DE2448310A1 - IC engine fuel injection system - heats injection valves for electronically-controlled period after engine has started - Google Patents

Abstract

The system is for use with mixture-compression spark-ignition engines, where fuel is continuously injected through valves in the inlet manifold, which contains a measuring device and an adjustable throttle one behind the other. The device is moved in proportion to the airflow against return action, varying the setting of a valve regulating fuel quantity. The force of the return action is provided by fluid under pressure, running at variable pressure continuously through a control circuit, and acting against a slide transmitting the return force. Pressure alteration is by a valve incorporating a heated and temperature-dependent control unit. After starting the engine the injection valves are electrically heated.

Description

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Patent and

Utility model registration

ROBERT BOSCH GMBH, 7 Stut tgartl

Fuel injection system

The invention relates to a fuel injection system for mixture-compressing, spark-ignited internal combustion engines with continuous injection through injection valves in the suction pipe, in which a measuring element and an arbitrarily actuatable throttle valve are arranged one behind the other and the measuring element is moved against a restoring force according to the amount of air flowing through, and the movable one Part of a valve arranged in the fuel line

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for the allocation of an amount of fuel proportional to the amount of air adjusted and in which the restoring force is generated by hydraulic fluid that is continuously under constant, but arbitrarily changeable pressure by a control pressure circuit promoted the restoring force applied control slide and its pressure change by at least one as a function Pressure control valve that can be controlled by engine parameters, which is a temperature-dependent, heatable control element contains, takes place. ;

Fuel injection systems of this type have the purpose for all operating conditions of the internal combustion engine to automatically create a favorable fuel-air mixture so as to To burn fuel as completely as possible and thereby with the highest possible performance of the internal combustion engine or the lowest possible fuel consumption to avoid or greatly reduce the formation of toxic exhaust gases. For this the amount of fuel must meet the requirements of each operating condition the internal combustion engine are accordingly measured very precisely.

In known fuel injection systems of this type, the amount of fuel is as proportional as possible to that through the intake manifold metered amount of flowing air, the ratio between metered amount of fuel and amount of air by changing the restoring force of the measuring element can be changed by a pressure control valve as a function of engine parameters.

With electrically heated injection valves, during ' the warm-up phase of the internal combustion engine achieve a mixture that results in an exhaust gas with significantly lower pollutant proportions than when using other warm-up devices. At the transition from heated to unheated

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However, the following undesirable phenomena occur when the injection valves are operated:

a. By condensation of the fuel vapor in the "dead volume" the injection valves, the fuel injection into the intake manifold is interrupted.

b. The wetting of the inner wall of the suction pipe is liquid Fuel greater than. in the case of vaporous fuel.

These phenomena result in a momentary lack of fuel in the combustion chambers of the internal combustion engine, what ever according to the operating state of the internal combustion engine leads to the internal combustion engine being either severe combustion misfires shows or stops completely.

The invention is based on the object of a fuel injection system to develop with heated injection valves during the transition from heated to unheated operation the injection valves do not suffer from the disadvantages indicated.

According to the invention, this object is achieved in that the injection valves are electrically operated after the internal combustion engine has been started. are heatable and after the end of the warm-up phase of the internal combustion engine, a first and a second, beyond the first predetermined period of time begin to run and after the first period of time, the circuit of the heater can be interrupted and during the second period of time the pressure of the pressure fluid in the control pressure circuit via a electromagnetically operated relief valve can be reduced V ■ -U-

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and controlling the first and second predetermined time periods by an electronic controller he follows.

According to an advantageous embodiment of the invention, the warm-up phase is concluded by a timer or a temperature switch can be determined. Another advantageous embodiment of the invention is characterized in that the conclusion of the warm-up phase by a Throttle switch and a time or temperature switch can be determined.

According to a further advantageous embodiment of the invention, the second time period is determined by the sum of the first and one then formed a third period of time.

Another advantageous embodiment of the invention is that after starting the internal combustion engine A starting transistor of the electronic control device is switched through via a resistor, the emitter of which is on the negative and its collector is connected to the positive lead via a relay winding, the energized relay a heating switch and thus the circuit from the positive lead to the heating windings and a feedback circuit from the positive lead via a feedback resistor to the base of the starting transistor closes and that the the first and third time duration determining timing elements of the electronic control device from a common Time capacitor and one resistor each are formed.

An embodiment of the invention is shown in simplified form in the drawing and is described in more detail below. Show it:

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Pig. 1. a fuel injector designed according to the invention z system,

2 shows a circuit diagram of the electronic control device.

In the fuel injection system shown in FIG the combustion air flows in the direction of the arrow through an intake pipe section 1 in which a measuring element 2 is in one Cone 3 is arranged and continues through a suction pipe section 4 and a connecting hose 5 in a suction pipe section 6 with an arbitrarily actuatable throttle valve 7 to one or more cylinders, not shown, of an internal combustion engine. The measuring element 2 is a transverse · Plate arranged to the direction of flow, which is located in the cone of the suction pipe according to an approximately linear function of the Moved through the suction pipe flowing amount of air, wherein for a constant acting on the measuring element 2 restoring force as well as a constant air pressure prevailing in front of the measuring organ 2, the pressure prevailing between the measuring element 2 and the throttle valve 7 also remains constant. The measuring element 2 directly controls a metering and flow divider valve 10. To transmit the adjusting movement of the measuring element 2, a lever 11 connected to it, which is shown in FIG is mounted on a pivot point 12 and during its pivoting movement with a nose 13 the movable valve part of the metering and flow divider valve, which is designed as a control slide 14 10 actuated. The end face 15 of the control slide 14 facing away from the nose 13 is acted upon by hydraulic fluid, the pressure of which on the end face 15 generates the restoring force on the measuring element 2.

The fuel is supplied by an electric motor 18 powered fuel pump 19, the fuel from

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a fuel tank 20 and a fuel supply line 21 supplies the metering and flow divider valve 10. One branches off from the fuel supply line 21 Line 22, into which a pressure relief valve 23 is connected, which, if the system pressure is too high, fuel into the fuel tank 20 can flow back.

From the fuel supply line 21, the fuel passes into a channel 26 in the housing of the metering and flow divider valve 10. The channel 26 leads to an annular groove 27 of the control slide I ¹ I and further via various branches to chambers 28, so that one side of a membrane 29 is acted upon by the fuel pressure. Depending on the position of the control slide 1Ί, the annular groove 27 opens more or less control slots 30, which each lead through channels 31 to a chamber 32 which is separated from the chamber 28 by the membrane 29. From the chambers 32, the fuel arrives via injection lines 33 to the individual injection valves 34, which are arranged in the vicinity of the engine cylinders in the intake manifold. The membrane 29 serves as a movable part of a flat seat valve which is held open by a spring 35 when the fuel injection system is not working. The diaphragm cans formed from a chamber 28 and 32 each cause the pressure drop at the metering valve 27.30 to remain largely constant regardless of the overlap between the annular groove 27 and the control slots 30, i.e. regardless of the amount of fuel flowing to the injection valves 3Ί. This ensures that the adjustment path of the control slide I ^ and the metered amount of fuel are proportional.

With a pivoting movement of the lever 11, the measuring element 2 is moved into the cone 3 of the suction tube 1, so that the

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Between the measuring element and the cone changing ring cross-section is proportional to the adjustment path of the measuring element 2.

The pressure fluid generating the constant restoring force on the control slide 14 is fuel. For this branches from the fuel supply line 21 a line 36, which via a control pressure line 37 into a pressure chamber 38 opens into which the control slide 14 protrudes with its end face 15. The control pressure circuit 37 is through a decoupling throttle 39 from the supply circuit to the metering and Flow divider valve separated. The pressurization of the pressure chamber 38 takes place via a damping throttle 40.

A pressure control valve 42 is located in the control pressure line 37 arranged over which the hydraulic fluid through a return line 43 can reach fuel tank 2o without pressure. Through the illustrated pressure control valve 42 is the The pressure of the hydraulic fluid generating the restoring force can be controlled as a function of temperature. The pressure control valve 42 is designed as a flat seat valve with a fixed valve seat

44 and a membrane 45, which in the closing direction of the pressure control valve is loaded by a spring 46. The closing force of the spring 46 is of a pin 47, which has a Support 48 and a spring plate 49 between the membrane

45 and the spring 46 is clamped, transferred. at At temperatures below the engine operating temperature, the spring 46 acts via the spring plate 49, a bimetallic spring

51, which at the other end with a into the Housing of the pressure control valve 42 pressed-in bolts

52 is screwed. By a between the bolt 52 and The insulating piece lying on the bimetallic spring 51 is the bimetallic spring largely against heat loss through conduction protected on the housing of the pressure control valve. on

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the bimetallic spring 51 is fitted with an electric heating element 53.

^{A line 5 1} I branches off from the control pressure circuit 37, in which a valve 56 which can be actuated by an electromagnet 55 is arranged. Downstream of the valve 56 there is a throttle 57, via which the control pressure circuit 37 can be relieved to the fuel tank 20 when the valve 56 is open.

The electromagnet 55 is arranged in a circuit 58, which is fed by a power source 59 ', e.g. the vehicle battery, and an ignition switch 60, a starter switch 61 and an electronic control device 62 contains. Also on the power source 59 are over the electronic control device heating coils 63 of the injection valves 3 ^.

The fuel injection system works as follows:

When the internal combustion engine is running, fuel is sucked in from the fuel tank 20 by the fuel pump 19 driven by the electric motor 18 and supplied to the metering and quantity divider valve 10 via the fuel supply line 21. At the same time, the internal combustion engine sucks in air through the intake manifold 1, through which the measuring element 2 experiences a certain deflection from its rest position. Corresponding to the deflection of the measuring element 2, the control slide 1 * 1 is also displaced via the lever 11, thereby releasing a larger cross section of the control slots 30. The direct connection between measuring element 2 and control slide I ¹ J results in a constant ratio of air volume and metered amount of fuel, provided that the characteristics of these two elements are sufficiently linear,

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what is strived for in itself. The air-fuel ratio would then be constant over the entire operating range of the engine be. But it is necessary, depending on the operating conditions of the internal combustion engine, the fuel-air mixture to keep richer or poorer, which is done by changing the restoring force on the measuring element 2. For this is in the Control pressure circuit 37, the pressure control valve 42 is arranged by influencing the pressure of the pressure fluid during the warm-up phase of the internal combustion engine to Reaching the operating temperature, depending on the temperature, influences the enrichment of the mixture. The from the pin 47 to the Diaphragm 45 transmitted closing force of the spring 46 is determined the control pressure. However, the bimetallic spring acts at temperatures below the operating temperature of the internal combustion engine 51 on the spring plate 49 against the spring 46, whereby the closing force transmitted to the diaphragm 45 is reduced will. Immediately after the start, however, the bimetallic spring is heated via the electric heater 53 51, with the result that the force transmitted by the bimetallic spring 51 to the spring plate 49 is reduced will. The desired basic bias of the bimetal spring 51 can be achieved in that the bolt 52 is different is pressed deep into the housing of the pressure control valve 42.

For further consideration of the mode of operation of the fuel injection system the circuit diagram of the electronic control device 62 shown in FIG. 2 should also be used. After the ignition switch 60 and the starter switch 61 have been closed, the resistor located on the starter terminal 50 is used 66 a starting transistor 67 is switched through, so that a relay 68 is energized and a heating switch 69 and the circuit from the positive lead to the heating coils 63 of the injection valves 34 close. When closed Heating switch 69 is the base of starting transistor 67

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via a feedback resistor 70 also to the positive lead, so that the starting transistor 67 at energized relay 68 remains switched through, even if there is no more base current via starter terminal 50 is delivered. The course of the warm-up phase of the internal combustion engine can be determined by a time switch 71 'which can also be designed as a temperature switch and a throttle valve switch 72, possibly arranged parallel to the time switch 71, which starts at a certain opening angle the throttle valve 7 opens. As long as the switches or 72 are closed, the also remains on the Heating switch 69 and a resistor 73 with its base coupled to the positive lead valve control transistor 7 ^ blocked.

After the end of the warm-up phase, the switches 71 and 72 open, so that the valve control transistor Ik switches through via the resistor 73 and the valve relay 75 connected to the collector of the valve control transistor 7 ¹ * is energized and a valve switch 76 closes so that the electromagnet 55 is connected of the positive supply line and the valve 56 in the line 5 ¹ I opens and the control pressure in the control pressure circuit 37 can be lowered. After closing the valve switch 76, a diode

77 current flow, however, through a capacitor

78 ensures that at the moment a transistor is switched on

79 is safely blocked »whose collector is connected to the negative lead via a resistor 80. The time capacitor 81, which is initially still discharged, is thus also at this negative potential via the diode 82 on one side. The time capacitor 8l is now charged to positive via a resistor 8 3 until the potential, after a first time period t ₁ predetermined by the resistor 83 and the time capacitor 8l, reaches a value that corresponds to the

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Voltage divider 8 ^ i, 85 plus the voltage between base and Emitter of a transistor 86 corresponds, which turns on with it. When the transistor 86 is conductive, however, they also switch the transistors 79, 87 and 88 through and the conductive The transistor 88 causes the starting transistor 67 to be blocked. The relay 68 and the heating switch are thus de-energized 69 open, so that the circuit to the heating windings 63 is interrupted. By opening the heating switch 69 the first predetermined period of time t. has expired.

Through the feedback via a resistor 89 and a diode 90, the conduction of the transistor 79 and thus also of the transistor 87 is ensured, with the valve control transistor J ^ now also remaining switched on when the transistor 87 is conductive via a resistor 91, even if the heating switch 69 is now open no base current for the valve control transistor 7 ^ is supplied via the resistor 73. With the valve control transistor 74 still switched on, the solenoid valve 55 * 56 remains open and the control pressure in the control pressure circuit 37 is thus reduced.

When the transistor 79 is conductive, the right side of the time capacitor 81 is now also adjusted via a resistor 92 Plus charged until after a third time period predetermined by the time capacitor 81 and the resistor 92 t, the switch-on threshold "of a transistor 93 is reached. With the conductive transistor 93 also becomes a transistor 94 conductive, whereby the transistor 87 is blocked and the Valve control transistor 7 ^ no longer receives base current and thus also locks. The valve relay 75 is thus de-energized and opens the valve switch 76, so that the solenoid valve 55,56 closes and the control pressure in the control pressure circuit returns to the level determined by the spring M6 of the

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Pressure control valve k2 certain value increases. The process initiated after the end of the warm-up phase by opening switches 71 and 72 has thus expired and completed once.

According to the invention, after the end of the warm-up phase of the internal combustion engine, the control pressure influencing the restoring force on the measuring element 2 and thus the metered amount of fuel is reduced; at the same time, a first predetermined period of time t. Begins to run, after which the electrical heating of the injection valves J> k is ended, and at the same time a third time period t begins to run, after which the control pressure reduction is ended. The control pressure reduction thus extends over a second predetermined time period t 1, which is made up of the sum of the first predetermined time period t 1 and the third predetermined time period t 1. The time periods t * and t are each in the range of seconds. According to the invention, however, after the engine's warm-up phase has elapsed, before the electrical heating of the injection valves is switched off, the fuel-air mixture is briefly enriched by lowering the control pressure and thus the restoring force on the measuring element with liquid fuel. But even after the electrical heating of the injection valves has been switched off, the richer fuel-air mixture continues to exist for a short time in order to quickly fill up the "dead volume" in the injection valves caused by condensation of the fuel vapor. It is thus ensured that the internal combustion engine can continue to be operated during the transition from the heated to the unheated operation of the injection valves without significant impairment of the running behavior.

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Claims (7)

-13- * 3 3 5 Expectations ί 1.) Fuel injection system for mixture-compressing, externally ignited Internal combustion engines with continuous injection through injection valves into the intake manifold in which a measuring element and an arbitrarily actuatable throttle valve are arranged one behind the other and the measuring element is moved against a restoring force according to the amount of air flowing through, and thereby the moving part a valve arranged in the fuel line for metering an amount of fuel proportional to the amount of air adjusted and in which the restoring force is generated by hydraulic fluid, which is continuously under constant, however arbitrarily changeable pressure by a control pressure circuit promoted a control slide that transmits the restoring force and its pressure change occurs at least one pressure control valve that can be controlled as a function of engine parameters and that is a temperature-dependent, heated one Contains control element, characterized in that the injection valves (34) after starting the internal combustion engine electrically are heatable and after the end of the warm-up phase of the internal combustion engine, a first (t ^) and a second (tg), beyond the first (t.) predetermined period of time start to run and after the expiry of the first period of time Ct-) the circuit of the heating (63) In 609817/0094 -111- ² 3 3 5 interruptible and during the second time period (tp) the pressure of the pressure fluid in the control pressure circuit (37) can be reduced via an electromagnetically actuated relief valve (55,56) and the control of the first (t ^) and second (tp) predetermined time period by an electronic control device (62) takes place. 2. Fuel injection system according to claim 1, characterized in that that the completion of the warm-up phase by a Time switch (71) can be determined. 3. Fuel injection system according to claim 1, characterized in that that the end of the warm-up phase can be determined by a temperature switch (71). k. Fuel injection system according to Claim 1, characterized in that the end of the warm-up phase can be determined by a throttle valve (72) and a time or temperature switch (71). 5. Fuel injection system according to claim 1, characterized in that that the second duration ^ 2) by the sum the first (t.,) and one following it third time period (t 1) is formed. -15- 609817/0094 2U8310 6. Fuel injection system according to claim 1, characterized characterized in that after the internal combustion engine has started, a starting transistor is provided via a resistor (66) (67) of the electronic control device (62) is switched through, its emitter to the negative and its collector via a relay winding (68) is on the positive lead, the excited Relay (68) a heating switch (69) and thus the circuit from the positive lead to the heating windings (63) and a feedback circuit from the positive lead through a feedback resistor (70) to the The base of the start transistor (67) closes. 7. Fuel injection system according to claim 5 and 6, characterized characterized in that the the first (tj) and third Time elements of the electronic control device (62) determining the duration (t 1) from a common time converter (8l) and one resistor (83 »92) each., 609817/0094