JP2576544B2 - Drive device for fluid control spool in fluid pressure drive circuit - Google Patents

Description

The present invention relates to a drive device for a fluid control spool in a fluid pressure drive circuit used in a fluid pressure drive circuit.

(Prior Art) Generally, in a hydraulic drive device for an industrial vehicle or the like, in order to freely control the movements of a motor and various cylinders, a directional switching valve incorporated in a hydraulic circuit is usually provided with a spool. The port is opened and closed by changing the position of the port. For this reason, it is extremely important to operate the spool at the correct timing.

As a directional switching valve of this type, for example, FIG.
There is one shown in FIG. That is, the valve chamber in the housing 50
51 is divided into left and right pressure chambers 53 and 54 by a spool 52, and both are communicated with a common pump P.
4 is separately connected to normally closed solenoid on-off valves 55 and 56.

Then, as shown in FIG. 7 (a), a constant pressure is applied to both the pressure chambers 53 and 54 by the pump P,
The spool 52 is held at the center position by a and Sb, and a pulse signal wave is output to one of the open / close valves 55 and 56 (the left open / close valve 55 in the drawing) as necessary. Then, the on-off valve 55 is opened only by an amount corresponding to the duty ratio of the pulse signal wave, and the pressure in the corresponding pressure chamber 53 is reduced by the outflow of the hydraulic oil. For this reason, as shown in FIG. 7 (b), the spool 52 is moved to one pressure chamber 53 side by the pressure in the pressure chamber 54,
The open / close state of two discharge ports (not shown) is switched,
Supply or stop supply of hydraulic pressure to the downstream pipeline connected to these grinding ports.

(Problems to be Solved by the Invention) However, the above-mentioned spool 52 slides on the inner wall of the holding portion 58 protruding in the center direction in the valve chamber 51.
Move while keeping your posture horizontal. Therefore, a strong frictional force is generated between the moving spool 52 and the inner wall of the holding portion 58, and when the moving force acting on the spool 52 falls below the frictional force, the movement is stopped.

The movement of the spool 52 described above is
Is performed against the force of the pressing spring Sa in one of the pressure chambers 53. Therefore, as shown in FIG.
Due to the reaction force of the pressing spring Sa gradually contracted by the movement of the 52, the moving force of the spool 52 decreases, and approaches the displacement command value indicating the desired moving distance of the spool 52 corresponding to the duty ratio of the pulse signal wave. When this occurs, this moving force falls below the frictional force. The position of the spool 52 is not fixed within the range below the moving force or the frictional force, and accurate positioning is not performed.Further, when the frictional force increases, the positioning error increases in proportion to this, so that It becomes increasingly difficult to stop the spool 52 at the correct position.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to stop the spool irrespective of the frictional force applied when the spool is moved. An object of the present invention is to provide a drive device for a fluid control spool that has an extremely small deviation from the position.

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a pressure source, a spool movably disposed in a valve chamber of a housing, and spools at both ends of the valve chamber. And connected to the pressure source via the first and second connection lines to hold the spool stationary by opposing internal pressure and to provide a differential pressure when an internal pressure differential occurs. The first and second driving pressure chambers for moving the spool based on the first and second driving pressure chambers communicate with the valve chambers and correspond to the first and second driving pressure chambers. As described above, and connected to the corresponding drive pressure chambers by being connected to the first and second connection conduits, the pressure equal to the corresponding drive pressure chambers is always supplied from the pressure source. ,internal First and second pressure chambers for reducing the pressure in the corresponding drive pressure chamber by supplying a pressure greater than the corresponding drive pressure chamber from the pressure source when the force is reduced; The first movement position and the second movement position sandwiching the same original position as the position
And a holding means for always holding the pilot spool in the original position, and a pilot spool provided on one side of the pilot spool so as to correspond to the first pressure chamber. And connected to a pressure source, selectively connected to and disconnected from the first pressure reducing valve, and when connected to the first pressure reducing valve, the internal pressure is reduced to hold the pilot spool in the holding force of the holding means. A first decompression chamber for moving to a first movement position in opposition to the first pressure chamber, and a second decompression chamber provided on the other side of the pilot spool corresponding to the second pressure chamber and connected to a pressure source. A second valve for selectively connecting and disconnecting to the valve and reducing the internal pressure when connected to the second pressure reducing valve to move the pilot spool to the second movement position against the force of the holding means; Decompression chamber When said pilot spool is situ, is blocked with respect to the first and second pressure chambers by the pilot spool, the second when the pilot spool is in the first position
To reduce the internal pressure of the second pressure chamber, and when the pilot spool is in the second position, the first pressure chamber is in the first position.
And a drain chamber connected to the first pressure chamber to reduce the internal pressure of the first pressure chamber.

(Operation) When the first pressure reducing valve communicates with the first pressure reducing chamber, the pilot spool moves to the second position, connects the first pressure chamber and the drain chamber, and connects the first pressure chamber with the first pressure chamber. Reduce the pressure.
As a result, the pressure value supplied from the pressure source to the first pressure chamber via the first connection pipe increases, and the pressure in the first driving pressure chamber decreases. Therefore, the spool moves to the first driving pressure chamber side. When the second source pressure valve and the second decompression chamber are communicated with each other, the pilot spool moves to the first position, connects the second pressure chamber with the drain chamber, and connects the second pressure chamber with the second pressure chamber. Reduce pressure. Thereby, the pressure value supplied from the pressure source to the second pressure chamber via the second connection pipe increases, and the pressure in the second driving pressure chamber decreases. Therefore, the spool moves to the second driving pressure chamber side.

(Embodiment) An embodiment of the present invention will be described below in detail with reference to FIGS.

In FIG. 1, a valve chamber 2 extending in a longitudinal direction is formed in a housing 1, and a spool 3 is disposed in the valve chamber 2. The spool 3 is formed to be slightly shorter than the valve chamber 2, and slides on the inner peripheral wall of the small diameter portion 4 of the valve chamber 2 to move. As shown in the figure, when the spool 3 is at a middle position separated from both end surfaces of the valve chamber 2, one end (right end) of the valve chamber 2 has a large-diameter first driving pressure chamber 5.
Is formed, and the spool 3 in the small-diameter portion 4 is formed.
A second driving pressure chamber 6 constituted by a non-arriving portion is provided at the other end. Then, the hydraulic pressure in each of the drive pressure chambers 5, 6 is appropriately reduced, so that the spool 3
The position is switched to the left position and the right position shown in the figure, respectively, and the open / close state of the discharge port (not shown) is switched.

Between the two driving pressure chambers 5 and 6 of the valve chamber 2, a decompression chamber 7 having the same diameter as the first driving pressure chamber 5, a first pressure chamber 8, a drain chamber 9,
A second pressure chamber 10 is formed side by side from one end to the other end,
Each of the chambers 7, 8, and 10 except the drain chamber 9 is connected to a hydraulic pump 11 as a pressure source. The two drive pressure chambers 5 and 6 are also connected to the hydraulic pump 11, and the pressure reduction chamber 7 in the spool 3 and the first and second pressure chambers 8 and 10 and the drive pressure chambers 5 and 6 of the valve chamber 2 are fixed. The working oil having the flow rate of? The drain chamber 9 is a drain tank.
The pressure reducing chamber 7 is further connected to a normally closed electromagnetic first high-speed on-off valve 14 via an orifice 15. The first high-speed on-off valve 14 is electrically connected to a pulse wave generating means (not shown), and is opened by an amount based on the duty ratio of a pulse signal wave to be output therefrom.

The pipe A from the pump 11 is branched into two pipes B and C, and a pipe branched from the pipe B at one end is connected to the decompression chamber 7 through an orifice D. Also, piping B
Is connected to the first pressure chamber 8 via an orifice E as a first connecting line, and further to the orifice E
Is connected to the first driving pressure chamber 5.

On the other hand, the pipe C at the other end is branched into pipes having orifices H and I, and the pipe having the orifice H is communicated with a biasing chamber 20 described later. In addition, the pipe having the orifice I as the second connection pipe is connected to the second pressure chamber 10.
The pipe K branched through the orifice I is further connected to the second driving pressure chamber 6.

In the housing 1, an urging chamber 20 is formed on the other end side of the valve chamber 2, and the valve chamber 2 and the urging chamber 0 are communicated with each other through a communication path 21 having a small diameter. Connecting passage from 20
A projection allowable path 22 having the same diameter as 21 slightly extends in the direction of the other end.
The urging chamber 20 is a normally-closed electromagnetic second high-speed on-off valve 27.
And the pump 11 through the orifice H, and the pressure reducing chamber 7, the pressure chambers 8, 10 and the driving pressure chamber 5,
As in the case of No. 6, a constant flow rate of hydraulic oil is supplied. The second high-speed opening / closing valve 27 is electrically connected to a pulse wave generator (not shown), and is opened by an amount based on the duty ratio of the pulse wave output from the pulse generator. Thus, the internal pressure of the urging chamber 20 is reduced by the same operation as that of the depressurizing chamber 7, and in the present invention, the urging chamber 20 urges the pressure reducing chamber 7 to constitute the first depressurizing chamber. The chamber 20 constitutes a second decompression chamber.

The other end face of the spool 3 is opened, and a storage chamber 16 as a second valve chamber extending from the opening to one side of the spool 3 is formed to have the same diameter as the communication passage 21. A small-diameter piston chamber 16a is provided at one end of the accommodation chamber 16.
The piston chamber 16a and the decompression chamber 7 are communicated via a first communication hole 17a. Also, the accommodation chamber 16 has second to fourth communication holes 17b, 17 arranged from one side to the other side.
c, 17d are provided, and the accommodation chamber is provided through each communication hole 17b, 17c, 17d.
16 communicates with the first pressure chamber 8, the drain chamber 9 and the second pressure chamber 10.

A pilot valve 18 is provided in the accommodation chamber 16 of the spool 3 as a pilot spool which slides and moves on the inner peripheral wall thereof.
Is accommodated over substantially half of its length direction, the large-diameter portion 18a at one end, the small-diameter portion 18b adjacent to the large-diameter portion 18a, and the large-diameter portion 18c at the other end adjacent to the small-diameter portion 18b. It consists of At the other end of the pilot valve 18, a small-diameter portion 23 projecting into the biasing chamber 20 through the communication passage 21 is provided with a stepped portion 23.
is formed through a. A retaining ring 25a is fixed to the other end of the small diameter portion 23 of the pilot valve 18, and a pair of holding members 24a and 24b opposed to each other are provided on the small diameter portion 23 between the step portion 23a and the retaining ring 25a. It is slidably mounted. Each of the holding members 24a and 24b includes a cylindrical spring receiving portion 25 and a flat plate-like stopper portion 26. The holding members 24a and 24b have a small diameter portion 23 and a pressing spring S.
At the same time, it constitutes holding means for always holding the pilot valve 18 at the original position (the position shown in FIG. 1).

The spool 3 with the pilot valve 18 in the neutral position
At the position corresponding to, the two holding members 24a and 24b are urged in the direction away from each other by the pressing spring S mounted between the two spring receiving portions 25, and the two stopper portions 26 are respectively provided with the retaining ring 25a and the stepped portion. It is in contact with the part 23a. Due to the force of the pressing spring S, the stepped portion 23a of the pilot valve 18
Are biased so as to be located on the same plane as the one end face of the first.

In the above state, the pilot valve 18 has the large-diameter portions 18a and 18c closing the second and fourth communication holes 17b and 17d, respectively, and is opened by the communication holes 17b and 17d and the small-diameter portion 18b in the accommodation chamber 16. The third communication hole 17c is blocked to prevent the first and second pressure chambers 8, 10 from communicating with the drain chamber 9.

Now, the operation of the directional control valve configured as described above will be described below.

In FIG. 1, a spool 3 is located in an original position in a valve chamber 2,
That is, each of the driving pressure chambers 5 and 6 and the decompression chamber 7 in the spool 3, each of the pressure chambers 8 and 10,
Is provided with a uniform hydraulic chamber from the pump 11,
The oil pressure in the urging chamber 20 and the oil pressure in the pressure reducing chamber 7, that is, the oil pressure in the piston chamber 16 a in the spool 3 are in opposition.

In order to move the spool 3 to the other end side by a predetermined amount in the above state, a pulse signal wave having a duty ratio predetermined in accordance with the desired movement amount is transmitted from the pulse generator to the second side.
Output to the high-speed on-off valve 27. Then, the second high-speed on-off valve 27 is opened by an amount based on the duty ratio of the pulse signal wave, and the operating oil in the urging chamber 20 flows out to the second high-speed on-off valve 27 according to the opening amount. The pressure in the urging chamber 20 is reduced according to the outflow amount of the hydraulic oil, and the piston chamber 16a in the spool 3 is reduced.
Is higher than the oil pressure in the urging chamber 20.

Then, as shown in FIG. 2, the pilot valve 18 is moved toward the other end by the distance based on the pressure difference between the two chambers 16a and 20 against the force of the pressing spring S, and is moved to the step 23a. Holding member 2
4a advances while being pushed to the other end side in the biasing chamber 20, and the tip of the small-diameter portion 23 projects from the biasing chamber 20 into the projection allowable path 22. At this time, the fourth communication hole 17d is opened by the displacement of the large diameter portion 18c of the pilot valve 18, and the inner peripheral wall of the spool 3 and the pilot valve 1
The drain chamber 9 and the second pressure chamber 10 communicate with each other via the third and fourth communication holes 17c and 17d by the gap between the outer peripheral walls of the small diameter portion 18b. For this reason, the hydraulic oil in the second pressure chamber 10 flows out into the drain chamber 9 through the fourth and third communication holes 17d and 17c,
Further, the oil flows from the drain chamber 9 into the oil drain tank 13, and the pressure in the second pressure chamber 10 is reduced.

As the pressure in the second pressure chamber 10 is reduced, the flow rate of the working oil flowing into the second pressure chamber 10 from the pump 11 via the pipe C and the orifice I increases, so that the pipe K branched from the orifice I The amount of oil flowing into the interior decreases. This allows
The amount of oil flowing from the pump 11 into the second driving pressure chamber 6 decreases, and the oil pressure in the second driving pressure chamber 6 becomes lower than the oil pressure in the first driving pressure chamber 5. Therefore, while the spool 3 is in sliding contact with the inner peripheral wall of the valve chamber 2 and the outer peripheral surface of the pilot valve 18 due to the above-described pressure difference, the other end, that is, the left first Move to the move position.

Then, as shown in FIG. 3, when the fourth communication hole 17d of the spool 3 reaches the large diameter portion 18c of the pilot valve 18 and is closed, the communication between the second pressure chamber 10 and the drain chamber 9 is cut off. Is done. Then, the outflow of the hydraulic oil from the second pressure chamber 10 ends, and the oil pressure in the chamber returns to the predetermined value. Therefore, the pump
Hydraulic oil flowing from the pipe 11 through the pipe C does not flow into the second pressure chamber 10 via the orifice I, but flows into the second drive pressure chamber 6 via the pipe K branched from the orifice I. Also, a predetermined amount of hydraulic oil is supplied. This allows
The oil pressure in the second drive pressure chamber 6 returns to a predetermined value, and the oil pressure in both drive pressure chambers 5, 6 becomes equal. Accordingly, the spool 3 is stopped at the left position shown in FIG. 3, and the relative positional relationship between the spool 3 and the pilot valve 18 is maintained as in the neutral position shown in FIG.

Conversely, when the spool 3 is moved to one end, a pulse signal wave is output from the pulse wave generator to the first high-speed on-off valve 14. When the first high-speed on-off valve 14 is opened based on the duty ratio of the pulse signal wave,
The hydraulic oil in the decompression chamber 7 flows out to the first high-speed on-off valve 14 side,
Further, the hydraulic oil in the piston chamber 16a in the spool 3 also flows out of the pressure reducing chamber 7 to the first high-speed on-off valve 14 through the first communication hole 17a.

Accordingly, the pressure in the piston chamber 16a is reduced, and the oil pressure in the urging chamber 20 becomes larger than the oil pressure in the piston chamber 16a and the large diameter portion of the housing chamber 16 communicating with the piston chamber 16a. Then, the pilot valve 18 pushes the small-diameter portion 23 on the other end side by a spring by the other holding member 24b locked by the ring 25a and the one holding member 24a that is prevented from moving from one end surface of the biasing chamber 20. It moves to one end side while shrinking S.

Then, as shown in FIG.
When the second communication hole 17b is opened along with the movement of the large diameter portion 18a of the pilot valve 18, the gap between the inner peripheral wall of the spool 3 and the outer peripheral wall of the small diameter portion 18b of the pilot valve 18 causes the second and the second. The first pressure chamber 8 and the drain chamber 9 communicate with each other through the three communication holes 17b and 17c. For this reason, after the hydraulic oil in the first pressure chamber 8 flows out into the drain chamber 9, the oil discharge tank 13
And the pressure in the first pressure chamber 8 is reduced.

Therefore, the flow rate of the working oil flowing from the pump 11 into the first pressure chamber 8 via the orifice E increases, and the amount of oil flowing into the first driving pressure chamber 5 via the pipe F branched from the orifice E Decreases to be smaller than the hydraulic pressure in the second driving pressure chamber 6. Therefore, the spool 3 is moved to one end side, that is, the second movement position on the right side by the oil pressure in the second drive pressure chamber 6.

When the spool 3 moves and the second communication hole 17b reaches the outer peripheral surface of the large diameter portion 18a of the spool 3 as shown in FIG. 5, the second communication hole 17b is closed again, and the first pressure The communication between the chamber 8 and the drain chamber 9 is cut off. Therefore, the hydraulic oil flowing through the orifice E is supplied to the first pressure chamber 8 and the orifice E
Flows uniformly into the first driving pressure chamber 5 via the pipe F branched from the first driving pressure chamber 5, the oil pressure in the first driving pressure chamber 5 becomes equal to the oil pressure in the second driving pressure chamber 6, and the spool 3 It is held at the position shown in FIG. 5, and the switching valve can perform a predetermined operation.

The switching valve described above selectively opens the first and second high-speed on-off valves 14, 27 in accordance with the duty ratio of the pulse signal wave, and is a pilot valve movably disposed in the spool 3.
18 is moved to one end side or the other end side in accordance with the opening amount, and further this movement causes the second or fourth communication holes 17b, 17b, which communicate the inside of the spool 3 with the first or second pressure chambers 8, 10. By opening 17d and connecting the first or second pressure chambers 8, 10 to the drain chamber 9, one of the driving pressure chambers 5, 6 is depressurized. As a result, the spool 3 moves toward the depressurized side by an amount that closes the second or fourth communication hole 17b, 17d, and the movement of the spool 3 is stopped.

Therefore, the stop of the spool 3 after the movement is
This is achieved by closing the communication holes 17b and 17d obtained by own movement. For this reason, when a moving force larger than these frictional forces acts on the spool 3 that moves while sliding on the inner peripheral wall of the valve chamber 2 and the outer peripheral wall of the pilot valve 18,
During the movement of the spool 3, a large force in the reverse direction does not act. Therefore, as shown in FIG. 6, when the spool 3 is moved, the pushing spring S in the biasing chamber 20 is provided between the displacement command value corresponding to the duty ratio of the pulse wave signal and the stop position of the spool 3. Only a small error due to force or the like is generated, and the movement of the spool 3 with high accuracy is realized. Therefore, unlike the conventional product, opening and closing of the two discharge ports are performed at accurate timing.

Effect of the Invention As described in detail above, according to the present invention, the spool can be stopped regardless of the frictional force applied when the spool is moved, and the error between the desired stop position and the actual stop position is reduced. It has an extremely small effect.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a state in which the directional control valve according to the present invention is in a neutral position, FIG. 2 is a sectional view showing a state in which a pilot valve has moved rightward, and FIG. FIG. 4 is a cross-sectional view showing a state in which the spool has moved rightward, FIG. 4 is a cross-sectional view showing a state in which the pilot valve has moved leftward, and FIG. 5 is a state showing a state in which the spool has moved leftward after the state of FIG. FIG. 6 is a diagram illustrating the use characteristics of the directional control valve according to the present invention, FIG. 7 (a) is a cross-sectional diagram illustrating a conventional example, and FIG. 7 (b) is a diagram of FIG. 7 (a). 8) is a cross-sectional view showing a change in the characteristic of FIG. Housing 1, valve chamber 2, spool 3, first driving pressure chamber 5, second driving pressure chamber 6, decompression chamber 7 as first decompression chamber, first pressure chamber 8, drain chamber 9, second chamber Pressure chamber 10,
A hydraulic pump 11 as a pressure source, an electromagnetic first high-speed on-off valve 14 as a first source pressure valve, a pilot valve 18 as a pilot spool, a biasing chamber 20 as a second decompression chamber, a small diameter portion
23, a holding member 24a, a holding member 24b, and a pressing spring S (holding means is constituted by the small diameter portion 23, the holding member 24a, the holding member 24b, and the pressing spring S).

Claims (1)

(57) [Claims] 1. A pressure source, a spool movably disposed in a valve chamber of a housing, and first and second connection conduits defined by spools at both ends of the valve chamber, the first and second connecting lines being connected to the pressure source. A first and a second drive pressure chambers connected via the first and second drive pressure chambers for holding the spool stationary by the opposing internal pressure, and for moving the spool based on the differential pressure when a difference occurs in the internal pressure; The first and second driving pressure chambers are communicated with the valve chamber, are defined by spools corresponding to the first and second driving pressure chambers, and are connected to the first and second connection pipes. The connection is made to communicate with the corresponding driving pressure chamber, and the same pressure as the corresponding driving pressure chamber is always supplied from the pressure source, and when the internal pressure is reduced, the pressure source increases the pressure greater than the corresponding driving pressure chamber. From First and second pressure chambers for reducing the pressure in the corresponding driving pressure chambers by performing the first movement position and the second movement position sandwiching the original position and the original position in the spool. A pilot spool movably arranged between the pilot spool, holding means for always holding the pilot spool in the original position, and a pressure source provided on one side of the pilot spool in correspondence with the first pressure chamber. Connected to
The first pressure reducing valve is selectively connected and disconnected to the first pressure reducing valve.
When the internal pressure is reduced, the first pressure reducing chamber moves the pilot spool to the first moving position against the holding force of the holding means, and the second pressure reducing chamber moves on the other side of the pilot spool. A pressure chamber is provided corresponding to the pressure chamber and connected to a pressure source, selectively connected to and disconnected from the second pressure reducing valve, and when connected to the second pressure reducing valve, the internal pressure is reduced. A second decompression chamber for moving the pilot spool to a second movement position against the force of the holding means; and, when the pilot spool is at the original position, the pilot spool causes the first and second pressure chambers to move relative to the first and second pressure chambers. When the pilot spool is in the first position, it is communicated with the second pressure chamber to reduce the internal pressure of the second pressure chamber when the pilot spool is in the first position, and the first pressure chamber is in the second position when the pilot spool is in the second position. Communicated with And a drain chamber for reducing the internal pressure of the first pressure chamber.