METHOD FOR THE VALVE CONTROL OF A HYDRAULIC VALVE

Abstract

A method for valve control of a hydraulic valve which, in an actuation device of a clutch, influences an actuation pressure for actuating the clutch in accordance with an electrical actuation variable that actuates the hydraulic valve. The method includes selectively switching the clutch at least between a first clutch actuation state, in which the actuation pressure has a pressure value in a first actuation pressure range, and a second clutch actuation state, in which the actuation pressure is outside of the first actuation pressure range. The method further includes, during the first clutch actuation state, changing the electrical actuation variable based on the actuation pressure.

Claims

1. A method for valve control of a hydraulic valve which, in an actuation device of a clutch, influences an actuation pressure for actuating the clutch in accordance with an electrical actuation variable that actuates the hydraulic valve, the method comprising: selectively switching the clutch at least between a first clutch actuation state, in which the actuation pressure has a pressure value in a first actuation pressure range, and a second clutch actuation state, in which the actuation pressure outside of the first actuation pressure, and during the first clutch actuation state, changing the electrical actuation variable is based on the actuation pressure.

2. The method according to claim 1, wherein a lower pressure value and an upper pressure value are defined within the first actuation pressure range based on the electrical actuation variable.

3. The method according to claim 2, comprising during the first clutch actuation state, when the lower pressure value is reached, increasing an absolute value of the electrical actuation variable.

4. The method according to claim 2, further comprising, during the first clutch actuation state, when the upper pressure value is reached, reducing an absolute value of the electrical actuation variable.

5. The method according to claim 1, wherein the electrical actuation variable is an electric current or an electric voltage.

6. The method according to claim 1, wherein the clutch is engaged for torque transmission in the first clutch actuation state and is disengaged for interruption of torque transmission in the second clutch actuation state.

7. The method according to claim 1, further comprising, during the first clutch actuation state, performing a re-pumping process to increase the actuation pressure within the first actuation pressure range, wherein an absolute value of the electrical actuation variable is set to be greater during the re-pumping process than outside of the re-pumping process.

8. The method according to claim 1, wherein a hydraulic tightness of the hydraulic valve influencing the actuation pressure at least during the first clutch actuation state depends on the electrical actuation variable.

9. The method according to claim 8, wherein the hydraulic tightness of the hydraulic valve in the first clutch actuation state increases as an absolute value of the electrical actuation variable increases.

10. The method according to claim 1, wherein the hydraulic valve is a discharge valve, which is closed in the first clutch actuation state and open in the second clutch actuation state in order to reduce the actuation pressure.

11. A hydraulic device, comprising: a pump; a clutch having an actuation device configured to switch the clutch at least between a first clutch actuation state and a second clutch actuation state; and a hydraulic valve arranged between the pump and the actuation device and actuatable via an electrical actuation variable, the hydraulic valve configured to influence an actuation pressure of the actuation device; wherein, in the first clutch actuation state, the actuation pressure of the actuation device has a first value that is within actuation pressure range, and, in the second clutch actuation state, the actuation pressure of the actuation device has a second value that is less than the first value; wherein, in the first clutch actuation state, the hydraulic valve is actuated, via a change in the electrical actuation variable, based on the first value.

12. The hydraulic device according to claim 11, wherein the clutch is engaged for torque transmission in the first clutch actuation state and is disengaged for interruption of torque transmission in the second clutch actuation state.

13. The hydraulic device according to claim 12, wherein, during actuation of the clutch from second clutch actuation state to the first clutch actuation state, the electrical actuation variable is increased in response to the first value of the actuation pressure increasing to a lower pressure value of the actuation pressure range.

14. The hydraulic device according to claim 13, wherein, after the first value reaches an upper pressure value of the actuation pressure range, the electrical actuation variable is reduced in response to the first value decreasing to a threshold value.

15. The hydraulic device according to claim 14, wherein the upper pressure value is greater than the lower pressure value.

16. The hydraulic device according to claim 14, wherein the threshold value is between the lower pressure value and the upper pressure value.

17. The hydraulic device according to claim 14, wherein, in the first clutch actuation state, in response to the first value decreasing to the lower pressure value: the pump is actuated to increase the actuation pressure; and the electrical actuation variable is increased.

18. The hydraulic device according to claim 17, wherein the pump is stopped in response to the first value reaching the upper pressure value.

19. The hydraulic device according to claim 17, wherein the electrical actuation variable is reduced in response to the first value decreasing to the threshold value.

20. The hydraulic device according to claim 12, wherein the hydraulic valve is a discharge valve, which is closed in the first clutch actuation state and open in the second clutch actuation state in order to reduce the actuation pressure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present disclosure is described in detail below with reference to the drawings. In the figures:

[0028] FIG. 1: shows a hydraulic device having a hydraulic valve for carrying out a method of an exemplary embodiment of the present disclosure.

[0029] FIG. 2: shows a course over time of an actuation pressure and an electrical actuation variable when carrying out a method of the exemplary embodiment of the present disclosure.

[0030] FIG. 3: shows a flow chart of a method of the exemplary embodiment of the present disclosure.

DETAILED DESCRIPTION

[0031] FIG. 1 shows a hydraulic device 10 having a hydraulic valve for carrying out a method of an exemplary embodiment of the present disclosure. The hydraulic device 10 is arranged in a vehicle, for example, and is designed to control a clutch 12 capable of transmitting torque between an internal combustion engine and a transmission, and to control a parking lock device 14 for limiting movement of the vehicle when the vehicle is in a parked position. The clutch 12 can be designed as a K0 clutch.

[0032] The clutch 12 is actuated depending on an actuation pressure p of a fluid in an actuation device 16. A clutch slave cylinder 18 is arranged for this purpose, which exerts a contact pressure on the clutch 12 as a function of the actuation pressure p and thereby, at an actuation pressure p with a pressure value within a first actuation pressure range, sets a first clutch actuation state corresponding to an engaged clutch 12 for transmitting torque.

[0033] The actuation pressure p is controlled by a fluid pressure of a fluid pump 20, which may be designed as a gear pump, and a switching valve 22. The fluid pump 20 may be a reversing pump which, when rotated in a first direction of rotation, provides the fluid pressure which causes the actuation pressure p via the switching valve 22 and, when rotated in an opposite second direction of rotation, provides a fluid flow 23 for cooling and/or lubricating the clutch 12, the parking lock device 14, the transmission or other components in the vehicle, for example an electric motor, via a heat exchanger 24 to a cooling device 26.

[0034] The fluid pump 20 is connected to a fluid reservoir 28 that accommodates the fluid. When the fluid pump 20 is rotated in the first direction of rotation, fluid is conveyed from the fluid reservoir 28 and directed through a hydraulic connection between the fluid pump 20 and the actuation device 16 to build up the actuation pressure p in order to set the first clutch actuation state. The switching valve 22 is operatively arranged between the fluid pump 20 and the actuation device 16, and allows for control of the actuation pressure p in the actuation device 16.

[0035] If the clutch 12 is actuated starting from a second clutch actuation state in which the actuation pressure p is zero, for example, and thereby the clutch slave cylinder 18 is unloaded by the actuation pressure p and thus, in turn, the clutch 12 is disengaged and torque transmission is interrupted, by increasing the fluid pressure and the switching valve 22 being open via the actuation pressure p increasing therewith and the clutch slave cylinder 18 being pressurized therewith, a check valve 30 operatively arranged between the switching valve 22 and the actuation device 16 prevents a pressure drop of the actuation pressure p irrespective of the actuation of the switching valve 22. In this manner, the energy consumption for maintaining the actuation pressure p can be reduced.

[0036] A hydraulic valve 32 is operatively arranged between the actuation device 16 and the fluid reservoir 28 and is designed as a discharge valve 34. The discharge valve 34 can be used to trigger a drop in the actuation pressure p via a return line 36, which is arranged between the discharge valve 34 and the fluid reservoir 28. The discharge valve 34 can be actuated by an electrical actuation variable 38, such as an electric current or electric voltage. For this purpose, the hydraulic valve 32 has an electromagnet that sets a valve position depending on the electrical actuation variable 38.

[0037] The switching valve 22 is designed as a two-way valve that builds up the fluid pressure provided by the fluid pump 20 as actuation pressure p or as actuation pressure for actuating the parking lock device 14 via a parking lock actuator 40, depending on a switching position. The switching valve 22, the parking lock actuator 40, and the hydraulic valve 32 are electrically connected to a control unit 42. The control unit 42 is electrically connected to a bus system 44 of the vehicle, for example a CAN bus. The parking lock device 14 has a displacement sensor 46, via which the information about the actuation position of the parking lock device 14 is acquired. The actuation pressure p is acquired by a pressure sensor 48.

[0038] Due to leaks, for example, in the switching valve 22, the actuation device 16 and/or the hydraulic valve 32, a drop in the actuation pressure p within the first actuation pressure range can occur in the first clutch actuation state, corresponding to an engaged clutch 12, which can be built up by a re-pumping process via the fluid pump 20 moved in the first direction of rotation and the resulting increase in fluid pressure with a suitable valve position of the switching valve 22. During the re-pumping process and the continued first clutch actuation state, the electrical actuation variable 38 for actuating the hydraulic valve 32 is changed depending on the actuation pressure p. The absolute amount of the electrical actuation variable 38 is set to be greater during the re-pumping process than outside of the re-pumping process. In this way, the requirement for hydraulic tightness of the hydraulic valve 32, which increases with increasing actuation pressure p, can be satisfied.

[0039] The greater the electrical actuation variable 38, the greater the hydraulic tightness of the hydraulic valve 32. By increasing the electrical actuation variable 38 during the re-pumping process, the hydraulic tightness of the hydraulic valve 32 can increase and thus the actuation pressure p can be built up more quickly and in a more energy-efficient manner. Once the re-pumping process is complete, the electrical actuation variable 38 can be reset to a lower value during the first clutch actuation state, thereby reducing the energy consumption required to actuate the hydraulic valve 32.

[0040] FIG. 2 shows a course over time of an actuation pressure and an electrical actuation variable when carrying out a method of the exemplary embodiment of the present disclosure. FIG. 2 a) shows a course over time of the actuation pressure p and FIG. 2 b) shows a course over time of the electrical actuation variable, in this case the electric current I for actuating the hydraulic valve 32. If the clutch 12 is switched from the second clutch actuation state C2, in which the actuation pressure p is approximately zero and the electric current I has a first current value I1, to the first clutch actuation state C1, the actuation pressure p is increased.

[0041] When the actuation pressure p reaches a predetermined lower pressure value pl within the first actuation pressure range 50 present in the first clutch actuation state C1, the electric current I is increased to a second current value 12 in order to actuate the hydraulic valve 32 designed as a discharge valve 34.

[0042] The pressure build-up of the actuation pressure p is terminated as soon as the actuation pressure p reaches a predetermined maximum pressure value pmax. The clutch 12 is still in the first clutch actuation state C1 and is engaged. The actuation pressure p slowly decreases due to leakage. As soon as a predetermined upper pressure value ph is reached within the first actuation pressure range 50, starting from a higher pressure value, the electric current I is switched to the first current value I1. Only when the actuation pressure p reaches the lower pressure value pl, starting from higher pressure values, is the electric current I for actuating the hydraulic valve raised again to the second current value I2 and the re-pumping process 51 is also initiated, which causes the actuation pressure p to be raised up to the maximum pressure value pmax via the fluid pump 20. The fluid pump 20 stops further pressure delivery when the maximum pressure value pmax is reached.

[0043] During the re-pumping process, the electric current I assumes the second current value I2 in order to increase the hydraulic tightness of the hydraulic valve 32 during the re-pumping process 51. Only when the actuation pressure p reaches the upper pressure value ph, starting from the maximum pressure value pmax, is the lower first current value I1 set, thereby reducing the energy consumption required to actuate the hydraulic valve 32.

[0044] FIG. 3 shows a flow chart of a method of the exemplary embodiment of the present disclosure. The method 100 for the valve control of the hydraulic valve 32 begins with an introduction step 102, followed by an initialization 104. A subsequent query 106 is directed to whether the clutch 12 should assume the first clutch actuation state C1, i.e., be engaged in order to transmit torque. Only when the changeover is to take place is the discharge valve 34 actuated in a subsequent step 108 by setting the electrical actuation variable to the higher second current value I2.

[0045] Depending on a subsequent query 110 as to whether the actuation pressure p reaches the predetermined upper pressure value ph, starting from higher pressure values, the electric current I is reduced to the first current value I1 in a subsequent step 112 if the query 110 is returned as true. A subsequent query 114 checks whether the clutch 12 should maintain the first clutch actuation state C1, and if so, a further query 116 checks the need for a re-pumping process 51 in order to increase the actuation pressure p. Depending on the actuation pressure p lying within the first actuation pressure range, the re-pumping process 51 is initiated if necessary, for example when the actuation pressure p reaches the lower pressure value pl starting from higher pressure values.

[0046] If a re-pumping process 51 is to occur, together with initiation of the re-pumping process 51, in a subsequent step 118 the electric current I is increased to the second current value I2 and then a query 120 is performed in accordance with the query 110. If the actuation pressure p reaches the lower pressure value pl starting from higher pressure values. the electric current I is reduced to the first current value I1 in a subsequent step 122, thus actuating the discharge valve 34 in a more energy-efficient manner. Then the sequence starts again with the query 114.

[0047] If the clutch 12 is to be disengaged during the query 114, thereby switching the first clutch actuation state C1 to the second clutch actuation state C2, the electric current I is reduced to zero in a subsequent step 124, thereby opening the discharge valve 34 in order to relieve the actuation pressure p for disengaging the clutch 12. The method 100 is terminated by a finalizing step 126.

LIST OF REFERENCE SYMBOLS

[0048] 10 Hydraulic device [0049] 12 Clutch [0050] 14 Parking lock device [0051] 16 Actuation device [0052] 18 Clutch slave cylinder [0053] 20 Fluid pump [0054] 22 Switching valve [0055] 23 Fluid flow [0056] 24 Heat exchanger [0057] 26 Cooling device [0058] 28 Fluid reservoir [0059] 30 Check valve [0060] 32 Hydraulic valve [0061] 34 Discharge valve [0062] 36 Return line [0063] 38 Electrical actuation variable [0064] 40 Parking lock actuator [0065] 42 Control unit [0066] 44 Bus system [0067] 46 Displacement sensor [0068] 48 Pressure sensor [0069] 50 First actuation pressure range [0070] 51 Re-pumping process [0071] 100 Method [0072] 102 Introduction step [0073] 104 Initialization [0074] 106 Query [0075] 108 Step [0076] 110 Query [0077] 112 Step [0078] 114 Query [0079] 116 Query [0080] 118 Step [0081] 120 Query [0082] 122 Step [0083] 124 Step [0084] 126 Finalizing step [0085] C1 First clutch actuation state [0086] C2 Second clutch actuation state [0087] I Electric current [0088] I1 First current value [0089] I2 Second current value [0090] P Actuation pressure [0091] ph Upper pressure value [0092] pl Lower pressure value [0093] pmax Maximum pressure value