Method for manufacturing resin gear with core metal

Patent metadata

Field	Value
Publication number	US-10682793-B2
Application number	US-201615189456-A
Country	US
Kind code	B2
Filing date	Jun 22, 2016
Priority date	Jul 3, 2015
Publication date	Jun 16, 2020
Grant date	Jun 16, 2020

Abstract

The present invention is intended to provide a method for manufacturing a resin gear with a core metal by which there is no reduction in strength even with gates allowing decrease in material costs such as pin gates in the molding die for injection molding.
The manufacturing method includes: gates at a primary molding step and gates at a secondary molding step are pin gates or the like. The number of the gates at the primary molding step and the number of the gates at the secondary molding step are plural and identical, and the gates are arranged circumferentially. Gate positions G 21 , . . . at the secondary molding step are circumferentially intermediate or nearly circumferentially intermediate between gate positions G 11 , . . . and weld positions W 11 , . . . adjacent to the gate positions G 11 , . . . in the primary molded article.

First claim

The invention claimed is:

1. A method for manufacturing a resin gear with a core metal composed of a metallic sleeve having opposing surfaces extending radially to a circumferential outer periphery of the sleeve and of a synthetic resin annular tooth part covering the outer periphery of the metallic sleeve, the method comprising:
a primary molding step of forming an annular inner member by injection molding a first molten resin in a first cavity molding die with the metallic sleeve as an insert, thereby forming a primary molded article in which the first resin contacts each of the opposing surfaces and outer periphery of the metallic sleeve; and
a secondary molding step of putting the primary molded article into a second cavity molding die and forming an annular outer member by injection molding a second molten resin that is a different material than the first molten resin, wherein:
the resin gear with the core metal is configured as a worm wheel of a worm gear;
the first cavity molding die and the second cavity molding die each have gates for injecting the respective first and second molten resins, the gates of each of the first and second cavity molding dies being pin gates, tunnel gates, or side gates;
the number of the gates of the first cavity molding die and the number of the gates of the second cavity molding die are plural and identical to one another and the gates of each of the first and second cavity molding dies are arranged circumferentially about the first cavity molding die and about the second cavity molding die, respectively;
the primary molded article has opposing surfaces extending radially to an outer circumference defining an outer peripheral surface of the primary molded article to have tooth-shaped projections configured to engage with the annular outer member, has gate marks corresponding to the position of the gates of the first cavity molding die during the primary molding step, and has radially extending weld lines circumferentially intermediate between adjacent ones of the gate marks of the primary molded article; and
in the secondary molding step, the second resin is charged between the tooth-shaped projections and into contact with each of the weld lines and opposing and outer peripheral surfaces of the primary molded article, and the positions of the gates of the second cavity molding die are radially outward from the gate marks of the primary molded article and circumferentially intermediate or nearly circumferentially intermediate between the gate marks and the respective weld lines adjacent to the gate marks of the primary molded article.

2. The method for manufacturing a resin gear with a core metal according to claim 1 , wherein the first molten resin and the second molten resin are fiber-reinforced resins.

3. The method for manufacturing a resin gear with a core metal according to claim 1 , wherein the primary and secondary molding steps are performed using a common movable molding die to which the metallic sleeve is affixed, with the primary molding step further performed by defining a primary molding cavity by the common molding die, a first fixed molding die, and a slide core, and with the secondary molding step further performed by defining a secondary molding cavity by the common molding die and a second fixed molding die.

4. The method for manufacturing a resin gear with a core metal according to claim 1 , wherein the primary and secondary molding steps are performed using a common movable molding die to which the metallic sleeve is affixed, the common die having a planar surface from which a first planar elevation extends, with a second planar elevation extending from the first planar elevation, and wherein said affixing of the metallic sleeve is about the second planar elevation, the primary molding step being performed such that the first resin contacts both the planar surface and first planar elevation, and the secondary molding step being performed such that the second resin contacts the planar surface.

5. The method for manufacturing a resin gear with a core metal according to claim 1 , wherein an injection point for each of the gates of the second cavity molding die lie at a base of the tooth-shaped projections of the primary molded article.

6. The method for manufacturing a resin gear with a core metal according to claim 1 , wherein a gate mark of the primary molded article, a gate mark of the annular outer member, a weld line of the primary molded article, and a weld line of the annular outer member are arranged in sequence circumferentially about the resin gear.

7. The method for manufacturing a resin gear with a core metal according to claim 1 , wherein teeth of the synthetic resin annular tooth part covering the outer periphery of the metallic sleeve are teeth that are formed on the annular outer member and configured to engage with the worm wheel.

8. The method for manufacturing a resin gear with a core metal according to claim 1 , wherein teeth of the synthetic resin annular tooth part are formed mechanically after completion of the secondary molding step.

9. The method for manufacturing a resin gear with a core metal according to claim 1 , wherein teeth of the synthetic resin annular tooth part are formed as part of the secondary molding step.

Assignees

• Nakanishi Metal Works Co

Inventors

• Nakamura Masayoshi
• Ayukawa Yuto

Classifications

• B29L2015/003

  Gears · CPC title

• B29C2045/1692

  one layer comprising fibres · CPC title

• B29C2045/2677

  The exchangeable mould parts being combinable or rearrangeable in different ways · CPC title

• B29C2045/0032

  sequential injection from multiple gates, e.g. to avoid weld lines · CPC title

• B29C45/2708

  Gates (B29C45/2703 takes precedence) · CPC title