WO2005010387A1

WO2005010387A1 - Joint boot

Info

Publication number: WO2005010387A1
Application number: PCT/JP2004/009060
Authority: WO
Inventors: Takenori Ohshita; Eiichi Imazu
Original assignee: Toyo Tire & Rubber Co., Ltd.
Priority date: 2003-07-25
Filing date: 2004-06-21
Publication date: 2005-02-03
Also published as: JP4520946B2; JPWO2005010387A1

Abstract

A joint boot capable of improving the sealability of a large diameter side mounting part against an outer case, comprising the large diameter side mounting part (2), a small diameter side mounting part (4), and a bellows part (5). A plurality of projected parts are formed on the inner peripheral part of the large diameter side mounting part, and fitted to a plurality of recessed parts formed in the mounted part (1A) of the outer case (1). The bellows part is formed of a resin material, and the large diameter side mounting part is formed of a resin material or a rubber material softer than the bellow part. A fitted inner peripheral part (50) smaller in diameter than the mounted part of the outer case and an enlarged inner peripheral part (71) larger in diameter than the mounted part are formed at the large diameter side mounting part so that the large diameter side mounting part can be fitted onto the mounted part and that the mounted part can be guided by an enlarged guide part when the large diameter side mounting part is fitted onto the mounted part.

Description

Description Join Tobu

〔Technical field〕

The present invention provides a cylindrical large-diameter side mounting portion that is externally fitted to a mounting portion of an outer case, a small-diameter side mounting portion that is mounted on a shaft, and a bellows portion that connects these. The outer peripheral surface of the radial mounting portion is formed in a circular cross section, and a plurality of convex portions projecting radially inward are dispersed in the inner peripheral portion of the large diameter mounting portion in the circumferential direction. The present invention relates to a joint boot, wherein the plurality of projections can be separately fitted to a plurality of recesses formed in a mounting portion of the outer case.

[Background Technology]

One of the constant velocity joints provided in a drive shaft or the like of an automobile is a constant velocity joint of a trip boat type capable of transmitting a rotational force by freely changing a position in an axial direction. As shown in Fig. 5 and Fig. 6, this constant velocity joint has three trunnions 31 with rollers protruding from the input side (or output side) shaft 3 in the direction perpendicular to the axis. The outer case 1 is provided at the end of the shaft 40 (or the input side), and three grooves 34 on which the rollers 32 roll are distributed in the inner periphery of the outer case 1 in the circumferential direction. It is set up and configured. 33 is a report. The joint boots described at the beginning are provided for such constant-velocity joints, prevent dust and foreign matter from entering the constant-velocity joint side, and hold grease around the constant-velocity joint. I have. The outer case 1 is provided with a plurality of recesses 8 that are recessed inward in the radial direction and distributed in the circumferential direction so as to reduce the weight of the case. Correspondingly, the large diameter boot joint A plurality of protrusions projecting radially inward are provided on the inner peripheral portion of the side mounting portion 2 so as to be dispersed in the circumferential direction.

Conventionally, the above-mentioned joint boot has been integrally formed of a resin material as a whole, as disclosed in Japanese Patent Application Laid-Open No. 2003-329590. According to the conventional configuration described above, since the entire joint boot is integrally formed of a resin material, the hardness of the large-diameter side mounting portion becomes hard, and the adhesion of the large-diameter side mounting portion to the outer case is not good. There was room for improvement in terms of sealing.

[Disclosure of the Invention]

An object of the present invention is to provide a joint boot capable of improving the sealing property of a large-diameter side attachment portion to an outer case.

A feature of the present invention is that a cylindrical large-diameter mounting portion that is externally fitted to a mounting portion of an outer case, a small-diameter mounting portion that is mounted on a shaft, and a bellows portion that connects these components. The outer peripheral surface of the large-diameter mounting portion is formed in a circular cross section, and a plurality of convex portions projecting radially inward are formed on the inner peripheral portion of the large-diameter mounting portion in the circumferential direction. A joint boot, wherein the joint boots are provided so as to be dispersed and the plurality of protrusions can be separately fitted to a plurality of recesses formed in a portion to be attached to the outer case.

The bellows portion is formed of a resin material, and 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 portion to one end of the bellows portion,

The large-diameter side mounting portion is provided with a sealing inner peripheral portion having a smaller diameter than the mounting portion of the outer case over the entire inner peripheral surface, and the large-diameter side mounting portion can be closely fitted to the mounting portion. And a straight hole having a diameter larger than that of the attached portion is provided at one end of the large-diameter attachment portion opposite to the bellows portion. In this embodiment, an enlarged inner peripheral portion for guiding the attached portion when the large-diameter-side attached portion is externally fitted to the attached portion is provided over the entire inner peripheral surface.

According to this configuration, since the large attachment side attachment portion is formed separately from the bellows portion and the bellows portion is formed of a resin material, the durability of the bellows portion can be improved. The large-diameter mounting portion is made of a resin material or rubber material that is softer than the bellows portion, and the large-diameter mounting portion has a tightly attached inner peripheral portion smaller in diameter than the outer case mounting portion over the entire inner peripheral surface. Since the large-diameter mounting portion is provided so as to be able to closely fit to the mounting portion, the adhesion of the large-diameter mounting portion to the mounting portion of the outer case can be improved.

Further, when the large-diameter mounting portion is fitted to the mounting portion in a straight hole shape having a diameter larger than that of the mounting portion at one end of the large-diameter mounting portion opposite to the bellows portion. Since the enlarged inner peripheral portion for guiding the mounted portion is provided over the entire inner peripheral surface, the large-diameter side mounting portion can be tightly and externally fitted to the mounted portion of the outer case. In addition, the large-diameter mounting portion can be easily fitted to the mounting portion of the outer case. In addition, since the fitting tube portion that is fitted to the large-diameter-side attachment portion is extended at one end of the bellows portion, the large-diameter-side attachment portion can be securely attached to the fitting tube portion.

In the present invention, a large-diameter portion capable of receiving an end surface of the fitting cylindrical portion in an axial direction is formed on an outer peripheral portion of the large-diameter-side mounting portion, and a length of the large-diameter portion in the axial direction is defined as If the thickness is set to be longer than the thickness of the fitting cylindrical portion, the rigidity in the axial direction of the enlarged diameter portion can be increased. As a result, it is possible to improve the assemblability.For example, when assembling the bellows portion and the large-diameter-side mounting portion with a robot hand, or when assembling artificially, the fitting tube portion has an enlarged diameter portion. It is possible to avoid an assembly defect that is pushed down and overcome.

In the present invention, if one end of the large-diameter side attachment portion on the bellows portion side is formed in a tapered cylindrical shape with a smaller diameter toward the bellows portion side, the fitting cylinder portion and the large-diameter side attachment are provided. When the portions are fitted, the fitting cylindrical portion can be guided by the one end portion of the tapered tubular shape, so that the two can be easily fitted.

In the present invention, when the length of the enlarged diameter portion in the axial direction is set to 1.5 mm to 5 mm, the rigidity of the enlarged diameter portion in the axial direction is increased while suppressing an increase in manufacturing cost. Can be easier. That is, if it 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 increases and the production cost becomes high. By setting to, these problems can be solved.

In the present invention, a plurality of first lightening holes opened on one end surface side of the large-diameter side mounting portion and arranged in the circumferential direction on the convex portion, and a plurality of first lightening holes opened on the other end surface side and aligned in the circumferential direction. 2 Form a lightening hole,

The width of the first partition wall that separates the adjacent first lightening holes, the width of the second partition wall that separates the adjacent second lightening holes, and the thickness of the fitting peripheral wall portion of the convex portion. When the same or almost the same setting is made, the following operation can be achieved. In other words, it is possible to cool the resin material (corresponding to the rubber material when the large-diameter side mounting portion is formed of a rubber member) corresponding to the convex portion in the molding process faster than a structure in which no lightening hole is formed. . Further, the fitting peripheral wall portion of the convex portion can be supported by the large diameter side mounting portion between the plurality of first lightening holes and the second lightening hole, and the thickness of the fitting peripheral wall portion of the convex portion can be increased. Need not be thick.

For example, in a structure in which only a lightening hole that opens on one end surface side of the large-diameter side mounting portion and no lightening hole that opens on the other end surface side is used, a resin material (rubber) corresponding to the other end surface side is used. Material) becomes larger than the amount of the resin material (rubber material) corresponding to the one end surface, and the cooling rate of the resin material (rubber material) corresponding to the other end surface corresponds to the one end surface. Although the cooling rate of the resin material (rubber material) is slower than the cooling rate of the resin material, the convex portion tends to be distorted after cooling. However, according to the above configuration of the present invention, the large-diameter side mounting portion is different from the bellows portion. Formed separately, one end side Since both the first lightening holes that open at the bottom and the second lightening holes that open at the other end face side are formed, it is difficult to make a large difference between the two cooling rates. The above problems can be avoided. By forming the large-diameter side attachment part separately from the bellows part, the die-cutting when forming a plurality of lightening holes in the large-diameter side attachment part can be performed without disturbing the bellows part. Can be.

In addition, by setting the width of the first partition wall, the width of the second partition wall, and the thickness of the fitting peripheral wall portion to be the same or almost the same, the resin material (rubber material) corresponding to the first partition wall is reduced. The difference between the cooling rate, the cooling rate of the resin material (rubber material) corresponding to the second partition wall, and the cooling rate of the resin material (rubber material) corresponding to the fitting peripheral wall portion can be reduced. 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 (rubber material), and to easily form the large-diameter side mounting portion into a desired shape with high accuracy. The adhesion of the large-diameter side mounting portion to the outer case can be further improved. In the present invention, the width of the first partition wall, the width of a second partition wall that separates adjacent second lightening holes, and the thickness of the fitting peripheral wall portion of the protrusion are defined in the circumferential direction. If the thickness of the peripheral wall of the large-diameter side mounting portion located between the adjacent convex portions is set to be the same or almost the same, the cooling rate of the resin material (rubber material) corresponding to the first partition wall and the second The cooling speed of the resin material (rubber material) corresponding to the partition wall, the cooling speed of the resin material (rubber material) corresponding to the fitting peripheral wall, and the resin material (rubber material) corresponding to the peripheral wall of the large diameter side mounting portion A large difference can be made between the cooling rate and the cooling rate. 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 (rubber material), and to easily form the large-diameter-side mounting portion into a desired shape with high precision.

In the present invention, the thickness of the large-diameter side mounting portion between the plurality of first lightening holes and the second lightening holes is determined by changing the width of the first partition wall and the width of the second partition wall. If the large diameter side mounting portion is tightened and fixed to the outer case with a tightening band, for example, when the tightening force is set to be greater than the thickness of the fitting peripheral wall portion, To the department.

In the present invention, the hardness of the large-diameter side attachment portion 2 is set to 55 to 85 degrees in JISA hardness, and the hardness of the bellows portion 5 is set to 40 to 50 degrees in JISD hardness (JISK The following effects can be achieved. That is, if the hardness of the large-diameter side mounting portion 2 is less than 55 degrees in JISA hardness, as shown in Table 1, it becomes too soft and the sealing property deteriorates, and if it exceeds 85 degrees, it becomes hard. Although there is a problem that the tightening property is deteriorated due to excessive bending, these problems can be solved by setting the hardness of the large-diameter side mounting portion 2 to 55 to 85 degrees in JISA hardness. The inventor has confirmed the characteristics of the above-described large-diameter side mounting portion by the following experiment. Five large-diameter mounting parts made of resin material with JISA hardness of 40 degrees, 55 degrees, 70 degrees, 85 degrees, and 90 degrees, respectively, were manufactured. Attach it to each of the five bellows. Then, attach the large-diameter side mounting section to the outer case of the report-type constant-velocity joint, mount the small-diameter side mounting section to the shaft, and seal the grease inside the joint boots. 5 and the structure of each member is described in the [Embodiment] section below). In this assembled state, the operation of moving the outer case and the shaft relative to each other (sliding) in the axial direction, the operation of bending the outer case and the shaft to the maximum angle, and the operation of moving the shaft around the axis And many times in any combination. After that, when grease leakage was observed between the large-diameter mounting portion and the outer case, grease leakage was observed at the large-diameter mounting portion having a JISA hardness of 40 degrees as shown in Fig. 7 ( Grease did not leak at the large-diameter side mounting part with other hardness (55 degrees, 70 degrees, 85 degrees, 90 degrees) except for the X mark in Table 1). . In addition, large-diameter mounting part A large diameter with a JISA hardness of 90 degrees when fitted to the outer case and externally fitted with a fitting tube extending from one end of the bellows part to the large-diameter mounting part and manually tightened with a tightening band. A large tightening force was required at the mounting part (marked by X in Fig. 6), but a large tightening force was required at the large-diameter mounting part of other hardness (40 degrees, 55 degrees, 70 degrees, 85 degrees). Was not required (〇 in Table 1).

【table 1】

〇 is good, X is bad

Also, if the bellows part 5 has a JISD hardness of less than 40 degrees in JISD hardness, the rigidity is low, and it becomes easy to be deformed by, for example, an impact force. However, these problems can be solved by setting the hardness of the bellows portion 5 to 40 degrees to 50 degrees in JISD hardness.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a joint boot.

FIG. 2 is a view of the large-diameter mounting portion from the outside of one end surface of the large-diameter mounting portion.

FIG. 3 is a view of the large-diameter mounting portion from the outside of the other end surface of the large-diameter mounting portion.

Fig. 4 shows a state where the joint boot is being assembled to the constant velocity joint. It is sectional drawing.

FIG. 5 is a diagram showing a state in which the joint tab is assembled to a constant velocity joint.

FIG. 6 is a diagram showing a state where the joint boss is assembled to a constant velocity joint.

[Best Mode for Carrying Out the Invention] Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. Figures 1, 2, and 3 show the joint boots provided for the constant velocity joints of the car's report evening.

As shown in FIGS. 5 and 6, the constant velocity joint has three trunnions 31 with rollers protruding from a shaft 3 on an input side in a direction perpendicular to an axis, and a shaft 40 on an output side. An outer casing 1 is provided at the end of the casing, and three grooves 3 4 on which the roller 3 2 rolls are distributed and arranged in the circumferential direction on the inner peripheral portion of the outer casing 1. is there. 33 is a report. The joint block is composed of a cylindrical large-diameter side mounting portion 2 that is externally fitted to the mounting portion 1A of the key case 1 and a cylindrical small-diameter mounting portion that is mounted on the shaft 3. A large-diameter-side mounting portion 2 and a bellows portion 5 formed separately from each other, and a fitting cylindrical portion that is externally fixed to the large-side mounting portion 2. 6 extends to one end 5 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, and the large-diameter side attachment portion 2 is formed of a resin material softer than the bellows portion 5. For example, the hardness of the large diameter side mounting portion 2 can be set to 55 to 85 degrees in JISA hardness, and the hardness of the bellows portion 5 can be set to 40 to 50 degrees in JISD hardness (JISK 6 25 3 Compliant). Construct the large-diameter side mounting part 2 As the resin material, TP0 (Thermo Plastic Olefin) can be cited, and as an example, Santoprene (trade name) manufactured by AES (Advanced Elastmer Systems) is available. Examples of the resin material forming the bellows portion 5 and the small-diameter side attachment portion 4 include TPEE and TP0.

On the outer peripheral portion of the large-diameter side mounting portion 2, a shallow annular groove 52 that fits into an annular convex portion 51 protruding from the inner peripheral portion of the fitting cylindrical portion 6 is provided. In addition, the outer peripheral surface 2A of the large-diameter mounting portion 2 is formed in a circular cross section, and three convex portions 7 protruding radially inward are formed on the inner peripheral portion of the large-diameter mounting portion 2. Are provided evenly in the circumferential direction at every 120 degrees, and three convex portions 7 are separately removed from three concave portions 8 formed on the outer peripheral portion of the attached portion 1A of the outer case 1. It is configured to be fittable. The convex portion の of the large-diameter mounting portion 2 is formed in a mountain shape having a gentle cross-sectional shape. Then, with respect to the center line L of the circumferential projection 7, the large diameter side mounting portion 2 is set to have a symmetrical shape when viewed in the axial direction of the large-diameter side mounting portion 2. It is connected to. The center lines L of the three projections 7 are located radially with respect to the axis 0 and at every 120 degrees in the circumferential direction.

The large-diameter mounting portion 2 and the small-diameter mounting portion 4 are concentric, and annular grooves 9 and 19 around which the tightening band 35 is wound are formed on both outer peripheral portions. The bellows portion 5 is formed into a tapered shape with a smaller diameter toward the smaller diameter side mounting portion 4 side, and the hollow portion is a grease filled space S.

A large inner diameter 50 is provided on the large mounting side mounting part 2 with a tight inner peripheral part 50 (the inner diameter is D2, see Fig. 4) with a smaller diameter than the mounting part 1A of the outer case 1. The side mounting portion 2 is configured so as to be able to be closely fitted to the mounted portion 1 A, and the one end portion 70 of the large-diameter side mounting portion 2 opposite to the bellows portion 5 is larger than the mounted portion 1 A. It is a straight hole with a diameter and has an enlarged inner peripheral part 7 1 that guides the mounting part 2 when fitting the large-diameter mounting part 2 to the mounting part 2 (the inner diameter is Dl, Is provided over the entire inner peripheral surface. The boundary between the enlarged inner peripheral portion 71 and the close contact inner peripheral portion 50 is a tapered hole. Similarly, the boundary between the enlarged diameter inner peripheral portion 71 and one end surface ΊA of the large diameter side mounting portion 2 is also a tapered hole.

As shown in FIGS. 2 and 3, two pairs of bottomed first lightening holes 2 1, which are open to the convex portion 7 on one end surface 7 A side of the large-diameter mounting portion 2 and are symmetrical with respect to the center line L. A, 22 A, 23 A, 24 A (see Fig. 2) and two pairs of bottomed second holes 2 1 B, 2 open to the other end face 7 B side and symmetrical about the center line L. 2 B, 23 B and 24 B (see Fig. 3) are sandwiched by the support wall 37 (corresponding to the large-diameter side mounting portion, see Fig. 1) on the center side in the axial direction of the large-diameter mounting portion 2. It is formed. In this way, the plurality of first lightening holes 21A, 22A, 23A, 24A are arranged in the circumferential direction, and the plurality of second lightening holes 21B, 22B, 23 B and 24 B are arranged in the circumferential direction. The depths of the plurality of first lightening holes 21A, 22A, 23A and 24A are the same. Also, multiple

The depths of the second lightening holes 21B, 22B, 23B, 24B are also the same, and the plurality of second lightening holes 21B, 22B, 23B, The depth of 24B is slightly shallower than the plurality of first lightening holes 21A, 22A, 23A and 24A.

The pair of inner first lightening holes 22A and 23A close to the center line L are trapezoidal shapes with the outer peripheral surface 2A side of the large-diameter mounting portion 2 narrowed. It is larger than the outer first lightening holes 21 A and 24 A, and all inner peripheral surfaces (excluding the bottom surface) are parallel to the axis 0. The width T2 of the central first partition wall 13 that separates the pair of inner first lightening holes 22A and 23A is constant over substantially the entire length.

The pair of outer first lightening holes 21A and 24A have a triangular shape, and all inner peripheral surfaces (excluding the bottom surface) are parallel to the axis 0. Separates the inner first lightening hole 22A (or 23A) and the outer first lightening hole 21A (or 24A). The other first partition wall 13 has an inclined posture closer to the center first partition wall 13 toward the outer peripheral surface of the large-diameter side mounting portion 2 when viewed in the axial direction. The width T2 of the other first partition wall 13 is also constant over substantially the entire length.

The structure of the second lightening holes 21B, 22B, 23B, 24B has the same structure as the first lightening holes 21A, 22A, 23A, 24A. And shape are the same. In other words, the first lightening hole 21A and the second lightening hole 21B have the same shape when viewed from the axial center of the large-diameter side mounting portion 2 and overlap each other, and the first lightening hole 22A The first lightening hole 23A and the second lightening hole 23B have the same shape and overlap each other, and the first lightening hole The hole 24A and the second lightening hole 24B have the same shape and overlap each other.

And, the width T2 of the first partition wall 13 and the width T5 of the second partition wall 14 that separates the adjacent second lightening holes 21B, 22B, 23B and 24B, The thickness T1 of the fitting peripheral wall portion 12 of the convex portion 7 and the thickness T4 of the peripheral wall 15 of the large diameter side mounting portion 2 located between the convex portions 7 adjacent in the circumferential direction (the annular groove 5). 2 is the wall thickness of the peripheral wall part where it is not formed (see Fig. 1).

In addition, the thickness T 3 (the thickness is constant) of the support wall 37 in the axial direction is made thicker than the thicknesses T 1, T 2, T 4, and T 5. The thickness is set to twice the thickness of Tl, Τ2, Τ4, Τ5.

A large-diameter portion 39 is formed on the outer periphery of the large-diameter side mounting portion 2 so that the end surface 6 の of the fitting cylindrical portion 6 can be received in the axial direction. The axial length X of the enlarged diameter portion 39 is set to the wall thickness Z of the engagement cylindrical portion 6 so that the fitted cylindrical portion 6 does not push down the enlarged diameter portion 39 as the fitting is performed. By setting it longer, the rigidity of the axially enlarged portion 39 is increased. In other words, the length X is a length that does not cause the fitting cylindrical portion 6 to push down the enlarged diameter portion 39. 1.5mm to 5mm can be set. The thickness Z of the fitting cylinder 6 is the maximum value of the thickness of a portion on the tip side (right side in the drawing) of the annular groove 9 around which the tightening band 35 is wound. Further, one end portion 61 of the large-diameter mounting portion 2 on the bellows portion 5 side is formed in a tapered cylindrical shape having a smaller diameter toward the bellows portion 5 side.

When the joint boot having the above structure is mounted on a constant velocity joint, as shown in FIGS. 4 and 5, the fitting tube 6 of the bellows portion 5 is externally fixed to the large-diameter side mounting portion 2 and fixed. The outer side mounting part 2 is externally fitted to the outer case 1, the smaller side mounting part 4 is externally fitted to the shaft 3, and the annular groove 9 of the large diameter mounting part 2 and the annular groove 19 of the small diameter mounting part 4 are fitted. Tighten the tightening band 35 to fix it. When the large-diameter mounting part 2 is externally fitted to the outer case 1, the large-diameter inner peripheral part 7 1 of the large-diameter mounting part 2 guides the mounting part 1 A of the outer case 1. The part 2 can be easily fitted to the outer case 1. The number of the lightening holes is not limited to the number shown in the above embodiment. The resin material forming the large-diameter-side mounting portion 2 may be TPE E (for example, Perprene (trade name) manufactured by Toyobo Co., Ltd., or Hitrel (trade name) manufactured by Toray Dupont). The large-diameter side attachment portion 2 may be formed of a rubber member such as, for example, C R (chlorobrene rubber) or NBR (two-port butadiene rubber). Also in this case, the large diameter side mounting portion 2 can be set to 55 to 85 degrees in JISA hardness.

[Possibility of industrial use]

ADVANTAGE OF THE INVENTION According to this invention, a large-diameter side mounting part can be shape | molded with desired shape with high precision, for example, when the large-diameter side mounting part is fastened and fixed to an outer case with a fastening band, A gap can be avoided between the concave portion of the large diameter side mounting portion and the convex portion of the large diameter side mounting portion, and the sealing performance of the large diameter side mounting portion with respect to the outer case can be improved. outer The present invention has provided a joint boot which can be easily fitted to a mounting portion of a case.

A large-diameter portion capable of receiving the end surface of the fitting cylindrical portion in the axial direction is formed on an outer peripheral portion of the large-diameter side mounting portion, and the length of the large-diameter portion in the axial direction is determined by the fitting cylindrical portion. If it is set longer than the wall thickness of the bellows, when the bellows part and the large-diameter side mounting part are assembled, it is possible to avoid the assembly failure in which the fitting cylinder part pushes over the enlarged diameter part and gets over it, and productivity is improved. Can be raised.

If one end of the large-diameter mounting portion on the bellows side is formed in a taper cylindrical shape having a smaller diameter toward the bellows portion, the fitting cylindrical portion and the large-diameter mounting portion may be fitted together. The fitting tubular portion can be guided by the one end of the tapered tubular shape, so that the two can be easily fitted together, and the assembling property can be further improved.

A plurality of first lightening holes opened on one end surface side of the large-diameter attachment portion and arranged in the circumferential direction on the convex portion, and a plurality of second lightening holes opened on the other end surface side and arranged in the circumferential direction. And form

The width of the first partition wall that separates the adjacent first lightening holes, the width of the second partition wall that separates the adjacent second lightening holes, and the thickness of the fitting peripheral wall portion of the convex portion. When they are set to be the same or substantially the same, the adhesion of the large-diameter side mounting portion to the outer case can be further improved, and the sealing property can be further improved.

The width of the first partition wall, the width of the second partition wall separating the adjacent second lightening holes, and the thickness of the fitting peripheral wall portion of the convex portion are defined between the convex portions adjacent in the circumferential direction. If the thickness of the peripheral wall of the large-diameter mounting portion is set to be the same or almost the same as that of the large-diameter mounting portion, the large-diameter mounting portion can be easily formed into a desired shape with high accuracy, and the sealing property is improved. Can be even better.

The thickness of the large-diameter side mounting portion between the plurality of first lightening holes and the second lightening holes is determined by the width of the first partition wall, the width of the second partition wall, and the fitting peripheral wall portion. meat of If it is set to be thicker than any of the thicknesses, for example, when the large-diameter side mounting part is tightened and fixed to the outer case with a tightening band, the tightening force can be transmitted to the fitting peripheral wall more reliably. As a result, the sealing performance can be further improved.

Claims

A cylindrical large-diameter side mounting portion that is externally fitted to the mounting portion of the outer case, a small-diameter side mounting portion that is mounted on the shaft, and a bellows portion that connects them are provided. The outer peripheral surface of the large-diameter mounting portion is formed in a circular cross section, and a plurality of convex portions projecting radially inward are dispersed in the inner peripheral portion of the large-diameter mounting portion in the circumferential direction. A joint boot, wherein the plurality of projections can be separately fitted to a plurality of recesses formed in a mounting portion of the outer case, respectively.

The bellows portion is formed of a resin material, and the large-diameter side attachment portion is formed separately from the bellows portion with a resin material or a rubber member softer than the bellows portion, and is externally fitted to the large-diameter side attachment portion. A fitting tube portion is extended to one end of the bellows portion, and a close contact inner peripheral portion having a smaller diameter than the attached portion of the outer case is provided on the large diameter side attaching portion over the entire periphery of the inner peripheral surface. The large-diameter side attachment portion is configured to be able to be closely fitted to the attached portion so as to be able to be closely fitted to the attached portion, and one end of the large-diameter side attachment portion opposite to the bellows portion has a larger diameter than the attached portion. A joint boot having a trough hole shape, wherein an enlarged-diameter inner peripheral portion for guiding the attached portion when the large-diameter-side attached portion is externally fitted to the attached portion is provided over the entire inner peripheral surface.

An enlarged portion capable of receiving the end surface of the fitting cylindrical portion in the axial direction is formed on an outer peripheral portion of the large-diameter side mounting portion, and the length of the enlarged diameter portion in the axial direction is set as described above. The joint boot according to claim 1, wherein the joint boot is set to be longer than a thickness of the joint tube portion.

3. The joint boot according to claim 2, wherein one end of the large-diameter side attachment portion on the bellows portion side is formed in a tapered cylindrical shape having a smaller diameter toward the bellows portion side. Set the length of the enlarged portion in the axial direction to 1.5 mm to 5 mm The joint boot according to claim 2 or 3, wherein the joint boot is formed.

A plurality of first lightening holes opened on one end surface side of the large-diameter side mounting portion and arranged in the circumferential direction, and a plurality of second lightening holes opened on the other end surface side and arranged in the circumferential direction. Forming a hole and

The width of the first partition wall that separates the adjacent first lightening holes, the width of the second partition wall that separates the adjacent second lightening holes, and the thickness of the fitting peripheral wall portion of the convex portion are the same. Or the joint boot according to any one of claims 1 to 4, which is set to be substantially the same.

The width of the first partition wall, the width of the second partition wall that separates the adjacent second lightening holes, and the thickness of the fitting peripheral wall portion of the convex portion are the adjacent convex portions in the circumferential direction. 6. The joint boot according to claim 5, wherein the thickness is set to be equal to or substantially equal to the thickness of the peripheral wall of the large-diameter side mounting portion located between the portions.

The thickness of the large-diameter side mounting portion between the plurality of first lightening holes and the second lightening holes is determined by the width of the first partition wall, the width of the second partition wall, and the fitting. 7. The joint boot according to claim 5, wherein the joint boot is set to be thicker than any of the thickness of the peripheral wall portion.

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 is set to 40 to 50 degrees in JISD hardness. Joint boots described in one.