JPS6329503B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a manufacturing method for manufacturing a rotor used in a small watch motor or the like by two-color molding.

The two-color molding technology itself is already a well-known technology,
It is applied to the production of various plastic parts.
In general, when performing two-color molding, two materials are often selected to weld together and easily bond together, such as plastic materials of the same type with different colors. Materials that have similar temperatures (injection temperatures) and are easy to weld are selected. However, for the rotor of a small motor,
The characteristics must be given first priority. In other words, the rotor magnet has its magnetic properties, and the rotor shaft (rotor pinion) has low wear and
Low friction and smooth gear meshing are of paramount importance. For this reason, when selecting materials suitable for the rotor magnet and rotor shaft, the weldability between the materials is extremely poor and they easily peel off, which is one of the obstacles to the practical application of two-color molded rotors. was.

As a product that prevented such peeling,
A rotor according to Publication No. 25285 is known. In this rotor, a columnar part is formed by filling the through hole of the rotor magnet from a disc part on the rotor shaft side, and the tip of this columnar part has a partially enlarged diameter to form a structure that prevents it from coming off. It was hot. However, this structure or method has the disadvantage that the molding process and mold structure for molding the rotor are complicated.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a rotor by two-color molding, which can prevent separation of the rotor magnet from the rotor shaft without complicating the molding process and mold structure.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

The two-color molded rotor manufactured by the manufacturing method of the present invention includes a rotor magnet 10 and a rotor shaft 20.
The rotor magnet 10 is made of, for example, a mixed material of strontium ferrite and 6-nylon, and the rotor stem 20 is made of, for example, polyacetal. Rotor magnet 1
0 has a shaft hole 11 in its center, and further has a through hole 12 spaced apart from the shaft hole 11.
On the other hand, the rotor stem 20 protrudes through the shaft hole 11, has tenon parts 21 and 22 at both ends thereof, and further has a gear part 23 and a disk part 24 integrally formed,
This disk portion 24 is joined to the upper end surface of the rotor magnet 10. From the disc part 24, the columnar part 2
5 and 25 are formed to hang down, and are fitted into the through hole 12. The columnar parts 25, 25 have recesses 26, 26 at their bases (near the joint surface), and the through holes 12
The protrusions 13, 13 which protrude inwardly at one end of the plate are bitten.

Next, a method for manufacturing a two-color molded rotor having the above structure will be explained.

First, in the first step, the rotor magnet 10
are formed using templates 31, 32, and 33 shown in the third figure. A pillar 34 for forming the shaft hole 11 is protruded from the template 33, and the tip thereof is connected to the template 31.
It abuts against a cavity 35 for forming the tenon part 22. Slide core 3 is attached to template 31.
6 and 36 are slidably fitted into each other, and chamfered portions 37 and 37 are formed at the distal ends thereof to make them tapered.
The slide cores 36, 36 are held in a position where they come into contact with the template 33 when forming the rotor magnet 10, and due to the presence of the chamfered portions 37, 37, a protruding portion protrudes inward at the end of the through hole 12. 13 is formed.

After the rotor magnet 10 is formed, the template 3
3 is opened, and in the next station, that is, the second step, a template 38 with cavities corresponding to the tenon part 21, gear part 23, and disc part 24 is attached to the template 32.
The slide cores 36, 36 are pulled down by a certain length, that is, by an amount less than the thickness of the rotor magnet 10 (FIG. 4). When the material for the rotor shaft 20 is injected into the template 38, it fills the cavity, the shaft hole 11 and the cavity 35, thereby completing the two-color molded rotor shown in FIG.

By forming in this way, it is possible to select the most suitable material for the rotor magnet 10 and the rotor shaft 20, and in that case, even if it is difficult to weld between the rotor magnet 10 and the rotor shaft 20, the rotor The through hole 13 and the columnar part 26 prevent relative rotation of the shaft 20, and at the same time, the protrusion 13 and the recess 26 prevent the rotor magnet 10 from coming off in the axial direction of the rotor shaft 10. Furthermore, the columnar portion 26 may be of any type as long as it has enough strength to prevent the rotor shaft 20 and the rotor magnet 10 from rotating relative to each other and to prevent them from coming off.
It is sufficient to slide it by an amount smaller than the thickness of the rotor magnet 10 and mold it to a predetermined length smaller than the thickness of the rotor magnet 10, and by doing so, the amount of resin used can be reduced. Since the molding cycle time is also shortened, it is also advantageous in terms of cost.

As described above, according to the rotor manufacturing method using two-color molding according to the present invention, the slide core 36 whose tip is chamfered to form the through hole 12 is formed in the first step, and the rotor magnet 10 is formed in the second step. By simply sliding the disk portion 24 in the opposite direction by an amount smaller than the thickness, the columnar portion 25 filled in a part of the through hole 12 becomes a retaining structure at its base, and the molding process and mold structure are prevented. It is simplified compared to the conventional method. Furthermore, the amount of resin used is small and the molding cycle time is shortened, so it is advantageous in terms of cost.

[Brief explanation of the drawing]

Figure 1 shows 2 produced by the production method of the present invention.
2 is a plan view of the rotor, FIG. 3 is a sectional view showing the first step of molding the rotor magnet, and FIG. 4 is the second step of joining the rotor shaft to the rotor magnet. FIG. 10...Rotor magnet, 11...Shaft hole, 1
2... Through hole, 20... Rotor shaft, 23... Gear part, 24... Disc part, 25... Column part, 36...
Slide core, 37... Chamfered portion.

Claims (1)

[Scope of Claims] 1. A first step of molding a rotor magnet, which has a shaft hole in the center and a through hole at a position spaced apart from the shaft hole, from a plastic magnet material; a rotor shaft passing through the rotor shaft, a disc part joined to one end surface of the rotor magnet, a gear part located on the top of the disc part, and a columnar part that hangs down from the disc part and enters the through hole. and a second step of integrally forming a slide core with a chamfered tip for forming the through hole in the first step, and a slide core with a chamfered tip for forming the through hole in the first step, and a slide core with a chamfered tip for forming the through hole in the second step. A method for manufacturing a rotor by two-color molding, characterized in that the columnar portion is formed by sliding in a direction opposite to the disk portion by an amount smaller than the thickness of the net.