EP2891805A2 - Control assembly and a control valve for such a control assembly - Google Patents

Abstract

Disclosed is a hydraulic control arrangement for controlling at least one consumer. The control arrangement forms an open-center system. For the at least one consumer, a control valve is provided, via which a circulation flow path extends. This is connected on the one hand to a hydraulic pump and on the other hand to a tank. To the hydraulic pump, the circulation flow path is connected via a pilot orifice, which is thus provided between the hydraulic pump and the control valve. If the control valve actuates the consumer via a metering orifice, the circulation flow path is simultaneously controlled and, in addition, a connection between the circulation flow path and the consumer downstream of the metering orifice is opened. By means of a differential pressure regulator, a pressure difference across the pilot diaphragm and the metering orifice is then kept constant, whereby a fluid volume flow to the load can be varied independently of the load pressure via the metering diaphragm.

Description

The invention is based on a hydraulic control arrangement according to the preamble of claim 1 and a control valve for such a hydraulic control arrangement.

From the data sheet RD 64 122 / 05.03 of the company Rexroth such a hydraulic control arrangement is known. This has a plurality of control valves or throttle control valves, which are each used to control an actuator. With the control valve, a pressure medium connection between the control valve associated actuator and a hydraulic pump and between the actuator and a tank controllable. The control arrangement and the control valves are designed in open-center (OC) construction. In this case, via the control valves extends a circulation channel, which starts from a high-pressure side or a pump line of the hydraulic pump and flows into the tank. In a respective basic position of a valve spool of a respective control valve, the circulation channel is opened. If the valve slide, starting from the basic position, is displaced in the direction of first switching positions or in the opposite direction in the direction of the second switching position, then a pressure medium connection between the hydraulic pump and the actuator is opened and the circulation channel is controlled at the same time. The Zuseuuerung of the circulation channel leads to an increase in pressure in the pump line. If the pump pressure then exceeds a load pressure of the actuated actuator, then a check valve associated with the control valve opens, and the actuator is supplied with pressure medium from the pump line. With such a control valve thus takes place a pressure control. A size of the fluid volume flow flowing to the actuator via the control valve can in this case only be controlled between 0 and a maximum fluid volume flow. The height of the fluid volume flow determines, for example, the speed of the actuator, which may be a hydraulic cylinder. A limitation of the height of the fluid volume flow below the maximum flow rate of the hydraulic pump is only possible if a part of the flow rate under a maximum pressure to the tank on the Circulating channel is throttled. Furthermore, the height of the fluid volume flow is not load pressure independent.

From the data sheet RE 64 121/01.95 of the company Rexroth a further embodiment of a hydraulic control arrangement is disclosed. In this, the circulation channel is connected via a pilot aperture on the pump channel.

Furthermore, it is known from the prior art, via a valve in the form of a differential pressure controller to keep a pressure difference across the pilot valve constant. The differential pressure regulator acts together with a control cylinder of a hydraulic pump in the form of a variable displacement pump. If the valve slide of the control valve is now moved from its basic position in the direction of switching positions, the circulation channel is closed, thus increasing a pressure downstream of the pilot aperture. This, in turn, causes the variable displacement pump to pivot the variable displacement pump so that a pressure upstream of the pilot orifice also increases to maintain the pressure difference across the pilot orifice constant. If the pressure in the pump line then exceeds the load pressure of the actuated actuator, then the check valve associated with the control valve opens and the actuator is supplied with pressure medium. Again, the height of a fluid flow to the actuator can not be controlled and limited load independent.

In contrast, the invention has for its object to provide a hydraulic control arrangement or a throttle control, which can control a size of a fluid volume flow to an actuator, in particular load pressure independent, in a simple manner. Another object of the invention is to provide a control valve for such a control arrangement which is simple and inexpensive.

The object with regard to the hydraulic control arrangement is achieved according to the features of claim 1 and with regard to the control valve according to the features of claim 11.

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

According to the invention, a hydraulic control arrangement, in particular a throttle control, is provided with a hydraulic pump for supplying pressure medium to at least one actuator. On a high-pressure side of the hydraulic pump or on a pump line, the actuator is connected via a control valve. For controlling the actuator, the control valve has a metering orifice. With the metering orifice, in this case, a flow cross-section between the hydraulic pump and the actuator can be set. Furthermore, a circulation flow path is connected to the high pressure side of the hydraulic pump via a pilot orifice. The circulation flow path can be connected to a tank via the control valve (throttle control valve) arranged downstream of the pilot valve. By means of a differential pressure regulator, a pressure difference across the pilot aperture can be kept constant. For this purpose, the differential pressure regulator can tap the pressure upstream and downstream of the pilot diaphragm in order to cooperate with the control arrangement for keeping the pressure difference constant. According to the invention, when the metering orifice of the control valve is closed, the pressure medium connection of the circulation flow path is opened, in particular completely, via the control valve. When controlling the metering orifice, the pressure medium connection of the circulation flow path is controlled by the control valve, and additionally a pressure medium connection between the circulation flow path and the actuator, in particular opened downstream of the metering orifice. The differential pressure regulator is thus connected to the actuator via the control valve when the metering orifice is controlled

Since the differential pressure regulator with controlled metering orifice now taps the pressure downstream of the pilot diaphragm and the metering orifice and upstream of the pilot diaphragm and the metering orifice, the pressure difference across the pilot diaphragm and, secondly, also via the metering orifice is thus kept constant. This advantageously leads to a fluid volume flow over the metering orifice thus being adjustable independently of the load. Via an opening cross section of the metering orifice, the fluid volume flow to the actuator can thus be adjusted independently of the load. So far, only throttling controls or from the prior art Control arrangements known whose characteristic property is that only one pump pressure is controllable. A control of a fluid volume flow from the hydraulic pump to the actuator was previously not possible. A maximum fluid flow rate could previously be provided only at a maximum pump pressure, resulting in high losses. Furthermore, a hydraulic control arrangement according to the invention has extremely low hydraulic losses, resulting in energy savings and cost reduction.

In a further embodiment of the invention, the hydraulic pump is preferably a variable displacement pump, which is pivotable via a control cylinder. The differential pressure regulator can in this case cooperate with the variable displacement pump and the actuating cylinder in such a way that the pressure difference across the pilot diaphragm and with the metering diaphragm open is also constant over the metering diaphragm.

The differential pressure regulator can be designed as a continuously adjustable 3/2-way valve. A valve slide can be acted upon by a spring force of a valve spring and the pressure downstream of the pilot diaphragm or upstream of the control valve in the direction of a basic position. In the basic position of the actuating cylinder can be relieved to the tank so that the variable displacement is pivoted in the direction of a higher flow rate. In the opposite direction of the valve spool can be acted upon by the pump pressure or by the pressure of the high pressure side of the hydraulic pump in the direction of switching positions. In these, the actuating cylinder can be supplied with pressure medium from the variable displacement pump such that the variable displacement pump is pivoted in the direction of a smaller flow rate.

Advantageously, a check valve is associated with the control valve and / or the actuator to hold a load of the actuator if the load pressure is higher than the pump pressure. The check valve is preferably arranged upstream of the metering orifice. It may for example be formed in the control valve or arranged outside the control valve.

Preferably, a further check valve is arranged for load-holding in the pressure medium flow path between the pilot diaphragm and the control valve. This check valve may also be formed in the control valve in the pressure medium flow path between the pilot orifice and the working port of the control valve. It is also conceivable to arrange this check valve outside of the control valve.

If a plurality of actuators or consumers are to be controlled, then it is advantageous to provide a plurality of control valves for each actuator. The control valves are fluidly connected in parallel to the high pressure side of the hydraulic pump. The circulation flow path extends over all the control valves. With regard to the circulation flow path, the control valves are thus arranged fluidly in series. With the hydraulic control arrangement according to the invention, the fluid volume flow for a respective actuator can thus be both controlled and limited and adapted to the individual requirements of a respective actuator.

If a plurality of actuators and thus a plurality of control valves are provided, the control and limitation of the fluid volume flow from the hydraulic pump to the respective actuator can be carried out independently of the load pressure in a single movement and, incidentally, for the load pressure-highest actuator.

The control valve preferably has two working ports to which the actuator is connected. Furthermore, it has a pressure connection for the hydraulic pump and a tank connection. In a basic position of the valve spool, all connections can be blocked. Upon a displacement of the valve spool outgoing from the basic position in the direction of first switching positions, the first working port can then be connected to the pressure port via the metering orifice and the second working port to the tank port. If the valve slide is moved from its basic position in the direction of second switching positions, the second working port can be connected to the pressure port via the metering orifice and the first working port to the tank port. It is conceivable to provide a control valve with only one working port, whereby the valve spool, starting from its basic position, can only be displaced in one direction.

For the circulation flow path, the control valve may have an input port and an output port. In the first switching positions, a pressure medium connection between the input connection and the first working connection can be controlled via the valve slide. With an opposite displacement in the direction of the second switching positions, a pressure medium connection can then be controlled between the input connection and the second working connection. Such a control valve is extremely simple in design and results in that the circulation flow path is connected in a simple manner to the load port subjected to working pressure.

In addition to the differential pressure regulator, the variable displacement pump can be assigned a maximum pressure regulator. This is designed such that it interacts when reaching a set maximum pump pressure in such a way with the variable displacement pump or the actuating cylinder, that the maximum pump pressure is not exceeded.

Advantageously, the valve spool of the control valve is spring-centered in its basic position. It can for example be electrically, hydraulically or manually operable.

As an actuator, for example, a hydraulic cylinder, in particular in the form of a differential cylinder, is provided.

The hydraulic control arrangement or the throttle control is preferably used in compact construction machines, in particular backhoe loaders, telescopic loaders, wheel loaders and mini and compact excavators for actuating their actuators or their working hydraulics.

In a further embodiment of the invention, the control valve or the control valves are arranged in a valve block. In this all other valves and possibly also the variable displacement can be arranged with the actuating cylinder. Alternatively, it is conceivable to provide a valve disc for a respective control valve.

Alternatively, the control valve may have an inlet connection and an outlet connection for the circulation flow path, wherein a displacement of the valve slide starting from the basic position in the direction of the first switching positions a pressure medium connection between the input port and the first working port is controlled, a pressure medium connection between the second working port and the tank port is controlled and in addition a pressure medium connection between the second working port and the pressure port is opened. This is extremely advantageous when the control valve is used to control a differential cylinder. The second working port is advantageously connected to the rod-side chamber of the differential cylinder. At the valve spool, only a comparatively small flow cross section for the pressure medium displaced from the rod side is released to the tank, so that a larger part of the pressure medium displaced from the rod side flows via the control valve to the first working port and thus to the bottom side of the differential cylinder due to the pressure ratio. About the metering orifice of the valve spool now flows a sum of the back flowing from the rod side of the differential cylinder and flowing from the variable flow of fluid. The differential pressure regulator of the variable displacement pump measures and limits the pressure difference across the metering orifice. In a limiting case, when the pressure fluid connection between the second working port and the tank is closed, the variable displacement pump only promotes the displaced by a piston rod of the differential cylinder volume.

Preferably, a control valve according to the invention for the hydraulic control arrangement has at least one working connection, preferably two working connections, for connecting an actuator. Further, the control valve preferably has a pressure port or pressure port for connecting a hydraulic pump, a tank port or tank passage, and an input and an output port or an input and output port for a recirculation flow path. With a displacement of a continuously adjustable valve slide starting from a basic position in the direction of switching positions, a pressure medium connection between the working port and the pressure port and the working port and the input port aufsteubar be. Furthermore, during this displacement, a pressure medium connection between the input connection and the output connection can be controllable.

Such a control valve is extremely simple in terms of device design and, when used in a conventional hydraulic control arrangement or throttle control, as a substitute for the control valves used there, leads to the advantages explained above.

In a valve housing of the control valve may be provided between the pressure port and the working port upstream of the valve spool in the direction of pressure fluid flow toward the valve spool opening check valve.

As already explained above, the control valve may have a further second working port.

Advantageously, the valve slide in a valve bore of the valve housing or a valve block or a valve disc is slidably disposed. In this case, the valve slide preferably has a first control edge for controlling the pressure medium connection between the pressure connection and the first working connection. With a second control edge, a pressure medium connection between the input port and the output port can be controlled in a first direction of displacement of the valve spool. The pressure medium connection between the input connection and the first working connection can be controlled via a third control edge. A fourth control edge can be used to control the pressure medium connection between the second working connection and the tank connection. A fifth control edge may be used to control the pressure medium connection between the inlet and outlet ports in a second direction of displacement of the valve spool. A sixth control edge preferably serves for controlling the pressure medium connection between the input connection and the second working connection. A seventh control edge is provided for controlling the pressure medium connection between the first working port and the tank port. With an eighth control edge can a Pressure fluid connection between the second working port and the input port to be controlled. If the control valve is designed for only one working connection, then it is conceivable to provide only the first, second, third and seventh control edges.

Preferably, upon a displacement of the valve slide, starting from a basic position in the direction of first switching positions, the first, the third and the fourth control edge open a flow cross-section. The second control edge in this case preferably controls a flow cross section. The sixth control edge can remain closed. In a displacement of the valve spool, starting from the basic position in the direction of second switching positions, the sixth, seventh and eighth control edge can open a flow cross-section, while the fifth control edge is heading for a flow cross-section. The third control edge can remain closed.

In terms of apparatus technology, the third and the eighth control edges can be formed by at least one radial bore in the valve slide. This can each open via a in the valve slide, in particular axially introduced blind hole, via which it is then fluidly connected to the respective working port, in particular via an introduced into the valve spool radial bore. The third and eighth control edge can also be designed in each case as a bore star. In the blind hole, a check valve opening in the direction of the pressure medium flow towards the working connection can be provided.

Advantageously, the blind hole is stepped and formed from an end face of the valve slide ago. At a step transition in this case a valve seat is formed, on which a valve body of the check valve can sealingly abut. The valve body is in this case arranged in a larger diameter portion having the blind hole. In the direction of the valve seat, the valve body is acted upon by a spring force of a valve spring, which is supported on a closure element occluding the blind hole bore. If the valve body lifted from the valve seat, so he gives a fluid connection between the Blind hole and at least one opening in the area of the working port radial bore free.

• Figur 1 einen hydraulischen Schaltplan einer erfindungsgemäßen Steueranordnung gemäß einer Ausführungsform,
• Figur 2 in einem Längsschnitt ein erfindungsgemäßes Steuerventil der Steueranordnung aus Figur 1 gemäß einer ersten Ausführungsform und
• Figur 3 in einem Längsschnitt das Steuerventil gemäß einer zweiten Ausführungsform.

In the following, preferred embodiments of the invention are explained in more detail with reference to drawings. Show it:

• FIG. 1 FIG. 2 shows a hydraulic circuit diagram of a control arrangement according to the invention according to an embodiment, FIG.
• FIG. 2 in a longitudinal section of an inventive control valve of the control arrangement FIG. 1 according to a first embodiment and
• FIG. 3 in a longitudinal section, the control valve according to a second embodiment.

FIG. 1 shows a hydraulic control assembly 1, which is used as a throttle control for compact construction machinery and a flow control and - limit allows. The control arrangement 1 has a first control valve 2 designed as a throttle valve and a second control valve 4 designed as a throttle valve. These serve to control a respective actuator 6 or 8. For supplying pressure medium to the actuators 6 and 8, a hydraulic machine in the form of a variable displacement pump 10 is provided with an actuating cylinder 12 intended. To regulate the variable displacement pump 10, the control arrangement 1 has a differential pressure regulator 14 and a maximum pressure regulator 16. The maximum pressure regulator 16 in this case limits a maximum pump pressure of the variable displacement pump 10.

The variable displacement pump 10 conveys pressure fluid from a tank line 20 connected to a tank 18 into a pump line 22, which constitutes the high-pressure side of the variable displacement pump 10. To the pump line 22, a respective control valve 2 and 4 connected to a pressure line 24. In the pressure line 24 in each case one in the pressure fluid flow direction away from the variable displacement pump 10 and toward the respective control valve 2 and 4 opening check valve 26 is provided. A respective pressure line 24 then opens into a pressure port P of the control valve 2 and 4, respectively. With a tank line 28, a respective control valve 2 or 4 is connected to the tank 18, wherein the Tank line 28 extends from a tank port T of the control valve 2 and 4, respectively. For the actuators 6 and 8, a respective control valve 2 or 4 has a first and second working port A and B. To a respective first working port A, a first working line 30 is connected and to a respective second working port B, a second working line 32. The actuators 6 and 8 are designed as hydraulic cylinders in the form of differential cylinders. They each have a piston 34 which separates a first cylinder chamber 36 from a second cylinder chamber 38. The second cylinder chamber 38 is in this case penetrated by a piston rod 40, whereby it is designed as an annular chamber.

Furthermore, a circulation flow path in the form of a circulation line 42 is connected to the pump line 22. This extends here via the control valves 2 and 4 and opens into the tank 18. For the circulation line 42, a respective control valve 2 or 4 has an input terminal D and an output terminal D '. In the pressure medium flow path between the pump line 22 and the first control valve 2, a pilot diaphragm 44 is arranged in the circulation line 42. The differential pressure regulator 14 in this case grips the pressure via a control line 48 downstream of the pilot orifice 44-between the latter and the first control valve 2 -via a control line 46 and upstream of the pilot orifice 44-between the variable displacement pump 10 and the pilot orifice 44. The differential pressure regulator 14 is designed in such a way that, in cooperation with the actuating cylinder 12 and the variable displacement pump 10, it keeps a pressure difference Δp constant over the pilot orifice 44. The differential pressure controller 14 is designed for this purpose as a continuously adjustable 3/2-way valve. A valve spool of the differential pressure regulator 14 is acted upon in the direction of a basic position 0 by the pressure medium of the control line 46 and a spring force of a valve spring 50 and opposite in the direction of switching positions a from the pressure medium of the control line 48. In the basic position 0 in this case a connecting line 52 is relieved to the maximum pressure regulator 16 to the tank 18 and in the switching positions a, the connecting line 52 is connected to the pump line 22.

The maximum pressure regulator 16 is also designed as a continuously adjustable 3/2-way valve. A valve spool is in this case via a valve spring 54 with a spring force in the direction of a basic position 0 applied. Furthermore, an effective in this direction pressure surface of the valve spool is connected via a branch line 56 to the tank 18. Opposite in the direction of switching positions a of the valve spool is acted upon via a control line 58 with pressure medium from the pump line 22. In the basic position 0 while a connection between the connecting line 52 and a cylinder line 60 is opened, wherein the cylinder line 60 is connected to the actuating cylinder 12. In the switching positions a, the cylinder line 60 to the pump line 22 in fluid communication.

The adjusting cylinder 12 is configured as a differential cylinder and has a piston 62 which separates a first cylinder chamber 64 from a second cylinder chamber 66. The second cylinder chamber 66 is in this case penetrated by a piston rod 68, wherein the piston rod 68 is connected to the variable displacement pump 10 in order to pivot it. The first cylinder chamber 64 is connected to the cylinder line 60. In the direction of a reduction of the first cylinder chamber 64, the actuating cylinder 12 pivots about its piston rod 18, the variable displacement pump 10 in the direction of a larger delivery volume. In the same direction, the variable displacement pump 10 is acted upon by a spring force of a spring 70. It is conceivable to design the differential cylinder alternatively as a plunger cylinder.

The structure of the control valves 2 and 4 is explained in more detail below with reference to the control valve 4. The control valve 4 is designed as a continuously adjustable 6/3-way valve. In a spring-centered position 0 of the valve spool the working ports A, B, the tank port T and the pressure port P are locked, and the input port D is connected to the output terminal D '. Upon a displacement of the valve spool, starting from the basic position 0 in the direction of first switching positions x, the pressure medium connection between the pressure port P and the first working port A is opened, with which the first cylinder chamber 36 of the actuator 8 can be supplied with pressure medium. Furthermore, the second working port B is connected to the tank port T and thus relieves the second cylinder chamber 38 of the actuator 8 to the tank. An opening cross-section between the pressure port P and the working port A depends on a displacement of the valve spool in the direction of the first switching positions x. Of the Valve spool is thus used as a metering orifice 72. Furthermore, when the valve slide is displaced in the switching positions x, the connection between the input connection D and the output connection D 'is controlled and, in turn, a pressure medium connection between the input connection D and the first working connection A is opened. Here, in the pressure medium flow path between D and the first working port A, a check valve 74 opening towards the actuator 8 is provided. In contrast to the prior art, not only the circulation line 42 is thus controlled, but at the same time a connection between the circulation line 42 and the load connection having a working connection, in this case the first working connection A, produced. If the valve spool, starting from the basic position 0, is displaced in the opposite direction in the direction of second switching positions y, the pressure port P is connected to the second working port B and the first working port A is connected to the tank port T. Thus, the second cylinder chamber 38 can be supplied with pressure medium from the variable displacement pump 10 and the first cylinder chamber 36 relieved to the tank. Upon a displacement of the valve spool in the direction of the switching positions y, the connection between the input terminal D and the output terminal D 'is also controlled again and at the same time a connection between the first working port B and the inlet port D via a check valve 76 is opened. In this case, the check valve 76 opens according to the check valve 74 in a pressure fluid flow direction from the input terminal D to the actuator 8 and the second working port B. In the switching positions x and y, the input terminal D downstream of the metering orifice 72 is connected to the respective working port A, B. ,

By the control valves 2 and 4, a load-independent flow control is now possible. If the valve spool of the control valve 2 is displaced, for example, from its basic position 0 in the direction of the switching positions x, then both the pressure port P and the input port D are connected to the first working port A. As a result, the differential pressure regulator 14 keeps the pressure difference constant both via the pilot orifice 44 and via the metering orifice 72. Thus, over the opening cross section of Zumessbrende 72 load pressure independent of the flow to the actuator 6 can be adjusted.

The check valves 26, 74 and 76 serve to load in the event that a pump pressure is below the load pressure.

In FIG. 2 the control valve 2 is shown. This has a valve housing 78, in which a slide bore 80 is formed for a valve spool 82. In the valve housing 78, a tank channel 84 is further provided, which extends approximately transversely to the longitudinal direction of the valve spool 82. Are the control valves 2 and 4 off FIG. 1 formed in a common valve block, the tank channel 84 may extend through the entire valve block and open into a tank connection to the valve block. Furthermore, a pump channel 86 is provided in the valve housing 78, which extends corresponding to the tank channel 84 approximately parallel to this. Furthermore, the working ports A and B are provided in the valve housing 78.

The spool bore 80 is included in the valve housing 78 of a total of nine annular grooves 88 to 104, which are arranged in series one behind the other. The two outer annular grooves 88 and 104 are in this case connected to the tank channel 84. The annular groove 88 adjacent to the annular groove 90 is connected to the first working port A and the annular groove 104 adjacent to the annular groove 102 with the second working port B. The provided after the annular groove 90 annular groove 92 is connected to the pump channel 86. The same applies to the annular groove 100, which is arranged in front of the annular groove 102. The connection with the pump channel 86 takes place via a check valve 106 arranged in the valve housing 78. This opens in a pressure medium flow direction away from the pump channel 86 to the annular grooves 92 and 100. The central annular groove 96 is connected to the outlet port D ', see also Fig.1 , connected. The annular grooves 94 and 98 adjacent to the central annular groove 96 are respectively connected to the input terminal D, see also Fig.1 ,

In the Fig. 2 shown basic position 0 of the valve spool 82 is the pressure medium connection between the annular grooves 94 and 96 via a control edge 108th the valve spool 82 is opened. Via a further control edge 110 and the pressure medium connection between the annular groove 98 and the annular groove 96 is opened. All other annular grooves 88, 90, 92, 100, 102, 104 are separated from each other. If the valve spool 82 from the in FIG. 2 shown shifted to the right, so he gets into the switch positions x, see also FIG. 1 , In this case, a pressure medium connection between the pump channel 86 and the first working port A is opened up via a control edge 112 of the valve slide 82. The flow cross section between the annular grooves 94, 96 and 98 is controlled via the control edge 108 and via a further control edge 114. Furthermore, the second working port B is connected to the tank channel 84 via a control edge 116 of the valve spool 82. The connection of the input terminal D to the first working port A, see also FIG. 1 , via a introduced into the valve spool 82 bore star 118 which opens into an axial blind hole 120 of the valve spool 82. In the switching positions x of the bore star 118 is disposed in the region of the annular groove 94 and represents a control edge 122. The blind hole 120 is introduced from an end face of the valve spool 82 and extends in the axial direction, in particular via the annular grooves 88 to 92. In the region of the annular groove 90, which is connected to the first working port A, 82 radial bores 124 are introduced in the valve spool. These also open in the blind hole 120. The blind hole 120 is stepped, whereby at the step transition, a valve seat is formed. This is located in the axial direction between the radial bores 124 and the bore star 118. The valve seat is in this case a valve body 126 of the check valve 74, see also FIG. 1 , assigned. The valve body 126 is slidably guided in the blind hole 120 and is acted upon by a spring force of a valve spring 128 in the direction of the valve seat. The valve spring 128 in turn is supported on a screw 130 (closure element), which is screwed into the valve spool 82 from. In the first switching positions x thus the input terminal D via the annular groove 94, the bore star 118, the blind hole 120, the check valve 74 with the radial bore 124 and thus the annular groove 90 is connected, which in turn is connected to the first working port A.

With a displacement of the valve spool 82 in the direction of the switching positions x thus the input terminal D is closed by the output terminal D 'with increasing displacement, whereby a pressure in the circulation line 42 from FIG. 1 is throttled. The check valve 74 or load-holding valve opens as soon as the pressure in the circulation line 42 or in the annular groove 94 exceeds the load pressure of the first working port A. The check valve 74 is then open. Thus, the load pressure is reported to the circulation line 42 and the differential pressure controller 14 holds a pressure difference Δp regardless of the controlled by the control edge 112 opening area constant.

If the valve spool 82 off FIG. 2 starting from the basic position shown in the direction of switching positions y, see also FIG. 1 shifted, a pressure medium connection between the second working port B and the pump channel 86 is controlled via a control edge 132 of the valve spool 82. With the control edge 110 then the pressure medium connection between the annular groove 98 and the annular groove 96 is controlled. With a further control edge 134, the pressure medium connection between the annular groove 96 and the annular groove 94 is controlled. With a control edge 136 of the valve spool 82, a pressure medium connection between the first working port A and the tank channel 84 is opened. The valve spool 82 is designed mirror-symmetrically and thus is also in the switching positions y a pressure medium connection between the input terminal D and the second working port B before. This is done via a bore star 136, which serves as a control edge 138, a blind hole 140, the check valve 76 and the radial bore 142nd

The control edges 124, 112, 108, 110, 132 and 116 each have fine control notches.

The operation of the control valve is in the second switching positions y substantially corresponding to the first switching positions x.

In the second embodiment of a control valve 144 according to FIG. 3 is a regeneration a volume flow provided when the valve spool 82 starting from his in the FIG. 3 shown basic position in the direction of the first switching position x is moved to the right. In contrast to the embodiment of FIG. 2 is the bore star 136 seen in the axial direction towards the radial bore 142 offset. This results in that when the valve spool 82 is fully moved in the direction of the switching positions x, the bore star 136 is located in the region of the annular groove 100 and thus connected to the pump channel 86. In the blind bore 140, a differently configured check valve 144 is further provided. The valve body 146 has a through-bore with a nozzle, with which pressure medium from the bore star 136 in the spring chamber 150 can flow. If the valve body 146 rests on the valve seat, the pressure in the bore star 136 acts in the opening direction on a pressure surface A ₁ and the pressure of the radial bore 142 via an annular pressure surface A ₂ and thus the pressure of the second working connection B. In the closing direction acts on a pressure surface A _{3 of} the valve body 146 then the pressure in the spring chamber 150. The pressure surface A ₃ is the sum of the pressure surface A ₁ and A ₂ . If the pressure of the working port B exceeds the pressure in the bore star 136 and thus the pressure in the pump channel 86, the valve body 146 is moved away from its valve seat and thus away from the bore star 136 and a connection between the bore star 136 and the radial bore 142 is opened. In turn, this is the second working port B with the pump channel 86 in communication. It can thus flow pressure medium from the second working port B to the first working port A, whereby a so-called "regeneration" of pressure medium is present. The variable 10 from FIG. 1 then has to promote less pressure medium.

Disclosed is a hydraulic control arrangement for controlling at least one consumer. The control arrangement forms an open-center system. For the at least one consumer, a control valve is provided, via which a circulation flow path extends. This is connected on the one hand to a hydraulic pump and on the other hand to a tank. To the hydraulic pump, the circulation flow path is connected via a pilot orifice, which is thus provided between the hydraulic pump and the control valve. If the control valve actuates the consumer via a metering orifice, the circulation flow path is simultaneously controlled and, in addition, a connection between the circulation flow path and the consumer downstream of the metering orifice is opened. About one Differential pressure regulator is then kept a pressure difference across the pilot diaphragm and the metering orifice constant, whereby a fluid volume flow to the load load pressure independent via the metering orifice is variable.

LIST OF REFERENCE NUMBERS

1

control arrangement

2

control valve

4

control valve

6

actuator

8th

actuator

10

variable

12

actuating cylinder

14

Differential pressure regulator

16

Maximum pressure regulator

18

tank

20

tank line

22

pump line

24

pressure line

26

check valve

28

tank line

30

first line of work

32

second working line

34

piston

36

first cylinder chamber

38

second cylinder chamber

40

piston rod

42

circulation line

44

pilot orifice

46

control line

48

control line

50

valve spring

52

connecting line

54

valve spring

56

branch line

58

control line

60

cylinder line

62

piston

64

first cylinder chamber

66

second cylinder chamber

68

piston rod

70

spring

72

metering orifice

74

check valve

76

check valve

78

valve housing

80

slide bore

82

valve slide

84

tank channel

86

pump channel

88

ring groove

90

ring groove

92

ring groove

94

ring groove

96

ring groove

98

ring groove

100

ring groove

102

ring groove

104

ring groove

106

check valve

108

control edge

110

control edge

112

control edge

114

control edge

116

control edge

118

bore star

120

Blind hole

122

control edge

124

radial bore

126

valve body

128

valve spring

130

screwing

132

control edge

134

control edge

136

bore star

138

control edge

140

Blind hole

142

radial bore

144

check valve

146

valve body

150

spring chamber

P

pressure connection

T

tank connection

A, B

working port

D

input port

D '

output port

0

initial position

a, x, y

switching positions

Claims (15)

Hydraulic control arrangement with a hydraulic pump (10) for supplying pressure medium to at least one actuator (6, 8), the actuator (6, 8) being connected to a high-pressure side (22) of the hydraulic pump (10) via a control valve (2, 8) having a metering orifice (72). 4), wherein with the metering orifice (72) a flow cross-section between the hydraulic pump (10) and the actuator (6, 8) is adjustable, and wherein on the high-pressure side (22) a circulation flow path (42) via a pilot diaphragm (44) is connected, wherein the circulating flow path (42) via the control valve (2, 4) with a tank (18) is connectable, and wherein a differential pressure regulator (14) is provided, which taps a pressure upstream and downstream of the pilot orifice (44) and so interacts with the control arrangement (1) in such a way that a ducking difference across the pilot orifice (44) is constant, characterized in that, when the metering orifice (72) is controlled, a pressure medium connection of the circulation flowpath (42) by the control Valve (2, 4) is opened, wherein when the metering orifice (72) is opened, the pressure medium connection of the circulation flow path (42) is controlled by the control valve (2, 4) and a pressure medium connection between the circulation flow path (42) and the actuator (6, 8 ) is controlled downstream of the metering orifice (72). Control arrangement according to claim 1, wherein the hydraulic pump is a variable displacement pump (10) which is pivotable via a control cylinder (12), wherein the differential pressure regulator (14) cooperates with the variable displacement pump (10) and the actuating cylinder (12) such that the pressure difference across the pilot diaphragm (44) is constant. Control arrangement according to claim 1 or 2, wherein the control valve (2, 4) is associated with a check valve (26) upstream of the metering orifice (72). A control arrangement according to any one of claims 1 to 3, wherein a check valve (74, 76) is disposed in the pressure medium flow path between the pilot orifice (44) and the control valve (2). Control arrangement according to one of claims 1 to 4, wherein a plurality of control valves (2, 4) for a respective actuator (6, 8) are provided, wherein the control valves (2, 4) with respect to a pressure medium connection between the hydraulic pump (10) and its respective actuators (6, 8) are arranged fluidically parallel to one another, and wherein the control valves (2, 4) are fluidly arranged in series with respect to the circulating flow path (42). Control arrangement according to one of the preceding claims, wherein the control valve (2, 4) has two working ports (A, B) to which the actuator (6, 8) is connected, a pressure port P and a tank port (T), wherein in a normal position the valve spool all ports (A, B, P, T) are locked, and wherein upon a displacement of the valve spool in the direction of first switching positions (x) of the first working port (A) with the pressure port (P) via the metering orifice (72) and the second working port (B) is connected to the tank port (T), and wherein upon displacement of the valve spool in the direction of second switching positions (y) the second working port (B) communicates with the pressure port (P) via the metering orifice (72) and the first working connection (A) is connected to the tank connection (T). A control arrangement according to claim 6, wherein the control valve (2, 4) has an input port (D) and an outlet port (D ') for the recirculation flow path (42), wherein upon displacement of the valve spool (82) from the home position (0) in FIG Direction of the first switching positions (x) a pressure medium connection between the input terminal (D) and the first working port (A) is controlled and / or upon displacement of the valve spool (82) starting from the basic position (0) in the direction of the second switching positions (y) a pressure medium connection between the input terminal (D) and the second working port (B) is opened. A control arrangement according to claim 6, wherein the control valve (2, 4) has an input port (D) and an outlet port (D ') for the recirculation flow path (42), wherein upon displacement of the valve spool (82) from the home position (0) in FIG Direction of the first switching positions (x) a pressure medium connection between the input terminal (D) and the first working port (A) is controlled and a pressure medium connection between the second working port (B) and the tank port (T) and / or between the second working port (B) and the pressure medium connection (P) is turned on. Control arrangement according to one of the preceding claims, wherein the variable displacement pump (10) is associated with a maximum pressure regulator (16). Control arrangement according to one of the preceding claims, wherein the control valve (2, 4) or the control valves (2, 4) are arranged in a valve block. Control valve for a hydraulic control arrangement according to one of the preceding claims with at least one working port (A, B) for connecting an actuator (6, 8), a pressure channel (P) for connecting a hydraulic pump (10), a tank channel (T), an input channel (D) for a recirculation flow path (42) and an outlet channel (D ') for the recirculation flow path (42), wherein in a displacement of a continuously adjustable valve spool (82) starting from a basic position (0) in the direction of switching positions (x) a pressure medium connection between the working port (A) and the pressure channel (P) and the working port (A) and the input channel (D) is aufsteuerbar and a pressure medium connection between the input channel (D) and the output channel (D ') is zusteuerbar. Control valve according to claim 11, wherein it has a further second working port (A, B). A control valve according to claim 12, wherein the valve spool (82) is slidably disposed in a valve bore (80) of a valve housing (78), wherein the valve spool (82) has a first control edge (112) for controlling a pressure medium connection between the pressure channel (P) and the first working port (A), a second control edge (108, 114) for controlling the pressure medium connection between the input port (D) and the output port (D ') in a first direction of displacement of the valve spool, a third control edge (122) for controlling the pressure medium connection between the input channel (D) and the first working port (A), a fourth control edge (116) for controlling the pressure medium connection between the second working port ( B) and the tank channel (T), a fifth control edge (110, 134) for controlling the pressure medium connection between the input channel (D) and the output channel (D ') in a second direction of displacement of the valve spool (82), a sixth control edge (132) for controlling the fluid connection between the pressure channel (P) and the second working port (B), a seventh control edge (124) for controlling the pressure means Connection between the first working port (A) and the tank channel (T) and an eighth control edge (138) for controlling a pressure medium connection between the input channel (D) and the second working port (B). Control valve according to claim 13, wherein upon displacement of the valve slide (82) starting from a basic position (0) in the direction of first switching positions (x), the first, third and fourth control edges (112, 122, 116) open a flow cross-section and the second control edge (108, 114) controls a flow cross-section, and wherein in a displacement of the valve spool (82) starting from the basic position (0) in the direction of second switching positions (y), the sixth, seventh and eighth control edge (138, 124, 132) has a flow cross-section aufsteuern and the fifth control edge (110, 134) controls a flow cross-section. Control valve according to claim 13 or 14, wherein the third and eighth control edges (122, 138) are each formed by at least one radial bore (118, 136) in the valve slide (82), each via a in the valve slide (82) introduced blind hole ( 120, 140) are fluidically connected to the respective working port (A, B).

Images