JPH0579209B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a synthetic resin pressure molding mold structure for embedding and fixing an insert part such as a nut into a synthetic resin member.

(Prior art and its problems) In order to join synthetic resin members and other members,
There are cases where it is necessary to embed metal fittings such as nuts made of different materials. For example, in recent years, as shown in FIGS. 5 and 6, it has been proposed to replaceably attach a hard top proof R to which a rear window W is attached to an open automobile body B. In order to fix the lock device M for attachment to the body B to the back pillar P, it is necessary to fix a nut N to the pillar inner I of the hard top proof R made of a synthetic resin member.

Conventionally, in order to fix a nut to a synthetic resin member, as shown in Fig. 7, the synthetic resin member P is post-processed.
Bolt holes H were opened, and a reinforcing iron plate F with nuts was attached to the back side of the synthetic resin member P using adhesive A and rivets L. However, the post-work installation has disadvantages in that it has poor workability, impairs the appearance of the mounting portion, and has poor mounting accuracy. Therefore, when molding a synthetic resin member, it is desirable to adopt a nut insert method in which a nut is embedded and fixed at the same time as molding, but if there is an insert part such as a nut, careful attention must be paid to the flow of resin around it. In other words, if the fluidity of the resin is too good, the molten resin will flow into the threaded portion, making it difficult to remove it after hardening. On the other hand, when resin fluidity is low, shoot and weld defects are likely to occur downstream of the insert part (see Figure 4).

(Problem of the Invention) An object of the present invention is to provide a mold structure suitable for embedding and molding an insert part in conventional resin pressure molding.

(Means for Solving the Problems) The present invention has been made with the focus on the fact that the drawbacks in molding of insert parts can be solved by controlling the flow direction of the resin toward the downstream side of the insert parts. A mold structure for pressure molding that pressurizes and fills a material into a mold to form a product, at a position facing the top of the insert part on the mold surface that molds the front side of the product in which the insert part is embedded and molded. , a mold structure for pressure molding of a synthetic resin, characterized in that a recess is formed between the top of the insert part and the mold surface to allow resin to flow during mold matching.

Especially if the insert part is a nut,
In order to make the height of the nut approximately match the product surface line, a nut storage recess is provided in the lower mold, while a recess is formed in the upper mold to form a predetermined gap for resin flow between it and the top of the nut. .

According to the present invention, even if the resin fluidity is low, as shown in FIG. 3, the part where shorts and welds are likely to occur, as shown in FIG. As a result, resin flow is induced, and defects such as shoots do not occur as a result.

In addition, this type of structure is applicable to the SMC (Sheet Mold Compound) method in order to be applied to the hard-bottom proofing of automobiles, but the BMC
The present invention may be employed in various pressure molding molds for synthetic resin products such as (bulk mold compound) method and injection molding method.

The parts to be inserted in the present invention may be fixed to the lower mold through a concave or convex part provided in the recess of the lower mold, but they can also be fixed to a predetermined surface side through a nest that holds a nut in a predetermined location. It is also possible to arrange nuts.

Hereinafter, the present invention will be described in detail based on specific examples shown in the accompanying drawings.

(Example) Fig. 1 is a cross-sectional view of the mold structure when the present invention is applied to molding a back pillar inner using the SMC method.
The bolt 3 protruding through the nut 2 is screwed onto the bolt 3 and fixed, and the head opening 21 of the nut 2 is closed with a silicone cap 4.

As shown in FIG. 2, the nut 2 has a circumferential flange 22 formed in the center of a cylindrical body 21 with an internal thread to improve heat transfer and change the resin capacity with the basic thick part. The nut insert prevents the molding cycle near the nut from becoming too long, while a portion of the nut insert is cut out to prevent rotation after the insert is inserted.

The nest assembly M is set in the recess 51 of the lower mold 5, and the recess 51 is formed to have an inverted trapezoidal cross section in order to securely attach the nest assembly M. On the other hand, the upper die 6 is formed with a hemispherical recess 61 corresponding to the head of the nut 2 fixed to the surface of the nest 1 and slightly larger than the outer diameter of the nut. Specifically, as shown in Figure 2, a recess with an outer diameter of 12 mm is formed for a nut with an outer diameter of 10 mm during mold matching, and a gap of 0.5 to 1.0 mm is formed between the top of the nut and the recess.
It is appropriate to form a gap between mm.

Therefore, the lower mold 5 and the upper mold 6 are matched,
When the uncured resin W is compression molded, the resin flows smoothly from both sides around the nut 2, and the resin flows from above through the upper mold recess 61 of the nut head into the shot or weld-prone area behind the nut. This will guide the flow (see Figure 3). Moreover, although the nut insert part is larger than the product wall thickness, the central flange 22 protrudes, which improves heat transfer to the surrounding area and minimizes changes in resin capacity from the basic thick part. This prevents the neighboring molding cycles from becoming longer (second
(see figure).

(b) After the resin has hardened, remove the molded product 7 together with the nest assembly M, remove the temporary fixing bolts 3, and remove the nest 1.
At the same time, the nut relief convex part 71 protruding from the nut insert part is ground with a grinder or the like, and then the silicone cap 4 is removed and the bolt can be screwed into the mounting nut 2.

(Effects of the Invention) As is clear from the above explanation, according to the present invention, when embedding and fixing an insert part such as a nut at the same time as molding a synthetic resin member, the front side of the product in which the insert part is embedded is molded. A recess was formed on the mold surface facing the top of the insert component to ensure resin flow between the top of the insert component and the mold surface during mold matching, thereby preventing the occurrence of shoots or welds downstream of the insert component. As a result of the resin flowing from above into the easily-prone areas, defects such as shoots do not appear at least on the surface of the product, and the insert-molded product can be molded with an excellent appearance. Further, even if the insert part is flush with the product surface, the recessed portion is formed in a portion that is likely to interfere with the upper mold, so that there is no possibility of interference with the upper mold and damage to the mold during mold clamping. Furthermore, since the nut release portion protrudes from the product surface, even if the insert part is buried in the resin, it serves as a mark and has the advantage of facilitating screw hole extraction during finishing.

[Brief explanation of drawings]

Figures 1a and b are a cross-sectional view of a nut insert molding die when the present invention is applied to molding a back pillar inner using the SMC method, and a cross-sectional view during demolding, and Figure 2 is a schematic view of the mold according to the present invention. cross-sectional view of the section,
Fig. 3 is an explanatory diagram showing the resin flow state of the mold of the present invention, Fig. 4 is an explanatory diagram showing the resin flow state of conventional insert molding, and Fig. 5 is a schematic side view of a specific example requiring insert molding. , Figure 6 shows the -
The sectional view and FIG. 7 are structural diagrams showing a conventional nut fixing method. 2... Nut, 5... Lower die, 51... Lower die recess, 6...
Upper mold, 61...upper mold recess.

Claims (1)

[Scope of Claims] 1. A mold structure for pressure molding in which a synthetic resin material is pressurized and filled into a mold to mold a product, the mold surface forming the front side of the product into which an insert part is embedded and molded. A mold structure for pressure molding of a synthetic resin, characterized in that a depression is formed at a position facing the top of the insert part to allow resin flow between the top of the insert part and the mold surface during mold matching. 2. The insert component is a nut, and the lower mold is provided with a nut storage recess that makes the height of the nut approximately match the product surface line, while the upper mold is provided with a predetermined gap for resin flow between the top of the nut and the nut. 2. The mold structure according to item 1 above, which is formed by forming a depression.