GB2295853A

GB2295853A - Control of direct injection engine fuel supply

Info

Publication number: GB2295853A
Application number: GB9525029A
Authority: GB
Inventors: John Heath Greenhough; Thomas Harry Greenhough; Alec John Greenhough
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-12-10
Filing date: 1995-12-07
Publication date: 1996-06-12
Also published as: GB9509568D0; GB9525029D0

Abstract

A main charge of fuel is injected near the end of the compression strokes. A tee branch in each main injector feed line (Figs. 1 to 5 and 8) or a further outlet of the fuel injection pump (Figs. 6 and 7) is connected to a single or a respective secondary injector in the intake manifold or one of the other main injectors (Fig. 9) so that fuel is supplied to the manifold or one of the other cylinders near the end of the charge intake. The secondary injector may operate above the pressure at which the main injector operates so that secondary injection only occurs above a certain engine load. The fuel control may be applied to a two or four-stroke, rotary or reciprocating, compression or spark-ignition engine.

Description

Control of Fuel Supply to a Compression Ignition Engine.

In my previous patents 2169960 and my patent application 2277776 a method was described for the introduction of secondary fuel into the cylinder of a diesel engine for the reduction of smoke and particulate matter in the exhaust gases.

Although it is practical to design the injection pump to achieve the desired requirements or incorporate an electrically controlled injection pump during the engine design stage, it will take many years before the beneficial effects on the reduction of smoke and particulate matter can substantially reduce the levels of atmospheric pollution therefore a simple method of retro fitting older diesel engines becomes apparent.

Until the present invention it has been necessary to fit a second injector pump to convert older vehicles. Although the benefits for the reduction of atmospheric pollution are very desirable the additional pump and necessary driving mechanisms add a considerable cost to the conversion.

Although the invention I am about to describe is applicable to the 2 stroke engine because the vast majority of engines in common use are 4 stroke I will describe the sequence of operation of this principle.

The 4 stroke engine requires two complete revolutions of the crank shaft in order to complete the four strokes of the piston. Starting from Top Dead Centre (rDC) on the downward movement of the piston air is drawn through the open inlet valve to fill the cylinder on the inlet stroke. The valve is then closed and the air is compressed by the upward movement of the piston on the compression stroke. Just before the completion of the compression stroke fuel is injected into the cylinder.

After a slight delay during which time the compression stroke is completed (TDC) spontaneous combustion occurs and the piston is driven down during the power stroke.

Just before the piston reaches bottom dead centre (BDC) the exhaust valve opens and the burned gases are expelled from the cylinder by the rising piston during the exhaust stroke.

At the completion of the exhaust stroke the inlet valve opens and the sequence of operation is repeated.

In a 4 stroke four cylinder engine with a firing order of 1 4 3 2 when the piston in number one cylinder reaches TDC on the compression stroke the piston will have reached BDC on the inlet stroke in cylinder 4.

It is a known characteristic of the fuel injector pump that as speed and load increases pressure increases.

In my previous patent 2169960 and my patent application 2277776 two separate charges of the same fuel are supplied to the engine. The main charge is injected into the cylinder at or near TDC on the compression stroke as in standard diesel engine practice. When the engine reaches a given load the main charge of fuel is supplemented by a second charge of fuel early on during the induction stroke of the engine. The commencement of the second charge is referred to as the transition point.

It is the object of this invention to take advantage of the fact that in a four cylinder engine there will always be one cylinder on the compression stroke and one cylinder on the intake stroke. Because of this it is practical to supply a charge of fuel to an injector placed in the inlet manifold. This injector must be in line with the appropriate cylinder during an intake stroke at the same time as the main charge is being supplied to a cylinder of the engine during its compression stroke.

It is common practice to have two stage lifting devices incorporated into diesel engine fuel injectors. This is usually achievedby incorporating two springs inside the injector body . When injection begins there is a low pressure injection of fuel into the cylinder. This is followed by the main injection when the pressure becomes high enough to lift the injector into its second stage.

At idle and at low speed and light load conditions the first stage of lift may stay in operation throughout the injection period.

In the engine of the invention the secondary injector in the inlet manifold is single stage and set at or above the second stage main injector pressure. By having a differential setting between the main and secondary injector a pressure can be selected so that secondary injection will commence at the speed and load required to coincide with the transition point specified in my previous patent.

In the high speed direct injection engine it is common practice to space four holes ninety degrees apart in the injector tip. This causes each hole to discharge 25% of the total fuel injected into the cylinder. In the engine of the invention a secondary injector is fitted into the inlet manifold with a hole drilled into the injector tip to discharge fuel. A tee branch is incorporated into the main injector fuel supply line to which the secondary injector is attached. This will cause the secondary injector to inject fuel into the inlet manifold when the main injector is activated. The hole in the secondary injector is of the same diameter as in the main injector nozzle.

Because the amount of holes available for the fuel to be discharged are increased to five per injection the amount of fuel injected per hole is 20%. When the injector pump pressure rises with speed and load the secondary injector is activated.

Once secondary injection commences, 80% of the fuel charge will be supplied to the cylinder by the main injector and 20% of the fuel charge will be supplied to the cylinder by the secondary injection through the inlet manifold. For example at half engine load 40% of the fuel is injected through the main injector directly into the cylinder and 10% of the fuel is injected into the inlet air manifold to give a total cylinder charge of 50%.

At full load 80% of the fuel is injected through the main injector direct into the cylinder and 20% is injected into the air inlet manifold to give a total cylinder charge of 100%.

It will be understood that a ratio of 80% main injection and 20% secondary injection is by way of example only and may be varied by increasing the number or diameter of holes in the main injector and or reducing the diameter of the hole in the secondary injector.

The invention will be described further by way of example with reference to the accompanying drawings wherein.

Fig. 1. is a set of drawings illustrating the operation of a 4 stroke 4 cylinder compression ignition engine with cylinder number one on a compression stroke and cylinder number four on an inlet stroke.

Fig. 2. is a similar drawing to Fig. 1. with cylinder number four on z compression stroke and cylinder number three on an inlet stroke.

Fig. 3. is a similar drawing to Fig. 1 and Fig 2 with cylinder number three on a compression stroke and cylinder number two on an inlet stroke.

Fig. 4. is a similar drawing to Fig.l, Fig 2 and Fig.3 with cylinder number two on a compression stroke and cylinder number one on an inlet stroke.

Fig. 5. is a set of drawings illustrating a second preferred method of the invention in which a single injector in the inlet manifold is activated in sequence with each main injection and air intake stroke of the engine.

Fig 6. is a set of drawings illustrating a third preferred method of the invention. Drawings Fig 6 A, B and C illustrate a four stroke single plunger rotary distribution pump. Drawing Fig 6A illustrates a single plunger rotary injection pump at the commencement of an injection stroke. Drawing Fig.6B illustrates the same rotary injection pump at the commencement of an injection stroke modified in accordance to the method of the invention a secondary injector placed in the inlet manifold is activated in sequence with the main injector and air intake stroke of the engine. Drawing Fig. 6C illustrates the same sequence when the injector pump has rotated 90 degrees.

Fig. 7. is a set of drawings illustrating the operation of a four stroke cylinder compression ignition engine with cylinder la near TDC at the start of the injection and cylinder 4a near BDC on the intake stroke. A single plunger rotary injection pump RP shows an injection sequence supplying fuel to a main and secondary injector. The secondary injection is into the inlet manifold during the air intake stroke of the engine.

Fig. 8. is a similar drawing to Fig.7 with cylinder 4a at the end of a compression stroke and cylinder 3a on the inlet stroke.

Fig. 9. is a set of drawing illustrating a fourth preferred method of the invention wherein a secondary charge of fuel is injected into the cylinder through the main injector during the inlet stroke of the engine.

In each of the set of drawings TDC indicates Top Dead Centre and BDC indicates Bottom Dead Centre of a stroke in the cylinder of a reciprocating piston engine. I indicates an inlet valve and E indicates an exhaust valve.

Numbers la, 2a, 3a and 4a represent cylinders 1 - 4 of a four cylinder engine.

Numbers lb, 2b, 3b and 4b represent the main injectors and their relative positions in relationship to cylinders 1, 2, 3 and 4.

P represents the fuel injection pump and Numbers 1,4,3, 2 indicate the fuel/pump injection sequence.

M represents the inlet manifold ofthe engine and Numbers lc, 2c, 3c and 4c indicate the inlet air feed duct to each cylinder of the engine.

ld, 2d, 3d and 4d represent Secondary fuel injectors in line with their appropriate cylinder inlet ducts.

5d represents a single fuel injector in the inlet manifold.

S represents a solenoid valve positioned in a secondary fuel line.

In the four stroke compression ignition engine cycle the crank shaft turns two revolutions. Starting from TDC the crank will rotate 180 degrees to BDC on the inlet stroke and the compression stroke will be completed when the crank shaft has revolved 360 degrees to TDC.

On the power stroke BDC equals 540 degrees and the cycle will be completed at the end of the exhaust stroke when the crank shaft has revolved 720 degrees. In a first preferred method of'the invention Fig.l cylinder la, the piston is at or near TDC 340 degrees - 360 degrees on the compression stroke and the piston in the cylinder 4a is at or near BDC 160 degrees to 180 degrees on the inlet stroke.

An injector pump P driven from the crank shaft and timed to deliver a metered amount of fuel at the end of the compression stroke is illustrated.

Although the injection sequence may be 1, 3, 4, 2, the engine of the invention has an injection sequence of 1,4,3, 2. This is indicated by the numbers 1, 4, 3, 2, below the pump P.

For reasons of clarity in Fig.l, 2, 3 and 4 one fuel line only is illustrated for each sequence of operation.

Fig.l cylinder la and injector lb is fed from pump element 1.

Cylinders 2a, 3a, 4a and their injectors 2b, 3b and 4b are fed from pump elements 2, 3 and 4.

In the compression ignition engine injection will start from 340 degrees to 360 degrees before TDC on the compression stroke. When the pump P element 1 is activated just before TDC on the compression stroke la the feed line to injector lb is pressurised. This causes the injector needle to lift and injection commences, This sequence of operation is common to all diesel engines.

In the engine of the invention Fig.l a branch line is connected to the main injector lb feed line. This supplies fuel to a secondary injector 4d which is located in the inlet manifold M. The tip of the injector 4d is positioned when activated to direct a stream of fuel into the air entering the inlet duct 4c of the cylinder 4a during the inlet stroke.

Because there is a pressure difference between the main and secondary injector when injection commences at light load and speed no secondary injection takes place.

Under engine acceleration the pump line pressure increases with speed and load. When the feed line pressure reaches the chosen point the secondary injector is activated and fuel is injected into the manifold.

The differential pressure between the main and secondary injector can be selected to coincide with the transition point as defined- in my patent No. 2169960. This may coincide with engine load of 25% - 45%. By varying the amount and size of holes in the main injector or reducing the size of hole in the secondary injector the correct ratio for any engine can be selected. This may be 0% - 10% from the transition point to full load or depending on the design of the engine this may be increased from o% at the transition point to 25% at full load.

Fig. 2 shows the injection sequence of a four stroke compression ignition engine when the crank shaft rotation has advanced by 180%. Cylinder 4a is near TDC on the compression stroke at the start of injection and cylinder 3a is near BDC on the inlet stroke. Element 4 of the injector pump P is connected to the main injector 4b with a branch line connected to a secondary injector 3d in the inlet manifold M. At low speed and load the main injector only is activated. When the speed and load is increased the transition point is reached and secondary injection commences. This causes fuel to be injected into air duct 3c to supply cylinder 3a.

Fig. 3 shows the injection sequence when the crank shaft has advanced 360 degrees. Cylinder 3a is on the compression stroke at the start of injection and cylinder 2a is on the inlet stroke. Element 3 of the injector pump P is connected to the main injector 3b with a branch line connected to a secondary injector 2d, in the inlet air duct 2c. As in Fig -l and 2 when the transition point is reached fuel is injected into the air duct 2d to feed cylinder 2a.

Fig.4 shows the injection sequence when the crank shaft has advanced by 540 degrees. Cylinder 2a is on the compression stroke at the start of injection and cylinder la is on the inlet stroke. Element 2 of the injector pump P is connected to the main injector 2b with a branch line connected to a secondary injector ld in the inlet air duct lc as in Fig.l, 2 and 3. When the transition point is reached fuel is injected into air duct lc to feed cylinder la.

In a second preferred method of the invention Fig.5 a single secondary injector is positioned in the main air stream of the inlet manifold M. A feed pipe from each main injector is connected to the secondary injector 5d by means of a common distribution manifold. When injection commences at the end of the compression stroke cylinder la the secondary injection feed line is pressurised.

When injector 5d in the inlet manifold M reaches its opening pressure fuel is discharged into the inlet manifold in time with the maximum air flow into cylinder 4a through duct 4c.

This is repeated through the complete engine cycle and causes secondary injection as each main injection commences.

This causes fuel to be pulsed into the inlet manifold in time with each cylinder air intake stroke.

In a third preferred method of the invention Fig. 6 illustrates a sequence of drawings of a single plunger rotary distribution pump. The rotary distribution pump in a four stroke four cylinder engine cycle is driven at half engine speed and is timed to inject fuel every 90 degrees of rotation.

The plunger P1 has two movements, rotary and reciprocal. The backward and forward movement is activated by cam plate CP and roller action.

In a four cylinder engine the cam plate is provided with four lobes, the output of the plunger chamber P2 is distributed by a groove in the plunger that when rotated opens the outlet ports supplying the injectors. The number of outlet ports in the pump cylinder wall corresponds to the number of cylinders in the engine.

The pumping chamber is filled through a passage way in the body of the pumping cylinder and a slot in the head of the plunger. This is closed by the plunger rotation before each pumping stroke begins. During pumping the fuel is supplied under high pressure to the injector through a hole drilled down the centre of the plunger and a slot on the plunger surface. Diagram 6s represents a standard injection sequence and the arrow denotes the injection of fuel to injector lb. In the standard rotary injection pump Fig.6A a central plug, P3, at the head of the pumping chamber is provided so that an indicator probe can be inserted to measure the position of the pumping plunger for engine timing when the pump is attached to the engine.

In the engine of the invention Fig. 6B. the timing plug P3 is removed and replaced by a metering valve P4 and this can be adjusted to allow from nought to 40% of the total fuel supplied to the engine by secondary injection into the air, entering through the air intake.

Fig. 6B is the same injection sequence as Fig. 6A and the arrow denotes the supply of fuel to the injector lb at the same time the arrow from metering valve P4 denotes the supply of fuel to injector 5d positioned in the inlet manifold M Fig.7.

Although 40% of the fuel can be injected into the inlet manifold when mixed with recirculated exhaust gas (EGR) this can vary with different types of engine.

In practice it has proved very successful for the removal of carbon particulates when 0 to 20% of the fuel is introduced into the engine through the air intake.

Fig. 6C denotes the start of an injection sequence when the pump has advanced by 90 degrees. The arrow denotes a supply of fuel to the main injector 4b and the metering valve supplying fuel to injector 5d positioned in the inlet manifold M.

Fig. 7 is a set of drawings illustrating the operation of a four stroke four cylinder compression ignition engine with the piston in cylinder la at or near T.D.C. on the compression stroke and the piston in cylinder 4a at or near B.D.C. on the inlet stroke.

A rotary distribution pump RP, driven from the crank shaft and timed to deliver a metered amount of fuel at the end of the compression stroke is illustrated. When injection commences fuel is supplied to injector lb and a secondary charge of fuel passes through metering valve P4 to supply injector 5d in the inlet manifold M to coincide with the intake of air into manifold duct 4c.

Fig.8 shows the injection sequence of a four stroke engine when the crank shaft rotation has advanced by 180 degrees and the rotary injection pump has advanced by 90 degrees.

Cylinder 4a is near T.D.C. on the compression stroke at the start of injection and cylinder 3a is near B.D.C. on the inlet stroke. Injection outlet 4 of rotary pump RP is connected to injector 4b and the metering valve P4 is connected to injector 5d in the inlet manifold M. When injection commences fuel is supplied to main injector 4b and a secondary charge of fuel passes through metering valve P4 to supply injector Sd in the inlet manifold M to coincide with the intake of air into manifold duct 3c.

In a fourth preferred method of the invention Fig.9 the method of operation is similar to Fig.l.

Cylinder la is on a compression stroke at or near TDC and cylinder 4a is at or near BDC on the inlet stroke.

A feed line from pump P supplies fuel to the main injector lb of cylinder la and a branch feed from this supply is connected to the main injector 4b of cylinder 4a.

A solenoid valve S is positioned in the secondary supply line so that the timing of fuel flow can be controlled.

A pressure switch set to activate the solenoid valve can be incorporated into the system so that when the transition point 25% - 45% engine load is reached the solenoid valve is opened, thus causing fuel to pressurise the injector 4b of cylinder 4a.

Although the method of the invention is controlled by a pressure switch other electronic methods can be used. The solenoid valve also incorporates a restricted oriface so that the quantity of fuel delivered to injector 4b can be restricted in accordance to the method of the invention.

The fuel supply may be varied from 0% - 25% of the main fuel injected. This method of operation is by way of example only and may be varied in many ways.

This method of operation is equally applicable to a six cylinder engine. In a six cylinder four stroke engine with a firing order of 153624 when cylinder 1 is at the end of a compression stroke cylinder No.3 will be at 120 degrees on the inlet stroke. This allows a main injector feed line to supply a secondary injection into the air supply of cylinder 3 when No.l cylinder injector is activated.

Another alternative method of operation is possible with a six cylinder engine. When cylinder No.1 is at the end of a compression stroke cylinder No.5 will be 240 degrees at the start of the compression stroke. By using the fourth preferred method of the invention as illustrated in Fig.9 with an appropriate solenoid valve and restricter valve and a connecting branch pipe between the main injector of cylinder 1 and the main injector of cylinder 5.

By this method when cylinder No.l injector is activated a secondary charge of fuel can be injected through the main injector in cylinder 5 at the commencement of a compression stroke.

Although the methods described are for a four stroke engine the invention is equally applicable to the two stroke.

In a two stroke engine when cylinder 1 is at TDC on the compression stroke, cylinder 2 will be at BDC on the inlet stroke, therefore it is practicable to feed a secondary injection from the main injector line of cylinder 1 to supply a charge of fuel into the inlet air of cylinder 2. This method of operation is equally applicable to eight and twelve cylinder engines or any other combination thereof.

The illustrations shown are by way of example only and may be varied by the use of a common rail fuel supply and solenoid controlled injectors and computer programmed sequences of operation, providing the same principles of operation are used.

Although the method of the invention is primarily for a compression ignition engine the same principle is equally applicable to the direct injection gasoline engine.

Claims

1. A method of operating a compression ignition internal combustion engine wherein a fuel injection pump is timed to deliver to each cylinder during each engine cycle a metered amount of fuel to a main and secondary injector, the main and secondary injectors being linked by a common feed line, the main injector when activated in the appropriate engine cycle delivers fuel to a cylinder with a piston at or near TDC at the end of a compression stroke and a secondary injector discharges fuel into the air duct of an adjacent cylinder of the engine with the piston at or near BDC at the end of the air intake stroke.

2. A method as claimed in Claim 1 wherein the main injector discharge pressure is set at a lower value than the secondary injector, so that over a lower part of the engine power range from tickover up to the differential pressure point, power is varied by varying the quantity of the main injection of fuel late on in the compression stroke from a minimum at tickover up to a higher pressure value and thereafter this transition point the secondary injector is activated to discharge fuel into the air supply of an adjacent cylinder with the piston late on in an air intake stroke.

3. A method as claimed in 1 and 2 wherein the transition point between the main and secondary injection is chosen to coincide with a main fuel injection quantity of 20 - 35%

4. A method as claimed in 1 and 2 wherein the transition point is chosen to coincide with a main fuel injection which is from 24 - 50%.

5. A method as claimed in 1, 2 3 and 4 wherein from the transition point to a full load the secondary injection of fuel will be from 0 - 10% of the total fuel injected and the main injection of fuel is varied in proportion to the amount of secondary fuel introduced.

6. A method as claimed in 1, 2, 3 and 4 wherein from the transition point to full load the secondary injection of fuel will be from 0 - 25% of the total fuel injected and the main injection of fuel is varied in proportion to the amount of secondary fuel introduced.

7. A method as claimed in 1, 2, 3 and 4 wherein from the transition point to full load the secondary injection of fuel will be from 0 - 45%.

8. A method of operating a four-stroke internal combustion engine as in Claim 1 and 2 in which injection takes place at the end of a compression stroke, injection commences simultaneously through a main and secondary injector when the piston in the compression cylinder is spaced by 180 degrees crankshaft rotation from a piston in a cylinder on an induction stroke.

9. A method of operating a four-stroke internal combustion engine as in Claim 1 and 2 in which injection takes place at the end of a compression stroke, injection commences simultaneously through a main and secondary injector when the piston in the compression cylinder is spaced by 120 degrees crankshaft rotation from a piston in a cylinder on an induction stroke.

10. A method of operating a four-stroke internal combustion engine as in Claim 1 and 2 in which injection takes place at the end of a compression stroke, injection commences simultaneously through a main and secondary injector when the piston in the compression cylinder is spaced by 240 degrees crankshaft rotation from a piston early in the commencement of a compression stroke.

11. A method of operating a direct injection internal combustion engine with a main injector in a cylinder and a secondary injector in an inlet manifold, said main injector having a lower injection pressure than the secondary injector, both injectors being supplied by a common pumping element controlled by electronic means.

12. A method as claimed in any preceding claim wherein the secondary fuel is introduced by a main injector in to the cylinder during an air induction stroke.

13. A method as claimed in any preceding claim wherein the secondary fuel is introduced into the air intake supply in time with each operation of a main injector.

14. An engine as claimed in any preceding claim being a two or four stroke reciprocating piston engine.

15. An engine as claimed in any preceding claim being a four or two cycle rotary engine.

16. A method of operating an internal combustion engine substantially as herewith before described with reference to and as illustrated in Figs 1 - 9 of the accompanying drawings.

17. A method as claimed in preceding claim wherein the fuel is gasoline and ignition is initiated by a spark after the main injection.