Steering rack shaft and method of manufacturing the same
AssigneeKabushiki Kaisha Yamada Seisakusho
InventorsHideji Sakamoto, Masayoshi Ozawa, Seiji Kanuki, Kenji Hoshino, Toshiaki Tanaka
Life of this patent
Estimating the term…
Abstract
A steering rack shaft having a shaft body and rack teeth formed in a predetermined axial region of the shaft body. This steering rack shaft is formed such that a workpiece is quenched, and is then heated for a predetermined time at a temperature exceeding 400.degree. C. so as to be thermally refined, and the rack teeth are subsequently formed. After the formation of the rack teeth, high-frequency induction hardening is provided to form a teeth-hardened layer. Hence, the machining of the rack teeth is facilitated while reducing strain, and the rigidity and toughness of the overall steering rack shaft are improved.
Claims11
A steering rack shaft comprising:
- a shaft body;
- and
- a rack-teeth forming portion provided over a fixed axial region of said shaft body;
- wherein said rack-teeth forming portion includes a first partial portion provided with rack teeth which are subjected to high frequency induction hardening to form a teeth-hardened layer, a second partial portion applied with partial thermal refining treatment to form a thermally refined structure, and a third partial portion formed as a non-refined portion.
A steering rack shaft comprising:
- a shaft body;
- and
- a rack-teeth forming portion provided over a fixed axial region of said shaft body;
- wherein at least an axial partial portion of said rack-teeth forming portion is provided with thermal refining treatment;
- wherein heat treatment is provided such that the hardness of said portion of said rack-teeth forming portion and the hardness of a rear-surface portion diametrically opposite thereto differ.
A steering rack shaft wherein heat treatment is provided such that at least an axial partial portion of a rack-teeth forming portion of a shaft body is quenched and tempered, only said rack-teeth forming portion is thermally refined, the hardness of said thermally refined portion of said rack-teeth forming portion and the hardness of a rear-surface portion diametrically opposite thereto differ.
A method of manufacturing a steering rack shaft, comprising the steps of:
- applying a thermal refining treatment to a first portion of at least an axial partial portion of a rack-teeth forming portion of a shaft body to form a thermal refining structure;
- forming rack teeth in a second portion of said rack-teeth forming portion;
- high-frequency induction hardening said rack teeth to form a teeth-hardened layer;
- and
- forming a remaining portion of said rack-teeth forming portion as a non-refined portion.
A method of manufacturing a steering rack shaft, comprising the steps of:
- applying a thermal refining treatment to at least an axial partial portion of a rack-teeth forming portion of a shaft body;
- forming rack teeth in said rack-teeth forming portion;
- and
- high-frequency induction hardening said rack teeth to form a teeth-hardened layer;
- wherein thermal refining is provided such that the hardness of said at least partial portion of said rack-teeth forming portion and the hardness of a rear-surface portion diametrically opposite thereto differ.
Dependencies are inferred from the claim text.