WO2011072759A1

WO2011072759A1 - Locking device

Info

Publication number: WO2011072759A1
Application number: PCT/EP2010/005306
Authority: WO
Inventors: Michael Casimir; Christian Groh
Original assignee: Hydac Electronic Gmbh
Priority date: 2009-12-18
Filing date: 2010-08-28
Publication date: 2011-06-23
Also published as: EP2513493A1; DE102009058977A1

Abstract

The invention relates to a locking device for hydraulic cylinders such as actuators for working equipment and/or working and/or auxiliary cylinders for vehicle steering systems, both ends of the piston of the cylinder adjoining pressure chambers of the cylinder which are filled with hydraulic fluid and in which hydraulic pressure can be built up for movements of the piston, characterised in that a valve assembly (51) is connected upstream of a pressure chamber and can be switched between an open state and a closed state, in which the cylinder is hydraulically locked, and a switching device (71, 73) is provided, which can be actuated for alternately switching the valve assembly (51) between the open state and the closed state.

Description

locking device

The invention relates to a locking device for hydraulic cylinders such as actuators for implements and / or working and / or auxiliary cylinders for steering systems of vehicles, wherein the piston of the cylinder on both sides of the piston is filled with hydraulic fluid filled pressure chambers of the cylinder, in which for piston movements Hydraulic pressure is buildable.

When using hydraulic cylinders to generate working or control movements, it is essential for safe operation of the associated devices to be actuated or controlled that piston movements can be reliably blocked. This applies in particular to hydraulic cylinders whose pistons can be acted upon by fluid pressure on both sides in order to generate control or working movements in one or the other direction. As examples of a variety of applications for such hydraulic cylinder only applications in the field of construction equipment and forklifts or in hydraulic or hydraulic assist steering systems of vehicles are mentioned here. In such applications, during certain phases of operation, such as the stoppage of the machine or the vehicle concerned, piston movements of the cylinder must be reliably prevented, while in other phases of operation safe release of the working or control movements must be ensured. In view of this problem, the invention has the object to provide a locking device available, which meets the above-mentioned, operational requirements in particular. According to the invention this object is achieved by a locking device having the features of claim 1 in its entirety.

Accordingly, the invention provides on the one hand a hydraulic locking of the cylinder, wherein in a simple manner high holding forces can be realized, so that a high level of security against unintentional unlocking is ensured. Characterized in that the cylinder further for locking and unlocking a valve assembly is connected upstream, which is controllable by means of a switching device which is actuated such that a switching of the valve assembly between the open state and closed state alternately, a safe operation of the locking device with low Control effort allows.

Due to the hydraulic locking of the cylinder Zyl and thus offered, compared to a mechanical locking of the cylinder significantly increased security against unwanted unlocking, the invention is particularly suitable for securing steerable vehicles, such as theft or unauthorized startup by a Steering cylinder or an auxiliary cylinder of the steering system is locked by the locking device according to the invention during downtime of the vehicle.

In advantageous embodiments, the valve arrangement has a directional control valve, preferably in the form of a 2/2-way valve but possibly also in the form of a directional seat valve, and the switching device for moving the valve piston of the directional control valve has a displacement system which can be actuated by trigger pulses, around the valve piston per triggering impulse only one control movement in alternation between open and closed position to grant, so that the directional control valve between trigger pulses each remain bistable in the open or closed state. Thanks to the bistable state, the valve arrangement meets the basic operational requirements for a cylinder of a steering system for a vehicle, namely that the directional control valve must never close while driving and never open in the park state. The fact that the directional control valve between trigger pulses each remains in a stable state, a triggering pulse is required for a switching operation in each case. The system also fulfills the requirement that energy consumption takes place only during a switching operation.

In particularly advantageous embodiments, the displacement system for moving the valve piston has a coaxial with its movement guided pressure actuator, against the end of the valve piston through

Spring force is biased, wherein the switching device comprises an electromagnet which as trigger pulses an actuator body of the displacement system each one axially in the direction of the pressure actuator moving pressure force pulse issued, and wherein the displacement system includes a pressure actuator and the actuator body with each other coupling latching device which controls the axial movements of the Actuator body respectively in movements of the pressure actuator in axial switching positions, which correspond to the change in the open and closed positions of the valve piston. Characterized in that the actuator body and the pressure actuator of the displacement system are coupled to each other via a latching device such that in each case a pressure force pulse which moves the actuator body axially in the direction of the pressure actuator, to movements of Druckbetäti- gers in changing switching positions, the alternating correspond to the open and the closing Stell ung the valve piston, the generation of the trigger pulse is particularly easy to effect by electromagnetic actuation, for example by means of a so-called dummy magnet. The arrangement can advantageously be made so that the valve piston is biased by the force pressing against the pressure actuator pressing spring force into the closed position of the directional control valve, the valve piston may be biased by a coil spring which surrounds the pressure actuator facing the end of the valve piston ,

In order to ensure a particularly safe operation of the device, a position monitoring device signaling the positions of the valve piston can be provided.

In this respect, the procedure may advantageously be such that the position monitoring device has a permanent magnet on the valve piston and a Hall sensor or reed switch which responds to the magnetic field.

Alternatively, the arrangement can also be made such that the position-monitoring device on the valve piston has a structure forming a marking, which can be recognized by a signaling device. If the valve piston is a physically scannable structuring, the signaling device can be formed by a microswitch. Likewise, an optical marking (light-dark) on the valve piston comes into consideration, wherein the signaling device includes an optical sensor. A physical structure on the valve piston can also be detected by means of a signaling device containing a permanent magnet with associated field sensor.

The invention is explained in detail below with reference to the drawing. Show it: Fig. 1 in a schematically simplified representation in the manner of a circuit diagram an embodiment of the security system according to the invention;

Fig. 2 is a comparison with a practical embodiment slightly enlarged and the insight into the housing interior enabling perspective oblique view of a directional valve of the valve assembly of the embodiment;

3A to 3C are schematic diagrams for illustrating the operation of a latching device of the embodiment, wherein 3A a pressure actuator in the opening state of the directional valve corresponding first switching position, 3B show the pressure actuator in an intermediate position and 3C the pressure actuator in a second switching position, the closing state of

Directional valve corresponds;

Fig. 4 shows a comparison with a practical embodiment enlarged, schematically simplified and partly broken drawn perspective view of the locking device, and

FIGS. 5A to 5C of FIG. 2 are similar, but to a smaller scale, views, with FIGS. 5A, 5B and 5C showing the switch positions corresponding to the respective positions of FIGS. 3A, 3B and 3C of FIG. 3, respectively.

The invention is described below with reference to an example in which a steering located in a vehicle has a cylinder 1 as a system component. Fig. 1 shows a simplified overview of a hydraulic system in which the double-acting cylinder. 1 his on both sides of the piston 3 adjacent pressure chambers 5 and 7 is filled with hydraulic fluid. The piston rod 9 of the piston 3 is connected to the steering linkage at both (not shown) stub axles of the associated vehicle such that pressure build-up in the pressure chambers 5 and 7 generates steering movements of the wheels. The cylinder 1 is connected via leads 15 and 17 with a hydraulic system in connection, of which in Fig. 1, only a specific, the pressure chamber 5 upstream valve assembly 51 is indicated schematically, which is dargestel in detail in Fig. 2 and 5A to 5C , As a main component, the valve arrangement 51 has a 2/2-way valve 53 with an axially displaceable valve piston 55. FIGS. 2 and 5A show the valve piston 55 in the open position, in which the supply line 1 5 to the cylinder 1 is open via the valve connections 57 and 59. In this open position, the valve piston 55 is biased by means of a compression spring 61 located in the valve housing, which surrounds the end region 63 of the valve piston 55. At the end of the valve piston 55 opposite the end region 63 there is a permanent magnet 65 which, in cooperation with a position monitoring device 67, which in the present example has a Hall sensor 69, supplies a position signal indicating the axial position of the valve piston 55. By means of a latching device 71, via which the end region 63 of the valve piston 55 is coupled to an actuator in the form of an electromagnet 73, the directional control valve 53 is adjustable in two stable states, namely in the opening state shown in FIGS. 2 and 5A and in the in FIG 5C

Closed state in which the supply line 1 5 is locked. When so switched valve assembly 51, the cylinder 1 is hydraulically locked, the steering linkage thus blocked by the immovable piston rod against steering movements and thereby secured the vehicle.

In order to initiate a switching operation of the directional control valve 53, the electromagnet 73 is actuated in such a way that an actuating force 75 is exerted on an actuator body 75, see FIGS. 3 to 5, in order to move the actuator body 75 in FIG Direction to move to a located on the end portion 63 of the valve piston 55 pressure actuator 79 back. This axial movement is converted by means of a coupling between the actuator body 75 and end portion 63 of the valve piston 55 forming latching device 71 alternately in one of the two stable switching states of the directional control valve 53. The operation of this locking device 71 is explained in more detail with reference to FIGS. 3 and 4.

As can be seen most clearly from Fig. 4, the axial movement of the actuator body 75 takes place within a control body 77, relative to which the pressure actuator 79 is rotatably mounted on the end portion 63 of the valve piston 55. At the peripheral region of the pressure actuator 79 are inclined surfaces 81, which act in a in Fig. 3 A to 3B in more detail explanatory manner with inclined surfaces 83 and 85 on the control body 77 together. The inclined surfaces 81 are arranged on the pressure actuator 79 in each case in the same axial positions, while the inclined surfaces 83 and 85 occupy different axial positions on the control body 77, wherein the inclined surfaces 83 are closer to the valve piston 55 than the inclined surfaces 85 and wherein the axial distance between the Sloping surfaces 83 and 85 corresponds to the axial displacement of the valve piston 55 between the open and closed positions. In the state shown in FIGS. 2, 3A and 5A, which corresponds to the unswitched state of the directional control valve 53 in which the supply line 15 to the cylinder 1 is open, the latching device 71 is in the state as shown in the schematic diagram of FIG. 3A is. In this case, the pressure actuator 79 rests on the end region 63 of the valve piston 55 with its inclined surface 81 on the inclined surface 85 of the control body 77, ie, the valve piston 55 is in the most approximated to the electromagnet 73 axial position, that shown in FIGS. 2 and 5A , unswitched opening state corresponds. 3B illustrates the state in which a trigger pulse for switching the directional control valve 53 in the closed state, which is shown in Fig. 5C, an axial movement of the actuator body 75 in Fig. 3 downwards, ie in Fig. 5B to the left, has caused, whereby the valve piston 55 has performed from the open position out a maximum displacement stroke. Upon reaching this state shown in Fig. 3B, the torque generated by the cooperating inclined surfaces 81 and 85 leads to a rotational movement of the pressure actuator 79, as indicated in Fig. 3B with a rotation arrow 87, whereby the inclined surface 81 from their abutment against the inclined surface 85 of the control body 77 transitions to the next control surface 83, the latching device 71 therefore changes from the operating state shown in FIG. 3B to the state shown in FIG. 3C, in which the pressure spring 61 controls the pressure actuator 79 and thus the valve piston 55 in FIG. 3C has returned to the top and to the right in FIG. 5C, so that now the directional control valve 53 is in the closed state. Between actuations of the latching device 71, ie between generated by the electromagnet 73 trigger pulses, in each case a transition of the inclined surface 81 of the pressure actuator 79 passes to the alternating inclined surfaces 83 and 85 of the Steuerköpers 77, which, to the sequence of inclined surfaces 83 and 85 recognizable 3A, 3B and 3C is shown schematized in development, the directional control valve 73 is in each case in a bistable manner in one of its two states. In other words, a positive trip pulse is required to lock or unlock the system.

If the locking device for the operation of the vehicle is not activated and the valve assembly 51 is in the release state, the steering system is normally operable, the directional control valve 29 is in the supply line 15 in the open position, so that the piston 3 of the cylinder 1 is free to move.

Claims

P a n t a n s p r e c h e

Locking device for hydraulic cylinders such as actuators for implements and / or working and / or auxiliary cylinders for steering systems of vehicles, wherein the piston (3) of the cylinder (1) on both sides of the piston filled with hydraulic fluid pressure chambers (5, 7) of the cylinder (1) adjacent, in which hydraulic pressure is buildable for piston movements, characterized in that a pressure chamber (5) upstream valve assembly (51) is present, which is switchable between an open state and a closed state in which the cylinder (1) is hydraulically locked, and that a switching device (71, 73) is provided, which is operable for an alternating switching of the valve arrangement (51) between the open state and the closed state.

Locking device according to claim 1, characterized in that the valve arrangement (51) has a directional control valve (53) and that the switching device (71, 73) for moving the valve piston (55) of the directional control valve (53) has a displacement system (75, 77, 79 ), which can be actuated by trigger pulses to give the valve piston (55) per trigger pulse only one control movement in alternation between open and Schließstell ung, so that the directional control valve (53) between each triggering bistable remains in the open or closed state.

Locking device according to claim 2, characterized in that the displacement system for moving the valve piston (55) has a coaxial with its movement guided pressure actuator (79), against the end of the valve piston (55) is biased by spring force (61) that the switching device a Electromagnet (73) which acts as triggering pulses on an actuator body (75) of the displacement system. because it imparts a compressive force pulse moving axially toward the pressure actuator (79), and that the displacement system includes a latching device (71) coupling the pressure actuator (79) and the actuator body (75) to each other to control the axial movements of the actuator body (75) respectively Moves the pressure actuator (75) converts into axial switching positions corresponding to the change in the open and closed positions of the valve piston (55).

Locking device according to claim 3, characterized in that the latching device (71) of the displacement system at the peripheral region of about the axis of the valve piston (55) rotatable pressure actuator (79) at least one inclined surface (81) on a non-rotatably held control body (77) more with the respective Inclined surface (81) of the pressure actuator (79) cooperating inclined surfaces (83, 85), which are located in the switching positions of the pressure actuator (79) corresponding, respectively, different, different axial positions and in the axial movements of the actuator body (75) rotation of the pressure actuator (79) for the transition from the inclined surface (81) on the change in each subsequent sloping surface (83 or 85) of the control body (77) effect.

Locking device according to claim 4, characterized in that the valve piston (55) by the force-locking against the pressure actuator (79) andrückende spring force (61) is biased in the closed position of the directional control valve (53).

Locking device according to claim 5, characterized in that the valve piston (55) by a coil spring (61) is biased, which surrounds the pressure actuator (79) facing the end region (63) of the valve piston (55).

7. Locking device according to one of claims 2 to 6, characterized in that the positions of the valve piston (55) signaling position monitoring device (67) is provided. 8. Locking device according to claim 7, characterized in that the position monitoring device (67) has a permanent magnet (65) on the valve piston (55) and responsive to the magnetic field Hall sensor (69) or reed switch. 9. Locking device according to claim 8, characterized in that the position monitoring device (67) on the valve piston (55) has a mark forming structure, which is recognizable by a signaling device. 10. Locking device according to claim 9, characterized in that the signaling device is formed by a permanent magnet with associated field sensor (69), a microswitch or an optical sensor.