EP1574720B1 - Electro-hydraulic control circuit and method of its deactivation - Google Patents

Abstract

The device has working lines, and load holding valves (LA, LB) in each working line. Each load holding valve is switched from a load holding position for opening respective working lines to a return system. A circulation switching assembly (U) is formed between a pressure source and the return system. Each load holding valve is designed as a 2/2-directional solenoid seat valve, which is switched open towards a return system.

Description

The invention relates to an electro-hydraulic control device specified in the preamble of claim 1 and according to claim 8, a method for switching off the control device.

In the generic, from DE 195 00 748 A known, electro-hydraulic control device, the circulation circuit has an adjustable throttle in the pressure supply line and upstream of the throttle directly from the pressure supply line against spring force pressure-controlled discharge valve in a provided from the pressure supply line to a return drain line.

At the EP 0 965 763 A known electro-hydraulic control device, the two load-holding valves of the working lines are hydraulically releasable check valves, and the two main-way solenoid seat valves are designed as 3/2-way magnetic seat valves, each of which blocks a working line from the pressure source and connects to the return, or shut off to the return and connects to the pressure source. The control line system is supplied with the control pressure from the respective higher working pressure leading working line to pressurize the circulation circuit. At the same time, the control pressure taken from the respective working pressure leading to the higher working pressure is used to unblock the load pressure in the load-bearing line closed by the pressure source, so that this working line is relieved to the return flow. Such electro-hydraulic control devices are preferably used for portable working devices such as screwdrivers, riveting tools, building displacement devices and the like. In these devices, extremely high working pressures can be built up, for example up to about 800 bar, with a pressure source operating at maximum pressure with a relatively low flow rate. Due to the high working pressures and the small flow, poppet valves are absolutely necessary, which have leak-free shut-off positions. With the hydraulically releasable check valves, which are used as load-holding valves, the effect occurs that after switching off the control device in at least one working line the working pressure is maintained. Due to the seat valves, this pressure remains for very long periods without noticeable waste. This is a significant operating hazard. In addition, it is sometimes necessary to disconnect the working line with the control device disconnected, which, however, can not be carried out at maintained working pressure or is dangerous for violent separation or pollutes the environment with the hydraulic fluid.

At one off US 2002/0162327 A known electro-hydraulic control device four 2/2-way proportional solenoid seat valves are provided in a bridge circuit between the two admission sides of the hydraulic motor and the pressure source or the tank. Between the pressure source and the return, a circulation circuit with two solenoid-operated 2/2-way valves is also provided. By means of a controller of the control device different operating modes are programmed, which can be controlled not only the speed-controlled retraction and extension of the hydraulic motor, but also a floating position, under load speed controlled retraction, a load-controlled under load extension, a tank make-up mode and include a tank and pump make-up mode. If, after the movement of the hydraulic motor controlled by the pressure source, the control device is switched off under pressure, then this increased pressure remains trapped in a working line.

At one off JP 571 07 486 A known multi-way valve without load-holding valves is in the neutral position a Abströmweg in Steuerkammem and loose loose fit of valve elements to the tank open. Only one working line can be relieved of pressure in each case.

In one EP 1338802 A known control device, both chambers of a hydraulic consumer via electro-hydraulic proportional valves are secured, each of which consists of a 2/2-solenoid proportional pressure control valve and a 2/2-hydraulic proportional valve. The load leak-free tight holding load-retaining valves are missing.

Also of interest are: US Pat. No. 6,705,079 B1 . US Pat. No. 6,328,275 B1 . US 2002/0162327 A1 ,

The invention has for its object to provide an electro-hydraulic control device of the type mentioned, whose operational hazard after switching off the Electro-hydraulic control device is reduced, and to provide a method for switching off the electro-hydraulic control device.

The stated object is achieved with the features of claim 1 and the method claim 8.

Since each load-holding valve is a 2/2-way magnetic seat valve which can be electrically switched to return flow, the working pressure in at least one working line need not be maintained permanently, but can be reduced to the return after a shutdown of the possibly high clogged working pressure by the switching magnet of a load-holding valve is briefly energized. This can be done routinely (via the associated control device) after each shutdown of the control device, or optionally in the event that a working pressure leading working line must be released after shutdown for some reason. The optional pressure relief of a working line under working pressure is expedient to carry out comfortably when it is derived after switching off the control device from the pressure source pending pressure on the circulation circuit. Then there is no significant pressure on the main-way seat valves, if to relieve a working line with a short switching pulse, the respective 2/2-way solenoid seat valve is switched to passage to the return. The circulation circuit is suitably operated by a load-dependent control pressure. The control pressure can be tapped directly or indirectly from the respective working line or via the control line system from the pressure line. Thus, the circulation circuit reliably enters the position for non-pressurized circulation, a magnetically confirmed control pressure relief seat valve is connected to the return line to the control line system for each working line. In normal operation, the relief seat valve is closed and leak-tight, so that the control pressure is reliably maintained. When the relief seat valve is opened, the control pressure collapses and the circulation circuit switches to the non-pressurized circulation position.

For structural and control simplification, it is expedient if the 2/2-way magnetic seat valve for the respective one working line and the main-way magnetic seat valve of the other working line have a common switching magnet. If one working line is acted on, the other working line is automatically relieved to return. A separate solenoid allows, however, to actuate the respective 2/2-way solenoid seat valve independently of the solenoid of the main-way solenoid seat valve, and to connect a pressurized working line to the return, by an optional actuation of the separate solenoid of the 2/2-way magnetic seat valve, whose working line is to be relieved.

Suitably, each relief seat valve is mitbetätigt by the solenoid of the main-way magnetic seat valve. Alternatively, however, it would be possible to give each relief seat valve its own switching magnet, which, for special situations, is actuated separately from the solenoid of the main path magnetic seat valve.

The relief seat valve may additionally be assigned the task of tapping the control pressure from the respective working line or, alternatively, from the pressure line. In this case, the relief seat valve is designed as a 3/2-way solenoid seat valve.

By contrast, in the event that the control pressure is tapped directly from the pressure line, the relief poppet valve may be a simple 2/2-solenoid seated valve designed only to process the pilot pressure, i. relatively compact, is to train.

As may be appropriate in such devices, the circulation circuit may include a 2/2-way pressure compensator circulation valve, conveniently also in poppet design, between the pressure line and the return. The seat valve design is suitable for high working pressures because of the leak-free shut-off position. In order to adjust the amount of the control pressure medium in the control line system exactly, it may be appropriate to assign the pressure compensator circulation valve a two-way flow regulator, which operates between the pressure line and the control line system.

• Fig. 1 ein Blockschaltbild einer nicht erfindungsgemäßen Ausführungsform einer elektrohydraulischen Steuervorrichtung zur Richtungssteuerung eines Hydroverbrauchers, wobei gestrichelt eine Ausführungsform angedeutet ist, bei der aus einer Druckquelle mehrere solcher elektrohydraulischer Steuervorrichtungen versorgt werden,
• Fig. 2 ein Blockschaltbild einer ersten erfindungsgemäßen Ausführungsform,
• Fig. 3 ein Blockschaltbild einer zweiten erfindungsgemäßen Ausführungsform,
• Fig. 4 ein Blockschaltbild einer dritten erfindungsgemäßen Ausführungsform,
• Fig. 5 ein Blockschaltbild einer vierten erfindungsgemäßen Ausführungsform, und
• Fig. 6 ein Blockschaltbild einer nicht erfindungsgemäßen Ausführungsform der elektrohydraulischen Steuervorrichtung.

Reference to the drawings, embodiments of the subject invention will be explained. Show it:

• Fig. 1 a block diagram of a non-inventive embodiment of an electro-hydraulic control device for direction control of a hydraulic consumer, wherein dashed lines an embodiment is indicated, are supplied from a pressure source, several such electro-hydraulic control devices,
• Fig. 2 a block diagram of a first embodiment of the invention,
• Fig. 3 a block diagram of a second embodiment of the invention,
• Fig. 4 a block diagram of a third embodiment according to the invention,
• Fig. 5 a block diagram of a fourth embodiment of the invention, and
• Fig. 6 a block diagram of a non-inventive embodiment of the electro-hydraulic control device.

An in Fig. 1 shown, non-inventive electro-hydraulic control device H is used for example for directional control of a hydraulic load or hydraulic motor, which is connected to two working lines A, B (not shown).

From a pressure source P, a pressure line 1 is supplied, from which a further pressure line 2 to two main-way solenoid seat valves VA, VB branches off for each working line A, B. In the embodiment in FIG Fig. 1 are the two main-way magnetic seat valves VA, VB 3/2-way magnetic seat valves, each actuated by a solenoid MA, MB. In non-energized solenoid MA, MB load lines A, B are shut off from the pressure line 2 and connected at the same time with return lines 3 and a return line 4 with a return R.

Leakage-free return valves 9 in the working lines A, B verhindem but a return flow.

Between the pressure line 1 and the return line 4, a circulation circuit U is contained in a line loop 5, which contains a conventional 2/2-way switching or control valve with leak-free seat function in the shut-off, with the derived from the pressure line 1 control pressure in the opening direction and is acted upon by a control line system 7 acting control pressure and a control spring in the closing direction.

The control line system 7 is connected to the working lines A, B output of the main-way magnetic seat valves VA, VB. The respective higher control pressure of a working line is brought via appropriately interconnected shuttle valves 8 to the closing side of the circulation circuit U.

The control line system 7 is connected via a bypass line 7 'to the return manifold 4, if the electro-hydraulic control device H is provided only for a hydraulic consumer. If, however, other similar or differently designed control devices connected to the pressure line 1 and the return manifold 4, then the control line system 7 shown can be connected via a connecting line 7 "to another shuttle valve 8 ', feeds the control pressure in the control line system, if the electro-hydraulic control device H. is not actuated or the control pressure in the shuttle valve 8 'is correspondingly high.

At a branch 10 of the working line B, a line 11 branches off to a branch 12 of the return line 3. In line 11, a 2/2-solenoid seat valve is provided as a load-holding valve LB, which is held by a spring 16 in the leak-free shut-off position shown. The 2/2-solenoid seat valve is solenoid operated, either via the solenoid MA of Hauptweg solenoid seat valve VA, or (indicated by dashed lines) via its own solenoid M, which can always be operated together with the solenoid MA.

Analog branches off for the working line A from a branch 13 a line 14 to a port 15 in the return line 3 from. In the line 14 is also included as a load-holding valve LA a 2/2-solenoid seat valve, which is actuated by the solenoid MB of the main-way magnetic seat valve VB (or optionally has its own switching magnet M).

Function:

In Fig. 1 the electro-hydraulic control device is switched off. If the pressure source P promotes the pressure medium is passed through the circulation circuit U in the return. If the hydraulic consumer to be acted upon via the working line A, at the same time the pressure medium is discharged via the working line B to the return, the solenoid MA is energized (function a) to change the main-way magnetic seat valve VA and the load-holding valve LB. Then, the pressure line 2 is connected to the working line A, and also the working pressure in the working line A is fed into the control line system 7. As a result, the circulation circuit U is brought into the shut-off position shown or held in this. The hydraulic consumer moves. Since the load-holding valve LB is in its passage position, the hydraulic medium is expelled from the working line B via the line 11 in the return line 3. If the solenoid MA de-energized again, then the results in Fig. 1 shown switching position. However, then in the working line A, the working pressure is locked up to the check valve 9 and the load-holding valve LA. The circulation circuit U connects the pressure line 1 with the return, so that the pressure line 2 is substantially depressurized. To reduce the working pressure from the working line A, it is then sufficient to briefly energize the solenoid MB and de-energize it, so that the load-holding valve LA briefly switches to passage and degrades the working pressure via the line 14 in the return line 3. Then both working lines A, B are substantially depressurized.

If the hydraulic consumer to move in the other direction of movement, then the solenoid MB is energized (function b), whereby the operation proceeds as explained, but with different flow directions, and with a control pressure in the control line system 7, which is effective on the other shuttle valve and the switching change-over valve 8 in the circulation circuit U.

In the electro-hydraulic control device A in Fig. 2 The two main-way magnetic seat valves VA, VB 2/2-way solenoid seat valves between the pressure line 2 and the working lines A, B. The load holding valves LB, LA are similar to the 2/2-solenoid seat valves of Fig. 1 , with the difference, in the shut-off position in both flow directions leak-tight shut off. The line parts 11a and 14a each lead directly to the return manifold 4. From the line part 11a branches off at a branch 17, a line 18 to a relief solenoid seat valve EA for the control line system 7, which also comes with a coming from a branch 19 line 20 with control pressure from the Working line A can be supplied. The relief solenoid seat valve EA in this embodiment is a 3/2-way magnetic seat valve operated by the solenoid MA, which also operates the load holding valve LB and the main-way solenoid seat valve VA. Alternatively (not shown) could the relief valve EA (or the load-holding valve LB) have their own switching magnet.

Similarly, at a branch 21 from the conduit part 14a, a conduit 22 branches off to a relief solenoid seat valve EB which is also formed as a 3/2-way magnetic seat valve and actuated by the solenoid MB of the other main-way solenoid seat valve VB. For tapping the control pressure for the control line system 7 via the relief solenoid seat valve EB, a branched off at a branch 23 of the working line B line 24 is connected, according to the line 20th

Function:

If the hydraulic consumer is to be controlled via the working line A, the switching magnet MA is energized (function a), which converts the valves VA, LB and EA substantially simultaneously into their other switching positions. The pressure line 2 is then connected to the working line A, while the working line B is connected via the line 11 and the conduit part 11 a to the return manifold 4. The control line system 7, which was previously relieved via the line 18 to return R, now leads the Control pressure from the working line A and the line 20. If the control device H is turned off, then initially the working pressure in the working line A is maintained, because the lines 20 and 14 are shut off leak-free, as well as the working line A itself. To the working pressure in the working line A, it is sufficient to energize the solenoid MB for a short time (function b) to reduce the working pressure via the line 14 and the load-holding valve LA and the line part 14a in the return line 4.

The embodiment of the electro-hydraulic control device H in Fig. 3 is different from that of Fig. 2 in that the control pressure for the control line system 7 is tapped directly from the pressure line 2. For this purpose lead from a branch 25 of the pressure line 2 lines 26 to the relief solenoid seat valves EA and EB. The other function corresponds to that of Fig. 2 ,

The embodiment of the Fig. 4 is different from those of Fig. 2 and 3 by another way of tapping the control pressure for the control line system 7. And although the control pressure is tapped directly at a branch 27 from the pressure line 1 here. The relief solenoid seat valves EA and EB are simple 2/2-way solenoid seat valves in the control line system 7, which also need to be designed only to the control pressure medium quantity, and leak-tight shut off only in the flow direction to the return R. The two relief magnetic seat valves EA and EB are arranged in series in the control line system 7. The function largely corresponds to that for the Fig. 2 and 3 explained function. To reduce the working pressure from the working line A after switching off the control device, the solenoid MB is briefly energized; however, to reduce the working pressure in the working line B briefly the solenoid MA.

The embodiment in Fig. 5 largely corresponds to that of Fig. 4 , The only difference is that in the control line system 7, the control pressure is tapped directly from the branch 27 in the pressure line 1, a two-way flow regulator Z is provided as part of the circulation circuit U, which doses the amount of the control pressure medium in the control line system 7 finely. The two-way flow regulator operates on the principle of a pressure compensator, the upstream of pilot pressures and downstream of a Throttle and a control spring is actuated. The other function corresponds to the in Fig. 4 explained.

The non-inventive embodiment in Fig. 6 corresponds largely to the embodiments of Fig. 4 and 5 , Different is the circulation circuit U, which is operated here without control line system with a working line 29, which leads from a branch 28 in the pressure line 1 via the series arranged in relief solenoid seat valves EA, EB to the return R. In this embodiment, the relief magnetic seat valves EA, EB are designed so that they can process the entire working flow from the pressure source in the non-pressurized circulation. The further function corresponds to that to the Fig. 4 and 5 described. To reduce the working pressure from the working line A, it is sufficient to briefly energize the switching magnet MB after switching off (function b); however, to reduce the working pressure in the working line B, a short-term actuation of the solenoid MA (function a).

Claims (8)

1. Electrohydraulic control device (H) for the directional control of at least one hydromotor, in particular for operating pressures up to more than about 450 bars in a portable working device, comprising two working lines (A, B), two main directional solenoid seat valves (VA, VB), and a pressure source (P), the working lines (A, B) and the pressure source (P) being selectively alternatingly connected and separated via a respective one of the main directional solenoid valves (VA, VB) all being separated from the pressure source (P), each working line (AB), containing a respective load holding valve (LA, LB) designed as a 2/2-ways solenoid seat valve, which is switched by a respective electrically excited switching solenoid (MA, MB, M) between a load holding position in the respective one working line into a through flow position towards a return system (R) for discharging pressure medium from the hydro-motor when the main directional solenoid seat valve (VA, VB) is in a switching position for connecting the pressure source (P) with the respective other working line, and a circulation switching assembly (U) which is active between the pressure source (P) and the return system (R) when the working lines (A, B) are separated from the pressure source (P), characterised in that the circulation switching assembly (U) is actuated via a pilot line system belonging to the electrohydraulic control device (H) by pilot pressure selectively taken directly or indirectly from a respective working line or from a pressure line connected to the pressure source (P), and that a solenoid actuated pilot pressure relieving solenoid seat valve (EA, EB) belonging to the electrohydraulic control device (A) is connected for each working line between the pilot line system (7) and the return (R) system.
2. Electrohydraulic control device according to claim 1, characterised in that the load holding 2/2-ways solenoid seat valve for one respective working line (A or B) and the main directional solenoid seat valve (VA, VB) for the respective other working line (B or) are actuated by a common switching solenoid (MA, MB).
3. Electrohydraulic control device according to claim 1, characterised in that the pilot pressure relieving seat valve (EA; EB) is switched open either by its own solenoid (M) actuated at the same time as the switching solenoid (MA; MB) of the main directional solenoid seat valve (VA, VB) associated to this working line (A or B), or is switched open directly by the switching magnet (MA, MB) of the main direction solenoid seat valve (VA, VB), respectively.
4. Electrohydraulic control device according to claim 1, characterised in that the pilot pressure relieving solenoid seat valve (EA, EB) is a 3/2-ways solenoid seat valve in a case where the pilot pressure is taken indirectly from the working line (A, B) or from the pressure line (1, 2), respectively.
5. Electrohydraulic control device according to claim 1, characterised in that the pilot pressure relieving solenoid seat valve (EA, EB) is a 2/2-ways solenoid seat valve in a case where the pilot pressure directly is taken from the pressure line (1, 2).
6. Electrohydraulic control device according to claim 1, characterised in that the circulation switching assembly (U) contains a 2/2-ways circulation pressure balance valve between the pressure line (1) and the return system (R), and that in the pilot line system a 2-ways flow regulating valve (Z) is associated to the 2/2-ways pressure balance circulation valve in the case that the pilot pressure directly is taken from the pressure line (1).
7. Electrohydraulic control device according to claim 1, characterised in that in the circulation switching assembly (U) both of the pilot pressure relieving solenoid seat valves (EA, EB) are designed to process the maximum pressure medium working flow and are arranged in series in a working flow path (29) from the pressure line (1) to the return system.
8. Method for switching-off the electrohydraulic control device (H) according to claim 1, characterised in that for relieving the working pressure out of one of the working lines (A or B) in which working line working pressure remained after switching off the electrohydraulic control device the switching solenoid (MA, MB, M) of that load holding valve (LA, LB) is electrically excited for a short time, which load holding valve (LA, LB) is associated to the working line (A or B) in which the working pressure remained.

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