EP2891805B1 - Control assembly and a control valve for such a control assembly - Google Patents

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.

Such a hydraulic control arrangement is known from data sheet RE 64 122 / 05.03 from Rexroth. This has a plurality of control valves or throttle control valves, which are each used to control an actuator. A pressure medium connection between the actuator assigned to the control valve and a hydraulic pump and between the actuator and a tank can be controlled with the control valve. The control arrangement and the control valves are designed in an open center (OC) design. A circulation channel extends from the control valves, starting from a high-pressure side or a pump line of the hydraulic pump and opening into the tank. The circulation channel is opened in a respective basic position of a valve spool of a respective control valve. If the valve slide is shifted from the basic position in the direction of the first switching positions or in the opposite direction in the direction of the second switching position, a pressure medium connection between the hydraulic pump and the actuator is opened and the circulation channel is closed at the same time. The control 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, a check valve assigned to the control valve opens, and the actuator is supplied with pressure medium from the pump line. Pressure control is thus carried out with such a control valve. A size of the fluid volume flow flowing through the control valve to the actuator can only be controlled between 0 and a maximum fluid volume flow. The level of the fluid volume flow determines, for example, the speed of the actuator, which can be a hydraulic cylinder. Limiting the level of the fluid volume flow below the maximum delivery volume flow of the hydraulic pump is only possible if a part of the delivery volume flow is below the maximum pressure to the tank Circulation channel is throttled. Furthermore, the level of the fluid volume flow is not independent of the load pressure.

From the data sheet RE 64 121 / 01.95 a further embodiment of a hydraulic control arrangement is disclosed by Rexroth. In this case, the circulation channel is connected to the pump channel via a pilot orifice. document US2013 / 220425 A1 discloses a hydraulic arrangement according to the preamble of claim 1 and a control valve according to the preamble of claim 11. Document US4089169 A discloses a control valve with a signal port.

Furthermore, it is known from the prior art to keep a pressure difference across the pilot valve constant via a valve in the form of a differential pressure regulator. The differential pressure controller interacts with an actuating cylinder of a hydraulic pump in the form of a variable pump. If the valve spool of the control valve is now moved from its basic position in the direction of switching positions, the circulation channel is closed, which increases the pressure downstream of the pilot orifice. This in turn leads to the variable pressure controller pivoting the variable pump such that a pressure upstream of the pilot orifice also rises in order to keep the pressure difference across the pilot orifice constant. If the pressure in the pump line then exceeds the load pressure of the actuated actuator, the check valve assigned to the control valve opens and the actuator is supplied with pressure medium. Here too, the level of a fluid volume flow to the actuator cannot be controlled and limited independently of the load.

In contrast, the invention has for its object to provide a hydraulic control arrangement or a throttle control that can easily control a size of a fluid volume flow to an actuator, in particular independent of the load pressure. 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 dependent claims.

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. The actuator is connected to a high-pressure side of the hydraulic pump or to a pump line via a control valve. The control valve has a metering orifice for controlling the actuator. A flow cross-section between the hydraulic pump and the actuator can be set with the metering orifice. Furthermore, a circulation flow path is connected to the high-pressure side of the hydraulic pump via a pilot orifice. The circulating flow path can be connected to a tank via the control valve (throttle control valve) arranged downstream of the pilot valve. A pressure difference across the pilot orifice can be kept constant using a differential pressure regulator. For this purpose, the differential pressure controller can tap the pressure upstream and downstream of the pilot orifice 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 circulating flow path via the control valve is opened, in particular completely. When the metering orifice is opened, the pressure medium connection of the circulating flow path is controlled by the control valve, and additionally a pressurized medium connection between the circulating flow path and the actuator downstream of the metering orifice is opened. The differential pressure controller is thus connected to the actuator via the control valve when the metering orifice is open
Since the differential pressure controller now taps the pressure downstream of the pilot orifice and the metering orifice and upstream of the pilot orifice and the metering orifice, the pressure difference is kept constant on the one hand via the pilot orifice and on the other hand also via the metering orifice. This advantageously leads to a fluid volume flow being adjustable via the metering orifice independently of the load. The fluid volume flow to the actuator can thus be set independently of the load via an opening cross section of the metering orifice. So far only throttle controls are from the prior art Control arrangements are known whose characteristic property is that only a pump pressure can be controlled. Control of a fluid volume flow from the hydraulic pump to the actuator has not previously been possible. Up to now, a maximum fluid volume flow could only be provided at a maximum pump pressure, which leads to high losses. A hydraulic control arrangement according to the invention furthermore has extremely low hydraulic losses, which leads to energy savings and cost reductions.

In a further embodiment of the invention, the hydraulic pump is preferably a variable displacement pump which can be pivoted via an actuating cylinder. The differential pressure controller can interact with the variable displacement pump and the actuating cylinder in such a way that the pressure difference across the pilot orifice and, when the metering orifice is open, is also constant via the metering orifice.

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 orifice or upstream of the control valve in the direction of a basic position. In the basic position, the actuating cylinder can be relieved of the load on the tank in such a way that the variable displacement pump is pivoted in the direction of a higher delivery volume flow. In the opposite direction, the valve slide can be acted upon by the pump pressure or by the pressure on the high-pressure side of the hydraulic pump in the direction of switching positions. In this, the actuating cylinder can be supplied with pressure medium from the adjusting pump in such a way that the adjusting pump is pivoted in the direction of a smaller delivery volume flow.

A check valve is advantageously assigned to the control valve and / or the actuator in order 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. For example, it can be formed in the control valve or arranged outside of the control valve.

Another check valve for holding the load in the pressure medium flow path is preferably arranged between the pilot orifice and the control valve. This check valve can also be formed in the control valve in the pressure medium flow path between the pilot orifice and the working connection of the control valve. It is also conceivable to arrange this check valve outside of the control valve.

If several actuators or consumers are to be controlled, 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 control valves. With regard to the circulation flow path, the control valves are thus fluidly arranged in series with one another. 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 several actuators and thus several control valves are provided, the control and limitation of the fluid volume flow from the hydraulic pump to the respective actuator can take place independently of the load pressure during a single movement and, moreover, for the actuator with the highest load pressure.

The control valve preferably has two working connections to which the actuator is connected. It also 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. When the valve spool is displaced from the basic position in the direction of the first switching positions, the first working connection can then be connected to the pressure connection via the metering orifice and the second working connection can be connected to the tank connection. If the valve slide is shifted from its basic position towards second switching positions, the second working connection can be connected to the pressure connection via the metering orifice and the first working connection can be connected to the tank connection. It is conceivable to provide a control valve with only one working connection, with which the valve spool can only be displaced in one direction from its basic position.

For the circulation flow path, the control valve can have an input port and an output port. In the first switching positions, a pressure medium connection between the input port and the first working port can be controlled via the valve slide. With an opposite shift in the direction of the second switching positions, a pressure medium connection between the input port and the second working port can then be opened. Such a control valve is designed to be extremely simple and leads to the circulation flow path being connected in a simple manner to the working connection to which the load pressure is applied.

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

The valve spool of the control valve is advantageously spring-centered in its basic position. For example, it can be actuated electrically, hydraulically or manually.

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

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. All other valves and possibly also the variable displacement pump with the adjusting cylinder can also be arranged in this. Alternatively, it is conceivable to provide a valve disk for a respective control valve.

Alternatively, the control valve can have an input connection and an output connection for the circulating flow path, with a pressure medium connection between the input connection and the first working connection being opened when the valve slide is shifted from the basic position in the direction of the first switching positions, a pressure medium connection between the second working connection and the tank connection is controlled and additionally a pressure medium connection between the second working connection and the pressure connection is controlled. This is extremely advantageous if the control valve is used to control a differential cylinder. The second working connection is advantageously connected to the rod-side chamber of the differential cylinder. Only a comparatively small flow cross-section is released at the valve slide for the pressure medium displaced from the rod side 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. A sum of the fluid volume flow flowing back from the rod side of the differential cylinder and flowing in from the variable displacement pump now flows via the metering orifice of the valve slide. The differential pressure regulator of the variable displacement pump measures and limits the pressure difference via the metering orifice. In a borderline case, when the pressure medium connection between the second working connection and the tank is closed, the variable displacement pump delivers only the volume displaced by a piston rod of the differential cylinder.

A control valve according to the invention for the hydraulic control arrangement preferably has at least one working connection, preferably two working connections, for connecting an actuator. Furthermore, the control valve preferably has a pressure connection or pressure channel for connecting a hydraulic pump, a tank connection or tank channel as well as an input and an output connection or an input and output channel for a circulation flow path. When a continuously adjustable valve spool is shifted from a basic position in the direction of switching positions, a pressure medium connection between the working connection and the pressure connection and the working connection and the input connection can be opened his. With this shift, a pressure medium connection between the input connection and the output connection can also be controllable.

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

In a valve housing of the control valve, a check valve that opens in the direction of pressure medium flow toward the valve slide can be provided between the pressure connection and the working connection upstream of the valve slide.

As already explained above, the control valve can have a further second working connection.

The valve slide is advantageously arranged to be displaceable in a valve bore of the valve housing or a valve block or a valve disk. The valve slide preferably has a first control edge for controlling the pressure medium connection between the pressure connection and the first working connection. A second control edge can be used to control a pressure medium connection between the input connection and the output connection in a first direction of displacement of the valve slide. The pressure medium connection between the inlet 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 can be used to control the pressure medium connection between the input and the output connection in a second direction of displacement of the valve spool. A sixth control edge is preferably used to control the pressure medium connection between the input port and the second work port. A seventh control edge is provided for controlling the pressure medium connection between the first working connection and the tank connection. With an eighth control edge, one Pressure medium connection between the second working port and the input port can be controlled. If the control valve is only designed for one working connection, it is conceivable to provide only the first, second, third and seventh control edge.

When the valve spool is displaced from a basic position in the direction of first switching positions, the first, third and fourth control edges can preferably open a flow cross section. The second control edge preferably controls a flow cross section. The sixth control edge can remain controlled. When the valve spool is displaced 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 controls a flow cross-section. The third control edge can remain controlled.

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

The blind hole is advantageously of stepped design and introduced from one end of the valve spool. In this case, a valve seat is formed on a step transition, on which a valve body of the check valve can rest in a sealing manner. The valve body is arranged in a section of the blind hole having a larger diameter. 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 closing the blind hole. If the valve body is lifted from the valve seat, it gives a pressure medium connection between the Blind hole and at least one radial bore opening in the area of the working connection.

• 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.

Preferred embodiments of the invention are explained in more detail below with reference to drawings. Show it:

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

Figure 1 shows a hydraulic control arrangement 1, which is used as a throttle control for compact construction machines and enables volume flow control and limitation. 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 and 8, respectively. A hydraulic machine in the form of a variable displacement pump 10 with an actuating cylinder 12 is used to supply pressure to the actuators 6 and 8 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 limits a maximum pump pressure of the variable displacement pump 10.

The variable displacement pump 10 pumps pressure medium from a tank line 20 connected to a tank 18 into a pump line 22, which represents the high pressure side of the variable displacement pump 10. A respective control valve 2 or 4 with a pressure line 24 is connected to the pump line 22. A check valve 26 which opens in the pressure medium flow direction away from the variable pump 10 and towards the respective control valve 2 or 4 is provided in the pressure line 24. A respective pressure line 24 then opens into a pressure connection P of the control valve 2 or 4. A respective control valve 2 or 4 is connected to the tank 18 with a tank line 28, the Tank line 28 extends from a tank port T of the control valve 2 or 4. For the actuators 6 and 8, a respective control valve 2 or 4 has a first and a second working connection A and B. A first working line 30 is connected to a respective first working connection A and a second working line 32 to a respective second working connection B. 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 penetrated by a piston rod 40, whereby it is designed as an annular chamber.

A circulation flow path in the form of a circulation line 42 is also connected to the pump line 22. This extends over 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 port D and an output port D '. A pilot orifice 44 is arranged in the circulation line 42 in the pressure medium flow path between the pump line 22 and the first control valve 2. The differential pressure regulator 14 taps downstream of the pilot orifice 44 - between the latter and the first control valve 2 - the pressure via a control line 46 and upstream of the pilot orifice 44 - between the variable displacement pump 10 and the pilot orifice 44 - the pressure via a control line 48. 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 via the pilot orifice 44. The differential pressure regulator 14 is designed 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 in the opposite direction in the switching positions a by the pressure medium of the control line 48. In the basic position 0, a connecting line 52 to the maximum pressure regulator 16 to the tank 18 is relieved 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 slide is in this case via a valve spring 54 with a spring force in the direction of a home position 0. Furthermore, a pressure surface of the valve slide that is effective in this direction is connected to the tank 18 via a branch line 56. In the opposite direction to switching positions a, the valve spool is pressurized with pressure medium from the pump line 22 via a control line 58. In the basic position 0, a connection between the connecting line 52 and a cylinder line 60 is opened, the cylinder line 60 being connected to the actuating cylinder 12. In switch positions a, the cylinder line 60 is in pressure medium connection with the pump line 22.

The actuating cylinder 12 is designed 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 penetrated by a piston rod 68, the piston rod 68 being 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 downsizing the first cylinder chamber 64, the actuating cylinder 12 pivots the variable displacement pump 10 in the direction of a larger delivery volume via its piston rod 18. In the same direction, the variable displacement pump 10 is acted upon by a spring force of an adjusting spring 70. It is conceivable to alternatively design the differential cylinder 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 basic position 0 of the valve slide, the working connections A, B, the tank connection T and the pressure connection P are blocked, and the input connection D is connected to the output connection D '. When the valve spool is shifted from the basic position 0 in the direction of the first switching positions x, the pressure medium connection between the pressure port P and the first working port A is opened, whereby 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 the second cylinder chamber 38 of the actuator 8 is relieved of the load on 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. The The valve slide is therefore used as a metering orifice 72. Furthermore, when the valve spool is shifted into the switching positions x, the connection between the input port D and the output port D 'is activated and, in return, a pressure medium connection between the input port D and the first working port A is opened. In this case, a check valve 74 opening towards the actuator 8 is provided in the pressure medium flow path between D and the first working port A. In contrast to the prior art, not only is the circulation line 42 controlled, but at the same time a connection is established between the circulation line 42 and the working connection having a load pressure, in this case the first working connection A. If the valve slide is moved in the opposite direction from the basic position 0 in the direction of the second switching positions y, then the pressure connection P is connected to the second working connection B and the first working connection A to the tank connection T. Thus, the second cylinder chamber 38 can be supplied with pressure medium from the variable pump 10 and the first cylinder chamber 36 is relieved to the tank. When the valve spool is displaced in the direction of the switching positions y, the connection between the input port D and the output port D 'is also activated again and at the same time a connection between the first working port B and the input port D is opened via a check valve 76. The check valve 76 opens in the same way as the check valve 74 in a pressure medium flow direction from the input port D to the actuator 8 or the second working port B. In the switching positions x and y, the input port D is thus connected downstream of the metering orifice 72 to the respective working port A, B. ,

Control valves 2 and 4 now enable load-independent volume flow control. If the valve slide of the control valve 2 is moved, for example, from its basic position 0 in the direction of the switching positions x, then both the pressure connection P and the input connection D are connected to the first working connection A. This means that the differential pressure controller 14 keeps the pressure difference constant both via the pilot orifice 44 and via the orifice 72. Thus over the opening cross section Metering orifice 72, the volume flow to the actuator 6 can be set independently of the load pressure.

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

In Figure 2 the control valve 2 is shown. This has a valve housing 78 in which a slide bore 80 for a valve slide 82 is formed. A tank channel 84 is also provided in the valve housing 78 and extends approximately transversely to the longitudinal direction of the valve slide 82. Control valves 2 and 4 are off Figure 1 formed in a common valve block, the tank channel 84 can extend through the entire valve block and open into a tank connection on the valve block. In addition, a pump channel 86 is provided in the valve housing 78, which extends approximately parallel to the tank channel 84. Furthermore, the working connections A and B are provided in the valve housing 78.

The slide bore 80 is comprised in the valve housing 78 by a total of nine ring grooves 88 to 104, which are arranged one behind the other in a row. The two outer ring grooves 88 and 104 are connected to the tank channel 84. The annular groove 90 adjacent to the annular groove 88 is connected to the first working connection A and the annular groove 102 adjacent to the annular groove 104 is connected to the second working connection B. The annular groove 92 provided after the annular groove 90 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 to 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 ring grooves 92 and 100. The central ring groove 96 is with the outlet connection D ', see also Fig.1 , connected. The annular grooves 94 and 98 adjacent to the central annular groove 96 are each connected to the input connection D, see also Fig.1 ,

In the Fig. 2 The basic position 0 of the valve slide 82 shown is the pressure medium connection between the annular grooves 94 and 96 via a control edge 108 of the valve slide 82 opened. The pressure medium connection between the annular groove 98 and the annular groove 96 is also opened via a further control edge 110. All other ring grooves 88, 90, 92, 100, 102, 104 are separated from one another. If the valve slide 82 from the in Figure 2 shown basic position shifted to the right, it reaches the switching positions x, see also Figure 1 , A pressure medium connection between the pump channel 86 and the first working port A is then opened 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 connection B is connected to the tank channel 84 via a control edge 116 of the valve slide 82. The connection of the input port D to the first working port A, see also Figure 1 , takes place via a bore star 118 which is introduced into the valve slide 82 and which opens into an axial blind hole 120 of the valve slide 82. In the switching positions x, the bore star 118 is arranged in the region of the annular groove 94 and represents a control edge 122. The blind bore 120 is introduced from an end face of the valve slide 82 and extends in the axial direction, in particular over the annular grooves 88 to 92. In the region of the annular groove 90, which is connected to the first working connection A, radial bores 124 are made in the valve slide 82. These also open into the blind bore 120. The blind bore 120 is of stepped construction, with which a valve seat is formed at the step transition. This is located in the axial direction between the radial bores 124 and the bore star 118. The valve seat is a valve body 126 of the check valve 74, see also Figure 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-in 130 (closure element) which is screwed into the valve slide 82. In the first switching positions x, the input connection D is thus connected via the annular groove 94, the bore star 118, the blind hole 120, the check valve 74 to the radial bore 124 and thus the annular groove 90, which in turn is connected to the first working connection A.

With a displacement of the valve slide 82 in the direction of the switching positions x, the input port D from the output port D 'is thus closed with an increasing displacement path, with the result that a pressure in the circulation line 42 is released Figure 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 connection A. The check valve 74 is then open. The load pressure is thus reported to the circulation line 42 and the differential pressure controller 14 keeps a pressure difference Δp constant, regardless of the opening cross-section opened by the control edge 112.

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

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

The operation of the control valve in the second switching positions y is essentially the same as the first switching positions x.

In the second embodiment of a control valve 144 according to Figure 3 regeneration of a volume flow is provided when the valve slide 82 goes out from its in the Figure 3 shown basic position in the direction of the first switching position x is moved to the right. In contrast to the embodiment Figure 2 the bore star 136 is offset towards the radial bore 142, viewed in the axial direction. This leads to the fact that when the valve slide 82 is completely moved in the direction of the switching positions x, the bore star 136 is located in the area of the annular groove 100 and is therefore connected to the pump channel 86. A differently designed check valve 144 is also provided in the blind bore 140. The valve body 146 has a through bore with a nozzle, with which pressure medium can flow from the bore star 136 into its spring chamber 150. If the valve body 146 rests on the valve seat, the pressure in the bore star 136 acts on a pressure surface A ₁ in the opening direction and the pressure of the radial bore 142 and thus the pressure of the second working connection B via an annular pressure surface A _2. In the closing direction, this acts on a pressure surface A _{3 of} the valve body 146 then the pressure in the spring chamber 150. The pressure area A ₃ is the sum of the pressure area A ₁ and A ₂ . If the pressure of the working connection 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. As a result, the second working connection B is in turn connected to the pump channel 86. Pressure medium can thus flow from the second working connection B to the first working connection A, with which there is a so-called "regeneration" of pressure medium. The variable pump 10 from Figure 1 must then convey less pressure medium.

A hydraulic control arrangement for controlling at least one consumer is disclosed. The control arrangement forms an open center system. A control valve is provided for the at least one consumer, 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. The circulation flow path is connected to the hydraulic pump via a pilot orifice, which is thus provided between the hydraulic pump and the control valve. If the control valve controls the consumer via a metering orifice, the circulating flow path is simultaneously closed and, in addition, a connection between the circulating flow path and the consumer downstream of the metering orifice is opened. About one The differential pressure controller then maintains a pressure difference across the pilot orifice and the orifice, which means that a fluid volume flow to the consumer can be varied independently of the load pressure via the orifice.

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 work leader

32

second work leader

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)

1. Hydraulic control assembly comprising a hydraulic pump (10) for the pressure medium supply of at least one actuator (6, 8), wherein the actuator (6, 8) is connected to a high-pressure side (22) of the hydraulic pump (10) via a control valve (2, 4) having a measuring diaphragm (72), wherein a flow cross section between the hydraulic pump (10) and the actuator (6, 8) is adjustable via the measuring diaphragm (72), and wherein a circulation flow path (42) is connected to the high-pressure side (22) via a pilot diaphragm (44), wherein the circulation flow path (42) can be connected via the control valve (2, 4) to a tank (18), and wherein a differential pressure regulator (14) is provided, which taps off a pressure upstream and downstream of the pilot diaphragm (44) and cooperates with the control assembly (1) in such a way that a pressure difference across the pilot diaphragm (44) is constant, characterized in that as the measuring diaphragm (72) is closed, a pressure medium connection of the circulation flow path (42) is opened by the control valve (2, 4), wherein as the measuring diaphragm (72) is closed, the pressure medium connection of the circulation flow path (42) is closed by the control valve (2, 4) and a pressure medium connection between the circulation flow path (42) and the actuator (6, 8) downstream of the measuring diaphragm (72) is opened.
2. Control assembly according to Claim 1, wherein the hydraulic pump is a variable displacement pump (10), which can be pivoted via an actuating cylinder (12), wherein the differential pressure regulator (14) cooperates with the variable displacement pump (10) and the actuating cylinder (12) in such a way that the pressure difference across the pilot diaphragm (44) is constant.
3. Control assembly according to Claim 1 or 2, wherein the control valve (2, 4) is assigned a non-return vavle (26) upstream of the measuring diaphragm (72).
4. Control assembly according to one of Claims 1 to 3, wherein a non-return vavle (74, 76) is arranged in the pressure medium flow path between the pilot diaphragm (44) and the control valve (2).
5. Control assembly 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) are arranged fluidically in parallel to one another with regard to a pressure medium connection between the hydraulic pump (10) and their respective actuator (6, 8), and wherein the control valves (2, 4) are arranged fluidically in series with one another with regard to the circulation flow path (42).
6. Control assembly 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 basic position of the valve spool, all the connections (A, B, P, T) are closed, and wherein in the event of a displacement of the valve spool in the direction of first switching positions (x), the first working port (A) is connected to the pressure port (P) via the measuring diaphragm (72), and the second working port (B) is connected to the tank port (T), and wherein in the event of a displacement of the valve spool in the direction of second switching positions (y), the second working port (B) is connected to the pressure port (P) via the measuring diaphragm (72), and the first working port (A) is connected to the tank port (T).
7. Control assembly according to Claim 6, wherein the control valve (2, 4) has an inlet port (D) and an outlet port (D') for the circulation flow path (42), wherein in the event of a displacement of the valve spool (82) starting from the basic position (0) in the direction of the first switching positions (x), a pressure medium connection between the inlet port (D) and the first working port (A) is opened, and/or in the event of a 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 inlet port (D) and the second working port (B) is opened.
8. Control assembly according to Claim 6, wherein the control valve (2, 4) has an inlet port (D) and an outlet port (D') for the circulation flow path (42), wherein in the event of a displacement of the valve spool (82) starting from the basic position (0) in the direction of the first switching positions (x), a pressure medium connection between the inlet port (D) and the first working port (A) is opened, 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 port (P) is opened.
9. Control assembly according to one of the preceding claims, wherein the variable displacement pump (10) is assigned a maximum pressure regulator (60) .
10. Control assembly 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.
11. Control valve having at least one working port (A, B) for the connection of an actuator (6, 8), a pressure channel (P) for the connection of a hydraulic pump (10), a tank channel (T), an inlet channel (D) for a circulation flow path (42), and an outlet channel (D') for the circulation flow path (42) and a valve spool (82), characterized in that the control valve is suitable for a hydraulic control assembly according to one of the preceding claims, and in that in the event of a displacement of the 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 inlet channel (D) can be opened, and a pressure medium connection between the inlet channel (D) and the outlet channel (D') can be closed.
12. Control valve according to Claim 11, wherein it has a further second working port (A, B).
13. Control valve according to Claim 12, wherein the valve spool (82) is displaceably arranged 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 inlet channel (D) and the outlet channel (D') in a first displacement direction of the valve spool, a third control edge (122) for controlling the pressure medium connection between the inlet 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 inlet channel (D) and the outlet channel (D') in a second displacement direction of the valve spool (82), a sixth control edge (132) for controlling the pressure medium connection between the pressure channel (P) and the second working port (B), a seventh control edge (124) for controlling the pressure medium 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 inlet channel (D) and the second working port (B).
14. Control valve according to Claim 13, wherein in the event of a displacement of the valve spool (82) starting from a basic position (0) in the direction of first switching positions (x), the first, third and fourth control edge (112, 122, 116) open a first flow cross section, and the second control edge (108, 114) closes a flow cross section, and wherein in the event of 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) open a flow cross section and the fifth control edge (110, 134) closes a flow cross section.
15. Control valve according to Claims 13 or 14, wherein the third and eighth control edge (122, 138) are each formed by at least one radial bore (118, 136) in the valve spool (82), which are each connected fluidically to the respective working port (A, B) via a blind bore (120, 140) introduced into the valve spool (82).

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