Method for controlling a parking lock and hydraulic system for actuating a parking lock

Abstract

The invention relates to a method for controlling a hydraulic system (1) and a hydraulic system (1) of a vehicle with a hydraulic actuator (3) for supplying hydraulic components (14, 15) and actuating a parking lock (11) by means of a pressure medium actuated by the actuator (3) to an adjustable system pressure, wherein an actuating mechanism (16) by means of a slave cylinder (10) with a slave cylinder piston (17) sets an engaged or disengaged state of the parking lock (11) depending on the system pressure along a detected actuating path (s), and a mechanically actuated emergency release device (25) by means of which the disengaged state of the parking lock (11) can be adjusted.In order to avoid a total failure of the hydraulic system (1) when the emergency release device (25) is actuated, an emergency release state is determined by means of the emergency release device (25) when the parking lock (11) is in the designed state, and the actuator (3) continues to operate in emergency mode.

Description

[0001] The invention relates to a method and a hydraulic system for controlling a parking lock by means of a hydraulic actuator that adjusts a system pressure in a controlled manner and an actuating mechanism that is displaced by the hydraulic actuator along a detected actuating path from a slave cylinder using the system pressure and that adjusts an engaged or disengaged state of the parking lock. Parking locks of this type and methods for controlling them are known, for example, from the publication DE 10 2021 117 215 A1. An adjustable system pressure is generated by means of a hydraulic actuator, which acts on a slave cylinder and, depending on the circuitry, engages or disengages the parking lock by means of an actuating mechanism.

[0002] From the publication DE 10 2019 118 485 A1 a method for detecting an emergency release of a parking lock actuated by means of an electrically operated actuator is known, in which a different behavior between an emergency-released and a non-emergency-released parking lock of the electrical current for operating the actuator is evaluated during the disengagement of the parking lock.

[0003] The object of the invention is to further develop a method for controlling a generic parking lock and a hydraulic system for actuating the same. In particular, the object of the invention is to propose a method and a device for detecting an emergency release device of the parking lock and the continued operation of the actuator in this case.

[0004] The object is solved by the subject matter of claims 1 and 8. The claims dependent on claim 1 represent advantageous embodiments of the subject matter of claim 1.

[0005] The proposed method is used to control a parking lock using a hydraulic actuator. The hydraulic actuator can be designed, for example, as a pump that pumps pressure fluid into a pressure line, thereby generating system pressure. The pump can be driven by an electric motor, for example, a contactless commutated electric motor, which drives the pump in a speed-controlled manner, so that the pump's pumping power is adjusted based on the electric motor's speed.

[0006] An actuating mechanism with a slave cylinder is connected to the pressure line. The slave cylinder piston is displaced along an actuating path depending on the system pressure, thereby driving an actuating element which, for example, actuates a parking claw, parking pawl, or the like of the parking lock, so that it engages or is released from a drive element connected directly to the drive wheels or, for example, via a transmission. The parking lock has two states: an engaged state in which the parking lock is effectively activated, and a disengaged state in which the parking lock is ineffective and a vehicle is moving in normal driving conditions. Depending on the design of the parking lock and its actuation, the parking lock can be engaged or disengaged when system pressure is applied.According to an embodiment of the parking lock described in detail below, the parking lock is engaged when system pressure is applied, i.e., the parking lock is engaged when there is insufficient system pressure and is in a zero position. To keep the parking lock in the disengaged state when the system pressure is applied, a locking device can be provided that positively holds the actuating element or the piston rod in this state, at least when the parking lock is disengaged. In addition, the locking device can be positively held in the engaged state.

[0007] The displacement of the actuating mechanism caused by the system pressure, for example, the displacement of the slave cylinder piston, is detected. For example, a displacement sensor is arranged on the actuating element or on a piston rod of the slave cylinder piston. For example, a displacement sensor can be provided fixed to the housing, which detects corresponding displacement markings on the displaced component—piston rod or actuating element—for example, detects displacement increments and converts them into a displacement signal.

[0008] In order to deactivate the parking lock, for example in the event of a parking lock failure, vehicle towing, and the like, a mechanical emergency release device is provided. This emergency release device can, for example, move the actuating element or the slave cylinder piston, for example on its piston rod, along the actuation path and fix it in the disengaged state of the parking lock. For example, the emergency release device can contain a manually operable lock, for example a screw connection, which acts directly or indirectly on the slave cylinder piston and is preloaded, for example. After the lock is released, this lock, for example spring-loaded, moves the slave cylinder piston, possibly preloaded in the zero position, to a maximum deflection relative to its zero position with the parking lock engaged and actuated, regardless of the applied system pressure.

[0009] Using this method, an emergency release state is determined when the parking lock is in the designed state set by the emergency release device. Based on the emergency release state detected or determined by a control unit with implemented software for controlling the hydraulic system, the actuator can continue to operate in emergency mode.

[0010] To determine the emergency release state, a detected driving state of the vehicle, such as towing the vehicle, an error message, or the like, and the actuation path can be used. For example, a driving state of the vehicle can be used to rule out the possibility of an emergency release state being prevented during regular vehicle travel with the parking lock in a normally engaged state by determining the emergency release state exclusively while the vehicle is stationary and, if necessary, regularly determining it while the vehicle is stationary or has come to a standstill again.

[0011] No additional components or sensors are required to check the status of the emergency release device, so that the determination of the emergency release status can be implemented cost-neutrally, for example, as a subroutine to the parking lock control routine in the control unit.

[0012] To clearly distinguish the emergency release state from a regular operating state of the actuated and disengaged parking lock, it can be alternatively or additionally provided that the emergency release state is determined based on an overtravel of the actuating element or the slave cylinder piston that exceeds a predetermined actuation travel when the parking lock is disengaged. This means that the slave cylinder piston is mechanically moved by the emergency release device beyond its position normally set by the system pressure. This overtravel along the actuation travel is detected by the travel sensor and interpreted by the control unit as an emergency release state.

[0013] For example, when the parking lock is engaged, the slave cylinder piston is positioned near a zero position at minimum system pressure and actuated under high system pressure when the parking lock is disengaged. To set the emergency release state, the slave cylinder piston is mechanically displaced to an overtravel of the actuation travel provided when the parking lock is disengaged. In an alternative, less relevant embodiment, the parking lock can be disengaged at high system pressure and engaged at the zero position at minimum system pressure. In this case, an emergency release state is detected by the slave cylinder piston being displaced by the emergency release device to negative actuation travels beyond the zero position by a predetermined overtravel.

[0014] In order to take into account, for example, random or system-related displacements of the slave cylinder piston and thus to avoid an interpretation as an emergency release state when the vehicle is stationary or - if desired or necessary - while driving, the emergency release state can be made plausible by only recognizing an emergency release state if the overtravel remains set over a predetermined time interval.

[0015] For example, the actuation path can be detected at least shortly before or after the vehicle is put into operation, wherein by means of a path sensor, path points of the slave cylinder piston or of the actuating member displaced by it along the actuation path are continuously detected at predetermined time intervals, wherein an emergency release state is detected when the overtravel is detected over a predetermined number of time intervals, in particular at three or more time intervals.

[0016] By detecting the emergency release state, it can be determined that the parking lock is inoperative, so that an actuator that might shut off in this state of a non-actuable parking lock due to an error message can continue to operate at least by means of an emergency release and supply the hydraulic components. For example, hydraulic components such as a hydraulically actuated clutch, such as a friction clutch, shift clutch, or the like, or components requiring cooling and / or lubrication, such as this clutch, and / or the like, can continue to be supplied.

[0017] The proposed hydraulic system contains a hydraulic actuator with an electrically operated pump, for example a reversing pump, which supplies the parking lock and, if applicable, a clutch with the appropriate system pressure in one direction of rotation via a pressure line by means of a valve plate or the like with valves, check valves and, if applicable, other hydraulic components, and lubricates or cools hydraulic components in the other direction of rotation.

[0018] The hydraulic system includes an actuating mechanism with a slave cylinder having a slave cylinder piston. A movable part of the actuating mechanism—the actuating member—is displaced by the slave cylinder piston along a linear actuation path, and this displacement is detected by a displacement sensor. A control unit with implemented software having at least one routine for actuating a parking lock controls the actuator and detects displacement signals from the displacement sensor. The actuating mechanism includes a mechanically actuated emergency release device. At least one routine, such as a subroutine of the software, for controlling the actuator is implemented in the control unit to carry out the proposed method.

[0019] The invention is based on the Fig. 1 to 3 are explained in more detail. These show: Fig. 1 a hydraulic system for operating a parking lock, Fig. 2 a slave cylinder with various settings for determining an emergency release state and Fig. 3 a diagram illustrating the functional relationship of determining an emergency release state when detecting travel signals over time.

[0020] The Fig. Figure 1 shows a schematic representation of the hydraulic system 1 for implementing the proposed method. The hydraulic system 1 contains the hydraulic circuit 2 with the actuator 3, which here consists of the pump 4 and the electric motor 5 driving it. In the illustrated embodiment, the pump 4 pumps fluid such as a pressure medium, hydraulic medium, for example, oil, from the unpressurized tank 6 to the branch 7.

[0021] Valve 8, for example a switching valve controlled by a control unit 29, is arranged downstream of branch 7 in the fluid flow. Valve 8 is electromagnetically controlled and transmits the system pressure generated by pump 4 via pressure line 9 to slave cylinder 10 of parking lock 11 or slave cylinder 12 of clutch 13.

[0022] The only indicated hydraulic components 14, 15, which, for example, provide cooling and lubrication for the clutch 13 and the like, are supplied with pressure medium via the reverse direction of rotation of the pump 4.

[0023] The slave cylinder 10 is part of the actuating mechanism 16, wherein the slave cylinder piston 17, by means of its piston rod 18, displaces the actuating member 19 linearly along the actuating travel s. The actuating travel s is detected by the travel sensor 20. Depending on its linear displacement, the actuating member 19 raises and lowers the parking claw 21 into the parking lock gear 22, for example by means of an involute curve (not shown). The parking lock gear 22 is connected in a rotationally fixed manner to at least one wheel of a vehicle with this hydraulic system 1. In the illustrated zero position of the slave cylinder piston 17, the parking claw 21 is sunk into the parking lock gear 22, i.e., the parking lock 11 is engaged.When system pressure is applied to the slave cylinder 10 by means of appropriate wiring of the valve 8, the slave cylinder piston 17 is linearly displaced, the actuating member 19 lifts the parking claw 21, which can be rotated to a limited extent about a rotational axis, from the parking lock gear 22, and the parking lock 11 is disengaged. In order to keep the disengaged or opened parking lock 11 open without continuously applying system pressure, the locking pin 23 engages the slave cylinder piston 17 or another linearly displaced component of the actuating mechanism 16 and, when the parking lock 11 is desired to be actuated, is pulled out of the slave cylinder piston 17 by the lifting magnet 24. The hydraulic system 1 has the mechanical emergency release device 25. The emergency release device 25 is activated manually, for example, when the engaged parking lock 11 can no longer be released.For this purpose, a locking mechanism is released, and the actuating member 19, including the slave cylinder piston 17—here supported by the compression spring 26—is pulled into a maximum position of the slave cylinder piston 17. For example, the solenoid valve can be actuated to set an emergency release position that can be shifted beyond the normal operating state of the disengaged parking lock 11 with an overtravel of the slave cylinder piston 17.

[0024] The system pressure is adjusted in the pressure line 9 of the parking lock and in the pressure line 27 of the clutch 13 by connecting the valve 8 and reduced by means of the valve 28. The control of the system pressure by means of a connection of the actuator 3 and the valves 8, 28 as well as the energization of the lifting magnet 24 and the acquisition of measurement signals from the displacement sensor 20 takes place in the control unit 29 of the actuator 3, which also contains the power electronics for controlling the electric motor 5, or optionally in the higher-level control unit 30, which is in signal communication with the control unit 29 via the data connection 31, for example CAN.

[0025] When the emergency release device 25 is activated, a mismatch may arise between the system pressure and the position of the slave cylinder piston 17. To prevent or misinterpret a related error message, the proposed method avoids a total shutdown of the actuator 3 due to this error message. Instead, the actuator 3 and, if applicable, the valve 8 are operated in an emergency mode in which at least the hydraulic components 14, 15 and, if applicable, the clutch 13 are supplied by the actuator 3.

[0026] In order to detect the emergency release state set when the emergency release device 25 is activated, measurement signals from the travel sensor 20 are continuously recorded and evaluated by one or both control units 29, 30. If a significant overtravel of the slave cylinder piston 17 is detected at the emergency release position, the actuator 3 is switched to emergency mode, and any error message that may occur is ignored. Alternatively, if an error message occurs, the position of the slave cylinder piston 17 can be checked based on the recorded measurement signals from the travel sensor 20. If an overtravel of the slave cylinder piston is detected, the error message is suppressed and the actuator 3 is switched to emergency mode.

[0027] The Fig. 2 shows with reference to the Fig. 1 shows the slave cylinder 10 for actuating the parking lock 11 in the partial views a), b), c), and d) in various states of actuation of the parking lock 11 with corresponding displacement of the slave cylinder piston 17 along the actuation path s in a schematic representation. The sensor 32 is arranged on the slave cylinder piston 17, the position of which is detected by the travel sensor 20.

[0028] In the partial illustration a), the slave cylinder piston 17 is in the zero position NP, the parking lock 11 is engaged as closed.

[0029] In partial illustration b), the slave cylinder piston 17 is in an intermediate position ZP between the zero position NP and the open position OP during an actuation process of the parking lock 11.

[0030] In the partial illustration c), the slave cylinder piston 17 is in the open position OP of the open as designed state of the parking lock 11. If necessary, the locking pin 23 is engaged in the slave cylinder piston 17.

[0031] In partial illustration d), the slave cylinder piston 17 is mechanically displaced by the overtravel s(NEP) to the emergency release position NEP by means of the emergency release device 25. The emergency release position NEP is detected by the travel sensor and recorded as such in the control unit 29, 30. Instead of switching off, the actuator is put into emergency operation. During actuation of the parking lock 11, the position of the slave cylinder piston 17 is not regulated. This means that the slave cylinder piston 17 can reach the emergency release position NEP, at least briefly, while the parking lock 11 is being disengaged. A significant distinction must therefore be made between a brief overtravel of the open position OP and a deliberately set emergency release position NEP.

[0032] The Fig. 3 shows with reference to the Fig. 1 and Fig.2 shows diagram 33 with various parameters for evaluating an actuation of the parking lock 11 over time t. Partial diagram I shows the various positions P of the slave cylinder piston 17 with the zero position NP when the parking lock 11 is closed or engaged, with the open position OP when the parking lock 11 is disengaged or open, and with the parking lock in the emergency release position NEP.

[0033] Partial diagram II shows the actuation travel s detected by the travel sensor 20 over time t. Time intervals Δt(s) are recorded, for example, at the level of one or more interrupts, with a trend of the actuation travel s as CONSTANT, GREATER, SMALLER within the time interval Δt(s). A travel position is considered to be set as plausible and significant if the number of time intervals Δt(s) exceeding the corresponding position is greater than or equal to three. The trend of the time intervals Δt(s) can be evaluated for a faster evaluation of the position P.

[0034] In the period Δt1 between t=0 and time t1, the parking lock 11 is considered to be significantly engaged due to several time intervals Δt(s) with a CONSTANT tendency at the path point s(NP) for the zero position NP. In the period Δt2 between times t2, t3, the parking lock 11 is considered to be significantly disengaged because at least three time intervals Δt(s) with a CONSTANT tendency at the path point s(OP) for the open position OP follow one another. In the period Δt3 between times t3, t4, the actuation travel s increases compared to the path point s(OP) and exceeds the path point s(NEP) for the emergency release position NEP by three time intervals Δt(s), so that the error threshold F is activated in sub-diagram III. However, a specified path tolerance Δs(F) is not exceeded and the following time interval Δt(s) shows the tendency SMALLER, so that the error threshold F in sub-diagram III is reset again.In the period Δt4 between times t6 and t7, the actuating travel s increases over more than three time intervals Δt(s) with a CONSTANT tendency above the travel point s(NEP) of the emergency release position NEP, so that at time t7, the error threshold F is activated and actuator 3 is switched to emergency operation. The error threshold F is deactivated again at time t8 because the actuating travel s falls below the travel point s(NEP) of the emergency release position NEP.

[0035] In a software architecture where an error is always set when there is a discrepancy between system pressure and actuation travel s, the procedure can be executed as follows: The error threshold F is activated when the currently detected actuation travel s is greater than the path point s(OP) for the open parking lock 11 and the current state of the time interval Δt(s) at this actuation travel s is CONSTANT, and when the number of consecutive time intervals Δt(s) is less than three. In this case, the error threshold F activated at time t4 is not recognized as an emergency release state by one or both control units 29, 30.

[0036] However, as soon as the actuation travel s is greater than or equal to the travel point s(NEP), as at time t7, and the number of time intervals Δt(s) is three or greater, the error threshold F is detected as an emergency release state. This may also mean that in this case, no error threshold F is set at all, and the emergency release state is immediately detected. List of reference symbols 1 hydraulic system 2 hydraulic circuit 3 Actuator 4 Pump 5 Electric motor 6 tanks 7 Branching 8 valve 9 Pressure line 10 slave cylinders 11 Parking lock 12 slave cylinders 13 Clutch 14 hydraulic components 15 hydraulic components 16 Operating mechanism 17 Slave cylinder pistons 18 Piston rod 19 Actuator 20 displacement sensor 21 parking clamp 22 Parking lock gear 23 Locking pin 24 lifting magnet 25 Emergency release device 26 compression spring 27 Pressure line 28 Valve 29 Control unit 30 Control unit 31 Data connection 32 donors 33 Diagram F error threshold NEP emergency release position NP zero position OP open position P Position ZP intermediate position s actuation path s(NEP) waypoint s(NP) waypoint s(OP) Waypoint t time t1 time point t2 time point t3 time point t4 time point t5 time point t6 time point t7 time t8 time I Partial diagram II Partial diagram III Partial diagram Δ's crossing Δs(F) travel tolerance Δt1 period Δt2 period Δt3 period Δt4 period Δt(s) time interval

Claims

[1] Method for controlling a hydraulic system (1) of a vehicle with a hydraulic actuator (3) for supplying hydraulic components (14, 15) and actuating a parking lock (11) by means of a pressure medium actuated by the actuator (3) to an adjustable system pressure, wherein an actuating mechanism (16) by means of a slave cylinder (10) with a slave cylinder piston (17) sets an engaged or disengaged state of the parking lock (11) depending on the system pressure along a detected actuating path (s), and a mechanically actuated emergency release device (25) by means of which the disengaged state of the parking lock (11) can be set, characterized by that by means of the method, an emergency release state is determined when the parking lock (11) is in the designed state set by means of the emergency release device (25) and the actuator (3) continues to operate in an emergency mode. [2] Method according to claim 1, characterized bythat the emergency release state is detected based on the actuation travel (s). [3] Method according to claim 1 or 2, characterized by that the emergency release state is determined on the basis of an overtravel (Δs) of the actuating element which exceeds a predetermined actuating travel (s) when the parking lock (11) is disengaged. [4] Method according to one of claims 1 to 3, characterized by that when the parking lock (11) is engaged, the slave cylinder piston (17) is arranged in the region of a zero position (NP) at minimum system pressure and is actuated under high system pressure when the parking lock is disengaged, wherein, in order to set the emergency release state, the slave cylinder piston (17) is mechanically displaced from an open position (OP) of the disengaged parking lock (11) by means of an overtravel (Δs) into an emergency release position (NEP). [5] Method according to claim 3 or 4, characterized bythat the emergency release state is made plausible by only detecting an emergency release state if the overtravel (Δs) remains set over a specified period of time (Δt4). [6] Method according to claim 5, characterized by that the actuating travel (s) is detected at least after the vehicle has been put into operation, wherein travel measuring points are continuously detected at predetermined time intervals (Δt(s)) by means of a travel sensor (20) and an emergency release state is detected when the overtravel (Δs) is detected over a predetermined number of time intervals (Δt(s)), in particular greater than or equal to three time intervals (Δt(s)). [7] Method according to one of claims 1 to 6, characterized by that during emergency operation the actuator (3) supplies the hydraulic components (14, 15) with pressure medium. [8] Hydraulic system (1) with a hydraulic actuator (3), an actuating mechanism (16) with a slave cylinder (10) with a slave cylinder piston (17) and a pressure line (9) arranged between the actuator (3) and the slave cylinder (10) and transmitting a system pressure adjustable by the actuator (3), a displacement sensor (20) detecting an actuating path (s) of the slave cylinder piston (17) and at least one control unit (29, 30) with implemented software with at least one routine for actuating a parking lock (11) by means of a control of the actuator (3), detecting actuating paths (s) of the displacement sensor (20), characterized by that the actuating mechanism (16) contains a mechanically actuable emergency release device (25) and in the at least one routine the method according to claims 1 to 5 is implemented.

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