JPH0783348A - Pilot valve - Google Patents

Abstract

PURPOSE:To prevent an internal pressure from rising even when a push rod is operated to a limit by providing a constitution such that the inside and the outside of a skirt part are communicated with each other via an oil relief hole and further the oil relief hole is communicated with a tank port when a pressing unit is in maximum press-in operation. CONSTITUTION:In a capped cylindrical push rod 11, a tank port 10 is arranged under a sliding case part 1b for internally slidably fitting a skirt part 11b. In a lower position of the tank port 10, so as to restrict moving the push rod 11 to a supply position side, a contact surface 1c of a valve case 1, brought into contact with a lower end surface of the skirt part 11b, is formed. In a lower part of the skirt part 11b, an oil relief hole 24 for connecting an inner side of the skirt part 11b to the tank port 10, when the push rod 11 is in maximum press-in operation, is formed in a plurality of parts.

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 of a hydraulic working device in a working machine such as an agricultural machine or a construction machine, and more particularly, to a spool which is biased to return to a neutral oil draining position. Equipped with a supply / discharge valve mechanism that generates pilot pressure for operating the control valve by forcibly moving it, and an operation body that can move the push rod (corresponding to the pressing body) toward the supply position against the return biasing force. Regarding the provided pilot valve.

[0002]

2. Description of the Related Art A pilot valve of this type is shown in FIG.
The cross operation type shown in is generally well known.
That is, the bottom surface of the valve case 1 is provided with a piping connection port 7 for piping to the control valve, and the connection port 7 and the pump pressure chamber 5 and the tank pressure chamber 6 formed vertically inside the case are slidable. A supply / discharge valve mechanism 3 including a movable movable spool 12 and a push rod 11 into which the spool 12 is fitted via a balance spring 16 for adjusting pilot pressure is provided. It is a structure that generates pilot pressure.

[0003]

In this case, the maximum operation stroke of the operation lever 2 is determined by the abutment between the lower end surface of the skirt portion 11b of the push rod 11 and the case step portion 1c. 11
Since the inner space of the spool 12 is substantially sealed, the pressure in the inner space rises near the maximum stroke and the lever operation becomes heavy, which deteriorates the operability and also causes the spool 12 to receive the inner pressure of the push rod 11. There was a risk that the pressure regulation state of would be disturbed and adversely affect the pilot pressure. An object of the present invention is to prevent the above inconvenience from occurring by preventing the internal pressure of the push rod from rising even when the push rod is operated to its limit.

[0004]

SUMMARY OF THE INVENTION The present invention is capable of reciprocating between a pilot pressure supply position that opens a pump port and a supply / discharge port and a neutral oil discharge position that opens a tank port and a supply / discharge port. A spool and a pressing body for pushing and moving the spool toward the supply position.The spool can be slid relative to the pressing body in a protruding biased state via a balance spring for pilot pressure adjustment. As well as
A pilot valve equipped with a return spring that urges the pressing body to return to the neutral oil draining position, and an operating body that can move the pressing body toward the supply position against the urging force of the return spring. The body is formed in a substantially cylindrical cover shape including a large-diameter hollow cylindrical skirt portion surrounding a return spring that is externally mounted on a spool, and a small-diameter rod portion that receives the operating force of the operating body. The tank port is disposed below the sliding case part that slidably fits inside, and the lower end surface of the skirt part is arranged so that the supply position of the pressing body is restricted below the tank port. The contact surface of the valve case that contacts with the valve case is formed, and the skirt portion is formed with an oil escape hole that communicates the inner space of the skirt portion and the tank port during the maximum pushing operation of the pressing body. And

[0005]

In other words, at the time of maximum pushing, which is the operation limit of the pressing body, the inside of the skirt portion communicates with the outside of the skirt portion by the oil escape hole, so that there is no pressure difference between the inside and outside of the pressing body. Further, since the oil escape hole communicates with the tank port, there is no inconvenience that the pressure inside the pressing body is excessively increased by communicating with the pump port, and the desired spool pressure regulating action is exhibited. , To generate a regular pilot pressure.

[0006]

Therefore, the internal pressure of the pressing body can be prevented from rising at the time of maximum operation by a simple modification such as forming a hole in the skirt portion, and stable operation can be achieved without deterioration of operability and unexpected disturbance of pilot pressure. I was able to provide a pilot valve that would

[0007]

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.

An 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, a disc-shaped operating portion 2c, and a connecting portion. 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 and the boom control valve V ₁ 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 in the valve case 1 in a state where 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 formed 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 is formed by 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 communicate the lower end surface 12a with 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 shown.
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 operation 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.

As shown in FIG. 3, the push rod 11 having a substantially tubular shape has a tank port 10 disposed below a sliding case portion 1b into which a skirt portion 11b is slidably fitted. A contact surface 1c of the valve case 1 that contacts the lower end surface of the skirt portion 11b is formed in order to restrict the feed position of the push rod 11 to the lower side of the position 10 below. Then, in the lower portion of the skirt portion 11b, oil escape holes 24 that communicate the inner space of the skirt portion 11b with the tank port 10 at the time of maximum pushing operation of the push rod 11 are formed. This prevents the internal pressure of the push rod 11 from rising at the time of maximum operation.

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 opened oil drain position T. When the spool 12 is at the predetermined position H, 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
_{If 1} is in any of the operating positions U or D, it slowly returns to the neutral position N and operates at the neutral position N.

(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 down of the push rod 11 by the operating lever 2, and the spool pushing down force due to its elastic force and the pushing up 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, an 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 a 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. The position 0 is maintained and the maximum opening area is maintained on the line d which is smaller than the line c.

[Other Embodiment] This embodiment is a cross-operated pilot valve A, but the present invention may be applied to a single-operated pilot valve provided with only a pair of supply / discharge valve mechanisms 3 and 3. .

It should be noted that although reference numerals are given in the claims for convenience of comparison with the drawings, the present invention is not limited to the configuration 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 pump port (9) and a supply / discharge port (7).
And a spool (12) reciprocally movable between a pilot pressure supply position for opening the tank and the neutral oil drain position for opening the tank port (10) and the supply / discharge port (7), and the spool (12). And a pressing body (11) for pushing and moving the sheet toward the supply position, the spool (12)
Is fitted in the pressing body (11) so as to be relatively slidable in a protruding biasing state via a balance spring (16) for adjusting pilot pressure, and the pressing body (11) is placed in the neutral oil drain position. A return spring (15) for urging the return body (15) is provided, and the pressing body (11) resists the urging force of the return spring (15).
A return valve (15) in which the pressing body (11) is externally mounted on the spool (12), the pilot valve having an operating body (2) that can be moved toward the supply position. ), A hollow cylindrical skirt portion (11b) having a large diameter, and a rod portion (11a) having a small diameter that receives an operating force of the operating body (2), and having a substantially cylindrical shape with a lid. The tank port (10) is arranged below a sliding case (1b) into which the (11b) is slidably fitted, and the pressing body (11) is located below the tank port (10). The contact surface (1) of the valve case that contacts the lower end surface of the skirt (11b) in order to regulate the movement of the supply position to the upper end.
c) is formed, and the inner space of the skirt portion (11b) and the tank port (1) are pushed into the skirt portion (11b) during the maximum pushing operation of the pressing body (11).
0) Pilot valve having an oil escape hole (24) communicating therewith.