JPH0647265B2 - Casting method for rotating body - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the production of synthetic resin rotors such as gears and pulleys, and more particularly to the resin from directly above a metal insert that constitutes the central portion of the rotor. The present invention relates to an insert casting method for injecting a resin to mold a rotating body.

2. Description of the Related Art When a synthetic resin rotating body such as a gear or a pulley is manufactured by injection molding, a central disgate is adopted in order to obtain the circularity of the rotating body. In the case of the specification in which the metallic insert is cast into the boss portion of the rotating body, the metal insert 3 is mounted on the centering shaft 2 installed in the mold 1 as shown in FIG. 4 for positioning, and then the mold 1, 1'is closed and resin 4 is injected. However, since the gate 5 is located right above the metal insert 3, the injected resin 4 is
It is easy to enter into the gap 6 between the metal insert 3 and the metal insert 3 attached thereto (shown in FIG. 5 in an enlarged view of a portion A in FIG. 4).

In the case of a resin that undergoes a melt-hardening reaction in the mold, such as phenolic resin, injection pressure of 500 kg / cm ² or more is applied, so the resin will enter even in a gap of 0.01 mm and burr will occur. . Also, if there are key grooves, splines, etc. on the inner wall of the hole of the metal insert, it is difficult to surely fill the space created between them with the centering shaft when mounted on the centering shaft. Since invasion is unavoidable, a large number of man-hours are required to remove burrs after molding.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As described above, when molding is performed by directly injecting resin from directly above the metal insert (which constitutes the central portion of the rotating body) arranged in the mold, the core with the metal insert attached It was difficult to prevent the resin from entering the gap between the feed shaft and the metal insert. An object of the present invention is to prevent the resin from entering and facilitate post-processing for removing burrs.

Means for Solving the Problems The present invention is an insert casting in which the above metal insert is passed through a centering shaft to be positioned in a mold, and a resin is injected from directly above the metal insert to form a rotating body. During molding, (a) a step of covering the upper surface of the metal insert positioned in the mold through the centering shaft with a cover with a diameter equal to or smaller than the outer diameter of the metal insert (b) then closing the mold and resin The feature is that the step of removing the cover together with the unnecessary resin is performed after the molding step (c) molding.

Action As described above, in the present invention, when the resin is injected, the gap between the metal insert and the centering shaft attached to the insert is covered with the cover, so that the resin is prevented from entering the gap. be able to. After the molding, the cover can be easily removed when the unnecessary resin such as the gate portion is separated from the molded product.

Examples Hereinafter, examples of the present invention will be described in detail.

As shown in FIG. 1, the metal insert 3 (made of S45C carbon steel) is passed through the centering shaft 2 provided in the mold 1. The tip of the centering shaft 2 is formed to have a small diameter, and a 1.6 mm thick steel plate cover 8 (same diameter as the outer diameter of the metal insert 3) is fixed to the small diameter portion 7 to fix the centering shaft 2 and the metal. Cover the gap formed between the inserts 3. After that, the molds 1 and 1 ′ were closed and the phenol resin containing the filler was injected to form the toothed pulley.

The cover was easily removed by separating the resin during the process of removing the gate from the molded product, and the resin did not enter the key groove on the inner wall of the hole at the center of the metal insert, so there was no need to remove it.

Embodiment 2 FIG. 2 shows a case where the metal insert 3 has a ball bearing built therein. The gap formed between the metal insert 3 and the centering shaft 2 and the gap formed between the inner ring and the outer ring of the ball bearing were covered with the cover 8 in the same manner as in Example 1, and injection molding was performed. The cover 8 is a steel plate having a thickness of 3 mm and having an outer diameter smaller than that of the metal insert 3 by 2 mm.

The resin was never allowed to enter the ball portion of the bearing, but the cover was pressed against the metal insert with a large force due to the pressure during injection molding, and the resin did not enter.

Embodiment 3 As shown in FIG. 3, this is an example in which a magnet 9 is embedded in the upper end surface of the centering shaft 3 as a fixing means for the cover 8 covering the gap. The cover 8 is attracted and fixed by the magnet 9. The small-diameter portion 7 is not always necessary as long as the suction and fixation are reliable.

EFFECTS OF THE INVENTION As described above, the present invention can prevent resin from entering the gap between the metal insert and the centering shaft in a simple step in insert casting, and can reduce the number of post-processing steps. Is. In addition, when the metal insert is a material having a low hardness such as aluminum or is galvanized, the metal insert may be deformed or the plating may be peeled off due to the pressure or flow of the injected resin. The existence of the above solves such a problem.

[Brief description of drawings]

1 to 3 are cross-sectional views of an essential part showing an embodiment of the present invention, FIG. 4 is a cross-sectional view of an essential part showing a conventional method, and FIG. 5 is an enlarged view of part A of FIG. 1, 1'is a mold, 2 is a centering shaft, 3 is a metal insert, 5 is a gate, 7 is a small diameter part, 8 is a cover, 9 is a magnet.

Claims (3)

[Claims] 1. A metal insert (constituting a central portion of a rotating body) is mounted on a centering shaft and positioned in a mold, and a resin is injected from directly above the metal insert to form a rotating body. In insert casting, (a) a step of covering the upper surface of the metal insert positioned in the mold through the centering shaft with a cover having an outer diameter equal to or smaller than the outer diameter of the metal insert, (b) After that, the mold is closed to inject the resin, and (c) the molding process of the rotating body is performed by the process of removing the cover together with the unnecessary resin after the molding. 2. The method according to claim 1, wherein the centering shaft has a tip with a diameter smaller than that of the mounting portion of the metal insert, and the cover is fixed to the small diameter portion. 3. The cast molding method for a rotating body according to claim 1, wherein a magnet is embedded in the upper end surface of the centering shaft, and the cover of the magnetic body is attracted and fixed to the magnet.