JPS6153937B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an insert molding method, and its purpose is to embed a thin plate to be inserted in a predetermined position without deforming it in order to improve heat dissipation, heat resistance, etc. The purpose of the present invention is to provide an insert molding method that can be used for insert molding.

Small household appliances such as electric razors are small,
Electronic circuits such as control circuits and charging circuits, motors, etc. are mounted with high density in order to make the product thinner, but internal heat generation from the electronic circuits, motors, etc. increases the temperature inside the housing made of synthetic resin. Poor heat dissipation reduces the reliability of individual electronic components, and also causes problems such as the surface temperature of the housing that is touched by hands becoming high in some areas, giving the user a sense of anxiety, and causing the housing to deform or discolor. occured.

As a way to solve this problem, as shown in Figure 9, a thin plate made of a thermally conductive material such as aluminum is placed on the inner surface of the two-part housing to increase the heat dissipation effect. There is a method of inserting an insulating board such as a press board between the conductive part (not shown), but it is also possible to insert the motor (not shown), battery (not shown), and live parts on the inside of the housing. The ribs for fixing protrude, and it is necessary to provide notches in the thin plate A and the insulating plate C to avoid these ribs, which causes the problem that the heat radiation area becomes smaller and the heat dissipation becomes worse. In order to attach the thin plate A and the insulating plate C to the inner surface of the housing, adhesive is used to attach the thin plate A and the insulating plate C to the inner surface of the housing. It was difficult to do so, and there was a problem of uneven heat dissipation.

The present invention has been made in view of the above-mentioned problems, and will be described below with reference to the drawings showing embodiments of the present invention. In FIGS. 1 and 2, the housing 1 is formed into two parts.
A motor 2, a battery 3, and a charging section 4 are housed inside, and an outer cutter 6 that slides in contact with an inner cutter 5 driven by the motor 2 is detachably provided. In the housing 1, a thin plate 8 made of a thermally conductive material such as aluminum and having a plurality of small holes 7 is embedded in substantially the entire housing position of the motor 2, battery 3, and charging section 4. The housing 1 includes a first synthetic resin material 1a having electrical insulation properties forming an inner layer, a thin plate 8, and a second synthetic resin material 1b forming an outer surface.
It is formed into a three-layer structure. The charging section 4 is composed of a printed wiring board 9 and an electronic component 10 mounted on the printed wiring board 9.
is supported by the inner wall of switch handle 11
is slidably disposed in one housing 1, and by operating the switch handle 11, electricity from the battery 3 is supplied to the motor 2 to rotate the motor 2.

Hereinafter, a method for manufacturing the housing 1 will be described based on FIGS. 3 to 8. In Figure 3,
The cavity 12 has a movable mold 13 and a gate 14a.
It is composed of a fixed mold 14 containing a. The movable mold 13 is provided with a plurality of gate pins 15 that can freely protrude into the cavity 12. The gate pin 15 can be restrained in a protruding state and is housed in the movable mold 13, and is locked at a position where it abuts against the thin plate 8. As shown in FIG. 5, at the tip of the gate pin 15, a plurality of protrusions 16 that support the periphery of the small hole 7 of the thin plate 8 are arranged concentrically and protrude in the axial direction of the gate pin 15. The height H of the convex portion 16 is formed to be equal to the distance L between the thin plate 8 and the movable mold 13. On the surface of the cavity 12 of the fixed mold 14, a thin plate 8 with small holes 7 arranged in a position facing the gate pin 15 and whose surface is coated with adhesive is placed. The end surface covers all of the small holes 7 and restrains the gate pin 15.
A thin plate 8 is held between the convex portion 16 of the mold 5 and the cavity 12 surface of the fixed mold 14. In this state, the first synthetic resin material 1a made of an insulating material is melted into the cavity 12 and injected from the gate 14a.
As shown in FIG. 4, the first synthetic resin material 1a does not move due to the injection flow of the first synthetic resin material 1a.
One side of the thin plate 8 is molded, and the two are integrally molded at the same time. At this time, as shown in FIG. 6, the thin plate 8 is exposed in the recess 18 at the part where the convex part 16 of the gate pin 15 is located, and the part where the recess 17 of the gate pin 15 is located is the part where the convex part 16 of the gate pin 15 is located. 1
The peripheral edge of the small hole 7 of the thin plate 8 is held by the first synthetic resin material 1a of this portion. Next, after opening the mold, the hardened first synthetic resin material 1 is applied to the convex portion 16 of the gate pin 15.
A is replaced with another fixed mold 19 with mold a still attached to form a cavity 20 with a large volume as shown in FIG.
Melt and inject b. At this time, if the restraint state of the gate pin 15 is released, the gate pin 15 is housed in the movable mold 13 by the resin pressure and is locked in a state where the cavity 20 surface and the convex part 16 of the gate pin 15 are flush with each other. , second synthetic resin material 1b
is filled into the small hole 7 and molded on the other side of the thin plate 8, as shown in FIG.
completely enveloped.

In this case, since the thin plate 8 can be completely wrapped by the first synthetic resin material 1a and the second synthetic resin material 1b, the first synthetic resin material 1a
The mechanical bonding force between the second synthetic resin material 1b and the thin plate 8 can be increased, and the bonding force of the adhesive applied to the thin plate 8 can also firmly bond the housing, thereby improving the strength of the housing. Furthermore, by using a synthetic resin material having elasticity for the first synthetic resin material 1a serving as the inner surface layer, the motor 2, battery 3, and It is also possible to absorb noise and vibration when the motor 2 and the inner cutter 5 are driven by providing a buffering effect to the charging part 4 or by using a sound absorbing material or a vibration isolating material.

As explained above, according to the present invention, the first synthetic resin material is injected in advance from one side of a thin plate made of a thermally conductive material, and the second synthetic resin material is injected from the other side of the thin plate. In the insert molding method, a small hole is formed in the thin plate, and a plurality of convex portions protruding in the axial direction are formed at the tip of the gate pin, and the convex portion of the gate pin closes the periphery of the small hole in the thin plate. After supporting the first synthetic resin material and molding one side of the thin plate, the second synthetic resin material was injected and filled into the small holes and the other side of the thin plate was molded. The heat sink and heat resisting plate can be attached at the same time as the assembly of step 1, which simplifies assembly.The heat dissipation area is not reduced due to ribs as in the past, and the heat dissipation effect is increased, so it is suitable for electronic circuits, motors, etc. This has the effect of not reducing the reliability of individual electronic components or causing a sense of anxiety to the user due to internal heat generation, and also eliminates the need to bond complicatedly shaped metal plates or insulating plates, allowing heat dissipation. This has the effect of making the effect uniform and eliminating variations in heat dissipation depending on the product.Furthermore, since the convex part of the gate pin supports the periphery of the small hole in the thin plate when injecting the first synthetic resin material, the first synthetic resin material The injection pressure of the material prevents the thin plate from shifting from the predetermined position, and the first synthetic resin material injected into the recess of the gate pin partially supports the periphery of the small hole in the thin plate, while the second synthetic resin is applied. Since the injection pressure of the second synthetic resin material deforms the periphery of the small hole in the thin plate toward the gate pin side, the thin plate may peel off from the first synthetic resin material, or the surface of the synthetic resin material and the thin plate may There is an advantage that the spacing is not uneven and the heat dissipation effect can be made uniform.

[Brief explanation of the drawing]

FIG. 1 is a front view of an electric shaver equipped with a housing formed by the insert molding method of the present invention, and FIG.
The figure is a cross-sectional view of the same as above, FIGS. 3 and 4, and FIGS. 7 and 8 are cross-sectional views showing a method of manufacturing the housing.
Figure 5 is an external perspective view of the gate pin, Figure 6 is the first
FIG. 9 is an exploded perspective view of the conventional example. 1a...First synthetic resin material, 1b...Second synthetic resin material, 7...Small hole, 8...Thin plate, 15...Gate pin, 16...Convex portion.

Claims (1)

[Claims] 1. In an insert molding method in which a thin plate made of a thermally conductive material is embedded with a first synthetic resin material injected in advance from one side of the thin plate and a second synthetic resin material injected from the other side of the thin plate, A small hole is formed in the thin plate, and a plurality of convex portions protruding in the axial direction are formed at the tip of the gate pin, and the convex portion of the gate pin supports the periphery of the small hole in the thin plate and the first synthetic resin material is formed. An insert molding method characterized in that after injecting and molding one side of the thin plate, a second synthetic resin material is injected to fill the small holes and the other side of the thin plate is molded.