The invention relates to a hydraulic valve device having a valve housing, with a pilot piston of a pilot valve, which piston can be actuated by an actuating device, and which piston can be moved in the direction of the valve seat of the valve housing by means of a first energy storage device, by means of the pilot piston a fluid port in the valve housing being connectable to a fluid chamber of a shut-off piston of a shut-off valve which activates at least one fluid-carrying connecting line of the valve device, and a fluid-carrying control line which discharges from the connecting line into the fluid chamber of the shut-off piston which can be moved in the direction of a second valve seat by a second energy storage device.
The hydraulic valve device according to the invention can be generically assigned to the so-called pilot-operated check valves which interact largely with directional valves and which are used to control a load. To initiate unblocking of the check valve, either an auxiliary pressure is connected via the directional valve, or the activating pressure of the directional valve is used directly. The auxiliary or activating pressure is then used as a so-called striking pressure in order to open a pilot valve which relieves the back of the shut-off piston. The load pressure in the working port then acts continuously on an annular surface on the shut-off piston and is opposed to the spring force of the now unloaded back. The activation piston of the pilot valve can then be oriented such that after opening of the pilot valve it also presses the shut-off piston in the opening direction. The activation piston of the pilot valve therefore presses from the side of the fluid-carrying, channel-like connecting line to the directional control valve on the indicated shut-off piston and there opens a pilot valve from the spring chamber of the shut-off piston into the connecting channel which is connected to the return of the entire valve device in this operating state.
Therefore, there is a throttled connection between the load side and the back via which a continuous control oil flow drains via the pilot valve to the low pressure or tank port of the device during unblocking. Then the hydraulic consumer connected to the respective operating port under load decreases by this leakage flow without the possibility of exerting any influence on the control piston with the control slide generally in the form of a control piston. Accordingly, two fundamental control concepts are distinguished:
The smallest required lowering flow can be assumed to be about 1 l/min. The leakage flow, depending on the design and level of the load pressure, can, however, assume a multiple thereof and thus is no longer acceptable. In particular, the connected machine can no longer be controlled with sufficient precision in the precision control range at high pressures.
In practice, various solutions are known for actuating the activation piston on the pilot valve. Mutual striking is mechanically simple under the action of the inflow pressure; however, for so-called leading loads the inflow pressure can collapse, and a cycle of closing and opening of the shut-off piston begins, accompanied by jerky movements of the connected hydraulic device. Improvement of operation yields an opening pressure which is independent of load in the form of the activating pressure for the control piston or control slide. This structure, however, leads to complicated channel routing within the valve device, and the activation piston which sits in the middle of the valve has a long control axis; this is accompanied by an increase in the overall size of the valve (WO 2006/105765 A1).
DE 199 19 014 A1 discloses another valve device with a pilot-controlled check valve for activating two working ports. In the known solution, the working pressure of the working port, which is under the inflow pressure, presses on the check valve of the opposite side. In the case of the leading loads, the inflow pressure then drops to the atmospheric pressure and the striking pressure can collapse. As a result, the check valve closes and the hydraulic consumer can shut down. In this case, the inflow pressure in turn rises spontaneously, and the check valve opens and accelerates the load until it leads again. The described control period then starts again from the beginning.
US 2002/0029810 A1 discloses a valve device in which unblocking is initiated via the control piston, for which a pilot valve which lies transversely to the axis of the control piston is used. The pilot valve which is arranged transversely in this way must be connected to the assigned connecting lines in a mechanically difficult manner and increases the valve installation height by a considerable amount. To increase production reliability, the aforementioned pilot valve is supported in an independent sleeve of the valve device. DE 10 2005 033 577 A1 describes in turn pilot valves which are mechanically struck and to reduce the transverse force on the control piston are not axially actuated, but are tilted in the manner of a pivoting motion. Mechanical unlocking is furthermore ready for operation in a possible failure of the hydraulic energy, the technical mechanical effort for triggering the pilot valves, however, being considerable, especially because an additional attachment housing must be provided which bears the pilot valves and a thin connecting bore must be routed from the respective check valve to the opposite side.
DE 103 25 294 A1 discloses a generic valve device in the manner of a hydraulic control arrangement for activation of a consumer independently of the load, with a housing section, preferably made as a valve disk in which a continuously adjustable directional valve which controls the flow of the pressurized fluid to the consumer is accommodated and to which an individual pressure compensator is assigned, and with at least one shut-off valve which is located in the flow path of the pressurized fluid between the directional valve and the consumer and which can be unblocked to enable flow of the pressurized fluid from the assigned consumer port, and with a replenishment valve via which pressurized fluid from the tank can be replenished when the consumer is undersupplied. In that, in the known solution, the shut-off valve is piloted via a pilot valve whose axis runs perpendicular to the axis of the directional valve and of the shut-off valve which is located axially parallel to it, the pilot valve being mechanically openable via a valve slide of the directional valve, and because the axis of the pressure limiting and replenishment valve runs perpendicular to the axes of the directional valve and of the pilot valve, the known solution is characterized by particular compactness, all essential components necessary in a so-called LUDV system being accommodated with minimum installation space.
Proceeding from this prior art, the object of the invention is to devise a valve device of mechanically simple structure which is likewise compact and reliable in operation and which ensures that leading loads cannot adversely affect unblocking. This object is achieved by a hydraulic valve device with the features of claim 1 in its entirety.
The hydraulic valve device according to the invention is characterized in that the pilot piston of the pilot valve and the shut-off piston of the shut-off valve are guided within the valve housing to be able to move parallel to one another and that the pilot piston and the shut-off piston can be moved in opposite directions to their respectively assignable valve seat by the action of at least one of the two energy storage devices. The seat-sealed pilot valve which is used here with its pilot piston relieves the back of the shut-off piston toward the tank and not as in the known solutions toward the control piston axis. The pilot valve here is activated by the unlocking pressure in the fluid activation line, this unlocking pressure Y being independent of the load and preferably being applied by an actuating device. Accordingly, the unblocking is not adversely affected by way of leading loads. Instead of the unlocking pressure Y, the actuating device can also use an actuating magnet for activating the activation piston.
The pilot valve is located in a space-saving manner on the back of the shut-off piston and on its middle axis such that its seat-sealed pilot piston projects into the spring chamber of the shut-off piston. The activating or striking piston of the pilot valve is therefore supported in the valve housing along the return valve axis, and since the opening stroke of the pilot valve is greater than that of the shut-off piston, reliable operation is ensured.
The pilot-operated check valve in the form of the hydraulic valve device is located axially parallel to the control piston so that space-saving installation within the directional valve is possible. Furthermore, secondary leak flows via the control line do not occur; this increases operating reliability.
In one especially preferred embodiment of the valve device according to the invention, the pilot-operated check valve is provided with a double seat-sealed function. The additional seat-sealed check valve is installed in the shut-off piston such that it opens from the inflow channel into the spring chamber. In this way, the inflow pressure in the spring chamber of the main shut-off piston can be represented and prevents the shut-off piston from opening unintentionally. Only when the seat-sealed pilot valve formed by the activation piston with a pilot valve on the back is actively opened can the shut-off piston also open in the flow direction. This also results in improved closing and passively holding closed for the valve device. So that a leak oil flow does not flow from the spring chamber provided with inflow pressure into the load space while being held closed with the shut-off piston, the throttle site to the load space is provided with an additional valve device with a valve part preferably in the form of a closing ball. The valve device opens in flow from the load space into the spring chamber of the shut-off valve. When the double seat-sealed shut-off piston is closed, the necessary displacement volume can furthermore flow into the spring chamber, but, conversely, a leak in the outflow direction (for example, toward a steering cylinder) cannot occur. Thus the indicated valve device is tight in both possible throughflow directions. This configuration is advantageously used for safety applications, which generally require redundant control concepts.
The invention is detailed below using exemplary embodiments shown in the drawings. The figures are schematic and not to scale.
The hydraulic valve device as shown in
As
At the site at which the fluid-carrying control line 26 discharges into the fluid chamber 22 of the shut-off piston 24, there is a discharge site 40 which can be closed by the free face end of the pilot valve 20. For this termination, the discharge site 40 is conically widened toward the fluid chamber 22 of the shut-off piston 24, and the pilot valve 20 on its free face side has a spherical closing cap 42 which can engage the discharge site 40 to form a seal. A throttle site 44 in the form of a throttle bore is located between the discharge site 40 and the other fluid-carrying control line 26. The spherical closing cap 42 of the pilot valve 20 on its bottom has a conically running sealing surface 46 which can be brought into contact with an additional conical sealing surface 48 of the valve housing 10, for obtaining a line-shaped sealing site 50 as the first valve seat 30 the incline of the other sealing surface 48 being chosen to be smaller than for the sealing surface 46 of the pilot valve 20. In the closed state of the valve device as shown in
Furthermore, the pilot valve 20 has a bridge-like extension 52 which establishes a connection between the pilot valve 20 and the activation piston 16. This connection can be in one piece. The inherently cylindrical activation piston 16 has through bores 54 which discharge into the cross channel 56 which emerges in turn into an annulus 58 which in each travel position of the activation piston 16 has a fluid-carrying connection to the fluid port T within the valve housing 10. Otherwise, the bridge-like extension 52 is routed in a widened through channel 60 in the valve housing 10 so that with the pilot valve 20 open, the first valve seat 30 is released, with the result that a fluid-carrying connection exists between a part 2 of the connecting line 1, 2 and the fluid port T, via the fluid-carrying control line 26, the throttle site 44, the discharge site 40, the fluid chamber 22, the through channel 60, the through bores 54, the cross channel 56, and the annulus 58.
The fluid activation line Y is moreover permanently connected to the chamber space 64 of the activation piston 16 via a throttle connection site 62 to carry fluid, the chamber space 64 as already described with the pilot valve 28 open establishing a fluid connection between the fluid port T in the valve housing 10 and the fluid chamber 22 of the shut-off piston 24. For a fluid-carrying connection of the chamber space 64 to the throttle connection site 62, in turn the cross channel 56 and the annuli 58 which are made in the lengthwise direction and which are located opposite one another diametrically to the longitudinal axis of the pilot valve 20 are used. Furthermore, the annulus 58 is separated fluid-tight from the chamber space 64 via a periphery-side widening 66 on the outer periphery of the activation piston 16.
To activate hydraulic equipment, in this case in the form of a hydraulic working cylinder 68, part 2 of the connecting line 1, 2 is connected to the so-called piston side 70 of the working cylinder 68 to carry fluid. The rod side 72 is in turn connected to a hydraulic control device which is not detailed and which is, however, omitted for the time being for the following simplified examination of operation. Moreover, depending on the actuating situation of the actuating device 18, for operation of the device, part 1 of the connecting line 1, 2 is connected to a pressure supply source, for example, in the form of a hydraulic pump by way of a pressure supply port P (see
At this point, for better understanding, the manner of operation of the hydraulic valve device as shown in
To lower the load at which the piston rod unit of the working cylinder 68 is retracted again in the direction of the piston side 70, in the fluid activation line Y a corresponding unlocking pressure is applied which moves the activation piston 16 viewed in the direction of
Even with leading loads, unblocking is not adversely affected and can be reliably carried out. With the valve device according to the invention, a secondary leak flow with uncontrolled lowering motion by a second seat valve between the pilot valve and shut-off piston, as shown to some extent in the prior art, is definitely avoided. The lowering motion is induced only by way of the actuating device 18 and is reliably carried out. Otherwise, the matching between the throttle site 44 in the shut-off piston 24 with the relief channels is not critical because the indicated throttle connecting site 44 is immediately closed again after opening by means of the pilot valve 20. Therefore, back pressures cannot form in the relief line and on the back. In this respect, at very low load pressures on the working cylinder 68, the shut-off piston 24 can also be raised without delay off its valve seat 34 in order to ensure unobstructed fluid return from part 2 to part 1 of the connecting line 1, 2, and, in this return case, part 1 of the connecting line 1, 2, as already described, is to be connected to the return port R by an actuating device 18.
The use of a pilot-operated check valve according to the aforementioned description is detailed below using a directional valve solution as shown in
A control device designated as a whole as 80, in the conventional manner which is not further detailed, has two pilot control valves 82, which are used among other purposes to activate a control piston 84 which is shown in
For the process of lifting a load or the extension process of the aforementioned piston rod unit, the control piston 84 is moved to the right by the actuating device 18, viewed in the direction of
The control piston of the directional valve 74 which is designated as 84 is also referred to as a control slide in the technical jargon, and, as an actuating device 18, an actuating magnet which is not detailed can replace the fluid activation line Y, for example, in the form of a proportional magnet which when electrically energized accordingly activates the activation piston 16 with the pilot valve 20 for hydraulic unblocking. The purely fluidic solution presented here, however, has the advantage that actuating current need not be made available for use of the directional valve 74, except for the pilot control valves 82. As already explained in the foregoing, the pilot-operated check valve can be used as a hydraulic valve device only for activation of the working port and a hydraulic consumer. The illustrated hydraulic working cylinder 68 can also be replaced by another hydraulically actuatable working device, for example, in the form of a hydraulic pivoting motor (not shown) and the like.
The altered embodiment as shown in
If the pilot-operated check valve as shown in
In addition to this defined opening process, closing and passively keeping closed are also improved. If, when the load is lowered or the piston rod unit is retracted into the working cylinder 68, in the valve position shown in
Thus the hydraulic valve device according to the invention is tight in both flow directions and a double seat-sealed pilot-operated check valve is formed. The alternative embodiment shown in
Number | Date | Country | Kind |
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10 2008 031 745.4 | Jul 2008 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2009/004663 | 6/27/2009 | WO | 00 | 1/27/2011 |