Method for detecting a defect in a switching valve of a fluid device in a motor vehicle

Abstract

The invention relates to a method for detecting a defect in a switching valve (46) of a fluid device (10) in a motor vehicle

Description

[0001] The invention relates to a method for detecting a defect in a switching valve of a fluid device in a motor vehicle according to the preamble of claim 1.

[0002] The ever-increasing complexity of vehicles requires the flawless function and interaction of all components. The functionality of electrical components is particularly important for enabling purely electric driving and increasing efficiency. Failure or defects of certain electronic components can have serious consequences for the vehicle.

[0003] DE 10 2020 111 970 A1 describes a hydraulic device that supplies an actuating device with an actuating fluid pressure. A hybrid disconnect clutch is actuated depending on the actuating fluid pressure. A relief valve is actuated to open the hybrid disconnect clutch, resulting in a pressure drop in the actuating fluid pressure.

[0004] Many automated clutch systems have an actuator that contains a movable piston, for example a master cylinder with a master cylinder piston and a slave cylinder CSC (Concentric Slave Cylinder) with a slave cylinder piston, whereby the pistons interact with each other via a hydraulic fluid in a hydraulic line. Thus, a certain volume of fluid is displaced when the clutch is actuated. If the pressure is to be kept constant, the piston remains in one position. If too low or too high a pressure is detected, it is regulated by moving the piston in the actuator. When no more pressure is required, the piston moves to its starting position and the pressure drops to 0 bar. The clutch is actuated with a clutch actuation device. The hydraulic fluid is also referred to below as oil.

[0005] According to the invention, a parking lock, like a clutch, is actuated by a pump actuator comprising a fluid pump. The pump actuator provides the required fluid flow to actuate both systems (parking lock and clutch), and a switching valve distributes the fluid flow to the parking lock or the clutch as needed. By default, the switching valve is in the "clutch" position. This means that as long as the switching valve is not energized, fluid pumped by the fluid pump is directed toward the clutch to close the clutch, while the switching valve blocks the line to the parking lock.

[0006] The operation of the fluid device, as used for example in Fig. 1 is carried out by means of a method for operating the fluid device, hereinafter also referred to as the control method, which controls, for example, the fluid pump and the switching valve but also the other valves and processes data from sensors, such as a pressure sensor and a displacement sensor.

[0007] The clutch, for example a "pressed-on" or "normally open" clutch, is not actuated by a master cylinder piston, but rather by a pump actuator that has a fluid pump. If the target "clutch engagement" is requested, for example by a higher-level or other conventional control method, the drain valve, also referred to below as the pressure relief valve, closes. The fluid pump supplies the fluid volume flow towards the slave cylinder piston of the CSC (Concentric Slave Cylinder) until the pressure, also referred to below as the CSC pressure or the actuating fluid pressure of the clutch actuation device, has reached a predetermined value for the target pressure. The CSC pressure can then be maintained for a desired time if requested. If the CSC pressure is to be reduced, the pressure relief valve is opened completely.For this purpose, the pressure relief valve is no longer energized and the pressure relief valve opens automatically, for example by means of a spring mechanism.

[0008] Like all mechatronic components, the switching valve can break. If, for example, the parking lock is in the "Park" state when the vehicle is started, a conventional control process will first set the parking lock to the "Emergency Park" state. This is done by requesting the "Emergency Park" target state and energizing the switching valve. The fluid pump then pumps the hydraulic fluid, i.e. the oil, towards the parking lock. If, however, the switching valve is defective, it does not switch to the "Parking Lock" position but remains in the "Clutch" position. Since the aforementioned conventional control process mistakenly assumes, due to the defect, that the fluid pump is actuating the parking lock, it continues to pump the oil until a predefined target state of the parking lock, for example a predefined position, is reached. This target state of the parking lock is of course not reached because the fluid pump actuates the clutch and not the parking lock.The aforementioned conventional control method fails to detect that, due to the defect in the shift valve, the clutch is being actuated rather than the parking lock, and the clutch would be engaged. Inadvertent engagement of the clutch leads to the unintended transmission of torque, which in certain cases could result in an accident. In such a fault, the wheels and one or more of the vehicle's drive units, such as one or more electric motors and / or the combustion engine, would be inadvertently coupled, and drive torque could be inadvertently transferred to the wheels.

[0009] The object of the present invention is to improve the conventional control method by fault monitoring and early fault detection on the switching valve.

[0010] These objects are achieved by a method for operating a fluid device having the features according to claim 1.

[0011] The fluid device may be a hydraulic device. The fluid may be a hydraulic fluid. The fluid may be an oil, in particular a hydraulic oil.

[0012] The vehicle may be a motor vehicle, in particular a hybrid vehicle or electric vehicle.

[0013] The fluid pump can be a gear pump. The fluid pump can be a reversing pump. In a first pumping mode, the fluid pump can generate the fluid volume flow to build up the actuating fluid pressure. In a second pumping mode, the fluid pump can supply at least one cooling device with a fluid volume flow. The fluid pump can be alternately switchable between the first and second pumping modes. The fluid pump can be driven by an electric motor.

[0014] The clutch may be a friction clutch or a dog clutch. The clutch may be a separating clutch, particularly a K0 clutch in a hybrid powertrain. The clutch actuation device may have a concentric slave cylinder (CSC) actuation.

[0015] The actuating fluid pressure may be a clutch actuation pressure.

[0016] The first actuation state can result in a closed clutch. The second actuation state can result in an open clutch.

[0017] The pressure relief valve can be a drain valve.

[0018] The first relief valve state may correspond to a fully closed pressure relief valve. The second relief valve state may correspond to a fully open pressure relief valve. The third relief valve state differs from a fully open and fully closed relief valve state, respectively.

[0019] A pressure relief valve may not be provided in the fluid device, at least for limiting the actuating fluid pressure.

[0020] The object is thus achieved by a method for detecting a defect in a switching valve of a fluid device in a motor vehicle, with at least the switching valve, which is actuated by means of current supply and a fluid pump as well as a control unit that controls at least the switching valve and the fluid pump, wherein the fluid pump is connected to the switching valve via a hydraulic pressure line and the switching valve has two switching positions and is connected via a first pressure line branch to a parking lock actuating device for actuating a parking lock device and via a second pressure line branch to a clutch actuating device for actuating a clutch, wherein the two pressure line branches can be alternately connected to the hydraulic pressure line by means of the switching valve, for example a 4 / 2 valve,wherein a change from energization to de-energization and from de-energization to energization each leads to a change in the switching position of the switching valve, wherein a pressure sensor connected to the control unit, which determines the actuating fluid pressure of the clutch actuating device, is installed in the clutch actuating device or in the pressure line branch actuating the clutch actuating device, and wherein a displacement sensor connected to the control unit, which determines the position of the parking lock actuating device, is installed in the parking lock actuating device. It is provided that the current switching position of the switching valve is known to the control unit, and wherein a change in the switching position is initiated by the control unit by switching between energization and de-energization at the switching valve and activating the fluid pump.as well as signals from the position sensor and signals from the pressure sensor are evaluated by the control unit and from this it is concluded which switching position of the switching valve is now the switching position following the previously current switching position, whereby the existence of a defect in the switching valve is concluded if the switching position following the previously current switching position to which it is closed continues to correspond to the previously current switching position.

[0021] In a preferred embodiment of the invention, it is provided that the current switching position of the switching valve is known to the control unit, since the control unit knows the current energization status of the switching valve and since the energized, fault-free switching valve assumes a first switching position, so that the fluid pump is connected to the parking lock actuating device via the hydraulic pressure line and the switching valve and via the first pressure line branch, and that the de-energized, fault-free switching valve assumes a second switching position, so that the fluid pump is connected to the clutch actuating device via the hydraulic pressure line and the switching valve and via the second pressure line branch.

[0022] In a further preferred embodiment of the invention, it is provided that the signals of the displacement sensor and the signals of the pressure sensor are determined and transmitted by the two sensors, at the latest when the fluid pump is activated, and are received and evaluated by the control unit.

[0023] In a particularly preferred embodiment of the invention, it is provided that the detection, transmission, reception and evaluation of the signals of the displacement sensor and the pressure sensor take place sufficiently quickly, for example in a 2 ms cycle.

[0024] In a further preferred embodiment of the invention, it is provided that the first switching position is concluded when the signals of the displacement sensor exceed a predetermined displacement max threshold value and the signals of the pressure sensor do not exceed a predetermined pressure min threshold value.

[0025] In a further preferred embodiment of the invention, it is provided that the second switching position is concluded when the signals of the pressure sensor exceed a predetermined maximum pressure threshold value and the signals of the displacement sensor do not exceed a predetermined minimum displacement threshold value.

[0026] In a particularly preferred embodiment of the invention, it is provided that the parking lock is engaged before the vehicle is put into operation and that the parking lock is disengaged during the start-up by energizing the switching valve and assuming the first switching position and activating the fluid pump.

[0027] In a further preferred embodiment of the invention, it is provided that when the error is detected and when the second switching position has been concluded, the fluid pump is prevented from delivering any further fluid volume flow in the direction of the clutch actuating device.

[0028] In a further preferred embodiment of the invention, it is provided that when the error is detected, the clutch is caused to open by causing a pressure relief valve to open, so that a second relief valve state of the pressure relief valve is present, so that the second actuation state of the clutch actuation device is thus established.

[0029] Further advantages and advantageous embodiments of the invention emerge from the description of the figures and the illustrations.

[0030] The invention is described in detail below with reference to the figures. They show in detail: Fig. 1: A fluid device in a specific embodiment of the invention. Fig. 2: A preferred embodiment of the invention with the variables relevant for the execution of the control method

[0031] Fig. 1 shows a fluid device in a specific embodiment of the invention. The fluid device 10 is arranged in a vehicle and is designed as a hydraulic device 12 containing a hydraulic fluid. The fluid device 10 comprises a fluid pump 14 driven by an electric motor 16, which in turn is electrically controlled by a motor controller 18.

[0032] The fluid device 10 further comprises an actuating device 20 for a clutch 28, hereinafter referred to as the clutch actuating device 26, which, depending on an actuating fluid pressure p, which is built up by a fluid volume flow provided by the fluid pump 14, can be switched between a first actuating state 22, in which the clutch actuating device 26 is actuated (shown here in the dashed area), and a second actuating state 24, in which the clutch actuating device 26 is not actuated. The actuating fluid pressure p is a clutch actuation pressure, which is also referred to as the CSC pressure in this document. The clutch actuating device 26 comprises a CSC actuation, which has a slave cylinder piston 30 that can be displaced depending on the actuating fluid pressure p.

[0033] The fluid volume flow is drawn by the fluid pump 14 from a fluid reservoir 32. A suction-side filter 34 is arranged between the fluid reservoir 32 and the fluid pump 14. The fluid pump 14 is designed as a reversing pump, which, with a first pump operation, builds up the fluid volume flow to build up the actuating fluid pressure p and, with a second pump operation, builds up a fluid volume flow to supply additional vehicle components, for example cooling devices 36, in particular for cooling a ring gear 38, a hollow shaft bearing 40, and one or more electric motors 42. The fluid is cooled by a heat exchanger 44.

[0034] An electrically controllable switching valve 46, here a 4 / 2 valve, is arranged between the fluid pump 14 and the clutch actuating device 26. The switching valve 46 controls the fluid volume flow between the fluid pump 14 and the clutch actuating device 26, as well as a parking lock actuating device 48, which is assigned to a parking lock device 50.

[0035] The parking lock 50, like the clutch 28, is actuated by the fluid pump 14 of the fluid device 10. The fluid pump 14 provides the required fluid volume flow to actuate the respective system, and the switching valve 46 distributes the fluid volume flow, as required, either entirely to the parking lock actuating device 48 of the parking lock 50 or entirely to the clutch actuating device 26 of the clutch 28, but not to both simultaneously. By default, i.e. in the fault-free, de-energized basic setting determined only by mechanical conditions such as springs, the switching valve 46 is in the "clutch" position and not in the "parking lock" position if the switching valve 46 is not jammed, blocked, or otherwise defective. As long as the switching valve 46 is not defective and is not energized, the oil is passed on towards the slave cylinder piston 30 of the CSC of the clutch 28 to close the clutch.

[0036] The fluid device 10 comprises a controllable pressure relief valve 52, here a 2 / 2-way valve, which can be switched at least between a first relief valve state C1, in which the pressure relief valve 52 is closed, and a second relief valve state C2, in which the pressure relief valve 52 is open. In the first actuation state 22, the pressure relief valve 52 has the first relief valve state C1, i.e., the pressure relief valve 52 is closed. To assume the second actuation state 24, starting from the first actuation state 22, the pressure relief valve 52 has the second relief valve state C2, i.e., it is opened, thus reducing the actuation fluid pressure p and disengaging the clutch 28.In the first actuation state 22, the clutch 28 is closed, and the actuation fluid pressure p remains above a first actuation pressure value due to the closed pressure relief valve 52, from which the first actuation state 22 exists. The check valve 54 prevents a backflow of the fluid into the fluid reservoir 32 and a pressure reduction of the actuation fluid pressure p. Temperature influences can cause pressure increases in the actuation fluid pressure p.

[0037] Fig. Figure 2 shows a specific embodiment of the invention, where four variables are shown in the temporal course of the control method: • Parking lock target state: The two possible target states of the parking lock are "Park" or "Emergency Park." "Emergency Park" means that the parking lock should leave the "Park" state or has already left it, meaning that the parking lock should be released or has already been released. ("Emergency" therefore means "not") The same applies to "Park." "Park" means that the parking lock should be in the "Park" state or has already entered it, meaning that the parking lock should be activated or is already activated, meaning it is locked. • CSC pressure: Pressure p in the clutch actuation device 26 is determined by means of the pressure sensor 58. • PL_Position: Position of the parking lock actuation device 48, determined by the travel sensor 56. (PL: Parklock) • Error status: The parking lock error status can take one of the two values ​​“True” or “False” and the control procedure can change the error status.

[0038] The control method provides for simultaneous evaluation of the signals of the displacement sensor 56, which determines the position of the parking lock actuating device 48, and the signals of the pressure sensor 58, which determines the actuating fluid pressure p of the clutch actuating device 26 in a predetermined cycle, preferably in a 2 ms cycle.

[0039] Is - as usual - when starting the vehicle ( Fig. 2, left side) the parking lock 50 is in the "Park" state, the parking lock is first set to the "Emergency Park" state. This occurs by requesting the "Emergency Park" target state and energizing the switching valve 46. The fluid pump is then activated. If the switching valve 46 is not defective, it switches to the "Park Lock" switching valve position, and the fluid pump pumps the hydraulic fluid, i.e., the oil, into the parking lock actuation device 48.

[0040] However, if the switching valve 46 is defective, it does not switch to the "parking lock" switching valve position, but remains in the "clutch" position. Just as in the case of the non-defective switching valve 46, the fluid pump 14 is then activated and inadvertently pumps the oil into the clutch actuation device 26. According to conventional control methods, this would go unnoticed until an unintended torque transfer occurs in the closing clutch.

[0041] The method according to the invention therefore provides for the determination of whether the switching valve is defective or not by simultaneously determining and evaluating the signals of the travel sensor 56, which determines the position of the parking lock actuating device 48 ( Fig. 2, “PL_Position”) and the signals of the pressure sensor 58, which determines the actuating fluid pressure p of the clutch actuating device 26 ( Fig. 2, “CSC Pressure”). Simultaneous detection and evaluation of the signals from both sensors should show, at the latest upon activation of the fluid pump, which of the two actuating devices is actuated by the fluid volume flow and which is not, so that the position of the switching valve 46 can be determined and thus a rapid error assessment is possible and appropriate reactions can be initiated sufficiently quickly to avoid safety-critical situations caused by the vehicle. In this case, it might even be necessary to prioritize the fastest possible detection of the data from the pressure sensor 58 over the detection of the data from the displacement sensor 56. This depends on whether an unexpectedly closing clutch or an unexpectedly opening parking lock is considered more critical by the expert. For this purpose, the expert would also take into account the sensitivity of the sensors (measuring range, measurement error) and select the sensors and their sensitivity accordingly.

[0042] Determination and transmission of the respective measured values ​​by displacement sensor 56 and pressure sensor 58, as well as reception and evaluation of these signals by a control unit 18, must occur sufficiently quickly. At the latest before the clutch is closed to the contact point, it should be determined whether the switching valve is in the intended position or whether it is defective or not receiving power. For this purpose, a timing for the determination and transmission of both sensors 56, 58, as well as the reception and evaluation of these signals by the control unit 18, is specified. This timing takes into account the timing of the control unit, the processing speed of the sensors involved, etc. A 2 ms timing is preferably specified.

[0043] In Fig. 2 shows the case of a defective switching valve, which, starting from an engaged parking lock, should actually be opened towards the parking lock ( Fig. 2, "Target position parking lock"), so that if the switching valve is faultless, the parking lock would be expected to be disengaged. Unexpectedly, the course of the position of the parking lock actuating device 48 ( Fig. 2, “PL_Position”) which is determined by the travel sensor 56, no change despite the active fluid pump 14, while, however, the pressure curve (actuating fluid pressure p) in the clutch actuating device 26 ( Fig. 2, "CSC Pressure") which is determined by the pressure sensor 58 increases. The error status ( Fig. 2, "Error Status") indicates an error on or in the switching valve. The switching valve is either blocked or without power.

[0044] In order to prevent torque from being transmitted to the vehicle wheels, the fluid pump is immediately stopped so that the clutch is not closed any further and, if necessary, the pressure relief valve 52 (drain valve) is also opened so that the clutch can open completely again automatically.

[0045] Both the engagement of clutch 28 and the disengagement of parking lock 50 require the oil volume flow provided by fluid pump 14 of fluid device 10. The switching valve 46 distributes the fluid volume flow, in a conventional manner initiated by a higher-level or other control method or the control method according to the invention, either entirely to the parking lock actuating device 48 of parking lock 50 or entirely to the clutch actuating device 26 of clutch 28, but not to both simultaneously. Therefore, it is not possible for both systems (parking lock 50 and clutch 28) to be actuated simultaneously.In a special embodiment of the invention, it is provided that subsequently, at the latest from the actual or erroneously assumed switching of the switching valve 46, the movement of the parking lock 50 is monitored by means of the displacement sensor 56, which measures the position of the parking lock actuating device 48, and the movement of the clutch 28 is monitored by means of the pressure sensor 58, which measures the pressure in the clutch actuating device 26. Alternatively, both measurements are initiated with the change of the target state of the parking lock from "Park" to "Emergency Park" or, alternatively, with the activation of the fluid pump 14 following the change of the target state of the parking lock.

[0046] Coming from the "Park" state of the parking lock, if the system is fault-free, as soon as the target state of the parking lock "Emergency Park" is requested, the piston of the parking lock actuating device 48 should move. This is detected based on the travel signal of the travel sensor 56, which is checked every 2 ms. In addition, as soon as the target state of the parking lock "Emergency Park" is requested, the actuating fluid pressure p of the clutch actuating device 26 of the clutch 28 is checked by means of the pressure sensor 58, also every 2 ms, to determine whether the pressure p increases even though the target state "Emergency Park" is requested. If it is detected that this pressure p increases and / or that the travel signal does not change, an error condition exists ( Fig.2, "CSC Pressure", "PL_Position"). This is immediately detected by the control process and results in the fluid pump 14 being switched off to prevent damage. The maximum permissible pressure p in the clutch actuation device 26 in this fault case is the pressure present at the contact point of the clutch, which is determined via characteristic curves and other parameters such as clutch temperature, etc. Before this pressure is reached, the fluid pump must switch off and, if necessary, also open the pressure relief valve 52 (drain valve) of the clutch 28, since otherwise torque is transmitted and unintentional starting may occur. List of reference symbols 10 Fluid device 12 Hydraulic device 14 Fluid pump 16 Electric motor 18 Control unit 20 Actuating device 22 first operating state 24 second operating state 26 Clutch operating device 28 Clutch 30 slave cylinder pistons 32 fluid reservoirs 34 filters 36 cooling devices 38 ring gear teeth 40 hollow shaft bearings 42 electric motor 44 heat exchangers 46 Switching valve 48 Parking lock actuation device 50 Parking lock device 52 Pressure relief valve 54 shut-off valve 56 displacement sensor 58 Pressure sensor C1 first relief valve state C2 second relief valve state p Actuating fluid pressure 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 2020 111 970 A1

[0003]

Claims

[1] Method for detecting a defect in a switching valve (46) of a fluid device (10) in a motor vehicle with at least the switching valve (46) which is actuated by means of current supply and a fluid pump (14) as well as a control unit (18) which controls at least the switching valve (46) and the fluid pump (14), wherein the fluid pump (14) is connected to the switching valve (46) via a hydraulic pressure line and the switching valve (46) has two switching positions and is connected via a first pressure line branch to a parking lock actuating device (48) for actuating a parking lock device (50) and via a second pressure line branch to a clutch actuating device (26) for actuating a clutch (28), wherein the two pressure line branches can be alternately connected to the hydraulic pressure line by means of the switching valve (46),wherein a change from energization to non-energization and from non-energization to energization each leads to a change in the switching position of the switching valve (46), wherein a pressure sensor (58) connected to the control unit (18) and determining the actuating fluid pressure (p) of the clutch actuating device (26) is mounted in the clutch actuating device (26) or in the pressure line branch actuating the clutch actuating device (26), and wherein a displacement sensor (56) connected to the control unit (18) and determining the position of the parking lock actuating device (48) is mounted in the parking lock actuating device (48), characterized bythat the current switching position of the switching valve (46) is known to the control unit (18), and wherein a change in the switching position is initiated by the control unit (18) by changing between energization and non-energization at the switching valve (46), and the fluid pump (14) is activated, and signals from the position sensor 56 and signals from the pressure sensor 58 are evaluated by the control unit (18), and a conclusion is drawn therefrom as to which switching position of the switching valve (46) is now present, the switching position following the previously current switching position, wherein the presence of a defect in the switching valve (46) is concluded if the switching position following the previously current switching position, to which the switch is closed, continues to correspond to the previously current switching position. [2] Method according to claim 1, characterized bythat the current switching position of the switching valve (46) is known to the control unit (18), since the control unit knows the current energization status of the switching valve (46) and since the energized, fault-free switching valve (46) assumes a first switching position, so that the fluid pump (14) is connected to the parking lock actuating device (48) via the hydraulic pressure line and the switching valve (46) and via the first pressure line branch, and that the de-energized, fault-free switching valve (46) assumes a second switching position, so that the fluid pump (14) is connected to the clutch actuating device (26) via the hydraulic pressure line and the switching valve (46) and via the second pressure line branch. [3] Method according to one of claims 1 or 2, characterized bythat the signals of the displacement sensor (56) and the signals of the pressure sensor (58) are detected and sent by the two sensors (56, 58) at the latest when the fluid pump (14) is activated and are received and evaluated by the control unit (18). [4] Method according to claim 1, characterized by that the detection, transmission, reception and evaluation of the signals of the displacement sensor (56) and the pressure sensor (58) takes place sufficiently quickly, for example in a 2ms cycle. [5] Method according to one of the preceding claims, characterized by that the first switching position is concluded when the signals of the displacement sensor (56) exceed a predetermined displacement max threshold value and the signals of the pressure sensor (58) do not exceed a predetermined pressure min threshold value. [6] Method according to one of the preceding claims, characterized bythat the second switching position is closed when the signals of the pressure sensor (58) exceed a predetermined maximum pressure threshold value and the signals of the displacement sensor (56) do not exceed a predetermined minimum displacement threshold value. [7] Method according to one of the preceding claims, characterized by that the parking lock (50) is engaged before the vehicle is put into operation and that the parking lock (50) is disengaged during commissioning by energizing the switching valve (46) and assuming the first switching position and activating the fluid pump (14). [8] Method according to one of the preceding claims, characterized by that when the error is detected and the second switching position has been closed, the fluid pump (14) stops delivering any further fluid volume flow in the direction of the clutch actuating device (26). [9] Method according to one of the preceding claims, characterized bythat when the error is detected, the clutch (28) is caused to open by causing a pressure relief valve (52) to open, so that a second relief valve state (C2) of the pressure relief valve (52) is present, so that the second actuation state (24) of the clutch actuation device (26) is thereby established.

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