Spool-type switching valve

Abstract

[Problem] To provide a spool-type switching valve which is capable of efficiently linking a spool valve and a piston. [Solution] This spool-type switching valve comprises first and second piston chambers 32 which are respectively at both end parts of a spool hole 25 that extends in the axis L direction, wherein first and second spool valves 11b are accommodated in the spool hole, and first and second pistons 33 are accommodated in the piston chambers. First and second connection parts 70b are provided between valve end surfaces 34 formed at end parts of respective spool valves and piston end surfaces 33a of respective pistons which face the valve end surfaces 34. The connection parts each have a protruding part 72 that protrudes from a respective valve end surface and an insertion recess part 77 on the inner side of a wall part 36 that is provided upright at a respective piston end surface. An engagement groove part 73 is provided to each protruding part. Each wall part has a cutout groove part that is cut out in the axial direction, a leg part that is disposed on the inside of the cutout groove part, and an engagement claw part 47 that is provided to the tip end part of the leg part. In a state where the protruding part is inserted in the insertion recess part, the engagement claw part and the engagement groove part engage to link a respective spool valve and piston.

Description

Spool type switching valve

[0001] The present invention relates to a spool-type switching valve in which a spool valve slidably housed in a spool hole is driven by a piston.

[0002] In a spool-type switching valve in which a piston drives a spool valve slidably housed in a spool bore, the spool valve and the piston are formed as separate bodies and connected to each other by a connecting part, such as that described in Patent Document 1. The connecting part is formed by mutually engaging an engaging part provided on the spool valve with an engaged part provided on the piston.

[0003] In such conventional spool-type switching valves, a structure has generally been adopted as the connecting portion 112 between the spool valve and the piston, in which the spool valve 110 and the piston 111 are moved relative to each other in a direction perpendicular to their respective axes, so that an engaging portion 113 and an engaged portion 114 are engaged with each other, as shown in FIG.

[0004] However, in such a conventional connecting structure, in order to connect the spool valve 110 and the piston 111, as described above, it is necessary to move the spool valve 110 and the piston 111 relative to each other in a direction perpendicular to their respective axes, which tends to make the connecting process complicated and not necessarily efficient.

[0005] JP 2013-24345 A

[0006] Therefore, the technical object of the present invention is to provide a spool-type switching valve in which the spool valve and the piston are formed separately and connected to each other, which is capable of connecting the spool valve and the piston more efficiently.

[0007] In order to achieve the above object, a spool type switching valve according to the present invention comprises a body having a spool hole extending in an axial direction and a piston chamber at an axial end of the spool hole, a spool valve slidably housed in the spool hole, and a piston slidably housed in the piston chamber, the body being provided with ports for intake, exhaust, and output, and the spool valve is driven together with the piston by supplying or discharging pilot air to or from the piston chamber, thereby enabling selective switching of a communication state between the ports, and a connecting portion is provided between a valve end face formed at an end of the spool valve on the piston chamber side in the axial direction and a piston end face of the piston opposing the valve end face, the connecting portion being provided on the valve end face of the spool valve and an insertion recess formed on the piston end face of the piston into which the protrusion is inserted, the protrusion having an engagement groove formed around the axis, the insertion recess formed inside an annular wall extending from the piston end face, the wall including a cutout groove cut along the axial direction and an engagement portion formed in the cutout groove and engaged with the engagement groove, the engagement portion having a leg extending along the axial direction and having a base end connected to the piston end face, and an engagement claw portion at a tip end of the leg protruding radially inward around the axis, the engagement claw portion engaging with the engagement groove when the protrusion is inserted into the insertion recess, and the leg is elastically deformable radially outward around the axis.

[0008] In this case, the engaging claws preferably have, at their radially inner tips, inclined surfaces that incline radially outward toward the valve end face of the spool valve. Also, preferably, a recess is provided in the piston end face on which the legs are provided, and the base ends of the legs are erected from the bottom surface of the recess.

[0009] Preferably, a stopper portion against which the tip of the protrusion abuts is provided at the bottom of the insertion recess, and when the tip of the protrusion abuts against the stopper portion, a gap is formed between the valve end face of the spool valve and the tip of the engaging portion facing it.

[0010] Preferably, the protrusion of the spool valve and the stopper of the piston abut against each other by flat end surfaces perpendicular to the axis, and the tip of the engagement portion and a top surface of the wall portion opposite the valve end surface are located on the same plane perpendicular to the axial direction.

[0011] Preferably, a plurality of the notched grooves are formed in the wall at equal angular intervals around the axis.

[0012] Preferably, piston chambers are provided at both axial ends of the spool hole, a piston is housed in each of the piston chambers, two spool valves are housed coaxially in the spool hole, the axial length of the spool hole is longer than the total axial length of the two spool valves, and the two spool valves housed in the spool hole and the pistons arranged adjacent to each of the spool valves are connected by the connecting portions.

[0013] As described above, according to the present invention, in a spool-type switching valve in which the spool valve and piston are formed separately and connected to each other, it is possible to provide a spool-type switching valve in which the spool valve and piston can be connected more efficiently.

[0014] 10 is a perspective view of a spool type switching valve according to one embodiment of the present invention. FIG. 11 is a plan view of the spool type switching valve. FIG. 12 is a side view of the spool type switching valve. FIG. 13 is a cross-sectional view of the spool type switching valve corresponding to the view taken along arrows IV-IV in FIG. 2. FIG. 14 is a side view of the second piston. FIG. 15 is a rear view of the second piston. FIG. 16 is an enlarged cross-sectional view of the portion taken along arrow VII in FIG. 4. FIG. 17 is an enlarged cross-sectional view of the connection diagram in a state where the second piston has moved to the forward position. FIG. 18 is a cross-sectional view of the connection portion corresponding to the view taken along arrows IX-IX in FIG. 8. FIG. 19 is an explanatory view when connecting the second piston to the second spool valve. FIG. 11 is an enlarged perspective view of the portion taken along arrows XI in FIG. 10. FIG. 19 is an explanatory view when connecting a piston to a conventional spool valve.

[0015] A spool type switching valve according to the present invention will be described below. In this embodiment, a pilot type solenoid valve having two spool valves housed in a spool hole will be described as an example of the spool type switching valve.

[0016] As shown in Figures 1 to 4, the spool-type switching valve 1 comprises a main valve section 10 incorporating first and second spool valves 11a, 11b, and a pilot valve section 40 having first and second pilot solenoid valves 41a, 41b. The main valve section 10 has a main valve body 13, which is formed in a rectangular parallelepiped shape extending in the front-to-rear direction perpendicular to the width direction. A port block 15, which is equipped with first and second output ports 14a, 14b, is attached to the front end of the main valve body 13. The pilot valve section 40 has a pilot body 43, which is connected to the rear end of the main valve body 13.

[0017] A pair of opposing side surfaces 16a, 16b, 44a, 44b of the main valve body 13 and the pilot body 43 are each provided with a switching valve air supply opening 17 through which air is supplied, a switching valve exhaust opening 18 through which air is exhausted, a switching valve pilot supply opening 19 through which pilot air is supplied, and a switching valve pilot exhaust opening 20 through which pilot air is exhausted.

[0018] In this embodiment, the switching valve air intake opening 17 and the switching valve exhaust opening 18 are opened in the front lower portions of the side surfaces 16 a, 16 b, respectively. In addition, in the front-to-rear direction, the switching valve pilot supply openings 19 opened in each of the side surfaces 16 a, 16 b are disposed horizontally rearward of the switching valve exhaust openings 18. In addition, the switching valve pilot exhaust opening 20 is disposed above and rearward of the switching valve pilot supply opening 19.

[0019] The switching valve air intake openings 17, 17 communicate with each other through a switching valve air intake communication passage 21 formed in the main valve body 13. The switching valve exhaust openings 18, 18 communicate with each other through a switching valve exhaust communication passage 22 formed in the main valve body 13. Furthermore, the switching valve pilot supply openings 19, 19 communicate with each other through a switching valve pilot supply passage 23 formed in the main valve body 13. The switching valve pilot exhaust openings 20, 20 communicate with each other through a switching valve pilot exhaust passage 24 formed in the main valve body 13.

[0020] Next, we will explain the main valve section 10 of the spool-type switching valve 1. As shown in Figure 4, the main valve section 10 has a piston box 60 attached to the rear end surface of a main valve body 13, and a port block 15 attached to the front end surface of the main valve body 13.

[0021] A spool hole 25 is formed between both front and rear end faces of the main valve body 13, penetrating along the axis L. The spool hole 25 communicates with an air intake passage 26 located in the center in the direction of the axis L, first and second output passages 27a, 27b located on both sides of the air intake passage 26, and first and second exhaust passages 28a, 28b located on both sides of the output passages 27a, 27b. The first and second exhaust passages 28a, 28b communicate with each other via the switching valve exhaust communication passage 22.

[0022] The first spool valve 11a is inserted into the rear side of the spool hole 25 so as to be slidable along the axis L, and the second spool valve 11b is inserted into the front side of the spool hole 25 so as to be slidable along the axis L. That is, the first and second spool valves 11a and 11b are housed in the spool hole 25 on the same axis L. The length of the spool hole 25 in the axis L is longer than the sum of the axial lengths of the first and second spool valves 11a and 11b.

[0023] Each of the spool valves 11a and 11b has a first land portion 12a located in the center of the axis L, a second land portion 12b and a third land portion 12c located on either side of the first land portion 12a, and a shaft portion 12d connecting adjacent land portions. The shaft portion 12d has a smaller diameter than the land portions 12a-12c.

[0024] In these spool valves 11a and 11b, a first seal member 29a is attached to the outer periphery of the first land portion 12a, a second seal member 29b is attached to the outer periphery of the second land portion 12b, and a third seal member 29c is attached to the outer periphery of the third land portion 12c. In this embodiment, the third seal member 29c is a lip-type seal member that opens toward the first land portion 12a.

[0025] In the first spool valve 11a, a first seal member 29a opens and closes a first exhaust passage 28a connecting the first output port 14a and the switching valve exhaust opening 18 (see FIG. 3). In the first spool valve 11a, a second seal member 29b opens and closes an air supply passage 26 connecting the first output port 14a and the switching valve air supply opening 17 (see FIG. 3). In the first spool valve 11a, a third seal member 29c allows air to pass from the first piston chamber 61 side to the first exhaust passage 28a side, but prevents air from flowing out from the first exhaust passage 28a side to the first piston chamber 61 side.

[0026] In the second spool valve 11b, the first seal member 29a opens and closes the second exhaust passage 28b connecting the second output port 14b and the switching valve exhaust opening 18 (see FIG. 3). In the second spool valve 11b, the second seal member 29b opens and closes the air supply passage 26 connecting the second output port 14b and the switching valve air supply opening 17 (see FIG. 3). In the second spool valve 11b, the third seal member 29c allows air to pass from the second piston chamber 32 side to the second exhaust passage 28b side, but prevents air from flowing out from the second exhaust passage 28b side to the second piston chamber 32 side.

[0027] The piston box 60 is formed with a first piston chamber 61 that opens forward. A first piston 62, which has a diameter larger than that of the first spool valve 11a, is inserted into this first piston chamber 61 so as to be slidable in the direction of the axis L. The port block 15 is also formed with a second piston chamber 32 that opens rearward. A second piston 33, which has a diameter larger than that of the second spool valve 11b, is inserted into this second piston chamber 32 so as to be slidable in the direction of the axis L.

[0028] The first spool valve 11a and the first piston 62, which are adjacent in the direction of the axis L, are connected by a first connecting portion 70a. The second spool valve 11b and the second piston 33 are connected by a second connecting portion 70b. Since the first and second connecting portions 70a, 70b have the same configuration, only the second connecting portion 70b will be described, and a description of the first connecting portion 70a will be omitted.

[0029] 5 to 11, the second connecting portion 70b connects between the valve end surface 34 formed at the end of the second spool valve 11b on the second piston chamber 32 side in the axial direction L and the opposing piston end surface 33a of the second piston 33. The second connecting portion 70b has a protruding portion 72 protruding from the valve end surface 34 of the second spool valve 11b, and an insertion recess 77 provided on the piston end surface 33a of the second piston 33 and into which the protruding portion 72 is inserted.

[0030] In this embodiment, the valve end surface 34 is formed in an annular shape extending in a direction perpendicular to the axis L (hereinafter referred to as the radial direction). A cylindrical protrusion 72 protrudes from this valve end surface 34. The protrusion 72 extends coaxially with the axis L, and an engagement groove 73 is provided on the rear side of the protrusion 72 around the axis L. The protrusion 72 has a polygonal outer shape around the axis L. In this embodiment, the protrusion 72 has an octagonal outer shape. The protrusion 72 has a smaller diameter than the outer diameter of the third land portion 12c of the second spool valve 11b.

[0031] A flat end surface 74 extending in the radial direction is provided at the tip end (front end in the direction of the axis L) of the protruding portion 72. This flat end surface 74 abuts against a flat end surface 35a of a stopper portion 35 of the second piston 33, which will be described later.

[0032] The second piston 33 is formed in a cylindrical shape. The second piston 33 has a front surface 33b on which pilot air acts and a piston end surface 33a that is a back surface facing away from the front surface 33b. The front surface 33b and the piston end surface 33a extend in the radial direction. As shown in FIGS. 5 to 11, an annular wall portion 36 is provided on the piston end surface 33a. An insertion recess 77 is formed inside the wall portion 36.

[0033] The inner surface of the insertion recess 77 is formed in a polygonal shape around the axis L when viewed in the direction of the axis L. In this embodiment, the wall portion 36 is formed in a cylindrical shape, and the insertion recess 77 is formed in an octagonal shape similar to the outer shape of the protruding portion 72 of the second spool valve 11b. Therefore, by inserting the protruding portion 72 into the insertion recess 77, the second spool valve 11b and the second piston 33 can be integrally connected around the axis L.

[0034] The wall portion 36 includes a notched groove 37 cut along the axis L, and an engaging portion 38 provided in the notched groove 37 and engaged with the engaging groove 73. The engaging portion 38 includes a leg 39 extending along the axis L and having a base end connected to the piston end face 33a, and an engaging claw 47 provided at the tip of the leg 39 and projecting radially inward from the axis L. In this embodiment, the notched grooves 37 are provided in the wall portion 36 at positions facing each other with the axis L as the center. That is, the notched grooves 37 are formed at equal angular intervals (approximately 180 degrees) around the axis L in the wall portion 36. The tip end of the notched groove 37 opens at the tip of the wall portion 36, and the base end of the notched groove 37 communicates with a recess 33c provided in the piston end face 33a. The recess 33 c extends radially outward from the base end of the notched groove 37 and opens onto the outer circumferential surface of the second piston 33 .

[0035] The leg portions 39 are disposed at positions spaced apart from the pair of inner surfaces of the wall portions that separate the cutout groove portion 37. The leg portions 39 are erected from the bottom surface of the recess 33c and extend along the axis L within the cutout groove portion 37. In this embodiment, the leg portions 39 are formed in a rectangular parallelepiped shape, and have holes 39a that penetrate radially through their middle portions. The leg portions 39 are elastically deformable in the radial direction.

[0036] With the protrusion 72 inserted into the insertion recess 77, the engagement claw 47 protrudes into and engages with the engagement groove 73. The engagement claw 47 also has an inclined surface 47a at its radially inner tip that inclines radially outward toward the valve end face 34 of the second spool valve 11b. Therefore, when the tip of the protrusion 72 is pressed against the inclined surface 47a when the protrusion 72 is inserted into the insertion recess 77, the engagement claw 47 is easily opened radially outward as the leg 39 elastically deforms, thereby enabling the protrusion 72 to be smoothly inserted into the insertion recess 77.

[0037] Furthermore, the tip of the engaging portion 38 and the top surface 36a of the wall portion 36 that faces the valve end surface 34 are located on the same plane perpendicular to the axis L. That is, the claw portion end surface 47b of the engaging claw portion 47 that faces the valve end surface 34 and the top surface 36a of the wall portion 36 are located on the same plane perpendicular to the axis L. Note that the tip of the engaging portion 38 may protrude toward the valve end surface 34 beyond the top surface 36a of the wall portion 36.

[0038] 6 and 9, the contact between the protruding portion 72 of the second spool valve 11b and the piston end surface 33a (stopper portion 35) of the second piston 33 is achieved by the contact between flat end surfaces 74, 35a that are perpendicular to the axis L. Specifically, the stopper portion 35 that the tip end of the protruding portion 72 contacts is provided at the bottom of the insertion recess 77, and this stopper portion 35 is the flat end surface 35a that extends radially perpendicular to the axis L.

[0039] In this embodiment, the flat end surface 35a is formed on the same plane as the piston end surface 33a and is formed in an elliptical shape when viewed in the direction of the axis L. The elliptical flat end surface 35a is formed symmetrically with respect to the central axis L1 that passes through the center of the bottom of the insertion recess 77 and connects the pair of legs 39. The shape of the flat end surface 35a is not limited to an elliptical shape and may be circular, rectangular, or the like. In addition, a groove 35b is formed in the flat end surface 35a.

[0040] On the other hand, the tip of the protruding portion 72 of the second spool valve 11b is provided with a flat end surface 74 that is perpendicular to the axis L. In this embodiment, this flat end surface 74 is also formed in an elliptical shape similar to the flat end surface 35a. Furthermore, when the protruding portion 72 is inserted into the insertion recess 77, the flat end surface 74 can come into close contact with the flat end surface 35a.

[0041] 7 and 8 show a state in which the second piston 33 moves to the rear end position (retracted position) and the front end position (advanced position) of the second piston chamber 32, and the tip of the protrusion 72 abuts against the stopper portion 35. In this state, the second connecting portion 70b forms a gap 48 between the valve end surface 34 of the second spool valve 11b and the tip of the engaging portion 38 facing thereto. In this embodiment, this gap 48 is formed between the valve end surface 34 of the second spool valve 11b and the claw portion end surface 47b of the engaging claw portion 47 facing thereto. This eliminates the risk of the valve end surface 34 of the second spool valve 11b abutting against the engaging claw portion 47, thereby preventing damage to the engaging portion 38.

[0042] Next, the pilot valve unit 40 will be described. As shown in FIG. 4 , the pilot valve unit 40 includes first and second pilot solenoid valves 41a and 41b that drive the first and second spool valves 11a and 11b. These first and second pilot solenoid valves 41a and 41b each include first and second pilot inlet flow paths 79a and 79b, first and second pilot output flow paths 80a and 80b, and first and second pilot exhaust flow paths 81a and 81b. The first and second pilot solenoid valves 41a and 41b are configured to selectively connect the first and second pilot output flow paths 80a and 80b to the first and second pilot inlet flow paths 79a and 79b or the first and second pilot exhaust flow paths 81a and 81b by energizing and de-energizing solenoids 41a1 and 41b1.

[0043] The first and second pilot inlet passages 79a, 79b communicate with the switching valve pilot supply passage 23 through a pilot input passage 109 formed between the pilot body 43 and the main valve body 13. The first pilot output passage 80a communicates with the first piston chamber 61 through a first pilot supply communication passage 104a formed between the pilot body 43 and the piston box 60. The second pilot output passage 80b communicates with the second piston chamber 32 through a second pilot supply communication passage 104b formed between the pilot body 43, the piston box 60, and the main valve body 13. The first and second pilot exhaust passages 81a, 81b communicate with a pilot discharge passage 105 formed between the pilot body 43 and the piston box 60. The pilot discharge passage 105 communicates with the switching valve pilot exhaust passage 24 on its upstream side.

[0044] The pilot discharge passage 105 extends across the pilot body 43 and the piston box 60, and further extends to the first exhaust passage 28a through a gap formed between the third seal member 29c and the spool hole 25. The third seal member 29c is a lip-shaped seal member that opens toward the second land portion 12b, and allows air to flow from the first piston 62 side to the first exhaust passage 28a side, while preventing air from flowing from the first exhaust passage 28a side to the first piston 62 side.

[0045] Each of the first and second pilot solenoid valves 41a, 41b includes a pilot valve body 82 on its front side. The pilot valve body 82 includes inlet valve bodies 45a, 45b and exhaust valve bodies 46a, 46b, which are arranged in the front-rear direction and interlock with each other. When the solenoid 41a1 or 41b1 is energized, the inlet valve body 45a or 45b is opened, individually connecting the first pilot inlet flow path 79a to the first pilot output flow path 80a, or the second pilot inlet flow path 79b to the second pilot output flow path 80b. When the solenoid 41a1 or 41b1 is energized, the exhaust valve body 46a or 46b is closed, individually blocking the flow path from the first pilot output flow path 80a or the second pilot output flow path 80b to the pilot discharge flow path 105. As a result, pilot air is supplied to the first piston chamber 61 or the second piston chamber 32.

[0046] Furthermore, when solenoid 41a1 or 41b1 is de-energized, inlet valve bodies 45a, 45b are closed and exhaust valve bodies 46a, 46b are opened. Then, the flow path from first pilot output path 80a or second pilot output path 80b to first pilot exhaust path 81a or second pilot exhaust path 81b is opened, and air supplied to first piston chamber 61 or second piston chamber 32 is individually discharged. As a result, the acting force of air flowing into spool hole 25 from switching valve air intake communication path 21 via air intake path 26 becomes a returning force for first and second spool valves 11a, 11b, and first and second spool valves 11a, 11b perform a returning operation.

[0047] Next, the connecting operation for connecting the second spool valve 11b and the second piston 33 will be described. As shown in Figure 10, the second piston 33 is placed on the tip side of the protruding portion 72 of the second spool valve 11b, with the insertion recess 77 of the second piston 33 facing the second spool valve 11b. Then, at least one of the second spool valve 11b and the second piston 33 is moved toward each other to insert the protruding portion 72 into the insertion recess 77. As a result, the engaging claws 47 of the second piston 33 and the engaging grooves 73 of the second spool valve 11b are engaged with each other, and the second spool valve 11b and the second piston 33 are connected together.

[0048] In this way, by linearly moving the second spool valve 11b and the second piston 33 toward each other, it is possible to couple the second spool valve 11b and the second piston 33. This simplifies the coupling process and allows the second spool valve 11b and the second piston 33 to be coupled efficiently.

[0049] REFERENCE SIGNS LIST 1 Spool type switching valve 11a First spool valve (spool valve) 11b Second spool valve (spool valve) 13 Main valve body (body) 14a First output port (output port) 14b Second output port (output port) 15 Port block (body) 17 Switching valve air supply opening (air supply port) 18 Switching valve exhaust opening (exhaust port) 25 Spool hole 32 Second piston chamber (piston chamber) 33 Second piston (piston) 33a Piston end face 33c Recess 34 Valve end face 35 Stopper portion 35a, 74 Flat end face 36 Wall portion 36a Top surface 37 Notched groove portion 38 Engagement portion 39 Leg portion 47 Engagement claw portion 47a Inclined surface 48 Gap 60 Piston box (body) 61 First piston chamber (piston chamber) 62 First piston (piston) 70a First connecting portion (connecting portion) 70b Second connecting portion (connecting portion) 72 Projecting portion 73 Engagement groove portion 77 Insertion recess L Axis (shaft)

Claims

1. A spool-type switching valve comprising a body having an axially extending spool hole and a piston chamber at an axial end of the spool hole, a spool valve slidably housed in the spool hole, and a piston slidably housed in the piston chamber, the body being provided with ports for supplying, exhausting, and outputting, and configured to selectively switch the communication state between the ports by driving the spool valve together with the piston by supplying and exhausting pilot air to and from the piston chamber, wherein a connecting portion is provided between a valve end face formed at the end of the spool valve on the piston chamber side in the axial direction and a piston end face of the piston opposing said valve end face, the connecting portion having a protruding portion protruding from the valve end face of the spool valve and an insertion recess provided on the piston end face of the piston into which the protruding portion is inserted, the protruding portion being provided with an engagement groove portion around the axis, and the insertion recess being formed on the inside of an annular wall erected from the piston end face, a spool type switching valve comprising: the wall portion includes a cutout groove portion cut along the axial direction; and an engagement portion provided in the cutout groove portion and engaged with the engagement groove portion; the engagement portion has a leg portion extending along the axial direction and having a base end portion connected to the piston end surface, and an engagement claw portion provided at a tip portion of the leg portion and protruding radially inwardly around the axis; the engagement claw portion is engaged with the engagement groove portion with the protrusion portion inserted into the insertion recess; and the leg portion is elastically deformable radially outwardly around the axis.

2. A spool type switching valve as described in claim 1, characterized in that the engaging claw portion has an inclined surface at its radially inner tip that inclines radially outward as it approaches the valve end face of the spool valve.

3. A spool-type switching valve as described in claim 1, characterized in that a recess is provided in the piston end face on which the leg is provided, and the base end of the leg is erected from the bottom surface of the recess.

4. A spool type switching valve as described in claim 1, characterized in that a stopper portion against which the tip of the protrusion abuts is provided at the bottom of the insertion recess, and when the tip of the protrusion abuts against the stopper portion, a gap is formed between the valve end face of the spool valve and the tip of the engaging portion facing thereto.

5. A spool type switching valve as described in claim 4, characterized in that the protrusion of the spool valve and the stopper portion of the piston abut against each other by means of flat end faces that are perpendicular to the axis.

6. A spool-type switching valve as described in claim 4, characterized in that the tip of the engagement portion and a top surface of the wall portion opposing the valve end surface are located on the same plane perpendicular to the axial direction.

7. The spool type switching valve according to claim 1, characterized in that a plurality of the notched grooves are formed in the wall portion at equal angular intervals around the axis.

8. A spool type switching valve as claimed in any one of claims 1 to 7, characterized in that: piston chambers are provided at both axial ends of the spool hole, a piston is accommodated in each of the piston chambers, two spool valves are accommodated coaxially in the spool hole, the axial length of the spool hole is longer than the combined axial length of the two spool valves, and the two spool valves accommodated in the spool hole and the pistons arranged adjacent to each of the spool valves are connected by the connecting parts.

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