the booster 222 (Fig. 1), the one-way valves 220 and 234 (Fig. 1) located upstream and downstream respectively from the booster 22, the fluid storage converter 42 and fluid pressure wave converter 43. The fluid storage converter 42 performs a different function than the fluid pressure wave converter 43, as will be explained subsequently herein. The fluid storage converter 42 is located upstream of and immediately adjacent to the one-way valve 220 of the pressure booster 22. The storage converter 42 provides an instantaneous source of fuel at pressure to the pressure booster 22 when the piston 224 is retracted against the force of the spring 228 and the one-way valve 220 opens. The device 260 employs a cylindrical housing 262 having a cylindrical bore. A piston 264 is slidably supported within the housing 262.A sealing means such as an O-ring 266 is supported in a groove in the piston 264. A guide bushing 270 is retained in the opposite end of the cylinder bore for supporting a pull rod 268. A relatively long first coil spring 272 surrounds the pull rod 268.

The ends of coil spring 272 bear against the rear of the piston 264 and the bushing 270. The first coil spring 272 biases the piston 264 toward movement to the right, as viewed in Fig. 11.

A cylinder volume of the bore between the rear end of the piston 264 and the opposing end of the bushing 270 is vented to atmosphere and/or to the fuel tank 16 (Fig. 1) by a hole 274 covered by a screen 276. The extreme end of the pull rod 268, at the left side of Fig. 11, beyond the guide bushing 270, extends through an oil seal 278 and has a cushion member 280 affixed to its extreme left end. The cushion member 280 projects into a housing 282 which is attached to a crankcase of the engine serviced by the injection system 2.

The end of the housing 262 through which the pull rod 268 projects is affixed to or integral with housing 282.

An elongated actuator arm 284 is pivotably supported on a fulcrum pin 286 within the housing 262. One end of the actuator arm 284 projects into the crankcase area and bears against a cam 288 formed on the engine cam-shaft. A second coil spring 290 connected to the actuator arm 284 on the opposite side of the fulcrum pin 286 and to the housing 262 urges the end of the actuator arm 284 against the cam 288. The opposite end of the actuator 284 is forked and surrounds the piston rod 268 between the cushion end 280 and oil seal 278. The action of the first coil spring 272 on the piston 264 causes the cushion member 280 to bear against the forked end of the actuator arm 284 in the absence of fuel within a chamber 285 forward (to the right in Fig.

11) of the piston 264. However, when the chamber 285 is filled with fuel, the piston 264 can only move to the right in Fig. 11 until it imposes a pressure on the fuel sufficient to offset the force of the spring 272.

The actuator arm 284 pivotably reciprocates under the force of the cam 288 as the engine cam shaft rotates. At one extreme of the reciprocation, the actuator arm 284 pushes cushion member 280 to the position shown in Fig. 11. The upper end of the actuator arm 284 then moves to the right allowing the piston 264 to bear against fuel in the chamber 285. On the return stroke of the actuator arm 284, it again resets the piston 264 into position.

A manifold 291 is retained at the piston end of the housing 262 by bolts 292. The manifold 291 contains an inlet port 294 which is connected to the outlet of the pump 18. The port 294 communicates with a first valve passage 295 which is the equivalent of the one-way valve 220, schematically illustrated in Fig. 1. The valve passage 295 has a valve member 296 which cooperates with an annular seat member 298 and is urged against the seat member 298 by a relatively light third coil spring 300. A stem 302 is connected to the end of the valve member 296 and slides in a guide 304 disposed in the opposite end of the valve passage 295. The valve passage 295 communicates with the chamber 285 having a cylinder volume forward of the piston 264 to allow flow into the chamber 285 but prevents flow out of the chamber 285.

The pressure imposed on the valve member 296 by the third spring 300 is sufficient to retain the valve member 296 against the seat member 298 in opposition to gravity forces.

The inlet port 294 also communicates with a volume 305 surrounding an inlet port side of a first pleated flexible diaphragm 306. The first diaphragm 306 cooperates with a wall 308 formed across the manifold, to seal a volume 310. The first diaphragm 306 and the volume 310 are the equivalents of the diaphragm 246 and the sealed volume 244 illustrated schematically as part of the fuel storage converter 42 in Fig. 1. When the pressure in the inlet port 294 exceeds the pressure in the chamber forward of the piston 264, the valve member 296 overcomes the spring 300 pressure and allows fuel flow from the volume 305 and inlet port 294 into the cylinder chamber 285.

The chamber 285 forward of the piston 264 discharges through a second valve passage 311 have a second conical valve member 312 which cooperates with an annular seat 314 to form a one-way valve equivalent to the one-way valve 234 of Fig. 1. A valve stem 316 moves in a guide 318 formed at the outlet of the valve passage 311. A fourth coil spring 320 is compressed between the rear side of the second valve member 312 and the guide 318 and urges the valve member 312 into abutment with the seat 314. The valve 312 and valve seat 314 allow flow out of the chamber 285 but prevent flow into the chamber 285.

Fuel flowing through the valve passage 311 goes through a passage 322 which leads to a volume 324 on the opposite side of the wall 308 from the volume 310. The volume 324 is bound by a second pleated flexible diaphragm 326 which cooperates with the end wall of the manifold 291 to form a sealed volume 328. This volume 328 and the second diaphragm 326 are the equivalent of the fluid wave converter 43 illustrated schematically in Fig. 1. Volume 324 discharges out of the manifold 291 through a passage 330, which connects to a discharge port 332. This discharge port 332 connects to the high pressure fuel line 21 shown in Fig. 1.

In operation, the inlet passage 294 of the pressure booster 260 is connected to the outlet of a relatively low pressure pump 18 (Fig. 1). The outlet port 332 is connected to fluid rails 14 (Fig. 1) through the pressure line 21 (Fig. 1). Assume that the fuel injection system 2 (Fig. 1) is initially empty of fuel and the engine ignition switch and starter switch are closed. The pump 18 will be energized and will draw fuel from the tank 16 and create a pressurized flow through the first valve passage 295, the chamber 285 of the cylinder 262, the second valve passage 311 and the line 21 (Fig. 1), filling up the rails 14 (Fig. 1).

During this time, the engine will cause the actuator arm 284 to reciprocate, forcing the piston 264 back against the spring 272.

Until the system 2 fills with fuel, the face of the piston 264 will not be sufficient to retain the piston 264 in a cocked position.

When the system 2 fills, the piston 264 will immediately exert its full force on the relatively incompressible fuel and will raise the pressure in the system, downstream of the valve 296, to substantially above the outlet pressure of the pump 18. For example, this pressure in fuel line 21 and rails 14 may be in the vicinity of 100 p.s.i.g.

This will force the valve member 296 to close, blocking off further flow from the pump 18.

The injector valves 11 are, preferably, opened in groups of two, thereby simultaneously injecting fuel into two cylinders at a time, in sequence with the intake stroke of the engine. But, in other embodiments may be opened simultaneously or in a serial sequence. In any event, when each injector 10 is opened, it tends to deplete the volume of the system 2 downstream of valve passage 295 (valve 220 in Fig. 1) and will effectively generate a low pressure wave which will move from the open injector 10 toward the pressure booster 22 (in Fig. 1) and device 260 (Fig. 11).

When it reaches the chamber 285, the lowered force on the piston 264 will allow the piston 264 to move slightly (to the right in Fig. 11) under the force of the spring 272 until the pressure imbalance is corrected. The motion will be sufficient to diminish the free volume of the chamber 285 by the quantity of fuel ejected through the injector 0. This action will effectively generate a pressure wave which will move back toward the injectors 10.

During one cycle of the engine, all of the injectors 10 will be opened once and the piston 264 will move forward to reduce the free volume of chamber 285 by substantially the volume of fuel ejected.

Once each cycle, the actuator arm 284 will move against the cushion member 280 to recock the piston 264 to its original position. Once the system 2 is filled with fuel, the cushion member 280 will not follow the actuator arm 284 through it full reciprocation, but will remain near the original position (left in Fig. 11) of the actuator arm 284.

Each time the piston 264 is withdrawn by motion of the actuator arm 284, the valve member 312 will close and the valve member 296 will open. During the closing of the valve member 312, the diaphragm 326 will move outwardly in response to expansion pressure waves in the fuel to maintain substantially constant pressure to the injectors. Such an expansion pressure wave propogating from the injectors 10 reaches the diaphragm 326 before it reaches the valve member 312.

Similarly, when the valve member 296 opens in response to a sharp drop in pressure in the chamber 285 occurring upon withdrawal of the piston 264, the expansion pressure wave hits the diaphragm 306 and causes it to move outwardly to effectively supply the quantity of fuel required to replenish the chamber 285. After the piston 264 moves to re-establish pressure in the chamber 285, the valve 296 closed and the pump 18 re-establishes the original position of the diaphragm 306.

When the engine is shut off, the first and second valve members 312 and 296 close the first and second passages 295 and 311 and retain the rails 14 full of fuel.

When the engine is shut-off, the valve members 312 and 296 will close. Over a period of time, there will necessarily be some leakage through valves 312 and 296 from the system 2 and the pressurization will not be maintained indefinitely, but sufficient residual fuel in the system 2 will allow rapid repressurization and a quick start-up of the engine.

Preferably, the first positive check valve 70 is positioned in the low pressure fuel line 17 close to the downstream side of its pump 18 to prevent leak back indefinitely.

A return fuel line 72 is disposed between the fuel line 38 and the fuel tank 16 for returning a portion of the fuel from the rails 14 to the fuel tank. A second positive check valve 74 is disposed in the return fuel line 72. The second valve 74 is closed when the engine is turned off to block flow of fuel through the return fuel line 72 when the engine is turned off. The second valve 74 maintains at least part of the pressure in the supply conducting means when the engine is turned off. The first valve 70 blocks the flow of fuel in the fuel line 17 between the booster 22 and the fuel tank 16. The first and second valves 70 and 74 cooperate with one another to maintain pressure in the supply conducting means while the engine is turned off at a high pressure level substantially equal to or at least approaching the elevated pressure established by the pressure booster 22.

Fig. 13 illustrates the pressure at an injector 10 during a maximum width injector pulse. At time T = zero, the beginning of the pulse, the pressure in the rail 14 is at a maximum level, which may be, for example, 100 pounds per square inch gauge. As the injector 10 opens, removing fuel from the system 2, the pressure at the injector 10 begins to gradually decrease.

At the same time, an expansion pressure wave is propagated down the rail 14 in the direction of the pressure booster 22. This pressure wave may reach the pressure booster 22 at time T1. The booster 22 then responds by providing a compression wave to the system which reaches the injector 10 at T2, raising the pressure back to 100 psig. During the balance of the stroke, the pressure in the rail 14 is equal to the pressure imposed on the fluid by the piston 264, but this pressure gradually decreases as the piston 264 moves, lengthening the first spring 272, since the force imposed by the first spring 272 is proportional to its elongation. At T3, the end of the injector pulse, the pressure will have dropped to some value that is dependent upon the configuration of the booster 22.

The average pressure provided to the injector 10 during the cycle is between the minimum and maximum pressures occurring during this cycle.

The decrease in pressure as a result of the piston 264 motion is a function of the length of the spring, the area of the piston 264 and the volume of fuel injected during one cycle. Fig. 14 is a plot of the angle of the cam 288, the stroke of the piston 264, and the resulting displacement in volume in the cylinder chamber. In this embodiment, the values for the stroke and volume displacement are for a .750 inch diameter piston and a 1.265 inch radius cam having a .700 inch throw. A typical 430 cubic inch displacement engine will require .660 cubic centimeters of fuel during one engine cycle. This means that the piston 264 must move .090 inches to displace that volume. The actuator arm 284 will then hit the cushion at approximately 56 angular degrees of the cam before a maximum actuator position.

Fig. 15 is a plot of spring force against spring deflection for a spring (used as the first coil spring 272) having a rate of 22 pounds per inch and having a maximum deflection of two inches. It will be seen that for a .090 inch variation in spring length between its two extremes of position the force exerted by the spring will only change by about two pounds, or 4%.

It should be noted that this variation in pressure in the rail 14 as a result of the elongation of the first spring 272 is a constant factor and may be weighted into the calculation of the injector pulse width to ensure a proper injection volume.

In alternative embodiments of the invention, it should be recognized that other forms of variable volume chambers other than a piston moving in a cylinder might be employed. For example, a bellows or a roll diaphragm might be likely forms for the variable volume chamber.

Thus, the pressure booster 22 is not a pump or an auxiliary pump. The maximum volumetric displacement of the pressure booster 22 is necessarily very small, e.g.

about 2.3 cu. cm. in order to be compatible with the maximum force which can be exerted by the engine cam. The inlet port 294 must be at a pressure above a vapor pressure for the fuel in the line 17. Thus, there must be a separate pump 18 in order to maintain the fluid in a liquid state at all times with the chamber 285. The pressure booster 22 raises and regulates the average pressure of the fuel.

Pressure Wave and Storage Converters The fluid storage converter 42 is connected to the low pressure fuel line 17 immediately upstream of the one-way valve 220; i.e. between the one-way valve 220 and the pump 18. Preferably, the fluid storage converter 42 is essentially of the same type disclosed in United States Patent 3,507,263, although the function is different. Schematically, it comprises an enclosed, sealed, variable-volume chamber 244 separated from the low pressure line 17 by an elastic diaphragm 246. The diaphragm 246 assumes a position wherein the forces on its opposite sides are equal.

Thus, when the pressure in the low pressure line 17 increases, the diaphragm 246 moves to contract the volume of the chamber 244 and thus pressurize the fluid sealed within the volume. Conversely, when the pressure in the low pressure line 17 falls, the diaphragm 246 moves to expand the volume of the chamber 44.

When the diaphragm 246 moves outwardly in response to a lowering in the fluid pressure in the low pressure line 17, it effec tively pumps a volume of fluid into the low pressure line 17, tending to raise the line pressure. Conversely, when the diaphragm contracts in response to an increase in the pressure in the low pressure line 17, it increases the flow volume connected to the low pressure line 17 and thus tends to decrease the pressure. The converter 42 thus acts to provide to the pressure booster 22 the high peak pulse flow requirements needed by the pressure booster 22 at higher engine speeds.

When the piston 224 of the pressure booster 22 (Fig. 1) is retracted at high instantaneous velocity against the bias of the spring 228 by the reset mechanism 232 so that the pressure in the fuel line 30 falls below the outlet pressure of the pump 18, and the flow valve 220 opens, the decrease in pressure at the inlet to the converter 42 causes the diaphragm 246 to expand and supply a volume of fuel which charges the rapidly expanding volume of the chamber of the pressure booster 22. In the absence of the storage converter 42, a sharp low pressure expansion wave generated by expansion of the volume in cylinder 226 would otherwise quickly vaporize the fuel in the low pressure line 17 between the pump 18 and the booster 22 and in the line 30.

A pressure wave converter 43 of similar structure to the fluid storage converter 42, but different function, is connected to the high pressure fuel line 21 immediately downstream of the one-way valve 234.

The pressure wave converter 43 provides a pressurized fuel source to the high pressure line 21 during the short interval when the piston 224 is resetting and, accordingly, the one-way valve 234 is isolating the line 30 from the rails 14. The pressure wave converter 43 also acts as a cushion to minimize the travel of expansion and compression waves through the high pressure line 21.

In the preferred embodiment of the invention of pair of pressure wave converters 52 and 54 are connected adjacent to the input ends of the fuel rails 14. A second pair of pressure wave converters 56 and 58 are connected adjacent to the outlet ends of the fuel rails 14, where they connect to the common fuel line 38. These pressure wave converters 52, 54, 56 and 58 regulate the instantaneous pressure at the injectors 10 by smoothing out the instantaneous fluid pressure expansion and compression waves during an engine cycle created in the rail 14 by the rapid opening and closing of the injectors 10.

A preferred form of converter, suitable for use as the fluid pressure wave converters 43, 52, 54, 56 and 58 and the fluid storage converter 42 in the schematic diagram of Fig. 1, is illustrated in Fig. 12. The converter, generally indicated by the numeral 340, includes a body member 342 having cavity 344 formed in one of its surfaces, and a cover member 346. The cover 346 is joined to the body 342 by bolts 350 and a pleated plastics diaphragm 352 is sandwiched between the two parts to separate the volume 344 from volume 348.

The body 342 has a first passage 354 formed through the body 342. A second outlet passage 356 is also formed through the body 342 and joins the first passage 354 at right angles. This arrangement allows the converters 340 to respond to pressure waves passing through the first passage 354 and minimize pressure waves though the second passage 356. That is, if a compression wave enters the device through the first passage 354 and causes the diaphragm 352 to move to contract the volume 348, and thereby generate an expansion wave which tends to nullify the compression wave, the waves are minimized through the second passage 356. The four converters 52, 54, 56 and 58 all serve the same function. They are positioned as closely as possible in the rails 14 to the injectors 10. The second passage may be suitably narrowed to throttle the flow through the connecting line 38.In some embodiments, the converters 56 and 58 may be substantially indentical to the converters 340 but the second passage 356 will be blocked. The second passage 356 is optional and may be replaced by an exterior T-connection. The converters 52, 54, 56 and 58 may have either of their passages at right angles to rail 14. The converters 52, 54, 56, and 58 smooth the instantaneous pressure in the rails 14 and minimize generation of spurious expansion and compression waves in the rails 14. In the common rail 14 configuration, the purpose of such smoothing is to provide substantially uniform engine cylinder to cylinder fuel distribution during an engine cycle for exhaust emission reduction.

Low Pressure Pump Referring to Figs. 25 and 26 of the drawings there is illustrated an electromagnetic pump incorporating a preferred form of pump located in the tank 16 for supplying combustible fluid from tank.

Other forms of pumps can also be used, including a pump located outside the tank 16. The pump system, shown generally at 360, should therefore be interpreted as illustrative and not in a limiting sense. As illustrated, the system 360 contains a pump 362. The pump 362 includes a housing 364 having an inlet chamber 366 and an outlet chamber 368. A cylinder 370 of non-magnetic material communicates with the inlet chamber 366 and outlet chamber 368. Slidably mounted in the cylinder 370 is a hollow piston 372 of magnetizable material. A spring 374 urges the piston 372 away from the inlet chamber 366. The cylinder 370 is surrounded by a coil 373 adapted, when energized, to draw the piston toward the inlet chamber 366. A valve means 385 cooperates with the coil 373 to cause fluid flow between the inlet chamber 366 and the outlet chamber 368 upon reciprocation of the piston 372.Coil 373 is connected to a circuit means 376 for transmitting therethrough an electrical current from power source 378 to energize the solenoid 380. A control means 382 connected to the circuit means 376, controls the time interval during which current is transmitted through circuit means 376.

The control means 382 is located externally to a tank 16 containing combustible fluid 384 such as gasoline or the like, and the pump 362 is at least partially submerged in the fluid 384 within the tank 16.

The housing 364 preferably contains a pump chamber 386. The housing 364 and the other exterior portions of the pump are preferably made of a non-sparking material, such as plastics or soft metal, to avoid the hazard of fire and explosions within the tank. A buffer spring within the cylinder 370 absorbs stress exerted thereon by piston 372. Inlet chamber 366 is provided with a filter 371 and a check valve 379. The valve 379 is mounted in a guide 381 extending axially of housing 364 from a seat 383 formed by partition 391 separating pump chamber 386 from inlet chamber 366. Filter 371 may be a ribbontype filter such as microban, a fine wire mesh screen or the like. Check valve 379 is stabilized within guide 381 by compression spring 389.

Cylinder 370 is axially mounted in the pump chamber 386 in position to connect inlet chamber 366 with outlet chamber 368. Hollow piston 372 is slidably mounted in cylinder 370 and associated with check valve 377 so located therein that reciprocation of the piston 372 effects fluid flow through cylinder 370 from inlet chamber 366 to outlet chamber 368.

Cylinder 370 is formed of non-magnetic material such as brass, stainless steel or the like. The cylinder 370 can, optionally, be formed of a mouldable plastics. The piston 372 is formed of magnetic material such as magnetic stainless steel, low carbon steel or the like. The buffer spring supported by surface 375 of cylinder 370 absorbs stress exerted thereon by piston 372.

Coil 373 is located in housing 364 surrounding cylinder 370. The electromagnetic solenoid 30 includes: coil 373, pole piece 392 and casing 394. Spring 374 is supported by partition 391 and urges piston 372 in the direction of the arrow A to a decentered position with respect to the solenoid. Energization of the coil 373 draws the piston 372 toward inlet chamber 366 cocking the spring 374. When the coil 373 is deenergized, the spring 374 expands and moves the piston 372 through its discharge stroke. Pole piece 392 and casing 394 are constructed of magnetic material such as a common steel or iron. Spring 374 can be a coiled compression spring or the like.

Circuit means 376 is connected to coil 373 via terminals 398 and 400. Electrical current transmitted through circuit means 376 for time intervals regulated by control means 382 periodically energizes coil 373 causing reciprocation of piston 372. The type of control means employed can vary depending on the temperature and viscosity of the fluid, the variation in demand placed on pump 362 and the enviroment in which the pump system is employed.

Accordingly, the form of control means 382 described herein should be interpreted as illustrative and not in a limiting sense.

One form of control means 382 which is suitable includes timing means 402, Fig.

27, connected through circuit means 376 to power source 378, which may comprise a battery of the type conventionally used in a motor vehicle. The timing means 402 is adapted, upon being energized, to transmit current therethrough for a preselected time interval, whereby the solenoid is energized for a corresponding time interval. The control means 382 additionally has an actuating means 404 for periodically actuating the timing means 402.

In assembly of the pump 362, the housing 364 is partially filled with a suitable adhesive such as epoxy resin to permanently and rigidly anchor the fixed components therein. The housing 364 can, itself, be formed of the adhesive.

In Fig. 27, there is shown schematically, an electrical diagram of one form of the pumping system 360. Other forms can also be used. Current from power source 378 reaches an asymmetrical, synchronizable, astable multivibrator 401 through lines 403, 405, 406 and 407. As a result, the multivibrator 401 turns on for a time interval determined by capacitor 408 and resistor 409. The capacitor 408 has a capacitance in the order of about 0.2 microfarads. Resistor 409 has a resistance value of about 100,000 to 200,000 ohms.

The connection between power source 378 and terminal 410 of multivibrator 401 permits the multivibrator 401 to operate in an astable form. During the "on" state, an electrical current is transmitted through line 411 to terminal 398 (Fig. 26) of coil 373, energizing the solenoid. During the "off' state, the current is not transmitted through line 411 but rather is transmitted through a suitable time delay circuit composed of capacitor 413, resistor 415, Zenor diode 417, transistor 419 and load resistor 421 to trigger 399 of the multivibrator 401. The time interval during which the current is transmitted through the time delay circuitry to retrigger multivibrator 401 via the output of trigger 399 is determined by resistor 415, capacitor 413 and Zenor diode 417. These components together with the trigger 399, transistor 419 and load resistor 421 form the actuating means 404.Capacitor 408 and resistor 409 form the timing means 402. Capacitor 413 has a capacitance in the order of about 0.2 microfarad. The resistance values of resistors 415 and 421 are about 200,000 to 300,000 ohms, respectively. As long as current is transmitted through line 411, the solenoid is energized, drawing piston 372 toward inlet chamber 362.

When the current is not transmitted through line 411, the solenoid is deenergized, whereby spring 374 expands and moves the piston 372 through its discharge stroke in the direction of arrow A. As a result, the current from power source 378 is transmitted periodically through the solenoid during a plurality of time intervals, the duration of each of the time intervals being preselected by regulation of multivibrator 401 in the conventional way.

Typically, each of the time intervals has a duration in the order of about 18 to 25 milliseconds.

Controller Computer Referring to Fig. 16, the electronic control computer 19 includes: a pulse shaper 426, a counter 430, and a plurality of variable width pulse generators. In this embodiment, four variable width pulse generators 440, 442, 444 and 446 are used, providing four separate computing channels, one channel for every two injectors. Each channel is capable of operation during more than 50%, and preferably substantially all, of an engine cycle period, e.g., 18 milliseconds out of a 20 millisecond engine cycle period. Preferably, the computer 19 further includes a phase pulse generator 450. The control computer 19 initiates a plurality of injector-opening pulses in sequential timed relationship to one another and to the operation of the engine.After start-up and warm-up on the engine, that is, during normal operation of the engine, the computer provides a single opening pulse to each injector during each engine cycle.

The counter 430 is incremented each time a firing pulse is applied to any of the engine's spark plugs 412. The pulse generators 440, 442, 444 and 446 are triggered by the various sequential outputs of the counter 430. The phase pulse generator 450 synchronizes the counter 430 once during each engine cycle to maintain a fixed and predetermined phase relationship between the condition of the counter 430 and the operation of the engine. The injectors 10 of the eight cylinder engine are arranged in four groups of two each and the opening of each group of two injectors 10 is controlled by a single pulse.This compromise between the expense of providing an independent control circuit for each injector 10, and the alternative of controlling all of the injectors 10 at the same time from a single time sharing control circuit, has been found to provide optimum control over the injection fuel metering function to give good engine response and minimize the emission of pollutants. The pulse width generators 440, 442, 444 and 446 receive the outputs of sensors 448 which measure engine variables such as speed, temperature, pressure and the like, and generate pulses of a duration calculated to provide the cylinders with an appropriate quantity of fuel during each actuation of the injectors.

The four variable width pulse generators 440, 442, 444 and 446 are triggered by four sequential outputs of the counter 430 incremented by pulses derived from the primary circuit 423 of the engine distributor and ignition system. These pulses are generated in timed relation to the operation of the engine and eight of the pulses are generated for each engine cycle.

Since only four control channels are employed, the preferred embodiment of the invention uses an eight-stage counter and the four variable width pulse generators are connected to separate outputs of the counter, i.e. outputs 0, 2, 4 and 6. The counter 430 inherently returns to zero after it receives eight pulses, but to lock the pulse generating circuit into synchronism with a selected angle of the engine crankshaft, the counter 430 is synchronized to the zero state once each engine cycle by a pulse derived from a selected spark plug lead. This pulse occurs in synchronism with the pulse derived from the primary 423 of the spark coil, but only occurs once in each engine cycle because of the distributor action. The control computer 19 will now be explained in more detail.

Referring to Fig. 16, the eight cylinder engine employs one injector 10 associated with each cylinder. An injected fuel charge is admitted to the cylinder when the intake valve opens. Each engine cylinder is also provided with a spark plug 412. Other known forms of igniters could be employed with alternative embodiments of the invention. The firing pulses for the spark plugs 412 are derived from a distributor, generally indicated at 414. The distributor 414 is illustrated as a single-pole, eightthrow switch and could be implemented with a conventional mechanical distributor or with electronic circuitry. In either event, the contact of a common member 416 of the distributor 414 to the terminals 418, which are connected to the spark plugs 412, is performed in synchronism with the rotation of the engine and the common member 416 makes one sweep of the terminals for each engine cycle.

The voltage pulses for generating sparks across the spark plug gaps are derived from the secondary circuit 420 of the spark coil generally indicated at 421. The opposite end of the secondary circuit 420 is grounded, as are the opposite terminals of the spark plugs 412. Application of current to the primary circuit 423 of the spark coil 421 is achieved by breaker points 422, shunted by a capacitor 424.

The breaker points 422 also operate in timed relation to the rotation of the engine. In alternative embodiments of the engine, the breaker points 422 and spark coil 421 could be replaced by suitable electronic apparatus.

To open the injectors 10 in timed relation to the operation of the engine and the firing of the spark plugs 412, a pulse shaper 426 is connected to the circuit of the spark coil primary 423 by a voltage limiting resistor 428. Each time the breaker points 422 open, i.e., eight times during each engine cycle, a voltage spike is applied to the pulse shaper 426.

The pulse shaper 426 differentiates, integrates and clips the signal received each time the points 422 open and close to produce a generally rectangular pulse.

These pulses are provided to the counter 430 which is also a decoder. The counter 430 includes a three-stage binary counter and associated circuitry for decoding the state of the counter to provide outputs on one of four lines 432, 434, 436 and 438.

Assuming the counter 430 to be in a zero state initially, an output is provided on line 432. An output is provided on line 434 after two pulses have been received from the pulse shaper 426; an output on line 436 is provided when the fourth pulse is received; and an output line 438 when the sixth pulse is received. The eighth pulse returns the counter 430 to the zero state and again causes an output on line 432.

Thus, one output is provided on each line 432, 434, 436 and 438 during each engine cycle wherein the breaker points 422 actuate eight times.

The output lines 432, 434, 436 and 438 are provided to four variable width pulse generators 440, 442, 444 and 446, respectively. These pulse generators each have inputs from a group of sensors 448 which sense various engine operating conditions such as manifold pressure and temperature, speed, throttle position and barometric pressure. Upon receipt of a pulse on one of the input lines 432, 434, 436 or 438, the associated variable width pulse generator provides an output pulse having a pulse length which is determined by the outputs of the sensors 448 from the engine. One form of pulse width generator, or modulator, is disclosed in U.S. Patent 3,500,502 (3,500,801).

The variable width pulse generator 440 is connected to one pair of injectors 10, and the pulse generators 442, 444, and 446 are each connected to another pair of injectors 10. An output pulse from one of the pulse generators causes its two associated injector valves 11 to open for the duration of the pulse width, injecting fuel into the intake valve area of the cylinders associated with those injectors 10. Assuming constant pressure of fuel in the injectors 10, the quantity of fuel injected is proportional to this pulse width. During a single engine cycle the four groups of two injectors 10 each provide fuel to their associated engine intake valves at timed intervals.

The counter 430 automatically returns to the zero state after eight counts. However, to ensure that the counter 430 operates in the correct phase relationship to the rotation of the distributor 414, and to prevent the counter 430 from getting out of synchronism by virtue of some extraneous signal a phase pulse generator 450 is connected to the reset input of the counter 430 and receives input from a pulse detector pick-up 452 surrounded or connected to the lead to one of the spark plugs 412.

Pick-up 452 simply consists of a conductive wire 454 supported in fixed parallel relation to a section of one of the leads of a spark plug 412. The section is enclosed in a metallic sheath 456 which is grounded. The details of this type of pick-up are illustrated in United States Patent 3,500,801. Each spark plug 412 is fired by the distributor 414 once during each engine cycle, and according the phase pulse generator 450 emits a synchronizing pulse to the counter 430 once each engine cycle. This ensures a proper phase relationship between the outputs of the counter 430 and the firing of the spark plugs 412.

A detailed circuit of a preferred embod iment of a pulse shaper 426 and a phase pulse generator 450 is disclosed in Fig. 17.

The signals occurring across the breaker points 422 when they open are applied through the resistance 428 to an integratmcapacitor 460. These signals are also differentiated by the combination of a capacitor 462 and a resistor 464. A diode 466 connected between the output of the capacitor 462 and ground clips any negative going components from the input signal. The resulting signal is coupled through a pair of resistances 468 and 470 to the positive input of a differential amplifier 472 connected in a comparative mode. The voltage at the negative terminal that the input at the positive terminal is compared against is derived from a Zenor diode voltage regulator 474 which is connected to the positive terminal of a voltage supply through a resistance 476.The Zenor voltage is applied to the negative terminal of differential amplifier 472 through a pair of resistances 478 and 480.

Accordingly, the differential amplifier 472 provides an output only when the conditioned pulse applied through the resistance 470 exceeds the regulated reference voltage through resistance 480. The output pulses from the differential amplifier 472 are supplied to the incrementing input of the integrated circuit which is a four place binary counter 430 and decoding matrix.

The four outputs of the counter 430, provided on lines 432, 434, 436 and 438, go high when the binary number represented by the four stages of the counter 430 are in a 0, 2, 4 and 6 states, respectively.

These outputs are provided to the variable width pulse generators 440, 442, 444 and 446, respectively, and trigger the start of an actuating pulse for their associated injectors 10.

Considering the phase pulse generator, generally indicated at 450 in Fig. 17, pulses from spark plug lead pick-up 452 are provided to the base of a transistor 482 through a resistance 484. The transistor 482, which has its emitter grounded, is biased so as to normally operate in the collector saturated region. A negative going pulse from the pick-up 452 applied through the resistor 484, will momentarily drive the base of the transistor 482 negative and cut off conduction of the transistor 482. The resistor 484 limits current from base to emitter when the base goes sufficiently negative to create a Zener action. During this short cutoff period, a capacitor 486 is charged through resistance 488. The time constant of capacitor 486 and resistance 488 is very short.After transistor 482 goes back into conduction, the capacitor 486 discharges through resistance 490, which is much larger than resistance 488 and accordingly discharges relatively slowly. Therefore, capacitor 486 will take on energy during the negative going portions of the complex spark plug voltage upon initiation of the spark coil discharge and acts as an energy integrator for these negative going portions of the spark plug voltage. Soon after initiation of the spark plug voltage, with which pick-up 452 is associated, transistor 482 goes back into conduction and capacitor 486 begins to discharge the previously accumulated energy through resistance 490. The capacitor 486 is connected to the base of a second transistor 492 which is normally biased into the collector saturated conduction.During the time period after receipt of a pulse from the pick-up 452, during which the capacitor 486 discharges its accumulated energy through resistance 490, the transistor 492 is cut off and accordingly positive voltage is applied to a differential amplifier 494 connected in a comparative mode, through a resistance 496. The regulated comparator voltage for the amplifier 494 is derived from the Zener regulated voltage through resistances 498 and 500. The differential amplifier 494 thus provides an output whenever the voltage at the collector of transistor 492 exceeds its reference voltage.This pulse, which occurs for a short period of time following discharge through the spark plug lead sensed by pick-up 452, is supplied to the reset input of the counter 430 assuring the synchronization of the counter 430 to the zero state, which normally should occur by virtue of the pulse applied to the incrementing input of the counter 430 through the pulse shaper 426.

The waveforms occurring at various points in the electrical circuitry of Fig. 17 during one complete engine cycle are illustrated in Fig. 18. Fig. 18A illustrates the eight voltage pulses received by the pulse shaper 426, through the resistance 428, from the spark coil primary 423, during an engine cycle. Fig. 1 8B illustrates the resulting, relatively noise-free pulses provided to the counter 430 by the signal conditioning circuitry of pulse shaper 426 upon receipt of the signal from the spark coil primary 423. Fig. 18C illustrates the output on line 432 from the counter 430 during the engine cycle. Assuming that the counter 430 is initially reset to zero, the output on line 432 will be initally high, and then will go to zero when the first pulse is received from the pulse shaper 426. Similarly, Fig.

18D illustrates the output on line 434; Fig.

18E illustrates the output on line 436; and Fig. 18F illustrates the output on line 438.

Each output is high once during each engine cycle for one-eighth of the cycle.

Fig. 18G illustrates the output from the spark plug pick-up 452, which occurs once during each engine cycle. Fig. 18H illustrates the synchronizing pulse provided by the differential amplifier 494 in response to that spark plug pulse. This signal will normally occur in substantial synchronism to the eighth pulse from the pulse shaper 426 and acts to synchronize the circuit.

Start-Up Circuit The injection time provided by prior art fuel injection systems may differ appreciably from those injection times which would make it easiest to start the automotive engine. During cold start-up, there is no emission advantage to injecting fuel with reference to a particular crankshaft angle. Further, the quantity of fuel injected during cold start-up is extremely critical if flooding, an overly rich or lean starting mixture with its attendant high levels of exhaust pollutants is to be avoided. The quantity of fuel to be injected to achieve quick start-up will vary principally with ambient temperature and the condition of the fuel, that is, the specific volatility of the fuel in the tank.

The quantity of the fuel injected into a cylinder during starting, based on the measurement of the normal engine operating parameters, may not be a proper amount to produce a fuel-air mixture in the cylinder for achieving flammability.

The exact amount of fuel required to achieve this condition varies in a complicated manner as a function of a number of parameters including the exact air to fuel required ratio in combination with the volatility of the particular volume of fuel being injected. For these reasons, considerable difficulty may be encountered in starting the vehicle with a conventional fuel system.

The start-up circuit provides the injectors 10 with a series of shorter than normal electrical pulses spaced more frequently over the engine cycle. The start-up circuit of this invention substantially increases the starting speed compared to the prior art techniques of starting the engine with temperature modulated longer than normal fuel injection pulses which are used during normal running operation.

The start-up circuit modulates discharge of fuel from the injectors 10 during start-up as a function of engine load, as well as engine temperature.

The present technique provides the fuel charge to each cylinder in a number of smaller portions spaced over the engine cycle has the effect of ensuring that during the first turnover of the engine one or more cylinders will receive a fuel charge required for starting purposes. Consider the first cylinder to have its intake valve open after the injection system provides the first small fuel charge to the engine cylinder. This cylinder will receive a fraction of the total fuel charge. The cylinder that receives a charge after the next opening of the injection valve will receive twice that charge and so on during the first engine cycle. The last cylinder to receive a charge will receive the total charge. This technique effectively scans the air to fuel ratios provided to the various cylinders during the first engine cycle.As a result, some engine cylinders will receive a combustible air to fuel ratio for rapid start-up independent of absolute temperature and fuel properties.

The eight injectors 10 for the eight cylinder engine are arranged in groups of two. During normal running operation of the engine, the four groups of injectors 10 are fired in sequence, at spaced times over the engine cycle, by pulses derived from the counter 430 that is incremented each time a pulse occurs in the ignition system primary. The trigger pulses from the counter 430 are used to initiate pulses from variable width pulse generators that are controlled by sensors which sense the engine operating parameters and adjust the injector pulse widths as a function of those parameters. During the start-up operation only, each pulse from the counter 430 triggers all four variable width pulse generators 440, 442, 444 and 446 to actuate all injectors 10 simultaneously.

The lengths of the injection pulses are decreased proportionately so that each cylinder receives the required total charge for start-up at the end of the engine cycle.

The variable width pulse generators 440, 442, 444 and 446 employ capacitors which are charged during the receipt of a triggering pulse from the counter 430 to a value dependent upon certain engine operating parameters. Upon termination of the trigger pulse from the counter 430, the capacitor discharges at a rate which is a function of certain other engine operating parameters. An output pulse for one of the groups of injectors 10 is generated during this discharge time. During starting, the voltage to which this capacitor is charged is limited so that the output pulse provided to the injector 10 has approximately one-quarter of the width of the pulse that would otherwise be provided to the engine at full throttle. This starting arrangement is highly effective and very economical to implement, requiring the addition of only a few low-cost electronic components to the fuel injection system 2.

Referring to Fig. 19, the electronic control computer 19 preferably further includes a start-up circuit for use during start-up of the engine. The start-up circuit generates a plurality of opening pulses to each injector 10 during each engme cycle during starting operation of the engine.

After start-up and during normal operation of the engine, the computer 19 provides a single opening pulse to each injector 10 once during each engine cycle, as previously explained.

The four outputs of the computer 19 are also provided to the four inputs of a first NOR gate 560. The output of the first NOR 560, which is normally high and goes low when any pulse is received at one of its inputs, is provided to a second NOR gate 562. The other input to the second NOR gate 562 is from the engine starter switch 564, which also provides power to the engine starter solenoid 566. The voltage relationship is such that the output of the second NOR gate 562 goes high when the starter switch 564 is closed and its other input goes low, indicating a high output on any of the four outputs of the counter 430.

The output of the second NOR gate 562 is provided to all four of the variable width pulse generators 440, 442, 444 and 446, and accordingly, triggers an injector actuating pulse from each of them. These pulses thus occur simultaneously during start-up. The starter switch 564 is also connected to each of the variable width generators 440, 442, 444 and 446 and acts to decrease the width of the pulse generated by them with respect the pulse that would be generated, based on the output of the sensors 448, during normal operation. Accordingly, whenever the starter switch 564 is closed, each of the injectors 10 is actuated four times during each engine cycle and each opening time is shortened relative to the opening time during normal operation of the engine.

Fig. 20 illustrates the detailed construction of each of the four variable width pulse generators 440, 442, 444 and 446.

The output of the counter 430 is applied to one input of differential amplifier 568 connected as a switch. The other input to the amplifier 568 is derived from the output of a second differential amplifier 570, also connected as a switch. One of the inputs to the amplifier 570 is connected to the positive terminal of the power supply and the other input is connected to the output of the NOR gate 562.

During normal operation of the engine, the output of the NOR gate 562 is low and the differential amplifier 570 provides a first level reference voltage to the differential amplifier 568. This reference voltage is at such a level that when the particular output of the counter 430 which is connected to that amplifier goes high, its output goes low and decreases the voltage applied to the base of the transistor 572, through resistance 574. When the output of NOR gate 562 goes low, the output of the differential amplifier 570 goes low and also causes a low output from the differential amplifier 568. Thus, a lowered voltage is applied to the base of a transistor 572 upon either the occurrence of a high output from the corresponding input of the counter 430 or a high output from gate 562 which occurs during starting, whenever any of the outputs of the counter 430 are high.

The emitter of transistor 572 is connected to the positive voltage supply through a resistance 576. Its collector is connected to ground through circuitry 578 which acts like a variable voltage source, and is schematically designated as such.

The circuitry 578 is controlled by various engine operating parameters and in the preferred embodiment of the invention it is primarily a function of the manifold vacuum. In alternative embodiments, other combinations of parameters could be used to determine the voltage of the circuitry 578.

The collector of transistor 572 is also connected to one terminal of a capacitor 580 which has its other terminal connected to the base of a second transistor 582 and also to ground through a second variable voltage engine parameter sensor 584. In the preferred embodiment of the invention the engine parameter sensor 584 is primarily sensitive to engine temperature, and may constitute a thermistor, but other parameters may be selected for controlling the voltage of circuitry associated with sensor 584 in other embodiments of the invention. The emitter of transistor 582 is connected to the positive terminal of the power supply through resistance 576 and its collector is connected to ground through a pair of resistances 586 and 588.

In the absence of a negative going output from the differential amplifier 568, the transistor 572 operates in a saturated conduction region. Transistor 582 is also conductive and the voltage at the capacitor 580 is maintained equal to the emitter voltage of transistor 582. When the differential amplifier 568 provides a negative going pulse to the base of a transistor 572, the transistor is switched out of conduction, allowing the capacitor 580 to charge to a voltage that is dependent upon the effective value of the manifold vacuum sensor circuitry 578 and the emitter voltage of transistor 582.

When the negative going pulse to the base of transistor 572 terminates, the transistor 572 immediately becomes conductive again and the voltage at the base of transistor 582 goes sharply positive by an amount proportional to the charge on the capacitor 580, turning of transistor 582. Capacitor 580 begins to discharge through the effective resistance 591 and the circuitry 584 at a rate dependent upon engine temperature. This discharge continues until the voltage across capacitor 580 reaches the emitter voltage of transistor 582, causing that transistor to turn on, and to clamp the voltage on capacitor 580 to a value substantially equal to the emitter voltage of transistor 582.

The time during which transistor 582 is turned off is therefore dependent upon the manifold vacuum pressure, which controls the voltage to which the capacitor 580 charges during the off time of transistor 582, and to the engine temperature, which controls the rate at which the capacitor 580 discharges after transistor 572 again becomes conductive. An amplifier 590 is connected between the resistances 586 and 588 and the collector circuit of transistor 582 and provides a sharp, negative going pulse, having a width controlled by these factors, to the injectors 10 associated with that variable width pulse generator.

When the starter switch 564 is closed, the collector of transistor 572 is also connected to the positive supply voltage through a diode 592 and a resistor 594.

This establishes a voltage level at the collector of transistor 572 which modifies the voltage to which the capacitor 580 charges during the off-time of transistor 572. Since manifold vacuum is essentially zero during starting, this voltage is such as to allow the capacitor 580 to charge to only about one-quarter of the voltage to which it would normally charge if the switch 564 were open. This decreases the width of the pulse produced by the circuit so that a fuel charge is distributed over the four pulses that an injector 10 receives in each engine cycle during starting.

Fig. 21 illustrates the waveforms occurring at various points in the circuit of Fig.

20 during a full cycle of engine operation.

Line 21A is a plot of the outputs of the pulse shaper 426 (Fig. 19) during one full engine cycle. The breaker points 422 open eight times during the engine cycle, providing eight outputs from the pulse shaper 426. Line 21B plots an output on one of the decoded counter 430 lines 432, 434, 436 or 438 during that engine cycle. The particular output goes high upon the receipt of the leading edge of one of the pulses from the pulse shaper 426 and returns to its low state upon receipt of the leading edge of the next pulse. It is high only once during the cycle. Line 21C illustrates the output of the variable width pulse generator controlled by the output of line 21B, during normal engine operation.

Upon receipt of the trailing edge of the pulse on line 21B, the variable width pulse generator controlled by the line goes high and remains high for a period of time determined by the conditions of the outputs of sensors 448 (Fig. 9).

Line 21D plots the inputs received by all of the variable width pulse generators during starting of the engine. Effectively, the inputs of all of the four lines 432, 434, 436 and 438 are provided to each of the variable width pulse generators and accordingly each one receives four spaced pulses of the type illustrated on line 21D, during the full engine cycle. Line 21E plots the pulse outputs generated by each of the variable width pulse generators during starting operation in response to the input plotted on line 21D.Upon occurrence of the trailing edge of each of the pulses illustrated in line 21D, the output of each of the variable width pulse generators goes high and remains high for a period that is a fraction of the period of the pulse generated during normal operation of the engine, as illustrated in line 21 C. Typically, the total width of the four output pulses from a variable width pulse generator during starting operation will equal the width of a single output pulse during normal operation with the other engine parameters being equal.

Correction for Incidental System Variables One source of inaccuracy in prior art fuel injection systems has resulted from incidental system variables, such as impedance variations of the injector solenoid coils 124 (Fig. 4), specific resistance of the wire used in the individual coils 124 of different injectors and the voltage supply to the fuel injection system. The coils 124 are positioned close to the engine. As a result their temperature and hence their resistance will vary between extremes ranging from a low when the engine starts cold in the winter and a high associated with normal engine operation. A temperature range from -20" to 300O F is not unusual for the injector coils. Such a variation in temperature will cause a wide variation in coil resistance.

Previous injector circuits have employed switched outputs which provide a substantially constant voltage source and provide the solenoid coils with current inversely proportion to their resistance. Thus, the current to the coil, and the actuation force of the coil, would vary with the engine temperature. The response time required for the injector to actuate after the start of an actuating pulse is in turn a function of the current applied to the coil. Accordingly, this response time varies with engine temperature and limits the accuracy with which fuel can be metered by the system.

Referring to Figs. 1, 22, 23, and 24, the fuel injection system may include a feature for applying a correction to the injector actuating pulse to correct for the effect of at least one incidental system variable on the effective response of the injector to the actuating pulse. The incidental system variables are: the impedance of the coil, the specific resistance of the wire used in the coil and the voltage supply to the fuel injection system such as that derived from the battery. As a result, variations in response time of the injector with engine temperature have been substantially reduced.In a preferred embodiment, which will subsequently be described in detail, such correction is achieved by driving the injector valve solenoid coil with a constant current circuit source switched into and out of a proportionately conductive mode by an output signal of a variable width pulse generator responsive to engine operating parameters. The constant current source includes an output transistor having the injector coil connected in its collector circuit and having its base driven by a switchable constant current input to the transistor. When the variable width pulse occurs and the current source is provided to its base, the transistor operates in a proportionately conductive mode, with its collector current being substantially independent of injector coil resistance.

That is, the collector current is a function of base current but is substantially independent of collector load resistance. As the slope of the output transistor collector load line changes with variations in the impedance of the injector coil, the collector to emitter voltage inherently varies to maintain the collector current substantially constant. The constant current input to the base of the output transistor is supplied by an emitter follower having its input current stabilized by a Zener diode.

The constant current circuit is simple, reliable and renders the response time of the injector valves substantially independent of engine temperature and the incidental variables to allow more precise metering of the engine fuel. The output of the variable width pulse generator 440 is provided to a constant current driver circuit 626 operative to supply current to the coil 124 (Fig. 4) of a solenoid actuated injector valve 11 (Fig. 3). The injector 10 is normally closed and opens upon receipt of an actuating pulse from the driver 626.

The injector 10 is supplied with fuel from a constant pressure source 21 (Fig. 1) so that the quantity of fuel metered to an associated engine cylinder by the injector 28 is a function of the time that the injecf the injector 10 relatively independent of incidental system variables, such as resis tance variations of the injector coil 124 resulting from temperature variations.

The detailed circuitry of the constant current drive circuit 626 is illustrated in Figure 23. The variable width pulse generator 440 provides the circuit 626 with negative going pulses 632 of control led width at regular intervals. These pulses 632 are provided to the base of an NPN transistor 634 having its collector con nected to the positive terminal of a power supply through a resistance 636. The trans istor 634 has its emitter grounded. Transis tor 634 is biased to be conductive in the absence of a negative going pulse 632 at its base. A Zener diode 638 is connected across the emitter-collector circuit of the transistor 634. The voltage at the collector of the transistor 634 is normally at ground and rises to the break-down voltage of the diode 638 when a negative pulse 632 at the base of the transistor 634 switches it into non-conduction.

The Zener diode limited voltage appear ing at the collector of the transistor 634 is applied to the base of a second NPN trans istor 640.

The emitter of the NPN transistor 640 is connected to ground through a resistance 642. Its collector is connected to the posi tive terminal of the power supply through a resistance 644 and to the base of an output transistor 646. When the transistor 634 is switched into non-conduction applying the regulated Zener voltage to the base of the transistor 640 the voltage across the resistance 642 rises to substantially the Zener voltage. The collector current of transistor 640 is substantially equal to its emitter current and both are highly stabilized by the action of Zener diode 638.

The collector current of transistor 640 is applied to the base of the PNP output transistor 646 having its collector connected to one end of the coil of the injector 10. The emitter of the transistor 646 is connected to the positive terminal of the power supply through a diode 648. In the absence of a relatively large current on the base of transistor 646, the diode 648 biases the transistor 646 into cut-off so that no current is applied to the solenoid coil of injector 124. When a negative going pulse 632 from the variable width pulse generator 440 cuts off transistor 634, and provides a stabilized current to the base of the transistor 646, transistor 646 is driven into a proportional conductive current mode. The resultant collector of transistor 646 current flows through the coil 124 of injector 10 and is precisely controlled as a function of the voltage of the Zener diode 638.When the negative going pulse 632 from the variable width pulse generator 440 terminates, the bias provided to the transistor 646 by the diode 648 drives transistor 646 sharply into non-conduction.

Fig. 24 is a plot of typical operating characteristics for transistor 646, illustrating the substantial independence of the collector current from variations in the collector to emitter voltage as a function of a particular base current. The collector current is a function of base current and the collector-to-emitter voltage inherently varies in response to changes in the collector resistance caused by changes in impedance of the coil of injector 124 to maintain a constant current in the collector circuit.

The transistor 646 acts as a constant current amplifier. With this configuration one end of the coil of injector 124 may be grounded.

Warm-up Circuit Preferably a warm-up circuit is included which operates in conjunction with the variable width pulse generators 440, 442, 444 and 446 (Fig. 19). The warm-up circuit employs a mode of control based on the engine sensor as well as a form of circuitry for achieving control of the pulse width as a function of the sensor output.

In previous fuel injection systems, as in carburetors, the quantity of fuel provided to the engine during each engine cycle was modified as a function of the manifold pressure of engine air flow which is a measure of the load on the engine during operation. As the manifold pressure is increased, the injection pulses were lengthened to provide a larger fuel charge to the engine cylinders. Since the degree to which this charge vaporizes and affects the actual air-fuel ratio in the cylinder is a function of temperature, at cold engine temperatures, it is necessary to enrich the fuel charge. In a carburetor, this enrichment is achieved by a choke mechanism.

In previous fuel injection systems, the pulse width was modulated as a function of engine temperature, but not as a function of manifold vacuum, to achieve the enrichment.

The prior art systems provided a constant percentage of enrichment independent of the load on the engine. This arrangement provided very adequate engine performance, but analysis of the engine exhausts have shown that it may provide an overly rich fuel-air mixture ratio at relatively low engine load conditions. In prior art port fuel injection systems, this ovelry rich ratio results from the fact that the degree of vaporization of the fuel is not only temperature dependent, but is also dependent on the manifold pressure. At relatively low manifold pressures associated with low engine loads, the fuel charge is more readily vaporizable than at high manifold pressures.

The warm-up circuit varies the degree of enrichment of the fuel charge not only during warm-up, but also at other times, as a function of load to provide a more correct air-fuel vapor ratio to the engine at all operating loads and temperatures.

In a preferred embodiment of the warm-up circuit, which will subsequently be disclosed in detail, the pulse width is controlled primarily as a function of the engine manifold pressure and the engine temperature. The pulse width is generally controlled proportional to manifold pressure. As a lower manifold pressure is developed, the pulse time is shortened accordingly. Low manifold pressure is typically below atmosphereic pressure and, thus, is a vacuum, sometimes referred to as manifold vacuum. Thus, lower manifold pressures are equivalent to higher manifold vacuums. The pulse time is also controlled as an inverse function of the engine temperature. At low temperatures, the pulse time is increased, enriching the fuel charge. The percentage of enrichment is decreased with increasing temperature.

The warm-up circuit also provides for modulation of the temperature-dependent enrichment. The modulation diminishes the enrichment in inverse proportion to engine load. When the manifold pressure is relatively high, such as occurs during acceleration or start-up of the engine, the full temperature enrichment factor is provided to the engine. As the load decreases, decreasing the manifold pressure, the temperature-dependent enrichment factor is diminished. The modulation compensates for the higher degree of evaporation of the fuel at low manifold pressures.

The warm-up circuit includes: a pressure receiving means for receiving an intake manifold pressure signal from a first sensor; a temperature receiving means for receiving an engine temperature signal from a second sensor; and a means for generating a modulated warm-up signal to a pulse generator when the engine temperature is below a predetermined level.

The modulated warm-up signal is a function of said manifold pressure signal and said temperature signal.

The modulated warm-up signal varies directly as a function of manifold pressure and inversely as a function of engine temperature. The temperature signal is modulated by the pressure signal to produce said warm-up signal. The predetermined level corresponds to substantially maximum evaporation of the injected fuel in the engine. The means for receiving the pressure signal and the means for receiving the temperature signal generate a mod ulated warm-up signal which is substantially identical to the temperature signal at engine temperatures above the predetermined level.

The variable width pulse generator 440, 442, 444 and 446 employ a capacitor and circuitry for charging the capacitor to a voltage proportional to a manifold pressure signal. The trigger pulse disconnects the capacitor from its charging source and connects it to a discharge path having an effective resistance controlled by a temperature sensor and the manifold pressure modulating signal. The output pulse from the circuit starts when this switching occurs and continues until the capacitor discharges to a predetermined voltage. Considering the plot of capacitor charge and discharge, the height of the curve, i.e., the maximum value to which the capacitor is charged, is a function of manifold pressure. The rate of discharge of the capacitor is a function of the engine temperature together with the manifold pressure modulation.The discharge time is proportional to manifold pressure and the combination of engine temperature and the manifold pressure modulating signal.

The switch that is employed with the preferred embodiment consists of a pair of transistors. Both are normally conductive and in their state effectively short the two ends of the capacitor. The first switch opens upon receipt of a trigger signal from a counter and creates a charging path for the capacitor. After the trigger pulse terminates, the first transistor closes and connects the negatively charged end of the capacitor to the second transistor, biasing that transistor into a non-conductive mode.

This allows the capacitor to discharge through a second resistance. The discharge path of the capacitor is effectively controlled as a function of the engine temperature and manifold vacuum modulation.

This discharge continues until the capacitor charge falls to a point at which the second transistor returns to conduction, effectively clamping the voltage on the capacitor. An output circuit provides the injector with a control pulse during this sharply defined capacitor discharge period. The pulse width control system of the present invention is highly effective and extremely simple in construction.

The fuel injection system 2 employing variable width pulse generators 440, 442, 444 and 446 and a warm-up modulation circuit is broadly illustrated in Fig. 16. The timing signals or the injector pulses are derived from the vehicle's ignition system which employs a spark coil 421 having engine actuated breaker points 422, shunted by a capacitor 424, connected in the primary circuit 423 of the spark coil 421. The secondary circuit 420 of the spark coil 421 is connected to a common arm 416 of a distributor generally indicated at 414. The engine spark plugs 412 are connected to the output terminals of the distributor 414.

The electrical signals generated each time the breaker points 422 open are applied through a resistor 428 to a pulse shaping network 426. Square wave output of the pulse shaper 426 generated each time the breaker points 422 open, are provided to a counter 430 which has a decoder circuit. The counter 430 is incremented each time it receives a pulse from the pulse shaper and the decoder portion provides outputs sequentially on lines 432, 434, 436 and 438 as the counter 430 state advances. An output may be provided on line 432 when the count is 0; an output on line 434 when the count is 2; and output on line 436 when the count is 4; and an output on line 438 when the count is 6.

These lines are connected to four variable width pulse generators 440, 442, 444 and 446. Each of the pulse generators also receives an input from a group of sensors 448 associated with the engine. Each time one of the pulse generators receives a signal from the counter on its input line, it provides an output pulse having a duration which is a function of the outputs of the sensors 448.

The pulse generator 440 is connected to the actuating solenoid of one pair of fuel injectors 10. The pulse generator 442 is connected to another pair of injectors 10; the pulse generator 444 is connected to another pair of injectors 10; and the pulse generator 446 is connected to a pair of injectors 10. In alternative embodiments of the invention, all of the fuel injectors could be energized simultaneously from a single variable width pulse generator or a separate variable width pulse generator could be provided for each injector. The preferred arrangement is to actuate two injectors simultaneously from a single variable width pulse generator.

Fig. 28 schematically illustrates one of the variable width pulse generators 440, 442, 444 or 446, which may be substantially identical, and the associated sensors 448 (Fig. 16). Referring to Fig. 28, the positive input pulses provided on the trigger lines 432, 434, 436, or 438 are fed to the base of a PNP transistor 652 having its collector connected to one terminal of a capacitor 654. The other terminal of the capacitor 654 is connected to the base of a second PNP transistor 656. The emitters of the two transistors 652 and 656 are connected to a positive voltage source.

The collector of transistor 656 is con nected to ground through resistors 658 and 660, and the mid-point of those resistors is connected to an output driving amplifier 662. The driving amplifier 662 may provide constant actuating current to the injectors, during the pulse time, independent of variables such as impedance of a solenoid in the injectors as a result of variations in engine temperature, specific resistance of the wire used in solenoid coil, and variation in the voltage supply in the fuel injection system 2.

In a quiescent state, biases on the transistors 652 and 656 are such that they are normally both conductive. Thus, both ends of the capacitor 654 are at substantially the same potential and no appreciable charge is stored on the capacitor 654.

When a positive pulse is applied to the base of the transistor 652 from the counter 654, transistor 652 is switched into nonconduction. The capacitor 654 then charges through a path that includes the base-emitter of transistor 656, the resistance 664, and circuitry associated with the resistance 664, which will be described subsequently. During this time, the transistor 656 remains conductive. Capacitor 654 charges with a negative potential on its end connected to the collector of transistor 652.

When the positive pulse to the base of the transistor 652 terminates, transistor 652 returns to its conductive mode. The charge on the capacitor 654 is coupled through the collector-emitter circuit of transistor 652, through the collectoremitter circuit of transistor 678 and through resistor 666, a connection to the base of transistor 656 causing, transistor 656 to be driven into a non-conductive state. Capacitor 654 then begins to discharge. The rate of this discharge of the capacitor 654 is dependent upon the inital charge placed on the capacitor 654 and effective resistance of the discharge path.

This discharging action continues until the sum of the voltages induced across discharge resistor 666 by the discharging action of capacitor 654 and the collectoremitter voltage of transistor 678 results in a voltage at the base of transistor 656 sufficient to forward bias the base-emitter junction of transistor 656, at the instant the base-emitter junction of transistor 656 becomes forward biased, the discharging action of capacitor 654 will cease and transistor 656 will return to the conductive state. Thus, the time during which transistor 656 is rendered non-conductive is determined substantially by the charge placed in capacitor 654 while charging, as well as the effective resistance of the discharging path for capacitor 654 while discharging.

The pulse applied to output driver 662 during the time that the transistor 656 is non-conductive represents the output pulse from the system. The voltage to which the capacitor 654 is charged is controlled by a PNP transistor 668 having its emitter connected to the capacitor 654 through the resistance 664. The collector of transistor 668 is grounded and its base is connected to a variable point of a potentiometer type manifold pressure sensor 670. One end of the sensor 670 is connected to a positive terminal of a voltage source through a resistance 672. The other end of the manifold pressure sensor 670 is connected to ground through a pair of resistances 674 and 676. The resistance 674 is an idle adjustment rheostat and the variable resistance 676 is a barometric pressure actuated bellows device.

The variable terminal on the manifold pressure sensor 670 is moved toward its positive end as the pressure decreases.

This increases the voltage on the base of transistor 668. Transistor 668 is connected in an emitter follower configuration and, thus, the voltage at its emitter substantially follows the voltage at its base. Thus, decreasing manifold pressure raises the voltage at the bottom of resistance 664 so that the net potential difference between the base of transistor 656 and the opposite end of capacitor 654 decreases as the manifold pressure decreases. This decreases the charge applied to the capacitor 654 during the off time of transistor 652.

The discharge path for the capacitor 654 includes the PNP transistor 678 having its emitter connected to the opposite end of the resistance 666 from the capacitor 654.

The base of transistor 678 is connected to ground through a thermistor 584, supported on the engine so as to measure engine temperature and connected to a positive voltage source through a resistor 680. The thermistor resistance decreases with increasing temperature. The collector of transistor 678 is grounded through a resistance 682 so that the voltage at the emitter of the transistor 678 varies in reverse relation to the temperature of the engine, decreasing as the engine warms up as the thermistor 584 lowers in resistance.

Since the voltage level to which capacitor 654 must discharge depends in part upon the collector to emitter voltage of transistor 678 before transistor 656 can be forward biased, as a result, a decreasing collector-emitter voltage of transistor 678 resulting from a decreasing resistance of the thermistor 584 will decrease the time required for the capacitor 654 to discharge to a voltage across resistor 666 to forward bias transistor 666.

Thus, so long as transistor 678 is rendered operable, the duration of the output signal to the injectors from amp iifier 662 will vary as on reverse function of thermistor 584 which senses engine temperature. The modulation of the fuel enrichment charge as a function of the engine load, is controlled by a modulating PNP transistor 684 having its base connected to the emitter of the manifold pressure emitter-follower transistor 668 through resistance 686 and 688. The emitter of transistor 684 is grounded and its collector is connected to a positive voltage source through a resistor 690. A resistor 692 connects the collector transistor 684 to the junction of resistors 686 and 688.

The collector of the modulating transistor 684 is connected to the emitter of transistor 678 through a diode 694. The emitter-collector circuit of the transistor 684 through the diode 694 will modulate the voltage at the emitter of transistor 678 as an inverse function of manifold pressure.

The amount of enrichment modulation obtained is a function of the magnitude of manifold pressure change and the circuit constants associated with modulating transistor 684. When the manifold pressure is high, the base circuit of the transistor 684 is near ground potential and transistor 684 is turned off, reverse biasing the diode 694 and allowing transistor 678 to become substantially unmodulated. As manifold pressure decreases, the base of transistor 684 becomes more positive and, when amplified by transistor 684, the resulting modulating signal is coupled through diode 694. At some predetermined low manifold pressure, the effective collector-emitter resistance of transistor 684 may become low enough to effectively ground the emitter of transistor 678. That simulates a decrease of resistance of the thermistor 584, effectively modulating enrichment.As the engine reaches a predetermined operating temperature, transistor 678 may become sufficiently conductive to substantially short-circuit resistor 666 to ground reference potential and there is no further enrichment and no modulation thereof.

Other embodiments could have the manifold pressure signal function having an inverse pressure output signal relationship in the discharge circuit of capacitor 654 and the modulating warm-up signal derived from a temperature sensor in the charge circuit of capacitor 654. The capaictor 654 is a voltage storage means.

Other embodiments having different circuitry could use a current storage means, such as an inductor.

Figures 29A, 29B, and 29C illustrate an equivalent circuit of the system for three modes of operation. Transistors 652 and 656 are illustrated as switches and the components associated with the collector of transistor 652 are termed a charge circuit 700 while the components associated with the base of transistor 656 are termed a discharge circuit 702.

In the absence of a pulse at the base of the transistor 652, as illustrated in Figure 29A, both transistors are conductive and there is no potential stored in the capacitor 654. As illustrated in Fig. 29B, when a pulse is received at the base of 652 that opens and allows the capacitor to charge through the transistor 656 and the charge circuit 700. As illustrated in Fig.

29C, after the pulse to the base of the transistor 652 terminates, the negative charge on the capacitor causes transistor 656 to open creating a discharge path through transistor 652 and the discharge circuit 702.

To further illustrate the prior art operation of enrichment as a function of temperature and load, Fig. 31 is a plot of the percentage enrichment for different temperatures as a function of manifold pressure for prior art systems lacking modulation of enrichment. Line 736 typically represents the percentage enrichment provided at -20 F; line 738 typically represents the percentage enrichment provided at 0 F; line 739 typically represents the percentage enrichment at 700F and line 740 typically represents the percentage enrichment at 100"F. While the pulse width increases as engine load increases, the percentage of enrichment remains constant independent of manifold pressure and load.

Fig. 32 is a plot of the percentage enrichment of the fuel charge, as a function of load, achieved with the present arrangement. Lines 746, 748, 750 and 752 represent the percentage enrichments for -20 F, 0 F, 70"F and 100"F respectively.

At all temperatures with relatively high loads, the amount of enrichment is initially a constant percentage; typically the same percentage indicated by the enrichment lines of the prior art in Fig. 31. At a predetermined lower manifold pressure, percentage enrichment begins to decrease with decreased pressure. In terms of the circuit of Fig. 28, this results from the fact that the lower predetermined manifold pressure begins to forward bias diode 694 thereby beginning to limit the voltage at the emitter of transistor 678 derived from the action of thermistor 584. The percent of enrichment curves in Fig. 32 then become concurrent, on line 754 until point 756 is reached, at which the transistor 684 is sufficiently conductive to fully override the enriching effect of the transistor 682.

Fig. 33 is a typical representation of the pulse width in milliseconds as a function of manifold pressure for a cold engine without the modulation feature (line 758); a hot engine without the modulation feature (line 760) and a cold engine with the modulation feature (line 762). Line 762 representing the pulse width of the engine with the enrichment feature follows the curve (line 758) of the conventional cold engine at high manifold pressures, then goes through a transition stage until it joins the curve (line 760) of the hot engine at low manifold pressures.

Control System for Fuel Pump Optionally, a control system for the pump 18 (Fig. 1) may be provided which controls the pump 18 as a function of engine operating conditions, as an alternative to the control means 382 of Fig. 25.

Electrically actuated fuel pumps provide a number of advantages over mechanically actuated pumps driven by the engine, and these electric pumps have been widely employed with engine carburetion systems and almost universally employed on engines having electronic fuel injection systems. Prior motor driven electric fuel pumps typically operate at a rate which may be independent of engine speed and have usually been powered at a rate controlled load criteria. However, in a typical automobile, such loads and speeds occur over relatively short intervals of time.

Most of the time, the automobile has substantially lower fuel requirements, associated with lower speed and engine load.

Since the prior set pumps are operating at all times for high fuel requirements, there is a waste of energy consumed by the pump and a waste of pump capacity. That part of the pump output which exceeds the instantaneous fuel demands of the engine is usually returned to the fuel tank through some form of overflow arrangement. This form of regulation results in unnecessary pump work, since the pumping rate is necessarily maintained substantially above the flow requirements, at most engine operating conditions, because of the relationship between pump load and engine fuel requirements.

This prior art method of controlling electric pumps does not represent the most efficient mode of operation because of the disparity between the pumping rate and the engine's fuel requirements. For one thing, the inherent pump noise is unnecessarily high and is particularly noticeable at idle and low engine speeds, when large flow volumes are not required. The relatively high pumping speed also shortens the pump life and is wasteful of engine fuel since the full pump load of power is assumed at all engine speeds. This increases the fuel consumption at idle and slow engine speeds. Finally, the excessive flow rates result in a constant recirculation of the overflow fuel through the system, causing churning of fuel, which is deleterious to its ignition properties.

The control system may be used to operate the pump 18 at a controlled rate, which is a function of the engine operating conditions, to eliminate such problems.

The pump control system includes means connected to the engine for sensing the engine speed and control circuitry for receiving the speed signal and for generating a powering signal that actuates the motor. Broadly, the motor is controlled to provide a flow that is in direct relation to the engine speed and thus its fuel consumption. Thus, at idle and low engine speeds, the pump is operated at a low rate, minimizing power consumption by the pump, pump noise, wear of the pump, and fuel churning.

In a preferred embodiment, which will subsequently be disclosed in detail, the control signal to the pump takes one of three forms, depending upon engine condition: During engine start-up, the control system provides a signal to drive the pump 18 at a higher than normal rate to insure that the fuel lines in the fuel injection system 2 are filled. After the engine starts, the pump 18 is controlled to provide a flow proportional to engine speed until a maximum pump speed is reached. The pump speed is maintained constant for engine speed increases above this point preventing overloading of the pump.

The pump control system is associated with the computer 19 of the fuel injection system. The preferred embodiment of the pump control system employs a piston pump. Constant width control pulses for cocking the piston of the pump are triggered by signals derived from the computer 19. The computer 19 provides one pulse per engine cycle during normal operating conditions and a plurality of pulses per cycle during starting. Each of these pulses trigger a single pump energizing pulse as long as the interval between the triggering pulses exceeds the predetermined limit. Intermittent trigger pulses are ignored at higher engine speeds to limit the pump speed to its maximum efficient rate.

In another embodiment, a variable displacement pump is controlled as a function of engine speed by a duty cycle regulating system controlled by trigger pulses derived from the computer 19.

Referring to Fig. 34, the preferred embodiment of the pump control system forms part of a fuel injection system 2 for the internal combustion engine. The engine is equipped with an ignition system 812, which may be of either the conven tional or electronic variety. The ignition system includes an element, such as a distributor, driven by the rotation of the engine, and the ignition provides the engine with firing pulses in timed relation to the rotation of the engine.

Certain signals from the ignition system 812 are also provided to the computer 19.

The computer 19 also receives signals from a group of engine sensors 448 which provide electric signals having characteristics which vary as a function of engine parameters, such as manifold vacuum, engine temperature and the like. The computer 19 acts to provide variable width control pulses to fuel injectors 10 which feed the engine, with the width of the pulses, and their rate of occurrence, being functions of its input signals, as previously described herein. The computer 19 provides each injector with one control pulse per cycle during normal engine operation and a plurality of pulses per cycle during starting cranking of the engine. These output pulses from the computer 19 are also provided to a control gate 818. The control gate in turn provides pulses to an output driver 820. The output driver 820 supplies actuation electric pulses to the solenoid of a fuel pump 18.

During normal operation of the system, the control gate 818 provides one output pulse to the driver 820 for each input pulse that it receives from the computer 19, and the driver provides one powering pulse to the fuel pump 18. However, when the frequency of the input pulses from the computer 19 exceed a predetermined level, a signal provided from the output driver 820 to the con trol gate 818 via line 824, inhibits provision of the next pulse to the output driver 820.

The inhibit signal occurs for a predetermined period of time after the output driver has terminated the pulse to the pump. Any pulses to the control gate from the computer 19 which occur during that period are not effective to cause the generation of an output pulse. The fuel pump 18 acts to pump fuel from the tank 16 to the injector booster 22 and regulator. This unit provides a regulated, pressurized fuel supply for the injector 10.

The circuitry of the control gate 818, out put driver 820, and the relevant portions of the computer 19, are illustrated schemati cally in Fig. 35. The computer 19 receives pulses from the primary of the ignition circuit which occur a plurality of times per engine cycle in timed relation to the engine opera tion. For an eight cylinder four stroke engine, the computer 19 will receive eight ignition pulses per engine cycle. These pulses are provided to a counter 430 and decoder which provides outputs on a plurality of lines 432, 434, 436 and 438, sequentially during an engine cycle. These pulses are provided to a plurality of injector pulse generators, which generate energizing pulses for each of the injectors 10 or for each group of injectors 10 where the injectors 10 are grouped together.

The output on line 432 is provided directly to a first OR gate 840. The outputs on lines 434, 436 and 438 are provided to a second OR gate 842. The output of the OR gate 842 is provided to an AND gate 844. The conditioning input on the AND gate 844 is provided from the engine start switch 564 which also controls the cranking motor. When the starting switch 564 is energized, the pulses provided to the AND gate 844 from the OR gate 842 are fed to the OR gate 840, and summed with the pulses provided to that OR gate on line 832. During normal operation of the engine, the start switch 564 will be open and the OR gate 840 will simply provide as its output the one pulse per engine cycle which occurs on line 832.During the starting conditions, when the start switch 564 is closed, the OR gate 840 will effectively provide the outputs of all four of the lines 832, 834, 836 and 840, in sequential relation, during an engine operating cycle. The output pulses from the OR gate 840 are fed through a diode 848 and a resistor 850 to the negative input of the control gate 818, which is a differential amplifier.

The other input to the control gate 818 is provided from another differential amplifier 852. At the beginning of the circuit operation, the output of the differential amplifier 852 is high and the output of the differential amplifier 818 is low. When a positive pulse is generated by the computer 19, the output of the differential amplifier 818 goes high. This pulse is provided to the positive input of a third differential amplifier 854 which has a fixed voltage in its other input, controlled by resistance 856. The output of the differential amplifier 854 is normally high, and goes low as soon as it receives the positive pulse from the differential amplifier 818. This negative pulse is fed back to the negative input of the differential amplifier 818 through a diode 858 connected to the junction between diode 848 and resistance 850.Therefore, the signal at the negative input of the differential amplifier 818 goes low a few milliseconds after the beginning of a positive control pulse is received from the computer 19, despite continuation of the control pulse. The period for which the input is high is simply a function of the feed back delay through the differential amplifier 854 and its associated circuitry.

When the output of differential amplifier 818 goes high upon receipt of an input pulse from the computer 19, the high output is provided to the negative terminal of a fourth differential amplifier 820. The other input to the differential amplifier 820 is the voltage across a resistance 860. This pulse from the output of the differential amplifier 818 to the negative input of the differential amplifier 820 is fed through a capacitor 863. The output of the differential amplifier 820 is fed to an amplifying transistor 862 which has its emitter grounded through a diode 864. The collector of transistor 862 is connected to the base of a second transistor 866. The pump solenoid 380 is connected in the collector circuit of transistor 866 and is shunted by a protective Zener diode 868.Accordingly, when the output of differential amplifier 820 goes high, that signal is amplified by the transistor 862, which drives the transistor 862 into saturated conduction. The output signal from transistor 862 is further ampliied by transistor 866 which provides an actuation signal to the pump solenoid 822.

The signal from the collector of transistor 862 is also fed back to the positive input of comparator 852, which has its output connected to the positive terminal of gate 818.

The output of comparator 852 goes low upon occurrence of the output pulse to the pump solenoid 380 and prevents the output of gate 818 from going high even after its negative input goes low because of the action of comparator 854.

After the output of differential amplifier 818 goes low, the capacitor 863 begins to charge through the resistance 856, providing an increasingly positive voltage to the negative input of the differential amplifier 820.

When the voltage at the negative input reaches the level of the positive input, the output of differential amplifier 820 goes low.

This acts through the transistors 862 and 866 to terminate the pulse to the pump solenoid 822. It also causes the output of differential amplifier 852 to go high again. Thus, the length of the output pulse to the pump solenoid 822 is controlled by the time delay provided by the capacitor 863 and the resistance 856.

Once the output of differential amplifier 852 has returned to high, the differential amplifier 818 could return to a high output, except that the voltage at the output is limited by the charge on the capacitor 863. This acts through differential amplifier 854 to retain the voltage at resistance 850, and the input of the differential amplifier 818 low. Capacitor 863 now charges in a reverse direction through the resistance 860. When a sufficient charge has built up in that direction, the differential amplifier 854 switches its output, and returns to its condition at the beginning of the cycle. Input pulses from the computer 19, received after this time, will trigger output pulses to the pump 18. Any signals from the computer 19 received before this time will be inhibited by the negative out put of differential amplifier 854.

Thus the time constant determined by the values of the capacitor 862 and the resistance 860, sets a minumum time interval between output pulses to the pump 18. The minimum is to ensure adequate time for the pump 18 to displace its output after having been cocked by the previous pulse. If the pump 18 were pulsed at a higher frequency, its output would deteriorate.

The operation of the circuitry of Fig. 35 is illustrated by the wave forms of Figs. 36 and 37. The seven wave forms of Fig. 36 illustrate the operation of the system after starting, up to the critical speed. The seven wave forms of Fig. 37 illustrate the operation of the system in the normal mode, above the critical speed.

Fig. 36, line 1 is a plot of trigger signals provided from the computer 19 to the diode 848. Fig. 36, line 2 is a plot of the resulting input to the negative terminal of the differential amplifier 818. The input goes high at the instant a positive going control signal is received from the computer 19 and then goes low a fraction of a second later as a result of feed-back through differential amplifier 854. Fig. 36, line 3 plots the output of differential amplifier 820 during a cycle. The output goes low when the control pulse is received at its negative input and stays low until the output of differential amplifier 820 terminates as a result of charging of the capacitor 863. The voltage at the output of differential amplifier 818 then gradually builds up as capacitor 863 charges in the opposite direction. Fig. 36, line 4 plots the output of differential amplifier 854.It goes low slightly after the control pulse is received and stays low until the capacitor 863 has discharged the charge that it receives while the output of the differential amplifier 818 is low. Fig. 36, line 5 is a plot of the output of transistor 862. It goes low slightly after receipt of the control pulse and then goes high after the charge on capacitor 863 has built up sufficiently to turn off the differential amplifier 820. Fig. 36, line 6 is a plot of the output of differential amplifier 852 which substantially folows the output of transistor 862.

Fig. 36, line 7 is a plot of the output of transistor 866 during the cycle. It should be noted that there is one output pulse for each control input of line 1 and the output lasts for a period of time determined by the time constant of the capacitor 863 and resistance 860.

Fig. 37 illustrates the comparable wave forms when the frequency of the control pulses increase to the point where the interval between the pulses is less than the time required for the capacitor 663 to charge and then discharge. The second and fourth control pulses in the train illustrated in Fig. 37, line 1 are terminated before the output of differential amplifier 854 regains its high level and accordingly they do not trigger the generation of control pulses to the pump solenoid.

In another embodiment using a pump driven by an electric motor, instead of a piston pump, the pulse output of transistor 866 in Fig. 35 could be averaged through additional circuit components to provide a D.C. voltage whose value would be proportioned to engine speed criteria to operate the pump motor. In an embodiment used with a fuel injection system, the duration of the injector actuating signal which is proportional to engine load varies directly as a function of engine load and may be used as an additional pump control parameter.

Exhaust Gas Recirculation Some internal combustion engines, such as those for automobiles, include an exhaust gas recirculation system which recirculates part of the exhaust gas from the engine. Recirculated exhaust gas and air are mixed with fuel for combustion in the engine. The mixture of recirculated exhaust gas and air contains less oxygen than air alone without recirculated exhaust gas. Means may be included for providing a signal to the computer to reduce fuel input to the engine to compensate for reduction of oxygen in the air-fuel mixture resulting from exhaust gas recirculation.

Such reduction of fuel input is accomplished to achieve a substantially constant air-fuel ration to the engine during normal operation of the engine, after start-up and warm-up of the engine.

Referring to Fig. 38 a control vacuum signal is obtained from a throttle body 900 on the engine intake manifold 15. The control signal is fed to an engine exhaust gas recirculation (EGR) control valve 902.

The control vacuum signal is a function of engine speed and throttle position. The engine EGR control valve 902 controls the operation of the exhaust gas recirculation (EGR) valve member 904. The EGR valve member 904 controls recirculation of the exhaust and determines how much of the exhaust gas is recirculated to the intake manifold 15 of the engine. The engine EGR control valve also provides a signal to a computer circuit control means 906 for correction of the air to fuel ratio.

The computer circuit control means 906 may be a switch, a potentiometer, or a rheostat. The computer circuit control means for air to fuel correction provides a signal to circuitry 578 of Fig. 20. Such signal to circuitry 578 modifies and typically reduces the fuel input to the engine in an amount proportional to the quantity of recirculated exhaust gas admitted to the intake manifold 15 to compensate for reduction of oxygen in the air-fuel mixture resulting from exhaust gas recirculation and maintain substantially constant air to fuel ratio.

Engine Temperature Sensor Referring to Figs. 1 and 20, the engine temperature sensor 584 is provided for sensing temeprature at the intake valve 6 in the engine. But, the temperature sensor 584 cannot be located at the intake valve 6 in the engine because it would not be feasible, due to motion of the intake valve 6 and spaced considerations. Instead, the temperature sensor 584 is placed at a loca tion remote from the intake valve. The location for the temperature sensor 584 is adjacent to an output port 802 of an exhaust manifold 804 for the engine. Such location has an amount of heat representa tive of the heat present at the intake valve 6 for any given condition of engine opera tion, including start-up of the engine, warm-up of the engine which occurs after start-up, and normal operation which occurs after warm-up.Such location is preferable to prior art locations for a temper ature sensor, such as adjacent to a water jacket for the engine. The exhaust manifold 804 is a preferable location because it is more responsive to changes in engine temperature. For example, the exhaust manifold warms up faster than do locations adjacent to the water jacket.

Alternative Pump In a previous section it was explained that another form of pump located outside the tank 16 may also be used. This alternative pump will now be described in detail.

Prior art pumps have long been used to transfer fluid such as fuel for vehicle engines and the like. Such prior art pumps are generally of the reciprocating type, having a solenoid energized periodically in response to the position of a member, such as a piston in a cylinder thereof. Upon being energized, the solenoid moves the piston to the inlet end of the cylinder, thereby arming a spring to urge the piston to the other end of the cylinder. During the discharge stroke, fluid is both displaced from the pump and drawn thereinto through a suction conduit communicating with a fluid supply source.

One of the major problems with such prior art pumps is the difficulty of drawing fluid thereinto from the conduit. Fluid flow through the conduit is interrupted periodically by movement of the piston toward the inlet end of the cylinder, increasing the force required to discharge fluid from the pump. The problem is particularly troublesome when the pump is located at a point distant from the fluid supply source. As a result, prior art pumps of the type described are expensive to construct and operate at relatively low pumping efficiencies.

The present disclosure provides an economical and highly efficient pump for transferring fluid from a conduit communicating with a fluid supply source.

Referring to Fig. 30, the pump, shown generally at 910, incorporating the pressure wave inversion means, includes a housing 912 having an inlet chamber 914 and an outlet chamber 916. A cylinder 918 communicates with the inlet and outlet chambers 914 and 916. The cylinder 918 has a piston 920 slidably mounted therein. A spring 922 urges the piston 920 away from the inlet chamber 914. The cylinder 918 is surrounded by a solenoid 924 adapted, when energized, to draw the piston 920 toward the inlet chamber 914.

A valve means 926 cooperates with the solenoid 924 to cause fluid flow between the inlet chamber 914 and the outlet chamber 916 upon reciprocation of the piston 920. The inlet chamber 914 has associated therewith a pressure wave inversion means, shown generally at 928, which is responsive to fluid pressure within the inlet chamber 914. The pressure wave inversion means 928 reduces pressure of the fluid in chamber 914 during movement of the piston 920 toward the inlet chamber 914 and increases such pressure during movement of the piston 920 away from the inlet chamber 914.

The housing 912 preferably contains a pump chamber 930 disposed between the inlet and outlet chambers 914 and 916.

Inlet chamber 914 is provided with a filter 932 and a movable check valve member 934 which is part of valve means 926 and cooperates with a seat 937. The valve member 934 is mounted in a guide 936 extending axially of housing 912 from the seat 937 formed in partition 938 separating pump chamber 930 from inlet chamber 914. Housing 912 has ports 944 and 946 communicating with inlet and outlet chambers 914 and 916, respectively, and adapted for connection to a fluid supply source (not shown). Housing 912 is formed of non-corrosive material such as nylon, Delrin (Registered Trade Mark) or other suitable plastics, or soft die cast materials such as zinc, aluminium or the like. Filter 932 may be a ribbon-type filter such as Microbon, a fine mesh screen or the like. Check valve member 934 is stabilized within guide 936 by compression spring 948.

Cylinder 918 is axially mounted in position to connect inlet chamber 914 with outlet chamber 916. Piston 920 is slidably mounted in cylinder 918 and associated with check valve 950 so located therein that reciprocation of the piston 920 effects fluid flow through cylinder 918 from inlet chamber 914 to outlet chamber 916.

Cylinder 918 is formed of non-magnetic material such as brass, stainless steel or the like. The cylinder 918 can, optionally, be formed of moldable plastics. The piston 920 is formed of magnetic material such as magnetic stainless steel, low carbon steel or the like. A buffer spring 952 supported by surface 954 of cylinder 918 absorbs stress exerted thereon by piston 920.

Solenoid 924 is located in housing 912 surrounding cylinder 918. The solenoid 924 has a coil 925 and a circular pole piece 940 connected with a cylindrical casing 942. Spring 922 is supported by partition 938 and urges piston 920 in the direction of the arrow A to a decentered position with respect to the solenoid 924.

Energization of the solenoid coil 925 draws the piston 920 toward inlet chamber 914, cocking the spring 922. When coil 925 of solenoid 924 is deenergized, the spring 922 expands and moves the piston 920 through its discharge stroke. Pole piece 940 and casing 942 are constructed of magnetic material such as a common steel or iron. Spring 922 can be a coiled compression spring or the like.

As previously noted, the pressure wave inversion means 928 is associated with inlet chamber 914. The type of pressure wave inversion means employed can vary depending on the temperature and viscosity of the fluid, the size and velocity of the piston 920 and the enviroment in which the pump is employed. Accordingly, the form of pressure wave inversion means 928 described herein should be interpreted as illustrative and not in a limiting sense.

One form of pressure wave inversion means 928 which is suitable includes a pressure responsive diaphragm 956 and a hollow compartment 958 having pressurized state between absolute zero pressure and ambient pressure, e.g. o psia - 14.7 psia. The diaphragm 956 separates the inlet chamber 914 from the hollow compartment 958. Preferably, housing 912 forms a portion of the hollow compartment 958. It should be understood that housing 912 can comprise a multi-piece structure including a bottom cover housing extension member 960 connected to gasket 962 and housing 912 by fastening means 964 such as rivets, bolts or the like.

Diaphragm 956 has a portion held in sealing engagement with housing 912 by sealing means 968. The remaining portion 970 of diaphragm 956 is spaced from housing 912, forming a wall of the hollow compartment.

The diaphragm 956 may be mad e of plastics, convoluted Mylar (Registered Trade Mark), rubber bellows, thin convoluted metals such as brass, steel or other suitable flexible material. The diaphragm 956 and member 960 define hollow compartment 958. The volume of compartment 958, for example, can vary from about 0.1 to 10 cubic inches, and preferably about .15 to .5 cubic inches. Sealing means 968 and gasket 962 can be secured to member 960 and diaphragm 956 by means of a suitable adhesive, such as Pliobond (Registered Trade Mark) or the like. Normally, air is used, but other gases suitable for use in the hollow compartment include those gases and gas mixtures which are inert, nonflammable and dry. Suitable gases include helium, argon, nitrogen, air and mixtures thereof. The pressure within the compartment 958 is preferably about 1 atmosphere.Following assembly of housing 912, the chamber 916 is filled with a suitable immobilizing agent such as epoxy resin to permanently and rigidly anchor the fixed components therein.

In operation, energization of solenoid 924 draws piston 920 toward inlet chamber 914, cocking spring 922. Diaphragm 956 moves toward hollow compartment 958, preventing undue pressure build up in the inlet chamber 914 and maintaining substantially constant flow of fluid thereinto from port 944. Upon deenergization of solenoid 924, spring 922 expands and moves the piston 920 through its discharge stroke in the direction of arrow A. Diaphragm 956 moves toward inlet chamber 914, preventing undue pressure drop therein and maintaining substantially constant flow of fluid through port 944.

The pump 910 disclosed herein can, of course, be modified in numerous ways.

Although it has been described as a piston-type pump 910 it should be understood that any pump can be used wherein the inlet flow is of an incremental, intermittent or pulse type, such as vane and multipiston pumps. Housing 912 can be a single or multi-piece structure. Piston 920 can be hollow or solid. The housing 912 and cylinder 918 can be composed of plastics or other lightweight non-magnetizable material. Outlet chamber 916 can be provided with a second pressure wave inversion means, such as a diaphragm 972, responsive to pressure therein, for reducing pressure of fluid therein during movement of the piston toward the outlet chamber and increasing the pressure during movement of the piston away from said outlet chamber, thereby maintaining constant flow of fluid through port 946 during reciprocation of piston 920.

It has been found that reducing fluid pressure in the inlet chamber as the piston moves toward it and increasing such fluid pressure as the piston moves in the opposite direction, improves continuity of fluid flow within the conduit. Fluid inertia due to pressure wave pulsations generated in the suction conduit line during reciprocation of the piston is minimized. Pumping efficiencies are increased by as much as 50 percent or more. The size, weight and cost of the pump is reduced and its output is increased. As a result, the pump may be smaller, lighter, less expensive to produce and more efficient in operation than pumps in which the pressure wave pulsations are dissipated primarily in the conduit.

Method of the Injection System The hereinbefore disclosed method for injecting fuel into an internal combustion engine includes: supplying fuel from a source to a plurality of injectors 10; and discharging the fuel withm the cylinder head 4 of the engine from the injectors 10.

The injectors 10 each have a discharge end at the nozzle 108 and the engine has a plurality of intake valves 6, each intake valve 6 having an upstream face within the cylinder head 4 of the engine. The step of discharging the fuel within the cylinder head 4 includes positioning the discharge end of the injectors 10 within the cylinder head 4 adjacent to the upstream faces of the intake valves 6. The injectors 10 each have a vapor pressure for the fuel therein.

The step of supplying the fuel from the fuel source to the injectors includes supplying the fuel at a pressure greater than the vapor pressure for the fuel in the injectors. The step of discharging the fuel within the cylinder head 4 further includes impinging the fuel from the injectors 10 directly on the upstream faces of the intake valves 6 in the cylinder head 4. The step of discharging the fuel within the cylinder head 4 also includes opening the injectors 10 for predetermined time intervals as a function of engine load, as well as one or more engine variables, all reflecting engine fuel requirements. The step of supplying fuel from a fuel source to the injectors 10 further includes supplying the fuel in a liquid state to the injectors 10.

A larger amount of fuel is injected during start-up of the engine to provide an enriched fuel-air mixture to the engine during start-up of said engine and the step of discharging fuel within said cylinder head 4 further includes: modulating the discharging of fuel from said injectors during start-up as a function of engine load, as well as engine temperature. A larger amount of fuel is injected during warm-up of the engine to provide an enriched fuelair mixture to the engine during warm-up of said engine; and the step of discharging fuel within said cylinder head further includes: modulating the discharging of fuel from said injectors during warm-up as a function of engine load, as well as engine temperature.

A portion of fuel supplied from the fuel source is returned to the fuel source; and such return of fuel to the fuel source is interrupted after turn-off of the engine.

The method further includes sensing heat at a point in the engine which is representative of the amount of heat present at the intake valves 6 in the engine. The heat is sensed at a point in the engine adjacent to an output port 802 of the exhaust manifold 804 of the engine. The method includes reducing the amount of fuel discharged within the cylinder head 4 by a proportionate amount sufficient to compensate for oxygen reduction resulting from an exhaust gas recirculation system in order to maintain a constant ratio of air to fuel. The method includes providing a phasing signal to the computer 19 to reset a counter 430 to inject fuel into said engine with reference to a predetermined crankshaft angle.

The method includes simultaneously injecting fuel into two cylinders of said engine at a time, in sequence with the intake stroke of the engine. The method includes providing a series of successive start-up pulses to injectors 10 during start-up of the engine. The start-up pulses have a time duration shorter than pulses provided to the injectors 10 after start-up of the engine has been achieved. The successive start-up pulses scan through an air to fuel ratio level needed for start-up of the engine. The method includes maintaining substantially constant energy in actuating pulses provided to the injectors 10 so that response time of the injectors and quantity of fuel metered by the injectors to the engine is maintained substantially constant independent of system variables.

This may be accomplished by varying the pulse length or by varying the applied voltage level of the actuating pulses. For starting the internal combustion engine, the method includes actuating all injectors 10 of the injection system simultaneously during start-up.

WHAT WE CLAIM IS: 1. A fuel injection system for use in combination with an internal combustion engine, the fuel injecting system comprising a plurality of fuel injectors to be selectively positioned in the engine; a source of fuel for the engine; a fuel supply conducting means disposed between the injectors and the source of fuel for conducting fuel under pressure from said source to the injectors; a low pressure pump for pumping fuel from the source of fuel to the supply conducting means; a pressure booster disposed in the supply conducting means between the pump and the injectors, the pump being adapted to pump fuel to the pressure booster at a low pressure which is less than the pressure applied by the pressure booster in use of the system but higher than the vapour pressure of the fuel in said source and the pressure booster comprising a variable volume chamber and means for urging the chamber into a condition of reduced volume so as to raise the pressure of fuel in the supply conducting means between the booster and the injectors to an elevated pressure higher than the pressure in the supply conducting means between the source of fuel and the booster and higher than the vapour pressure for fuel in the injectors, said urging means being adapted to reduce the volume of said chamber only by an amount that is substantially equivalent to the volume of fuel ejected by said injectors; and an electronic control computer for providing electrical injection pulses of predetermined length, at predetermined time intervals, for actuating the injectors.

2. A fuel injection system according to claim 1, wherein the means for reducing the volume of said chamber comprises a spring loaded variable displacement booster member.

3. A fuel injection system according to claim 1 or 2, wherein the pressure booster comprises a one-way valve.

4. A fuel injection system according to claim 1, 2 or 3, wherein the pressure booster comprises an input to said chamber for receiving fuel from the source of fuel; an output from said chamber for transmitting fuel to the injectors; a one-way valve at the input to prevent return flow of fuel within the supply conducting means from the booster chamber to said source; and a one-way valve at the output of the booster to prevent return flow of fuel from the injectors to the booster chamber.

5. A fuel injection system according to any one of the preceding claims, wherein said pressure booster comprises a body having an inlet passage connected to a section of the fuel supply conducting means leading to the pump and an outlet passage connected to a section of the fuel supply conducting means leading to the injectors, the chamber being formed in said body; a movable wall forming one boundary of the chamber; means for urging the movable wall toward motion in such a direction as to contract the volume of the chamber; and means for periodically causing motion of the movable wall in a direction so as to expand the volume of the chamber.

6. A fuel injection system according to any one of the preceding claims, wherein

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. fuel within said cylinder head further includes: modulating the discharging of fuel from said injectors during warm-up as a function of engine load, as well as engine temperature. A portion of fuel supplied from the fuel source is returned to the fuel source; and such return of fuel to the fuel source is interrupted after turn-off of the engine. The method further includes sensing heat at a point in the engine which is representative of the amount of heat present at the intake valves 6 in the engine. The heat is sensed at a point in the engine adjacent to an output port 802 of the exhaust manifold 804 of the engine. The method includes reducing the amount of fuel discharged within the cylinder head 4 by a proportionate amount sufficient to compensate for oxygen reduction resulting from an exhaust gas recirculation system in order to maintain a constant ratio of air to fuel. The method includes providing a phasing signal to the computer 19 to reset a counter 430 to inject fuel into said engine with reference to a predetermined crankshaft angle. The method includes simultaneously injecting fuel into two cylinders of said engine at a time, in sequence with the intake stroke of the engine. The method includes providing a series of successive start-up pulses to injectors 10 during start-up of the engine. The start-up pulses have a time duration shorter than pulses provided to the injectors 10 after start-up of the engine has been achieved. The successive start-up pulses scan through an air to fuel ratio level needed for start-up of the engine. The method includes maintaining substantially constant energy in actuating pulses provided to the injectors 10 so that response time of the injectors and quantity of fuel metered by the injectors to the engine is maintained substantially constant independent of system variables. This may be accomplished by varying the pulse length or by varying the applied voltage level of the actuating pulses. For starting the internal combustion engine, the method includes actuating all injectors 10 of the injection system simultaneously during start-up. WHAT WE CLAIM IS:

1. A fuel injection system for use in combination with an internal combustion engine, the fuel injecting system comprising a plurality of fuel injectors to be selectively positioned in the engine; a source of fuel for the engine; a fuel supply conducting means disposed between the injectors and the source of fuel for conducting fuel under pressure from said source to the injectors; a low pressure pump for pumping fuel from the source of fuel to the supply conducting means; a pressure booster disposed in the supply conducting means between the pump and the injectors, the pump being adapted to pump fuel to the pressure booster at a low pressure which is less than the pressure applied by the pressure booster in use of the system but higher than the vapour pressure of the fuel in said source and the pressure booster comprising a variable volume chamber and means for urging the chamber into a condition of reduced volume so as to raise the pressure of fuel in the supply conducting means between the booster and the injectors to an elevated pressure higher than the pressure in the supply conducting means between the source of fuel and the booster and higher than the vapour pressure for fuel in the injectors, said urging means being adapted to reduce the volume of said chamber only by an amount that is substantially equivalent to the volume of fuel ejected by said injectors; and an electronic control computer for providing electrical injection pulses of predetermined length, at predetermined time intervals, for actuating the injectors.

the pressure booster includes as means for urging the variable volume chamber into a state of contracted volume an elongated spring having one end connected to the chamber and the other end fixed relative to the engine.

7. A fuel injection system according to any one of the preceding claims, including means for causing the variable volume chamber to move to a condition of expanded volume at periodic intervals.

8. A fuel injection system according to claim 7 wherein said means for causing the variable volume chamber to move to a condition of expanded volume at periodic intervals is powered by the engine to expand the chamber in timed relation to operation of the engine

9. A fuel injection system according to claim 8, wherein the variable volume chamber comprises a cylinder and a piston movable within the cylinder and which includes a cam driven by the engine, and mechanism, powered by the cam, for moving the piston within the cylinder so as to expand the volume of the chamber in timed relation to the speed of the engine.

10. A fuel injection system according to claim 9, wherein the mechanism comprises an arm, pivotably supported with respect to the engine, and means for biasing the arm into a position where one end is in abutment to the cam and the other end is positioned relative to the piston so as periodically to retract the piston to enlarge the chamber during operation of the engine.

11. A fuel injection system according to any preceding claim, wherein said pressure booster comprises a body having a cavity connected to the fuel supply conducting means; a flexible diaphragm supported in the body to seal the cavity, a first side of the diaphragm facing the cavity in the body and a second opposite side of the diaphragm being exposed to the fuel in the fuel supply conducting means, said diaphragm being arranged to assume a position dependent upon the pressure exerted on the diaphragm by fuel in the fuel supply conducting means whereby the diaphragm stabilizes the fuel pressure within the fuel supply conducting means in use of the system.

12. A fuel injection system according to claim 11, wherein the diaphragm is exposed to the connecting means at a location between the pump and the pressure booster valve closest to the fuel pump in the fluid circuit, immediately adjacent to such uni-directional valve.

13. A fuel injection system according to claim 11 or 12, wherein the diaphragm is exposed to the connecting means at a location between the pressure booster and the injectors.

14. A fuel injection system according to any preceding claim, wherein said source of fuel is a fuel tank; and the low pressure pump is located within said tank.

15. A fuel injection system according to claim 14 wherein the pump comprises a housing having an inlet chamber and an outlet chamber; a cylinder communicating with said chambers; a piston slidably mounted in the cylinder; a spring urging the piston away from the inlet chamber; a solenoid surrounding the cylinder and adapted, when energized, to draw the pis ton toward the inlet chamber; and valve means for causing fluid flow only from the inlet chamber to the outlet chamber upon reciprocation of the piston in the cylinder.

16. A system as claimed in claim 15, including pressure wave inversion means associated with the inlet chamber for reducing the increase of pressure of the fluid therein during movement of the piston toward said inlet chamber and reducing the decrease of fluid pressure therein during movement of the piston away from the inlet chamber.

17. A system as claimed in claim 16, wherein said pressure wave inversion means includes a pressure responsive diaphragm and a hollow pressurized compartment, said diaphragm separating the inlet chamber from the hollow compartment.

18. A system as claimed in claim 17, wherein the housing forms a portion of the hollow compartment and the diaphragm has a portion in sealing engagement with said housing and the remaining portion is spaced from the housing, forming a wall of the hollow compartment.

19. A system as claimed in claim 18, wherein said hollow compartment has a volume in the order of from 0.1 to 10 cubic inches.

20. A system as claimed in any one of claims 16 to 19, including second pressure wave inversion means disposed in the outlet chamber for reducing the increase of pressure of fluid therein during movement of the piston toward said outlet chamber and decreasing the reduction of pressure therein during movement of the piston away from the outlet chamber.

21. A system as claimed in any one of claims 15 to 20, wherein said cylinder is composed of non-magnetic material.

22. A system as claimed in any one of claims 15 to 21, wherein said piston is hollow and is composed of magnetizable material.

23. A system as claimed in any one of claims 15 to 22, including a circuit connected to the solenoid for transmitting an electrical current therethrough to energize said solenoid and control means located externally of said tank connected to the circuit for controlling the time interval of current transmitted through the circuit.

24. A system as claimed in claim 23, wherein said pump housing is composed of plastics material.

25. A system as claimed in claim 14 or 20, wherein said pump housing is formed of a non-sparking material.

26. A system as claimed in claim 23, 24 or 25, wherein said control means comprises an astable multivibrator connected between a power source and said solenoid.

27. A system as claimed in claim 23, 24, 25 or 26, wherein said control means includes timing means connected to said circuit and adapted upon energization to transmit current thereto for a preselected time interval, wherein said solenoid is energized for a corresponding time interval, actuating means being included for periodically actuating the timing means.

28. A system as claimed in claim 27, wherein said preselected time interval ranges from about 18 to 25 milliseconds.

29. A fuel injection system according to any preceding claim, wherein said engine has an ignition system and said computer comprises an electrical input and an electrical output; and a counter means connected to the ignition system and connected to the input of the computer.

30. A fuel injection system according to claim 29, wherein said ignition system comprises a distributor having a speed sensing output and a phasing output; the input of the counter being connected to the speed sensing output and the phasing output of the distributor.

31. A fuel injection system according to claim 29 or 30, wherein the control computer comprises a multiple stage counter with means connected to the ignition distributor and to the counter operative to increase the count contained in the counter each time a firing pulse is provided to a cylinder of the engine; and means, controlled by the state of the counter, for generating the pulses for actuating the injectors.

32. A fuel injection system according to claim 31, wherein means are connected between the distributor and the igniter for one cylinder of the engine for generating a reset pulse for the counter once during each engine cycle.

33. A fuel injection system according to any preceding claim, wherein the computer comprises a start-up circuit comprising means for generating an electrical signal during start-up operation of the engine; and means, conditioned by such electrical siena. for causing each of the injectors to open a plurality of times dur ing each cycle of the engine.

34. A fuel injection system according to claim 33, wherein the computer includes means for substantially shortening the injector pulses during start-up of the engine relative to the injection pulses generated during normal operation of the engine whereby the injectors can open a plurality of times during each engine cycle during start-up of the engine.

35. A fuel injection system according to any preceding claim, wherein said computer comprises: a constant current source having the injectors connected in its output circuit, and means for switching the constant current source on and off under control of the computer to provide the injector with a driving current independent of its impedance when the constant current source is switched on.

36. A fuel injection system according to claim 35, wherein said fuel injectors each have an energizing coil and said computer comprises pulse generator means connected to said engine for generating said injection pulses having a width which is a function of various engine operating parameters in timed relation to the operation of the engine; and an injector coil drive circuit having its output connected to at least one of the injector coils and having said variable width pulse as its input, the drive circuit constituting the switchable current source operative to be switched into conduction by said variable width pulse and operative to provide the coil with a current substantially independent of the impedance of the coil.

37. A fuel injection system as claimed in any preceding claim, wherein the computer has a plurality of separate computing channels each connected to at least one injector.

38. A fuel injection system according to any preceding claim, comprising a warm-up circuit comprising a pressure receiving means for receiving an intake manifold pressure signal from a first sensor; a temperature receiving means for receiving an engine temperature signal from a second sensor; and a means for generating a modulated warm-up signal to the pulse generator when the engine temperature is below a predetermined level, said modulated warm-up signal being a function of the manifold pressure signal and the temperature signal.

39. A fuel injection system according to claim 38, wherein the computer comprises an electric voltage and/or current storage device; said pressure receiving means being operative to apply a first variable voltage which is a function of a first engine parameter to one end of said stor age device; said temperature receiving means being operative to apply a second variable voltage which is a function of said first engine operating parameter and a second engine operating parameter to the other end of the storage device; and switch means operative to connect both sides of the storage device to a voltage source, the switching means having a first mode of operation wherein both ends of the storage device are connected to said voltage source so that no net charge is stored in the storage device, a second mode of operation wherein a first end of the storage device is disconnected from the voltage source, allowing the storage device to assume a charge which is a function of said variable voltage, and a third mode of operation wherein said first end of the storage device is reconnected to the voltage source and the second end of the storage device is disconnected from the voltage source, allowing the storage device to discharge as a function of the first and second variable voltages; and means for generating an output pulse during the time of discharge of the storage device.

40. A fuel injection system according to any preceding claim, wherein the computer includes a variable width pulse generator operative, upon receipt of a triggering signal, to provide an output electrical pulse having a time duration controlled by operating parameters of the engine, said pulse generator comprising: a first sensor for generating a first electrical signal having a characteristic which is a function of the engine manifold vacuum; a second sensor for generating a second electrical signal having a characteristic which is a function of engine temperature; a pulse generator circuit connected to receive said first signal to control the duration of its output pulse as an inverse function of manifold vacuum, and to receive said second signal to control its output pulse duration as an inverse function of temperature; and means controlled by said first signal for modifying the second signal.

41. A fuel injection system according to claim 40, comprising a heat sensor located adjacent to an output part of an exhaust manifold for the engine.

42. A fuel injection system according to any preceding claim, and further comprising an engine exhaust gas recirculation control valve for controlling recirculation of exhaust gas to the intake manifold of the engine; a circuit control means for correction of air to fuel ratio; and means for modifying the fuel input to the engine in an amount proportional to the quantity of recirculated exhaust gas to maintain substantially constant air to fuel ratio.

43. A fuel injection system according to claim 31 or any preceding claim when appendant thereto, wherein the injectors are arranged in a plurality of circuits and each circuit is connected to a different output state of the counter so that the circuits receive injection pulses sequentially.

44. A fuel injection system as claimed in claim 43, wherein the number of states of the counter is an integral multiple of the number of injector circuits and the injection circuits are connected to output states of the counter separated from one another by the same integral multiplier.

45. A fuel injection system as claimed in claim 43 or 44, wherein the distributor includes a spark coil and said means for increasing the count contained in the counter each time a firing pulse is provided to one of igniters comprises means for sensing discharge of the spark coil and for providing a pulse to the counter upon the occurrence of each discharge.

46. A fuel injection system as claimed in claim 43, 44 or 45, including means, driven by the engine, for resetting the counter at a regular time in each complete cycle of the engine.

47. A fuel injection system as claimed in claim 46, wherein the means, driven by the engine, for resetting the counter at a regular time in each complete cycle of the engine includes a sensor connected between the engine distribution system and one of the igniters, operative to sense a firing pulse provided to the igniter.

48. A fuel injection system according to claim 43, 44, 45, 46, or 47, wherein the engine has M cylinders, the injectors are arranged in a plurality of circuits, each containing N injectors, and the counter has a number of states equal to an integral multiple of M/N.

49. A fuel injection system as claimed in claim 33 or any preceding claim appendant thereto, wherein said means for causing the injectors to open a plurality of times during each cycle of the engine is adapted to cause all of said injectors to open simultaneously.

50. A fuel injection system according to claim 49, wherein said means for causing the injectors to open once during each operating cycle of the engine, during operation of the engine, includes means for generating a series of electrical pulses sequentially during each operating cycle of the engine, and said means for causing the injectors to open a plurality of times during each operating cycle of the engine during start-up includes a gate conditioned by said electrical signal occurring during start-up and the presence of any one of said electrical pulses.

51. A fuel injection system according to any preceding claim, wherein the com puter includes means for sensing engine operating parameters and controlling the width of the injector opening pulses as a function of said parameters, such means being operable to sense start-up operation of the engine and generate substantially shorter opening pulses during the start-up operation relative to the pulses generated during normal operation of the engine.

52. A fuel injection system according to claim 51, wherein said means for sensing the engine parameters and controlling the width of the injector opening pulses as a function of said parameters includes a capacitor, a charging circuit for the capacitor having a configuration controlled by certain engine operating parameters, and a discharging circuit for the capacitor having a configuration controlled by other engine operations.

53. A fuel injection system according to claim 52, wherein the means for generating opening pulses includes a first transistor and a second transistor, circuitry connecting the first transistor to the second transistor and the capacitor to the second transistor so as to maintain the second transistor in a conductive mode unless the first transistor is in a conductive mode and the capacitor is charged, and circuitry for charging the capacitor when the first transistor is in a non-conductive mode.

54. A fuel injection system as claimed in claim 53 including circuitry for normally maintaining the first transistor in a conductive mode and switching the first transistor into a non-conductive mode at intervals occurring in timed relation to the operation of the engine.

55. A fuel injection system according to claim 53 or 54, wherein the engine parameters which control the rate of charging of the capacitor include a signal indicative of whether the engine is in starting position.

56. A fuel injection system as claimed in any one of claims 1 to 28, wherein the computer comprises a first means for operatively providing actuating pulses to the injectors to cause each injector to actuate once during each engine cycle during normal operation of the engine; a second means for providing an electrical start-up signal during start-up operation of the engine; and a third means conditioned by said start-up signal for causing each of the injector means to actuate a plurality of times during each engine cycle during start-up operation of the engine.

57. A system according to claim 56, wherein said first means for causing the injector means to actuate once during each engine cycle during normal operation of the engine generates first trigger pulses sequentially during each engine cycle.

58. A system according to claim 56 or 57, wherein the third means, for causing the injectors to actuate a plurality of times during each engine cycle during start-up operation, causes all of said injectors to actuate simultaneously.

59. A system according to claim 56, 57 or 58, wherein said third means comprises an electronic gate conditioned by said start-up signal occurring during start-up operation.

60. A system according to claim 59, wherein said third means further comprises an electronic combinor connected to said first means for receiving said first trigger pulses sequentially from said first means, said combinor providing second trigger pulses serially to the electronic gate.

61. A system according to any one of claims 56 to 60, wherein said first means, for providing first triggering pulses sequentially during each engine cycle comprises a counter and a fourth means for incrementing the counter at a plurality of regular intervals during normal and start-up operation of the engine.

62. A system as claimed in any one of claims 56 to 61, wherein said second means is additionally operative to modify said actuating pulses to said injectors to shorten the pulse width of said actuating pulses during the start-up operation relative to the width of the actuating pulses provided during normal operation of the engine.

63. A system as claimed in claim 62, and further comprising a fifth means for modulating said shortened actuating pulse provided during start-up operation as a function of engine temperature during start-up operation.

64. A system as claimed in claim 63, and further comprising a sixth means for controlling the width of the injector actuating pulses as a function of engine parameters.

65. A system as claimed in claim 64, wherein said sixth means comprises a capacitor, a charging circuit for the capacitor and a discharging circuit for the capacitor.

66. A system as claimed in claim 65, wherein said sixth means further comprises a first transistor and a second transistor, circuitry connecting the first transistor to the second transistor and connecting the capacitor to the second transistor to maintain the second transistor in a conductive mode unless the first transistor is a conductive mode and the capacitor is charged, and circuitry for charging the capacitor when the first transistor is a nonconductive mode.

67. A system according to claim 66, and further comprising circuitry for normally maintaining the first transistor in a conductive mode and switching said first transistor into a non-conductive mode at intervals occurring in timed relation to the operation of the engine.

68. A system according to claim 65, 66 or 67, wherein said fifth means and sixth means in combination control the rate of discharge of the capacitor when the engine is in start-up operation.

69. A system as claimed in claim 65, 66, 67 or 68, wherein said variable width pulse generator comprises a capacitor and means for charging said capacitor from a voltage source at regular intervals during operation of the engine, said second means for shortening the injector actuating pulses during start-up operation of the engine including a means for modifying the voltage from said voltage source to said capacitor.

70 .A system as claimed in claim 69, wherein said second means comprises an engine start-up switch and said means for modifying the voltage is operative responsive to closure of the start-up switch.

71. A fuel injection system according to any preceding claim, and further comprising a return conducting means disposed between said supply conducting means and said source of fuel for returning a portion of said fuel from said supply conducting means to said source of fuel; and a valve in said return conducting means arranged to block flow of fuel through the return conducting means line when the engine is turned off to maintain at least part of the pressure in the supply conducting means while the engine is turned off.

72. A fuel injection system according to any preceding claim, wherein said engine has intake valves and said injectors are each positioned adjacent to an intake valve.

73. A fuel injection system as claimed in any preceding claim, wherein each injector has an energizing coil with the computer comprising correction means for applying a correction to the injector actuating pulse to correct for the effect of at least one incidental system variable on the effective response of the injector to the actuating pulse, such incidental system variables being the impedance of the energizing coil, the specific resistance of the wire used in the coil and the voltage supply to the fuel injection system.

74. A system as claimed in claim 73, wherein said correction means is a constant current source having an output device with the injector connected in the output device; and means for switching the constant current source on and off under control of said injector actuating pulse to provide the injector with an actuating current independent of said incidental system variables when the constant current source is switched on.

75. A system according to claim 74, wherein the energizing coil of the injector is connected to the output device of the constant current source.

76. A system according to claim 74 or 75, wherein the constant current source employs an output device that provides an output current proportional to an input signal controlled by an avalanche type constant voltage semi-conductor junction.

77. A system according to claim 76, wherein the avalanche type constant voltage semi-conductor junction is a Zener diode.

78. A system according to claim 76 or 77, wherein the output device that provides an output current proportional to its input signal is comprised by a transistor.

79. A system according to any preceding claim wherein each injector comprises an electromagnetically operated valve comprising a discharge means; a sealing means for intermittently opening and closing said discharge means; a fluid conduit for supplying fluid from the fuel supply conducting means to said discharge means; an electrical conductor for supplying an electrical signal to actuate said valve; an electromagnet circuit comprising: an armature, a pole having a downstream end, a housing, a coil for magnetizing said electromagnetic circuit in response to said electrical signal, and a flux path; said armature having an upstream face, said armature slidably disposed within said housing between said pole and said discharge means, said armature having an upstream position, a downstream position, a travel distance between said upstream position and said downstream position, and a substantially close fitting relationship with said housing; said armature, said pole, and said housing cooperating to define a single series air gap in said flux path between said upstream face of said armature and said downstream end of said first pole and a biasing means disposed within said housing for biasing said armature in its downstream position.

80. A system as claimed in claim 79, wherein said armature is a disc having a substantially circular outer circumference, and a cut-out section on a portion of said circumference for allowing passage of fluid.

81. A system according to claim 80, wherein said armature is the sole movable member within said electro-magnetically operated valve, and is highly responsive to said electrical signal.

82. A system according to claim 79, 80 or 81, wherein said sealing means comprises an annular ridge between said downstream face of the armature and the upstream face of the discharge means.

83. A system according to any one of claims 79 to 82, further comprising a travel limiter defining a residual air gap; said single series air gap comprising said residual gap and said travel distance of the armature.

84. A system according to any one of claims 79 to 83, wherein said injector further comprises a spray member disposed within an outlet orifice of said discharge means for producing at least partial atomization of fuel passing through the orifice.

85. A system according to claim 84, wherein said spray member has an interior bore having a longitudinal axis and said orifice has an interior wall and a longitudinal axis, said longitudinal axis of said bore being disposed at an angle with reference to said longitudinal axis of said orifice for achieving impact of the fuel against the interior wall of the orifice during use of the system.

86. A fuel injection system according to claim 1 for an engine having an engine cycle time, a rotating output shaft, and at least one engine operating parameter sensor, wherein said computer comprises a plurality of independent computing channels operatively coupled to said at least one engine operating parameter sensor and each operatively coupled to at least one fuel injector, each channel having a variable width pulse generator, each channel available for operation for a time duration which is equal to more than 50% of an engine cycle, each channel operatively coupled to the same said at least one injector means for substantially the entire cycle; and means for triggering each computing channel once per engine cycle during normal operation of the engine in timed relationship to the engine output rotation.

87. A fuel injection system according to claim 1, wherein said injectors have an energizing coil and an effective response to said injection pulses there being provided correction means for applying a correction to the injection pulses to correct for the effect of at least one incidental system variable on the effective response of the injector to the pulses, wherein said incidental system variables are the impedance of the energizing coil, the specific resistance of the wire used in the coil and the voltage supply to the fuel injection system.

88. A fuel injection system according to claim 1, wherein said source of fuel includes an electrically energized fuel pump operative to supply fuel to the engine and said system further comprises a control system for said fuel pump comprising means connected to the engine for generating an electric signal having a characteristic which varies as engine speed; and means controlled by said electric signal for energizing the pump to provide a fuel flow at a rate which is a function of said characteristic.

89. A fuel injection system constructed and arranged to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.