# US 2021/0277933 A1 · Drive shaft and method of producing drive shaft

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- Number: US 2021/0277933 A1
- Document ID: US20210277933A1
- Status: Published application
- Kind: A1
- Application number: 17/191,742
- Filed: 2021-03-04
- Published: 2021-09-09
- Earliest claimed: 2020-03-06
- Assignees: Honda Motor Co., Ltd.
- Applicants: Honda Motor Co., Ltd.
- Inventors: Mitsuru Kamikawa; Takahiro Ueda; Masafumi Yamamoto; Masaru Suzuki
- Web page: https://patentgrep.com/patent/US20210277933A1

## CPC

- F16C 3/023: {made of several parts, e.g. by welding}
- B23K 20/12: the heat being generated by friction; Friction welding
- B23K 20/129: {specially adapted for particular articles or work}
- B23K 20/227: with ferrous layer
- C21D 1/18: Hardening (C21D1/02 takes precedence); Quenching with or without subsequent tempering (quenching devices C21D1/62)
- C21D 9/28: for plain shafts
- C21D 9/50: for welded joints
- F16D 1/068: involving gluing, welding or the like
- B21K 1/063: {hollow (hollow racks B21K1/768)}
- B23K 2101/006: {Vehicles}
- B23K 2101/04: Tubular or hollow articles
- B23K 2103/04: Steel {or steel} alloys
- C21D 1/32: Soft annealing, e.g. spheroidising
- C21D 7/02: by cold working
- C21D 7/10: of the whole cross-section, e.g. of concrete reinforcing bars
- C21D 2211/003: Cementite
- C21D 2211/004: Dispersions; Precipitations
- C21D 2211/005: Ferrite
- C22C 38/002: {containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60}
- C22C 38/02: containing silicon
- C22C 38/04: containing manganese
- C22C 38/06: containing aluminium
- C22C 38/08: containing nickel {(C22C38/105 takes precedence)}
- C22C 38/16: containing copper
- C22C 38/18: containing chromium
- C22C 38/20: with copper
- C22C 38/22: with molybdenum or tungsten
- C22C 38/26: with niobium or tantalum
- C22C 38/28: with titanium or zirconium
- C22C 38/32: with boron
- C22C 38/40: with nickel
- F16C 2204/64: Medium carbon steel, i.e. carbon content from 0.4 to 0,8 wt%
- F16C 2220/46: by forging
- F16C 2226/36: by welding
- F16C 2326/06: Drive shafts
- F16C: SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- B23K: SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- C21D: MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B)
- F16D: COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
- 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)
- C22C: ALLOYS (treatment of alloys C21D, C22F)

## Abstract

A drive shaft includes a first annular wall and a second annular wall joined together via a friction-welded portion. The first annular wall and the second annular wall have outer diameters of 30 to 50 mm and wall thicknesses of 3 to 5 mm. A burr created at the friction-welded portion has a connection radius of greater than or equal to 0.5 mm, a base radius of greater than or equal to 0.5 mm, a burr base angle of less than or equal to 40°, and a burr slope length of 0.2 to 5 mm.

## Claims

### Claim 1

A drive shaft comprising:
a first annular wall with an annular shape provided at an end part of a hollow tubular body made of a medium carbon steel; and
a second annular wall with an annular shape provided at an end part of a solid stub shaft made of a medium carbon steel, the first and second annular walls being joined together in an axial direction via a friction-welded portion, wherein:
the first annular wall and the second annular wall have outer diameters of 30 to 50 mm and wall thicknesses of 3 to 5 mm;
at the friction-welded portion, a burr is partially raised from a first inner wall surface, which is an inner wall surface of the first annular wall, and from a second inner wall surface, which is an inner wall surface of the second annular wall;
the burr includes a burr base part, which is a basal end at which the burr is raised from the first inner wall surface, and an orthogonal part orthogonal to the first inner wall surface;
a connection radius, which is a radius of curvature of the burr base part, is greater than or equal to 0.5 mm;
a base radius, which is a minimum radius of curvature of a part between the burr base part and the orthogonal part of the burr, is greater than or equal to 0.5 mm;
a burr base angle, which is an angle of inclination of the burr base part relative to the first inner wall surface, is less than or equal to 40°; and
a burr slope length, which is an axial length of the part between the burr base part and the orthogonal part, is in a range of 0.2 to 5 mm.

### Claim 2 (depends on 1)

The drive shaft according to claim 1, wherein the connection radius is less than or equal to 3 mm, and the base radius is less than or equal to 2.5 mm.

### Claim 3 (depends on 1)

The drive shaft according to claim 1, wherein:
the burr includes a first curved portion and a second curved portion, the first curved portion being raised from the first inner wall surface and curved away from the second inner wall surface in the axial direction, the second curved portion being raised from the second inner wall surface and curved away from the first inner wall surface in the axial direction; and
when a virtual line passing through a valley bottom portion, which is formed between the first curved portion and the second curved portion, in a radial direction of the first annular wall and the second annular wall is defined as a virtual centerline, an axial end part of the second annular wall expands toward the first annular wall beyond the virtual centerline by 1 to 30 μm at the friction-welded portion.

### Claim 4 (depends on 1)

The drive shaft according to claim 1, wherein at least one of NbC, Mo2C, and TiC deposits in a grain boundary in metal structure of the second annular wall at the friction-welded portion.

### Claim 5 (depends on 1)

The drive shaft according to claim 1, wherein the medium carbon steel serving as a material of the solid stub shaft contains, by weight, 0.45 to 0.51% C, 0.20% or less Si, 0.30 to 0.50% Mn, 0.010% or less P, 0.008 to 0.020% S, 0.1% or less Cu, 0.1% or less Ni, 0.1 to 0.2% Cr, at least one of 0.05 to 0.25% Mo, 0.03 to 0.08% Nb, and 0.01 to 0.05% Ti, 0.02 to 0.04% Al, and 10 to 30 ppm B; rest of the medium carbon steel consists of Fe and unavoidable impurities; and grain size number ranges from #9 to #11.

### Claim 6 (depends on 1)

The drive shaft according to claim 1, wherein the medium carbon steel serving as the material of the hollow tubular body contains, by weight, 0.43 to 0.47% C, 0.30% or less Si, 0.60 to 0.90% Mn, 0.010% or less P, 0.020% or less S, 0.1% or less Cu, 0.1% or less Ni, 0.05% or less Cr, and 0.02 to 0.04% Al; rest of the medium carbon steel consists of Fe and unavoidable impurities; and grain size number ranges from #5 to #9.

### Claim 7

A method of producing a drive shaft, the drive shaft comprising:
a first annular wall with an annular shape provided at an end part of a hollow tubular body made of a medium carbon steel; and
a second annular wall with an annular shape provided at an end part of a solid stub shaft made of a medium carbon steel, the first and second annular walls being joined together in an axial direction via a friction-welded portion to obtain the drive shaft,
the method comprising:
a forging step of obtaining the solid stub shaft by cold forging; and
a friction-welding step of joining the first annular wall and the second annular wall together by friction welding, the first annular wall and the second annular wall having outer diameters of 30 to 50 mm and wall thicknesses of 3 to 5 mm, wherein:
in the friction-welding step, the friction-welded portion is formed in a manner that a burr is partially raised from a first inner wall surface, which is an inner wall surface of the first annular wall, and from a second inner wall surface, which is an inner wall surface of the second annular wall; that the burr includes a burr base part, which is a basal end at which the burr is raised from the first inner wall surface, and an orthogonal part orthogonal to the first inner wall surface; that a connection radius, which is a radius of curvature of the burr base part, is greater than or equal to 0.5 mm; that a base radius, which is a minimum radius of curvature of a part between the burr base part and the orthogonal part of the burr, is greater than or equal to 0.5 mm; that a burr base angle, which is an angle of inclination of the burr base part relative to the first inner wall surface, is less than or equal to 40°; and that a burr slope length, which is an axial length of the part between the burr base part and the orthogonal part, is in a range of 0.2 to 5 mm.

### Claim 8 (depends on 7)

The method of producing the drive shaft according to claim 7, wherein in the friction-welding step, the friction-welded portion is formed in a manner that the connection radius is less than or equal to 3 mm and that the base radius is less than or equal to 2.5 mm.

### Claim 9 (depends on 7)

The method of producing the drive shaft according to claim 7, further comprising:
after the friction-welding step, an annealing step of annealing the drive shaft under a condition where the drive shaft is maintained at a temperature of 650 to 720° C. for 30 to 90 minutes; and
after the annealing, a hardening step of hardening the drive shaft, wherein:
at least one of NbC, Mo2C, and TiC deposits in a grain boundary in metal structure of the solid stub shaft.