Method and control unit for operating drive train of motor vehicle, and motor vehicle

Abstract

The invention relates to a method and a control unit for operating a drive train of a motor vehicle and the motor vehicle, the drive train (1) having at least a drive unit (2), a transmission (3), a differential (6) and an oil pump (9) for supplying oil at least to the differential (6) for lubrication and / or cooling, a target oil volume flow or target rotational speed for the oil pump (9) is ascertained as a function of a rotational speed difference at the differential (6), as a function of a torque applied to the differential (6) or a torque associated therewith, and as a function of the presence of a respective rotational speed difference and a duration of a respective torque.

Description

Field of the Invention

[0001] The present invention relates to a method and a controller for operating a drive train of a motor vehicle. Furthermore, the present invention also relates to a motor vehicle. Background Art

[0002] Motor vehicles known from practice have a drive train which has a drive unit and a transmission. The transmission converts the rotational speed and the torque and supplies the tractive force of the drive unit to the driven members. A differential is typically connected between the transmission providing one or more transmission ratios and the driven members, wherein the differential distributes the output torque of the transmission to the wheels of the driven axles.

[0003] The differential of the drive train of a motor vehicle must be supplied with oil for lubrication and / or cooling. For this purpose, an oil pump is used. In order to reliably avoid wear of the differential, a constant and large oil volume flow rate is supplied to the differential according to practice, but thereby a drag torque is caused. Thereby, the overall efficiency of the drive train is reduced.

[0004] Therefore, there is a need for a method for operating a drive train, a controller, and a motor vehicle having such a controller, which can achieve an increase in the overall efficiency of the drive train. Summary of the Invention

[0005] The object of the present invention is to provide a method and a controller for operating a drive train of a motor vehicle and a motor vehicle.

[0006] This object is solved by a method for operating a drive train according to claim 1, a controller according to claim 6, and a motor vehicle according to claim 7.

[0007] According to the present invention, a target oil volume flow rate or a target rotational speed for the oil pump is determined as a function of the rotational speed difference at the differential, as a function of the torque applied at the differential or a torque associated therewith, and as a function of the duration of the respective rotational speed difference and the respective torque.

[0008] The method according to the present invention allows the differential to be supplied with oil on demand for lubrication and / or cooling of the differential, more precisely as a function of the rotational speed difference at the differential, as a function of the torque applied at the differential or a torque associated therewith, and as a function of the duration of the respective rotational speed difference at the respective torque. For this purpose, a target oil volume flow rate or a target rotational speed of the oil pump is determined as a function of these parameters, and the oil pump is controlled as a function of the target oil volume flow rate or the target rotational speed. In normal driving operation, the drag torque can be reduced and there is no excess oil in the differential. Only when more oil actually needs to be supplied to the differential due to operating conditions, the oil pump supplies the corresponding target oil volume flow rate to the differential.

[0009] Preferably, depending on the rotational speed difference at the differential, depending on the torque applied at the differential or a related torque, and depending on the duration of the respective rotational speed difference and the respective torque and depending on a comprehensive characteristic curve, a target oil volume flow rate or a target rotational speed for the oil pump is determined by means of an empirically known comprehensive characteristic curve. It is particularly preferred to determine the target oil volume flow rate or the target rotational speed for the oil pump depending on the comprehensive characteristic curve.

[0010] Preferably, the target oil volume flow rate or the target rotational speed for the oil pump is also determined depending on the oil temperature of the oil for lubrication or cooling. This allows for a more demand-based determination of the target oil volume flow rate or the target rotational speed for the oil pump.

[0011] Preferably, an oil temperature determination coefficient or offset is determined, and the coefficient or offset is used to calculate the target oil volume flow rate obtained depending on an empirically known comprehensive characteristic curve or the target rotational speed obtained depending on an empirically known comprehensive characteristic curve, wherein the higher the oil temperature, the greater the coefficient or offset. This is also used for a more demand-based supply of oil to the differential. Description of the Drawings

[0012] Preferred improvements result from the dependent claims and the subsequent description. Embodiments of the present invention are explained in more detail with the aid of the drawings, but the embodiments of the present invention are not limited thereto. In the figures:

[0013] Figure 1 shows a schematic view of a first drive train of a motor vehicle; and

[0014] Figure 2 shows a schematic view of a second drive train of a motor vehicle. Detailed Description of the Embodiments

[0015] Figure 1 A first drive train 1 of a motor vehicle is shown very schematically, wherein the drive train 1 has a drive unit 2, a transmission 3, a driven axle 4 with two wheels 5, and a differential 6. In Figure 1 the transmission 3 is a shiftable transmission with at least two gears in order to be able to provide different gear ratio levels depending on the gear. The transmission 3 converts the rotational speed and the torque and supplies the traction force of the drive unit 2 to the driven axle 4, wherein the differential 6 distributes the traction force supply to the two driven wheels 5 of the axle 4.

[0016] Figure 1 An engine controller 7 for controlling and / or regulating the operation of the drive unit 2 and a transmission controller 8 for controlling and / or regulating the operation of the transmission 3 are also shown. According to Figure 1, the engine controller 7 exchanges data with the drive unit 2 and the transmission controller 8 exchanges data with the transmission 3. In addition, the engine controller 7 and the transmission controller 8 also exchange data with each other.

[0017] According to Figure 1 , the transmission 3 includes an oil pump 9. The oil pump 9 can supply oil to the structural components of the transmission 3 and the differential 6. The oil pump 9 can also be a structural component outside the transmission.

[0018] It is proposed by the present invention that, depending on the rotational speed difference at the differential 6, depending on the torque applied at the differential 6 or a related torque, and depending on the duration of the respective rotational speed difference and the respective torque, the target oil volume flow rate or the target rotational speed for the oil pump 9 is determined in order to supply oil to the differential 6 as required, i.e., depending on the load on the differential 6. If the rotational speed difference and the torque applied at the differential 6 are relatively small, then a small target oil volume flow rate is sufficient to lubricate and / or cool the differential 6. Conversely, if the rotational speed difference and / or the torque at the differential 6 are relatively large, then a higher target oil volume flow rate is required in order to lubricate and / or cool the differential 6.

[0019] Figure 1 A rotational speed sensor 10 is shown, which is assigned to the wheels 5 of the driven axle 4 and provides its measured values, i.e., the rotational speed measured at the wheels 5, to the transmission controller 8. The transmission controller 8 determines the rotational speed difference existing at the differential 6 based on these rotational speeds. The torque equivalent to the torque of the drive unit 2 applied at the transmission input of the transmission 3 is provided to the transmission controller 8 by the engine controller 7. Depending on the current transmission ratio of the transmission 3, the transmission controller 8 determines the torque applied at the differential 6. The duration of the respective rotational speed difference and the respective torque can also be determined by the transmission controller 8, so as to subsequently determine the target oil volume flow rate or the target rotational speed for the oil pump 9 based on this, and then drive or operate the oil pump 9 depending on the target oil volume flow rate or the target rotational speed in order to supply oil to the differential 6 as required for cooling and / or lubrication.

[0020] Preferably, a comprehensive characteristic curve known from experience is stored or saved in the transmission controller 8 in order to determine the target oil volume flow rate or the target rotational speed for the oil pump 9 depending on the comprehensive characteristic curve, depending on the rotational speed difference at the differential 6, depending on the torque applied at the differential 6 or a related torque, and depending on the duration of the respective rotational speed difference and the respective torque.

[0021] In an advantageous refinement of the present invention, it is provided that the target oil volume flow rate or the target rotational speed of the oil pump 9 is also determined depending on the oil temperature of the oil for lubrication and / or cooling. Therefore, inFigure 1 In [reference], a temperature sensor 11 is assigned to the transmission 3, which can measure the oil temperature of the oil. The measured temperature is provided by the temperature sensor 11 to the transmission controller 8. The transmission controller 8 preferably obtains a coefficient or a bias based on the oil temperature, and uses this coefficient or bias to calculate the target oil volume flow obtained based on an empirically known comprehensive characteristic curve or the target rotational speed obtained based on the comprehensive characteristic curve. The larger the coefficient or bias, the higher the oil temperature.

[0022] When determining the coefficient based on the oil temperature, the target oil volume flow obtained based on the comprehensive characteristic curve or the target rotational speed obtained based on the comprehensive characteristic curve is preferably calculated by multiplying with this coefficient. In contrast, the bias is calculated additively.

[0023] Figure 2 A simplified diagram of an alternative drive train 1 of a motor vehicle is shown, wherein, to avoid unnecessary repetition, the same reference numerals are used for the same structural components as in Figure 1 and only the details in which the embodiment of Figure 2 differs from the embodiment of Figure 1 will be discussed hereinafter.

[0024] In Figure 1 , the transmission 3 is switchable, i.e., it can provide different gears, while Figure 2 the transmission 3 is a pre-transmission ratio transmission (Vorübersetzungsgetriebe) with a fixed transmission ratio.

[0025] Figure 2 The transmission of Figure 1 is thus not switchable, and thus this transmission does not have a separate controller. More precisely, the engine controller 7 assumes the function of the transmission controller 8, and the engine controller 7 thus controls and / or regulates the operation of the drive unit 2 and the transmission 3. In Figure 2 , the oil pump 9 can also be a structural component outside the transmission. In Figure 1 , the sensors 10, 11 provide their measurement values to the engine controller 7, and the engine controller is then configured to automatically implement the method according to the invention. Thus, in Figure 2 , the transmission controller 8 is configured to automatically implement the method according to the invention, while in

[0026]

[0027] In addition to the method according to the invention, the present invention also relates to respective controllers, which are configured to automatically implement the method according to the invention on the control side.Furthermore, the invention also relates to a motor vehicle having a drive train 1 with such a controller.

[0028] Preferably, the drive unit 2 of the drive train 1 is an electric motor, and the motor vehicle is then preferably embodied as an electric vehicle.

[0029] The transmission 3 is preferably a non-switchable front-ratio transmission with a fixed transmission ratio as shown in Figure 2 . However, the transmission 3 can also be switchable in order to provide at least two gears with different transmission ratios.

[0030] List of reference numerals

[0031] 1 Drive train

[0032] 2 Drive unit

[0033] 3 Transmission

[0034] 4 Axle

[0035] 5 Wheel

[0036] 6 Differential

[0037] 7 Engine controller

[0038] 8 Transmission controller

[0039] 9 Oil pump

[0040] 10 Speed sensor

[0041] 11 Temperature sensor

Claims

1. A method for operating a drive train of a motor vehicle, wherein, The drive train (1) has at least a drive unit (2), a transmission (3), a differential (6), and an oil pump (9) for supplying oil to at least the differential (6) for lubrication and / or cooling, characterized in that a target oil volume flow rate or a target rotational speed for the oil pump (9) is determined as a function of the rotational speed difference at the differential (6), as a function of the torque applied at the differential (6) or a torque associated therewith, and as a function of the duration of the respective rotational speed difference and the respective torque.

2. The method according to claim 1, wherein As a function of the rotational speed difference at the differential (6), as a function of the torque applied at the differential (6) or a torque associated therewith, as a function of the duration of the respective rotational speed difference and the respective torque, and as a function of an overall characteristic curve, a target oil volume flow rate or a target rotational speed for the oil pump (9) is determined by means of an empirically known overall characteristic curve.

3. The method according to claim 1 or 2, characterized in that The target oil volume flow rate or the target rotational speed for the oil pump (9) is also determined as a function of the oil temperature of the oil for lubrication and / or cooling.

4. The method according to claims 2 and 3, characterized in that, A coefficient or an offset is determined as a function of the oil temperature, and the coefficient or the offset is used to calculate the target oil volume flow rate determined as a function of an empirically known overall characteristic curve or the target rotational speed determined as a function of an empirically known overall characteristic curve.

5. The method according to claim 4, characterized in that, The higher the oil temperature, the greater the coefficient or the offset.

6. A controller (7, 8) for operating a drive train of a motor vehicle, wherein, The drive train (1) has at least a drive unit (2), a transmission (3), a differential (6), and an oil pump (9) for supplying oil to at least the differential (6) for lubrication and / or cooling, characterized in that the controller is configured to automatically carry out the method according to any one of claims 1 to 5.

7. A motor vehicle having a drive train (1), the drive train having at least a drive unit (2), a transmission (3), a differential (6) and an oil pump (9) for supplying oil at least to the differential (6) for lubrication and / or cooling, characterized in that It has a controller (7, 8) according to claim 6.

8. The motor vehicle according to claim 7, characterized in that, The drive unit (2) is an electric machine.

9. The motor vehicle according to claim 7 or 8, characterized in that, The transmission (3) is a non-switchable pre-transmission ratio transmission with a fixed transmission ratio.

10. The motor vehicle according to claim 7, 8 or 9, characterized in that, The motor vehicle is an electric vehicle.

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