EP2153072B1 - Valve arrangement having individual pressure scale and load-lowering valve - Google Patents

Abstract

The invention discloses a valve arrangement for supplying pressure medium to a hydraulic load (2) having a directional valve (8), which has an inflow measuring diaphragm (10, 12) and a directional part (14, 16) flowing in the flow direction. The directional valve is associated with an individual pressure scale (18). In a return from the load, a load-lowering valve (44, 46) is provided, to which a pilot pressure is applied in the opening direction. According to the invention, said pilot pressure is tapped in channel between the pressure scale and the directional part.

Description

The invention relates to a valve arrangement for the pressure medium supply of a hydraulic consumer according to the preamble of claim 1.

Such valve arrangements are designed, for example, in disk construction and used in mobile control blocks for controlling hydraulic consumers of mobile equipment, such as compact construction equipment such as backhoe loaders, mini and compact excavators, telehandlers. A requirement of the hydraulic system of such mobile work tools is that the lowering of a large negative or pulling load is controlled. For this purpose, so-called counter-holding or lowering brake valves are usually used on the outlet side, which generate in the return a bias voltage which acts against the main drive pressure, so that the load for the entire system is positive again and thus remains controllable.

Such a lowering brake valve, as for example in the data sheet VPSO-SEC-42; 04.52.12-X-99-Z of the company Oilcontrol, a subsidiary of the applicant described, is in principle a check valve, which can be unlocked by the pressure in the inlet and allows for pressing load a controlled lowering. The known lowering brake valve is designed with a pressure medium supply to the consumer enabling check valve and further designed as a seat valve, so that a-leakage-free support of the load is possible. Another advantage of these known lowering brake valves is that they act as a secondary pressure limiting valve, so that the pressure in the return line can not exceed a maximum value set on the lowering brake valve.

Such lowering brake valves can in so-called LS control blocks, as shown in the DE 197 15 020 A1 or the datasheet RE 64 276 / 06.06 are removable or at LUDV control blocks according to the data sheet RD 64 125 / 07.05 Bosch Rexroth AG. In the latter LUDV control blocks, a pressure medium volume flow distribution independent of the load pressure and of the available volume flow to the various consumers of the mobile implement is ensured via the valve arrangement. In this case, each consumer is associated with a directional control valve element with two consumer connections, which can be connected via a directional control valve with a LS pump or a tank. The directional valve is continuously adjustable executed and has a speed part for adjusting the pressure medium volume flow and a direction part for adjusting the flow direction. Downstream of a variable inlet orifice forming speed part, a pressure compensator is provided, which is acted upon in the closing direction by the maximum load pressure of all consumers and in the opening direction of the pressure downstream of the inlet orifice, so that a load pressure independent volume flow distribution to the different consumers. In order to avoid an uncontrolled drop in a towing load, one of the above-described lowering brake valves can be provided in the return from the consumer. This lowering brake valve can be controlled by the pressure in the flow to the consumer to build the aforementioned backpressure. In order to ensure both directions of movement of the consumer in terms of a negative load, each of the consumer connections is assigned a lowering brake valve, which are then aufsteuerbar practically crosswise from the pressure at the other consumer terminal. In particular, in such LUDV control blocks, however, a considerable manufacturing effort is required to tap this to open the required return valve located in each return brake pilot pressure from the flow at the other consumer port.

From the CA 2 551 947 A1 is a circuit diagram of a mobile control block with valve arrangements known which serve to supply pressure medium of hydraulic consumers. These known valve arrangements comprise in a housing an adjustable inlet orifice plate and a directional part directional control valve, one of the inlet orifices associated individual pressure compensator and two unlockable load-holding valves. A pilot pressure for acting on the load-holding valves in the opening direction is tapped in a channel between the pressure balance and the directional part of the directional control valve.

The invention has for its object to provide a simply constructed valve assembly, with an uncontrolled drop in a consumer can be prevented.

This object is achieved by a valve arrangement having the features of patent claim 1.

According to the invention, the valve arrangement has a directional valve accommodated in a housing, which has an adjustable inlet orifice and a directional part

for adjusting the flow direction. The adjustable inlet orifice plate is associated with a pressure compensator and in a return from the consumer a Senkbremsventil is arranged, which is acted upon in the opening direction with a pilot pressure. To the lowering brake valve and a direction to the consumer opening check valve is connected in parallel. The pilot pressure is tapped in a channel between the pressure compensator and the directional part, wherein the channel is an arc passage between a pressure compensator output and in each case an intermediate chamber of a flow-side or return-side directional part of the directional control valve

According to the invention, an already existing channel is thus used and only drilled, so that a complex ducting, for example, around the pressure compensator around to the return side consumer connection is not required. It has been found that the tapping of the pilot pressure in the region between the pressure compensator and the directional part over the conventional solution, in which the pilot pressure is tapped downstream of the directional part, brings no functional disadvantages.

The valve assembly according to the invention is preferably designed as a LUDV valve arrangement with the inlet orifice downstream pressure compensator, which is acted upon in the direction of a reduction of the opening cross section by the highest load pressure of all consumers and in the direction of increasing the opening cross section of the pressure downstream of the inlet orifice plate.

In a preferred embodiment of the invention, each consumer connection is associated with a lowering brake valve, which is acted upon in each case by the same pilot pressure. This is an essential difference to conventional solutions, in which the pilot pressure is tapped crosswise at the other consumer port.

The construction of the valve arrangement is particularly compact if this pilot pressure acts on the front side on a pilot surface of the lowering brake valve, so that only a short channel has to be provided in order to connect the pressure chamber bounded by this pilot area with the arc channel.

The compactness can be further improved if the two lowering brake valves are arranged approximately V-shaped relative to each other in the housing, in which case the pressure compensator is preferably arranged approximately in the axis of symmetry between the two lowering brake valves.

According to the invention it is preferred if the two connected to the load terminals of the valve assembly working ports of the directional control valve are connected in its basic position with a tank connection.

The structure of the lowering brake valve is particularly compact, when the check valve and the lowering brake valve are arranged on a common axis.

The valve arrangement is preferably designed as a valve disk or directional control valve element of a LUDV mobile control block.

Other advantageous developments of the invention are the subject of further subclaims.

• Figur 1 ein Schaltschema eines erfindungsgemäßen Wegeventilelementes;
• Figur 2 einen Schnitt durch ein nach diesem Schaltschema ausgeführtes Wegeventilelement und
• Figur 3 eine vergrößerte Darstellung eines Senkbremsventils des Wegeventilelementes aus Figur 2.

In the following, a preferred embodiment of the invention is explained in more detail with reference to schematic drawings. Show it:

• FIG. 1 a circuit diagram of a directional control valve element according to the invention;
• FIG. 2 a section through a executed according to this scheme switching valve element and
• FIG. 3 an enlarged view of a lowering brake valve of the directional control valve element FIG. 2 ,

In FIG. 1 a directional control valve element 1 of a mobile control block for controlling a mobile implement is shown. Such a mobile control block is disk-shaped and typically has an input member, a plurality of directional control valve members, and an end member. Via each directional control valve element 1, a consumer 2 can be connected to a pump 4 or a tank 6. In the illustrated embodiment, the control block is designed as a LUDV control block, in which the volume flow distribution to the individual consumers of the implement is independent of the load pressure and the available via the pump 4 pressure medium flow rate. The basic structure of the directional control valve 1 according to FIG. 1 corresponds to a conventional LUDV-way block of the type SX, as described in the aforementioned data sheet RD 64 125, so that in the following only required to understand the application designs are made.

The disc-shaped directional control valve element 1 has two consumer ports A, B, a pressure port P, a tank port T and a LS (load pressure) port LS. About the LS connection, the highest load pressure of all consumers 2 is tapped and led to a pump controller, not shown, of the pump 4 executed in the present case as a variable. Via this pump regulator, the pump pressure is adjusted so that it always lies above this highest load pressure by a predetermined pressure difference. Instead of the variable displacement pump shown can also be a constant displacement pump with bypass pressure relief valve can be used.

The directional control valve 1 consists essentially of, for example, a manually operated, continuously adjustable directional control valve 8 which is designed with a pressure connection P, a tank connection T, a further input connection P ", two working connections A, B and a pressure compensator connection P ' In the spring-biased basic position of the directional control valve 8, the two working ports A, B are connected to the tank T, respectively, for adjusting the pressure medium volumetric flow and directional parts 14, 16.

In an adjustment of the directional control valve element in one of the directions marked (a), the port T is connected to the working port B, the pressure compensator port P 'to the input port P and the working port A to the port P " In turn, the pressure port P is connected to the pressure compensator port P ', and the further input port P "is connected to the working port B and the working port A is connected to the tank port T. Downstream of the two inlet orifices 10, 12, an individual pressure compensator 18 is provided, which together with the inlet orifices 10, 12 forms a volumetric flow regulator, by means of which the pressure medium volumetric flow to the consumer can be kept constant. The pressure compensator 18 has an input port P and an LS port LS and an output port C, which is connected to the further input port P "of the directional control valve element 1 via an arc passage 20. The input port P of the pressure compensator 18 is connected to the pressure compensator port P 'via a pressure compensator channel 22. connected to the directional control valve 8. The pressure in this pressure compensator channel 22 also acts in the opening direction on the pressure compensator 18. The LS connection of the pressure compensator 18 opens via an LS connection channel 24 in one LS channel 27, in which the maximum load pressure tapped by the individual consumers via a shuttle valve cascade is present. This LS channel 27 opens into the LS port of the directional control valve element 1. The pressure in the LS channel 27 acts on the pressure compensator 18 in the closing direction.

In the illustrated basic position of the pressure compensator 18, which can be adjusted via a weak spring, the ports P, C and LS of the pressure compensator 18 are shut off. When a pressure buildup in the pressure compensator channel 22, the pressure compensator 18 is adjusted in the opening direction, so that an opening cross-section between the input port P and the pressure compensator port C is opened. When the pressure compensator 18 is fully opened, the input connection P is connected to the LS connection of the pressure compensator 18, so that the pressure then present in the pressure compensator duct 22 is reported to the LS channel 27.

The pressure port P of the directional control valve element 1 is connected via a pump line 24 to the pressure port of the pump 4. The pressure medium volume flow provided by the pump 4 is guided within the directional control valve 1 via an inlet channel 26 to the inlet connection P of the directional control valve 8. The tank port T of the directional control valve element 1 is connected via a tank line 28 to the tank 6 and is connected via an outlet channel 30 to the directional control valve 8 in pressure medium connection.

The two working ports A, B are called working channels, in the following flow channel 34 and return channel 32 and via consumer channels 33, 35 with the two load ports A and B of the directional control valve element 1 in conjunction. These are then connected via working lines 36, 38 with an annular space 40 and a bottom-side cylinder space 42 of the consumer 2 designed as a hydraulic cylinder.

In each of the flow and return channels 32, 34, a lowering brake valve 44, 46 is provided, to each of which a check valve 48 or 50 is assigned, which opens in the direction of the respective consumer port A, B. As will be explained in more detail below, the check valves 48, 50 are integrated into the respective lowering brake valve 44 and 46, respectively. By Senkbremsventile 44, 46 a leakage-free support of the load is possible. Furthermore, they act as secondary pressure relief valves and prevent the uncontrolled drop of a negative load. Furthermore, in such a load case, the formation of cavitations in the Can be prevented channels to the increasing pressure chamber of the consumer 2.

The basic structure of such a lowering brake valve is described in the above-mentioned data sheet 04.52.12-X-99-Z Oilcontrol. Each of the lowering brake valves 44 is acted upon by an adjustable closing spring 52 or 54 in the closing direction and in the opening direction by the load pressure in the region of the consumer channels 33, 35 and by a pilot pressure which is tapped off from the arc channel 20 via a pilot channel 56. As FIG. 1 can be removed, this pilot pressure acts simultaneously on both lowering brake valves 44, 46 in the opening direction. In the illustrated embodiment, the lowering brake valves 44, 46 are additionally acted upon by the way valve-side pressure in the channels 32 and 34 in the closing direction. However, variants of these lowering brake valves are provided, in which this so-called "back pressure" also acts in the opening direction and is thus compensated. In this regard, reference is made to the corresponding literature on the "counterbalance valves" of Oilcontrol.

FIG. 2 shows a sectional view of a directional control valve element 1, which is constructed according to the above-described circuit concept, the only difference is that the in FIG. 2 illustrated directional control valve element is hydraulically actuated while in the FIG. 1 shown directional control valve element is operated by hand.

The directional control valve 1 has according FIG. 2 a disk-shaped housing 58, on which the two consumer terminals A, B are formed. In this housing 58, the directional control valve 8, the pressure compensator 18 and the two lowering brake valves 44,46 are added.

The directional control valve 8 has a directional valve spool 60 which is slidably guided in a valve bore 62 of the housing 58. On both sides out of the housing 58 guided out end portions of the valve spool 60 engages a Zentrierfederanordnung 64, which is received in laterally flanged spring housings 66, 68. The respectively enclosed spring chamber 70 can be acted upon in the illustrated embodiment, in each case via a control connection x, y with a control pressure to move the valve spool 60. In many cases, however, this displacement is done manually by means of a control lever, so that the spring chambers are then ventilated accordingly.

The valve slide 60 is provided in a known manner with a plurality of annular grooves, so that in each case a direction control edge 76, 78 is formed on a central control collar two orifice control edges 72, 74 and on two sides thereof arranged control. At two end collars of the valve spool 60, a tank control edge 79 and 81 are respectively provided.

The valve bore 62 is widened in the central region to an inlet chamber 80 connected to the inlet channel 26. In the illustration according to FIG. 2 to the left of this is a pressure compensator chamber 82 is provided, which is connected via the two orifice plate control edges 72, 74 depending on the adjustment of the valve spool 60 with the inlet chamber 80. The metering orifice chamber 82 is connected via the above-described pressure compensator channel 22 with the in FIG. 2 underlying axial input of the pressure compensator 18 is connected.

On both sides of the two chambers 80, 82, the valve bore 62 is carried out, each with an intermediate chamber 84, 86, via the in FIG. 1 described arc channel 20 are connected to the radial output of the pressure compensator 18, wherein the arc channel 20 surrounds the outer periphery of the pressure compensator 18 annularly, so that both legs of the sheet channel 20 are interconnected.

On both sides of the intermediate chambers 84, 86 are each a working chamber 88 and 90 and a tank chamber 92 and 94, respectively. The working chambers 88, 90 are connected via the flow channel 34, the return channel 32 and the consumer channels 35, 33 with the load ports B and A, wherein the Senkbremsventile 44, 46 are used in the pressure fluid flow paths to these terminals A, B.

The two outer tank chambers 92, 94 are both with the in FIG. 2 not shown drain passage 30, via which the pressure medium can be returned to the tank 6.

In the in the FIGS. 1 and 2 illustrated basic position of the valve spool 60, the pressure medium connection between the chambers 80, 82 and 86, 90 and 84, 88 shut off. The pressure medium connection of the two working chambers 88, 90 to the adjoining tank chambers 92, 94 is controlled by the respective tank control edge 79, 81, so that the channels 32, 34 are relieved to the tank.

In the illustration according to FIG. 2 the axis of the directional control valve 8 extends approximately in the horizontal, while the pressure compensator axis is perpendicular to it in the vertical. The valve axes of the two Senkbremsventile 44, 46 are V-shaped obliquely employed, so that there is an extremely compact design. In this case, the outer surfaces of the housing 58 are bevelled in accordance with the employment of Senkbremsventilachsen. As shown in FIG. 2 are the two lowering brake valves 44, 46 executed in cartridge design and each inserted in a stepped Senkbremsventilbohrung 96, 98, the radially recessed end portions each open into a leg of the sheet channel 20. The basic structure of the lowering brake valves 44, 46 is exemplified by the enlarged view of the lowering brake valve 46 in FIG. 3 explained, again only essential components are described and reference is otherwise made to the above-mentioned data sheet 04.52.12-X-99-Z of the valve VBSO-SEC-42.

The lowering brake valve 46 has a housing cartridge 100 which is screwed into the Senkbremsventilbohrung 98, wherein the housing cartridge 100 receives only a portion of the movable components, since they are guided substantially directly in the Senkbremsventilbohrung 98. Each lowering brake valve has a closing body 102, which is prestressed with a cone 104 against a valve seat 106. This biasing takes place by means of the closing spring 52 accommodated in the housing cartridge 100, which acts on the rear end wall of the cone 104 via an axially displaceable spring plate 108. The spring plate 108 is sealingly guided in the housing cartridge 100. The closing spring 52 is in turn supported on an adjusting screw 110 which is adjustably received in the housing cartridge 100, so that the bias of the closing spring 52 and thus the preset by the lowering brake valve 46 maximum pressure is variable. The adjusting screw 110 is countered by means of a lock nut 111. As shown in FIG. 3 the housing cartridge 100 projects beyond the return passage 32 into the lowering brake valve bore 98. In the region of the return channel 32, the lowering brake valve bore 98 is expanded to form an annular chamber 112. This is connected via a radial jacket bore 114 of the housing cartridge 100 with a closing spring 52 receiving spring chamber 116, so that in this the pressure in the working chamber 90 is applied.

Also in the area of the annular chamber 112, a plurality of recesses 118 is provided in the jacket of the housing cartridge 100, via which the region of the housing cartridge interior situated between the valve seat 106 and the sealingly guided spring plate 108 is connected to the return channel 32.

At the provided with the recesses 118 end portion of the housing cartridge 100, a valve seat 106 forming seat sleeve 120 is supported. This is sealingly guided along a portion of the counterbore valve bore 98 adjoining the housing cartridge 100 and biased against the adjacent end wall of the housing cartridge 100 via a weak spring 122. This spring 122 is supported on a support bushing 124, which in turn bears against a radial shoulder 126 of the Senkbremsventilbohrung 98. Through the seat sleeve 120 and the support bushing 124, the check valve 48 is formed, can be performed by the pressure medium from the return passage 32 to the lowering brake valve 46 to the working port A.

An in FIG. 3 on the left of the cone 104 subsequent projection of the closing body 102 carries at its end portion a pilot collar 128, the sealing in the in FIG. 3 left, stepped back end portion of the Senkbremsventilbohrung 98 is guided, so that an end-side pilot surface 130 is acted upon by the pressure in the arc duct 20. The Senkbremsventilbohrung 98 is open to the consumer channel 33, so that the in FIG. 3 To the left of the valve seat 106 located region of the closing body 102 of the pressure in the consumer channel 33 acts. The axial length of the recesses 118 is selected so that the in FIG. 3 left end face of the spring plate 108 is also acted upon by the pressure in the return channel 32.

Accordingly, the lowering brake valve 98 is acted upon in the closing direction by the force of the closing spring 52, wherein the spring plate 108 is pressure balanced, since both end faces are acted upon by the pressure in the return channel 32. In the closing direction, the pressure in the return channel 32 also acts on the differential surface of the closing body 102 corresponding to the valve seat surface. In the opening direction, the pressure in the arc channel 20 acts on the pilot surface 130 and the pressure in the consumer channel 33 on the surface difference between valve seat surface and pilot collar surface (characterized by valve seat diameter or pilot seat area) Pilot collar diameter).

As is clear from the representations according to the Figures 2 and 3 shows, the channel guide in the directional control valve element 1 according to the invention is extremely simple, since no additional channels for tapping a pilot pressure are required by the direct connection of the Senkbremsventilbohrung 96, 98 with the arc channel 20. In the conventional solutions, the pilot surface 130 had to be connected to the respective consumer channel 33, 35 via a channel guided around the pressure compensator 18, so that the housing 58 could be manufactured considerably more complexly.

If now, for example, the hydraulic cylinder to be extended, the directional control valve 8 is moved to one of its marked with b positions, the valve spool 60 in the illustration according to FIG. 2 is moved to the right. As a result, the connection between the inlet chamber 80 and the metering orifice chamber 82 is opened via the metering orifice control edge 72, so that the pressure medium flows via the pressure compensator 18 into the arcuate channel 20. The pressure medium volume flow is determined by the inlet orifice aperture 10 set by means of the measuring orifice control edge 72 (see FIG FIG. 1 ) certainly. At the same time via the direction control edge 76, the pressure medium connection between the intermediate chamber 84 and the working chamber 88 is controlled, so that the pressure medium enters the flow channel 34 and acts in the opening direction on the seat sleeve 120 of the check valve 48 of the lowering brake valve 44, so that the seat sleeve 120 against the force the weak spring 122 lifts off from the cone 104 of the lowering brake valve 44 and, without appreciable loss, permits a flow of pressure medium into the consumer channel 35 and from there via the working line 38 to the bottom-side cylinder chamber 42 of the consumer 2. The hydraulic cylinder is extended, wherein the pressure medium displaced from the piston rod-side annular space 40 flows via the working line 36, the working port A to the lowering brake valve 46. This is, as explained above, acted upon by the pressure in the arc passage 20 and by the pressure in the annular space 40 in the opening direction, so that it opens against the force of the closing spring 52 and the effective closing pressure in the return channel 32, so that the cone 104 of Valve seat 106 lifts off and the effluent from the consumer 2 pressure fluid via the lowering brake valve 46 in the return passage 32 to the working chamber 90 and via the controlled from the tank control edge 81 cross section finally flows into the tank chamber 94 and from there to the tank 6 out.

Upon adjustment of the directional control valve 8 in one of its positions marked with a, the load is lowered, so that pressure medium is displaced from the cylinder chamber 42 and conveyed into the enlarging annular space 40. The uncontrolled drop is reliably prevented because at a sagging of the load, the pressure in the arc duct 20 drops and accordingly the lowering brake valve 44 is controlled to build the back pressure described above.

In the illustrated embodiment, the working ports A, B of the directional control valve 8 are connected in the basic position with the tank 6. In principle, it is also possible to use directional control valves in which the two working connections A, B with respect to the tank 6 are shut off in the basic position, or they can also be the input port P and the tank port 6 are connected to each other in the home position. The lowering brake valves 44, 46 can in principle be designed with a control surface acting in the closing direction, with spring space vented to the atmosphere or with a pressure compensation, in which the pressure in the channels 32, 34 has no effect on the lowering brake valve function.

Disclosed is a valve arrangement for the pressure medium supply of a hydraulic consumer with a directional control valve, which has a pressure medium volume flow predetermining inlet orifice plate and a flow direction controlling direction part. The directional valve is associated with an individual pressure compensator. In a return from the consumer, a lowering brake valve is provided, which is acted upon in the opening direction by a pilot pressure. According to the invention, this pilot pressure is tapped in a channel between the pressure compensator and the directional part.

Claims (9)

1. Valve arrangement which serves for supplying pressure medium to a hydraulic consumer (2) and which has in a housing (58) a directional valve (8) possessing an adjustable inflow metering orifice (10, 12) and a direction part (14, 16), an individual pressure balance (18) assigned to the inflow metering orifice (10, 12), a load-lowering valve (44, 46) which is provided in a return from the consumer (2) and is acted upon in the opening direction by a pilot pressure, and a non-return valve (48, 50) opening in the direction of the consumer (2) and connected in parallel to the load-lowering valve (44, 46), the pilot pressure being picked off in a duct (20) between the pressure balance (18) and the direction part (14, 16), and the duct being a curved duct (20) between a pressure-balance outlet (C) and in each case an intermediate chamber (84, 86) of a forward-side or return-side direction part (14, 16) of the directional valve.
2. Valve arrangement according to Patent Claim 1, the pressure balance (18) following the inflow metering orifice (10, 12) and being acted upon in the direction of a reduction of the opening cross section of the highest load pressure of all the consumers (2) and in the opening direction by the pressure downstream of the inflow metering orifice (10, 12).
3. Valve arrangement according to Patent Claim 1 or 2, a load-lowering valve (44, 46) being provided both in the forward and in the return flow, and both being acted upon by the same pilot pressure.
4. Valve arrangement according to Patent Claim 3, the pilot pressure acting on the end face upon a pilot face (130) of the load-lowering valve (44, 46), and the latter being arranged with its pilot face (130) pointing towards the curved duct (20).
5. Valve arrangement according to Patent Claim 4, the two load-lowering valves (44, 46) being arranged in a V-shaped manner with respect to one another.
6. Valve arrangement according to Patent Claim 5, the pressure balance (18) being arranged approximately in the mid-axis between the two load-lowering valves (44, 46).
7. Valve arrangement according to one of the preceding patent claims, two working connections (A, B) of the directional valve (8) being connected in the basic position of the latter to a tank (6).
8. Valve arrangement according to one of the preceding patent claims, the non-return valve (48, 50) and the load-lowering valve (44, 46) lying on a common axis.
9. Valve arrangement according to one of the preceding patent claims, the valve arrangement being a directional valve element (1) of a mobile control block.

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