JPH09169041A - Rim molding apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the cavity inferiority of an RIM molded product caused by residual air by preventing air from remaining in a mold in RIM molding performed under reduced pressure. SOLUTION: The positioning guide mechanism 50 of a fixed mold 2 and a movable mold 3 consists of a guide pin 51 and a guide bush 52 and, at a time of mold clamping, a space part is formed in the guide bush 52 under the lower end surface of the guide pin 51. Air remains in the space part at a time of the reduction of pressure and there is possibility such that air is gradually leaked to the cavity 4 through the gap between the guide pin 51 and the guide bush 52 and PL surfaces 2a, 3a. Then, the communication passage 54 opened to a vacuum chamber K is formed to the lower part of the guide bush 52 and the interior of the movable mold 3 and the space part is allowed to communicate with the vacuum chamber by the communication passage 54. A gap part where air remains in a film form is filled with a seal material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an RIM molding apparatus, for example, a polyurethane foam such as a steering wheel, a steering wheel pad, an instrument panel, a lid for a console box or a glove box, a headrest, an armrest, an air spoiler for an automobile. It is particularly suitable for RIM molding (reaction injection molding) of integral skin foam.

[0002]

2. Description of the Related Art Integral skin foam (hereinafter referred to as ISF) made of semi-rigid polyurethane having a low-foaming self-skin layer and a high-foaming core portion is RIM-molded.
Freon has been used as a foaming agent for many years, but its use is being prohibited due to problems such as ozone layer depletion.
Therefore, the applicant of the present application previously proposed a new ISF RIM molding method in which a polyurethane material to which a foaming agent is not substantially added is foamed in a cavity of a depressurized mold. An apparatus including a mold having a vent portion, a decompression chamber communicating with the cavity through the vent portion, and a vacuum pump for decompressing the cavity through the decompression chamber has been proposed (JP-A-6-71769). . According to this RIM molding method and molding apparatus, an ISF having a better appearance, feel, and physical properties than when CFCs are used without using CFCs.
The product could be RIM molded.

[0003]

However, when a large number of RIM moldings are carried out using the above-mentioned molding apparatus, IS rarely occurs.
Poor cavities sometimes appeared in the self-skin layer of the F product. As a result of the inventors pursuing the cause, when decompressing the cavity of the mold through the decompression chamber, there is a part where air does not escape to the decompression chamber and remains in a part of the mold other than the cavity. It was found that when the residual air leaked into the cavity leaked into the cavity, the polyurethane material engulfed this air and caused a cavity defect.

An object of the present invention is to solve the above problems and to prevent air from remaining in a mold in RIM molding performed under reduced pressure, and to prevent cavity defects in RIM molded products due to residual air. To provide a device.

[0005]

To achieve the above object, in the invention of claim 1, a mold having a cavity and a vent portion, a decompression chamber communicating with the cavity through the vent portion, and the decompression chamber. In a RIM molding apparatus provided with a decompression device for decompressing the cavity via the air, when the cavity is decompressed through the decompression chamber, the air remains as a part of the mold and the air is It is characterized in that a space portion that can leak into the cavity is communicated with the decompression chamber through a communication passage.

According to the second aspect of the invention, the mold has a cavity and a vent portion, a decompression chamber communicating with the cavity through the vent portion, and a decompression device for decompressing the cavity through the decompression chamber. In the RIM molding device,
When the cavity is decompressed through the decompression chamber, a part of the mold, in which air remains in a film shape and a gap in which the air can leak into the cavity, is filled with a sealing material. I am trying. The sealing material preferably has fluidity when filling at least the gap,
After being filled, it may be fluid, soft, or hard.

Here, examples of the vent portion include a vent hole provided at the final filling position of the mold, a gap (air vent land) generated between the PL surfaces of the mold, and the like.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments in which the present invention is applied to a RIM molding apparatus for ISF coating of a steering wheel will be described below with reference to the drawings. As shown in FIGS. 1 to 3, the present RIM molding apparatus includes a molding die 1 composed of two split dies, a vacuum box 11 in which the molding die 1 can be arranged, and a vacuum box 11 It comprises a vacuum pump 20 as a decompression device for decompressing the inside, and a material injection mechanism 21 attached to the vacuum box 11 and capable of injecting a polyurethane material into the cavity 4 of the molding die 1. The core metal 42 of the steering wheel 41 used in the present embodiment includes a ring portion, a spoke portion, and a central boss portion, and an ISF coating 43 is formed on the entire ring portion and a part of the spoke portion. You.

The molding die 1 is composed of two divided dies, an upper fixed die 2 and a lower movable die 3, and both dies 2 and 3 are accurately positioned and closed. The positioning guide mechanism 50 is provided. Positioning guide mechanism 50
Will be described later. Forming grooves 4a having a substantially U-shaped cross section that form a substantially ring-shaped cavity 4 when the molds are closed are formed on the PL surfaces (mold splitting surfaces) 2a, 3a that are opposed to each other. More specifically, as shown in FIG. 6, the molding groove 4a is formed in an electroformed shell 60 having a substantially U-shaped cross section, which is formed by nickel electroforming, and the electroformed shell 60 is made of aluminum molds 2, 3 It is attached via a resin layer 62 to an attachment recess 61 formed in the main body of the.

The fixed die 2 has a support pin mechanism 70 for correctly supporting the cored bar 42 in the center of the cross section of the cavity 4.
Is provided. Details of the support pin mechanism 70 will be described later. Further, a cored bar 4 is provided at the center of the fixed mold 2 and the movable mold 3.
Recess 32 and pedestal 3 for accommodating and holding the boss 2
3 are provided.

The outer peripheral side of the electroformed shell 60 of both molds 2 and 3 and FIG.
Further, at the left end in FIG. 2, a gate block 63 that is divided into two parts, that is, an upper part and a lower part, is attached. A sprue 6, which is a material flow path to the cavity 4, a runner 7, and a gate 8 are recessed in the gate block 63, and the gate 8 is opened in the molding groove 4a. Therefore, the polyurethane material is injected from the gate 8 into the cavity 4 and divided into two directions to flow, and joins and is filled at the final filling position at the right end in FIG.

A vent hole 5 is provided in the fixed mold 2 at the final filling position. The diameter of the vent hole 5 is usually 1 to 10 mm, and in this embodiment, the straight vent hole 5 has a diameter of 3 mm and a length of 15 mm. Further, between the PL surfaces 2a and 3a at the time of closing the mold, 0.03 to 0.06 m over the entire circumference of the cavity 4 due to the processing accuracy of the mold.
Although a gap of m is generated, the gap acts as an air vent land for decompressing and degassing.

The vacuum box 11 is composed of an upper case 12 to which the fixed die 2 is fixed and a lower case 13 to which the movable die 3 is fixed, and the mounting groove provided at the mating portion of the upper case 12 is O-shaped.
When the ring-shaped seal member 14 is mounted and the vacuum box 11 is closed, the inside thereof is sealed.
As shown in FIGS. 1 to 3, a vacuum pump 20 is connected to a suction nozzle 16 provided in the lower case 13 via a suction hose 15 and a leak valve 17.
This vacuum box 11 can arrange the molding die 1 inside,
Moreover, it is formed in such a size that the decompression chamber K is formed between the molding die 1 and the molding die 1.

As shown in FIGS. 1 and 2, the lower case 13 of the vacuum box 11 is provided with a see-through window 48 through which the vicinity of the vent hole 5 can be viewed from the outside of the lower case 13. Fixed mold 2 and upper case 12, movable mold 3 and lower case 13
Are integrated into each. The lower case 13 is attached to a hydraulic cylinder ram or the like (not shown). The lower case 13 is raised until the peripheral edge of the lower case 13 hits the peripheral edge of the upper case 12, and is lowered when the mold is opened.

The material injection mechanism 21 includes a tank (not shown) for storing the polyol mixture component and the isocyanate component, and a mixing head 22 for colliding and mixing the polyol mixture component and the isocyanate component. The injection nozzle of the mixing head 22 is provided. 23 is an O-ring 24, 2
It is possible to connect to the sprue 6 portion of the molding die 1 via 4. The polyurethane material used in this example is composed of a polyol component and an isocyanate component as main components, and substantially no freon or other foaming agent added.

In the above RIM molding apparatus, when the cavity 4 is decompressed through the decompression chamber K, air remains in the molding die 1 and the air can leak into the cavity 4 in the following three areas. Is. (1) The positioning guide mechanism 50, as shown in FIG.
It comprises a rod-shaped guide pin 51 protruding downward from the inside of the fixed die 2 and a tubular guide bush 52 vertically inserted into the inside of the movable die 3. When the mold is closed, the guide pin 51 enters into the guide bush 52 for positioning. At this time, a space 53 is formed in the guide bush 52 below the lower end surface of the guide pin 51. The air trapped in a lump in the space 53 is decompressed in the decompression chamber K during decompression.
It does not slip out, remains in the space 53, and gradually becomes the guide pin 5.
1 and the guide bush 52, and there is a possibility of leaking into the cavity 4 via the PL surfaces 2a and 3a. Therefore, a communication passage 54 that extends laterally and opens to the decompression chamber K is formed in the lower portion of the guide bush 52 and inside the movable mold 3, and the space 53 is communicated with the decompression chamber K by the communication passage 54.

(2) As shown in FIG. 5, the support pin mechanism 70 has a female screw hole 71 formed in the upper portion of the fixed mold 2.
A pin hole 72 penetrating the fixed mold 2 and the electroformed shell 60 so as to be coaxial with the female screw hole 71, an adjusting male screw 73 screwed to the female screw hole 71 so as to be positionally adjustable, and the adjusting And a support pin 74 extending from the male screw 73 through the pin hole 72 into the cavity 4. When the mold is closed, the support pin 74 presses the cored bar 42 and correctly supports it in the center of the cross section of the cavity 4, but there is a space 75 in the female screw hole 71 below the lower end surface of the adjusting male screw 73. The air trapped in a lump in the space portion 75 may remain in the space portion 75 without leaking to the decompression chamber K during depressurization, and may gradually leak to the cavity 4 through the space between the support pin 74 and the pin hole 72. There is. Therefore, a communication passage 76 is formed in the upper portion of the fixed mold 2 from the female screw hole 71 in a planar keyhole shape, and the communication passage 76 allows the space 75 to communicate with the decompression chamber K.

(3) As shown in FIG. 6, in the gap 64 formed at the joint between the right end face of the gate block 63 and the left end face of the molds 2 and 3 (including the electroformed shell 60 and the resin layer 62). , Air is trapped in a film. This air does not escape to the decompression chamber K during decompression, remains in the gap 64, and gradually becomes the PL surface 2
There is a possibility of leaking into the cavity 4 via a and 3a.
Therefore, the gap 64 is filled with the sealing material 65,
There is no room for air to enter. The sealing material 65 has fluidity at the time of application, but is soft and hardened after application.

Next, the RIM molding method according to this embodiment will be described in the order of steps. As shown in FIG. 1, a core metal (not shown) is set on the movable mold 3 with the molding die 1 opened. As shown in FIG. 2, when the molding die 1 is closed, the vacuum box 11 is closed almost at the same time. When the vacuum pump 20 is operated and the decompression chamber K is decompressed from the suction nozzle 16, the cavity 4 also has PL surfaces 2a, 3
The pressure is reduced to the same degree of vacuum as the space K through the air vent land between a and the material flow path such as the sprue 6 and the vent hole 5. At this time, the air trapped in the space 53 of the positioning guide mechanism 50 is discharged from the communication passage 54 into the decompression chamber K.
Exit to. Further, the air trapped in the space 75 of the support pin mechanism 70 escapes from the communication passage 76 to the decompression chamber K. In addition, the gap 6 between the gate block 63 and the molds 2 and 3
As described above, air does not enter in No. 4.

While continuously depressurizing the cavity 4, a polyurethane material is injected into the cavity 4 from the injection nozzle 23, and the R of the ISF coating 43 as shown in FIG. 7 is injected.
IM molding is performed. That is, the occluded gas contained in the polyurethane material (a small amount of various gases originally contained, and a small amount of air that is naturally entrained in or dissolved in the circulating polyurethane material) rapidly decreases under reduced pressure. By the bumping, a highly foamed core portion 45 is formed.
In addition, the polyurethane material in contact with the cavity surface or the cored bar 42 escapes heat to suppress material thickening, and is easily degassed under reduced pressure.
4 or a self-adhesive layer 47 is formed. At this time, since no air remains in the space portions 53 and 75 and the gap portion 64, no air leaks into the cavity, and a cavity defect can be prevented. With the flow of the polyurethane material, the gap between the PL surfaces 2a and 3a is self-sealed in order as the polyurethane material flows. Then, when the flow front end of the polyurethane material reaches the final filling position and is slightly blown out from the vent hole 5, the flow front end is reactively cured and self-seals the vent hole 5. This balloon can be confirmed through the transparent window 48.

After the polyurethane material is reactively cured,
As shown in FIG. 3, the steering wheel 41 with the ISF coating 43 is removed from the mold.

The present invention is not limited to the configuration of the above-described embodiment, but may be embodied with appropriate modifications within the scope not departing from the spirit of the invention, for example, as follows. (1) In the case where a similar space portion other than the space portion 53 and the space portion 75 occurs due to the structure change of the molding die,
The space portion is communicated with the decompression chamber K by the communication passage. (2) When a similar gap is formed in addition to the gap 64 due to the structure change of the molding die, the gap is filled with the seal material.

[0023]

Since the RIM molding apparatus of the present invention is configured as described above, air can be prevented from remaining in the mold during RIM molding performed under reduced pressure, and void defects in the RIM molded product due to residual air can be prevented. Can be prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a RIM molding apparatus according to an exemplary embodiment of the present invention when a mold is opened.

FIG. 2 is a cross-sectional view of the same RIM molding apparatus when the mold is closed.

FIG. 3 is a plan view of the RIM molding apparatus and an ISF-coated steering wheel molded by the apparatus.

FIG. 4 is a sectional view of a positioning guide mechanism of the RIM molding apparatus.

FIG. 5 is a sectional view of a support pin mechanism of the RIM molding apparatus.

FIG. 6 is a sectional view of a support pin mechanism of the RIM molding apparatus.

FIG. 7 is a sectional view of an ISF coating molded by the same RIM molding apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molding die 2 Fixed type 2a PL surface 3 Movable type 3a PL surface 4 Cavity 5 Vent hole 20 Vacuum pump 50 Positioning guide mechanism 53 Space part 54 Communication path 63 Gate block 64 Gap 65 Seal material 70 Support pin mechanism 75 Space Part 76 Communication passage K Decompression chamber

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B29L 31:58

Claims (2)

[Claims] 1. A mold having a cavity and a vent portion,
In a RIM molding apparatus provided with a decompression chamber communicating with a cavity via the vent portion and a decompression device for decompressing the cavity via the decompression chamber, the mold is used when depressurizing the cavity via the decompression chamber. The RIM molding apparatus, wherein a part of the air, in which air remains in a lump form, and the air can leak into the cavity is communicated with the decompression chamber through a communication passage. 2. A mold having a cavity and a vent portion,
In a RIM molding apparatus provided with a decompression chamber communicating with a cavity via the vent portion and a decompression device for decompressing the cavity via the decompression chamber, the mold is used when depressurizing the cavity via the decompression chamber. A RIM molding apparatus, characterized in that a gap, which is a part of the air and remains in the form of a film, and in which the air can leak into the cavity is filled with a sealing material.