DE102020200412A1 - Hydrostatic drive system with a pressure compensator that has two control surfaces acting in parallel - Google Patents

Abstract

The invention relates to a hydraulic drive system (10) with several actuators (20), each of which is assigned a pressure compensator (30) with a continuously adjustable first diaphragm (40) Orifice (40) is arranged between a second and a third control point (12; 13). According to the invention, the pressure compensator (30) has a first and a separate second control surface (31; 32) the second control surface (31; 32) is adjustable in the closing direction of the first diaphragm (40), the first control surface (31) via the load reporting line (16) further via an adjustable second diaphragm (52) with the third control point (13) fluidically is connected, wherein the second shutter (52) is open in the third position (43), wherein it is closed in the first and second position (41; 42), wherein the second control surface (32 ) is fluidically connected to the third control point (13) at least in the second position (42) via a third panel (53) and bypassing the load reporting line (16).

Description

The invention relates to a hydraulic drive system according to the preamble of claim 1.

From the U.S. 5,305,789 a hydraulic drive system is known. This hydraulic drive system has a pump which supplies several actuators with pressure fluid in parallel. The movement speed of the actuators is set with a continuously adjustable main panel. The main orifice is followed by a pressure compensator with a continuously adjustable first orifice. The pressure compensator is configured in such a way that it regulates the pressure at the second control point between the main orifice and the first orifice to the highest load pressure. With this system, the highest load pressure is not determined with a changeover valve cascade. Rather, use is made of the fact that the pressure compensator with the highest load is the most open. Only this most widely open pressure compensator establishes a connection between the pressure downstream of the fully opened first aperture and a load reporting line, so that the highest load pressure is present in the load reporting line.

One advantage of the present invention is that the pressure compensator reacts more quickly to changes in pressure at a third control point downstream of the first orifice. Cavitation is also avoided when the actuator is exposed to pulling loads.

According to the independent claim, it is proposed that the pressure compensator has a first and a separate second control surface, whereby it can be adjusted in the closing direction of the first diaphragm by applying pressure to both the first and the second control surface, the first control surface via the load reporting line further over an adjustable second diaphragm is fluidically connected to the third control point, the second diaphragm being open in the third position, being closed in the first and second positions, the second control surface in any case via a third diaphragm and in the second position is fluidically connected to the third control point by bypassing the load reporting line. This accelerates the load report from the third control point to the pressure compensator in the closing direction of the first orifice. The comparatively large volume of the load reporting line is bypassed for a short time just before the second shutter opens.

The hydraulic drive system is preferably operated with a liquid pressure fluid, most preferably with hydraulic oil. The pump preferably has a continuously adjustable displacement volume. A pump regulator is preferably assigned to the pump, which regulates the pressure at the first control point by adjusting the displacement volume to a target pressure which depends on the pressure in the load reporting line. The target pressure is, for example, a predetermined pressure difference above the pressure in the load reporting line. If there are several pressure compensators according to the invention, the corresponding fluid flow paths preferably coincide up to the first control point, after which they branch off in parallel so that the pump supplies the actuators with pressure fluid in parallel. In addition to the actuators with the pressure compensator according to the invention, there may be actuators with other pressure compensators, in particular with pressure compensators according to FIG U.S. 5,305,789 , in which in particular the third aperture and the separate second control surface are missing. The pressure compensator is preferably configured in such a way that it regulates the pressure at the second control point essentially to the pressure in the load reporting line. It should be noted that the invention consists precisely in the fact that the exact control behavior according to the U.S. 5,305,789 just no longer takes place, but is deliberately slightly falsified by means of the second control surface. It should also be noted that the connection of the first control surface to the load reporting line causes the first control surface to be pressurized with the pressure in the load reporting line.

Advantageous developments and improvements of the invention are specified in the dependent claims.

It can be provided that the flow resistance of the third orifice is essentially independent of the position of the pressure compensator. A corresponding pressure compensator is designed to be particularly simple and inexpensive. It is conceivable that the third diaphragm has a different flow resistance in the first and in the third position than in the second position.

It can be provided that the first and the second control surface are in fluid exchange connection via a fourth diaphragm. In the second position, there is preferably a fluid exchange connection between the load reporting line and the third control point exclusively via the fourth panel. The third and fourth diaphragms together form a pressure divider between the pressure in the load reporting line or the pressure at the first control surface and the pressure at the third control point, the corresponding center pressure of the pressure divider being the pressure at the second control surface. This pressure divider is effective when the pressure compensator is in the second position. In the third position, the pressure in the load reporting line and the pressure at the third control point are the same and therefore equal to the center pressure at the second control surface. The third aperture then effects opposite that Prior art only dampens the movement of the pressure compensator in the direction of the third position. In the first position, the pressure divider has no effect, since the actuator cannot move due to the closed first diaphragm. Compared to the well-known pressure compensator of the U.S. 5,305,789 causes the said pressure divider in the second position that the first diaphragm is closed somewhat less than is the case in the prior art, depending on the pressure at the third control point. As a result, the corresponding actuator is less prone to cavitation in the event of rapid load changes or rapid changes in the pressure at the third control point or in the case of pulling loads. As a result, it is no longer necessary to permanently supply the actuator with a little too much pressure fluid in order to avoid cavitation. This results in an energy saving.

It can be provided that a flow resistance of the fourth orifice is essentially independent of the position of the pressure compensator. A corresponding pressure compensator is designed to be particularly simple and inexpensive. It is conceivable that the fourth diaphragm has a different flow resistance in the first and in the third position than in the second position.

It can be provided that the pressure compensator comprises a control slide which can be moved in the direction of a longitudinal axis and an essentially immovable stator, the third and / or the fourth diaphragm each being formed by a gap between the control slide and the stator. A corresponding pressure compensator has a particularly compact design. The fluid connections according to the invention can be implemented in a particularly simple manner.

It can be provided that the control slide has a stator recess, the stator being elongated, whereby it protrudes into the stator recess, the third and / or the fourth aperture being arranged in the area of the stator recess. The third and / or the fourth diaphragm can each be formed by at least one annular gap between the stator and the stator recess. At least in the area of the annular gap, the stator and the stator recess are preferably circular-cylindrical. The gap width of the annular gap or the corresponding play between the stator and stator recess is preferably designed so that the desired flow resistance results. The stator is preferably designed to be elongated in the direction of the longitudinal axis. It is preferably designed to be essentially circular-cylindrical.

It can be provided that the stator recess is designed in the form of a blind hole, a corresponding base of the blind hole forming the second control surface. As a result, the second control surface can be provided in a particularly simple and inexpensive manner. The stator also seals the first control surface against the second control surface.

It can be provided that the third and / or the fourth diaphragm each include at least one notch on the stator or on the control slide that runs in the direction of the longitudinal axis. The notch is preferably so narrow with respect to the adjacent parts of the corresponding fluid flow path that it essentially alone defines the flow resistance of the corresponding diaphragm. Because of its comparatively long friction path for the pressure fluid, such a fourth orifice is also referred to as a throttle.

It can be provided that the stator is formed by a separate component which is held on a housing by means of a locking ring, the control slide being movably received in the housing, the stator being permanently subjected to pressure on an end face pointing in the direction of the longitudinal axis is applied. The cost-effective fastening by means of a locking ring is typically subject to play. The abovementioned application of pressure on the front side has the effect that the stator is permanently pressed into an end position of the play area during operation, so that it does not move.

It can be provided that the end face of the stator is acted upon by the pressure in the load reporting line. The corresponding fluid connection can be produced in a particularly simple and cost-effective manner. It is conceivable that the end face of the stator is acted upon by the pressure at the first, the second or the third control point.

It can be provided that the sum of the hydraulically effective areas of the first and second control surfaces is equal to the hydraulically effective area on which the pressure at the second control point acts on the pressure compensator.

It goes without saying that the features mentioned above and those yet to be explained below can be used not only in the respectively specified combination, but also in other combinations or on their own, without departing from the scope of the present invention.

• 1 einen Schaltplan eines erfindungsgemäßen hydraulischen Antriebssystems;
• 2 einen Längsschnitt einer erfindungsgemäßen Druckwaage, wobei sich der Steuerschieber in der ersten Stellung befindet;
• 2a einen Längsschnitt einer erfindungsgemäßen Druckwaage, wobei sich der Steuerschieber in der dritten Stellung befindet;
• 3 eine perspektivische Ansicht der Verschlussschraube, des Stators und des Steuerschiebers;
• 4 eine perspektivische Ansicht des Stators; und
• 5 eine perspektivische Schnittansicht des Steuerschiebers.

The invention is explained in more detail below with reference to the accompanying drawings. It shows:

• 1 a circuit diagram of a hydraulic drive system according to the invention;
• 2 a longitudinal section of a pressure compensator according to the invention, wherein the control slide is in the first position;
• 2a a longitudinal section of a pressure compensator according to the invention, wherein the control slide is in the third position;
• 3 a perspective view of the screw plug, the stator and the control slide;
• 4th a perspective view of the stator; and
• 5 a perspective sectional view of the control slide.

1 shows a circuit diagram of a hydraulic drive system according to the invention 10 . The hydraulic drive system 10 includes a pump 14th , which pressurized fluid from a tank 15th sucks in and into a pump line 18th where there is essentially the same pressure everywhere. The pump line 18th forms the first control point 13th . The pressure fluid is preferably a liquid and most preferably hydraulic oil. All tank symbols 15th in 1 denote the same tank.

The pump 14th preferably has an adjustable displacement volume, which is controlled by a pump regulator 17th is adjustable in the sense of a manipulated variable. The actual size of the pump regulator 17th is the pressure at the first control point 11 or in the pump line 18th . The target size of the pump regulator 17th depends on the pressure in the load reporting line 16 from, for example, the setpoint is a predetermined pressure difference higher than the pressure in the load reporting line 16 .

The hydraulic drive system 10 preferably comprises several actuator sections 19th , where in 1 only a single actuator section 19th is shown. This is in 1 edged with a dotted line. The actuator sections 19th each include an actuator 20th , which can be designed as a hydraulic cylinder or as a hydraulic motor. The remaining actuator section 19th is often formed by a separate valve disk, with all valve disks of the hydraulic drive system 10 are assembled into a valve block in such a way that the pump line 18th and the load reporting line 16 each result in a line running uninterrupted through the valve block. The actuators 20th are thus in parallel with the pump 14th supplied with pressurized fluid. The load reporting line 16 is on from the pump controller 17th remote end preferably closed in a fluid-tight manner. The pump line 18th is on from the pump 14th remote end preferably closed in a fluid-tight manner.

Every actuator 20th is a continuously adjustable main panel 21 , a pressure compensator 30th and a directional control valve 22nd assigned. The main bezel 21 and the directional control valve 22nd are preferably formed by a common valve slide and are in 1 shown separately from one another solely for the sake of clarity. With the main panel 21 becomes the speed of movement of the actuator 20th adjusted, using the directional control valve 22nd whose direction of movement is set.

Every actuator 20th a fluid flow path is assigned, which starts from the tank 15th , continue about the pump 14th , continue via the first control station 11 , continue on the relevant main panel 21 , then via a second control station 12th , continue over a first aperture 40 the relevant pressure compensator 30th , then via a third control point 13th , continue via the relevant directional control valve 22nd to the actuator 20th runs. That from the actuator 20th Returning pressurized fluid flows through the directional control valve 22nd back in the tank 15th .

The pressure balance 30th has a first, a second and a third position 41 ; 42 , 43 which are arranged next to one another in the specified order. In the first position 41 is the first aperture 40 completely closed. In the second position 42 is the first aperture 40 partially open. In the third position 42 is the first aperture 40 fully open. The first and the third position 41 ; 43 essentially refer to the two opposite end positions of the pressure compensator 30th , with the second position 42 denotes the adjustment range of the pressure compensator in between, in which the opening cross-section of the first diaphragm is located 40 changes steadily from fully closed to fully open.

In the opening direction of the first aperture 40 becomes the pressure compensator 30th from the pressure at the second control point 12th applied. Here is the pressure compensator 30th not equipped with a spring. But it is conceivable that the pressure compensator 30th equip with a spring, which the pressure compensator 30th in the first position 41 pretensioned. This spring is preferably designed so weak that it is essentially only effective in the unpressurized state.

In the closing direction of the first aperture 40 is the pressure compensator 30th with a first and a separate second control surface 31 ; 32 fitted. By applying pressure to each of these two control surfaces 31 ; 32 can the pressure compensator 30th in the closing direction of the first diaphragm 40 adjusted. The first control surface 31 is from the pressure in the load reporting line 16 applied. These Connection causes the pressure compensator 30th in a first approximation the pressure at the second control point 12th on the pressure in the load reporting line 16 regulates. The higher the pressure at the third control point 13th the wider is first aperture 40 open. When multiple actuators 20th is the pressure compensator 30th in the third position 43 , at which the pressure at the third control point 13th is highest.

Alone in the third position 43 opens the second aperture 52 which in the first and in the second position 41 ; 42 is locked. The second aperture 52 establishes a connection between the third control point 13th and the load reporting line 16 here. Correspondingly lies in the load reporting line 16 always the highest pressure from all pressures at the third control points 13th at. This pressure is also called the highest load pressure.

The second control surface according to the invention 32 is acted upon by the center pressure of a pressure divider, which is from a third and a fourth aperture 53 ; 54 is formed. This pressure divider is between the pressure in the load reporting line 16 and the pressure at the third control point 13th switched. Accordingly, the pressure is on the second control surface 32 between the two mentioned pressures. The following is in the pressure compensator according to the invention 30th the first aperture 40 at least in the second position 42 a little less open than the one from the U.S. 5,305,789 known pressure compensator. This creates cavitation in the actuator in an energy-saving manner 20th prevented. In addition, the third aperture alone has an effect 53 that the pressure compensator reacts faster to changes in pressure at the third control point 13th reacts, this behavior especially in the case of the actuator with the highest load 20th is significant.

The flow resistances of the third and fourth orifice 53 ; 54 are preferably each independent of the position of the pressure compensator 30th . In the context of the invention, however, it is only important that the third and fourth diaphragms 53 ; 54 in the second position 42 are effective. In particular the third aperture 53 could be in the first position 41 also be completely closed. The third aperture 53 could be in the third position 43 also be more open than in the second position 42 the case is.

2 shows a longitudinal section of a pressure compensator according to the invention 30th , with the spool 33 in the first position 41 is located. 2a shows a longitudinal section of a pressure compensator according to the invention 30th , with the spool 33 in the third position 43 is located. The 2 and 2a differ only in terms of the position of the control slide 33 .

The pressure balance 30th includes a spool valve 33 , which in one housing 39 with respect to a longitudinal axis 38 is recorded linearly movable. The corresponding hole is with a retaining screw 35 and a screw plug 36 fluid-tight closed, with between the retaining screw 35 and the case 39 a sealing ring 37 is built in. In the retaining screw 35 is a separate stator 50 by means of a locking ring 51 held. The locking screw 36 enables the stator to be installed 50 with the locking ring 51 into the retaining screw 35 so that the locking ring 51 on a shoulder of the retaining screw 35 is present. The locking screw 36 is against the retaining screw 35 braced, with between the locking screw 36 and the stator 50 a gap remains. The pressure in the load reporting line is essentially located in this gap 16 regardless of the position in which the pressure compensator is 30th is located. The circular cylindrical ring gap 57 between stator 50 and retaining screw 35 is designed so large that a corresponding fluid exchange is possible. The front side 56 of the stator 50 is therefore permanent with the pressure in the control line 16 applied so that the locking ring 51 permanently against the assigned shoulder on the retaining screw during operation 35 is pressed.

The stator 50 protrudes into a stator recess 44 of the control spool 33 into it, the stator recess 44 except for the third and fourth aperture explained below 53 ; 54 fluid-tight to the stator 50 is adapted. The stator recess 44 is essentially as with respect to the longitudinal axis 38 circular cylindrical blind hole formed. The bottom of the stator recess 44 forms the second control surface 32 . The circular surface on which the retaining screw is located 35 facing end of the control spool 33 forms the first control surface 31 . The first and second controls 31 ; 32 are through the stator 50 sealed against each other, the stator 50 together with the stator recess 44 a defined fourth aperture 54 forms, which fluidly connects the first and the second control surface to one another. The flow resistance of the fourth orifice 54 is independent of the position of the control spool 33 , with further details referring to 4th explained.

On the stator 50 opposite end of the control spool 33 is the first aperture 40 arranged. The reference number 40 in 2 and 2a denotes the corresponding one with respect to the longitudinal axis 38 circular control edge on the housing 39 . The counter office on the control slide 33 is referring to 5 explained in more detail. The first aperture 40 is in the in 2 shown first position completely closed. The control slide is in this position 33 with that of the first aperture 40 associated longitudinal end on the housing 39 in. In the in 2a The third position shown is the first aperture 40 opened to the maximum, with the control slide 33 with that of the stator 50 associated longitudinal end on the retaining screw 35 is present. At this point, attention should be paid to the perforations (No. 80 in 3 ) on the first control surface 31 to point out. These ensure that there is no full-surface contact. Rather, there is always at least part of the first control surface 31 the pressure in the load reporting line 16 exposed even if the spool is 33 is in the third position.

The case 39 is with a third ring groove 63 provided which the control slide 33 surrounds in every position. To the third ring groove 63 is the load reporting line 16 permanently connected. Via the fourth longitudinal groove (No. 74 in 3 and 4th ) on the outside of the control spool 33 the corresponding pressure becomes the first control surface 31 directed. The fourth longitudinal groove is designed so that this fluid connection in every position of the pressure compensator 30th exists, the corresponding throttling effect being low. The fourth longitudinal groove could also be on the housing 39 be arranged, where it is more difficult to manufacture there.

The third ring groove 63 also forms the control edge of the second diaphragm 52 on the housing 39 . The counter contour on the control spool 33 is supported by a third longitudinal groove (No. 73 in 3 and 5 ) on the outer circumferential surface of the control spool 33 educated. That the stator 50 facing end of the third longitudinal groove is arranged so that it is only in the in 2a the third position shown is the third annular groove 63 covered. The second aperture is only in this position 52 open. In all other positions there is no such overlap, so that the second diaphragm 52 is locked.

The third control point 13th is from a channel in the housing 39 formed, which the control slide 33 surrounds in a ring in every position. This channel is preferably made using a casting process. The control edge of the first diaphragm is on a side wall of this channel 40 incorporated by machining. The above-mentioned third longitudinal groove (No. 73 in 3 and 5 ) is so long that you can use this channel in every position of the control slide 33 covered. The second aperture is accordingly 52 permanently to the third control point 13th connected.

The second control point 12th is from a channel in the housing 39 formed, which is on the front side of the control slide 33 empties. The pressure at the second control point 12th acts on the control slide 33 to the stator 50 down, with the first aperture 40 opens with a corresponding movement. Then there is over the first aperture 40 a fluid exchange connection between the second and third control points 12th ; 13th .

Inside the stator 50 is a connecting channel 60 arranged. This connects the second control surface 32 opposite end face of the stator 50 permanent with a second ring groove (No. 62 in 4th ) on the outer peripheral surface of the stator 50 . The connecting channel 60 includes a first bore along the longitudinal axis 38 and at least one second bore radial to the longitudinal axis 38 . The second bore opens into the second annular groove and the first bore.

3 shows a perspective view of the locking screw 36 , the stator 50 and the control spool 33 . The fourth longitudinal groove already mentioned can be seen 74 that extends from the frontal first control surface 31 in the direction of the longitudinal axis 38 up to a fourth ring groove 64 outside on the control slide 33 extends. A comparison of the 2 and 2a shows that the fourth ring groove 64 in every position of the control spool 33 the third ring groove (No. 63 in 2 and 2a) covered so that there is permanent pressure in the load reporting line 16 is present.

The stator 50 and the control spool 33 are on their outer circumferential surfaces each with several circular around the longitudinal axis 38 running grooves 81 Mistake. This causes the control slide to jam 33 avoided.

4th Figure 3 shows a perspective view of the stator 50 . This is on an outer circumferential surface with a slot-like second groove 72 provided, which is parallel to the longitudinal axis 38 extends. The second groove 72 is about a notch 55 with the second ring groove 62 connected, the flow resistance of the notch 55 is significantly higher than that of the second longitudinal groove 72 . The flow resistance of the fourth orifice 54 is accordingly essentially from the notch 55 determines which of one with respect to the longitudinal axis 38 circular cylindrical section of the stator recess (No. 44 in 2 and 2a) is covered in every position of the control spool (No. 33 in 2 and 2a) . The flow resistance of the fourth orifice 54 is therefore independent of the position of the control slide.

In 3 it can be seen that the second longitudinal groove 72 to the first control surface 31 extends. At the first control surface 31 is the pressure in the load reporting line (No. 16 in 1 ), which is therefore also in the second longitudinal groove 72 is applied regardless of the position of the pressure compensator. The fourth aperture 54 connects this pressure with the second ring groove 62 which reduces the pressure on the second control surface (No. 32 in 1 ), as already explained above.

The stator is at the end facing the second control surface 50 on its outer circumferential surface with a first annular groove 61 provided, in which has a first longitudinal groove 71 joins. The first longitudinal groove 71 ends at a distance from the second ring groove 62 . This area is circular-cylindrical with respect to the longitudinal axis 38 and executed smoothly. This area is also defined by a smooth area on the stator recess, which is also circular cylindrical (no.44 in 2 and 2a) covered in every position of the control slide. A defined game is provided there, which is a first part of the third panel 53 forms. Another part of the third aperture 53 is made up of a comparable annular gap between the first annular groove 61 and the longitudinal end of the stator facing the second control surface 50 educated. The flow resistance of the third diaphragm is accordingly 53 regardless of the position of the control spool (No. 33 in 2 and 2a) .

5 shows a perspective sectional view of the control slide 33 . The cutting plane runs through the longitudinal axis 38 and through the third and fourth longitudinal grooves 73 ; 74 .

The crown-like longitudinal end of the control slide can be seen 33 , which is part of the continuously adjustable first aperture 40 forms. There is a blind hole there 84 intended. The corresponding radial wall has larger first recesses 40a interspersed, which the coarse control area of the first aperture 40 define. The first recesses 40a are designed as circular openings or as U-shaped recesses. The fine control area near the closed first aperture 40 form the smaller second recesses 40b , which are designed as circular breakthroughs.

Next is the radial holes 83 point out which each has an associated third longitudinal groove 73 with a fifth ring groove 65 on the inner peripheral surface of the stator recess 44 connect. In the fifth ring groove 65 accordingly, the pressure at the third control point (No. 13 in 2 and 2a) regardless of the position in which the control spool is 33 is located. The fifth ring groove 65 covered in every position of the control slide 33 the first longitudinal groove (No. 71 in 4th ), so that there is also permanent pressure at the third control point.

List of reference symbols

10

Hydraulic drive system

11

first control station

12th

second control point

13th

third control station

14th

pump

15th

tank

16

Load reporting line

17th

Pump regulator

18th

Pump line

19th

Actuator section

20th

Actuator

21

Main aperture

22nd

Directional control valve

30th

Pressure compensator

31

first control surface

32

second control surface

33

Control spool

35

Retaining screw

36

Screw

37

Sealing ring

38

Longitudinal axis

39

casing

40

first aperture

40a

first recess

40b

second recess

41

first position

42

second position

43

third position

44

Stator recess

50

stator

51

Circlip

52

second aperture

53

third aperture

54

fourth aperture

55

score

56

Face of the stator

57

Annular gap

60

Connection channel

61

first ring groove

62

second ring groove

63

third ring groove

64

fourth ring groove

65

fifth ring groove

71

first longitudinal groove

72

second longitudinal groove

73

third longitudinal groove

74

fourth longitudinal groove

80

Performance

81

groove

83

Radial bore

84

Blind hole

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• US 5305789 [0002, 0005, 0008, 0028]

Claims (11)

Hydraulic drive system (10) with a pump (14) and at least one actuator (20), with at least one actuator (20) being assigned a continuously adjustable main panel (21) and a pressure compensator (30), the pressure compensator (30) being a has continuously adjustable first diaphragm (40), the pressure compensator (30) having a first, a second and a third position (41; 42; 43) which are arranged next to one another in the specified order, wherein in the first position (41) the first diaphragm (40) is completely closed, the first diaphragm (40) being partially open in the second position (42), the first diaphragm (40) being fully open in the third position (43), with at least one A fluid flow path is assigned to each actuator (20) which, starting from the pump (14) via a first control point (11), via the relevant main panel (21), via a second control point (12), via the relevant first panel ( 40), keep practicing r a third control point (13), extending the pressure at the second control point (12) acts upon the pressure scales (30) in the opening direction of the first aperture (40) for its actuator (20), wherein a load-sensing line (16) is provided, characterized characterized in that the pressure compensator (30) has a first and a separate second control surface (31; 32), whereby it can be adjusted in the closing direction of the first diaphragm (40) by applying pressure to both the first and the second control surface (31; 32), the first control surface (31) via the load reporting line (16) further via an adjustable second The shutter (52) is fluidically connected to the third control point (13), the second shutter (52) being open in the third position (43), being closed in the first and second positions (41; 42), the second control surface (32) in any case in the second position (42) being fluidically connected to the third control point (13) via a third panel (53) and bypassing the load reporting line (16). Hydraulic drive system according to Claim 1 , wherein the flow resistance of the third diaphragm (53) is essentially independent of the position of the pressure compensator (30). Hydraulic drive system according to one of the preceding claims, wherein the first and the second control surfaces (31; 32) are in fluid exchange connection via a fourth diaphragm (54). Hydraulic drive system according to Claim 3 , wherein a flow resistance of the fourth diaphragm (54) is essentially independent of the position of the pressure compensator (30). Hydraulic drive system according to one of the preceding claims, wherein the pressure compensator (30) comprises a control slide (33) movable in the direction of a longitudinal axis (38) and a substantially immovable stator (50), the third and / or fourth aperture (53; 54) are each formed by a gap between the control slide (33) and the stator (50). Hydraulic drive system according to Claim 5 , wherein the control slide (33) has a stator recess (44), wherein the stator (50) is elongated, wherein it protrudes into the stator recess (44), the third and / or the fourth aperture (53; 54) in the area the stator recess (44) are arranged. Hydraulic drive system according to Claim 6 , wherein the stator recess (44) is designed in the form of a blind hole, a corresponding base of the blind hole forming the second control surface (32). Hydraulic drive system according to one of the Claims 5 to 7th wherein the third and / or the fourth diaphragm (53; 54) each comprise at least one notch (55) on the stator (50) or on the control slide (33) running in the direction of the longitudinal axis (38). Hydraulic drive system according to one of the Claims 5 to 8th , the stator (50) being formed by a separate component which is held on a housing (39) by means of a locking ring (51), the control slide (33) being movably received in the housing (39), the stator ( 50) is permanently acted upon by a pressure on an end face (56) pointing in the direction of the longitudinal axis (38). Hydraulic drive system according to Claim 9 , wherein the end face (56) of the stator (50) is acted upon by the pressure in the load reporting line (16). Hydraulic drive system according to one of the preceding claims, wherein the sum of the hydraulically effective areas of the first and the second control surface (31; 32) is equal to the hydraulically effective area on which the pressure at the second control point (12) on the pressure compensator (30) acts.

Images