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

Abstract

The invention relates to a method for controlling a hydraulic system (1), and to a hydraulic system (1) of a vehicle, comprising a hydraulic actuator (3) for supplying hydraulic components (14, 15) and actuating a parking lock (11) by means of a pressure medium which is applied to an adjustable system pressure by means of the actuator (3), and a mechanically actuatable emergency unlocking device (25), according to the invention, the actuating mechanism (16) sets the engaged or disengaged state of the parking lock (11) as a function of the system pressure by means of a slave cylinder (10) having a slave cylinder piston (17) along the detected actuating stroke (s), the disengaged state of the parking lock (11) being settable by means of an emergency unlocking device. In order to avoid a complete failure of the hydraulic system (1) when the emergency unlocking device (25) is actuated, an emergency unlocking state is determined for a set release state of the parking lock (11) by means of the emergency unlocking device (25) and the actuator (3) continues to be operated during emergency operation.

Description

Technical Field

[0001] The present invention relates to a method and a hydraulic system for controlling a parking lock by means of a hydraulic actuator and a control mechanism. The actuator adjusts the system pressure in a controlled manner, and the control mechanism is moved by the actuator along a detected control stroke by a slave cylinder by means of the system pressure and sets the engaged or disengaged state of the parking lock. Background Art

[0002] For example, this type of parking lock and its control method are known from document DE 10 2021 117 215 A1. Here, an adjustable system pressure is generated by means of a hydraulic actuator, which acts on the slave cylinder and engages or disengages the parking lock by means of the control mechanism depending on the switching state.

[0003] A method for recognizing an emergency unlocking of a parking lock actuated by means of an electric actuator is known from document DE 10 2019 118 485 A1, in such a way that during the disengagement of the parking lock, different characteristics of the current for operating the actuator between the emergency unlocking and non-emergency unlocking states of the parking lock are evaluated. Summary of the Invention

[0004] The object of the present invention is to improve the method for controlling this type of parking lock and the hydraulic system for actuating the parking lock. The method of the present invention in particular provides a method and a device for recognizing an emergency unlocking device of a parking lock and a method for the continued operation of the actuator during this mode.

[0005] This object is achieved by the subject matters of claims 1 and 8. The dependent claims of claim 1 provide advantageous embodiments of the subject matter of claim 1.

[0006] The proposed method is for controlling a parking lock by means of a hydraulic actuator. The hydraulic actuator can for example be configured as a pump, which pumps a pressure medium into a pressure line and thus generates a system pressure. The pump can be driven by an electric motor, for example a non-contact commutation motor, the rotational speed of which is controlled and drives the pump, whereby the pump power of the pump is adjusted by means of the rotational speed of the electric motor.

[0007] The actuating mechanism is connected to the slave cylinder via a pressure line. The slave cylinder piston of the slave cylinder moves along the actuating stroke according to the system pressure and thereby drives the actuating element. The actuating element is, for example, a pawl or a ratchet for actuating a parking lock, such that the actuating element engages or disengages from a drive element directly connected to the drive wheel or, for example, connected via a transmission. Here, two states of the parking lock occur, namely an engaged state in which the parking lock is effectively activated and a disengaged state in which the parking lock is inoperative and the vehicle moves in a normal driving state. Depending on the design of the parking lock and its actuation, the parking lock can be engaged or disengaged when the system pressure is applied. According to the embodiments of the parking lock described in detail below, the parking lock is engaged when the system pressure is applied, i.e., the parking lock is engaged in the absence of sufficient system pressure and is in the zero position. In order to keep the parking lock in the disengaged state when not actuated and when the system pressure is applied, a locking device can be provided, which holds the actuating element or the piston rod in a form-fitting manner at least in the disengaged state of the parking lock. In addition, the locking device can be held in the engaged state in a form-fitting manner.

[0008] Detect the movement of the actuating mechanism generated by the system pressure, such as the movement of the slave cylinder piston. For this purpose, for example, a displacement sensor is arranged at the actuating mechanism or at the piston rod of the slave cylinder piston. For example, the displacement sensor can be fixedly arranged relative to the housing, and the displacement sensor detects the corresponding displacement markings of the moving component, the piston rod or the actuating element, for example, detects the displacement increment and converts it into a displacement signal.

[0009] In order to deactivate the parking lock, for example, in the event of a parking lock failure or during vehicle towing, a mechanical emergency unlocking device is provided. The emergency unlocking device can, for example, move the actuating element or the slave cylinder piston, for example, along its piston rod, along the actuating stroke and fix it in the disengaged state of the parking lock. For example, the emergency unlocking device can include a manually operable locking part, directly or indirectly acting on the slave cylinder piston, for example, a preloaded locking part, such as a screw connection, which, independently of the applied system pressure, enables the slave cylinder piston, which may be preloaded at the zero position, to move, for example, by spring loading, to a position with a maximum offset relative to its zero position when the parking lock is engaged or actuated after the locking part is released.

[0010] In the case where the parking lock is set to the disengaged state by the emergency unlocking device, the emergency unlocking state is determined by means of the method. Due to the emergency unlocking state detected or determined by the control unit with software for controlling the hydraulic system, the actuator can continue to operate in the emergency mode.

[0011] For determining the emergency unlocking state, for example, detected driving states of the vehicle (e.g. towing of the vehicle, error messages, etc.) and operating travel can be used. For example, the driving state of the vehicle can be used to prevent the emergency unlocking state from being set when the parking lock is normally disengaged during normal driving of the vehicle, by the emergency unlocking state being determined only when the vehicle is stationary, and if necessary regularly when the vehicle is stationary or is stationary again.

[0012] For this purpose, no additional components or sensors are required for checking the state of the emergency unlocking device, so that the emergency unlocking state can be determined cost-neutral, for example as a subroutine of a program for controlling the parking lock in a control unit.

[0013] In order to clearly distinguish between an actuated emergency unlocking state, such as a disengaged parking lock, and a normal operating state, it can alternatively or additionally be provided that the emergency unlocking state is determined based on an overtravel of the actuating element or the slave cylinder piston beyond a predefined actuating travel when the parking lock is disengaged. This means that the slave cylinder piston is mechanically moved by the emergency unlocking device beyond its position which is usually set by the system pressure, and this overtravel along the actuating travel is detected by the travel sensor and interpreted by the control unit as an emergency unlocking state.

[0014] For example, when the parking lock is engaged, the slave cylinder piston is arranged in the region of the zero position at minimum system pressure, and when the parking lock is disengaged, the slave cylinder piston is actuated at high pressure, wherein, in order to set the emergency unlocking state, the slave cylinder piston is mechanically moved to an overtravel of the actuation travel provided in the disengaged state of the parking lock. In an alternative embodiment, the parking lock can be disengaged at high system pressure and engaged in the zero position at minimum system pressure. In this case, the emergency unlocking state is recognized in that the slave cylinder piston is moved by the emergency unlocking device with a negative actuation travel to an overtravel preset beyond the zero position.

[0015] For example, in order to take into account accidental or system-induced movements of the slave cylinder piston and thereby avoid an interpretation as an emergency unlocking state when the vehicle is stationary or (if desired or necessary) while the vehicle is moving, the plausibility of the emergency unlocking state can be checked in such a way that an emergency unlocking state is only identified if the overtravel persists for more than a preset time interval.

[0016] For example, the operating stroke can be detected at least before or shortly after the vehicle starts to operate, wherein the stroke points of the slave cylinder piston or the operating element moved along the operating stroke by the displacement sensor are continuously detected at preset time intervals, wherein when an overtravel exceeding a preset number of time intervals, in particular three or more time intervals, is detected, an emergency unlocking state is identified.

[0017] By recognizing the emergency unlocking state, it is possible to recognize that the parking lock is not functioning. Therefore, the actuator that is closed due to an error message in a state where the parking lock cannot be operated continues to operate at least by means of an emergency release and can supply the hydraulic components. For example, it is also possible to continue supplying hydraulic components, hydraulically actuated clutches such as friction clutches, switching clutches, etc., components with cooling and / or lubrication requirements such as clutches, etc.

[0018] The proposed hydraulic system includes a hydraulic actuator with an electrically operated pump, such as a reversing pump. The pump supplies the corresponding system pressure to the parking lock and possibly the clutch via a pressure line in one rotational direction by means of a valve disk, etc., through a valve, a check valve, and possibly other hydraulic components, and lubricates or cools the hydraulic components in the other direction.

[0019] The hydraulic system includes an operating mechanism with a slave cylinder. The slave cylinder has a slave cylinder piston. Among them, the movable part (operating element) of the operating mechanism moves along a linear operating stroke by means of the slave cylinder piston, and this movement is detected by a displacement sensor.

[0020] The control unit with the implemented software controls the actuator and detects the displacement signal of the displacement sensor. The software has at least one program for operating the parking lock. The operating mechanism includes a mechanically operable emergency unlocking device. At least one program, such as a subroutine of the software for controlling the actuator to execute the proposed method, is implemented in the control unit. Description of the Drawings

[0021] According to the embodiment shown in Figures 1 to 3 The present invention is described in detail. The drawings show:

[0022] Figure 1 A hydraulic system for operating a parking lock is shown.

[0023] Figure 2 A slave cylinder with different settings for determining the emergency unlocking state is shown, and

[0024] Figure 3 A diagram showing the functional relationship for determining the emergency unlocking state when detecting the stroke signal over time is shown. Detailed Description of the Invention

[0025] Figure 1 A schematic diagram of a hydraulic system 1 for implementing the proposed method is shown. The hydraulic system 1 includes a hydraulic circuit 2 with an actuator 3. Here, the actuator is composed of a pump 4 and a motor 5 driving the pump 4. In the shown embodiment, a fluid such as a pressure medium, a hydraulic medium, for example, oil is conveyed from a non-pressure storage tank 6 to a branch 7 by means of the pump 4.

[0026] Downstream of the fluid flow in branch 7, there is a valve 8, such as a switching valve controlled by a control unit 29. The valve 8 is controlled electromagnetically and transmits the system pressure generated by the pump 4 via a pressure line 9 to the slave cylinder 10 of the parking lock 11 or the slave cylinder 12 of the clutch 13.

[0027] The only shown hydraulic components 14, 15 supply cooling and lubrication, for example, for the clutch 13, etc., and the only shown hydraulic components are supplied with pressure medium via the reverse rotation direction of the pump 4.

[0028] The slave cylinder 10 is part of an actuating mechanism 16, wherein the input cylinder piston 17 moves the actuating element 19 linearly along the actuating stroke s by means of its piston rod 18. The actuating stroke s is detected by a displacement sensor 20. The actuating element 19 raises or lowers the pawl 21 into the parking lock wheel 22, for example, by means of an involute curve (not shown) according to its linear movement. The parking lock wheel is non-rotatably connected to at least one wheel of the vehicle having this hydraulic system 1. In this case, in the shown zero position of the slave cylinder piston 17, the pawl 21 drops into the parking lock wheel 22, i.e., the parking lock 11 is engaged. When the slave cylinder 10 is applied with system pressure by correspondingly actuating the valve 8, the slave cylinder piston 17 moves linearly, and the actuating element 19 lifts the pawl 21, which can be torsionally restricted about the axis of rotation, out of the parking lock wheel 22, and the parking lock 11 is disengaged. In order to keep the disengaged, for example, open parking lock 11 open without continuously applying system pressure, the locking pin 23 engages in the slave cylinder piston 17 or another linearly moving component of the actuating mechanism 16, and the locking pin is pulled out of the slave cylinder piston 17 by a solenoid 24 when the parking lock 11 is to be actuated as desired.

[0029] The hydraulic system 1 has a mechanical emergency unlocking device 25. When the engaged parking lock 11 can no longer be released, the emergency unlocking device is activated, for example, manually. For this purpose, the locking mechanism is released, and hereby, the actuating element 19 together with the slave cylinder piston 17 is pulled into the maximum position of the slave cylinder piston 17 by the support of a compression spring 26. In this case, for example, the solenoid valve can be actuated to set an emergency unlocking position, which can move beyond the normal operating state of the disengaged parking lock 11 with the overtravel of the slave cylinder piston 17.

[0030] In the pressure line 9 of the parking lock and in the pressure line 27 of the clutch 13, the system pressure is set by the on - valve 8 and the system pressure is reduced by means of the valve 28. The control of the system pressure by means of the on - actuator 3 and the valves 8, 28, the energization of the solenoid 24 and the detection of the measurement signal by the displacement sensor 20 are carried out in the control unit 29 of the actuator 3. The control unit 29 also includes the power electronics for controlling the electric motor 5 or is alternatively located in a superior control unit 30. The superior control unit is signal - connected to the control unit 20 by means of a data connection element 31, such as CAN.

[0031] In the case of activation of the emergency unlocking device 25, there may be a mismatch between the system pressure and the position of the slave - cylinder piston 17. In order to prevent or misinterpret error messages related thereto, in the proposed method, a complete shutdown of the actuator 3 based on this error message is avoided. Instead, the actuator 3 and possibly the valve 8 operate in an emergency mode, in which the actuator 3 supplies at least the hydraulic components 14, 15 and possibly the clutch 13.

[0032] In order to recognize the emergency unlocking state set in the case of activation of the emergency unlocking device 25, the measurement signal of the displacement sensor 20 is continuously detected and evaluated by one or two control units 29, 30. If a significant over - travel at the emergency unlocking position of the slave - cylinder piston 17 is recognized, the actuator 3 is switched to the emergency mode and possible error messages are ignored. Alternatively, when an error message occurs, the position of the slave - cylinder piston 17 can be checked based on the detected measurement signal of the displacement sensor 20. In this case, when an over - travel of the slave - cylinder piston is recognized, the transmission of the error message is blocked and the actuator 3 is switched to the emergency mode.

[0033] Figure 2 Reference Figure 1 A schematic view of the slave cylinder 10 is shown, which is used to operate the parking lock 11 as the slave - cylinder piston 17 moves along the operating stroke s in different operating states of the parking lock 11 in the sub - schematic views a), b), c), d). Here, transmitters 32 are respectively arranged at the slave - cylinder piston 17, and the position of the transmitter is detected by the displacement sensor 20.

[0034] In sub - schematic view a), the slave - cylinder piston 17 is located at the zero position NP and the parking lock 11 is engaged, for example, closed.

[0035] In sub - schematic view b), during the operation of the parking lock 11, the slave - cylinder piston 17 is located at the intermediate position ZP between the zero position NP and the open position OP.

[0036] In sub - schematic c), the slave cylinder piston 17 is in the open position OP of the open, for example disengaged, state of the parking lock 11. If necessary, the locking pin 23 engages in the slave cylinder piston 17.

[0037] In sub - schematic d), the slave cylinder piston 17 is mechanically moved by an emergency unlocking device 25 by an over - travel S (NEP) to the emergency unlocking position NEP. The emergency unlocking position NEP is detected by a displacement sensor and is also detected in the control units 29, 30. The actuator enters the emergency mode instead of shutting down. During the actuation of the parking lock 11, the position of the slave cylinder piston 17 is not adjusted. This means that the slave cylinder piston 17 can at least temporarily reach the emergency unlocking position NEP during the disengagement of the parking lock 11. Thus, a clear distinction is made between temporarily passing the open position OP and the deliberately set emergency unlocking position NEP.

[0038] Figure 3 Reference Figure 1 and Figure 2 shows a diagram 33 with different parameters for evaluating the actuation of the parking lock 11 over time t.

[0039] Sub - diagram I shows different positions P of the slave cylinder piston 17, including: the zero position NP when the parking lock 11 is closed, for example engaged, the open position OP when the parking lock 11 is disengaged, for example open, and the emergency unlocking position NEP when the parking lock is emergency - unlocked.

[0040] Sub - diagram II shows the actuation stroke s detected by the displacement sensor 20 over time t. For example, time intervals Δt(s) are detected at one or more degrees of interruption, where the trend of the actuation stroke s is constant, greater, or smaller within the time interval Δt(s). If the number of time intervals Δt(s) exceeding the corresponding position is greater than or equal to three, the stroke position is considered reasonable and significant. Here, the trend of the time interval Δt(s) can be evaluated to more quickly evaluate the position P.

[0041] In the time period Δt1 between t = 0 and time point t1, the parking lock 11 is clearly recognized as engaged because a plurality of time intervals Δt(s) have a constant trend at the travel point S(NP) of the zero position NP. In the time period Δt2 between time points t2 and t3, the parking lock 11 is clearly recognized as disengaged because at least three time intervals Δt(s) with a constant trend succeed in sequence at the travel point S(OP) of the open position OP. In the time period Δt3 between time points t3 and t4, the operating travel s increases relative to the travel point S(OP) and exceeds the travel point S(NEP) of the emergency unlocking position NEP over three time intervals Δt(s), so the error threshold F is activated in sub-chart III. However, the preset travel error Δs(F) is not exceeded and the subsequent time intervals Δt(s) show a smaller trend, so the error threshold F is reset in sub-chart III. In the time period Δt4 between time points t6 and t7, the operating travel s increases and exceeds the travel point S(NEP) of the emergency unlocking position NEP over more than three time intervals Δt(s) with a constant trend, so the error threshold F is activated at time point t7 and the actuator 3 switches to the emergency mode. The error threshold F is deactivated again at time point t8 because the operating travel s drops below the travel point S(NEP) of the emergency unlocking position NEP.

[0042] In a software architecture where errors are set in cases where there is usually a discrepancy between the system pressure and the operating travel s, the method can be implemented as follows:

[0043] When the currently detected operating travel s is greater than the travel point S(OP) of the parking lock 11 for opening and the current state of the time interval Δt(s) on this operating travel s is constant, and when the number of successive time intervals Δt(s) is less than three, the error threshold F is activated. In this case, one or two control units 29, 30 do not recognize the error threshold F activated at time point t4 as an emergency unlocking state.

[0044] However, as at time point t7, once the operating travel s is greater than or equal to the travel point S(NEP) and the number of time intervals Δt(s) is three or more, the error threshold F is recognized as an emergency unlocking state. This can also mean that in this case, the error threshold F is not set at all and the emergency unlocking state is recognized immediately.

[0045] List of reference numerals

[0046] 1 Hydraulic system

[0047] 2 Hydraulic circuit

[0048] 3 Actuator

[0049] 4 Pump

[0050] 5 Electric motor

[0051] 6 Storage tank

[0052] 7 Branch

[0053] 8 Valve

[0054] 9 Pressure pipeline

[0055] 10 Slave cylinder

[0056] 11 Parking lock

[0057] 12 Slave cylinder

[0058] 13 Clutch

[0059] 14 Hydraulic components

[0060] 15 Hydraulic components

[0061] 16 Operating mechanism

[0062] 17 Slave cylinder piston

[0063] 18 Piston rod

[0064] 19 Operating element

[0065] 20 Displacement sensor

[0066] 21 Parking pawl

[0067] 22 Parking lock wheel

[0068] 23 Locking pin

[0069] 24 Solenoid

[0070] 25 Emergency unlocking device

[0071] 26 Compression spring

[0072] 27 Pressure pipeline

[0073] 28 Valve

[0074] 29 Control unit

[0075] 30 Control unit

[0076] 31 Data connection

[0077] 32 Transmitter

[0078] 33 Chart

[0079] F Error threshold

[0080] NEP Emergency Unlock Position

[0081] NP Zero Position

[0082] OP Open Position

[0083] P Position

[0084] ZP Intermediate Position

[0085] s Manipulation Stroke

[0086] s(NEP) Stroke Point

[0087] s(NP) Stroke Point

[0088] s(OP) Stroke Point

[0089] t Time

[0090] t1 Time Point

[0091] t2 Time Point

[0092] t3 Time Point

[0093] t4 Time Point

[0094] t5 Time Point

[0095] t6 Time Point

[0096] t7 Time Point

[0097] t8 Time Point

[0098] I Sub - Chart

[0099] II Sub - Chart

[0100] III Sub - Chart

[0101] Δs Over - travel

[0102] Δs(F) Stroke Error

[0103] Δt1 Time Period

[0104] Δt2 Time Period

[0105] Δt3 Time Period

[0106] Δt4 Time Period

[0107] Δt(s) Time Interval

Claims

1. A method for controlling a hydraulic system (1) of a vehicle, the hydraulic system having a hydraulic actuator (3) and a mechanically actuable emergency release device (25), the actuator being used to supply hydraulic components (14, 15) and to actuate a parking lock (11) by means of a pressure medium, the pressure medium being applied by the actuator (3) to an adjustable system pressure, wherein, The actuating mechanism (16) sets the engaged or disengaged state of the parking lock (11) along the detected actuating stroke (s) according to the system pressure by means of a slave cylinder (10) having a slave cylinder piston (17). The disengaged state of the parking lock (11) can be set by means of the emergency unlocking device. It is characterized in that, in the disengaged state of the parking lock (11) set by the emergency unlocking device (25), the emergency unlocking state is determined by means of the method, and the actuator (3) continues to operate in the emergency mode.

2. The method according to claim 1, characterized in that The emergency unlocking state is identified according to the actuating stroke (s).

3. The method according to claim 1 or 2, characterized in that, The emergency unlocking state is determined according to the overtravel (Δs) of the actuating element that exceeds a preset actuating stroke (s) when the parking lock (11) is disengaged.

4. The method according to any one of claims 1 to 3, characterized in that, When the parking lock (11) is engaged, the slave cylinder piston (17) is arranged in the region of the zero position (NP) at the minimum system pressure, and when the parking lock is disengaged, the slave cylinder piston is actuated at a high pressure. For setting the emergency unlocking state, the slave cylinder piston (17) mechanically moves from the open position (OP) of the disengaged parking lock (11) by the overtravel (Δs) to the emergency unlocking position (NEP).

5. The method according to claim 3 or 4, characterized in that The credibility of the emergency unlocking state is checked in such a way that the emergency unlocking state is only recognized if the overtravel (Δs) remains above a preset time interval (Δt4).

6. The method according to claim 5, wherein The actuating stroke (s) is detected at least after the vehicle starts to run. The stroke measuring points are continuously detected by means of a displacement sensor (20) at a preset time interval (Δt(s)). When an overtravel (Δs) that exceeds a preset number of time intervals (Δt(s)), in particular greater than or equal to three time intervals (Δt(s)), is detected, it is recognized as the emergency unlocking state.

7. The method according to any one of claims 1 to 6, characterized in that In the emergency mode, the actuator (3) supplies the hydraulic components (14, 15) with pressure medium.

8. A hydraulic system (1), the hydraulic system having: A hydraulic actuator (3); An actuating mechanism (16) having a slave cylinder (10) including a slave cylinder piston (17) and a pressure line (9) arranged between the actuator (3) and the slave cylinder (10) for transmitting the system pressure that can be set by the actuator (3); A displacement sensor (20) that detects the actuating stroke (s) of the slave cylinder piston (17); and At least one control unit (29, 30) having implemented software that has at least one program for manipulating the parking lock (11) by controlling the actuator (3) and detecting the actuating stroke (s) of the displacement sensor (20), It is characterized in that The actuating mechanism (16) includes a mechanically actuable emergency unlocking device (25) and implements the method according to any one of claims 1 to 5 in the at least one program.

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