Method for operating a hybrid powertrain, as well as electronic control unit

Abstract

A method for operating a hybrid powertrain of a motor vehicle, wherein the powertrain comprises an internal combustion engine (VM), an electric machine (EM), and a disconnect clutch (K0) arranged between the internal combustion engine (VM) and the electric machine (EM), wherein a rotational position sequence is performed to set an angular position of the internal combustion engine (VM) that is advantageous for starting the internal combustion engine (S), wherein the following steps are performed in the rotational position sequence while the internal combustion engine (VM) is operated without fuel: - operating the electric machine (EM) in a speed control mode, - setting a torque-transmitting state of the disconnect clutch (K0), - monitoring an angular position of the internal combustion engine (VM) until the angular position reaches a target value or a target range, characterized in thatthat if, during the execution of the rotary angle position sequence, starting the internal combustion engine (ICE) is requested, the rotary angle position sequence is immediately aborted, and the internal combustion engine (ICE) is immediately started.

Description

The invention relates to a method for operating a hybrid powertrain of a motor vehicle. The invention further relates to an electronic control unit for use in a motor vehicle, which is configured to carry out such a method. Patent application DE 198 38 853 A1 describes a hybrid drive device for a vehicle, comprising a machine, an electric motor, a coupling between the machine and the electric motor, a transmission unit for transferring the power of the machine and the electric motor to the wheels, and a control device for controlling the machine, the electric motor, and the transmission of the power of the machine and the electric motor to the wheels. A standby control device is provided to rotate the machine into a start-up position before the machine is started. Patent application DE 10 2016 005 122 A1 describes a method for operating a hybrid drive system of a motor vehicle, which comprises an internal combustion engine and an electric motor. In a first operating mode, the crankshaft position of the internal combustion engine is deliberately adjusted to a target position before the engine is started, in order to prevent vibrations during the starting process. In a second operating mode, this adjustment is omitted. The choice between the first and second operating modes depends on the vehicle's speed. In DE 10 2011 075 216 A1 a method for starting an internal combustion engine of a hybrid drive is disclosed. DE 11 2012 006 913 T5 discloses a control and regulating device for a vehicle drive device with which it is possible to suppress a shock generated by starting the internal combustion engine while driving with an electric motor. The object of the invention is now to provide a method for the further development of processes known in the prior art. The problem is solved by a method with the features of claim 1. Claim 5 further specifies an electronic control unit which is configured to carry out the method according to the invention. Advantageous embodiments are described in the dependent claims, the description, and the figures. A method for operating a hybrid powertrain of a motor vehicle is proposed. The powertrain comprises an internal combustion engine, an electric machine, and a disconnect clutch arranged between the internal combustion engine and the electric machine. To set an advantageous rotational angular position of the internal combustion engine for starting the engine, a rotational angular position sequence is performed, wherein the following steps are carried out in the rotational angular position sequence while the internal combustion engine is running without fuel: - Operating the electric machine in a speed control mode, - Setting a torque-transmitting state of the disconnect clutch, - Monitoring the rotational angular position of the internal combustion engine until the rotational angular position reaches a setpoint or a setpoint range. According to the invention, the rotation angle position sequence is immediately aborted if the combustion engine is requested to start during the sequence. Such a start request can be triggered, for example, by a hybrid strategy setting in the vehicle control unit or by the driver, such as by forcefully pressing the accelerator pedal. The combustion engine starts immediately upon receiving the start request. This sequence eliminates any delay in the starting process. A delay in starting the combustion engine would be incomprehensible to the driver and therefore considered a disadvantage. Preferably, the internal combustion engine is started regardless of its current rotational position. Such a starting procedure can be perceived as inconvenient, depending on the engine's current rotational position. However, this type of starting procedure increases the dynamics of the engine start. When a starting request is received, the electric motor is preferably used to accelerate the combustion engine to its starting speed. For this purpose, the torque transmission capacity of the disconnect clutch must be adjusted to a suitable value. Alternatively, the combustion engine can be accelerated to the starting speed using its own starter motor. To solve the problem, an electronic control unit is also proposed, which is configured to carry out the procedure described above. The electronic control unit may also be designed to perform other powertrain control functions. The invention is described in detail by way of example with reference to the following figures. Figures 1 and 2 show schematic representations of a motor vehicle powertrain; Figures 3 and 4 show schematic representations of a section of a motor vehicle powertrain. Fig. 1 shows a schematic representation of a motor vehicle powertrain according to a first embodiment. The powertrain comprises an internal combustion engine VM, which is functionally connected to a hybrid module HY. The hybrid module HY houses an electric machine (not shown in Fig. 1). The hybrid module HY is functionally connected to a transmission G, which is configured to provide various gear ratios. A friction element (not shown in Fig. 1) may be present in the transmission G. On the output side, the transmission G is connected to a differential AG, which is configured to distribute the power applied to an output shaft W2 of the powertrain to the drive wheels DW. Fig. 2 shows a schematic representation of a motor vehicle powertrain according to a second embodiment. The transmission G now includes an electric machine (not shown in Fig. 2) and is functionally connected to the internal combustion engine VM. The hybrid module HY included in the embodiment according to Fig. 1 is omitted. Fig. 3 schematically shows a section of a motor vehicle powertrain according to the embodiment shown in Fig. 1. A disconnect clutch K0 is arranged in the operative connection between the internal combustion engine VM and the electric machine EM. A rotor of the electric machine EM is connected to a shaft W1. When the disconnect clutch K0 is open, rotation of the rotor does not cause rotation of the internal combustion engine shaft, so that the internal combustion engine VM is decoupled from the powertrain when the disconnect clutch K0 is open. The disconnect clutch K0 can be closed by actuating an actuator (not shown in Fig. 3). A starter RS ​​is associated with the internal combustion engine VM. The starter RS ​​is formed by an electric motor, which is configured to accelerate the internal combustion engine VM to a starting speed. A starting element C2 is functionally arranged between the rotor and the gearbox G. Here, the starting element C2 is formed by a clutch. The starting element C2 can also be a component of the gearbox G. For example, the starting element C2 can participate in the formation of the gear stages of the gearbox G. Alternatively, the starting element C2 can be located upstream of the gearbox G, as shown in Fig. 3. The starting element C2 can, for example, be a lock-up clutch of a hydrodynamic torque converter. The starting element C2 can be actuated by an actuator C2_A against a spring force. The actuator C2_A can be designed, for example, as a hydraulic or electromechanical actuator. An electronic control unit (ECU) is provided for controlling the electric machine EM and the starting element C2. This ECU communicates with an inverter (INV), which controls the current supply to the stator of the electric machine EM. The ECU also communicates with the actuator C2_A. The internal combustion engine VM has its own control unit (ECU_VM), which is configured to control the engine. The ECU_VM communicates with the ECU, allowing signals to be exchanged between them. The ECU also receives speed signals n1 and n2. Speed ​​signal n1 represents the rotational speed of shaft W1. Speed ​​signal n2 represents the rotational speed of the output half of the starting element C2. Fig. 4 schematically shows a section of the gearbox G according to the drive train depicted in Fig. 2. The gearbox G has at least one planetary gear set P. The starting element C2 is designed as a multi-disc brake and acts between a ring gear of the planetary gear set P and a rotationally fixed housing GG of the gearbox G. The rotor of the electric machine EM acts via the shaft W1 on a sun gear of the planetary gear set P. A planet carrier of the planetary gear set P is connected to a shaft W3 of the gearbox G, which acts on a section TG of the gearbox G, shown only schematically. The shaft W1 is coupled to the internal combustion engine VM (not shown in Fig. 4) via the disconnect clutch K0. The starting element C2, according to the embodiment shown in Fig. 4, is actuated by an actuator (not shown in Fig. 4) in the same manner as in Fig. 3. The speed signals n1, n2, which represent the differential speed of the starting element C2, are supplied to the control unit ECU. The control unit ECU communicates with the inverter INV, which controls the current supply to the stator of the electric machine EM. The control unit ECU_VM communicates with the control unit ECU, allowing signals to be exchanged between the control unit ECU and the control unit ECU_VM. If, in a drive train as described in Figs. 1, 2, 3 to 4, the internal combustion engine VM is to be brought to a rotational angle position favorable for starting, the electronic control unit ECU performs a rotational angle position sequence which includes the following steps: - Operating the electric machine EM in a speed control mode, - Setting a torque-transmitting state of the disconnect clutch K0, - Monitoring a rotational angle position of the internal combustion engine VM until the rotational angle position reaches a target value or a target range. If, during the execution of the rotary angle position sequence, a starting command is issued for the internal combustion engine VM, the rotary angle position sequence is immediately aborted. This aborting occurs regardless of the currently executed process step or any progress within the current process step. In other words, the internal combustion engine VM is started as soon as the starting command is received. To successfully start the VM combustion engine, it must first be accelerated to a suitable starting speed. This can be done either using the EM electric machine or the RS starter motor. Reference sign VM Internal combustion engine ECU_VM Electronic control unit RS Starter K0 Disconnect clutch HY Hybrid module G Transmission TG Transmission section GG Transmission housing W2 Output shaft AG Differential gear DW Drive wheel EM Electric machine INV Inverter ECU Electronic control unit C2 Starting element C2_A Actuator W1 Shaft W3 Shaft P Planetary gear set n1, n2 Speed ​​signal

Claims

Method for operating a hybrid powertrain of a motor vehicle, wherein the powertrain comprises an internal combustion engine (VM), an electric machine (EM), and a disconnect clutch (K0) arranged between the internal combustion engine (VM) and the electric machine (EM), wherein a rotational position sequence is performed to set an angular position of the internal combustion engine (VM) that is advantageous for starting the internal combustion engine (S), wherein the following steps are performed in the rotational position sequence while the internal combustion engine (VM) is operated without fuel: - operating the electric machine (EM) in a speed control mode, - setting a torque-transmitting state of the disconnect clutch (K0), - monitoring an angular position of the internal combustion engine (VM) until the angular position reaches a setpoint or a setpoint range, characterized in thatthat if, during the execution of the rotary angle position sequence, starting the internal combustion engine (ICE) is requested, the rotary angle position sequence is immediately aborted, and the internal combustion engine (ICE) is immediately started. Method according to claim 1, characterized in that the internal combustion engine (VM) is started independently of its angle of rotation. Method according to claim 1 or claim 2, characterized in that, for starting the internal combustion engine (VM), a torque delivered by the electric machine (EM) is used to accelerate the internal combustion engine (VM) to a starting speed of the same. Method according to claim 1 or claim 2, characterized in that, for starting the internal combustion engine (IM), the same is accelerated to a starting speed by means of its own starter. Electronic control unit (ECU) for use in motor vehicles, characterized in that the electronic control unit (ECU) is configured to carry out the method according to one of claims 1 to 4.

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