Power transmission shaft
AssigneeNtn Corporation
InventorsKatsuhiro Sakurai, Kisao Yamazaki
Life of this patent
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Abstract
A technique for improving a strength, especially a fatigue strength of a power transmission shaft provided with a serrated portion for torque transmission such as a spline shaft. A power transmission shaft is serration-fitted to an inner joint member of respective constant velocity joints. A driveshaft is provided with a serrated portion as well as a smooth portion having a cylindrical outer circumferential surface. A cut-up portion is formed at the end portion of the serrated portion. When applying an induction hardening to the smooth portion and the serrated portion, a hardening ratio of the smooth portion is set at a different value from that of the serrated portion, and such that a fatigue strength of the smooth portion becomes equal to or greater than that of the serrated portion.
Claims4
A power transmission shaft coupled to one of an inner joint member and an outer joint member of a constant velocity joint, and provided with a smooth portion having an outer circumferential surface of a cylindrical shape and a serrated portion for torque transmission having a cut-up portion at an end portion thereof,
- wherein a core portion of the shaft is formed to have a dual phase structure of a ferrite and a martensite, and
- wherein said smooth portion and said serrated portion for torque transmission are respectively induction-hardened,
- a hardening ratio of said smooth portion is set at a different value from a hardening ratio of said serrated portion;
- a fatigue strength of said smooth portion is equal to or greater than a fatigue strength of said serrated portion;
- the hardening ratio of said serrated portion is equal to a depth of hardening of a minor diameter portion divided by a radius of the minor diameter portion;
- and
- a diameter ratio of an outer diameter portion of the smooth portion with respect to the minor diameter portion of the serrated portion is set within a range of 0.95 to 1.05.
Dependencies are inferred from the claim text.