JPH0440057Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a switching valve that has a function of self-maintaining the position of an operated switching valve, and is used in a control circuit of a hydraulic cylinder, etc.

[Conventional technology]

An example of a machine using this type of switching valve is a pump for pumping a highly viscous substance such as fresh concrete, as shown in FIG.

This pump has a hopper to which a highly viscous substance is supplied, and two pumping sections that suck the highly viscous substance from the hopper and forcefully feed it to a discharge port.
In FIG. 5, 43 and 44 are valve cylinders that drive valves that open and close between the hopper and the pressure-feeding section, and 40 and 41 are pressure-feeding cylinders that operate the pressure-feeding section. 45 is a switching valve for supplying and discharging pressure oil to the valve cylinders 43 and 44; when the switching valve 45 is switched from one side to the other, one of the piston rods of the valve cylinders 43 and 44 extends and the other contracts;
This expansion and contraction of the piston rod opens and closes the gap between the hopper and the pumping section, and between the pumping section and the discharge port. The pressure chambers on the rod side of the pressure feeding cylinders 40, 41 are connected to a pressure oil source (accumulator ACC) via a stop valve, and the pressure chamber on the head side is connected to a hydraulic source and tank via a switching valve 46. Activate.

The aforementioned switching valves 45 and 46 are pilot type switching valves, and the pilot chamber thereof is connected to the output port of the switching valve 30. The switching valve 30 is also a pilot type switching valve, and the pilot part is connected to the pressure feeding cylinders 40, 4.
It is connected to pilot switching valves 22 and 23 that detect when the piston No. 1 reaches the stroke end.

The pump with the above configuration has pressure feeding cylinders 40, 41
is operated in the direction of the arrow, and the piston of the pressure feed cylinder 41 operates the pilot switching valve 23. Pilot pressure oil is supplied from the pilot valve 23 to the pilot switching valve 30, and the pilot switching valve 30 is moved away from the position shown in FIG. The position changes. Therefore, the switching valves 45 and 46 are similarly switched from the position shown in FIG. 5 to another position. Therefore, the pressure feeding cylinder 40,
41 and the valve cylinders 43, 44 are switched in the opposite direction to that shown in FIG. Next, when the pilot switching valve 22 is operated, the switching valve 30 is operated again, and the pressure-feeding cylinders 40, 41, the valve cylinder 43,
The operation of 44 is in the direction shown in FIG.

In this pump, in order to repeat the above operation sequentially, the switching valve 30 is operated by the pilot valve 22 or 2.
When the hydraulic pressure from the pilot valve 23 or 22 is applied, it is necessary to quickly switch to one position and hold that position until the hydraulic pressure from the pilot valve 23 or 22 is applied.For this purpose, the switching valve shown in FIG. It is used.

This switching valve 30 has a spool 4' slidably inserted into a valve body 2', and a pilot chamber L at both ends of the spool 4'.
1, L2, a brake section 35 (FIG. 7), and a detent section 36. The brake section 35 has rubbers 33a and 33b arranged on both sides of the spool 4', and presses the rubbers 33a and 33b with screws 37a and 37b to apply a braking force to prevent the spool 4' from easily moving. . The detent device 36 is formed by grooves 31a, 31b of the spool 4' and balls 32 pressed by springs, and holds the spool 4' in its position by fitting the balls 32 into the grooves 31a, 31b. It is the composition.

Pressure oil is supplied to the pilot chamber L1 or L2 in the switching valve 30, and when the pressing force due to the oil pressure overcomes the resistance force of the detent device 36 and the brake device 35, it operates to the left or right. During this operation, the ball 32 of the daint device 36
When the ball 32 is removed from the groove 31a, the resistance force becomes correspondingly smaller, so that the ball 32 operates quickly until the ball 32 is inserted into the groove 31b, resulting in so-called snap action switching. Then, stable switching is ensured by supplying a predetermined hydraulic pressure that overcomes the starting force of the snap action and the brake device to the pilot chamber L1 or L2.

In addition, as a switching valve to ensure the switching position,
In Utility Model Publication No. 56-30778, a central pump port, output ports on both sides of the central pump port, and tank ports on both sides are provided in the through hole of the valve body, and a spool is slidably installed in this through hole. A pilot chamber for operating the spool and a holding chamber for securing the operating position of the spool are provided in order from the end at both ends, and the spool is operated by supplying and discharging pressure oil to the pilot chamber to change the direction of the flow of pressure oil and hold it. A switching valve is disclosed that has a self-holding function that maintains the switching position of a spool by supplying and discharging pressurized oil to a chamber.

In this switching valve, each of the holding chambers is directly connected to the output port of the actuator. That is, when pressure oil is supplied to one side of the pilot chamber and the spool is operated, one of the actuator output ports is connected to the atmosphere and the other is connected to a pressure oil source. Therefore, the holding chamber on the pilot chamber side to which pressure oil is supplied is connected to the output port connected to the pressure oil source, and even if the pilot pressure disappears, the working pressure of the actuator acts on the holding chamber to maintain the switching position. At this time,
The other holding chamber is connected to an output port that is open to the atmosphere, and pressure is released. When the supply of fluid pressure to the pilot chamber is switched, the pressure states of the holding chambers become completely reversed.

[The problem that the idea aims to solve]

The switching valve 30 in the above-mentioned prior art uses a detent device and a brake device to maintain the switching position of the spool and ensure the stability of the switching operation. However, since the detent device and the brake device are configured to apply frictional force to the spool, the ball 32 of the detent device is
, grooves 31a, 31b, and rubber 33 of the brake device.
a and 33b wear out and the frictional force decreases, causing the above-mentioned snap action to no longer operate, and in extreme cases, the switching position cannot be maintained and switching may occur due to machine vibration or pressure fluctuations to the pilot section. There are problems such as valve switching.

In addition, Utility Model Publication No. 56-30778 applies the operating pressure after switching the output port that operates the actuator to the holding chamber to maintain the switching position of the spool, so it is a snap action that can switch quickly. The problem is that it doesn't work. Furthermore, due to the self-propelling of the actuator (self-propelling in the same direction as the operating direction by hydraulic pressure), oil pressure fluctuation occurs at the output port, and there is also the problem that the holding force of the spool also fluctuates.

[Means to solve the problem]

In this invention, a central pump port, output ports at both ends, and tank ports on both sides are provided in the through hole of the valve body, a spool is slidably installed in this through hole, and a spool is installed at both ends of the spool. A pilot chamber to operate and a holding chamber to maintain the operating position of the spool are provided in order from the end, and the spool is operated by supplying and discharging pressure oil to the pilot chamber to switch the flow direction of pressure oil and supply pressure oil to the holding chamber. In the switching valve having a self-holding function that maintains the switching position of the spool by discharging the spool,
A center hole is provided with which the pump port always communicates, and vertical holes are provided on both sides of the center hole that communicate with the center hole and open to the outer periphery of the spool, one of which is connected to the spool by the operation of the spool. When opening into the holding chamber, the other side is closed by the valve body, and at both ends of the spool, the vertical hole is closed by the valve body when opening into the holding chamber,
The switching valve has a self-holding function and is provided with a slit that communicates the holding chamber with a tank port when the vertical hole is closed by the valve body.

[Effect]

In the switching valve according to the present invention, when the spool is operated in either direction by pilot hydraulic pressure, one of the holding chambers provided at both ends of the spool is connected to the pump port through the center hole of the spool, and the other is connected to the pump port through the center hole of the spool. is connected to the tank port through a slit, so even if the load acting on the actuator fluctuates, the hydraulic pressure at the output port of the switching valve is unlikely to act on the holding chamber. In other words, pressure oil flows from the pump port to the output port via the spool, so due to the pressure loss due to that flow, the oil pressure at the load port is kept sufficiently higher than the tank port, and the other holding chamber is connected to the tank port. Since they are connected, the oil pressure in the holding chamber acts in the same direction as the pilot oil pressure. Therefore, the self-holding action is reliably performed. Further, as described above, since the difference in the hydraulic pressure acting on the two holding chambers is a large pressure difference between the pump discharge pressure and the tank pressure, the spool can be switched extremely quickly.

〔Example〕

Examples of the present invention will be described below.

FIG. 1 shows an embodiment in which a switching valve according to the present invention is used in a control circuit for controlling the reciprocating motion of a hydraulic cylinder 24.

In FIG. 1, 1 is a switching valve, and this switching valve 1 has a central pump port 5, output ports 8, 9 on both sides thereof, and tank ports 6, 7 on both sides in a through hole 2a of a valve body 2. A spool 4 is slidably provided in the through hole 2a, and a pilot chamber 1 for operating the spool 4 is provided at both ends of the spool 4.
1 and 12 and holding chambers 13 and 14 for holding the operating position of the spool 4 are provided in order from the end.

A center hole 17 is provided in the center of the spool 4 and is always in communication with the pump port 5 via a hole 15 that is always open to the pump port 5. Also, vertical holes 16a, 16 are provided at both ends of the center hole 17, which communicate with the center hole 17 and open to the outer periphery of the spool 4.
b. One of the vertical holes 16a, 16b is opened to the holding chambers 13, 1 by the operation of the spool 4.
4, the other side is closed by the valve body 2 (in the example shown in the first figure, the vertical hole 16
b opens into the holding chamber 13, and the vertical hole 16a opens into the valve body 2.
In the example shown in the third figure, the vertical hole 16a is closed.
opens into the holding chamber 14, and the vertical hole 16b is closed by the valve body 2). Further, at both ends of the spool 4, vertical holes 16a, 16b are closed by the valve body 2 when opened to the holding chambers 13, 14.
slits 20, 21 that communicate the holding chambers 13, 14 with the tank ports 6, 7 when the valve body 2 is closed by the valve body 2;
(In the example shown in the first diagram, the vertical hole 16
b is a slit 20 that is closed by the valve body 2 when it opens into the holding chamber 13, and a slit 21 that communicates the holding chamber 14 with the tank port 7 when the vertical hole 16a is closed by the valve body 2. In the example, vertical hole 16
(a) is a slit 21 that is closed by the valve body 2 when the vertical hole 16b opens into the holding chamber 14, and a slit 20 that communicates the holding chamber 13 with the tank port 6 when the vertical hole 16b is closed by the valve body 2).

The switching position of the switching valve 1 shown in FIG.
This shows the position where the switch has switched to the left side.

In this switching position, pump port 5 is connected to output port 9 and output port 8 is connected to tank port 6.
connected to. In addition, the holding chamber 13 has a hole 15 and a center hole 1.
7 and the vertical hole 16b, and the holding chamber 14 is connected to the tank port 7 through the slit 21. In addition, the holding chambers 13 and 14
The spool 4 and the large diameter portion 18 provided at its end,
It is formed by the difference in cross-sectional area from 19. Therefore, its pressure receiving area is smaller than that of the pilot chambers 11 and 12.

In the hydraulic cylinder 24, when the switching valve 1 is in the position shown in FIG. 1, pressure oil is supplied to the hydraulic chamber 24a and pressure oil in the hydraulic chamber 24b is discharged to the tank, so that the piston 25 moves in the direction of arrow a. do. When the piston 25 reaches its left stroke end and the pilot valve 22 is operated by the piston 25, pressure oil is supplied to the pilot chamber 11 and the holding chamber 1
Hydraulic pressure equivalent to the hydraulic pressure acting on 3 is applied.
Therefore, spool 4 begins to move to the right, and the second
As shown in the figure, when the spool 4 reaches the position where it closes the pump port 5 and the tank ports 6 and 7, the holding chambers 13 and 14 are connected to the tank ports 6 and 7 through the slits 20 and 21, and the center hole 17 The vertical holes 16a and 16b that are open to the valve body 2 are closed by the valve body 2. Therefore, the central hole 17 is charged with pressure oil corresponding to the pump discharge pressure due to the closed state. Then, when moving further to the right from the position shown in FIG. The vertical hole 16a is connected to the tank port 6 through the valve body 2.
remains closed. Therefore, the pushing force of the pressure oil corresponding to the pump discharge pressure in the holding chamber 14 is added to the pushing force of the hydraulic pressure acting on the pilot chamber 11 on the spool 4, so that the spool 4 is pushed up by the pushing up of the holding chamber 14. is a snap action that switches quickly. Furthermore, since the pilot chamber 12 is connected to the tank via the pilot valve 23, even if the hydraulic pressure acting on the pilot chamber 11 disappears, the holding chamber 14
The spool 4 is self-propelled by the hydraulic pressure acting on the spool 4. Further, when the spool 4 reaches the rightward switching position (FIG. 3), that position is held by the force of the holding chamber 14.

The spool 4 of the switching valve 1 moves from the position shown in Figure 2 to the third position.
When the position shown is reached, pump port 5 is connected to output port 8, and output port 9 is connected to tank port 7.
Since it is connected to the hydraulic cylinder 24 and the hydraulic chamber 24
Pressure oil is supplied to b, and the pressure oil in the hydraulic chamber 24a flows out to the tank, so the piston 25 moves in the direction of arrow b.
The direction changes. When the piston 25 reaches the stroke end in the direction of arrow b and the pilot valve 23 is operated, hydraulic pressure acts on the pilot chamber 12 and the spool 4 moves from the position shown in FIG. 3 to the position shown in FIG. Switch to the position shown in the illustration.

In addition, in FIG. 2, the valve body 2 or the holding chamber 1 of the vertical holes 16a, 16b and the slits 20, 21
By shifting the positional relationship of the openings 2 and 13, the timing at which the aforementioned snap action acts can be changed.

Pilot chambers 11 and 12 and holding chamber 1 in the above explanation
The relationship of pressure receiving area with holding chambers 13 and 14 is
However, the pressure receiving area is determined by the relationship of the pilot oil pressure, and if the oil pressure acting on the pilot chambers 11 and 12 can be made higher than the oil pressure acting on the holding chamber, the pressure receiving area relationship is determined. does not have to be as above.

FIG. 4 shows another embodiment, and FIGS.
This is a modified version of the switching valve 1 explained with reference to FIG.
3 and auxiliary pilot chambers 27 and 29 are installed in series. In this auxiliary pilot compartment 27, 29,
By supplying and discharging pilot pressure oil with the manual switching valve 34, the spool 4 can be operated in any direction other than the operation of the pilot valve.

The switching valve 1' shown in FIG.
12 is provided with auxiliary pilot chambers 27, 29 via pistons 26, 28. Since the construction and operation are the same as those explained with reference to FIGS. 1 to 3, the explanation thereof will be omitted. The position shown in FIG. 4 is the same as the position shown in FIG. 1, so the piston 25 of the hydraulic cylinder 24 is operating in the direction of arrow a.
At this time, when the manual switching valve 34 is operated to the switching position 34a, the switching valve 1' switches to the auxiliary pilot chamber 27.
Since the hydraulic pressure acts on the pilot chamber 11, the result is the same as when the hydraulic pressure acts on the pilot chamber 11, and the switching valve 1' moves the spool 4 in the right direction by the same effect as explained in FIGS. 2 and 3. The piston 25 of the hydraulic cylinder 24a is operated in the same position as in FIG. 3, and the piston 25 of the hydraulic cylinder 24a is switched in the direction of arrow b from that position.

If the switching valve 1' shown in FIG. 4 and having the above-mentioned function is replaced with the switching valve 30 shown in FIG.
4 can be operated to control the strokes of the pressure feeding cylinders 40, 41.

[Effect of idea]

In the present invention, the spool is provided with a center hole through which the pump port is constantly connected, and vertical holes are provided at both ends of the center hole that communicate with the center hole and open on the outer periphery of the spool. When the spool opens into the holding chamber by actuation, the other side is closed by the valve body, and at both ends of the spool, a vertical hole is closed by the valve body when it opens into the holding chamber, and a vertical hole is closed by the valve body. A slit is provided to communicate the holding chamber with the tank port, and the push-up of the holding chamber into which pressurized oil from the pump port is introduced enables a so-called snap action in which the spool can be quickly switched. Since there are no frictional parts, there is no fear that the snap action will stop working due to wear due to repeated operation of the switching valve, and a constant snap action can be maintained for a long period of time. Furthermore, by changing the positions of the vertical holes and slits in the spool, the timing at which the snap action is actuated can be easily changed at which position in the amount of movement of the spool. Furthermore, since the switching position of the spool is maintained at the pump port having a higher pressure than the output port, the switching position is reliably maintained.

[Brief explanation of the drawing]

FIG. 1 is a control circuit diagram of a hydraulic cylinder including a sectional view of the switching valve according to the present invention, FIGS. 2 and 3 are explanatory diagrams of the operation of the switching valve shown in FIG. 1, and FIG. 5 is a sectional view of another embodiment of the invention, FIG. 5 is a circuit diagram of a pump for pumping a highly viscous substance, and FIG. 6 is a sectional view of a part of a conventional switching valve used in the circuit shown in FIG. The front view shown in Figure 7 is taken from B-B in Figure 6.
A sectional view showing a cross section. 1...Switching valve, 2...Valve body, 4...Spool, 5...Pump port, 7...Tank port,
11, 12... Pilot chamber, 13, 14... Holding chamber, 16a, 16b... Vertical hole, 17... Center hole, 20, 21... Slit.

Claims (1)

[Scope of Claim for Utility Model Registration] A central pump port, output ports at both ends of the central pump port, and tank ports on both sides are provided in the through hole of the valve body, a spool is slidably provided in the through hole, and the spool is provided at both ends A pilot chamber for operating the spool and a holding chamber for maintaining the operating position of the spool are provided in order from the end, and by supplying and discharging pressure oil to the pilot chamber, the spool is operated and the flow direction of the pressure oil is switched, and the flow direction of the pressure oil is transferred to the holding chamber. In the switching valve having a self-holding function that maintains the switching position of the spool by supplying and discharging pressurized oil, the spool is provided with a center hole with which the pump port is constantly communicated, and both ends of the center hole are provided with a center hole that communicates with the center hole. A vertical hole is provided on the outer periphery of the spool, and when one of the vertical holes opens into the holding chamber by the spool operation, the other is closed by the valve body, and a vertical hole is provided at both ends of the spool. is characterized in that it is provided with a slit that is closed by the valve body when the vertical hole opens into the holding chamber, and that communicates the holding chamber with the tank port when the vertical hole is closed by the valve body. A switching valve with a holding function.