JP2018100685A - Detent mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a detent mechanism which can keep a function as a detent irrespective of a material constituting a seal ring.SOLUTION: A detent mechanism 30 prevents the rotation of a seal ring in a mechanical seal 1 relative to an attached member. The detent mechanism 30 includes an annular member 31 interposed between a seal ring 10 and an attached member 2, and a protrusion piece 35 protruding from both ends of the annular member 31 in the axial direction. The protrusion piece is arranged in respective holes 13, 14 formed in the seal ring and the attached member with the annular member 31 sandwiched between the seal ring and the attached member.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a seal ring rotation prevention mechanism in a mechanical seal that limits leakage of a sealed fluid.

  The mechanical seal is composed of a rotating seal ring that can move in the axial direction by a biasing force of a spring or the like and a stationary seal ring that does not move in the axial direction according to the wear of the sliding surface. It restricts leakage of the sealed fluid on the moving surface. For example, in the mechanical seal described in Patent Document 1, a rotary seal ring is attached to a rotary shaft (shaft) so as to rotate synchronously with the rotary shaft, and the stationary seal ring is formed on the stationary seal ring. The pins that are respectively fitted into the holes and the holes formed on the housing side (fixed seat) function as a detent mechanism, whereby the rotation is restricted with respect to the housing side.

  By the way, as a material constituting the stationary seal ring of such a mechanical seal, a coated metal member, cemented carbide material, SiC (silicon carbide) or the like is used. After a hole is formed, a pin with an outer diameter slightly larger than the inner diameter is pressed into the hole, for example, so that it cannot be dropped off, or a hole having an inner diameter slightly larger than the outer diameter of the pin in a stationary seal ring The pin is inserted into the pin, and the gap between the pin and the hole is filled with an adhesive or the like to fix the pin so that it cannot fall off. On the other hand, in the case of cemented carbide, SiC, etc., there is a risk of damage when the pin is driven. Therefore, the pin is inserted into a hole having an inner diameter slightly larger than the outer diameter of the pin, and an adhesive or the like is used to The gap is filled and fixed so that it cannot be dropped off.

Japanese Utility Model Publication No. 4-63870 (page 3, Fig. 1)

  However, when a method of press-fitting, such as driving a pin, is adopted, the tightening allowance between the pin and the hole decreases due to aging, and the pin falls out of the hole and does not sufficiently function as a detent for the stationary seal ring. There is a fear. On the other hand, when a method of filling the gap between the pin and the hole with an adhesive or the like is adopted, the adhesive strength decreases due to deterioration over time, the pin may fall out of the hole, and may not function sufficiently as a detent for the stationary seal ring. There is. As described above, in the method of constructing the detent mechanism by directly fixing the pin to the stationary seal ring, it is necessary to appropriately select a fixing method according to the material of the stationary seal ring, There was a problem that the function as a detent could not be maintained.

  The present invention has been made paying attention to such problems, and can provide a detent mechanism that can be employed regardless of the material constituting the seal ring and can maintain the function as a detent. Objective.

In order to solve the above problems, the detent mechanism of the present invention is
A housing which is a mounted member through which a rotating shaft of a rotary machine is inserted, a stationary seal ring held by the housing, and a rotating member which is held by the mounted member on the rotating shaft side and rotates together with the rotating shaft. At least one of the seals in a mechanical seal comprising: a rotary seal ring that is in sliding contact with the seal ring; and a spring that biases the stationary seal ring and the rotary seal ring in an axially pressed state. A detent mechanism that prevents the ring from rotating relative to the attached member;
The detent mechanism includes an annular member interposed between the sealing ring and the attached member, and projecting pieces that project from both sides in the axial direction of the annular member,
The protruding pieces are respectively disposed in holes formed in the sealing ring and the attached member in a state where the annular member is sandwiched between the sealing ring and the attached member.
According to this feature, the annular member provided with the projecting piece disposed in the hole formed in the sealing ring and the attached member is sandwiched between the sealing ring and the attached member, and thus protruded. Since the piece is held at a predetermined position, it is not necessary to directly fix the rotation prevention mechanism to the sealing ring, and the rotation prevention mechanism can be provided regardless of the material constituting the sealing ring. In addition, since the anti-rotation mechanism is not directly fixed to the sealing ring, the function as an anti-rotation can be maintained regardless of the passage of time.

A ring-shaped step portion is provided on a surface of the sealing ring facing the attached member, and the annular member is disposed on the step portion.
According to this feature, the annular member is arranged on the step provided in the sealing ring, thereby aligning the annular member with respect to the sealing ring, and consequently, the protrusion piece, the sealing ring, and the hole formed in the attached member. Positioning can be performed easily.

The step portion is characterized in that an axial depth is smaller than an axial thickness of the annular member.
According to this feature, the annular member protrudes in the axial direction from the step portion, the sealing ring and the attached member do not directly contact each other, and the contact area between the annular member and the sealing ring is the sealing ring. Since it is smaller than the area facing the mounted member, even if there is distortion such as irregularities and undulations on the sealing ring or the facing surface of the mounted member, the inclination of the annular member due to the influence of this distortion Therefore, the inclination of the sealing ring itself contacting the annular member can be suppressed, and the sliding surfaces of the stationary-side sealing ring and the rotating-side sealing ring can be brought into precise contact with each other.

The annular member is characterized in that the inner diameter of the hole formed at the center in the radial direction is formed slightly larger than the outer diameter of the rotating shaft.
According to this feature, it is possible to easily align the sealing ring and the attached member with the annular member by fitting the annular member to the rotating shaft.

A through hole penetrating in the axial direction is formed in the annular member,
The protruding piece is a pin inserted into the through hole.
According to this feature, the shape and size of the protruding piece can be changed by changing the pin according to the shape of the hole formed in the sealing ring and the attached member.

A hole formed in the sealing ring and the attached member is formed in a bottomed shape, and one end in the axial direction of the pin has a head having an outer diameter larger than the through hole, and the axial direction of the hole The length of the pin in the axial direction is longer than the length.
According to this feature, it is possible to prevent the pin from falling off due to the bottomed hole and the head provided on the pin.

The radial gap between the through hole and the pin of the annular member is formed smaller than the radial gap between the hole on the attached member side and the pin.
According to this feature, by reducing the gap with the through-hole, it is possible to reduce the swirl range of the tip of the pin on the seal ring side and make it difficult to collide with the seal ring. Further, high machining accuracy is not required when forming a hole in the attached member.

The seal ring is disposed in a step portion formed on the radially inner side of the attached member, and an annular recess is formed on the outer peripheral surface of the seal ring facing the inner peripheral surface of the step portion, The space between the sealing ring and the mounted member is sealed by an O-ring disposed in the annular recess.
According to this feature, since the O-ring that seals between the sealing ring and the attached member can be held in the annular recess formed on the outer peripheral surface of the sealing ring, the sealing ring and the O-ring are integrated. Thus, it can be mounted in the stepped portion of the member to be attached and can be easily assembled.

It is sectional drawing which shows the rotation prevention mechanism in an Example. It is an exploded view which shows a stationary sealing ring, a detent mechanism, and a housing. It is a figure which shows an annular member. It is a figure which shows a pin. It is a partially expanded view which shows the positional relationship of a stationary sealing ring, a rotation stop mechanism, and a housing.

  EMBODIMENT OF THE INVENTION The form for implementing the mechanical seal which concerns on this invention is demonstrated below based on an Example. The present invention is not construed as being limited thereto, and various changes, modifications, and improvements can be added based on the knowledge of those skilled in the art without departing from the scope of the present invention.

  The anti-rotation mechanism according to the embodiment will be described with reference to FIGS.

  As shown in FIG. 1, the mechanical seal 1 is mainly composed of a mating ring (stationary seal ring) 10, a seal ring (rotary seal ring) 20, a spring 40, and a collar 50. Yes. The mechanical seal 1 is mounted between a housing (attached member) 2 of the rotating machine and a rotating shaft 4 arranged so as to pass through the shaft hole 3 of the housing 2 and communicate with the outside A side of the rotating machine. Has been. The outside A side is an atmosphere such as seawater, water, air, and the inside M side is sealed with a sealed fluid.

  The rotary shaft 4 is configured such that a sleeve 6 is fitted on the outer periphery of a stepped rotary shaft main body 5, and the rotary shaft main body 5 and the sleeve 6 are integrally fixed in a state of being prevented from rotating by a rotation stopper 7. .

  The mating ring 10 is disposed in a step portion 2a formed inside the housing 2 in the radial direction, and an annular recess 10d is formed on the outer peripheral surface 10b of the mating ring 10 facing the inner peripheral surface 2b of the step portion 2a. It is formed, and the space between the mating ring 10 and the housing 2 is sealed by an O-ring 12 disposed in the annular recess 10d. According to this, since the O-ring 12 can be held in the annular recess 10d formed in the mating ring 10, the mating ring 10 and the O-ring 12 are integrated into the step 2a of the housing 2. It can be attached and can be easily assembled.

  The seal ring 20 is mounted on the rotating shaft 4 side and rotates integrally with the rotating shaft 4. The mating ring 10 and the seal ring 20 are arranged so as to face each other along the axial direction of the rotating shaft 4, and the sliding surfaces 10 a and 20 a which are the opposed end surfaces are in close contact with each other, Seal the sealed fluid. That is, the mechanical seal 1 is an outside type that restricts leakage of the sealed fluid from the inner diameter side to the outer diameter side.

  Both the mating ring 10 and the seal ring 20 are made of a hard sliding material (for example, ceramics such as SiC). These may be formed of a cemented carbide material, a carbon material, or the like.

  As shown in FIG. 1, the spring 40 is disposed in a compressed state between the seal ring 20 and the collar 50, and both end portions 41 and 42 abut against the seal ring 20 and the collar 50, respectively. The collar 50 is fixed in a non-rotating state with respect to the rotating shaft 4 (the rotating shaft main body 5 and the sleeve 6) by screwing the set screw 51 into the screw hole 52, and is recessed on the outer diameter side on the inner periphery thereof. An O-ring 54 is attached to the annular recess 53.

  As shown in FIG. 2, a ring-shaped step portion 11 that is recessed in the coaxial direction of the mating ring 10 is formed at the end of the mating ring 10 opposite to the sliding surface 10 a. Further, a stepped portion 11 of the mating ring 10 is formed with a bottomed hole 13 that is recessed toward the sliding surface 10a in the axial direction, and the housing 2 is axially positioned at a position facing the hole 13. A bottomed hole 14 is formed to be depressed on the side opposite to the sliding surface 10a. The hole 14 does not have to be bottomed.

  As shown in FIGS. 1 and 2, a detent mechanism 30 is disposed between the mating ring 10 and the housing 2, and projecting pieces (the heads of the pins 35) projecting on both sides in the axial direction of the detent mechanism 30. 36, the body portion 37) is disposed in the hole 13 of the mating ring 10 and in the hole 14 of the housing 2, so that the mating ring 10 is prevented from rotating with respect to the housing 2.

  The detent mechanism 30 includes an annular member 31 and a pin 35. As shown in FIG. 3, the annular member 31 is formed in a ring shape having a hole 32 through which the rotary shaft 4 (sleeve 6) is inserted at the center in the radial direction. The hole 32 is formed slightly larger than the outer diameter of the rotating shaft 4 (the outer diameter of the sleeve 6), and the outer diameter of the annular member 31 is smaller than the outer diameter of the mating ring 10. The annular member 31 is made of a softer material than the mating ring 10 and the seal ring 20.

  The outer edges of the contact surfaces 31a and 31b on both sides in the axial direction of the annular member 31 are chamfered. Further, the annular member 31 is formed with a through hole 33 penetrating in the axial direction, and a pin 35 is fitted into the through hole 33 as shown in FIG.

  As shown in FIG. 2, the pin 35 is inserted into the through-hole 33, the head 36 at one end in the axial direction is from the contact surface 31 a side with the mating ring 10 of the annular member 31, and the body 37 at the other end is from the side. The annular member 31 is inserted so as to protrude from the contact surface 32a side with the housing 2, and the head portion 36 protruding from the contact surface 31a side is mating as shown in FIGS. As a projecting piece disposed in the hole 13 of the ring 10, the body portion 37 projecting from the abutting surface 32 a functions as a projecting piece disposed in the hole 14 of the housing 2, and the mating ring 10 is attached to the housing 2. On the other hand, it is preventing rotation.

  As shown in FIG. 4, the pin 35 has a stepped shape having a difference in the outer diameter in the axial direction, and the outer diameter of the head portion 36 is the outer diameter of the trunk portion 37 and the through hole 33 of the annular member 31. It is formed larger than the inner diameter. Therefore, in addition to preventing the pin 35 from dropping out to the housing 2 side through the through hole 33, when the pin 35 is attached, the pin 35 is inserted until the head 36 comes into contact with the periphery of the through hole 33. The pin 35 can be easily aligned with the through hole 33 of the annular member 31 in the axial direction (position where the pin 35 protrudes with a predetermined dimension on both sides of the annular member 31 in the axial direction).

  Although not described in detail here, the pin 35 and the through hole 33 of the annular member 31 may be bonded together with an adhesive or the like and fixed integrally.

  As shown in FIGS. 1, 2, and 5, the inner diameter of the inner peripheral surface 11 b of the step portion 11 formed on the mating ring 10 is slightly larger than the outer diameter of the annular member 31. 11, an annular member 31 is inserted and arranged.

  As shown in FIG. 2, the hole 13 on the mating ring 10 side is formed in a bottomed shape having a bottom in the axial direction, and a contact end surface (step 11) between the mating ring 10 and the annular member 31. Since the axial length W4 of the pin 35 is longer than the distance W3 from the axial bottom surface 11a) to the axial bottom surface 13a of the hole 13, the pin 35 temporarily moves in the axial direction. Also, it can be prevented from falling off to the mating ring 10 side.

  Further, as shown in FIG. 2, the step portion 11 formed in the mating ring 10 has an inner diameter side opened to the rotary shaft 4 side, and the thickness of the annular member 31 is determined from the axial depth dimension W1. The direction dimension W2 is slightly larger. Therefore, the annular member 31 is disposed in the step portion 11, and the annular member 31 is in the state where the contact surface 31 a of the annular member 31 with the mating ring 10 is in contact with the axial bottom surface 11 a of the step portion 11. 11 (see FIGS. 1 and 5). Thereby, the contact surface 31b of the annular member 31 contacts the facing surface 2c of the housing 2, and the facing surface 10c that is the side surface opposite to the sliding surface 10a of the mating ring 10 and the step 2a of the housing 2 are connected. The opposing surface 2c, which is the side surface to be defined, is separated and does not contact directly.

  As described above, the annular member 31 provided with the projecting pieces (the head portion 36 and the body portion 37 of the pin 35) disposed in the hole 13 and the hole 14 formed in the mating ring 10 and the housing 2, Since the pin 35 is held in a predetermined position by being held between the mating ring 10 and the housing 2, for example, the pin 35 is driven or bonded to a hole provided in the mating ring 10, It is not necessary to fix the pin 35 directly to the mating ring 10. Therefore, the detent mechanism 30 can be provided regardless of the material constituting the mating ring 10. In addition, since the pin 35 is not directly fixed to the mating ring 10, there is no risk of the pin 35 dropping off due to deterioration over time, and the function as a detent can be maintained regardless of the passage of time.

  Further, since the pin 35 is fitted in the through hole 33 provided in the annular member 31 that is sandwiched between the mating ring 10 and the housing 2 and prevented from tilting, the pin 35 rotates around the housing 2. The tilting of the pin 35 to be stopped is prevented, the stress concentration on the pin 35 is suppressed, and the rotation of the pin 35 can be reliably prevented while preventing the adhesion portion of the pin 35 and the pin 35 itself from being damaged. Can be maintained.

Further, the contact surface 31b of the annular member 31 with the housing 2 contacts the facing surface 2c of the housing 2, and the facing surface 10c of the mating ring 10 and the facing surface 2c of the housing 2 are in direct contact with each other. In addition to the absence, the annular member 31 interposed between the mating ring 10 and the housing 2 is disposed on the step portion 11 formed inside the mating ring 10 in the radial direction. The contact surface 31 a of the annular member 31 with the mating ring 10 and the contact surface 31 b of the annular member 31 with the housing 2 have a smaller surface area than the facing surface of the mating ring 10 and the housing 2. That is, the contact area between the contact surface 31a of the annular member 31 with the mating ring 10 and the axial bottom surface 11a and the contact area of the annular member 31 with the facing surface 2c with the housing 2 are reduced.
Therefore, even if the axial bottom surface 11a of the step portion 11 of the mating ring 10 has a distortion due to unevenness or undulation, the inclination of the annular member 31 itself due to the influence of the distortion, and thus the mating ring. 10 is restrained from tilting, the sliding surfaces 10a and 20a between the mating ring 10 and the seal ring 20 can be brought into precise contact with each other, and the sealing performance of the mechanical seal 1 can be enhanced.

  Further, since the pin 35 is fitted in the through hole 33 formed in the annular member 31 that is in contact with the axial bottom surface 11a of the step portion 11, the pin 35 is difficult to tilt with respect to the hole 13 on the mating ring 10 side. Will be placed. According to this, the head portion 36 of the pin 35 does not locally contact the inner peripheral surface of the hole 13, and there is no stress concentration or the like.

  Further, as shown in FIG. 5, compared to the radial gap W <b> 5 between the hole 14 on the housing 2 side and the body portion 37 of the pin 35, the through hole 33 of the annular member 31 and the body portion 37 of the pin 35. The radial gap W6 is formed small. According to this, by reducing the gap W6 between the body portion 37 of the pin 35 and the through hole 33, the swivel range of the tip of the pin 35 on the mating ring 10 side can be reduced, and the head portion 36 of the pin 35 can be reduced. It is possible to make it difficult to collide with the inner peripheral surface of the mating ring 10. Therefore, when forming the hole 14 on the housing 2 side, high machining accuracy is not required, and the machining operation is facilitated.

  Further, the annular member 31 is arranged on the step portion 11 formed on the inner side in the radial direction of the mating ring 10, so that the positioning to the mating ring 10 is easy.

  Further, the annular member 31 is formed of a soft material (for example, stainless steel similar to the housing 2) compared to the mating ring 10 and the seal ring 20. Therefore, it is relatively easy to perform grinding and polishing for surface processing, and the contact surfaces 31a and 31b with the mating ring 10 and the housing 2 can be formed on a flat surface with high accuracy. Even if there is a strain on the axial bottom surface 11a and the axial facing surface 2c of the housing 2, it is difficult to be affected by the strain. Further, the pin 35 is preferably formed of the same material as the annular member 31.

  The annular member 31 is formed such that the inner diameter of the hole 32 formed at the center in the radial direction is slightly larger than the outer diameter of the rotating shaft 4 (the outer diameter of the sleeve 6). 6), the mating ring 10 and the housing 2 and the annular member 31 can be easily aligned with each other.

  The annular member 31 has an outer diameter smaller than the outer diameter of the mating ring 10, and the annular member 31 and the pin 35 and the O-ring 12 do not overlap in the axial direction of the mating ring 10. While forming the part 11 and the hole 13, the dimension of the mating ring 10 in the axial direction can be reduced.

  As shown in FIG. 3, the annular member 31 is formed such that the outer diameter W7 of the contact surface 31 a with the axial bottom surface 11 a of the step portion 11 is smaller than the outer diameter W8 of the outer peripheral surface of the annular member 31. ing. Therefore, even if there is a rounded portion as an unprocessed portion on the axial bottom surface 11a of the stepped portion 11, the annular member 31 does not ride on the rounded portion, and the axial bottom surface 11a of the annular member 31 and the stepped portion 11 is ensured. Can be interviewed. The annular member 31 is symmetrical in the axial direction, and the outer diameter of the annular member 31 is smaller than the outer diameter W8 of the outer peripheral surface of the annular member 31 on the opposite side in the axial direction.

  Although the embodiments of the present invention have been described with reference to the drawings, the specific configuration is not limited to these embodiments, and modifications and additions within the scope of the present invention are included in the present invention. It is.

  For example, in the above-described embodiment, the annular member 31 is externally fitted to the rotating shaft 4 and the outer diameter thereof is smaller than the outer diameter of the mating ring 10. However, the mating ring 10 of the annular member 31 is described. If the contact area with the housing 2 is smaller than the surface area of the facing surface between the mating ring 10 and the housing 2, the present invention is not limited to this configuration. For example, the annular member 31 does not directly face the rotating shaft 4, It may be formed in a ring shape that is biased toward the outer diameter side of the mating ring 10, or may be formed in a ring shape at the center between the outer diameter and inner diameter of the mating ring 10.

  Further, in the above-described embodiment, the anti-rotation mechanism 30 includes the annular member 31 and the pin 35, and the projecting piece is formed by projecting the head portion 36 and the body portion 37 of the pin 35 from both axial sides of the annular member 31. Although it comprises, it is not restricted to this, For example, you may comprise by forming a protrusion piece directly in the both sides of the axial direction of an annular member.

  The fixing of the annular member 31 and the pin 35 is not limited to adhesion. For example, the inner diameter of the through-hole 33 provided in the annular member 31 is formed slightly smaller than the outer diameter of the pin 35, and the pin is driven and fixed. It is good also as an aspect to do.

  Further, the annular member 31 may be configured such that the annular member 31 does not protrude from the step portion 11 by making the axial thickness dimension of the annular member 31 substantially the same as the axial depth dimension of the step portion 11.

  In addition, a plurality of projecting pieces projecting on both sides in the axial direction of the rotation preventing mechanism 30 may be formed in the circumferential direction of the annular member 31.

  In addition, the annular member 31 is not limited to the configuration arranged in the step portion 11 formed in the mating ring 10, for example, omits the processing work when forming the step portion 11 formed in the mating ring 10, The annular member 31 may be interposed between the facing surface 10c in the axial direction of the mating ring 10 and the step 2a of the housing 2 and the facing surface 2c of the step 2a. In this case, the hole 13 of the mating ring 10 in which the head portion 36 of the pin 35 is disposed is directly formed on the facing surface 10c.

  Moreover, it is good also as a structure which forms the step part equivalent to the step part 11 formed in the mating ring 10 in the opposing surface 2c of the housing 2, and fits the annular member 31 in this step part. Furthermore, a step portion in which the annular member 31 is fitted may be provided on both the mating ring 10 and the housing 2. In this case, by setting the sum of the axial depths of the step portions provided in the mating ring 10 and the housing 2 to be shorter than the thickness dimension of the annular member 31, the mating ring 10 and the housing 2 are axially arranged. It becomes the structure which does not contact | abut directly.

  Moreover, in the said Example, although the rotation prevention mechanism 30 demonstrated in the structure utilized when rotating the mating ring (sealing side sealing ring) 10 with respect to the housing 2, it is not restricted to this, For example, a seal | sticker The ring 20 (rotating seal ring) may be used to prevent rotation. In this case, the rotation prevention mechanism is provided in a hole provided on the seal ring 20 side and a hole provided on the collar 50 side which is a member to be attached. The head and the body of the pin are inserted respectively.

1 Mechanical seal 2 Housing (attached member)
2a Step 2b Inner circumference 2c Opposing surface 3 Shaft hole 4 Rotating shaft 5 Rotating shaft body 6 Sleeve 7 Rotation stop 10 Mating ring (static ring on the stationary side)
10a Sliding surface 10b Outer peripheral surface 10c Opposing surface 11 Step portion 11a Axial bottom surface 11b Inner peripheral surface 12 O-ring 13 Hole 13a Axial bottom surface 14 Hole 20 Seal ring (sealing ring on the rotating side)
30 Non-rotating mechanism 31 Annular member (anti-rotating mechanism)
31a, 31b Abutting surface 32 Hole 33 Through hole 35 Pin (rotation prevention mechanism, protruding piece)
36 Head 37 Body 40 Spring 50 Collar 51 Set screw A Outside machine M Inside machine

Claims (8)

A housing which is a mounted member through which a rotating shaft of a rotary machine is inserted, a stationary seal ring held by the housing, and a rotating member which is held by the mounted member on the rotating shaft side and rotates together with the rotating shaft. At least one of the seals in a mechanical seal comprising: a rotary seal ring that is in sliding contact with the seal ring; and a spring that biases the stationary seal ring and the rotary seal ring in an axially pressed state. A detent mechanism that prevents the ring from rotating relative to the attached member;
The detent mechanism includes an annular member interposed between the sealing ring and the attached member, and projecting pieces that project from both sides in the axial direction of the annular member,
The detent is characterized in that the projecting pieces are respectively disposed in holes formed in the sealing ring and the mounted member in a state where the annular member is sandwiched between the sealing ring and the mounted member. mechanism.   The ring-shaped step part is provided in the surface on the side facing the said to-be-attached member of the said sealing ring, The said annular member is arrange | positioned at this step part. Non-rotating mechanism.   3. The detent mechanism according to claim 2, wherein the step portion is formed so that an axial depth is smaller than an axial thickness of the annular member.   4. The detent mechanism according to claim 1, wherein the annular member is formed such that an inner diameter of a hole formed at a center in a radial direction is slightly larger than an outer diameter of the rotating shaft. A through hole penetrating in the axial direction is formed in the annular member,
The rotation preventing mechanism according to any one of claims 1 to 4, wherein the protruding piece is a pin inserted into the through hole.   A hole formed in the sealing ring and the attached member is formed in a bottomed shape, and one end in the axial direction of the pin has a head having an outer diameter larger than the through hole, and the axial direction of the hole 6. The detent mechanism according to claim 5, wherein the axial length of the pin is longer than the length.   The radial gap between the through hole and the pin of the annular member is formed smaller than the radial gap between the hole on the attached member side and the pin. Detent mechanism described in 1.   The seal ring is disposed in a step portion formed on the radially inner side of the attached member, and an annular recess is formed on the outer peripheral surface of the seal ring facing the inner peripheral surface of the step portion, The detent mechanism according to any one of claims 1 to 7, wherein a space between the sealing ring and the attached member is sealed by an O-ring arranged in the annular recess.

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