JPH0293104A - Three-way servo valve - Google Patents

Abstract

PURPOSE:To offset the axial force of a spool and improve its control accuracy by connecting respective control rooms to each other on both sides of a high pressure valve room by a displacement of a spool to one side and both control valve rooms to respective low pressure valve rooms by the displacement of the spool to the other side. CONSTITUTION:In a three-way servo valve, control ports 8a, 8b of fluid are connected to a high pressure port 7 and tank ports 19a, 19b selectively in response to displacement of a spool 3 by an electro-magnetic drive part. Control valve rooms 15, 16 connecting to the control ports are positioned in both adjacent places of a high pressure valve room 6 connecting to the high pressure port 7, low pressure valve rooms 17, 18 connecting to the tank ports are positioned on both outsides thereof, lands 4, 5 of the spool 3 are positioned in the high pressure valve room 6 and bucket parts 13, 14 for axial force compensation are formed respectively on both outsides thereof. Lands 20, 21 are arranged so that respective control valve rooms 15, 16 may be connected to each other on both sides of the high pressure valve room 6 by the displacement of the spool 3 to one side and both control valve rooms 15, 16 may be connected to low pressure valve rooms 17, 18 respectively by its displacement to the other side. Thus, the axial forces acting on the spool are offset each other and accurate control can be performed regardless of a flow amount.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement of a three-way servo valve that is most suitable for controlling high-pressure fluid.

(Prior Art) A three-way servo valve for controlling the flow rate or pressure of a working fluid for a high-pressure ram or gloss is disclosed in Japanese Patent Laid-Open No. 101466/1983.

A three-way servo valve selectively connects the working chamber of a ram or jack to a high-pressure source and a low-pressure tank.
The valve spool is connected to an electromagnetic drive unit so that the operating speed can be accurately controlled, and the valve spool makes small strokes in response to an external control current to control the flow of working fluid. Precisely control flow rate and pressure.

(Problem to be solved by the invention) However, since the control fluid is at high pressure, a large axial force acts on the spool along with the flow of the control fluid, and the displacement of the spool cannot accurately correspond to the control current value, causing control problems. Easy to cause confusion.

In order to compensate for this, the spool is formed with a bucket portion (fluid ejection curved surface portion) for axial force compensation.

However, in the past, flow control and axial force compensation were performed at the same edge, so the axial force compensation function was not necessarily sufficient.
In particular, there was a tendency for the compensation ability to be small in low flow areas, and on the contrary, to be too large in high flow areas.

The present invention aims to solve such problems.

(Means for Solving the Problems) The present invention provides a spool that slides via an electromagnetic drive section,
In a three-way servo valve that selectively connects a fluid control port to a high pressure port and a tank port according to the displacement of the spool, control valve chambers connected to the control port are located on both sides of a high pressure valve chamber connected to the high pressure port. are formed respectively,
Further, low pressure valve chambers connected to the tank port are formed on both outsides of each control valve chamber, two lands formed on the spool are located in the high pressure valve chamber, and buckets for axial force compensation are placed on both outsides of these lands. one bucket part is located in one control valve chamber, the other bucket part is located in one low pressure valve chamber, and further located between the control valve chamber in which the bucket part is located and the low pressure valve chamber. A land is provided on the spool, and displacement of the spool to one side communicates with each control valve chamber on both sides of the high-pressure valve chamber, and displacement to the other side causes both control valve chambers to communicate with each low-pressure valve chamber. .

(Function) When supplying high pressure fluid to loads such as rams and jacks,
The high-pressure fluid from the high-pressure valve chamber is divided into two parts, one fluid measuring part and the other axial force compensating part, and exerts axial forces on the spool in opposite directions. The forces cancel each other out.

Also, when high-pressure fluid is discharged, the high-pressure fluid from the control valve chamber is divided into two low-pressure valve chambers, and at this time, axial forces are exerted on the spool in opposite directions, so the axial forces are canceled out in the same way as above. Ru.

Furthermore, since the controlled flow rate is divided into two flows, a large flow rate can be controlled.

(Example) The drawings are cross-sectional views showing embodiments of the present invention.

A spool 3 is slidably inserted into a sliding hole 2 formed in a valve body 1. An electromagnetic drive unit (not shown) is connected to one end of the spool 3, and the spool 3 slides left and right in response to an exciting current of the electromagnetic drive unit.

Two lands 4.5 are formed in the center of the spool 3, and the area surrounded by these lands 4 and 5 is a high pressure valve chamber 6, and a high pressure port 7 connected to a pressure source is opened. .

Located on the left and right sides of the high pressure valve chamber 6, the sliding hole 2 has a control bow) 8
A and 8B are open, and these control ports 8A and 8B merge with each other to form a control passage 8, which is connected to a working chamber 10 of a cylinder 9 constituting a high-pressure ram or jack.

In the cylinder 9, a piston 11 is moved by a working fluid supplied to a working chamber 10, and drives a load 12 in the vertical direction.

Adjacent to both outer sides of the lands 4.5 of the spool 3, the spool 3 is formed with curved bucket portions 13 and 14 for axial force compensation.

Low-pressure valve chambers 17 and 18 are formed on both sides of control valve chambers 15 and 16, which are opened by the control valves 8A and 8B, respectively. Tank ports 19A and 19B open in these low pressure valve chambers 17 and 18, respectively, and these tank ports 19A and 19B merge with each other to form a tank passage 19 that connects to a tank (not shown).

Lands 20 and 21 are formed on the spool 3 near the tank bows 19A and 19B.

As the spool 3 is displaced, one of the lands 4 and 5 in the center controls the flow from the high pressure valve chamber 6 to the control valve chamber 15 at the edge A, which is the axial force compensator at the right end. However, the other land 5 controls the flow from the high pressure valve chamber 6 to the control valve chamber 16 with an edge B serving as a flow metering portion on the right end, and controls flow from the control valve chamber 16 through an edge C serving as an axial force compensation portion on the left end. The control valve D controls the flow to the low pressure valve chamber 18 and serves as the flow metering section at the left end of the land 20.
5 to the low pressure valve chamber 17.

Next, the effect will be explained.

When the spool 3 is in the state shown, the left and right control valve chambers 15
and 16 are both shut off, so that the working chamber 10 of the syringe 9 is filled with working fluid, the piston 11 is held in its position, and the load 12 is stationary.

When raising the load 12, the spool 3 is driven to the left in the figure by an electromagnetic drive section (not shown). As a result, the high-pressure valve chamber 6 and the left and right control valve chambers 15.16 communicate simultaneously, and high-pressure working fluid is ejected from the edges A and B into the control valve chambers 15.16. , 8B to the shilling 9 to move the piston 11 upward.

In this case, the spool 3 receives an axial force to the left in the figure due to the fluid force ejected from the edge B to the control valve chamber 16. On the other hand, when the fluid ejected from the edge A portion into the control valve chamber 15 flows at high speed along the bucket portion 13, it generates an axial force that directs the spool 3 to the right in the figure.

These axial forces in opposite directions increase and decrease in response to changes in the valve opening degree, that is, the flow rate, and each increases as the flow rate increases.

As a result, the axial forces in opposite directions always cancel each other out regardless of the flow rate, and the displacement of the spool 3 is no longer affected by the axial force generated by the control fluid.
Accurate fluid flow or pressure control.

When lowering the load 12, the spool 3 is displaced to the right in the figure. The control valve chambers 15 and 16 thereby communicate with the low pressure valve chambers 17 and 18, respectively.

Therefore, the working fluid in the working chamber 10 of the syringe 9 is pushed out by the pressure generated according to the load 12, and the piston 11 moves downward.

At this time, fluid is ejected from the control valve chamber 15.16 through the edges D and C to the low pressure valve chamber 17.18, and the descending speed of the piston 11 is determined according to the flow rate of this ejection.

The spool 3 receives a rightward axial force from the ejected fluid at the edge D, but the ejected fluid from the edge C generates a leftward axial force by the axial force compensation bucket part 14. As a result, the generated axial forces cancel each other out, and their influence on the displacement of the spool 3 disappears, as described above.

In this way, when the spool 3 is displaced in any direction, the influence of the axial force due to the fluid can be removed, and the flow rate of the controlled fluid is divided into two control bows 8A and 8B. Therefore, it is possible to control up to twice the flow rate compared to a normal valve.

Note that by appropriately shifting the amount of overlap between edges A and B or edges C and D formed on each land, it is possible to adjust the flow rate gain.

(Effects of the Invention) As described above, according to the present invention, the working fluid is divided into the fluid measuring section and the axial force compensating section on both the supply side and the return side of the high-pressure fluid as the spool is displaced. Regardless of the flow rate, the axial forces acting on the spool cancel each other out, allowing highly accurate control. Also, since the fluid is divided into two paths, the same valve size can
It also has the effect of being able to control up to double the flow rate.

[Brief explanation of the drawing]

The figure is a sectional view of an embodiment of the invention. 1... Valve body, 3... Spool, 4, 5...
・Land, 6...High pressure valve chamber, 7...High pressure port, 8
A, 8 B...Control port, 9...Schilling, 1
3.14...Bucket part, 15.16...Control valve chamber, 17.18...Low pressure valve chamber, 19A, 19B=tank port, 20...Land. 1-11 Valor body 3--Product pool 9-m-Cylinder 7--High, pressure-port, 8B--Constant 1 Yellow port 20-11 Land

Claims (1)

[Claims] A three-way servo valve that includes a spool that slides via an electromagnetic drive unit and selectively connects a fluid control port to a high pressure port and a tank port according to displacement of the spool, the high pressure valve connected to the high pressure port. Control valve chambers connected to the control port are formed on both sides of the chamber, and low pressure valve chambers connected to the tank port are formed on both sides of each control valve chamber, and two lands formed on the spool are connected to the high pressure located in the valve chamber, forming bucket portions for axial force compensation on both outsides of these lands, and positioning one bucket portion in one control valve chamber and the other bucket portion in one low pressure valve chamber, Furthermore, a land is provided on the spool located between the control valve chamber where the bucket portion is located and the low pressure valve chamber,
A three-way servo valve characterized in that the displacement of the spool to one side causes the high-pressure valve chamber to communicate with each control valve chamber on both sides, and the displacement to the other side causes both control valve chambers to communicate with each low-pressure valve chamber. .