GB2208893A

GB2208893A - Process for timing the electronically controlled injection of fuel into an I C engine

Info

Publication number: GB2208893A
Application number: GB8815545A
Authority: GB
Inventors: Rainer Ballik; Heinrich Hutten; Georg Lutkewitte; Paul Rodrigo
Original assignee: Pierburg GmbH
Current assignee: Pierburg GmbH
Priority date: 1987-08-22
Filing date: 1988-06-30
Publication date: 1989-04-19
Also published as: FR2619598A1; GB8815545D0; IT1224862B; DE3728118A1; IT8848253A0

Description

1 1 POOR ' GUALITY 2208893 PROCESS FOR TIMING THE ELECTRONICALLY

CONTROLLED INJECTION OF FUEL INTO AN INTERNAL COMBUSTION ENGINE The invention relates to a process for timing the electronically controlled injection of fuel into the air-intake passages of an internal combustion engine. In particular it relates to a process for timing, relative to the instant of closing of the inlet valve, the beginning and end of fuel injection to each cylinder of an internal combustion engine of the kind in which fuel is injected, for each cylinder, through an individual electromagnetically actuated fuel-injection valve into an individual air-intake passage, one for each cylinder.

From the German Patent Specification DE-OS 23 31 266 a process is known for timing the injection of fuel into the air-intake passage of each individual cylinder of an internal combustion engine. An electronic timer governed by engine speed determines the beginning and end of fuel injection during the suction stroke of each piston.

On the other hand. it is known from practical experience that for the best results the end of fuel injection, in each injection pulse, should be timed to agree with the design characteristics of the particular engine. such as location of the injection valve relative to the inlet valve of the cylinder. and with other engine parameters. But in the process known from the DE-OS 23 31 266 the end of each fuel-injection pulse is timed to occur. each time, when the crankshaft has reached a certain angle of rotation and, consequently, this known process cannot be expected to deliver the best torque, the lowest fuel consumption and the least emission of toxins in the exhaust gases.

The intention in the present invention is to provide a process for timing fuel injection, arranged so as to optimise delivered torque under all operating conditions. irrespective of the design characteristics of the particular engine.

2 The problem is solved by the characteristics claimed in Claim 1. Further favourable developments of the process are described in the subsidiary claims.

Advantages of the process of the invention can be derived from the following description of the example represented in the drawing. in which:

Figure 1 is a diagrammatical representation of an internal combustion engine.

Fiqure 2 represents diagramatically, onan axis representing crankshaft angle of rotation as determined by signals delivered by a sensor, the opening and closing of the inlet and exhaust valves of the cylinders of a multicylinder 4stroke engine, as well as the timing of ignition and the opening and closing of the fuel-injection valves.

The internal combustion engine 1 represented in Figure 1 has an airintake pipe, or induction pipe, from which branch out individual airintake passages 2. one for each cylinder of the engine. Opening into each individual air-intake passage 2 is an electromagnetically actuated fuelinjection 3 which responds to command signals delivered by an electronic fuel-injection timer 4.

The timer 4 determines the duration of each fuel-injection pulse from signals recieved over electric conductors and representing various engineoperating parameters. The beginning and end of fuel injection is determined by signals received from a crankshaft-angle transmitter 5. For example. as crankshaft-angle transmitter. there may be mounted on the engine crankshaft. a slotted disc 6 rotating with the crankshaft and cooperating with a Hall sensor 7. Each cylinder of the engine is represented by a slot in the disc 6. a reference cylinder. for example Cylinder 1 of the engine, being represented by an extra-wide slot for recognition.

6 3 1 In Figure 2 the angular position of the crankshaft is represented on the axis 8, (after conversion by the timer 4 to give a 2-revolution cycle. as is necessary in the case of. a 4-stroke engine), and it will be observed that the wider recognition signal occurs once in every two revolutions of the crankshaft. Figure 2 also shows signals 9 and 10. for Cylinders 1 and 2. delivered by the Hall sensor 7. from which the injection timer 4"derived a sequence of command signals for opening and closing the fuel- injection valves 3.

Figure 2 shows, under the axis 8, for the first two cylinders of a 4cylinder, 4-stroke engine, at 12 the opening and closing of the inlet valve, at 13 the ignition timing range and at 14 the opening and closing of the fuel-injection valve. In Figure 2 the engine is assumed to be operating at full load. During part-load operation the duration of fuel injection is, of course, shorter, as represented for example. by the cross-hatched rectangle near the right in the graph. In the process of the invention the interval of time between the end of fuel injection 14 and the closing of the inlet valve 11 varies in dependence on operating conditions, such as engine speed, mass rate-of-flow of air in the induction pipe and/or engine temperature, these parameters being conveniently stored in an operating-conditions memory in the electronic timer 4.

Method of fuctioning:

Let it be assumed that the engine is operating at a constant speed and delivering a medium torque, as determined by the mass-rate-of-flow of air in each intake passage. The duration of each fuel-injection pulse is determined by the timer 4, in the conventional manner, from the operating conditions data fed to it over electric cables. In the process of the invention the crankshaft-angle transmitter 5 signals the closing of each inlet valve and, responding to this signal. the end of fuel injection for each cylinder is derived by the timer 4, in dependence on engine speed, air-flow in the induction pipe and/or engine temperature.

4 from signals received from the operating-conditions memory 15. The beginning of each fuel-injection pulse is determined by the pulse duration.

In the process of the invention the injection pulse is timed so that after fuel ceases to flow through the injection valve 3 the inlet valve of the cylinder still remains open for just long enough to draw all remaining fuel out of air-intake passage 2, this timing being established by practical testing.

The advantage. compared.with the previously known process, is that cross flow of fuel between the individual airintake passages is prevented and an accurate distribution of fuel to the cylinders is obtained, reducing fuel consumption and minimising toxic exhaust effluents.

When operating conditions are changing, due to changing engine speed or to a movement of the throttle valve in the induction pipe of the engine, it is desirable to obtain a prompt response by the timer 4 in re- adjusting injection-pulse duration and timing. For this purpose the timer 4 compares the desired injection-pulse duration with the period still remaining available, in the operation of each fuel-injection valve 3. before the end of injection and selects, on the basis of thi s comparison. which injection valve 3 should first have its beginning-of-injection timed to occur by the duration of the injection pulse before the end of injection. This method ensures a rapid response. in re-adjusting injection-pulse duration and timing. to changing operating conditions.

The signals emitted by the crankshaft-angle transmitter 5 are in digital form. the signal identifying the reference cylinder having an extra-long duration.

Claims

1. A process for timing. relative to the instant-of-closing of the inlet valve. the beginning and end of fuel injection to each cylinder of an internal combustion engine of the kind in which fuel is injected, for each cylinder. through an individual electromagnetically actuated fuelinjection valve into an individual air-intake passage. one for each cylinder. characterised in that the instant of closing of the inlet valve of each cylinder is detected by sensor responsive to the angle of rotation of the engine crankshaft. the sensor emitting a signal at this instant which, after being time-shifted. i.e. shifted to an earlier or to a later instant. by the influence of other operational parameters, determines the end of fuel injection to this cylinder. the beginning of fuel injection being determined by the duration of injection.

2. A process as claimed in claim 1. characterised in that the electonically determined desired duration is compared with the period still remaining available before the end of injection. the electronic injection timer choosing from thi comparison the closing of which inlet valve shall determine the beginning of injection.

S

3. A process as claimed in claims 1 or 2, characterised in that the end of injection is influenced by an operating-conditions memory responsive to engine speed. the mass-rate-of-flow of air in the induction pipe and/or engine temperature.

4. A process as claimed in one of the above claims. characterised in that the sensor repsonsive to crankshaft angle-of-rotation delivers a digital signal.

4 1 6

5. A process as claimed in Claim 4. characterised in that for identifying the reference cylinder. the reference inlet valve and the reference injection valve. the crankshaft-angle sensor delivers a special signal which differs from the normal digital signal.

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6. Apparatus for carrying out the process defined in any one or more of the preceding claims, and substantially as hereinbefore described with reference to the accompanying drawings.

Published 1988 at The Patent Office. State House. 66"71 High HcPborn. London WCIR 4TP. Further copies inky be obtained from The Patent OfficeSales Branch, St Mary Cray, Orpington. Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray. Kent. Con. 1/87.