JP6791090B2 - How to manufacture a case for a power module - Google Patents

Description

The present invention relates to a method for manufacturing a case for a power module.

The power module case is molded by pouring a thermoplastic resin into the mold. Conventionally, since the mounting holes were formed during resin molding, welds were generated in the mounting holes. For this reason, when the customer tightens the screw into the mounting hole, the case may crack with the weld as the base point. In order to prevent this cracking, a reinforcing metal bush was press-fitted into the mounting hole (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2012-028552

However, there is a problem that the work man-hours and the manufacturing cost increase due to the bush press fitting. Further, although it is possible to form a mounting hole after resin molding, it is not possible to adjust the rigidity around the mounting hole.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to prevent cracking of a case, reduce work man-hours and manufacturing costs, and adjust the rigidity around a mounting hole. A method for manufacturing a case for a power module is obtained.

The method for manufacturing a case for a power module according to the present invention is a process of pouring resin into a mold to form a resin case and heating a cylindrical cylinder blade protruding from the lower surface of a height stopper to make a difference between the resin case and the resin case. The step of inserting, the step of crushing the flange formed of the resin discharged from the resin case by inserting the blade with the lower surface of the height stopper, and the step of hollowing out the resin case with the blade and being surrounded by the flange. It is characterized by including a step of forming a mounting hole.

In the present invention, since the resin case is molded without the mounting holes, the weld is not formed at the position of the mounting holes. Further, the flange is formed of the resin discharged from the resin case by inserting the blade. Since the structural rigidity of the mounting hole is strengthened by this flange, it is possible to prevent the case from cracking. Further, since it is not necessary to press-fit the metal bush, the work man-hours and the manufacturing cost can be reduced. Further, by crushing the flange with the height stopper, the rigidity around the mounting hole can be adjusted.

It is a top view which shows the manufacturing method of the case for power module which concerns on Embodiment 1. FIG. It is a top view which shows the manufacturing method of the case for power module which concerns on Embodiment 1. FIG. It is a perspective view which shows the molded resin case. It is sectional drawing which shows the manufacturing method of the case for power module which concerns on Embodiment 1. FIG. It is sectional drawing which shows the manufacturing method of the case for power module which concerns on Embodiment 1. FIG. It is sectional drawing which shows the manufacturing method of the case for power module which concerns on Embodiment 1. FIG. It is sectional drawing which shows the manufacturing method of the case for power module which concerns on Embodiment 1. FIG. It is sectional drawing which shows the manufacturing method of the case for power module which concerns on Embodiment 1. FIG. It is sectional drawing which shows the manufacturing method of the case for power module which concerns on Embodiment 1. FIG. It is sectional drawing which shows the manufacturing method of the case for power module which concerns on Embodiment 1. FIG. It is a top view which shows the mounting hole formed by the manufacturing method of the case for power module which concerns on Embodiment 1. FIG. It is a top view which shows the manufacturing method of the case for a power module which concerns on a comparative example. It is a top view which shows the manufacturing method of the case for a power module which concerns on a comparative example. It is a top view which shows the mounting hole formed by the manufacturing method of the case for power module which concerns on Embodiment 2. FIG. It is a perspective sectional view which shows the mounting hole formed by the manufacturing method of the case for power module which concerns on Embodiment 3. FIG.

A method of manufacturing a case for a power module according to an embodiment will be described with reference to the drawings. The same or corresponding components may be designated by the same reference numerals and the description may be omitted.

Embodiment 1.
1 and 2 are plan views showing a method of manufacturing a power module case according to the first embodiment. FIG. 3 is a perspective view showing a molded resin case. 4 to 10 are cross-sectional views showing a method of manufacturing the power module case according to the first embodiment.

First, as shown in FIG. 1, the thermoplastic resin 3 is poured into the mold 1 from the gate 2 connected to the upper part and the lower part of the drawing of the mold 1. As a result, the resin case 4 is molded as shown in FIG. Weld 5 is generated at the center of the drawing of the molded resin case 4. As shown in FIG. 3, the marking 6 is attached to the portion where the mounting hole of the resin case 4 is formed by the mold 1. This makes it easier to recognize the location where the mounting hole is formed in a later step.

Next, as shown in FIG. 4, the resin case 4 is placed on the jig 7. The blade 9 of the cylindrical cylinder protruding from the lower surface of the block-shaped height stopper 8 is arranged at a position where the mounting hole of the resin case 4 is formed. Next, as shown in FIG. 5, the blade 9 is heated by using the high frequency induction coil 10. The blade 9 is a conductive band heated by high frequency induction. An impulse or a heat ray heater can also be used to heat the blade 9.

Next, as shown in FIG. 6, the heated blade 9 is inserted into the resin case 4. Next, as shown in FIG. 7, the flange 11 formed of the thermoplastic resin 3 discharged from the resin case 4 by inserting the blade 9 is crushed by the lower surface of the height stopper 8. Next, as shown in FIG. 8, air is ejected from the air ejection groove 12 to cool the blade 9 in order to prevent stringing of the resin.

Next, as shown in FIG. 9, the resin case 4 is hollowed out by the blade 9 raised to the original position to form the mounting hole 13 surrounded by the flange 11. The extracted thermoplastic resin 3 stays in the blade 9 of the cylindrical cylinder. Therefore, as shown in FIG. 10, the thermoplastic resin 3 staying in the blade 9 is discharged by the discharge rod 14.

FIG. 11 is a plan view showing a mounting hole formed by the method for manufacturing the power module case according to the first embodiment. A flange 11 is formed around the round mounting hole 13. The lower surface of the height stopper 8 is crushed, and the upper surface of the flange 11 is flattened. Regardless of the shape of the mounting hole 13, the flange 11 enhances the rigidity.

Subsequently, the effects of the present embodiment will be described in comparison with the comparative examples. 12 and 13 are plan views showing a method of manufacturing a power module case according to a comparative example. In the comparative example, since the mounting hole 13 was formed at the time of resin molding, the weld 5 is generated in the portion of the mounting hole 13. When tightening the screw into the mounting hole 13, a reinforcing metal bush must be press-fitted into the mounting hole 13 in order to prevent cracking from the weld 5 as a base point.

On the other hand, in the present embodiment, since the resin case 4 is molded without the mounting holes, the weld 5 is not formed at the position of the mounting holes 13. Further, the flange 11 is formed of the thermoplastic resin 3 discharged from the resin case 4 by inserting the blade 9. Since the structural rigidity of the mounting hole 13 is strengthened by the flange 11, it is possible to prevent the case from cracking. Further, since it is not necessary to press-fit the metal bush, the work man-hours and the manufacturing cost can be reduced.

Further, the flange 11 is crushed by the height stopper 8. The difference in height between the upper surface of the resin case 4 and the lower surface of the height stopper 8 is the height of the flange 11. Therefore, since the height of the flange 11 can be adjusted, the rigidity around the mounting hole 13 can be adjusted. Further, the blade 9 is a conductor of a cylindrical cylinder, and since the inside is hollow and the volume is small, the heat capacity is small and the temperature can be easily adjusted. Therefore, the manufacturing accuracy of the flange 11 is improved.

Embodiment 2.
FIG. 14 is a plan view showing a mounting hole formed by the method for manufacturing the power module case according to the second embodiment. A hexagonal marking 6 is attached to a portion where the mounting hole 13 of the resin case 4 is formed by the mold 1. Then, like the marking 6, the mounting hole 13 having a hexagonal outer shape is formed. With such a hexagonal mounting hole 13, a metal nut can be directly inserted. Other configurations and effects are the same as in the first embodiment.

Embodiment 3.
FIG. 15 is a perspective sectional view showing a mounting hole formed by the method for manufacturing a power module case according to a third embodiment. A screw groove 15 is formed in the mounting hole 13 by inserting the blade 9 of the cylindrical cylinder having a screw thread into the resin case 4 while rotating the blade 9. A metal screw thread may be attached to the blade 9 in advance before the attachment hole 13 is formed. In this case, the threads are attached to and detached from the blade 9 due to the effects of thermal expansion and cooling contraction of the blade 9. Other configurations and effects are the same as in the first embodiment.

1 mold, 3 thermoplastic resin (resin), 4 resin case, 6 marking, 8 height stopper, 9 blades, 11 flange, 13 mounting holes, 15 screw grooves

Claims (4)

The process of pouring resin into the mold to mold the resin case,
The process of heating the blade of a cylindrical cylinder protruding from the lower surface of the height stopper and inserting it into the resin case.
A step of crushing a flange formed of resin discharged from the resin case by inserting the blade with the lower surface of the height stopper.
A method for manufacturing a case for a power module, which comprises a step of hollowing out the resin case with the blade to form a mounting hole surrounded by the flange. The method for manufacturing a case for a power module according to claim 1, wherein a marking is made on a portion of the resin case where the mounting hole is formed by the mold. The method for manufacturing a case for a power module according to claim 1 or 2, wherein the mounting holes having a hexagonal outer shape are formed. The method for manufacturing a case for a power module according to claim 1 or 2, wherein a screw groove is formed in the mounting hole by inserting the blade of a cylindrical cylinder having a screw thread into the resin case while rotating the blade. ..

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