JPS58196371A - Direction change-over valve - Google Patents

Abstract

PURPOSE:To stabilize the operation of an actuator by arranging in a spool two check valves for affording communication between two ports connected to the actuator and opening two check valves when pressure in one port exceeds that in the other port. CONSTITUTION:Since working oil flow flowing from a port A to A tank port T is limitted by a throttle portion 25d, oil pressure in the port A is increased to open a check valve 40 in the extension of a hydraulic cylinder. When the check valve 40 is opened, pressurized oil in the port A opens also a check valve 50 to afford communication between the ports A and B so that a portion of pressurized oil in the port A is circulated to the port B to prevent pressure reduction in the port B. As a result, the extension speed of the hydraulic cylinder is regulated so that the operation of the hydraulic cylinder is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a directional control valve that allows pressure oil to flow back to the other boat when the oil pressure of one boat becomes high.

Cargo handling work using a hydraulic system For example, in a cargo handling work in which the top of a load 4 is lowered by a hydraulic cylinder 1 as shown in FIG. When raising the cylinder 1, the cylinder 1 operates stably and there are no side problems. However, on the contrary, Bo)A
When pressure oil is supplied to B to extend the cylinder 1 and lower the load 4, the force of the cylinder 10 moving downward is applied to the load 4.
As a result, the cylinder 1 is pulled downward by the load 4.

If such an external force is applied, the operation of the cylinder 1 will become unstable, and if the load 4 is too heavy, the expansion speed of the cylinder 1, that is, the descending speed of the load 4 will become too fast, which is extremely dangerous. This causes a drop in the pressure in the upper cylinder chamber 3, causing bubbles to form in the hydraulic oil, causing problems such as the cargo wobbling when the cylinder is stopped, and the cargo suddenly moving when trying to raise it. .

Various measures have been taken to solve this problem, but all of them have disadvantages such as the complicated configuration of the hydraulic circuit and the resulting high single-track pitch.

The present invention has been made for the purpose of eliminating the above-mentioned drawbacks of the conventional directional control valve, and its purpose is to stabilize the operation of the actuator by using the housing of the conventional directional control valve as is and replacing only the spool. It is something. In order to achieve this object, the present invention provides a directional control valve that switches the position of a spool movably inserted into a housing to switch the direction of pressurized oil supplied from the pump boat to the A boat and the B boat. a hollow chamber formed in the axial direction within the spool, and first and second check valves disposed within the hollow chamber, the upstream side of which is connected to the hollow chamber, and the downstream side of which is connected to the A and B ports, respectively; A first through hole is formed behind the first check valve of the spool and communicates with the A boat in the neutral position of the spoon and closes the first check valve, and the stool is operated with one side pressure. a 20th through hole that connects the back of the first check valve to a tank boat when the A boat is turned on and opens the first check valve when the pressure of the A boat becomes high; a constriction part provided in a constriction communicating the A port and the tank boat to limit the flow rate of pressure oil from the A boat to the tank boat to increase the oil pressure of the A boat; Said 1st. The second check valve is closed to shut off the A and B boats and the tank boat, and when the spool is operated on one side and the pressure at the A port becomes high, the first check valve is closed. This book provides a directional switching valve in which an actuator is operated stably by opening the check valve of No. 2 and circulating pressure oil from the A boat to the B boat through the hollow chamber.
Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 shows a longitudinal section of the directional control valve according to the present invention, in which a hollow chamber, for example, a hole 12, is formed penetrating through the directional control valve 11.
A boat that communicates with 4. B, a pump boat P, a tank boat T, and a neutral boat N are formed. The pump boat P is communicated with an oil passage Pα formed in the housing 11, and the oil passage pa is connected to a hydraulic pump (not shown) YC via an oil passage not shown. The tank boat T is also communicated with an oil passage (not shown) formed in the tank 11, and the oil passage is connected to an oil tank (not shown).

The neutral boat N is divided into six ports N, ~N, which communicate with each other within the housing 11, and N, , N, is the neutral boat on the upstream side, and is connected to the housing 11. The oil passage is connected to a downstream neutral boat of a control valve (not shown) connected to the upstream side of the hydraulic circuit. At the neutral port of the central boat N, ld lower flH,
It communicates with an oil passage (not shown) formed in the housing 11, and the oil passage is connected to the downstream side of the hydraulic circuit.

Pump boat PK in housing 11 is check valve 30
is disposed, and the valve body 31 closes the communicating portion ph between the pump boat P and the oil passage pa by the pressing force of the valve ring 32. When the oil pressure of the oil passage pa exceeds the pressing force of the gooseberry/g 32, the pressure body 31 is pushed up, and the pump boat P
The pressure oil is fitl, 6.

two boats, 4. B is an actuator for each port 1, 4 of the hydraulic cylinder 1 in Figure 1. IZ? It is connected to the. These ports A and B = When one port becomes an outflow port, the other port becomes an inflow port.

20 spools are movably inserted into holes 12 of the housing 11, and lands 22 to 26 are formed at predetermined locations. The lands 22 and 25 close the pump port P when the spool 20 is in the neutral position shown in the figure. A notch 25C is formed at the end of the land 25 on the constriction 927 side, and a constricted portion 25d is formed between the land 25 and the inner wall surface of the hole 12. One end of this converging portion 25d is connected to the spool 20.
The other end is always open to port A regardless of the position of the spool 20, and the other end is disconnected from the pump boat T when the spool 20 is in the neutral position, and when the spool 20 moves in the direction of arrow F and reaches the ``push'' position, it opens to the ``tank boat''. The tank port T and port A are communicated with each other.

A through hole 21 is formed at the axial center of the spool 20, and both open ends 21'α and 21b of this hole 210 are concentric holes that are larger than the main hole 21. A plurality of holes 27α are formed radially in the bottom end sides of these holes 21g and 21, respectively.

261 through the constriction 27. The outer peripheral surface of the land 26 is opened at a predetermined position tK. When the spool 20 is in the illustrated neutral position, the hole 2711 faces the port A, and the hole 26α is closed by the inner wall surface between the port B and the tank port T of the hole 12.

A check valve 40 is disposed in the hole 21a, and the bottom end of the hole 42 formed at a precise position in the valve body 41 is connected to the check valve through a plurality of holes 43 formed radially in the radial direction. body 4
It opens into an annular groove 44 formed on the outer circumferential surface of 1. One end of the spring 45 is in contact with the bottom of the hole 42, and the other end is in contact with the end surface of the stopper 29 fixed to the open end of the spool 20 at the opening 21Z. It is pressed against the stepped part. In this state, holes 21 and 2
74 is completely shut off by the valve body 41.

Two holes 25α and 25b are bored in the land 25 of the spool 20, communicating with the hole 21a from the outer periphery. The m-opening ends of these holes 254, 25j face the annular groove 44 of the valve body 41, and the other open end of the hole 25α communicates with port A at the spool neutral position shown, and the other side of the hole 25b The open end is the hole 12 between port A and tank boat T.
is closed by the inner wall of the

A check valve 50 is disposed within the hole 21b, and the bottom end of the hole 52 bored at the axial center position of the valve body 51 is connected to the bottom end of the hole 52 through a plurality of holes 53 drilled radially in the radial direction. The valve body 5
It opens on the outer peripheral surface of 1.

One end of the spring 55 is in contact with a step formed in the hole 53, and the other end is in contact with a stopper fitted in the open end of the hole 21A of the spool 20, so that the valve body 51 is connected to the holes 21 and 21. 6
It is pressed against the stepped part. In this state, the holes 21 and 26α are blocked by the valve body 51. The spool 20 can be freely moved in the direction of the arrow E or F within the hole 12 of the housing 11 as described above by operating the operating lever 15 (FIG. 3) attached to the end 20hKR1. The spool 2o is the operating lever 15
When not operated, it is positioned at the neutral position 11 shown in the figure by a soft spring 16 (FIG. 3).

In this configuration, when the spool 2o is in the neutral position W111oc shown in FIGS. 2 and 3, the pump boat P is blocked by the land 22.23, and the pump boat P and ports A and B are connected to each other. It is disconnected. The pressure oil in port A passes through the hole 254 in the 2° valve body 41.
enters the annular groove 44 and presses the valve body 41 from behind,
Check valve 4° is closed. When the check valve 40 is closed, the ball 1- is in the hole 21 of the spool 20.
Pressure oil from A does not flow in, and the check valve 5o is closed. Refreshingly, in this neutral position, the boat, 1°B, and the tank boat T are connected to each other by the land 25.26, so the operating γU+ of ports A and H does not flow to the tank boat TK, and the hydraulic pressure /S/Rail 1 (FIG. 1) is held in place. (The hydraulic oil flowing into the directional control valve 10 from the upstream side of the hydraulic circuit passes through the neutral boat N and flows out to the downstream side.

When the spool 20 is pulled in the direction of the arrow E by lever operation, it is switched to the position 10J shown in FIG. T is communicated with through the constricted portion 28. At the same time, upstream neutral boat N,
, N, and the downstream neutral boat N, are land 22.2
4, and the oil passage on the upstream side and the wave path on the downstream side are blocked. Further, the check valves 40 and 50 are closed as in the case of the neutral position.

Oil path Pα from the hydraulic pump (not shown) to the housing 11
The pressure oil flowing into the check valve 30 pushes up the valve body 31 of the check valve 30 against the spring 32 to open the valve, and the pump boat P
From <, the boat enters 4Kfl through the fin 27. The pressure oil flowing out from the boat A is supplied to the hydraulic cylinder 1 (FIG. 1) K, and the hydraulic cylinder 1 is retracted to raise the cargo 4 (FIG. 1). The return oil from the hydraulic cylinder 1 flows into the boat B and enters the constriction 28. Tank port T
through which it is returned to a tank (not shown). The operation of the directional control valve 1o during retraction of the cylinder is similar to that of a conventional directional control valve.

Contrary to the above, when the spool 20 is pushed in the direction of the arrow F, the directional control valve 10 is switched to tjjt10B as shown in FIG. Pump boat P and boat A
are blocked by the land 22, and the boat A and the tack boat T are communicated with each other via the constricted portion 25d. The hole 25α of the spool 2o opens to the low pressure tank boat T,
This tank boat T and the convex groove 44 of the valve body 41 of the check valve 4o are communicated with each other, and the hole 25h is closed. In this way, the back of the check valve 40 is connected to the low pressure side of the tank boat 1-T, and it can be operated (opened) depending on the pressure oil in the boat A. In addition, upstream neutral boats N, , N,
and downstream neutral port N, and spool 200 land 24
．． 23 from the hydraulic pump to the housing 1
Pressure oil flowing into the oil passage PgH 1 pushes up the valve body 61 against the spring 32, opens the check valve 30, and flows into the boat BK from the bong boat P through the constriction 28. The pressure oil that leaked from this boat B is the hydraulic cylinder 1.
is extended and the load 4 is lowered. This hydraulic cylinder 1
The return oil flows into the boat IK, flows into the tank boat T through the constriction part 25d, and is returned to the tank.

When the hydraulic cylinder 1 is extended, the flow rate of hydraulic oil flowing from the boat A to the tack boat TK is restricted by the throttle portion 25d, so that the oil pressure of the tack boat TK becomes high. When the oil pressure of the boat A becomes high and exceeds the sum of the pressing force of the spring 45 of the check valve 40 and the oil pressure of the tank boat T, pressure is applied from the hole 27a of the spool 20 to the end of the valve body 41. The valve body 41 is moved rightward in the figure by the pressure oil J, and the check valve 40 is opened. When the check valve 40 is opened, pressure oil from the boat A flows into the hole 21 from the hole 27a and the valve body 5 of the check valve 50
1 to the left in the figure against the spring 55 to open the check valve 50. Along with this, boat A
and boat B have holes 27g and 21.26g in spool 20.
A part of the pressure oil of boat A is returned to boat B, and a drop in pressure of boat B is prevented. As a result, the extension of the hydraulic cylinder 10 is restricted and the hydraulic cylinder 10 operates stably.

In this way, even if an external force is applied to the hydraulic cylinder 1, the hydraulic cylinder 1 can be operated stably.

In this embodiment, a case has been described in which a hydraulic cylinder is used as an actuator, but it is needless to say that the present invention is not limited to this.

As explained above, according to the present invention, two check valves that communicate with the two boats connected to the actuator are provided in the subru, and the back of one check valve is communicated with the low pressure side of the tack boat. In addition, a constriction part is provided in the constriction connecting one boat on one side of the check side and the tank boat to limit the amount of oil and increase the pressure in the one boat, thereby increasing the pressure in the one boat. When the pressure exceeds the pressure of the other boat, the two check valves are opened to allow pressure oil to flow back from the one boat to the other boat, thereby reducing the pressure drop in the other boat. This allows the actuator to operate stably even when an external force is applied to the actuator, and also prevents the generation of bubbles in the hydraulic oil. In addition, it is sufficient to simply replace the spool with the one with the above configuration without changing the housing of the conventional directional control valve, resulting in excellent effects such as being able to provide a directional control valve with a simple and inexpensive circuit configuration. There are 8

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of cargo handling work using a hydraulic cylinder, and FIG. 2 is a longitudinal sectional view showing an embodiment of a directional control valve according to the present invention.
FIG. 3 is a block diagram of the directional control valve shown in FIG. 2. 1-... Hydraulic pressure 7 cylinder, 4... Load, 10... Directional switching valve, 11... Housing, 20... Spool,
30°40.50...Check valve, 41.51...Valve body, A. B...Cylinder boat, P...Pump boat, T.
・Tank boat. Applicant: Diesel Kiki Co., Ltd. Representative Patent Attorney: Toshihiko Watanabe

Claims (1)

[Claims] 1. In a directional switching valve that switches the position of a spool that is movably inserted into a housing and switches the direction of pressure oil supplied from a pump boat to an L boat and a B boat, a hollow space is formed in the axial direction in the spool. a first chamber, and a first. a second check valve; a first through hole formed behind the first check valve of the spool and communicating with the l boat in the neutral position of the spool to close the first check valve; a second check valve that connects the back of the first check valve to a tank port when the spool is operated to one side and opens the first check valve when the pressure in the l-boat becomes high; a through hole, and a constriction part provided in the constriction part of the spool that communicates the l-boat and the tank boat to limit the flow rate of pressure oil from the l-boat to the tank port and increase the pressure of the l-boat. In the neutral position of the spool, the first. The second check valve is closed to shut off the A and B ports and the tank port, and when the spool is operated to the one side -j and the pressure of the l boat becomes high, the first check valve is closed. A directional switching valve characterized in that a second check valve is opened to allow pressure oil to flow back from the L boat to the B port through the hollow chamber.