EP0416270B1 - Method and apparatus to control and regulate an engine with self-ignition - Google Patents

Description

State of the art

The invention relates to a method and a device for controlling and regulating a self-igniting internal combustion engine according to the preambles of the main claims.

Such a method and such a device is known from US-A 4 790 277. This document describes a method and a device for controlling and regulating a self-igniting internal combustion engine. With this device, correction means are activated under certain conditions, which provide cylinder-specific correction values for cylinder equalization and store them permanently. This document does not contain any information on how to determine these correction values.

EP-A-170 891 describes an optimization method for determining the correction values. In the described method, with a constant intake air quantity, the injection quantity for two cylinders of the internal combustion engine is wobbled in opposite directions such that the total injection time or the total injection quantity of all cylinders is kept constant. It is then determined at which phase position of the wobble signal the maximum possible torque for the internal combustion engine is achieved. With this method, two pairs of values of the injection quantity must always be wobbled. This process is very complex and quite time-consuming.

Furthermore, from DE-OS 37 33 992 a method for controlling the fuel supply for a multi-cylinder engine is known. A fuel pump driven by the internal combustion engine has a plurality of outlets for connection to corresponding injection nozzles of the assigned internal combustion engine. Electromagnetically actuated valves control the amount of fuel to be delivered through each outlet. Depending on a fuel quantity signal, the valves are controlled by a power module. A comparison circuit compares the engine speed over a work cycle of the engine with the engine speed over the previous work cycle. Depending on this comparison, a distribution device delivers cylinder-specific control signals to the power modules.

This method has the disadvantage that the adjustment processes are carried out every combustion cycle. This is associated with a considerable amount of computing time.

From DE-OS 33 36 028 a method for influencing control variables of an internal combustion engine is known. To avoid swinging and "shaking" at idle, which are based on different amounts of fuel that are supplied to the individual cylinders, each cylinder is assigned a separate control system that determines the amount of fuel to be injected depending on a setpoint and an actual value. A controller is therefore required for each cylinder, which results in a very large number of components. With this method, the corrections have to be recalculated with every metering.

Furthermore, a device for drift compensation of fuel metering systems is known from DE-OS 30 11 595. This device does not regulate the measured quantity but only the position of a quantity-determining signal box. The task of this facility is to make the originally applicable assignment between the to maintain the total amount of fuel injected and the position signal of the quantity-determining member. Variations in the fuel supply to the individual cylinders are not compensated for.

Object of the invention

The invention is based on the object, in a method and a device for controlling and regulating an internal combustion engine of the type mentioned, to show ways of recognizing and compensating for variations in the fuel metering to the individual cylinders of the internal combustion engine. This should be done with the least amount of computing time and components.

Advantages of the invention

The methods and the corresponding devices according to the invention have the advantage over the prior art that the correction values are only calculated when certain operating conditions are present and are then available for the subsequent fuel metering. Scattering of the amount of fuel to be injected, which are based on manufacturing tolerances of the injection system, can be corrected when the internal combustion engine is operated for the first time. These correction values are then available for the further operation of the internal combustion engine and do not have to be recalculated with every metering. Scattering that only occurs when the internal combustion engine is operating can also be corrected.

Advantageous and expedient refinements and developments of the invention are characterized in the subclaims.

drawings

The invention is explained below with reference to the embodiments shown in the drawings. Figure 1 shows schematically an electronic control and regulating device for a self-igniting internal combustion engine, Figure 2 shows the relationship between control pulses and measured value, Figure 3 shows a flow chart for determining the correction values based on the measured value of the individual cylinders, Figure 4 shows the measured value depending on which cylinder is switched off 5 shows a flowchart to show the determination of the correction value as a function of the quantity reduction in the individual cylinders, FIG. 6 shows the course of the control signal for the individual cylinders, FIG. 7 shows a flowchart of a correction method in which the reduction in the fuel supply to a cylinder by an additional quantity in other cylinders is balanced. FIG. 8 shows the control pulses, FIG. 9 shows a flow diagram of a correction method in which a defined load is switched on.

Description of the embodiments

FIG. 1 shows an electronic control and regulating device for a self-igniting internal combustion engine. Various transducers 20 are arranged on the internal combustion engine 10. The signals from the transducers arrive on the one hand at an electronic control device 30 and on the other hand at an evaluation circuit 60. The electronic control device 30 generates a quantity signal depending on the output signals of the transducer 20 and the target value specification 35. The control device 40 processes the quantity signal, the control pulses of the evaluation circuit 60, and the correction values stored in a memory 50 into metering signals for the signal boxes 45 assigned to each cylinder. The signal boxes 45 determine the fuel quantity injected into the individual cylinders by pump elements. The evaluation circuit 60 receives measured values from the measured value sensor 20, and outputs control pulses to the control device 40 and correction values to the memory 50.

In normal operation, the device according to FIG. 1 operates as follows: Different measuring sensors 20 record measured values that characterize the operating state of the internal combustion engine. In particular, the speed N, the lambda value of the exhaust gas, the torque Md, the exhaust gas temperature T and possibly other variables can be detected. The electronic control device 30 calculates the fuel quantity to be injected on the basis of the actual value and the desired value. The actual value results from the signal of the measuring sensor 20. The output signal of the setpoint specification 35 serves as the setpoint.

The setpoint specification determines the setpoint based, among other things, on the accelerator pedal position, but the output signal of a vehicle speed controller 36 can also be used. The electronic control device also takes into account special operating conditions, such as. B. the start case, errors or emergency situations. You can also limit the amount of fuel to be injected, so that certain sizes, for. B. exhaust gas temperature, speed, lambda, smoke or load are not exceeded.

In conventional devices, this quantity signal is fed to an interlocking system which applies the same quantity of fuel to all cylinders. Other devices have a control device for each cylinder. In contrast, the device according to the invention comprises only one electronic control device for all cylinders, which emits a quantity signal. Based on this quantity signal and the correction values stored in the memory 50, the control device 40 calculates the metering signals for the signal boxes 45 assigned to the individual cylinders. Only one signal box per internal combustion engine can be present, then fuel is metered into the individual cylinders one after the other, or it is for each cylinder has an interlocking.

So z. B. diesel engines are known in which the signal boxes 45 are designed as solenoid valves. Depending on the presence of a metering signal, the solenoid valves open or close and thereby determine the start and end of the fuel supply to the individual cylinders.

The correction values are designed in a particularly advantageous manner so that the same amount of fuel is supplied to all cylinders, or so that the measured values (speed, torque or exhaust gas temperature) of internal combustion engine 10 are the same as a result of the burns in the individual cylinders.

If certain operating conditions exist, the evaluation circuit 60 is activated. The evaluation circuit 60 then outputs control pulses to the control device 40 and observes the reaction at the measurement sensors 20. Depending on the reaction of the measurement sensors 20, it then calculates correction values which are stored in the memory 50. The memory 50 is in a particularly advantageous manner a memory which does not lose its content when the internal combustion engine is switched off, but can be rewritten at any time.

The procedure is carried out in a particularly advantageous manner at different speed and load points, the correction values are then stored in a characteristic diagram depending on the speed and load. The quantity signal of the control device 30 is divided between the individual cylinders. These metering signals for the individual cylinders are then modified additively and / or multiplicatively by means of the correction values stored in the memory 50.

In order to compensate for manufacturing tolerances of the solenoid valves, the pump elements or the other components influencing the fuel quantity to be injected, the correction values are determined when the internal combustion engine is operated for the first time. This can e.g. B. in the last step of the manufacture of the internal combustion engine. After the internal combustion engine has been installed, a first test run takes place, in which the correction values are determined and stored.

If all of the measurement sensors required for the correction are present in the internal combustion engine installed in the motor vehicle, the correction can also be carried out as part of the service or at suitable stationary operating points.

The function of the evaluation circuit 60 is explained below with reference to the figures and flow diagrams. This is done, for example, for a 4-cylinder internal combustion engine, but the methods can also be easily transferred to an internal combustion engine with a different number of cylinders.

The metering signals with and without correction and the associated measured values are plotted in FIG. Figure 2a shows the original metering pulses, in which the duration of the metering pulses are the same for the individual cylinders. Figure 2 b shows the torque curve over a combustion cycle, that is, combustion takes place in all cylinders. Instead of the torque signal, a lambda signal, an exhaust gas temperature signal, or a speed signal can also be used. Figure 2 c shows the corrected metering signals. In this example, the metering signals for cylinders 1 to 3 are longer by the value DZ than the original metering signal Zi (i = 1,2,3,4). The metering signal of the cylinder 4, on the other hand, is shorter than the original metering signal Z4 by the time period DZ4. When activated with these corrected metering signals, the transducers deliver measured values corresponding to FIG. 2 d. They show a torque curve that is uniform for all cylinders.

If only one sensor is available for all cylinders, this must have sufficient temporal resolution. This means that the transducer must react to changes so quickly that the contributions of the individual cylinders can be distinguished in the course of the signal. If such a fast sensor is not available, e.g. B. in exhaust gas temperature measurement, each cylinder must be assigned a transducer, and the measured values of the sensors are evaluated directly.

The correction values are determined as shown in the flow chart in FIG. 3. After the start 100 of the correction value determination, in a first step 102 the evaluation circuit 60 sends a control pulse to the control device 40, on which the control device 40 measures a defined amount of fuel. In our case, the actuators of the individual cylinders become equal with metering signals Zi Duration Z applied. The duration Zi (i = 1,2,3,4) of the metering signals for the individual cylinders is shown in FIG. 2a. FIG. 2 b shows the course of a measured value, here the torque. A torque measurement value Mi (i = 1, 2, 3, 4) is assigned to each cylinder and is measured in step 104. In a further step 106, the evaluation circuit calculates the mean value MM of the measured values Mi. In a step 108, the differences Di (i = 1, 2, 3, 4) between the mean value MM, the individual measured values, and the measured values Mi of the individual cylinders educated. If the decision stage 110 recognizes that all measured values Mi are the same, that is to say that the differences Di are zero, that is to say smaller than a threshold, the correction values DZi are stored in the memory 50 in step 112 and the correction value determination is ended The correction values DZi determined by the evaluation circuit 60 are permanently stored in the memory 50.

In step 114, the evaluation circuit 60 calculates correction values DZi (i = 1, 2, 3, 4) depending on the differences Di between the measured values Mi for the individual cylinders and the mean value MM. The correction values DZi are proportional to the difference Di or to the ratio of the differences Di and the mean value MM. In step 116, the evaluation circuit 60 uses a control pulse to cause the control device 40 to take the determined correction values into account for the next fuel metering. The fuel is metered using the corrected metering signals.

A further exemplary embodiment of the evaluation circuit 60 is shown in FIGS. 4 and 5. To determine the correction values, the fuel supply to the individual cylinders is interrupted one after the other and the reaction of the measured value detected by the measured value sensor 20 is observed. If the same amount of fuel is metered to all cylinders with the same metering signal, this always results in the switching off of the fuel supply to the individual cylinders same change in measured value. If a cylinder, in this example cylinder 4, receives a larger amount of fuel, then when this cylinder is switched off, the measured value decreases more than that of the others.

FIG. 4 shows the reaction of the measured value when the individual cylinders are switched off. If all cylinders are supplied with fuel, the measured value M0 results. If the fuel supply to one cylinder is interrupted for a period T, this is reflected in a decrease in the measured value by the value Mi.

The flowchart in FIG. 5 shows the correction value determination. After the start step 200, the evaluation circuit 60 emits a control pulse to the control device 40 in step 202. This generates metering signals Zi (i = 1,2,3,4), on the basis of which all cylinders are supplied with a defined amount of fuel. It is particularly advantageous if all metering signals Zi have the same length. Then in step 204, the sensor 20 detects the measured value M0. In a particularly advantageous manner, one of the values exhaust gas temperature, lambda value of the exhaust gas, rotational speed or torque is used as the measured value, only one sensor being necessary.

In step 206, a counter i is now set to the value 1. In step 202, the metering signals Zi for the i-th cylinder are selected such that no fuel metering takes place Zi = 0. In step 210, the new measured value MNi is recorded. The fuel supply must remain switched off until the measured value MNi assumes a constant value. The difference Mi of the measured value from the measured value M0 before the i-th cylinder is switched off and the new measured value MNi after the switch-off is formed in the difference formation 212. These values are stored in step 214 until further processing. The subsequent interrogation unit 216 recognizes whether the counter has already reached the value 4. If i is less than 4, the counter is increased 218 by one. The query thereby recognizes whether the values Mi have been recorded for all cylinders.

If all measured values Mi for the individual cylinders have been recorded, the further processing takes place as described in FIG. 3, the interrogation unit 110 being omitted. The steps 226, averaging 106, forming a difference 108, calculating the correction values 114 for the individual cylinders and storing 112 the correction values DZi, are carried out in succession. It is particularly advantageous in this embodiment that only one transducer is required. This can e.g. B. be a transducer that is already available for controlling the internal combustion engine.

A further exemplary embodiment is shown in FIGS. 6 and 7. FIG. 7 shows a flow diagram of the correction value determination, FIG. 6 shows individual sequences of metering signals during the course of the correction value determination. In the first correction step 300, the evaluation circuit 60 generates a control pulse, upon which the control device 40 emits metering signals. These metering signals are shown in FIG. 6 a, the metering signals Zi (i = 1, 2, 3, 4) for the individual cylinders are all of the same duration Z. With this activation, the sensor 20 detects the measured value M0 in step 302, which is for the operation of all cylinders is characteristic.

In step 304, a counter i is initialized with 1. In a further step 306, a control pulse from the evaluation circuit 60 causes the control device 40 to apply such a metering signal Z = 0 to the signal box of the i th cylinder that no fuel is supplied to this cylinder, ie the cylinder is switched off. Furthermore, an additional signal ZD is calculated by which the metering signals Zm of the other cylinders are extended. In step 308, the duration of the metering signals Zm for the remaining cylinders is calculated as the sum of the original metering signal Z and the additional signal ZD.

The new measured value MN is then acquired in step 310. The difference formation 312 determines the difference D from the measured value M0 before the i-th cylinder is switched off and the measured value MN after the increase in quantity by ZD. Depending on the difference D, decision stage 314 selects the next step. If the new measured value MN is greater than the value M0 before switching off, the additional quantity ZD is reduced by a small amount b. If the new measured value is smaller than the old M0, the additional quantity ZD is increased by a small amount b. Step 308 then follows again. However, if the difference is zero, that is to say less than a predetermined threshold, Mi = 3 * ZD is set in step 320.

Query 322 recognizes from counter i whether the fuel supply to all cylinders has been interrupted once and the above method has been carried out once. If this is not the case, the counter i is increased 324 by one. The further calculation of the mean values MM, the difference values Di and the correction values DZi and the storage of the correction values is carried out in accordance with FIG. 3 (steps 106, 108, 112 and 114) described.

With the described methods, only a statement about the absolute outlet scatter results. The following modification provides information about the behavior of the signal box at a defined operating point. At the desired operating point, ie for a certain amount of fuel to be injected, the correction signal is determined by injecting an amount of fuel reduced by a certain amount. Instead of Zi = 0, Zi is only reduced by a small amount. The correction values for various operating points are calculated from the reaction of the measured value to this quantity reduction, as explained in the previous exemplary embodiment. By means of this modification, a statement can be made about the change in the quantity of fuel injected when the duration of the metering signal changes, at any operating point.

A further embodiment of the evaluation circuit 60 is shown in FIGS. 8 and 9. FIG. 9 again shows the corresponding flow chart. Figures 8 a and 8 b different sequences of metering signals in the course of the correction value determination. In the first step 400 of the correction, all signal boxes are subjected to the same metering signals Zi = Z according to FIG. 8 a. In the second step 402, the sensor 20 detects the measured value M0. By connecting a defined consumer in the third step 406, the internal combustion engine is subjected to a higher load. A defined load e.g. B. the alternator is switched on, it is known by how much the fuel supply must be increased. The additional signal ZD results from the additional fuel quantity.

As in FIG. 7, the counter i is set to one in step 404. In order to keep the speed or the delivered torque at the original value M0, the evaluation circuit 60 sends a control pulse to the control device 40, which increases the control pulses Zi (see also FIG. 8b) by the value ZD in the i-th cylinder. Corresponding to FIG. 7 (310, 312, 314), the new measured value MN is recorded 410 and compared 412 with the original M0. Depending on this comparison 414, the additional quantity ZD is increased 418 or decreased 416. The measured value acquisition outputs the original measured value M0 so Mi is set equal to ZD. The further evaluation takes place as described in the previous figures. The query device 422 (corresponding to FIG. 7 322) queries whether the increase ZD has already been determined for all cylinders. If this is the case, the counter i is increased 424 by 1. The further evaluation by averaging and the difference formation follows accordingly, as described in FIG. 3.

Claims (7)

1. Method for open-loop control and closed-loop control of an internal combustion engine with auto-ignition and with at least one measurement value sensor (20), one electronic closed-loop control device (30) for forming an amount signal for metering fuel, one open-loop control device (40) for cylinder-specific actuation of an actuator (45) which determines the amount of fuel injected in a cylinder by a pump element, correction means (50, 60) which provide cylinder-specific correction values for cylinder equalization and permanently store them being activated under certain conditions, the open-loop control device (40) feeding the actuators (45) with metering signals as a function of the amount signal and the correction values, characterized in that in order to determine the correction values a defined load is connected into the circuit, the correction value for a specific cylinder being produced from the change in the metering signal of the specific cylinder, which change is necessary in order to obtain the measurement value of at least one of the variables: exhaust gas temperature, lambda value, engine speed or torque, which measurement value was present before the connection of the defined load into the circuit.
2. Method for open-loop control and closed-loop control of an internal combustion engine with auto-ignition and with at least one measurement value sensor (20), one electronic closed-loop control device (30) for forming an amount signal for metering fuel, one open-loop control device (40) for cylinder-specific actuation of an actuator (45) which determines the amount of fuel injected in a cylinder by a pump element, correction means (50, 60) which provide cylinder-specific correction values for cylinder equalization and permanently store them being activated under certain conditions, the open-loop control device (40) feeding the actuators (45) with metering signals as a function of the amount signal and the correction values, characterized in that, in order to determine the correction values, the amount of fuel to be fed to a specific cylinder is reduced, the correction value for the specific cylinder being produced from the change in the metering signals of the other cylinders, which change is necessary in order to obtain the measurement value of at least one of the variables: exhaust gas temperature, lambda value, engine speed or torque, which measurement value was present before the reduction in the supply of fuel.
3. Method according to one of Claims 1 to 3, characterized in that the correction means (50, 60) are activated at the end of the line of the motor manufacturer, at certain intervals and/or at selected stationary operating points.
4. Method according to one of Claims 1 to 4, characterized in that the correction values are determined at various working points.
5. Method according to one of the preceding Claims 1 to 5, characterized in that the correction values are stored as a function of load and engine speed.
6. Device for open-loop control and closed-loop control of an internal combustion engine with auto-ignition and with at least one measurement value sensor (20), one electronic closed-loop control device (30) for forming an amount signal for metering fuel, one open-loop control device (40) for cylinder-specific actuation of an actuator (45) which determines the amount of fuel injected in a cylinder by a pump element, having means which under certain conditions activate correction means (50, 60) which provide cylinder-specific correction values for cylinder equalization and permanently store them, the open-loop control device (40) feeding the actuators (45) with metering signals as a function of the amount signal and the correction values, characterized in that means are provided which connect a defined load into the circuit, the means determining the correction value for a specific cylinder from the change in the metering signal of the specific cylinder, which change is necessary in order to obtain the measurement value of at least one of the variables: exhaust gas temperature, lambda value, engine speed or torque, which measurement value was present before the connection of the defined load into the circuit.
7. Device for open-loop control and closed-loop control of an internal combustion engine with auto-ignition and with at least one measurement value sensor (20), one electronic closed-loop control device (30) for forming an amount signal for metering fuel, one open-loop control device (40) for cylinder-specific actuation of an actuator (45) which determines the amount of fuel injected in a cylinder by a pump element, having means which under certain conditions activate correction means (50, 60) which provide cylinder-specific correction values for cylinder equalization and permanently store them, the open-loop control device (40) feeding the actuators (45) with metering signals as a function of the amount signal and the correction values, characterized in that means are provided which, in order to determine the correction values, reduce the amount of fuel to be fed to a specific cylinder, the means determining the correction value for the specific cylinder from the change in the metering signals of the other cylinders, which change is necessary to obtain the measurement value of at least one of the variables: exhaust gas temperature lambda value, engine speed or torque, which measurement value was present before the reduction in the supply of fuel.

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