Hydraulic system for actuating a parking lock cylinder of a parking lock

Abstract

Hydraulic system (1) for actuating a parking lock cylinder (2) of a parking lock with two valve assemblies (PSV1, PSV2) to which a working pressure (p_sys) can be applied, which, depending on a pilot pressure (p_VS3) adjustable in the area of ​​an electro-hydraulic actuator (3), can be directed via the valve assemblies (PSV1, PSV2) towards the parking lock cylinder (2), wherein a spring force of a spring assembly (6, 7) acts on each of the valve spools (4, 5) of the valve assemblies (PSV1, PSV2), which actuates the valve assemblies (PSV1, PSV2) in the direction of the first operating states, characterized in that - in the first operating states of the valve devices (PSV1, PSV2) a connection of the parking lock cylinder (2) to a section (8) carrying the working pressure (p_sys) in the area of ​​the valve devices (PSV1, PSV2) is separated and - the pilot pressure (p_VS3) in the area of ​​a first control surface (9) of the valve slide (4) of the first valve assembly (PSV1) can be applied in a manner that counteracts the spring force, - while the pilot pressure (p_VS3) in the area of ​​a first control surface (10) of the valve spool (5) of the second valve assembly (PSV2) can be applied in a manner that counteracts the spring force of the spring assembly (7) and a pressure signal (p_DS) that can be applied in the area of ​​a second control surface (11), - wherein a connection provided between the first valve assembly (PSV1) and the parking lock cylinder (2) is separated in the first operating state of the first valve assembly (PSV1) in the area of ​​the first valve assembly (PSV1) from the working pressure (p_sys) area (8). - and the parking lock cylinder (2) in the first operating state of the second valve assembly (PSV2) is coupled in the area of ​​the second valve assembly (PSV2) with a pressureless area (12), - wherein the working pressure (p_sys) in a second operating state of the first valve device (PSV1) can be applied to the second valve device (PSV2) via the first valve device (PSV1). - and the parking lock cylinder (2) is separated from the pressureless area (12) in a second operating state of the second valve device (PSV1) and the working pressure (p_sys) can be directed towards the parking lock cylinder (2) when the first valve device (PSV1) is simultaneously present in the second operating state, - and wherein the working pressure (p_sys) in the second operating state of the first valve device (PSV1) can be applied to its valve slide (4) in the area of ​​a third control surface (13) counteracting the spring force of the spring device (6) and, when the second valve device (PSV2) is simultaneously present in the second operating state, can be applied to its valve slide (7) in the area of ​​a third control surface (14) counteracting the spring force of the spring device (7).

Description

[0001] The invention relates to a hydraulic system for actuating a parking lock cylinder of a parking lock according to the type defined in more detail in the preamble of claim 1.

[0002] From EP 2 469 129 A1, a device for actuating a parking lock of an automatic transmission of motor vehicles is known. The parking lock comprises a pawl interacting with a parking lock gear, which is actuated by a spring accumulator to engage the parking lock and can be actuated hydraulically against the preload force of the spring accumulator to disengage the parking lock by a hydraulic transmission control unit with corresponding control valves. The control valves are electrically actuated according to the operating parameters of the motor vehicle and a selector device. An electromagnetically actuated locking element additionally holds the pawl in the disengaged position in defined operating states of the motor vehicle when actuated. A purely hydraulically acting self-holding valve is integrated into the hydraulic transmission control unit, which opens when the parking lock actuation is pressurized.maintains the controlled system pressure when the parking lock is deployed.

[0003] Disadvantageously, the hydraulic transmission control system includes two actuators required exclusively for the parking lock system and, in particular, for controlling a follower valve. The follower valve is a self-holding valve, controlled via a shut-off valve and a pressure control valve for engaging and disengaging the parking lock. This results in a complex and costly design.

[0004] Furthermore, a hydraulic switching device for an automatic transmission is known from DE 10 2012 200 202 A1, in which, to activate a self-holding of a parking lock in the event of an entry into an emergency running mode, an actuating pressure of a switching element of the automatic transmission, which is switched on to represent an emergency gear, is to be applied in the area of ​​parking lock valves.

[0005] However, the proposed embodiments of the hydraulic switching device are not suitable for use in automatic transmissions, where none of the existing switching elements are subjected to actuation pressure during emergency operation, in order to implement the actuation of a parking lock to the proposed extent.

[0006] To enable the use of the known hydraulic shift device in automatic transmissions without an additional shift element during emergency operation, the hydraulic shift device must be extended with two separate additional actuators. This prevents both the unintended disengagement and unintended engagement of the parking lock. However, this latter extension of the hydraulic shift device with two additional actuators increases both the manufacturing costs and the installation space required for the shift device.

[0007] The present invention is based on the objective of providing a space-saving and cost-effective hydraulic system for actuating a parking lock cylinder of a parking lock, by means of which unintentional actuations of a parking lock are avoided even during an emergency running operation of an automatic transmission with minimal design effort.

[0008] According to the invention, this problem is solved with a hydraulic system having the features of claim 1.

[0009] The hydraulic system according to the invention for actuating a parking lock cylinder of an automatic transmission comprises two valve assemblies to which a working pressure can be applied. The working pressure, dependent on a pilot pressure adjustable in the area of ​​an electro-hydraulic actuator, can be directed via the valve assemblies towards the parking lock cylinder. A spring force from a spring assembly acts on each valve spool of the valve assemblies, actuating the valve assemblies in the direction of the first operating states.

[0010] According to the invention, the connection of the parking lock cylinder to a working pressure-carrying area is separated in the first operating states of the valve devices in the area of ​​the valve device, whereby both valve devices prevent the pressure supply to the parking lock cylinder in the initial state and thus both valve devices must be in the reversed state in order to enable actuation of the parking lock cylinder via the main pressure.

[0011] The pilot pressure can be applied in the area of ​​a first control surface of the valve spool of the first valve assembly, opposing the spring force, while the pilot pressure in the area of ​​a first control surface of the valve spool of the second valve assembly can be applied in the same way as the spring force of the spring assembly and opposing a pressure signal that can be applied in the area of ​​a second control surface. A connection provided between the first valve assembly and the parking lock cylinder is, in the first operating state of the first valve assembly, isolated from the working pressure area in the area of ​​the first valve assembly. Additionally, in the first operating state of the second valve assembly, the parking lock cylinder is coupled to a pressureless area in the area of ​​the second valve assembly.In a second operating state of the first valve assembly, the working pressure can be applied to the second valve assembly via the first valve assembly, and the parking lock cylinder is separated from the pressureless area in a second operating state of the second valve assembly. Furthermore, if the first valve assembly is also present in the second operating state, the working pressure can be directed towards the parking lock cylinder.

[0012] The hydraulic system according to the invention thus comprises a valve system by means of which both an unintentional deployment of the parking lock is prevented and, in the event of existing working pressure and the occurrence of a simple fault, a parking lock can be brought into its designed operating state.

[0013] Furthermore, in the hydraulic system according to the invention, the working pressure in the second operating state of the first valve device is applied to its valve spool in the area of ​​a third control surface, counteracting the spring force of the spring device, and, when the second valve device is simultaneously present in the second operating state, can be applied to its valve spool in the area of ​​a third control surface, counteracting the spring force of the spring device, thus providing a self-holding mechanism for the parking lock in a structurally simple way on the hydraulic system side, which holds the parking lock in the designed operating state in the event of an emergency running operation, without the need for pressure channels that are required for clutch or dog control in the area of ​​the automatic transmission.

[0014] The two valve devices of the hydraulic system according to the invention are controlled by the electrohydraulic actuator, wherein the first valve device, to which the working pressure is applied, is transferred to its second operating state when pilot pressure is applied, while the second valve device is forcibly held in its first operating state by the pilot pressure.

[0015] Following the application of the pilot pressure to the first valve assembly, the first valve assembly is transferred from the working pressure to its second operating state and held, whereby the pilot pressure in the area of ​​the actuator can be switched off again.

[0016] Then the second valve assembly can be switched to its second operating state via a separate control signal or pressure signal, whereby the working pressure can be directed towards the parking lock cylinder and the parking lock can be switched to its designed operating state and is hydraulically stable.

[0017] When a request is made to engage the parking lock, the second valve assembly can be returned to its initial position or its first operating state by re-actuating the electro-hydraulic actuator and thereby applying the pilot pressure to the second valve assembly, whereby the parking lock cylinder is coupled to the pressureless area via the second valve assembly and vented.

[0018] The first valve assembly remains in its second operating state until the pressure supply is switched off or until the working pressure drops below a predefined pressure level, since only then can it be transferred into this state by the spring force of the spring assembly acting on the valve spool.

[0019] This means that actuating the electro-hydraulic actuator does not automatically lead to the deployment of the parking lock; instead, the electro-hydraulic actuator must first be actuated and then switched off again to deploy the parking lock.

[0020] In a structurally simple and easily operable further development of the hydraulic system according to the invention, an undesired deployment of the parking lock is avoided by the fact that the pressure applied to the third control surfaces in the first operating states of the valve devices corresponds to a pressure present in a substantially pressureless area.

[0021] If the pressure signal corresponds to a pressure intended for actuating a switching element of a transmission, the hydraulic system according to the invention can be operated with minimal effort and the requested actuation of the parking lock in the direction of the designed or in the direction of the engaged operating state can be implemented in a structurally simple manner.

[0022] In an alternative embodiment of the hydraulic system according to the invention, the pressure signal in the area of ​​an actuator is adjustable, making it possible to operate the parking lock with a high degree of freedom.

[0023] If the third control surfaces correspond to a surface area difference between mutually facing end faces of diameter ranges of the valve slides of the valve devices, the valve devices can each be designed with a small installation space requirement in the axial direction.

[0024] If the control surfaces of the valve spool of the second valve assembly and the spring force of the spring assembly are coordinated in such a way that the second valve assembly can be brought into its first operating state by the pilot pressure independently of the pressure signal and the working pressure, it is ensured that even in the event of a malfunction in the area of ​​the electro-hydraulic actuator, the parking lock does not unintentionally enter its designed operating state.

[0025] In contrast, an unwanted engagement of the parking lock can be avoided by ensuring that the control surfaces of the valve spool and the spring force of the spring assembly of the second valve assembly are coordinated in such a way that the second valve assembly can be maintained in its second operating state regardless of the pilot pressure above the working pressure, since then, despite an incorrect imprint of the second valve assembly by the electro-hydraulic actuator, the second valve assembly remains in its second operating state and the parking lock is kept in the designed operating state with minimal effort.

[0026] If the connection between the electro-hydraulic actuator and the valve assembly is operatively linked to a hydraulic delay element, a misactivation of the parking lock due to faulty control of the valve assembly by the electro-hydraulic actuator is delayed for a defined period in a structurally simple manner. Within this period, countermeasures to prevent misactivation of the parking lock can be initiated and implemented. This prevents the so-called ratcheting of the parking lock in the event of a misactivation while driving.

[0027] If a throttling device is provided downstream of the electrohydraulic actuator and upstream of the second valve assembly and the delay element, the flow rate between the actuator and at least the second valve assembly and the delay element is limited when the actuator is controlled accordingly. This allows the pressure downstream of the throttling device and upstream of the second valve assembly and the delay element to be limited in such a way that the period within which an actuator-side incorrect control of the parking lock can be avoided to the desired extent by initiating appropriate countermeasures can be implemented in a structurally simple manner to a defined extent, and a defined fault latency time can be provided to the desired extent.

[0028] In a structurally simple and cost-effective embodiment of the hydraulic system according to the invention, the delay element comprises a piston element which can be displaced in a cylinder between two end positions by means of the pilot pressure against a spring force of a spring device.

[0029] If the electrohydraulic actuator is designed as a solenoid valve which, in the unenergized operating state, is held by a spring device in an operating state in which the pilot pressure is essentially zero, while the pilot pressure in the energized operating state of the solenoid valve is equal to the working pressure applied to the solenoid valve, the hydraulic system according to the invention is characterized by low manufacturing costs and can also be operated with low actuation effort.

[0030] In the following, a vented space refers to a space within a hydraulic system or automatic transmission where ambient pressure prevails. A space connected to a vent and operating at ambient pressure is also referred to as vented. The term "pressureless" is also used, which is not physically accurate, but expresses the fact that no force can be generated from the ambient pressure in this system, as it acts on all surfaces in all directions.

[0031] Furthermore, the term working pressure is understood below to mean the pressure applied to a consumer, such as a hydraulic motor or a hydraulic cylinder, which is the consumer of a hydraulic system in which the pressure is converted into a force or torque. In contrast to working pressure, control pressure or pilot pressure does not supply a consumer with hydraulic energy, but rather moves, actuates, or switches a hydraulic valve.

[0032] Both the features specified in the patent claims and the features specified in the following embodiments of the hydraulic system according to the invention are each suitable on their own or in any combination with each other to further develop the subject matter according to the invention.

[0033] Further advantages and advantageous embodiments of the hydraulic system according to the invention will become apparent from the claims and the exemplary embodiments described below with reference to the drawing, wherein, for the sake of clarity, the same reference numerals are used in the description of the various exemplary embodiments for structurally and functionally identical components.

[0034] It shows: Fig. 1 a hydraulic diagram of a first embodiment of the hydraulic system according to the invention with the parking lock engaged; Fig. 2 the hydraulic system according to Fig. 1 with the parking barrier in place; Fig. 3 one Fig. 1. Corresponding representation of a second embodiment of the hydraulic system according to the invention with the parking lock engaged; Fig. 4 the hydraulic system according to Fig. 3 with the parking barrier in place; Fig. 5 a Fig. 1. Corresponding illustration of a third embodiment of the hydraulic system according to the invention with the parking lock engaged; and Fig. 6 the hydraulic system according to Fig. 5 with the parking barrier in place.

[0035] In Fig. Figure 1 shows a hydraulic diagram of a part of a hydraulic system 1 for actuating a parking lock cylinder 2 of a parking lock 3, with two valve assemblies PSV1 and PSV2. A working pressure p_sys can be applied to the two valve assemblies PSV1 and PSV2, which, depending on a pilot pressure p_VS3 adjustable in the area of ​​an electro-hydraulic actuator 3 (in this case, a solenoid valve), can be directed via the valve assemblies PSV1 and PSV2 towards the parking lock cylinder 2. A spring force from a spring assembly 6, 7 acts on the valve spools 4 and 5 of the valve assemblies PSV1 and PSV2, actuating the valve assemblies PSV1 and PSV2 respectively towards their first operating states.

[0036] In the initial operating states of the valve assemblies PSV1 and PSV2, the connection of the parking lock cylinder 2 to a section 8 of the hydraulic system 1, which carries the working pressure p_sys, is disconnected in the area of ​​the valve assemblies PSV1 and PSV2. The pilot pressure p_sys can be applied in the area of ​​a first control surface 9 of the valve spool 4 of the first valve assembly PSV1, opposing the spring force of the spring assembly 6, while the pilot pressure p_VS3 can be applied in the area of ​​a first control surface 10 of the valve spool 5 of the second valve assembly, acting in the same way as the spring force of the spring assembly 7 and opposing a pressure signal p_DS that can be applied in the area of ​​a second control surface 11.

[0037] In the first operating state of the first valve assembly PSV1, a connection between the first valve assembly PSV1 and the parking lock cylinder 2 is separated from the area 8 carrying the working pressure p_sys in the region of the first valve assembly PSV1. Furthermore, in the first operating state of the second valve assembly PSV2, the parking lock cylinder 2 is coupled to a pressureless area 12, or a vented chamber, in the region of the second valve assembly PSV2. In a second operating state of the first valve assembly PSV1, the working pressure p_sys is applied to the second valve assembly PSV2 via the first valve assembly PSV1. In this second operating state of the second valve assembly PSV2, the parking lock cylinder 2 is separated from the pressureless area 12, and the working pressure p_sys can be directed towards the parking lock cylinder 2 while the first valve assembly PSV1 is simultaneously present in the second operating state.

[0038] Additionally, in the second operating state of the first valve assembly PSV1, the working pressure p_sys can be applied to its valve spool 4 in the area of ​​a third control surface 13, counteracting the spring force of the spring assembly 6. When the second valve assembly PSV2 is simultaneously in its second operating state, this pressure can also be applied to its valve spool 5 in the area of ​​a third control surface 14 of the valve spool 5, counteracting the spring force of the spring assembly 7. The pressure applied to the third control surfaces 13 and 14 in the first operating states of the valve assemblies PSV1 and PSV2 corresponds to a pressure present in the pressureless area 12. The pressure signal p_DS is either adjustable in the area of ​​an actuator or corresponds to a pressure intended for actuating a switching element of a transmission.

[0039] The third control surfaces 13 and 14 of the valve slides 4 and 5 of the valve assemblies PSV1 and PSV2 each correspond to an area difference between mutually facing end faces 15, 16 and 17, 18 of diameter ranges 41, 42 and 51, 52 of the valve slides 4, 5.

[0040] The control surfaces 10, 11 and 14 of the valve slide 5 of the second valve assembly PSV2 and the spring force of the spring assembly 7 are coordinated in such a way that the second valve assembly PSV2 can be brought into its first operating state by the pilot pressure p_VS3, independently of the pressure signal p_DS and independently of the working pressure p_sys.

[0041] At the in Fig. 1 and Fig. In the first embodiment of hydraulic system 1 shown in 2, the working pressure p_sys is in the Fig. 2 shown second operating state of the first valve assembly PSV1, in which the first valve assembly PSV1 is held in the second operating state by the working pressure p_sys, on a fourth control tongue PSV24 of the second valve assembly PSV2 and is also shown in Fig. In the second operating state of the second valve assembly PSV2, as shown in Figure 2, in which the fourth control tongue PSV24 is connected to a third control tongue PSV23, the pressure is directed towards the parking lock cylinder 2 in the area of ​​the second valve assembly PSV2. A parking lock piston 19 is then moved from its position in the working pressure p_sys. Fig. 1. The first end position, as shown and corresponding to the engaged operating state of the parking lock, is moved into its in Fig. The second end position shown in Figure 2 is adjusted and held in this position, which corresponds to the designed operating state of the parking lock. Additionally, the parking lock is equipped with a locking device 20, by means of which the parking lock piston 19 can be mechanically locked and held in its second end position, corresponding to the designed operating state of the parking lock, in a manner known per se.

[0042] When a request is made to engage the parking lock, the actuator 3 is first energized accordingly, and the working pressure p_sys is applied to the first control surface 10 of the valve spool 5 of the second valve assembly PSV2, and the valve spool 5 is moved from its position in Fig. 2 shown end position in its in Fig. The first end position shown in Figure 1 is transferred, in which the parking lock cylinder 2 is disconnected from the working pressure p_sys in the area of ​​the second valve assembly PSV2 and is connected to the pressureless area 12. Furthermore, the locking device 20 is deactivated, thereby releasing the parking lock piston 19. Due to a spring device acting on the parking lock piston in the direction of the engaged operating state of the parking lock, the parking lock piston 19 is moved by this into the Fig. The end position shown in section 1 is moved and the parking lock is engaged. The first valve assembly PSV1 remains in the position shown in the diagram. Fig. 2 shown second operating state, since the working pressure p_sys is still present at the valve slide 4 in the area of ​​the third control surface 13.

[0043] In contrast, in the second embodiment of the hydraulic system 1, the parking lock cylinder 2 is according to Fig. 3 and Fig. 4 directly connected to the first valve unit PSV1 and additionally coupled downstream of the first valve unit PSV1 to the second valve unit PSV2. In the Fig. In the first operating state of the second valve assembly PSV2 shown in Figure 3, the first valve assembly PSV1 and the parking lock cylinder 2 are connected to the pressureless area 12 via the second valve assembly PSV2, thus preventing the parking lock piston 19 from being actuated in the direction of the designed operating state of the parking lock.

[0044] The second valve device PSV2 is activated by applying the pressure signal p_DS from the in Fig. 3 first operating state shown in the in Fig. 4, the second operating state shown, is transferred, the connection between the first valve device PSV1 and the parking lock cylinder 2 and the pressureless area 12 in the area of ​​the second valve device PSV2 is separated and the parking lock cylinder 2 can be pressurized with the working pressure p_sys to an extent required to deploy the parking lock.

[0045] The in Fig. 5 and Fig. The third embodiment of the hydraulic system 1 shown in Figure 6 represents an extension of the first embodiment of the hydraulic system 1 according to Figure 6. Fig. 1 and Fig. Figure 2. The third embodiment of the hydraulic system 1 additionally features a delay element 21, with which the connection area between the electrohydraulic actuator 3 and the valve assemblies PSV1 and PSV2 is operatively connected. The delay element 21 comprises a piston element 24 that is displaceable in a cylinder 23 by the pilot pressure p_VS3 against a spring force of a spring assembly 22 and which can be subjected to the pilot pressure p_VS3 in the area of ​​an end face 25. The delay element 21 acts as a damper, which safeguards against possible faulty actuations of the actuator 3 during operation.

[0046] During normal operation, when the parking lock is engaged, actuator 3 is in an unenergized state and the pilot pressure p_VS3 is essentially zero or corresponds to the ambient pressure, thus exerting no force on the valve assemblies PSV1 and PSV2. When a request is made to engage the parking lock, actuator 3 is energized, causing the second valve assembly PSV2 to immediately return to its initial operating state or its starting position.

[0047] Should actuator 3 be activated or energized during operation due to a faulty control, for example due to a short circuit or a faulty controller, a defined fault latency time is required within which the faulty activation can be reset or interrupted during an activated emergency program.

[0048] By using the delay element 21, the fault latency time, after which the second valve device PSV2 is brought into its first operating state by the pilot pressure p_VS3, is reduced compared to the first embodiment of the hydraulic system 1 according to Fig. 1 extended. This results from the fact that the pilot pressure p_VS3 in the energized operating state of the actuator 3 initially actuates the delay element 21, which has a lower response limit than the second valve assembly PSV2, and thereby moves the piston element 24 out of the in Fig. The piston element 24 moves against the spring force of the spring assembly 22 in the end position shown in Figure 5. The pressure value of the pilot pressure p_VS3 remains below the response limit of the second valve assembly PSV2 until the piston element 24 reaches its second end stop 26. Only when the piston element 24 is at the second end stop 26 does the pressure of the pilot pressure p_VS3 increase and move the second valve assembly PSV2. This allows countermeasures to be initiated in a timely manner, preventing the effects of a faulty actuator 3 on the operating state of the parking lock. For example, ratcheting noise in the area of ​​the parking lock, which impairs driving comfort, can be prevented to the desired extent.

[0049] Additionally, the third embodiment of the hydraulic system 1 comprises according to Fig. 5 and Fig. 6 Downstream of actuator 3, a throttling device 27 is provided, by means of which the flow rate present in the area of ​​actuator 3 can be limited to the desired extent during the actuator-side control of the two valve devices PSV1 and PSV2. The throttling device 29 ensures that the piston element 24 only moves from its position after a desired error latency period has elapsed. Fig. 5. The first end position shown at the second end stop 26 is reached and the aforementioned countermeasures to prevent incorrect operation of the parking lock can be initiated and carried out.

[0050] Alternatively, the throttling device 27 can also be arranged downstream of a branch point 28, but upstream of another branch point 29, whereby the first valve device PSV1 is supplied with the full flow of the actuator 3 and only the second valve device PSV2 and the delay element 21 are supplied with the flow limited in the area of ​​the throttling device 27.

[0051] All embodiments of the hydraulic system 1 shown in the drawing are based on the basic operating principle described in more detail below.

[0052] In the off-state of a vehicle, the operating pressure p_sys is typically zero or corresponds to the ambient pressure. During system startup, for example, a main transmission pump delivers a hydraulic fluid flow rate, and the operating pressure p_sys is adjusted in the area of ​​a valve assembly depending on the operating state. Without corresponding energization of actuator 3, the two valve assemblies PSV1 and PSV2 are in their initial operating states after such a system startup.

[0053] Starting from an engaged operating state of the parking lock, a driver request to start a vehicle equipped with the parking lock, which typically requires moving the selector lever from position P (parking) towards position D or R (for forward or reverse travel), triggers a request to disengage the parking lock. For this to occur, the parking lock cylinder 2 must be pressurized with hydraulic pressure, or the operating pressure p_sys, via the two valve assemblies PSV1 and PSV2. This is achieved by energizing the actuator 3 and applying the pilot pressure p_VS3 to the two valve assemblies PSV1 and PSV2.

[0054] The first valve assembly PSV1 is thereby transferred from its first operating state to its second operating state by the pilot pressure p_VS3 against the spring force of the spring assembly 6. As soon as a second control tongue PSV12 of the first valve assembly PSV1 is blocked by the valve spool 4, the working pressure p_sys acts in addition to the pilot pressure p_VS3 in the area of ​​the third control surface 13 of the valve spool 4 and transfers the first valve assembly PSV1 to its second operating state and holds the first valve assembly PSV1 in the second operating state, thus activating the self-holding function in the area of ​​the first valve assembly PSV1.

[0055] Furthermore, the current to actuator 3 is switched off and the second valve assembly PSV2 is actuated with the pressure signal p_DS to transition the second valve assembly PSV2 from its first operating state to its second operating state and to actuate the parking lock cylinder 2 with the desired working pressure p_sys. In the second operating state of the second valve assembly PSV2, it is also held in its second operating state by the working pressure p_sys applied in the area of ​​the control surface 14 against the spring force of the spring assembly 7 due to the then activated self-holding of the second valve assembly PSV2.

[0056] If a request to engage the parking lock is made based on a corresponding driver request, the actuator 3 is energized and the second valve assembly PSV2 is subjected to the pilot pressure p_VS3 in the area of ​​its first control surface 10 and the second valve assembly PSV2 is moved by the pilot pressure p_VS3 from the second operating state towards the first operating state, whereby the parking lock cylinder 2 is depressurized and the parking lock is engaged to the desired extent with the locking device 20 deactivated accordingly.

[0057] All embodiments of the hydraulic system 1 include a valve system for controlling the parking lock, consisting of two valve assemblies, PSV1 and PSV2, both of which, in their initial state, prevent the pressure supply to the parking lock valve 2. To enable hydraulic actuation of the parking lock valve 2, both valve assemblies, PSV1 and PSV2, must be moved into their reversed operating state.

[0058] Since both valve assemblies PSV1 and PSV2 are controlled by actuator 3, and the first valve assembly PSV1, at which the working pressure p_sys is applied, transitions to its reversed operating state when the pilot pressure p_VS3 is applied, the second valve assembly PSV2 is forcibly held in its first operating state by the pilot pressure p_VS3 of actuator 3. Actuation of actuator 3 activates the working-pressure-side self-holding mechanism of the first valve assembly PSV1, allowing the current to be switched off again. Subsequently, the second valve assembly PSV2 is switched to its second operating state via the separate control signal or pressure signal p_DS. This results in the system pressure p_sys being applied in the area of ​​the parking lock cylinder 2, which moves the cylinder to engage the parking lock and holds it in the operating state equivalent to the engaged operating state of the parking lock.

[0059] To engage the parking lock, the second valve assembly PSV2 is pushed back into its initial position by reactivating or energizing the actuator 3, thereby connecting the working pressure line of the parking lock cylinder 2 to the unpressurized area 12 or the tank line. Until the pressure supply or the working pressure p_sys is switched off, the first valve assembly PSV1 remains in its second operating state or in its reversed position.

[0060] An incorrect activation of actuator 8 does not automatically lead to the deployment of the parking lock; instead, actuator 3 must first be activated and then switched off again to deploy the parking lock.

[0061] This means that the valve system of the hydraulic systems 1 is in accordance with Fig. 1 to Fig.Six systems each provide a high level of protection against incorrect activation of the parking lock, which could cause the parking lock to be deployed unintentionally. Furthermore, the valve system of hydraulic systems 1 allows the parking lock to be deployed to the desired extent even under existing operating pressure and despite the occurrence of a simple fault.

[0062] In addition, the self-holding mechanism in the area of ​​the valve devices PSV1 and PSV2 also provides self-holding of the parking lock itself, which, in the event of an automatic transmission entering emergency mode, keeps the parking lock in its designed state without the need for pressure channels required for clutch or dog actuation. Reference sign 1 Hydraulic system 2 parking lock cylinders 3 Actuator 4, 5 valve slides 6, 7 Spring mechanism 8 Working pressure leading area 9, 10 first control surface 11 second control surface 12 pressureless area 13, 14 third control surface 15 to 18 frontal area 19 parking lock pistons 20 Locking device 21 Delay element 22 Spring assembly 23 cylinders 24 piston elements 25 End face of the piston element 26 End stop 27 Throttle device 28 Branching point 29 further branching point 41, 42 diameter range 51, 52 diameter range p_DS pressure signal PSV1 first valve assembly PSV2 second valve assembly PSV12 control tongue PSV23, PSV24 control tongue p_sys working pressure p_VS3 Input pressure

Claims

[1] Hydraulic system (1) for actuating a parking lock cylinder (2) of a parking lock with two valve devices (PSV1, PSV2), to which a working pressure (p_sys) can be applied, which can be guided in the direction of the parking lock cylinder (2) via the valve devices (PSV1, PSV2) as a function of a pilot pressure (p_VS3) adjustable in the area of ​​an electrohydraulic actuator (3), wherein a spring force of a spring device (6, 7) acts on valve slides (4, 5) of the valve devices (PSV1, PSV2), which actuate the valve devices (PSV1, PSV2) in the direction of first operating states, characterized by , that - in the first operating states of the valve devices (PSV1, PSV2), a connection of the parking lock cylinder (2) to an area (8) carrying the working pressure (p_sys) in the area of ​​the valve devices (PSV1, PSV2) is disconnected and - the pilot pressure (p_VS3) can be applied in the region of a first control surface (9) of the valve spool (4) of the first valve device (PSV1) in a manner counteracting the spring force, - while the pilot pressure (p_VS3) in the region of a first control surface (10) of the valve slide (5) of the second valve device (PSV2) can be switched on in the same way as the spring force of the spring device (7) and in a counteracting manner to a pressure signal (p_DS) that can be applied in the region of a second control surface (11), - wherein a connection provided between the first valve device (PSV1) and the parking lock cylinder (2) is separated from the area (8) carrying the working pressure (p_sys) in the first operating state of the first valve device (PSV1) in the area of ​​the first valve device (PSV1) - and the parking lock cylinder (2) is coupled to a pressure-free area (12) in the first operating state of the second valve device (PSV2) in the area of ​​the second valve device (PSV2), - wherein the working pressure (p_sys) in a second operating state of the first valve device (PSV1) can be applied to the second valve device (PSV2) via the first valve device (PSV1) - and the parking lock cylinder (2) is separated from the pressureless area (12) in a second operating state of the second valve device (PSV1) and the working pressure (p_sys) can be guided in the direction of the parking lock cylinder (2) when the first valve device (PSV1) is simultaneously present in the second operating state, - and wherein the working pressure (p_sys) in the second operating state of the first valve device (PSV1) can be applied to the valve slide (4) thereof in the region of a third control surface (13) so as to counteract the spring force of the spring device (6) and, when the second valve device (PSV2) is simultaneously present in the second operating state, can be applied to the valve slide (7) thereof in the region of a third control surface (14) so ​​as to counteract the spring force of the spring device (7). [2] Hydraulic system according to claim 1, characterized by that the pressure applied to the third control surfaces (13, 14) in the first operating states of the valve devices (PSV1, PSV2) corresponds to a pressure present in a substantially pressure-free region. [3] Hydraulic system according to claim 1 or 2, characterized by that the pressure signal (p_DS) corresponds to a pressure intended for actuating a switching element of a transmission. [4] Hydraulic system according to one of claims 1 to 3, characterized by that the pressure signal (p_DS) is adjustable within the range of an actuator. [5] Hydraulic system according to one of claims 1 to 4, characterized by that the third control surfaces (13, 14) each correspond to a surface difference between mutually facing end surfaces (15, 16, 17, 18) of diameter regions (41, 42, 51, 52) of the valve slides (4, 5) of the valve devices (PSV1, PSV2). [6] Hydraulic system according to one of claims 1 to 5, characterized by that the control surfaces (10, 11, 14) of the valve slide (5) of the second valve device (PSV2) and the spring force of the spring device (7) are coordinated with one another in such a way that the second valve device (PSV2) can be transferred into its first operating state by the pilot pressure (p_VS3) independently of the pressure signal (p_DS) and the working pressure (p_sys). [7] Hydraulic system according to one of claims 1 to 5, characterized bythat the control surfaces (10, 11, 14) of the valve slide (5) and the spring force of the spring device (7) of the second valve device (PSV2) are coordinated with one another in such a way that the second valve device (PSV2) can be maintained in its second operating state independently of the pilot pressure (p_VS3) via the working pressure (p_sys). [8] Hydraulic system according to one of claims 1 to 7, characterized by that the connecting area between the electro-hydraulic actuator (3) and the valve devices (PSV1, PSV2) is operatively connected to a hydraulic delay element (21). [9] Hydraulic system according to claim 8, characterized by that a throttle device (27) is provided downstream of the electro-hydraulic actuator (3) and upstream of the second valve device (PSV2) and the delay element (21). [10] Hydraulic system according to claim 8 or 9, characterized bythat the delay element (21) comprises a piston element (24) which can be displaced between two end positions by the pilot pressure (p_VS3) against a spring force of a spring device (22) in a cylinder (23). [11] Hydraulic system according to one of claims 1 to 10, characterized by that the electro-hydraulic actuator (3) is designed as a solenoid valve which, in the de-energized operating state, is held by a spring device in an operating state in which the pilot control pressure (p_VS3) is substantially equal to zero, while the pilot control pressure (p_VS3) in the energized operating state of the solenoid valve (3) is equal to the working pressure (p_sys) applied to the solenoid valve (3).

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