EP1687542B1 - Hydraulic control system for mobile equipment - Google Patents

Abstract

What is disclosed is a hydraulic control arrangement for a mobile equipment, such as for a backhoe loader or a wheel loader, wherein a working tool of the equipment is adapted to be actuated by means of a hydraulic cylinder whose pressure chambers may jointly be connected with a hydraulic accumulator 14 for attenuating pitching oscillations of the working tool.

Description

The invention relates to a hydraulic control arrangement for a mobile working device according to the preamble of claim 1.

Such hydraulic control arrangements for a mobile implement, such as a wheel loader, a backhoe loader, are used for damping pitching vibrations. The DE 44 16 228 A1 shows a hydraulic control arrangement in which the lifting cylinder of a loading shovel of a wheel loader via a directional control valve and a damping valve with pressure medium can be supplied. About the directional valve, the two pressure chambers of each lift cylinder to raise or lower the bucket are connected to a pump or a tank. In a spring-biased center position of this directional control valve, the connections to the pressure chambers are shut off. By means of the damping valve can be in the neutral position of the directional valve, the pressure chambers of the lift cylinder either with a tank (floating position) or in the support direction of a load effective pressure chambers (cylinder chambers) with a hydraulic accumulator and the other pressure chambers (annuli) connect to a tank, so that vibrations the loading shovel can be steamed. These pitching vibrations occur especially when the loading bucket is full and the driving speed is higher.

The damping valve can be switched to the "pitching vibration damping" switch position by the driver or automatically as soon as pitching vibrations occur or as soon as the vehicle speed exceeds a predetermined limit. The switching position "swimming" of the damping valve is controlled by the driver, for example, when the loading shovel is to be drawn over this for leveling the soil.

A disadvantage of this solution is that the damping valve must be made relatively expensive, as this to realize the two functions "swimming" and "pitch damping" via two connected to the lift cylinders working lines and at least four connections (connections for the above working lines, tank connection, connection for hydraulic accumulator) must have.

In contrast, the invention has for its object to provide a hydraulic control arrangement for a mobile work unit, in which the functions "swimming" and "pitch vibration damping" are made possible with little effort.

This object is achieved by a hydraulic Steueranordung for a mobile implement according to the preamble of claim 1.

According to the invention, the hydraulic control arrangement has a directional control valve, via which the pressure medium flow between the pressure chambers of the hydraulic cylinder and a pump or a tank can be controlled. The directional control valve is associated with a damping valve arrangement, via which both pressure chambers of the hydraulic cylinder can be connected to a hydraulic accumulator in order to switch over to the function "pitching oscillation damping".

That In contrast to the prior art, not a pressure chamber with the hydraulic accumulator and the other pressure chamber connected to the tank, but both pressure chambers acted upon together with the pressure in the hydraulic accumulator, so that the load acting on the hydraulic cylinder in principle only from the rod surface, i. the differential area between the piston bottom side pressure chamber and the piston rod side pressure chamber is supported. In the direction of damping, a comparatively high pressure thus acts, so that in practice a large load is simulated and accordingly the pitching vibration damping is more effective than in the prior art mentioned at the outset.

Another significant advantage is that the damping valve assembly must be designed with only one working port, since both in the function "pitching vibration damping" as well as in the function "swimming" both pressure chambers of the hydraulic cylinder with the same pressure, i. the pressure in the hydraulic accumulator or the tank pressure are applied.

The damping valve assembly can also be designed with a small nominal diameter, since it is only flowed through by a low pressure medium flow, which corresponds to the volume displaced by the piston rod.

The hydraulic control arrangement can be further simplified if the directional control valve in its neutral position connects the supply and discharge lines leading to the two pressure chambers of the hydraulic cylinder, so that the working connection of the damping valve arrangement only has to be connected to the supply or discharge line via a single damping line , so that the Verrohrungsaufwand compared to the conventional solution is further reduced.

In a particularly preferred embodiment of the invention, the damping valve is designed as a 3/3-way valve, wherein the two input terminals are connected to the hydraulic accumulator or the tank and the working port with leading to the drain or flow line damping line. In the neutral position of the damping valve these connections are shut off against each other, while in the two switching positions either the hydraulic accumulator or the tank are connected to the damping line. Instead of the 3/3-way valve and two 2/2-way valves can be used, with one of the function "swimming" and the other of the function "pitching vibration damping" is assigned.

The control of the damping valve arrangement is preferably carried out electrically, wherein the control signals can be issued by the driver, for example by actuation of switches of a pilot control device. The actuation of the directional control valve is preferably carried out hydraulically via the aforementioned pilot control device.

The hydraulic accumulator can be designed as a piston accumulator.

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

A preferred embodiment of the invention will be explained below with reference to a schematic representation showing a diagram of the hydraulic control arrangement.

The hydraulic control device 1 according to the invention is applied, for example, to two lift cylinders a pressure bucket of a wheel loader or backhoe loader with pressure medium to supply. In the circuit diagram, by way of example, only one lift cylinder 2 is shown, whose pressure chambers can be connected via a directional control valve 4 to a pump 6 or a tank T. The control of the directional control valve 4 via a hydraulic pilot unit 8 by operating a joystick 10 by the driver of the mobile implement. To dampen pitching oscillations or to set a floating position, the pressure chambers of the lifting cylinders 2 can be connected via a damping valve 12 to a hydraulic accumulator 14 or the tank T. The damping valve 12 is electrically actuated and can be actuated via switches which are arranged on the joystick 10.

The loader supporting the lifting cylinder 2 are designed as differential cylinders, wherein in the figure, the weight of the bucket and the load recorded therein are marked with M. The piston bottom side cylinder chamber 16 of the lift cylinder 2 is connected via a feed line 20 with a working port A and an annular space 18 via a drain line 22 to a working port B of the directional control valve 4. This is carried out, for example, as a proportionally adjustable directional control valve, wherein in the "LIFT" designated positions of a spool, not shown, connected to the pump 6 pump port P is connected to the working port A, while the working port B with a tank connected to the tank T terminal S is connected so that the pump 6 promotes pressure medium in the cylinder chamber 16 and 18 pressure medium is displaced from the annular space in the tank T - the load M is raised, the speed of the path of the spool and / or the flow rate of the pump. 6 depends.

In the "LOW" designated positions of the spool, the load M is lowered by the cylinder chamber 16 is connected to the tank T and the annulus 18 to the pump 6.

As already mentioned, the control of the directional control valve 4 is hydraulically via control lines 24, 26, via the control surfaces of the spool with a control pressure difference can be applied to move the spool in the desired position. These control pressures are generated by the hydraulic pilot control device 8, via which a system control pressure can be reduced to the desired control pressure by means of pressure reducing valves which can be actuated as a function of the position of the joystick 10 and can be tapped off at the control connections 1, 2 of the pilot control device 8. The function of such hydraulic pilot control devices is known, so that further embodiments are dispensable.

The spool of the directional control valve 4 is biased by springs 28, 30 in a middle position in which the two working ports A, B connected to each other and the two input terminals P and S are shut off. That in this middle position, the two pressure chambers 16, 18 of the lift cylinder 2 are interconnected.

The damping valve 12 is designed in the illustrated embodiment as a 3/3-way valve, wherein an output or working port A is connected via a damping line 32 to the drain line 22. A tank connection T of the damping valve 12 is connected to the tank T and a pressure connection P to a hydraulic accumulator 14. The valve spool of the damping valve 12 is about centering springs 33, 34 in biased a neutral position in which the three terminals A, T, P are shut off against each other.

In the illustrated embodiment, the damping valve 12 is electrically actuated, wherein the actuation of the valve slide via electromagnets 36, 38, which are connected via signal lines 40, 42 with switches on the joystick 10. The damping valve 12 is designed as a switching valve, wherein in its marked with (a) switching position of the working port A is connected to the tank port T, so that both the annular space 18 and the pressure chamber 16 are connected to the tank T with unconfirmed directional control valve 4 - with (a) marked switching position thus stands for the function "swimming" in which the loading bucket practically rests only by its own weight and the loaded load on the ground and follows during leveling unevenness of the soil.

In the switching position marked with (b), the working port A is connected to the pressure port P, so that in both pressure chambers 16, 18, the pressure in the hydraulic accumulator 14 is applied. In this switching position, the load M is supported by the piston rod surface corresponding pressure force equivalent, it acts in the cylinder chamber 16, a comparatively high pressure, so that a higher load is "simulated" than is the case with the conventional solutions, in which the annulus to the tank T is relieved. This higher pressure allows a more effective pitch vibration damping.

In this position, pressure medium between the cylinder chamber 16 and the annular space 18 can be pushed back and forth, wherein on the damping valve 12 only that amount of pressure medium flows, which corresponds to the changing piston rod volume. Because of this comparatively low pressure medium volume flow, the damping valve 12 can be performed with a smaller nominal diameter than in conventional solutions. The damping valve 12 can be - as stated above - switch by pressing a switch in its "pitch vibration damping" function, in principle it is also possible to automatically switch to this function when a certain driving speed is reached or the vibration amplitude exceeds a predetermined maximum value.

To raise or lower the bucket, the damping valve 12 is switched back to its neutral position by the electromagnets 36, 38 are de-energized and the directional control valve 4 is set by means of the Vorssteuergeräts 8 in one of its positions "LIFT" or "LOW" to the lift cylinder 2 extend or retract.

Instead of the 3/3-way valve used in the embodiment, the damping valve 12 can also be performed by two 2/2-way valves, one of the function "swimming" and the other of the function "pitching vibration damping" is assigned. The hydraulic accumulator 14 is preferably designed as a piston accumulator, since this is particularly well suited for high pressures.

Of course, the damping line 32 can also be connected to the flow line 20. In principle, the connection of the two pressure chambers 16, 18 can also be integrated into the damping valve 12.

Disclosed is a hydraulic control assembly for a mobile implement, such as a backhoe loader or a wheel loader, wherein a Working tool of the implement by means of a hydraulic cylinder is actuated, the pressure chambers for damping of pitch oscillations of the working tool together with a hydraulic accumulator 14 are connected.

LIST OF REFERENCE NUMBERS

1

control arrangement

2

lift cylinder

4

way valve

6

pump

8th

pilot control unit

10

joystick

12

damping valve

14

hydraulic accumulator

16

cylinder space

18

annulus

20

supply line

22

drain line

24

control line

26

control line

28

feather

30

feather

32

attenuation line

33

centering

34

centering

36

electromagnet

38

electromagnet

40

signal line

42

signal line

Claims (7)

1. Hydraulic control arrangement for a mobile equipment, comprising a directional control valve (4) whereby pressure chambers (16, 18) of a hydraulic cylinder (2) may be connected via a drain line and a delivery line (22, 20) with a tank (T) or with a hydraulic pump (6), respectively, and comprising an attenuation valve arrangement (12) whereby the pressure chambers (16, 18) may be connected with the tank (T) or with a hydraulic accumulator (14) for attenuation of oscillations and for adjusting a floating position, characterized in that the pressure chambers (16, 18) of the hydraulic cylinder (2) are both connected with the hydraulic accumulator (14) in the attenuation position.
2. The control arrangement according to claim 1, wherein the delivery and drain lines (22, 20) are connected with each other in a center position of the directional control valve (4), and a work port (A) of the attenuation valve arrangement (12) is connected via an attenuation line (32) with the delivery or drain line (22, 20).
3. The control arrangement according to claim 2, wherein the attenuation valve arrangement (12) is a 3/3-way directional control valve having a neutral position in which the work port (A) is blocked relative to the hydraulic accumulator (14) and the tank (T), and having two switching positions (a, b) in which the work port (A) is connected with the tank (T) or with the hydraulic accumulator (14).
4. The control arrangement according to claim 1 or 2, wherein the attenuation valve arrangement (12) comprises two 2/2-way directional control valves whereby in an opened position a connection with the tank (T) or with the hydraulic accumulator (14), respectively, may be controlled open.
5. The control arrangement according to claim 3 or 4, wherein the attenuation valve arrangement (12) is adapted to be actuated electrically through the intermediary of a pilot control device (8).
6. The control arrangement according to any one of the preceding claims, wherein the directional control valve (4) is adapted to be actuated hydraulically through the intermediary of a pilot control device (8).
7. The control arrangement according to any one of the preceding claims, wherein the hydraulic accumulator (14) is a piston-type accumulator.

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