JP2016053327A - Scroll-type compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance flexibility of design and reduce the size in a scroll-type compressor having a swing link type turning radius adjustment mechanism.SOLUTION: In a scroll-type compressor 10, a crank pin 76 eccentric to the axis of a drive shaft 64 is arranged at the other end of a support body 68 of the drive shaft 64, and the crank pin 76 includes a flat portion 80 that is formed by linearly cutting out a portion of the circular cross section and that is cut out at a portion on the central side of the support body 68. The flat portion 80 is provided to avoid interference with a tool C engaged with a center hole 74 formed at the center of the other end of the support body 68. The crank pin 76 is inserted to an eccentric hole 88 of a bush 54 so that the bush 54 is swingably turned by the drive shaft 64. Due to this configuration, a movable scroll 20 functions as a swing link type turning radius adjustment mechanism that can be turned while varying the turning radius.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a scroll compressor that compresses a refrigerant in a housing by turning a movable scroll with respect to a fixed scroll.

  Conventionally, a fixed scroll having a fixed plate and a spiral fixed wall upright on the fixed plate, and a movable scroll arranged so that the movable plate and the spiral movable wall upright on the movable plate are engaged with the fixed wall. And the movable scroll of the fixed scroll, the movable wall of the movable scroll, the fixed plate, and the movable plate, by rotating the movable scroll via a crank pin provided to be eccentric to the drive shaft. There is known a scroll compressor that compresses a refrigerant in a compression chamber formed between the two.

  In such a scroll compressor, for example, as disclosed in Patent Document 1, a slide key is provided at the rear end of the drive shaft, and the slide key is inserted into a slide hole of the counterweight and the drive bush, respectively. It has a turning radius adjustment mechanism.

  This slide key type turning radius adjusting mechanism adjusts the turning radius of the movable scroll by supporting the counterweight and the drive bush so as to be linearly displaceable in the radial direction via the slide key inserted into the slide hole. . In addition, a center hole that engages the center of the lathe when the drive shaft is machined is formed at the center (axial center) at the rear end of the drive shaft, and the center hole engages with the center hole. In order to avoid interference, the slide key is arranged radially outward with respect to the center hole.

JP-A-6-280759

  In the scroll compressor having the slide key type turning radius adjusting mechanism as described above, the slide key layout can be set relatively freely at the rear end of the drive shaft due to the structure of the turning radius adjusting mechanism. It is.

  On the other hand, in addition to the slide key type turning radius adjusting mechanism described above, an eccentric pin eccentric from the shaft center is provided at the rear end of the drive shaft, and the eccentric pin is inserted into the eccentric hole of the bush provided at the center of the movable scroll. A swing link type turning radius adjusting mechanism is known in which the turning radius of the movable scroll can be adjusted by swinging a counterweight provided on the outer peripheral side of the bush around the eccentric pin.

  However, in the case of the swing link type turning radius adjusting mechanism, it is necessary to secure a radial space for swinging around the eccentric pin, and the layout range in the radial direction of the eccentric pin is limited. . In addition, even when trying to reduce the size of a scroll compressor equipped with a swing link type turning radius adjusting mechanism, the radial layout restriction of the eccentric pin described above becomes a problem, and the size reduction in the radial direction is reduced. difficult.

  The present invention has been made in consideration of the above-mentioned problems, and even when a swing link type turning radius adjusting mechanism is provided, a scroll type compression that can increase the degree of freedom of design and can be miniaturized. The purpose is to provide a machine.

To achieve the above object, the present invention provides a fixed scroll, a movable scroll meshed with the fixed scroll, a bush rotatably supported by a boss portion of the movable scroll, and a drive shaft provided on the drive shaft. A scroll type compressor provided with an eccentric pin that is eccentric from the shaft center and fitted into an eccentric hole of the bush, and a swing link type turning radius adjusting mechanism that adjusts the turning radius by swinging the bush with the eccentric pin as a fulcrum. In
The drive shaft is formed with a center hole for engaging the jig at the center of the end where the eccentric pin is provided, and the eccentric pin is for avoiding interference with the jig engaged with the center hole. A relief portion is formed.

  According to the present invention, in a scroll compressor, an eccentric pin provided on a drive shaft and eccentric from an axis is fitted into an eccentric hole of the bush, and the turning radius is adjusted by swinging the bush with the eccentric pin as a fulcrum. A swing link type turning radius adjusting mechanism is formed, and a center hole in which a jig is engaged is formed in the shaft center of the end portion where the eccentric pin is provided in the drive shaft, and the center hole is formed in the eccentric pin. An escape portion for avoiding interference with the jig to be engaged is formed.

  Accordingly, since the eccentric pin can be disposed at a position closer to the shaft center (center hole) of the drive shaft by providing the relief portion, the degree of freedom of layout in the radial direction of the eccentric pin can be increased. In addition, the drive shaft can be downsized in the radial direction by arranging the eccentric pin more radially inward than when no escape portion is provided, and accordingly, the diameter of the scroll compressor is reduced. Can be achieved.

  In addition, a retraction portion is provided to prevent contact between the boundary portion formed between the arc portion of the eccentric pin and the escape portion and the inner surface of the eccentric hole, and the retraction portion is formed in at least one of the eccentric hole and the eccentric pin. Good. Thereby, since the contact between the boundary portion of the eccentric pin and the inner surface of the eccentric hole can be suitably prevented by the retracting portion formed in at least one of the eccentric hole and the eccentric pin, the eccentric pin caused by the contact and Occurrence of abnormal wear or the like of the eccentric hole is prevented, and accordingly, durability can be improved.

  Furthermore, by forming the escape portion by cutting out a part of the eccentric pin formed in a circular cross section, it is possible to easily provide the escape portion and reliably avoid interference with the jig.

  Furthermore, by providing the retracting portion at the boundary portion and forming a circular arc shape in the cross section, the boundary portion of the eccentric pin does not become square, and contact with the inner surface of the eccentric hole can be suitably avoided.

  Furthermore, by providing the retracting portion in the eccentric hole and forming a recess formed by bulging outward from the inner surface of the eccentric hole, the boundary portion of the eccentric pin comes into contact with the inner surface of the eccentric hole. Can be suitably avoided.

  According to the present invention, the following effects can be obtained.

  That is, a swing link type turning radius adjusting mechanism that adjusts a turning radius by an eccentric pin that is provided on the drive shaft being fitted to an eccentric hole of the bush, and the bush swings with the eccentric pin as a fulcrum. In the scroll compressor having the above, the drive shaft is formed with a center hole engaged with the jig on the shaft center of the end provided with the eccentric pin, and the eccentric shaft is engaged with the center hole. By forming an escape portion to avoid interference with the shaft, it is possible to place the eccentric pin at a position close to the shaft center (center hole) of the drive shaft, so the freedom of layout in the radial direction of the eccentric pin Compared to the case where no escape portion is provided, the eccentric shaft is arranged on the radially inner side, so that the drive shaft can be reduced in the radial direction. Diameter of the scroll compressor can be downsized.

1 is an overall cross-sectional view of a scroll compressor according to an embodiment of the present invention. 2A is a front view showing the other end of the drive shaft and the bush in the scroll compressor of FIG. 1, FIG. 2B is an enlarged front view of the vicinity of the crankpin in FIG. 2A, and FIG. FIG. 2D is an enlarged front view showing the vicinity of a crankpin of a drive shaft according to a modification, and FIG. 2D is an enlarged front view showing the vicinity of a crankpin of a drive shaft according to a second modification.

  A preferred embodiment of a scroll compressor according to the present invention will be described in detail below with reference to the accompanying drawings. In FIG. 1, reference numeral 10 indicates a scroll compressor according to an embodiment of the present invention.

  As shown in FIG. 1, the scroll compressor 10 includes a front housing 12 formed in a lid shape and a rear housing 14 formed in a cup shape, and on the outer peripheral side of the rear housing 14, For example, a suction port 16 for introducing a gas composed of a refrigerant or the like into the interior and a discharge port (not shown) through which the compressed gas compressed in the rear housing 14 is led out are formed.

  Then, a fixed scroll 18 and a movable scroll 20 that turns with respect to the fixed scroll 18 are inserted into the rear housing 14 from the opened one end side (in the direction of arrow A).

  The front housing 12 includes a cylindrical portion 22 that is formed at one end of the front housing 12 and supports a drive shaft 64 of the drive portion 62 described later, and a connecting portion 24 that is enlarged in diameter with respect to the cylindrical portion 22 and connected to the rear housing 14. Have.

  The rear housing 14 is formed in, for example, a bottomed cylindrical shape, and has a large diameter portion 26 formed on one end side (in the direction of arrow A) of the opening, and the other end portion side (arrow) with respect to the large diameter portion 26. A small-diameter portion 28 formed in the B direction) and having a reduced diameter, and a gas discharge chamber 30 formed inside the small-diameter portion 28. The gas discharge chamber 30 communicates with a discharge port (not shown).

  The large-diameter portion 26 has, for example, an inner peripheral surface having a substantially constant diameter along the axial direction (the directions of arrows A and B), and the connecting portion 24 of the front housing 12 abuts on the front end portion thereof. The front housing 12 and the rear housing 14 are connected to each other in the axial direction by a plurality of fastening bolts 32. On the other hand, the suction port 16 formed in the large-diameter portion 26 penetrates toward the inner peripheral side, and enters the gas suction chamber 34 formed between the fixed scroll 18 and the fixed spiral wall 38 through the suction port 16. Gas is introduced.

  The fixed scroll 18 includes a fixed-side substrate portion 36 and a fixed-side spiral wall 38 that is erected from the fixed-side substrate portion 36 toward the movable scroll 20 (arrow A direction) and is formed in a spiral shape.

  The fixed-side substrate portion 36 is formed, for example, in a disk shape having a predetermined thickness, and a compressed gas outlet hole 40 communicating from a gas compression chamber 60 (described later) to the gas discharge chamber 30 is axially disposed at a substantially central portion thereof. It is formed to penetrate in the direction of arrows A and B. The fixed-side substrate portion 36 is accommodated inside the large-diameter portion 26 of the rear housing 14.

  The center of the back surface of the fixed-side substrate portion 36 is formed to be depressed toward the movable scroll 20 (in the direction of arrow A), and a compressed gas outlet hole 40 penetrating the fixed-side substrate portion 36 is formed. A discharge valve 44 is provided that closes the hole 40 and opens to discharge the compressed gas to the gas discharge chamber 30 when the compressed gas compressed in the gas compression chamber 60 reaches a predetermined pressure.

  The movable scroll 20 has a movable side substrate portion 46 and a movable side which is formed in a spiral shape standing from the movable side substrate portion 46 to the fixed scroll 18 side (in the direction of arrow B) and meshes with the fixed side spiral wall 38. And a spiral wall 48.

  Further, the movable side substrate portion 46 is formed with a circular concave portion 50 opened in the back side (in the direction of arrow A) in the central portion, and a bush 54 is rotatably inserted into the inside thereof via a swivel bearing 52. It is.

  Further, a pair of engaging recesses 56 that allow the movable scroll 20 to be reciprocally displaced only in the radial direction are formed on the back side (in the direction of arrow A) of the movable side substrate portion 46. An Oldham ring 58 that restricts the rotation of the movable scroll 20 and allows the movable scroll 20 to turn is slidably engaged.

  The movable scroll 20 described above is arranged in the rear housing 14 such that the movable-side spiral wall 48 is on the fixed scroll 18 side (in the direction of arrow B), and the fixed-side substrate portion 36 constituting the fixed scroll 18 and the fixed scroll 18 are fixed. A gas compression chamber 60 is formed by the side spiral wall 38, the movable side substrate portion 46 and the movable side spiral wall 48 constituting the movable scroll 20.

  The drive unit 62 includes a drive shaft 64 that extends along the axial direction (the directions of arrows A and B), and a bush 54 that is coupled to the end of the drive shaft 64.

  The drive shaft 64 is formed of, for example, a metal material by casting or the like, and includes a shaft portion 66 having a substantially constant diameter and a support body 68 that is provided at an end portion of the shaft portion 66 and has an enlarged diameter. The formed shaft portion 66 is inserted into the cylindrical portion 22 of the front housing 12 and is rotatably supported via the first bearing 70, and a pulley (not shown) is attached to the tip portion thereof. And it rotates by the rotational drive force of an engine being provided to the drive shaft 64 via the pulley which is not illustrated.

  On the other hand, the support 68 is formed, for example, in a circular cross section, and is disposed on the other end side of the front housing 12 on the fixed scroll 18 side (arrow B direction). Two bearings 72 are rotatably supported.

  Further, as shown in FIGS. 1 and 2A, a center hole 74 is formed in the central portion of the axis on the other end surface of the support 68 on the movable scroll 20 side (arrow B direction). A crankpin 76 is provided at a position radially outside the center hole 74. That is, the crankpin 76 is provided eccentrically in the radial direction with respect to the axis of the support 68 and is formed substantially parallel to the center hole 74 (see FIG. 1).

  As shown in FIG. 1, the center hole 74 is formed at a predetermined depth from the other end surface of the support 68, and performs support and centering when processing the outer peripheral surface of the support 68 using, for example, a lathe. The lathe jig C (center) is inserted into and supported by the center hole 74 in a state where a drive shaft 64 serving as a work is held by a chuck or the like (not shown).

  On the other hand, as shown in FIGS. 1 and 2B, the crank pin 76 is formed in a shaft shape projecting from the other end surface of the support 68 to the movable scroll 20 side (in the direction of arrow B) with a predetermined length. The section 68 is formed in a substantially semicircular cross-section in which the inner radius of the body 68 is cut away (see FIGS. 2A and 2B). That is, as shown in FIG. 2B, the crank pin 76 includes a circular arc portion 78 having a circular arc shape formed radially outward with the center hole 74 of the support 68 as a center, and a radially inner side facing the center hole 74. And a flat portion 80 formed in a substantially straight line, and an edge-shaped corner portion (boundary portion) 82 is formed at a joint portion between the both ends of the arc portion 78 and the flat portion 80.

  For example, the flat portion 80 does not overlap the center hole 74 in the axial direction (in the directions of arrows A and B), and does not come into contact with the center hole 74 when the jig C is inserted. (See FIG. 2B). In other words, the crank pin 76 has a relief portion (flat portion 80) cut out so as to avoid interference when the jig C is inserted into the center hole 74.

  Moreover, the flat part 80 is good also as a processed surface which processed the raw material surface at the time of being formed by casting by cutting etc., and is good also as the said raw material surface. That is, since the dimensional accuracy is not required for the flat portion 80, the flat portion 80 may have any shape that does not contact the jig C without any particular processing. The advantage that the process can be reduced is obtained.

  For example, as shown in FIGS. 1 and 2A, the bush 54 includes a disc-shaped main body 84 having a predetermined length in the axial direction, and a balance extending radially outward from the outer peripheral surface of the main body 84. An eccentric hole 88 is formed in the main body portion 84 at a position eccentric in the radially outward direction from the center.

  The eccentric hole 88 penetrates along the axial direction of the bush 54, and faces the substantially semicircular first hole 90 corresponding to the cross-sectional shape of the crankpin 76, and the radially inner side of the first hole 90. The second hole 92 having a substantially semicircular shape is formed as described above. As shown in FIG. 2B, the eccentric hole 88 is a curved portion in which the opening end that is the radially inner side of the first hole portion 90 and the opening end that is the radially outer side of the second hole portion 92 each have a predetermined radius. 94. Thereby, it is prevented that the boundary part of the 1st hole part 90 and the 2nd hole part 92 becomes edge shape, and it protrudes inside, and it is joined smoothly and the amount of protrusion to the inside is also suppressed.

  In other words, the eccentric hole 88 includes the first hole portion 90 and the second hole portion 92 whose centers are offset in the radial direction of the support 68 by a predetermined interval.

  Further, as shown in FIGS. 2A and 2B, the second hole portion 92 is formed so that a part thereof faces the center hole 74.

  Furthermore, as shown in FIG. 1, the eccentric hole 88 is inserted with the crank pin 76 inserted into the first hole 90 and the flat portion 80 facing the second hole 92. A locking ring 96 is attached to the groove formed in the portion, and the crank pin 76 is prevented from coming off in the axial direction with respect to the bush 54.

  The main body 84 of the bush 54 is rotatably supported by a swivel bearing 52 provided inside the front housing 12, and the crank pin 76 is inserted into the eccentric hole 88 of the bush 54, thereby driving the drive shaft 64. Is turned so as to be swingable. Thus, the movable scroll 20 functions as a swing link type turning radius adjusting mechanism that can turn while the turning radius of the movable scroll 20 is varied under the rotational action of the drive shaft 64. The support body 68 is rotatably supported by a second bearing 72 provided in the front housing 12.

  The scroll compressor 10 according to the embodiment of the present invention is basically configured as described above. Next, the operation, action, and effect thereof will be described.

  First, when the rotational driving force of the engine is transmitted to the drive shaft 64 through a pulley (not shown), the support body 68 rotates through the second bearing 72, and accordingly, the crank pin provided on the support body 68 76 turns in a state of being eccentric with respect to the axis of the drive shaft 64. As a result, the bushing 54 rotates via the crank pin 76, the Oldham ring 58 slides and its rotation is restricted, so that the movable scroll 20 pivots with respect to the fixed scroll 18 in a state where the rotation is restricted. To do.

  The gas supplied from the suction port 16 is introduced into the rear housing 14 and is formed between the fixed-side spiral wall 38 of the fixed scroll 18 and the movable-side spiral wall 48 of the movable scroll 20. 60, and the movable-side spiral wall 48 turns while being in contact with the fixed-side spiral wall 38 of the fixed scroll 18, thereby compressing the gas in the gas compression chamber 60 formed between them and the center portion. Proceed toward the side.

  Further, the movable scroll 20 is swung to compress the gas in the gas compression chamber 60. Thereafter, the compressed gas is discharged from the compressed gas outlet hole 40 to the gas discharge chamber 30 and discharged (not shown). It is discharged through a port to a refrigerant circulation system (not shown).

  Further, when the bush 54 swings with the crank pin 76 as a fulcrum under the rotational action of the drive shaft 64, as shown in FIG. 2B, the second hole 92 is formed at a portion facing the corner portion 82 of the crank pin 76. The inner peripheral surface of the second hole portion 92 is formed so as to be gradually separated from the corner portion 82. Therefore, the contact between the corner 82 and the eccentric hole 88 is preferably avoided, and the curved portion 94 is provided at the joint portion between the first hole 90 and the second hole 92, and thus the corner 82. Is more preferably avoided from contacting the inner peripheral surface of the eccentric hole 88.

  As described above, in the present embodiment, the crank pin 76 provided on the drive shaft 64 is fitted into the eccentric hole 88 of the bush 54, and the bush 54 swings about the eccentric pin, thereby moving the scroll. In the scroll type compressor 10 having a swing link type turning radius adjusting mechanism capable of adjusting the turning radius of 20, the crank pin 76 has a center hole 74 provided in the center of the support 68 in the drive shaft 64. The flat part 80 which can avoid the contact with the jig | tool C engaged is provided.

  Therefore, for example, even when the crankpin 76 has to be disposed at a position close to the axis of the drive shaft 64 due to restrictions on the peripheral layout, the crankpin 76 is centered while avoiding interference with the jig C. It becomes possible to arrange in the vicinity.

  As a result, in the support body 68 of the drive shaft 64, the degree of freedom of layout in the radial direction of the crankpin 76 can be increased.

  In addition, compared with the case where the crank pin 76 is not provided with a relief portion, the crank pin 76 can be disposed more radially inward, so that the drive shaft 64 can be reduced in the radial direction, and accordingly, the scroll compressor. 10 can be reduced in diameter.

  Furthermore, the eccentric hole 88 can secure a large gap between the corner 82 and the inner peripheral surface of the eccentric hole 88 by providing the second hole 92 at a position where the corner 82 of the crank pin 76 faces. Therefore, it is possible to suitably avoid contact between the corner portion 82 and the second hole portion 92. In other words, the second hole portion 92 is a retracting portion that retracts the inner peripheral surface of the eccentric hole 88 radially outward in order to avoid contact with the corner portion 82 of the crank pin 76. As a result, the occurrence of abnormal wear or the like due to the contact between the corner 82 of the crankpin 76 and the eccentric hole 88 can be reliably prevented, and the durability can be improved.

  Furthermore, since the eccentric hole 88 in the bush 54 is provided with a curved portion 94 having an arcuate cross section at the joint portion between the first hole 90 and the second hole 92 where the corner 82 of the crank pin 76 faces, Contact between the corner portion 82 and the inner peripheral surface of the eccentric hole 88 can be suitably avoided, and the occurrence of abnormal wear or the like of the eccentric hole 88 or the crank pin 76 due to the contact can be further reliably prevented. It is possible to further improve the durability.

  On the other hand, the eccentric hole 88 is not limited to the case where the first and second hole portions 90 and 92 are configured as described above. For example, as shown in FIG. A circular eccentric hole 100 may be provided, and a pair of retracting portions 106 a and 106 b that bulge outward from the inner peripheral surface of the eccentric hole 100 and face the corner portion 104 of the crankpin 102 may be provided. The retracting portions 106a and 106b are formed, for example, in a substantially semicircular cross section, and their end portions and the inner peripheral surface of the eccentric hole 100 are joined by a curved portion 108 having an arcuate cross section.

  Thus, even when the crank pin 102 rotates in the eccentric hole 100 under the rotational action of the drive shaft 64, the eccentric hole 100 facing the corner 104 is expanded by the retreating portions 106a and 106b, and the retraction portion Since 106a, 106b and the eccentric hole 100 are smoothly joined by the curved portion 108, the contact between the eccentric hole 100 and the corner portion 104 is preferably avoided, and the eccentric hole 100 and the crank pin 102 are It is possible to reliably prevent the occurrence of abnormal wear or the like due to the contact.

  Further, as shown in FIG. 2D, a substantially circular eccentric hole 120 is formed, and a set of chamfered portions 124 are formed in which the corners of the crank pin 122 inserted into the eccentric hole 120 are formed in a circular arc shape. May be. For example, the chamfered portion 124 is formed by chamfering into a smooth circular arc shape by processing a corner portion that becomes a boundary portion between the arc portion 78 and the flat portion 80.

  Thereby, even when the crank pin 122 rotates in the eccentric hole 120 under the rotational action of the drive shaft 64, a gap between the inner peripheral surface of the eccentric hole 120 is formed by forming the chamfered portion 124 at the corner. And the contact between the eccentric hole 120 and the corner is preferably avoided, such as abnormal wear due to contact between the eccentric hole 120 and the crank pin 122. Occurrence can be reliably prevented.

  That is, the chamfered portion 124 is a retracted portion that retracts the crankpin 122 side in order to avoid contact between the crankpin 122 and the eccentric hole 120.

  The scroll compressor according to the present invention is not limited to the above-described embodiment, and can of course have various configurations without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 10 ... Scroll type compressor 12 ... Front housing 14 ... Rear housing 18 ... Fixed scroll 20 ... Movable scroll 54 ... Bush 62 ... Drive part 64 ... Drive shaft 68 ... Support body 74 ... Center hole 76, 102, 122 ... Crank pin 78 ... arc part 80 ... flat part 82, 104 ... corner part 84 ... main body part 86 ... balance weight part 88, 100, 120 ... eccentric hole 90 ... first hole part 92 ... second hole part 94, 108 ... curved part 106a, 106b ... evacuation part 124 ... chamfering part

Claims (5)

A fixed scroll, a movable scroll meshed with the fixed scroll, a bush rotatably supported by a boss portion of the movable scroll, an eccentric hole of the bush provided on a drive shaft and eccentric from an axis of the drive shaft A scroll type compressor provided with an eccentric pin fitted to and a swing link type turning radius adjusting mechanism that adjusts the turning radius by swinging the bush with the eccentric pin as a fulcrum,
The drive shaft is formed with a center hole engaged with a jig at the axial center of the end where the eccentric pin is provided, and the eccentric pin is connected with the jig engaged with the center hole. A scroll compressor characterized in that a relief portion for avoiding interference is formed. The scroll compressor according to claim 1, wherein
A retracting portion for preventing contact between a boundary portion formed between the arc portion of the eccentric pin and the escape portion and an inner surface of the eccentric hole;
The scroll type compressor, wherein the retracting portion is formed in at least one of the eccentric hole and the eccentric pin. In the scroll compressor according to claim 1 or 2,
2. The scroll compressor according to claim 1, wherein the escape portion is formed by cutting out a part of the eccentric pin having a circular cross section. The scroll compressor according to claim 2,
The scroll type compressor, wherein the retracting portion is provided in the boundary portion and formed in a circular arc shape in cross section. The scroll compressor according to claim 2,
The scroll compressor according to claim 1, wherein the retracting portion is a concave portion provided in the eccentric hole and formed to bulge toward an outer peripheral side with respect to an inner peripheral surface of the eccentric hole.

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