CN116075662A - Pilot-operated electrically actuated valve - Google Patents

Abstract

Provided is a pilot electrically driven valve which can effectively suppress noise generated when the valve is opened. A pilot electrically driven valve (1) is provided with: a valve body (10) provided with a valve Chamber (CA) which communicates with an inflow port (12 d) and an outflow port (13 a); a pilot valve element (35) that is relatively movable with respect to the valve body (10); a main valve element (15) that is capable of relative movement with respect to the valve body (10) and is capable of being seated on or separated from a valve seat (14) in the valve Chamber (CA); and a sub-valve body (16) configured to be capable of being abutted against or separated from the pilot valve body (35) and capable of being moved relative to the main valve body (10), wherein a back pressure Chamber (CD) containing a fluid is formed between the pilot valve body (35) and the sub-valve body (16), and a pressure equalizing Chamber (CB) containing a fluid is formed between the main valve body (15) and the sub-valve body (16).

Description

Pilot-operated electrically actuated valve

Technical Field

The present invention relates to a pilot-operated electrically actuated valve.

Background

Conventionally, a pilot electrically driven valve is known in which a pilot valve element is driven to open and close by an electromagnetic actuator, and a main valve element is opened and closed in response to the pilot valve element, thereby opening and closing a fluid flow path.

Patent document 1 discloses a pilot-operated electrically driven valve as follows: when the coil is energized, the plunger is attracted to the attraction element, and as the pilot spool moves in the valve opening direction, the fluid in the back pressure chamber is discharged through the pilot passage, the back pressure chamber is depressurized, and the main spool is lifted by the biasing force of the valve opening spring, and opens the valve.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2007-92826

Technical problem to be solved by the invention

In the electric valve of patent document 1, since the main spool starts to move immediately after the pilot spool moves in the valve opening direction, a large pressure loss occurs in the fluid passing through the valve seat between the high-pressure inlet port and the low-pressure outlet port, and thus a large noise may occur in some cases.

Disclosure of Invention

The invention aims to provide a pilot-operated electrically-driven valve capable of effectively suppressing noise generated during valve opening.

Technical means for solving the technical problems

The pilot-operated electrically-operated valve according to the present invention includes:

a valve body having a valve chamber communicating with the inlet opening and the outlet opening;

a pilot spool that is relatively movable with respect to the valve body;

a main valve element that is movable relative to the valve body and that can be seated on or separated from a valve seat in the valve chamber; and

a sub spool configured to be capable of abutting against or separating from the pilot spool and capable of relative movement with respect to the main spool,

a back pressure chamber containing fluid is formed between the pilot spool and the sub spool,

a pressure equalizing chamber containing a fluid is formed between the primary spool and the secondary spool.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a pilot electrically driven valve capable of effectively suppressing noise generated when the valve is opened can be provided.

Drawings

Fig. 1 is a longitudinal sectional view showing a pilot-operated electrically-operated valve according to a first embodiment.

Fig. 2 is a cross-sectional view showing the main spool and the sub-spool in a state of being disassembled.

Fig. 3 is a main part sectional view for explaining the operation of the pilot-operated valve, and shows a valve-closed state.

Fig. 4 is a main part sectional view for explaining the operation of the pilot-operated valve, and shows a state in which the pilot spool is separated from the sub spool.

Fig. 5 is a main part sectional view for explaining the operation of the pilot-operated valve, and shows a state in which the sub spool starts to separate from the main spool.

Fig. 6 is a main part sectional view for explaining the operation of the pilot-operated valve, and shows a state in which the sub valve element is in contact with the pilot pipe.

Fig. 7 is a main part sectional view for explaining the operation of the pilot-operated valve, and shows a valve-opened state.

Fig. 8 is a longitudinal sectional view showing a pilot-operated electrically-operated valve according to a second embodiment.

Detailed Description

Hereinafter, an embodiment of an electrically operated valve according to the present invention will be described with reference to the drawings. In the present specification, the direction from the pilot spool toward the suction element is set to be upward, and the opposite direction is set to be downward.

First embodiment

Fig. 1 is a longitudinal sectional view showing a pilot-operated valve 1 according to a first embodiment, and shows the valve in a closed state.

The pilot-operated electrically driven valve 1 of the illustrated example is used in a refrigeration cycle such as a chiller, for example, and is used in combination with an electromagnetic actuator 20.

The pilot electrically driven valve 1 includes a valve body 10, a main spool 15 slidably inserted in the valve body 10, and a sub spool 16 slidably inserted in the main spool 15. The axis of the pilot-operated valve 1 is L.

The valve body 10 has a valve chamber CA inside, and the valve body 10 has a bottomed cylindrical shape connecting the side wall 12 and the bottom wall 13. An outlet opening 13a is formed in the center of the bottom wall 13, and the upper end of the outlet opening 13a constitutes a valve seat 14. The outflow tube OT is connected and fixed to the bottom wall 13 by brazing or the like so as to communicate with the outlet opening 13a.

The side wall 12 of the valve body 10 is formed by connecting a lower side wall 12a on the bottom wall 13 side, an intermediate side wall 12b having a larger inner diameter than the lower side wall 12a, and an upper side wall 12c having a larger inner diameter than the intermediate side wall 12 b. The upper side wall 12c has a thin wall shape to such an extent that caulking is possible. The lower side wall portion 12a is formed with an inlet opening 12d, and the inflow tube IT is connected and fixed to the lower side wall portion 12a by brazing or the like so as to communicate with the inlet opening 12 d. The axis of the inflow tube IT is set to O.

Fig. 2 is a cross-sectional view showing the main spool 15 and the sub-spool 16 in a state of being disassembled, and shows the first coil spring (second elastic member) 17 and the second coil spring (first elastic member) 18 together.

In fig. 2, main valve element 15 has a circular tube shape with an outer diameter that decreases stepwise toward the lower end. More specifically, main valve element 15 has, from its lower end, a first outer peripheral portion 15a, a second outer peripheral portion 15b having a larger diameter than first outer peripheral portion 15a, a third outer peripheral portion 15c having a larger diameter than second outer peripheral portion 15b, and a fourth outer peripheral portion 15d having a larger diameter than third outer peripheral portion 15 c.

The main valve element 15 has, from its lower end, a first inner peripheral portion 15e, a second inner peripheral portion 15f having a larger diameter than the first inner peripheral portion 15e, a third inner peripheral portion 15g having a larger diameter than the second inner peripheral portion 15f, and a fourth inner peripheral portion 15h having a larger diameter than the third inner peripheral portion 15 g.

The first inner peripheral portion 15e is formed radially inward of the first outer peripheral portion 15a, the second inner peripheral portion 15f and the third inner peripheral portion 15g are formed radially inward of the second outer peripheral portion 15b, and the fourth inner peripheral portion 15h is formed radially inward of the third outer peripheral portion 15c and the fourth outer peripheral portion 15d. A tapered portion 15i is formed between the first outer peripheral portion 15a and the lower end of the main spool 15, and a reduced diameter opening (second pilot port) 15j having an inner diameter smaller than that of the first inner peripheral portion 15e is formed between the first inner peripheral portion 15e and the lower end of the main spool 15.

Further, a first pressure equalizing hole 15k is formed so as to pass through between the first inner peripheral portion 15e and the first outer peripheral portion 15a, and a second pressure equalizing hole 15m is formed so as to pass through between the second inner peripheral portion 15f and the second outer peripheral portion 15 b. In the present embodiment, the inner diameter of the first pressure equalizing hole 15k is larger than the inner diameter of the second pressure equalizing hole 15m, but the present invention is not limited thereto.

The sub valve element 16 has a shaft portion 16a and a disk portion 16b coaxially connected to the upper end of the shaft portion 16 a. A countersunk surface 16c is formed on the upper surface of the circular plate portion 16b coaxially with the shaft portion 16a so as to be lower than the surrounding area by one step. The communication hole 16d formed in the shaft portion 16a opens at the lower end of the shaft portion 16a and the upper surface of the disk portion 16b. A reduced diameter portion (first pilot port) 16e having a reduced diameter compared with other portions is formed at the upper end of the communication hole 16 d.

Referring to fig. 1 and 2, when main valve body 15 is assembled in valve chamber CA of valve body 10, fourth outer peripheral portion 15d is slidably fitted to the inner periphery of intermediate side wall portion 12 b. At this time, a minute gap is formed between the lower side wall portion 12a of the valve body 10 and the second outer peripheral portion 15b of the main valve body 15.

In the closed state of fig. 1, the tapered portion 15i of the main valve element 15 is seated on the valve seat 14 to close the outlet opening 13a.

Referring to fig. 1 and 2, the lower end of the second coil spring 18 is in contact with a stepped surface 12e (fig. 1) between the lower side wall portion 12a and the intermediate side wall portion 12b of the valve body 10, and the upper end of the second coil spring 18 is in contact with a stepped surface 15p (fig. 2) between the third outer peripheral portion 15c and the fourth outer peripheral portion 15d of the main valve element 15, and the second coil spring 18 biases the main valve element 15 upward with respect to the valve body 10.

When the sub-valve body 16 is assembled in the main valve body 15, the outer periphery of the circular plate portion 16b is slidably fitted in the fourth inner peripheral portion 15h. At this time, a minute gap is formed between the first inner peripheral portion 15e of the main spool 15 and the shaft portion 16a of the sub-spool 16.

In the closed state of fig. 1, the lower end of the shaft portion 16a of the sub-spool 16 bottoms out on the main spool 15 to close the reduced diameter opening 15j.

Here, the lower surface (top surface) of the circular plate portion 16b of the sub-valve body 16; an outer peripheral surface (inner peripheral surface) of the shaft portion 16 a; a second inner peripheral portion 15f, a third inner peripheral portion 15g, and a fourth inner peripheral portion 15h (outer inner peripheral surface) of the main valve body 15; and a step surface 15r (bottom surface) between the first inner peripheral portion 15e and the second inner peripheral portion 15f of the main spool 15 forms an inner pressure equalizing chamber CB.

A step surface 15p (top surface) formed between the third outer peripheral surface 15c and the fourth outer peripheral portion 15d of the main valve element 15; a second outer peripheral portion 15b and a third outer peripheral portion 15c (inner peripheral surface) of the main valve body 15; an inner peripheral surface (outer inner peripheral surface) of the intermediate side wall portion 12b of the valve main body 10; and a stepped surface 12e (bottom surface) between the lower side wall portion 12a and the intermediate side wall portion 12b of the valve body 10 forms an external pressure equalizing chamber CC.

The lower end of the first coil spring 17 is in contact with a stepped surface 15q (fig. 2) between the second inner peripheral portion 15f and the third inner peripheral portion 15g of the main spool 15, and the upper end of the first coil spring 17 is in contact with the lower surface of the circular plate portion 16b of the sub spool 16, and the first coil spring 17 biases the sub spool 16 and the main spool 15 apart from each other in the axis L direction.

In fig. 1, the electromagnetic actuator 20 includes: the coil unit 22 for energization excitation, the case 21 disposed so as to cover the outer periphery of the coil unit 22, the bottomed cylindrical or columnar suction element 25 disposed on the upper inner periphery side of the coil unit 22 and fixed to the case 21 by the bolts 28, and the plunger 30 disposed so as to face the suction element 25.

A holding hole 31 is provided at the tip of the plunger 30. A pilot valve element 35 formed of a ball is accommodated in the holding hole 31. The pilot valve element 35 is fixed by being swaged inside to a swage portion 31a that protrudes cylindrically from the lower end of the plunger 30 in a state where a part of the lower surface thereof is exposed.

When the plunger 30 moves downward, the pilot valve element 35 is moved in the valve closing direction, and when the plunger 30 moves upward, the pilot valve element 35 is moved in the valve opening direction. A back pressure chamber CD is formed between the plunger 30 and the sub-valve element 16.

A vertical hole (spring chamber) 30a and a horizontal hole (pressure equalizing hole) 30b into which the valve closing spring 26 formed of a coil spring is inserted and locked are formed in the upper portion of the plunger 30.

A guide tube 32 is disposed between the coil unit 22 and the suction member 25. The plunger 30 is slidably inserted into the guide tube 32. The upper end 32a of the guide tube 32 is fixed to the outer circumferential step portion of the suction member 25 by TIG welding or the like. The outer peripheral portion of the lower end flange portion 32b of the guide tube 32 abuts against a stepped surface between the intermediate side wall portion 12b and the upper side wall portion 12c of the valve body 10.

The lower end flange portion 32b of the guide tube 32 is fixed to the upper side wall portion 12c of the valve body 10 by being swaged inside in a state where the annular member 27 is placed on the upper surface thereof, so as to sandwich the annular member 27. Further, the upper side wall 12c, the annular member 27, and the guide tube 32 are sealed and fixed by welding.

(action of Pilot operated electrically operated valve)

The operation of the pilot-operated valve 1 will be described. Here, the fluid pressure at the time of closing the valve in the inflow tube IT is P1, and the pressure in the upper space CF (see fig. 6) of the valve chamber is P2. The fluid pressure (pressure in the outlet opening 13 a) at the time of closing the valve in the outflow pipe OT is set to P3.

Although the valve chamber upper space CF is a space partitioned during the ascent of the sub-spool 16, for convenience of description in the present description, a space located on the opposite side of the external pressure equalizing chamber CC in the axial direction across the upper end portion of the main spool 15 will be described as the valve chamber upper space CF. In the following description, it is assumed that the outlet pressure (pressure in the outlet opening 13 a) P3 is zero for simplicity.

Fig. 3 to 7 are main part sectional views for explaining the operation of the pilot-operated valve 1.

Fig. 3 shows a state where the main valve element 15 is closed. At this time, the pilot valve body 35 closes the reduced diameter portion 16e of the communication hole 16d of the sub valve body 16, and the tapered portion 15i of the main valve body 15 is seated on the valve seat 14.

In the closed valve state, the fluid introduced from the inflow tube IT into the valve chamber CA through the inlet opening 12d is introduced into the inner pressure equalizing chamber CB, the outer pressure equalizing chamber CC, and the back pressure chamber CD through between the outer peripheral surface of the main valve body 15 and the inner peripheral surface of the valve body 10 (between sliding surfaces), the first pressure equalizing hole 15k, the second pressure equalizing hole 15m, and the like. Referring to fig. 1, the fluid introduced into the back pressure chamber CD is also guided to a clearance space CE formed between the lower end surface of the suction element 25 and the plunger 30 through a gap between the outer peripheral surface of the plunger 30 and the inner peripheral surface of the guide tube 32 (between sliding surfaces) and the lateral hole 30b and the vertical hole 30 a.

In the pilot electrically driven valve 1 in the valve-closed state, when the coil unit 22 is energized from a power source not shown, the plunger 30 is attracted to the attraction element 25, and thereby the pilot valve element 35 is lifted in the valve-opening direction as shown in fig. 4. Since the internal pressure of the back pressure chamber CD and the internal pressure of the clearance space CE are equal, the operation of the plunger 30 is not hindered.

Further, since the back pressure chamber CD is filled with fluid having a pressure substantially equal to the fluid pressure P1 in the inflow pipe IT, the sub valve element 16 is biased downward by the pressure, and does not immediately follow the pilot valve element 35.

However, when the reduced diameter portion 16e of the sub valve body 16 is opened by the rising of the pilot valve body 35, the fluid in the back pressure chamber CD flows out to the outlet opening 13a through the communication hole 16d (see fig. 4). At this time, the disc portion 16b is biased from below by the fluid pressure P1 in the internal pressure equalizing chamber CB and the biasing force of the first coil spring 17, and therefore, the sub-valve body 16 starts to rise as shown in fig. 5 as the back pressure chamber CD is depressurized. As further shown in fig. 6, the sub valve body 16 is engaged by the outer periphery of the upper surface of the circular plate portion 16b abutting against the lower surface of the lower end flange portion 32b of the guide tube 32.

Here, even if the sub spool 16 is lifted, the main spool 15 stays at the valve-closing position. The following describes the conditions.

At the time point when the sub-valve body 16 starts to rise (see fig. 5), the valve chamber upper space CF is not divided into a space distinguishable from the back pressure chamber CD but is connected to the back pressure chamber CD, so that the pressure P2 is equal to the pressure of the back pressure chamber CD. In addition, the pressure of the back pressure chamber CD is almost the same as P3. At this time, the force applied upward to the main spool 15 is a differential pressure between the fluid pressure P1 in the external pressure equalizing chamber CC and the internal pressure P2 (at this time, p2=p3) in the valve chamber upper space CF, and the biasing force of the second coil spring 18. On the other hand, the downward force applied to the main spool 15 is the fluid pressure P1 (differential pressure between P1 and P3 if P3 is not zero) in the internal pressure equalizing chamber CB and the biasing force of the first coil spring 17.

Here, referring to fig. 6, when the bearing area of the main spool 15 (the area of the surface facing along the axis L, the same applies hereinafter) of the outer pressure equalizing chamber CC and the valve chamber upper space CF is S1, and the bearing area of the inner pressure equalizing chamber CB is S2, S1 < S2. In addition, when the spring force of the first coil spring 17 is further set to K1, and the spring force of the second coil spring 18 is set to K2, K1 < K2. In order to hold the main spool 15 at the valve-closing position, the following expression (1) may be satisfied. (1) The left side of the expression indicates an upward pressing force, and the right side indicates a downward pressing force.

(P1－P2)×S1+K2＜P1×S2+K1 (1)

The formula (1) is deformed to obtain the formula (2).

K2－K1＜P1×S2－(P1－P2)×S1 (2)

In the present embodiment, since S1, S2, K1, and K2 are set so as to satisfy the equation (2), even if the sub-valve element 16 starts to rise, as shown in fig. 5, the main valve element 15 remains in the valve-closing position, and the tapered portion 15i does not immediately separate from the valve seat 14.

However, when the sub-valve body 16 is lifted, the lower end of the shaft portion 16a opens the diameter-reduced opening 15j as shown in fig. 6. In this way, a defined amount of fluid flows out from the valve chamber CA toward the outlet opening 13a through the first pressure equalizing hole 15k and the gap between the shaft portion 16a and the first inner peripheral portion 15 e.

The relationship of the force to hold the main spool 15 at the valve-closing position is expressed by the above-described formula (2). Therefore, the main spool 15 does not rise when formula (2) is satisfied, but if formula (2) becomes unsatisfied, the main spool 15 rises.

When the sub-valve body 16 is lifted, the back pressure chamber CD is closed in the valve chamber upper space CF, and the pressure equalizing chamber CB communicates with the valve chamber upper space CF from the gap between the disk portion 16b of the sub-valve body 16 and the fourth outer peripheral portion 15d of the main valve body 15, so that P2 becomes equal to P1, and p1—p2=0. Therefore, the formula (2) is shown below.

K2－K1＜P1×S2 (3)

Since the pressure equalization P1 decreases as the pressure equalization proceeds, the upper expression is not satisfied, and the main valve element 15 rises. The value of P1 at this time (when equation (3) is not satisfied) is determined by the settings of S2 and K2-K1.

When the main spool 15 is lifted, the tapered portion 15i is separated from the valve seat 14, so that the fluid flowing from the inflow tube IT into the valve chamber CA flows out to the outflow tube OT via the valve seat 14 and the outlet opening 13a. As shown in fig. 7, the upper end of the main valve element 15 abuts against the lower surface of the lower end flange portion 32b of the guide tube 32, and is locked in the valve opening position.

In contrast, when the power supplied from the power supply, not shown, to the coil unit 22 is disconnected from the valve-open state of fig. 7, the plunger 30 is lowered by the urging force of the spring 26, the pilot valve element 35 closes the sub-valve element reduced diameter portion 16e, the pressures of the back pressure chamber CD and the clearance space CE are increased, the sub-valve element 16 is depressed by a downward load, and the lower end of the shaft portion 16a bottoms out on the main valve element 15. Further, when the pressure in the upper portion of the main valve element increases, the pilot valve element 35, the sub valve element 16, and the main valve element 15 are integrally lowered, and the tapered portion 15i is seated on the valve seat 14, and the valve is restored to the closed position shown in fig. 3.

According to the present embodiment, even if the pilot valve element 35 is raised by energizing the coil unit 22, the main valve element 15 does not rise immediately, and rises to open the valve seat 14 after the pressure change in the internal pressure equalizing chamber CB is further generated. Therefore, the flow rate of the fluid flowing from the inflow tube IT to the outflow tube OT can be gradually increased when the valve is opened, and thus the noise generated can be effectively suppressed.

Since the condition for raising the main valve element 15 does not satisfy the equation (2), the spring force K2 of the second coil spring 18 is increased or decreased with respect to the spring force K1 of the first coil spring 17, whereby P1 for raising the main valve element 15 can be arbitrarily changed. In addition, when the diameter of the first pressure equalizing hole 15k is made small, the speed at which the pressures of the inner pressure equalizing chamber CB and the outer pressure equalizing chamber CC decrease becomes slow, and the time point at which the main valve element 15 rises can be delayed. In the pilot electrically driven valve 1, the first coil spring 17 may not be provided, and k1=0 in this case.

In the above description, P3 is described as zero, but if P3 is not zero, main spool 15 starts to rise when differential pressure (P1-P3) is smaller than a predetermined value. If the differential pressure at which the main spool starts to rise is set to the threshold value Δp, the point in time at which the main spool rises can be delayed when the threshold value is small.

Second embodiment

Fig. 8 is a longitudinal sectional view showing the pilot-operated valve 1A according to the second embodiment, and shows a state when the valve is closed. The pilot operated valve 1A of the present embodiment is different from the first embodiment in that it does not have a first pressure equalizing hole.

Even in the case where the first pressure equalizing hole 15k is not provided, when the diameter-reduced opening 15j is opened at the lower end of the shaft portion 16a at the time of the ascent of the sub-valve body 16, a limited amount of fluid flows out from the valve chamber CA toward the outlet opening 13a via the second pressure equalizing hole 15m, the inner pressure equalizing chamber CB, and the gap between the shaft portion 16a and the first inner peripheral portion 15 e. Therefore, the main spool 15 can be kept at the valve-closed position until the differential pressure (P1-P3) between P3 and the internal pressure P1 of the external pressure equalizing chamber CC becomes equal to or less than the threshold Δp.

The present invention is not limited to the above-described embodiments. Any of the components of the above embodiments can be modified within the scope of the present invention. In the above embodiment, any component may be added or omitted. For example, instead of the electromagnetic actuator 20, a motor actuator having a screw elevating mechanism may be used, or a normally open electromagnetic actuator may be used.

Symbol description

1. 1A pilot type electrically driven valve

10. Valve body

14. Valve seat

15. Main valve core

16. Auxiliary valve core

17. First spiral spring (second elastic component)

18. Second spiral spring (first elastic component)

20. Electromagnetic actuator

30. Plunger piston

35. Pilot valve core

CA valve chamber

CB internal pressure equalizing chamber

CC external pressure equalizing chamber

CD back pressure chamber

Claims (8)

1. A pilot-operated electrically actuated valve, comprising:

a valve body having a valve chamber communicating with the inlet opening and the outlet opening;

a pilot spool that is relatively movable with respect to the valve body;

a main valve element that is movable relative to the valve body and that can be seated on or separated from a valve seat in the valve chamber; and

a sub spool configured to be capable of abutting against or separating from the pilot spool and capable of relative movement with respect to the main spool,

a back pressure chamber is formed between the pilot spool and the sub spool,

a pressure equalizing chamber is formed between the primary spool and the secondary spool.

2. The pilot-operated valve of claim 1, wherein,

the valve body is provided with a first elastic member which biases the main valve element in a direction away from the valve seat.

3. The pilot-operated valve of claim 1 or 2, wherein,

when the pilot spool moves in the valve closing direction, the main spool is seated on a valve seat in the valve chamber via the sub spool.

4. The pilot-operated valve as claimed in any one of claims 1 to 3, wherein,

the secondary spool has a first pilot port,

when the pilot spool moves in the valve opening direction, the first pilot port of the sub spool is opened, and the fluid in the back pressure chamber flows out to the outlet opening through the first pilot port, whereby the sub spool moves in the valve opening direction.

5. The pilot operated valve of any one of claims 1 to 4,

the valve body is provided with a second elastic member which biases the main valve element in a direction approaching the valve seat with respect to the valve body.

6. The pilot-operated valve of claim 4, wherein,

the primary spool does not follow the secondary spool to move in the valve opening direction until the differential pressure between the outlet opening and the pressure equalizing chamber falls below a threshold value.

7. The pilot-operated valve of claim 6, wherein,

the main spool has a second pilot port,

when the sub spool moves in the valve opening direction, the pressure equalizing chamber and the outlet opening are communicated by opening the second pilot port of the main spool.

8. The pilot-operated valve of claim 7, wherein,

when the differential pressure between the pressure equalizing chamber and the outlet opening is reduced to the threshold value or less by communicating the pressure equalizing chamber and the outlet opening, the main valve spool moves in the valve opening direction and is separated from the valve seat in the valve chamber.

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