EP0950148B1 - Method and device for controlling a drive unit of a vehicle - Google Patents

Abstract

The invention relates to a method and a device for controlling a drive unit of a vehicle. A maximum allowable moment is predetermined and if this maximum allowable moment is exceeded, the moment of the drive unit is reduced. The maximum allowable moment is determined in dependence on at least the position of the operating element and in dependence on the nominal moment of at least one external function if this nominal moment is greater than the allowable moment determined according to the position of the operating element.

Description

State of the art

The invention relates to a method and a device to control the drive unit of a motor vehicle according to the preambles of the independent claims.

DE-A 195 36 038 describes a method and a device to control the drive unit of a motor vehicle known, in which a torque of the drive unit is dependent controlled by a setpoint for this torque becomes. To ensure the operational safety of this control system is also a maximum permissible torque Drive unit formed, this with an actual Drive unit torque compared and fault response measures initiated when the actual torque the drive unit exceeds the maximum permissible torque. In an embodiment described there the maximum permissible torque depends on the target torque value educated. This in turn is based on the Position of a control element that can be actuated by the driver, for example of an accelerator pedal, or depending on that of others Control systems or functions predetermined target torque, for example depending on a target torque an engine drag torque control and / or an idle speed control calculated. The maximum allowable torque becomes dependent on the target torque value using a characteristic curve or a map is formed. A consideration of Tolerances of the drive unit, which e.g. through internal friction is not described. This is also permissible Moment depending on the driver's desired torque, so that at a theoretically conceivable error in the calculation of this Moments the permissible torque is also incorrect.

It is an object of the invention to take measures to monitor a Motor control based on a maximum allowable Specify moments by which this monitoring is optimized becomes.

This is due to the distinctive features of the independent Claims reached.

Advantages of the invention

Monitoring a control of a drive unit Torque base is significantly improved because the Formation of the maximum permissible torque, which of the monitoring underlying, tolerances are taken into account, too when external intervention works.

By using external functions Target torques when forming the maximum permissible Moments becomes independent of the pedal characteristics Formation of the maximum allowable torque reached so that the Torque monitoring taking into account the tolerances is also possible when external functions work and in extreme cases the driver has released the pedal (e.g. Driving speed control mode, engine drag torque control mode, Etc.).

It is also advantageous that the driver's desired torque is not in the calculation of the permissible torque is received.

Further advantages result from the description below from exemplary embodiments or from the dependent ones Claims.

drawing

The invention is described below with reference to the drawing illustrated embodiments explained in more detail. It shows 1 shows an overview of a control unit for Control the torque of the drive unit while in Figure 2 shows a preferred embodiment in the form of a Flow diagram for monitoring the control on a torque basis is shown.

Description of exemplary embodiments

In Figure 1 is a control device for a multi-cylinder Internal combustion engine 10 shown. The control device comprises an electronic control unit 12, which consists of at least a microcomputer 14, an input 16 and one Output unit 18 exists. Input unit 16, output unit 18 and the at least one microcomputer 14 are via one Communication bus 20 for mutual data exchange with one another connected. The input unit 16 are the input lines 22, 24, 28 and 30 fed. The line 22 comes a measuring device 32 for detecting the pedal position, the line 24 from a measuring device 34 for detection the engine speed, the line 28 from a measuring device 38 for detecting a motor load representative Size and line 30 of at least one other Control device 40, for example a control device for traction control for transmission control, for engine drag torque control, for driving speed control, etc. To record the quantity representing the engine load are air mass, air flow meter depending on the embodiment or pressure sensors to record the intake manifold pressure intended. In addition to the farm size shown, the Control unit other sizes essential for engine control like engine temperature, driving speed, the time after Start, intake air temperature, etc.

An output line 42 is connected to the output unit 18, on an electrically operated throttle valve 44, which is arranged in the air intake system 46 of the internal combustion engine is leads. Output lines 48, 50, 52, 54, etc. shown, which with actuators for Fuel metering in each cylinder of the internal combustion engine 10 are connected or for setting the ignition angle in serve each cylinder.

The under the described by programs of the microcomputer realized engine control takes place through coordination the filling intervention (air intervention), the ignition angle setting and the change in fuel metering (Blanking of individual cylinders, displacement of the air / fuel composition) based on the torque the drive unit. Depending on the driver's request, determined by the position of the pedal and corresponding signals of the further control units 40 becomes a target torque Control of the drive unit selected. This target torque is converted into a setpoint for the filling to be set, in an ignition angle and / or a fuel metering correction converted. In this way, the torque of the drive unit approximates the specified target torque.

To ensure operational safety, it is also provided that on the basis of operating variables such as engine speed, the quantity representing the load, the current ignition angle and fuel metering setting as in the aforementioned State of the art describes the actual torque of the drive unit to investigate. It also becomes a maximum allowable Torque formed, compared with the actual torque and one Torque reduction carried out when the actual torque is the maximum permissible torque exceeds. In a preferred one Embodiment are at least two in the microcomputer 14 Program levels provided that work separately from each other. The described torque monitoring takes place in a higher level monitoring, while the Motor control shown above itself in a so-called Functional level is calculated. It is also provided to the safety function triggered due to the torque comparison, which preferably as switching off the fuel supply is realized as long as the actual torque is the permissible torque exceeds, to avoid the target torque value for control the torque of the drive unit depending on a maximum Limit moment. This maximum moment is in usually less than the maximum permissible torque, so the security response only happens if an error condition actually exists.

When determining the maximum permissible torque, how shown below using the flow diagram according to FIG. 2, based on accelerator pedal position and engine speed from at least one map in which the essential Tolerances are taken into account, the maximum permissible Moment read. Furthermore, in a preferred embodiment another map is provided, which according to Start of the drive unit, especially when the drive unit is cold increased tolerances, for example as a result of Friction considered. This maximum allowable moment in Post-start also depends on the accelerator pedal position and Engine speed determined according to another map. This map is switched to if after Start certain conditions exist, for example the Temperature of the engine, the intake air temperature and / or the elapsed time after the start within specified value ranges lie.

The maximum allowable moment determined in this way becomes for the above-mentioned torque monitoring and / or for limitation of the target torque. The maximum allowable The moment depends on the driver's request. Are functions active, which replace the driver's request or the torque versus that increases or decreases the driver's request maximum permissible moment, which in the above-mentioned way is formed, the actual situation of the controller not again. This is particularly important for interventions, which is the moment of the drive unit versus the driver's request increase, such as in a cruise control or an engine drag torque control. Around even during the effectiveness of such external interventions reliable torque monitoring (and / or limitation) too ensure is provided based on the driver's request formed maximum permissible moment with that of the to compare external interventions with the target torque. The larger of the two values is considered permissible Moment of monitoring and / or limitation supplied. In addition, an additional offset value is formed, that from a map depending on the resulting permissible torque and the engine speed is formed. This Offset value takes into account depending on the operating state different tolerance and leads to change in the resulting maximum permissible moments and therefore to be taken into account that depend on the operating condition of the engine Tolerance.

The corresponding solution is shown in Figure 2 as a flow chart shown, which is running in the microcomputer 14 Program represents.

The torque setpoints formed by external interventions such as engine drag torque control (mimsr) or a vehicle speed control (mifgr) and the moment of the drive unit compared to the driver's request a maximum value selection 100 fed. There the larger of these nominal torques becomes external interventions must be continued as the target torque. The target torque value for the external interventions is then in a maximum value selection 102 with that depending on the driver's request formed maximum permissible torque compared. The each larger of the two moment values is the resultant maximum permissible torque with torque monitoring fed. The maximum permissible depending on the driver's wishes Moment is either in a first map 104 or in determines a second map 106, depending on which operating state is present. The accelerator pedal position becomes the two maps wped and the engine speed nmot supplied. In The maximum permissible torque is above the two maps stored these two input values, the map values be applied. Outside the post-start phase, which by the solid position of the switching element 108 is represented, the one read from the map 104 maximum permissible torque value during the post-start phase the maximum permissible value read from the map 106 to the maximum value selection 102. The switching element 108 becomes dependent on the condition for the post-start B_next start switched. The post-start phase is preferred Embodiment before when a certain time the engine temperature has not expired since the start indicates a cold drive unit and / or the intake air temperature is in a certain range of values.

The resultant determined in the maximum value selection 102 maximum permissible moment is in a link 110 mizul corrected to the maximum permissible moment. The latter is fed to a comparator 112. This will further An actual torque miist is supplied, which depends on input variables in 114 like the actual filling depending on the measured air mass rl, the engine speed nmot, the current ignition angle and Engine fueling setting is formed becomes. The actual torque miist is compared with that in the comparator 112 maximum permissible moment mizul compared. Exceeds it the maximum permissible torque is particularly by switching off the fuel supply a safety reaction (SKA) triggered. The fuel supply remains switched off until until the actual torque falls below the maximum permissible torque falls.

The resulting point becomes maximum in the junction 110 admissible torque corrected with a torque offset value mioff. In a map 116, this is dependent on the engine speed and the resulting maximum allowable moment, the initial value of the maximum value selection 102. The Map values are also applied.

The map 116 shows the tolerance values (e.g. due to friction generated tolerances, component tolerances, etc.) filed depend on the operating state of the drive unit. There one Input variable of the map 116, even with external interventions represents the maximum permissible torque these tolerance values are also taken into account when external Interventions work. The offset value, the tolerances is not dependent on the accelerator pedal position formed so that the torque monitoring even during the Intervention of external functions is guaranteed. Further goes the target torque is not in the formation of the maximum allowable Moments so that theoretically occurring errors in the The calculation of the target torque should not be included in the monitoring.

In another embodiment, the input variable for the map 116 is not the maximum permissible torque that is called a measure of the torque request considered, but the filling request derived therefrom, i.e. the maximum permissible to be set via the throttle valve Should fill. Monitoring then becomes the basis of Fill values carried out. With this in mind, use the term moment also the filling as a monitoring variable to understand.

Claims (8)

1. Method for controlling the drive unit of a vehicle, the torque of the drive unit [lacuna] as a function of a driver's desired torque derived from the position of an operator control which can be activated by the driver, and as a function of at least one setpoint torque which is predefined by at least one external function which influences the torque instead of or in addition to the driver's prescription, a maximum permitted torque being predefined and the torque being reduced when this maximum permitted torque is exceeded by the corresponding actual value, characterized in that the maximum permitted torque is formed at least as a function of the position of the operator control independently of the driver's desired torque and the maximum permitted torque is formed as a function of the setpoint torque of the at least one external function if said setpoint torque is greater than the permitted torque which is dependent on the position of the operator control.
2. Method according to Claim 1, characterized in that the at least one external function increases the torque with respect to the driver's requirement in the manner of an engine torque control and/or a driving speed control.
3. Method according to one of the preceding claims, characterized in that a maximum permitted torque is predefined as a function of the driver's requirement, in particular the position of the accelerator pedal, and of the engine speed as a function of the operating state of the drive unit.
4. Method according to one of the preceding claims, characterized in that in the post-starting phase a different maximum permitted moment is predefined from the one outside this phase.
5. Method according to one of the preceding claims, characterized in that tolerances which are applied to the permitted torque as an offset value are taken into account in the maximum permitted torque.
6. Method according to Claim 5, characterized in that the offset value is dependent on variables which directly describe the engine torque.
7. Method according to Claim 5 or 6, characterized in that the offset value is dependent on the rotational speed and the resulting maximum permitted torque.
8. Device for controlling the drive unit of a vehicle, having a control unit which [lacuna] the torque of the drive unit as a function of at least one driver's desired torque derived from the position of an operator control which can be activated by the driver, and as a function of at least one setpoint torque which is predefined by at least one external function, the control unit has at least one microcomputer (14) which predefines a maximum permitted torque and, when this maximum permitted torque is exceeded by the torque of the drive unit, reduces the torque of the drive unit, characterized in that the microcomputer is embodied in such a way that the maximum permitted torque is formed at least as a function of the position of the operator control independently of the driver's desired torque, and the maximum permitted torque is formed as a function of the setpoint torque of the at least one external function if this said setpoint torque is greater than the permitted torque which is dependent on the position of the operator control.

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