JP2012021477A - Sealing member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealing member that can be reliably fixed to a head cover with a simple structure and reliably perform sealing between the seal member and the head cover without increasing the number of components nor the assembling man-hours.SOLUTION: The sealing member comprises: a cylindrical portion extending in the axial direction of an ignition plug mounting hole and having a spiral screw groove formed on the outer circumferential face thereof; and a mounting action portion having a counter face opposing to the head cover and formed at one end in the axial direction of the cylindrical portion. The ignition plug mounting hole has a screw groove formed on the inner circumferential face, the screw groove to be fitted to the above screw groove, and a step portion protruding in the inner circumferential direction opposing to the other end of the cylindrical portion in the axial direction. A surface sealing means is provided to one of, or both of the other end in the axial direction of the cylindrical portion and the counter face, the sealing means to be brought into pressure-contact with the head cover in the axial direction.

Description

  The present invention relates to a seal member, and more particularly to a structure of a seal member interposed between a spark plug mounting hole formed in a head cover of an internal combustion engine and a mounting member through which the spark plug is inserted.

  Conventionally, a synthetic resin head cover has been attached to the upper part of the internal combustion engine for the purpose of reducing the weight and improving the design. An ignition plug is attached to the upper part of the internal combustion engine. The ignition plug is inserted into an attachment member such as a cylindrical plug tube, and further the plug tube is inserted into an ignition plug attachment hole formed in the head cover. It has been.

  A seal member is interposed between the plug tube and the spark plug mounting hole for the purpose of liquid-tightly sealing the gap between the spark plug mounting hole and the plug tube. The structure is known.

Japanese Utility Model Publication No. 5-87253 JP 2004-52705 A JP 2007-321605 A

  The sealing member described in Patent Document 1 is a synthetic resin rocker cover for an internal combustion engine in which an opening for inserting a plug tube is provided in a ceiling wall, and a sealing member made of an elastic material is provided around the opening. The screw is attached to the inside of the cylindrical wall that hangs around the opening and the outer surface of the seal member by screwing.

  As described above, since the sealing member described in Patent Document 1 employs an attachment method in which the cylindrical wall and the sealing member are screwed together, the holding of the sealing member is performed by contacting the screw surface, that is, in the vertical direction or This is done by compression and friction of the diagonal threads. Accordingly, the force in the direction of enlarging the cylindrical wall out of the force for tightly holding the seal member can be made smaller than that in the press-fitting method.

  The seal member described in Patent Document 2 is formed of a rigid material so as to be elastically in close contact with the entire outer periphery of the plug tube, and is detachable from the head cover. A ring-shaped holding seal portion that is integrally supported by the support member to be fastened and elastically contacts the inner surface of the head cover around the spark plug mounting hole when the support member is fastened to the head cover is formed integrally with the seal member. Has been.

  As described above, the seal member described in Patent Document 2 can securely fix the seal member to the head cover by fastening the support member to the head cover. Even if the head cover is deformed, the seal member has a sealing function. It can be reliably maintained.

  The seal member described in Patent Document 3 is assembled by inserting the seal member into the hole peripheral wall portion of the mounting hole of the synthetic resin head cover, and the inner periphery of the hole peripheral wall portion and the outer periphery of the seal member in close contact therewith, As irregularities to be fitted to each other, a cylindrical portion and a flange portion are formed on the hole peripheral wall portion side, and a large diameter portion, a small diameter portion and a protrusion are formed on the seal member side.

  As described above, the sealing member described in Patent Document 3 inserts the sealing member into the hole peripheral wall portion so that the inner periphery of the hole peripheral wall portion where the irregularities are formed and the outer periphery of the seal member are in close contact with each other. It can be firmly assembled to the peripheral wall portion without wobbling in the axial direction or the radial direction, so that inadvertent dropping or misalignment due to vibration from the internal combustion engine or the like does not occur. Further, since there is no need for parts such as clasps and brackets for attaching the seal member to the hole peripheral wall portion, the number of parts is small, the weight and size can be reduced, and the assembly work can be easily performed.

  However, according to the attachment method of the seal member described in Patent Document 1, the screw part is formed of an elastic material such as rubber, and the screw part has two functions such as holding of the seal member and a sealing function. When the contact force on the thread surface is increased to exert the sealing function, there is a problem that when the seal member is screwed, the assembly resistance increases and the assembly becomes difficult.

  Further, according to the mounting method of the seal member described in Patent Document 2, since the support member of the seal member is fastened and fixed with a bolt or the like, the number of parts increases, the weight and the mounting man-hour increase, and the seal member There was a problem that it was very difficult to put on and take off.

  Furthermore, according to the mounting method of the seal member described in Patent Document 3, since the seal member and the head cover are assembled by uneven engagement, there is a possibility that deviation may occur due to thermal deformation, vibration, wear, etc. There was a problem of damage.

  Therefore, the present invention has been made in view of the above problems, and can securely fix the seal member to the head cover with a simple structure without increasing the number of parts and the number of assembling steps. It is an object of the present invention to provide a sealing member that can reliably seal the seal.

  The seal member according to the present invention has a spark plug attachment hole formed in a head cover attached to an internal combustion engine, and is interposed between the ignition plug attachment hole and the attachment member inserted through the ignition plug attachment hole. The seal member has a cylindrical portion that extends in the axial direction of the spark plug mounting hole and has a helical thread groove formed on the outer peripheral surface thereof, and a facing surface that faces the head cover, and the cylindrical portion An attachment action portion formed at one end in the axial direction, and the spark plug attachment hole has a threaded groove that engages with the screw groove on the inner peripheral surface, and the other axial direction of the cylindrical portion. A step portion projecting in the inner circumferential direction is formed so as to face the end, and is pressed against the head cover in the axial direction on one or both of the other end of the cylindrical portion in the axial direction and the facing surface. Characterized in that it comprises a face seal means.

  Further, in the sealing member according to the present invention, a radial seal that is pressed against the head cover in the radial direction of the spark plug mounting hole on one of the other end in the axial direction of the cylindrical portion and the facing surface. It is preferable to provide means.

  In the sealing member according to the present invention, it is preferable that the cylindrical portion is made of rubber.

  Moreover, the sealing member which concerns on this invention WHEREIN: The said cylinder part is provided with the reinforcement part extended in an axial direction, and it is suitable when the said attachment effect | action part is formed integrally with the said reinforcement part.

  In the sealing member according to the present invention, it is preferable that the cylindrical portion is made of a synthetic resin.

  In the sealing member according to the present invention, it is preferable that the attachment action portion is formed integrally with the cylindrical portion.

  The above summary of the invention does not enumerate all the necessary features of the present invention, and sub-combinations of these features can also be the invention.

  The seal member according to the present invention includes the surface seal means that is pressed against the head cover in the axial direction on one or both of the other end in the axial direction of the cylindrical portion and the opposing surface. Since the surface sealing means is pressed in the axial direction, the contact force of screwing of the sealing member is increased by the repulsive force, and the sealing member can be configured with a simple structure without using bolts or other fastening parts. It is possible to secure the holding and sealing function.

  Further, the seal member according to the present invention is provided with a diameter seal means that is in pressure contact with the head cover in the radial direction of the spark plug mounting hole at one of the other end in the axial direction of the cylindrical portion and the opposing surface. Therefore, the head cover and the mounting member can be more reliably sealed, and the magnitude of the repulsive force of the surface sealing means can be adjusted, so that the balance between the assembling property and the sealing function is adjusted. be able to.

  Moreover, since the cylindrical part is formed of rubber, the sealing member according to the present invention can integrally form the screw part and the surface sealing means, reduce the number of parts, and suppress the manufacturing cost. can do.

  In the sealing member according to the present invention, since the cylindrical portion includes a reinforcing portion extending in the axial direction, the shape can be maintained even when the cylindrical portion is formed of rubber. Generation | occurrence | production of the assembly defect by deform | transforming by attachment can be prevented.

  Moreover, since the cylinder part is formed with the synthetic resin, the sealing member which concerns on this invention can provide a sealing member easily and cheaply.

  Moreover, since the attachment action | operation part is integrally formed with the cylinder part, the sealing member which concerns on this invention can be manufactured collectively in resin molding, and can suppress manufacturing cost.

The perspective view for demonstrating the outline | summary of the sealing member which concerns on 1st Embodiment. The longitudinal cross-sectional view of the sealing member which concerns on 1st Embodiment. The longitudinal cross-sectional view for demonstrating the attachment state of the sealing member which concerns on 1st Embodiment. The longitudinal cross-sectional view for demonstrating the modification of the sealing member which concerns on 1st Embodiment. The longitudinal cross-sectional view for demonstrating the other modification of the sealing member which concerns on 1st Embodiment. The longitudinal cross-sectional view of the sealing member which concerns on 2nd Embodiment. The longitudinal cross-sectional view for demonstrating the modification of the sealing member which concerns on 2nd Embodiment. The longitudinal cross-sectional view for demonstrating the other modification of the sealing member which concerns on 2nd Embodiment.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments for carrying out the invention will be described with reference to the drawings. The following embodiments do not limit the invention according to each claim, and all combinations of features described in the embodiments are not necessarily essential to the solution means of the invention. .

  Note that the insertion direction F in FIG. 3 is along the axial direction of the mounting member 30, the spark plug mounting hole 21, and the cylindrical portion 11 of the seal member 10. In the following description of the embodiment, “up and down” in FIG. The downward insertion direction F is defined as the downward direction, and the direction along the insertion direction is defined as the vertical direction.

[First Embodiment]
FIG. 1 is a perspective view for explaining an outline of the seal member according to the first embodiment, FIG. 2 is a longitudinal sectional view of the seal member according to the first embodiment, and FIG. FIG. 4 is a longitudinal sectional view for explaining a mounting state of the sealing member according to the first embodiment, and FIG. 4 is a longitudinal sectional view for explaining a modification of the sealing member according to the first embodiment. FIG. 5 is a longitudinal sectional view for explaining another modified example of the sealing member according to the first embodiment.

  As shown in FIG. 1, the sealing member 10 according to the present embodiment includes a cylindrical portion 11 that is formed in a hollow cylindrical shape and has a helical thread groove 12 formed on the outer peripheral surface thereof, and an axial direction of the cylindrical portion 11. And an attachment action portion 14 extending in the radial direction of the cylindrical portion 11 from one end. The outer shape of the mounting action portion 14 is formed, for example, in a 12-face square shape so that it can be engaged with a tool when the seal member 10 according to this embodiment is screwed into the head cover 20.

  Next, the structure of the seal member 10 according to the present embodiment will be described with reference to FIG. As shown in FIG. 2, the sealing member 10 according to the present embodiment is made of an elastic material in a state in which a reinforcing portion 17 and an urging member 18 extending in the axial direction of the cylindrical portion 11 are included in the cylindrical portion 11. It is integrally formed. In addition, the attachment action part 14 is standingly formed from the axial direction lower end of the reinforcement part 17, and the reinforcement part 17 and the attachment action part 14 are formed integrally. Furthermore, the reinforcement part 17 and the attachment action part 14 are formed with iron materials, such as general carbon steel (SP material), stainless steel, an aluminum alloy, etc.

  Further, the spiral thread groove 12 formed on the outer peripheral surface of the cylindrical portion 11 is formed substantially equal to the pitch of the threaded groove 23 formed on the inner peripheral surface of a spark plug mounting hole 21 of the head cover 20 described later. In addition, the shape of the thread groove 12 in the axial section of the cylindrical portion 11 is such that the thread groove is assembled with the threaded groove 23 through a gap in a state where the seal member 10 is screwed into the spark plug mounting hole 21. The diameter of the cylinder portion 11 is formed to be smaller than the diameter of the spark plug mounting hole 21 so that the height of catching, which is the height of the surface where 12 and the threaded groove 23 come into contact, becomes small. Thus, if the thread groove 12 is formed, the contact force between the thread groove 12 and the threaded groove 23 when the seal member 10 is screwed into the spark plug mounting hole 21 can be reduced. The head cover 20 can be easily assembled. As the elastic material constituting the cylindrical portion 11, acrylic rubber, silicon rubber, nitrile rubber (NBR), ethylene propylene rubber (EPDM), or the like can be used.

  Further, a holding portion 19 that is in close contact with the outer periphery of a mounting member 30 to be described later is formed on the inner peripheral side of the cylindrical portion 11, and is formed integrally with the lower end of the cylindrical portion 11 via a connecting portion 19a. . Note that the holding portion 19 includes the biasing member 18 described above. The urging member 18 is, for example, an annular coil spring, and the holding portion 19 is strongly brought into close contact with the outer peripheral surface of the mounting member 30 by the elastic force of the coil spring.

  Further, an upper surface of the mounting action portion 14 is formed with a facing surface 13 that faces the head cover 20, and a surface sealing means 15 that is pressed against the head cover 20 in the axial direction of the cylinder portion 11 is formed on the facing surface 13. Has been. The surface sealing means 15 is formed of the same material as that of the tube portion 11 and is formed integrally with the tube portion 11.

  As described above, the cylindrical portion 11, the surface sealing means 15, the holding portion 19, and the connecting portion 19 a are integrally formed of an elastic material and include the reinforcing portion 17 and the urging member 18. Thus, in order to enclose the reinforcement part 17 and the biasing member 18, the sealing member 10 which concerns on this embodiment can be manufactured by insert-molding the reinforcement part 17 and the biasing member 18. FIG.

  Next, with reference to FIG. 3, the attachment method of the sealing member 10 which concerns on this embodiment is demonstrated. As shown in FIG. 3, the head cover 20 has a spark plug mounting hole 21 drilled along the insertion direction F of a cylindrical mounting member 30 having a spark plug (not shown). The seal member 10 according to the present embodiment is a member interposed between the spark plug mounting hole 21 and the mounting member 30, and a threaded groove 23 formed on the inner peripheral surface of the spark plug mounting hole 21 and the cylinder It is attached by screwing the thread groove 12 of the part 11.

  On the upper part of the threaded groove 23 formed on the inner peripheral surface of the spark plug mounting hole 21, a step portion 22 protruding in the inner peripheral direction is formed so as to face the upper end in the axial direction of the cylindrical portion 11. Yes. In addition, as described above, the pitch of the thread groove 12 is formed to be substantially equal to the pitch of the thread groove, and the diameter of the cylindrical portion 11 is reduced so that the height of the catch between the thread groove 12 and the thread groove 23 becomes small. Is smaller than the diameter of the spark plug mounting hole 21, the contact force between the thread groove 12 and the threaded groove 23 can be reduced, and the mounting operation of the seal member 10 can be performed easily. ing.

  In the state where the seal member 10 according to the present embodiment is mounted in the spark plug mounting hole 21, the surface sealing means 15 is crushed by the head cover 20 and the facing surface 13, so that the cylindrical portion 11 is in contact with the head cover 20. It is pressed in the axial direction. The surface sealing means 15 is pressed to seal the bottom and top of the head cover 20.

  Further, when the surface sealing means 15 is crushed, the surface sealing means 15 is made of an elastic material and thus has a restoring force, and this restoring force acts as a repulsive force in the vertical direction. The repulsive force acts downwardly on the opposing surface 13 to urge the seal member 10 together with the reinforcing portion 17, and when the seal member 10 is urged downward, the screw 10 The contact force between the groove 12 and the threaded groove 23 can be increased. As described above, the contact force between the thread groove 12 and the thread groove 23 is increased, so that the seal member 10 can be securely attached to the head cover 20 without being loosened or detached due to heat or vibration of the internal combustion engine. . Note that the crushing allowance of the surface sealing means 15 can be appropriately adjusted according to the required contact force and sealing performance.

  As described above, the seal member 10 according to the present embodiment reduces the contact force between the screw groove 12 and the threaded groove 23 to improve the assembling property of the seal member 10, and the seal member 10 is assembled. In this state, the seal member 10 can be securely attached to the head cover 20 by applying the repulsive force of the surface sealing means 15 pressed in the axial direction to the contact force between the thread groove 12 and the thread groove 23. Further, the sealing member 10 according to the present embodiment does not need to be assembled using bolts or the like, and the number of parts is small, so that the manufacturing cost associated with the manufacturing of the sealing member 10 and the assembling work to the head cover 20 can be reduced. it can.

  The sealing member according to the present embodiment described above has been described with respect to the case where the surface sealing means 15 is formed on the facing surface 13, but various modifications can be applied. As a modification of the seal member according to the present embodiment, as shown in FIG. 4, the surface seal means 15 is not only the facing surface 13 but also a seal member 10 a formed at the upper end in the axial direction of the cylindrical portion 11. You can also. The surface sealing means 15 a formed at the upper end of the cylinder part 11 is pressed against the step part 22 formed in the spark plug mounting hole 21 in a state where the seal member 10 a is assembled to the head cover 20. By being crushed in the axial direction, a repulsive force is generated in the axial direction of the cylindrical portion 11.

  Thus, since the surface sealing means 15 and 15a are formed in the upper end of the opposing surface 13 and the cylinder part 11 in the axial direction, the repulsive force which the surface sealing means 15 and 15a exhibits can be increased, and the seal In a state where the member 10 a is assembled to the head cover 20, the contact force between the screw groove 12 and the threaded groove 23 can be increased, and the seal member 10 a can be more reliably assembled to the head cover 20. Further, since the sealing member 10a and the head cover 20 are sealed by the two surface sealing means 15 and 15a, the sealing can be performed more reliably.

  As another modification of the seal member according to the present embodiment, as shown in FIG. 5, a surface seal means 15 a is formed at the upper end in the axial direction of the cylindrical portion 11, and the diameter seal means 16 is formed below the screw groove 12. Alternatively, the sealing member 10b may be formed.

  Thus, when the surface sealing means 15a is formed at the upper end of the cylindrical portion 11 and the diameter sealing means 16 is formed at the lower portion of the thread groove 12, the diameter sealing means 16 does not generate a repulsive force in the axial direction of the cylindrical portion 11. Further, sealing can be performed reliably by sealing at two locations without increasing the repulsive force of the surface sealing means 15a more than necessary.

  As described above, the sealing members 10, 10 a, 10 b according to the present embodiment can select the position to which the surface sealing means 15, 15 a is applied, and the thread groove 12 by applying the diameter sealing means 16 on one side. The contact force and sealability with the threaded groove 23 can be adjusted.

  The sealing members 10, 10a, 10b according to the first embodiment described above have been described with respect to the case where the cylindrical portion 11 is formed of an elastic material such as rubber. However, the sealing member according to the present invention is the first embodiment. However, the present invention is not limited to the case where the cylindrical portion 11 is formed of an elastic material. Therefore, the sealing member according to the second embodiment will be described next.

[Second Embodiment]
FIG. 6 is a longitudinal sectional view of a sealing member according to the second embodiment, FIG. 7 is a longitudinal sectional view for explaining a modification of the sealing member according to the second embodiment, and FIG. FIG. 10 is a longitudinal sectional view for explaining another modified example of the seal member according to the second embodiment. In addition, the same code | symbol is attached | subjected about the same or similar member as 1st Embodiment mentioned above, and the detailed description is abbreviate | omitted.

  As shown in FIG. 6, the sealing member 10c according to this embodiment includes a resin screw portion 41 as a cylindrical portion that is formed in a hollow cylindrical shape and has a helical thread groove 12a formed on the outer peripheral surface, and a resin screw. And an attachment action portion 14 extending in the radial direction of the resin screw portion 41 from one end of the portion 41 in the axial direction. Further, a surface sealing means 15 is formed on the facing surface 13 of the mounting action portion 14. The resin screw portion 41 can be formed of various synthetic resins such as polypropylene and polyethylene.

  In the sealing member 10c according to the present embodiment, a rubber cylinder portion 11a extending in the axial direction of the resin screw portion 41 is formed on the inner peripheral side of the resin screw portion 41, and the biasing means 18 is provided in the rubber cylinder portion 11a. The holding part 19 provided with is integrally formed through the connecting part 19a. In addition, the rubber cylinder part 11a, the holding part 19, the communication part 19a, and the surface sealing means 15 are formed of an elastic material like the sealing member according to the first embodiment described above.

  Thus, since the sealing member 10c according to the present embodiment has the resin screw portion 41 in the cylindrical portion, the resin screw portion 41 can be formed by resin molding without performing iron sheet metal or the like. , Manufacturing costs can be reduced.

  Furthermore, as shown in FIG. 7, the sealing member according to the present embodiment is also provided at the upper end in the axial direction of the resin screw portion 41 as the cylindrical portion, similarly to the sealing member 10 a according to the modified example of the first embodiment described above. It can be set as the sealing member 10d to which the surface sealing means 15a is applied.

  Thus, since the surface sealing means 15 and 15a are integrally formed with the rubber cylinder portion 11a at the upper end in the axial direction of the opposing surface 13 and the resin screw portion 41, the repulsive force exerted by the surface sealing means 15 and 15a is obtained. In the state where the seal member 10d is assembled to the head cover 20, the contact force between the screw groove 12 and the threaded groove 23 can be increased, and the seal member 10d is more reliably assembled to the head cover 20. be able to. Further, since the sealing member 10d and the head cover 20 are sealed by the two surface sealing means 15 and 15a, the sealing can be performed more reliably.

  Further, as shown in FIG. 8, the seal member according to the present embodiment has a rubber at the upper end in the axial direction of the resin screw portion 41 in the same manner as the seal member 10 b according to another modified example according to the first embodiment described above. It is possible to form a seal member 10e in which the surface sealing means 15a is formed integrally with the cylinder portion 11a and the diameter sealing means 16 is applied to the lower part of the thread groove 12a.

  Thus, when the surface sealing means 15a is formed at the upper end of the resin screw portion 41 and the diameter sealing means 16 is formed at the lower portion of the screw groove 12a, the diameter sealing means 16 generates a repulsive force in the axial direction of the resin screw portion 41. Therefore, sealing can be performed reliably by sealing at two locations without increasing the repulsive force of the surface sealing means 15a more than necessary.

  As described above, the seal members 10c, 10d, and 10e according to the present embodiment can select the position to which the surface seal means 15 and 15a are applied, and the thread groove 12a by applying the diameter seal means 16 on one side. The contact force and sealability with the threaded groove 23 can be adjusted.

  In addition, the seal members 10, 10a, 10b, 10c, 10d, and 10e according to the above-described embodiment have been described with respect to the case where the attachment action portion 14 is formed in a 12-face square shape. It is not restricted to such a form. For example, it can be formed in a hexagonal shape according to the tool used, or can be formed so as to be attached manually by forming a slip stopper along the circumferential direction.

  Furthermore, the seal members 10, 10 a, 10 b, 10 c, 10 d, and 10 e according to the above-described embodiment have been described with respect to the case where a coil spring is used as the urging member 18, but if the holding portion 19 can be in close contact with the mounting member 30. It is not limited to the coil spring, and an elastic member such as rubber may be used. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  10, 10a, 10b, 10c, 10d, 10e seal member, 11 tube portion, 11a rubber tube portion, 12, 12a thread groove, 13 facing surface, 14 mounting action portion, 15, 15a surface seal means, 16 diameter seal means, 17 reinforcing part, 18 biasing member, 19 holding part, 19a connecting part, 20 head cover, 21 spark plug mounting hole, 22 step part, 23 threaded groove, 30 mounting member, 41 resin screw part, F insertion direction.

Claims (6)

An ignition plug attachment hole is formed in a head cover attached to the internal combustion engine, and a seal member interposed between the ignition plug attachment hole and an attachment member inserted through the ignition plug attachment hole,
The seal member has a cylindrical portion that extends in the axial direction of the spark plug mounting hole and has a helical thread groove formed on the outer peripheral surface thereof, and an opposing surface that faces the head cover, and one end of the cylindrical portion in the axial direction. An attachment action portion formed on
The spark plug mounting hole has a threaded groove that is threadedly engaged with the threaded groove on the inner circumferential surface, and a stepped portion projecting in the inner circumferential direction so as to face the other end in the axial direction of the cylindrical portion. Formed,
One or both of the other end of the cylinder part in the axial direction and the opposing surface are provided with a surface sealing means that is pressed against the head cover in the axial direction. The seal member according to claim 1,
One of the other end in the axial direction of the cylindrical portion and the opposed surface is provided with a diameter sealing means that is pressed against the head cover in the radial direction of the spark plug mounting hole. . The seal member according to claim 1 or 2,
The said cylindrical part consists of rubber | gum, The sealing member characterized by the above-mentioned. The sealing member according to claim 3,
The cylindrical portion includes a reinforcing portion extending in the axial direction,
The attachment member is formed integrally with the reinforcing part. The seal member according to claim 1 or 2,
The said cylindrical part consists of synthetic resins, The sealing member characterized by the above-mentioned. The seal member according to claim 5,
The attachment member is formed integrally with the cylindrical portion.

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