CN-121993575-A - Resin gear for power transmission and method for manufacturing resin gear for power transmission

CN121993575ACN 121993575 ACN121993575 ACN 121993575ACN-121993575-A

Abstract

Provided is a resin gear for power transmission, which can inhibit deformation caused by forced extraction without forming a tooth shape with a special shape. A resin gear 1 for power transmission is provided with teeth 10 of a gear on the outer peripheral surface of a circular ring-shaped resin part 3. The annular resin portion 3 is composed of an annular inner resin member 4 covering the outer periphery of the mandrel bar 2 and an annular outer resin member 5 covering the outer periphery of the annular inner resin member 4. The annular inner resin member 4 has a plurality of axially thinned portions 6 arranged apart in the circumferential direction. The annular outer resin member 5 has a filling portion 8 filled in the axially thinned portion 6 and an axial face cover portion 9 covering the filling portion 8 and located radially inward RI of the side portion 10C of the tooth 10.

Inventors

Ueda Hiroshio
Ju Dixin
YAMAMOTO TAICHI
Nakamura Jia Cheng
NAKAMOTO TADASHI

Assignees

株式会社捷太格特
中西金属工业株式会社

Dates

Publication Date: 20260508
Application Date: 20251011
Priority Date: 20241101

Claims (4)

1. A resin gear for power transmission, wherein teeth of the gear are provided on the outer peripheral surface of a circular ring-shaped resin portion, The annular resin part is composed of an annular inner resin component covering the outer periphery of the mandrel and an annular outer resin component covering the outer periphery of the annular inner resin component, The annular inner resin member has a plurality of axially thinned portions arranged apart in a circumferential direction, The annular outer resin member has a filling portion filled in the axially thinned portion and an axial face cover portion covering the filling portion and located radially inward of the side portion of the tooth.
2. The resin gear for power transmission according to claim 1, wherein, The tooth is arc-shaped, the tooth root is along the peripheral shape of the worm, the tooth surface is the curved surface of the arc-shaped, The power transmission resin gear is a worm wheel used as a worm speed reducer in combination with the worm.
3. The resin gear for power transmission according to claim 1 or 2, wherein, The outer peripheral surface of the annular inner resin member radially inward of the teeth of the outer peripheral surface of the annular outer resin member has a plurality of axial ridges arranged circumferentially apart, and the radially inward of the axial ridges has the axially thinned portion.
4. A method for manufacturing a resin gear for power transmission, which is provided with teeth of a gear on the outer peripheral surface of a circular resin part, wherein, The annular resin part is composed of an annular inner resin component covering the outer periphery of the mandrel and an annular outer resin component covering the outer periphery of the annular inner resin component, The annular inner resin member has a plurality of axially thinned portions arranged apart in a circumferential direction, The annular outer resin member has a filling portion filled in the axially thinned portion and an axial face cover portion covering the filling portion and located radially inward of the side portion of the tooth, The manufacturing method comprises a primary molding process and a secondary molding process, In the one-step molding process, the first molding step is performed, Injecting a molten resin for primary molding into a cavity of a primary molding die with the mandrel bar being disposed in the primary molding die with an axial direction of a die opening and closing direction, injection molding the annular inner resin member, and producing a primary molded article comprising the mandrel bar and the annular inner resin member, In the secondary molding process, the secondary molding process is performed, Injecting a molten resin for secondary molding into a cavity of a secondary molding die in a state where the primary molded body is set in the secondary molding die in which a die opening/closing direction is an axial direction, injection molding the annular outer resin member provided with the teeth, The filling portion and the axial face cover portion of the annular outer resin member are provided on the parting surface side of the secondary molding die.

Description

Resin gear for power transmission and method for manufacturing resin gear for power transmission Technical Field The present invention relates to a power transmission resin gear comprising a core rod and an annular resin portion. Background In order to meet the demands for weight reduction, quietness, and the like, as a power transmission resin gear composed of a core rod and an annular resin portion covering the outer periphery thereof, there is a worm wheel used in combination with a worm of a worm wheel speed reducer, for example (for example, refer to patent documents 1 to 3). In the case of forming the teeth of the worm wheel formed on the outer peripheral surface of the annular resin portion by injection molding, the teeth are formed in an undercut shape with respect to a mold for molding the teeth. Therefore, the worm wheel as a molded product is forcibly pulled out when the worm wheel is removed from the mold, and therefore the teeth of the worm wheel removed from the mold are deformed. In patent document 1, a mold structure is adopted in which a plurality of slide cores for forming tooth grooves are radially arranged around a core, and the slide cores are supported so as to be movable in the radial direction. Thus, forced pulling-out is avoided. In patent document 2, the tooth root of half of the tooth width on the side of the parting surface of the die that is axially away from the die opening/closing direction is formed as a tooth shape of a special shape that is formed parallel to the axial direction. Thus, forced pulling-out is avoided. In patent document 3, the tooth shape on the side away from the parting surface of the die in the axial direction is a tooth shape having a special shape in which the undercut amount is reduced. This enables forced extraction. Prior art literature Patent literature Patent document 1 Japanese patent laid-open No. 2002-254478 Patent document 2 Japanese unexamined patent publication No. 4-49254 Patent document 3 Japanese patent laid-open No. 2009-41595 Disclosure of Invention Problems to be solved by the invention In the case of using the mold structure including the slide core as in patent document 1, the difficulty in mold production is high, the mold becomes large, the mold cost increases, and productivity decreases. Further, the quality of the molded product may be degraded due to burrs generated on the parting surface of the slide core. In the case of the special-shaped tooth profile as described in patent document 2, it is necessary to change the design specification of the tooth profile of the worm wheel. Further, the tooth thickness of the worm wheel becomes thin, and the contact surface of the worm engaged with the worm wheel is reduced, so that the strength of the worm wheel is reduced. In the case of the special-shaped tooth profile as described in patent document 3, it is necessary to change the design specification of the tooth profile of the worm wheel. Further, since the molded article is forcibly pulled out, deformation of the molded article cannot be suppressed. The invention provides a resin gear for power transmission, which can inhibit deformation caused by forced pulling without forming tooth shape with special shape. Means for solving the problems The resin gear for power transmission according to the first aspect of the present invention is a resin gear for power transmission in which teeth of a gear are provided on an outer peripheral surface of an annular resin portion. The annular resin portion is composed of an annular inner resin member covering the outer periphery of the mandrel and an annular outer resin member covering the outer periphery of the annular inner resin member. The annular inner resin member has a plurality of axially thinned portions arranged apart in a circumferential direction. The annular outer resin member has a filling portion filled in the axially thinned portion and an axial face cover portion covering the filling portion and located radially inward of the side portion of the tooth. In the power transmission resin gear according to the second aspect of the present invention, in the power transmission resin gear according to the first aspect, the tooth is a circular arc shape having a tooth root along an outer peripheral shape of the worm, and the tooth surface is a curved surface of a circular arc shape, and the gear is used as a worm wheel of a worm speed reducer in combination with the worm. In the power transmission resin gear according to the third aspect of the present invention, in the power transmission resin gear according to the first or second aspect, the outer peripheral surface of the annular inner resin member radially inward of the teeth of the outer peripheral surface of the annular outer resin member has a plurality of axial ridges arranged at intervals in the circumferential direction, and the axially thinned portion is provided radially inward of the axial ridges. A method for manufacturing a powe