JPH0449126B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a pressure control valve that controls secondary pressure in accordance with pilot pressure.

(Prior art and its problems) As shown in Fig. 1, a conventional pressure control valve is equipped with a pilot control valve 5 in a pressure control valve 1, and controls the secondary side pressure (control pressure) P2 of the pressure control valve ₁ . A part of the pressure oil is guided to one end surface 3a of the spool 3 through a passage 2a provided in the housing 2, and the end surface 3a is
From there, it reaches the opposite end surface 3b and leads to the pilot control valve 5 through a passage 3c provided with an orifice, and adjusts the set load of the spring 7 with the dial 6 to set the valve opening pressure (pilot pressure) Pc of the valve body 8. When the secondary pressure _P2 led through the orifice exceeds this pilot pressure Pc, the pilot control valve 5 is opened, and the pilot pressure Pc acting on the end face 3b of the spool 3 and the set load of the return spring 4 are adjusted. The spool 3 is displaced to a position where the force in the valve opening direction of the spool 3 due to the pressure F and the force in the valve closing direction of the spool 3 due to the secondary pressure P ₂ acting on the end face 3a are balanced, and the primary side supply pressure P ₁
The pressure is reduced to obtain a secondary pressure _P2 corresponding to the pilot pressure Pc, and this secondary pressure _P2 has characteristics as shown in FIG.

According to this configuration, the secondary pressure _P2 is controlled to be less than the ratio of the force in the valve opening direction due to the set load F of the return spring 4 to the pressure receiving area _A0 of the end surface 3a of the spool 3, that is, F/ _A0 . unable to
As shown in FIG. 2, when the secondary pressure _P2 reaches the pressure F/ _A0 , it rapidly rises from 0 to a predetermined pilot pressure Pc. For this reason, it is impossible to control the secondary side pressure _P2 at a low pressure between 0 and F/ _A0 . Also, if the set load F of the return spring 4 is reduced in order to perform low pressure control, 2
It becomes impossible to stably control the next side pressure (control pressure) _P2 .

(Object of the Invention) The present invention has been made in view of the above points, and enables low pressure control of the secondary side pressure (control pressure) of a pressure control valve, and stable control from 0 to a set pilot pressure. The purpose is to obtain.

(Summary of the invention) In order to achieve the above object, the present invention includes:
The pilot pressure, which is regulated to a predetermined pressure by the pilot control valve and displaces the spool in the valve opening direction, works together with the return spring that displaces the spool in the valve closing direction to control the position of the spool and reduce the primary side supply pressure. In the pressure control valve, which is configured to obtain a predetermined secondary side pressure by a passageway, an orifice means for introducing the primary side supply pressure into the passageway, and two step portions formed on the circumferential surface of the spool, the spool having the pilot pressure acting in the valve closing direction. A pressure receiving area difference between the first pressure receiving surface on the one end surface and the second pressure receiving surface on the other end surface of the spool on which the pilot pressure acts in the valve opening direction, and 3rd on one side of the stepped part
The difference in the pressure receiving area between the pressure receiving surface and the other fourth pressure receiving surface of the stepped portion on which the pilot pressure acts in the valve opening direction is set equal, and the difference between the pilot pressure and the second pressure receiving surface is set equal.
The spool is positioned at a position where the force in the valve opening direction acting on the spool due to the downstream side pressure is balanced with the force in the valve closing direction acting on the spool due to the pilot pressure, the secondary side pressure, and the return spring. The present invention provides a pressure control valve in which the secondary pressure is controlled in accordance with the pilot pressure, thereby making it possible to control the secondary pressure at a low level.

(Embodiment of the Invention) An embodiment of the present invention will be described below in detail based on the accompanying drawings.

FIG. 3 shows a longitudinal section of a pressure control valve 10 to which the present invention is applied and a pilot control valve, such as an electromagnetic relief valve 15, which is integrally attached to the pressure control valve 10 and controls the pressure control valve 10. valve 10
The housing 11 has spool insertion holes 11a, 1
Next side inlet port 11b, second side outlet port 11c
and a tank port 11d, and a spool 12 is fitted into the spool fitting hole 11a so as to be slidable in the axial direction. Two lands 12a and 12b are provided at both ends of the spool 12, one land 12a has a larger diameter than the other land 12b, and a through hole (passage) 12c is bored in the axial center.
An orifice 12d is drilled in the radial direction at a predetermined location of the land 12b, with one end opening on the outer circumferential surface and the other end opening on the inner circumferential surface of the hole 12c.
2d is always communicated with the inlet port 11b regardless of the displacement of the spool 12.

The pressure receiving area A ₁ of the end face 12e of the land 12a of the spool 12 is larger than the pressure receiving area A ₂ of the end face 12f of the land 12b (A ₁ >A ₂ ), and the pressure receiving area A 3 of the inner end face 12g of the land 12a is larger than the pressure receiving area A ₂ of the end face 12f of the land 12b. It is larger than the pressure receiving area A ₄ of the inner end surface 12h (A ₃ >
_A4 ) is set. Then, the difference in pressure receiving area between the end surfaces 12e and 12f (A ₁ −A ₂ ) and the end surface 1
The difference (A ₃ −A ₄ ) in pressure receiving area between 2g and 12h is equal, and is set to, for example, the value A ₀ (difference in pressure receiving area).

A ₁ −A ₂ =A ₃ −A ₄ =A ₀ (1) When the spool 12 moves upward, the inlet port 11b and the outlet port 11c are communicated with each other, and the tank port 11d is closed, and when the spool 12 moves downward, the inlet port 11b and the outlet port 11c are connected. 11
b and the outlet port 11c are cut off, and the outlet port 11c and the tank port 11d are communicated with each other.

The housing 16 of the electromagnetic relief valve 15 is fluid-tightly screwed onto the end surface 11e of the housing 11 via a valve seat 17 by bolts (not shown). The housing 16 includes a solenoid 18 and a solenoid 1.
8 and a plunger 19 driven by the valve seat 17.
A valve body 20 that closes one side open end of the hole (passage) 17a, and a spring 21 that is interposed between the plunger 19 and the valve body 20 and presses the valve body 20 to the open end of the hole 17a are housed, The other open end of the hole 17a faces the hole 12c of the spool 12. A relief port 16b is bored in the side wall of the housing 16 in the radial direction, with one end opening on the inner peripheral surface of the hole 16a in which the valve body 20 is housed, and the other end opening on the outer peripheral surface of the housing 16.

The return spring 13 connects one end of the spool 12 and the valve seat 17.
One end is inserted into the opening end 12c' of the hole 12c of the spool 12, which widens with a step on the land 12b side, and presses against the step surface, and the other end is inserted into the opening end 12c' of the hole 12c of the spool 12. Pressed against the opposing end surface 17b of 17,
The spool 12 is urged in the valve closing direction. Therefore, the pressure control valve 10 is a normally closed control valve.

When the solenoid 18 is deenergized, the plunger 19 of the electromagnetic relief valve 15 is pressed by the spring force of the spring 21 and moves upward, and its end surface 19a abuts the opposite end surface 16c of the housing 16, and the solenoid 18 is energized. Then, the spring 21 is compressed according to the suction force and moves downward, and stops at a position balanced with the spring force of the spring 21. Therefore, the set load of the spring 21 is at its minimum when the solenoid 18 is deenergized, and increases in accordance with its magnetic attraction force, that is, the excitation current i of the solenoid 18 when it is energized.
That is, the opening pressure (hereinafter referred to as pilot pressure) Pc of the electromagnetic relief valve 15 is controlled by the excitation current i of the solenoid 18.

The excitation current i of the solenoid 18 is, for example, duty-controlled, and the pilot pressure Pc varies as the duty ratio ranges from about 30% to 100%, as shown by the solid line in Fig. 4.
% with good linearity.

The primary inlet port 11b of the pressure control valve 10 is connected to a hydraulic pump, the secondary outlet port 11c is connected to an actuator (both not shown), and the tank port 11d and the relief port 16b of the electromagnetic relief valve 15 are connected to the tank T, respectively. connected to.

The action will be explained below.

When pressure oil is not supplied to the primary side inlet port 11b of the pressure control valve 10, the spool 12 is moved downward by the set load F of the return spring 13 to close the valve, and the inlet port 11b and the outlet port 11c are cut off. . Further, the outlet port 11c is communicated with the tank port 11d.

When hydraulic pressure _P1 pressure oil is supplied to the inlet port 11b, a part of this pressure oil flows into the passage 12c through the orifice 12d of the spool 12 and is guided to the electromagnetic relief valve 15. As mentioned above, the electromagnetic relief valve 15 is set to the valve opening pressure according to the excitation current i of the solenoid 18, that is, the pilot pressure Pc,
The oil pressure in the passage 12c of the spool 12 is regulated to this pilot pressure Pc. This pilot pressure Pc is applied to the end faces 12e and 12f of the spool 12. The pressure receiving area _A1 of the end face 12e of the spool 12 is larger than the pressure receiving area _A2 of the end face 12f, and the difference ( _A1 - _A2 = _A0 ) is the pilot pressure on the spool.
Pc is the area that acts in the valve opening direction (upward movement direction), and the product with the pilot pressure Pc, that is, the force in the valve opening direction (Pc, A ₀ ) is the set load F of the return spring 13 (force in the valve closing direction) (Pc・A>F), the spool 12 is displaced in the valve opening direction, and the inlet port 11b
and the outlet port 11c are communicated with each other, and the outlet port 1
Pressure oil is supplied to the actuator from 1c. The pressure oil (hereinafter referred to as secondary oil pressure) P ₂ in the outlet port 11c is determined by the valve opening position of the spool 12.

This pressure oil _P2 on the secondary side is the end face 1 of the spool 12.
Added to 2g and 12h. Force F ₁ in the upward movement direction (valve opening direction) of the spool 12 due to the pilot pressure Pc and the secondary pressure P ₂ , the pilot pressure Pc and the secondary pressure
The force P ₂ in the downward movement direction (valve closing direction) of the spool 12 due to P ₂ and the set load F of the return spring 13 is expressed by the following equations (2) and (3), respectively.

F ₁ = Pc・A ₁ +P ₂・A ₄ ……(2) F ₂ =Pc・A ₂ +P ₂・A ₃ +F ……(3) The spool 12 receives the force F 1 in the valve opening direction and the force F ₁ in the valve closing direction. It stops at the position where the force F ₂ is balanced. Therefore,
The following equation (3) can be obtained from the previous equations (2) and (3).

Pc・A ₁ +P ₂・A ₄ =Pc・A ₂ +P ₂・A ₃ +F ……(3) ∴Pc(A ₁ −A ₂ )=P ₂ (A ₃ −A ₄ )＋F ……(4) The left side of this equation (4) is the force in the valve opening direction of the spool 12 due to the pilot pressure Pc, and the right side is the secondary side pressure.
It represents the force of the spool 12 in the valve closing direction due to P ₂ and the set load F of the return spring 13.

Substituting the above equation (1) into the above equation (4), the secondary side pressure P ₂ will be rearranged.

Pc=P ₂ +F/A ₀ ……(5) ∴P ₂ =Pc−F/A ₀ ……(6) The pilot pressure Pc on the right side of this equation (6) is controlled by the excitation current i of the solenoid 18. The second term (F/A ₀ ) is the ratio between the set load F (constant) of the return spring 13 and the difference A ₀ (constant) in the pressure receiving area of the spool 12, and is constant. Therefore, the secondary pressure P ₂ becomes 0 until the pilot pressure Pc reaches the pressure (F/A ₀ ), and when the pilot pressure Pc exceeds the pressure (F/A ₀ ), the solid line in FIG. As shown in , it increases as the pilot pressure Pc increases. The pilot pressure Pc is determined by the duty ratio of the excitation current i of 30, as shown by the solid line in Figure 4.
The duty ratio is controlled linearly or proportionally between % and 100%. Therefore, by setting the pilot pressure Pc when the duty ratio is 30% to be equal to the pressure (F/A ₀ ), the secondary side pressure P ₂ can be increased from 0 to P as shown by the straight line in Figure 4. It is possible to control the pressure up to ₁ in proportion to the pilot pressure Pc shown by the straight line in the same figure.

In this way, low pressure control of the secondary side pressure _P2 becomes possible.

FIG. 5 shows another embodiment of the present invention, and the same parts as those in FIG. 3 are given the same reference numerals and the explanation thereof will be omitted.

In FIG. 5, the pressure control valve 10' is
It has a structure in which the pressure control valve 10 shown in the figure is inverted, and a passage 11'e is provided in the side wall of the housing 11', one end of which opens to the inner peripheral surface of the inlet port 11'b on the side opposite to the electromagnetic relief valve. and the passage 1
An orifice 11'f is provided at 1'e.
Also, the spool 1 that closes the inlet port 11'b
The land 12'b of 2' has the inlet port 11'b.
No orifice is provided to communicate the passage 12'c of the spool 12' with the passage 12'c of the spool 12'. That is, in place of the orifice 12d of the spool 12 (FIG. 3), a passage 11'e and an orifice 11' are provided in the housing 11'.
f, and supply pressure oil on the primary side to the orifice 1.
1'f to the end face 12'f side of the spool 12'c, and to the electromagnetic relief valve 15 through the hole 12' of the spool 12'.

Note that a large diameter hole 12'i is formed in the end surface 12'e of the spool 12' opposite to the end surface 17b of the valve seat 17.
2'c is concentrically drilled, and the pilot pressure
Pc is designed to easily join the end face 12'e. This hole 12'i is not necessarily required and may be formed in the same manner as the end surface 12e of the spool 12 (FIG. 3).

This pressure control valve 10' also operates in the same manner as the pressure control valve 10, and the secondary side pressure _P2 changes from 0 to the primary side pressure P1 _.
The pressure is controlled in proportion to the pilot pressure Pc, making low pressure control possible.

In the present invention, a case has been described in which an electromagnetic relief valve is used as the pilot control valve, but the present invention is not limited to this, and a manually operated pilot control valve as shown in FIG. 1 may also be used. Of course.

(Effects of the Invention) As explained above, according to the present invention, the pilot pressure which is regulated to a predetermined pressure by the pilot control valve and which displaces the spool in the valve opening direction cooperates with the return spring which displaces the spool in the valve closing direction. The pressure control valve is configured to control the position of the spool by reducing the primary supply pressure to obtain a predetermined secondary pressure. a passage consisting of a through hole opening at an end face and the other end face opposite to the pilot control valve; orifice means for introducing the primary side supply pressure into the passage; and two step portions formed on the circumferential surface of the spool. a first pressure receiving surface on the one end surface of the spool on which the pilot pressure acts in the valve closing direction and a second pressure receiving surface on the other end surface of the spool on which the pilot pressure acts in the valve opening direction. A pressure receiving area difference between a third pressure receiving surface on one side of the stepped portion on which the pilot pressure acts in the valve closing direction and a fourth pressure receiving surface on the other side of the stepped portion on which the pilot pressure acts in the valve opening direction. The pressure receiving area difference is set to be equal, and the force in the valve opening direction acting on the spool due to the pilot pressure and the secondary side pressure, and the force on the spool due to the pilot pressure, the secondary side pressure, and the return spring. The spool is moved to a position that balances the force in the valve closing direction that is applied, and the secondary pressure is controlled according to the pilot pressure, so the secondary pressure is increased from 0 to the primary pressure. It is possible to control up to the side supply pressure, and it is possible to stably perform low pressure control of the secondary side pressure, reducing the secondary side pressure to 0.
This allows for smooth control. Further, it has excellent effects such as a simple structure.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view of a conventional pressure control valve, Fig. 2 is a characteristic diagram of the pressure control valve shown in Fig. 1, and Fig. 3 is an embodiment of the pressure control valve of the present invention equipped with an electromagnetic relief valve. FIG. 4 is a characteristic diagram of the pressure control valve of the present invention shown in FIG. 3, and FIG. 5 is a longitudinal cross-sectional view of another embodiment of the pressure control valve of the present invention. 10, 10'...pressure control valve, 11, 11'...
Housing, 12, 12'...Spool, 13...
...Return spring, 15...Solenoid relief valve.

Claims (1)

[Claims] 1 The position of the spool is controlled by the cooperation of the pilot pressure, which is regulated to a predetermined pressure by the pilot control valve and displaces the spool in the valve-opening direction, and the return spring, which displaces the spool in the valve-closing direction, and the primary side supply pressure is adjusted. In a pressure control valve configured to reduce pressure to obtain a predetermined secondary pressure, a through hole is formed in the spool and opens at one end surface of the spool on the pilot control valve side and the other end surface on the side opposite to the pilot control valve. said spool, said spool comprising: a passageway consisting of a passage, an orifice means for introducing said primary side supply pressure into said passageway, and two step portions formed on a circumferential surface of said spool, said pilot pressure acting in a valve closing direction; a pressure receiving area difference between the first pressure receiving surface on the one end surface of the spool and the second pressure receiving surface on the other end surface of the spool on which the pilot pressure acts in the valve opening direction, and the pilot pressure acting in the valve closing direction. The pressure receiving area difference between the third pressure receiving surface on one side of the stepped portion and the fourth pressure receiving surface on the other side of the stepped portion on which the pilot pressure acts in the valve opening direction is set equal, and the pilot pressure and the second pressure receiving surface are set to be equal. The spool is positioned at a position where the force in the valve opening direction acting on the spool due to the downstream side pressure is balanced with the force in the valve closing direction acting on the spool due to the pilot pressure, the secondary side pressure, and the return spring. A pressure control valve characterized in that the pressure control valve is configured to be displaced and to control the secondary side pressure according to the pilot pressure.