JPH0771417A - Pilot valve - Google Patents

Abstract

PURPOSE:To provide a pilot valve having improved responsiveness to the quick operation of a manipulator, while maintaining the smooth return operation of a control valve to a neutral position. CONSTITUTION:When an operation lever 2 is in a free condition, push rods 11 lower 1mm from an upper limit and a spool 12 is at the preset position H. When the lever 2 is turned, one of the push rods 11 moves down from the position H and the other push rod 11 is made to ascend from the position H toward an upper limit maximum oil discharge position. Thereafter, when the lever 2 is further turned and one of the push rods 11 is moved to a shutout position, the other push rod 11 is already at a maximum oil discharge position and kept thereat, until the remaining push rod 11 is moved to a maximum oil feed position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pilot valve suitable as an operating means for a hydraulic working device in a working machine such as an agricultural machine or a construction machine. The present invention relates to a valve structure that realizes excellent responsiveness at low cost.

[0002]

2. Description of the Related Art A pilot operating means for switching a control valve with a pilot valve is disclosed in, for example, Japanese Patent Laid-Open No. 4-343925
As in the hydraulic circuit disclosed in Japanese Patent Publication, there is known a supply / discharge oil passage that connects a pair of control cylinders of a control valve and a pair of supply / discharge valve mechanisms of a pilot valve, respectively. Is supplied, the other oil supply / drain passage is drained to switch the control valve from the neutral position to each operating position. That is, as shown in FIG. 10, the spool 12 is reciprocally movable between a supply position that opens the pump port 9 and the supply / discharge port 7, and an oil drain position that opens the tank port 10 and the supply / discharge port 7. And the operating body 2 that moves the spools 12 and 12 in a contradictory manner toward the supply position. Then, as the spool 12 moves from the oil discharge position toward a predetermined position between the oil discharge position and the oil supply position, the open areas of the supply / discharge port 7 and the tank port 10 decrease, and
The supply port 9 is closed when the spool 12 is located between the oil drain position and the predetermined position, and the supply port 9 is moved as the spool 12 moves from the predetermined position toward the supply position.
When the open area of the tank increases and the spool 12 is located between the predetermined position and the supply position, the tank port 1
In the state where 0 is closed, the spool 12 and each port 7, 9, 1
A pair of supply / discharge valve mechanisms 3 configured to be linked with 0 are provided.

[0003]

In the pilot valve described above, when the operating body 2 is in the non-operating position where the operating body 2 is not operated, the spools 12 and 12 are urged upward by the return spring 15 and the maximum oil drainage together with the push rod 11. It has returned to the position, and the supply / discharge port 7 and the tank port 10 are in communication with each other through the communication hole 12b with the largest opening area. When the operating body 2 is tilted rightward in the drawing, for example, the spool 12 on the right side is pushed downward via the push rod 11, and the opening area to the tank port 10 is gradually reduced to reach the cutoff position. Then, the land portion 12c and the case supporting portion 1d overlap each other to close the flow path to the tank port 10, and the spool 12 on the left side is biased to the maximum oil discharge position during this time. When the operating body 2 is tilted to the right, the land portion 12c instead of the tank port 10 faces the supply port 9 and the flow passage is gradually opened to generate the pilot pressure.

This pilot pressure is applied to the lower end surface 12 of the spool.
It is caused by relative movement of the spool 12 with respect to the push rod 11 to a position where the upward pushing force due to the area difference between a and the land portion 12c and the elastic force of the balance spring 16 are balanced. When the push rod 11 is pushed in the most, the compression amount of the balance spring 16 becomes the maximum and the spool 12 becomes the maximum supply position, and the largest pilot pressure is supplied. Is maintained in the maximum oil drain position. With the above operation, the opening of the control valve at the operating position is controlled by the pilot pressure generated according to the operation amount of the operating body 2. However, the operability may be changed depending on the operating state of the operating body 2. There was something unfavorable.

That is, the opening area between the supply / drain port 7 and the tank port 10 at the maximum oil drain position is such that when the operating body 2 is returned to the non-operating position, the return operation to the neutral position of the control valve is smooth and has less shock. A small value (for example 0.
It is set to 025mm ² ), and the oil supply and discharge operations to the control valve will be performed relatively slowly. However, when the operating body 2 is operated relatively quickly, oil is rapidly supplied to one supply / exhaust port 7 and the pilot pressure tries to rise rapidly in order to quickly switch the control valve. Since the opening area of the other spool 12 in the oil position to the tank port 10 is small, the actual switching speed of the control valve is restricted by the slow discharging speed, and the responsiveness of the actuator to the operation of the operating body 2 is restricted. It is not good. An object of the present invention is to improve the responsiveness when the operating body is quickly operated, while maintaining the smooth return operation of the control valve at the time of neutral operation, by devising the structure inside the pilot valve.

[0006]

In order to achieve the above object, the present invention provides a maximum oil drainage position where the tank port and the supply / discharge port are opened in the maximum area, and a pump port and a supply / discharge port in the maximum area. It has a spool that can reciprocate between it and the maximum supply position that opens, and the maximum supply position and maximum supply position are the cut-off position where the oil supply port does not communicate with the tank and pump ports. Between the maximum oil drainage position and the shutoff position as the spool moves from the maximum oil drainage position to the shutoff position. When located in between, the flow path between the supply / discharge port and the supply port is closed, and the opening area between the supply / discharge port and the supply port increases as the spool moves from the blocking position toward the maximum supply position, Or When the spool is located between the shut-off position and the maximum supply position, a pair of supply / discharge valve mechanisms are provided in which the spool and each port are linked so that the flow paths of the supply / discharge port and the tank port are closed. When the pilot valve is provided with an operating body for operating the spools of each of these supply / discharge valve mechanisms in a contradictory manner, and when the operating body is in the non-operated position, both spools have the maximum discharge capacity. When operated to a predetermined position set between the oil position and the cutoff position and moving the operating body from the non-operating position to one operating position, one spool moves from the predetermined position to the maximum supply position. When the other spool is moved from the predetermined position toward the maximum oil discharge position and the operating body is moved from the non-operating position toward the other operating position, the other spool is moved to the predetermined position. The operating body and both spools are arranged so as to be linked to each other in a state in which the spool is moved from the position toward the maximum supply position and one spool is moved from the predetermined position toward the maximum oil discharge position. It is a thing.

[0007]

In detail, as will be described in the embodiment, when the operating body is in the operated position, both the supply / discharge valve mechanisms have the spools in the predetermined positions, and the supply / discharge ports and the tank port have a small area. When the operating body is operated toward one of the operating positions, which corresponds to the oil discharge position after opening, the opening area between the supply / discharge port and the tank port is reduced in one supply / discharge valve mechanism, and In the discharge mechanism, the opening area between the supply / discharge port and the tank port is increased. When one of the spools reaches the cutoff position, the supply port of the one supply / discharge valve mechanism is in the oil passage closed state, but the other spool is maintained at the maximum oil discharge position. Furthermore, when the operating body is operated toward one of the operating positions, the supply / discharge port and pump port of the one supply / discharge valve mechanism are opened while the other spool is maintained at the maximum oil discharge position, and the opening area Is increased, and the pilot pressure commensurate with the movement amount of the operating body is generated.

That is, the opening area between the supply / discharge port and the tank port is conventionally set to the maximum when the operating body is at the operated position, whereas in the means of the present application, the operating body is moved from the operated position to the operated position. It is set so that it becomes maximum when stroked to some extent. As a result, when the operating body is operated quickly so that the pilot pressure rises rapidly,
By discharging the oil in the maximum opening area larger than before, oil is quickly discharged from the control valve, the actuator operation corresponding to the rapid operation is revealed, and if the operating body is returned to the operated position. By draining the oil in a small opening area, a slow neutralization operation of the control valve can be realized smoothly.

[0009]

As a result, the modification to the extent that the relative position setting between the operation lever and the return position of the spool is changed, that is,
Without complicating the structure and increasing the number of parts, while maintaining the conventional smooth return operation of the control valve to neutral,
A quick switching operation of the control valve could provide a pilot valve with improved responsiveness that could be revealed.

[0010]

Embodiments of the present invention will be described below with reference to the drawings of a pilot valve for a backhoe. 1 and 4 show a cross-operated pilot valve A for switching between the boom control valve V ₁ and the bucket control valve V ₂ , where 1 is a valve case, 2 is an operating lever, and 3 is a boom. First supply / discharge valve mechanism, 4 second bucket supply / discharge mechanism, 5 pump pressure chamber, 6 tank pressure chamber, 7 boom supply / discharge port, 8 bucket supply / discharge port, 9 Is a pump port, and 10 is a tank port. For reference, symbol symbols in the hydraulic circuit of the pilot valve A are shown in FIG.

The operating lever (corresponding to an operating body) 2 is connected to a base portion 2a screwed to the valve case 1, an operating portion 2b connected to the base portion 2a by a universal joint structure, and a disc-shaped operating portion 2c. It is composed of a cylinder 2d and a lever portion 2e.
It is possible to freely operate the cross swing by holding e. As shown in FIG. 7, when the operation lever 2 is swung in the front-back direction, the first supply / discharge valve mechanism 3 is operated to operate the boom control valve V _{1, and} when it is swung in the left-right direction, the second supply / discharge valve is operated. It is arranged so that the valve mechanism 4 operates to operate the bucket control valve V ₂ .

The first and second supply / discharge valve mechanisms 3 and 4 have the same structure, and include a push rod (corresponding to a pressing body) 11, a spool 12, an upper first spring receiver 13, and a lower first spring receiver 13. Two
The plug 1 includes a spring receiver 14, a first winding spring (corresponding to a returning spring) 15 for returning the push rod, and a second winding spring 16 which is a balance spring for adjusting pilot pressure.
It is installed inside the valve case 1 in a state in which it is prevented from coming off by 7.
The four plugs 17 are held by a base plate 2a by a lid plate 18 fixedly mounted on the upper surface of the valve case 1.

The push rod 11 is constructed by integrally forming a rod portion 11a which is pressed by the operating portion 2c and a hollow cylindrical skirt portion 11b which is slidably supported by the valve case 1, and a plug 17 and Both the sliding portion with the rod portion 11a, the sliding portion with the skirt portion 11b and the sliding portion with the valve case 1 allow smooth vertical sliding. The drain hole 11c formed in the lower end portion of the rod portion 11a is an oil flow passage to an air gap formed between the push rod 11 and the plug 17, and the push rod 11 formed by the first winding spring 15 has a good flowability. It contributes to the return operation and the light downward pushing operation.

A communication hole 12b is formed in the lower portion of the spool 12 so as to connect the lower end surface 12a and a land portion 12c formed in the middle of the shaft, and the push rod 11 is slidably fitted in the upper portion thereof. The sliding portion 12d and the first spring receiver 13
And a small-diameter washer fitting shaft portion 12e for mounting the second spring receiver 14 are formed in the middle portion of the washer fitting shaft portion 12e.

As shown in FIG. 4, the bottom portion 1 of the valve case 1 is
In a, a pair of supply / drain ports 7 and 7 for boom, a pair of supply / drain ports 8 and 8 for bucket, a pump port 9 and a tank port 10 are formed, and a pipe is connected to each of them. Is. The through hole 19 extending between the bottom surface portion 1a and the pump pressure chamber 5 is for extracting the core of the pump pressure chamber 5 portion by sand casting, and is a plug 20 as a product.
Will be blocked.

As shown in FIGS. 7 and 8, a predetermined return mechanism B for returning and maintaining the operating lever 2 in the upright operated position is provided between the supply / discharge valve mechanisms 3, 4, 3, 4. It is located at a total of 4 places. That is, the predetermined returning mechanism B includes the pressing rod 21 that comes into contact with the operating portion 2c, the spring 22 that biases the pressing rod 21 upward, and the retaining member 2.
3 and 3 are mounted on the valve case 1, and the pressing rod 21
Four predetermined return mechanisms B are linked to each other so that the top portion of the pressing rod 21 just contacts the operation portion 2c in a state where the flange portion 21a is in contact with the retaining member 23. still,
The position maintaining action of the operation lever 2 by the predetermined return mechanism B is set to be stronger than the return urging force of the first winding spring 15 for returning the push rod 11 to the maximum raised position.

Next, the operation of the pilot valve A will be described with reference to the first supply / discharge valve mechanism 3. (1) When the operating lever 2 is in the non-operating position, when the fingers are released from the operating lever 2 to be in the free state, the operation lever 2 is returned and maintained in the non-operating position by the action of the predetermined return mechanism B, and the push rod 11 is It is located 1mm below the bottom of the plug 17, and both spools 12, 1
2 are both returned to and maintained at the predetermined position H (states of FIGS. 1 and 6). In this state, the land portion 12c faces the tank pressure chamber 6 and the lower end surface 12a of the spool 12 faces the supply / discharge port 7, and the supply / discharge port 7 and the tank port 10 respectively.
And are in the open oil drain position. Spool 1 at predetermined position H
2, the communication area between the supply / discharge port 7 and the tank port 10 is opened with a very small amount (0.025 mm ² ), and the control valve V ₁
Is in any of the operation positions U or D, the neutral position N is slowly returned to the neutral position N and the neutral position N is maintained.

(2) Move the operating lever 2 to one operating position (see FIG. 1).
When the operation lever 2 is tilted to the right against the return biasing force of the predetermined return mechanism B when operated in the right direction), the right push rod 11 moves to the first position.
The second coil spring 16 is pushed downward against the coil spring 15,
The spool 12 on the right side is moved downward from the predetermined position H via the to reduce the exposed portion of the land portion 12c to the tank pressure chamber 6, and the opening area between the supply / discharge port 7 on the right side and the tank port 10 is gradually reduced. At the same time, the left spool 12 is moved back toward the upper maximum oil discharge position (Tmax) as the push rod 11 is pushed up by the first winding spring 15. When the spool 12 on the right side reaches the shutoff position S, the land portion 12 c is moved to the bearing portion 1 of the valve case 1.
The oil passage surrounded by d is closed and the flow path of the right supply / discharge port 7 is closed, and the left spool 12 is located at the maximum oil discharge position Tmax (state in FIG. 2).

When the operating lever 2 is subsequently tilted, the right spool 12 is moved toward the maximum supply position Kmax at the supply position K between the shutoff position S and the maximum supply position Kmax, and the right second coil spring 16 is compressed. By increasing the amount, the land portion 12c faces the pump pressure chamber 5, and the opening area between the right supply / discharge port 7 and the pump port 9 is gradually increased. In this state, the step portion 12g of the land portion 12c and the spool lower end surface 1
A force for pushing up the spool 12 is generated due to the difference in area with 2a, and the spool 12 is pushed up to a position where the pushing force and the elastic force of the compressed second winding spring 16 are balanced.

That is, the second winding spring 16 is compressed in accordance with the amount of pushing of the push rod 11 by the operating lever 2, and the spool pushing force due to its elastic force and the pushing force due to the area difference are balanced. Since the spool 12 stops, the compression amount of the second winding spring 16 also increases as the tilt angle of the operation lever 2 increases, that is, as the push-down amount of the push rod 11 increases. The pilot pressure is generated and supplied to the control valve V ₁ . When the operating lever 2 is tilted as much as possible, the push rod 11 is moved 8.0 mm downward from the lower surface of the plug 17 to generate the maximum pilot pressure (state of FIG. 3). Kmax
Is different depending on the strength of the second winding spring 16, and the movement limit is not uniquely determined unlike the push rod 11.

(3) When the operation lever 2 is operated to the other operation position (to the left), except when the phenomena of the supply / discharge valve mechanisms 3 and 3 of the above (2) are reversed, the case of tilting to the right The same effect is exhibited.

In FIG. 9, the opening area (line a) between the supply / discharge port 7 and the tank port 10 in the supply / discharge valve mechanism 3 with respect to the movement stroke of the push rod 11 (line a) and the connection between the supply / discharge port 7 and the pump port 9 are shown. The relationship graph between the area (line b) and the opening area (line c) between the supply / discharge port 7 and the tank port 10 in the supply / discharge valve mechanism 3 on the other side is shown. When the push rod stroke is 0 when the operation lever 2 is in the non-operation position and the position of the push rod 11 is --1 mm, it corresponds to the maximum oil discharge position Tmax of the spool 12, --1 mm and 1.1 When it is 0 mm, it corresponds to the predetermined position H of the spool 12, and when it is between 1.1 mm and 1.3 mm, it corresponds to the cutoff position S of the spool 12,・ Supply position K of spool 12 between 1.3mm and 7.0mm
The spool 12 has a maximum supply position Kmax of 3 to 4 mm.
It means that

The stroke of the push rod 11 is 1 m.
Above m, the opening area (line c) between the supply / discharge port 7 and the tank port 10 of the other supply / discharge valve mechanism 3 is maintained at the maximum value, but in the conventional pilot valve, the upper limit of the push rod 11 rises. Since the maximum opening area is maintained at the line 0, which is the position 0, and the maximum opening area is smaller than the line c, the advantage of the present invention can be clearly understood.

[Other Embodiment] Although the present embodiment is a cross-operated pilot valve A, the present application may be applied to a single-operated pilot valve having only a pair of supply / discharge valve mechanisms 3 and 3. .

It should be noted that reference numerals are given in the claims for convenience of comparison with the drawings, but the present invention is not limited to the configurations of the accompanying drawings by the entry.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a pilot valve.

FIG. 2 is a sectional view of the pilot valve showing a state where one spool is in a shutoff position.

FIG. 3 is a sectional view of the pilot valve showing a state where one spool is in a maximum supply position.

[Fig. 4] Bottom view of the pilot valve

FIG. 5 is a symbol diagram showing a symbol mark of a pilot valve.

FIG. 6 is a partially enlarged view showing a state where the spool is at a predetermined position.

FIG. 7 is a plan view showing an operation form of an operation lever.

FIG. 8 is a sectional view showing the structure of a predetermined return mechanism.

FIG. 9 is a diagram showing a relationship graph between a push rod and each opening area.

FIG. 10 is a sectional view showing a pilot valve having a conventional structure.

[Explanation of symbols]

 2 Operating body 3 Supply / discharge valve mechanism 7 Supply / discharge port 9 Pump port 10 Tank port 12 Spool Tmax Maximum oil discharge position Kmax Maximum supply position S Shutoff position H Predetermined position

Claims (1)

[Claims] 1. A maximum oil discharge position (Tmax) for opening the tank port (10) and the supply / discharge port (7) in the maximum area.
And a spool (12) reciprocally movable between a pump port (9) and a maximum supply position (Kmax) that opens the discharge port (7) with the maximum area, and the supply / discharge port (7) ) Is a shut-off position (S) in which the oil passage is closed without communicating with any of the ports (10) and (9) of the tank and the pump, the maximum oil discharge position (Tmax) and the maximum supply position (Kmax) And a tank port (10) as the spool (12) moves from the maximum oil discharge position (Tmax) toward the cutoff position (S). When the opening area of the spool is reduced and the spool (12) is located between the maximum oil drainage position (Tmax) and the shutoff position (S), the supply / discharge port (7) and the supply port (7) 9)
The flow path is closed, and as the spool (12) moves from the shutoff position (S) toward the maximum supply position (Kmax), the supply / discharge port (7) and the supply port (9) are connected. When the opening area of the spool (12) is increased and the spool (12) is located between the shut-off position (S) and the maximum supply position (Kmax), the supply / discharge port (7) and the tank port ( 10), the spool (1
2) and a pair of supply / discharge valve mechanisms (3) in which the ports (7), (9), and (10) are linkedly arranged, and
The spool (1) of each of these supply / discharge valve mechanisms (3), (3)
A pilot valve provided with an operating body (2) for displacing 2) and (12) in an antithetical manner, wherein the operating body (2) is in a non-operating position where it is not operated,
Both the spools (12), (12) are operated to a predetermined position (H) set between the maximum oil discharge position (Tmax) and the cutoff position (S), and the operating body (2) is moved. When a moving operation is performed from the non-operation position toward one operation position,
One of the spools (12) is moved from the predetermined position (H) toward the maximum supply position (Kmax), and the other spool (12) is moved from the predetermined position (H) to the maximum oil discharge position. Moved towards (Tmax),
When the operation body (2) is operated to move from the non-operation position to the other operation position, the other spool (12)
Is moved from the predetermined position (H) toward the maximum supply position (Kmax), and one spool (12) is moved from the predetermined position (H) toward the maximum oil discharge position (Tmax). In such a state that the operating body (2) and the spools (12), (12) are arranged in a linked manner.