Methods for controlling a hybrid powertrain and hybrid powertrain for this purpose

Abstract

The invention relates to a method for controlling a hybrid powertrain of a vehicle and a hybrid powertrain with a drive unit comprising an internal combustion engine with a crankshaft and a first electric machine with a first rotor shaft, wherein the crankshaft and first rotor shaft are connected to each other by means of a rotary connection, a second electric machine with a second rotor shaft, wherein rotational characteristics of the rotor shafts and the crankshaft are detected by means of sensors and the rotor shafts can be connected to each other by means of a clutch switched by a hydraulic actuator depending on the rotational characteristics.In order to maintain the operational readiness of the hybrid powertrain even in the event of a sensor failure and to avoid vehicle breakdowns in this regard, substituted rotational parameters are generated based on rotational parameters of the crankshaft or the first rotor shaft, taking into account a translation of the rotary connection, in the event of a sensor failure of the first rotor shaft or the crankshaft.

Description

[0001] The invention relates to a method for controlling a hybrid powertrain of a vehicle and a hybrid powertrain with a drive unit comprising an internal combustion engine with a crankshaft and a first electric machine with a first rotor shaft, wherein the crankshaft and first rotor shaft are connected to each other by means of a rotary connection, a second electric machine with a second rotor shaft, wherein rotational characteristics of the rotor shafts and the crankshaft are detected by means of sensors and the rotor shafts can be connected to each other by means of a clutch switched by a hydraulic actuator depending on the rotational characteristics.

[0002] Hybrid powertrains and their control methods are used in vehicles such as motor vehicles. Such hybrid powertrains are known, for example, from German patent application DE 10 2010 049 931 A1. In addition to a drive unit with an internal combustion engine and a first electric motor connected to it by means of a rotary coupling, a further electric motor is provided, wherein the drive unit and the further electric motor can be separated and connected to each other by means of a coupling. The coupling is actuated automatically by an actuator, for example hydraulically by means of a slave cylinder, which is axially displaced by means of a system pressure supplied by a pump and opens or closes the coupling via an actuating mechanism. The coupling is controlled depending on the rotational speeds of the drive unit and the further electric motor applied to the coupling.

[0003] Depending on the clutch's operating state, the hybrid powertrain allows for several driving modes. For example, with the clutch disengaged, the vehicle can be driven exclusively by electric power or it can recuperate energy. Simultaneously, the electric motor of the drive unit, driven by the combustion engine, can charge a vehicle battery, start the combustion engine, operate auxiliary systems when the combustion engine is off, and / or perform similar functions. With the clutch engaged, the combustion engine can drive the vehicle exclusively, or additionally with one or both electric motors.

[0004] The vehicle's operating conditions are monitored, among other methods, by continuously recording the rotational movements of the rotor shafts of the electric motor and the internal combustion engine. Appropriate sensors are used for this purpose. If, for example, the sensor of the electric motor fails, the clutch's engagement state becomes unclear, and the vehicle switches to an emergency mode in which at least the clutch remains permanently disengaged to prevent damage.

[0005] The object of the invention is the further development of a method for controlling a generic powertrain and the further development of such a hybrid powertrain. In particular, the object of the invention is to enable the vehicle to continue operating even when implausible information regarding the rotational characteristics at the clutch is received. This object is achieved by the subject matter of claims 1, 2, and 10. The dependent claims describe advantageous embodiments of the subject matter of claims 1 and 2.

[0006] The proposed method serves to control a hybrid powertrain with a drive unit comprising an internal combustion engine with a crankshaft and a first electric motor with a first rotor shaft. The crankshaft and the first rotor shaft are connected to each other by means of a rotary coupling. A rotary coupling is understood to be a device that transmits torque from one shaft to an axially spaced shaft without significant backlash and with a predetermined gear ratio. Here, torque is transmitted from the internal combustion engine to the first electric motor and vice versa. A common output shaft, preferably coaxial with the crankshaft, transmits any combined torque to an output of the vehicle.

[0007] Furthermore, a second electric machine with a second rotor shaft is provided, wherein the output shaft and the second rotor shaft are rotationally connected to each other and form a common output for driving drive wheels, for example, via a gearbox, a differential, a multi-axle distribution drive, and / or the like. The second electric machine can be housed in a so-called dedicated hybrid gearbox or in a common housing with the first electric machine.

[0008] The rotational parameters of the rotor shafts and crankshaft are recorded using sensors. These parameters include, for example, rotational speed, angular velocity, acceleration, and / or angle of rotation. The sensors can be, for example, Hall effect sensors or similar devices.

[0009] A coupling, such as a friction coupling or a positive-lock coupling, is arranged between the first rotor shaft (or output shaft of the drive unit) and the second crankshaft of the second electric machine. This coupling is engaged by a hydraulic actuator based on the rotational characteristics of the rotor shafts. The coupling is preferably open without pressure and is closed by means of a slave cylinder piston that is axially displaced by system pressure supplied by the hydraulic actuator. For example, after a closing operation is requested by a control unit of the hydraulic actuator following the detection of rotational characteristics, such as a predetermined differential speed of the rotor shafts, system pressure is built up by an electrically driven pump.The rotation parameters are recorded by the control unit of the hydraulic actuator or another control unit of the vehicle and transmitted to the control unit of the hydraulic actuator via a data network, for example CAN bus.

[0010] To prevent an emergency driving condition or vehicle shutdown in the event of a sensor failure on the first rotor shaft—and thus an undefined and implausible clutch state—substitute rotational parameters of the first rotor shaft are generated based on the rotational parameters of the crankshaft, taking into account the gear ratio of the rotary connection. The crankshaft rotational parameters, which can be used, for example, to control the internal combustion engine (ignition timing, valve dwell angle, fuel injection, etc.), are transmitted via a data network, such as a CAN bus, from the engine control unit of the internal combustion engine to the control unit of the hydraulic actuator. Alternatively, a higher-level control unit can acquire all rotational parameters and / or, if necessary, control the internal combustion engine and the hydraulic actuator.Alternatively, a method is proposed for controlling a hybrid powertrain with a drive unit comprising an internal combustion engine with a crankshaft and a first electric machine with a first rotor shaft, wherein the crankshaft and first rotor shaft are connected to each other by means of a rotary connection, a second electric machine with a second rotor shaft, wherein rotational characteristics of the rotor shafts and the crankshaft are detected by means of sensors and the rotor shafts can be connected to each other by means of a clutch switched by a hydraulic actuator depending on the rotational characteristics, wherein in the event of a failure of the sensor of the crankshaft substituted rotational characteristics are formed on the basis of rotational characteristics of the first rotor shaft taking into account a translation of the rotary connection.

[0011] For example, the internal combustion engine can be coaxial with the output shaft of the drive unit, or an input part of the clutch can be directly connected to the crankshaft, with the first rotor shaft arranged parallel to the crankshaft and coupled to the crankshaft or output shaft via a rotary joint. In this configuration, a gear ratio between the first rotor shaft and the input part of the clutch is already incorporated during normal operation, for example, to create a speed differential between the first rotor shaft and the second rotor shaft, which is arranged coaxially at the output part of the clutch. If the sensor on the first rotor shaft fails, this gear ratio is lost because the crankshaft and second rotor shaft are arranged coaxially. However, the gear ratio remains in effect if the sensor on the crankshaft fails.Similarly, in the case of a coaxial arrangement of the rotor shafts, if the sensor of the first rotor shaft fails, the rotational characteristics of the crankshaft sensor are converted into substituted rotational characteristics of the first rotor shaft by taking into account the translation of the rotary connection.

[0012] The rotary connection can be formed by a belt drive with pulleys of different diameters providing the transmission ratio, the ratio being determined by the quotient of the pulley diameters. Preferably, the rotary connection is formed by a gear connection with meshing gears having a predetermined number of teeth. In this case, the transmission ratio can be determined based on the ratio of the number of teeth on the gears.

[0013] For example, a gear connection can be formed on two meshing spur gears. Alternatively, a ring gear and a planet gear arranged within it can be provided for an axially parallel arrangement between the first rotor shaft and the crankshaft. For example, the gear ratio can be set by connecting the crankshaft coaxially or integrally to a ring gear with internal teeth, and by means of a spur gear such as a planet gear with external teeth meshing with the internal teeth, the first rotor shaft being arranged axially offset from the crankshaft by means of a spur gear such as a planet gear. It is understood that if the second rotor shaft is arranged axially parallel to the output of the clutch, for example via one or more transmission shafts or the like, the resulting output gear ratio is also taken into account during normal operation and in the event of a failure of one of the sensors on the crankshaft or the first rotor shaft.

[0014] According to an advantageous embodiment of the method, in the event of a failure of the sensor of the first rotor shaft, actuation of the hydraulic actuator is enabled upon a requested signal to close the clutch, depending on the differential speed between a substituted speed of the first rotor shaft and a speed of the second rotor shaft. This means, for example, that the clutch is only closed after a request for actuation when the clutch slip is sufficiently small, corresponding to falling below a threshold value for the differential speed.

[0015] Alternatively or additionally, it can be provided that if the clutch is engaged and a differential speed exceeds a predetermined or predefinable limit between the substituted speed of the first rotor shaft and the speed of the second rotor shaft, the clutch is opened. In this case, it is assumed that the clutch can no longer transmit the torque to be transferred, for example, due to a defect in the clutch and / or the hydraulic actuator. To prevent further damage, the clutch remains open, and in emergency operation mode, the system is driven exclusively using the second electric motor.

[0016] It has also proven advantageous to continuously validate the sensors of the rotor shafts, for example, using the rotational characteristics of the other sensors, the power outputs of the electric motor and / or the internal combustion engine, the battery voltage, the vehicle speed, the system pressure of the hydraulic actuator, the pump speed of the hydraulic actuator, a position signal from the slave cylinder piston actuating the clutch, and / or the like, and to keep the clutch open if there is a lack of plausibility.

[0017] The proposed and previously described hybrid powertrain serves to carry out the methods according to any one of claims 1 to 9. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2010 049 931 A1

[0002]

Claims

[1] Method for controlling a hybrid powertrain with a drive unit comprising an internal combustion engine with a crankshaft and a first electric machine with a first rotor shaft, wherein the crankshaft and the first rotor shaft are connected to each other by means of a rotary connection, a second electric machine with a second rotor shaft, wherein rotational characteristics of the rotor shafts and the crankshaft are detected by means of sensors and the rotor shafts can be connected to each other by means of a clutch switched by a hydraulic actuator depending on the rotational characteristics, characterized by , that in the event of a failure of the sensor of the first rotor shaft, substituted rotational parameters are formed based on rotational parameters of the crankshaft, taking into account a translation of the rotary connection. [2] Method for controlling a hybrid powertrain with a drive unit comprising an internal combustion engine with a crankshaft and a first electric machine with a first rotor shaft, wherein the crankshaft and the first rotor shaft are connected to each other by means of a rotary connection, a second electric machine with a second rotor shaft, wherein rotational characteristics of the rotor shafts and the crankshaft are detected by means of sensors and the rotor shafts can be connected to each other by means of a clutch switched by a hydraulic actuator depending on the rotational characteristics, characterized by , that in the event of a failure of the crankshaft sensor, substituted rotational parameters are formed based on rotational parameters of the first rotor shaft, taking into account a translation of the rotary connection. [3] Method according to claim 1 or 2, characterized by, that the rotary connection is formed from a gear connection with meshing gears with predetermined numbers of teeth. [4] Method according to claim 3, characterized by that the translation is determined based on a ratio of the number of teeth on the gears. [5] Method according to claim 4, characterized by , that the translation is set by connecting the crankshaft coaxially with a ring gear with internal teeth in a rotationally fixed manner and by arranging the first rotor shaft axially offset to the crankshaft a spur gear with external teeth meshing with the internal teeth. [6] Method according to any one of claims 1 to 5, characterized by , that rotational parameters such as rotational speed, rotational velocity, rotational acceleration and / or rotational angle are recorded. [7] Method according to claim 6, characterized by, that depending on a differential speed of a substituted speed of the first rotor shaft and a speed of the second rotor shaft, an actuation of the hydraulic actuator is released when a signal is requested to close the clutch. [8] Method according to claim 6 or 7, characterized by , that if the clutch is closed and a speed difference is exceeded between the substituted speed of the first rotor shaft and the speed of the second rotor shaft, the clutch is opened. [9] Method according to any one of claims 1 to 8, characterized by , that the sensors of the rotor shafts are continuously checked for plausibility and, if there is a lack of plausibility, the clutch is kept open. [10] Hybrid powertrain for carrying out the method according to any one of claims 1 to 9.