Hybrid drivetrain

Abstract

The invention relates to a hybrid powertrain (3) for a vehicle (1). The hybrid powertrain (3) comprises an internal combustion engine (4), an electric motor (6) configured to drive the internal combustion engine (4) in a coasting mode, a coolant supply unit (10) configured to supply coolant for cooling the internal combustion engine (4) and connected to the internal combustion engine (4) in such a way that it is driven by the internal combustion engine (4) during operation, and a control unit (12) configured and set up to control the operation of the internal combustion engine (4) and the operation of the electric motor (6) as a function of the temperature of the internal combustion engine (4) such that the internal combustion engine (4) is operated in coasting mode when the temperature of the internal combustion engine (4) exceeds a predetermined threshold value.Furthermore, the invention relates to a vehicle (1) with a hybrid powertrain (3) and a method for operating a vehicle (1) with a hybrid powertrain (3).

Description

[0001] The invention relates to a hybrid powertrain and a vehicle with a hybrid powertrain. Furthermore, the invention relates to a method for operating a vehicle with a hybrid powertrain.

[0002] From DE 10 2009 023 235 A1 a vehicle with a hybrid powertrain is known, comprising an internal combustion engine, an electric motor and a coolant delivery unit.

[0003] The hybrid powertrain according to the invention is intended for use in vehicles and comprises an internal combustion engine, an electric motor configured to drive the internal combustion engine in a coasting mode, and a coolant supply unit configured to supply coolant for cooling the internal combustion engine. The coolant supply unit is connected to the internal combustion engine in such a way that it is driven by the internal combustion engine during operation. Furthermore, the hybrid powertrain according to the invention comprises a control unit configured and set up to control the operation of the internal combustion engine and the operation of the electric motor, depending on the temperature of the internal combustion engine, such that the internal combustion engine is operated in coasting mode when the temperature of the internal combustion engine exceeds a predetermined threshold.

[0004] The coolant delivery unit is, for example, a coolant pump that delivers liquid coolant in a cooling circuit, or an engine fan that delivers cooling air.

[0005] The term "towing operation" means that a torque is applied externally to the internal combustion engine, driving it.

[0006] By operating the internal combustion engine in coasting mode when the threshold is exceeded, the coolant pump is driven and coolant is pumped to cool the engine. This ensures highly reliable and demand-based cooling of the engine, even when no torque is being supplied to propel the vehicle.

[0007] For example, if the driver requests a deceleration torque to slow the vehicle, or if no torque is requested at all, the control unit can decide, depending on the temperature of the internal combustion engine, that cooling of the internal combustion engine is necessary. This cooling can then be achieved through intelligent control of both the internal combustion engine and the electric motor.

[0008] In one variant, the control unit is designed and configured to control the electric motor in such a way that it provides a torque to drive the internal combustion engine in drag mode when the internal combustion engine's temperature exceeds a predefined threshold. The torque applied externally to the internal combustion engine can therefore be a drag torque provided by the electric motor. This allows the drag operation of the internal combustion engine, and consequently its cooling, to be very precisely adapted to the current operating conditions.

[0009] Alternatively or additionally, it is also conceivable that the torque applied externally to the internal combustion engine is provided wholly or partially by the hybrid powertrain or the vehicle itself. This can be achieved, for example, in hybrid vehicles with a P2 hybrid powertrain by having the control unit keep a clutch engaged between the internal combustion engine and a wheel-side output shaft of the vehicle when the driver requests a deceleration torque to slow the vehicle down.

[0010] In another embodiment, the control unit is designed and configured to control the electric motor in such a way that it provides the torque to drive the internal combustion engine during coasting when the vehicle is switched off. "Switched off" means that the vehicle is not actively being driven. Even if the vehicle has been parked and locked by the driver after a journey, the control unit can still control the electric motor so that it provides a coasting torque to drive the internal combustion engine during coasting, thus maintaining cooling of the internal combustion engine.

[0011] Furthermore, the hybrid powertrain may include a transmission, and the control unit may be designed and configured to control the electric motor in such a way that it provides the torque to drive the internal combustion engine during coasting when the transmission is in park or neutral. This makes it possible to cool the internal combustion engine even when the vehicle is running but not actively moving.

[0012] In a particularly simple technical implementation, the electric motor can be operated in generator mode to provide electrical energy for powering the vehicle via a second electric motor. For example, in series hybrid vehicles, the drag torque for operating the combustion engine can be provided by the motor-generator typically coupled to the combustion engine. Thus, in series hybrid vehicles known from the prior art, existing components can be cleverly controlled by the control unit to achieve the desired cooling.

[0013] Alternatively or additionally, the electric motor can be designed to drive at least one wheel of the vehicle. For example, in hybrid vehicles with a parallel P2 hybrid powertrain, the electric motor typically used for propulsion can be controlled in such a way that it provides a drag torque to drive the internal combustion engine.

[0014] In a further embodiment, the control unit is designed and configured to determine the level of torque to be provided by the electric motor based on a desired torque requested by the driver and a deceleration torque provided by the internal combustion engine, and then to operate the electric motor with the determined torque level. For example, if a driver requests a deceleration torque to slow the vehicle, and the control unit has determined that cooling of the internal combustion engine is necessary, the control unit can control the internal combustion engine and the electric motor separately so that they together provide the requested desired torque.For example, the internal combustion engine can be used as an engine brake, so that it itself provides at least part of the requested deceleration torque. If the desired torque requested by the driver is less or more than the deceleration torque provided by the internal combustion engine, the control unit can determine the necessary differential torque and control the electric motor to provide it. Compared to simply decoupling and switching off the internal combustion engine, this allows for significantly better cooling, as the internal combustion engine and thus also the associated coolant supply unit remain active.

[0015] In another variant, the control unit is designed and configured to determine the temperature of the internal combustion engine using a thermal model based on measured model input parameters and to determine, based on the determined temperature, whether the predefined threshold has been exceeded. Alternatively, a computing unit, such as a second control unit, can be provided, which is designed and configured to determine the temperature of the internal combustion engine using a thermal model based on measured model input parameters and to transmit this information to the control unit. The control unit can then determine, based on the transmitted temperature, whether the predefined threshold has been exceeded.This makes it possible to reliably determine whether cooling of the internal combustion engine is required, even if no sensors for direct temperature measurement are present on the internal combustion engine.

[0016] Model input parameters can include, for example, the power output of the internal combustion engine or the catalyst temperature. Of course, this is not meant to be restrictive. Numerous different vehicle-related data and / or measurements can be used as model input parameters. In principle, previously modeled and / or estimated values ​​can also be used as model input parameters.

[0017] Alternatively, the temperature of the internal combustion engine can also be determined directly by means of a measurement. For example, the oil temperature of the internal combustion engine can be measured and compared with the specified threshold value.

[0018] The vehicle according to the invention comprises a hybrid powertrain according to the invention.

[0019] The inventive method for operating a vehicle with a hybrid powertrain according to the invention comprises the following steps: - Determining the temperature of the internal combustion engine; - Determine whether towing operation of the internal combustion engine is possible; - Operating the electric motor and the internal combustion engine, such that the internal combustion engine is driven in towing mode when the determined temperature of the internal combustion engine exceeds a predetermined threshold and towing of the internal combustion engine is possible; and - Driving the coolant delivery unit by means of the internal combustion engine driven in towing mode.

[0020] The advantages mentioned for the hybrid powertrain according to the invention apply equally to the vehicle according to the invention and to the method according to the invention.

[0021] Preferred embodiments are explained in more detail with reference to the following figures. These show - Fig. 1 a schematic representation of an embodiment of a vehicle according to the invention with a series hybrid powertrain; and - Fig. 2 a schematic representation of a further embodiment of a vehicle according to the invention with a parallel P2 hybrid powertrain.

[0022] The in Fig. 1 The vehicle shown is a hybrid vehicle with four wheels 2 and a series hybrid powertrain 3.

[0023] The hybrid powertrain 3 comprises an internal combustion engine 4, for example a gasoline or diesel engine, and a fuel tank 5 from which the internal combustion engine 4 obtains fuel to be burned.

[0024] The hybrid powertrain 3 further comprises an electric motor 6 which is connected to the internal combustion engine 4 in such a way that a torque provided by the internal combustion engine 4 can be transferred to the electric motor 6 and vice versa.

[0025] The electric motor 6 is designed to drive the internal combustion engine 4 in a towing operation, i.e. to provide a towing torque with which the internal combustion engine 4 can be acted upon.

[0026] The electric motor 6 can also be operated in generator mode, in which it is driven by the internal combustion engine 4 and converts mechanical energy into electrical energy. The electrical energy can then be stored, for example, in an electrical energy storage device 7.

[0027] The hybrid powertrain 3 also includes a second electric motor 8 which can use electrical energy to provide torque to drive the wheels 2 of the vehicle 1.

[0028] A gearbox 9 is optionally arranged between the second electric motor 8 and the driven wheels 2. This gearbox can be switched between a park and / or neutral position and at least one driving position. In the park and / or neutral position, the second electric motor 8 and the wheels 2 are decoupled from each other, so that no torque transmission can take place between them.

[0029] The hybrid powertrain 3 also includes a coolant supply unit 10, for example a coolant pump, which is designed to supply a coolant for cooling the internal combustion engine 4 in a cooling circuit. The coolant supply unit 10 is connected to the internal combustion engine 4 in such a way that it is driven by the engine when the engine is operating. In the exemplary embodiment, the coolant supply unit 10 is connected to the internal combustion engine 4 via a belt 11.

[0030] Furthermore, the hybrid powertrain 3 includes a control unit 12, which is designed and configured to control the operation of the internal combustion engine 4 and the operation of the electric motor 6 as a function of the temperature of the internal combustion engine 4, such that the internal combustion engine 4 is operated in towing mode when the temperature of the internal combustion engine 4 exceeds a predetermined threshold.

[0031] To determine whether the specified threshold has been exceeded, the control unit 12 applies a thermal model 13, which uses model input parameters to determine the current temperature of the internal combustion engine 4 and then compares it with the threshold. Measured values ​​or values ​​known from vehicle operation can be used as model input parameters, for example, the power output profile of the internal combustion engine 4, a coolant temperature, or a measured or modeled catalyst temperature. Alternatively, the current temperature of the internal combustion engine 4 can also be determined by another system of the vehicle 1 and / or another processing unit and transmitted to the control unit 12 to determine whether the specified threshold has been exceeded.

[0032] If the comparison shows that the current temperature of the internal combustion engine 4 is above the threshold value, i.e., the internal combustion engine 4 is too hot, then the control unit 12 can decide that cooling of the internal combustion engine 4 is necessary.

[0033] Depending on the respective operating situation of the vehicle 1, the control unit 12 can then control the internal combustion engine 4 and the electric motor 6 in such a way that the internal combustion engine 4 is operated in towing mode.

[0034] For example, if during a journey of the Fig. If it is determined in the vehicle 1 shown that the temperature of the internal combustion engine 4 is above the specified threshold, but no power from the internal combustion engine 4 is required because the electrical energy storage device 7 is sufficiently charged, the control unit 12 can control the electric motor 6 so that it provides a drag torque to drive the internal combustion engine 4 in towing mode.

[0035] During towing operation of the internal combustion engine 4, the coolant supply unit 10 is driven via the belt 11, resulting in effective cooling of the internal combustion engine 4.

[0036] At the in Fig. In the vehicle 1 shown in Figure 1, the control unit 12 is also designed and configured to control the electric motor 6 in such a way that it provides the torque to drive the internal combustion engine 4 during towing operation even when the vehicle 1 is switched off and the temperature of the internal combustion engine 4 exceeds the specified threshold. For example, if the vehicle 1 is switched off by the driver after a journey, the control unit 12 can still remain active and determine whether the temperature of the internal combustion engine 4 exceeds the specified threshold. Based on this, the control unit 12 can then decide whether cooling is necessary and initiate or maintain towing operation of the internal combustion engine 4 by means of the electric motor 6 in order to drive the coolant pump unit 10.

[0037] Since at the in Fig. In the vehicle 1 shown with the series hybrid drivetrain 3, since no direct torque transmission takes place between the internal combustion engine 4 or the electric motor 6 and the wheels 2, the cooling of the internal combustion engine 4 is technically simple and independent of the switching state of the transmission 9, regardless of whether the vehicle 1 is stationary or moving, by controlling the electric motor 6.

[0038] Fig. Figure 2 shows a second embodiment of a vehicle 1 according to the invention.

[0039] The second embodiment corresponds to the first embodiment in several essential aspects, so only the differences will be discussed below. The same reference numerals are used for identical or functionally equivalent components.

[0040] The in Fig. 2 Vehicle 1 shown is also a four-wheeled hybrid vehicle 2 and features a parallel P2 hybrid powertrain 3.

[0041] The hybrid powertrain 3 comprises an internal combustion engine 4 and a fuel tank 5 from which the internal combustion engine 4 draws fuel to be burned.

[0042] The hybrid powertrain 3 further comprises an electric motor 6 and an electrical energy storage device 7, from which the electric motor 6 draws electrical energy.

[0043] A coupling 14 is arranged between the internal combustion engine 4 and the electric motor 6, which connects the internal combustion engine 4 and the electric motor 6 in a separable manner. When the coupling 14 is engaged, the internal combustion engine 4 and the electric motor 6 are torque-connected.

[0044] The hybrid powertrain 3 of the in Fig. The vehicle 1 shown in Figure 2 further comprises a switchable transmission 9 arranged between the electric motor 6 and the driven wheels 2, which can be switched between a park and / or neutral position and at least one driving position. In the park and / or neutral position, the second electric motor 6 and the wheels 2 are decoupled from each other, so that no torque transmission can take place between them.

[0045] In the driving position, the driven wheels 2 are connected to the electric motor 6 via torque. If, in addition, the clutch 14 is also engaged, torque can be provided to drive the wheels 2 by both the internal combustion engine 4 and the electric motor 6.

[0046] The hybrid powertrain 3 of the in Fig. The vehicle 1 shown in Figure 2 also has a control unit 12 which is designed and configured to control the operation of the internal combustion engine 4 and the operation of the electric motor 6 as a function of the temperature of the internal combustion engine 4, such that the internal combustion engine 4 is operated in towing mode when the temperature of the internal combustion engine 4 exceeds a predetermined threshold.

[0047] In principle, temperature-dependent towing of the internal combustion engine 4 is possible when the vehicle 1 is stationary or when it is moving.

[0048] In the Fig. In the vehicle 1 shown in Figure 2, the control unit 12 is designed and configured to control the electric motor 6 in such a way that it provides a torque to drive the internal combustion engine 4 in towing operation when the vehicle 1 is stationary, the transmission 9 is in a park or neutral position and the temperature of the internal combustion engine 4 exceeds the specified threshold.

[0049] In this case, the torque provided by the electric motor 6 is transmitted to the internal combustion engine 4 via the closed clutch 14. The internal combustion engine 4 is driven by the torque during towing operation, which also drives the coolant supply unit 10 connected to the internal combustion engine 4. Since the transmission 9 is in the park and / or neutral position and therefore no torque transmission takes place between the electric motor 6 and the wheels 2, the entire torque provided by the electric motor 6 can be used for towing the internal combustion engine 4 and thus for its cooling.

[0050] As already explained, towing operation of the internal combustion engine 4, and thus efficient cooling of the same, is possible even when the vehicle 1 is moving. In addition to or as an alternative to the torque provided by the electric motor 6, the kinetic energy of the moving vehicle 1 can also be used to drive the internal combustion engine 4 during towing operation.

[0051] The control unit 12 of the in Fig. The vehicle 1 shown in 2 is designed and equipped to determine, during a journey, a level of torque to be provided by the electric motor 6 based on a desired torque requested by a driver and a deceleration torque provided by the internal combustion engine 4, and then to operate the electric motor 6 with the torque to be provided at the determined level.

[0052] If, during a journey of vehicle 1, the driver requests, for example, a desired torque of -30 Nm (the negative sign indicates that a deceleration torque is requested) by releasing the accelerator pedal, and the temperature of the internal combustion engine 4 exceeds the predefined threshold, the control unit 12 can decide that cooling of the internal combustion engine 4 is necessary. The control unit 12 can then ensure that the internal combustion engine 4 is not switched off, but continues to operate in a coasting mode. This can be achieved, for example, by the control unit 12 adjusting the transmission 9 and the clutch 14 so that the internal combustion engine 4 remains torque-connected to the wheels 2.

[0053] The internal combustion engine 4 can then be used as an engine brake during towing. Put simply, the internal combustion engine 4 itself can provide a speed-dependent deceleration torque that slows down the vehicle 1.

[0054] The control unit 12 can then determine a differential torque to be additionally provided by the electric motor 6 by subtracting the deceleration torque provided by the internal combustion engine 4 from the desired torque.

[0055] If, for example, the desired torque is -30 Nm and the deceleration torque provided by the internal combustion engine 4 is -20 Nm, then an additional deceleration torque of -10 Nm must be provided by the electric motor 6.

[0056] If the desired torque is -30 Nm and the deceleration torque provided by the internal combustion engine 4 is -40 Nm, then an additional torque of +10 Nm must be provided by the electric motor 6.

[0057] In contrast to simply switching off the internal combustion engine 4 while driving, its towing operation drives the coolant delivery unit 10, resulting in effective cooling of the internal combustion engine 4.

[0058] Both the in Fig. 1. Vehicle shown 1 with the series hybrid powertrain 3, i.e., also the one in Fig. 2 The vehicle 1 shown with the parallel P2 hybrid powertrain 3 can be operated using a method according to the invention.

[0059] An embodiment of the method is described below using the example in Fig. The vehicle shown in section 1 is briefly explained below.

[0060] In a first step of the procedure, the control unit 12 determines a temperature of the internal combustion engine 4.

[0061] In a second step of the procedure, the control unit 12 determines whether towing operation of the internal combustion engine 4 is possible. For example, towing operation of the internal combustion engine 4 is not possible if, when the vehicle 1 is stationary, no torque can be provided to drive the internal combustion engine 4 in towing mode due to an insufficient charge level of the electrical energy storage device 7, or if the torque would lead to an undesirable drive of the wheels 2.

[0062] In a third step of the procedure, the control unit 12 operates the electric motor 6 and the internal combustion engine 4 in such a way that the internal combustion engine 4 is driven in towing mode when the determined temperature of the internal combustion engine 4 exceeds a predetermined threshold and towing mode of the internal combustion engine 4 is possible.

[0063] In a fourth step of the process, the internal combustion engine 4, driven in towing mode, drives the coolant delivery unit 10 and thus effectively cools the internal combustion engine 4. 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 2009 023 235 A1

[0002]

Claims

[1] Hybrid drive train for a vehicle (1), comprising an internal combustion engine (4), an electric motor (6) which is designed to drive the internal combustion engine (4) in a towing operation, a coolant delivery unit (10) which is designed to deliver a coolant for cooling the internal combustion engine (4) and which is connected to the internal combustion engine (4) in such a way that it is driven by the internal combustion engine (4) during operation, and a control unit (12) which is designed and configured to control the operation of the internal combustion engine (4) and the operation of the electric motor (6) as a function of a temperature of the internal combustion engine (4) such that the internal combustion engine (4) is operated in towing mode when the temperature of the internal combustion engine (4) exceeds a predetermined threshold value. [2] Hybrid drive train according to claim 1, wherein the control unit (12) is designed and configured to control the electric motor (6) such that it provides a torque with which the internal combustion engine (4) is driven in towing mode when the temperature of the internal combustion engine (4) exceeds the predetermined threshold value. [3] Hybrid drive train according to claim 2, wherein the control unit (12) is designed and configured to control the electric motor (6) such that it provides the torque for driving the internal combustion engine (4) in towing mode when the vehicle (1) is switched off. [4] Hybrid drive train according to claim 2 or 3, further comprising a transmission (9), wherein the control unit (12) is designed and configured to control the electric motor (6) such that it provides the torque for driving the internal combustion engine (4) in towing mode when the transmission (9) is in a park or neutral position. [5] Hybrid drive train according to one of the preceding claims, wherein the electric motor (6) is operable in a generator mode to provide electrical energy for driving the vehicle (1) by means of a second electric motor (8). [6] Hybrid drive train according to one of the preceding claims, wherein the electric motor (6) is designed to drive at least one wheel (2) of the vehicle (1). [7] Hybrid drive train according to one of the preceding claims, wherein the control unit (12) is designed and configured to determine a level of a torque to be provided by the electric motor (6) based on a desired torque requested by a driver and a deceleration torque provided by the internal combustion engine (4) and to operate the electric motor (6) with the torque to be provided at the determined level. [8] Hybrid drive train according to one of the preceding claims, wherein the control unit (12) is designed and configured to determine the temperature of the internal combustion engine (4) by means of a thermal model (13) based on measured model input parameters and to determine, based on the determined temperature, whether the predetermined threshold value is exceeded. [9] Vehicle comprising a hybrid powertrain (3) according to any one of the preceding claims. [10] Method for operating a vehicle (1) with a hybrid drive train (3) according to one of claims 1 to 8, comprising the following steps: - determining a temperature of the internal combustion engine (4); - Determine whether towing operation of the internal combustion engine (4) is possible; - operating the electric motor (6) and the internal combustion engine (4) so ​​that the internal combustion engine (4) is driven in towing mode when the determined temperature of the internal combustion engine (4) exceeds a predetermined threshold value and the towing mode of the internal combustion engine (4) is possible; and - Driving the coolant delivery unit (10) by means of the internal combustion engine (4) driven in towing mode.

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