EP2600011A2 - Hydraulic directional valve for the lifting gear of an agricultural vehicle - Google Patents

Abstract

The hydraulic directional valve (10) has a pump port (P), tank port (T) and one and another working ports (A,B), where the working ports are connected with a hydraulic cylinder (30) of a lifting unit of a mobile work machine, particularly an agricultural vehicle. The pump port is connectable with a hydraulic pump (40), where the pump port, the tank port and the working ports are blocked in one switching position (11). The pump port and former working port are blocked and the tank port is connected with latter working port in fifth switching position (15).

Description

The invention relates to a hydraulic directional control valve according to the preamble of claim 1.

In the US Pat. No. 6,971,453 B2 is related to the local Fig. 1 and 2 described the hydraulic hoist of an agricultural vehicle. The hoist comprises two hydraulic cylinders 12; 14 for lifting and lowering the hoist. These are connected to the first and the second working port of a hydraulic directional control valve 24. The directional control valve also has a pump port connected to a hydraulic pump which can deliver hydraulic fluid from a reservoir tank 18 to the hydraulic cylinders. Next, the directional control valve has a tank connection, which is connected to the storage tank.

The hydraulic directional valve is designed as a proportional valve and has four switching positions. In the first switching position, the pump connection, the tank connection and the first and the second working connection are blocked, so that the position of the hoist can not be changed.

In the second switching position of the pump port to the first working port and the tank port to the second working port are connected, so that the hoist is lowered, whereby the attached implement can be pressed against the ground.

In the third switching position, the pump connection to the second working connection and the tank connection to the first working connection are connected so that the lifting mechanism can be raised.

Further, a fourth switching position is provided, which is designed as a free position, i. the first and second working ports are connected to the tank port with the pump port blocked. In this switching position, the hoist can be freely raised and lowered by externally applied forces. This switching position is used when a working device is mounted on the hoist, which is supported while driving the agricultural vehicle on the ground, it should follow this. The implement may be, for example, a mower.

Next is at the US Pat. No. 6,971,453 B2 a separate switching valve 42 is provided, with which a further switching state is realized, in which the first working port is connected to the storage tank. This switching valve is blocked in the already explained switching positions of the directional control valve. In said further switching state, it is open, wherein the directional control valve is in the second switching position. The hydraulic pump thus promotes no load in the tank, so that no pressure builds up on the hydraulic cylinder. In this switching state, the hoist can only be lowered by the weight of the connected implement. This switching state is used, for example, to lower the hoist before it is brought into the already mentioned open position.

The object of the invention is to provide a hydraulic directional control valve in which the separate switching valve can be dispensed with in order to realize said further switching state.

According to the independent claim, this object is achieved in that a fifth switching position is provided, in which the tank connection is connected to the second working port, wherein the pump port and the first working port are locked. As a replacement for the separate switching valve, the directional valve is equipped with a further, fifth switching position. In this fifth switching position, the pump connection is blocked. In contrast to the solution explained above, the pump delivery flow does not reach the storage tank via the directional control valve derived. The first work connection is also blocked. Through this embodiment of the directional control valve can be dispensed with an additional switching valve.

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

• dritte Schaltstellung;
• erste Schaltstellung;
• fünfte Schaltstellung;
• zweite Schaltstellung; und
• vierte Schaltstellung

durchlaufen werden. Mit dieser Ausführungsform kann das hydraulische Wegeventil besonders einfach realisiert werden. Im Unterschied zum bekannten Wegeventil muss nur die Lage einer einzigen Feinsteuerkerbe verändert werden, um die erfindungsgemäße fünfte Schaltstellung zu realisieren. Dies wird mit Bezug auf Fig. 3 noch näher erläutert.The hydraulic directional control valve may comprise a linearly movable valve spool, during its movement, the switching positions in the order

• third switch position;
• first switching position;
• fifth switch position;
• second switching position; and
• fourth shift position

to go through. With this embodiment, the hydraulic directional control valve can be realized particularly easily. In contrast to the known directional valve only the position of a single Feinsteuerkerbe must be changed to realize the fifth switching position according to the invention. This will be with reference to Fig. 3 explained in more detail.

An LS port may be provided on the hydraulic directional control valve connectable to the pressure regulator of the hydraulic pump, the LS port being connected to the pump port in the second and third shift positions, being in the first, fourth and fifth Switching position is connected to the tank connection. Hydraulic hoist controls that operate on the load-sensing principle are known from the prior art. In this case, the load pressure acting on the hydraulic cylinder is fed back to the pressure regulator of the pump in order to regulate the pump pressure. As a result, an energy-saving operation of the hydraulic pump is made possible. With the proposed solution, the application of the load-sensing principle is also possible in fifth Schaltzugstand invention.

The directional control valve can be designed as a proportional valve in which all fluid connections open and close continuously. This allows the hoist to be moved sensitively, i. as desired by the operator, slow and fast movement speeds can be adjusted with fine gradation.

The valve spool can pass through a first transition region between the second and the fourth switching position, in which the pump port is connected to the first working port, the fluid connection being blocked from the first working port to the tank port. The transition between the second and the fourth switching position requires several changes in the connection of the connections of the directional control valve. Due to the introduction of the proposed transition region, which is always only briefly traversed during operation and essentially not used for the motion control, these interconnection changes can be realized particularly easily.

The valve spool can pass through a second transition region between the first transition region and the fourth switching position, in which the fluid connection from the tank connection to the first working port opens continuously. By this measure, a simple realization of the directional control valve is also possible.

Fig. 1

eine Schaltungsanordnung mit einem erfindungsgemäßen hydraulischen Wegeventil gemäß einer ersten Ausführungsform der Erfindung;

Fig. 2

eine Schaltungsanordnung mit einem erfindungsgemäßen hydraulischen Wegeventil gemäß einer zweiten Ausführungsform der Erfindung; und

Fig. 3

ein Diagramm, in dem die Öffnungsquerschnittsfläche der verschiedenen Verbindungspfade des Wegeventils über dem Bewegungsweg des Ventilschiebers aufgetragen ist.

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

Fig. 1

a circuit arrangement with a hydraulic directional control valve according to the invention according to a first embodiment of the invention;

Fig. 2

a circuit arrangement with a hydraulic directional control valve according to the invention according to a second embodiment of the invention; and

Fig. 3

a diagram in which the opening cross-sectional area of the various connection paths of the directional control valve is plotted over the path of movement of the valve spool.

Fig. 1 shows a circuit arrangement with a hydraulic directional control valve 10 according to the invention according to a first embodiment of the invention. The hydraulic cylinder 30 is part of a (not shown) hoist of an agricultural vehicle. By pressurizing the piston bottom side cylinder chamber 31 ago the hoist is lowered. The piston bottom side cylinder chamber 31 is connected to the first working port A of the directional control valve 10. By pressurization from the opposite annular surface side cylinder chamber 32 ago the hoist is raised. The annular surface side cylinder chamber 32 is connected to the second working port B of the directional control valve 10.

The hydraulic cylinder 30 is driven by a hydraulic pump 40 which sucks hydraulic fluid from a storage tank 43 and delivers it under pressure to the hydraulic cylinder 30. The hydraulic pump 40 is connected to the pump port P of the directional control valve 10. The corresponding pump line 41 is connected to a pressure limiting valve 42 which limits the pump pressure upwards, in particular when the pump connection P of the directional control valve 10 is blocked. The corresponding flow is discharged into the storage tank 43. The tank connection T of the directional control valve 10 is likewise connected to the storage tank 43.

The directional control valve 10 is held in the first switching position 11 via the two return springs 20 acting in the opposite direction. In the first switching position 11, the pump connection P, the tank connection T and the first and the second working connection A are; B locked. The hoist is thus immovably held in its current position, wherein the hydraulic pump 40 promotes via the pressure relief valve 42 in the storage tank 43. To save energy, a hydraulic pump with adjustable displacement volume can be provided. In order to set the third switching state 13, the valve spool is moved to the right with the first electromagnetic actuator 21, so that the pump port P is connected to the second working port B and the first working port A is connected to the tank port T. As a result, the hoist is raised.

With the second electromagnetic actuator 22, the valve spool is moved to the left, wherein he successively in the fifth 15, the second 12 and the fourth switching position 14 passes.

In the fifth switching position 15 according to the invention, the pump port P and the first working port A are blocked, the second working port B being connected to the tank port T. The hydraulic fluid in the annular surface-side cylinder chamber 32 is pressurized by the weight of the working device attached to the lifting device, wherein it can flow into the storage tank 43 in a controlled manner via the opening cross-sectional area set in the directional control valve 10. The hoist is thus lowered solely by its own weight.

If the valve slide is now moved further into the second switching position 12, then the pump port P is connected to the first working port A, so that the lifting gear can be pressed down with the implement in addition to its own weight with hydraulic force.

In the fourth switching position 14, the first and the second working port A; B connected to the tank port T, wherein the pump port P is locked. In this switching position, the hoist can move freely due to the forces acting from the outside.

Fig. 2 shows a circuit arrangement with a hydraulic directional control valve 10 according to the invention according to a second embodiment of the invention. In contrast to the first embodiment, in the second embodiment, an LS port LS is provided on the directional control valve 10, which with a pressure regulator 44, a hydraulic adjustment device 45 and a hydraulic pump 40 is connected to an adjustable displacement volume. In the second and the third switching position 12; 13, in which the hydraulic cylinder 30 is to be moved by the fluid flow of the hydraulic pump 40, the pump port P of the directional control valve is connected to the LS port LS. The displacement volume of the hydraulic pump 40 is thus adjusted according to the volume flow required at the hydraulic cylinder 30, so that no excess fluid flow has to be discharged into the storage tank 43.

In the remaining shift positions one 11, four 14 and five 15, in which the hydraulic pump 40 does not drive the hoist, the LS port LS is connected to the tank port T, so that the displacement volume of the hydraulic pump 40 is adjusted substantially to zero. The hydraulic pump 40 thus promotes substantially no hydraulic fluid and accordingly requires very little drive power.

Incidentally, the second embodiment of the invention corresponds to the first embodiment, so that in this regard to the comments on Fig. 1 can be referenced.

Fig. 3 shows a diagram in which the opening cross-sectional area Q of the various connection paths of the directional control valve is plotted over the movement path s of the valve spool. Not shown are the fluid connections to the LS connection according to the second embodiment of the invention, since only very small volume flows flow, so that the design of the corresponding switching transitions is less critical.

In the horizontal of the movement path s of the valve spool is plotted. In the vertical, the opening cross-sectional area Q of the corresponding fluid connection is plotted. The origin of the coordinates corresponds to the position of the valve spool which is controlled by the two return springs (No. 20; Fig. 1; 2 ) is set.

The first shift position 11 is arranged in the region of the coordinate origin. In the first switching position 11 all fluid connections are substantially completely closed. There are possibly due to unavoidable leakage volume flows.

When the valve spool is moved to the third shift position 13, the fluid connection A-T from the first workport to the tank port opens slightly earlier than the fluid connection P-B from the pump port to the second workport. In addition, the opening cross-sectional area of the fluid connection A-T is always greater than the opening cross-sectional area of the fluid connection P-B, so that the hydraulic fluid flowing back into the storage tank is exposed to a small back pressure. The graphs of the two connections P-B and A-T show a fine control range 51 with a smaller pitch, which serves for the sensitive movement of the lifting mechanism. The remaining area with a larger pitch was introduced in order to be able to set large volume flows even by small changes in the gate travel s. As a result, the Gesamtschieberweg and thus the size of the directional control valve can be kept small.

When the valve spool is moved from the first shift position 11 to the fifth shift position 15, first, the fluid connection B-T opens from the second workport to the tank port. This point marks the beginning of the fifth shift position 15. Again, a fine control range 52 is provided with a low slope. When the end of the fine control region 52 of the fluid connection B-T is reached, the fluid connection P-A also opens from the pump port to the first working port. This point marks the beginning of the second switching position 12.

If the valve spool is now moved further in the direction of the end position, then the fluid connection BT reaches its maximum opening cross-sectional area, which remains constantly open up to the mentioned end position. Shortly after the fluid connection BT has reached its maximum opening cross-sectional area, the fluid connection PA also reaches its maximum opening cross-sectional area 50, which drops back to zero during the further movement of the valve slide. there the maximum opening cross-sectional area 50 of the fluid connection PA is smaller than the maximum opening cross-sectional area of the fluid connection BT, so that here too the hydraulic fluid flowing back to the storage tank is exposed to a low back pressure.

At the latest, the maximum 50 of the opening cross-sectional area of the fluid connection P-A marks the end of the second switching position 12. Preferably, however, the second switching position 12 terminates slightly earlier. The first transition region 16 starting here extends to the point at which the fluid connection P-A is completely closed. This is followed by a second transition region 17, in which the fluid connection A-T from the first working port to the tank port opens quickly but continuously up to a maximum opening cross-sectional area. The maximum opening cross-sectional areas of the fluid connections A-T and B-T are the same size. At this point, the fourth shift position 14 begins, in which the opening cross-sectional areas of the fluid connections A-T and B-T remain constant.

It should be noted that the first and second transition regions 16; 17 are only briefly traversed during operation of the directional control valve.

LIST OF REFERENCE NUMBERS

P

pump connection

T

tank connection

A

first work connection

B

second work connection

LS

LS connection

P-A

Fluid connection from the pump connection to the first working connection

P-B

Fluid connection from the pump connection to the second working connection

AT

Fluid connection from the first working connection to the storage tank

B-T

Fluid connection from the second working port to the storage tank

Q

Opening cross-sectional area

s

Movement path of the valve spool

10

hydraulic directional valve

11

first switching position

12

second switch position

13

third shift position

14

fourth shift position

15

fifth shift position

16

first transition area

17

second transition area

20

Return spring

21

first electromagnetic actuation

22

second electromagnetic actuation

30

hydraulic cylinders

31

piston bottom side cylinder space

32

ring-sided cylinder space

40

hydraulic pump

41

pump line

42

Pressure relief valve

43

storage tank

44

pressure regulator

45

adjustment

50

Maximum of the opening cross-sectional area of the fluid connection P-A

51

Fine control range

52

Fine control range

Claims (6)

Hydraulic directional control valve (10) having a pump port (P), a tank port (T) and a first and a second working port (A; B), wherein the first and the second working port (A; B) with a hydraulic cylinder (30) of a hoist a mobile work machine, in particular an agricultural vehicle can be connected, wherein the pump port (P) with a hydraulic pump (40) is connectable,
wherein in a first switching position (11) the pump connection (P), the tank connection (T) and the first and the second working connection (A; B) are blocked,
wherein in a second switching position (12) the pump connection (P) to the first working port (A) and the tank port (T) to the second working port (B) are connected,
wherein in a third switching position (13) the pump connection (P) to the second working port (B) and the tank port (T) to the first working port (A) are connected,
wherein in a fourth switching position (14) the first and the second working connection (A, B) are connected to the tank connection (T), the pump connection (P) being blocked,
characterized in that a fifth switching position (15) is provided in which the tank port (T) is connected to the second working port (B), wherein the pump port (P) and the first working port (A) are locked. Hydraulic directional control valve according to claim 1,
characterized in that the hydraulic directional control valve (10) comprises a linearly movable valve spool, during its movement, the switching positions (11- 15) in the order - Third switching position (13); - first switching position (11); - fifth switch position (15); - second switching position (12); and fourth switching position (14) to go through. Hydraulic directional control valve according to one of the preceding claims,
characterized in that an LS connection (LS) is provided, which is connectable to the pressure regulator (44) of the hydraulic pump (40), wherein the LS connection (LS) in the second and the third switching position (12; is connected to the pump port, wherein it is in the first, the fourth and the fifth switching position (11; 14; 15) connected to the tank port (T). Hydraulic directional control valve according to one of the preceding claims,
characterized in that the directional control valve (10) is designed as a proportional valve, in which all fluid connections (PA, PB; AT; BT) open and close continuously. Hydraulic directional control valve according to claim 4, based on claim 3
characterized in that the valve spool between the second and the fourth switching position (12; 14) passes through a first transition region (16) in which the pump port (P) is connected to the first working port (A), wherein the fluid connection (AT) of first working connection (A) to the tank connection (T) is blocked. Hydraulic directional control valve according to claim 5,
characterized in that the valve slide between the first transition region (16) and the fourth switching position (14) passes through a second transition region (17) in which the fluid connection (TA) from the tank connection (T) to the first working port (A) opens continuously.

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