JPH01158796A - Circuit shielding apparatus - Google Patents

Abstract

PURPOSE:To avoid electrical contact between a conductive housing and a conductive shielding cover, avoid misoperation and maintain a stable performance by providing insulators between the conductive housing and the conductive shielding cover. CONSTITUTION:Insulators 9 made of felt, rubber or the like are bonded to the three outside surfaces of a shielding cover 8. The shielding cover 8 is attached to a housing 6 with the insulators 9 therebetween. The insulators 9 are used as spacers to keep a certain insulation distance between the shielding cover 8 and the housing 6 and are also used as positioning members of a printed board 7. Thus, by providing the insulators 9 between the shielding cover 8 and the housing 6, shielding cover 8 is not brought into contact with the housing 6. Therefore, the printed board 7 is protected from noise interference from the housing 6 caused by the contact and the misoperation of the equipment can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a circuit shielding device for a sensor or the like mounted on an automobile.

[Background Art] Generally, high immunity circuits and circuits with high gain amplifiers are susceptible to foreign noise and oscillation and require shielding. Conventionally used methods include reducing the impedance of the circuit itself, applying a conductive cover, and connecting it to the circuit ground to obtain a shielding effect.

Of course, if the housing enclosing the circuit device is a conductor, it is often used as a shield plate. However, for example, in the case of automobile equipment, when the housing is a conductor and is grounded to the body of the car,
Even if the housing is used as a shield plate, not only will the shielding effect not be obtained, but on the contrary, various noises from the vehicle will be received from the body ground, causing equipment to malfunction.

FIG. 5 shows a state in which a 7-ender hump 3 with a sensor is installed on the left front bumper 2 of the seat 1, and FIG. 6 shows the 7-ender hump 3. 7 A sensor 4 for measuring the distance between an obstacle and the vehicle is built into the base of the engine lamp 3, and a lamp section 5 is provided at the top to serve as a guide for a part of the corner of the vehicle 1 from the driver's perspective. It is a provision. A housing 6 constituting the outer shell of the base of the engine lamp 3 is made of a conductive material, and the housing 6 is grounded to the body of the vehicle 1. A printed circuit board 7 on which electronic circuit components constituting the sensor 4 are mounted is disposed within the housing 6.

FIG. 7 shows a cutaway side view of a portion of the sensor 4, in which the housing 6 is attached to the body of the vehicle 1 as described above and is at the same potential as body ground. A shield cover 8 made of a conductive material is arranged on the component side of the printed circuit board 7 on which the components are mounted.The shield cover 8 is connected to the ground of the circuit of the printed circuit board 7, and the shield cover 8 to exert a shielding effect. However, since the shield cover 8 and the housing 6 are close to each other, when the shield cover 8 comes into contact with the inner wall of the housing 6 due to vibrations of the car 1, etc., various noises superimposed on the housing 6 are generated. There was a problem in that it could jump into the circuit and cause equipment to malfunction as described above.

[Object of the Invention] The present invention has been provided in view of the above-mentioned points, and aims to obtain stable performance by insulating a conductive housing and a conductive shield cover. A circuit shielding device is provided.

[Disclosure of the Invention] (Structure) The present invention includes a housing made of a conductive material, and a shield cover made of a conductive material that covers at least a component surface of a printed circuit board to perform shielding and is disposed within the housing. By interposing an insulating material between the conductive housing and the shield cover, the insulating material prevents electrical contact between the conductive housing and the conductive shield cover, thereby preventing equipment malfunction. It is characterized by:

(Example 1) Hereinafter, an example of the present invention will be described with reference to the drawings. still,
The overall structure is the same as the conventional one, and the main points will be described in detail. In FIG. 1, an insulating material 9 made of felt, rubber, etc. is attached to three outer surfaces of the shield cover 8, and the insulating material 9 is interposed between the shield cover 8 and the housing 6. It is. This insulating material 9 is used as a spacer, and this insulating material 9 maintains a constant insulation distance from the housing 6 and also serves as a positioning material for the printed circuit board 7. . In this way, by interposing the insulating material 9 between the shield cover 8 and the housing 6, the shield cover 8 does not come into contact with the housing 6, and the noise from the housing 6 caused by contact with the printed circuit board 7 is prevented. This eliminates the need to jump upwards and prevents equipment from malfunctioning.

FIG. 2 shows a shield cover 8 with holes 11 for circuit adjustment. If you have adjustment points on the circuit,
For example, adjustment may not be possible unless the shield cover 8 is applied.

At this time, by providing a hole 11 having an adjustable diameter directly above the adjustable component, post-adjustment can be performed even if the shield cover 8 covers the printed circuit board 7. Therefore, even after the shield cover 8 is applied, adjustment is possible using the holes 11, which does not impose constraints on the process and is also useful for positioning the printed circuit board 7. Regarding this adjustment, there is a sensitivity adjustment volume for absorbing sensitivity variations inherent to the sensor 4 with the circuit amplifier gain and obtaining a constant performance. A hole 11 is bored above this volume knob 12.

(Embodiment 2) FIG. 3 shows another embodiment, in which a tape 10 made of an insulating material is applied to the entire surface of the shield cover 8. This tape 10 constitutes the insulating material 9.

In Figure 4, not only the component side of the printed circuit board 7 but also the pattern side is shielded to prevent the influence of external noise. The plates 13 are placed one on top of the other so that the conductive plates do not come into contact with the patterned surface of the printed circuit board 7, and the conductive plates and the circuit ground of the printed circuit board 7 are connected by lead wires 14. The molded plate 13 is fixed by being tightened together with fixing screws 15 of the printed circuit board 7. Although an insulating material is not shown in FIG. 4, an insulating material 9 as shown in FIG. 1 may be used, or a tape 10 as shown in FIG. 3 may be used.

[Effects of the Invention] As described above, the present invention includes a housing made of a conductive material, and a shield cover made of a conductive material that covers at least a component surface of a printed circuit board to perform shielding and is disposed within the harassment song. Since an insulating material is interposed between the housing and the shield cover, the insulating material prevents electrical contact between the conductive housing and the conductive shield cover, thereby preventing equipment malfunction. This has the effect of ensuring stable performance of the circuit equipment.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are a broken side view and a sectional view seen from below of an embodiment of the present invention, FIG. 2 is a sectional view of the same as seen from below,
Fig. 3 is a cutaway side view of another embodiment of the same as above, Fig. 4 is a cutaway side view of a case where the same molded plate as above is also provided on the lower surface of the printed circuit board, and Fig. 5 is a cutaway side view of another embodiment of the same as above, Fig. 5 is a 7 engine lamp mounted on the bumper of a car. FIGS. 6(a) and 6(b) are a front view and a cutaway side view of a conventional seven engine lamp, and FIG. 7 is a cutaway side view of the conventional example. 6 is a housing, 7 is a printed circuit board, 8 is a shield cover, 9 is an insulating material, and 10 is a tape.

Claims (4)

[Claims] (1) A housing made of a conductive material, and a shield cover made of a conductive material placed inside the housing to provide shielding by covering at least the component surface of a printed circuit board, and an insulating material between the housing and the shield cover. A circuit shielding device characterized by comprising: (2) The circuit shield device according to claim 1, wherein the insulating material also serves as a spacer, and the spacer uniquely determines the relationship between the reprinted board and the housing. (3) The circuit shield device according to claim 1, wherein a tape made of an insulating material is attached to the surface of the shield cover. (4) A patent characterized in that a molded plate with a conductive plate on one side is stacked on the pattern side of the printed circuit board so that the conductive plate does not come into contact with the pattern side, and the conductive plate and the ground of the printed circuit board are connected. A circuit shielding device according to claim 1.