The present invention relates to a method for monitoring torque in a hybrid drive made up of an internal combustion engine having an associated engine control unit and an intrinsically safe electric drive having an associated control unit, a protected communication taking place in which the engine control unit emits a setpoint torque to the control unit of the intrinsically safe electric drive and receives a status signal from it, and the engine control unit emitting an error signal in response to the exceeding of an permissible torque or in response to a negative status signal.
Torque monitoring is used in order to establish a possible error function of a control unit for a vehicle drive or of the drive itself, for the protection of the vehicle's passengers as well as of the external traffic. For the torque monitoring, a permissible torque is ascertained constantly from the vehicle driver's command during operation, and is compared to an actual torque of the drive. In a hybrid drive made up of an internal combustion engine and an electric drive, the actual torque is ascertained from the sum of the actual torques of the internal combustion engine and the electric drive. For this purpose, data are exchanged between an engine control unit for the internal combustion engine and a controller of the electric drive.
It is an object of the present invention to provide a method that makes possible the simplification of the communication between the controllers for the internal combustion engine and the electric drive.
The object is attained in that the intrinsic safety of the electric drive is used for the constant torque monitoring according to the specifications of the setpoint torque within the control unit. The communications effort (expenditure) may thereby be reduced. For reasons of safety, since the communication has to be executed as a protected communication, this also reduces the effort for monitoring of the communication between the engine control unit of the internal combustion engine, functioning in this case as powertrain coordinator and the control unit for the electric drive.
If only the setpoint torque of the intrinsically safe electric drive is passed on by the engine control unit to the control unit, the actual torque present in the control unit being used for the torque monitoring and only a status signal, that indicates a correct functioning of the communication and of the intrinsically safe electric drive, is passed on to the engine control unit, and if an error signal is emitted in response to the exceeding of a permissible torque or in response to a negative status signal, it may be achieved that the torque monitoring is safe, although the actual torque of the electric drive is not reported to the powertrain coordinator. The reduced communications effort simplifies the overall system.
In one preferred specific embodiment of the method, the permissible torque of the drive is compared to the sum of an actual torque of the internal combustion engine and the setpoint torque of the intrinsically safe electric drive, and an error signal is emitted if the sum, thus formed, exceeds the permissible torque. It may thereby be achieved that a reliable torque monitoring is able to take place, although the actual torque of the electric drive is not reported to the powertrain coordinator.
In one refinement of the method, the engine control unit sends a setpoint torque, internally checked for plausibility, to the intrinsically safe electric drive, and the control unit emits a positive status signal if the actual torque reaches the setpoint torque, and emits a negative status signal if the actual torque does not reach the setpoint torque. In this embodiment, as compared to an intrinsically safe design of the electric drive, no additional signals have to be generated or derived, and the system may advantageously be developed as simply as possible, the required safety being able to be achieved in spite of this.
The transmission of actual torque 32 of electric drive 40, as well as its processing in engine control unit 20 may be omitted. Because of this, the requirement for communication between engine control unit 20 and control unit 40 may be reduced.
Number | Date | Country | Kind |
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102005041663.2 | Sep 2005 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2006/065534 | 8/22/2006 | WO | 00 | 3/24/2009 |