JP2826461B2 - solenoid valve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

This invention is operated by an electromagnet,
The present invention relates to a solenoid valve that controls the start and stop and the operation direction of an actuator.

[0002]

2. Description of the Related Art Among the switching valves for controlling the start and stop and operation direction of an actuator, as a solenoid valve operated by an electromagnet, a single solenoid solenoid valve operating a valve with one solenoid and two solenoids are used. There is a double solenoid solenoid valve that operates the valve with.

The single solenoid solenoid valve has a structure in which the valve shaft returns to its original position when the power supply to the solenoid, that is, the electromagnet is released, that is, a self-return type structure. On the other hand, the double solenoid solenoid valve has a structure in which the position of the valve shaft at the time of energization is maintained even when the energization of the energized solenoid is released, that is, a self-holding type structure. Therefore, when energization of the solenoid is released, the valve shaft of the single solenoid solenoid valve returns to the state before energization, whereas the valve axis of the double solenoid solenoid valve maintains the state before energization. Will be.

In recent years, as described on page 479 of the new edition hydraulic and pneumatic handbook "Ohm Co., Ltd. (issued on Feb. 25, 1989)", a plurality of solenoid valves are mounted on one manifold block. Manifold solenoid valves have been developed and are widely used. This manifold solenoid valve
A common supply port and exhaust port are formed in the manifold block, and air supply and exhaust to and from a plurality of solenoid valves are performed through the manifold block.

[0005]

For example, when a manifold solenoid valve is used in an assembly plant for parts and products, a single solenoid solenoid valve and a double solenoid solenoid valve are used in accordance with the type of actuator and its control method. One of the valves will be selected, but specifications such as change of actuator and control method will be changed, and single solenoid solenoid valve, that is, self-return type solenoid valve, and double solenoid solenoid valve, that is, self-holding type will be selected. May be replaced.

In this case, one of a plurality of solenoid valves mounted on the manifold block is removed from the manifold block and replaced with another type of solenoid valve. However, there is a problem that it is necessary to stop the assembly or production line of parts and products in the above for a long time, and the workability is not good.

An object of the present invention is to provide a solenoid valve which can be easily changed to a self-return type solenoid valve or a self-holding type solenoid valve without replacing the solenoid valve itself.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0009]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

That is, the solenoid valve of the present invention has a large-diameter piston at one end and a small-diameter piston at the other end, and accommodates a valve shaft provided with a plurality of valve elements so as to be slidable in the axial direction. A main valve portion having a hole formed therein, a plurality of output ports formed in the main valve portion communicating with the valve hole, and communicating with the valve shaft, each of which is formed to open on the same surface of the main valve portion. An air supply port, and a plurality of exhaust ports, a solenoid portion mounted at one end of the main valve portion on an extension of the valve shaft, and reciprocates in the solenoid portion in the same direction as the valve shaft. A first plunger movably provided and operating at a position where the first operation passage communicating with the large-diameter pressure chamber accommodating the large-diameter piston communicates with the air supply port and a position where the first operation passage is closed and the solenoid; Reciprocating in parallel with the first plunger A second plunger provided in the main valve portion, the second plunger being operated at a position for closing and closing a second operation passage having an opening surface at the other end surface of the main valve portion and the air supply port; A bypass passage formed in communication with an air supply port and having an open surface at the other end surface of the main valve portion; and a switch passage mounted on the other end surface of the main valve portion so as to be switchable between a self-return position and a self-holding position, At the self-return position, the second operation passage and the small-diameter pressure chamber are closed, and the bypass passage is communicated with the small-diameter pressure chamber. At the self-holding position, the bypass passage is closed, and the second operation passage is closed. A switching member for communicating with the small-diameter pressure chamber.

In this case, the switching member has a non-concentric circular second operation passage communication hole for communicating the second operation passage with the small-diameter pressure chamber and a bypass communication hole for communicating the small-diameter pressure chamber with the bypass passage. , Or on concentric circles. It is also possible to open a communication hole for selectively communicating the second operation passage or the bypass passage with the small-diameter pressure chamber.

[0012]

According to the solenoid valve having such a configuration, if only the first plunger is operated with the position of the switching member being the self-return position, the solenoid valve is set to a single solenoid type solenoid valve, and the self-holding position is set. If both plungers are actuated, a double solenoid type solenoid valve is set. Therefore, the specifications of the solenoid valve can be easily changed in a short time without replacing the solenoid valve itself.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is a perspective view showing a manifold solenoid valve in which a plurality of solenoid valves of the present invention are mounted on a manifold block, FIG. 2 is a sectional view showing a main valve portion of the solenoid valve of the present invention, 3 is a sectional view showing a pilot portion of the solenoid valve of the present invention, FIG. 4 is a perspective view showing an inner surface side of a switching member used for the solenoid valve, and FIG. 5 is a switching member and a second operation passage and a bypass passage. FIG. 6 is an explanatory diagram showing the positional relationship with
FIG. 3 is a sectional view showing an operation state of the solenoid valve of the present invention.

As shown in FIG. 1, an air supply port 2 connected to a fluid pressure source and two exhaust ports 3 and 4 are formed in a manifold block 1. A plurality of solenoid valves 5a to 5c are mounted on the manifold block 1. In the manifold block 1, each solenoid valve 5
a to 5c, two output ports 6a to 6
c, 7a to 7c are formed, and one of the output ports 6a to 6c or 7a to 7c is operated by the operation of the solenoid valves 5a to 5c.
The fluid is discharged from c. An arbitrary number of solenoid valves are mounted on the manifold block 1.

The output ports 6a, 6b, 7a, 7b are connected to pneumatic cylinders 8a, 8b as actuators, and the rods 9a, 9b of the corresponding pneumatic cylinders 8a, 8b are operated by operating the solenoid valves 5a, 5b. Are respectively driven.

As shown in FIGS. 2 and 3, the solenoid valve according to the present invention has a main valve portion 11 and a solenoid portion 12 integrally formed to form a housing 13 of the solenoid valve.
The housing 13 of the solenoid valve is fixed to the manifold block 1 (FIG. 1) at a lower portion thereof.

As shown in FIG. 2, a valve hole 16 is formed in the main valve portion 11, and an air supply port P which opens into the valve hole 16 is formed in a central portion of the main valve portion 11 in the axial direction. There is formed, at both ends of the main valve portion 11, opening to the exhaust port R ₁ and R ₂ are formed on the valve hole 16. The air supply port P communicates with the air supply port ₂ of the manifold block 1, and the respective exhaust ports R ₁ and R ₂ communicate with the exhaust ports 3 and 4 of the manifold block 1. Between the supply port P and the respective exhaust ports R ₁ and R ₂ ,
The output ports A and B are formed so as to open in the valve hole 16, and the respective output ports A and B are respectively connected to the output ports 6a and 7a of the manifold block 1 shown in FIG. ing.

A valve shaft 17 is slidably mounted in the valve hole 16 in the axial direction. In the illustrated case, six valve bodies 18 are mounted on the valve shaft 17. Therefore, as shown in FIG. 2, when the valve shaft 17 is moved rightward in the figure, the air supply port P and the output port B are in communication, and the output port A and the exhaust port R ₁ are in communication. Become. On the other hand, as shown in FIG. 6, the valve shaft 17 is moved leftward, the supply port P and the output port A is communicated with each other, the output port B and the exhaust port R ₂ is a communicating state.

A large-diameter piston 21 is provided at one end of the valve shaft 17, that is, on the right side (left side in FIG. 3) of the valve shaft 17, and on the other end, that is, on the left side of the valve shaft 17 (left end in FIG. 2). ) Is provided with a small-diameter piston 22 (see FIG. 2) having a smaller diameter than the large-diameter piston 21. In the case shown, the pressure receiving area of the large diameter piston 21 is set to twice the pressure receiving area of the small diameter piston. The large-diameter piston 21 is housed in a large-diameter pressure chamber 23 formed in the solenoid portion 12,
The small-diameter piston 22 is housed in a small-diameter pressure chamber 24 (see FIG. 2) formed on the left side of the housing 13.

As shown in FIG. 3, a common communication chamber 25 is formed in the solenoid section 12, and this common communication chamber 25 is formed.
Is connected to the air supply port P by the communication passage 26.
Therefore, the fluid is always supplied from the air supply port P to the common communication chamber 25. Further, in the common communication chamber 25, a manual operation rod 29 for manually retreating plungers 27a, 28a of a first solenoid 27 and a second solenoid 28 described later is housed. That is, the manual operation rod 29 is inserted into the common communication chamber 25 with the operation part 29a formed at one end facing the outside, and is entirely moved in the direction of the operation part by the spring member 30 mounted at the other end. Being energized. The manual operation rod 29 is formed with two cam portions 29b,
By rotating the operation portion 29a to change the cam position of the cam portion 29b in the circumferential direction, the plunger 28a is manually moved backward through the pin 29c.

The first communication port 31 formed in the common communication chamber 25 communicates with the large-diameter pressure chamber 23 through the first operation passage 33. To open and close the passage 33, a plunger 27 a of the first solenoid 27 is arranged to face the first communication port 31.

The second communication port 32 formed in the common communication chamber 25 communicates with the small-diameter pressure chamber 24 through the second operation passage 34. The second communication port 32, that is, the second operation passage The plunger 28 a of the second solenoid 28 is arranged to face the second communication port 32 to open and close the valve 34.

A valve body 27b which presses against the first communication port 31 is provided at the tip of the plunger 27a of the first solenoid 27.
Is provided, and the plunger 27a is slidably mounted in the bobbin 27d mounted on the yoke 27c in the axial direction. A fixed core 27e is fixed to the rear end of the bobbin 27d.
The first solenoid 27 is formed by winding f.

The plunger 27a is urged by a compression coil spring 27g in the direction in which the valve body 27b is pressed against the first communication port 31. When the coil portion 27f is energized, the elastic force, that is, the spring force is applied. Plunger 2 against
7a is separated from the first communication port 31.

The second solenoid 28 is connected to the first solenoid 2
7 is provided adjacent to and in parallel with the first solenoid 2.
7 has the same structure. In the members forming the second solenoid 28, members corresponding to the members forming the first solenoid 27 are denoted by the same reference numerals a to g as 28.
Is attached.

A fluid chamber 35 is formed in the solenoid portion 12 so as to extend from the plunger 27a. The fluid chamber 35 is formed with a fluid chamber 36 formed outside the distal end of the plunger 27a and a first operation passage 33. Communication. Accordingly, the coil portion 27f is energized and the valve body 2
7b moves away from the first communication port 31, the fluid chamber 36,
The fluid in the common communication chamber 25 is supplied to the large-diameter pressure chamber 23 via the first operation passage 33 and the fluid chamber 35.

On the other hand, a fluid chamber 41 is formed on the extension of the plunger 28a, and the fluid chamber 41 is communicated with a fluid chamber 42 formed outside the distal end portion of the plunger 28a by the second operation passage 34. ing. Therefore,
When the solenoid 28f is energized and the valve body 28b moves away from the second communication port 32, the fluid in the common communication chamber 25 is reduced through the fluid chamber 42, the second operation passage 34, and the fluid chamber 41 to the small-diameter pressure chamber. 24.

An exhaust port 4 is provided in the fluid chambers 35 and 41.
Valve bodies 45 and 46 for opening and closing the valves 3 and 44 are urged by compression coil springs 47 and 48 in a direction to close the exhaust ports 43 and 44 connected to the exhaust port 49. The valve bodies 45 and 46 are provided in the first and second operation passages 33 and 34, and one end thereof is provided in the plunger 27.
a, 28a is in contact with the other end of the opening / closing pin (not shown) contacted with 28a. Thereby, the valve body 4 is synchronized with the forward and backward movements of the plungers 27a and 28a.
5, 46 are to be moved.

Therefore, when the plungers 27a, 28a move backward and the first and second communication ports 31, 32 are opened, the exhaust ports 43, 44 are closed by the valve bodies 45, 46 via the opening / closing pins, and Fluid from the common communication chamber 25 is supplied to the large-diameter pressure chamber 23 or the small-diameter pressure chamber 24. On the other hand, when the plungers 27a, 28a move forward, the valve bodies 45, 46 pushed by the open / close pins are moved in a direction against the spring force of the compression coil springs 47, 48, whereby the exhaust ports 43, 44 are opened. Large diameter pressure chamber 2
The fluid in the 3 or small-diameter pressure chamber 24 is discharged from the exhaust port 49.

While the air supply port P communicates with the communication passage 26 as described above, the air supply port P also communicates with the bypass passage 50 leading to the small-diameter pressure chamber 24 as shown in FIG. And
A switching member 51 having a second operation passage communication hole 51a corresponding to the second operation passage 34 and a bypass communication hole 51b corresponding to the bypass passage 50 is provided on the small-diameter piston 22 side of the housing. It is provided detachably. Therefore, the second operation passage 34
The bypass member 50 and the switching member 51
Is connected to the small-diameter pressure chamber 24 via a second operation passage communication hole 51a and a bypass communication hole 51b which are opened at the second position. As shown in FIG.
The operation passage communication hole 51a and the bypass communication hole 51b are provided on non-concentric circles with respect to the rotation center axis of the valve shaft 17, respectively.

Then, as shown in FIG.
To rotate the bypass communication hole 51b and the bypass passage 50.
By matching the positions of the holes, the bypass passage 50 and the small-diameter pressure chamber 24 communicate with each other as shown in FIG. Conversely, the second operation passage communication hole 51a and the second
By matching the hole positions of the operation passage 34, the second operation passage 34 and the small-diameter pressure chamber 24 communicate with each other as shown in FIG.

When the switching member 51 is set to the self-return position shown in FIG. 2, even if the second communication port 32 is closed by the valve body 28b of the second solenoid 28, the air supply port P can be connected through the bypass passage 50. Fluid is always small diameter pressure chamber 24
It will be in the state supplied inside. Accordingly, when the coil portion 27f of the first solenoid 27 is energized in this state, the valve shaft 17 moves to the left in FIG. 2, and returns to the original position when the energization is released. On the other hand, when the switching member 51 is set to the self-holding position shown in FIG.
When the coil portion 27f of No. 7 is energized, the first operation passage 33 is opened and the fluid is supplied into the large-diameter pressure chamber 23, so that the valve shaft 17 moves to the left as shown in FIG. When the coil portion 28f of the second solenoid 28 is energized, the second operation passage 34 is opened and the fluid is supplied into the small-diameter pressure chamber 24, so that the valve shaft 17 moves to the right. Regardless of the position of the valve shaft 17, when the energization to the coil portions 27 f and 28 f is stopped, the valve shaft 17 maintains the position set by the operation of one of the solenoids. Become.

Next, the operation of the above-described solenoid valve will be described. FIG. 2 is a view showing a case where the solenoid valve is used as a single solenoid type, and the coil portion 28f of the second solenoid 28 shown in FIG. 3 is not energized, so that the second solenoid 28 is set to the rest state. ing. The switching member 51 is connected to the bypass passage 50 as shown in FIG.
Is set to a self-return position in which it communicates with the small-diameter pressure chamber 24 via the bypass communication hole 51b. In this case, the fluid from the air supply port P is supplied from the bypass passage 50 to the small-diameter pressure chamber 24 through the bypass communication hole 51b.
Therefore, when no current is supplied to the coil portion 27f of the first solenoid 27, the valve shaft 17 is at the position shown in FIG. Flows out to the output port B.

On the other hand, the coil portion 27 of the first solenoid 27
When a current is supplied to the first communication port f, the valve body 27b is separated from the first communication port 31, so that the common communication chamber 25 and the fluid chambers 35, 3
6 is in a communicating state, and the fluid from the air supply port P is supplied to the large-diameter pressure chamber 23 via the first operation passage 33. As described above, the pressure receiving area of the large-diameter piston 21 is
2, the valve shaft 17 is shown in FIG. 2 by the fluid supplied into the large-diameter pressure chamber 23 even if the fluid is supplied into the small-diameter pressure chamber 24. Move to the left of the position. Thus, the fluid supply port P flows to the output port A, the fluid from output port B flows into the exhaust port R _2.

Next, when the solenoid valve is used as it is as a double solenoid solenoid valve, the switching member 51 is set to 180
゜ The posture is changed to the self-holding position shown in FIG. 6, that is, a position where the second operation passage 34 is communicated with the small-diameter pressure chamber 24 through the second operation passage communication hole 51a,
The state is set such that electric power can be supplied to the coil portion 28f of the second solenoid 28.

Under the state set as described above, the second
When power is supplied to the coil portion 28f of the solenoid 28,
Fluid is supplied from the second operation passage 34 into the small-diameter pressure chamber 24, and the valve shaft 17 moves to the left from the position shown in FIG. On the other hand, the energization of the coil portion 28f of the second solenoid 28 is released, and the coil portion 27f of the first solenoid 27 is released.
When electricity is supplied to the large-diameter pressure chamber 23, fluid is supplied to the large-diameter pressure chamber 23,
The valve shaft 17 moves to the position shown in FIG. In this case,
When the energization is released, the valve shaft 17 is held at the moved position.

As described above, by switching the position of the switching member 51 between the self-return position and the self-holding position, one solenoid valve can be used as a single solenoid self-return type solenoid valve, while a double solenoid is used. Can also be used as a self-holding type solenoid valve. Therefore, when the solenoid valve is used in an assembly line for parts and products, the type of the solenoid valve can be easily changed.

(Embodiment 2) FIG. 7 is an explanatory view showing a positional relationship between a switching member used in an electromagnetic valve according to another embodiment of the present invention and a second operation passage and a bypass passage.

According to the switching member 61 in this embodiment,
A second operation passage communication hole 61a for communicating the second operation passage 34 with the small-diameter pressure chamber and a bypass communication hole 61b for communicating the small-diameter pressure chamber with the bypass passage 50 are concentric with the rotation center axis of the valve shaft. It is established in. As shown, the second operation passage 34 and the bypass passage 50
Is formed at a position where it is communicated with the small-diameter pressure chamber via the second operation passage communication hole 61a and the bypass communication hole 61b opened by switching the hole position of the switching member 61, respectively.

As shown in this embodiment, the second operation passage communication hole 61a and the bypass communication hole 6
The hole position of 1b may be concentric.

(Embodiment 3) FIG. 8 is an explanatory view showing a positional relationship between a switching member, a second operation passage, and a bypass passage used in a solenoid valve according to still another embodiment of the present invention.

As shown in FIG. 8, according to the switching member 71 in this embodiment, a communication hole 71a for selectively communicating the second operation passage 34 or the bypass passage 50 with the small-diameter pressure chamber.
Has been established. The second operation passage 34 and the bypass passage 50 are formed at positions where they are communicated with the small-diameter pressure chamber via the communication holes 71a by switching the hole positions of the switching member 71, respectively.

As in the case of the switching member 71 shown in this embodiment, only a single communication hole 71a is opened, and this is connected to the second operation passage 34.
Alternatively, it is also possible to selectively communicate with the bypass passage 50.

As described above, the invention made by the inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and can be variously modified without departing from the gist of the invention. Needless to say.

For example, in this embodiment, all the five-port valves are used. However, the number of ports is not limited to this, and the present invention can be applied to a four-port two-position switching valve or a three-port two-position switching valve. Can be applied.

[0047]

Advantageous effects obtained by typical ones of the inventions disclosed in the present application will be briefly described.
It is as follows.

(1) According to the present invention, a self-returning type solenoid valve, ie, a single solenoid type solenoid valve, and a self-holding type solenoid valve, ie, a double solenoid type solenoid valve, without replacing the solenoid valve itself. It can be easily changed to any of

(2) Therefore, in the assembly or processing line of parts and products using the solenoid valve, when the specification of the assembling apparatus is changed, it is possible to quickly respond to the change, and Efficiency will be greatly improved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a manifold solenoid valve in which a plurality of solenoid valves according to Embodiment 1 of the present invention are mounted on a manifold block.

FIG. 2 is a sectional view showing a main valve portion of the solenoid valve.

FIG. 3 is a sectional view showing a pilot portion of the solenoid valve.

FIG. 4 is a perspective view showing an inner surface side of a switching member used for the solenoid valve.

FIG. 5 is an explanatory diagram showing a positional relationship between the switching member, a second operation passage, and a bypass passage.

FIG. 6 is a sectional view showing an operation state of the solenoid valve.

FIG. 7 is an explanatory diagram showing a positional relationship between a switching member used in an electromagnetic valve according to a second embodiment of the present invention and a second operation passage and a bypass passage.

FIG. 8 is an explanatory diagram illustrating a positional relationship between a switching member, a second operation passage, and a bypass passage used in an electromagnetic valve according to a third embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Manifold block 2 Air supply port 3 Exhaust port 4 Exhaust port 5a, 5b, 5c Solenoid valve 6a, 6b, 6c Output port 7a, 7b, 7c Output port 8a, 8b Pneumatic cylinder 9a, 9b Rod 11 Main valve part 12 Solenoid part 13 Housing 16 Valve Hole 17 Valve Shaft 18 Valve Element 21 Large Diameter Piston 22 Small Diameter Piston 23 Large Diameter Pressure Chamber 24 Small Diameter Pressure Chamber 25 Common Communication Chamber 26 Communication Path 27 First Solenoid 27a Plunger 27b Valve 27c Yoke 27d Bobbin 27e Fixed Core 27f Coil part 27g Compression coil spring 28 Second solenoid 28a Plunger 28b Valve body 28c Yoke 28d Bobbin 28e Fixed core 28f Coil part 28g Compression coil spring 29 Manual operation rod 29a Operation part 29b Cam part 29c Pin 30 Member 31 First communication port 32 Second communication port 33 First operation passage 34 Second operation passage 35 Fluid chamber 36 Fluid chamber 41 Fluid chamber 42 Fluid chamber 43 Exhaust port 44 Exhaust port 45 Valve element 46 Valve element 47 Compression coil spring 48 Compression coil spring 49 Exhaust port 50 Bypass passage 51 Switching member 51a Second operation passage communication hole 51b Bypass communication hole 61 Switching member 61a Second operation passage communication hole 61b Bypass communication hole 71 Switching member 71a Communication hole A Output port B Output port P Air supply port R ₁ exhaust port R ₂ exhaust port

──────────────────────────────────────────────────続 き Continuation of the front page (56) References Japanese Utility Model Hei 6-82479 (JP, U) Japanese Utility Model Hei 5-44625 (JP, Y2) (58) Fields surveyed (Int. Cl. ⁶ , DB name) F16K 31/06 F16K 27/00

Claims (4)

(57) [Claims] A large diameter piston is provided at one end and a small diameter piston is provided at the other end.
A valve shaft with a plurality of valve elements is provided in the axial direction.
A main valve portion having a valve hole slidably housed therein, and a plurality of outputs formed in the main valve portion in communication with the valve hole.
Port and the same axis of the main valve part respectively communicating with the valve shaft
Air supply port and multiple exhaust ports
And one end of the main valve portion, which is located on an extension of the valve shaft.
The solenoid part attached thereto and reciprocally move in the same direction as the valve shaft in the solenoid part.
Large-diameter pressure chamber, which is provided
A first operation passage communicating with the air supply port and the air supply port;
Plunger operative between a closed position and a closed position
In the solenoid section in parallel with the first plunger.
The main valve portion has an opening at the other end surface.
Where the second operation passage to communicate with the air supply port communicates
And a second plunger that operates to a position to be closed, and a main plunger formed in communication with the air supply port in the main valve portion.
A bypass passage having an opening surface at the other end surface of the valve portion, and a self-return position and a self-holding position at the other end surface of the main valve portion.
It is mounted so that it can be moved freely, and is in the self-return position.
To close the second operation passage and the small-diameter pressure chamber
The bypass passage and the small-diameter pressure chamber communicate with each other.
Closing the bypass passage in the self-holding position and
An electromagnetic valve , comprising: a switching member for communicating a second operation passage with the small-diameter pressure chamber . 2. The switching member has a second operation passage communication hole that communicates the second operation passage with the small diameter pressure chamber, and a bypass communication hole that communicates the small diameter pressure chamber with the bypass passage. 2. The solenoid valve according to claim 1, wherein the solenoid valves are respectively provided on non-concentric circles with respect to a rotation center axis of the valve shaft. 3. The switching member includes a second operation passage communication hole that communicates the second operation passage with the small-diameter pressure chamber, and a bypass communication hole that communicates the small-diameter pressure chamber with the bypass passage. 2. The solenoid valve according to claim 1, wherein the solenoid valve is formed concentrically with the center axis of rotation of the valve shaft. 4. The solenoid valve according to claim 1, wherein the switching member is provided with a communication hole for selectively communicating the second operation passage or the bypass passage with the small-diameter pressure chamber.