# US 8,770,054 B2 · Manufacturing method for hollow rack shaft, and hollow rack shaft > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,770,054 B2 - Document ID: US8770054B2 - Status: Granted - Kind: B2 - Application number: 12/961,775 - Filed: 2010-12-07 - Published: 2011-06-16 - Granted: 2014-07-08 - Earliest claimed: 2009-12-14 - Assignees: Jtekt Corporation - Applicants: Tomonari Yamakawa - Inventors: Tomonari Yamakawa - Web page: https://patentgrep.com/patent/US8770054B2 ## CPC - B21K 1/768: {hollow} - B21K 1/767: {Toothed racks} - B62D 3/126: {characterised by the rack} - F16H 55/26: Racks - Y10T 74/18808: with rack - Y10T 74/1967: Rack and pinion - B21K: MAKING FORGED OR PRESSED METAL PRODUCTS, e.g. HORSE-SHOES, RIVETS, BOLTS OR WHEELS (making particular articles by working sheet metal without essentially removing material B21D; processing wire B21F; making pins, needles or nails B21G; making particular articles by rolling B21H; forging machines, pressing machines, hammering machines, in general B21J; making chains B21L; plating B23K) - B62D: MOTOR VEHICLES; TRAILERS (steering, or guiding on a desired track, of agricultural machines or implements A01B69/00; wheels, castors, axles, increasing wheel adhesion B60B; vehicle tyres, tyre inflation or tyre changing B60C; connections between vehicles of a train or the like B60D; vehicles for use on rail and road, amphibious or convertible vehicles B60F; suspension arrangements B60G; heating, cooling, ventilating or other air treating devices B60H; windows, windscreens, non-fixed roofs, doors or similar devices, protective coverings for vehicles not in use B60J; propulsion plant arrangements, auxiliary drives, transmissions, controls, instrumentation or dashboards B60K; electric equipment or propulsion of electrically-propelled vehicles B60L; power supply for electrically-propelled vehicles B60M; passenger accommodation not otherwise provided for B60N; adaptations for load transportation or to carry special loads or objects B60P; arrangement of signalling or lighting devices, the mounting or supporting thereof or circuits therefor, for vehicles in general B60Q; vehicles, vehicle fittings or vehicle parts not otherwise provided for B60R; servicing, cleaning, repairing, supporting, lifting, or manoeuvring, not otherwise provided for, B60S; brake arrangements, brake control systems or parts thereof B60T; air-cushion vehicles B60V; motor-cycles, accessories therefor B62J, B62K; testing of vehicles G01M) - F16H: GEARING - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract In a manufacturing method for a hollow rack shaft, and a hollow rack shaft, a tubular member (23) having a planar flat portion (22) that is formed in part of a tubular body portion (21) is sandwiched and held between a cope (25) and a drag (26) that has a tooth-shaped portion (29) substantially symmetrical with rack teeth (7) so that a surface (22a) of the flat portion (22) is in contact with the tooth-shaped portion (29). A back die (14) having a plurality of protrusions (15) is arranged so that the protrusions (15) face groove portions (29a) of the tooth-shaped portion (29) across the flat portion (22), and the back die (14) is pressed against the flat portion (22) to form the rack teeth (7) to thereby manufacture the rack shaft. ## Claims ### Claim 1 A manufacturing method for a hollow rack shaft comprising: using a tubular member as a raw material, having a planar flat portion formed in part of a tubular body portion; and forming rack teeth at the flat portion; wherein the tubular member is held with a back die having a tooth-shaped portion substantially symmetrical with the rack teeth so that a surface of the flat portion is in contact with the tooth-shaped portion, the back die having protrusions is arranged so that the protrusions face groove portions of the tooth-shaped portion across the flat portion, the rack teeth are formed by pressing the back die against the flat portion such that a surface of the back die opposite the plurality of protrusions and an inner peripheral surface of the tubular body portion define a hollow gap therebetween, and the surface of the back die opposite the plurality of protrusions is parallel to the planar flat portion. ### Claim 2 (depends on 1) The manufacturing method for a hollow rack shaft according to claim 1, wherein the back die is fixed to an inner surface of the rack teeth, and the back die and the tubular member are handled as one to manufacture the hollow rack shaft. ### Claim 3 (depends on 2) The manufacturing method for a hollow rack shaft according to claim 2, wherein in a state where gaps are formed between an inner peripheral surface of the body portion and both side ends of a pressing member for pressing the back die in a short-side direction that is perpendicular to an axial direction of the rack shaft and is parallel to the flat portion, the back die is pressed against the flat portion to form the rack teeth and to form, integrally with the body portion, a fixing portion that fixes the back die to the inner surface of the rack teeth. ### Claim 4 A hollow rack shaft comprising: a tubular body portion; a planar flat portion that is formed in the body portion; rack teeth that are formed in the flat portion; and a back die that is used to form the rack teeth, wherein the back die has a plurality of protrusions that are formed at positions facing tooth portions of the rack teeth, the back die is fixed to an inner surface of the rack teeth, a surface of the back die opposite the plurality of protrusions and an inner peripheral surface of the tubular body portion define a hollow gap therebetween, and the surface of the back die opposite the plurality of protrusions is parallel to the planar flat portion. ### Claim 5 (depends on 4) The hollow rack shaft according to claim 4, wherein the body portion has a fixing portion that protrudes toward an inner peripheral side of the body portion and that is crimped to secure the back die, wherein the back die is fixed to the inner surface of the rack teeth by the fixing portion.