JPH01120492A - Direction change over valve - Google Patents

Abstract

PURPOSE:To change pressure at a change over point according to increasing and decreasing direction of change over pressure by making land portion having larger pressure receiving area than pressure receiving area for changing over pressure correspond to a port for pressure making change over pressure have a width. CONSTITUTION:A spool 1 has land portions 1a-1d in large diameter and a spring seat 1e in one body on one end. A coil spring 4 for opposing to changing over pressure is fixed between the spring seat 1e and the land 1d. Land portions 1a-1d are made to oppose to a port for pressure Ps making changing over pressure have a width and it is made so as to act offset force on a position of spool degree delta0 according to differential-area in the spool 1. In this way, pressure value with which is performed opening and closing valve can be changed according to direction of changing over pressure Pe.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a directional control valve, and particularly to a directional control valve that can change the switching point and vary the timing of opening and closing.

(Prior art and its problems) Conventional hydraulic switching valves, check valves, etc. have the following problems because the direction of opening and closing of the valve is determined by the magnitude relationship between spring force and pressure.

1) The switching pressure is constant (Figure 3 Po).

2) As shown in FIG. 3, since the ON pressure and the OFF pressure are the same, a chattering phenomenon may occur at pressures near the switching pressure.

3) Depending on the usage conditions, it may be necessary to create a difference between the ON pressure and the OFF pressure, but in this case, it is difficult to achieve this with conventional hydraulic switching valves, check valves, etc. It is necessary to use a combination of multiple valves.

(Object of the Invention) In view of the problems of the prior art, it is an object of the present invention to provide a directional control valve that can change the switching point in the directional control valve and vary the timing of opening and closing.

(Solving Means by the Invention) A spool is fitted into a valve hole provided in the sleeve via a spring that opposes the switching pressure Pe, and the spool is fitted with the switching pressure Pe.
A land portion having a pressure receiving area ΔA larger than the pressure receiving area Ae is provided, and the pressure P that makes the land portion have a width in the switching pressure is provided.
The offset force ΔA-Ps is made to work at the position of the spool displacement δo due to the area difference ΔA of the spools, and the pressure value for opening and closing the valve can be changed depending on the direction of the switching pressure. did.

(Example) This will be explained with reference to FIG. A spool 1 is fitted into a valve hole 3 provided in a sleeve 2.

The spool 1 has large diameter land portions 1a, lb, lc,
ld, and has an integral spring seat 1e at one end. A coil spring 4 for counteracting the switching pressure is fitted between the spring seat 1e and the land portion 1d. 5 is 3[! ! The resistance to the spool 1 can be adjusted by screwing or loosening a screw into the top of the spring seat 1e. 6 is a casing, 7 is a cover provided with a switching pressure supply port, and 8 is a cover on the adjusting screw side.

The valve hole 3 has a supply port 9 for a pressure P4 selected by switching, a supply port 10 for a control pressure Pc, and a supply port 11 for a pressure P2 selected by switching, and a supply pressure to be supplied to give a width to the switching pressure. A port 12 of Ps and a port 13 communicating with tank P are provided. Note that 14 is the switching pressure P
This is the supply port of e.

(Operation) 1) When switching pressure Pe=O, pressure P is supplied to control pressure Pc in the state shown in FIG.

2) When the switching pressure Pe increases as shown in FIG. 2, the switching pressure Pe pushes the spool 1 to the left of the spring 4,
The displacement is made to a point where the spring force and the pressure Pe are balanced.

If the effective pressure receiving area receiving the switching pressure Pe is Ae, and the spool displacement is δ, then PeAe=δ (where: spring constant).

3) Next, as shown in the figure, the spool 1 has a switching pressure Pe=P. When the displacement reaches δ=δo, the supply pressure Ps at port 1
2 opens and PT port 13 closes.

Therefore, the force opposing the spring force at this point is given by: kδ=ΔA-Ps+AePe...■ds:
Diameter of land portion 1b, dT: Diameter of land portion 1a Therefore, kδo = A e P 2゜, P2゜ = δo/A
From the switching pressure P2° that becomes e, when Pe≧P2°,
The pressure of P2 is always selectively added to Pc.

4) When the switching pressure Pe exceeds P2° once and then decreases (Fig. 4), Pe=P. Since there is additional pressure even if
-Pe, and the pressure selection remains P2. Furthermore, Pe decreases, □(Δ
A−Ps+AePe)<δo.

Pe=P□. When the pressure decreases to , the Ps port closes and the PT port opens as there is no additional pressure. At this time, Pzo=
(kδo-ΔA-Ps)<P2゜Ae Pe≦P engineering. Then the pressure of Pl is always selected.

By the method described above, the set value of the switching pressure Pe that opens and closes the valve can be arbitrarily changed depending on the direction of increase or decrease of the switching pressure Pe.

(Effect) A spool is fitted into the valve hole provided in the sleeve via a spring that opposes the switching pressure Pe, and the spool is fitted with the switching pressure Pe.
A land portion having a pressure receiving area ΔA larger than the pressure receiving area Ae is provided, and the pressure P that makes the land portion have a width in the switching pressure is provided.
1) As shown in FIG. 4, the pressure at the switching point can be changed depending on the direction of increasing or decreasing the switching pressure Pe.

2) The pressure at the switching point and the width of the switching pressure can be arbitrarily designed. Moreover, these can be achieved simultaneously with one switching valve.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a directional control valve according to the present invention. FIG. 2 is a graph showing the relationship between switching pressure Pe and spool displacement in the directional switching valve. FIG. 3 shows the operating mode of a conventional directional control valve. FIG. 4 shows the operating mode of the directional control valve according to the present invention. In the figure: 1 Spools la, lb, lc, ld Large diameter land portion 1e Spring seat 2 Sleeve 3 Valve hole
4 Coil spring 5 Adjustment screw 6 Casing 7 Cover 8 Cover 9 Supply port 1 (L Pc supply port 11
P2 supply port 12 Ps supply port 13P,
Port 14 leading to v Supply port Pe Switching pressure Ps Supply pressure P,,P,
Pressure Pc Control pressure P□ Above tank Figure 2

Claims (1)

[Claims] A spool is inserted into the valve hole provided in the sleeve via a spring that opposes the switching pressure Pe, and the switching pressure P is applied to the spool.
A land portion having a pressure receiving area ΔA larger than the pressure receiving area Ae of e is provided, and the land portion is made to correspond to a port of pressure Ps that gives a width to the switching pressure. A directional switching valve that operates at a position of displacement δo and that can change the pressure value for opening and closing the valve depending on the direction of switching pressure.