EP0837984B1 - Method and device for controlling an internal combustion engine - Google Patents

Abstract

The invention concerns a method and device for controlling a motor vehicle internal combustion engine, according to which a desired torque value is predetermined and divided into at least two desired values, which are used to adjust the filling of the internal combustion engine, and at least one further performance parameter which brings about a rapid variation in torque, the at least two desired values having different values in at least one operating state.

Description

State of the art

The invention relates to a method and a device for controlling an internal combustion engine according to the Preambles of the independent claims.

Such a method or such Device is known from DE-A 42 39 711. There will by the driver or in special operating conditions by others Control or regulating systems a setpoint for a torque the internal combustion engine specified. This setpoint will on the one hand into a target filling value and then into one Setpoint for controlling the air supply to the internal combustion engine for example implemented via a throttle valve, on the other hand in an ignition angle setting and / or Number of cylinders to which the fuel supply is interrupted. By controlling the The actual torque is the performance parameter of the internal combustion engine the internal combustion engine the predetermined target torque value approximated.

In addition to this, it is known from WO-A 95/24550, in addition to Ignition angle adjustment and / or cylinder blanking Influencing the mixture composition of the Make internal combustion engine.

Torque reduction in an internal combustion engine desired (if the target value is specified accordingly), see above is usually with the desired dynamics set because of the very quickly on the torque interventions in the ignition angle, in the Fuel supply to the cylinders and / or in the Mixture composition immediately reduces the engine torque can be. The slower filling procedure is with the Torque reduction of this quick torque change overlaid. However, if an increase in torque is required, then so this can only be done by increasing the filling, if all cylinders are fired, the mixture composition stoichiometric and the ignition angle not late is moved. The dynamic of this filling increase is however limited by the dynamics of the throttle valve actuator and / or the intake manifold dynamics.

It is an object of the invention to control the dynamics of the Torque of an internal combustion engine, at least in some Optimize operating conditions.

This is due to the distinctive features of the independent claims achieved.

Advantages of the invention

The dynamics of the change in torque, especially with one Torque increase is optimized. It is particularly advantageous that even in such operating conditions, the actual torque Internal combustion engine essentially the target torque with the required dynamics follows.

The solution according to the invention is particularly advantageous in Operating states in which the torque change, especially the moment build-up, known in advance is. This applies, for example, to a change in torque by the driver using the pedal, during interventions a traction or engine drag torque controller, a driving dynamics controller or similar control systems, at the connection of loads such as air conditioning, in Start case and / or warm-up in connection with Catalyst heating measures too. In these operating conditions is achieved by splitting the torque setpoint to a Setpoint for the fill path and a setpoint for the quick interventions that take on different values can make the moment change dynamically correct.

It is particularly advantageous that through the formation of so-called reserve moments the working point of the Internal combustion engine can be moved stationary, so that all torque requirements with the required dynamics can be realized.

It is particularly advantageous that through the introduction appropriate limits ensure that requested moment, especially in the fill path, is actually feasible.

Further advantages result from the following Description of exemplary embodiments or from the dependent claims.

drawing

The invention is described below with reference to the drawing illustrated embodiments explained in more detail. Figure 1 shows the structure using an overview block diagram the torque control according to the invention. In the figures 2 and 3 are block diagrams showing a show preferred embodiment. Another one Exemplary embodiment is based on the block diagrams of Figures 4 and 5 shown. Figure 6 finally shows based on time charts when using the invention Solution.

Description of exemplary embodiments

An electronic control unit 10 is shown in FIG Control of the torque of an internal combustion engine shown, the at least one, not shown Contains microcomputer. The implemented in the microcomputer Programs are shown as blocks in FIG. About the Output lines 12, 14 and 16 affect the control unit 10 the air supply to the internal combustion engine, the Fuel supply (blanking and / or Mixture composition) and the ignition angle of the Internal combustion engine. Via input lines 20, 22 and 24 to 26 are the control unit 10 for Torque control processed operating quantities fed. From at least one further control unit 28, for example, a traction control unit, the Control unit 10 is supplied with a setpoint for a torque. From a measuring device 30 for detecting the Accelerator pedal actuation is via the control unit 10 Input line 22 an the degree of actuation β representing signal supplied. Furthermore, the Control unit 10 of measuring devices 32 to 34 via the Input lines 24 to 26 signals supplied, the further Operating variables of the internal combustion engine and / or the Vehicle, for example engine speed, engine load, Represent engine temperature, etc.

The operating variables supplied to the control unit 10 are separated in a first program block 36 in the manner described below into a target torque value MI _target-L for the filling path and into a target value MI _target for influencing the fuel metering and / or the ignition angle. The torque _setpoint MI _Soll-L for the filling path is entered in a subsequent program block 38, taking into account selected operating variables which are supplied to the control unit 10 via the lines 24 to 26, or variables derived therefrom in the manner known from the prior art mentioned at the outset Filling _setpoint rl _setpoint converted. This setpoint charge value is converted in program block 40, as described in the prior art mentioned at the beginning, in the context of control loops into a control signal for an electrically actuable throttle valve for adjusting the air supply. The filling of the internal combustion engine is therefore set in such a way that it approximates the target value and thus the actual torque the target torque value. In parallel, the torque _setpoint MI _Soll for the rapid torque intervention is converted in the known manner in the program block 42 into control signals for the mixture supply (cylinder blanking and / or setting the mixture composition) and / or for setting the ignition angle and output via the lines 14 and 16 shown symbolically.

The basic idea of the solution according to the invention is that a Present torque setpoint into a setpoint for the Fill path and the ignition angle path is separated. In the two setpoints have at least one operating state different torque values and become parallel to each other by adjusting the filling or Fuel supply and / or ignition angle realized. It is provided in a preferred embodiment that the Separation only takes place when the future value the torque setpoint is greater than the current setpoint, i.e. with torque increases.

Figure 2 shows a first embodiment of the separation the torque setpoints. The solution shown is applied when the result of the actuation signal β derived driver request in the direction of increasing torques changes. It is assumed that only the Driver request determines the target torque and no further Interventions (e.g. from a traction control system) available.

In a first map 100, the torque MI _Ped set by the driver via the pedal actuation is determined from the actuation degree signal β and at least the engine speed N _Mot . This pedal torque is interpolated between a minimum and a maximum torque value in the subsequent interpolation program 102. These values are predetermined and are preferably at least speed-dependent. The driver's desired torque MIFAR formed by the interpolation is then filtered in the filter element 104 in accordance with a predetermined filter function (eg first-order low-pass filter). In the described operating situation, the filtered value is considered as the target torque MI _target and is supplied to the block 42 for determining the influencing of the fuel supply and / or the ignition angle. In a known manner, block 42 calculates from the supplied setpoint torque value setpoints for the number of cylinders to be blanked (RED _setpoint ) a setpoint value for the mixture composition λ setpoint and a setpoint value for the ignition angle setting (ZW _setpoint ). These are set via the symbolic output lines 14 and 16.

In a steady operating state or when the torque is reduced, the filtered target torque value MI _{Soll is,} in a preferred embodiment, also the target torque value evaluated to determine the target filling. However, if the driver changes the pedal position in a way that leads to an increase in torque, the setpoints, which are separate for filling path and quick interventions, assume different values. In the exemplary embodiment according to FIG. 2, the determination of the target filling value is then based not on the filtered target torque value but on the unfiltered target torque value MIFAR. This setpoint torque value is fed to program block 38 for determining setpoint charge rl _setpoint , which in turn is converted in program block 40 into control signals for a throttle valve and possibly a turbocharger for influencing the cylinder charge.

In certain operating situations, for comfort and / or exhaust gas reasons, the target torque value is only achieved by adjusting the filling and the ignition angle. It must be ensured that the target torque specified by the driver or other regulating or control systems can actually be set. Adjustable ignition angles must therefore be taken into account at the latest for the respective operating point. This firing angle is a function of operating variables, preferably the engine speed and the engine load, and is determined by the running limit of the engine. According to the broken line in FIG. 2, in this case the target torque specified for the air path is limited on the basis of the _target torque MI _{target to be set} and at least the latest possible ignition angle. In this way, the torque change specified by the driver can be implemented by adjusting the filling and quickly adjusting the ignition angle. The actual torque is then quickly brought to the target torque.

This limitation is shown in the block diagram of Figure 3. The target torque for the air path MI _{target-L is determined} on the basis of a minimum value selection 200 from the _target torque value MI _target corrected in accordance with the ignition angle conditions and an unlimited target value MI _{target-L *} predefined for the filling path.

Three maps 202, 204 and 206 are provided in which, depending on the engine speed and engine load, the optimal ignition angle ZW _Opt , at which the internal combustion engine has the highest efficiency, the basic ignition angle at the current operating point ZW _Base , which adjusts the ignition angle without external intervention (for example by traction control) and the ignition angle ZWM that can be set as late as possible at the current operating point is stored. The basic ignition angle describes the ignition angle that is set at the current operating point of the internal combustion engine without external intervention. The difference between the optimum ignition angle and the basic ignition angle is formed in a first connection point 208, while the difference between the optimum and the latest possible ignition angle is formed in a second connection point 210. The two difference values are converted into correction moments (etazwbase, etazwm) in efficiency curves 212 and 214. These correction torques represent the change in efficiency or the change in torque that would occur when the respective ignition angle was set due to the deviation from the optimum value.

The correction values are used to correct the target torque value MI _target . The ignition angle set in the current operating point is the basic ignition angle. The greatest change in torque can be achieved by setting the latest possible ignition angle. The target torque for the filling must therefore be limited down to a predetermined minimum value in order to ensure that the desired target torque can be achieved by changing the filling and adjusting the ignition angle. This lower limit forms the corrected target torque MI _target for the ignition angle intervention. The correction takes into account the latest possible setting of the ignition angle by dividing the setpoint by the efficiency etazwm (division point 216). The result sets the target torque value when setting the latest possible ignition angle. Furthermore, since the subsequent conversion of the target torque into a target charge value takes place on the basis of the basic ignition angle (see equation 2), the corrected target torque value is multiplied in the multiplication point 218 by the efficiency of the basic ignition angle in order to obtain the optimal torque to be set.

The result is the target torque value, which can be adjusted from the basic ignition angle using the largest possible ignition angle adjustment. The target torque for the filling must not fall below this value, since otherwise the target torque MI _target cannot be realized. A minimum value selection between the two values is therefore carried out in the minimum value selection stage 200 and the smaller desired value is fed into the conversion into the desired filling value.

A second embodiment is the increase in Setpoints for the filling path in certain Operating situations, which automatically leads to an adjustment of the ignition angle leads to late. These operating situations occur especially with active idle control active catalyst heating and / or during the Startup process. These operating states have in common that a quick adjustment of the moment towards larger moments must be possible. A quick adjustment however, is only about changing the ignition angle, the Fuel supply and / or the mixture composition possible. In the preferred embodiment, therefore, in a reserve torque in these operating states set which by increasing the over the Filling set moments with simultaneous opposite change in the ignition angle, the Fuel supply and / or the mixture composition is pictured. The total moment is not changed. in the preferred embodiment is only the Ignition angle considered.

It should be noted that the reserve torque is different Can have reference points. In particular, it can optimal moment (moment with highest efficiency) or on the currently effective moment.

FIG. 4 shows a first embodiment for the specification in the filling path, which is used in particular by an idle control or in catalyst heating functions. The torque _setpoint MI _Soll , which is specified by the driver or other control systems and is used to set the ignition angle and the other output variables that bring about a rapid change in torque, is led to a link point 300. The torque reserve value DMROPT stored in the memory location 302 is added in this connection point. The torque reserve is either fixed or stored in a characteristic curve depending on the operating parameters. Operating variables are, for example, engine speed, engine temperature, the equipment in the vehicle, the time after starting, etc. The sum of the torque setpoint and the torque reserve is multiplied in a multiplication point 302 by the basic ignition angle efficiency, which is also the basis for the calculation of the target fill value. In the preferred exemplary embodiment, the result is compared in a maximum value selection stage 304 with the target torque value MI _target and the respectively larger of the two values is output as target torque for the air path MI _target-L .

In this embodiment, the reserve torque is on the optimal values (optimal torque, optimal ignition angle) based. This allows a defined firing angle to be stationary to adjust. The multiplication by the basic ignition angle efficiency is used to calculate the reference point for the Conversion of the target torque value for the filling path into one Target filling value.

Here, too, is a limitation of the target torque value for the Fill path necessary. The limitation is made to the maximum Firing angle. Assuming that the base firing angle is the earliest possible ignition angle is (the ignition angle is optimal in terms of moment or at the knock limit), so is by the Maximum value selection ensures that never too little filling is specified. Will the moment go through additionally Mixture influencing and / or cylinder blanking controlled, this limitation can be dispensed with.

If the torque reserve value is related to the momentarily effective torque, this limitation can be omitted and the much simpler structure according to FIG. 5 results. In this case, the torque _setpoint for the filling path is obtained by adding the torque _setpoint MI _setpoint for the quick intervention and the reserve torque DMR.

The rapid intervention is set in the exemplary embodiments according to FIGS. 4 and 5 in accordance with the target torque value MI _target .

The effect of the solution according to the invention, in particular according to the first exemplary embodiment, is illustrated using the example in FIG. 6. The time course of the _target torque value MI _target and of the torque contribution through the filling (dashed) is shown in FIG. 6a. FIG. 6b shows the time course of the torque contribution by adjusting the ignition angle and FIG. 6c shows the time course of the actual torque.

The target torque is reduced at a time T0. The The target torque value is determined by adjusting the ignition angle and Filling adjustment implemented. As a result of the faster The ignition angle adjustment (see FIG. 6b) takes Fill proportion only slowly. The actual moment changes 4c according to the setpoint. At time T1 the target torque is increased again. Through the separation according to the invention between the filling path and Ignition angle path is largely due to this torque increase the ignition angle correction is carried out. The beneficial Effect is that the actual moment also in torque increasing direction follows the setpoint almost exactly.

In addition to a calculation based on torque values in an advantageous embodiment, the calculations performed on the basis of performance values, being moment and power are related to engine speed.

Instead of the ignition angle setting is in another advantageous embodiment, the mixture composition or the fuel supply to a cylinder or a any combination of these three sizes. The Torque determination on the basis of parameters, setting limits, etc. are to be applied accordingly.

Claims (9)

1. Method for controlling an internal combustion engine of a vehicle, a setpoint value for a torque or a power of the internal combustion engine being specified, said setpoint value being set at least by influencing the charging of the internal combustion engine and at least one parameter which brings about a rapid change in moment, the influencing of the charging and the influencing of the at least one parameter taking place in each case according to a separate setpoint value which is derived from the prescribed setpoint value, characterized in that the setpoint values assume different values at least in one operating state.
2. Method according to Claim 1, characterized in that the at least one operating state is an operating state in which the moment or power is increased, in which the idling control is active and in which a catalytic converter heater is active, and/or during the starting phase.
3. Method according to one of the preceding claims, characterized in that the setpoint value which is derived from the activation signal of an accelerator pedal is used in unfiltered form to set the charge and in filtered form to set the at least one power parameter.
4. Method according to one of the preceding claims, characterized in that the setpoint value for the charge is limited on the basis of the parameter which can be set in order to generate a maximum change in moment or power, and on the basis of the setpoint value for this at least one parameter.
5. Method according to one of the preceding claims, characterized in that the setpoint value for the charge path is the minimum of the unfiltered and filtered corrected driver's request.
6. Method according to one of the preceding claims, characterized in that a standby value is formed for the moment or the power, which value is added to the setpoint value and forms the setpoint value for the charge path.
7. Method according to Claim 6, characterized in that the standby value is referred to the optimum moment value or power value or to the current value.
8. Method according to one of the preceding claims, characterized in that the setpoint value for the charge path is the maximum formed from the setpoint value and the setpoint value corrected with the standby value.
9. Device for controlling an internal combustion engine of a vehicle, having an electronic control unit which determines a setpoint value for a torque or a power of the internal combustion engine, which value is made available by setting the charge and at least one further power parameter which brings about a rapid change, in each case a setpoint value which is derived from the setpoint value which is determined being used to calculate the charge setting and the at least one power parameter, characterized in that the setpoint values for the charge setting and the setting of the at least one power parameter have different values in at least one operating state.

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