Method for valve control, method for pressure reduction, pressure relief valve and fluid device

Abstract

The invention relates to a method for the valve control (60) of a pressure relief valve (50) of a fluid device (10) of a vehicle, said fluid device having a fluid, said method comprising the steps of: providing (62) the pressure relief valve (50), which is designed to trigger a pressure reduction of the fluid in at least one fluid branch (42, 44) of the fluid device (10) when the valve is open, said pressure reduction being dependent on an opening time of the pressure relief valve (50); carrying out (64) a pressure reduction process (66) in order to reduce the fluid pressure (p) in the fluid branch, with a first pressure reduction step (68) comprising opening (70) the pressure relief valve (50) at a specified first opening time (t1), wherein, during the pressure reduction process (66) and subsequent to the first pressure reduction step (68), the following are carried out: detecting (72) the fluid pressure (p) in the fluid branch (42, 44) reduced by the amount of the pressure reduction of the first pressure reduction step (68), comparing (76) the detected fluid pressure (p) with a target fluid pressure (ps) and specifying (78) a second opening time (80), which is specified for a chronologically subsequent second pressure reduction step (80) and is to be applied, during opening (70) of the pressure relief valve (50) depending on the comparison (76). The invention also relates to a method for pressure reduction (84), a pressure relief valve (50) and a fluid device (10).

Description

[0001] Method for valve control, method for pressure reduction, pressure relief valve and fluid device

[0002] Description introduction

[0003] The invention relates to a method for valve control according to the preamble of claim 1. Furthermore, the invention relates to a method for reducing the pressure of a fluid pressure, a pressure relief valve and a fluid device.

[0004] DE 102020 111 970 A1 describes a hydraulic device that supplies an actuating device with an actuating fluid pressure. A pressure relief valve is controlled to reduce the actuating fluid pressure and open the actuating device.

[0005] The objective of the present invention is to carry out the pressure reduction of the fluid pressure more precisely. The fluid device should operate more safely.

[0006] At least one of these objects is achieved by a valve control method having the features of claim 1. As a result, pressure reduction by the pressure relief valve can be more targeted and precise. The fluid pressure can reach a target fluid pressure more accurately. The fluid pressure can be achieved more independently of environmental influences, such as temperature influences.

[0007] The vehicle may be a motor-driven vehicle, in particular a motor vehicle, a goods vehicle or a two-wheeler.

[0008] The fluid device may comprise at least one fluid pump for building up a fluid pressure of the fluid and / or a fluid volume flow of the fluid. The fluid pump may be driven by an electric motor.

[0009] The fluid device may have at least one fluid branch. The fluid branch may have at least one switching valve for changing a fluid pressure in the fluid branch.

[0010] The fluid device can be connected to an actuating device. The actuating device can be connected to the fluid branch. The actuating device can be actuated depending on a fluid pressure in the fluid branch. The fluid device can have at least one switching valve for adjusting the fluid pressure at the actuating device. The switching valve can be operatively arranged between the fluid pump and the actuating device.

[0011] The pressure relief valve can be operatively arranged between the switching valve and the actuating device. The pressure relief valve can be completely closed while the fluid pressure in the fluid branch is being detected. The pressure relief valve can be closed after the respective opening time has elapsed. The pressure relief valve can be actuated electrically, preferably electromagnetically.

[0012] The second opening time can be set depending on a temperature. The temperature can be a fluid temperature of the fluid of the fluid device.

[0013] The start of the second pressure reduction step can be delayed by a certain time from the completion of the first pressure reduction step. The second pressure reduction step can be performed during the pressure reduction process or during a subsequent pressure reduction process.

[0014] Sensing fluid pressure may include measuring fluid pressure.

[0015] The pressure reduction can be provided to reduce a thermally induced overpressure in the fluid branch.

[0016] In a preferred embodiment of the invention, it is advantageous if the second opening time is specified depending on a difference between the detected fluid pressure and the target fluid pressure. The second opening time can be specified depending on a sign of the difference.

[0017] In an advantageous embodiment of the invention, if the detected fluid pressure is below the target fluid pressure or corresponds to the target fluid pressure, the second opening time is set shorter than the first opening time, and / or if the detected fluid pressure is above the target fluid pressure, the second opening time is set longer than the first opening time. This allows the target fluid pressure to be reached precisely yet quickly.

[0018] In a specific embodiment of the invention, it is advantageous if a predetermined time interval is maintained between the completion of the first pressure reduction step and the detection of the fluid pressure. By maintaining this time interval, any dynamic behavior of the fluid pressure caused by the opening of the pressure relief valve, such as oscillations, can be absorbed, and the fluid pressure can be detected more accurately.

[0019] The time interval can be dependent on the respective opening time or independent of the respective opening time. The time interval can overlap with the time offset. The time interval can be shorter than the time interval. The time interval and any subsequent fluid pressure acquisition period can be shorter than the time offset or equal to the time offset.

[0020] A preferred embodiment of the invention is advantageous in which the predetermined second opening time is changed by a predetermined period compared to the first opening time. The period can be less than 100 ms, preferably less than 10 ms, in particular 1 ms.

[0021] In a specific embodiment of the invention, it is advantageous that, if the detected fluid pressure corresponds to or is below the target fluid pressure, the next opening time to be applied is set shorter by a predetermined period of time than the last opening time applied. This prevents the target fluid pressure from being undershot during the subsequent pressure reduction step, in which the next opening time is applied. The last opening time applied can be the first opening time. The next opening time to be applied can be the second opening time.

[0022] Furthermore, within the scope of the invention, a method for pressure reduction with the features of claim 7 is proposed to solve at least one of the above-mentioned problems.

[0023] In a specific embodiment of the invention, it is advantageous if, during the pressure reduction process, starting from an existing fluid pressure in the fluid branch and moving toward the target fluid pressure in the fluid branch, at least the first pressure reduction step and the specification of the second opening time are carried out. During the pressure reduction process, the second pressure reduction step can also be carried out. During the pressure reduction process, only the first pressure reduction step can be carried out. During the pressure reduction process, more pressure reduction steps than the first and second pressure reduction steps can be carried out.

[0024] Furthermore, within the scope of the invention, a pressure relief valve with the features of claim 9 is proposed to achieve at least one of the aforementioned objects. The pressure relief valve can assume at least one open valve position, in which the pressure relief valve is open, and a closed valve position, in which the pressure relief valve prevents fluid passage.

[0025] Furthermore, within the scope of the invention, a fluid device having the features of claim 10 is proposed to achieve at least one of the aforementioned objects. The fluid device may comprise a pressure sensor for measuring the fluid pressure, in particular for detecting the fluid pressure.

[0026] Further advantages and advantageous embodiments of the invention emerge from the description of the figures and the illustrations.

[0027] Character description

[0028] The invention is described in detail below with reference to the figures. They show in detail:

[0029] Figure 1: A fluid device in a specific embodiment of the invention.

[0030] Figure 2: A method for valve control in a specific embodiment of the invention.

[0031] Figure 3: A method for pressure reduction in a specific embodiment of the invention.

[0032] Figure 1 shows a fluid device in a specific embodiment of the invention. The fluid device 10 is designed as a hydraulic device 12 in a vehicle and comprises a fluid, in particular a hydraulic fluid. A fluid pump 14 conveys the fluid from a fluid reservoir 16 via a fluid filter 18 and supplies a first fluid line 20 with a fluid volume flow to supply at least one vehicle component of the vehicle, for example, for lubricating and / or cooling the vehicle component. The first fluid line 20 comprises a cooling device 22, in particular a heat exchanger 24, for cooling the fluid. The fluid pump 14 is driven by an electric motor 26.

[0033] Furthermore, the fluid pump 14 is connected to a second fluid line 28, in which the fluid pump 14, depending on the switching position of a switching valve 30, builds up a fluid pressure p for actuating a first actuating device 32, here for example a parking lock 34, and a further fluid pressure p for actuating a second actuating device 36, here for example a clutch 38, in particular a K0 clutch. The switching valve 30 has two switching positions; in the first switching position 40, the fluid pump 14 is connected to a first fluid branch 42 connecting the parking lock 34. A second fluid branch 44 connected to the clutch 38 is blocked with respect to the fluid pump 14. In the second switching position 46 of the switching valve 30, the fluid pump 14 is connected to the second fluid branch 44, and the first fluid branch 42 is connected to a return line 48 to the fluid reservoir 16.

[0034] The second fluid branch 44 has a pressure relief valve 50 between the clutch 38 and the switching valve 30. The pressure relief valve 50 can assume two valve positions. In an open valve position D1, the second fluid branch 44 is connected to a return line 52 to the fluid reservoir 16, and in a closed valve position D2, the connection to the fluid reservoir 16 is blocked.

[0035] A check valve 54 is effectively arranged between the switching valve 30 and the pressure relief valve 50, which prevents a pressure reduction in the second fluid branch 44 in the direction of the fluid pump 14.

[0036] The switching valve 30 and the pressure relief valve 50 are electrically actuated, meaning the switching position and the valve position can be changed electrically. The switching valve 30 and the pressure relief valve 50 are electrically connected to a control unit 56, which electrically controls the switching valve 30 to change the switching position and the pressure relief valve 50 to change the valve position. The control unit 56 also controls the electric motor 26 driving the fluid pump 14.

[0037] The fluid pressure p in the second fluid branch 44 is measured by a pressure sensor 58 which is electrically connected to the control unit 56.

[0038] Figure 2 shows a method for valve control in a specific embodiment of the invention. The pressure relief valve of the fluid device shown as an example in Figure 1 can be controlled by a method for valve control 60 of the pressure relief valve 50. The method first comprises providing 62 the pressure relief valve 50, which, when the valve position is open, triggers a pressure reduction of the fluid in the second fluid branch that depends on an opening time of the pressure relief valve 50. The method for valve control 60 comprises carrying out 64 a pressure reduction process 66 for reducing the fluid pressure p with a first pressure reduction step 68, for example, in order to reduce an overpressure in the second fluid branch when the clutch is closed. In the first pressure reduction step 68, the pressure relief valve 50 is opened 70 with a predetermined first opening time t1, in that the pressure relief valve 50 assumes the open valve position.During the pressure reduction process 66, a detection 72 of the fluid pressure p in the second fluid branch reduced by the pressure drop then takes place, for example by the pressure sensor 58 and a comparison 76 of the fluid pressure p detected by the pressure sensor 58 with a target fluid pressure ps and a specification 78 of a second opening time t2 which is predetermined and to be used for a subsequent second pressure reduction step 80.

[0039] The second opening time t2 for the second pressure reduction step 80 is set depending on a difference 82 between the detected fluid pressure p and the target fluid pressure ps. If the detected fluid pressure p is below the target fluid pressure ps or corresponds to the target fluid pressure ps, the second opening time t2 is set shorter than the first opening time t1. If the detected fluid pressure p is above the target fluid pressure ps, the second opening time t2 is set longer than the first opening time t1.

[0040] The second pressure reduction step 80 is carried out in particular during the pressure reduction process 66, during which the first pressure reduction step 68 is also carried out. This means that the pressure reduction in the pressure reduction process 66 takes place in particular stepwise in several pressure reduction steps.

[0041] Figure 3 shows a method for pressure reduction in a specific embodiment of the invention. The pressure reduction method 84 is explained in more detail below using a time curve as an example.

[0042] Starting from an existing fluid pressure pO in the fluid branch, the fluid pressure p is to be reduced to the target fluid pressure ps. This is achieved by the pressure reduction method 84 described below. The valve control method previously described in Figure 2 is used, in which the pressure reduction starting from the existing fluid pressure pO to the target fluid pressure ps is carried out with the pressure reduction process 66 and initially begins with the first pressure reduction step 68, with which the pressure relief valve is opened from the closed valve state D2 to the open valve state D1 during the first opening time t1 and closed when the first opening time t1 elapses.

[0043] A predetermined time interval 86 is maintained between the elapse of the first opening time t1 and the detection 72 of the fluid pressure p. A renewed opening 70 of the pressure relief valve 50 in the second pressure reduction step 80 during the pressure reduction process 66 over a second opening time t2 occurs by a time offset 88 after the elapse of the first opening time t1. The detection 72 of the fluid pressure p in the fluid branch occurs within the time offset 88. The detection 72 of the fluid pressure p occurs over a detection period 90, and the time offset 88 is, for example, the same length as the time interval 86 and the detection period 90 combined. The second opening time t2 is set higher by a predetermined time interval 92 than the first opening time t1, since the fluid pressure p present after the end of the first pressure reduction step 68 is still above the target fluid pressure ps.Since the existing fluid pressure p remains above the target fluid pressure ps even after the second pressure reduction step 80 has ended, a subsequent third pressure reduction step 94 is performed with a third opening time t3. The third opening time t3 is increased compared to the second opening time t2 by a period 92, which is particularly similar to the period 92 between the first and second opening times t2, t2. After the third pressure reduction step 94 has ended, the existing fluid pressure p is below the target fluid pressure ps, and the pressure reduction process 66 is terminated.

[0044] For a next opening time to be applied in a possible subsequent pressure reduction step, the opening time tn specified for this purpose is set to be a predetermined time period 96 shorter than the last opening time applied, here the third opening time t3.

[0045] List of reference symbols

[0046] 10 Fluid device

[0047] 12 Hydraulic device

[0048] 14 Fluid pump

[0049] 16 fluid reservoirs

[0050] 18 fluid filters

[0051] 20 first fluid line

[0052] 22 Cooling device

[0053] 24 heat exchangers

[0054] 26 electric motor

[0055] 28 second fluid line

[0056] 30 switching valve

[0057] 32 first actuating device

[0058] 34 Parking lock

[0059] 36 second actuating device

[0060] 38 Clutch

[0061] 40 first switching position

[0062] 42 first fluid branch

[0063] 44 second fluid branch

[0064] 46 second switching position

[0065] 48 Return line

[0066] 50 Pressure relief valve

[0067] 52 Return line

[0068] 54 Check valve

[0069] 56 Control unit

[0070] 58 Pressure sensor

[0071] 60 valve control procedures

[0072] 62 Provision 64 Execution

[0073] 66 Pressure reduction process

[0074] 68 first pressure reduction step

[0075] 70 Open

[0076] 72 Recording

[0077] 76 Comparison

[0078] 78 Specification

[0079] 80 second pressure reduction step

[0080] 82 Difference

[0081] 84 Pressure relief procedures

[0082] 86 time interval

[0083] 88 Time offset

[0084] 90 recording time

[0085] 92 Magazine

[0086] 94 third pressure reduction step

[0087] 96 Duration

[0088] D1 open valve position

[0089] D2 closed valve position p fluid pressure ps target fluid pressure t1 first opening time t2 second opening time t3 third opening time

Claims

Patent claims 1. Method for valve control (60) of a pressure relief valve (50) of a fluid device (10) of a vehicle comprising a fluid, comprising the steps of providing (62) the pressure relief valve (50) which is configured to trigger, when the valve is in the open position, a pressure reduction of the fluid in at least one fluid branch (42, 44) of the fluid device (10), which pressure reduction is dependent on an opening time of the pressure relief valve (50), Carrying out (64) a pressure reduction process (66) for reducing the pressure of the fluid pressure (p) in the fluid branch, with a first pressure reduction step (68) comprising opening (70) the pressure relief valve (50) with a predetermined first opening time (t1), characterized in that during the pressure reduction process (66) and following the first pressure reduction step (68), a detection (72) of the fluid pressure (p) in the fluid branch (42, 44) reduced by the pressure reduction of the first pressure reduction step (68), a comparison (76) of the detected fluid pressure (p) with a target fluid pressure (ps) and a specification (78) of a second opening time (80) predetermined and to be used for a temporally subsequent second pressure reduction step (80) when the pressure relief valve (50) is opened (70) depending on the comparison (76).

2. Method for valve control (60) according to claim 1, characterized in that the second opening time (t2) is predetermined as a function of a difference (82) between the detected fluid pressure (p) and the target fluid pressure (ps).

3. Method for valve control (60) according to claim 1 or 2, characterized in that if the detected fluid pressure (p) is below the target fluid pressure (ps) or corresponds to the target fluid pressure (ps), the second opening time (t2) is set smaller than the first opening time (t1) and / or if the detected fluid pressure (p) is above the target fluid pressure (ps), the second opening time (t2) is set greater than the first opening time (t1).

4. Method for valve control (60) according to one of the preceding claims, characterized in that between the completion of the first pressure reduction step (68) and the detection (72) of the fluid pressure (p) a predetermined time interval (86) is maintained.

5. Method for valve control (60) according to one of the preceding claims, characterized in that the predetermined second opening time (t2) is changed by a predetermined time (92) compared to the first opening time (t1).

6. Method for valve control (60) according to one of the preceding claims, characterized in that if the detected fluid pressure (p) corresponds to the target fluid pressure (ps) or is below the target fluid pressure (ps), the next opening time (t2, t3) to be applied is set smaller by a predetermined time period (96) compared to the last applied opening time (t1, t2).

7. Method for reducing pressure (84) of a fluid pressure (p) in at least one fluid branch (42, 44) of a fluid device (10) of a vehicle, comprising the steps Providing (62) the fluid device (10) with a fluid, an actuating device (32, 36) which can be actuated depending on a fluid pressure (p) of the fluid in the fluid branch (42, 44) and a pressure relief valve (50) which can reduce the fluid pressure (p) in the fluid branch (42, 44), Carrying out a pressure reduction process (66) for reducing the fluid pressure (p) in the fluid branch (42, 44) by controlling the pressure relief valve (50) with a valve control method (60) according to one of the preceding claims.

8. Method for pressure reduction (84) according to claim 7, characterized in that in the pressure reduction process (66) starting from an existing fluid pressure (p) in the fluid branch (42, 44) in the direction of the target fluid pressure (ps) in the fluid branch (42, 44), at least the first pressure reduction step (68, 80) and the specification (78) of the second opening time (t2) are carried out.

9. Pressure relief valve (50) for a fluid device (10) which is arranged to be controlled according to a valve control method (60) according to one of claims 1 to 6.

10. Fluid device (10) for at least one actuating device (32, 36) of a Vehicle, comprising a fluid and a pressure relief valve (50) according to claim 9.

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