Abstract:
A hydraulic valve device, especially an LS current regulating valve, includes a fluid connection arrangement ( 10 ). As the respective control device ( 14 ) associated with a useful connection (A) comprises a control slide ( 16 ) upstream of which a pressure balance ( 18 ) is mounted in the fluid direction towards each useful connection (A, B), any system vibrations occurring in the load sensing regulating circuit can be better controlled and the respectively connected hydraulic consumer can be subjected to a constant current regulation.

Description:
FIELD OF THE INVENTION 
     The invention relates to a hydraulic valve device, in particular a LS flow control valve, with a fluid connector arrangement containing at least a pressure supply connector (P), a return flow connector (R), a section load sensing connector (LS), two control connectors (P′ A ) and (P′ B ), two utility connectors (A, B) and at least one displaceable control for at least partially triggering connectors of the fluid connector arrangement. 
     BACKGROUND OF THE INVENTION 
     DE 10 2005 033 222 A1 discloses a LUDV valve arrangement in which a control valve forms an inlet metering orifice to which an individual pressure compensator is connected downstream. By the LUDV valve arrangement, a hydraulic consumer connected to two consumer connectors of the control arrangement is triggered. To set a quick traverse, two pressure spaces of the consumer can be connected to one another and to a source of hydraulic fluid. To prevent sagging of the consumer pressure, this connection of the two consumer connectors takes place by the flow path of the hydraulic fluid having a check valve. By the directional control valve, only the connection to one of the consumer connectors is opened. The connection of the other consumer connector to the source of hydraulic fluid and/or the former consumer connector is possible in quick traverse only via the flow path of the hydraulic fluid and the opened check valve. Inadvertent movement of a hydraulic consumer in the quick traverse position of the valve arrangement is prevented with the known solution. The known LUDV control constitutes a special case of load sensing control in which the highest load pressure of the hydraulic consumer is reported to an adjusting pump. The adjustive pump is controlled such that the pump line contains a pump pressure exceeding the load pressure by a certain pressure difference Δ P . In the known LUDV control, the individual pressure compensators are located downstream from the metering orifices and choke the fluid flow between the metering orifice and the load so dramatically that the pressure following all metering orifices is the same, preferably equal to the highest load pressure or slightly above it. The greatest weakness of these hydraulic LS systems is their susceptibility to system vibrations in the load sensing control circuit, among other things due to the load change on the respective consumer. 
     EP 1 370 773 B1 discloses as a hydraulic valve device a directional control valve for controlling the pressure and the flow of hydraulic oil from and to working connectors of at least one fluid consumer, in which the pressure and flow rate can be controlled by a valve spool moveable in the spool bore and actuatable by at least one drive. By annular channels dynamically connected to the fluid consumer, at a symmetry center point of the valve arrangement, a tank connector annular channel (R) and on either side other annular channels one arranged symmetrically. For implementation of hydraulic pump triggering on one side of the axis of symmetry, with an A-annular channel assigned to one working connector, a first pump pressure annular channel, a first load sensing annular channel and a first end space annular channel are assigned. On the other side of the axis of symmetry, with a B-annular channel assigned to the other working connector, a second pump pressure annular channel, a second load sensing annular channel, and a second end space annular channel are assigned. The first load sensing annular channel is connected to the second load sensing annular channel by a load sensing connecting line. With the known valve solution, a type of quantitative divider for the connected consumers is attained. In these quantitative divider valves, the pressure compensators not controlling the pressure drop over the valve orifice, but accept the highest load pressure of the system. Fluctuating pressure losses in the feed line then directly disrupt the available pressure difference on the controller orifice to hinder constant flow control. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide improved the valve solutions such that system vibrations in the load sensing control circuit can be better managed and such that constant flow control for the respectively connected hydraulic consumer is possible. 
     This object is basically achieved by a hydraulic valve device where the respective control assigned to each utility connector A, B has a valve spool to which a pressure compensator is connected upstream in the fluid direction to the respective utility connector A, B. The hydraulic LS system is less susceptible to system vibrations. As a result of the upstream pressure compensator, it can have a decisive effect on system stability. Pressure oscillations are often produced by mechanical vibrations of resilient structures in the respectively connected hydraulic consumers (crane arms) and are then transmitted by the load sensing circuit (LS) to the pressure compensator. The LS pressure (load reporting pressure) then constitutes the reference variable for the upstream pressure compensator in this respect and can smooth pressure oscillations even before the pressure is relayed to the following valve spool of the respective control, depending on its respective spool or piston position, then ensures constant supply for the respectively connected hydraulic consumer. 
     In addition to the indicated system smoothing, by the fluid succession from the pressure compensator with a downstream valve spool, regardless of the pressure difference on the control for the respective consumer, a constant useful volumetric flow is then available so that the total flow rate remains constant independently of changing load pressures on the consumer. In this way reliable operation for the respectively connected hydraulic consumer is ensured. 
     In one preferred embodiment of the valve device according to the invention, the pressure compensator is integrated within the valve spool. Both the pressure compensator and the valve spool are guided to be longitudinally moveable in relative motion to one another within the valve housing. This coaxial arrangement of the valve spool and pressure compensator is especially space-saving and leads to valve housings with a small structure. This arrangement still is especially reliable. 
     Shown to be especially reliable in one preferred embodiment of the valve device according to the invention, both the pressure compensator and the valve spool are held spring-centered in the initial position. The pressure compensator is triggerable by a LS pressure routed at the same time to one connection side of the valve spool which in turn can be triggered by the control pressure of a pilot valve. A control connector pressure tapped between the valve spool and pressure compensator triggers the pressure compensator by acting in the opposite direction to the LS pressure. 
     Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring to the drawings which form a part of this disclosure and which are schematic and not to scale: 
         FIG. 1  is a hydraulic circuit diagram of the fundamental structure of the hydraulic valve device in the form of a LS flow control valve according to an exemplary embodiment of the invention; 
         FIG. 2  is a front elevational view in section of a practical implementation of the circuit diagram of  FIG. 1  in a valve product shown in part with its essential components; 
         FIG. 3  is an enlarged front elevational view in section of the control at right when viewed in the direction of  FIG. 2 , with a pressure compensator and valve spool. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The hydraulic valve device as shown in  FIG. 1  has a fluid connector arrangement  10 , containing a pressure supply connector P, a return flow connector R, a section load sensing connector LS with LS max , two control connectors P′ A , P′ B , two utility connectors A, B, and two hydraulic motors  12 . Motors  12  are independent of one another, are connected to the utility connectors A, B as consumers and are connected to a common tank connector T 0 . The hydraulic valve device also has two controls  14  for at least partial triggering of the connectors of the fluid connector arrangement  10 . The respective control  14  has, assigned to each utility connector A, B, a valve spool  16  to which a pressure compensator  18  is connected upstream. The valve spool  16  and pressure compensator  18  are built in the form of proportional valves, the respective valve spool  16  being provided with a throttle or orifice  20 . Both the pressure compensator  18  and the valve spool  16 , as shown in  FIG. 1 , are held spring-centered in the initial position. The valve spool  16  for this purpose has one compression spring  22  and the pressure compensator  18  having another compression spring  24 . 
     The respective pressure compensator  18  can be triggered by the LS pressure designated as LS A  and LS B  in  FIG. 1 . This LS pressure LS A , LS B  is also routed at the same time to the connection side  26  of the valve spool  16 . The respective valve spool  16  can furthermore be triggered against the action of the compression spring  22  by the control pressure X A , X B  of a conventional pilot valve P A , P B . A control connector pressure P′ A  and P′ B  tapped between the valve spool  16  and pressure compensator  18  triggers the pressure compensator  18  by acting in the opposite direction to the LS pressure LS A , LS B . The LS pressure prevailing directly at the input of the pressure compensator  18  is designated as LS A1 , and LS B1 . 
     Another connection side  28  of the valve spool  16  is connected to a return flow connector R and the LS pressure LS A  and LS B  can be triggered by a selector valve  30  connected by a check valve  32  to LS max . The check valve  32  opens in the direction of LS max . The pilot valves P A , P B  are connected to a control pressure P ST  as the supply source and further to the tank connector T 0 . 
     The hydraulic valve device of  FIG. 1  in the form of a hydraulic circuit diagram is shown as a mechanical valve solution according to the longitudinal section as shown in  FIG. 2 . The valve device has a valve housing  34  implemented as a modular concept. In particular, the pilot valves P A , P B  with their connection housing parts  36  are connected to the middle housing  38 . As viewed in the direction of  FIG. 2  in the upper region of the middle housing  38 , the utility connectors A, B are connected in the form of screw-in cartridges. The lower region of the middle housing  38  is penetrated by a through channel  40  in which overall the pump pressure P prevails. Channel  40  is connected via connector lines  42  to a middle channel bore  44  into which the two control  14  are inserted. Analogously to the through channel  40 , the middle channel bore  44  also extends transversely to the center longitudinal axis of the overall valve housing  34  and along this center longitudinal axis which is not detailed, viewed in the direction of  FIG. 2 , underneath the middle channel bore  44  is the return flow connector R which discharges into the middle channel  44  via another connector line  46 . The middle channel  44  is preferably made in the form of a bore and is connected by connecting lines  48  to the utility connectors A, B to carry fluid. The check valve  32  in  FIG. 1  is likewise integrated in the valve housing  34 , but for reasons of simplification is not shown in  FIG. 2 . 
     The axis of the respective valve spool  16  extends horizontally as viewed in  FIG. 2 . The middle channel bore  44  in the middle housing  38  is sealed on both sides with the respective pilot housing as the connector housing part  36  for the supply of a trigger pressure X A , X B . Outside the valve middle is the return flow connector R. Viewed from the return flow connector R, on one side A, P, and LS A  follow to the outside, and B, P and LS B  follow on the opposite side. As already described, the LS annular channels LS A  and LS B  are connected to the selector valve  30  which separates the two pressures from one another. The selector valve  30  is preferably made as a round insert part and is mounted on the flange side (not shown) of the disk-like valve body  34 . The output connector of the selector valve  30  leads, by the pressure channel, to the check valve  32  sealing against higher pressure in the LS reporting channel (LS max ). If the load pressure LS A  or LS B  exceeds the pressure in the reporting channel, this pressure is relayed by the check valve  32  in the control block and from there further to a system pressure control (not shown) for the entire valve system. 
     The entire space in the form of the through channel  40  in the lower part of the middle housing  38  is under the pump pressure P. From this space, one channel line at a time leads to the cavity axis of the respective valve spool  17  to the vicinity of the annular channels leading to utility connectors A and B. The two valve spools  16  are made identically and in a coaxial arrangement hold an inside pressure compensator  18  connected upstream from the valve orifice. They are also structurally identical to one another. As shown in  FIG. 2 , the neutral positions of the valve spools  16  are held by housing-mounted stops and their respective working springs (compression springs  22 ). The working spring (compression spring  22 ) is supported on the one hand against the housing  34  of the valve and on the other hand against a screw plug  50  screwed tightly to the valve spool  16 . In this initial or neutral position, the respective valve spool  16  separates the working connector A or B from the pump connector P. 
     As  FIG. 3  shows in particular, the variable valve orifice is made in the form of first radial openings  52  within the hollow spool arrangement of the valve spool  16  and pressure compensator  18 . A sealing crosspiece P to A and P to B is formed within the valve housing  34 . The inner pressure compensator  18  is also permanently connected to the pump channel P by second radial openings  54  in the valve spool  16 . The spring chamber with the other compression spring  24  of the pressure compensator  18  is permanently connected to the respective LS A  or LS B  annular channel by third radial openings  56  in the valve spool  16 . In the neutral position, the third radial openings  56  of the valve spool  16  are additionally connected to the spring chamber with the compression spring  22  of the valve spool  16  to carry pressure. This connection takes place through the corresponding radial passages in the control piston of the pressure compensator  18 . The indicated spring chamber of the pressure compensator  18  is then relieved in the neutral position. The valve spool  16  can be provided with fourth radial openings  57  whose edge lying toward the valve center is at the same axial length as the first openings (control edge  52 ). These fourth openings  57 , in contrast to the first three openings, do not have corresponding passages in the control piston of the pressure compensator  18 . The correct orientation of the corresponding openings with passages is ensured by a locking element  58  in the form of a catch ball offering radial protection between the valve spool  16  and the control piston of the pressure compensator  18 . 
     In the unpressurized state the control spring  24  presses the control piston of the pressure compensator  18  against the end of the blind hole of the valve spool  16 . This pressure compensator piston is likewise made as a hollow piston and has a second radial passage  60  closing the connection to the opening  54  as a P-opening in the valve spool  16  in the stroke against the pressure compensator spring  24  (control edge of the pressure compensator  18 ). A first radial passage  62  is permanently connected to the valve orifice in the form of the first opening  52  in the valve spool  16 . The spring chamber of the pressure compensator  18  is connected by the third radial opening  56  to the respective third passage  64  of the valve spool  16  and to the longitudinal grooves  66  on the jacket or outer surface of the control piston of the pressure compensator  18 . These longitudinal grooves  66 , of which only one is shown by the broken line in  FIG. 3 , extend in the direction of the R channel to the control edge of the control piston. Viewed on the periphery, grooves  66  lie between the radial openings and passages. The respective longitudinal groove  66  is permanently connected to the fourth radial opening  57  in the valve spool  16 . This longitudinal groove connection constitutes the LS reporting connector from the working connector into the spring chamber with the compression spring  24  of the pressure compensator  18 . The connection site  57 , as shown in  FIG. 1 , corresponds to the branch point LS B , the opening  56  on one input control side of the pressure compensator  18  forms the repotting connector LS B1 , and the above designated LS pressure LS B  constitutes the sensing connector. 
     When the pump pressure prevails over the pump connector P, this pressure also acts in the P′ A  or P′ B  chamber of the pressure compensator  18  and presses the control piston against the spring until the corresponding control edge closes. The P′ A  and P′ B  pressure is then adjusted exactly to the amount of the control spring  24  of the pressure compensator  18 . The aforementioned radial openings and passages, as also shown in  FIG. 3 , can be arranged repeatedly along the outer peripheries of the valve spool  16  and control piston of the pressure compensator  18 . 
     If, at this point, a pilot pressure is selected by the pilot valves P A  or P B , the pilot valve preferably being an electrohydraulic pressure reducing valve, with central supply from a control oil circuit P St , the valve spool  16  is pushed against the spring force of the compression spring  22  in the direction of the R channel (compare  FIG. 2 ). The valve orifice then begins to open an opening cross section between the pressure compensator  18  and the respective working connector A or B. Accordingly the P′ A  or P′ B  pressure breaks through because volume is draining. The control spring  24  can then push the control piston in the direction of the opening control edge. Oil continues to flow out of the pump connector P until upstream from the valve orifice a dynamic pressure is formed again which is in equilibrium of forces with the control spring and the reported load pressure. The load pressure is then reported from the fourth radial opening  57  of the valve spool  16  into the longitudinal groove  66  which can likewise extend repeatedly around the periphery of the control piston, and is routed from there through the third radial opening  64  in the control piston into the spring chamber with the other compression spring  24 . With the solution according to the invention, a system-stable valve device is defined to perform a LS flow control function in a space-saving manner. 
     While one embodiment has been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the appended claims.