EP0385969B1 - Apparatus for the control and regulation of a diesel engine - Google Patents

Abstract

A device for controlling a diesel engine, comprising an electronic base controller (3) which is supplied with signals from transmitters and sensors (4, 5, 6) for detecting operating variables of the engine and the output signal of which is utilised for driving an actuator (2) for the quantity of fuel supplied to the engine. This device has a soot value sensor (8), with a setpoint memory (12) for the maximum permissible soot value (AGMS), a memory (13) for values of an operating point vector (AP(tM)), which consists of values of operating variables, which values are retarded by the measuring dead time ( DELTA t) of the soot value sensor with respect to the time (tv) of the setpoint comparison, an adaptive engine map (15) in which a maximum permissible drive signal (RWM) is determined in dependence on the operating point vector (AP), a minimum-value selection stage (10) for driving the actuator (2), which is supplied with the drive signal (RWM) of the adaptive engine map (15) and the drive signal (RWB) calculated in the base controller (3), and a limit controller (14), which is supplied with the maximum permissible soot value (AGMS) of the setpoint memory (15), the actual soot value (AGi) and a status signal (S) of the minimum-value selection stage (10) and the output signal of which is supplied as a correction signal ( DELTA RW) to the input of the adaptive engine map (15). <IMAGE>

Description

The invention relates to a device according to the preamble of claim 1.

Devices for regulating diesel internal combustion engines of this type have become known in a large number, reference being made only to DE-A-31 22 553, for example.

In connection with such devices, various solutions are also known which relate to a limitation of the smoke emission, for which purpose different operating variables, in particular the speed, the fuel temperature as well as the pressure and temperature of the intake air, determine the maximum permissible number of smoke as input variables of a smoke map (DE-A-28 20 807).

An adaptive control of the exhaust gas turbidity caused by soot at full load has become known from DE-AS-36 38 474. The soot content in the exhaust gases is determined using an electro-optic soot sensor. If the soot sensor detects an excessive amount of soot, this amount is reduced in small steps in a device for adjusting the full-load injection quantity until the predetermined number of smoke is reached again. If the number of smoke falls below the predetermined number, the full-load injection quantity can be gradually increased again until the predetermined number of smoke is reached. A regulation depending on the speed or other operating parameters is not described in this document.

An adaptive control of an internal combustion engine with the aid of characteristic diagrams, the values of which are modified in accordance with the current operating conditions of the machine, can be seen, for example, from DE-A-34 08 215, 35 39 395 and 36 03 137 (time delay of parameters can be found, for example, in US Pat. A-4 130 095.)

EP-A2-148 107 further describes a full-load control of a diesel engine, which is based on the measured value of a soot value sensor, which obviously works on an inductive basis. Maximum amounts of fuel are recorded in a fixed full-load map. Depending on the soot value determined, the lower limits (signal T _L ) contained in the full-load map can be increased by increments ΔT _L. The control according to the soot value is always based on a fixed map, which means that due to the only gradual increase in the maximum fuel value, it is not optimally possible to adapt to rapidly changing processes, such as a sudden depression of the accelerator pedal for full acceleration.

DE-A1-28 29 958 relates to the control of an Otto engine according to the λ value. The oxygen content of the exhaust gases is measured before and after a catalyst 170 with O₂ sensors 184, 186, the measured values are processed in a circuit 200 and fed to a λ control circuit 246. Here, a PI controller is used to determine the value by which a setting factor in a table 244 has to be increased or decreased in order to be able to reach λ = 1 during the next operation at this operating point. Since an oxygen sensor only responds after a certain delay time T, the "history" of the engine (last measured values) must be temporarily stored in a short-term memory 250 in order to also have an operating point available if a correction is made to the working point in time associated with the delay time Setting value is necessary. The amount of the delay time is calculated from the speed and absolute pressure.

Although this known controller has an adaptive characteristic map, no limit value is determined, but is normally regulated according to the λ value, which, combined with the description of the delay time, leads to a high computing effort and corresponding computing times, which in connection with the the present problem are undesirable.

The object of the invention is to provide a control system for a diesel engine, the starting point of which is primarily the actual speed, but which also takes into account the soot content in the exhaust gases and ensures full load limitation which is adapted to different operating conditions. Particular attention should be paid to the fact that the soot measurement and evaluation is delayed for physical reasons, for example because the measurement is carried out in the exhaust pipe at a certain distance from the exhaust valves. The limitation should be quick, but the machine should have the maximum possible amount of fuel available in every operating situation.

The object of the invention is achieved with a device of the type mentioned at the outset, which is designed in accordance with the characterizing part of claim 1.

The invention enables a quickly effective full load limitation with optimal utilization of the machine performance and consideration of the maximum permissible soot value, whereby manufacturing tolerances and in particular signs of aging do not prevent the machine performance from being exploited to the smoke limit.

Further important features are characterized in the subclaims.

The invention and its advantages are explained in more detail below using an exemplary embodiment which is illustrated in the drawing. 1 shows a block diagram of a device according to the invention, FIG. 2 shows a diagram of the time sequence of the calculation processes in a device according to the invention, and FIGS. 3 and 4 show this flow in structure diagrams, and FIG. 5 shows a variant of the invention in FIG a section of a block diagram according to FIG. 1.

Fig. 1 shows schematically a diesel engine 1 with an injection pump 2, the control rod in a known manner electro mechanically, according to a signal RW, can be adjusted. To regulate the machine 1, a basic controller 3 is provided, which calculates a control rod control signal RW _{B as} a function of supplied operating variable signals. The essential operating variable signals are a speed signal n originating from a speed sensor 4 and an accelerator pedal signal f originating from an accelerator position transmitter 5. When calculating the control signal RW _B , further operating variables, such as, for example, the machine temperature, the air pressure, etc., can be taken into account, which is indicated by sensors 6.

In order to achieve a full load limitation in the control of the machine 1, which takes into account the soot value actually occurring, a soot value sensor 8 is provided in or on the exhaust pipe 7 of the machine 1, which sensor sensor evaluation, for example by optical turbidity measurement or other slower measurement methods 9 generates a signal AG _i corresponding to the actual value of the soot value.

As described in detail below, the soot value AG _i determined during operation influences a maximum permissible control signal RW _M for the control rod. The control signal RW _B calculated in the basic controller 3 and the maximum permissible control signal RW _M are fed to a minimum value selection stage 10. This has the consequence that the control of the machine 1 proceeds normally as long as the calculated control signal RW _{B is} smaller than the maximum permissible control signal RW _M present at the moment. Otherwise a limitation occurs, ie, RW = RW _M. The selection stage 10 contains a memory 10 'and, together with this memory, is set up to emit a status signal S which indicates whether the limitation at the time t _{M was} effective or not.

The following explains how the maximum permissible control signal RW _{M is} obtained according to the invention. A starting point is that the soot value sensor 8 or the sensor evaluation 9 has a measurement delay Δt, thus related a soot value signal AG _i (t _v -Δt) is present at the time tv of the setpoint comparison. This measurement delay is system-related and caused by one or more of the following factors: runtime of the exhaust gases up to the sensor, response time of the sensor, duration of the evaluation in the sensor evaluation.

The soot value signal AG _i is fed to a subtractor 11, to which a maximum target soot value AG _{MS is} fed as a second signal. In the simplest case, this value can be constant and stored in a setpoint memory. In the present exemplary embodiment, however, the maximum soot value AG _MS (t _M ) is generated in a setpoint map 12, specifically as a function of operating variables, such as at least the average speed n (t _M ), which lie behind the measurement dead time Δt and are stored in a memory 13. This memory 13 is shown in Fig. 1 as part of the basic controller 3, but it should be clear that the division into blocks is only for better understanding. In fact, the device according to the invention is largely implemented in software in one or more microcomputers. If the setpoint map 12 is not only the average speed n (t _M ) but other operating parameters, such as the machine temperature at time (t _M ), there is a multi-dimensional map instead of a two-dimensional one.

The output signal Δ AG = AG _MS - AG _{i of} the subtracting element 11 is fed to a control unit 14 ', which is formed in FIG. 1 together with the subtracting element 11 as a limiting controller 14. As further information, this limit controller 14 or the control unit 14 'also contains the status signal S already mentioned. Depending on these signals, the limit controller outputs a correction signal ΔRW for an adaptive map 15 in a manner described in more detail below.

In principle, this adaptive characteristic map 15 is a memory for working point-dependent values of the maximum permissible control signal RW _M , these values of the respective soot situation adjusted, so can be changed. For example, explanations of adaptive maps can be found in the three references mentioned at the beginning.

In order to synchronize the reading in and reading out, the characteristic diagram 15 is supplied with strobe signals sync-in and sync-out by the basic controller. Furthermore, the map receives 15 operating point vector signals AP (to) or AP (t _M ), which in the simplest case are signals of the average speed n (to) or n (t _M ) are, however, may also contain other operating variable signals which are representative, for example, of the machine temperature, air pressure, boost pressure etc. The operating point vector signal AP (t _M ) is available in the memory 13 for operating variable values which are past the measurement dead time Δt; it is required for the correct reading in of the correction signal ΔRW.

Without taking into account the adaptive properties of the characteristic diagram 15, a very specific, maximum permissible control signal RM _M is thus available for the limitation, depending on the working point vector AP (to) currently present.

Now results in the comparison of the soot actual value AG _i with the soot target value AG _MS in the subtractor 11 or in the limiting controller 14 ', whereby it should be noted that the values t associated with the time t _M are compared with one another, that the actual value is greater than the target value, ie that ΔAG <0, the limiting controller 14 requests a reduction in the corresponding map value in the map 15 by setting ΔRW = -c (c is a predetermined constant value), so that the corresponding map value is reduced by this size.

If, on the other hand, the actual value is less than the setpoint, that is AG> 0, which means that the limitation is selected too low, the limitation controller 14 requests an increase in the corresponding map value by setting ΔRW = + c, but only if in accordance with the status signal S (t _M ) the limitation at time t _{M was} active. If not was the case, the limiting controller 14 does not output a correction value, ie Δ RW = 0.

It should be mentioned that the limiting controller 14 can also be set up, for example, to emit a correction signal Δ RW which is proportional to the difference ΔAG.

The course of the calculations is shown in FIGS. 3 and 4 in structure diagrams and in addition in FIG. 2 in a time diagram. In the structure diagram it is assumed that the operating variable for determining the maximum permissible soot value AG _MS on the one hand and for controlling the adaptive map on the other hand not only the average speed n but also the machine temperature 9 is used.

The division into two structure diagrams of a computer level A and a computer level B is to be understood in such a way that the actual control of the machine in the basic controller 3 is carried out with high priority, whereas the exhaust gas treatment and also various other calculations, such as cylinder equalization, with low priority.

In another representation, the functional sequence is also evident from the diagram according to FIG. 2. This process begins at any time t₋₃. The basic controller (computer level A) reads in the measured values that it needs for control and provides the operating point vector of t₋₃ (INPUT). The operating point AP (t₋₃) is stored in the memory 13. The values stored there will later be required for the control measurement of the setpoint map 12 and the adaptive map 15.

On the other hand, shortly after the time t₋₃ if the LIMIT step is carried out on computer level A, it is determined whether the limitation is active at this time. Whether yes or no is determined in the LIMIT YES / NO MEMORY 10 ′ held, since this will later be required as information for the LIMIT CONTROLLER (computer level B) (status signal S).

At the time t₋₃ there is of course still an old map in the adaptive map 15, namely that which was updated, for example, with data from t₋₇. This old map is used in the LIMIT step (computer level A) until the process on computer level B of the soot measurement, the subsequent evaluation of the measurement, the use of the limit controller, which determines the change in the map, and the map correction is completed, so in the adaptive map, the new map, which has just been updated with the data from time t₋₃, is present. In this example, the new map is used for the first time at time to.

A major advantage of the invention lies in its independence from the measurement dead time required for soot measurement and the processing time which fluctuates as a result of different computer loads. Thanks to the invention, the full-load limitation based on a constant soot measurement can be carried out quickly and with the best possible use of the maximum possible machine power.

1 controls the control rod of an injection pump 2. However, the invention can also be applied to a machine which is equipped with individual pump nozzles, which will be briefly explained with reference to FIG. 5.

The basic controller 1 calculates an associated control signal RW _Bi for each of, for example, six pump nozzles 16 _i (in the case of a six-cylinder machine), which runs via the minimum value selection stage 10. This stage 10 is followed by a cylinder selection unit 17, which is controlled by a selection signal i originating from the basic controller 10. The individual control signals RW₁ to RW₆ are still a latch 18 supplied and from here to the electromechanical actuator drives of the individual pump nozzles 16 _i , the necessary driver circuits and possibly servo circuits are not shown for the sake of simplicity. Further details regarding the controlled single cylinder control can be found, for example, in the applicant's application DE 38 22 582, where further references to the technical background are also mentioned.

Finally, it should be mentioned that the invention could be applied in multiples according to the number of cylinders in a controlled single cylinder control, ie that an adaptive limitation according to the invention is assigned to each cylinder. In contrast, in the simplified embodiment according to FIG. 5, a maximum control signal RW _M acting jointly on all the individual cylinder control signals RW _{Bi is} calculated.

The term "soot" used in connection with the invention is of course intended to include any particle loading of the engine exhaust gases which is related to the "soot" or "smoking" of an internal combustion engine.

Claims (8)

1. A device for automatically controlling the amount of fuel supplied to a diesel engine, comprising

   - an electronic base controller (3) which is supplied with signals from transmitters and sensors (4, 5 and 6) for determining operating parameters of the engine, such as the speed (n), the accelerator pedal position and the engine temperature, and which in dependence on these operating parameters generates an actuating output signal for driving at least one electromechanical actuator (2) for controlling the fuel supply to the engine,

   - a soot value sensor (8) for measuring the soot load in the exhaust gas and a sensor signal evaluating means (9) delivering an actual soot value (AG_i),

   - a set value store (12) for the maximum permissible soot value (AG_MS),

   - a performance graph (15) in which a maximum permissible actuating signal (RW_M) is determined in dependence on a working point vector (AP) consisting of values of operating parameters, and from which the values of the actuating signal (RW_M(t_o)) at the actual time (t_o), controlled by a working point vector (AP(t_o)) of the base controller (3), are read out, and

   - a limitation controller (14) for comparing the set value (AG_MS) for the maximum permissible soot value in the set-value store (12) with the actual soot value (AG_i) and for generating a signal (ΔAG) corresponding to the result of the comparison and used as the corrective signal (ΔRW),

      characterised in that a store (13) or a delay element is provided for values of the working point vector (AP(t_M)) which lag behind the time (t_v) of the set-value comparison by an amount equal to the idle measuring time (Δt) of the exhaust-gas sensor and the sensor evaluation,
      the performance graph is an adaptive performance graph (15),
      a minimum value selection stage (10̸) is provided and is supplied with the actuating signal (RW_M) of the adaptive performance graph (15) and the actuating signal (RW_B) calculated in the base controller (3), and outputs a signal (RW) used for actuating the electromagnetic actuator (2), and
      the output signal from the limitation controller (14) is used as the corrective signal (ΔRW) and supplied to the input of the adaptive performance graph (15) controlled by a working point vector (AP(t_M)) which lags by the idle measuring time.
2. A device according to claim 1, characterised in that the limitation controller (14) contains a subtraction element (11) supplied with the actual soot value (AG_i) and the maximum permissible set soot value (AG_MS) from the set-value store (12), and also contains a control unit (14′) supplied with the output signal (ΔAG) from the subtraction element (11) and the status signal (S) from the minimum value selection stage (10̸).
3. A device according to claim 1 or 2, characterised in that the adaptive performance graph (15) is synchronised by strobe signals (sync in, sync out) from the base controller (3) in order to synchronise the reading-in and reading-out of the performance graph values.
4. A device according to any one of claims 1 to 3, characterised in that the set value store is a set value performance graph (12) controlled by values of at least one operating parameter, preferably the average speed n (t_M), lagging by the idle measuring time (Δt), and outputs a signal in the form of a set value (AG_MS(t_M)) for the maximum permissible soot value which is representative of a time (t_M) which lags by the idle measuring time (Δt).
5. A device according to any of claims 1 to 4, characterised in that the limitation controller (14) delivers a collective signal (ΔRW), the value of which is proportional to the difference (ΔAG) between the set value (AG_MS) and the actual value (AG_i) of the soot value.
6. A device according to any of claims 1 to 5, characterised in that the status signal (S) relates to an instant (t_M) which lags behind the actual time (to) by the idle measuring time (Δt), and a store (10̸′) is provided for this status signal (S).
7. A device according to claim 5, characterised in that the limitation controller (14) delivers a negative corrective signal (ΔRW) if AG_i ≧ AG_MS, a positive corrective signal if AG_i ≦ AG_MS and also if RW_M ≦ RW_B in accordance with the status signal (S), and a zero signal (ΔRW=0̸) if AG_i ≦ AG_MS and also if RW_B ≦ RW_M in accordance with the status signal (S).
8. A device according to any of claims 1 to 7, characterised in that when monobloc injection pumps and nozzles (16_i) in an engine (1) are actuated, the minimum value selection stage (10̸) is followed by a cylinder selection unit (17) actuated by the base controller (10̸) and followed by a store (18) for holding the selected actuation signals (RW_i) for the monobloc injection pumps and nozzles (16_i).

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