EP0353217B1 - 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 (8), to which performance quantity signals of the engine are fed and an output signal of the base controller is used for setting the fuel and/or air quantity, with a rotational speed calculator (9) for calculating a cylinder-specific rotational speed (ni) and a mean rotational speed signal () with a comparator unit (11) for outputting alteration values ( DELTA Qi) for each cylinder if the cylinder-specific rotational speeds (ni), are below or above the mean rotational speed (), with a correction value memory (19) with z cylinder memories (19-i) for the cylinder-specific correction values, it being possible for the alteration values ( DELTA Qi) to be fed to the cylinder memories (19-i). Each cylinder is allocated its own final controlling element for the fuel quantity, the output signal of each cylinder memory (19-i) together with the output signal of the base controller (8) being fed in each case to a control unit (3-i) for the allocated final controlling element, each cylinder memory (19-i) having k working- point-dependent memory areas (19-ij) and a memory-area selection unit (18) allocating the input and output of each cylinder memory (19-i) to a selected memory area or selected memory areas as a function of the mean rotational-speed signal (n) and/or other performance quantities according to a predetermined selection characteristic via an allocation unit (23-i, 24-i; 31) controlled by it. <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, the signals from sensors and sensors for detecting operating variables of the engine or vehicle, such as, for example, the speed, the accelerator pedal position and the engine temperature etc. are supplied and an output signal of the basic controller is used to adjust the amount of fuel and / or air supplied to the engine, with a speed computer to which signals from a speed sensor are supplied and which is set up to calculate a cylinder-specific speed n _{i of} each cylinder, and with an average value calculator for determining an average speed signal n , with a comparator unit for the output of positive or negative change values for each cylinder, if the cylinder-specific speeds n _i below or above the average speed n lie, with a correction value memory with z> 1 cylinder memories for the cylinder-specific correction values, the cylinder memories, synchronized by a synchronization unit, the change values can be supplied, and with a summing device, which can be supplied with the output signal of the basic controller and the correction values of the correction value memory.

In the case of multi-cylinder diesel engines, due to manufacturing tolerances and different wear and tear, 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 thus 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. Attempts are therefore made to compensate for the irregularities mentioned by individually correcting the quantity of fuel supplied to the individual cylinders, using as an output variable mostly the periodic speed fluctuations are used, 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 - March 4, 1988. The deviation between the 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 at idle speed are described in DE-OS 3 609 245 and 3 644 639, the speed of the previous 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 takes place in a conventional manner via the basic controller.

A single cylinder control is also known from EP-A-140 065, the main aim of which is to avoid low-frequency vibrations of the "vehicle / engine" system is. The known control has a number of speed memories corresponding to the number of cylinders (here z = 4), the outputs of which are all supplied on the one hand to an averager and on the other hand each to one of four controllers. The output of the mean value generator is fed to the controllers as a reference signal. A synchronizing device synchronously places the outputs of the four regulators at the input of a fuel metering device, to which the accelerator pedal signal and the output of an idle control are also fed. Individual actuators associated with each cylinder are not disclosed in the document. However, it should be noted that drift compensation is provided which is intended to ensure that the sum of the z = 4 manipulated values is zero, ie that the control can only influence the injection system dynamically.

The object of the invention is to enable effective and stable single-cylinder control not only in idle mode but as far as possible over the entire speed range of the engine.

This object is achieved with a device of the type mentioned at the outset, in which, according to the invention, each cylinder is assigned its own actuator for the fuel quantity, the output signal of each cylinder memory together with the output signal of the basic controller being fed to a control unit for the associated actuator, each cylinder memory k > 1 has memory areas dependent on the operating point, a memory area selection unit is provided which contains the average speed signal n , and / or other operating variables, such as average actuator travel, engine temperature etc., are supplied as selection criteria and the storage area selection unit as a function of these selection criteria according to a predetermined selection characteristic via an assignment unit controlled by the input and output of each cylinder memory to a selected storage area or selected storage areas assigns.

The division according to the invention into memory areas dependent on the operating point takes into account the speed-dependent behavior of the engine or the individual cylinders and the corresponding individual cylinder correction that is required as a function of speed.

Further important 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, based on a possible block diagram, the device according to the invention, applied to a 6-cylinder diesel engine, FIG. 2 shows a similar block diagram, but goes into more detail, FIG. 2a shows the block diagram of a modified cylinder memory and FIG. 3 shows a possible one Structogram for single cylinder control in a device according to the invention.

In Fig. 1, a 6-cylinder diesel engine 1 is shown schematically with six pump nozzles 2-i, the flow control elements are adjustable electromechanically by means of associated servo drives 3-i. Such pump nozzles and the drives of their volume control elements are, for example, the subject of DE application 38 11 844 of the applicant, in which reference is also made to DE-A-2845 139 and AT-PS 372 502 in relation to the prior art.

Regarding the term "actuator" used, it should be noted that the invention relates not only to those injection elements in which, for example, a control rod is adjusted, i.e. is shifted or a quantity actuator is rotated, but in general on each controlled injection unit, e.g. also on solenoid valves.

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, inserted on the flywheel 4 and accordingly delivers pulses during engine rotation which correspond to specific angular positions of the flywheel 4. Such speed sensors are also known and are disclosed, for example, in DE-A-31 22 533 (FIG. 3 and associated description). For safety reasons, two speed sensors can also be used, wherein the alternator of the vehicle can be used as a speed sensor, as described in DE-A-35 01 435 by the applicant. Further sensors 6 are also provided, which provide signals with information about various operating states of the engine 1 or of the vehicle, e.g. Temperature and pressure sensors. In addition, a needle stroke sensor 7-i is generally provided in each pump nozzle 2-i, which provides information about the position of the valve needle of an injection valve, e.g. in DE-A-37 26 712 of the applicant.

For the regulation or control of the motor 1, an electronic controller, here called basic controller 8, is known, used. Such a controller contains computing units which calculate an output signal RW from supplied operating variable signals, which, via the servo drives 3-i, determines the current position of the quantity control element of each pump nozzle 2-i and thus the amount of fuel to be injected. The operating variable signals of the sensors 6 and 7-i are thus fed to the basic controller 8 and at least one output signal of a speed computer 9, 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 the applicant's DE application 38 08 819 and the literature cited therein. The speed calculator 9 is shown in the general part of the basic controller 8 and only here, for the sake of clarity, separately from it. Finally, the output signal of an accelerator pedal position sensor 10 is fed to the basic controller.

A basic controller 8, as used here, generally has a PID control characteristic, as can be seen, for example, from DE-A-27 35 596. It forms, in principle, via which the servo drives 3-i, the motor 1 and the speed sensor 5 form a closed control loop, the actual variable being the average speed n and the target variable in the basic controller 8 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 11 n and also a cylinder-specific speed signal n _i determined in the speed computer 9. This signal n _i is determined by measuring the time period T _i via the combustion strokes of the individual cylinders, specifically by counting the time in a time counter 12 and generating reciprocal values in a reciprocal value generator 13. The time counter 12, the reciprocal value generator 13 and an average value generator 14 are here shown as blocks of the speed calculator 9 (Fig. 2). The time is counted between pulses from the speed sensor 5, which correspond to pins on the flywheel 4 and successive top dead centers of the cylinders (in the chronological order of ignition). The pulses do not have to correspond exactly to the top dead center, they can 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 11 in this exemplary embodiment contains a subtractor 15 to which the middle or cylinder-specific speed signal n or n _{i are} fed, and a signal generator 16 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 does not differ from the mean speed, or not significantly n deviates, no change value is output. However, the comparator unit 11 can generally output a change value Δ Q _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 11 with Δ Q _i .

The change values Δ Q _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 Δ Q _i are fed via a memory control unit 17 and a memory area selection unit 18 to a correction value memory 19 which has z, here z = 6, cylinder memories 19-i with k memory areas 19-ij each. This can be seen from FIG. 2, where the division into three memory areas 19-1j is shown for the cylinder memory 19-1.

A synchronization unit 20 is provided for the necessary synchronization, to which the signal from the speed sensor 5 on the one hand and the signal from at least one of the needle stroke sensors 7-i are supplied on the one hand, so that an absolute, i.e. cylinder-related synchronization is possible. Instead of the signal from a needle stroke sensor, another signal can also be used, e.g. is derived from moving engine parts and enables absolute synchronization. If the invention is applied to a gasoline engine, it could e.g. are signals derived from the electrical ignition.

The synchronizing unit 20 controls the memory control unit 17 by means of a synchronizing signal s in such a way that the change values Δ Q _i always reach the assigned cylinder memory 19-i. This is illustrated in FIG. 2 by a controlled switch 21. 2 also shows a controlled switch 22 which is located between the comparator unit 11 and the memory control unit 17 and is shown here as a multiplier. The switch 22 is controlled by a status signal st of the synchronization unit 20. This status signal has the value "0" as long as no synchronization has taken place, which is possible, for example, when starting the engine, and the value "1" if synchronization is present. The change values .DELTA.Q _i are thus only passed on with existing synchronization.

The memory area selection unit 18, for example, as shown in FIG. 2, consists of z-controlled switches 23-i, 24-i at the input and at the output of each cylinder memory 19-i, each switch having a k position. In the example according to FIG. 2, all z switches 23-i, 24-i are controlled by a speed range discriminator 25, which is the mean speed signal n is fed and connects via the switches 23-i, 24-i to the speed range corresponding to this speed range memory area 19-ij with the input and output of each cylinder memory 19-i. In the example according to FIG. 2, the range is thus selected exclusively according to the selection criterion "average engine speed", but other operating variable signals can also be supplied to the function of the memory area selection unit 18, such as a signal r according to FIG. Each cylinder memory 19-i thus represents a three-dimensional correction field for each cylinder.

The cylinder memories 19-i and their memory areas 19-ij are each designed as summing or integrating memories, so that the stored correction value Δ RW _ij increases or decreases depending on the sign (and size) of the corresponding supplied change value Δ Q _i . If desired, the correction values Δ RW _i may be multiplied in a respective multiplier 27-i with a dynamic adjustment factor K _EZR before their supply to a respective summer 26-i, in which they are added to the respective output signal RW of the base regulator 8. This may be advisable due to the digital development of the correction values for numerical reasons.

2, the summers 26-i are drawn with an additional subtracting input, to each of which a feedback signal m from an actuator feedback 28-i is supplied. The servo drives 3-i namely have an analog servo controller 29-i which acts on the actuator 30-i mechanically connected to the feedback 28. This provides a closed servo circuit for the actuator of each pump nozzle 2-i. With regard to further details of such servo circuits, reference can be made to the applicant's DE-A-37 40 443.

A modification of the cylinder memories 19-i is shown in FIG. 2a, in which an interpolation and arithmetic unit 31 is assigned to each memory area 19-ij. This unit takes on the one hand the function of the switches 23-i, 24-i of FIG. 2 and on the other hand enables an interpolation between speed bases n _j . This means, that the memory areas 19-ij are assigned to discrete speed values and, thanks to the unit 31, the output of interpolated intermediate values is possible.

1 and 2 also show a drift compensator 32 which prevents the correction values from "running away". During longer acceleration phases, for example, 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 memories or memory areas would quickly have reached a limit value which would make further regulation difficult. The drift compensator 32 has k summers 33-j (FIG. 2), each summator being supplied with the z correction values of the memory areas 19-ij with the same index j. The arithmetic mean value Δ RW _ij / z is formed in each divider 34-j. A subtractor 35-ij 35-ij is connected upstream of each input of each memory area 19-ij, on the one hand the change value Δ Q _ij determined by the comparator unit 11 and assigned by the selection unit 18 and on the other hand the mean value of the correction values coming from the corresponding divider 34-j is fed.

The drift compensator 32 is also supplied with an activation signal as (FIG. 1) of the synchronizing unit 20, which occurs in rotation-synchronous fashion, for example every 10 or 20 revolutions, and the actual calculation or output of the arithmetic mean value to the subtracting elements 35-ij causes 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.

A possible embodiment of the memory areas 19-ij is shown in FIG. 2 for the first cylinder memory 19-1. Each memory area 19-1k acts as a digital integrator or totalizer with limitation. At the input of a limiting unit 36-1j is a summing element 37-1j, on the one hand the output signal of the corresponding subtracting element 35-1j of the drift compensator 32 and on the other hand the output signal of a reset element 38-1j located in the feedback branch of the integrator 19-1j (symbol z⁻¹: see Isermann, "Digital Control Systems", Springerverlag, Berlin / Heidelberg 1977). Such memories belong to the prior art.

Each memory area with limiter unit 36-1j can be set up to emit an indicator signal which occurs if the stored correction value Δ RW-ij reaches an upper or lower limit. This is indicated in Fig. 2 for the first cylinder memory 19-1 for a memory area 19-1j with the signal d-1j. All indicator signals d-ij can be supplied with an OR operation 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 purpose is illustrated in the structure diagram according to FIG. 3, which does not require any further explanation in view of the above explanations.

Claims (15)

1. Device for controlling and adjusting the combustion engine of a vehicle, in particular a diesel engine, having a base adjuster (8), to which signals from emitters and sensors are supplied to record operating parameters of the engine or vehicle, such as for example the speed, the accelerator position, the engine temperature etc., and an output signal from the base adjuster is used to set the amount of fuel and/or air supplied to the engine, having a speed computer (9), to which signals from a speed sensor (5) are supplied and which is equipped to calculate a cylinder-dependent speed n_i for each cylinder and to determine an average speed signal (n), having a comparator unit (11) to emit positive or negative modification values (Δ Q_i) for each cylinder if the cylinder-dependent speeds (n_i) are below or above the average speed (n), having a correcting value store (19) with z > 1 cylinder stores (19-i) for the cylinder-dependent correcting values, wherein the modification values (Δ Q_i) can be supplied to the cylinder stores (19-i) synchronised by a synchronising unit (20), and having a summation device, to which the output signal from the base adjuster (8) and the correcting values from the correcting value store (19) can be supplied, characterised in that a separate adjuster (30-i) for the amount of fuel is assigned to each cylinder, wherein the output signal of each cylinder store (19-i) together with the output signal of the base adjuster (8) is supplied in each case to a control unit (3-i) for the assigned adjuster (30-i), each cylinder store (19-i) has k > 1 operating point-dependent store regions (19-ij), a store region selection unit (18) is provided, to which the average speed signal (n) and/or other operating parameters, such as average adjuster path, engine temperature etc., are supplied as selection criteria, and the store region selection unit (18) assigns input and output of each cylinder store (19-i) to a selected store region or selected store regions via an assigning unit (23-i, 24-i, 31) controlled by it as a function of these selection criteria according to a predetermined selection characteristic.

2. Device according to claim 1, characterised in that the average speed signal (n) is supplied to the store region selection unit (18), the selection is carried out according to k speed ranges and each cylinder store (19-i) has k store regions (19-ij).

3. Device according to claim 1 or 2, characterised in that a drift compensator (32) is provided, to which the z.k correcting values of each of the k store regions (19-ij) of all z cylinder stores (19-i) stored in the correcting value store (19) are supplied, and which is equipped to form k averages of each of the z correcting values of the first to the k-th store regions (19-ij), and a subtracting member (35-ij), to which the correcting value determined in the comparator unit (11) on the one hand and the associated average formed in the drift compensator (32) on the other, is supplied, is connected upstream of each input of each store region (19-ij) of the z cylinder stores (19-i).

4. Device according to claim 3, characterised in that the average formation in the drift compensator (32) is carried out at sequential fixed time intervals or speed-synchronously.

5. Device according to claim 4, characterised in that activating signals (as) from the synchronising unit (20) are supplied to the drift compensator (32).

6. Device according to one of claims 3 to 5, characterised in that the drift compensator (32) is equipped to form the arithmetic average of the correcting values.

7. Device according to one of claims 1 to 6, characterised in that a store control unit (17) synchronised by the synchronising unit (20) is connected upstream of the correcting value store (19) for cylinder-dependent assignment of the particular correcting values at the cylinder stores (19-i).

8. Device according to one of claims 1 to 7, characterised in that each store region (19-ij) of the cylinder stores (19-i) of the correcting value store (19) is designed as an adding or integrating store.

9. Device according to one of claims 1 to 8, characterised in that each store region (19-ij) of the cylinder stores (19-i) of the correcting value store (19) preferably contains a limiter (36-ij).

10. Device according to claim 9, characterised in that each limiter (36-ij) is equipped to emit an indicator signal (d-ij) on reaching the fixed limiting value.

11. Device according to one of claims 1 to 10, characterised in that at least one interpolation and computing unit (31) assigned to the store regions (19-ij) of each cylinder store (19-i) is provided.

12. Device according to one of claims 1 to 11, characterised in that output signals from a speed sensor (5) and at least one needle stroke sensor (7-i) are supplied to the synchronising unit (20).

13. Device according to one of claims 1 to 12, characterised in that the synchronising unit (20) is equipped to emit a synchronising status signal (s_t) which only makes a change in the correcting values possible if the synchronising status is achieved.

14. Device according to one of claims 1 to 13, characterised in that a multiplier (27-i) is inserted after each of the z cylinder stores (19-i) for multiplication using a constant dynamic matching factor (K_EZR).

15. Device according to one of claims 1 to 14, characterised in that the speed computer (9) is equipped to determine the cylinder-dependent speed (n_i) by measuring the duration (T_i) of the particular combustion stroke, which starts in the region of the upper dead point of a cylinder and stops in the region of the upper dead point of the next cylinder to ignite.

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