JPS6347583A - Holding valve - Google Patents

Abstract

PURPOSE:To miniaturize a valve as a whole, by regulating a quantity of flow running into the low pressure side from a spring chamber and controlling differential pressure in front and rear of the orifice formed in a control spool. CONSTITUTION:When a selector valve V is selected to a right position, discharge oil out of a pump P is fed to a rod side chamber 46 of a cylinder S, while a hydraulic fluid in a bottom side chamber 45 flows into a second port 23. If this hydraulic fluid flows into the second port 23, it also flows into a spring chamber 23 via an orifice 34. At this time, a flow control valve L is operated, and when the hydraulic fluid inside the spring chamber 23 is made to flow into a tank T, a differential pressure is produced in front and rear of the orifice 34 and a throttle 35 according to a control flow rate of this flow control valve L, thus a control spool CS is moved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a holding valve that holds a load.

(Prior Art) The conventional technology of this type of holding valve is disclosed in, for example, Japanese Patent Application Laid-open No. 82008/1983, but the patent No. 7 specifically shows what was disclosed in this publication.
It is a diagram.

In the example shown in FIG. 7, a cylinder S for raising and lowering a load W, a switching valve V for controlling the direction of hydraulic oil, a pump P, a tank T, and a counterbalance valve C as a holding valve are provided. ing.

The counterbalance valve C includes a main body 1, a control spool C8, a pilot spool PS, a pilot pump PP, and a proportional solenoid 17.

The main body 1 has first to fourth ports 2 to 5 and a valve hole 6 formed therein.

The first port 2 is connected to the switching valve ■, and the second port 3
is connected to the bottom side chamber of the cylinder S, and the third port 4 is connected to the pilot pump PP.

The fourth port 5 is communicated with the tank T.

The control spool C5 is formed hollow and is slidably inserted into the valve hole 6 formed in the main body 1. Also, the control spool C5 has a second boat 3 and a first port 2.
A control section 7 that communicates with or blocks the communication and controls the degree of opening during communication, and an annular recess 8 that is continuous with the control section 7 are formed.

The pilot spool PS is slidably inserted into the control spool C8.

A pilot path is formed between the fourth port 5, the control spool C8, and the pilot spool ps, which can communicate with the annular recess 9 → hole 10 → annular groove 11 → hole 12 → annular passage 13 → pilot chamber 14. This pilot path is closed when the counterbalance valve C is in the normal position.

The control spool C5 is pushed in the closing direction by the spring 15, and the pilot spool PS is pushed in the direction of the proportional solenoid 17 by another spring 1B and held at the normal position shown.

In the counterbalance valve C, when the proportional solenoid 17 is excited to cause the bushing rod 18 to protrude, the biloft spool PS moves in the direction of arrow a against the spring 1B and stops at a position corresponding to the bushing amount of the bushing rod 18. do.

When the pilot spool PS moves in the direction of arrow a, the annular groove 11 communicates with the hole 10, thereby opening the biloft passage. For this purpose, pressure oil from the pilot pump PP is supplied to the pilot chamber 14, and the pressure in the pilot chamber 14 causes the control spool C8 to move in the direction of arrow a against the spring 15.

When the control spool CS also moves in this way and catches up with the pilot spool PS, the communication between the hole 10 and the annular groove 11- is closed again, so that the control spool C8
It stops while maintaining the relative position shown in the figure with the pilot spool PS.

When the control spool C3 moves as described above, the second boat 3 and the first port 2 communicate with each other via the control section 7 and the annular recess 8. The opening degrees of the first and second ports 2.3 at this time are controlled by the control section 7.
The opening degree of is determined by the amount of movement of control spool C8. The amount of movement of the control spool C8 is equal to the amount of movement of the control spool C8.
It is determined by the amount of movement of S in the direction of arrow a. The amount of movement of the pilot spool PS is determined by the stroke kjL of the bushing rod 18, and the stroke amount of the bushing rod 18 is determined by the amount of current applied to the proportional solenoid 17.

Therefore, the opening degree of the control section 7 is determined by a proportional solenoid! It is determined by the amount of electricity supplied to 7.

(Problems to be Solved by the Invention) In the conventional holding valve as described above, as described above, the opening degree of the control section of the control spool CS is determined by the amount of current applied to the excitation solenoid. By the way, as shown in FIG. 8, the suction force by the proportional solenoid decreases in inverse proportion to the stroke amount of the bushing rod, etc.

Therefore, in order to obtain a predetermined suction force over the entire stroke amount of the bush rod, etc.

It is necessary to make the proportional solenoid larger. As a result, conventional valves have had the problem of increasing the size of the entire valve.

SUMMARY OF THE INVENTION An object of the present invention is to provide a holding valve that can be miniaturized as a whole even when the stroke amount of a moving member moved by pilot pressure is long.

(Means for Solving the Problems) In order to achieve the above object, the present invention is configured as follows.

That is, a throttle and a flow rate control valve are provided in the flow path that communicates the spring chamber of the control spool with the low pressure side, and the boat on the load side is communicated with the spring chamber through an orifice formed in the control spool. The control spool is configured to open in response to the differential pressure across the orifice.

(Operation of the present invention) In the present invention, the pressure difference before and after the orifice formed in the control spool is controlled by controlling the flow rate flowing from the spring chamber to the low pressure side. When the orifice prepressure becomes greater than the spring chamber pressure, the control spool opens.

(Effects of the present invention) According to the present invention described above, the flow rate control valve allows
Since the control spool can be operated simply by controlling the flow rate flowing from the spring chamber to the low-pressure side, the flow rate control valve and the operating section that operates it can be made smaller, which has the effect of making the entire valve smaller.

(Example of the present invention) Embodiments of the present invention will be described below with reference to the drawings.

In the first embodiment shown in FIGS. 1 to 3, the valve body 21 includes:
A first port 22 connected to the switching valve V and a second port 23 connected to the cylinder S are formed, and a valve hole 24.25 is formed substantially perpendicular to both boats 22.23.

A control spool C8 is slidably housed in the valve hole 24, and a control portion 26, a poppet portion 27, and a sliding portion 28 are formed in this order from the tip of the control spool C8 toward the rear. There is.

The control section 28 constitutes a variable orifice together with an annular protrusion 28 formed on the inner periphery of the valve hole 24, and as the control spool C8 moves rightward in the drawing, the opening area of the variable orifice increases. I'm trying to make it happen.

The poppet portion 27 comes into pressure contact with a seat portion 30 formed on the inner periphery of the valve hole 24 to close the seat portion 3o. When the seat portion 30 is closed in this way, the opening of the variable orifice The area is also made to be almost zero. When the seat section 30 is opened, the first boat 21 and the second boat 22 communicate with each other via the control section 26.

The sliding portion 28 is slidable in the valve hole 24, and has a cross-sectional area D2 larger than the opening area of the seat portion 30.

The control spool CS configured as described above is provided with a spring 33 in a spring chamber 32 formed between the spring chamber 32 and the closing member 31 that closes the outer end of the valve hole 24, and the poppet portion 27 is normally pressed into contact with the seat portion 30. I try to do that.

The spring chamber 32 communicates with the second boat 22 via an orifice 34 formed in the control spool C8, and also communicates with the tank T via a throttle 35 and a flow rate control valve formed in the closing member 31. are doing.

The flow rate control valve is as shown in FIG.

It is a normally closed type, and when the solenoid 3 is in a non-energized state, the poppet 3 comes into pressure contact with the seat portion 33 due to the action of the spring 37, thereby closing the seat portion 39. Then, when the solenoid 3' is energized, the poppet 38 is moved by the bushing rod 40 against the spring 37, and the seat section 3s is opened. When the seat section 39 is opened in this way, the spring chamber 32 is moved from the aperture 35 to
The inflow port 41 communicates with the tank T via the seat portion 39.

The flow rate control valve configured as described above controls the energization time and demagnetization time of the solenoid 38 during a certain period of time using an electric signal that changes depending on the load and the like, thereby controlling the flow rate through the flow rate control valve.

A check poppet 41 is installed inside the other valve hole 25, and a plug 42 is installed to block the outside of the valve hole 25.
A spring 43 is interposed between the check poppet 41 and the seat portion 44, and the check poppet 41 is normally brought into pressure contact with the seat portion 44. In other words, the check valve having the check poppet 41 as its main element has a 4X1 configuration that allows flow only from the first port 22 to the second port 23.

Now, when the switching valve V is switched from the neutral position shown in the figure to the left position in the figure, the oil discharged from the pump P flows into the first port 22, and the check valve is pushed open from the first port 22 to the second port. 23 and is supplied to the bottom side chamber 45 of the cylinder S.

At this time, the hydraulic oil in the rod side chamber 48 of the cylinder S is returned to the tank T via the switching valve (2), so the load W increases.

When the switching valve ■ is switched to the right side view, contrary to the above, the discharge oil of the pump P is supplied to the rod side chamber 46 of the cylinder S, and the hydraulic oil in the bottom side chamber 45 is supplied to the second port 2.
3.

When hydraulic oil flows into the second port 23 as described above, the hydraulic oil passes through the orifice 34 and enters the spring chamber 32.
It also flows into If the flow rate control valve is completely closed at this time, the poppet portion 27 of the control spool CS will maintain the closed state due to the acting force of the pressure aIPX surface M D + of the spring chamber 32.

When the flow rate control valve is operated from the above state to cause the hydraulic oil in the spring chamber 32 to flow into the tank T, the flow rate is adjusted to the front and rear of the orifice 34 and the orifice 3 according to the controlled flow rate of the flow rate control valve.
A differential pressure occurs around 5. The conditions for the control spool C5 to move and open the seat portion 30 due to the above pressure action are (P+ -D+)÷(P2・(Dz-D+)))(h
・Dz)+F.

In addition, in the above formula, PI is the pressure on the first boat 22 side, P
2 is the pressure on the second port 23 side, P3 is the spring chamber 32
The pressure inside, F is the spring force of the spring 33.

Therefore, the lower the pressure P3 in the spring chamber 32, the greater the movement of the control spool C8, and the larger the opening area of the control section 2B.
The higher the pressure 2, the smaller the amount of movement of the control spool C8, and the smaller the opening area of the control section 26 becomes.

The pressure within the spring chamber 32 can be controlled by adjusting the flow rate flowing into the tank T by operating a flow rate control valve.

In any case, if the control spool CS is moved by controlling the quantity control valve Ii and the control section 26 is opened, the cylinder S
The hydraulic oil in the bottom side chamber 45 returns to the tank T via the second port 23 → seat part 30 → control part 26 → first port 22 → switching valve V, but the return flow rate at this time, that is, the cylinder S The descending speed is determined according to the opening degree of the control section 26.

Since the opening degree of the control section 26 is determined according to the control flow rate of the flow control valve as described above, the opening degree of the control section 26 is determined according to the excitation time for the solenoid 3B of the flow control valve. The lowering speed of the cylinder S can be controlled by controlling the lowering speed of the cylinder S.

Note that when supplying pressure oil to the bottom side chamber 45 of the cylinder S, if the flow rate control valve is fully opened, the control spool C8 is pushed open by the discharge pressure from the pump P. The check valve is not an absolute component. FIG. 4 shows an embodiment in which this check valve is omitted.

Further, in the other embodiment shown in FIG. 5, the throttle 35 is provided on the downstream side of the flow control valve, and in the embodiment shown in FIG. 1st boat 2
In any case, the functions of each of these embodiments are substantially the same.

[Brief explanation of the drawing]

Drawings 1 to 3 show embodiments of this invention.
The figure is a circuit diagram, Figure 2 is a sectional view, Figure 3 is a sectional view of the flow control valve, Figures 4 to 6 are circuit diagrams of different embodiments, Figure 7 is a conventional sectional view, and Figure 8. is a graph showing the relationship between the stroke of the bushing rod and the suction force of the solenoid. 22...1st port, 23...2nd boat, cs.
...Control spool, 32...Spring chamber, 34...
- Orifice, 35... throttle, L... flow control valve.

Claims (1)

[Claims] A throttle and a flow control valve are provided in the flow path that communicates the spring chamber of the control spool with the low pressure side, and the port on the load side is communicated with the spring chamber through an orifice formed in the control spool, and the flow path before and after the throttle A holding valve configured so that the control spool opens according to the differential pressure.