Methods for valve control, pressure reduction, pressure relief valve and fluid device

Abstract

The invention relates to a method for controlling the valve (60) of a pressure relief valve (50) of a fluid device (10) of a vehicle, comprising the steps of providing (62) the pressure relief valve (50), which is configured 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 in the open position, the pressure reduction of which depends on an opening time of the pressure relief valve (50), and performing (64) a pressure reduction process (66) 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) with a predetermined first opening time (t1), wherein during the pressure reduction process (66) and subsequently after the first pressure reduction step (68), the fluid pressure (p) in the fluid branch (42) reduced by the pressure reduction of the first pressure reduction step (68) is detected (72). 44),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) to be applied for a subsequent second pressure reduction step (80) when the pressure relief valve (50) is opened, depending on the comparison (76), are performed. The invention further relates to a method for pressure reduction (84), a pressure relief valve (50), and a fluid device (10).

Description

[0001] The invention relates to a method for valve control according to the preamble of claim 1. Furthermore, the invention relates to a method for pressure reduction of a fluid pressure, a pressure relief valve and a fluid device.

[0002] In DE 10 2006 022 858 A1, a method for a hydromechanical coupling of a motor vehicle with a pressure relief valve is disclosed, wherein the pressure relief valve is controlled by an evaluation and control circuit depending on a predetermined vehicle state.

[0003] German patent DE 10 2020 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 pressure of the actuating fluid to open the actuating device.

[0004] The object of the present invention is to carry out the pressure reduction of the fluid pressure more precisely. The fluid device should be operated more safely.

[0005] At least one of these problems is solved by a valve control method with the features of claim 1. This allows the pressure reduction by the pressure relief valve to be carried out more precisely and in a more targeted manner. The fluid pressure can reach a target fluid pressure more accurately. The fluid pressure can be achieved less dependent on environmental influences, such as temperature influences.

[0006] The vehicle can be a motor-driven vehicle, in particular a motor vehicle, truck or two-wheeler.

[0007] The fluid device can include at least one fluid pump for generating fluid pressure and / or fluid flow rate. The fluid pump can be driven by an electric motor.

[0008] The fluid device can have at least one fluid branch. The fluid branch can have at least one switching valve for changing the fluid pressure in the fluid branch.

[0009] 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.

[0010] The fluid device may include at least one switching valve for adjusting the fluid pressure at the actuating device. The switching valve may be effectively arranged between the fluid pump and the actuating device.

[0011] The pressure relief valve can be effectively positioned 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 electrically actuated, preferably electromagnetically.

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

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

[0014] Detecting fluid pressure can include measuring fluid pressure.

[0015] Pressure reduction can be used to reduce thermally induced overpressure in the fluid branch.

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

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

[0018] In a specific embodiment of the invention, it is advantageous to maintain a predetermined time interval between the completion of the first pressure reduction step and the measurement 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 subside, and the fluid pressure can be measured more accurately.

[0019] The time interval can depend on the respective opening time or be independent of it. 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 measurement period for the fluid pressure 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 time step compared to the first opening time. The time step can be less than 100 ms, preferably less than 10 ms, and 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 time compared to the last applied opening time. 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 applied opening time can be the first opening time. The next applied opening time can be the second opening time.

[0022] Furthermore, within the scope of the invention, a method for pressure reduction with the features according to claim 7 is proposed to solve at least one of the previously specified 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 towards the target fluid pressure in the fluid branch, at least the first pressure reduction step and the setting of the second opening time are carried out. The second pressure reduction step can also be carried out during the pressure reduction process. Alternatively, only the first pressure reduction step can be carried out during the pressure reduction process. More pressure reduction steps than just the first and second can also be carried out during the pressure reduction process.

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

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

[0026] Further advantages and advantageous embodiments of the invention will become apparent from the description of the figures and the illustrations. Character description

[0027] The invention is described in detail below with reference to the illustrations. These show, in detail: Fig. 1: A fluid device in a special embodiment of the invention. Fig. 2: A method for valve control in a special embodiment of the invention. Fig. 3: A method for pressure reduction in a special embodiment of the invention.

[0028] Fig. 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 delivers the fluid from a fluid reservoir 16 via a fluid filter 18 and supplies a first fluid line 20 with a fluid flow rate to supply at least one vehicle component, for example, for lubrication and / or cooling of 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.

[0029] Furthermore, the fluid pump 14 is connected to a second fluid line 28, in which the fluid pump 14 generates a fluid pressure p for actuating a first actuating device 32, for example, a parking lock 34, and a further fluid pressure p for actuating a second actuating device 36, for example, a coupling 38, in particular a K0 coupling, depending on the switching position of a switching valve 30. The switching valve 30 has two switching positions. In the first switching position 40, the fluid pump 14 is connected to a first fluid line 42 connecting the parking lock 34. A second fluid line 44 connected to the coupling 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 line 44, and the first fluid line 42 is connected to a return line 48 to the fluid reservoir 16.

[0030] The second fluid branch 44 has a pressure relief valve 50 between the coupling 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 the fluid accumulator 16 via a return line 52, and in a closed valve position D2, the connection to the fluid accumulator 16 is blocked.

[0031] 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.

[0032] The switching valve 30 and the pressure relief valve 50 are electrically actuated, meaning that their switching position and 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 its switching position and the pressure relief valve 50 to change its valve position. The control unit 56 also controls the electric motor 26 that drives the fluid pump 14.

[0033] 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.

[0034] Fig. Figure 2 shows a method for valve control in a special embodiment of the invention. The method described in Figure 2 shows a method for valve control in a special embodiment of the invention. Fig. The pressure relief valve of the fluid device shown as an example is controllable by a valve control method 60 of the pressure relief valve 50. The method first comprises providing 62 the pressure relief valve 50, which, when in the open position, triggers a pressure reduction of the fluid in the second fluid branch, the duration of which depends on an opening time of the pressure relief valve 50. The valve control method 60 comprises performing 64 a pressure reduction process 66 to reduce the fluid pressure p with a first pressure reduction step 68, for example, to reduce overpressure in the second fluid branch when the coupling is closed. In the first pressure reduction step 68, the pressure relief valve 50 opens 70 with a predetermined first opening time t1 by assuming the open valve position.During the pressure reduction process 66, the fluid pressure p in the second fluid branch, reduced by the pressure drop, is subsequently detected 72, for example by the pressure sensor 58, and the fluid pressure p detected by the pressure sensor 58 is compared 76 with a target fluid pressure ps, and a second opening time t2 is specified 78 for a subsequent second pressure reduction step 80 and applied.

[0035] 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 or equal 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.

[0036] The second pressure reduction step 80 is carried out in particular during the pressure reduction process 66, in 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 stages, in particular in several pressure reduction steps.

[0037] Fig. Figure 3 shows a method for pressure reduction in a special embodiment of the invention. The pressure reduction method 84 is explained in more detail below using the example of a time course.

[0038] Starting from an existing fluid pressure p0 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 procedure described below (84). In this process, the previously described Fig.The described method for valve control is applied, in which the pressure reduction from the existing fluid pressure p0 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, in 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 has elapsed.

[0039] A predetermined time interval 86 is maintained between the elapse of the first opening time t1 and the measurement 72 of the fluid pressure p. The pressure relief valve 50 is reopened 70 in the second pressure reduction step 80 during the pressure reduction process 66, over a second opening time t2, with a time offset 88 after the elapse of the first opening time t1. The measurement 72 of the fluid pressure p in the fluid branch takes place within this time offset 88. The measurement 72 of the fluid pressure p occurs over a measurement duration 90, and the time offset 88 is, for example, equal to the time interval 86 and the measurement duration 90 combined. The second opening time t2 is set a predetermined time step 92 higher than the first opening time t1 because the fluid pressure p present after the completion of the first pressure reduction step 68 is still above the target fluid pressure ps.

[0040] Since the existing fluid pressure p is still above the target fluid pressure ps even after the second pressure reduction step 80 has ended, a subsequent third pressure reduction step 94 is executed with a third opening time t3. The third opening time t3 is increased compared to the second opening time t2 by a time step 92, which is in particular equal to the time step 92 between the first and second opening times t2. After completion of the third pressure reduction step 94, the existing fluid pressure p is below the target fluid pressure ps and the pressure reduction process 66 is terminated.

[0041] For the next opening time to be applied in a possible subsequent pressure reduction step, the specified opening time tn is set to be a specified time duration 96 less than the last applied opening time, here the third opening time t3. Reference symbol list 10 Fluid device 12 Hydraulic device 14 Fluid pump 16 fluid storage tanks 18 fluid filters 20 first fluid strand 22 Cooling device 24 heat exchangers 26 Electric motor 28 second fluid strand 30 switching valve 32 first actuating device 34 Parking restrictions 36 second actuating device 38 Clutch 40 first switching position 42 first fluid branch 44 second fluid branch 46 second switch position 48 Return line 50 Pressure relief valve 52 Return line 54 Check valve 56 Control unit 58 Pressure sensor 60 methods for valve control 62 Provide 64 Perform 66 Pressure reduction process 68 first pressure reduction step 70 Open 72 Recording 76 Comparison 78 Specification 80 second pressure reduction step 82 difference 84 methods for pressure reduction 86 time interval 88 Time offset 90 Recording time 92 time step 94 third pressure reduction step 96 Duration D1 open valve position D2 closed valve position p Fluid pressure PS Target fluid pressure t1 first opening time t2 second opening time t3 third opening time

Claims

Method for valve control (60) of a pressure relief valve (50) of a fluid device (10) of a vehicle, comprising the steps of providing (62) the pressure relief valve (50), which is configured 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 in the open position, the pressure reduction of which depends on an opening time of the pressure relief valve (50); performing (64) a pressure reduction process (66) 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) with a predetermined first opening time (t1); characterized in that during the pressure reduction process (66) and subsequently after the first pressure reduction step (68), the fluid pressure (p) in the fluid branch (42, 44) reduced by the pressure reduction of the first pressure reduction step (68) is detected (72). 44),a comparison (76) of the measured fluid pressure (p) with a target fluid pressure (ps) and a specification (78) of a second opening time (t2) to be applied for a subsequent second pressure reduction step (80) when the pressure relief valve (50) is opened (70) depending on the comparison (76). Method for valve control (60) according to claim 1, characterized in that the second opening time (t2) is predetermined depending on a difference (82) between the detected fluid pressure (p) and the target fluid pressure (ps). Method for valve control (60) according to claim 1 or 2, characterized in that if the detected fluid pressure (p) is below or equal to the target fluid pressure (ps), the second opening time (t2) is set to be 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 to be larger than the first opening time (t1). Method for valve control (60) according to one of the preceding claims, characterized in that a predetermined time interval (86) is maintained between the completion of the first pressure reduction step (68) and the detection (72) of the fluid pressure (p). 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 step (92) compared to the first opening time (t1). Method for valve control (60) according to one of the preceding claims, characterized in that if the detected fluid pressure (p) corresponds to or is below the target fluid pressure (ps), the next opening time to be applied (t2, t3) is set to be shorter by a predetermined time period (96) compared to the last applied opening time (t1, t2). Method for reducing the 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 of 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), and 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 method for valve control (60) according to one of the preceding claims. Method for pressure reduction (84) according to claim 7, characterized in that during 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. Pressure relief valve (50) for a fluid device (10) which is configured to be controlled according to a method for valve control (60) according to one of claims 1 to 6. 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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