DE102016215747A1 - Valve arrangement for a first and a second pump - Google Patents

Abstract

The invention relates to a valve arrangement (30) having a first and a second supply point (31; 32), at least one return point (35) and a first control point (33), between the first and the second supply point (31; Check valve (36) is arranged, which permits only a fluid flow from the second supply point (32) to the first supply point (31), wherein a first pressure compensator (40) is provided, via which pressurized fluid from the second supply point (32) to an associated Return point (35) is conductible, wherein the first pressure compensator (40) in the direction of a closed position (42) is acted upon at least by a first spring (41), wherein the first spring (41) defines a first pressure difference, wherein the first pressure compensator ( 40) in the direction of an open position (43) from the pressure at the first supply point (31) is acted upon. According to the invention, the first pressure balance (40) in the direction of the closed position (43) is acted upon by the pressure at a second control point (34), the pressure at the second control point (34) being dependent on the pressure at the first control point (33).

Description

The invention relates to a valve arrangement according to the preamble of claim 1.

From the DE 10 2012 208 938 A1 a valve arrangement is known, via which a plurality of actuators are supplied by a first and a second pump with pressurized fluid. The first pump has an adjustable displacement volume, wherein it is associated with a pump regulator, which regulates the delivery pressure of the first pump by adjusting the displacement volume. The second pump has a constant displacement volume, wherein the second pressure compensator is associated with a first pressure compensator, via which pressurized fluid from an associated second supply point to the tank can be conducted. The first pump primarily supplies the prioritized steering of a mobile work machine, the second pump primarily supplying the other actuators of the mobile work machine. These will be controlled by an open-center control, where no load feedback occurs. A supply of the steering by the second pump is not possible.

An advantage of the present invention is that all the actuators of the first and second pumps can be supplied in parallel with pressurized fluid. In this case, all actuators may be provided with a load feedback, which can be used to control the delivery pressure of the first and the second pump. As long as the flow rate of the second pump is not needed, it runs with very little back pressure in the standby state, so that there are only low energy losses. In addition, the second pump can be completely deactivated.

According to claim 1 it is proposed that the first pressure compensator is acted upon in the direction of the closed position by the pressure at a second control point, wherein the pressure at the second control point is dependent on the pressure at the first control point. The load feedback of the actuators at the first control point can thus act on both the first and on the second pump.

The at least one return point is preferably connected to a tank, most preferably low flow resistance. Preferably, only a single return site is present.

In the dependent claims advantageous refinements and improvements of the invention are given.

It can be provided that the pressure at the second control point is at least a first operating state of the valve arrangement by a predetermined second pressure difference above the pressure at the first control point. The first spring on the first pressure compensator can thus be designed so weak that results in the standby state of the second pump a lowest possible pressure drop across the first pressure compensator, so that the corresponding energy losses are low. In a second operating state, the pressure at the second control point is preferably substantially equal to the pressure at an associated return point. By a corresponding influence on the pressure at the second control point can thus be switched between the aforementioned operating conditions. In the first operating state, the first and the second pump can supply the hydraulic drive system in parallel. In the second operating state, the hydraulic drive system is supplied exclusively by the first pump, regardless of whether their delivery capacity is sufficient for this purpose.

It can be provided with a first and a second position, a switching valve, wherein the second control point is connected exclusively in said second position via the switching valve with an associated return point. By means of the switching valve can be switched between the first and the second operating state. Preferably, the first operating state corresponds to the first position of the switching valve, wherein the second operating state corresponds to the second position of the switching valve. Preferably, the second control point is connected directly via the switching valve with said return point. The switching valve is preferably designed as a 2/2-way valve. However, it is also conceivable that the switching valve is designed as a 3/2-way valve, wherein it connects the second control point with the first control point in the first position, wherein it connects the second control point with the associated return point in the second position. In this embodiment, the first pressure difference of the first pressure compensator is preferably slightly smaller than the third pressure difference of the pump controller.

It may be provided a second pressure compensator, which is continuously adjustable between a first and a second position, wherein the second pressure compensator is acted upon in the direction of its first position by a second spring and the pressure at the first control point, wherein they are in the direction of the second position is acted upon by the pressure at the second control point, wherein the second spring defines the second pressure difference. As a result, a weak first spring can be selected, so that the pressure drop across the first pressure compensator in the standby state of the second pump is low. The second pressure compensator thereby causes the pressure at the second control point in the first operating state to be greater than the pressure at the first control point by the second pressure difference.

It can be provided that in the first position of the second pressure compensator, the second control point is connected to the first supply point, wherein in the second position of the second pressure compensator, the second control point is connected to an associated return point. As a result, a pressure fluid source and a pressure fluid sink for the regulation of the pressure at the second control point are provided, wherein the second pressure compensator operates in the manner of a 3-way pressure reducing valve.

It can be provided that a first throttle is connected between the second pressure compensator and the second control unit. This prevents excessive pressure fluid from flowing from the first supply point via the switching valve into the tank in the second operating state. Furthermore, the pressure at the second control point in the second operating state can be lowered particularly close to the pressure in the tank.

It can be provided that the second pressure compensator has a slide which is received linearly movably in an associated slide bore, wherein the first throttle is formed by a groove in the slide, which is covered by the slide bore such that a free cross-sectional area of the first throttle does not change with a movement of the slider. The first throttle is thus provided in a particularly simple and space-saving manner.

It may be provided that the entire valve assembly is received in a base body, wherein the first and the second supply point, the first control point and the at least one return point are each formed by at least one separate terminal, which is arranged on the outside of the main body. The valve assembly may thus be provided as a separate assembly which may be fabricated in advance as a whole and which may be installed as a whole in a hydraulic drive system. Preferably, the main body is fluidly connected via pipe and / or hose lines with the other components of the hydraulic drive system. The first supply point is preferably formed by a first bore, which passes through the base body, so that the first supply point two ports are assigned to the outside of the housing. Preferably, only a single return point is provided, which is associated with only a single port. The above-mentioned slide bore is preferably formed by the main body.

Protection is also claimed for a hydraulic drive system with a first and a second pump, at least one actuator, a tank and a valve assembly according to the invention, wherein by means of the first pump pressure fluid from the tank to the first supply point can be conveyed, wherein by means of the second pump pressure fluid from the Tank to the second supply point is conveyed, wherein the first pump has an adjustable displacement volume, wherein the second pump has a constant displacement volume, wherein the at least one actuator, possibly parallel, is connected to the first supply point, wherein the pressure at the first control point of a highest load pressure of all actuators is dependent, wherein a pump regulator is provided, with which the pressure at the first supply point by adjusting the displacement volume of the first pump is einregelbar to a desired value, the oberhal by a predetermined third pressure difference b is the pressure at the first control point, wherein the third pressure difference is greater than the first pressure difference. Thus, the second pump only delivers to the system when the first pump can not maintain its third pressure difference because its delivery capacity is insufficient to meet the needs of all actuators.

It can be provided that the third pressure difference is greater than the sum of the first and the second pressure difference. Thus, the first spring on the first pressure compensator, which defines the first pressure difference, be made weak. As a result, the energy loss of the second pump running in the standby state is low. The second pressure difference is preferably defined by the above-mentioned second spring on the second pressure compensator.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

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

1 a circuit diagram of a hydraulic drive system with a valve assembly according to the invention, and

2 a longitudinal section of the valve assembly according to 1 ,

1 shows a circuit diagram of a hydraulic drive system 10 with a valve arrangement according to the invention 30 , The hydraulic drive system 10 includes a first and a second pump 11 ; 12 , which in the present case two actuators 20 supply with pressurized fluid, with any number of actuators 20 can be provided. The pressurized fluid is preferably a liquid and most preferably hydraulic oil. The actuators 20 can each be designed as a cylinder or as a hydraulic motor. The first pump 11 has an adjustable displacement volume, for example, it is designed as an axial piston pump. The second pump 12 has a constant displacement volume, being designed for example as external gear pump. The first and the second pump 11 ; 12 each suck pressurized fluid out of a tank 13 and promote it to a first or second supply point 31 ; 32 , The first and the second supply point 31 ; 32 are part of the valve arrangement according to the invention 30 , They are over a first check valve 36 fluidly connected to each other, wherein the first check valve 36 only a fluid flow from the second supply point 32 to the first supply point 31 allows. In 1 denote all tank symbols 13 the same tank.

All actuators 20 are parallel to the first supply point 31 connected. Every actuator 20 are a second check valve 24 , a second throttle 23 and a directional valve 21 assigned. With the continuously adjustable second throttle 23 is the movement speed of the relevant actuator 20 adjusted, with the directional control valve whose direction of movement is set. The second throttle 23 and the directional valve 21 are preferably formed by a common valve spool, so that they are adjustable together. With the second check valve 24 prevents pressurized fluid against the intended flow direction of the actuator 20 back to the first supply point 31 flows. The directional valves 21 each have a central locking position in which the associated actuator is hydraulically clamped. The load tap 22 of the relevant directional control valve 21 is then depressurized, taking, for example, with the tank 13 connected is. In the other positions of the directional control valve 21 , in which the associated actuator moves, is due to the load tap 22 the pressure downstream of the second throttle 23 at.

The load taps 22 are by means of a cascade of shuttle valves 25 interconnected, whose output is the first control unit 33 forms. At the first control point 33 the highest pressure is from a group of pressures which are the pressures at all load taps 22 includes. The delivery pressure of the pumps 11 ; 12 is set to be higher than the pressure at the first control unit 33 is. The actuators 20 In each case, a pressure compensator (not shown) may be associated with which the pressure drop across the second throttle 23 adjusted to a constant value, allowing the movement speed of the actuators 20 essentially solely by the setting of the associated second throttle 23 and not of the actuator in question 20 attacking load is dependent.

The hydraulic drive system 10 is primarily from the first pump 11 supplied with pressurized fluid. Only when the maximum volume flow of the first pump 11 or whose maximum drive power is no longer sufficient to all actuators 20 to supply with pressurized fluid, promotes the second pump 12 via the second supply point 32 and the first check valve 36 to the first supply point 31 ,

The first pump 11 has an adjustable displacement volume, which with a positioning cylinder 16 is adjustable. The first pump 11 is for example designed as a swash plate pump, wherein by means of the actuating cylinder, the swivel angle of the swash plate is adjusted. A pump regulator 14 regulates the pressure at the first supply point 31 to a value which is higher than the pressure at the first control point by a predetermined third pressure difference 33 is. The third pressure difference is present by a preloaded third spring 15 at the pump regulator 14 Are defined. Instead of the hydraulic pump regulator shown can also be provided an electro-hydraulic pump regulator, in which the third pressure difference is electrically or electronically adjustable. The pump regulator 14 can have other functions in addition to the explained pressure control. For example, it can have a power limiting function with which the maximum drive power of the first pump 11 is limited to the top. It can also be provided a pressure cut, with which the maximum delivery pressure of the first pump 11 is limited to the top.

The second pump 12 has a constant displacement volume. About the first pressure balance 40 can pressure fluid from the second supply point 32 to a return point 35 be directed with the tank 13 connected is. The first pressure balance 40 is between a closed and an open position 42 ; 43 continuously adjustable. The pressure at the first supply point 31 acts on the first pressure balance 40 in the direction of an adjustment to the open position 43 out. In the opposite direction is the first pressure compensator 40 from the pressure at a second control station 34 and a preloaded first spring 41 applied.

In the simplest conceivable embodiment, the second control unit could 34 from the first control point 33 be formed. The embodiment according to 1 However, compared to this conceivable simplest embodiment, a higher energy efficiency, wherein the connection of the second pump 12 Moreover, it is deactivated.

With the switching valve 70 can be switched between a first and a second operating state. In the first operating state, the pressure is at the second control point 34 one second pressure difference greater than the pressure at the first control point 33 wherein the second pressure difference is through a preloaded second spring 53 is defined. In the second operating state, the second control point 34 essentially depressurized, in particular via a return point 35 with the tank 13 connected is.

The third pressure difference, which is due to the third spring 15 is formed on the pump controller is greater than the sum of the first and the second pressure difference. In the first operating state and as long as the performance of the first pump 11 sufficient for all actuators 20 to supply with pressurized fluid acts on the spring side of the first pressure compensator 40 the pressure at the first control point 33 , increased by the first and second pressure difference. On the opposite side, the pressure acts on the first control point 33 Increased by the third pressure difference. The latter pressure prevails, leaving the first pressure compensator 40 in the open position 43 is moved. The first spring 41 is preferably designed as weak as possible, so that the pressure drop across the first pressure compensator 40 and therefore the corresponding energy losses are small. As a result, the first pressure difference is small.

When the delivery capacity of the first pump 11 is no longer sufficient to all actuators 20 to supply, the third pressure difference can no longer be maintained. As a result, in the first operating state, the first pressure compensator 40 towards the closed position 42 adjusted. This increases the pressure at the second supply point 32 until it is greater than the pressure at the first supply point 31 is, making the first check valve 36 opens. As a result, the pressure at the first supply point 31 adjusted to a value corresponding to the pressure at the first control point 33 increasingly corresponds to the first and the second pressure difference. The displacement volume of the first pump 11 is set to its maximum value, so that both pumps 11 ; 12 promote in parallel.

The pressure at the second control point 34 is by means of the second pressure compensator 50 provided. This is between a first and a second position 51 ; 52 continuously adjustable. In the first position 51 is the second control point 34 with the first supply point 31 or connected to another source of pressure. In the second position 52 is the second control point 34 via a return point 35 with the tank 13 connected. Towards an adjustment to the first position 51 there will be the second pressure compensator 50 from the pressure at the first control point 33 and a preloaded second spring 53 applied. In the opposite direction, the second pressure compensator 50 from the pressure at the second control point 34 applied. As a result, regulates the second pressure compensator 50 the pressure at the second control station 34 on the pressure at the first control point 33 Increased by the second pressure difference, wherein the second pressure difference by the second spring 53 is defined.

Between the second pressure balance 50 and the second control unit 34 is a first throttle 54 switched, the switching valve 70 in the form of a 2/2-way valve between the second control point 34 and one with the tank 13 associated rewind point 35 is switched. The switching valve 70 is present by means of an electromagnet in the first position 71 switched, it by a spring in the second position 72 is moved. When the switching valve 70 in the closed first position 71 is, ie in the first operating state, the pressure at the second control point 34 as explained above. When the switching valve 70 in the open second position 72 is the second control point 34 over a very small flow resistance with the tank 13 connected, wherein the flow resistance of the first throttle 54 is much larger. This has the consequence that the second pressure compensator 50 permanently in the first position 51 stands, wherein pressurized fluid from the first supply point 31 over the first throttle 54 , the second control unit 34 and the switching valve 70 to the tank 13 flows. The corresponding pressure drop at the first throttle 54 causes the pressure on the second control unit 34 slightly larger than the pressure in the tank 13 is. The first pressure balance 40 is in the sequence in the open position 43 because the pressure at the first supply point 31 almost always larger than the first pressure difference increased by the pressure in the tank 13 is. The second pump 12 Accordingly, does not contribute to the supply of actuators 20 at, even if the delivery capacity of the first pump 11 this is not enough.

The first and / or the second supply point 31 ; 32 can each be connected to a (not shown) pressure relief valve to avoid overload and to smooth pressure peaks. Next, the first control unit 33 be connected to a pressure relief valve. As a result, pressure peaks are avoided in particular when moving large masses.

2 shows a longitudinal section of the valve assembly 30 to 1 , All components of the valve assembly 30 , namely the first check valve 36 , the first and the second pressure balance 40 ; 50 and the switching valve 70 , are in a body 80 recorded, which may be formed multi-part if desired. The first and the second supply point 31 ; 32 , the return office 35 and the first control unit 33 each form a connection 81 attached to the outer surface of the main body 80 is arranged. This can be done in 2 illustrated module to the piping system of the hydraulic Drive system after 1 be connected. The first supply point 31 is doing from a first hole 83 formed, which is the basic body 80 parallel to the drawing plane of the 2 interspersed, so they have two connectors 81 forms. At one end of the first hole 83 the first pump (no. 11 in 1 ) connected to the opposite end of the actuators (no. 20 in 1 ) are connected in parallel. The second control unit 34 is from the second hole 84 formed, being between the first and the second pressure compensator 40 ; 50 is arranged. The first control point 33 comes from a separate stopper 85 formed, which in the second hole 84 is screwed.

The slides of the first and the second pressure balance 40 ; 50 and the corresponding springs 53 ; 41 are in the second hole 84 taken parallel to the first hole 83 is arranged. The second supply point 32 and the return office 35 are each formed by a hole perpendicular to the plane of the 2 is aligned. The switching valve 70 is designed in the form of an electromagnetically actuated Einschraubventils, which in the body 80 is screwed. In addition, several more holes are provided, with which the connections according to the wiring diagram 1 getting produced. These are outward each with a sealing plug 82 sealed fluid-tight.

Attention is still on the groove 57 on the slide 55 the second pressure balance 50 , This is independent of the position of the second pressure compensator 50 from the relevant slide bore 56 covered. Their flow resistance is accordingly essentially independent of the position of the second pressure compensator 50 , The groove 57 makes the first throttle 54 ,

LIST OF REFERENCE NUMBERS

10

hydraulic drive system

11

first pump

12

second pump

13

tank

14

pump regulator

15

third spring

16

actuating cylinder

20

actuator

21

way valve

22

load tap

23

second throttle

24

second check valve

25

shuttle valve

30

valve assembly

31

first supply point

32

second supply point

33

first control point

34

second control station

35

Return point

36

first check valve

40

first pressure balance

41

first spring

42

closed position

43

open position

50

second pressure balance

51

first position of the second pressure compensator

52

second position of the second pressure compensator

53

second spring

54

first throttle

55

pusher

56

slide bore

57

groove

70

switching valve

71

first position of the switching valve

72

second position of the switching valve

80

body

81

connection

82

sealing plug

83

first hole

84

second hole

85

Sealing plug for first control unit

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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.

Cited patent literature

• DE 102012208938 A1 [0002]

Claims (10)

Valve arrangement ( 30 ) with a first and a second supply point ( 31 ; 32 ), at least one rewind point ( 35 ) and a first control unit ( 33 ), wherein between the first and the second supply point ( 31 ; 32 ) a first check valve ( 36 ), which only a fluid flow from the second supply point ( 32 ) to the first supply point ( 31 ), whereby a first pressure compensator ( 40 ) is provided via which pressurized fluid from the second supply point ( 32 ) to an associated rewind point ( 35 ) is conductive, the first pressure compensator ( 40 ) towards a closed position ( 42 ) at least from a first spring ( 41 ) is applied, wherein the first spring ( 41 ) defines a first pressure difference, wherein the first pressure compensator ( 40 ) towards an open position ( 43 ) from the pressure at the first supply point ( 31 ), characterized in that the first pressure compensator ( 40 ) towards the closed position ( 42 ) from the pressure at a second control point ( 34 ), wherein the pressure at the second control point ( 34 ) from the pressure at the first control point ( 33 ) is dependent. Valve arrangement according to claim 1, wherein the pressure at the second control point ( 34 ) in at least a first operating state of the valve arrangement ( 30 ) by a predetermined second pressure difference above the pressure at the first control point ( 33 ). Valve arrangement according to one of the preceding claims, wherein a switching valve ( 70 ) with a first and a second position ( 71 ; 72 ), the second control unit ( 34 ) only in the said first position ( 71 ) via the switching valve ( 70 ) with an associated return station ( 35 ) connected is. Valve arrangement according to one of the preceding claims, wherein a second pressure compensator ( 50 ) is provided, which between a first and a second position ( 51 ; 52 ) is continuously adjustable, the second pressure compensator ( 50 ) towards their first position ( 51 ) of a second spring ( 53 ) and the pressure at the first control point ( 33 ) is acted upon, in the direction of the second position ( 52 ) from the pressure at the second control point ( 34 ) is applied, wherein the second spring ( 53 ) defines the second pressure difference. Valve arrangement according to claim 4, wherein in the first position ( 51 ) of the second pressure balance ( 50 ) the second control unit ( 34 ) with the first supply point ( 31 ), in the second position ( 52 ) of the second pressure balance ( 50 ) the second control unit ( 34 ) with an associated return station ( 35 ) connected is. Valve arrangement according to claim 4 or 5, wherein between the second pressure compensator ( 50 ) and the second control unit ( 34 ) a first throttle ( 54 ) is switched. Valve arrangement according to claim 6, wherein the second pressure compensator ( 50 ) a slider ( 55 ), which in an associated slide bore ( 56 ) is received linearly movable, wherein the first throttle ( 54 ) of a groove ( 57 ) in the slide ( 55 ) is formed, which from the slide bore ( 56 ) is covered, that a free cross-sectional area of the first throttle ( 54 ) during a movement of the slide ( 55 ) does not change. Valve arrangement according to one of the preceding claims, wherein the entire valve arrangement ( 30 ) in a basic body ( 80 ), the first and second supply points ( 31 ; 32 ), the first control unit ( 33 ) and the at least one rewind point ( 35 ) each of at least one separate connection ( 81 ) are formed, the outside of the body ( 80 ) is arranged. Hydraulic drive system ( 10 ) with a first and a second pump ( 11 ; 12 ), at least one actuator ( 20 ), a tank ( 13 ) and a valve assembly ( 30 ) according to one of the preceding claims, wherein by means of the first pump ( 11 ) Pressure fluid from the tank ( 13 ) to the first supply point ( 31 ) is conveyed, wherein by means of the second pump ( 12 ) Pressure fluid from the tank ( 13 ) to the second supply point ( 32 ), the first pump ( 11 ) has an adjustable displacement volume, wherein the second pump ( 12 ) has a constant displacement volume, wherein the at least one actuator ( 20 ), possibly in parallel, to the first supply point ( 31 ), whereby the pressure at the first control point ( 33 ) is dependent on a highest load pressure of all actuators, wherein a pump regulator ( 14 ) is provided, with which the pressure at the first supply point ( 31 ) by adjusting the displacement volume of the first pump ( 11 ) can be adjusted to a desired value, which by a predetermined third pressure difference above the pressure at the first control point ( 33 ), wherein the third pressure difference is greater than the first pressure difference.  A hydraulic drive system according to claim 9, when dependent on claim 2, wherein the third pressure difference is greater than the sum of the first and second pressure differences.

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