An apparatus for manufacturing a rack bar includes a pre-forming machine forming a flattened portion on an outer peripheral surface of a hollow shaft member, a teeth forming machine forming rack teeth on the flattened portion, a heat treatment machine quenching the rack teeth, a first conveying machine carrying the shaft member into and from the pre-forming machine, a second conveying machine carrying the shaft member into and from the teeth forming machine, and a third conveying machine carrying the shaft member into and from the heat treatment machine. The first conveying machine, the second conveying machine, and the third conveying machine hold one end of the shaft member from a radially inner side of the shaft member. The apparatus of the rack bar are suitable for manufacturing a relatively short hollow rack bar having rack teeth formed over substantially an entire length of a shaft member.

A rack bar includes a shaft portion and a rack toothed portion provided on the shaft portion. The rack toothed portion includes a plurality of rack teeth provided side by side in an axial direction of the shaft portion to mesh with a pinion gear. Each of the rack teeth includes a tooth tip portion, a contact face arranged obliquely relative to the axial direction and configured to contact the pinion gear, and a rounded corner portion between the tooth tip portion and the contact face. A first radius defining a central area of the rounded corner portion with respect to a tooth width direction is larger than a second radius defining another area of the rounded corner portion other than the central area.

An apparatus for manufacturing a rack bar includes a pre-forming machine forming a flattened portion on an outer peripheral surface of a hollow shaft member, a teeth forming machine forming rack teeth on the flattened portion, a heat treatment machine quenching the rack teeth, a first conveying machine carrying the shaft member into and from the pre-forming machine, a second conveying machine carrying the shaft member into and from the teeth forming machine, and a third conveying machine carrying the shaft member into and from the heat treatment machine. The first conveying machine, the second conveying machine, and the third conveying machine hold one end of the shaft member from a radially inner side of the shaft member. The apparatus of the rack bar are suitable for manufacturing a relatively short hollow rack bar having rack teeth formed over substantially an entire length of a shaft member.

A hollow rack bar and a method of manufacturing the hollow rack bar are provided. The hollow rack bar includes a hollow blank pipe portion having a uniform wall thickness, and a rack toothed portion. The rack toothed portion includes teeth, a flat portion having a flat surface and arranged side by side with the teeth in a direction along a center axis of the blank pipe portion, and a slanted portion provided at an end of the flat portion with respect to a direction perpendicular to the center axis and arranged to be lower than the flat portion. A length of the slanted portion projected on a straight line perpendicular to the center axis and parallel to the surface of the flat portion is longer than zero and equal to or shorter than the wall thickness of the blank pipe portion.

A rack bar includes a shaft member having a toothed section. The toothed section has a plurality of rack teeth, and extends over a portion of an entire length of the shaft member along a longitudinal direction of the shaft member. The shaft member has a grinding-finished outer peripheral surface extending over the entire length of the shaft member including the toothed section. A method for manufacturing the rack bar includes forming the toothed section by plastic working and grinding the outer peripheral surface to improve shape accuracy.

Provided are a method of manufacturing a hollow rack bar including a rack portion that is engaged with a pinion gear and faces supported by a yoke easily and accurately, and the hollow rack bar. The hollow rack bar (10) includes: the rack portion (21) engaged with the pinion gear (29); and the supported faces (23) provided on a back side of teeth of the rack portion (21) and supported by the yoke (31). The rack portion (21) is formed by locating a toothed mold (39) on an outer face of a circular tube material, and inserting a cored bar (41) into the circular tube material to pressurize an inner face, thereby transferring a shape of the toothed mold (39). The supported faces (23) are formed by removal processing or deformation processing of a back side of the teeth rack portion (21) of the circular tube material.