JPS5857305B2 - Composite part molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for molding a composite part by press-fitting and solidifying a plastic material such as a synthetic resin into a cylinder, square tube, box shape, etc. made of a hard material.

The hard materials referred to in the present invention include metals, sintered bodies such as ferrite, inorganic materials such as gypsum, or synthetic resins that are already solidified or unfilled, and are solid materials that are used when forming the composite material that is the object of the present invention. means.

Plastics include thermoplastic resins such as polyacetal,
A substance that can be injected and solidified during molding of a bonded product.

The content and significance of the present invention will be explained below using an example of a micromotor rotor.

As shown in FIG. 1, the micromotor rotor has a ferrite ring 1 filled with a synthetic resin 2 such as polyacetal, and a rotating shaft 3 in the center.

Conventionally, an article having such a shape has a ferrite ring 1 placed in the recesses 6 and 7 provided in the upper and lower molds 4 and 5, as shown in FIG.
The insert metal rod 3 was attached, and after the mold was clamped, the resin 2 was injected and solidified through the gate 8, thereby producing an L.

In this way, when mold clamping is completed, the outer circumference of the ring does not receive any pressure from the mold surface, and to exaggerate it, the ring 1 and mold 50 face each other as shown in FIG. 3, which is a partially enlarged view of FIG. 2. There is a slight gap 9 between the surfaces.

If synthetic resin is injected into the ring 1 in this state, tensile stress will be applied to the ring 1 due to internal pressure as shown by the arrow in FIG. 4, and this stress will not be supported by the mold surface.

Therefore, cracks 10 in the ring as shown in FIG. 4 often occur.

This phenomenon does not cause any actual damage to materials such as metal rings that have high tensile strength and high elongation, but it becomes a serious problem when materials such as ferrite have low tensile strength and extremely low elongation.

Therefore, in the case of a micromotor rotor, a method of maintaining the pressure balance by using resin 11 as the outermost layer as shown in FIG. 5, for example, has been considered.

However, this product does not have sufficient performance.

The present invention provides a method for easily manufacturing an article whose outermost shell is made of a material with low tensile strength by devising a mold.

That is, the present invention is characterized in that the mold surface in contact with the hard outer shell is divided into a plurality of parts, and furthermore, in the mold clamping state, the pressure on the hard outer shell surface is always lower than that of the mold surface. Concerning the molding method of composite parts.

Therefore, unlike in the past, the internal pressure against the outer shell material is supported by the mold surface, and it does not crack due to tension.

As can be easily understood from the principles described above, the method of the present invention allows the outer shell material to be made of a sintered material such as ferrite, a highly concentrated inorganic-filled synthetic resin, or a material with low tensile strength and elongation such as gypsum, and which has a low compressive strength. This is especially useful when the material is of high quality.

In this case, relatively little attention is required regarding excessive pressure on the shell.

For materials that are weak against compression, it is preferable to use a mold clamp stopper or an elastic body to prevent excessive compressive strain or excessive pressure from being applied.

A more preferable method is to detect pressure and strain and feed them back to the hydraulic pressure.

These pressures can be easily relieved by moving the mold in contact with the shell material using the method used for mold movement in ordinary injection molding.

In the simplest case, the objective can be achieved by making the cavity slightly smaller than the outer diameter of the outer shell material.

In this case, the mold in contact with the shell material stops slightly before the free clamping position, but due to the elasticity of the mold material, mold surface, pins, and other mold systems, mold clamping of other mold surfaces is prevented. There is no hindrance.

In order to apply pressure to the outer shell without interfering with the movement of other mold surfaces, hydraulic pressure or the like can be connected independently from other molds.

In addition to utilizing the natural elasticity described above, various elastic bodies can be inserted between the mold moving pressure source and the shell material.

The pressure on the outer shell is g for a normal cavity-like shape.
It is also possible to shade the entire surface or to use multiple points or lines.

Generally, if the compressive strength is high, it is sufficient to support it by points or lines, and if it is low, it is preferable to support the entire surface.

An example of a mechanism for achieving the object of the present invention will be described below with reference to the drawings using an example of a ring-shaped hard material.

In the figure, parts not directly related to the present invention are omitted.

Also, since the ring is symmetrical, only a portion of the ring is shown unless otherwise required.

FIG. 6 shows a mold of the present invention corresponding to FIG. 2, in which the movable mold 12 on the side surface of the ring moves laterally as shown by the arrow.

The movable mold 12 is provided on a lower mold 5' corresponding to the lower part of the lower mold 5 in FIG.

This movement can be achieved, for example, by providing tapered surfaces 4', 12' on the upper mold 4 and the movable mold 12, as shown in FIG. 7, and using these to move the movable mold 12 laterally in conjunction with the upper mold 4. I can do it.

This movable type may be divided into two parts, or as shown in Fig. 10.
It is possible to move them in the directions of the arrows by dividing them into three parts, 2A, 12B, and 12C, or to divide them into many parts.

FIG. 8 shows an example in which an elastic body 13 is inserted into a part of the movable mold 120 surface.

Figure 9 shows an elastic body 14 such as elastic rubber in the part that contacts the outer shell.
This is an example of inserting .

Figure 11 shows an example where it is supported not on the entire surface but on a part of the outer periphery.
In the figure, 15 is a mold that does not move, and 12 is a mold that moves in the direction of the arrow, and the ring 1 is supported by their three tops.

FIG. 12 shows an example in which the entire circumference of the movable mold 12 is supported only by the central portion 12'.

The method of the present invention can be effectively applied to, in addition to the ring shape used in the above-mentioned example, to shapes such as rectangular tubes and boxes whose outer shells are deformed by the internal pressure of resin press-fitting.

Examples of articles having such a shape include a rotating shaft fitted with a ring made of ceramic or oil-impregnated metal, a sliding component having a box-shaped outer shell, and an abrasive tool whose outer periphery is made of inorganic-filled resin.

When combining shell materials with high elongation such as aluminum, it is sufficient to simply make split molds using a mold similar in shape to that of the present invention.

The "mold" used in the above description is not necessarily limited to metal, but refers to a general mold such as a mold made of inorganic-filled resin or the like.

[Brief explanation of the drawing]

Figures 1 to 5 show the conventional method of molding a micromotor rotor. Figure 1 is a cross-sectional view of the molded product, Figure 2 is a cross-sectional view of the mold, Figure 3 is a partially enlarged view, and Figure 4 is a cross-sectional view of the molding die. The figure is a perspective view of the ring, Figure 5 is a sectional view of a modified example of the molded product, and Figures 6 to 12
The figures show various examples of the movable mold of the present invention, and FIG. 6 is a sectional view showing an example of the mold that can be used in the present invention, and FIG.
The figure is a conceptual diagram showing various modifications of the mobile type. 1... Ferrite, 2... Synthetic resin, 3... Shaft,
4゜5.5'...mold, 6,7...cavity
12...Movable type, 13.14...Elastic body.

Claims (1)

[Claims] 1. A method for manufacturing a composite article by press-fitting and solidifying a plastic material inside a hard shell material. A composite part molding method characterized by filling a plastic material in a state where the outer shell material is compressed inward by a mold surface divided into a plurality of parts.