JPH07108540B2 - Method for manufacturing resin molded products - Google Patents

Abstract

PURPOSE:To prevent the inflow of the resin of a skin layer onto the rear of a core body and the deformation of the core body by mounting the core body, from an outer circumferential section of which a holding piece protrudes, to the cavity of split molds, holding the holding piece by the periphery of the cavity and injecting a resin to the surface side of the core body when the skin layer is formed to the core body made of the resin by the resin. CONSTITUTION:When a cover body covering the air bag of an automobile is manufactured, a core body 32 made of a rigid resin is molded first. A core body 31 has a plate section 31 and a leg section 30. A side face section 41 is formed to the peripheral section of the plate section 31, and a holding piece having an L-shaped cross section protrudes from the lower side of the outer circumferential section of the side face section 41. When the core body 32 is installed and a mold 45 is clamped, a cavity 51 is formed on the surface side of the core body 32 while the holding piece 43 is fast stuck to and held by a parting surface 54. A resin is injected into the cavity 51 and a skin layer 33 is formed, the mold is released, and the holding piece 43 is cut and removed. Accordingly, the resin shaping the skin layer 33 does not intrude to the rear of the core body 32, and the deformation of the core body 32 is also prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a two-layer molded resin molded product in which a skin layer is formed on the surface of a core.

[0002]

2. Description of the Related Art For example, in an automobile, an airbag that protects an occupant from a collision is normally stored in a folded state in a boss portion of a steering wheel and covered with a synthetic resin cover. ing. Then, this airbag expands and inflates due to the inflow of gas in the event of a collision, and the cover body is broken by the pressure of this inflation,
It is designed to project toward the occupant.

In order to further improve the safety and the appearance and feel of the cover body for covering such an air bag, for example, JP-A-63-199 is used.
As shown in Japanese Patent Publication No. 149, a double-layer molded resin molded product is used in which a skin layer made of a soft synthetic resin is formed in close contact with the surface of a core made of a hard synthetic resin.

In the conventional method for producing a two-layer-molded resin molded product, after molding the core, the core is once removed from the mold, and the core is newly re-molded for forming the skin layer. It is mounted on a mold, clamped, and a synthetic resin is injected into the cavity to form a skin layer on the surface of this core body by contact molding. There is known a method of so-called two-color molding (double injection), in which only the mold is replaced with a mold for molding a skin layer, the mold is clamped, and a synthetic resin is injected into the cavity to mold the skin layer.

[0005]

However, the above-mentioned conventional methods of double injection and insert molding have a problem that the core body is apt to be deformed by heat and pressure during the molding of the skin layer and the appearance is impaired. is doing. In order to prevent this, it is necessary to give sufficient strength to the core body, so it is necessary to mold the core body to a thick wall, and there are problems such as an increase in weight and an increase in cost. Furthermore, if deformation occurs due to heat or pressure during molding of the skin layer, a gap may be created between the mold and the core, or the shape of the core after shrinkage due to insert molding may change depending on the individual core. Therefore, these cores may not be completely adhered to the mold for forming the skin layer, and an unnecessary gap is generated between the mold and the core, whereby the resin forming the skin layer is not formed. Since it flows into the back side of the core, there is a problem that the quality is deteriorated, the yield is poor, and the productivity is low.

The present invention has been made in view of the above circumstances, and in a method for producing a two-layer molded resin molded article in which a skin layer is formed on the surface of a core body, the resin forming the skin layer is a core body. It is an object of the present invention to provide a method for producing a resin molded product, which can prevent the resin molded product from flowing into the back surface side of the resin and also can improve the appearance of the resin molded product, and can obtain a high quality molded product.

[0007]

According to the method of manufacturing a resin molded product of the present invention, a resin molded product 5 of two-layer molding in which a skin layer 33 is formed of resin on the surface of a core body 32 formed of resin. In the manufacturing method, the core body 32 is provided with a holding piece 43 projecting from the outer peripheral portion thereof, and the core body 32 is attached to the cavities 51 of the split molds 46 and 48 for molding the skin layer 33. In a state where the split molds 46 and 48 are clamped and the holding piece 43 is closely held in the peripheral portion of the cavity 51, a resin is injected into the surface side of the core body 32 in the cavity 51 to form the skin layer. To form 33.

[0008]

According to the method for manufacturing a resin molded product of the present invention, the holding piece 43 is provided on the outer peripheral portion of the core body 32, and the holding piece 43 is used for the split molds 46, 48.
In order to form a skin layer 33 in the cavity 51 by injecting a resin in a state where the resin is in close contact with the periphery of the cavity 51, the resin forming the skin layer 33 injected into the cavity 51 is the core 32. The back surface side is prevented from entering, and the skin layer 33 is formed only on the front surface side of the core body 32. Further, since the sandwiching pieces 43 of the core body 32 are clamped and held by the split molds 46 and 48 when the skin layer 33 is formed, the core body 32 is not deformed by the pressure or heat of the resin forming the skin layer 33. To be prevented.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of an embodiment of the method for producing a resin molded product of the present invention will be described below with reference to the drawings.

In this embodiment, as a resin molded product, a method of manufacturing a cover body for covering an automobile airbag will be described.

In FIG. 2, reference numeral 1 is a steering wheel body of an automobile, and this steering wheel body 1 is
The central boss portion 2 and the annular rim portion 3 are connected by a plurality of spoke portions 4, and the upper portion of the boss portion 2 is covered with a cover body 5 as a resin molded product.

Further, as shown in FIG.
Has a tubular metal boss 11 which is fitted and fixed to a steering shaft of an automobile (not shown), and a metal boss plate 12 is fixed to the upper portion of the metal boss 11 by welding or the like.

Numeral 15 is an air bag device, which has a substantially box-shaped base plate 16 having an opening at the bottom, and the base plate 16 is fixed to the boss plate 12 through a mounting means (not shown). By doing so, it is attached to the upper part of the boss plate 12. Then, a substantially circular opening 17 is formed at a substantially central portion of the base plate 16, and a substantially cylindrical gas generator 18 for ejecting gas upward is attached to the opening 17, and A circular opening 22 of the folded airbag 21 is fixed to a peripheral portion of the opening 17 on the upper surface of the base plate 16 by a fixing plate 23 or the like.

Further, the side surface portion of the base plate 16 described above.
A leg portion 30 protruding from the back surface side of the cover body 5 is fixed to the cover 24 by a rivet 25 or the like.

The cover body 5 is the above-mentioned base plate.
A plurality of plate-like leg portions 30 formed so as to surround the side surface portion 16 of 16 and a flat plate portion 31 that covers the upper portion of the boss portion 2 are integrally molded with a hard synthetic resin to form a core body 32. Further, on the surface of the flat plate portion 31, a skin layer 33 made of a soft synthetic resin such as foamed thermoplastic polyurethane elastomer is adhered and formed. Further, each leg 30 is formed with a through hole 34 through which the rivet 25 is inserted.

Further, on the back surface side of the flat plate portion 31, a thin-walled portion 35 recessed in a substantially U-shaped section or a substantially V-shaped section is provided.
However, it has a substantially H shape and is formed in the left-right direction passing through the central portion of the flat plate portion 31 and in the front-back direction passing both side portions of the flat plate portion 31.

With such a structure, in the event of a vehicle collision, a shock sensor (not shown) is activated to rapidly release gas from the gas generator 18 to the inside of the airbag 21. The gas causes the airbag 21 to inflate rapidly. During the inflation, the airbag 21 breaks the thin portion 35 of the cover body 5 by the inflation pressure to open the cover body 5 into a door shape, and the airbag 21 projects from the cover body 5 to the driver. Expand towards. And
The inflated airbag 21 prevents the driver from colliding with the steering wheel 1 and the front glass, and absorbs the impact at the time of the collision.

Next, a method of manufacturing the cover body 5 will be described with reference to the drawings.

First, a core body 32 made of a hard synthetic resin as shown in FIG. 4 is formed by injection molding or the like. This core 32
Is the boss portion 2 of the steering wheel 1 as described above.
A flat plate portion 31 that covers the flat plate portion 31 and each leg portion 30 that projects substantially vertically from the back surface side of the flat plate portion 31 are integrally formed, and the back surface side of the flat plate portion 31 has a substantially cross-sectional shape. A thin portion 35 that is recessed in a U shape is formed in a substantially H shape.

The peripheral portion of the flat plate portion 31 is bent toward the rear surface to form a side surface portion 41 so as to cover the side surface portion of the boss portion 2 except for the portion connected to the spoke portion 4. Further, the outer peripheral portion of the side surface portion 41 is thinly provided so as to project downward and is bent outward, so that a holding piece 43 having a substantially L-shaped cross section is formed.

Then, the core body 32 is mounted on a mold 45 for molding the skin layer 33 as shown in FIG. This mold 45
Is a lower mold 46 as a split mold for fixing the back side of the core 32.
And an upper die 48 as a split die having a cavity surface 47. Also, attach the core body 32 to this mold 45,
With the lower mold 46 and the upper mold 48 mated and clamped, the core 32
Between the surface side of the upper surface of the mold and the cavity surface 47 of the upper mold 48.
A cavity 51 that forms 33 is formed, and the holding piece 43 of the core 32 is closely held by the parting surface 54 of the lower mold 46 and the upper mold 48 at the peripheral edge of the cavity 51. . Further, in order to enhance the adhesion, a recess 55 matching the shape of the holding piece 43 is formed on the parting surface 54 of the lower mold 46.

Then, with the mold clamped as described above, a synthetic resin liquid such as polyurethane is injected into the cavity 51, and the skin layer 33 is injection-molded on the surface of the core body 32.

The skin layer 33 can also be formed by reaction injection molding, that is, RIM (Reaction Injection Molding) molding in which, for example, isocyanate, polyol and catalyst in polyurethane are mixed and injected immediately before molding.

After forming the skin layer 33, the mold is opened to take out the cover body 5, and the holding piece having a substantially L-shaped cross section is further provided.
43 is removed by cutting with a hot blade or a press blade, and the cover body 5 of two-layer molding is completed.

When the holding piece 43 is removed, the holding piece 43 is removed.
It is also possible to simultaneously remove the surplus portion such as a molding gate, an in-mold coat, and a urethane overflow, which are not shown and which are in close contact with.

Thus, according to the method for manufacturing a resin molded product of the present embodiment, the parting surface 54 at the peripheral edge of the cavity 51 between the lower mold 46 and the upper mold 48 during injection molding of the skin layer 33. The gripping piece 43 formed on the core body 32 is firmly held by the skin layer.
The resin forming 33 is prevented from entering the back surface side of the core body 32, particularly the thin portion 35, and the skin layer 33 is formed only on the front surface side of the core body 32.
Can be formed. Therefore, the quality can be improved and the cost can be reduced, and the weight of the cover body 5 can be reduced.
It is possible to simplify the mounting structure, further improve the deployment performance of the airbag 21, and stabilize the airbag.

Further, at the time of injection molding of the skin layer 33, the lower mold 46
Since the sandwiching piece 43 of the core body 32 is sandwiched and held by the upper mold 48 and the upper die 48, it is possible to prevent the core body 32 from being deformed due to pressure or heat of the resin forming the skin layer 33, such as waviness. The thickness can be made uniform. Further, for this reason, the core 32 can be thinned.

In this embodiment, a pair of lower molds
The mold 45 was formed by 46 and the upper mold 48.
As shown in, the parting surface of the lower mold 46 and the upper mold 48
It is also possible to combine a plurality of slide pieces 58 that move laterally with 54. Since this slide piece 58 adheres to the upper surface of the sandwiching piece 43 and the end of the skin layer 33 in a clamped state, even if the skin layer 33 is formed to be thick, the slide piece 58 retains the adhesion to the sandwiching piece 43. It is possible to prevent the synthetic resin liquid from flowing out, and improve the releasability between the cover body 5 and the mold 45.

Further, as shown in FIG. 7, when the piece 59 made of an elastic material such as silicon is attached to the close contact portion of the upper die 48 with the holding piece 43, the piece 59 is elastically deformed. As a result, the adhesion to the holding piece 43 can be improved, and the releasability between the cover body 5 and the mold 45 can be improved.

The holding piece 43 can also be formed on the flat plate portion 31 of the core body 32.

[0031]

According to the method for producing a resin molded product of the present invention, a holding piece is provided so as to project from the outer peripheral portion of the core body, and the holding piece is held in close contact with the periphery of the cavity of the mold. Since the skin layer is formed by injection into the cavity, the resin forming the skin layer injected into the cavity is prevented from entering the back surface side of the core body, and the skin layer is formed only on the front surface side of the core body. You can Therefore, it is possible to reduce the cost, reduce the weight of the resin molded product, and improve the quality. Further, when the skin layer is molded, the holding piece of the core body is held by being held by the mold, so that the core body can be prevented from being deformed due to the pressure or heat of the resin forming the skin layer, and the uniform thickness can be obtained. You can

[Brief description of drawings]

FIG. 1 is a work process diagram showing an embodiment of a method for producing a resin molded product of the present invention.

FIG. 2 is a plan view of a steering wheel according to an embodiment of the same method for manufacturing a resin molded product.

3 is a cross-sectional view of the steering wheel of FIG. 2 taken along line AA of FIG.

FIG. 4 is a perspective view of the back surface in the manufacturing process of the same core body.

FIG. 5 is a work process diagram showing another embodiment of the method for producing a resin molded product of the present invention.

FIG. 6 is a work process diagram of the above.

FIG. 7 is a working process diagram according to another embodiment of the method for producing a resin molded product of the present invention.

[Explanation of symbols]

 5 Cover body as resin molding 32 Core body 33 Skin layer 43 Holding piece 46 Lower mold as split mold 48 Upper mold as split mold 51 Cavity

Claims (1)

[Claims] 1. A method for producing a two-layer molded resin molded product, wherein a skin layer is formed of a resin on the surface of a core body made of a resin. The core body is mounted in the cavity of the split mold for forming the skin layer, the split molds are clamped, and the sandwiching piece is closely held at the peripheral portion of the cavity. A method for producing a resin molded article, characterized in that a resin is injected into a surface side of the core body in a cavity to form the skin layer.