JPH0582807B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a skin forming method selected from pressure forming, blow molding, and vacuum forming. The present invention relates to a method for molding automotive interior parts such as console box slids, grab box slids, crash pads, armrests, headrests, and door trims, and skin materials for furniture and the like.

(Prior Art) In recent years, as the external shapes of automobile interior parts and other molded products have become more complex and diversified, demand for skin materials having strong undercut portions has increased in the industry.

By the way, vacuum forming, pressure forming, blow molding, etc. are widely used for the above-mentioned automotive interior parts and other skins due to the requirement of mass productivity. When molded using conventional vacuum forming, etc., the undercut part is strongly stretched, the thickness of this part becomes particularly thin compared to other parts, and sometimes that part breaks, making it impossible to actually mold it. It often ends.

Therefore, as a method for forming a skin having a strong underside that is difficult to achieve with normal draping molding, a method for forming the base material of Doortom as disclosed in Japanese Patent Application Laid-Open No. 56-93511 was applied. do,
Attempts have been made to mold the main part by sandwiching a sheet between an upper mold and a lower mold, and to mold the undercut part by folding it using a separate auxiliary mold, or to mold it by slush molding.

(Problems to be Solved by the Invention) However, among the methods described above, the method using an auxiliary mold requires precisely manufactured upper molds, lower molds, and auxiliary molds, and it takes a considerable amount of time to manufacture these molds. The disadvantage is that it takes time and money, and when the undercut part is formed by draping, such as vacuum forming, there is a disadvantage that the slush material becomes clogged and the thickness becomes too thick, for example. When performing integral foam molding using the skin, problems arise such as the inability to insert inserts.

The present invention focuses on the above-mentioned drawbacks of the prior art, and aims to provide a skin molding method that does not require a large number of molds and can mold skin materials with small variations in skin pressure. .

(Means for Solving the Problem) Therefore, the feature of the present invention for solving the above-mentioned problem is that in a skin forming method selected from pressure forming, blow molding, and vacuum forming, the undercut portion of the mold is A heat-softened thermoplastic resin sheet is applied by moving at least a portion of the mold in a vertical direction from the normal molding position to cover the mold with at least a portion of the undercut portion separated. Then, after sealing the ends of the thermoplastic resin sheet, the undercut portion of the mold is moved to a regular position in the mold as molding progresses.

(Example) Hereinafter, specific examples of the present invention will be described with further reference to the accompanying drawings.

Figures 1 to 3 are cross-sectional views of a pressure molding die in various states when the method of the present invention is applied to pressure molding, and Figures 4 and 5 show the method of the present invention for forming a skin material having cloth on the surface. FIG. 3 is a cross-sectional view of a mold showing a molding process when applied to.

Moreover, FIGS. 6 to 8 are cross-sectional views of the vacuum forming mold in various states when the method of the present invention is applied to vacuum forming, and FIG. 9 is a modified example of the undercut portion of the mold in the method of the present invention. .

In each of the above figures, numeral 1 in Fig. 1 is an air pressure mold to which the skin mold of the present invention is applied. It consists of an upper mold 5 having a wall-like protrusion 4 that presses the sheet 3 while maintaining airtightness, and a lower mold 7 having a molding surface 6, and the end 13 of the molding surface 6 of the lower mold 7 extends all around The end portion 13 has an undercut portion 9 and has an undercut portion 9.
is manufactured separately from the other molding surface 6, and has a rod 10 integrally molded on its lower surface.
is inserted into a hole 11 provided in the lower mold 7, and the bottom surface of the rod 10 is pressed upward by a spring 12 inserted into the hole 11.

Further, the molding surface 6 and undercut portion 9 of the lower die 7 are provided with a large number of small holes 8 for air venting.

Below, based on the above-mentioned mold, the operation of each part and the skin molding method will be explained according to the molding process.
First, when the end 13 of the lower mold 7 is moved vertically from its normal position relative to the mold, that is, as shown in FIG. 1, the spring 12 is stretched.
The rod 10 is in a state protruding from the hole 11 of the lower mold 7.

Then, heat softened PVC resin (polyvinyl chloride), ABS resin, a mixture of PVC resin and ABS resin, PVC resin and foamed PVC, ABS resin and foamed
Thermoplastic resin single sheets or composite sheets made of PP, ABS resin and foamed PE, etc., or composite sheets of these sheets and stretchable fabrics such as tricot, jersey, etc., or fabrics with flocking on the surface of the fabric. A thermoplastic resin sheet 3 is tightly tightened from above the lower die 7 to cover the end portion 13 having the molding portion 6 and the undercut portion 9 without any gaps so as to prevent air leakage.

Then, the upper mold 5 is placed on the thermoplastic sheet 3, and the thermoplastic resin sheet 3 is sandwiched between the end 13 of the lower mold 7 and the protrusion 4 of the upper mold 5 so as to prevent air leakage.

Thereafter, compressed air is injected from the injection port 2, and the upper mold 5 is gradually pressed against the end 13 of the lower mold 7.
is brought closer to the proper position of the lower mold 7.

By doing the above, the heat-softened thermoplastic resin sheet 3 is expanded by the compressed air injected from the injection port 2, and is pressed against the molding surface 6 of the lower mold 7, and the molding surface excluding the undercut portion 9 is 6, the thermoplastic resin sheet 3 is molded. (See Figure 2) At this time, the air existing between the thermoplastic resin sheet 3 and the molding surface 6 of the lower mold 7 is released by compressed air through the small air vent holes 8 provided in the molding surface of the lower mold 7. When the upper mold 5 is sequentially pressed while pouring and the end 13 of the lower mold 7 is placed in the proper position of the lower mold 7, the thermoplastic resin sheet 3 further expands, and the details of the molded part 6 of the lower mold 7 are , the undercut portion 9 of the end portion 13 of the lower mold 7 is tightly adhered to the undercut portion 9, but at this time, regarding the undercut portion 9, the thermoplastic resin sheet 3 is more tightly attached to the lower mold 7 than in conventional pressure molding. amount of movement,
That is, since the thermoplastic resin sheet 3 is supplied as long as the length a in FIG. 2, the thermoplastic resin sheet 3 is tightly attached and molded to the undercut portion 9 without being forcibly stretched and locally thinned.

Also, as the molding progresses, the end portion 1 of the lower mold 7
3 is moved to the proper position of the lower die 7, and as the molding progresses, the thermoplastic resin sheet 3 is sequentially delivered to the molding surface 6 and the undercut portion 9, so that no wrinkles are formed on the skin.

In addition, in the above operation, the means for pressing down the end portion 13 of the mold 7 having the undercut portion 9 is as follows.
There are no particular limitations, and when molding small skin materials, such as the lids of console boxes or club boxes, it is possible to press down from above using human force.
Usually, a means such as a cylinder is used to apply force from above the upper mold or directly to the end 13 of the lower mold.

The skin molding method of the present invention can mold a thermoplastic resin sheet without forcibly stretching it locally or causing wrinkles as described above, so that It is also possible to directly utilize a thermoplastic resin sheet having a fabric on the surface for molding.

FIGS. 4 and 5 show other embodiments of molding a skin material having a fabric on the surface by applying the skin molding method of the present invention, and show a lower mold having the same function as the lower mold 7 of FIG. 1. 14, and a cutout surface 16 that abuts the end 15 of the lower mold 14 over the entire circumference, has a downwardly convex cross-sectional shape, and has an air injection tube 17 in the center with an acute angle at the tip. Between the upper and lower molds 14 and 18 of the air-pressure forming mold 19 consisting of an upper mold 18 having A cloth 20 coated with an adhesive such as an acrylic adhesive or an emulsion of a vinyl acetate co-acrylate ester on the side surface, and a PVC resin or other resin similar to the thermoplastic resin sheet 3 shown in FIG. A thermoplastic resin sheet 21 that has been heat-softened and extruded into a parison shape is placed between a lower mold 14, a cloth 20, and a cloth 20 as shown in FIG.
Layer the thermoplastic resin sheet 21 and the upper mold 18 in this order,
This is a molding method in which compressed air is injected from the air injection pipe 17 while pushing down the upper mold 18. This molding method is
By pressing the upper mold 18 against the lower mold 14, the air injection tube 17 of the upper mold 18 breaks through the upper side of the parison-shaped thermoplastic resin sheet 21, enters into the bag-shaped thermoplastic resin sheet 21, and fills the bag-shaped thermoplastic resin sheet 21. Compressed air is injected into the thermoplastic resin sheet 21 to expand the thermoplastic resin sheet 21 into a balloon shape, and the cloth 20 is pressed together with the lower side of the thermoplastic resin sheet 21 against the molding surface of the lower mold 14, forming the mold and as shown in FIG. Although not shown, the undercut portion is also brought into close contact over its entire surface, and the cloth 20 and thermoplastic resin sheet 21 are bonded together.

Compared to the above method, this method can easily prevent air leakage between the thermoplastic resin sheet 21 and the upper mold 18, and allows the thermoplastic resin sheet 21 and cloth 20 to be strongly pressed against the molding surface of the lower mold 14. There are advantages that can be achieved.

Next, a case where the skin forming method of the present invention is applied to vacuum forming will be explained.

6 and 7 show a vacuum forming mold, and 22 in the figure indicates the same mold, and there are many air outlet ports 23 at the molding surface 34 and at the corners of the undercut portion 27 of the end portion 26.
35, the air outlet 23 of the molding surface 34 opens into a vacuum chamber 24 provided on the back surface of the molding surface 34, and
The air outlet 35 of the undercut portion 27 opens at the lower surface of the end portion 26 and opens into the vacuum chamber 24 through a hole 37 provided in the body of the mold 22 .

The vacuum chamber 24 has an air delivery pipe 25 at the center of the surface opposite to the molding surface 34, and the air delivery pipe 25 is connected to a vacuum source such as an external vacuum pump.
(Not shown) Also, the end portion 26 of the molding surface 34 forms an undercut portion 27 over the entire circumference, similar to the air pressure molding die 1 shown in FIG. A rod 28 of a cylinder 29, which is manufactured separately from the other molding surface 34 and placed outside the mold 22, passes through the vacuum chamber 24 of the mold 22 and is connected to the bottom of the end 26.

Therefore, between the end portion 26 of the mold 22 and the main body portion 30, there is provided a sheet 31 having elasticity such as rubber.
A seal is applied to prevent air from leaking.
On the end 26 of the mold 22, there is a mechanism (not shown) that presses against the end 26 of the mold 22 using a spring or the like.
There is a clamp 32 having a
It moves together with the end 26 of the mold 22.

The operation and usage of each part of the vacuum forming mold 22 will be explained step by step in the following.

Initially, the end portion 26 of the mold 22 is moved vertically from its normal position with respect to the mold 22,
That is, as shown in FIG. 6, the rod 28 of the cylinder 29 is extended and the rod 28 protrudes from the mold 22.

Then, a thermoplastic resin sheet 33 similar to the thermoplastic resin sheet of the previous embodiment is covered over the end 26, and tightly attached to the end 26 with a clamp 32 to prevent air leakage.

Then, while reducing the pressure in the vacuum chamber 24 of the vacuum mold 22 and sucking the thermoplastic resin sheet 33 onto the molding surface 34 of the mold 22, the rod 28 of the cylinder 29 is
is shortened to bring the end 26 of the vacuum forming mold 22 closer to its normal position.

By doing this, the thermoplastic resin sheet 33
are formed sequentially from the center of the molding surface 34 of the mold 22, and the undercut portion 27 is formed by fitting the main body 30 of the mold 22 and the end 26 as shown in FIG. and the hole 37 of the main body match,
The air inside can be more strongly exhausted from the air outlet at the end 26, and the air can be sucked and molded.

In the above embodiments according to the method of the present invention, the case where the undercut portion moves perpendicularly to the mold has been described, but the present invention is not particularly limited to this, and when the amount of undercut is large. In some cases, it may be appropriate to move diagonally as shown in FIG. 9, and such an application is also possible.

In addition, in FIG. 9, the same reference numerals as in each of the above figures indicate the same parts.

(Effects of the Invention) As explained above, the present invention utilizes a mold having the function of moving the undercut portion of the molding part from the regular position of the mold in at least the vertical direction with respect to the mold, and During the process, the undercut part is gradually brought closer to the normal position of the mold, and the undercut part of the mold, where the thermoplastic resin sheet is normally stretched strongly, is placed in the undercut part of the mold during molding. Because of this effect, the part is less likely to be strongly stretched and thinned as in the past, and it is possible to form a skin material with small variations in overall thickness and excellent strength. Since the partial elongation of the sheet is small, the patterns such as grains and stripes on the raw material sheet do not lose their shape, and since the thermoplastic resin sheet is fed gradually, wrinkles do not occur on the skin material, resulting in a good external shape. This has the effect of being able to mold the skin material.

Furthermore, due to these effects, the present invention makes it easy to use a thermoplastic resin sheet laminated with cloth, etc., which was difficult to do in the past, and basically, as a whole,
Since it is draping molding, there is no disadvantage that the inner thickness is too thick, which is common with slush molding.
It has a remarkable effect with good molding efficiency.

Further, the present invention does not require large equipment or a large number of precision molds from the above-mentioned method, and the cost required for equipment etc. can be kept low, and has great industrial merits.

[Brief explanation of the drawing]

Figure 1 is a sectional view of the air pressure mold when the method of the present invention is applied to air pressure forming, and Figures 2 and 3 are partial sectional views of the air pressure mold of Figure 1 during the skin forming process. , 4 and 5 are partial cross-sectional views of a skin molding die showing the molding process when the skin molding method of the present invention is applied to molding a skin material having cloth on the surface. In addition, Fig. 6 is a cross-sectional view of a vacuum forming mold when the molding method of the present invention is applied to vacuum forming, and Figs. 7 and 8 are
The figure shows a part of the sectional view of FIG. 6 during the skin molding process, and FIG. 9 shows a modified example of the undercut portion of the mold. 1, 14, 22... Molding die, 3, 21, 33... Thermoplastic resin sheet, 9, 27... Undercut portion.

Claims (1)

[Claims] 1. In a method of forming a skin by a molding method selected from pressure forming, blow molding, and vacuum forming using a mold having an undercut part, at least a part of the undercut part of the mold is pressed against another molding surface. , is formed into a separate body that can be moved apart, and the undercut part of the separate body is moved away from the normal molding position in the vertical direction with respect to the other molding surface of the mold, so that the separate undercut part is separated. A heat-softened thermoplastic resin sheet is applied to the existing mold so as to cover the entire molding surface, and after sealing and fixing the edges, as molding progresses, the separate undercut portion of the mold is A skin molding method characterized by moving the material to the proper position of the mold.