DE102015216737A1 - Hydraulic control device for two pumps and several actuators - Google Patents

Abstract

The invention relates to a hydraulic control device (20) which has a continuously adjustable first orifice (21), via which pressurized fluid, starting from a first and a second pump (11, 12), respectively, can be supplied to an associated first actuator (13) at least one continuously adjustable second diaphragm (22) is provided, via which pressurized fluid starting from the second pump (12) can be fed to an associated second actuator (14), wherein a pressure compensator (26) with a continuously adjustable third diaphragm (28) is provided , via which pressurized fluid from the first pump (11) can be fed to the tank (15), the pressure compensator (26) being acted upon by a first spring (27) in a closing direction of the third orifice (28), the bias of the first Spring (27) defines a first pressure difference. According to the invention, a first non-return valve (25) is connected between the first pump (11) and the at least one first orifice (21), which only permits fluid flow from the first pump (11) to the at least one first orifice (21) third orifice (28) is connected between the first pump (11) and the check valve (25), the second pump (12) being connected between the check valve (25) and the at least one first orifice (21).

Description

The invention relates to a hydraulic control device according to the preamble of claim 1 and a hydraulic drive system with such a control device.

From the DE 10 2012 208 938 A1 For example, a hydraulic drive system with a control device is known which can be used, for example, in a wheel loader. Several first actuators and a second actuator are provided. Further, a first and a second pump are provided, wherein the first pump has a constant displacement volume, wherein the second pump has an adjustable displacement volume. As long as the actuators take little pressure fluid, they are powered by the second pump, which is very energy efficient. The low-cost first pump promotes with little back pressure in the tank. Only if the first actuators need a lot of pressure fluid, the first pump promotes high pressure.

An advantage of the present invention is that the volume flow, which is discharged via the pressure compensator in the tank, is small. In particular, closed-center directional control valves can be used. Furthermore, the control device is particularly cost-effective. In addition, the fine controllability of the actuators is particularly good.

According to the independent claim, it is proposed that between the first pump and the at least one first orifice a first check valve is connected, which allows only a fluid flow from the first pump to the at least one first orifice, the third orifice between the first pump and the first Check valve is connected, wherein the second pump is fluidly connected between the check valve and the at least one first aperture.

Preferably, all of the first shutters are fluidly connected in parallel to a common branch point, wherein a single first check valve is fluidly connected between the branch point and the first pump.

By adjusting the continuously adjustable first or second aperture, the movement speed of the associated first and second actuator is adjustable. The first and second actuators can each be assigned a first or second directional valve, with which the direction of movement of the relevant actuator is adjustable. The continuously adjustable first and second orifice and the associated first and second directional control valves are preferably actuated jointly, wherein they are most preferably formed by a common valve spool. Preferably, a single second aperture is present.

Preferably, the hydraulic control device has a first and a second pump connection point, at least one tank connection point and for each first and second actuator a first and a second work connection point, which are most preferably part of a system of fluid lines. The first pump preferably has a constant displacement volume. For reasons of energy efficiency, the second pump preferably has a continuously variable displacement volume, wherein it may also have a constant displacement volume.

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

It can be provided that each first orifice is associated with a first load pressure, which is dependent on the pressure downstream of the respective first orifice, wherein a second load pressure from the pressure downstream of the second orifice is dependent, wherein a pump regulator is provided, with which the delivery pressure of second pump is adjustable by adjusting the displacement volume of the second pump to a value which is by a predetermined second pressure difference above the highest pressure from a group of pressures, which is formed by the at least one first load pressure and the second load pressure. Thus, the delivery pressure of the second pump is sufficient to supply all the first and second actuators with pressurized fluid. The first and the second load pressures are preferably connected on the input side to a shuttle valve cascade, wherein an output of the shuttle valve cascade is connected to the pump regulator. The first or second load pressure is preferably equal to the pressure downstream of the associated first and second orifice, as long as the associated fluid flow path is not blocked. When said fluid flow path is blocked, the respective load pressure is preferably equal to the pressure in the tank. As a result, energy is saved if at least one of the actuators is stationary.

It can be provided that the second pressure difference is greater than the first pressure difference. Thus, the delivery pressure of the second pump is greater than the delivery pressure of the first pump, as long as the maximum flow rate of the second pump is sufficient to supply all actuators with pressurized fluid. The first check valve is pressed in this operating condition from the delivery pressure of the second pump in the closed position, wherein the entire flow rate of the first pump via the pressure compensator with low back pressure flows into the tank. Thus, all actuators energy-saving supplied by the adjustable second pump me pressurized fluid.

It can be provided that the pressure compensator is acted upon in a closing direction of the third orifice by the highest pressure from a group of pressures, which is formed by the at least one first load pressure. In the mentioned group of pressures, therefore, the second load pressure of the second actuator is not included since the second actuator is supplied with pressurized fluid exclusively from the second pump. A particularly high second load pressure thus does not lead to energy losses at the first pump. The last-mentioned highest pressure is preferably tapped at the above-mentioned shuttle valve cascade, namely at the first control point.

It can be provided that the pressure compensator is acted upon in the opening direction of the third diaphragm by a pressure which rests between the check valve and the at least one first diaphragm. Preferably, said pressure is the pressure at the above-discussed branching point. The pressure compensator thus does not directly control the delivery pressure of the first pump, but rather the pressure downstream of the first check valve. However, this pressure is equal to the delivery pressure of the second pump, as long as their delivery capacity is sufficient to supply all actuators with pressurized fluid. As long as the first check valve is closed, the pressure compensator is pressed by this pressure in the fully open position, so that the first pump promotes very low backpressure on the pressure compensator in the tank.

There may be provided a priority valve with a continuously variable fourth orifice and a continuously variable fifth orifice, which are adjustable together, the fourth orifice being open in any position of the priority valve, the fifth orifice being open only when the pressure downstream of the fourth diaphragm exceeds a predetermined value, wherein the second pump is fluidly connected via the fourth diaphragm with the second diaphragm, wherein the second pump is fluidly connected via the fifth diaphragm with the at least one second diaphragm. Preferably, the second pump is connected via the fifth orifice to the branching point. If the flow rate of the second pump is no longer sufficient to supply pressurized fluid to all the actuators, the fifth orifice closes, so that only the second actuator is supplied with pressurized fluid by the second pump. This ensures that the second actuator is sufficiently supplied in each operating condition with pressurized fluid, regardless of how the first actuators are driven.

It can be provided that the priority valve is acted upon in a closing direction of the fifth diaphragm by a second spring and by the second load pressure, wherein it is acted upon in an opening direction of the fifth diaphragm from the pressure downstream of the fourth diaphragm. As a result, the priority valve can be acted upon in a simple manner with the pressure downstream of the first diaphragm. The second load pressure is preferably connected to the tank when the second actuator is not moved, being otherwise connected to the pressure downstream of the second orifice. As a result, the delivery flow of the second pump can also be used to supply the first actuators when the first actuator is stationary, with a large external force acting on it.

Protection is also sought for a hydraulic drive system having a first and a second pump and at least a first actuator and a second actuator, which are fluidly connected to each other via a hydraulic control device according to the invention, wherein the first pump has a constant displacement volume, wherein the second pump having continuously adjustable displacement.

It can be provided that the first and the second pump are in rotary drive connection with a common motor. The engine is preferably an internal combustion engine, most preferably a diesel engine.

Protection is also desired for a mobile machine with a hydraulic drive system according to the invention, wherein the second actuator and the second panel are part of a steering of the mobile machine, wherein the at least one first panel with the associated first actuator part of a working hydraulics of the mobile machine. The mobile work machine may be, for example, an excavator, a wheel loader, an agricultural tractor or a municipal vehicle.

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 hydraulic drive system with a control device according to the invention.

1 shows a hydraulic drive system 10 with a control device according to the invention 20 , The control device 20 has a first pump connection point 70 to which a first pump 11 connected to a constant displacement volume. The first pump 11 sucks pressurized fluid out of a tank 15 and conveys it via the first pump connection point 70 parallel to several first apertures 21 , The pressurized fluid is preferably a liquid, most preferably hydraulic oil. In the 1 illustrated tank symbols all refer to the same tank 15 ,

The distribution of the pressure fluid on the various first panels 22 happens at the branching point 75 the corresponding system of fluid lines. Between the first pump connection point 70 and the branching point 75 is a first check valve 25 installed, which only a fluid flow from the first pump 11 to the first screens 21 hints.

Next is a pressure compensator 26 with a continuously adjustable third aperture 28 intended. The third aperture 28 is between the first pump connection point 70 and the first check valve 25 fluidly connected, allowing pressurized fluid from the first pump 11 over the third aperture 28 in the tank 15 can be directed. The pressure balance 26 is this with a tank connection point 72 the control device 20 connected to which the tank 15 is fluidically connected. In the closing direction of the third panel 28 is the pressure balance 26 with a first spring 27 and the pressure at a first control station 76 applied. The bias of the first spring 27 defines a first pressure difference, which is for example 5 bar. In the opening direction is the pressure balance 26 with the pressure at the branching point 75 applied. Accordingly, the pressure balance regulates 26 the pressure at the branching point 75 to a value which is about the first pressure difference above the pressure at the first control point 76 lies. The pressure at the first control point 76 is the highest load pressure on the first actuators 13 as far as they are moved.

At the first actuators 13 These are, for example, hydraulic cylinders or hydraulic motors, which are preferably installed in the working hydraulics of a mobile working machine, for example an excavator, a wheel loader, an agricultural tractor or a municipal vehicle. The first actuators 13 each have a first and a second employment connection point 73 ; 74 to the control device 20 fluidly connected. Every first actuator 13 is a continuously adjustable first aperture 21 and a first directional valve 23 assigned. With the first aperture 21 becomes the moving speed of the associated first actuator 13 adjusted, with the first directional control valve 23 whose direction of movement is set.

In a first working position of the first directional valve 23 becomes pressurized fluid from the branching point 75 over the first aperture 21 to the assigned first work connection 72 directed, wherein pressurized fluid from the respective second working port 74 in the tank 15 is directed. The first employment interface 73 is there with a check-in register 45 at the first way valve 23 fluidly connected. In a second working position of the first directional valve 23 becomes pressurized fluid from the branching point 75 over the first aperture 21 to the assigned second working connection 74 passed, wherein pressurized fluid from the respective first working port 73 in the tank 15 is directed. The second employment interface 74 is with the check-in register 45 at the first way valve 23 fluidly connected. In the middle blocking position is the load reporting point 45 with the tank 15 connected, with all other fluid flow paths are blocked. This is due to the check-in point 45 the pressure downstream of the first orifice 21 when the relevant first actuator 13 moved, as far as this is stationary, is located at the check-in point 45 the pressure in the tank 15 which is essentially zero. The first way valves 23 are preferably pressed by means of at least one spring in the direction of the blocking position. The first aperture 21 and the first directional valve 23 are preferably adjustable together, they are most preferably formed by a common valve spool. The same applies to the second aperture 22 and the second directional valve 24 ,

Every first aperture 21 is preferably a second check valve 29 associated with which only a fluid flow from the branching point 75 to the first aperture 21 hints.

The load registration points 45 the first way valves 23 are each input side to an associated first shuttle valve 41 connected, which is part of a shuttle valve cascade 40 is. The already mentioned first control unit 76 forms the output of the shuttle valve cascade 40 , which all first shuttle valves 41 includes. So there is the highest load pressure of all first actuators 13 as far as they move. The free entrance of the first shuttle valve 41 , which comes first in the shuttle valve cascade 40 is preferably to the tank 15 connected. He can also go to a check-in point 45 be connected, so this first shuttle valve 41 two load reporting points 45 assigned.

The second directional valve 24 , which is the second actuator 14 is assigned, is identical to the first directional control valve 23 constructed so that reference is made in this regard to the above statements becomes. The same applies to the first and the second aperture 21 ; 22 , At the second actuator 14 it is preferably a hydraulic cylinder, which is most preferably part of a steering of the already mentioned mobile machine. The second actuator 14 is in turn by means of a first and a second employment interface 73 ; 74 to the control device 20 connected.

The second directional valve 24 is a second shuttle valve 42 assigned to the input side, the first control unit 76 and the check-in point 45 of the second directional valve 24 are connected. Accordingly, all first and second shuttle valves 41 ; 42 to a shuttle valve cascade 40 connected together. The output of the second shuttle valve 42 forms a second control unit 77 , at which the highest load pressure of all first and second actuators 13 ; 14 as far as they move.

The second pump 12 has an adjustable displacement volume, passing to a second pump port 71 the control device 20 is fluidically connected. The second pump 12 may also have a constant displacement volume, wherein the pump regulator 60 is then designed as a pressure balance, which excess volume flow into the tank 15 passes. The second pump 12 will be together with the first pump 11 from a common engine 16 , preferably an internal combustion engine, most preferably a diesel engine driven. It sucks pressurized fluid out of the tank 15 and conveys it under pressure to a priority valve 50 , The priority valve 50 causes primarily the second actuator 14 from the second pump 12 supplied with pressurized fluid. Only if the second pump 12 promotes more pressurized fluid than at the second actuator 14 is taken off, pressurized fluid flows through the branching point 75 to the first actuators 13 ,

The priority valve 50 has a fourth and a separate fifth aperture 51 ; 52 , which are constantly adjustable together. The fourth aperture 51 is over the entire displacement of the priority valve 50 at least partially open. The fifth aperture 52 on the other hand has a completely closed end position. Pressurized fluid can, starting from the second pump 12 over the fourth aperture 51 , continue over the continuously adjustable second aperture 22 , continue via the second directional control valve 24 to the second actuator 14 flow. In addition, pressurized fluid from the second pump 12 over the fifth aperture 52 to the branching point 75 flow. In the closing direction of the fifth panel 52 is the priority valve 50 with the pressure at the check-in point 45 of the second directional valve 24 and a second spring 53 applied. In the opening direction of the fifth panel 52 is the priority valve 50 with the pressure upstream of the second orifice 22 applied. The priority valve thus regulates the pressure drop across the second orifice 22 on the pressure equivalent of the second spring 53 one. When the flow rate of the second pump 12 is insufficient to maintain this pressure difference, closes the fifth aperture 52 completely, leaving only the second actuator 14 supplied with pressurized fluid.

The second pump 12 is a pump regulator 60 assigned, which the delivery pressure 62 the second pump 12 adjusted by adjusting the displacement of the second pump to a value which by a predetermined second pressure difference above the pressure at the second control point 77 lies. The second pressure difference is for example 15 bar, wherein it is greater than the first pressure difference, which by the first spring 27 on the pressure balance 26 is defined. This is the delivery pressure of the second pump 12 higher than the delivery pressure of the first pump 11 as long as the maximum flow of the second pump 12 sufficient for all actuators 13 ; 14 to supply with pressurized fluid.

The delivery pressure 62 the second pump 12 pushes the first check valve 25 thus in the closed position, the entire flow of the first pump 12 over the third aperture 28 the pressure balance 26 in the tank 15 flows. The pressure balance 26 is thereby the pressure at the branching point 75 adjusted to the fully open position, so that at the third panel 28 Only a small pressure drop takes place, resulting in only a small loss of energy. This operating condition exists when one or more first actuators 13 be moved slowly, so if they are operated in the fine control range.

Is from the actuators 13 ; 14 more pressure fluid removed than the second pump 12 can promote, so closes the fifth aperture 52 at the priority valve 50 , This regulates the pressure balance 26 the delivery pressure of the first pump 11 or the pressure at the branching point 75 to a value which is about a first pressure difference above the pressure at the first control point 76 is, ie the maximum load pressure of all first actuators 13 , lies. The first pressure difference is the pressure equivalent of the first spring 27 defined, which is for example 5 bar. The second pump 12 promotes in this operating state exclusively to the second actuator 14 ,

Attention is still on the pressure relief valve 61 which is at the branching point 75 connected. If the pressure there exceeds a predetermined limit value, then pressure fluid flows from the branching point 75 in the tank 15 , so the pressure at the branching point 75 again sinks.

It should be noted that the first and / or the second directional control valve 23 ; 24 can also be designed as open-center valves. Instead of the blocking position then a circulation position is present, which forms a circulation channel in which only a small volume flow flows, the adjustment of the second pump 12 is being used.

LIST OF REFERENCE NUMBERS

10

hydraulic drive system

11

first pump

12

second pump

13

first actuator

14

second actuator

15

tank

16

engine

20

hydraulic control device

21

first aperture

22

second aperture

23

first way valve

24

second way valve

25

first check valve

26

pressure compensator

27

first spring

28

third aperture (the pressure balance)

29

second check valve

40

Cascade of shuttle valves

41

first shuttle valve

42

second shuttle valve

43

first load pressure

44

second load pressure

45

Last registration office

50

priority valve

51

fourth aperture

52

fifth aperture

53

second spring

60

pump regulator

61

Pressure relief valve

62

Delivery pressure of the second pump

70

first pump connection point

71

second pump connection point

72

Tank Junction

73

first employment connection

74

second employment interface

75

branching point

76

first control point

77

second control station

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)

Hydraulic control device ( 20 ) for use with a first and a second pump ( 11 ; 12 ), at least one first actuator ( 13 ) and a second actuator ( 14 ), wherein the control device ( 20 ) a continuously adjustable first aperture ( 21 ), via which pressurized fluid from the first and the second pump ( 11 ; 12 ) each associated with a first actuator ( 13 ), wherein at least one continuously adjustable second diaphragm ( 22 ) is provided over which pressurized fluid from the second pump ( 12 ) an associated second actuator ( 14 ), whereby a pressure compensator ( 26 ) with a continuously adjustable third diaphragm ( 28 ) is provided via which pressurized fluid from the first pump ( 11 ) a tank ( 15 ), whereby the pressure compensator ( 26 ) from a first spring ( 27 ) in a closing direction of the third diaphragm ( 28 ) is applied, wherein the bias of the first spring ( 27 ) defines a first pressure difference, characterized in that between the first pump ( 11 ) and the at least one first aperture ( 21 ) a first check valve ( 25 ), which exclusively supplies a fluid flow from the first pump ( 11 ) to the at least one first aperture ( 21 ), whereby the third diaphragm ( 28 ) between the first pump ( 11 ) and the check valve ( 25 ), the second pump ( 12 ) between the check valve ( 25 ) and the at least one first aperture ( 21 ) is fluidly connected. A hydraulic control device according to claim 1, wherein each first diaphragm ( 21 ) a first load pressure ( 43 ) associated with the pressure downstream of the respective first diaphragm ( 21 ), wherein a second load pressure ( 44 ) from the pressure downstream of the second orifice ( 22 ), whereby a pump regulator ( 60 ) is provided, with which the delivery pressure ( 62 ) of the second pump ( 12 ) by adjusting the displacement volume of the second pump ( 12 ) is adjustable to a value which is above a predetermined second pressure difference above the highest pressure from a group of pressures which is dependent on the at least one first load pressure ( 43 ) and the second load pressure ( 44 ) is formed.  Hydraulic control apparatus according to claim 2, wherein the second pressure difference is greater than the first pressure difference. Hydraulic control device according to claim 2 or 3, wherein the pressure compensator ( 26 ) in a closing direction of the third diaphragm ( 28 ) of the highest pressure from a group of pressures which is dependent on the at least one first load pressure ( 43 ) is applied, is applied. Hydraulic control device according to one of the preceding claims, wherein the pressure compensator ( 26 ) in the opening direction of the third panel ( 28 ) is acted upon by a pressure which between the check valve ( 25 ) and the at least one first aperture ( 21 ) is present. Hydraulic control device according to one of the preceding claims, wherein a priority valve with a continuously variable fourth diaphragm ( 51 ) and a continuously adjustable fifth diaphragm ( 52 ), which are adjustable together, wherein the fourth aperture ( 51 ) in each position of the priority valve ( 50 ), the fifth diaphragm ( 52 ) is open only when the pressure downstream of the fourth orifice ( 51 ) exceeds a predetermined value, the second pump ( 12 ) over the fourth aperture ( 51 ) with the second diaphragm ( 22 ) is fluidically connected, wherein the second pump ( 12 ) over the fifth aperture ( 52 ) with the at least one second aperture ( 22 ) is fluidly connected. Hydraulic control device according to claim 6, when dependent on claim 2, wherein the priority valve ( 50 ) in a closing direction of the fifth diaphragm ( 52 ) of a second spring ( 53 ) and the second load pressure ( 44 ) is applied, wherein it in an opening direction of the fifth diaphragm ( 52 ) from the pressure downstream of the fourth orifice ( 51 ) is acted upon. Hydraulic drive system with a first and a second pump ( 11 ; 12 ) and at least one first actuator ( 13 ) and a second actuator ( 14 ), which via a hydraulic control device ( 20 ) are fluidly connected to each other according to one of the preceding claims, wherein the first pump ( 11 ) has a constant displacement volume, the second pump ( 12 ) has a continuously adjustable displacement volume. A hydraulic drive system according to claim 8, wherein the first and second pumps ( 11 ; 12 ) in rotary drive connection with a common motor ( 16 ) stand. Mobile work machine with a hydraulic drive system according to claim 8 or 9, wherein the second actuator ( 14 ) and the second aperture ( 22 ) Are part of a steering of the mobile work machine, wherein the at least one first aperture ( 21 ) with the associated first actuator ( 13 ) Are part of a working hydraulics of the mobile work machine.

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