JPH0526681Y2 - - Google Patents

Description

[Detailed description of the invention] A. Field of industrial application This invention includes a detection coil housed in a ferrite core in a case, a transmission circuit using the detection coil as a transmission element, and a transmission circuit that responds to changes in the output of the transmission circuit. The present invention relates to a high-frequency emitting proximity switch that houses a printed circuit board incorporating a detection circuit for detecting the approach of a detected object, is electrically connected to the printed circuit board, and is equipped with a cable led out to the outside. .

(b) Prior Art A high-frequency oscillation type proximity switch has a core portion in which a detection coil is housed shielded to prevent external noise from entering the detection coil. The shielding process is conventionally used, for example, in
As described in the publication, the conductive plate 13 is arranged so as to overlap the back surface of the ferrite core 2, and the conductive plate 13 and the printed circuit board 4 are fixed in position via the holder 14. There is one that is electrically connected to a printed circuit board by a lead wire 15.

C. Problems to be solved by the invention The conventional shielding process described above requires a holder separate from the conductive plate, and is electrically connected to the printed circuit board via lead wires, making the assembly work complicated. .

D. Means for solving the problems The present invention aims to improve assembly work and at the same time ensure high shielding performance, and its configuration is as follows:
A board guide is provided on one side with a protrusion that fits into the center hole and notch of the core, and on both sides of the other side is a receiver with a U-shaped cross section that holds both ends of the printed circuit board with the open side facing each other. A shield body made of conductive synthetic resin that protrudes and has a metal plate molded inside so that a part of the metal plate is exposed is placed between the ferrite core and the printed circuit board and is brought into close contact with the ferrite core. , electrically connected to the printed circuit board.

E. Function By fitting the protrusion provided on one side of the shield body into the central hole and notch of the core, the shield body can be reliably positioned and prevented from rotating, and both ends of the printed circuit board can be attached to the board guide. By inserting and holding, the printed circuit board can be held and the electrical connections can be aligned at the same time.Furthermore, the detection coil is shielded with a conductive shield made of a molded metal plate.

F. Example A proximity switch according to the present invention will be explained based on the drawings.

Reference numeral 1 denotes a cylindrical case, and a ferrite core 2 having a cylindrical outer shape is disposed at the tip inside the case 1.
A detection coil 3 housed in a coaxial attitude is disposed in the. The ferrite core 2 has a central hole 2a passing through its center, and cutouts 2b, 2b parallel to the central hole 2a are formed on the peripheral surface. 4
is a printed circuit board, and this printed circuit board 4 includes a transmitting circuit using the detection coil 3 as a transmitting element and a detecting circuit that detects the approach of a detected object according to a change in the output of the transmitting circuit. There is. 5 is a shield body, and this shield body 5 has a disc-shaped body having the same diameter as the ferrite core 2 on one side,
Projections 6, 6a corresponding to the central hole 2a and one (lower) notch 2b of the ferrite core 2
is formed, and on both sides of the other surface, a substrate guide 7 is provided protrudingly provided with receivers 7a, 7a each having a U-shaped cross section with their opening sides facing each other, and the protrusion 6 has a through hole in the center. It has 6b. Also, on the side opposite to the protrusion 6a on the circumferential surface of the disc-shaped main body, there is a notch 5a.
is formed. Further, a metal plate 8 is molded in the shape of a sandwich on the disc-shaped main body, and the metal plate 8 is placed in the middle part of the receivers 7a, 7a.
A section 8a formed by cutting and raising a part of the is protruding. The shield body 5 is formed by inserting the protrusions 6, 6a into the central hole 2a and the notch 2b on one side (lower side) of the ferrite core 2, and tightly fixing the protrusions 6, 6a to one side of the ferrite core 2 using a conductive adhesive. In the board guide 7, both ends of the printed circuit board 4 are inserted and held in receivers 7a, 7a. In this state, the section 8a is attached to the printed circuit board 4.
It comes in contact with the ground pattern and is soldered. The lead wire of the detection coil 3 is led out from the notch 2b on one side (upper side) of the ferrite core 2 and the notch 5a of the shield body to the printed board side, and is soldered to a predetermined pattern part of the printed board 4. . Further, the cable 9 led out to the outside of the case 1 is connected to the external connection terminal pattern portion of the printed circuit board 4 on the flexible printed circuit board 9a.
(FPC), and when the flexible printed circuit board 9a is soldered to the printed circuit board 4, it is pressed and fixed by a staple fitting 4a. Further, the tip of the case 1 is covered with a front cap 10, while the rear end is closed with a rear cap 10a molded with the end of the cable 9, and the inside is filled with epoxy resin 11. In addition, 12 shown in the drawing is O
It's a ring.

The proximity switch formed in this way can position and prevent the shield body 5 from rotating by inserting the protrusions 6, 6a of the shield body 5 into the central hole 2a and the notch 2b on one side of the ferrite core 2, respectively. This can be easily done by simply holding the end of the printed circuit board 4 with the board guide 7, and the shield body 5
The piece 8a of the metal plate serving as the grounding terminal contacts the grounding pattern portion of the printed circuit board 4, and can be directly soldered to the printed circuit board 4. Since the metal plate 8 is molded into the shield body 5, it has an excellent shielding effect, and the epoxy resin 11 filled in the case 1 passes through the through hole 6b of the shield body 5 and into the center hole 2a of the ferrite core 2. This has the advantage that the air in the central hole 2a is eliminated and the sensing coil 3 is not affected by temperature changes.

Effects According to the present invention, the ferrite core, the shield body, and the printed circuit board can be easily positioned and fixed, so the assembly work efficiency is greatly improved. , excellent shielding effect.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view of a proximity switch according to the present invention, FIG. 2 is an assembled sectional view of the same, and FIG. 3 is an explanatory diagram of a conventional example. 1...Case, 2...Ferrite core, 2a...
...Central hole, 2b... Notch, 3... Detection coil, 4... Printed circuit board, 4a... Staple fitting, 5... Shield body, 5a... Notch,
6, 6a...Protrusion, 6b...Through hole, 7...Substrate guide, 7a...Receiver, 8...Metal plate,
8a... Section, 9... Cable, 9a... Flexible printed circuit board, 10... Front cap, 10a... Rear cap, 11... Epoxy resin, 12... O-ring, 13... Conductive plate, 14... Holder, 15...Lead wire.

Claims (1)

[Scope of utility model registration request] A printed circuit board in which a detection coil housed in a ferrite core, a transmission circuit using the detection coil as a transmission element, and a detection circuit that detects the approach of a detected object according to changes in the output of the transmission circuit are incorporated into the case. A high-frequency emitting type proximity switch that is electrically connected to the printed circuit board and has a cable led out to the outside; A board guide is provided on both sides of the other surface with a U-shaped cross section facing each other, and board guides are provided to hold both ends of the printed circuit board, and a metal plate is molded inside. A shield body made of conductive synthetic resin with a part of the plate exposed is placed between the ferrite core and the printed circuit board, and is brought into close contact with the ferrite core, and is electrically connected to the ferrite core and the printed circuit board. Proximity switch.