# US 2018/0017149 A1 · Worm wheel, electric power steering system, and manufacturing method for worm wheel

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- Number: US 2018/0017149 A1
- Document ID: US20180017149A1
- Status: Published application
- Kind: A1
- Application number: 15/646,197
- Filed: 2017-07-11
- Published: 2018-01-18
- Earliest claimed: 2016-07-14
- Assignees: Jtekt Corporation
- Applicants: Jtekt Corporation
- Inventors: Akihiro TAKEUCHI; Yu SUEMATSU; Yuji WAKUGAWA; Yoshitomo NAGAI; Koji OKUMURA; Hiroshi Kutsumi
- Web page: https://patentgrep.com/patent/US20180017149A1

## CPC

- F16H 55/22: for transmissions with crossing shafts, especially worms, worm-gears
- B29C 45/0025: {Preventing defects on the moulded article, e.g. weld lines, shrinkage marks (preventing defects on the preformed parts or layers B29C45/14836)}
- B29C 45/1459: {Coating annular articles}
- B62D 5/0454: {Worm gears}
- B29C 2045/0027: {Gate or gate mark locations}
- B29L 2015/00: Gear wheels or similar articles with grooves or projections, e.g. control knobs
- B29L 2031/7754: {Worms}
- F16H 2055/065: {Moulded gears, e.g. inserts therefor}
- F16H: GEARING
- B29C: SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00)
- 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)
- B29L: INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES

## Abstract

A worm wheel includes: a sleeve; and a toothed portion provided by injection molding so as to cover a part of the sleeve, the toothed portion including a first thick portion provided on a first side face, which is a surface of the sleeve on a side closer to an injection-mold gate in an axial direction, and a second thick portion provided on a second side face, which is a surface on an opposite side to the first side face. A central part, in the axial direction, of the outer peripheral surface of the sleeve projects in the radial direction relative to both ends in the axial direction. The first thick portion of the toothed portion has a smaller thickness in the axial direction than the second thick portion.

## Claims

### Claim 1

A worm wheel comprising:
a sleeve having an annular shape; and
a toothed portion provided by injection molding so as to cover a part of the sleeve, the toothed portion including a tooth forming portion provided on an outer peripheral surface, which is a surface of the sleeve in a radial direction, a first thick portion provided on a first side face, which is a surface of the sleeve on a side closer to an injection-mold gate in an axial direction, and a second thick portion provided on a second side face, which is a surface of the sleeve on an opposite side to the first side face in the axial direction, wherein:
a central part, in the axial direction, of the outer peripheral surface of the sleeve projects in the radial direction relative to both ends in the axial direction; and
the first thick portion of the toothed portion has a smaller thickness in the axial direction than the second thick portion.

### Claim 2 (depends on 1)

The worm wheel according to claim 1, wherein
a diameter of the outer peripheral surface of the sleeve increases from the both ends toward the central part.

### Claim 3 (depends on 1)

The worm wheel according to claim 1, wherein
the outer peripheral surface of the sleeve is provided flat with respect to a circumferential direction.

### Claim 4 (depends on 1)

The worm wheel according to claim 1, wherein:
the sleeve has an engaging hole having a depth in the axial direction and provided in a part of at least one of the first side face and the second side face, the part being opposed to the thick portion of the toothed portion; and
the thick portion opposed to the side face having the engaging hole, out of the first thick portion and the second thick portion, engages with the engaging hole.

### Claim 5 (depends on 4)

The worm wheel according to claim 4, wherein:
the sleeve has respective engaging holes having a depth in the axial direction and provided in respective parts of both the first side face and the second side face, the respective parts being opposed to the first thick portion and the second thick portion of the toothed portion; and
the first thick portion and the second thick portion engage with the respective engaging holes.

### Claim 6 (depends on 5)

The worm wheel according to claim 5, wherein:
the engaging hole provided on the second side face has a smaller depth in the axial direction than the engaging hole provided on the first side face.

### Claim 7 (depends on 4)

The worm wheel according to claim 4, wherein
the outer peripheral surface of the sleeve is provided flat with respect to a circumferential direction.

### Claim 8 (depends on 1)

An electric power steering system comprising:
the worm wheel according to claim 1; and
a motor configured to generate a steering force to steer steered wheels of a steering mechanism, wherein:
the worm wheel mechanically connects the steering mechanism to the motor so as to transmit the steering force generated by the motor to the steered wheels; and
the steered wheels are steered when the steering force generated by the motor is transmitted to the steered wheels.

### Claim 9

A manufacturing method for a worm wheel obtained such that a toothed portion is injection-molded so as to cover a part of a sleeve having an annular shape, the toothed portion including a tooth forming portion on an outer peripheral surface, which is a surface of the sleeve in a radial direction, a first thick portion on a first side face, which is one surface of the sleeve in an axial direction, and a second thick portion on a second side face, which is a surface of the sleeve on an opposite side to the first side face in the axial direction, the manufacturing method comprising:
placing the sleeve in a die so that a gate from which resin is injected is positioned on a side closer to the first side face of the sleeve, wherein a central part, in the axial direction, of the outer peripheral surface of the sleeve projects in the radial direction relative to both ends in the axial direction, and an axial interval between the first side face of the sleeve and an inner surface of the die, the inner surface being opposed to the first side face is smaller than an axial interval between the second side face of the sleeve on an opposite side to the first side face and an inner surface of the die, the inner surface being opposed to the second side face; and
supplying the resin into the die in a state where the sleeve is placed inside the die.

### Claim 10 (depends on 9)

The manufacturing method according to claim 9, wherein:
the supplying is performed on an engaging hole of the sleeve;
the outer peripheral surface of the sleeve is provided flat with respect to a circumferential direction; and
the sleeve has the engaging hole having a depth in the axial direction and provided in a part opposed to the thick portion of the toothed portion, the thick portion being opposed to at least one of the first side face and the second side face.