JPH0565748B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a balanced piston type hydraulic control valve, and more particularly to a balanced piston type hydraulic control valve that controls the pressure of a hydraulic circuit. .

[Background of prior art and invention]

Conventionally, a general balanced piston type hydraulic control valve applies the hydraulic pressure to be controlled to the front surface of a piston housed in a housing, and applies this hydraulic pressure to the rear surface of the piston by reducing the pressure through an orifice formed in the piston. The back pressure of the piston is controlled by the degree of opening of the pilot hole which is opened and closed by a pilot valve, thereby controlling the oil pressure on the front side of the piston. The pilot valve is operated by, for example, a proportional solenoid mechanism, and the stroke of the pilot valve is controlled according to the current value applied to this solenoid mechanism, so the opening degree of the pilot hole is adjusted. It's summery.

Next, the overall structure of the conventional balanced piston type hydraulic control valve will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view of a conventional pilot balanced piston type hydraulic control valve, in which numeral 1 indicates a pressure control section and numeral 2 indicates a proportional solenoid section. The pressure control unit 1 includes a piston 5 that is slidable within a sleeve 4 that is fitted into a housing 3. The piston 5 has a cylindrical shape with a bottom, and a spring 6
It is pressed forward by. piston 5
The front surface of the control pressure chamber 7 formed in the housing 3
This control pressure chamber 7 is connected to a hydraulic circuit whose pressure is to be controlled. Therefore,
When the hydraulic pressure in the control pressure chamber 7 is controlled, this hydraulic pressure is transmitted to the hydraulic circuit, and the pressure in the hydraulic circuit is regulated. An annular groove 8 is formed in the inner peripheral surface of the sleeve 4, and this annular groove 8 communicates with a return passage 9 formed in the housing 3. This return passage 9 communicates with an oil tank T. The piston 5 is pushed by the spring 6 and comes into contact with the small diameter end 4a of the sleeve 4, but when the hydraulic pressure in the control pressure chamber 7 overcomes the pressing force of the spring 6, the piston 5 separates from the small diameter end 4a and this Therefore, the oil in the control pressure chamber 7 is released to the oil tank T via the annular groove 8 and the return passage 9. An orifice 10 is formed in the piston 5, and this orifice 10 communicates between the control pressure chamber 7 on the front side of the piston and the back pressure chamber 11 on the back side of the piston. The back pressure chamber 11 is the partition wall 1
2 and a return space 13. It is opened and closed by a pilot valve 15 on the partition wall 12 side.
However, the tip of the pilot valve 15 has a conical shape, and the pilot hole 14 provided in the partition wall
has a fixed aperture.

The return space 13 is connected to the oil tank T via an annular groove 16 formed in the housing 3 and a return port 17.
is connected to. When the pilot hole 14 is opened by the pilot valve 15, the oil in the back pressure chamber 11 flows through the pilot hole 11, the return space 13, and the annular groove 1.
6 and return port 17 to the oil tank T.

The pilot valve 15 is actuated by the proportional solenoid section 2. That is, the pilot valve 15 is supported by a bearing 19 attached to another partition wall 18, and is integrally connected to the plunger 20. The electromagnetic coil 22 around which the bobbin 21 is wound is covered by a yoke 23.
A core 24 is attached to the central part of 1.
A holder 26 is slidably inserted into a through hole 25 formed in the center of the core 24, and a rear end portion of the pilot valve 15 is supported within this holder 26 by a bearing 27. . A return spring 28 is spanned between the holder 26 and the plunger 20. Further, the holder 26 is in contact with an adjustment screw 29 that threads through the yoke 23 and the core 24. The adjustment screw 29 displaces the holder 26 in the axial direction to adjust the initial load of the spring 28, and also fastens the yoke 23 and the core 24. Note that 30 is a locking nut.

Note that 34 is an air hole for promoting the movement of air to eliminate air resistance when the plunger 20 reciprocates.

When a current is passed through the electromagnetic coil 22, the yoke 23, core 24, air gap 31, plunger 20, air gap 32 and yoke top 33
A magnetic flux is generated that passes through the core 24 and the plunger 20.
An attractive force proportional to the current flowing through the coil 22 is generated between the coil 22 and the coil 22. The plunger 20 is therefore actuated to the left in FIG. 1 against the return spring 28, causing the pilot valve 15 to move away from the bulkhead 12 and open the pilot hole 14. Since the magnetic attraction force changes in accordance with the value of the current flowing through the electromagnetic coil 22, the stroke of the plunger 20 changes, thereby controlling the degree of opening of the pilot hole 14 by the pilot valve 15.

In addition, a filter 35 is provided in the back pressure chamber 11.
is provided. The filter 35 is made of a stainless wire mesh of about 200 meshes, and has a cylindrical shape with one end closed. This filter 35 is housed in a cylindrical holder 36, and the open end of the filter 35 is attached to one end of the large cylindrical holder 36 with a circlip 37. A flange portion 38 is formed at one end of the holder 36, and this flange portion 38 is brought into contact with the piston 5 and is pressed by the spring 6. Therefore, the filter 35 is substantially attached to the piston 5 to capture the foreign matter in the oil that has flowed into the back pressure chamber 11 through the orifice 10, and to remove the foreign matter from the pilot hole 14 and between the piston 5 and the sleeve 4. It is designed so that it does not flow into the gap 39.

In the conventional balanced piston type hydraulic control valve having the above configuration, as described above, the orifice 10 which is a fixed throttle is formed in the piston 5, and the pilot hole 14 which is a fixed throttle is formed upstream of the pilot valve 15. The operating characteristics are as shown in FIG.
When both are small, the pressure control range is 5 to 30Kg/cm ²
However, in the region where the valve opening x < 0.1 mm, as shown in Fig. 2b, foreign matter 100 of 200 mesh or less that has passed through the filter 35 may clog the pilot valve and cause an abnormality in pressure control. I end up. Therefore, the diameter of the orifice 10 is increased to increase the pilot flow so that the valve opening x > 0.1 mm.
Regarding characteristic b, since the diameter of the pilot hole 14 is too small, no matter how much the pilot valve 15 is opened, the pressure cannot be lowered below the target control pressure. In order to avoid this, the diameter of the pilot hole 14 is increased to obtain characteristic c, but by increasing the diameter of the pilot hole 14, the damping effect of the pressure fluctuation due to the restriction becomes smaller, resulting in a problem in the high pressure region. The pressure becomes stable and pressure fluctuations occur as shown in FIG. Therefore, the pressure control range is 5~30Kg/
There is a problem in that there is no combination area of the orifice 10 ^and the pilot hole 14 where the valve opening x > 0.1 mm and where the throttle effect is effective and the valve is stable. In conventional hydraulic control valves, in order to increase valve stability while maintaining the required valve opening, the diameter of the pilot hole, which is a fixed restriction installed upstream of the pilot valve, is reduced to obtain the necessary stability. Therefore, there is a problem that the minimum control pressure becomes high.

[Object of the present invention]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a balanced piston type hydraulic control valve in which a pilot valve is provided with a variable throttle, thereby increasing the stability of the valve and reducing the minimum control pressure. be.

[Configuration of the present invention]

The present invention applies a hydraulic pressure to be controlled to the front surface of a piston housed in a housing, and also applies this hydraulic pressure to a rear pressure chamber surrounded by the piston and a partition wall through an orifice formed in the piston. In a balanced piston type hydraulic control valve that controls the hydraulic pressure on the front side of the piston by controlling the pressure in the pressure chamber on the back side of the piston by the opening degree of a pilot flow control section opened and closed by a pilot valve, the pilot valve of the pilot flow control section A protrusion forming a columnar variable throttle valve disposed at the tip of the partition wall and a yoke provided on the partition wall through which fluid passes are positioned at a predetermined angle with respect to each other.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention shown in the drawings will be described. FIG. 4 is a longitudinal sectional view showing the overall configuration of one embodiment of the balanced piston type hydraulic control valve according to the present invention;
The figure is an enlarged cross-section of the variable throttle part, which is a main part of the present invention shown in FIG.
A plurality of chiyokes 12a are radially opened toward holes 12c formed in the partition wall 12. There is a gap 45 of about 0.1 mm between the hole 12c and the protrusion 15a, and the tip of the protrusion 15a opens and closes by moving the tip of the protrusion 15a. Chiyoke 12
A variable aperture 44 consisting of a is formed. In addition, the protrusion 15a has a through hole 15c, and the oil that has passed through the chain yoke 12a passes through the gap 45 and flows through the pilot hole 42 and the pilot flow rate control section 43, as well as through the hole 12c and the through hole 15c. Pilot flow control unit 4 through hole 42
Two paths leading to 3 exist at the same time.
The balanced piston type hydraulic control valve according to the present invention has the same structure as that shown in FIG. 1, except for the above-mentioned variable throttle section.

In the balanced piston type hydraulic control valve of the present invention having the above configuration, as shown in FIG. The opening degree of 44 is small, increasing the stability of the valve.
Further, as shown in FIG. 6, in a low pressure region where the valve opening x of the pilot valve 15 is large, the opening of the variable throttle 44 is large and is not throttled by this variable throttle section.
The pressure decreases to the target value, which is the minimum control pressure. Its characteristics are as shown in the characteristic diagram shown in FIG. In FIG. 7, when controlling the pressure at 5 to 30 kg/cm ² , the end face 15b of the protrusion 15a is located at a position where the variable throttle 44 is almost closed at the valve opening x _p , and the valve opening x _O +
At _xC , it is preferable to position the protrusion end surface 15b at a position where the variable diaphragm 44 is almost fully opened.

In addition, in order to effectively operate the present invention, the seventh
In the case of the characteristics shown in the figure, when x≒0.1 S _A ≦S _B When x≒0.4 S _A ≦S _C ≦S' _B However, S _A = πDxsinθ S _A : Effective area of pilot flow control part D: High-rot hole 42 x: Pilot valve opening degree θ: Pilot valve half apex angle S _B = (π/4) {d ₁ ² - d ₂ ² ) S _B : Effective area when variable throttle is closed d ₁ : Inner diameter of hole 12c d ₂ : Inner diameter of pilot valve protruding portion 15a S _C = n (π/4) d ₃ ² S _C : Effective area of cheese yoke n: Number of cheese yokes 12a d ₃ : Inner diameter of cheese yoke 12a S' _B = (π/4) {d ₁ ² −d ₂ ² )+(π/4) d ₄ ² d ₄ : Inner diameter S′ of the conduction hole 15c _B : Effective area when the variable throttle is closed.

In the above embodiment, the yokes 12a are provided radially, but they may be branched in the axial direction as shown in FIG. In addition, the chi yoke 12a and the hole 12
c was provided on the partition wall 12 in the above embodiment, but the eighth
As shown in the figure, the partition wall 1 is processed into a separate body 50.
It may be integrally fixed to 2.

In addition, in the above embodiment, the pilot valve 1
Although the case has been described in which a solenoid mechanism is used as the drive mechanism for operating the drive unit 5, the present invention is not limited to this, and may be a hydraulic, pneumatic, or other mechanical drive mechanism.

[Effects of the present invention]

As mentioned above, in the balanced piston type hydraulic control valve of the present invention, the valve opening degree of the pilot valve is always set to 0.1 mm or more, so that it is possible to prevent foreign matter that has passed through the filter from clogging the pilot valve. In the high pressure region, the variable orifice opening is made small to prevent pressure fluctuations and improve valve stability.In the low pressure region, the variable orifice opening is made large, so the minimum control pressure is This has the great effect of reducing the pressure to the target value and providing a high-performance hydraulic control valve.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view showing the overall structure of a conventional balanced piston type hydraulic control valve, FIG. 2a is a characteristic diagram illustrating the operation of the conventional balanced piston type hydraulic control valve shown in FIG. 1, and FIG. b is a partially enlarged cross-sectional view of the pilot valve portion of the conventional balanced piston type hydraulic control valve shown in FIG. 1, FIG. 3 is a characteristic diagram for explaining the conventional hydraulic control valve shown in FIG. 1, and FIG. 5 is a vertical cross-sectional view showing the overall structure of one embodiment of the balanced piston type hydraulic control valve according to the present invention, FIG. 5 is an enlarged cross-sectional view of the variable restrictor shown in FIG.
The figures are an enlarged cross-sectional view when the variable throttle opening degree of the variable throttle section shown in Figure 5 is large, Figure 7 is an operational characteristic diagram of the balanced piston type hydraulic control valve according to the present invention shown in Figure 4, and Figure 8 1 is a sectional view showing the overall configuration of another embodiment of the variable aperture section according to the present invention, and the same reference numerals in the drawings indicate the same or equivalent parts. 3... Housing, 4... Sleeve, 5... Piston, 7... Control pressure chamber, 10... Orifice, 11... Back pressure chamber, 15... Pilot valve, 20... Plunger, 22... Electromagnetic coil ,
23... Yoke, 35... Filter, 15a...
Projection portion, 12...Partition wall, 12a...Chiyoke, 1
2c... Hole drilled in partition wall 12, 45... Gap,
44...Variable throttle consisting of protrusion 15a and choke 12a, 15c...Conducting hole, 42...Pilot hole, 43...Pilot flow rate control section.

Claims (1)

[Claims] 1. A hydraulic pressure to be controlled is applied to the front surface of a piston housed in a housing, and this hydraulic pressure is applied to a rear pressure chamber surrounded by the piston and a partition wall through an orifice formed in the piston. In the balanced piston type hydraulic control valve, the hydraulic pressure on the front side of the piston is controlled by controlling the pressure in the rear pressure chamber of the piston by the opening degree of a pilot flow rate control unit opened and closed by a pilot valve, wherein the pilot flow rate control unit A balanced valve characterized in that a protrusion forming a columnar variable throttle valve disposed at the tip of the pilot valve and a choke provided on the partition wall through which fluid passes are located at a predetermined angle to each other. Piston type hydraulic control valve.