Cage for constant-velocity joint and method for manufacturing the same

• US 20010002369A1
• Filed: 11/29/2000
• Published: 05/31/2001
• Est. Priority Date: 11/30/1999
• Status: Active Grant

• Current Assignee: NTN Corporation
• Original Assignee: NTN Corporation
• Inventors: Kobayashi, Masazumi, Maeda, Takao, Tanio, Masayuki, Katou, Takuya
• Granted Patent: US 6,506,121 B2
• Time in Patent Office: Days
• US Class Current: 464/145
• CPC Class Codes: B23P 15/00 Making specific metal objects by operations not covered by a single other subclass or a group in this subclass
• CPC Class Codes: B23P 2700/11 Joints, e.g. ball joints, universal joints
• CPC Class Codes: F16D 2003/22303 Details of ball cages
• CPC Class Codes: F16D 2250/00 Manufacturing; Assembly
• CPC Class Codes: F16D 2250/0023 Shaping by pressure
• CPC Class Codes: F16D 2250/003 Chip removing
• CPC Class Codes: F16D 2250/0053 Hardening
• CPC Class Codes: F16D 3/223 the rolling members being guided in grooves in both coupling parts
• CPC Class Codes: F16D 3/2245 where the groove centres are offset from the joint centre
• CPC Class Codes: Y10S 148/909 Tube
• CPC Class Codes: Y10S 464/906 Torque transmitted via radially spaced balls

Abstract

It is proposed to increase the strength of a cage of a constant-velocity joint. A pair of end faces of each pocket formed in the cage that oppose each other in a circumferential direction of the cage are formed by surfaces cut after hardening and their surface hardness is reduced to a value lower than the surface hardness of a pair of side faces of each pocket that oppose each other in an axial direction of the cage to impart toughness to the bridge portions defined between the pockets and thus to increase the strength of the cage.

Claims

1. A cage of a stationary type constant-velocity joint having an outer ring and an inner ring, said cage having a cylindrical portion formed with a plurality of pockets at equal angular intervals to receive balls for transmitting a turning torque between said outer ring and said inner ring, said cage having a spherical outer surface kept in contact with and guided by a spherical inner surface of said outer ring and a spherical inner surface kept in contact with and guided by a spherical outer surface of said inner ring, characterized in that said pockets each have a pair of end faces that oppose to each other in a circumferential direction of the cage and a pair of side faces that oppose to each other in an axial direction of the cage, and said pair of end faces are formed by cutting after hardening and have a lower surface hardness than said pair of side faces.

2. The cage of

claim 1

wherein the center of curvature of the spherical outer surface of said cylindrical portion is spaced from the center of curvature of the spherical inner surface of said cylindrical portion in an axial direction of said cylindrical portion.

3. The cage of

claim 1

or

2

wherein said cylindrical portion is made of case-hardened steel hardened by carburizing.

4. The cage of any of claims 1-3 wherein only said pair of end faces of said pockets are formed by cutting after hardening.

5. The cage of any of claims 1-4 wherein said pair of end faces of said pockets are inclined surfaces that incline so as to diverge radially outwardly.

6. The cage of any of claims 1-5 wherein the number of said pockets formed in said cylindrical portion is eight.

7. A method of manufacturing a cage of a constant-velocity joint comprising the steps of turning outer and inner surfaces of a tubular cage blank to form spherical outer and inner surfaces, pressing said cage blank to form a plurality of pockets at equal regular intervals, hardening said cage blank by carburizing, grinding said spherical outer and inner surfaces of said cage blank after heat treatment, and cutting a pair of end faces of each of said pockets so that said pair of end faces will have a lower surface hardness than a pair of side faces of said pockets.

8. A stationary constant-velocity joint comprising an outer ring, an inner ring, said outer ring being formed with a plurality of curved track grooves in a spherical inner surface thereof and said inner ring being formed with a plurality of curved track grooves in spherical outer surface thereof, the center of curvature of said track grooves of said outer ring and the center of curvature of said track grooves of said inner ring being offset by equal distances in opposite derections from the angular center of the joint, torque-transmitting balls mounted between said track grooves formed in said outer ring and said track grooves formed in said inner ring, and a cage having a cylindrical portion formed with a plurality of pockets at equal angular intervals to receive said balls for transmitting a turning torque between said outer ring and said inner ring, characterized in that said pockets each have a pair of end faces that oppose to each other in a circumferential direction of the cage and a pair of side faces that oppose to each other in an axial direction of the cage, and said pair of end faces are formed by cutting after hardening and have a lower surface hardness than said pair of side faces.