EP0353216B1 - Device for controlling and regulating the combustion engine of a vehicle - Google Patents

Abstract

A device for controlling and regulating a diesel engine, with a base controller (7) to which performance quantity signals of the engine are fed and an output signal of the base controller is used for driving an electromechanical final controlling element for the fuel and/or air quantity, with a rotational-speed calculator (8) for calculating a cylinder-specific rotational speed (n1) and a mean engine speed (), with a comparator unit (10) for outputting positive or negative alteration values ( DELTA Qi) for each cylinder if the cylinder- specific rotational speeds (ni) lie below or above the mean rotational speed (), with a correction value memory (18) with z cylinder memories (18-i) for cylinder-specific correction values ( DELTA RWi), to which the alteration values ( DELTA Qi) can be fed, and with a cylinder selection unit (24) for outputting the correction values. A drift compensator (31), to which the cylinder-specific correction values ( DELTA RWi) stored in the cylinder memories (18-i) are fed, is set up to form a mean value of the correction values and has subtracting elements (34-i) which are connected upstream of each input of the correction memory (18) and to which, on the one hand, each cylinder- specific alteration value ( DELTA Qi) determined in the comparator unit (10) and, on the other hand, a mean value of the correction values is in each case fed. <IMAGE>

Description

The invention relates to a device for controlling and regulating the internal combustion engine of a vehicle, in particular a diesel engine, with a basic controller which receives signals from sensors and sensors for detecting operating variables of the engine or vehicle, such as e.g. the speed, the accelerator pedal position, the engine temperature, etc. are supplied and an output signal of the basic controller for driving an electromechanical actuator for the fuel and / or air quantity supplied to the engine is used, with a speed calculator, to which signals from a speed sensor are supplied and which is used for the calculation a cylinder-specific speed of each cylinder is set up, as well as with a mean value computer for determining an average engine speed, with a comparator unit for outputting positive or negative change values for each cylinder, if the cylinder-specific speeds are below or above the mean speed, with a correction value memory with z cylinder memories, which, synchronized by a synchronization unit, the change values can be supplied, for cylinder-specific correction values, and with a cylinder connected downstream of the correction value memory and synchronized by the synchronization unit Selection unit for the output of the correction values, as well as with a summer, to which the output signal of the basic controller and the output signal of the cylinder selection unit are fed.

In the case of multi-cylinder diesel engines, due to manufacturing tolerances and different wear, there is a different output of the individual cylinders, even if the quantity control element, generally the control rod of the injection pump, remains unchanged. The same applies analogously to gasoline engines. Such a scatter in the performance of the individual cylinders not only causes uneven running and thereby a greater load on the bearings etc., but also increases the amount of harmful exhaust gas components or makes it difficult to set predetermined maximum values of such components. One tries therefore by individual Correction of the quantity of fuel supplied to the individual cylinders to compensate for the irregularities mentioned, the periodic fluctuations in speed usually being used as the output variable, which make it possible to draw conclusions about excessive or insufficient output of individual cylinders.

A device of the type mentioned at the outset is from the publication "The Nippondenso Electronic Control System for the Diesel Engine", F. Murayama and Y.Tanaka, in SAE paper 880489 on the International Congress and Exposition, Detroit, Michigan, Feb. 29 - 4th March 1988, became known. The deviation between maximum and minimum speed is determined for each cylinder and the arithmetic mean of these deviations is calculated. The deviations are then compared to this mean. If the cylinder-specific deviation is smaller than the mean value, a cylinder-specific correction value is increased, if the deviation is larger than the mean value, this correction value is decreased and if the deviation corresponds to the mean value, the correction value remains unchanged. These correction values determined in idle mode are added during operation to the value determined by the basic controller for the adjustment of the injection quantity actuator in order to compensate for cylinder-specific deviations in the combustion, but obviously the primary aim is quiet idling of the engine.

Similar devices for single-cylinder control of a diesel engine when idling are described in DE-OS3609245 and 3644639, the speed of the preceding cylinder always being used as a reference value for the speed deviation. Since instabilities of the single-cylinder control can very easily occur, this control is switched off immediately above the idling speed or in the event of changes in the accelerator pedal position, and the control is carried out in a conventional manner via the basic controller.

Another device disclosed in EP-A1-0140065 for single-cylinder control, which is intended to counteract vibrations of the vehicle when idling, is equipped with drift compensation, with an average value of the actuator signal being subtracted from the output signals of the integrating components of the controls assigned to the individual cylinders. The solution disclosed here has the disadvantage that since the mean value signal is not fed to the inputs of the integrator, but only acts after it, the integrator can start up very high values, which results in circuitry problems, as well as a few effective drift compensation, so that too only the idle case is dealt with.

The aim of the invention is to achieve stable operation of the additional single cylinder control, so that load change processes and in particular acceleration of the engine speed when the accelerator pedal is depressed with the single cylinder control switched on are also possible. The individual cylinder control should also be able to be carried out not only at idling speed but over the largest possible speed range.

This goal can be achieved with a device of the type mentioned at the beginning, in which according to the invention a drift compensator is provided, the number of cylinders corresponding to the number of inputs corresponding to the cylinder-specific correction values stored in the cylinder memories of the correction value memory and for the formation of an average value of the correction values is set up and which has subtracting elements which are connected upstream of each input of the correction memory and to which each cylinder-specific change value determined in the comparator unit and on the other hand an average value of the correction values are supplied.

The drift compensator constructed according to the invention prevents the correction values from "running away" during e.g. For longer acceleration phases, the mean value of the engine speed is naturally lower than the cylinder-specific engine speed values, and in this case the single-cylinder control would attempt an undesirable correction for lower amounts of fuel in all cylinders. The regulation would become unstable, but at least all the individual stores would quickly reach a limit value which would make further regulation difficult. This undesirable effect can be effectively combated by the invention.

Further features are characterized in the subclaims.

The invention and its further advantages are explained in more detail below with reference to exemplary embodiments which are illustrated in the drawing. 1 shows a block diagram of the device according to the invention, applied to a 6-cylinder diesel engine, FIG. 2 shows a similar block diagram, but in more detail, and FIG. 3a, b shows a possible flow diagram for single-cylinder control in a device the invention.

1 schematically shows a 6-cylinder diesel engine 1 with an injection pump 2 of known type, the control rod of which is adjustable by means of an electromechanical drive 3. For example, in the vicinity of the flywheel 4 of the engine 1, a speed sensor 5 is provided, which scans pins, not shown here, which are inserted on the flywheel 4 and which accordingly delivers pulses during engine rotation which correspond to specific angular positions of the flywheel 4. Such speed sensors are known and are disclosed, for example, in DE-A-3122533 (FIG. 3 and associated description). For safety reasons, two speed sensors can also be used, the alternator of the vehicle being used as a speed sensor, as described in the applicant's DE-A-3501435. There are further sensors 6 which provide signals with information about various operating states of the engine 1 or of the vehicle, e.g. B. temperature and pressure sensors. Also at least one needle stroke sensor 6 'is provided, which provides information about the position of the valve needle of an injection valve, such as in DE-A-3726712 by the applicant. In general, e.g. six such needle stroke sensors are used.

For the regulation or control of the motor 1, an electronic controller, here called basic controller 7, is used in a known manner. Such a controller contains arithmetic units that generate an output signal RW from supplied operating quantity signals calculate which determines the current control rod travel and thus the fuel quantity via the electromechanical drive 3.

The basic controller 7 are thus fed the operating variable signals of the sensors 6, 6 'and at least one output signal from a speed computer 8, which is an average speed or a corresponding signal n determined. The calculation of speed signals or average speeds is also known, reference being made to EP-A-333701 and the literature cited therein. The speed calculator 8 is shown in the general part of the basic controller 7 and only here, for the sake of clarity, separately from it. Finally, the output signal of an accelerator pedal position sensor 9 is fed to the basic controller.

A basic controller 7, as used here, generally has a PID control characteristic, as can be seen, for example, from DE-A-2735596. In principle, it forms a closed control loop via the control rod drive 3, the motor 1 and the speed sensor 5, the actual variable being the average speed n and the target variable in the basic controller 7 is calculated as a function of the supplied operating variable signals, of which of course the signal indicating the accelerator pedal position is an essential signal.

In addition to the control by the basic controller, there is a single cylinder control, which is explained in more detail below. The middle speed signal becomes a comparator unit 10 n as well as a cylinder-specific speed signal n _i determined in the speed computer 8. This signal n _i is determined by measuring the time period T _i via the combustion strokes of the individual cylinders, specifically by counting time in a time counter 11 and generating reciprocal values in a reciprocal value generator 12. The time counter 11, the reciprocal value generator 12 and an average value generator 13 are here as blocks of Speed calculator 8 shown (Fig. 2). The time is counted between pulses of the speed sensor 5, the pins on the Flywheel 4 and successive top dead centers of the cylinders (in the chronological order of ignition) correspond. The pulses do not have to correspond exactly to the top dead center, they can also each be generated a small angle of rotation before or after the top dead center, but should occur essentially in the vicinity of the top dead center, since in this case the most reliable information about the speed fluctuations is obtained.

As can be seen from FIG. 2, the comparator unit 10 in this exemplary embodiment contains a subtractor 14 to which the mean or the cylinder-specific speed signal n or n _{i are} supplied, and a signal generator 15 connected downstream of the subtractor, which outputs a change value + 1 if n _i < n , and a change value - 1 if n _i > n . If the cylinder-specific speed n _{i is} not or not significantly from the mean speed n deviates, no change value is output. However, the comparator unit 10 can generally output a change value ΔQ _i , the size of which also depends on the measure of the deviation between n _i and n can depend, as indicated in Fig. 1 at the output of the comparator unit 10 with ΔQ _i .

The change values ΔQ _i form the starting point for the single-cylinder control, because according to these change values the respective cylinders should receive more or less fuel so that uneven running is compensated for. The change values ΔQ _i are fed via a controlled switch 16 to a memory control unit 17 and from there to a correction value memory 18 with z, here z = 6, cylinder memories 18-i (FIG. 1).

For the required synchronization, a synchronization unit 19 is provided, on the one hand the signal of the speed sensor 5 and on the other hand the signal of at least one needle stroke sensor 6 'are supplied, so that an absolute, ie cylinder-related synchronization is possible. Instead of the signal from a needle stroke sensor, another signal can just as well can be used, which is derived, for example, from moving engine parts and enables absolute synchronization. If the invention is applied to a gasoline engine, it could be, for example, signals derived from the electrical ignition.

The synchronization unit 19 thus controls the memory control unit via an input 20 by means of a synchronization signal s in such a way that the signals ΔQ _i always get into the assigned memory 18-i. This is illustrated in FIG. 2 by a controlled switch 21.

The above-mentioned switch 16 is controlled by a comparator 22, which prevents the change values ΔQ _i from being supplied to the correction value memory 18 if the average speed n is above a predetermined value nKB, since it is not sensible to utilize the change values ΔQ _i at high speeds. As shown symbolically in FIG. 2, the comparator 22 can also be subject to hysteresis, ie — which has proven to be expedient — the switch-off threshold nKB-off is at higher speeds n than the switch-on threshold nKB-on.

2, a decision unit 23, shown as a multiplier, can be seen, which is connected upstream of the memory control unit 17 and which outputs the output signal Q _{i of} the comparator unit 10, the output signal ("0") or ("1") from the comparator 22 and a status signal st the synchronization unit 19 are supplied. This status signal has the value "0" as long as no synchronization has taken place, which is possible, for example, when the engine is started, and the value "1" if synchronization is present. Thus, the change values ΔQ _{i are} only passed on with existing synchronization and below a certain speed limit. The decision unit 23 corresponds to the controlled switch 16 of FIG. 1, but has an expanded function.

The cylinder memories 18-1 to 18-6 are each designed as summing or integrating memories, so that the correction value ΔRW _i stored _in each case increases or decreases depending on the sign (and size) of the corresponding change value ΔQ _i supplied. For the output of the correction values is also provided by the synchronization unit 19 via a synchronization signal s' synchronized cylinder selection unit 24, which is shown again in FIG. 2 as a controlled switch 25 and which serves for the correctly assigned output of the correction values to the corresponding cylinders. If desired, the correction values can ΔRW _i prior to their feed to a summer 26 where they are added to the respective output signal RW of the base controller 7, are multiplied in a multiplier 27 with a dynamics adaptation factor K _EZR. This may be advisable due to the digital development of the correction values for numerical reasons.

1, the cylinder selection unit 24 (or the multiplier 27) is followed by a switch 29 controlled by a comparator 28. The comparator 28 and the switch 29 have essentially the same function as the comparator 22 and the switch 16; the output of the correction values ΔRW _{i is} prevented if the average speed n is above a predetermined value nKA. As shown symbolically in FIG. 2, the comparator 28 can also be subject to hysteresis, ie the switch-off threshold nKA-aus at higher speeds n lie than the switch-on threshold nKA-on.

FIG. 2 shows a decision unit 30, represented as a multiplier, which is connected downstream of the cylinder selection unit 24 (or the multiplier 27) and to which the correction values Δ RW _i are thus supplied. Furthermore, the output signal ("0" or "1") from the comparator 28 and the status signal st of the synchronization unit 19 are fed to it, so that the correction values can only be output when synchronization is present and the average speed below one certain limit. The decision unit 30 corresponds to the controlled switch 29 of FIG. 1, however, has an expanded function.

For the reasons mentioned at the outset, a drift compensator 31 is provided which has z inputs (here z = 6), to which the z correction values of the cylinder memories 18-i are supplied. The arithmetic mean ΣΔ RW _i / z is formed in the drift compensator 31 by summing in a summer 32 (FIG. 2) and then dividing by k (here k = 6) in a divider 33. A subtractor 34-i is connected upstream of each cylinder memory 18-i or each input of the correction value memory 18, to which the change value ΔQ _i determined by the comparator unit 10 and the mean value of the correction values are supplied. The drift compensator 31 is also supplied with an activation signal from the synchronization unit 19, which occurs in synchronism with the rotation, for example every 10 or 20 revolutions, and the actual calculation or output of the arithmetic mean value to the subtracting elements 34-i, for which purpose controlled switches (not shown) or The like can be provided. Alternatively, the activation signal as can also occur at fixed time intervals, for example every second, in which case it is generated in a clock. It is in no way necessary to carry out the drift compensation with every combustion stroke, so that computing time can be saved for other calculations if the drift compensation is only carried out at intervals at which it is likely to be required.

The synchronization of the memory control unit 17 and the cylinder selection unit 24 by means of the signals s and s' causes the correct storage value to be output at the correct time. If the cylinder-specific speed for the i-th cylinder was measured, the injection into the (i + 1) -th cylinder begins almost simultaneously with the completion of this measurement, so that not only the injection in the i-th but also in the (i + 1) -th cylinder is "missed". It therefore makes sense to put the control rod in one Bring position that was calculated for the (i + 2) th cylinder. In other words, a phase shift of the synchronization between the memory control unit 17 and the cylinder selection unit 24 is ensured by at least one, preferably by two cylinders. This is symbolically represented in FIG. 2 by corresponding positions of the switches 21 and 25.

A possible embodiment of the cylinder memory 18-i is shown in FIG. 2. Each of the memories 18-i acts as a digital integrator or totalizer with limitation. At the input of a limiting unit 35-i is a summing element 36-i, on the one hand the output signal of the corresponding subtracting element 34-i of the drift compensator 31 and on the other hand the output signal of a reset element 37-i located in the feedback branch of the integrator (symbol z⁻¹: see Isermann , "Digital control systems", Springerverlag, Berlin / Heidelberg 1977). Such arrangements belong to the prior art.

Each cylinder memory 18-i with limiting unit 35-i can be set up to emit an indicator signal si which occurs if the stored correction value ΔRW _{i reaches} an upper or lower limit. This is indicated in FIG. 2 for a limiting unit 35-i. The indicator signals si can be OR-fed and used to trigger an error display or an alarm signal.

The drawing shows block diagrams with individual function blocks, but in practice, all or most of the function blocks are implemented in software in a microcomputer or a microcomputer system. A possible program sequence for this is illustrated in FIG. 3. In this flowchart, which otherwise does not require any further explanation in view of the preceding explanations, the term "limitations" is entered as the penultimate process. Hereby are mostly out Safety reasons and limitations of the actuator control signal RW + ΔRW _i addressed to comply with the prescribed exhaust gas limit values. Such a limiter is shown symbolically in FIG. 1 and designated 38. 1 also shows a controlled switch 39, which is controlled by a ready signal bs of the basic controller 7. This switch 39 is only closed when current values of the output signal RW are present at the output of the basic controller 7 in order to prevent the transmission of the mere correction values ΔRW _i to the drive 3 of the controller rod. The drive 3 for the control rod is usually integrated into its own servo loop, which has a feedback for the control rod position.

Claims (17)

1. A device for controlling and regulating the internal-combustion engine of a vehicle, in particular a diesel engine, with a base regulator (7), to which signals are supplied from transmitters and sensors for the detection of operating variables of the engine or respectively of the vehicle, such as e.g. the revolution rate, the gas-pedal position, the engine temperature, etc., an output signal of the base regulator being utilised for the drive of an electromechanical adjusting member for the amount of fuel and/or air supplied to the engine, with a speed calculator (8), to which signals of a speed sensor (5) are supplied and which is set up for the calculation of a cylinder-specific speed (n_i) of each cylinder as well as for the determination of a mean engine speed (i), with a comparator unit (10) for the issuance of positive or negative alteration values (Δ Q_i) for each cylinder, if the cylinder-specific speeds (n_i) lie under or above the mean speed (n), with a correction value store (18) with z cylinder stores (18-i) for cylinder-specific correction values (Δ RW_i), to which synchronised by a synchronisation unit (19), the alteration values (Δ Q_i) can be supplied, and with a cylinder selection unit (24), connected subsequent to the correction value store (18) and synchronised by the synchronisation unit, for the issuance of the correction values, as well as with a summator (26), to which the output signal of the base regulator (7) as well as the output signal of the cylinder selection unit (24) are supplied, characterised in that a drift compensator (31) is provided, to whose inputs, corresponding in their number to the number z of cylinders, the cylinder-specific correction values (ΔRW_i) deposited in the cylinder stores (18-i) of the correction value store (18) are supplied and which is set up for taking the mean of the correction values and which has subtraction members (34-i), which are connected prior to each input of the correction store and to each of which, on the one hand, each cylinder-specific alteration value (ΔQ_i) ascertained in the comparator unit (10) and, on the other hand, a mean value of the correction values is supplied.

2. A device according to claim 1, characterised in that mean value determination in the drift compensator (31) is effected in successive fixed intervals of time or in a speed-synchronous manner.

3. A device according to claim 2, characterised in that activation signals (as) of the synchronisation unit (19) are supplied to the drift compensator (31).

4. A device according to one of claims 1 to 3, characterised in that connected prior to the correction value store (18) is a store control unit (17), synchronised by the synchronisation unit (19), for the cylinder-specific assignment of the respective correction values to the cylinder stores (18-i).

5. A device according to one of claims 1 to 4, characterised in that each cylinder store (18-i) of the correction value store (18) is designed as a summating or an integrating store.

6. A device according to one of claims 1 to 5, characterised in that each cylinder store (18-i) of the correction value store (18) contains a limiter (35-i).

7. A device according to claim 6, characterised in that each limiter (35-i) is set up for the delivery of an indicator signal (si) when the fixed limiting value is reached.

8. A device according to one of claims 1 to 7, characterised in that output signals of a speed transmitter (5) and of at least one needle stroke sensor (6′) are supplied to the synchronisation unit (19).

9. A device according to one of claims 1 to 8, characterised in that the synchronisation unit (19) is set up for the delivery of a synchronisation status signal (st).

10. A device according to one of claims 1 to 9, characterised in that a first comparator (22) is provided, which delivers a first control signal, which below a speed limit (nKB) makes the calculation of the alteration values possible and which above this speed limit inhibits the calculation.

11. A device according to one of claims 1 to 10, characterised in that a second comparator (28) is provided, which delivers a second control signal, which below a speed limit (nKA) makes the issuance of the correction values possible and which above this speed limit inhibits the issuance.

12. A device according to claim 10 or 11, characterised in that the comparator (22, 28) is hysteresis-affected with respect to the speed limit (nKB, nKA).

13. A device according to one of claims 9 to 12, characterised in that the synchronisation status signal (st) makes the alteration of the correction values and the issuance of the correction values (RW_i) possible only if the synchronisation status is reached.

14. A device according to claim 1 and 4, characterised in that the store control unit (17) and the cylinder selection unit (24) are synchronised by means of the synchronisation unit (19) so as to be mutually phase-shifted by at least one cylinder.

15. A device according to one of claims 1 to 14, characterised in that a multiplier (27) for multiplication with a dynamics adaptation factor (K_EZR) is arranged subsequent to the cylinder selection unit (24).

16. A device according to one of claims 1 to 15, characterised in that the drift compensator (31) is set up for the formation of the arithmetical mean value of the correction values.

17. A device according to one of claims 1 to 16, characterised in that the speed calculator (8) is set up to determine the cylinder-specific speed (n_i) by measuring the duration (T_i) of the respective combustion stroke, which begins in the region of the upper dead centre of a cylinder and ends in the region of the upper dead centre of the next-firing cylinder.

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