JPH07119020B2 - Insert molding method for polyurethane molded products - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insert molding method for a polyurethane molded product used for molding a pad portion of a steering wheel as an automobile part.

[0002]

2. Description of the Related Art Conventionally, a pad portion having an insert is
It is molded by the following molding method. That is, FIG.
As shown in FIG. 3, a cavity 23 having a shape of a molded product is formed by the concave portion 21a of the lower mold 21 and the convex portion 22a of the upper mold 22. Inside the cavity 23, an insert 24 is attached along the outer peripheral portion of the convex portion 22a of the upper die 22. As shown in FIG. 7, the upper mold 2
On the side surface of the second convex portion 22a, a locking claw 25 having a triangular cross section is projected. On the other hand, the insert 24 is provided with a locking hole 26 through which the locking claw 25 is fitted.

The insert 24 can be attached to the outer peripheral portion of the convex portion 22a of the upper die 22 by engaging the engaging claws 25 in the engaging holes 26 provided at a plurality of positions of the insert 24.

[0004]

However, when the shape of the molded product, that is, the shape of the cavity 23 is thin as shown in FIG. 8, the convex portion 22a of the upper die 22 is thin, the insert 24 also has the same convex portion 22a. And the side surface becomes smaller. As a result, it is necessary to provide the engaging claw 25 at the corner of the convex portion 22a of the upper die 22 and the engaging hole 26 corresponding to the engaging claw 25 in the insert 24. Therefore, since the locking claw 25 is directed obliquely downward, the amount of undercut in the vertical direction, which is the locking direction, is reduced. Therefore, there is a problem that a strong engaging force cannot be obtained between the locking claw 25 and the locking hole 26 of the insert 24.

Further, when the locking claw 25 is engaged with the locking hole 26, since the locking claw 25 is in the locking hole 26, it is difficult to see the engaged state of the both from the surface. It is difficult to confirm whether or not the claw 25 is locked in the locking hole 26, so that there is a problem that the work time required to mount the insert 24 on the convex portion 22a of the upper mold 22 becomes long. The present invention has been made to solve the above problems, and an object thereof is to improve the engaging force of the insert with respect to the mold body, and to easily and surely mount the insert when mounting the mold body, Moreover, it is an object of the present invention to provide an insert molding method for a polyurethane molded product that can reduce the working time.

[0006]

To achieve the above object, in the present invention, a cavity having a shape of a molded product is provided by a pair of mold bodies, and an insert is attached to the mold body facing the cavity, In the insert molding method of a polyurethane molded product, which is molded by injecting a polyurethane molding raw material from the gate into the cavity, at least 1 is provided in the mold body on the side where the insert is attached.
A fitting concave portion is provided at a position, and an engaging projection having an engaging portion whose tip portion has a diameter increased is provided in the fitting concave portion, and the insert is fitted into the fitting concave portion of the mold body. A boss portion is provided so as to project, and an insertion hole through which the engaging projection is inserted is provided through the boss portion, and the engaging portion of the engaging projection is engaged with the boss portion to insert the insert into the mold body. After mounting on
The gist is the insert molding method for polyurethane molded products, which is formed by closing the mold body.

[0007]

[Operation] With the mold body opened, the engaging protrusion of the mold body is inserted into the insertion hole of the boss portion of the insert, and the boss portion of the insert is fitted into the fitting concave portion of the mold body.
Engage the insert with the mold body. At this time, the engagement protrusion of the mold body is inserted into the insertion hole of the insert, and the engagement portion of which the diameter of the tip is enlarged is inserted and engaged with the boss portion of the insert. Therefore, a reliable engagement state between the boss portion of the insert and the engagement protrusion of the mold body can be obtained,
Moreover, this engagement state can be confirmed from the surface side of the insert.

[0008]

EXAMPLES Examples of the present invention embodied in an insert molding method for molding a pad portion of a steering wheel will be described below with reference to FIGS. As shown in Figure 1,
A cavity 3 having a shape of a molded product is provided by a concave portion 1a of a lower mold 1 serving as a mold body and a convex portion 2a of an upper mold 2 serving as a mold body. The lower mold 1 is a fixed mold and the upper mold 2 is a movable mold. An insert 4 is attached to the outer peripheral portion of the convex portion 2a of the upper mold 2 forming the cavity 3. The insert 4 is made of polypropylene (PP) containing talc as a hard resin. Then, in the cavity 3, a soft skin layer 5 made of polyurethane is formed so as to cover the insert 4.

A fitting concave portion 6 is provided at a left and right position below the convex portion 2a of the upper mold 2, and an engaging projection 7 having an engaging portion 7a having a diameter enlarged at its tip portion is provided in the fitting concave portion 6. It is formed to project. On the other hand, as shown in FIG. 2, the insert 4 is formed with a boss portion 8 having a shape corresponding to the fitting concave portion 6, and the boss portion 8 has an insertion hole 8a through which the engaging projection 7 can be inserted. It is transparently installed. Further, a housing recess 9 is formed below the boss 8 for housing the engagement portion 7a having the enlarged diameter of the engagement projection 7 inserted into the insertion hole 8a.

Since the engaging portion 7a of the engaging protrusion 7 is slightly larger than the diameter of the insertion hole 8a of the insert 4, the engaging protrusion 7
After the engaging portion 7a of is inserted into the insertion hole 8a,
The a is surely engaged with the boss portion 8. Further, after the two are engaged, the engagement protrusion 7 protruding into the accommodation recess 9 can be seen from below, whereby the engagement state can be confirmed. The number of the engaging projections 7 is preferably three or more for positioning the insert 4 on the upper die 2, but may be one depending on the shape of the molded product, that is, the shape of the insert 4. In that case, the insert 4 is positioned and fixed to the upper mold 2 by adopting the above-described conventional engagement structure in the other portions.

Further, the lower surface of the engaging projection 7 is the insert 4
Since the molding material is located slightly above the lower surface, the engaging projections 7 do not hinder the flow of the molding material when the molding material flows in the cavity 3 and are formed by the boss portion 8. It is designed so that air will not be entrapped in the accommodation recess 9 to cause defective molding. The tip surface of the engaging projection 7 is the same as the lower surface of the insert 4, or the distance d between the tip surface of the engaging projection 7 and the lower surface of the insert 4 is, for example, within ± 1 mm with respect to the thickness 5 mm of the molded product. Preferably there is.

As shown in FIG. 1, a gate 10 for injecting a polyol or polyisocyanate, which is a raw material for molding polyurethane, into the cavity 3 is opened in the upper right portion of the cavity 3. Now, the insert molding method of a polyurethane molded product using the mold configured as described above will be described.

First, with the upper die 2 moved upward and separated from the lower die 1, as shown in FIG. 3, the insert 4 is attached to the convex portion 2a of the upper die 2. That is, the insert 4 is moved to the upper mold 2 side so that the engaging protrusion 7 of the upper mold 2 is inserted into the insertion hole 8a of the boss portion 8 of the insert 4,
The boss portion 8 is fitted into the fitting recess 6 of the upper mold 2. At this time, since the tip of the engaging projection 7 of the upper die 2 is an engaging portion 7a having a diameter larger than that of the insertion hole 8a of the insert 4, the engaging projection 7 is forcibly pushed in by inserting the insert 4. Is inserted into the insertion hole 8a and engaged therewith.

Then, the engaging portion 7a having the enlarged diameter of the engaging projection 7 is formed.
Enters the accommodation recess 9 of the boss portion 8 of the insert 4 and engages with the boss portion 8. At the time of this engagement, there is a small sound and there is a feeling of response, and after engagement, it can be visually confirmed that the engagement projection 7 projects from the surface of the insert 4. Therefore, the engaging portion 7a of the upper die 2 can be securely engaged with the boss portion 8 of the insert 4 by a strong engaging force, and the vertical and horizontal positioning accuracy of the insert 4 can be maintained by the conventional engagement. This can be improved as compared with the engagement between the pawl and the locking hole.

Next, as shown in FIG. 4, the upper mold 2 to which the insert 4 is attached is moved downward, and the lower mold 1 is closed. Then, the convex portion 2a of the upper mold 2 and the concave portion 1a of the lower mold 1 form a cavity 3 having a shape of a molded product. In that state, as shown in FIG. 1, polyol, polyisocyanate, etc. are poured from the gate 10 into the cavity 3 as a polyurethane molding material from the side. Then, the forming raw material is engaged with the engaging projections 7 housed in the housing recesses 9.
The part of is flowing.

At this time, the tip surface of the engaging projection 7 is slightly above the lower surface of the insert 4, that is, in the accommodating recess 9,
Since it is arranged so as to occupy the accommodating recessed portion 9, air will not be entrained in the accommodating recessed portion 9 and that portion will not be defectively molded. Further, since the engaging protrusion 7 does not project from the lower surface of the insert 4, when the engaging protrusion 7 is removed, that portion does not become an extra cavity. When a cavity is formed, when the skin layer 5 is pressed from the outer surface of the molded product, that portion is dented and a feeling of strangeness appears.

Then, the polyol, which is a forming raw material, reacts with polyisocyanate to produce polyurethane, and a molded product corresponding to the shape of the cavity 3 is molded. continue,
As shown in FIG. 5, the upper mold 2 is moved upward together with the molded product and separated from the lower mold 1. Then, the molded product is extruded downward according to a conventional method. At this time, the engaging projection 7 of the upper die 2 is forcibly pulled out through the insertion hole 8a of the boss portion 8 of the insert 4. In the skin layer 5, the portion of the engaging portion 7a of the engaging protrusion 7 is a hollow portion.

As described above, according to the insert molding method of this embodiment, although the side surface of the molded product is thin, it is not the conventional weak engagement by the locking claw and the locking hole, but the upper side. Since the enlarged engagement portion 7a of the engagement protrusion 7 of the die 2 is engaged with the boss portion 8 of the insert 4 in an undercut shape, the engagement force of the insert 4 with the upper die 2 is strong. Also, the boss portion 8 of the insert 4 is fitted into the fitting concave portion 6 of the upper mold 2 so that the engaging projection 7 is inserted into the insertion hole 8a and engaged, and at that time, an engaging sound is produced, and There is a light response, and since the engaging projection 7 can be confirmed from the surface of the insert 4 after mounting, the mounting at the time of mounting to the upper mold 2 is reliable. As a result, insert 4
The present invention is not limited to the above-described embodiment, in which the mounting accuracy with respect to the upper mold 2 can be improved and the work time required for mounting can be shortened. For example, the present invention may be configured as follows. That is, the material forming the insert 4 may be a hard resin, and may be, for example, PP containing glass fiber. Further, the boss portion 8 may be provided with a slit for adjusting the locking force of the engagement protrusion 7.

[0019]

According to the present invention, the engaging force of the insert with respect to the mold body is improved, and the mounting of the insert on the mold body is easy and reliable, and the working time can be shortened. Has the effect.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a mold showing an embodiment of the present invention and showing a state in which a molding raw material is injected into a cavity with an insert attached to an upper mold as a mold main body.

FIG. 2 is an enlarged sectional view of a main part of FIG.

FIG. 3 is a cross-sectional view showing a state before the insert is attached to the upper mold.

FIG. 4 is a cross-sectional view of a mold showing a state in which an upper mold with an insert attached is moved to a lower mold side.

FIG. 5 is a cross-sectional view of a mold showing a state in which a molding raw material is injected into a cavity, molding is performed, and then the mold is opened.

FIG. 6 is a view showing a conventional example, which is a cross-sectional view of a mold showing a state in which an insert is mounted in a cavity.

FIG. 7 is an enlarged cross-sectional view of the main parts of FIG.

FIG. 8 is a sectional view of a mold showing another conventional example.

[Explanation of Codes] 1 ... Lower mold as mold main body, 2 ... Upper mold as mold main body, 3 ... Cavity, 4 ... Insert, 6 ... Fitting recess,
7 ... Engaging protrusion, 7a ... Engaging portion, 8 ... Boss portion, 8a ... Inserting hole, 10 ... Gate.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area B29K 105: 20

Claims (1)

[Claims] 1. A cavity (3) having a shape of a molded article is provided by a pair of mold bodies (1, 2), and an insert (4) is attached to the mold body (2) facing the cavity (3). Then, in the insert molding method of the polyurethane molded product, which is molded by injecting the polyurethane molding raw material from the gate (10) into the cavity (3), the mold body (on the side where the insert (4) is attached ( In 2),
The fitting recess (6) is provided in at least one place, and the fitting recess (6) is provided with an engaging projection (7) having an engaging portion (7a) whose tip portion has an enlarged diameter, and the insert. A boss portion (8) that fits into the fitting recess (6) of the mold body (2) is projectingly provided on (4), and the engaging projection (7) is inserted into the boss portion (8). A through hole (8a) to be inserted therethrough, and the engaging portion (7a) of the engaging protrusion (7) is engaged with the boss portion (8) to insert the insert (4) into the mold body (2). A method for insert molding a polyurethane molded article, characterized in that the mold main body (1, 2) is closed and molded after being mounted on the.