Worm wheel, electric power steering system, and manufacturing method for worm wheel

{
  "publication_number": "US10724620B2",
  "country": "US",
  "kind": "B2",
  "title": "Worm wheel, electric power steering system, and manufacturing method for worm wheel",
  "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": [
    "1. A worm wheel comprising: a sleeve having an annular shape and: an outer peripheral surface, which is a surface of the sleeve in a radial direction, the outer peripheral surface having a central part, in an axial direction, that projects in the radial direction relative to both ends in the axial direction; a first side face which is a surface of the sleeve on a side closer to an injection-mold gate in the axial direction; and a second side face which is a surface of the sleeve on an opposite side to the first side face in the axial direction; and a toothed portion provided by injection molding so as to cover a part of the sleeve, the toothed portion having: a tooth forming portion provided on the outer peripheral surface; a first thick portion provided on the first side face; and a second thick portion provided on the second side face, the first thick portion having a smaller thickness in the axial direction than the second thick portion.",
    "2. 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.",
    "3. The worm wheel according to claim 1, wherein the outer peripheral surface of the sleeve is provided flat with respect to a circumferential direction.",
    "4. 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.",
    "5. 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.",
    "6. 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.",
    "7. The worm wheel according to claim 4, wherein the outer peripheral surface of the sleeve is provided flat with respect to a circumferential direction.",
    "8. 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.",
    "9. The worm wheel according to claim 1, wherein the sleeve comprises: a boss composed of a first material; and an annular portion composed of a second material different from the first material and comprising the outer peripheral surface and inner ribs.",
    "10. An assembly comprising: an injection mold having the injection mold gate; and the worm wheel according to claim 1 disposed in the injection mold."
  ],
  "description_excerpt": "The present disclosure a worm wheel, an electric power steering system, and a manufacturing method for a worm wheel.\n\nAn electric power steering system for steering steered wheels of a steering mechanism by transmitting a rotational force of a motor to the steering mechanism employs a worm speed reducer using a worm wheel described in Japanese Patent Application Publication No. 2010-014253 (JP 2010-014253 A), for example, so as to transmit a motor rotational force to the steering mechanism.\n\nThe worm wheel described in JP 2010-014253 A is constituted by a sleeve (a core metal portion 2 and an annulus portion 3) to be fitted to an output shaft such as a steering shaft of the steering mechanism, and a toothed portion provided by injection molding on an outer peripheral surface, which is a radial surface of the sleeve, so as to reach both side faces, which are axial surfaces of the sleeve. The toothed portion includes a tooth forming portion provided on the outer peripheral surface of the sleeve, and a thick portion provided on the both side faces of the sleeve. Further, the toothed portion has a rugged shape on the both side faces of the sleeve, and a relative rotation of the toothed portion to the sleeve is restricted through the engagement with a rugged portion reaching the outer peripheral surface of the sleeve.\n\nFurther, as described in Japanese Patent Application Publication No.",
  "cpc": [
    "F16H 55/22",
    "B29C 2045/0027",
    "B29C 45/0025",
    "B29C 45/1459",
    "B29L 2015/00",
    "B29L 2031/7754",
    "B62D 5/0454",
    "F16H 2055/065"
  ],
  "ipc": [
    "B62D 5/04",
    "F16H 55/22",
    "B29C 45/00",
    "B29C 45/14"
  ],
  "assignees": [
    "JTEKT Corp"
  ],
  "inventors": [
    "Akihiro Takeuchi",
    "Yu SUEMATSU",
    "Yuji Wakugawa",
    "Yoshitomo NAGAI",
    "Koji Okumura",
    "Hiroshi Kutsumi"
  ],
  "filing_date": "2017-07-11",
  "publication_date": "2020-07-28",
  "grant_date": "2020-07-28",
  "priority_date": "2016-07-14",
  "application_number": "US-201715646197-A",
  "family_id": "59325219",
  "cited_by_count": 4,
  "citations": [
    "EP0657340A1",
    "EP1614935A1",
    "WO2008000220A2",
    "US20090282939A1",
    "JP2009541679A",
    "JP2010014253A",
    "US20120000307A1",
    "JP2015155757A",
    "US20120111144A1",
    "JP2015113967A",
    "US20170152926A1"
  ]
}