JPH10200283A - Shield case for electronic circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shield case having satisfactory stable electromagnetic shielding effect at a screw part without impairing external appearance. SOLUTION: In the shield case 1 assembled by superposing an inner surface of a first case member 11 and an outer surface of a second case member 12, clamping the superposed parts with a screw 15 and electromechanically coupling both members 11, 12, a sharp pawl 20a such as a cut part is integrally projected from an inner surface of a screw-clamped part of the member 11, the pawl 20a is positively intruded into an outer surface of the member 12 by a clamping force at the time of screw-clamping the members 11, 12. Thus, both members 11, 12 are effectively brought into electric contact one another to increase an electromagnetic shielding effect of the case 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shield case for housing an electronic circuit such as an electric component of an automobile and electromagnetically shielding it.

[0002]

2. Description of the Related Art Electronic circuits of electronic control devices such as ABS (anti-lock brake system) and TCS (traction control system) used for safe driving and fuel-efficient driving of automobiles are generated by external electromagnetic noise. Because it is easily affected, it is housed in a shield case with an excellent electromagnetic shielding effect. This type of shield case is generally assembled by electrically and mechanically fastening two metal case members with metal screws, and specific examples thereof are shown in FIGS. This will be described with reference to B).

A shield case 1 'shown in FIG. 4 accommodates an electronic circuit 4 in which a circuit component 3 is mounted on a printed circuit board 2, and includes a first case member 11 and a second case member 12 made of metal.
Having. As shown in FIGS. 5A and 5B, a screw insertion hole 13 is partially formed in the opening peripheral portion of the first case member 11, and a screw insertion hole 13 is partially formed in the opening peripheral portion of the second case member 12. A screw hole 14 is formed. An outer surface of a peripheral portion of the second case member 12 is overlapped on an inner surface of a peripheral portion of the first case member 11,
Screw insertion hole 13 and screw hole 14 of both case members 11 and 12
And the screw 15 from the screw insertion hole 13 to the screw hole 14
Is tightened via, for example, a spring washer 16 so that the peripheral edges of the two case members 11 and 12 are partially screwed to each other, and a shield case 1 ′ that houses the electronic circuit 4 by electromagnetic shielding is assembled.

[0004]

The two case members 11, 1
The better the electrical contact state of the peripheral portion where the 2 overlaps, the better the electromagnetic shielding effect of the shield case 1 '. Therefore, the first case member 11 is screwed with the second case member 12
5, the two case members 1
The electrical contact state between the screw insertion hole 13 and the threaded portion of the screw hole 14, which are fastened together by the screws 15 of the first and the second 12, becomes unstable, and the electromagnetic shielding effect is reduced. Or the electromagnetic wave noise inside the case may leak outside. Such intrusion of external electromagnetic noise may cause the electronic circuit 4 in the shield case 1 'to malfunction, and external leakage of the electromagnetic noise from the electronic circuit 4 may cause a nearby electronic control device to malfunction.

In particular, when the shield case 1 'is used in a harsh environment of high temperature and high humidity such as electric parts of an automobile, both the case members 11 and 12 are coated with sheet metal or non-conductive material in order to prevent rust. However, the non-conductive film such as paint on the surfaces of the two case members 11 and 12 hinders the electrical contact between the two case members 11 and 12, further improving the electromagnetic shielding effect of the shield case. May be reduced. Further, if both the case members 11 and 12 are plated with a conductive metal such as gold or nickel, the electrical contact state between the two becomes good and stable, but the material cost of the shield case increases and it is difficult to realize. There's a problem.

Therefore, as means for improving and stabilizing the electromagnetic shielding effect of the shield case as described above, a toothed washer 17 as shown in FIGS. 6A and 6B can be used, and FIG. A) Screw with projection 1 as shown in FIG.
5 is known to be used.

More specifically, the toothed washer 17 shown in FIG. 6 is pressed against the outer surface of the first case member 11 by the head 15 ′ of the screw 15, so that the toothed washer 17 bites into the outer surface of the first case member 11. The bite breaks the non-conductive coating of the first case member 11 and improves the electrical contact between the first case member 11 and the screw 15. Further, since the screw 15 is screwed into the screw hole 14 of the second case member 12, the electrical contact between the screw 15 and the second case member 12 is improved, and as a result, the two case members 11, 12 The electrical contact state is improved, and the electromagnetic shielding effect of the shield case is improved.

The screw 15 shown in FIG. 7 is formed by integrally forming a small projection 18 on the bearing surface of the head 15 ′, and the screw 15 is directly inserted into the screw insertion hole 13 of the first case member 11. When screwed to the second case member 12, the small projections 18 of the head 15 ′ bite into the outer surface of the first case member 11. Also in this case, the electrical contact between the first case member 11 and the screw 15 is good, and as a result, the electrical contact between the two case members 11 and 12 is good, and the electromagnetic shielding effect of the shield case is improved.

However, in the shield case shown in FIGS. 6 and 7, since the two case members 11 and 12 are electrically connected via the screw 15, the contact resistance between the first case member 11 and the screw 15 is reduced. And the contact resistance of the second case member 12 increases, making it difficult to reduce the electrical contact resistance between the two case members 11 and 12, and the electromagnetic shielding effect of the shield case becomes unstable. In the shield case of FIGS. 6 and 7, the washer 17 and the small protrusion 18 of the screw 15 bite into the outer surface of the first case member 11, which is the outer surface of the shield case, so that the shield case is damaged. In some cases, the appearance was poor.

Therefore, the object of the present invention is to
The electromagnetic shielding effect in the screwed part is stable and stable.
Another object of the present invention is to provide a shield case whose appearance is not impaired.

[0011]

SUMMARY OF THE INVENTION The present invention relates to a first metal member.
A shield case of an electronic circuit assembled by partially overlapping an outer surface of a metal second case member on an inner surface of a case member and partially fastening the overlapped portion of the two case members with a metal screw, A sharp nail is integrally formed on an inner surface of a threaded portion which is overlapped and screwed on the second case member of the first case member, and the sharp nail is formed by the screw fastening force when the two case members are screwed. The above-mentioned object is achieved by making the two case members electrically connected by cutting into the outer surface of the threaded portion of the two case members.

Here, the sharp claw formed on the inner surface of the screwed portion of the first case member is a bent claw which is cut and raised at the periphery of a screw insertion hole, which is a screwed portion of the first case member. Also, a press claw formed when press-forming the first case member is desirable. When screwing the overlapped portion of the first case member and the second case member, the sharp claws of the first case member bite into the outer surface of the second case member, and the first case member and the second case member are directly electrically connected. As a result, the electrical contact state between the two case members is always good and stable, and a shield case having a good electromagnetic shielding effect is assembled. Further, the sharp surface of the first case member damages the outer surface of the second shield member. However, since the outer surface is a portion hidden by the first case member, the appearance of the shield case does not deteriorate.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment will be described below with reference to FIGS. It should be noted that the same or corresponding parts are denoted by the same reference symbols throughout all the drawings including FIGS.

The shield case 1 of the first embodiment shown in FIGS. 1A and 1B is a first case member 1 made of metal.
The peripheral edges of the openings of the first and second case members 12 are superimposed,
The overlapping portion is partially fastened with a metal screw 15. The second case is provided on the inner surface of the peripheral portion of the first case member 11.
The outer surfaces of the peripheral portion of the case member 12 are overlapped, and the screw insertion hole 13 of the first case member 11 and the screw hole 1 of the second case member 12 are overlapped.
4 and the screws 15 are tightened from the screw insertion holes 13 to the screw holes 14 directly or via spring washers 16 or the like, whereby the peripheral edges of the two case members 11 and 12 are partially screwed. Then, the shield case 1 for housing the electronic circuit 4 by electromagnetic shielding is assembled.

In the shield case 1 of the embodiment shown in FIG. 1, a plurality of sharp claws 20a are integrally protruded from an inner surface of a screwed portion which is a peripheral portion of the screw insertion hole 13 of the first case member 11, and this sharp case is formed. It is characterized in that the claws 20a are cut into the outer surface of the second case member 12. The sharp nail 20a is shown in FIG.
At the tip of the bent claw as shown in (B), for example, as shown in FIG. 2, a plurality of cuts 21 formed radially at equal intervals around the screw insertion hole 13 of the first case member 11 are used. Formed. That is, by twisting the fan-shaped portion between the pair of cuts 21 adjacent to the periphery of the screw insertion hole 13 in the plate thickness direction, a toothed washer-shaped sharp nail 20 a is formed on the lower surface of the periphery of the screw insertion hole 13. You.

When the outer surface of the second case member 12 is superimposed on the inner surface of the first case member 11 and the screw holes 13 and 14 are aligned with each other and the screw 15 is tightened from the screw hole 13 to the screw hole 14, The sharp nail 20a bites into the outer surface of the second case member 12 by the screw tightening force of (1). Therefore, even if there is a non-conductive coating such as paint on the surfaces of the two case members 11 and 12, this coating is broken by the sharp nails 20a biting into the second case member 12, and the two case members 11 and 12 are broken. Polymerizes directly and in a good and stable electrical contact state.
As described above, the two case members 11 and 12 are in direct electrical contact without depending on conduction by the screw 15,
The electromagnetic shielding effect at the screwed portion is always good, and the electromagnetic shielding effect of the shield case 1 assembled by the two case members 11 and 12 can be easily improved.

Further, the sharp claw 20a is connected to the second case
In this case, the outer surface of the second case member 12 will be damaged. However, since the outer surface of the second case member 12 that is damaged by the sharpened nail 20a is a portion hidden by the first case member 11, the appearance of the shield case 1 does not change as a result, and the appearance of the shield case 1 depends on its use. No failures occur.

The shield case 1 of the second embodiment shown in FIGS. 3A and 3B is characterized in that the sharp nail 20b of the first case member 11 is press-formed. That is, when the first case member 11 is press-formed from a sheet metal, the ring-shaped sharp claw 20 b having a mountain-shaped cross section is press-formed around the lower surface of the screw insertion hole 13.

Also in the case of the shield case 1 of FIG. 3, the outer surface of the second case member 12 is superimposed on the inner surface of the first case member 11,
When the screw 15 is tightened from the screw insertion hole 13 to the screw hole 14 by aligning the screw insertion hole 13 with the screw hole 14,
Ob cuts into the outer surface of the second case member 12. As a result, even if a non-conductive coating such as paint is present on the surfaces of the case members 11 and 12, the coating is broken by the sharp nail 20b, and the case members 11 and 12 are directly in good electrical contact. Thus, the shield case 1 having an always good electromagnetic shielding effect is assembled. In addition, the sharp claw 20b damages the outer surface of the second case member 12, but in this case, there is no problem similarly to the shield case in FIG.

The present invention is not limited to the above embodiment, but is also effective in, for example, a shield case having a structure in which a screw is penetrated through the overlapped portion of the first case member and the second case member and the overlapped portion is fastened with a screw and a nut. Applied to

[0021]

According to the present invention, when the outer surface of the second case member is overlapped on the inner surface of the first case member and screwed, the first
The sharp claws on the inner surface of the case member bite into the outer surface of the second case member, and the two case members are superimposed directly and always in good electrical contact. Therefore, the shield case can be used without using special toothed washers or screws with protrusions. The electromagnetic shielding effect can be improved. Further, even if the sharp nail on the inner surface of the first case member damages the outer surface of the second shield case, the outer surface of the second shield case is hidden by the first shield case, so that there is no concern that the appearance of the shield case is deteriorated.

[Brief description of the drawings]

FIG. 1A is a partial sectional view of a shield case according to a first embodiment of the present invention, and FIG. 1B is an exploded sectional view of a sectional portion of FIG. 1A.

FIG. 2 is a bottom view of a sharp claw portion of a first case member in FIG. 1 (B).

FIG. 3A is a partial cross-sectional view of a shield case according to a second embodiment of the present invention, and FIG. 3B is an exploded cross-sectional view of a cross-sectional part of FIG. 2A.

FIG. 4 is a side view including a partial cross section of a conventional shield case.

5 (A) is a partially enlarged sectional view of the shield case of FIG. 4, and FIG. 5 (B) is an exploded sectional view of a sectional portion of FIG. 5 (A).

6 (A) is a partially enlarged sectional view of a conventional shield case, and FIG. 6 (B) is an exploded sectional view of a sectional portion of FIG. 6 (A).

7 (A) is a partially enlarged cross-sectional view of a conventional shield case, and FIG. 7 (B) is an exploded cross-sectional view of a cross-sectional portion of FIG. 7 (A).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Shield case 4 Electronic circuit 11 1st case member 12 2nd case member 15 Screw 20a Sharp nail 20b Sharp nail

Claims (1)

[Claims] An inner surface of a first metal case member is partially overlapped with an outer surface of a second metal case member, and the overlapped portion of the two case members is partially fastened with a metal screw to assemble. In a shield case for an electronic circuit, a sharp nail is integrally formed on an inner surface of a threaded portion which is overlapped with the second case member of the first case member and screwed, and this sharp nail is attached to both case members. A shield case for an electronic circuit, wherein the two case members are electrically connected by cutting into an outer surface of a screwed portion of the second case member by a screw fastening force at the time of screwing.