JPH04296521A - Resin-molded gear - Google Patents

Abstract

PURPOSE:To improve the accuracy of tooth shape and to keep its strength surely in a resin-molded gear. CONSTITUTION:Double ribs 4 are formed at the upper and lower parts of hollow part 3 by providing said hollow part 3 in the part connecting a tooth shape 1 to a boss 2, whereby the deformation of the tooth shape due to the sink in molding or the tension of the reinforcing rib may be prevented, and the improvement of accuracy and the guarantee of strength may be obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin molded gear having ribs connecting tooth profiles and bosses.

0002

BACKGROUND OF THE INVENTION In recent years, various efforts have been made to improve the precision of tooth profiles in resin-molded gears.

A conventional resin molded gear will be explained below with reference to FIGS. 2 and 3. As shown in the figure, the gear has a rib 5 that connects the tooth profile 1 and the boss 2. In order to maintain the accuracy of the tooth profile 1, it is necessary to keep the thickness of the resin at each part uniform, and the thickness of the rib 5 cannot be increased due to sink marks. Therefore, reinforcing ribs 6 are provided separately.

0004

SUMMARY OF THE INVENTION Such conventional gears have had the problem that, when reinforcing ribs 6 are provided to maintain the strength of the gear, the tooth profile is deformed due to tension.

The present invention solves the above-mentioned problems, and aims to provide a resin-molded gear that improves the accuracy of tooth profile and ensures strength.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a hollow portion in the portion connecting the tooth profile and the boss, and forms double ribs above and below the hollow portion. It is something.

[0007]

[Operation] With this configuration, the thickness of the rib can be reduced and the strength can be ensured, so that the precision of the tooth profile can be improved.

[0008]

[Embodiment] An embodiment of the resin-molded gear of the present invention will be described below with reference to FIG. Note that the same numbers are used for the same constituent members as those explained in the conventional example.

As shown in the figure, a hollow part 3 is provided at the part where the tooth profile 1 of the gear and the boss 2 are connected, and two holes are provided above and below the hollow part 3.
A heavy rib 4 is formed. The hollow portion 3 is formed by sending gas into the resin that remains melted during injection molding. This configuration prevents sink marks due to non-uniform resin wall thickness, improves the precision of the tooth profile 1, and ensures strength.

0010

Effects of the Invention As is clear from the description of the embodiments above, according to the present invention, a hollow portion is provided in the portion connecting the tooth profile and the boss, and double ribs are formed above and below the hollow portion. It is possible to prevent deformation of the tooth profile due to sink marks during molding and tension of reinforcing ribs, improve precision and ensure strength at the same time, and produce molded gears of good quality.

[Brief explanation of the drawing]

[Fig. 1] Side sectional view of a resin molded gear according to an embodiment of the present invention.

[
Figure 2: Side sectional view of a conventional resin molded gear

[Figure 3] Plan view of conventional resin molded gear

[Explanation of symbols]

1 Tooth profile 2 Boss 3 Hollow part 4 Ribs

Claims (1)

[Claims] 1. A resin-molded gear in which a hollow portion is provided in a portion where the tooth profile and the boss are continuous, and double ribs are formed above and below the hollow portion.