JP2559516Y2 - U-shaped resin cover - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a box-shaped head cover for fixing a flange on the opening side to a rigid body such as an engine cylinder head, and more particularly to a weld line formed by injection molding. The present invention relates to a resin cover having a U-shaped cross section suitable for reducing tensile stress during shrinkage.

[0002]

2. Description of the Related Art For example, as shown in FIG. 5, a head cover 1a is mounted above a cylinder head 8 fixed to a cylinder block 7 via a head cover packing 9. A resin material is used for the head cover 1a to reduce the weight of the engine, and is generally formed by injection molding.
As shown in FIGS. 5 and 6, the head cover 1a is formed by integrally injection-molding a box body 3a having an opening 5a below and a flange 4a formed on the periphery of the opening. . The connection between the head cover 1a and the cylinder head 8 is performed by mounting the flange portion 4a on the cylinder head 8 and fastening the flange portion 4a to the cylinder head 8 side with a bolt 10 or the like. Flange part 4
Since a is higher in rigidity than the box body 3a and is fastened to the cylinder head 8 as described above, the flange 4a is hardly deformed even when the head cover 1a changes in heat.

[0003]

As shown in FIG. 6, when the head cover 1a is injection-molded, a resin material is supplied from an injection hole 11 indicated by a dotted line. Adjacent injection holes 11, 1
When the resin is injected from the nozzle 1, the resin material collides at almost the center between the injection holes 11, 11, and a so-called weld line 12 is formed.
(Injection boundary layer) is formed (shown by a two-dot chain line in FIG. 6).
Since the weld line 12 is a boundary layer, its strength is about 30% lower than that of the other parts. In the prior art, in order to prevent the strength from being deteriorated due to the generation of the weld line 12, the number of the injection holes 11 is reduced as much as possible, the injection pressure is adjusted, the preheating of the molding die and the thickness of the head cover are increased, and the like. However, there is a limit because the generation of the weld line 12 itself cannot be avoided during mass production. On the other hand, since the resin material generally has a large thermal distortion, the head cover 1a shrinks greatly in a cold state or the like. As described above, since the flange portion 4a of the head cover 1a is fixed to the cylinder head 8 side, only the box portion 3a greatly contracts when cold, as shown in FIG. A tensile force is created. As described above, since the strength of the weld line 12 is low, a large tensile stress is generated in the weld line 12 by the tensile force, and a crack is generated in the head cover 1a in the weld line 12 in some cases.

On the other hand, as an example of a known technique for improving the strength of a head cover, there is one disclosed in Japanese Utility Model Laid-Open No. 150699/1983. The present technology relates to a rocker arm cover of an engine. Specifically, an elongated rib is provided in a depth direction of the wall surface on the opposite wall surface of a cover made of heat-resistant and oil-resistant synthetic resin having a substantially U-shaped cross section. It extends along and is integrally formed. The entire cover is made of a synthetic resin and formed as thin as possible, and the ribs are formed on the wall surface to compensate for the lack of strength. With the above structure, this rocker arm cover has pressure resistance and heat resistance, and the degree of shrinkage during cold is less than that of the shape shown in FIG. However, generation of a weld line during injection molding is not avoided, and when the weld line is formed between the ribs, a large tensile stress is generated at that portion.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and reduces a large tensile stress generated in a weld line generated by injection molding, thereby improving the strength and life of the resin. The purpose is to provide a birch cover.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention has an opening at the bottom and a cross section substantially U-shaped.
A resin cover obtained by injection-molding a U-shaped box portion and a fastening flange portion formed on the periphery of the opening into an integral structure, wherein the injection of the box portion used during injection molding is performed. A resin cover having a U-shaped cross section is formed by forming a recess substantially parallel to a weld line formed between the holes in the box body.

[0007]

In the cold state, the upper surface of the box portion of the resin cover shrinks and a tensile force acts on the weld line, but the concave portion formed almost parallel to the weld line absorbs the shrinkage strain and the weld line shrinks. Reduce distortion. Thereby, the tensile stress acting on the weld line is reduced, and the strength can be improved.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In this embodiment, a case of a head cover mounted on a cylinder head of an engine will be described. As shown in FIG. 1, a resin head cover 1 is an elongated rectangular box 3.
And a flange portion 4, and a plurality of concave portions 2
Is formed. As shown in FIGS. 2 and 3, the box 3 has a U-shaped cross section having an opening 5 below. On the other hand, the flange portion 4 is a flange formed on the peripheral edge of the box portion 3 on the opening 5 side, and has a bolt hole 6 for fastening and fixing the resin head cover 1 to a cylinder head (not shown). The box 3, the flange 4, and the recess 2 are integrally formed by injection molding. The concave portion 2 is provided along the U-shaped contour of the box portion 3 and is formed substantially parallel to a weld line 12 (FIG. 1) indicated by a two-dot chain line. Of course, the concave portion 2 may be formed on the weld line 12, but in the present embodiment, a plurality of the concave portions 2 are arranged side by side with the weld line 12 interposed therebetween. Although the shape of the concave portion 2 is not particularly limited, it is desirable that the shape is relatively shallow and continuous with the upper surface side of the box body portion 3 with a smooth curve, and is appropriately set according to the size of the box body portion 3. . The box 3 and the flange 4
Preferably, the resin material has heat resistance and oil resistance.

Next, the operation of this embodiment will be described. The flange portion 4 of the resin head cover 1 is a rigid cylinder head 8
(FIG. 5), heat deformation mainly occurs in the box body 3. When the engine operates in a heat cycle operation that repeats a cooling and heating state, the box body 3 contracts at a cold time,
A large tensile force is generated on the upper surface of the box body 3. However, when the concave portion 2 is formed, as shown in FIG. 4, the concave portion 2 itself is deformed by the tensile force and absorbs the tensile strain, so that the amount of distortion in portions other than the concave portion 2 decreases. Therefore, the tensile stress of the weld line 12 is greatly reduced. That is, by forming the concave portion 2, the tensile force accompanying the shrinkage of the box portion 3 at the time of cold is consumed for the deformation of the concave portion 2, and the tensile force acting on the weld line 12 is greatly reduced. I do. As described above, even if the strength of the weld line 12 is low, the crack and damage are prevented.

In the above embodiment, the recess 2 is formed at the position sandwiching the weld line 12. However, as described above, the recess 2 may be provided on the weld line 12 or formed near the weld line 12. Good. Thereby, the tensile force acting on the weld line 12 can be further reduced. Although the present embodiment has been described for the case of the engine head cover, the present invention is similarly applied to other covers which are injection-molded with a resin cover having a U-shaped cross section.

[0011]

According to the present invention, the following remarkable effects are obtained. (1) Even when the cover shrinks in the cold state and the tensile force acts, the strain is absorbed by the concave portion, and the tensile force acting on the concave portion and other portions is reduced. As a result, even if there is a low-strength portion such as a weld line in the cover, the occurrence of cracks, damage, and the like in that portion is prevented. (2) By reducing the tensile force acting on the cover, the tensile stress generated in the cover is reduced, and the life of the cover can be improved. (3) The concave portion is integrally formed at the time of injection molding of the resin cover, and can be formed into an arbitrary shape and can be implemented at a low cost. (4) The concave portion also functions as a reinforcing rib, and can improve the rigidity of the cover. In addition, the weight of the hippo can be reduced accordingly.

[Brief description of the drawings]

FIG. 1 is a perspective view of one embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG. 1;

FIG. 4 is an enlarged partial cross-sectional view for explaining the operation of the embodiment.

FIG. 5 is a side view with a partial cross section showing a state of mounting a head cover of a conventional engine.

FIG. 6 is a perspective view of a conventional head cover.

FIG. 7 is a sectional view showing a contracted state of a conventional head cover when it is cold.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Resin head cover 2 Concave part 3 Box body part 4 Flange part 5 Opening part 6 Bolt hole 11 Injection hole 12 Weld line

Claims (1)

(57) [Scope of request for utility model registration] 1. A resin having an opening at a lower part, a box having a substantially U-shaped cross section, and a fastening flange formed on a periphery of the opening by injection molding into an integral structure. A resin having a U-shaped cross-sectional shape, wherein a recess substantially parallel to a weld line formed between injection holes of the box body used during injection molding is formed in the box body. Hippo made.