JPS61290014A - Mold for slush molding - Google Patents

Abstract

PURPOSE:To obtain a mold whose heat loss is small and heating/cooling periods are short, by making the cavity forming wall, especially the bottom surface only, elevate its temp. by means of induction heating. CONSTITUTION:A cavity forming wall 1 of a thin box type (the cross section is approx. of H type), for example, made of nickel and a coil-like shaped cupper pipe placed in the cavity below the cavity forming wall 1 heat conductivity, electrical insulating property and non-magnetic property and a lining reinforcing material 5, having poor heat conductivity and is an insulator and a non-magnetic material, are placed thereunder. A microwave generator is equipped at both ends 6, 6 of the pipe coil 4, which are, for example, connected with water pipes. It is possible thereby to inductively heat the bottom surface 5 of the cavity forming wall 1 by turning on the microwave electric current and to cool the mold by passing through water.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a slush mold.

<Prior art> Slash molding is a method of molding skin materials used for instrument panels, console boxes, headrests, etc., which are self-propelled car interior parts. Conventionally, this slush molding involves filling resin powder (usually PVC powder) into a mold cavity, placing the mold into a heating furnace, and partially fusing the resin powder to each other (sintering). After that, the unsintered resin powder is removed, reheated to form a resin film, and finally the mold is cooled by immersing it in water, etc., and the resin film is released from the mold. I was getting molded products. However, this method of using a heating furnace has problems in that the equipment requires a large area and workers are exposed to high-temperature work. Therefore, as shown in FIG. 5, there is a mold in which a heating wire 20 is embedded as a heating means, and a cooling pipe 24 through which cooling water flows is embedded as a cooling means. still,
In the figure, 21 is a cavity forming wall, 23 is a filler that has good thermal conductivity and is an insulator to prevent short circuits, 25 is a backing reinforcing material made of a heat insulating material, and 28 is a temperature sensor. Of course, in this mold, the heat of the heating wire 20 is transmitted to the bottom surface 22 of the cavity forming wall 21 via the filler 23, and the resin powder is melted. Thereafter, during cooling, the bottom surface 22 is cooled by the heat radiated from the entire mold and the cooling water flowing through the cold water pipe 24 via the filler 23, allowing the molded product to be released from the mold.

<Problems to be Solved by the Invention> According to the mold shown in FIG.
When the temperature reaches the predetermined temperature for melting the resin powder, the temperature of the entire mold (excluding the reinforcing lining portion 25) has also been raised, and in order to cool the bottom surface 22 to the desired temperature during cooling, it is necessary to The entire system will be cooled down. In other words, there were problems in that the amount of heat loss was large and the heating time and cooling time were also long.

The present invention solves such problems and provides a mold in which heating means and cooling means are embedded, and the amount of heat loss is small, that is,
The purpose is to provide a mold that requires short heating and cooling times.

Means for Solving the Problems> As a result of extensive research aimed at achieving the above object, the present inventor focused on the induction heating effect of ferromagnetic materials and invented a mold having the following configuration.

That is, at least the cavity forming wall is formed of a ferromagnetic material, and the requirements below the bottom surface of the cavity forming wall are (a) good thermal conductivity, (b) an insulator, and (c) a nonmagnetic material. It had a surface that was almost the same as the bottom surface (
This mold is equipped with a tube coil that satisfies the following requirements: i) the bottom surface can be heated by induction, and (ii) a refrigerant can flow through it.

<Example> Hereinafter, an example of a mold according to the present invention will be described based on the drawings.

Figure 1 is a cross-sectional view of the mold (cross-sectional view taken along the line A-A in Figure 2), Figure 2 is a perspective view of the mold, and Figure 3 shows the connection between the tube coil 4 and the high-frequency generator 7. FIG.

This mold has a cavity forming wall l (H-shaped cross section) made of, for example, nickel that forms a thin box-shaped cavity, and a mold as shown in Fig. 3 arranged in the lower recess of the cavity forming wall l. A coiled steel pipe (tube coil 4) is fixed with a filler material 3 (e.g., thermocement) that satisfies the requirements of (a) good thermal conductivity, (b) insulator, and (c) non-magnetic material, and The structure is such that a reinforcing backing material 5 (for example, asbestos), which is an insulating and non-magnetic material with poor thermal conductivity, is provided below these. Note that a high frequency generator 7, which is a conventional means, is disposed at both ends 6.6 of the tube coil 4, and
One end 6 is connected to, for example, a water supply (not shown);
The other end 6 serves as a drain port. Further, 8 is a temperature sensor.

In the above, the material of the cavity forming wall 1 is not particularly limited as long as it is a ferromagnetic material, but for example, in addition to the above-mentioned nickel, iron and alloys thereof can be used. Then, the cavity forming wall 1 is formed by electroforming using these materials. The bottom surface 2 of the cavity forming wall l is desirably thin due to the characteristics of induction heating (skin effect), and if necessary, pattern forming grooves (leather grain pattern, stitch pattern, etc.) are carved into the bottom surface 5. Ru. Further, although a cavity forming wall l having an H-shaped cross section is illustrated, the portion forming the lower recess does not need to be formed integrally, and may of course be formed from a separate member.

Further, the tube coil 4 is electrically conductive and can heat the bottom surface 5 of the cavity forming wall 1 by induction through the high frequency current generated by the high frequency generating bag N7. The tube coil 4 is preferably made of copper because it does not generate heat when an electric current is passed therethrough and from the viewpoint of material cost.

The need for the filler 3 to satisfy the requirements (a), (b), and (c) is as follows. (a) Good thermal conductivity; when cooling the mold, filler 3
If the thermal conductivity of the tube coil 4 is poor, the effect of the refrigerant flowing through the tube coil 4 will not be exhibited.

(b) Insulator; prevents short circuit between the tube coil 4 and the cavity forming wall 1.

(c) Non-magnetic material: If it is assumed that the filler material 3 is a magnetic material, the filler material 3 will be inductively heated by the high frequency, resulting in a loss of energy and time during heating.

Also, from the viewpoint of the skin effect of induction heating, it is undesirable that it takes a long time for the bottom surface 2 of the cavity forming wall 1 to reach a predetermined temperature.

Further, it is desirable that the thickness of the filler 3 is such that the magnetic flux generated by the tube coil 4 is applied to the bottom surface 2 on average.As such a filler 3, in addition to the above-mentioned thermocement, ceramics are exemplified. be able to.

In addition, the reason why the backing reinforcing material 5 is made of an insulating material and a non-magnetic material is for the same reason as mentioned above, and the reason why it is made of a heat insulating material is to prevent wasteful radiation of heat and cooling and ensure ease of work. . In addition to the above-mentioned asbestos, examples of materials for the backing reinforcing material 5 include glass wool, general ceramics, and the like.

Next, an example of slush molding using the above mold will be shown (A-I in FIG. 4).

(i; A in Figure 4) Tube carp jlz 4 27 KHz (1~5 K
W ) (7) High frequency current is applied to the cavity forming wall 1
The bottom surface 2 of the is heated by induction to around 240°C, and resin powder 9 (manufactured by Sumitomo Chemical Co., Ltd., trade name Sumiritz FLX) is added (ii; B in Figure 4). After 4 to 5 seconds, the bottom surface 2 is heated. The resin powder 9 in the vicinity is partially fused to form a semi-sintered resin film 10 (film thickness 0°3 to 0.4 mm), and the unsintered resin powder 9
remove.

(iii: C in Fig. 4) Subsequently, the bottom surface 2 is set to 200 to 240°C, and the temperature is set to 0.5 to 1.
When the temperature is maintained for 5 minutes, the resin film 1O, which was in a semi-sintered state, is completely melted, and a uniform resin film 11 is formed.

(ii: D in Figure 4) The high frequency current applied to the tube coil 4 is stopped, and then tap water is passed through the tube coil 4. After 1 to 1.5 minutes, the bottom surface 2 and the resin film 11 are cooled. It becomes possible to release the mold.

It is of course possible to use plastisol such as bisol chloride instead of the resin powder 9 as the raw material.

In addition, in Table 1, this mold and the conventional example (heating furnace method)
Compare the heating time and cooling time of the bottom surface 2. still,
The mold of the conventional example is made entirely of nickel and is the same as the present mold, and the heating furnace temperature is 350°C.

Table 1 <Effects of the Invention> As explained above, the mold of the present invention makes it possible to raise the temperature of only the cavity forming wall, especially the bottom surface, by utilizing induction heating in slush molding. Therefore, compared to the conventional example, the energy and time required to raise the temperature of the bottom surface of the cavity forming wall to a predetermined temperature are significantly reduced.

Similarly, during cooling, the cooling time is shortened because there are few parts that remain heated. Furthermore, in this mold, the tube coil serves both as a heating means and a cooling means for the mold, so the number of parts is reduced compared to the mold shown in Fig. 5, and the tube coil can be wound more uniformly and densely. Therefore, the temperature distribution on the bottom surface of the cavity can be made more uniform than before.

[Brief explanation of the drawing]

1 to 4 show a mold according to an embodiment of the present invention, FIG. 1 is a cross-sectional view of the mold (cross-sectional view taken along the line A-A in FIG. 2), and FIG. 2 is a perspective view of the mold. , FIG. 3 is a schematic explanatory diagram showing the connection between the tube coil 4 and the high-frequency generator 7, and FIG. A is the state in which resin powder has been added, B in Figure 4
C in FIG. 4 shows a state in which a semi-sintered resin film 10 is formed; C in FIG. 4 shows a state in which a completely sintered resin film 11 is formed;
D in the figure shows a state in which the resin film 11 is released from the mold after cooling the mold. FIG. 5 is a cross-sectional view of a conventional example. l...Cavity forming wall, 2...Bottom surface 3...Filling material, 4...Tube coil. Patent application Toyoda Gosei Co., Ltd. 1 Figure 3

Claims (1)

[Claims] In a slush molding die, at least the cavity forming wall is made of a ferromagnetic material, and below the bottom surface of the cavity forming wall, the following requirements are met: (a) good thermal conductivity; b) an insulator; (c) a non-magnetic material; and the following requirements: (i) induction heating of the bottom surface is possible; (ii) A mold for slush molding, characterized in that it is equipped with a tube coil that is capable of circulating a refrigerant.