Device for actuating a locking mechanism, in particular for actuating a parking lock device

Abstract

Device (1) for actuating a locking mechanism, in particular for actuating a parking lock device of a drive train of a vehicle equipped with an automatic transmission, comprising at least one piston unit (3) spring-loaded in the closing direction of the locking mechanism and hydraulically actuated in the opening direction of the locking mechanism and axially displaceable, a detent device (4) which automatically activates in an axial position of the piston unit (3) equivalent to an open state of the locking mechanism for holding the piston unit (3) in the axial position equivalent to the open state of the locking mechanism, and an actuating device (5) with an electromagnet (17) for actuating a release element (6) which is provided for deactivating the detent device (4) and which is operatively connected to an armature element (8) associated with the electromagnet (17),wherein the release element (6) and the armature element (8) are acted upon by an adjusting device (9) with an actuating force acting in the direction of a position equivalent to the deactivated operating state of the locking device (4), characterized in that the actuating device (5) is designed with a permanent magnet (14) by means of which the armature element (8) with the release element (6) is held in a position equivalent to the activated operating state of the locking device (4) against the actuating force of the adjusting device (9) in the unenergized operating state of the electromagnet (17) and when the distance between the permanent magnet (14) and the armature element (8) is less than a predefined air gap, and a magnetic field of the permanent magnet (14) is superimposed on the magnetic field of the electromagnet (17) in the energized operating state of the electromagnet (17) in such a way thatthat the release element (6) with the armature element (8) can be moved via the adjusting device (9) into its position that deactivates the locking device (4), such that, when a corresponding request exists to engage a parking lock device or to close the locking mechanism, the electromagnet (17) is energized, thereby generating a so-called extinguishing pulse from the electromagnet (17), which weakens the magnetic field of the permanent magnet (14) to such an extent that the locking device (4) is deactivated and the armature element (8) and the release element can no longer be held by the permanent magnet (14) in the position equivalent to the activated operating state of the locking device (4) against the actuating force of the adjusting device.

Description

The invention relates to a device for actuating a locking mechanism, in particular for actuating a parking lock device of the type defined in more detail in the preamble of claim 1. From DE 10 2005 001 548 A1, a device for actuating a parking lock mechanism is known, in which a parking lock pawl is actuated via a hydraulic parking lock cylinder. The parking lock is engaged by hydraulically pressurizing a differential surface of the parking lock cylinder. In the engaged position, the parking lock cylinder can be fixed by means of an electromechanical locking device, so that when the hydraulic actuating pressure is released, the parking lock cylinder remains in its current position, which is equivalent to the designed operating state of the parking lock pawl or the parking lock itself. Vehicles equipped with such functionality are preferably fitted with automatic transmissions or automated transmissions, in order to enable, for example, the use of a car wash while, as required, a drive engine designed as an internal combustion engine is switched off and while a power flow of a vehicle drive train in the area of ​​the transmission is interrupted. Since in many transmission systems the transmission oil pump, which supplies oil to the transmission and also to the parking lock system, is driven by the drive engine, the oil supply is interrupted when the drive engine is switched off without additional measures such as an electrically driven auxiliary pump. In such operating conditions, the previously described locking device, known from the prior art, prevents the parking lock from engaging on its own. A disadvantage is that a coil of the electromagnet in the electromechanical locking device must be continuously energized to maintain the operating state of the device, in which the spring-loaded parking lock cylinder is held in the position equivalent to the designed operating state of the parking lock. This continuous energization of the electromechanical actuator leads, on the one hand, to undesirable heating in the area of ​​the electromagnet and, on the other hand, to a strain on the vehicle's electrical system and the electromagnet itself, as well as reducing the electromagnet's lifespan. If the parking lock system known from DE 10 2005 001 548 A1 is used in combination with an automatic hybrid transmission, in which the connection of an internal combustion engine to the automatic hybrid transmission is made via an engine disconnect clutch that opens when a mechanical transmission emergency mode is engaged to disconnect the internal combustion engine from the transmission input of the automatic hybrid transmission, the transmission pump driven by the internal combustion engine for the hydraulic supply of the automatic hybrid transmission is also decoupled from the drive of the internal combustion engine. If a vehicle-side ABS system fails simultaneously during a locking braking maneuver, a so-called mechanical transmission emergency mode is triggered in the automatic hybrid transmission, thereby simultaneously failing the pressure and power supply to the transmission control unit of the automatic hybrid transmission. If such an unfavorable operating condition of a vehicle occurs, the parking lock cylinder cannot be held in its position equivalent to the designed operating state of the parking lock by either the hydraulic system or the electromechanical locking device. Consequently, the parking lock engages due to the spring mechanism acting on the parking lock cylinder in the direction of its engaged position, permanently blocking the vehicle's movement via the parking lock. The parking lock remains engaged even after the end of full braking. From DE 103 47 667 A1, a locking unit for locking the movement of a piston in a parking lock system of automatic transmissions is also known. An armature or armature rod of an electromagnet is associated with an actuating element and interacts with it in such a way that a detent element, which in turn can be actuated by the actuating element, blocks the movement of the piston in a locking position, or the detent element releases the movement of the piston in an unlocking position. The armature or armature rod is moved against the force of a spring, thus allowing the electromagnet, or the armature or armature rod, to be reliably moved between two end positions depending on the current applied to the electromagnet. A first position of the armature or armature rod is determined by the arrangement of the spring acting on the armature or armature rod when the electromagnet is not energized, while the second position is assumed when the electromagnet is energized and the force acting on the armature due to the current is greater than the force of the spring. Passive safety is ensured by the fact that the piston's unlocked position is present when the electromagnet is de-energized. This guarantees that if the electromagnet's power supply fails, for example, when a vehicle is parked or in the event of a system fault, the actuating element is moved directly or indirectly by the armature rod, so that the spring moves the actuating element from the locked to the unlocked position. The unlocked piston is then moved in such a way that a parking pawl can be engaged in the drivetrain to block the drivetrain. Alternatively, it is also proposed that the actuating element be held in the unlocked position against the spring force when the electromagnet is energized. However, a disadvantage of this approach is that the electromagnet must be continuously energized to maintain the unlocked position. The magnetic force required to move the actuating element from the locked to the unlocked position, and which must be provided by the electromagnet, is very high due to its characteristics. This high force can only be achieved by using a sufficiently large electromagnet. Such a large electromagnet, in turn, leads to an undesirably large installation space requirement for the locking unit and also results in high manufacturing costs. Further locking units are known from DE 10 2007 000 637 A1 or DE 10 2004 030 007 A1. The present invention is therefore based on the objective of providing a space-saving and cost-effective device for actuating a locking mechanism, by means of which an unwanted activation of the locking mechanism in the event of a power and pressure failure is reliably avoided. According to the invention, this problem is solved with a device having the features of claim 1. The device according to the invention for actuating a locking mechanism, in particular for actuating a parking lock device of a drive train of a vehicle equipped with an automatic transmission, comprises at least one piston unit which is spring-loaded in the closing direction of the locking mechanism and hydraulically actuated in the opening direction of the locking mechanism and arranged to be displaceable in the axial direction, a detent device which automatically activates in an axial position of the piston unit equivalent to an open state of the locking mechanism in order to hold the piston unit in the axial position equivalent to the open state of the locking mechanism and an actuating device with an electromagnet for actuating a release element which is provided for deactivating the detent device and which is operatively connected to an armature element associated with the electromagnet.The release element and the anchor element are acted upon via an adjusting device with an actuating force acting in the direction of a position equivalent to the deactivated operating state of the locking device. According to the invention, the actuating device is equipped with a permanent magnet by means of which the armature element with the release element is held in a position equivalent to the activated operating state of the de-energized electromagnet and when the distance between the permanent magnet and the armature element is less than a predefined air gap, against the adjusting force of the adjusting device. Additionally, a magnetic field of the permanent magnet is superimposed on the magnetic field of the electromagnet when the electromagnet is energized, such that the release element with the armature element can be moved via the adjusting device into its position that deactivates the deactivating the deactivating device. With the device according to the invention, it is thus possible to open the locking mechanism when the piston unit is pressurized and to close it via a spring device when the piston unit is depressurized. To open the locking mechanism, the piston unit is pressurized with hydraulic pressure until the self-activating detent device holds the piston unit in a position equivalent to the open operating state of the locking mechanism. Simultaneously, the release element, together with the armature element, is guided towards the permanent magnet and, when the predefined air gap is breached, is held by the permanent magnet in a position equivalent to the activated operating state of the detent device, against the adjusting force of the adjusting device. If a corresponding request is made to engage a parking lock or to close the locking mechanism, the electromagnet is energized, generating a so-called extinguishing pulse. This pulse weakens the magnetic field of the permanent magnet to such an extent that the locking mechanism is deactivated. Consequently, the permanent magnet can no longer hold the armature and release elements in the position equivalent to the activated operating state of the locking mechanism, contrary to the actuating force of the adjusting mechanism. The release element is then moved by the adjusting mechanism into the position equivalent to the deactivated operating state of the locking mechanism. This, in turn, causes the now depressurized piston unit to be moved by the spring in the closing direction of the locking mechanism, thus closing the locking mechanism. Both holding the locking mechanism in the closed operating state and holding the locking mechanism in the open operating state are ensured when the electromagnet is not energized, thus eliminating the need for a permanent energization of the electromagnet to represent the two essential operating states of the locking mechanism, preventing heat generation in the area of ​​the electromagnet, and avoiding an undesirably high load on the vehicle's electrical system. Furthermore, the electromagnet can be dimensioned smaller compared to solutions known from the prior art, since the electromagnet only needs to reduce the magnetic field of the permanent magnet to a value at which the armature element and the release element can be moved together by the adjusting device into their position equivalent to the deactivated operating state of the locking device against the magnetic force of the permanent magnet. Additionally, unwanted engagement or closing of the locking mechanism or a parking lock device is prevented in the event of a simultaneous failure of the pressurization of the piston unit and the power supply to the electromagnet, since the armature element and the release element are held by the permanent magnet in the open operating state of the locking mechanism in a position equivalent to the activated operating state of the detent device and are only moved to the position equivalent to the deactivated operating state of the detent device when the electromagnets are energized, at which point the locking mechanism can be moved to its closed operating state. In a further development of the device according to the invention that is particularly space-saving in the axial direction, the anchor rod can be guided by the permanent magnet. If the permanent magnet is arranged radially within a coil of the electromagnet, the device can also be designed to be space-saving in the axial direction. In a further advantageous embodiment of the device according to the invention, the electromagnet has two coils, one coil being energized by a circuit controlled by an electronic transmission control unit, and the second coil being arranged in a circuit supplied with current by another electronic control unit. Thus, even in the event of a failure of one electronic transmission control unit, the device according to the invention can be actuated via the second coil, and the locking mechanism can be moved from its open operating state to its closed operating state by energizing the second coil accordingly. Another advantageous embodiment of the device according to the invention is equipped with a switch by means of which the coil, which is supplied with current via the additional electrical control unit, can be switched on in the event of a fault in the area of ​​the electronic transmission control unit. Advantageously, it is possible to actuate the switch automatically in the event of a fault or to switch it manually by an operator in order to manually activate the full functionality of the device for actuating the locking mechanism. The switching device can include a flip-flop switch or a diode circuit. In further advantageous embodiments of the device according to the invention, the coils are arranged at least partially at least approximately coaxially to each other and / or at least partially at approximately next to each other in the axial direction. Both the features specified in the claims and those specified in the following embodiments of the device according to the invention are each suitable, individually or in any combination, for further developing the subject matter of the invention. The respective combinations of features do not represent any limitations with regard to the further development of the subject matter according to the invention, but are essentially merely exemplary. Further advantages and advantageous developments of the device according to the invention will become apparent from the claims and the exemplary embodiments described below with reference to the drawing, whereby the same reference numerals are used in the description of the various exemplary embodiments for structurally and functionally identical components for the sake of clarity. Figure 1 shows a longitudinal sectional view of various exemplary embodiments of the device according to the invention for actuating a locking mechanism in the open operating state of the locking mechanism with the detent device activated simultaneously; Figure 2 shows the embodiments of the device according to Figure 1 with the locking mechanism closed and the deactivated detent device simultaneously; and Figure 3 shows a longitudinal sectional section of an exemplary further development of the device according to Figure 1. Fig. 1 shows a schematic longitudinal sectional view of a device 1 for actuating a locking mechanism (not shown in detail), which in this case is a parking lock device of a motor vehicle drive train equipped with an automatic transmission, as is known per se. The device 1 comprises, in a manner known per se, a piston unit 3, which can be pressurized with a fluid and, depending on the fluid pressure, actuates in the opening direction of the locking mechanism against a spring device (not shown in detail) acting in the closing direction of the locking mechanism, and is axially displaceable in a cylinder 2. In the assembled state, the piston unit 3 is connected to a parking rod of the parking lock device in a manner not shown in detail, wherein the parking rod in turn is coupled to a parking lock pawl in such a way that the parking lock pawl can be brought into engagement with a parking lock wheel connected to the output of the drive train in a rotationally fixed manner due to an axial movement of the piston unit 3 and the parking rod connected thereto, in order to represent an output that is rotationally fixed, or can be led out of engagement with the parking lock wheel, whereby the output is then rotatable. Furthermore, the device 1 is designed with a detent device 4 that automatically activates in an axial position of the piston unit 3 equivalent to an open position of the locking mechanism, in order to hold the piston unit 3 in the axial position equivalent to the open position of the locking mechanism. Additionally, the device 1 is designed with an electromagnetic actuating device 5 for actuating a release element 6, which is provided for deactivating the detent device 4 and is connected to an anchor rod 7 and, together with the anchor rod 7 and an anchor element 8 operatively connected thereto, is arranged to be longitudinally movable inside the cylinder 2. The release element 6, the anchor rod 7, and the anchor element 8 are acted upon by an adjusting device 9 with an actuating force acting in the direction of a position equivalent to the deactivated operating state of the locking device 4. For this purpose, the adjusting device 9 comprises a spring assembly 10, which is arranged between a housing-fixed component 11 and the release element 6 and is pushed onto the anchor rod 7. The release element 6, which is arranged to be longitudinally movable on the anchor rod 7 opposite the spring assembly 10, is pressed by the spring assembly 10 against a stop 12 of the anchor rod 7 in the direction of the piston unit 3. The device 1 shown in Fig. 1 has the following operating mode in normal operation, during which the piston unit 3 can be pressurized with fluid pressure in the area of ​​an effective surface 13 and the electromagnetic actuating device 5 can be energized: Starting from the operating state shown in Fig. 1, in which the release element 6, the anchor rod 7 and the anchor element 8 are held in their axial position equivalent to an activated operating state of the detent device 4 against the spring force of the spring device 10 by a permanent magnet 14 of the electromagnetic actuating device 5, the piston unit 3 is in an axial position equivalent to an open state of the locking mechanism or the parking lock device. The detent device 4 is activated, so that the piston unit 3 is held by spring arms 15, 16, of which 16 are shown in Fig. 1.Figure 1 shows only two of preferably four spring arms, which are arranged evenly distributed around the circumference of the piston unit 3, held in such a way that automatic engagement of the parking lock pawl is reliably prevented even when no fluid pressure is applied to the working surface 13 of the piston unit 3. The permanent magnet 14 is arranged radially within a coil 24 of the electromagnet 17 to minimize space requirements. If the parking lock is to be engaged based on a driver request, preferably via a gear selector, an electromagnet 17 of the electromagnetic actuating device 5 is energized. This causes the magnetic field of the electromagnet 17 to superimpose on the magnetic field of the permanent magnet 14, thus reducing the magnetic holding force of the permanent magnet 14. Due to the reduced magnetic force of the permanent magnet 14, the release element 6 is moved by the spring force of the spring assembly 10 of the adjusting device 9 from the position shown in Fig. 1 to the axial position shown in Fig. 2, which deactivates the locking device 4. In doing so, the release element 6, together with the armature rod 7 and the armature element 8, is increasingly pushed towards the piston unit 3 between the spring arms 15 and 16 of the locking device 4. As the adjustment path increases, the release element 6, with its end facing the piston unit 3 and featuring a conical guide surface 18, engages with guide areas 19 of the spring arms 15 and 16 that correspond to the guide surface 18 of the release element 6 and are at least approximately cylindrical. The spring arms 15 and 16 are thereby pushed further and further outwards by the release element 6 against an inherent, radially inward spring force preload until the frictional connection between the detent device 4 and the piston unit 3 is released. This frictional connection is between the claw areas 20 of the spring arms 15 and 16 and a detent area 21 of the piston unit 3, which adjoins a reduced diameter area 22. If a resultant force component acting in the closing direction of the locking mechanism or the parking lock device acts on the piston unit 3, and this force component is composed of a spring force from the spring assembly acting in the piston unit 3 and the fluid pressure currently applied to the working surface 13, the piston unit 3 is displaced away from the electromagnetic actuating device 5 until the parking lock device is engaged. With the parking lock device engaged, the piston unit 3 is displaced from the engagement range of the spring arms 15, 16, and the detent device 4 is simultaneously deactivated. The current to the electromagnet 17 is switched off in this operating state of the device 1. The release element 6 is held in the axial position shown in more detail in Fig. 2 by the spring force of the spring assembly 10. If, starting from the aforementioned operating state of the device 1, the working surface 13 is again subjected to a fluid pressure, preferably pneumatically or hydraulically generated, and a resulting total force component acts on the piston unit 3 in the direction of the release element 6, the piston unit 3 is displaced in the direction of the detent device 4. If, due to the fluid pressure acting on the working surface 13, the piston unit 3 is moved axially from its axial position equivalent to the closed state of the locking mechanism towards the electromagnetic actuating device 5, the piston unit 3, with its detent area 21, comes to rest against the anchor rod 7 and displaces it together with the release element 6 and the anchor element 8 against the spring force of the spring device 10 of the adjusting device 9.The release element 6 is disengaged from the engagement with the spring arms 15 and 16, and the spring arms 15 and 16 pivot inwards due to their spring preload into the position equivalent to the activated operating state of the detent device 4. When the piston unit 3 is in a corresponding axial position, the spring arms 15, 16 engage with their claw areas 20 behind the detent area 21 in the region of the reduced diameter area 22 of the piston unit, as shown in Fig. 1. Due to the axial adjustment of the armature element 8 with the armature rod 7 and the release element 6, the air gap between the armature element 8 and the permanent magnet 14 decreases. When the air gap between the armature element 8 and the permanent magnet 14 falls below a predefined threshold, the attractive force exerted on the armature element 8 by the magnetic field of the permanent magnet 14, while the electromagnet 17 is simultaneously de-energized, is greater than the spring force of the spring assembly 10 of the adjusting device 9. The armature element 8, together with the armature rod 7 and the release element 6, is then held by the permanent magnet 14 in a position equivalent to the deactivated operating state of the locking device 4. In the movement of the release element 6, the armature rod 7 and the armature element 8 described above in the direction of the permanent magnet 14, the armature rod 7, which is arranged coaxially to the permanent magnet 14 and also to the electromagnet 17, is pushed through the permanent magnet 14 in the direction of a housing-side end stop 23. In further alternative embodiments of the device 1 shown in Figs. 1 and 2, the electromagnet 17 is each configured with two coils 24a, 24b, which are either arranged side by side in the axial direction or coaxially. The coils 24A and 24B arranged side by side in the axial direction are indicated by the line L1, shown in Figs. 1 and 2 and rendered as a dashed line, which represents the dividing line between the two coils 24A and 24B. In the embodiment of the device 1 in which coil 24A radially surrounds coil 24B, a dividing line L2 between coils 24A and 24B is shown as a double-dotted line. Both the axially adjacent coils 24A and 24B and the coaxially arranged coils 24A and 24B are each supplied with current via separate circuits, wherein the coil 24A can be controlled by an electronic transmission control unit of the automatic transmission via the associated circuit, while the second coil 24B is arranged in a circuit separate from the circuit of the coil 24A, which can be supplied with current via another preferably vehicle-side electrical control unit 25. A switching device is provided by means of which coil 24B, which is supplied with power via the additional electrical control unit, can be activated in the event of a fault in the area of ​​the electronic transmission control unit. The switching device can be implemented, for example, with a flip-flop switch or a diode circuit. In the embodiments of the device 1, each equipped with two coils 24A, 24B, in the event of a power failure in the area of ​​the electrical transmission control, it is possible to deactivate the locking device 4 and close the locking mechanism or engage the parking lock device via the additional coil 24B and the second independent current path. Fig. 3 shows a schematic longitudinal section of the device 1 shown in Fig. 1, now supplemented by possible further development details, in which it is proposed to extend the device 1 by a mechanically acting emergency release mechanism. For this purpose, it is provided that the armature element 8 can be pushed away from the permanent magnet 14 to release the locking mechanism of the parking lock device when the electromagnet 17 is in the de-energized state during a power failure, by applying a mechanical force F to the armature element 8 from the outside. In the embodiment shown in Fig. 3, the emergency release force F can be transmitted via a pressure pin 26 to the end stop 23 of the anchor rod 7, which is firmly connected to the anchor element 8. In this process, a section of this pressure pin 26 passes through a plug 27, which is arranged here by way of example on the end face of the electromagnet 17 opposite the locking device 4 for electrical contacting the electromagnet 17, and engages centrally in a housing element 28 of the electromagnetic actuating device 5 opposite the locking device 4 and the armature element 8. As already mentioned, the emergency release device shown in Fig. 3 is to be considered exemplary. Depending on the design-specific installation conditions, the person skilled in the art will modify both the position of the plug 27 and the design of the push pin 26 in a suitable manner.

Claims

Device (1) for actuating a locking mechanism, in particular for actuating a parking lock device of a drive train of a vehicle equipped with an automatic transmission, comprising at least one piston unit (3) spring-loaded in the closing direction of the locking mechanism and hydraulically actuated in the opening direction of the locking mechanism and axially displaceable, a detent device (4) which automatically activates in an axial position of the piston unit (3) equivalent to an open state of the locking mechanism for holding the piston unit (3) in the axial position equivalent to the open state of the locking mechanism, and an actuating device (5) with an electromagnet (17) for actuating a release element (6) which is provided for deactivating the detent device (4) and which is operatively connected to an armature element (8) associated with the electromagnet (17),wherein the release element (6) and the armature element (8) are acted upon by an adjusting device (9) with an actuating force acting in the direction of a position equivalent to the deactivated operating state of the locking device (4), characterized in that the actuating device (5) is designed with a permanent magnet (14) by means of which the armature element (8) with the release element (6) is held in a position equivalent to the activated operating state of the locking device (4) against the actuating force of the adjusting device (9) in the unenergized operating state of the electromagnet (17) and when the distance between the permanent magnet (14) and the armature element (8) is less than a predefined air gap, and a magnetic field of the permanent magnet (14) is superimposed on the magnetic field of the electromagnet (17) in the energized operating state of the electromagnet (17) in such a way thatthat the release element (6) with the armature element (8) can be moved via the adjusting device (9) into its position that deactivates the locking device (4), such that, when a corresponding request exists to engage a parking lock device or to close the locking mechanism, the electromagnet (17) is energized, thereby generating a so-called extinguishing pulse from the electromagnet (17), which weakens the magnetic field of the permanent magnet (14) to such an extent that the locking device (4) is deactivated and the armature element (8) and the release element can no longer be held by the permanent magnet (14) in the position equivalent to the activated operating state of the locking device (4) against the actuating force of the adjusting device. Device according to claim 1, characterized in that the release element (6) and the anchor element (8) are operatively connected to each other via an anchor rod (7). Device according to claim 2, characterized in that the anchor rod (7) can be guided by the permanent magnet (14). Device according to one of claims 1 to 3, characterized in that the permanent magnet (14) is arranged radially within a coil (24; 24A, 24B) of the electromagnet (17). Device according to one of claims 1 to 4, characterized in that the electromagnet (17) has two coils (24A, 24B), wherein one coil (24A) can be supplied with current by a circuit which can be controlled by an electronic transmission control unit, and the second coil (24B) is arranged in a circuit which can be supplied with current via another electrical control unit. Device according to claim 5, characterized in that the coils (24A, 24B) are arranged at least partially at least approximately coaxially to each other. Device according to claim 5 or 6, characterized in that the coils (24A, 24B) are arranged at least approximately next to each other in the axial direction, at least in certain areas. Device according to one of claims 5 to 7, characterized in that a switching device is provided by means of which the coil (24B) which can be supplied with current via the further electrical control unit can be switched on in the event of a fault in the area of ​​the electronic transmission control unit. Device according to claim 8, characterized in that the switching device comprises a flip-flop switch. Device according to claim 8, characterized in that the switching device comprises a diode circuit. Device according to one of claims 1 to 10, characterized in that the locking device (4) is designed with at least one spring arm (15, 16) operatively connected to the piston unit (3) in the axial position of the piston unit (3) equivalent to the open state of the locking mechanism, by means of which the piston unit (3) can be held in the axial position equivalent to the open state of the locking device (4) in the activated operating state. Device according to claim 11, characterized in that the spring arm (15, 16) is designed with a spring force preload which pivots the spring arm (15, 16) into its position locking the piston unit (3) and in a position of the release element (6) equivalent to a deactivated operating state of the locking device (4) is led by the release element (6) out of engagement with the piston unit (3) against the spring force preload. Device according to one of claims 1 to 12, characterized in that an emergency release device is provided with which, in order to release the previously activated locking device (4) in the current-free state of the electromagnet (17), the armature element (8) can be separated from the permanent magnet (14) by applying a mechanical force (F). Device according to claim 13, characterized in that the emergency release device has a pressure pin (26) which is axially displaceable into the electromagnet (17) and through which the mechanical force (F) can be transmitted to the anchor rod (7) connected to the anchor element (8).

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