Method of producing injection-molding die for worm wheel, and method of producing worm wheel

Patent metadata

Field	Value
Publication number	US-9643269-B2
Application number	US-201414181293-A
Country	US
Kind code	B2
Filing date	Feb 14, 2014
Priority date	Feb 7, 2008
Publication date	May 9, 2017
Grant date	May 9, 2017

Abstract

A worm wheel is provided in which a step is not formed near a tooth face meshing with a worm, and noise does not easily occur during power transmission.
A worm wheel 1 includes a circular arc-shaped tooth section 5 that is a portion meshing with a worm 101 and configuring a circular tube worm gear, and a helical tooth section 4 that is connected to one end side of the circular arc-shaped tooth section 5 . An angle of torsion at an arbitrary reference point 14 in a tooth depth direction of a tooth 3 on a boundary 7 between the circular arc-shaped tooth section 5 and the helical tooth section 4 is equal to an angle of torsion at a second reference point 15 corresponding to the first reference point 14 in the tooth depth direction of the tooth 3 in a diameter portion P 0 of a throat of the circular arc-shaped section 5 . As a result, a step is not formed on a tooth face on the boundary 7 between the circular arc-shaped tooth section 5 and the helical tooth section 4 . A tooth face of the circular arc-shaped tooth section 5 and a tooth face of the helical tooth section 4 are smoothly connected.

First claim

The invention claimed is:

1. A method of producing an injection-molding die for a worm wheel in which a master electrode having a shape similar to the worm wheel is formed and a cavity for injection-molding the worm wheel is formed using the master electrode, wherein:
the worm wheel
(1) has a circular arc-shaped tooth section that is a portion meshing with a worm and configuring a circular tube worm gear and a helical tooth section that is connected to one end side of the circular arc-shaped tooth section, and
(2) has an angle of torsion at an arbitrary first reference point in a tooth depth direction of a tooth in a connecting section between the circular arc-shaped tooth section and the helical tooth section equal to an angle of torsion at a second reference point corresponding to the first reference point in the tooth depth direction of the tooth in a diameter portion of a throat of the circular arc-shaped tooth section; and

the master electrode
(1) has a first tooth section corresponding to the circular arc-shaped tooth section of the worm wheel and a second tooth section corresponding to the helical tooth section of the worm wheel,
(2) has an angle of torsion at a position corresponding to the first reference point in the tooth depth direction of the tooth in a connecting section between the first tooth section and the second tooth section equal to an angle of torsion at a position corresponding to the first reference point in the tooth depth direction of the tooth at a position corresponding to the diameter portion of the throat of the first tooth section,
(3) is divided at a position corresponding to the diameter portion of the throat of the first tooth section into a first divided master including a portion of the first tooth section and the second tooth section, and a second divided master including the other portion of the first tooth section, in which
(4) the first divided master moves led by the first tooth section, while rotating with a lead of the first tooth section, and electrical-discharge-machines a die material from one side of the die material and
(5) the second divided master moves led by the first tooth section, while rotating with a lead of the first tooth section, and electrical-discharge-machines a die material from the other side of the die material, and
(6) forms the cavity in the die material.

2. A method of producing a worm wheel, wherein an injection-molding die for a worm wheel formed by a method of producing an injection-molding die for a worm wheel according to claim 1 is used to injection-mold a worm wheel, said worm wheel having a circular arc-shaped tooth section that is a portion meshing with a worm and configuring a circular tube worm gear and helical tooth sections that are respectively connected to one end side of the circular arc-shaped tooth section, and an angle of torsion of an arbitrary first reference point in a tooth depth direction of a tooth in a connecting section between the circular arc-shaped tooth section and the helical tooth section being equal to an angle of torsion of a second reference point corresponding to the first reference point in the tooth depth direction of the tooth in a diameter portion of a throat of the circular arc-shaped tooth section.

Assignees

• Akiyama Koji
• Enplas Corp

Inventors

• Akiyama Koji

Classifications

• F16H1/16

  comprising worm and worm-wheel · CPC title

• F16H55/22

  for transmissions with crossing shafts, especially worms, worm-gears · CPC title

• B22D17/2245 Primary

  having walls provided with means for marking or patterning · CPC title

• B29C45/37

  Mould cavity walls {, i.e. the inner surface forming the mould cavity, e.g. linings} · CPC title

• B23H9/00

  Machining specially adapted for treating particular metal objects or for obtaining special effects or results on metal objects (heat treatment by cathodic discharge C21D1/38) · CPC title