JP3932386B2 - Joint boots - Google Patents

Description

  The present invention is provided with a cylindrical large-diameter side attachment portion that is externally attached to the outer case, a small-diameter side attachment portion that is attached to the shaft, and a bellows portion that connects these, and the large-diameter side attachment portion The outer peripheral surface is formed in a circular shape in cross section, and a plurality of convex portions projecting radially inward are provided on the inner peripheral portion of the large-diameter side attachment portion, and are distributed in the circumferential direction. The present invention relates to a joint boot in which a plurality of convex portions are separately fitted into a plurality of concave portions formed on an outer peripheral portion.

  One of the constant velocity joints provided on a drive shaft of an automobile is a tripod type constant velocity joint that can change its position in the axial direction and transmit rotational force. As shown in FIGS. 4 and 5, the constant velocity joint has three trunnions 31 with rollers protruding from the shaft 3 on the input side (or output side) in the direction perpendicular to the axis, and the output side (or input side). The outer case 1 is provided at the end of the shaft 40, and three grooves 34 on which the roller 32 rolls are distributed in the circumferential direction on the inner peripheral portion of the outer case 1. 33 is a triport.

  The joint boot described at the beginning is provided with respect to such a constant velocity joint, prevents dust and foreign matter from entering the constant velocity joint, and holds grease around the constant velocity joint. The outer case 1 is provided with a plurality of concave portions 8 that are recessed radially inward in the circumferential direction to reduce the weight of the case. Correspondingly, a plurality of convex portions 7 projecting radially inward are provided on the inner peripheral portion of the large-diameter side attachment portion 2 of the joint boot in a circumferential direction.

Conventionally, the entire joint boot is integrally formed of a resin material as disclosed in JP-A-2003-329059.
JP 2001-165188 A JP 2003-329059 A

  According to the above-described conventional configuration, since the entire joint boot is integrally formed of a resin material, the hardness of the large-diameter side mounting portion becomes hard, the adhesion of the large-diameter side mounting portion to the outer case is not good, and the seal There was room for improvement in terms of sex.

  An object of the present invention is to provide a joint boot that can improve the sealing performance of the large-diameter side attachment portion with respect to the outer case.

The present invention is characterized in that a cylindrical large-diameter side mounting portion that is externally fitted to the outer case, a small-diameter side mounting portion that is attached to the shaft, and a bellows portion that connects these are provided, and the large-diameter side mounting portion And forming a plurality of convex portions projecting radially inward on the inner peripheral portion of the large-diameter side mounting portion in a circumferential direction. A joint boot configured such that the plurality of convex portions can be separately fitted to a plurality of concave portions formed on an outer peripheral portion of the case, wherein the bellows portion is formed of a resin material, and the large-diameter side attachment portion is Formed by a resin material or a rubber member that is softer than the bellows part separately from the bellows part, extending a fitting tube part that fits outside the large diameter side attachment part to one end of the bellows part, One end portion of the large-diameter side attachment portion on the bellows portion side is smaller as the bellows portion side is smaller. Constitute the tapered cylindrical, the convex portion, the plurality of first lightening hole opening on one end face of the large-diameter attachment part arranged in the circumferential direction, in the circumferential direction and opening on the other end face side Forming a plurality of second hollow holes arranged side by side, the width of the first partition wall partitioning adjacent first hollow holes, the width of the second partition wall partitioning adjacent second hollow holes, The thickness of the fitting peripheral wall portion of the convex portion and the thickness of the peripheral wall of the large-diameter mounting portion located between the convex portions adjacent in the circumferential direction are set to be the same or substantially the same .

  According to this configuration, the large-diameter side attachment portion is formed separately from the bellows portion, the bellows portion is formed of a resin material, and the large-diameter side attachment portion is made of a resin material or rubber member that is softer than the bellows portion. Since it forms, while being able to improve the durability of a bellows part, the adhesiveness of the large diameter side attaching part with respect to an outer case can be improved.

  Moreover, since the one end part of the said large diameter side attaching part by the side of the said bellows part is comprised in the taper cylinder shape of a small diameter as the bellows part side, when fitting a fitting cylinder part and a large diameter side attaching part, The fitting tube portion can be guided by the one end portion of the tapered tube shape, and it becomes easy to fit both.

  And the large diameter side attaching part can be reliably assembled | attached to a fitting cylinder part by extending the fitting cylinder part which is externally fitted by the large diameter side attaching part in the one end part of a bellows part.

  In the present invention, an enlarged diameter portion capable of receiving the end surface of the fitting cylinder portion in the axial direction is formed on an outer peripheral portion of the large diameter side attachment portion, and the length of the enlarged diameter portion in the axial direction is If it is set longer than the thickness of the fitting cylinder part, the rigidity in the axial direction of the enlarged diameter part can be increased. As a result, the assemblability can be improved. For example, when assembling the bellows part and the large-diameter side mounting part with a robot hand or when assembling artificially, the fitting cylinder part pushes down the enlarged diameter part. Assembly failure that can be overcome is avoided.

According to the present invention, the convex portion has a plurality of first cutout holes that are open on one end surface side of the large-diameter side attachment portion and are arranged in the circumferential direction, and a plurality of holes that are open on the other end surface side and are arranged in the circumferential direction. Forming the second cutout hole, the width of the first partition wall partitioning the adjacent first cutout holes, the width of the second partition wall partitioning the adjacent second cutout holes, and the convex portion Since the thickness of the fitting peripheral wall portion is set to be the same or substantially the same, the following effects can be obtained.

  That is, it is possible to cool the resin material corresponding to the convex portion in the molding process (a rubber material when the large-diameter side attachment portion is formed of a rubber member) faster than a structure in which no hollow hole is formed. Moreover, the fitting peripheral wall part of a convex part can be supported by the large diameter side attachment part between a some 1st hollow hole and a 2nd hollow hole, and the thickness of the fitting peripheral wall part of a convex part It is not necessary to increase the thickness.

  For example, in a structure in which only a hollow hole opened on one end surface side of the large-diameter side mounting portion is formed and no hollow hole opened on the other end surface side is formed, a resin material (or rubber) corresponding to the other end surface side is formed. The amount of the material) is larger than the amount of the resin material (or rubber material) corresponding to the one end surface side, and the cooling rate of the resin material (or rubber material) corresponding to the other end surface side corresponds to the one end surface side. However, according to the above configuration of the present invention, the large-diameter side attachment portion is defined as the bellows portion, which is slower than the cooling rate of the resin material (or rubber material) to be distorted and tends to be distorted after the cooling. Are formed separately, and both of the plurality of first hollow holes opened on one end surface side and the plurality of second hollow holes opened on the other end surface side are formed. It is possible to make it difficult to make a large difference in speed, and to avoid the above-mentioned problems. And, by forming the large-diameter side attachment part separately from the bellows part, performing die cutting when forming a plurality of lightening holes in the large-diameter side attachment part without being obstructed by the bellows part Can do.

  In addition, since the width of the first partition wall, the width of the second partition wall, and the thickness of the fitting peripheral wall portion are set to be the same or substantially the same, the resin material (or rubber material) corresponding to the first partition wall It may be difficult to make a large difference between the cooling rate, the cooling rate of the resin material (or rubber material) corresponding to the second partition wall, and the cooling rate of the resin material (or rubber material) corresponding to the fitting peripheral wall portion. it can. As a result, it is possible to prevent the occurrence of distortion on the convex side due to the different cooling rates of the resin material (or rubber material) and to easily mold the large-diameter side mounting portion into a desired shape with high accuracy. Further, the adhesion of the large-diameter side attachment portion to the outer case can be further improved.

According to the present invention, the width of the first partition wall, the width of the second partition wall partitioning the adjacent second hollow holes, and the wall thickness of the fitting peripheral wall portion of the convex portion, Since the thickness of the peripheral wall of the large-diameter side mounting portion located between adjacent convex portions in the circumferential direction is set to be the same or substantially the same, the cooling rate of the resin material (or rubber material) corresponding to the first partition wall The cooling rate of the resin material (or rubber material) corresponding to the second partition wall, the cooling rate of the resin material (or rubber material) corresponding to the fitting peripheral wall portion, and the peripheral wall of the large-diameter side attachment portion A large difference in the cooling rate of the resin material (or rubber material) can be prevented. As a result, it is possible to prevent occurrence of distortion on the convex portion side due to different cooling rates of the resin material (or rubber material), and to easily mold the large-diameter side attachment portion into a desired shape with high accuracy. .

  In the present invention, the thickness of the large-diameter side attachment portion between the plurality of first hollow holes and the second hollow hole, the width of the first partition wall, the width of the second partition wall, If it is set to be thicker than any of the wall thickness of the fitting peripheral wall portion, for example, when the large diameter side mounting portion is fastened and fixed to the outer case with a tightening band, the tightening force is applied to the fitting peripheral wall portion, Can be communicated more reliably.

  In the present invention, when the length in the axial direction of the enlarged diameter portion is set to 1.5 mm to 5 mm, it is easy to increase the rigidity in the axial direction of the enlarged diameter portion while suppressing an increase in manufacturing cost. Can do. That is, if the length is less than 1.5 mm, there is a problem that the rigidity is low, and if it exceeds 5 mm, there is a problem that the rubber material is increased and the manufacturing cost is increased, but the length is set to 1.5 mm to 5 mm. By doing so, these problems can be solved.

In the present invention, when the hardness of the large-diameter side mounting portion is set to 55 to 85 degrees in JISA hardness and the hardness of the bellows portion 5 to 40 to 50 degrees in JISD hardness (conforming to JISK6253), There is an effect. That is, if the hardness of the large-diameter side mounting portion 2 is less than 55 degrees in terms of JIS hardness, the large-diameter side mounting portion 2 becomes too soft and the sealing performance becomes poor, and if it exceeds 85 degrees, it becomes too hard and the tightening performance is high. Although there is a problem of lowering, these problems can be solved by setting the hardness of the large-diameter side attachment portion 2 to 55 degrees to 85 degrees in terms of JIS hardness. The present inventor confirmed the characteristics of the large-diameter side mounting portion by the following experiment. 5 large-diameter side mounting parts made of resin materials having a JISA hardness of 40 degrees, 55 degrees, 70 degrees, 85 degrees, and 90 degrees, respectively, are manufactured, and these five large-diameter side attachment parts are formed into five bellows parts. Install to each. Then, the large-diameter side mounting part is attached to the outer case of the triport type constant velocity joint, the small-diameter side mounting part is attached to the shaft, and grease is sealed in the joint boot (see FIGS. 4 and 5 for the assembly structure). The structure of each member is described in the section [Embodiment] described later). In this assembled state, an operation of relatively moving (sliding) the outer case and the shaft in the axial direction, an operation of bending the outer case and the shaft to a maximum angle, and an operation of rotating the shaft around the axis. Is repeated a number of times in any combination. After that, when leakage of grease from between the large-diameter side mounting portion and the outer case was observed, as shown in Table 1 showing the characteristics of the joint boot, grease leakage occurred at the large-diameter side mounting portion having a JISA hardness of 40 degrees. (X in Table 1) was observed, but there was no leakage of grease at the large-diameter side mounting portions with other hardnesses (55 degrees, 70 degrees, 85 degrees, and 90 degrees) (circle marks in Table 1). . In addition, when the large-diameter side attachment part is attached to the outer case, the fitting cylinder part extended to one end of the bellows part is externally fitted to the large-diameter side attachment part, and when tightened manually with a tightening band, the JISA hardness is A large tightening force was required for the 90 ° large-diameter side mounting part (indicated by X in Table 1), but large tightening was required for large-diameter side mounting parts with other hardness (40 °, 55 °, 70 °, 85 °). No force was required (circles in Table 1).

  If the hardness of the bellows portion 5 is less than 40 degrees in terms of JISD hardness, the rigidity decreases, and for example, it is easily deformed by impact force, and if it exceeds 50 degrees, it becomes too hard and the durability decreases. These problems can be solved by setting the hardness of the part 5 to 40 degrees to 50 degrees in terms of JISD hardness.

According to the present invention, the large-diameter side mounting portion can be accurately formed into a desired shape. For example, when the large-diameter side mounting portion is fastened and fixed to the outer case with a tightening band, It is possible to avoid the formation of a gap between the convex portion on the large-diameter side mounting portion side, the sealing performance of the large-diameter side mounting portion with respect to the outer case can be improved, and the large-diameter side on the bellows portion side Since one end portion of the attachment portion is configured in a tapered cylinder shape having a smaller diameter toward the bellows portion side, when the fitting tube portion and the large diameter side attachment portion are fitted, the one end portion of the tapered cylinder shape is fitted into the fitting tube. It is possible to provide a joint boot that can guide the parts and easily fit them together, improve the assembling property, and increase the productivity.
Further, a plurality of first cutout holes opened on one end surface side of the large-diameter side attachment portion and arranged in the circumferential direction, and a plurality of second meat openings opened on the other end surface side and arranged in the circumferential direction are formed in the convex portion. The width of the 1st partition wall which forms a piercing hole and partitions adjacent 1st hollow hole, the width of the 2nd partition wall which divides adjacent 2nd hollow hole, and the fitting surrounding wall of the said convex part Since the thickness of the portion is set to be the same or substantially the same, the adhesion of the large-diameter side attachment portion to the outer case can be further improved, and the sealing property can be further improved.
Further, the width of the first partition wall, the width of the second partition wall partitioning adjacent second hollow holes, and the thickness of the fitting peripheral wall portion of the convex portion are adjacent convex portions in the circumferential direction. Since the wall thickness of the peripheral wall of the large-diameter side mounting portion located between them is set to be the same or substantially the same, the large-diameter side mounting portion can be easily formed into a desired shape with high accuracy, and the sealing property can be further increased. Can be better.

  Further, an enlarged diameter portion capable of receiving the end surface of the fitting cylinder portion in the axial direction is formed on an outer peripheral portion of the large diameter side attachment portion, and the length of the enlarged diameter portion in the axial direction is set to the fitting If it is set longer than the wall thickness of the cylindrical part, when assembling the bellows part and the large-diameter side mounting part, it is possible to avoid an assembly failure in which the fitting cylindrical part pushes over the enlarged part and gets over, Productivity can be further increased.

  The thickness of the large-diameter side mounting portion between the plurality of first and second hollow holes, the width of the first partition wall, the width of the second partition wall, and the fitting peripheral wall portion For example, when the large-diameter side mounting part is tightened and fixed to the outer case with a tightening band, the tightening force is more reliably transmitted to the mating peripheral wall part. The sealing property can be further improved.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. 1, 2 and 3 show a joint boot provided for a triport type constant velocity joint of an automobile.

  4 and 5, the constant velocity joint includes three trunnions 31 with rollers protruding from the shaft 3 on the input side in a direction perpendicular to the axis, and an outer case at the end of the shaft 40 on the output side. 1, and three grooves 34 on which the roller 32 rolls are dispersedly arranged in the circumferential direction on the inner peripheral portion of the outer case 1. 33 is a triport. The joint boot includes a cylindrical large-diameter side attachment portion 2 that is externally fitted to the outer case 1, a cylindrical small-diameter side attachment portion 4 that is attached to the shaft 3, and a bellows portion 5 that connects them. The large-diameter side attachment portion 2 and the bellows portion 5 are formed separately, and a fitting tube portion 6 that is externally fitted and fixed to the large-diameter side attachment portion 2 is extended to one end portion 5 </ b> A of the bellows portion 5.

  The bellows portion 5 and the small-diameter side attachment portion 4 are integrally formed of a thermoplastic elastomer resin material, the large-diameter side attachment portion 2 is formed of a resin material softer than the bellows portion 5, and the large-diameter side attachment portion 2 An inner peripheral portion 50 having a smaller diameter than that of the case 1 is provided, and the large-diameter side attachment portion 2 is configured to be tightly fitted to the outer case 1. For example, the hardness of the large-diameter side attachment portion 2 can be set to 55 degrees to 85 degrees in terms of JIS hardness, and the hardness of the bellows portion 5 can be set to 40 degrees to 50 degrees in terms of JIS D hardness (conforming to JISK6253). An example of the resin material constituting the large-diameter side attachment portion 2 is TPO (Thermo Plastic Olefin), and an example is Santoplane (trade name) manufactured by AES (Advanced Elastmer Systems). Examples of the resin material constituting the bellows portion 5 and the small diameter side attachment portion 4 include TPEE and TPO.

  A shallow annular groove 52 is provided on the outer peripheral portion of the large-diameter side attachment portion 2 to be fitted to the annular convex portion 51 protruding from the inner peripheral portion of the fitting cylinder portion 6. In addition, the outer peripheral surface 2A of the large-diameter side mounting portion 2 is formed in a circular shape in cross section, and three convex portions 7 projecting radially inward are provided on the inner peripheral portion of the large-diameter side mounting portion 2. The three convex portions 7 are provided so as to be separately fitted to the three concave portions 8 formed on the outer peripheral portion of the outer case 1 by being uniformly distributed every 120 degrees in the circumferential direction.

  The convex portion 7 of the large-diameter side attachment portion 2 is formed in a mountain shape with a gentle cross-sectional shape. The center line L of the convex portion 7 in the circumferential direction is set to a symmetrical shape when viewed from the axial direction of the large-diameter side mounting portion 2, and is smoothly connected to the arc-shaped peripheral wall 15 between the adjacent convex portions 7. ing. The center lines L of the three convex portions 7 are located radially with respect to the axis O and at every 120 degrees in the circumferential direction.

  The large-diameter side attachment portion 2 and the small-diameter side attachment portion 4 are concentric, and annular grooves 9 and 19 around which the fastening band 35 is wound are formed on each outer peripheral portion. The bellows portion 5 is formed in a taper shape having a smaller diameter toward the smaller diameter side attachment portion 4 side, and the hollow portion serves as a grease filled space S.

  As shown in FIGS. 2 and 3, two pairs of bottomed first hollow holes 21 </ b> A and 22 </ b> A that open to the convex portion 7 on the one end surface 7 </ b> A side of the large-diameter side attachment portion 2 and are symmetric about the center line L. , 23A, 24A (see FIG. 2), and two pairs of bottomed second hollow holes 21B, 22B, 23B, 24B (see FIG. 3) that open to the other end surface 7B side and are symmetric about the center line L. The support wall 37 (corresponding to the large-diameter side attachment portion, see FIG. 1) is formed on the center side in the axial direction of the large-diameter side attachment portion 2. As described above, the plurality of first lightening holes 21A, 22A, 23A, and 24A are arranged in the circumferential direction, and the plurality of second lightening holes 21B, 22B, 23B, and 24B are arranged in the circumferential direction. . The depths of the plurality of first hollow holes 21A, 22A, 23A, 24A are the same. Further, the depths of the plurality of second hollow holes 21B, 22B, 23B, and 24B are also the same, and the depths of the plurality of second hollow holes 21B, 22B, 23B, and 24B are the plurality of first holes. It is slightly shallower than the punched holes 21A, 22A, 23A, 24A.

  The pair of inner first hollow holes 22A, 23A close to the center line L are trapezoidal with the outer peripheral surface 2A side of the large-diameter side attachment portion 2 narrowed, and the pair of outer first first hollow holes far from the center line L It is larger than the holes 21A and 24A, and all inner peripheral surfaces (except for the bottom surface) are parallel to the axis O. The width T2 of the central first partition wall 13 that partitions the pair of inner first cutout holes 22A and 23A from each other is substantially constant over the entire length.

  The pair of outer first hollow holes 21A, 24A are triangular, and all inner peripheral surfaces (except the bottom surface) are parallel to the axis O. Another first partition wall 13 that divides the inner first hollow hole 22A (or 23A) and the outer first hollow hole 21A (or 24A) is an outer periphery of the large-diameter side attachment portion 2 in the axial direction view. The surface side is closer to the central first partition wall 13 and is inclined. The width T2 of the other first partition wall 13 is also constant over the entire length.

  The structure of the second hollow holes 21B, 22B, 23B, and 24B is the same as that of the first hollow holes 21A, 22A, 23A, and 24A, and the position and shape are the same. That is, when viewed from the axial direction of the large-diameter side mounting portion 2, the first cutout hole 21 </ b> A and the second cutout hole 21 </ b> B have the same shape and overlap each other, and the first cutout hole 22 </ b> A and the second cutout hole 22B has the same shape and overlaps each other, and the first and second cutout holes 23A and 23B have the same shape and overlap each other, and the first and second cutout holes 24A and 24B have the same shape. And overlap each other.

  And the width T2 of the 1st partition wall 13, the width T5 of the 2nd partition wall 14 which partitions off the adjacent 2nd lightening hole 21B, 22B, 23B, 24B, and the thickness of the fitting peripheral wall part 12 of the convex part 7 Thickness T4 and the thickness T4 of the peripheral wall 15 of the large-diameter mounting portion 2 located between the convex portions 7 adjacent in the circumferential direction (the thickness of the peripheral wall portion where the annular groove 52 is not formed). Are set to be the same or almost the same.

  Further, the wall thickness T3 (the wall thickness is constant) of the support wall 37 in the axial direction is made thicker than the wall thicknesses T1, T2, T4, and T5, and the wall thicknesses T1, T2, and the like. The thickness is set twice as large as T4 and T5.

  An enlarged-diameter portion 39 capable of receiving the end surface 6A of the fitting cylinder portion 6 in the axial direction is formed on the outer peripheral portion of the large-diameter side attachment portion 2, and the fitting cylinder portion 6 and the large-diameter side attachment portion 2 are fitted. The length X in the axial direction of the enlarged diameter portion 39 is set to be longer than the wall thickness Z of the fitted cylinder portion 6 so that the fitting cylindrical portion 6 does not push down the enlarged diameter portion 39 with the fitting. Thus, the rigidity of the enlarged diameter portion 39 in the axial direction is increased. That is, the length X is such a length that the fitting cylinder portion 6 does not push down the enlarged diameter portion 39, and can be set to 1.5 mm to 5 mm, for example. The thickness Z of the fitting cylinder portion 6 is the maximum value of the thickness of the tip side (right side in the drawing) of the annular groove 9 around which the fastening band 35 is wound.

  Furthermore, the one end portion 61 of the large-diameter side attachment portion 2 on the bellows portion 5 side is configured in a tapered cylindrical shape with a smaller diameter toward the bellows portion 5 side.

  When the joint boot having the above structure is attached to the constant velocity joint, as shown in FIG. 4, the fitting tube portion 6 of the bellows portion 5 is externally fitted and fixed to the large diameter side attachment portion 2, and the large diameter side attachment portion 2 is fixed. The outer case 1 is externally fitted, the small diameter side mounting portion 4 is externally fitted to the shaft 3, and the fastening band 35 is fastened and fixed to the annular groove 9 of the large diameter side mounting portion 2 and the annular groove 19 of the small diameter side mounting portion 4. .

  The number of the hollow holes is not limited to the number shown in the above embodiment. The resin material constituting the large-diameter side attachment portion 2 may be TPEE (for example, Perprene (trade name) manufactured by Toyobo Co., Ltd., Hytrel (trade name) manufactured by Toray Du Pont). The large-diameter side attachment portion 2 may be formed of a rubber member such as CR (chloroprene rubber) or NBR (nitrilobutadiene rubber). Also in this case, the large-diameter side attachment portion 2 can be set to 55 degrees to 85 degrees in JISA hardness.

It is a longitudinal cross-sectional view of a joint boot. It is the figure which looked at the large diameter side attachment part from the outer side of the one end surface of a large diameter side attachment part. It is the figure which looked at the large diameter side attachment part from the outer side of the other end surface of a large diameter side attachment part. It is sectional drawing which shows the state which assembled | attached the joint boot to the constant velocity joint. It is a figure which shows the state which assembled | attached the joint boot to the constant velocity joint.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Outer case 1A Attached part 2 Large-diameter side attachment part 3 Shaft 4 Small-diameter side attachment part 5 Bellows part 5A One end part of a bellows part 6 Fitting cylinder part 6A End face of fitting cylinder part 7 Convex part 7A One end face 7B Other end face 8 recessed portion 12 fitting peripheral wall portion 13 first partition wall 14 second partition wall 15 peripheral wall 21A, 22A, 23A, 24A first cutout hole 21B, 22B, 23B, 24B second cutout hole 37 large diameter side attachment portion 39 Expanded portion 61 One end portion of the large-diameter side attachment portion T1 Thickness of the fitting peripheral wall portion T2 Width of the first partition wall T3 Thickness of the large-diameter side attachment portion T4 Thickness of the peripheral wall T5 Width of the second partition wall X Expansion Length in the axial direction of the diameter Z Thickness of the fitting tube

Claims (1)

A cylindrical large-diameter side mounting portion that is externally fitted to the outer case, a small-diameter side mounting portion that is attached to the shaft, and a bellows portion that connects these are provided, and the outer peripheral surface of the large-diameter side mounting portion is cross-sectional Formed in a circular shape, and provided on the inner peripheral portion of the large-diameter side mounting portion, a plurality of convex portions projecting radially inward in the circumferential direction, and formed on the outer peripheral portion of the outer case It is a joint boot configured to be able to externally fit the plurality of convex portions separately to the plurality of concave portions,
The bellows portion is formed of a resin material, the large-diameter side attachment portion is formed of a resin material or a rubber member that is softer than the bellows portion separately from the bellows portion, and is externally fitted to the large-diameter side attachment portion. Extending the fitting tube part to one end of the bellows part,
One end portion of the large-diameter side mounting portion on the bellows portion side is configured in a tapered cylindrical shape with a smaller diameter toward the bellows portion side ,
A plurality of first cutout holes opened on one end surface side of the large-diameter side attachment portion and arranged in the circumferential direction, and a plurality of second cutout holes opened on the other end surface side and arranged in the circumferential direction on the convex portion. And form the
The width of the first partition wall partitioning the adjacent first cutout holes, the width of the second partition wall partitioning the adjacent second cutout holes, the thickness of the fitting peripheral wall portion of the convex portion, and A joint boot in which the thickness of the peripheral wall of the large-diameter side mounting portion located between adjacent convex portions in the circumferential direction is set to be the same or substantially the same .

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