Boot for constant-velocity universal joint

Abstract

A boot for constant-velocity universal joint includes a major-diameter fastener, a minor-diameter fastener, and a bellows. The bellows includes a first root, a first crest, a second root, a second crest, a third root, a third crest, a fourth root, a fourth crest, a fifth root and a fifth crest. The first crest, the second crest, the third crest, the fourth crest and the fifth crest have a top, respectively, and the tops of the second crest, third crest and fourth crest are disposed on an outer peripheral side with respect to a line “L1,” which the tops of the first crest and fifth crest make therebetween, in a cross section involving the central axis of the bellows.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the present invention and many of its advantages will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings and detailed specification, all of which forms a part of the disclosure.

FIG. 1 is an axial cross-sectional view of a boot for constant-velocity universal joint according to Example No. 1 of the present invention.

FIG. 2 is an enlarged axial cross-sectional view for illustrating a major portion of the boot according to Example No. 1.

FIG. 3 is an axial cross-sectional view for illustrating the boot for constant-velocity universal joint 1 according to Example No. 1 when it is assembled with mating members.

FIG. 4 is an axial cross-sectional view of a boot for constant-velocity universal joint according to Comparative Example.

FIG. 5 is an enlarged axial cross-sectional view for illustrating the boot according to Comparative Example No. 1 when it is assembled with mating members.

Claims

1. A boot for constant-velocity universal joint, the boot comprising: a major-diameter fastener to be fitted around a major-diameter retainer;a minor-diameter fastener disposed separately away from the major-diameter fastener and coaxially therewith, having a minor diameter, which is smaller than that of the major-diameter fastener, and to be fitted around a minor-diameter retainer; anda bellows connecting the major-diameter fastener with the minor-diameter fastener integrally, and formed as a truncated cone shape substantially;the boot further exhibiting a dimension between the major-diameter fastener and the minor-diameter fastener, dimension which equals a dimension between a major-diameter side fastening position for the major-diameter retainer and a minor-diameter side fastening position for the minor-diameter retainer;wherein:the bellows comprises a first root, a first crest, a second root, a second crest, a third root, a third crest, a fourth root, a fourth crest, a fifth root and a fifth crest, which are disposed in this order in the direction away from the major-diameter fastener to the minor-diameter fastener, and the first crest, the second crest, the third crest, the fourth crest and the fifth crest have a top, respectively, the tops of the second crest, third crest and fourth crest are disposed on an outer peripheral side with respect to a line “L1,” which the tops of the first crest and fifth crest make therebetween, in a cross section involving the central axis of the bellows; andthe bellows reduces diametrically from large to small in the direction away from the first crest to the fifth crest sequentially.

2. The boot set forth in claim 1, wherein: the first root, the second root, the third root, the fourth root and the fifth root of the bellows have a bottom, respectively;the bellows comprises the second root and third root whose bottoms are disposed on an inner peripheral side with respect to a line “L2,” which the bottoms of the first root and fifth root make therebetween, in a cross section involving the central axis of the bellows; andthe bellows reduces diametrically from large to small in the direction away from the first root to the fifth root sequentially.

3. The boot set forth in claim 2, wherein: the bellows comprises the fourth root whose bottom is disposed on an outer peripheral side with respect to the line “L2” in a cross section involving the central axis of the bellows.

4. The boot set forth in claim 1, wherein the second crest, the third crest and the fourth crest have an outside radius, which is larger than a radial dimension between the central axis of the bellows and the line “L1” by a factor of from 105 to 120%, respectively.

5. The boot set forth in claim 1, wherein the second root and the third root have an inside radius, which is smaller than a radial dimension between the central axis of the bellows and the line “L2” by a factor of from 80 to 95%.

6. The boot set forth in claim 1 being formed of a thermoplastic polyester elastomer, the thermoplastic polyester elastomer comprising: a polyester block copolymer; andan epoxy compound exhibiting bifunctionality or more in an amount of from 0.01 to 10 parts by weight with respect to the polyester block copolymer taken as 100 parts by weight.

7. A boot for constant-velocity universal joint, the boot comprising: a major-diameter fastener to be fitted around a major-diameter retainer;a minor-diameter fastener disposed separately away from the major-diameter fastener and coaxially therewith, having a minor diameter, which is smaller than that of the major-diameter fastener, and to be fitted around a minor-diameter retainer; anda bellows connecting the major-diameter fastener with the minor-diameter fastener integrally, and formed as a truncated cone shape substantially;the boot further exhibiting a dimension between the major-diameter fastener and the minor-diameter fastener, dimension which equals a dimension between a major-diameter side fastening position for the major-diameter retainer and a minor-diameter side fastening position for the minor-diameter retainer;wherein:the boot is formed of a thermoplastic polyester elastomer, the thermoplastic polyester elastomer comprising:a polyester block copolymer; andan epoxy compound exhibiting bifunctionality or more in an amount of from 0.01 to 10 parts by weight with respect to the polyester block copolymer taken as 100 parts by weight.

8. The boot set forth in claim 7, wherein the bellows comprises a first root, a first crest, a second root, a second crest, a third root, a third crest, a fourth root, a fourth crest, a fifth root and a fifth crest, which are disposed in this order in the direction away from the major-diameter fastener to the minor-diameter fastener.