EP1875084B1 - Directional control valve and control system provided therewith - Google Patents

Abstract

The valve has two slides (4, 5) which are spring-loaded towards the center of a bore (42). The slides share a common control system which allows pressure to be applied simultaneously to their front surfaces (44, 46) and to their rear surfaces (60, 62), which are smaller in area. An independent claim is included for LS-control systems for hydraulic fluid which contain the valve.

Description

The invention relates to a directional control valve with two guided in a slide bore coaxially arranged valve spools according to the preamble of patent claim 1 and an executed with such a directional control valve LS control arrangement.

Especially in mobile hydraulics directional valves are often required with four slide positions, in addition to a neutral position in which a pressure port and two working ports are shut off and a floating position in which the two working ports are connected to a tank connection two more working positions must be taken from the directional control valve, in which one working connection with the pressure connection and the other working connection with the return connection and in the other positions according to the former working connection with the tank connection and the further working connection is connected to the pressure connection.

Such conventional directional control valves are designed with a main slide, the control functions being placed in the path of this slide. This has some disadvantages, since, for example, to reach the floating position a working position must be completely overrun. The required large spool stroke leads to a relatively long slide and thus to a correspondingly long valve body.

In an electro-hydraulic actuation, the frequently set for a longer time floating position is driven in the end position of the slider. This requires that the valve spool with a constant high Control pressure is applied, so that accordingly a high electrical input current must be maintained. Furthermore, the resolution for the spool stroke is reduced in its working positions, since a part of the control pressure range is required for the floating position.

To eliminate at least some of these disadvantages, directional valves with two valve slides are known from the prior art, which are accommodated in a common valve housing bore. The EP 1 500 825 A2 For example, the applicant discloses a solution in which the two valve spools are spaced from each other by a central spring, wherein the maximum distance between the two valve spools is limited by a tie rod or the like.

Similar solutions are in the EP 0 114 470 B1 and the EP 0 573 191 B1 discloses, in which the directional control valve is also designed with two coaxially arranged valve spools, between which a spring is provided.

Such solutions are relatively expensive, since the spring must be taken in a suitable manner. A disadvantage of the in the EP 0 114 470 B1 and the EP 0 573 191 B1 shown solutions is further that the adjustment of the valve slide by means of electromagnets and operated therefrom plunger, so that the device-technical effort is further increased.

In the WO 02/075162 A1 In Fig. 10, a directional control valve with two coaxial valve slides is disclosed, in which the two valve spools are arranged directly without interposed spring. However, the operation is also by means of electromagnets. Fig. 12 shows a Embodiment in which the actuation is performed hydraulically, to the rear control surfaces of the two valve spools is assigned in each case a drive piston which is designed with two control surfaces whose surfaces are designed with the ratio 1: 2. In the basic position, the smaller area is correspondingly charged with twice the control pressure. The shifting takes place in which the control pressure acting on one of the control surfaces is lowered or lowered. A disadvantage of this solution is that the drive pistons firmly connected to the valve slide are comparatively complicated and that only half the control pressure is available for the axial displacement of the valve slide in the working positions, so that correspondingly the resolution is low.

On the other hand, the invention has for its object to provide a directional control valve and a LS-control arrangement designed therewith, which is designed to be simple and compact and allows exact displacement of the valve spool in predetermined working positions.

This object is achieved with regard to the directional control valve by the features of patent claim 1 and with respect to the LS control arrangement by the features of claim 9.

According to the directional valve is formed with two coaxially arranged valve spools, which are directly, ie, without the interposition of a spring or a tie rod or the like in abutment with each other. The adjacent end faces of the valve slide can be acted upon with the same control pressure as rear control surfaces, the effective area, however, is smaller than that of the end faces. By applying this control pressure, the two valve spools be moved apart in accordance to very quickly and accurately take a predetermined slide position, for example, a floating position. Accordingly, in the solution according to the invention neither directly on the valve spool engaging electrical components (such as plunger of an electromagnet) required for the shift, nor must a component be provided between the two valve spools to limit the stroke. The adjustment in the predetermined slide position is due to the area difference, wherein the end faces and the control surfaces are acted upon by the same control pressure, so that the channel guide over the conventional solutions is substantially simplified.

In one embodiment, this surface difference is formed by flasks that dip into the rear end portions of the valve spool and which are supported on the housing. These flasks limited with the respective valve spool a piston chamber which is acted upon by the control pressure.

In an alternative embodiment, in kinematic reversal to form the area difference, the end portions of the valve spools are radially recessed and each dive into a cap, with the spigot faces forming the control surfaces of reduced cross-section. Such a construction is per se from the DE 3732445 A1 ( Fig. 5 ) known.

The bias of the two valve spool in its basic position, for example, via two each received in a spring chamber centering springs, which engage in each case at a rear end portion of the valve spool. The spring chamber accommodating the centering spring is subjected to tank pressure. Everyone from the valve spool and Kolbchen limited piston chamber is preferably connected via at least one shell breakthrough with a control pressure leading control chamber of the valve bore and acted upon by a shift with tank pressure.

The structure of the directional control valve is particularly simple when this shell breakthrough connects the piston chamber with the spring chamber after the displacement of the valve spool.

According to the invention, it is preferred if two tank chambers carrying the tank or return pressure are arranged on the outside in the valve bore, so that two pressure chambers connected to a pressure connection and two working chambers connected to one working connection and a central central control chamber acted upon by the control pressure and optionally further control chambers are arranged between the tank chambers.

The central control chamber is connected in the basic position via an inverse shuttle valve with the piston chambers of the valve spool, so that in the central control chamber always the lower of the control pressures is applied.

The hydraulic control of the directional control valve is preferably carried out by two proportionally acting pressure reducing valves, via which the control surfaces of the two valve spool can be acted upon by the control pressure and connect the control surfaces in their basic position with tank pressure and thus relieve.

The LS control arrangement is preferably carried out with an individual pressure compensator and at least one work connection assigned a blocking block.

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

• Fig. 1 ein Schaltschema einer erfindungsgemäßen LS-Steueranordnung;
• Fig. 2 eine konkrete Ausführung der LS-Steueranordnung gemäß Fig. 1 in Neutralstellung;
• Fig. 3 eine vergrößerte Darstellung der Ventilschieber des Wegeventils aus Fig. 2;
• Fig. 4 die Ausführung gemäß Fig. 2 in einer Arbeitsstellung;
• Fig. 5 die Ausführung gemäß Fig. 2 in einer Schwimmstellung und
• Fig. 6 ein weiteres konkretes Ausführungsbeispiel einer erfindungsgemäßen LS-Steueranordnung.

In the following preferred embodiments of the invention will be explained in more detail with reference to schematic drawings. Show it:

• Fig. 1 a circuit diagram of an LS control arrangement according to the invention;
• Fig. 2 a concrete embodiment of the LS control arrangement according to Fig. 1 in neutral position;
• Fig. 3 an enlarged view of the valve spool of the directional valve Fig. 2 ;
• Fig. 4 the execution according to Fig. 2 in a working position;
• Fig. 5 the execution according to Fig. 2 in a floating position and
• Fig. 6 a further concrete embodiment of an LS control arrangement according to the invention.

Fig. 1 shows a circuit diagram of a valve disc of a LS mobile control block, via which hydraulic consumers of a tractor can be controlled. The valve disc 1 has two working ports A, B, which lead for example to the two pressure chambers of a hydraulic cylinder, a pressure port P, two drain or tank ports R1 and R2, a LS port LS, a control pressure port P _x and a tax return port R _x . The basic structure of such LS control arrangements in applications in mobile hydraulics is essentially the same, they include a proportionally adjustable directional control valve 2, which contains a speed part and a direction part for adjusting the pressure medium volume flow to or from the consumer. In the illustrated embodiment, the directional control valve 2 with two valve spools 4, 6 executed in a common valve bore Coaxially with each other are received and are biased via a Zentrierfederanordnung with a right centering spring 8 and a left centering spring 10 in the illustrated basic position in which the two valve spool 4, 6 abut each other frontally. The actuation of the valve slide assembly via two electrically actuated pressure reducing valves 12, 14, whose input port P to the control pressure port P _X , at which a relatively high input control pressure is applied and the tank port T is connected to the control return port R _X. The output port A of the pressure reducing valves 12, 14 is connected to the control side of the respective associated valve spool 4 and 6 respectively.

The speed part of the directional control valve 2 is formed in each case by an orifices 16, 18 formed by control edges of the valve spool 4, 6, to which an individual pressure compensator 20 is connected upstream. This is acted upon in the sense of an enlargement of the opening cross section by the force of a pressure compensator spring 22 and the load pressure of the associated consumer, which rests on an LS channel 26 at the effective in the opening direction control surface of the pressure compensator 20. The load pressure of the consumers controlled via the other valve disks of the LS mobile pressure is applied via the control connection Y _W to the input of a shuttle valve 24 and compared with the load pressure of the consumer connected to the valve disk, the largest load pressure is then tapped at the LS connection. In the illustrated embodiment, the larger of the load pressures at the working ports A, B is tapped via another shuttle valve 28, at the output of the LS channel 26 is connected. In the closing direction, the pressure compensator 20 is acted upon by the pressure in the pressure medium flow path between the pressure compensator 20 and the directional control valve 2. The pressure compensator 20 holds in its control position the pressure drop above the set metering orifice 16, independent of load pressure, constant. As usual with such LS control arrangements, the highest load pressure of all controlled by the mobile control block consumer is led to a pump governor of a variable or bypass pressure compensator of a constant pump, whereby the pump pressure in a pump line is adjusted so that it always by a predetermined Δp above this maximum load pressure lies.

To set a floating position, the two valve slides 4, 6 can be moved out of the illustrated basic position against the force of the centering springs 8, 10 to the outside. For this purpose, the mutually facing end faces of the valve slide 4, 6 project into a common central pressure chamber 30, which is acted upon by the output pressure of the pressure reducing valves 12 or 14. In the event that these pressure reducing valves 12, 14 are set to different control pressures, the smaller of these control pressures is tapped via an inverse shuttle valve 32 and forwarded to the central control pressure chamber 30 connected to the output of this inverse shuttle valve 32. If both pressure reducing valves 12, 14 are set to the same control pressure, this control pressure is also present in the central control pressure chamber 30.

In the pressure medium flow path between the directional control valve and the associated working ports A, B is a respective blocking block 34, 36 is provided, the structure of which Fig. 2 is explained in more detail. Such blocking blocks 34, 36 allow a flow of pressure fluid to the associated working port A, B to. In order to allow a pressure medium backflow from the consumer, the locking block 34, 36 can be unlocked by means of a poppet piston. When pulling loads this lock block 34, 36 then acts as Pressure compensator, which makes it possible to perform a load pressure-independent pressure medium control with the over the directional control valve open drain orifice 38, 40. About the additional shuttle valve 28, the greater pressure on the discharge side is then tapped and reported in the LS channel 26 in the case of a towing load, so that a sufficient pressure medium supply is ensured even in the case of a towing load and cavitations can be prevented. Further details can be the DE 103 21 914 A1 taken from the applicant.

The course of in Fig. 1 shown control and pressure medium channels is based on the specific embodiment in Fig. 2 explained.

Fig. 2 shows a concrete embodiment of the valve disc 1 of a mobile control block. This valve disk 1 is traversed in the transverse direction by a valve bore 42, in which the two valve spools 4, 6 are guided axially displaceably. The two valve slides are biased by the centering springs 8, 10 in an abutment position in which the end faces 44, 46 of the valve slide 4, 6 abut each other. The centering springs 8, 10 are supported on the valve bore 42 axially final spring caps 48, 50, each defining a spring chamber in which always the tank or return pressure is applied, which is above the in Fig. 2 adjacent to the spring chamber, only shown in cross section channel is tapped.

In each plunging into the spring chamber end portion of the valve slide 4, 6, a piston chamber 52 and 54 is formed, wherein the piston chamber of the valve spool 6 is indicated only by dashed lines. In the piston chambers 52, 54 each have a piston 56, 58 is inserted, the are supported with a protruding from the valve spool 4, 6 end portion at the bottom of the spring cap 48 and 50 respectively. The flasks 56, 58 close the two piston chambers 52, 54 in the axial direction pressure medium-tight. The bottom surfaces of each piston chamber 52, 54 each form a control surface 60, 62 whose effective area is less than the cross-sectional area of the end face 44, 46 of the respective valve slide 4 and 6. In the two piston chambers 52, 54 open respectively axially spaced shell bores 64, 66 and 68, 70, the function of which will be discussed below. Instead of these jacket bores 64, 66; 67, 70, a slot could be provided in each case. They should not be covered by the flasks 56, 58.

Instead of the flasks 56, 58, the control surfaces 60, 62 designed with lower effective surfaces can also be formed in kinematic reversal, in which the end sections of the valve spools 4, 6 are recessed in the form of pegs and dipped into caps, so that in each case by a cap and an end portion is formed by the control surface 60, 62 limited space, which can be acted upon by channels in valve spool 4, 6 with the control pressure or tank pressure.

In the valve bore are in the illustration according to the Figures 2 and 3 from outside to inside two outer tank chambers 72, 74, two working chambers 76, 78, two inlet chambers 80, 82, two control pressure chambers 84, 86, two inside thereof arranged control chambers 88, 90 and the central central control chamber 92 is formed. The two tank chambers 72, 74 are not shown channels with the spring chambers and the two return ports R1, R2 ( Fig. 1 ) of the valve disc 1 is connected. The two inside arranged working chambers 76, 78 lead via a flow channel 94 to the working port A. or via a return channel 96 to the working port B. The two inlet chambers 80, 82 are connected to one another via an inlet channel 98 into which the output of the individual pressure compensator 20 opens, the input via a pressure compensator input chamber 100 to the pressure port P ( Fig. 1 ) of the valve disc 1 is connected. A compression chamber spring 22 receiving spring chamber 102 of the pressure compensator 20 is connected via the LS channel 26 to the output of the shuttle valve 24 and further guided to the output of the further shuttle valve 28, the two inputs via an approximately U-shaped connecting channel 104 with the working chamber 76 and 78 are connected.

As in Fig. 2 indicated, the input terminals P of the two pressure reducing valves 12, 14 are connected to the control pressure port P _X and the tank ports T with control return port R _X. The two output ports A are guided via pilot control channels 106, 108 to the inputs of the inverse shuttle valve 32, the output of which is connected to the central control chamber 92.

As in particular the enlarged view of the two valve spool 4, 6 according to Fig. 3 can be removed, are at these from the outside to the inside tank control edges 110, 112, inlet control edges 114, 116, control edges 118, 120 and further control edges 158, 159 formed, which are each formed by peripheral edges of a piston collar. Like next Fig. 3 can be removed, open the shell bores 64, 68 in the pilot channel 106 and 108, the two other shell bores 66, 70 are covered in the basic position.

The two blocking blocks 34, 36 are according to Fig. 2 used in the flow channel 94 and the return channel 96. You have a running with a pilot opening closing body 122 and 124, each of a Closing spring 126, 128 is biased against a valve seat 130, 132. In each valve body 122, 124, a pilot valve body 134, 136 is received and biased against another pilot valve seat. Each pilot valve body 134, 136 can be lifted off its pilot valve seat by means of a poppet piston 138, 140 by applying a control pressure to its piston surface 142, 144. For this purpose, the piston surface 142, 144 limits a pressure chamber, which is connected via control channel sections 146, 148 with the two control chambers 88, 90, which are connected via the further control edges 158, 159 with the central control chamber 92. A spring chamber 150, 152 of the blocking block 34, 36 is connected to the pilot channel 106, 108 via a short channel section. The spring chamber 150, 152 is further connected to the working port A, B.

In the in the FIGS. 1 to 3 shown basic position (neutral position) of the directional control valve 2, the pressure medium flows through the individual pressure compensator 20 and is in the inlet channel 98 at. The two pressure reducing valves 12, 14 are de-energized, so that the two pilot control channels 106, 108 are relieved to the return port R _X out. Accordingly, the two piston surfaces 142, 144 of the poppet 138, 140 are relieved to the return port R _X out. The two slides 4, 6 take due to the bias of the centering springs 8, 10 their illustrated center position in which the control edges 112, 114 and 116, 118 shut off the pressure fluid connection of the working ports A, B to the pressure port P and to the return ports R1 and R2. The two working chambers 76, 78 and thus the flow channel 94 and the return channel 96 are respectively formed in the valve slide 4 and 6 connecting bores 154, 156 (dashed in the Figures 2 and 3 ) With the tank chambers 72, 74 and thus connected to the return ports R1 and R2 and thus also depressurized. The load pressure signal, which is tapped via the connecting channel 104 and arranged therein another shuttle valve 28 is then corresponding to this valve disc 1 also at tank pressure level. The two locking blocks 34, 36 are locked because the two valve bodies 122, 124 are pressed by the respective load pressure and the closing springs 126, 128 against the associated valve seats 130, 132.

If, for example, the pressure medium now flows back via the working port A to the consumer and from this via the working port B, the pressure reducing valve 12 is energized. The control pressure, which adjusts in proportion to the energization of the pressure reducing valve, is guided via the outlet port A of the pressure reducing valve 12, the pilot passage 108 and the jacket bores 70 and, after an axial displacement of the valve slide 68, into the left piston chamber 54. The right piston chamber 52 is - as in the neutral position - still relieved via the no-load pressure reducing valve 14 to return R _X out. Accordingly, the tank pressure is also present in the right pilot control channel 106. The set via the pressure reducing valve 12 control pressure is applied to the left input of the inverse shuttle valve 32, while at its right input via the pilot passage 106, the tank pressure is applied - the inverse shuttle valve 32 is thus opened to the tank pressure, so that it acts in the central control chamber 92 ,

The two valve spools 4, 6 are by the pressure on the control surface 62 as shown in FIG Fig. 4 shifted to the right, with the piston 58 is further supported on the spring cap 50. The stroke of the valve slide 4, 6 is determined by the diameter of the piston 58, the surface of the control surface 62, the force of the centering spring 8 and the size of the pressure reducing valve 12th set control pressure. Due to the axial displacement to the right, the connection from the inlet chamber 82 to the working chamber 78 is opened via the inlet control edge 116 so that the pressure medium can flow from the outlet of the pressure compensator 20 into the inlet channel 94. The now acting as a check valve body 124 is lifted from its valve seat 132 and released the pressure medium flow to the working port A. The piston surface 144 of the poppet 140 is acted upon by the central control chamber 92 and the inverse shuttle valve 32 with tank pressure. About the further control edge 158 of the valve spool 4, the connection of the control chamber 88 is shut off with the pressure-relieved central control chamber 92 and via the control edge 118 opens a connection with the input control pressure of the pressure reducing valve 12, 14 leading control pressure chamber 84, so that the piston surface 42 of the poppet 138 with the high input control pressure of the pressure reducing valve 12 is acted upon. The poppet 138 is characterized according to Fig. 4 shifted to the right and raises the pilot valve body 134 against the force of its valve spring from the pilot seat, so that the pressure in the spring chamber 150, which previously corresponded to the load pressure of the consumer, is reduced. Once this pressure in the spring chamber 150 has dropped so far that a balance of forces between the pressure in the spring chamber, which acts on the spring-side end face of the valve body 122 and the load pressure acting on the differential surface, from the piston diameter of the valve body 122 and the diameter of the Valve seat 130 is formed, the valve body 122 follows the pilot valve body 134 and the pressure medium can flow from the consumer via the working port B, the return channel 96 and the controlled by the tank control edge 110 connection between the working chamber 76 and the tank chamber 72 to the return port R2. The pressure at the tank control edge 110 and thus rests in the return channel 96, acts on the topping piston 138, so that this acts together with the valve body 130 of the locking block 34 as a discharge pressure compensator, which keeps the discharge pressure at the tank control edge 110 of the valve spool 4 constant, and thus pulling loads one load pressure independent sequence control allows. The two jacket bores 64, 66 open during the axial displacement of the valve slide 4 towards the spring chamber of the centering spring 8, in which also tank pressure is applied.

To set the other working positions in which the pressure fluid flows through the working port B to the consumer and the working port A from the consumer, is adjusted accordingly by energizing the pressure reducing valve 14.

To set the floating position in which the two working ports A, B are both connected to the return port R1 / R2 and the pressure port P is shut off, both pressure reducing valves 12, 14 are energized, so that at their outputs A, the same output control pressure is set. This output control pressure of the two pressure reducing valves 12, 14 is then via the pilot control channels 106, 108 also at the two inputs of the inverse exchange valve 32 and on the control surfaces 60, 62 of the piston chambers 52, 54 (see Fig. 2 ) at. Since the same output control pressure is present at both inputs of the inverse shuttle valve 32, the central control chamber 92 is also subjected to this pressure. Since the end surfaces 44, 46 of the valve spools 4, 6 adjoining the central control chamber 92 are larger than the control surfaces 60, 62 of the piston chambers 52, 54 (in FIG Fig. 5 only 52, 60 shown), the two valve spool 4, 6 moved apart against the force of the comparatively weak centering springs 8, 10. It is about the Control edges 118, 120, the connection of the control chambers 88, 90 controlled to the control pressure chambers 84, 86, so that the piston surfaces 142, 144 of the two poppet pistons 138, 140 are acted upon by the high control input pressure at the control port P _X. Both check valves 34, 35 are - as mentioned above in connection Fig. 4 - Open and thus the two working ports A, B via the flow channel 94, the return channel 96, the two working chambers 76, 78, the tank control edges 110, 112 and the outer tank chambers 72, 74 connected to the return ports R1 / R2. The inlet control edges 114, 116 block the connection to the inlet channel 98 and thus to the output of the pressure compensator 20 - the floating position is set.

As further Fig. 5 can be removed, open the two casing bores 64, 66 of the valve slide 4 and 68, 70 of the valve spool 6, the connection between the spring chamber of the centering spring 8 and 10 with the respective piston chamber 52, 54 (the latter not shown in FIG Fig. 5 ), so that the control surfaces 60, 62 (see Fig. 2 ) are no longer acted upon as previously by the control pressure set via the pressure reducing valves 12, 14, but by the tank pressure applied in the spring chambers. Since the two end faces 44, 46 are substantially larger than the control surfaces 60, 62 and these are depressurized, the pressure reducing valves 12, 14 can be set to a much lower output pressure to the valve spool 4, 6 for a long time against the force of the centering springs. 8 To keep 10 in their floating position.

As the embodiment according to Fig. 6 can be removed, the LS control arrangement can be formed with only one locking block 34, wherein the channel guide substantially corresponds to the above-described embodiment, with the exception that now the connecting channel 104, via which the load pressure is tapped no longer leads to the working chamber 78 but to a chamber 160 which in the illustrated basic position on the slightly longer than in the previously described embodiments executed connecting bore 156 with the left tank chamber 74 is connected. During the axial displacement of the valve slide 6 to the right, the connection to the control chamber 90 is then opened via an additional control edge 162, via which the load pressure at the working connection A is then signaled into the connection channel 104. That is, the chambers on the valve spool 4, 6, which serve in the use of blocking blocks for controlling the impact pressure, are used in this embodiment for tapping off the load pressure. In the embodiment according to Fig. 6 Accordingly, the two valve spools 4, 6 are no longer identical.

In principle, both shut-off valves and the individual pressure compensator can be omitted.

Disclosed are a directional control valve and a LS control arrangement, wherein the directional control valve is designed with two coaxially arranged valve slides whose adjacent end faces are larger than rearward control surfaces and are directly engageable with each other.

LIST OF REFERENCE NUMBERS

1

valve disc

2

way valve

4

valve slide

6

valve slide

8th

right centering spring

10

left centering spring

12

Pressure reducing valve

14

Pressure reducing valve

16

metering diaphragm

18

metering diaphragm

20

Individual pressure compensator

22

Compensator spring

24

shuttle valve

26

LS-channel

28

another shuttle valve

30

Central pressure chamber

32

inverse shuttle valve

34

locking block

36

locking block

38

Drain measuring orifice

40

Drain measuring orifice

42

valve bore

44

face

46

face

48

spring cap

50

spring cap

52

piston chamber

54

piston chamber

56

flask

58

flask

60

control surface

62

control surface

64

jacket bore

66

jacket bore

68

jacket bore

70

jacket bore

72

tank chamber

74

tank chamber

76

working chamber

78

working chamber

80

inlet chamber

82

inlet chamber

84

Control pressure chamber

86

Control pressure chamber

88

control chamber

90

control chamber

92

Central control chamber

94

forward channel

96

Return channel

98

inlet channel

100

Pressure compensator inlet chamber

102

spring chamber

104

connecting channel

106

pilot passage

108

pilot passage

110

Tank control edge

112

Tank control edge

114

Inlet control edge

116

Inlet control edge

118

control edge

120

control edge

122

valve body

124

valve body

126

closing spring

128

closing spring

130

valve seat

132

valve seat

134

Pilot valve body

136

Pilot valve body

138

topping

140

topping

142

piston area

144

piston area

146

Control channel section

148

Control channel section

150

spring chamber

152

spring chamber

154

connection hole

156

connecting bore

158

further control edge

159

further control edge

160

chamber

162

Additional control edge

Claims (11)

1. A directional control valve comprising two coaxially disposed valve slides (4, 6) guided in a valve bore (42) which are biased toward each other in a home position via a centering spring arrangement (8, 10) and which can be moved apart for adjusting a particular slide position from the home position in which two adjacent end faces (44, 46) of the valve slides (4, 6) are in contact with or neighboring to each other without interposing elastic supporting elements and which are jointly movable for adjusting further working positions, characterized in that a common control pressure which also acts on rear control surfaces (60, 62) of the valve slides (4, 6) distant from the end faces (44, 46) and designed to have a smaller active area can be applied to the end faces (44, 46).
2. A directional control valve according to claim 1, wherein for forming the control surfaces (60, 62) a respective end portion of the valve slides (4, 6) is reset radially with respect to a pivot immersing in a cap indirectly or directly supported on the valve housing (48) so that by the cap and the pivot a space is formed which on front is restricted by the control surface (60, 62).
3. A directional control valve according to claim 1, wherein for forming the control surfaces (60, 62) small pistons (56, 58) are guided in the end portions of the valve slides (4, 6) distant from the end faces (44, 46), each of said small pistons immersing with an end portion in a piston chamber (52, 54) of the valve slides (4, 6) and with other end portion being supported directly or indirectly on the valve housing (48).
4. A directional control valve according to claim 1, 2 or 3, wherein a centering spring (8) accommodated in a spring chamber acts upon each end portion of the valve slides (1, 2), wherein tank pressure is applied to the spring chamber.
5. A directional control valve according to any one of the preceding claims, wherein the control pressure and after a displacement tank pressure can be applied to each piston chamber (52, 54) or chamber restricted by the pivot and the cap via at least one shell breakthrough (64, 66; 68, 70) or conduit.
6. A directional control valve according to claim 5, wherein after displacement the shell breakthrough (64, 66; 68, 70) or conduit connects the piston chamber (52, 54) or chamber to the spring chamber of the allocated centering spring (8, 10).
7. A directional control valve according to any one of the preceding claims, wherein two working chambers (76, 78) connected to respective working ports (A, B), two supply chambers (80, 82) connected to a pressure port (P), further control chambers (84, 86; 88, 90) as well as an approximately centrally arranged central control chamber (92), to which the control pressure can be applied, are formed in the valve bore (42) between two axially outer tank chambers (72, 74) connected to a tank port (R1, R2).
8. A directional control valve according to claim 7, wherein the central control chamber (92) is connected to the piston chambers (52, 54) of the valve slides (4, 6) in the particular slide position via an inverse shuttle valve (32).
9. A directional control valve according to any one of the preceding claims, comprising two pilot valves in the form of pressure reducing valves (12, 14) by which a control pressure can be applied to the control surfaces (60, 62) and which in their home position connect the control surfaces (60, 62) with tank pressure.
10. An LS control system for supplying a consumer connected to two working ports (A, B) with hydraulic medium, comprising a directional control valve (2) according to any one of the preceding claims to which an individual pressure regulator (20) is allocated.
11. An LS control system according to claim 10, wherein a stop block (34, 36) is disposed between the directional control valve (2) and at least one of the working ports (A, B).

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