Rack and manufacturing method thereof
AssigneeNsk Ltd.
InventorsKazuto Kobayashi, Yuki Mizushima, Kotaro Hirota, Akira Tsubouchi
Life of this patent
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Abstract
To sufficiently secure the width dimension, strength and rigidity of the rack teeth 10, and to realize the light weight construction and the manufacturing method of the rack 8, the rack teeth 10 is formed by plastic working on one side surface in the radial direction of part in the axial direction of a rod unit 9 having a circular cross-sectional shape, and the curvature radius of the portion which is separated in the radial direction from the portion where the rack teeth 10 is formed, is made greater than that of the cross sectional shape of the outer surface of the axial remaining portion of the rod unit 9.
Claims17
A manufacturing method for a rack that comprises:
- a rod unit that is made of a metal material and of which at least part in the axial direction has a solid circular cross section;
- and
- rack teeth that are formed by plastic working of the surface on one side of the solid portion in the radial direction of part in the axial direction of the rod unit, the radius of curvature of the cross sectional shape of a portion that is separated in the circumferential direction from the portion where the rack teeth are formed of the outer surface of the solid portion of the part in the axial direction, being larger than the radius of curvature of the cross sectional shape of the outer surface of the remaining portion in the axial direction of the rod unit, comprising steps of:
- performing a first plastic working on part in the axial direction of a rod shaped material that will become the rod unit, by compressing a portion in the circumferential direction of the part in the axial direction, and forming a partial cylindrical surface on the remaining portion in the circumferential direction of the part in the axial direction, the radius of curvature of the partial cylindrical surface being larger than the radius of curvature of the outer surface of the rod shaped material, to obtain an intermediate material;
- and
- performing a second plastic working to form rack teeth on the portion in the circumferential direction of the part in the axial direction of the intermediate material.
A rack manufacturing method for a rack comprising:
- a rod unit that is made of metal and has a circular cross sectional shape, and
- rack teeth that are formed by plastic working of the surface on one side in the radial direction of part in the axial direction of the rod unit, comprising a step of:
- performing an ironing work in which a circular rod shaped material that will become the rod unit is passed through an ironing die so as to reduce the outer diameter of at least a portion in the axial direction of the material, at least either:
- before performing a first plastic working in which a flat surface portion where the rack teeth will be formed on part in the axial direction of the material by compressing a portion in the circumferential direction of the part in the axial direction, or
- after performing the first plastic working and before performing a second plastic working of forming the rack teeth on the flat surface.
Dependencies are inferred from the claim text.