Boot for constant velocity universal joint

• US 20020185825A1
• Filed: 04/05/2002
• Published: 12/12/2002
• Est. Priority Date: 04/20/2001
• Status: Active Grant

• Current Assignee: Toyoda Gosei Company Limited (Toyota Motor Corporation)
• Original Assignee: Toyoda Gosei Company Limited (Toyota Motor Corporation)
• Inventors: Watanabe, Kazuya, Miyamoto, Kenji
• Granted Patent: US 6,715,771 B2
• Time in Patent Office: Days
• US Class Current: 277/636
• CPC Class Codes: F16D 3/845 allowing relative movement of joint parts due to the flexing of the cover
• CPC Class Codes: F16J 3/041 Non-metallic bellows

Abstract

A boot for a constant velocity universal joint includes a minor-diameter cylindrical member, a major-diameter cylindrical member, and a bellows member. At least the bellows member is formed of a thermoplastic elastomer exhibiting a kinetic friction coefficient of less than 0.6 when water intervenes in-between, and including crests. In the cross section of the bellows member involving the central axis, the peaks of the crests, excepting the crest neighboring the major-diameter cylindrical member as well as the crest neighboring the minor-diameter cylindrical member, are disposed on an inner diametric side with respect to a line connecting the peak of the crest neighboring the major-diameter cylindrical member with the peak of the crest neighboring the minor-diameter cylindrical member. Not only it is possible to downsize the boot, but also it is possible to inhibit abnormal noises from generating when water intervenes in-between.

Claims

1. A boot for a constant velocity universal joint, comprising:

a minor-diameter cylindrical member being held to a shaft;

a major-diameter cylindrical member being separated from the minor-diameter cylindrical member, being disposed coaxially with the minor-diameter cylindrical member and having a diameter larger than that of the minor-diameter cylindrical member; and

a bellows member connecting the minor-diameter cylindrical member with the major-diameter cylindrical member integrally, being substantially formed as a truncated cone shape, being formed of a thermoplastic elastomer exhibiting a kinetic friction coefficient of less than 0.6 when water intervenes in-between and including crests, in the cross section of the bellows member involving the central axis, the peaks of the crests, excepting the crest neighboring the major-diameter cylindrical member as well as the crest neighboring the minor-diameter cylindrical member, being disposed on an inner diametric side with respect to a line connecting the peak of the crest neighboring the major-diameter cylindrical member with the peak of the crest neighboring the minor-diameter cylindrical member.

2. The boot according to claim 1, wherein at least said bellows member is formed of a thermoplastic elastomer including a compound exhibiting a high affinity to water as well as a low friction coefficient and being capable of leaching out on the surface of the bellows member.

3. The boot according to claim 1, wherein, when the crest, neighboring said major-diameter cylindrical member, has an outside diameter of S₁, and the crest, next to said crest, has an outside diameter of S_2, a two-crest compact ratio, expressed by “

S₂/S₁,”

is 0.77≦

“

S₂/S₁”

≦

0.85.

4. The boot according to claim 1, wherein, when said bellows member is cut by a plane involving the axis, a line, connecting the peaks of the crests, is formed as an arc shape having a radius “

R”

of from 100 to 200 mm.

5. The boot according to claim 1, wherein said bellows member includes a plurality of crests and roots, at least a first root, a first crest, a second root, a second crest, a third root and a third crest, being disposed alternately in this order from the side of said major-diameter cylindrical member, and the outside diameter of the first crest is substantially identical with the outside diameter of said major-diameter cylindrical member, and, in the cross section when said bellows member is cut by a plane involving the axis, the length of a line, extending from the peak of the first crest, passing over the second root and connecting the peak of the first crest with the peak of the second crest, is substantially equal to the length of a line, extending from the peak of the second crest, passing over the third root and connecting the peak of the second crest with the peak of the third crest, and, when the second root has a depth of “

h” and

the third root has a depth “

H,”

the depth “

h”

falls in a range of “

H”

/1.3≦

“

h”

≦

“

H”

/1.1.