GB2239962A

GB2239962A - Controlling I.C. engine fuel metering and/or ignition angle

Info

Publication number: GB2239962A
Application number: GB9027860A
Authority: GB
Inventors: Bernhard Miller; Matthias Philipp
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1989-12-23
Filing date: 1990-12-21
Publication date: 1991-07-17
Anticipated expiration: 2010-12-21
Also published as: FR2656379A1; DE3942966A1; JPH04140450A; GB9027860D0; KR910012524A; GB2239962B; FR2656379B1

Abstract

A control valve is generated from a periodically fluctuating parameter of an internal combustion engine, such as the manifold pressure, the intake air mass or the rotation speed of one of the shafts. The instantaneous value of this parameter is measured once per ignition in synchronism with the crank angle and is compared with the present control value of this parameter. Also the content of a counter is increased by 1 with each of these measurements, with the maximum to which it counts being equal to the number of cylinders of the engine. If the instantaneous value of this parameter differs from the present control value by a predetermined amount, or if the counter has reached the number equivalent to the number of cylinders, the instantaneous value is then substituted for the adopted value and used for control and/or regulation. Thus if the parameter changes rapidly, the control value can be updated every ignition cycle but if the parameter changes slowly, the control value is updated once every complete engine cycle. <IMAGE>

Description

1 - 2:2 Z3,5) a 6, -1DESCRIPTION :2 A DEVICE FOR CONTROLLING AND/OR

REGULATING THE FUEL METERING AND/OR THE IGNITION ANGLE OF AN INTERNAL COMBUSTION ENGINE The present invention relates to a device for controlling and/or regulating the fuel metering and/or the ignition angle of an internal combustion engine.

The operating parameters of the internal combustion engine, which are normally detected by sensors, for example the intake manifold pressure, the intake air mass or the rotational speed of one of the shafts, are quasi-continuous values which fluctuate during the operating cycle of the internal combustion engine.

In order to regulate the internal combustion engine when the accuracy or actuality of the measured value does not need to be precise, a mean value over a period of time of these measured values can be used, which takes into account an average of the periodic fluctuations. However, for the precise regulation of a modern internal combustion engine, in particular when determining the fuel metering or the optimum ignition angle setting, it is necessary to monitor the various operating parameters as precisely and as directly as possible. This is because the formation of an average value from a plurality of previously measured values can differ from the prevailing value and therefore cannot be used for the precise regulation of the internal combustion engine.

DE-OS 32 23 328 discloses a measuring device for detecting a periodically fluctuating operating parameter of an internal combustion engine, in which measurement of.this value, for example the pressure in the intake manifold, is measured once per ignition interval in synchronism with the ignition. That is, the actual measured value is registered in a fixed crank shaft position and a mean of the value concerned is calculated therefrom. However, since the amplitude of the periodically fluctuating operating parameter concerned varies due to the differing operational reliability of the individual cylinders, undesirable fluctuations in the measured values can occur, particularly during steady state operation of the internal combustion engine, which can lead to the inaccurate determination of the fuel supply and/or to jumps in the ignition angle.

In accordance w#h the present invention there is provided a device for controlling and/or regulating the fuel metering and/or the ignition angle of an internal combustion engine in accordance with a measured value of a periodically fluctuating parameter, comprising a sensor for measuring the i -3instantaneous value of the periodically fluctuating parameter once per ignition in synchronism with the crank angle in order to detect the load, and means for comparing this instantaneous value with the measured value used for control and/or regulation purposes and for performing a counting operation in which the content of a counter is increased by 1 with each of these measurements, with the maximum to which the counter counts being equal to the number of cylinders of the internal combustion engine, this instantaneous value being substituted for and adopted as the value used for control and/or regulation if it differs from the prevailing control and/or regulation value in a selectable respect, in the event of a dynamic operation of the internal combustion engine, or if the counting operation has reached its maximum value, in the event of steady state operation of the internal combustion engine.

This has the advantage that precise detection of the periodically fluctuating operating parameter is possible under all operating conditions, and at the same time it is ensured that a change in the load, that is the transition from steady state operat:Lon of the internal combustion engine to dynamic operation, is quickly recognised.

1 This high accuracy in detection of the measured value is made possible by the fact that the periodically fluctuating parameter of concern is measured in the steady state case once per ignition in synchronism with the crankshaft, but only once for every two crankshaft revolutions for controlling and/or regulating the fuel metering and/or the ignition angle. Therefore, independent of the operational reliability of the individual cylinders, the same measured value is always used to control or regulate the internal combustion engine.

In the dynamic case, that is following recognition of a change in load, the periodically fluctuating operating parameter is also detected once per ignition in synchronism with the crankshaft, although in this case each measured value is used for controlling or regulating the fuel metering or the ignition angle of the internal combustion engine. Although, in the dynamic case, differences arising from the varying operational reliability of the individual cylinders cannot thereby be compensated, this is not necessary, because the changes due to the change in load are substantially greater. Therefore, during dynamic operation, a very high degree of actuality is in turn achieved for the values used for control and/or regulation.

1 j 1 By way of example only, a specific embodiment of the invention will now. be described, with reference to the accompanying drawings, in which:- Fig.1 is a graph illustrating the intake manifold pressure p against the crankshaft angle t; and Figs. 2 to 4 show flow diagrams each representing different ways of detecting the instantaneous value of a periodically fluctuating measured value within two crankshaft revolutions.

In Fig.l. the pressure in the intake manifold of an internal combustion engine is plotted against the crankshaft angle for an eight-cylinder engine during steady state operation. This particular example has been used to illustrate the course of the measured value of a parameter which fluctuates periodically during the working cycle of an internal combustion engine. The intake manifold pressure p is given in millibar and the crankshaft angle is given as the number t of revolutions of the crankshaft. Furthermore, the ignition sequence of the individual cylinders is plotted. The course of the intake manifold pressure with respect to the crankshaft angle is shown for a speed of 5,250 r.p.m.

It can be seen from Fig.1 that the instantaneous value of the intake manifold pressure p in the working cycle of the internal combustion engine fluctuates about a constant mean value. In the eight-cylinder engine, during steady state operation, the period duration is 900 crank angle. The maximum pressures and/or the minimum pressures are dependent upon the operational ability of the individual cylinders, the design of the intake manifold and the pressure removal point. If the pressure is always determined at the same location relative to the position of the crankshaft, for example at the location marked X, and is used to control or regulate fuel metering or the ignition angle of the internal combustion engine, there is obtained a precise value which is independent of the fluctuations of the intake manifold pressure and of the varying operational quality of the individual cylinders. As set forth in the description of Fig.2, in the case of pressure determination at location X as shown in Fig.1, a measured value would be adopted for control and/or regulation at location Y.

During dynamic operation of the internal combustion engine, that is in the event of increasing or decreasing load, the periodically fluctuating portion of the intake manifold pressure is superimposed on a definite increase or decrease in the overall intake manifold pressure; in this case, that is in the event of a pronounced change in load, the 1 component coming from it is higher than the oscillations during steady state operation, pressure detection as during steady state operation thus not being possible in the dynamic case.

According to the invention, the intake manifold pressure is always, that is during steady state and dynamic operation, detected using a pressure sensor once per ignition in synchronism with the crankshaft, that is, for an 8-cylinder engine, every 900 crank angle, and passed to an evaluation circuit. In this circuit, each measured value is compared with the adopted value, the adopted value being the current value used for control and/or regulation. At the same time, a counter contained in the evaluation device, which counts up to a maximum equal to the number of cylinders, (in the example of an 8-cylinder engine, up to a maximum of eight), is put into operation. The content of the counter is increased by 1 for each registered measured value.

The combination of the content of the counter and the instantaneous value of the intake manifold pressure supplies the value of the intake manifold pressure which can be used for controlling and/or regulating the fuel metering and/or the ignition angle of an internal combustion engine, and permits the transition from steady state to dynamic operation to be recognised rapidly. The precise course of this evaluation operation is illustrated by the flow diagrams in Figs. 2 to 4. Each flow diagram represents a possible evaluation.

Fig. 2 shows one way of determining the value of the intake manifold pressure required f9r control and/or regulation. To do this, the program illustrated in the flow diagram is run in a computing device once per ignition in synchronism with the crankshaft. In the first step 10, the content of the counter is increased by 1 with each measurement. In the following step 11, it is checked whether the figure reached by the counter corresponds to the number of cylinders of the internal combustion engine. If the number in the counter is the same as the number of- cylinders, the counter is reset to 0 in step 12 and the computing device jumps to step 13, as it does when the number in the counter is less than the number of cylinders.

In step 13, the actual load value PLI that is the instantaneous value of the intake manifold pressure, is read in and is compared at step 14 with the previous or adopted load value PL-1. The adoptqd load value PL-1 is the last value of the intake manifold pressure which was uied for control and/or regulation purposes. It is thus not necessarily the immediately 1, 1 i preceding instantaneous value of the intake manifold pressure. It would only be this during dynamic operation.

If the actual load value PL is smaller than the adopted load value PL-P it is checked in a further step 15 whether the counter has.reached the number equal to the number of cylinders of the internal comnbustion engine. If it has no t, the actual i.e. instantaneous load value PL 'S forgotten and the adopted load value PL-1 is used for control and/or regulation. If, however, the actual load value PL in step 14 is greater than the adopted load value PLlr or if the counter has reached a count equal to the number of cylinders, the program jumps to step 16, in which the actual i.e. the then instantaneous load value is then adopted for control andlor regulation. In this case the counter is reset to 0 at step 17 and a new program run commences thereafter.

With this method of detecting the intake manifold pressure, it is thus ensured that during steady state operation,, that is when there is no change in load, the maximum intake manifold pressure is always recognised within two crankshaft revolutions and is used for control and/or regulation. whilst all other measured values are disregarded. In Fig. 1, in which the steady state operation is illustrated, the therein -10indicated value would thus always.be used. In the dynamic case, however, in the event of an increase in the intake manifold pressure, each measured value would then be used for control and/or regulation, since each instantaneous value of the pressure would be greater than the previously measured.value and hence the prevailing adopted value. In the event of a reduction in load, with this method, the maximum intake manifold pressure is also always used for control and/or regulation.

Fig. 3 shows a further flow diagram in which the value for control and/or regulation is detected with the smallest sensor signal respectively within two engine revolutions. The program used remains in principle the same, although comparison with the adopted value of the intake manifold pressure is carried out in such a way that, if there is a reduction in the intake manifold pressure value, this lower value would then be used for control and/or regulation. The difference between this and Fig. 2 is in step 14, with the comparison of the actual i.e. instantaneous load value PL with the adopted load value PL-11 with adoption of a new control and/or regulation value being effected in this embodiment at PL OPL-1) R Fig. 4 shows a third embodiment, in which the mean value of the intake manifold pressure is calculated in synchronism with ignition. In this case, the value which is used for control and/or regulation is half the sum, that is the mean value PL(MW) of the load values determined in accordance with Figs. 2 and 3 respectively, that is 1/2 HPL-1) (PL-1)'] = PL (MW)e -----------------------------------------------------

Claims

1. A device for controlling and/or regulating the fuel metering and/or the ignition angle of an internal combustion engine in accordance with a measured value of a periodically fluctuating parameter, comprising a sensor for measuring the instantaneous value of the periodically fluctuating parameter once per ignition in synchronism with the crank angle in order to detect the load, and means for comparing this instantaneous value with the measured value used for control and/or regulation purposes and for performing a counting operation in which the content of a counter is increased by 1 with each of these measurements, with the maximum to which the counter counts being equal to the number of cylinders of the internal combustion engine, this instantaneous value being substituted for and adopted as the value used for control and/or regulation if it differs from the prevailing control and/or regulation value in a selectable respect, in the event of a dyn ic operation of the internal combustion engine, or if the counting operation has reached its maximum value, in the event of steady state operation of the internal combustion engine.

2. A device as claimed in claim 1, where the instantaneous value is adopted for control and/or k - 13regulation purposes when it is larger than the prevailing control and/or regulation value.

3. A device as claimed in claim 1, where the instantaneous value is adopted for control and/or regulation when it is smaller than the prevailing control and/or regulation value.

4. A device as claimed in claim 1, wherein a mean value is obtained from two measured values formed in accordance with claims 2 and 3.

5. A device as claimed in any of the preceding claims, wherein during steady state engine operation, the instantaneous value of the parameter is measured once every ignition, but only one of these values is adopted for control and/or regulation purposes within two crankshaft rotations.

6. A device as'claimed in ciaim 5, wherein during steady state engine operation, a prominent point in the course of the periodically fluctuating measured parameter, preferably a maximum value or a minimum value, is used to fix the value to be adopted for control and/or regulation.

7. A device as claimed in claims 1 to 4, wherein, during dynamic operation, the instantaneous value of the parameter is measured once per ignition, and each of these values is used for,control and/or regulation.

i 0 B. A device as claimed in claim 1, wherein when the counter, in the event of cylinder recognition being provided, the counting operation is always reset at a particular cylinder and thus a particular cylinder is used for adoption of the measured value.

9. A device for controlling and/or regulating the fuel metering and/or the ignition angle of an internal combustion engine constructed and adapted to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

Published 1991 at7be Patent Office. State House. 66/71 PightiolbOrn, LoondonWCIR47?. Further copies nay be obtained from Saks Brainch. Unit 6. Nine Mile Point Cwmielinfach. Cross Keys, Newport. NPI 7HZ. Printed by Multiplex techniques ltd. St Mary Cmy. Kent.

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