Device for operating a parking lock of a motor vehicle transmission

Abstract

The invention relates to a device for operating a parking lock of a transmission in a motor vehicle, comprising an engagement spring for engaging the parking lock and a hydraulic actuator for disengaging the parking lock, an electrohydraulic control device for hydraulically actuating the actuator and a shift element, and an electronic control device for electrically actuating the actuator and the electrohydraulic control device. The actuator has a hydraulic piston which is in operative connection with the parking lock and which, when disengaging the parking lock, is loaded with system pressure via a pressure line and can be mechanically locked in a piston position which is assigned to the engaged state and the disengaged state by means of a locking device. A pre-choke unit is installed in the pressure line downstream of the hydraulic piston, comprising a choke and a non-return valve. The choke acts in a volume flow-restricting manner not only in the input direction towards the pressure chamber but also in the return direction of the pressure chamber. The non-return valve is closed in the input direction towards the pressure chamber and open in the return direction of the pressure chamber.

Description

Technical Field

[0001] This invention relates to a device for a parking lock for a transmission in a motor vehicle. Background Technology

[0002] Typically, automatic transmissions used in motor vehicles have a parking lock, in which a pawl engages with the teeth of a parking lock wheel connected to the driven gear of the automatic transmission and thus acting on the axle of the vehicle. As an operative connection between the parking lock and the operating device within the vehicle's interior space, modern automatic transmissions employ an electro-hydraulic system, also known as an "E-line" or "shift-by-wire system." The electrical connection between the automatic transmission's operating device and the electro-hydraulic transmission control unit within the vehicle's interior space causes the electrical signal for parking lock operation to be converted into mechanical movement of the pawl. For this purpose, a hydraulically operable actuator can be provided, the hydraulic supply of which is part of the transmission's hydraulic system. Here, a piston, typically axially movable in the cylinder cavity of the actuator and operatively connected to the pawl, is pressurized to disengage the parking lock from its locked position against the spring force of the engagement spring used to engage the parking lock.

[0003] For example, DE4127991A1 discloses a hydraulically operable actuator for operating a transmission parking lock. Here, the spring force of the parking lock's engagement spring acts on the actuator piston in the parking lock's engagement direction. In the parking lock's disengagement direction, the actuator piston can be loaded with system pressure from the electro-hydraulic transmission control device. For this purpose, the input line of the actuator pressure chamber can be connected to the pressure side of the transmission's oil pump via an electrically operable solenoid valve, and the actuator piston is axially movable within this input line. In the first switching position of the solenoid valve, the actuator pressure chamber is vented, thereby causing the spring force of the engagement spring acting on the actuator piston to engage the parking lock. In the second switching position of the solenoid valve, the actuator pressure chamber is loaded with system pressure provided by the oil pump, thereby causing the actuator piston to operate the parking lock against the spring force of the engagement spring in the parking lock's disengagement direction.

[0004] To avoid continuously maintaining the pressure acting on the actuator piston in the disengaged state of the parking lock at a level sufficient to hold the parking lock in that state, the actuator can additionally have an electromagnetically operable locking device by means of which the actuator piston can be mechanically fixed. A parking lock actuator with a locking device is known, for example, from DE102012013373A1, which mechanically locks the actuator piston in a piston position associated with the engaged state of the parking lock and a piston position associated with the disengaged state of the parking lock. Therefore, such a locking device is also called a "bistable piston locking device." To disengage the parking lock, and when disengaging the parking lock, the mechanical piston lock must be deactivated, i.e., disengaged, and a clutch pressure must be applied to the actuator piston, thereby placing the parking lock in the disengaged state against the spring force of the engagement spring. In the disengaged state of the parking lock, the mechanical piston lock is reactivated, thus preventing undesirable movement of the actuator piston.

[0005] In the actuator shown in DE1020120133373A1, locking of the actuator piston is achieved by means of a ball radially movably supported in a fixed ball holder and a cone fixedly connected to the armature rod of an electromagnet of the locking device, which can be placed in an unlocked or locked position depending on the switching state of the electromagnet. In the locked position, the ball, thus moving radially outward into the corresponding inner contour of the actuator piston, prevents the actuator piston from axial movement. As an alternative, a system with pins arranged on the side of the piston rod of the actuator piston is also known for locking the actuator piston, the pins engaging in one of two circumferential grooves of the piston rod according to the switching position of the actuator piston, so as to mechanically fix the actuator piston.

[0006] If the actuator piston is mechanically fixed in the piston position associated with the disengaged state of the parking lock by means of a locking device, and system pressure is simultaneously applied to resist the spring force of the engagement spring, pressure fluctuations in the system pressure, especially short-term pressure drops and short-term pressure peaks, will cause wear on the mechanical piston locking device. If the actuator piston is mechanically fixed in the piston position associated with the disengaged state of the parking lock by means of a locking device, and the system pressure previously acting on the actuator piston is technically separated from the actuator's pressure chamber, so that only the spring force of the engagement spring is now acting on the actuator piston, then a brief pressure peak will appear in the actuator's pressure chamber when the system pressure is re-engaged, and this pressure peak will also cause wear on the mechanical piston locking device. Summary of the Invention

[0007] Therefore, the object of the present invention is to provide an alternative device for operating this type of transmission parking lock, wherein the parking lock actuator of the transmission parking lock has an actuator piston that, in order to disengage the parking lock, is loaded against the spring force of the parking lock engagement spring by system pressure provided by the transmission pump to the electro-hydraulic control device of the transmission under pressure, and is mechanically locked not only in the piston position associated with the engaged state of the parking lock but also in the piston position associated with the disengaged state of the parking lock. Firstly, it is necessary to better protect the mechanical piston locking device from wear caused by pressure fluctuations.

[0008] Therefore, the present invention proposes a device for a parking lock in a transmission of a motor vehicle. The device includes an engagement spring for engaging the parking lock, a hydraulically actuated actuator for disengaging the parking lock, an electro-hydraulic control device, and an electronic control device. The electro-hydraulic control device, depending on the situation, hydraulically operates a shift element of the transmission that forms a gear and the actuator using pressure provided by a pump in the transmission. The electronic control device electrically operates a hydraulically actuated valve of the electro-hydraulic control device to pre-define different shift positions and gears in the transmission. The electro-hydraulic control device generates a system pressure pre-determined by the electronic control device via one of the electromagnetically actuated hydraulic valves. This system pressure ensures the pressure supply required by the shift element and the actuator as needed. The actuator has a hydraulic piston operatively connected to the parking lock. This hydraulic piston is axially movably supported in the actuator housing and forms a pressure chamber together with the housing. This pressure chamber is routed through a pressure line when the parking lock is disengaged. The hydraulic valve that generates the system pressure loads the system pressure and vents it through the pressure line when the parking lock is engaged. The hydraulic piston can be mechanically locked in the engaged position associated with the parking lock and in the disengaged position associated with the parking lock by means of a locking device operable by the electronic control device. A pre-throttling unit, comprising a throttling section and a check valve, is installed in the pressure line between the hydraulic valve that generates the system pressure and the pressure chamber. A pressure relief valve is fluidly connected to the pressure line between the pre-throttling unit and the pressure chamber in the flow direction. A hydraulic damper is fluidly connected to the pressure line between the pre-throttling unit and the pressure chamber in the flow direction. The pressure relief valve is integrated into the hydraulic damper. The throttling section acts to limit the volumetric flow rate not only in the input direction toward the pressure chamber but also in the return direction of the pressure chamber. The check valve is closed in the input direction toward the pressure chamber and open in the return direction of the pressure chamber.

[0009] Therefore, the present invention relates to a device for operating a parking lock in a motor vehicle transmission, the device comprising an engagement spring for engaging the parking lock, a hydraulically actuated actuator for disengaging the parking lock, an electro-hydraulic control unit, and an electronic control unit. The electro-hydraulic control unit, depending on the situation, controls not only the shifting elements of the transmission that form gear positions but also the actuator via an electromagnetically actuated hydraulic valve using pressure provided by a pump in the transmission. For this purpose, the electronic control unit operates the electromagnetically actuated hydraulic valve to pre-determine different shifting positions and gears in the transmission. Here, the electro-hydraulic control unit generates a system pressure pre-determined by the electronic control unit via the electromagnetically actuated hydraulic valve, the system pressure ensuring the pressure supply required by the shifting elements and actuator for gear positions as needed.

[0010] The actuator has a hydraulic piston operatively connected to the parking lock. This hydraulic piston is axially movably supported within the actuator housing and, together with the housing, forms a pressure chamber. This pressure chamber is pressurized via a pressure line through an electromagnetically operable hydraulic valve that generates system pressure when the parking lock is disengaged, and is emptied via the same pressure line when the parking lock is engaged. Additionally, the actuator's hydraulic piston can be mechanically locked in the engaged position associated with the parking lock and in the disengaged position associated with the parking lock using an electronically controllable locking device.

[0011] According to the invention, a pre-throttling unit is installed in the pressure line leading to the pressure chamber of the actuator, in the region between the hydraulic valve that generates the system pressure and the pressure chamber. This pre-throttling unit includes a throttling section and a check valve. Here, the throttling section acts not only in the input direction toward the pressure chamber of the actuator but also in the return direction of the pressure chamber, limiting the volumetric flow rate delivered to the pressure chamber of the actuator when the parking lock is disengaged. This advantageously reduces the structural space of the actuator itself and also reduces the structural space of the hydraulic components optionally provided for protecting the actuator. The check valve of the pre-throttling unit closes in the input direction toward the pressure chamber of the actuator and opens in the return direction of the pressure chamber, thereby ensuring a predetermined evacuation time of the pressure chamber when the parking lock is engaged.

[0012] In a preferred design of the pre-throttling unit, its throttling section and check valve are connected in parallel in a fluidic manner. This enables a large bandwidth with a simple structure, allowing the filling and emptying rates of the actuator pressure chamber to be individually matched to different applications.

[0013] In an alternative design to the pre-throttling unit, the throttling section and the check valve are connected in series in terms of fluid technology, which brings structural space advantages compared to the parallel connection of the throttling section and the check valve.

[0014] The check valve of the pre-throttling unit may have, for example, a ball as the closing element, but may also have a plate, wherein the ball or the plate is then pre-tightened in the closing direction by a spring against system pressure. Preferably, the flow cross-section and spring characteristic curve of the check valve are structurally sized such that the flow resistance of the check valve is as small as possible when emptying the actuator pressure chamber, i.e., when engaging the parking lock.

[0015] The inner diameter of the throttling section of the pre-throttling unit is preferably determined in such a structural way that its flow resistance does not excessively affect the filling time of the actuator pressure chamber even at low operating temperatures when the parking lock is disengaged, but also provides a sufficiently high hydraulic buffering effect to mechanically protect the mechanical load of the actuator piston locking device.

[0016] In terms of space, the pre-throttle unit can be an integral part of the electro-hydraulic control device of the transmission, but alternatively it can also be an integral part of the actuator.

[0017] To effectively protect the actuator from damage or destruction due to overpressure, a further improvement of the invention proposes to additionally fluidically connect a pressure relief valve to the pressure line leading to the actuator's pressure chamber in the region between the pre-throttling unit and the pressure chamber (i.e., along the flow direction). This pressure relief valve can be structurally simple, for example, a ball valve or plate valve spring-preloaded against the dominant system pressure in the pressure line, spatially integrated into the electro-hydraulic control unit of the transmission or alternatively integrated into the actuator. Because the pressure relief valve is positioned between the pre-throttling unit and the pressure chamber in the flow direction, the volumetric flow restriction generated by the pre-throttling unit in the pressure line leading to the actuator's pressure chamber acts on the pressure relief valve in a load-reducing manner, thereby allowing the pressure relief valve to be structurally relatively small.

[0018] To effectively protect the actuator, especially the locking device of the actuator piston, from wear and damage caused by pressure fluctuations, high-frequency temporary pressure drops, and high-frequency temporary pressure peaks, a further improvement of the invention proposes, in the region between the pre-throttling unit and the pressure chamber (i.e., along the flow direction), to additionally connect a hydraulic damper, fluidically speaking, to the pressure line leading to the pressure chamber of the actuator. Preferably, such a hydraulic damper is implemented as an integral part of the electro-hydraulic control device of the transmission; alternatively, it can also be an integral part of the actuator.

[0019] Structurally, this hydraulic damper is preferably configured as a piston axially movable within a housing bore leading to the transmission cavity for exhaust. This piston is spring-preloaded to resist the dominant system pressure in the pressure line leading to the actuator pressure chamber. As already shown, the housing bore can be located in the electro-hydraulic control unit of the transmission or in the actuator housing. Alternatively, the hydraulic damper can also be configured as a pressure-deformable elastomeric element engaged in a branch of the pressure line leading to the actuator pressure chamber that is closed off towards the transmission cavity. In both cases, the elasticity of the hydraulic damper for buffering the amplitude of dynamic and high-dynamic pressure fluctuations, pressure peaks, and pressure drops, depending on the situation, can be structurally matched to the corresponding usage, i.e., to current parking lock systems. The solution according to the invention enables, in an advantageous manner, passive buffering of the amplitude of dynamic and high-dynamic pressure inhomogeneities, depending on the situation, in the pressure delivery of hydraulically operated parking lock actuators of various structural types.

[0020] Then, passive buffering of pressure fluctuations that occur under the pressure loading of the actuator piston can be achieved in a particularly advantageous manner, especially when the parking lock is held in the disengaged state, significantly reducing wear at the mechanical locking device of the actuator piston. That is, the component tolerances determined by design allow for a certain small axial movement of the actuator piston even when the piston locking device is activated, so that pressure fluctuations and pressure peaks of the system pressure acting on the actuator piston, as highly dynamic axial forces, can be transmitted from the actuator piston to the mechanical mechanism of the piston locking device even when the piston locking device is activated. It is known that such highly dynamic shocks promote wear. With the buffered pressure loading of the actuator piston according to the invention, this shock load on the piston locking device of the locking device can be significantly reduced, which advantageously improves the reliability and service life of the actuator.

[0021] In one embodiment of the invention, a pressure-relieving valve, proposed as a first further improvement, is combined with a hydraulic damper, proposed as a second further improvement. In a preferred embodiment, the pressure-relieving valve is integrated into the hydraulic damper in a space-saving manner. In this case, the maximum pressure level to be protected by the pressure-relieving valve is always numerically higher than the pressure fluctuations and pressure peaks to be buffered by the hydraulic damper.

[0022] The pressure relief valve integrated into the hydraulic damper can be formed or shown, for example, by the interaction of the spring force of an existing damper spring with a predetermined control edge dimension. If the damper piston now moves along its central axis at the control edge dimension, the existing inlet of the hydraulic damper is fluidly connected to the correspondingly positioned outlet of the hydraulic damper leading to the transmission cavity. For this purpose, the damper spring can have a progressive spring characteristic curve, such that the inlet of the hydraulic damper is fluidly connected to the outlet of the hydraulic damper only when it is above a predetermined clutch pressure level. The "soft" portion of the progressive spring characteristic curve thus provides the desired buffering against high-frequency pressure fluctuations and pressure peaks. Alternatively, the damper spring can also be constructed by mechanically connecting two springs, preferably mechanically connected in series, with different spring characteristic curves. The first spring of the two springs has a gentle spring characteristic curve designed to dampen the damper piston, while the second spring of the two springs has a steep spring characteristic curve designed to open the pressure relief valve.

[0023] The pressure-limiting valve integrated into the hydraulic damper can, for example, be configured as a spring-preloaded valve. This valve is integrated into the damper piston such that the existing inlet of the hydraulic damper is fluidly connected to the outlet of the hydraulic damper leading to the transmission cavity when the pressure is above a predetermined system pressure level. Such a pressure-limiting valve can be structurally simple, either as a ball valve preloaded against system pressure by means of a pressure-limiting spring or a plate valve preloaded against system pressure by means of a pressure-limiting spring. Here, the pressure-limiting spring can be centrally located inside the damper spring that always acts on the damper piston, saving structural space. Attached Figure Description

[0024] The invention will now be described in detail with reference to the accompanying drawings. Herein:

[0025] Figure 1 A schematic diagram of a motor vehicle is shown, which includes a transmission with a parking lock.

[0026] Figure 2 Showing according to Figure 1 A schematic diagram of a first embodiment of a device for operating a parking lock according to the present invention;

[0027] Figure 3 Showing according to Figure 1 A schematic diagram of a second embodiment of a device for operating a parking lock according to the present invention;

[0028] Figure 4 Showing according to Figure 1 A schematic diagram of a third embodiment of a device for operating a parking lock according to the present invention;

[0029] Figure 5 A schematic diagram showing a first structural example of a buffer piston with an integrated pressure-limiting piston;

[0030] Figure 6 A schematic diagram showing a second structural example of a buffer piston with an integrated pressure-limiting piston;

[0031] Figure 7 A schematic diagram showing an example of a third structure for a buffer piston with an integrated pressure-limiting piston. Detailed Implementation

[0032] Figure 1 A schematic diagram of a motor vehicle 1 with an automatic transmission 3 is shown. This motor vehicle has multiple shift elements that form gear positions and can be driven by a drive motor 2 via a starting element 30. In this way, the drive power of the drive motor 2 can be transmitted from the drive shaft 31 of the automatic transmission 3 to the driven shaft 32 in preferably multiple different gears or gear levels. The driven shaft 32 is connected via other... Figure 1 The motor vehicle components shown are only implicitly connected to the drive axle 4 of the motor vehicle 1.

[0033] Furthermore, the automatic transmission 3 has a parking lock 34, which secures the driven shaft 32 of the vehicle 1 and thus the drive shaft 4. To control the automatic transmission 3, a combination of an electro-hydraulic control unit 35 and an electronic control unit 36 ​​is provided. The electro-hydraulic control unit 35, on the one hand, hydraulically controls the starting element 30, which is exemplarily configured as a clutch, to establish a force lock between the crankshaft 20 of the drive motor 2 and the drive shaft 31 of the automatic transmission 3. On the other hand, the electro-hydraulic control unit 35 hydraulically controls the shifting element 33 inside the transmission, which forms the gear position, to generate the appropriate gear in the automatic transmission 3. Furthermore, the electro-hydraulic control unit 35 also hydraulically controls the actuator 340, which must be supplied with hydraulic fluid to disengage the parking lock 34. To control the starting element 30, the shifting element 33, and the actuator 340, a plurality of electromagnetically operable hydraulic valves are provided in the electro-hydraulic control device 35. The hydraulic valves associated with each shifting element 33 are indicated by 350, while the hydraulic valves used to generate the system pressure required by the shifting element 33 and actuator 340 to ensure the formation of the gear position are indicated by reference numeral 351. Correspondingly, the electromagnetically operable hydraulic valve 351 can also be referred to as a system pressure regulating valve.

[0034] The electronic control unit 36 ​​determines the switching commands for the electromagnetically operable hydraulic valve 351 as needed, controls and adjusts the technical settings, and operates the hydraulic valve accordingly. Here, the electronic control unit 36 ​​particularly processes signals from the selection device 5 provided in the vehicle 1, by which the driver of the vehicle 1 can pre-select various switching positions for the automatic transmission, especially the switching positions "Park" (P), "Neutral" (N), "Drive Forward" (D), and "Reverse" (R).

[0035] The pressure medium required to operate the starting element 30, shifting element 33, and actuator 340 is provided by the pump 37 of the transmission 3. The area inside the transmission cavity of the transmission 3 that serves as a reservoir for the hydraulic fluid drawn in by the pump 37 and returns it to the excess pressure medium constitutes a tank indicated by 38.

[0036] Next and refer to Figure 2 The schematic diagrams in the figure illustrate in detail the invention for use in operating in Figure 1 The first embodiment of the parking lock 34 shown is shown.

[0037] exist Figure 1 The hydraulic actuator 340 shown for operating the parking lock 34 is known in the prior art. The actuator 340 has a hydraulic piston 341 that is suitably connected to a locking element of the parking lock 34 (not shown for simplicity) and is subjected to a system pressure P_sys of the hydraulic control unit 35 for disengaging the parking lock 34. This system pressure is sufficiently high for the pressure supply required by the shift element 33 for gear positioning and, depending on the situation, the actuator 340. For this purpose, the hydraulic piston 341, together with the housing components of the actuator 340, forms a pressure chamber 346, which can be filled via a pressure line 347 with hydraulic fluid at the system pressure P_sys. The actuator 340 is hydraulically operated at the system pressure P_sys by an electromagnetically operable system pressure regulating valve 351, which generates the system pressure P_sys from a pump pressure P_p provided by a pump 37 on the transmission side according to a setting of the electronic control unit 36.

[0038] To establish a gear position, the shift element 33 is hydraulically controlled by an electromagnetically operable hydraulic valve 350 of the electro-hydraulic control device 35. The hydraulic valve 350 itself is supplied with system pressure P_sys via a system pressure regulating valve 351 through a hydraulic line 357. The system pressure P_sys of the shift element 33, used for establishing the corresponding gear, generates a required clutch pressure P_k according to a setting value from the electronic control device 36. Preferably, each shift element 33 is equipped with its own hydraulic valve 350.

[0039] The operational connection between the actuator 340 and the parking lock 34 is implemented such that the parking lock 34 is locked when the hydraulic piston 341 is in the engaged position E, and unlocked when the hydraulic piston 341 is in the disengaged position A. If pressure is applied to the hydraulic piston 341, it moves against the spring force of the engagement spring 345 to the disengaged position A. Due to the spring force of the engagement spring 345, when the pressure application on the hydraulic piston 341 is cut off, the hydraulic piston 341 moves toward the engaged position E, resulting in the mechanical engagement of the parking lock 34. The operating logic for engaging and disengaging the parking lock 34 provided herein should be understood as exemplary. Accordingly, in an alternative embodiment of the parking lock, reverse operating logic may also be provided, wherein the parking lock is engaged by hydraulic pressure and disengaged by spring force.

[0040] Additionally, the actuator 340 includes a locking device 342 for mechanically securing the hydraulic piston 341. The locking device 342 exemplarily includes a pin 344 and an electromagnet 343 for actuating the pin 344, wherein the pin 344 preferably selectively locks the hydraulic piston 341 in an engaged position E or a disengaged position A when the electromagnet 343 is de-energized, i.e., preventing undesirable axial movement.

[0041] To improve hydraulic control of the pressure chamber 346 of the actuator 340, a pre-throttling unit 352 is provided. This unit is installed in the pressure line 347 in the region between the system pressure regulating valve 351 (which generates the system pressure P_sys) and the pressure chamber 346, and includes a throttling section 353 and a check valve 354. Here, the throttling section 353 acts to limit the volumetric flow rate not only in the input direction toward the pressure chamber 346 but also in the return direction of the pressure chamber 346. The check valve 354 is closed in the input direction toward the pressure chamber 346 and open in the return direction of the pressure chamber 346.

[0042] exist Figure 2 In the embodiment shown, the throttling unit 353 and the check valve 354 are connected in parallel in terms of fluid technology, which provides designers with some freedom to match the pre-throttling unit 352 to different application requirements, while keeping the basic structure the same in all other respects.

[0043] exist Figure 2In the illustrated embodiment, the check valve 354 is exemplarily configured as a spring-preloaded ball valve, comprising a ball as a closing body 3540, an internally open truncated cone as a closing body seat 3541, and a spring 3542 preloaded against system pressure P_sys to close the closing body seat 3541 via the closing body 3540. The achievable flow rate through the check valve 354 is many times greater than the flow rate through the throttle portion 353. The open inner diameter of the throttle portion 353 is structurally coordinated with the application-specific filling time of the actuator pressure chamber 346 when disengaging the parking lock 34, i.e., with the application-specific disengagement speed of the parking lock 34, while the open inner diameter of the closing body seat 3541 is coordinated with the application-specific evacuation time of the actuator pressure chamber 346 when engaging the parking lock, i.e., with the application-specific engagement speed of the parking lock 34. The numerical examples of the structural design of the pre-throttling unit 352 illustrate this relationship: the through diameter of the throttling section 353 is 1.2 mm; the through diameter of the check valve 354 is 3 mm and the closing pressure is 0.1 bar.

[0044] As mentioned at the beginning, measures to prevent actuator 340 from being damaged or destroyed due to excessive system pressure P_sys are meaningful. Therefore, in Figure 3 The second embodiment of the device according to the invention shown (the device is based on...) Figure 2 The parking lock operating system shown herein proposes that a pressure line 347 leading to a pressure chamber 346 of the actuator 340 is fluidically connected to a pressure relief valve 355. In the structural example shown here, the pressure relief valve 355 is configured as a plate valve that resists system pressure P_sys spring preload. The plate valve includes a piston-type closing body 3550, an annular closing body seat 3551, a pressure relief spring 3552 clamped between the closing body 3550 and a housing section, a cylindrical inlet 3553 fluidly connected to the pressure line 347 (the inlet is on the end side of the closing body 3550, on its side opposite to the pressure relief spring 3552), an outlet 3554 leading to a reservoir 38 (the outlet is on the side of the closing body 3550), and an venting device 3555 in the spring chamber of the closing body 3550 leading to the reservoir 38.

[0045] In order to also utilize the advantages of the pre-throttling device 352 in determining the size of the pressure relief valve 355, the pre-throttling device 352 is fluidically connected to a section of the pressure line 347 leading to the actuator pressure chamber 346, which is located between the pre-throttling device 352 and the pressure chamber 346. Here, Figure 3 The relative in Figure 2 The additional pressure relief valve 355 is exemplarily an integral part of the actuator 340, while Figure 2The pre-throttling device 352 used in the process is an integral part of the electro-hydraulic control device 35. An example of the structural design of the pressure relief valve 355 illustrates the advantages mentioned: if the pressure relief valve 355 opens at a pressure threshold of 22 bar, a spring force of approximately 27.6 Newtons is calculated for the pressure relief spring 3552 when the effective diameter of the closing body 3551 is 4 mm; the required structural space is also correspondingly small.

[0046] As mentioned at the beginning, when the locking device 342 is in the locked position, the pressure pulsations, temporary pressure peaks, and temporary pressure drops of the system pressure P_sys applied to the hydraulic piston 341 of the actuator 340 can also cause damage to the actuator 340, especially causing undesirable wear to the mechanical components of the locking device 342. Therefore, in this example, this leads to wear on the pin 344 and piston rod groove of the locking device 342, where the pin 344 engages in the piston rod groove in position E of the hydraulic piston 341. That is, even when the pin 344 is locked, the forced component tolerances allow for a certain small axial movement of the hydraulic piston 341, causing a highly dynamic axial force acting on the hydraulic piston 341 (which may be due to the highly dynamic irregularities mentioned in the system pressure P_sys) to act as a highly dynamic impact on the piston rod / pin at the contact point. Disruptive pressure peaks and disruptive pressure drops may occur, for example, during gear shifting in the transmission (3).

[0047] To protect the locking device 342 from mechanical damage that may be caused by pressure spikes and drops in the supply pressure of the pressure chamber 346 of the actuator 340, Figure 4 The device according to the invention shown (which is further described as) Figure 2 In the third embodiment (based on the parking lock operating system shown), the pressure line 347 leading to the pressure chamber 346 of the actuator 340 is fluidically connected to the hydraulic buffer 356. To also utilize the advantages of the pre-throttle device 352 in determining the size of the hydraulic buffer 356, the interface is located on the section of the pressure line 347 between the pre-throttle device 352 and the pressure chamber 346. Figure 2 The pre-throttling device 352 used in the middle and Figure 4 The relative in Figure 2 The additional hydraulic buffer 356 is, for example, an integral part of the electro-hydraulic control device 35.

[0048] exist Figure 4In the structural example shown, the hydraulic damper 356 is configured as a piston / spring damper. Here, the piston of the damper 356 is axially movable in a hole in the housing of the electro-hydraulic control device 35 of the transmission (3), wherein the spring of the damper 356 preloads the piston of the damper 356 against the dominant system pressure P_sys in the pressure line 347. The spring chamber of the damper 356 is correspondingly vented toward a reservoir 38, for example, formed by the oil sump of the transmission (3). An inlet throttling section is additionally provided, for example, in the fluid flow between the pressure line 347 and the piston chamber of the damper 356.

[0049] exist Figure 4 In this case, the parking lock (34) of the transmission (3), which is not shown in detail here, is engaged. Accordingly, the hydraulic piston 341 of the parking lock actuator 340 is in the switching position E and is fixed in the axial direction by a pin 344 that is engaged in the circumferential groove of the piston rod of the hydraulic piston 341 by the locking device 342.

[0050] If the parking lock (34) is disengaged from the engaged state, the pressure chamber 347 of the actuator 340 is loaded with system pressure P_sys by the electromagnetically operable system pressure regulating valve 351 via the throttling section 353 of the pre-throttling unit 352 and the pressure line 347. This causes the hydraulic piston 341 of the actuator 340 to move axially from piston position E toward piston position A with the pin 344 of the locking device 342 disengaged, and then the pin 344 fixes the hydraulic piston 341 axially. The fluid-technical connection of the pressure line 346, now leading to the actuator pressure chamber 346, on the hydraulic damper 356 effectively and reliably prevents high-dynamic pressure fluctuations and pressure peaks in the system pressure P_sys from reaching levels that would interfere with the locking device 342. In other words, the hydraulic damper 356 in the pressure delivery of the hydraulic piston 341 of the actuator 340 prevents excessive wear of the mechanical lock of the hydraulic piston 341.

[0051] If the parking lock (34) is engaged from the disengaged state, the pressure chamber 346 of the actuator 340 is vented toward the reservoir 38 through the pressure line 347, the check valve 354 of the pre-throttle unit 352 and the system pressure regulating valve 351. As a result, the hydraulic piston 341 of the actuator 340 moves axially from piston position A toward piston position E due to the spring force of the engagement spring 345 of the parking lock (34) when the pin 344 of the locking device 342 is released. Then the pin 344 fixes the hydraulic piston 341 in the axial direction.

[0052] Next and refer to Figures 5 to 7Three structural examples are described in detail, in which a pressure relief valve 355 and a hydraulic damper 356 are provided to protect the actuator 340. In these three structural examples, the pressure relief valve 355 is integrated into the hydraulic damper 356 in a space-saving manner. Similar to... Figure 4 The third embodiment of the device according to the invention for hydraulically operating a parking lock actuator, shown in all three structural examples, includes a hydraulic damper 356 comprising a damper piston 3481 preloaded by the spring force of a damper spring 3562 against the system pressure P_sys provided by a system pressure regulating valve (351), the damper piston being movably arranged along its central axis in a bore in the housing 3560 facing the transmission (3). In any case, the maximum pressure level to be protected by the pressure relief valve 355 is numerically higher than the pressure fluctuations and pressure peaks to be buffered by the hydraulic damper 356.

[0053] exist Figure 6 In the first structural example shown, the pressure relief valve, indicated by position mark 355, is formed by the spring force of the damper spring 3562 and the cooperation of a predetermined control edge dimension 3569. The damper piston 3561 must move along its central axis with the control edge dimension in order to fluidly connect the inlet 3567 of the hydraulic damper 356, which supplies hydraulic fluid under system pressure P_sys, to the outlet 3568 of the hydraulic damper 356 leading to the cavity of the transmission (3) or the reservoir (38).

[0054] Preferably, multiple lateral outlet openings 3568 are provided because at least three star-shaped, i.e., symmetrically distributed working surfaces are required for the proper functioning of the buffer piston 3561. The gaps between these working surfaces can be used without problems as lateral outlet openings 3568.

[0055] exist Figure 5 In the upper part, the buffer piston 3561 is in its initial position, in which the system pressure P_sys does not have pressure fluctuations and pressure peaks that require hydraulic buffering, and in which the maximum pressure to be protected by the pressure relief valve 355 has not yet been reached. Figure 5 In the lower part, the system pressure P_sys present at the inlet 3567 exceeds the maximum permissible pressure, so that the damper piston 3561 releases the outlet edge of the outlet 3568 arranged on the side of the damper piston 3561 by the control edge dimension 3569. As a result, hydraulic fluid is now discharged into the transmission cavity or reservoir (38) to such an extent that the system pressure P_sys at the inlet 3567 is limited to the maximum permissible pressure.

[0056] exist Figure 5In the structural example shown, the buffer spring 3562 has a progressive spring characteristic curve, wherein the "soft" portion of the spring characteristic ensures the desired buffering function, while the switching point where overpressure is to be prevented is within the range of the "hard" portion of the spring characteristic curve.

[0057] As an alternative, two springs with different spring characteristic curves can be connected in series, wherein the first spring is thus configured as a damper spring, having a gentle spring characteristic curve designed to dampen the damper piston 3561, while the second spring of the two springs thus has a steep spring characteristic curve designed to open the outlet 3568, defined by the control edge size 3569.

[0058] In another alternative, two concentrically nested springs with different spring characteristic curves can be used. The first spring is thus configured as a damper spring, having a gentle spring characteristic curve designed to dampen the damper piston 3561, while the second spring of the two springs has a steep spring characteristic curve designed to open the outlet 3568, defined by the control edge dimension 3569. In this case, the length of the first spring must be greater than the length of the second spring, so that the "stiff" second spring does not obstruct the stroke required by the "soft" first spring for damping. It is also meaningful that the shorter of the two springs, the "stiff" second spring, is either fixed to the damper piston 3561 or to the bottom of the damper housing 3560 away from the inlet 3567, or fixed to the "soft" first spring. As long as the hydraulic damper 3568 is located in its buffer area, only the "soft" damper spring is active. The parallel spring forces of the two springs are generated on the other side of the buffer area, whereby the damper 356 now functions as a pressure relief valve 356.

[0059] exist Figure 6In the second structural example shown, the pressure relief valve 355 is configured as a ball valve preloaded by a pressure relief spring 3552, which is integrated into a buffer piston 3561 preloaded by the spring force of a buffer spring 3562, such that the existing inlet 3567 of the hydraulic buffer 356 (through which the buffer piston 3561 can be loaded or subjected to system pressure P_sys) is fluidly connected to the outlet 3568 of the hydraulic buffer 356 leading to the cavity or housing (38) of the transmission (3) when the system pressure is above a predetermined system pressure level. Here, the buffer piston 3561 constitutes a housing element movable within the housing 3560 of the hydraulic buffer 356 for the pressure relief valve 355. Here, an inlet 3553 is provided in the buffer piston 3561, which is fluidly connected to the inlet 3567 of the hydraulic buffer 356. On its rear side, i.e., on the side opposite to inlet 3567, is a closing body seat 3551 for the closing body 3550 of the pressure relief valve 355, which is exemplarily implemented as a ball. A pressure-limiting spring 3552 presses the closing body 3550 against the closing body seat. Here, the spring force of the pressure-limiting spring 3552 is selected such that the closing body 3550 is only forced out of the closing body seat 3551 when the system pressure P_sys exceeds a predetermined maximum pressure for the actuator (340), thereby allowing hydraulic fluid to flow from inlet 3567 through inlet 3553 into the cavity 3565 of the buffer piston 3561. The pressure-limiting spring 3552 of the closing body 3550 and the pressure relief valve 355 is located within the cavity 3565.

[0060] On its side away from the inlet 3567, i.e., in the spring chamber of the damper spring 3562, the hydraulic damper 356 or damper housing 3560 exhausts gas toward the transmission cavity or reservoir (38) through a lateral outlet 3568. The cavity 3565 of the damper piston 3561 also has a lateral outlet 3554. The damper piston 3561 itself is axially movable in a known manner within the bore of the housing 3560 of the hydraulic damper 356. Because the pressure-limiting spring 3552 is spatially arranged inside the cavity 3565 and the damper spring 3562 is spatially arranged above the cavity 3565 of the damper piston 3561, the damper spring 3562 and the pressure-limiting spring 3552 are connected in series on the force side.

[0061] exist Figure 6In the upper part, the buffer piston 3561 is in its initial position, in which the system pressure P_sys does not have pressure fluctuations and pressure peaks that require hydraulic buffering, and in which position the maximum pressure to be protected by the pressure relief valve 355 has not yet been reached. The spring characteristic curve of the buffer spring 3562 of the preloaded buffer piston 3561 is in harmony with the pressure fluctuations and pressure peaks to be buffered and is relatively flat. The spring characteristic curve of the pressure relief spring 3552 of the preloaded closing body 3550 is in harmony with the maximum pressure to be protected and is therefore relatively steep.

[0062] exist Figure 6 In the lower part, the system pressure P_sys is at such a high level that the damper piston 3561 presses the damper spring 3562 to its block size. As a result, the cavity 3565 of the damper piston 3561 is now fluidly connected to the outlet 3568 of the damper housing 3560 via its outlet 3554 and thus also exhausts towards the transmission cavity or reservoir (38). Furthermore, in Figure 6 In the lower part, the system pressure P_sys present at the inlet 3567 exceeds the maximum allowable pressure, thereby opening the pressure relief valve 355. As a result, hydraulic fluid is now partially discharged into the transmission cavity or reservoir (38), so that the system pressure P_sys at the inlet 3567 is limited to the maximum allowable pressure.

[0063] exist Figure 7 The third structure example shown is in Figure 6 The pressure relief valve 355 shown is a simplified and space-saving variant that is also integrated into the damper piston 3561 of the hydraulic damper 356. This damper piston 3561 is similar to... Figure 6 The damper piston 3561 is axially movable within a bore in the housing 3560 of the hydraulic damper 356, wherein the upper end face of the damper piston 3561 can be loaded or be loaded by system pressure P_sys via an inlet 3567 provided in the housing 3560. This system pressure P_sys also acts on the hydraulic piston (341) of the parking lock actuator (340), which is not shown here. On the lower side of the damper piston 3561 opposite to the inlet 3567, the damper piston forms a spring chamber for a damper spring 3562, which preloads the damper piston 3561 relative to the housing 3560. Here, the spring chamber vents through an outlet 3568 toward the interior of the transmission (3) or the reservoir (38). Figure 6 As in the example, the spring characteristic curve of the buffer spring 3562 is coordinated with the pressure fluctuations and pressure peaks to be buffered.

[0064] and Figure 6Unlike other valves, the pressure relief valve 355 is now implemented as a spring-preloaded plate valve, arranged inside the longitudinal bore 3563 of the buffer piston 3561. A pressure-relief spring 3552, for preloading the pressure relief valve 355, is also arranged inside the longitudinal bore 3563 and presses the closing body 3550 of the pressure relief valve 355, now configured as an annular disc, against the now flat closing body seat 3551 on the buffer piston 3561. Here, the pressure-relief spring 3552 is supported on the buffer piston 3561 by a disc 3556 on a safety ring or locking ring 3558 engaging in the annular groove 3557 of the longitudinal bore 3563, such that the closing body 3550 is axially clamped between the closing body seat 3551 and the annular groove 3557. Spatially, the pressure-relief spring 3552 is arranged at least partially concentrically within the buffer piston spring 3562 according to the length of the guide of the buffer piston 3561 in the bore of the housing 3560.

[0065] The closing body 3550 of the pressure relief valve 355 is loaded with hydraulic fluid through an inlet 3553 located in the damper piston 3561 on its side opposite the pressure relief spring 3552. This inlet is permanently fluid-technically connected to an inlet 3567 located in the housing 3560 of the hydraulic damper 356. The spring characteristic curve of the pressure relief spring 3552 is designed such that the pressure relief valve 355 opens once the system pressure P_sys exceeds a predetermined maximum value. If the pressure relief valve 355 is open, the longitudinal orifice 3563 of the damper piston 3561 simultaneously serves as an outlet for excess hydraulic fluid caused by overpressure, which is then discharged via an outlet 3568 of the damper housing 3560 toward the interior of the transmission (3) or the reservoir (38).

[0066] and Figure 7 Conversely, as illustrated in the diagram, it can also be specified that the disc-shaped closing body 3550 of the pressure relief valve 355 is laterally guided within the longitudinal bore 3563 of the buffer piston 3561. In this case, the closing body 3550 requires at least three star-shaped, i.e., symmetrically distributed working surfaces around its periphery. When the pressure relief valve 355 is open, the gaps between these working surfaces thus serve as lateral overflow channels for fluid transport from the inlet 3553 through the longitudinal bore 3563 to the outlet 3568.

[0067] Figure Labels

[0068] 1 motor vehicle

[0069] 2. Motor vehicle drive motor

[0070] 20 drive motor crankshaft

[0071] 3. Motor vehicle transmission

[0072] 30 Starting element between drive motor and transmission

[0073] 31 drive shaft of the transmission

[0074] Driven shaft of 32 gearbox

[0075] 33 transmission shift elements

[0076] Parking lock of 34-speed transmission

[0077] 340 parking lock actuator

[0078] 341 actuator hydraulic piston

[0079] 342 locking device

[0080] 343 Electrical components of locking device

[0081] 344 Locking Device Pin

[0082] 345 Parking Lock Engagement Spring

[0083] Pressure chamber of 346 actuator

[0084] 347 Pressure line to pressure chamber

[0085] Electro-hydraulic control device for 35 transmission

[0086] 350 Electromagnetically operable hydraulic valve for an electro-hydraulic control device used to operate shift elements.

[0087] 351 Electromagnetically operable hydraulic valve for an electro-hydraulic control device for generating system pressure

[0088] 352 Pre-throttling unit

[0089] Throttling section of 353 pre-throttling unit

[0090] Check valve of 354 pre-throttling unit

[0091] Closing body of 3540 check valve

[0092] 3541 Check Valve Closing Body Seat

[0093] 3542 check valve spring

[0094] 355 pressure relief valve

[0095] 3550 pressure relief valve closing body

[0096] 3551 pressure relief valve closing body seat

[0097] 3552 pressure limiting spring

[0098] 3553 pressure relief valve inlet

[0099] 3554 pressure relief valve outlet

[0100] 3555 pressure relief valve exhaust device

[0101] 3556 disks

[0102] 3557 Annular Groove

[0103] 3558 Safety Ring

[0104] 356 Hydraulic Buffer

[0105] 3560 buffer housing

[0106] 3561 Buffer Piston

[0107] 3562 shock absorber spring

[0108] Longitudinal bore in the piston of 3563 damper

[0109] Inlet in the 3564 buffer piston

[0110] The cavity in the piston of the 3565 buffer

[0111] 3566 cavity outlet

[0112] 3567 buffer entry

[0113] 3568 buffer output

[0114] 3569 Control edge dimensions

[0115] 357 hydraulic lines

[0116] 36 Electronic control unit of the transmission

[0117] 37 transmission pump

[0118] 38. Storage tank; oil pan

[0119] 4. Drive axles of motor vehicles

[0120] 5. Operating device for transmission

[0121] A. Position of the hydraulic piston when the parking lock is disengaged.

[0122] E is the position of the hydraulic piston when the parking lock is engaged.

[0123] P_k clutch pressure

[0124] P_p pump pressure

[0125] P_sys system pressure

Claims

1. A device for operating a parking lock (34) of a transmission (3) in a motor vehicle (1), the device comprising an engagement spring (345) for engaging the parking lock (34), a hydraulically actuated actuator (340) for disengaging the parking lock (34), an electro-hydraulic control device (35), and an electronic control device (36), the electro-hydraulic control device hydraulically actuating a gear-forming shift element (33) of the transmission (3) and the actuator (340) as appropriate by pressure provided by a pump (37) of the transmission (3), the electronic control device electrically actuating electromagnetically actuated hydraulic valves (350, 351) of the electro-hydraulic control device (35) to pre-given different shift positions (P, R, N, D) and gears in the transmission (3). The electro-hydraulic control device (35) generates a system pressure (P_sys) pre-given by the electronic control device (36) as needed via one of the electromagnetically operable hydraulic valves. This system pressure ensures the pressure supply required by the shifting element (33) that forms the gear position and the actuator (340) as needed. The actuator (340) has a hydraulic piston (341) operatively connected to the parking lock (34). The hydraulic piston is axially movably supported in the housing of the actuator (340) and together with the housing forms a pressure chamber (346). This pressure chamber is loaded with system pressure (P_sys) through a hydraulic valve that generates the system pressure (P_sys) via a pressure line (347) when the parking lock (34) is disengaged, and is emptied through the pressure line (347) when the parking lock (34) is engaged. The hydraulic piston (341) can be mechanically locked in the engaged piston position (E) and the disengaged piston position (A) of the parking lock (34) by means of a locking device (342) operable by the electronic control device (36). Its features are, In the pressure line (347), a pre-throttling unit (352) is installed in the region between the hydraulic valve that generates the system pressure (P_sys) and the pressure chamber (346). The pre-throttling unit includes a throttling section (353) and a check valve (354). A pressure relief valve (355) is fluidically connected to the pressure line (347) between the pre-throttling unit (352) and the pressure chamber (346). A hydraulic damper (356) is fluidly connected to the pressure line (347) between the pre-throttling unit (352) and the pressure chamber (346). The pressure relief valve (355) is integrated into the hydraulic damper (356). The throttling section (353) acts to limit the volumetric flow rate not only in the input direction toward the pressure chamber (346) but also in the return direction of the pressure chamber, while the check valve (354) is closed in the input direction toward the pressure chamber (346) and open in the return direction of the pressure chamber (346).

2. The device according to claim 1, characterized in that, The throttling unit (353) and the check valve (354) are connected in parallel in fluid technology.

3. The device according to claim 1, characterized in that, The throttling unit (353) and the check valve (354) are connected in series in fluid technology.

4. The device according to any one of claims 1 to 3, characterized in that, The hydraulic damper (356) is configured as a deformable elastomeric element under pressure, which engages in a branch of the pressure line (347) that is closed toward the inner cavity of the transmission (3).

5. The device according to any one of claims 1 to 3, characterized in that, The hydraulic damper (356) is configured as a damper piston (3561) preloaded against the system pressure (P_sys) by the spring force of the damper spring (3562), the damper piston being movably arranged in an exhaust port of the housing (3560) of the hydraulic damper (356) facing the inner cavity of the transmission (3).

6. The device according to claim 5, characterized in that, The pressure relief valve (355) is formed by the spring force of the damper spring (3562) in conjunction with a predetermined control edge dimension (3569), and the damper piston (3561) must move at the control edge dimension to fluidly connect the inlet (3567) of the hydraulic damper (356) to the outlet (3568) of the hydraulic damper (356) leading to the inner cavity of the transmission (3).

7. The device according to claim 6, characterized in that, The damper spring (3562) has a progressive spring characteristic curve, such that the inlet (3567) of the hydraulic damper (356) is fluidically connected to the outlet (3568) of the hydraulic damper (356) only when the pressure is above a predetermined system pressure level.

8. The device according to claim 6, characterized in that, The damper spring (3562) is formed by mechanically connecting two springs with different spring characteristic curves, wherein the first spring of the two springs has a flat spring characteristic curve designed to dampen the damper piston (3561), while the second spring of the two springs has a steep spring characteristic curve designed to open the pressure relief valve (355).

9. The device according to claim 8, characterized in that, The two springs are mechanically connected in series.

10. The device according to claim 5, characterized in that, The pressure relief valve (355) is configured as a valve preloaded by a pressure relief spring (3552), which is integrated in the damper piston (3561) such that the inlet (3567) of the hydraulic damper (356) is fluidly connected to the outlet (3568) of the hydraulic damper (356) leading to the cavity of the transmission (3) when the pressure is above a predetermined system pressure level.

11. The device according to claim 10, characterized in that, The pressure-limiting spring (3552) is arranged concentrically inside the buffer spring (3562).

12. The device according to any one of claims 1 to 3, characterized in that, The pre-throttle unit (352) is an integral part of the electro-hydraulic control device (35) of the transmission (3).

13. The device according to any one of claims 1 to 3, characterized in that, The pre-throttling unit (352) is an integral part of the actuator (340).

14. The device according to any one of claims 1 to 3, characterized in that, The throttle section (353) and the check valve (354) are integral components of the electro-hydraulic control device (35) of the transmission (3), while the pressure relief valve (355) is integral component of the actuator (340).

15. The device according to any one of claims 1 to 3, characterized in that, The throttle section (353), check valve (354) and hydraulic damper (356) are integral components of the electro-hydraulic control device (35) of the transmission (3), while the pressure relief valve (355) is integral component of the actuator (340).

16. The device according to any one of claims 1 to 3, characterized in that, The throttle section (353) and the check valve (354) are integral components of the electro-hydraulic control device (35) of the transmission (3), while the pressure relief valve (355) and the hydraulic damper (356) are integral components of the actuator (340).

Images