Control device of a motor vehicle and method for operating a hydraulic system of a motor vehicle

Abstract

Control device (12) of a motor vehicle, in particular hybrid control device or transmission control device of a hybrid vehicle, for controlling a hydraulic system of the motor vehicle, which has a main pump (8) mechanically driven by a drive unit (1) of the motor vehicle via a transmission shaft (9) of a transmission (5) of the motor vehicle and an electrically driven auxiliary pump (10), wherein the control device (12) then, when the rotational speed of the transmission shaft (9) driving the main pump (8) reaches or falls below a limit value during a hydraulic pressure request, controls the auxiliary pump (10) to provide the hydraulic pressure request, characterized in that the control device (12) takes into account the start-up behavior of the auxiliary pump (10) and determines the limit value at which it reaches or falls below the auxiliary pump (10) to provide the hydraulic pressure request.increased by a variable offset, wherein the offset depends on the time gradient of the rotational speed of the transmission shaft (9) driving the main pump (8) such that the offset is greater the greater the time gradient.

Description

[0001] The invention relates to a control device of a motor vehicle according to the preamble of claim 1. Furthermore, the invention relates to a method for operating a hydraulic system of a motor vehicle according to the preamble of claim 3.

[0002] Fig. Figure 1 shows a highly schematic, exemplary drive train diagram of a motor vehicle designed as a hybrid vehicle, which is known from practice. Such a hybrid vehicle comprises a drive unit 1, which is formed by an internal combustion engine 2 and an electric motor 3. A transmission 5 is connected between the drive unit 1 and an output 4. The transmission 5 is, in particular, an automatic or automated manual transmission. Furthermore, Fig. 1, that a clutch 6 is connected between the internal combustion engine 2 and the electric machine 3 of the drive unit 1, wherein when the clutch 6 is disengaged, the internal combustion engine 2 is decoupled from the output 4 and can then be shut down in order to operate the hybrid vehicle exclusively by electric motor via the electric machine 3 of the drive unit. However, when the clutch 6 is engaged, the internal combustion engine 2 is coupled to the output 4 and the hybrid vehicle can be driven by both the internal combustion engine 2 and the electric machine 3. An electrical energy storage device 7 interacts with the electric machine 3, which is discharged more intensively during motor operation of the electric machine 3 of the drive unit 1 and charged more intensively during generator operation of the electric machine 3 of the drive unit 1. The drive train of the Fig. 1 further comprises a hydraulic system comprising a main pump 8, which can be mechanically driven from the drive unit 1 via a transmission shaft 9 of the transmission 5. If, for example, during purely electric travel at low speed, the rotational speed of the transmission shaft 9 driving the main pump 8 is too low, the main pump 8 may not be able to provide a hydraulic pressure demand.

[0003] For this purpose, it is already known from practice that a hydraulic system of a motor vehicle has, in addition to the mechanically driven main pump 8, an electrically driven auxiliary pump 10 which is electrically driven by an electric motor 11 of the auxiliary pump 10.

[0004] Furthermore, Fig. 1 a control device 12, which in Fig. 1 for controlling and / or regulating the operation of the electric machine 3, the transmission 5, and the electric motor 11 of the auxiliary pump 10, exchanges data with these assemblies in the direction of the double arrows shown. In a hybrid vehicle, this control device 12 can be a hybrid control device or a transmission control device.

[0005] It is already known from practice that when the speed of the transmission shaft 9 driving the main pump 8 reaches or falls below a limit value in response to a hydraulic pressure request, the control device 12 activates the auxiliary pump 10 to provide the hydraulic pressure request. In practice, this limit value also depends on hydraulic oil leaks in the components of the motor vehicle's hydraulic system involved. For example, it is common practice for control devices known from practice to determine the leakage in the hydraulic system based on a leakage model of the motor vehicle's hydraulic system and, depending on this, to determine the limit value for the speed of the transmission shaft 9 driving the main pump 8. When this limit value is reached or fallen below, the auxiliary pump 10 is activated to provide the hydraulic pressure request.

[0006] DE 10 2009 014 593 A1 discloses a hydraulic system of a motor vehicle with a main pump and an auxiliary pump as well as details of a control system for operating this hydraulic pressure system.

[0007] US 2011 / 0 082 630 A1 discloses a motor vehicle having a mechanically driven main pump and an electrically driven auxiliary pump. A deceleration rate of the motor vehicle is calculated based on the speed of the motor vehicle, and the auxiliary pump is activated based on this speed-dependent deceleration rate.

[0008] There is a need for a control device for a motor vehicle and a method for operating a hydraulic system of a motor vehicle with which the control of the electrically driven auxiliary pump can be improved.

[0009] Based on this, the present invention is based on the object of creating a novel control device of a motor vehicle and a novel method for operating a hydraulic system of a motor vehicle.

[0010] This object is achieved by a control device according to claim 1. According to this, in order to take into account the starting behavior of the additional pump, the control device increases the limit value, upon reaching or falling below which the additional pump controls or switches on or turns on the additional pump to provide the hydraulic pressure request, by a variable offset, wherein the offset depends on the temporal gradient of the speed of the gear shaft driving the main pump in such a way that the offset is greater the greater the temporal gradient.

[0011] The present invention proposes, for the first time, to determine the limit value for the speed of the transmission shaft driving the main pump, upon reaching or falling below which the auxiliary pump is activated to provide the hydraulic pressure demand, also depending on the auxiliary pump's startup behavior. This can improve the control of the electrically driven auxiliary pump in the motor vehicle's hydraulic system.

[0012] The method according to the invention for operating a hydraulic system of a motor vehicle is defined in claim 3.

[0013] Preferred developments of the invention will become apparent from the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail, without being limited thereto, with reference to the drawings. Herein: Fig. 1 shows an exemplary diagram of a hybrid vehicle in which the method according to the invention for operating a motor vehicle can be used; and Fig. 2-3 diagrams to illustrate the method according to the invention for operating a hybrid vehicle.

[0014] The functioning of a control device according to the invention and a method according to the invention for operating a hydraulic system of a motor vehicle is explained below with reference to Fig. 2 and Fig. 3 described.

[0015] The control device 12 of the Fig. 1, the motor vehicle shown as an example controls the electrically driven auxiliary pump 10 or the electric motor 11 thereof or switches the same on in order to provide a hydraulic pressure request when the target pressure of a hydraulic pressure request can no longer be provided or can no longer be provided solely by the mechanically driven main pump 8, that is to say when a speed n9 of the transmission shaft 9 driving the main pump 8 reaches or falls below a limit value.

[0016] In order to take account of the starting behavior of the additional pump 10, the control device 12 according to the invention increases the limit value, upon reaching or falling below which the additional pump 10 is activated or switched on to provide the hydraulic pressure request, by an offset OF.

[0017] The offset OF, by which the limit value for the speed n9 of the gear shaft driving the main pump 8 is increased, is variable.

[0018] This shows Fig. 2 shows an embodiment of the invention in which the offset OF depends on the temporal gradient dn9 / dt of the rotational speed n9 of the gear shaft 9 driving the main pump 8, namely such that the offset OF is greater the greater the temporal gradient of the rotational speed of the gear shaft 9 driving the main pump 8. With a small temporal gradient dn9 / dt of the rotational speed n9, the offset OF is relatively small, whereas with a relatively high temporal gradient dn9 / dt, the offset OF is relatively large.

[0019] In the execution of the Fig.3, the offset OF depends on a deviation Δp between a target pressure of the hydraulic pressure request and an actual pressure of the hydraulic pressure request, namely such that the offset OF is greater the greater the deviation Δp. Therefore, if the deviation Δp between the target pressure of the hydraulic pressure request and the actual pressure of the hydraulic pressure request is small, a small offset OF can be used. However, if the deviation Δp between the target pressure of the hydraulic pressure request and the actual pressure of the hydraulic pressure request is relatively large, a high offset is used.

[0020] With the present invention, namely the control device 12 according to the invention and the method according to the invention for operating the hydraulic system of a motor vehicle, in particular the hydraulic system of an automatic or automated transmission of the motor vehicle, the starting behavior of the electrically driven auxiliary pump 10 is taken into account when determining the switch-on condition of the electrically driven auxiliary pump 10. Depending on the start-up behavior of the electrical auxiliary pump 10, an offset OF is determined for the limit value of the rotational speed of the transmission shaft 9 driving the main pump 8. Upon reaching or falling below this value, the auxiliary pump 10 is controlled or switched on by the control device 12 to provide the hydraulic pressure request.This offset OF is variable, whereby the offset OF is greater the greater the temporal gradient of the rotational speed n9 of the gear shaft 9 driving the main pump 8 and, if applicable, the greater the deviation Δp between the target pressure and the actual pressure of the hydraulic pressure request.

[0021] Then, if the offset value OF is determined variably, the switching behavior of the electric auxiliary pump 10 can be particularly advantageously improved. Reference symbol 1 drive unit 2 combustion engine 3 electric machine 4 downforce 5 gearboxes 6 Clutch 7 electrical energy storage 8 Main pump 9 Gear shaft 10 Additional pump 11 electric machine 12 Control device

Claims

[1] Control device (12) of a motor vehicle, in particular a hybrid control device or transmission control device of a hybrid vehicle, for controlling a hydraulic system of the motor vehicle, which has a main pump (8) which can be mechanically driven by a drive unit (1) of the motor vehicle via a transmission shaft (9) of a transmission (5) of the motor vehicle and an electrically driven auxiliary pump (10), wherein the control device (12) controls the auxiliary pump (10) to provide the hydraulic pressure request when the speed of the transmission shaft (9) driving the main pump (8) reaches or falls below a limit value in the case of a hydraulic pressure request, characterized byin that the control device (12) increases the limit value, upon reaching or falling below which the additional pump (10) activates the additional pump (10) to provide the hydraulic pressure request, by a variable offset in order to take account of the start-up behavior of the additional pump (10), wherein the offset depends on the temporal gradient of the rotational speed of the gear shaft (9) driving the main pump (8) in such a way that the offset is greater the greater the temporal gradient. [2] Control device (12) according to claim 1, characterized by that the offset further depends on a deviation between a target pressure of the hydraulic pressure request and an actual pressure of the hydraulic pressure request such that the offset is greater the greater the deviation is. [3] Method for operating a hydraulic system of a motor vehicle, which has a main pump (8) which can be mechanically driven by a drive unit (1) of the motor vehicle via a transmission shaft (9) of a transmission (5) of the motor vehicle and an electrically driven auxiliary pump (10), wherein when, in the case of a hydraulic pressure request, the rotational speed of the transmission shaft (9) driving the main pump (8) reaches or falls below a limit value, the auxiliary pump (10) is controlled to provide the hydraulic pressure request, characterized byin that, in order to take account of the starting behavior of the additional pump (10), the limit value, upon reaching or falling below which the additional pump (10) activates the additional pump (10) to provide the hydraulic pressure request, is increased by a variable offset, wherein the offset is determined as a function of the temporal gradient of the rotational speed of the gear shaft (9) driving the main pump (8) in such a way that the offset is greater the greater the temporal gradient. [4] Method according to claim 3, characterized by that the offset is determined depending on a deviation between a target pressure of the hydraulic pressure request and an actual pressure of the hydraulic pressure request in such a way that the offset is greater the greater the deviation is.

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