Method and control unit for operating a hydraulic system and motor vehicle with a hydraulic system

Abstract

Method for operating a hydraulic system, in particular a hydraulic system of a motor vehicle, which has a hydraulic pump (10) driven by a speed-controlled electric motor (11) for drawing hydraulic oil from an oil reservoir (6) and for supplying at least one assembly (8) to be cooled and / or lubricated with the hydraulic oil, wherein, depending on a temperature of the hydraulic oil and depending on an actual electrical current of the electric motor (11) driving the hydraulic pump (10) and / or an actual speed of the hydraulic pump (10) or of the electric motor (11) driving it, it is determined whether a sufficiently high oil supply to the at least one assembly (8) to be cooled and / or lubricated is ensured.

Description

[0001] The invention relates to a method and control device for operating a hydraulic system and a motor vehicle with a hydraulic system.

[0002] Motor vehicles have a multitude of components that require cooling and / or lubrication. In the case of an electric or hybrid vehicle, these components include, in particular, an electric machine, which can be supplied with hydraulic oil as a cooling fluid, for example. For this purpose, the respective component to be cooled and / or lubricated is integrated into a hydraulic system. The hydraulic system of a motor vehicle, into which the component to be cooled and / or lubricated with hydraulic oil is integrated, has a hydraulic pump that draws hydraulic oil from an oil reservoir and supplies it to the respective component to be cooled and / or lubricated with hydraulic oil. The hydraulic pump is driven by an electric motor.

[0003] A leak can develop in the hydraulic system, potentially leading to oil loss. If there is no longer enough hydraulic oil in the hydraulic system, this can lead to a drop in system pressure and, in extreme cases, to the hydraulic pump running dry. Sufficient cooling and / or lubrication can then no longer be guaranteed for the respective component to be cooled and / or lubricated. It is also possible that plugs, particularly on hydraulic lines, are not removed during production, which means that a sufficiently high oil supply cannot be provided for the component to be lubricated and / or cooled.A sufficiently high oil supply for the assembly to be lubricated and / or cooled may not be guaranteed, for example, due to a production defect, such as a drilling failure or failure to drill a hole in the hydraulic system, or foreign particles in the hydraulic system. There is a need for a simple, reliable means of checking whether a sufficiently high oil supply can be guaranteed for at least one assembly to be cooled and / or lubricated, without the need for a level sensor in the oil reservoir or an oil pressure sensor.

[0004] DE 10 2017 210 885 A1 discloses a method for detecting dry running of a pump device. A dry test run step is activated depending on a pump characteristic function and a timer function.

[0005] Based on this, the invention is based on the object of creating a novel method and control device for operating a hydraulic system and a motor vehicle with a hydraulic system.

[0006] This object is achieved by a method according to claim 1, a control device according to claim 14 and a motor vehicle according to claim 15.

[0007] According to the invention, depending on a temperature of the hydraulic oil and depending on an actual electrical current of the electric motor driving the hydraulic pump and / or an actual speed of the hydraulic pump or the electric motor driving the same, it is determined whether a sufficiently high oil supply to the at least one assembly to be cooled and / or lubricated is ensured.

[0008] The present invention proposes determining, depending on the temperature of the hydraulic oil, whether a sufficiently high oil supply is ensured for at least one component to be cooled or lubricated. This takes into account not only the temperature of the hydraulic oil, but also the actual electrical current of the electric motor driving the hydraulic pump and / or the actual speed of the hydraulic pump or the electric motor driving the hydraulic pump.

[0009] The invention is based on the finding that, depending on the temperature, the actual electrical current of the electric motor driving the hydraulic pump and / or the actual speed of the hydraulic pump or of the electric motor driving the hydraulic pump can be advantageously used to determine whether a sufficiently high oil supply to the at least one component to be cooled and / or lubricated is ensured.

[0010] Depending on the temperature of the hydraulic oil, either the actual electrical current of the electric motor driving the hydraulic pump or the actual speed of the hydraulic pump or the electric motor driving the hydraulic pump is more suitable for the above determination. Depending on the temperature of the hydraulic oil, both the actual electrical current of the electric motor driving the hydraulic pump and the actual speed of the hydraulic pump or the electric motor driving the same can be used to determine whether a sufficiently high oil supply is ensured for at least one component to be cooled and / or lubricated.

[0011] The invention makes it possible to monitor the maintenance of a sufficiently high oil supply, depending on the temperature of the hydraulic oil, based on existing measured variables, namely the actual current of the electric motor driving the hydraulic pump and / or the actual speed of the hydraulic pump or the electric motor driving the hydraulic pump. This eliminates the need for an oil level sensor in the area of ​​the oil reservoir or an oil pressure sensor in the hydraulic system. Although the invention can be used particularly advantageously in a hydraulic system of a motor vehicle, it can also be used in other hydraulic systems.

[0012] Preferably, when the temperature of the hydraulic oil is greater than a first temperature limit, it is determined whether a sufficiently high oil supply to the at least one component to be cooled and / or lubricated is ensured depending on the actual electrical current of the electric motor driving the hydraulic pump. At relatively high hydraulic oil temperatures, the determination of whether a sufficiently high oil supply is ensured is based on the temperature of the hydraulic oil and the actual current of the electric motor driving the hydraulic pump. This is based on the finding that at relatively high oil temperatures, the electrical current of the electric motor driving the hydraulic pump is particularly suitable for determining whether the hydraulic pump is providing sufficient oil.

[0013] Preferably, when the temperature of the hydraulic oil is lower than a second temperature limit, it is determined, depending on the actual speed of the hydraulic pump or the electric motor driving the same, whether a sufficiently high oil supply to the at least one component to be cooled and / or lubricated is ensured. At relatively low hydraulic oil temperatures, the determination of whether a sufficiently high oil supply is ensured is based on the actual speed of the hydraulic pump or the electric motor driving the same. This is based on the finding that at low hydraulic oil temperatures, the actual speed is more suitable for determining whether a sufficiently high oil supply is ensured than the actual electrical current.

[0014] The first temperature limit and the second temperature limit can be identical. If the first temperature limit and the second temperature limit differ from each other, and if the temperature of the hydraulic oil is lower than the first temperature limit and higher than the second temperature limit, it is determined, preferably depending on the actual electrical current of the hydraulic pump and also depending on the actual speed of the hydraulic pump or the electric motor driving it, whether a sufficiently high oil supply to the at least one component to be cooled and / or lubricated is ensured.According to this development of the invention, when the oil temperature is in a medium temperature range, i.e. lower than the first temperature value but higher than the second temperature limit value, the determination of a sufficiently high oil supply can be carried out both on the basis of the actual electrical current and on the basis of the actual speed, preferably for plausibility purposes.

[0015] Preferred developments emerge 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 a drive train diagram of a motor vehicle, Fig. 2 a hydraulic system diagram, Fig. 3 a first diagram to illustrate the invention, and Fig. 4 a second diagram to illustrate the invention.

[0016] Fig. Figure 1 shows a highly schematic diagram of the drive train of a motor vehicle. Fig. 1 has a drive unit 1 and a transmission 3 connected between the drive unit 1 and an output 2. The drive unit 1 can be an electric machine. Fig. 1 further shows an engine control unit 4 for controlling and / or regulating the operation of the drive unit 1 and a transmission control unit 5 for controlling and / or regulating the operation of the transmission 3. According to Fig. 1, the engine control unit 4 exchanges data with the drive unit 1, and the transmission control unit 5 exchanges data with the transmission 3. Furthermore, the engine control unit 4 and the transmission control unit 5 exchange data with each other.

[0017] A motor vehicle has several components that require hydraulic oil for cooling and / or lubrication. For this purpose, the drive train can be Fig. 1 includes both the gearbox 3 and the drive unit 1.

[0018] In order to supply components to be cooled and / or lubricated with hydraulic oil, a motor vehicle has a hydraulic system, whereby Fig. 2 shows a diagram of a hydraulic system. Fig. 2 shows an oil reservoir 6, a motor-pump unit 7 comprising a hydraulic pump 10 and an electric motor 11 driving the same, as well as an assembly 8 to be cooled and / or lubricated, wherein the hydraulic pump 10 serves to suck hydraulic oil from the oil reservoir 6 and to supply the assembly 8 to be cooled and / or lubricated with the hydraulic oil. Fig. The assembly 8 shown in Figure 2 to be cooled and / or lubricated can be, for example, the drive unit 1 designed as an electric machine or the transmission 3 of the Fig. 1. The electric motor 11 and thus the hydraulic pump 10 are designed to be speed-controlled.

[0019] Fig. Figure 2 also shows a control unit 9. The control unit 9 exchanges data with the assembly 8 to be cooled and / or lubricated as well as with the motor-pump unit 7. In the case of the motor vehicle, the control unit 9 can be the Fig. 1 could be the engine control unit 4 or the transmission control unit 5.

[0020] During operation, an oil leak, i.e., oil loss, can occur. This can lead to an insufficient oil quantity in the hydraulic system, and a sufficient oil supply can no longer be provided to the assembly 8 that needs to be cooled and / or lubricated. In extreme cases, this can even lead to the hydraulic pump 7 running dry.

[0021] It is also possible that an oil line in the hydraulic system is blocked, for example, due to an assembly or production error because a transport plug was not removed. In this case, too, a sufficiently high oil supply for the component to be cooled and / or lubricated cannot be ensured. The invention relates to a method and control device for determining whether a sufficiently high oil supply to the at least one component to be cooled and / or lubricated is or can be ensured by the hydraulic system, without the need for a fill level sensor for the oil reservoir 6 and without the need for an oil pressure sensor in the hydraulic system.

[0022] According to the invention, depending on the temperature of the hydraulic oil and depending on an actual electrical current of the electric motor 11 driving the hydraulic pump 10 and / or depending on an actual speed of the hydraulic pump 10 or of the electric motor 11 driving the hydraulic pump 10, it is determined whether a sufficiently high oil supply to the at least one assembly 8 to be cooled and / or lubricated is ensured.

[0023] The invention is based on the finding that, depending on the temperature of the hydraulic oil, either the actual electrical current of the electric motor 11 driving the hydraulic pump 10 or the actual rotational speed of the hydraulic pump 10 or of the electric motor 11 driving the same or both actual variables, i.e. both the actual electrical current and the actual rotational speed, are particularly suitable for determining whether a sufficiently high oil supply to the at least one assembly 8 to be cooled and / or lubricated is or can be ensured by the hydraulic system.

[0024] If the temperature of the hydraulic oil, which can be measured using at least one temperature sensor, is greater than a first temperature limit value, it is determined, depending on the actual electrical current of the electric motor 11 driving the hydraulic pump 10, whether a sufficiently high oil supply to the at least one assembly 8 to be cooled and / or lubricated is ensured. The actual electrical current of the electric motor 11 driving the hydraulic pump 10 is a known, measurable, or calculable variable on the control side, wherein the actual current is in particular the actual phase current of the electric motor 11.

[0025] When determining whether a sufficiently high oil supply is ensured, both the actual value of the actual electrical current as such and a temporal gradient of the actual electrical current can be taken into account at hydraulic oil temperatures that are greater than the first temperature limit. If, at a defined hydraulic oil temperature and at a defined target speed of the electric motor 11 driving the hydraulic pump 10 in a speed-controlled manner, the actual value of the actual electrical current of the electric motor 11 is less than a target current and / or a temporal gradient of the actual electrical current of the electric motor 11 is greater than a first gradient limit, it is determined that a sufficiently high oil supply to the at least one assembly 8 to be cooled and / or lubricated is not provided or ensured.

[0026] Fig. 3 shows, in the case where the temperature T of the hydraulic oil is greater than the first temperature limit value, the dependence of the oil pressure p provided by the hydraulic pump 10 on the actual electrical current I of the electric motor 11 driving the hydraulic pump 10 for different temperatures T of the hydraulic oil at a predetermined target speed of the hydraulic pump 10. Fig. 3 shows that at high temperatures T of the hydraulic oil, which are greater than the first temperature limit, there is an almost linear relationship between the actual electrical current I of the electric motor 11 driving the hydraulic pump 10 and the oil pressure p provided by the pump 10. For several target speeds, characteristic maps can be generated according to Fig. 3 must be stored on the control side.

[0027] If, therefore, at a defined temperature T of the hydraulic oil which is greater than the first temperature limit value and at a defined target speed of the electric motor 11 driving the hydraulic pump 10, the actual value of the actual electrical current I of the electric motor 11 driving the hydraulic pump 10 is smaller than a target current which is determined depending on a desired target pressure p, for example via the characteristic map of the Fig. 3 can be determined depending on the temperature, it can be concluded that a sufficiently high oil supply is not guaranteed.

[0028] Likewise, at temperatures T of the hydraulic oil that are greater than the first temperature limit, the temporal gradient of the actual electrical current of the electric motor 11 driving the hydraulic pump 10 can be evaluated to determine whether a sufficiently high oil supply is guaranteed. If, at a defined target speed of the electric motor 11 driving the hydraulic pump 10, the actual electrical current I of the electric motor 11 is subject to strong fluctuations, i.e., if the temporal gradient of the actual electrical current is greater than a first gradient limit, it can also be determined that a sufficiently high oil supply is no longer guaranteed. Both the actual current as such and the temporal gradient of the actual current can be continuously evaluated by the control unit 9.

[0029] In a further development of the invention, it is possible to take at least one alternative measure, such as a warning message or even an emergency operation of the hydraulic system, depending on the deviation between the actual value of the electrical current of the electric motor 11 driving the hydraulic pump 10 and the target current determined as a function of the temperature of the hydraulic oil and the desired target pressure, and / or depending on the deviation of the temporal gradient of the actual electrical current from the first gradient limit value, depending on the deviation between the actual value of the electrical current and the first gradient limit value. If the respective deviation is small, i.e., smaller than a corresponding limit value, only a warning message can be generated. If, however, the respective deviation is large, i.e., greater than the corresponding limit value, an emergency operation of the hydraulic system can also be initiated, for example to protect the hydraulic pump 10 from damage.

[0030] At a temperature T of the hydraulic oil which is greater than the first temperature limit value, it is also possible, depending on the temperature T of the hydraulic oil, depending on the actual electrical current I of the electric motor 11 driving the hydraulic pump 10 and depending on a defined target speed of the electric motor 11 at which it is to be operated, depending on the Fig. 3, a developing actual pressure p is calculated and compared with a desired target pressure. If the deviation between the actual pressure and the target pressure is greater than a corresponding limit, it can be concluded that a sufficiently high oil supply can no longer be guaranteed. Depending on the deviation between the actual pressure and the target pressure, at least one countermeasure can then be taken.

[0031] If the temperature of the hydraulic oil is lower than a second temperature limit, it is intended to determine whether a sufficiently high oil supply is ensured, depending on the actual speed of the hydraulic pump 10 or the electric motor 11 driving it. This is preferably done based on a temporal gradient of the actual speed.

[0032] If, at a defined temperature of the hydraulic oil and at a defined target speed of the speed-controlled electric motor 11, which serves to drive the hydraulic pump 10, the temporal gradient of the actual speed is greater than a second gradient limit value, it is determined that the hydraulic pump 10 no longer ensures a sufficiently high oil supply. Fig. Figure 4 illustrates the procedure for determining whether a sufficiently high oil supply is ensured in the case where the temperature of the hydraulic oil is lower than the second temperature limit, i.e., where the temperature of the hydraulic oil is relatively low. Fig. 4 shows several curves over time, namely curve 12 represents a target speed for the electric motor 11 driving the hydraulic pump 10, and curve 13 represents an actual speed of the same. Fig. 4, the curve 14 shows the actual electrical current of the electric motor 11 driving the hydraulic pump 10.

[0033] Before time t1, the actual speed 12 of the motor 11 driving the hydraulic pump 10 is lower than the target speed 12 due to the high viscosity of the hydraulic oil at low temperatures. Starting at time t1, the actual speed 13 of the electric motor 11 driving the hydraulic pump 10 increases sharply, i.e., with a high temporal gradient, toward the target speed 12. As the load on the hydraulic pump 10 and thus on the electric motor 11 caused by the high viscosity of the oil is removed, the electric motor 11, and thus also the hydraulic pump 10, accelerates with a large temporal gradient toward its target speed 12. During the acceleration phase of the motor 11 between times t1 and t2, the actual electrical current 14 of the motor remains virtually unchanged. Only after the acceleration phase after time t2 does the actual electrical current 14 drop.At relatively low temperatures of the hydraulic oil, which are lower than the second temperature limit value, the evaluation of the temporal gradient of the actual speed 13 of the electric motor 11 driving the hydraulic pump 10 is therefore primarily suitable for determining whether a sufficiently high oil supply is guaranteed.

[0034] If the temperature of the hydraulic oil is lower than the first temperature limit and higher than the second temperature limit, the determination of whether a sufficient hydraulic oil supply is ensured can be made depending on the temperature of the hydraulic oil, the actual electrical current of the electric motor 11 driving the hydraulic pump 10, and additionally the actual speed of the hydraulic pump 10 or the electric motor 11 driving the same. The evaluation of the actual electrical current can be carried out as described above for temperatures higher than the first temperature limit. The evaluation of the actual speed can be carried out as described above for temperatures lower than the second temperature limit.The results of these determinations can be used for plausibility checks, whereby it is only concluded that a sufficiently high oil supply is no longer guaranteed if, on the one hand, the actual electrical current is smaller than the target current and / or the temporal gradient of the actual electrical current is smaller than the first gradient limit value and, on the other hand, the temporal gradient of the actual speed is greater than the second gradient limit value.

[0035] Alternatively, it is also possible to evaluate the two evaluation criteria based on the actual current and the actual speed using an OR logic, thus concluding that there is no longer a sufficient oil supply if either the actual electrical current is lower than the target current and / or the temporal gradient of the actual electrical current is greater than the first gradient limit, or the temporal gradient of the actual speed is greater than the second gradient limit. The above evaluation criteria can also be weighted depending on the temperature.

[0036] The first temperature limit and the second temperature limit can be identical. In particular, the first temperature limit is +20°C and the second temperature limit is 0°C. However, these temperature limits are purely exemplary.

[0037] The above evaluation can be carried out during the ongoing operation of the hydraulic system and thus of the motor vehicle at different temperatures.

[0038] The above monitoring can also be used at the end of a production run to verify proper assembly and thus the functionality of a hydraulic system. For example, at the end of a production line, there is typically a defined hydraulic oil temperature that is greater than the first temperature limit. Depending on this hydraulic oil temperature and a specified target speed for the hydraulic pump 10, the actual electrical current of the electric motor 11 driving the hydraulic pump 10 can be evaluated to verify whether the hydraulic pump 10 is providing a sufficient oil supply. As described above with reference to Fig.As described in Section 3, the hydraulic pressure provided by the hydraulic pump 10 is determined from the actual current for the defined hydraulic oil temperature and for the defined target speed of the hydraulic pump based on a characteristic map stored in the control unit. If this hydraulic pressure is high enough, it can be concluded that the oil supply is sufficiently high.

[0039] At the end of production, during the functional test of the hydraulic system for the electric motor 11 driving the hydraulic pump 10, a speed ramp can also be run through in order to determine a reference characteristic curve for the electrical current of the electric motor 11 for selected speeds along the speed ramp. If it is determined over the service life that, at defined speeds and at the temperature at which the reference characteristic curve was determined, the actual electrical current of the electric motor 11 driving the hydraulic pump 10 deviates from the determined reference characteristic curve, this can indicate aging or a defect in the hydraulic pump 10 or the electric motor 11.

[0040] The invention further relates to a control unit for operating a hydraulic system, in particular a hydraulic system of a motor vehicle. The control unit is configured to execute the method described above on the control side. Furthermore, the invention relates to a motor vehicle with a hydraulic system and such a control unit.

[0041] The control unit configured to carry out the method described above can be the transmission control unit 5. This is preferably an electronic control unit having hardware and software means for carrying out the method according to the invention. The hardware means include data interfaces for exchanging data with the assemblies involved in carrying out the method according to the invention, for example with a sensor for detecting the temperature of the hydraulic oil, with a sensor for detecting the actual electrical current of the electric motor driving the hydraulic pump, and / or a sensor for detecting the actual speed of the hydraulic pump or of the electric motor driving the same. The aforementioned sensors can be integrated, for example, in the motor-pump unit 7.The data to be exchanged can be transmitted via a data bus, for example, a CAN bus (Controller Area Network). The hardware means also include a processor for data processing and a memory for data storage. The software means include program modules implemented in the control unit to carry out the method according to the invention. Reference symbol 1 drivetrain 2 drive unit 3 Downforce 4 Engine control unit 5 Transmission control unit 6 oil reservoirs 7 Motor-pump unit 8 Assembly 9 Control unit 10 Hydraulic pump 11 Electric motor 12 Curve of target speed 13 Curve of actual speed 14 Curve of actual electrical current QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] DE 10 2017 210 885 A1

[0004]

Claims

[1] Method for operating a hydraulic system, in particular a hydraulic system of a motor vehicle, which has a hydraulic pump (10) driven by a speed-controlled electric motor (11) for sucking hydraulic oil from an oil reservoir (6) and for supplying at least one assembly (8) to be cooled and / or lubricated with the hydraulic oil, characterized by , that depending on the temperature of the hydraulic oil and depending on an actual electrical current of the electric motor (11) driving the hydraulic pump (10) and / or an actual speed of the hydraulic pump (10) or the electric motor (11) driving the same it is determined whether a sufficiently high oil supply to the at least one assembly (8) to be cooled and / or lubricated is ensured. [2] Method according to claim 1, characterized bythat when the temperature of the hydraulic oil is greater than a first temperature limit value, it is determined whether a sufficiently high oil supply is guaranteed depending on the actual electrical current of the electric motor (11) driving the hydraulic pump (10). [3] Method according to claim 2, characterized by that this determination is based on the evaluation of the actual value of the actual electrical current and / or on the evaluation of a temporal gradient of the actual electrical current. [4] Method according to claim 3, characterized bythat if, at a defined temperature of the hydraulic oil and at a defined target speed of the hydraulic pump (10) or the electric motor (11) driving the same, the actual value of the actual electrical current is less than a target current and / or a temporal gradient of the actual electrical current is greater than a first gradient limit value, it is determined that a sufficiently high oil supply to the at least one assembly to be cooled or lubricated is not ensured. [5] Method according to claim 4, characterized by that at least one alternative measure is taken depending on the deviation between the actual value of the actual electrical current and the target current and / or depending on the deviation of the temporal gradient of the actual electrical current from the first gradient limit value. [6] Method according to one of claims 1 to 5, characterized bythat when the temperature of the hydraulic oil is lower than a second temperature limit value, it is determined whether a sufficiently high oil supply is guaranteed depending on the actual speed of the hydraulic pump (10) or the electric motor (11) driving the same. [7] Method according to claim 6, characterized by that this determination is based on the evaluation of a temporal gradient of the actual speed. [8] Method according to claim 7, characterized by that if, at a defined temperature of the hydraulic oil and at a defined target speed of the hydraulic pump (10) or of the electric motor (11) driving the same, the temporal gradient of the actual speed is greater than a second gradient limit value, it is determined that a sufficiently high oil supply to the at least one component to be cooled or lubricated is not ensured. [9] Method according to claim 8, characterized bythat at least one alternative measure is taken depending on the deviation of the temporal gradient of the actual speed from the second gradient limit value. [10] Method according to one of claims 2 to 5 and one of claims 6 to 9, characterized by that when the temperature of the hydraulic oil is lower than the first temperature limit value and higher than the second temperature limit value, it is determined whether a sufficiently high oil supply is ensured depending on the actual electrical current of the hydraulic pump (10) and depending on the actual speed of the hydraulic pump or the electric motor (11) driving the same. [11] Method according to claim 10, characterized bythat if, at a defined temperature of the hydraulic oil and at a defined target speed of the hydraulic pump (10) or the electric motor (11) driving the same, on the one hand the actual value of the actual electrical current is smaller than the target current and / or the temporal gradient of the actual electrical current is greater than the first gradient limit value and, on the other hand, the temporal gradient of the actual speed is greater than the second gradient limit value, it is determined that the hydraulic pump (10) does not ensure a sufficiently high oil supply. [12] Method according to claim 10, characterized bythat if, at a defined temperature of the hydraulic oil and at a defined target speed of the hydraulic pump (10) or the electric motor (11) driving the same, either the actual value of the actual electrical current is less than the target current and / or the temporal gradient of the actual electrical current is greater than the first gradient limit value or the temporal gradient of the actual speed is greater than the second gradient limit value, it is determined that the hydraulic pump (10) does not ensure a sufficiently high oil supply. [13] Method according to one of claims 1 to 12, characterized by that the same is carried out in a continuous operation of the hydraulic system, and / or in a production of the hydraulic system at a production end. [14] Control device for operating a hydraulic system, in particular a hydraulic system of a motor vehicle, characterized bythat the control device is set up to automatically execute the method according to one of claims 1 to 13 on the control side. [15] Motor vehicle with a hydraulic system and control device according to claim 14.

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