DE102005040784A1 - Method for controlling a vehicle drive unit - Google Patents

Abstract

The invention relates to a method for controlling a vehicle drive unit, the vehicle drive unit comprising at least two individual motors, characterized by DOLLAR A a) determining torques (1, 2) to be requested for each of the at least two motors by at least one control device, DOLLAR A b ) Comparing the torques to be requested (1, 2; 4) with permissible torques (5; 19, 20), DOLLAR A c) Limiting the torques to be requested (1, 2) for at least one of the at least two individual motors, if the torques to be requested ( 1, 2; 4) are greater than the permissible torques (5; 19, 20), and DOLLAR A d) controlling the at least two motors (9, 10) with the possibly limited torques (1, 2; 11, 12) to be requested .

Description

The The invention relates to a method for controlling a vehicle drive unit, comprising at least two individual motors, in particular one Hybrid drive, the at least one internal combustion engine and at least comprises an electric motor.

In the prior art (eg DE 103 20 017 A1 ) Control devices for a drive unit are known, which control or regulate the drive unit, in particular with regard to a delivered drive torque, wherein the drive unit is an internal combustion engine of a motor vehicle. In this case, the motor vehicle usually comprises a driver request recording device which can be actuated by the driver of the motor vehicle, in particular a foot-operated accelerator pedal which is provided to emit an output signal representing a current actuation state of the driver request recording device. A control unit receives the output signal from the driver request recording device and assigns to the received output signal at least one desired output variable, in particular a desired drive torque of the drive unit. The drive unit is controlled by the control unit in such a way that an actual output quantity output by the drive unit approaches the desired output variable. Such control devices are known in various designs for conventional motor vehicle engines, especially gasoline engines and diesel engines, z. B. Bosch Engine Control Systems with Electronic Accelerator (EGAS).

Further It is known in the art, a continuous torque monitoring to detect malfunctions in the control unit. This is especially useful the protection of vehicle occupants in the motor vehicle and external Road users. It should be an unwanted acceleration of the Vehicle can be prevented. The core of continuous torque monitoring is the comparison of an actual torque provided by the engine with a permissible Moment. Normally, the actual torque is smaller than the permissible torque. If the actual torque exceeds the allowable torque, is a fault in the engine control unit before and one leading to a safe vehicle condition error response initiated.

The supervision the engine control units usually takes place according to a 3-level monitoring concept. The engine control itself, in particular the specification of the desired torque, takes place in the designated as a functional level first level. The second level (monitoring level) is executed as the continuous torque monitoring. In This level will depend, inter alia, on vehicle and vehicle Motor functions a permissible Moment determined and compared with an engine-actual torque. The Level 2 becomes expensive secured (double storage of all variables, cyclic RAM and ROM check, program control, Command Test). Level 3 is used for computer backup.

DE 102 10 684 A1 relates to a method for monitoring a moment of a drive unit of a vehicle. The torque to be monitored is compared with a permissible torque, the permissible torque is readjusted to the torque to be monitored and an error is detected if the torque to be monitored deviates more than a first predetermined value from the permissible torque, the error only in that case is detected, in which a position of a control element, in particular an accelerator pedal position, at least for a first predetermined time is within a predetermined tolerance range.

DE 197 39 565 A1 relates to a method for controlling the torque of a drive unit of a motor vehicle, wherein the torque of the drive unit is set at least in accordance with the driver's request, wherein the actual torque of the drive unit is determined and at least on the basis of the driver's request, a maximum allowable torque is determined. There is a torque reduction and / or limitation when the maximum permissible torque is exceeded by the actual torque. In this case, at least one operating state is determined, in which the torque of the drive unit is increased by additional load. During this at least one operating state, the maximum permissible torque is increased. In particular, the permissible torque is thereby increased during operation with a cold drive unit and / or load-consuming consumers during operation.

DE 197 48 355 A1 The invention relates to a method for controlling the drive unit of a vehicle, wherein the torque of the drive unit depends on a driver command torque derived from the position of a driver-actuatable control element and depending on at least one target torque dictated by at least one external function instead of or in addition to the driver specification affects the torque. A maximum permissible torque is specified and when this maximum permissible value is exceeded, a reduction of the torque is made by the corresponding actual value. The maximum permissible torque is at least formed depending on the position of the operating element and the maximum permissible torque is formed depending on the target torque of the at least one external function, if this target torque is greater than the permissible torque dependent on the control element position. The external function can, for. B. increase the torque over the driver's request, such as a motor drag torque control or a vehicle speed control.

Around the availability to increase an engine, becomes additional in the prior art to continuous torque monitoring in level 2, the requested torque before driving the motor in Level 1 for plausibility checked. If the requested moment is marked too high, then the moment is limited to a plausible moment. Through this torque limit can the above-described, in level 2 of the monitoring concept triggered error response be avoided, even if the requested moment is too high. Such an error reaction should be avoided if possible since they are for an occupant of the vehicle can be very uncomfortable.

The described, known from the prior art method for torque limiting is not readily transferable to hybrid vehicles. In hybrid vehicles In addition to an internal combustion engine comes at least one other torque source (Engine) used. In most cases these are around one or more electric drives.

In the engine control system, the desired torque required by the driver, which is set, for example, by operating an accelerator pedal, must now be divided between the existing torque source (at least two motors). This is done depending on numerous environmental variables, inter alia, with the aim of setting the most favorable operating point in terms of fuel consumption, torque, the charge balance, the formation of pollutants, etc. for all torque sources. Such a method is for example in DE 102 02 531 A1 described.

So far However, in the prior art is not a concept for torque limiting provided that the specific requirements of such Hybrid drive with one or more electric motors in addition to an internal combustion engine enters the drive train of a vehicle. A connected to the drive train additional electric motor can at too high drive currents just as unwanted Vehicle acceleration cause like a "continuous" internal combustion engine and therefore also requires continuous torque monitoring and a torque limit.

Advantages of invention

The proposed according to the invention A method for controlling a vehicle drive unit avoids the disadvantages of the known from the prior art method. In particular, it allows the method according to the invention, Error in torque control of hybrid vehicles to detect and intercept and so availability of the overall system.

Of the The basic idea of the invention is to carry out a torque comparison in level 1 of the torque monitoring concept, wherein the moments to be requested of the individual motors of the vehicle drive unit with admissible Moments are compared. This will be done in an advantageous manner a simple concept that provides at least one extra Torque adjusters, in particular additional electric motors, in the existing concept of torque comparison for torque limitation integrated. This is a very simple and universal treatment the additional Moments, z. B. additional Electric motor, for all vehicle configurations possible.

at has the inventive method the vehicle drive unit has at least two individual motors or Moment sources on. This can be, for example, a Internal combustion engine, in particular a gasoline or diesel engine, and act around an electric motor or multiple electric motors.

The according to the invention at least one control device, in particular to be requested by a central engine control unit certain Moments for each of the at least two engines are in this context the individual setpoints, which of the at least one control unit in the individual motors are requested. It determines z. B. the engine control unit to be requested Summation moment and divides this into individual requests to be requested on. With these individual moments to be requested, the engine control unit either controls even the individual engines or it transmits messages the moments to be requested to further, the individual motors associated control devices, the then control the respective motor.

The determination of the torques to be requested for the individual motors by the control unit takes place in accordance with a preferred embodiment of the present invention taking into account vehicle and / or engine functions, which engage in the torque control or regulation of the vehicle drive unit. For example, at The vehicle functions to be considered for determining a torque to be requested are a driver request function, a driver assistance function or external intervention functions. The driver request function can, for. B. in the form of an accelerator pedal signal in the determination of the torque to be requested. Possible driver assistance functions to be taken into account are, for example, an electronic stability program (ESP-usually ABS + ASR), an anti-lock braking system (ABS), a drive slip control (ASR), a cruise control (FGR) or an Adaptive Cruise Control (ACC) ). Optionally to be taken into account external intervention functions can, for. B. disturbing influences of electrical consumers such as an air conditioner, an electric sunroof or a servomotor. Engine functions that engage in the torque control or regulation of the vehicle drive unit and that can be taken into account in the determination of the torque to be requested of the respective engine are, for. As a speed limitation or torque loss, especially due to friction or generator losses. A start request can likewise be a signal to be taken into account in the determination of the torque to be requested, since, for example, B. an additional electric motor, where appropriate, only in the case of a start request to generate an additional moment. These and / or other functions are taken into account in the determination of the torque to be requested in level 1 (functional level) of a monitoring concept with at least two levels, in particular a 3-level monitoring concept, as is known in the prior art.

The Thus determined certain moments to be inventively with allowable moments compared. The permissible Moments are also calculated in level 1. The calculation of the permissible moments, the maximum allowable represent moments to be requested, taking into account the same and / or other vehicle and engine functions, such as those mentioned above, the can go into the determination of the moments to be requested. Especially become the allowed ones Moments preferably considering at least a size selected from an accelerator pedal signal, one generated by a driver assistance system Signal, a moment generated by external intervention Lost torque or a start request calculated.

at the method according to the invention will be the moments to be requested for at least one of the at least limited to two individual motors, if the moments to be requested bigger than that permissible Moments are. A limitation of the moments to be requested takes place by setting the torques to be requested for at least one of the motors (possibly for all engines of the vehicle drive unit) to a predetermined value, z. B. on the permissible Torque value with which the engine is to be requested instead of the one that has to be determined first Moments is driven. This will further the availability the engines through another, not too uncomfortable operation guaranteed and advantageously one more in vehicle operation engaging error reaction of the continuous torque monitoring in level 2 of the surveillance concept first avoided.

at the driveline configuration of the parallel hybrid includes the vehicle drive unit in the present invention, preferably an internal combustion engine and an electric motor, wherein by the at least one engine control unit to request a Internal combustion engine torque and a requested electric motor torque be determined and the engine and electric engine torques to be requested with admissible Moments are compared, whereby, if the combustion engine and electric motor torque greater than the permissible Moments are, at least one of the burning and to be requested Electric motor torques is limited.

The The invention further relates to an engine control unit for carrying out the inventive method for controlling a vehicle drive unit with at least two individual motors. The engine control unit according to the invention comprises Means for determining moments to be requested for at least two individual motors, means for comparing the requested Moments with allowed Moments and means for limiting the moments to be requested for at least one of the at least two individual motors, if requested Moments bigger than the permissible moments are.

drawing

Based the drawing, the invention is explained in more detail below.

It shows:

1 a flowchart for a first embodiment of a method according to the invention for controlling a vehicle drive unit with two motors and

2 a flowchart for a second embodiment of a method according to the invention for controlling a vehicle drive unit with two motors.

In 1 shows a preferred embodiment of the method according to the invention, in which a torque path common torque limitation of two individual motors takes place. In this case, a total torque to be requested is calculated from the torques of the at least two motors to be determined by the at least one control unit in step A) of the method according to the invention, which is compared with a permissible total torque in step B) of the method according to the invention.

For each engine is a requesting moment 1 . 2 certainly. For these moments to be requested 1 . 2 is through a function, here as an addition 3 symbolizes a total moment to be requested 4 calculated. Furthermore, a permissible total torque 5 determined in accordance with the inventive method (step B) in a comparator 6 with the total moment to be requested 4 is compared. The comparator 6 compares, whether the permissible total moment 5 smaller than the total torque to be requested 4 is. If the permissible total torque 5 not less than the total torque to be requested 4 is, becomes a correct determination of the moments to be requested 1 . 2 detected by the controller and causes no torque limit. The specific moments to be requested 1 . 2 are then in accordance with the upper switching position of in 1 illustrated, introduced for illustration switching elements 7 . 8th to the respective engines or the engines associated control units 9 . 10 passed. If the permissible total torque 5 smaller than the total torque to be requested 4 is, is an erroneous specification of the moments to be requested 1 . 2 detected by the controller. It is caused by a torque limit. Limited requested moments 11 . 12 are then according to the lower switching position of the switching elements 7 . 8th by a limitation calculation 13 . 14 provided. These limited moments to request 11 . 12 are directly with the respective engines or indirectly with the control units assigned to the engines 9 . 10 requested.

According to a preferred embodiment of the present invention, the vehicle drive unit has an internal combustion engine 17 and an electric motor with its own electric motor control unit 18 on, so according to 1 the total moment to be requested 4 as the sum of a combustion engine torque to be requested 15 and an electric motor torque to be requested 16 is calculated. The limited or unlimited moments to be requested become in the internal combustion engine 17 and the electric motor control unit 18 requested.

• • Start: Während des Starts sollte ein zu hohes Summenmoment besser durch Reduktion des Moments des Verbrennungsmotors korrigiert werden, da sonst eventuell der Start abbricht.
• • Bei hoher Drehzahl sollte das Moment besser durch Reduktion des Verbrennungsmotormoments korrigiert werden, da – in der Triebstrangkonfiguration des Parallelhybrids – der Stellbereich des Elektromotors vergleichsweise klein ist.
• • Bei kleinem Summenmoment und einer Betriebsweise des Verbrennungsmotors nahe dessen Minimalmoment ohne Zylinderabschaltung sollte das Elektromoment begrenzt werden, da das stetig erfolgen kann, während eine Momentenbegrenzung des Verbrennungsmotors zu einer Zylinderabschaltung führen könte, und so Unstetigekeiten im Gesamtmoment auftreten würden.

According to a preferred embodiment of the method according to the invention, the requested torques are limited for at least one of the two motors if the total torque to be requested is greater than the permissible total torque. It can only be one of the moments to be requested 1 . 2 or both can be requested moments 1 . 2 be limited. Preferably, the limiting of the moments to be requested takes place 1 . 2 in step C) of the method according to the invention for at least one of the motors as a function of an operating point of the vehicle drive unit. The following parameters, for example, can influence the limiting algorithm:

• • Start: During the start, too high a cumulative torque should be better corrected by reducing the torque of the internal combustion engine, as otherwise the start may be interrupted.
• • At high speed, the torque should be better corrected by reducing the engine torque, since - in the drive train configuration of the parallel hybrid - the adjustment range of the electric motor is comparatively small.
• • At low summation torque and a mode of operation of the internal combustion engine near its minimum torque without cylinder deactivation, the electric torque should be limited because this can be done continuously, while a torque limit of the engine could lead to a cylinder shutdown, and so discontinuities in the total torque would occur.

This means, for example, in the case of a vehicle drive unit with an internal combustion engine and an electric motor that at certain operating points, the electric torque is more important than the combustion torque. At these operating points, a torque limitation to the requested engine torque 15 be limited, wherein the requested electric motor torque 16 is maintained indefinitely. If the priority of the moments in the current operating point is reversed, is a sole limitation of the requested electric motor torque 16 possible.

In 2 another preferred embodiment of the method according to the invention is shown, in which a torque-separated moment limitation of two individual motors, in particular an internal combustion engine and an electric motor, takes place. In this case, the torque to be determined by the control unit in step A) of the method according to the invention is compared for each individual motor in step B) of the method according to the invention with one permissible single torque for each individual motor, and optionally in step C) of the method according to the invention Limiting the individual moments to be requested for the individual motors independently of each other.

For both engines is each a requesting moment 1 . 2 and a valid moment 19 . 20 certainly. The requested moment 1 the first engine is in a comparator 21 with the allowable moment 19 compared to the first engine. If the requested moment 1 of the first motor smaller than the first permissible moment 19 is, is no torque limit of the first requesting moment 1 performed.

According to the upper switching position of in 2 shown first switching element 7 becomes in this case the non-limited requesting moment 1 to the first motor or to the first motor associated with the control unit 9 transmitted.

If the requested moment 1 of the first motor is greater than the allowable torque 19 of the first motor, there is a torque limit. Instead of the requesting moment 1 becomes the first engine 9 (or its controller) the allowed torque 19 transmitted as a limited requestable moment.

The procedure is analogous for the second engine. A second comparator 22 compares the requested moment 2 second motor with the allowable moment 20 of the second motor and transmitted to the second motor / controller 10 depending on the result of the comparison, the second requesting moment 2 or the second allowed moment 20 limited requestable moment.

Claims (10)

Method for controlling a vehicle drive unit, wherein the vehicle drive unit comprises at least two individual motors, characterized by a) Determining moments to be requested ( 1 . 2 ) for each of the at least two motors by at least one control unit, b) comparing the moments to be requested ( 1 . 2 ; 4 ) with permissible moments ( 5 ; 19 . 20 ), c) limiting the moments to be requested ( 1 . 2 ) for at least one of the at least two individual motors, if the moments to be requested ( 1 . 2 ; 4 ) greater than the allowable moments ( 5 ; 19 . 20 ) and d) driving the at least two motors ( 9 . 10 ) with the possibly limited requestable moments ( 1 . 2 ; 11 . 12 ). A method according to claim 1, characterized in that from the at least one control unit in step A) certain moments to be requested ( 1 . 2 ) of the at least two motors to request a total moment ( 4 ) calculated in step B) with a permissible total moment ( 5 ) is compared. Method according to claim 2, characterized in that limiting the moments to be requested ( 1 . 2 ) for at least one of the at least two engines, if the total torque to be requested ( 4 ) greater than the permissible total moment ( 5 ). Method according to claim 3, characterized in that limiting the moments to be requested ( 1 . 2 ) in step C) for at least one of the motors in response to an operating point of the vehicle drive unit. Method according to claim 1, characterized in that the torque to be requested by the control unit in step A) ( 1 . 2 ) for each individual motor in step B), each having a permissible single torque ( 19 . 20 ) is compared for each individual engine and in step C) limiting the individual moments to be requested ( 1 . 2 ) for each motor independently. A method according to claim 5, characterized in that when limiting a requesting moment ( 1 . 2 ) for a motor a permissible single torque for this motor ( 19 . 20 ) drives the motor as a limited requesting torque. Method according to claim 1, characterized in that the permissible moments ( 5 ; 19 . 20 ) is calculated taking into account at least one quantity selected from an accelerator pedal signal, a signal generated by a driver assistance system, a torque generated by an external intervention, a loss torque, and a start request. Method according to claim 1, characterized in that the at least one control unit to request the Moments considering at least a size, selected from an accelerator pedal signal, one generated by a driver assistance system Signal, a moment generated by external intervention Loss torque and a start request is calculated. A method according to claim 1, characterized in that the vehicle drive unit comprises an internal combustion engine and an electric motor, wherein by an engine control unit to request a combustion engine torque ( 15 ) and an electric motor torque to be requested ( 16 ) and the engine and electric motor torques to be requested with permissible moments ( 5 ; 19 . 20 ), wherein if the engine and electric motor torques to be requested ( 15 . 16 ) greater than the allowable moments ( 5 ; 19 . 20 ), at least one of the engine and electric engine torques ( 15 . 16 ) is limited. Engine control unit to carry out the method according to a the claims 1 to 9, comprising means for determining moments to be requested for at least two individual motors, means for comparing the requested Moments with allowed Moments and means for limiting the moments to be requested for at least one of the at least two individual motors, if requested Moments bigger than the permissible Moments are.