JPH0436189Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial field of application] This invention is applicable to bent cantilever-shaped locking arms used in electrical parts such as branch junction boxes, which are molded from materials with a high molding shrinkage rate. The present invention relates to a locking arm deformation prevention structure that can prevent cooling distortion during mold molding caused by the difference in surface area between the inner and outer surfaces of a bent portion.

[Conventional technology and problems]

BACKGROUND ART A bent cantilever-shaped locking arm is widely used for electrical parts and the like because it is a simple mechanism for removably locking parts when assembling the parts.

For example, as shown in FIGS. 7 and 8, an electrical connection box A that is attached to the vehicle body has an engaging piece that is attached to the vehicle body inserted into the frame wall 2 at the end of the case body 1. A hole 3 is provided, and a bent cantilever-shaped locking arm 4 is provided within the insertion hole 3 (see FIG. 9).

A protrusion 5 is provided on the outer surface of the locking arm 4, and an engagement hole 7 is provided in an engagement piece 6 attached to the vehicle body B (see FIGS. 9 to 12).

When the engagement piece 6 is inserted into the insertion hole 3, the protrusion 5 comes into contact with the engagement piece 6, and the elastic deformation of the locking arm 4 causes the protrusion 5 to retreat, and the engagement piece 6 remains in the insertion hole 3. When the engagement hole 7 of the engagement piece 6 overlaps the protrusion 5, the protrusion 5 is fitted into the engagement hole 7 by the elastic force of the locking arm 4, and the electrical connection box A is locked to the vehicle body B. Ru.

To unlock the electrical connection box A and the vehicle body B, insert a tool or the like into the tip of the locking arm 4 to elastically deform the locking arm to the opposite side of the engagement piece 6, and the protrusion 5 will be released. Since it is disengaged from the engagement hole 7, the lock is released and the two parts can be separated.

As described above, the locking arm 4 can lock and unlock parts by elastically deforming the free end using the bent portion as a fulcrum, but when molding the locking arm 4, the following problems arise. There is.

When the locking arm 4 is molded from a material with a high molding shrinkage rate (for example, polypropylene), the first
As shown in Figure 0, the difference in surface area between the inner side 4a and the outer side 4b of the bent portion causes a difference in the cooling rate within the mold.

That is, the larger the surface area, the larger the heat dissipation area, and therefore the faster the cooling.If the cooling is faster, the crystals will solidify before they advance, and the distance between molecules will become larger, resulting in larger dimensions.

Therefore, the free end side of the locking arm 4 is distorted inward, as shown by the dashed line in FIG.

If the locking arm 4 is distorted in this way, the amount by which the projection 5 fits into the engagement hole 7 will be reduced, resulting in a problem that the locking will be insufficient.

If the lock is insufficient, the reliability of the lock holding force will be lacking, and problems such as local load being applied to the shallow engagement portion between the protrusion 5 and the engagement hole 7 will occur.

The present invention solves these problems and provides a locking arm that does not suffer from cooling distortion even when molded from a material with a large amount of molding shrinkage.

[Means for solving problems]

In the present invention, an engagement piece having an engagement hole is inserted into the insertion hole in the form of a bent cantilever, and a protrusion protruding from the side surface is inserted into the engagement hole of the engagement piece. In the locking arm that locks the locking arm, an arm corresponding to the locking arm from the bent portion to the free end is provided on the opposite side of the free end to form a structure for preventing deformation of the locking arm.

[Effect]

With the above configuration, the surface areas of both the inner and outer sides near the bending part of the locking arm are approximately equal, so the cooling rate during mold molding is almost balanced on both the inner and outer sides, and solidification occurs almost simultaneously. Therefore, distortions caused by differences in cooling and solidification timing as in the prior art are prevented.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings.

Note that the same parts as in the conventional example are given the same reference numerals.

1 to 6, the locking arm 4 extending upward from the case body 1 through the bent portion 8 is similar to the conventional example in that it has a protrusion 5 on the outer surface side, but the locking arm 4 extends upwardly from the case body 1 through the bent portion 8. An arm 9 is provided opposite the free end of the arm 4.

Further, the arm 9 is provided with ribs 10 connected to the main body 1 at both ends to protect the bent portion 8 from applying a bending moment to the bent portion 8 when the arm 9 receives an external force.

The length l ₁ of the locking arm 4 and the length l ₂ of the arm 9 configured as described above are approximately equal to the length L from the tip of the locking arm 4 to the tip of the arm 9, and L≒(l ₁ +l ₂ ) The relationship is as follows.

Therefore, since the heat radiation areas of the inner and outer surfaces of the locking arm 4 are approximately equal, the cooling rates of both sides are approximately balanced, and solidification occurs approximately at the same time.

Also, the inner and outer surfaces of the arm 9 are similarly
They are cooled in almost the same way and solidified almost at the same time.

Therefore, the locking arm 4 and the arm 9 do not buckle to either the inner or outer side.

On the other hand, the shapes of the inner surface 4a of the locking arm and the inner surface 9a of the arm 9 in the vicinity of the bending portion 8 are substantially the same, and cooling is performed under the same conditions.
The bent portion 8 does not warp in either the upper or lower direction.

Therefore, when the engagement piece 6 is inserted into the insertion hole 3, the locking arm 4 is inserted into the engagement hole 7 of the engagement piece 6.
The protrusion 5 of is completely inserted, and the electrical connection box A is connected to the vehicle body B.
The engagement surface between the protrusion 5 and the engagement hole 7 is securely locked, and no local excessive load is applied to the engagement surface between the projection 5 and the engagement hole 7 that are completely fitted.

As described above, the locking arm 4 can be prevented from being deformed during molding by providing the arm 9.

〔effect〕

The present invention provides an arm at the bent part of the locking arm in the opposite direction to the free end of the locking arm, thereby eliminating the locking arm that is unavoidable when the locking arm is molded using a material with a high molding shrinkage rate. deformation could be prevented.

Therefore, it has become possible to improve the reliability of locking the locking arm and to prevent damage to the engaging portion.

[Brief explanation of drawings]

Figures 1 to 6 show embodiments of the present invention;
The figure is a front view of the main parts of the locking arm, Figure 2 is a side view of the above, Figure 3 is a plan view of the same, Figure 4 is a rear view of the same, Figure 5 is a longitudinal sectional view of the same, and Figure 6 is a perspective view of the same. 7 is a plan view of the electrical connection box, FIG. 8 is a front view of the same as above, FIG. 9 is a vertical sectional view of the locking arm in the conventional example, FIG. 10 is a perspective view of the same as above, and FIG. 11 is an engagement FIG. 12 is a perspective view of the piece, and a vertical sectional view of a main part showing the locked state of the locking arm and the engagement piece in the conventional example. A...Electrical connection box, B...Vehicle body, 1...Case body, 1...Frame wall, 3...Insertion hole, 4...Locking arm, 5...Protrusion, 6...Engaging piece, 7 ……
Engagement hole, 8... bending part, 9... arm, 10... rib.

Claims (1)

[Scope of utility model registration request] The locking arm has an engaging portion that engages with a hole or protrusion of a mating component near the free end of an elastic locking arm provided in the shape of a bent cantilever, and locks both components. A structure for preventing deformation of a locking arm, characterized in that an arm having substantially the same thickness as that of the locking arm is provided in a direction opposite to the free end at the bent portion of the locking arm.