Method and control system for operating a drive train

Abstract

Method for operating a powertrain of a motor vehicle, wherein the powertrain comprises a drive unit (1), an automatic or automated transmission (2) and an output (3), wherein, in preparation for an anticipated increase in speed, a leading drive unit speed signal and additionally a leading torque signal are specified via a torque to be transmitted by the transmission (2) during the anticipated increase in speed and a torque required to accelerate the masses within the transmission, on the basis of which a torque reserve for the drive unit (1) is determined, wherein the drive unit (1) is controlled on the basis of the torque reserve in such a manner thatthat the drive unit (1) when changing from a first operating state before an actual speed increase request to a second operating state before the actual speed increase request, while providing the torque reserve in the second operating state compared to the first operating state, is operated in a torque-neutral manner or as far as possible, characterized in that if the drive unit (1) is operated with overrun cut-off in the first operating state and the torque reserve requires a change from overrun operation to traction operation, the overrun cut-off is aborted in the second operating state.

Description

[0001] The invention relates to a method for operating the powertrain of a motor vehicle. Furthermore, the invention relates to a control system for operating the powertrain of a motor vehicle.

[0002] A motor vehicle's powertrain consists of a drive unit, a transmission, and an output shaft, with the transmission positioned between the drive unit and the output shaft. The transmission converts speed and torque, thus providing the tractive force from the drive unit to the output shaft.

[0003] German patent application DE 102 25 448 A1 discloses a method for operating the powertrain of a motor vehicle with an internal combustion engine and an automatic or automated transmission. According to this prior art, an operating condition of the internal combustion engine is specified for a shift, in particular an output torque of the drive unit or a speed of the drive unit. Furthermore, a torque reserve is specified for rapid adjustment of the specified operating condition, whereby the torque reserve is determined as a function of a driver-requested torque or a current engine speed. During operation of the powertrain, the torque reserve is adjusted by shifting the ignition timing.

[0004] Based on this, the invention aims to provide a method for operating a drive train and a control system for carrying out the method, by means of which the motor vehicle can be operated with improved dynamics. This objective is achieved by a method according to claim 1.

[0005] According to the invention, to prepare for a speed increase that is expected to be carried out (e.g. within a circuit or outside of a circuit), a leading drive unit speed signal and additionally a leading torque signal are specified via a torque to be transmitted by the transmission during the speed increase that is expected to be carried out and a torque required to accelerate the masses inside the transmission, on the basis of which a desired torque reserve for the drive unit is determined.

[0006] The drive unit is controlled based on the desired torque reserve determined in this way, such that when switching from a first operating state before an actual speed increase request to a second operating state before the actual speed increase request, the drive unit is operated in the second operating state with a torque reserve that is available and thus callable, compared to the first operating state, in a torque-neutral manner or as far as possible.

[0007] In the method according to the invention, to prepare for a speed increase request that is expected to be executed, the transmission control unit provides the engine control unit with, on the one hand, the leading drive unit speed signal and, on the other hand, the leading torque signal. The leading drive unit speed signal contains information about a speed to be set for the speed increase request that is expected to be executed, in particular about a corresponding speed profile of the drive unit, while the leading torque signal contains information about a torque to be transmitted by the transmission during the speed increase that is expected to be executed and a torque required to accelerate the masses within the transmission. Based on the leading drive unit speed signal and the leading torque signal, the engine control unit determines a desired speed orThe required torque reserve for the drive unit is determined by controlling the drive unit based on this torque reserve requirement. This control is achieved by switching from the first operating state to the second operating state before an actual speed increase is requested. Specifically, the drive train operates in a torque-neutral state, or as torque-neutral a state as possible, while providing and thus making available the torque reserve. This allows the drive unit to provide the required speed and torque quickly and with good dynamics when the actual speed increase is requested.

[0008] Preferably, the torque reserve is accessed and utilized when an increase in speed is actually required, while it is reduced again when an increase in speed is not required. This allows for particularly advantageous operation of the drive train.

[0009] When an increase in engine speed is actually requested, the torque reserve is accessed and used. Conversely, if an increase in engine speed is not requested, the torque reserve is reduced again. It can be configured that if the torque reserve is not actually accessed within a defined period after being made available, it is subsequently reduced automatically.

[0010] The torque reserve of the drive unit is preferably made available in a torque-neutral or as torque-neutral as possible manner in the second operating state compared to the first operating state by increasing the throttle valve position and / or the valve lift, and simultaneously adjusting the ignition timing from an optimum, particularly retarding it, and / or optionally activating cylinder deactivation (provided that the use of cylinder deactivation does not cause excessive loss of comfort depending on the operating state). To actually access the torque reserve, the ignition timing is subsequently adjusted towards the optimum and / or the corresponding cylinders are activated.

[0011] Following further development, if the drive unit is operated in the first operating state with at least one cylinder deactivated and the torque reserve for the drive unit cannot be provided while maintaining cylinder deactivation, particularly by increasing the throttle position and / or the valve lift, then in the second operating state at least one previously deactivated cylinder is activated, optionally in combination with an increase in the throttle position and / or the valve lift. Preferably, to provide torque-neutral or as torque-neutral as possible operation of the drive unit in the second operating state compared to the first operating state, the ignition timing is then retarded relative to an optimum set in the first operating state.Subsequently, the ignition timing is adjusted back to its optimal position to ensure the actual utilization of the torque reserve compared to the second operating state. This further development of the invention allows cylinder deactivation on a drive unit to be used particularly advantageously while ensuring good dynamics. If the torque reserve cannot be provided while maintaining cylinder deactivation, at least one cylinder is automatically activated. This allows for improved dynamics even when cylinder deactivation is in use.

[0012] Furthermore, if the drive unit is operating with overrun cut-off in the first operating state and the torque reserve necessitates a switch from overrun to traction operation, the overrun cut-off is deactivated in the second operating state. This allows for improved drivetrain dynamics even when overrun cut-off is in use.

[0013] The control system according to the invention is defined in claim 7.

[0014] Preferred embodiments are described in the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail with reference to the drawing, without being limited thereto. The drawing shows: Fig. 1. A diagram of a powertrain.

[0015] The invention relates to a method for operating a drive train of a motor vehicle and a control system for operating a drive train of a motor vehicle.

[0016] Fig. Figure 1 shows a highly schematic representation of a motor vehicle's powertrain with a drive unit 1 and a transmission 2, which is connected between the drive unit 1 and an output 3. The transmission 2 converts rotational speeds and torques, thus providing the tractive force of the drive unit 1 at the output 3.

[0017] Transmission 2 is preferably an automatic or automated transmission in which gear changes or shifts are performed automatically. For this purpose, at least one previously closed shift element of the transmission must be opened and at least one previously opened shift element of transmission 2 must be closed.

[0018] The drive unit 1 is preferably a gasoline engine.

[0019] The powertrain of the Fig. 1 further comprises an engine control unit 4 and a transmission control unit 5, wherein the engine control unit 4 serves to control and / or regulate the operation of the drive unit 1 and for this purpose according to the dashed arrow of the Fig. The transmission control unit 5 exchanges data with the drive unit 1. The transmission control unit 5 serves to control and / or regulate the operation of the transmission 2 and, for this purpose, exchanges data with the transmission 2 in the direction of the dashed arrow. Furthermore, the engine control unit 4 and the transmission control unit 5 exchange data in accordance with the further dashed arrow. Fig. 1. Data is exchanged among each other.

[0020] To prepare for a planned increase in engine speed, the transmission control unit 5, which automatically determines shift points based on available data, provides the engine control unit 4 with both a leading drive unit speed signal and a leading torque signal. The leading drive unit speed signal contains information about the speed or speed profile that the transmission 2 requires to execute the planned increase in engine speed. The torque signal contains information about the torque that the transmission 2 will transmit during the planned increase in engine speed and the torque required to accelerate the masses within the transmission.

[0021] Based on the drive unit speed signal and torque signal provided by the transmission control unit 5, the engine control unit 4 automatically determines a desired torque reserve for the drive unit 1, which is required to provide the speed or speed profile of the leading torque signal while providing the torque to be transmitted by the transmission 2 during the expected speed increase.

[0022] Before an actual speed increase request, the drive unit 1 is controlled via the engine control unit 4 on the basis of the determined torque reserve, in such a way that the drive unit 1 switches from a first operating state to a second operating state before an actual speed increase request, in which, with the torque reserve available or retrievable at the drive unit 1, the drive unit 1 is operated in a torque-neutral manner or as far as possible with respect to the torque actually provided compared to the first operating state.

[0023] When switching from the first operating state to the second operating state based on the previously determined, desired torque reserve before an actual speed increase request, the operating state of the drive unit 1 is changed in such a way that the drive unit 1 behaves torque-neutrally on the output side, but a corresponding torque reserve is available for call-up.

[0024] Then, when the speed increase is actually requested, the torque reserve is called up and used to dynamically provide the speed of the leading drive unit speed signal and the torque of the leading torque signal.

[0025] However, if the expected increase in speed is not subsequently requested, for example within a defined period of time after the torque reserve has been provided, the torque reserve is automatically reduced again by means of a corresponding shift in the operating state for the drive unit 1 via corresponding control by the engine control unit 4.

[0026] It is therefore in line with the invention that, based on a torque signal of a torque to be transmitted by the transmission 2 during the expected increase in speed, and based on a speed signal of a speed to be provided by the drive unit 1 for the expected increase in speed, a desired torque reserve is automatically determined by the engine control unit 4, and depending on this, the drive unit 1 is automatically controlled in such a way that it is subsequently operated initially in a torque-neutral manner or as far as possible in a torque-neutral manner, and the torque reserve is available for retrieval.

[0027] If an increase in speed is subsequently requested, the required speed or speed profile and the required torque are provided by actual use or by calling up the available torque reserve, within a short time with good dynamics.

[0028] The available torque reserve of the drive unit 1 is preferably provided in a torque-neutral or as torque-neutral manner as possible in the second operating state compared to the first operating state by increasing the throttle position of a throttle valve of the drive unit 1 compared to the first operating state and / or increasing the valve lift of cylinders of the drive unit 1 compared to the first operating state and simultaneously adjusting the ignition timing position relative to an optimum used in the first operating state, in particular retarding it, and / or optionally activating cylinder deactivation (provided that the use of cylinder deactivation does not cause excessive loss of comfort depending on the operating state).To actually access the torque reserve, the ignition timing is subsequently adjusted back to optimal and / or the corresponding cylinders are activated.

[0029] According to a preferred embodiment, the invention is then used when the drive unit in the first operating state, i.e. before a request for an increase in speed and before control of the drive unit 1 depending on the torque reserve, is operated with at least one deactivated cylinder using a so-called cylinder deactivation in a so-called partial engine operation.If, in this operating state, the engine control unit 4 determines a desired torque reserve based on the drive unit speed signal and the torque signal, and based on the torque to be transmitted by the transmission 2 during the anticipated increase in engine speed, and this reserve cannot be provided while maintaining cylinder deactivation, particularly by simply increasing the throttle position and / or valve lift, then in the second operating state, i.e., even before an actual increase in engine speed is requested, at least one previously deactivated cylinder, and in particular all previously deactivated cylinders, are activated. If necessary, the throttle position and / or valve lift can also be increased.This is done in a way that is torque-neutral, or as torque-neutral as possible, with respect to the torque actually provided by the drive unit 1 on the output side. To achieve this, in the second operating state, the ignition timing is simultaneously retarded, particularly in comparison to the first operating state. If an increase in engine speed is subsequently requested, the ignition timing is adjusted back to its optimal position compared to the second operating state to actually utilize the available torque reserve. This allows for a highly dynamic response to the speed increase request, providing both the requested engine speed and torque.

[0030] According to this further development of the invention, a cylinder deactivation is therefore prematurely terminated, so that the drive unit 1 can provide the torque reserve in good time and in sufficient quantity for a speed and torque to be provided in the course of an actual speed increase request.

[0031] The invention can also be advantageously used if the drive unit 1 is operated with overrun cut-off in the first operating state. If it is determined that a torque reserve, determined on the basis of the leading drive unit speed signal and the leading torque signal, necessitates a change from overrun to traction operation, the overrun cut-off is terminated in the second operating state. This occurs in a torque-neutral manner, or as far as possible, with respect to the torque provided by the drive unit 1 on the output side, analogous to the manner described for cylinder deactivation.

[0032] The invention further relates to a control system for operating the drive train and for carrying out the method described above, wherein the control system comprises the engine control unit 4 and the transmission control unit 5. The transmission control unit 5 provides the engine control unit 4 with the leading drive unit speed signal and the leading torque signal before an actual speed increase request, so that the engine control unit 4 can determine the torque reserve for the drive unit 1 based on this information and control the drive unit 1 accordingly, depending on this torque reserve.

[0033] Engine control unit 4 and transmission control unit 5 comprise means for this purpose, namely hardware-related means and software-related means. The hardware-related means include data interfaces for exchanging data with the participating assemblies. Furthermore, the hardware-related means include a processor for data processing and a memory for data storage. The software-related means of the transmission control unit 5 and the engine control unit 4 include program modules that are stored in them for carrying out the method according to the invention.

[0034] The invention is preferably used in drive trains whose transmission 2 is designed as an automatic or automated transmission and whose drive unit 1 is designed as a gasoline engine. Reference sign 1 drive unit 2 gearboxes 3 Drive 4 Engine control unit 5 Transmission control unit

Claims

[1] Method for operating a drive train of a motor vehicle, wherein the drive train comprises a drive unit (1), an automatic or automated transmission (2) and an output (3), wherein, in preparation for an anticipated increase in speed, a leading drive unit speed signal and additionally a leading torque signal are specified via a torque to be transmitted by the transmission (2) during the anticipated increase in speed and a torque required to accelerate the masses within the transmission, on the basis of which a torque reserve for the drive unit (1) is determined, wherein the drive unit (1) is controlled on the basis of the torque reserve in such a manner thatthat the drive unit (1) when changing from a first operating state before an actual speed increase request to a second operating state before the actual speed increase request, while providing the torque reserve in the second operating state compared to the first operating state, is operated in a torque-neutral manner or as far as possible in a torque-neutral manner, . characterized by , that if the drive unit (1) is operated with overrun cut-off in the first operating state and the torque reserve requires a change from overrun operation to traction operation, the overrun cut-off is aborted in the second operating state. [2] Method according to claim 1, characterized by , that when the speed increase is actually requested, the torque reserve is called up and used, and that when the speed increase is not requested, the torque reserve is reduced again. [3] Method according to claim 1 or 2, characterized by , that if the drive unit (1) is operated in the first operating state with at least one cylinder deactivated and the torque reserve cannot be provided while maintaining the cylinder deactivation, at least one previously deactivated cylinder is switched on in the second operating state. [4] Method according to any one of claims 1 to 3, characterized by , that in order to provide the torque-neutral or as far as possible torque-neutral operation of the drive unit (1) in the second operating state compared to the first operating state, a throttle valve position and / or a valve lift is increased, and / or a cylinder deactivation and / or a fuel cut-off is terminated to form the torque reserve, and furthermore an ignition angle position is adjusted from an optimum and / or a cylinder deactivation is activated in order to be able to compensate for the built-up torque reserve. [5] Method according to claim 4, characterized by, that subsequently, in order to actually utilize the torque reserve compared to the second operating state, the ignition timing is adjusted back towards the optimum and / or the cylinder deactivation is deactivated. [6] Control system for operating a powertrain of a motor vehicle, comprising an engine control unit (4) for controlling and / or regulating the operation of a drive unit (1) and a transmission control unit (5) for controlling and / or regulating the operation of an automatic or automated transmission (2), wherein, in preparation for an anticipated increase in engine speed, the transmission control unit (5) provides the engine control unit (4) with an advance drive unit speed signal and additionally with an advance torque signal indicating a torque to be transmitted by the transmission (2) during the anticipated increase in engine speed and a torque required to accelerate the masses within the transmission, on the basis of which the engine control unit (4) determines a torque reserve for the drive unit (1), wherein the engine control unit (4) controls the drive unit (1) on the basis of the torque reserve in such a manner thatthat the drive unit (1) when changing from a first operating state before an actual speed increase request to a second operating state before the actual speed increase request, while providing the torque reserve in the second operating state compared to the first operating state, is operated in a torque-neutral manner or as far as possible in a torque-neutral manner, . characterized by , that when the drive unit (1) is operated with overrun cut-off in the first operating state and the torque reserve requires a change from overrun operation to traction operation, the engine control unit (4) controls the drive unit (1) in the second operating state to terminate the overrun cut-off. [7] Control system according to claim 6, characterized by, that when the transmission control unit (5) actually requests the speed increase, the engine control unit (4) controls the drive unit (1) by calling up and using the torque reserve, and that when the transmission control unit (5) does not request the speed increase, the engine control unit (4) controls the drive unit (1) by reducing the torque reserve. [8] Control system according to claim 6 or 7, characterized by , that if the drive unit (1) is operated in the first operating state with at least one cylinder deactivated and the torque reserve cannot be provided while maintaining the cylinder deactivation, the engine control unit (4) controls the drive unit (1) in the second operating state by activating at least one previously deactivated cylinder. [9] Control system according to any one of claims 6 to 8, characterized by, that the engine control unit (4) in order to provide the torque-neutral or as far as possible torque-neutral operation of the drive unit (1) in the second operating state compared to the first operating state, controls a throttle valve to increase a throttle valve position and / or controls a valve lift control system to increase a valve lift and / or terminates a cylinder deactivation and / or terminates a fuel cut-off and furthermore controls a fuel ignition device to adjust an ignition angle position from an optimum and / or activates a cylinder deactivation in order to compensate for the built-up torque reserve. [10] Control system according to claim 9, characterized by , that the engine control unit (4) controls the fuel ignition device to adjust the ignition angle position towards the optimum and / or deactivates active cylinder deactivation in order to subsequently utilize the torque reserve of the drive unit (1).

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