JPH02103832A - Contactless switch - Google Patents

Abstract

PURPOSE:To make the thickness of resin film constant and prevent a positional change of an oscillation coil by projecting the holding section of an oscillation coil from the detection side of the oscillation coil to restrict the thickness of a molding resin film at the detection side with the height of the oscillation coil holding section. CONSTITUTION:After wiring between a printed wiring board 2 and an oscillation coil 1 and a cable 4, the oscillation coil 1 is pressed in an oscillation coil holding section 8 through its lower part to hit a detection side 1a against a rib 8a. Next, the printed wiring board 2 where an LED 3 is mounted is pressed in the side wall 9a of a printed wiring board holding section 9 and a holder 7 is positioned sticking the front of the rib 8a fast to a mold to form molding resin by casting. At the time of molding, the front of the rib 8a of the holder 7 is pushed and pressed by a mold due to injection pressure and sticked fast to the face of the mold with the result that the resin at the detection side 1a of the oscillation coil 1 is pured in the fan-shaped spaces of the ribs 8a only, and the film thickness is restricted by the height t of the rib 8a. As the oscillation coil is held by the holder 7, it becomes free from a positional change caused by the injection pressure of resin.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a proximity switch, and in particular, an oscillation coil,
The present invention relates to an integrally molded high frequency oscillation type proximity switch in which a printed wiring board and a cable end are coated with a molded resin.

[Conventional technology]

A high-frequency oscillation type proximity switch detects an object approaching the detection surface without contacting it, and is equipped with a detection circuit including an oscillation coil, an output circuit that performs switching operation based on the signal from this detection circuit, an operation indicator light, etc. There is. When a metal object approaches the high-frequency magnetic field emitted by the oscillation coil, the impedance of the oscillation coil changes, a signal is sent from the detection circuit to the output circuit, and a switching element such as a transistor is activated. As this type of proximity switch, the one shown in FIG. 4 is conventionally known. In Fig. 4, ■ is an oscillation coil, 2
indicates various circuits such as detection circuits and LEs as operation indicator lights.
4 is a cable connected to the printed wiring board 2 on which D3 is mounted. The illustrated proximity switch is of an integrally molded type in which the oscillation coil 1, the printed wiring board 2, and the terminal of the cable 4 are coated with a molded resin 6 by insert molding. The resin molding involves press-fitting the printed wiring board 2 with the wiring between the oscillation coil 1 and the cable 4 into the resin holder 5, and then inserting the oscillation coil 1 and the oscillation coil 1 placed on the top surface of the holder 5 into a metal holder. This is done by positioning it in a mold and injecting the resin.

[Problem to be solved by the invention]

By the way, in the integrally molded proximity switch described in ``-'', the detection surface 1a of the oscillation coil 1 is covered with the molded resin 6, but the thickness of the coating of the molded resin on the detection surface 1a tends to vary during molding. . In addition, the oscillation coil 1 was sometimes lifted up or bent around f due to the injection pressure of the resin during molding. Such variations in coating thickness and positional deviation of the oscillation coil 1 do not adversely affect the detection distance accuracy of the proximity switch. Therefore, the detection distance accuracy of the integrally molded proximity switch is
A so-called filled-type proximity switch is constructed by housing an oscillation coil and a circuit in a resin case and filling it with resin.
(see Publication No.). Therefore, the present invention aims to provide a proximity switch in which the thickness of the molded resin coating on the detection surface of the oscillation coil is made constant, and furthermore, the positional shift of the oscillation coil during molding is prevented to improve the detection distance accuracy. This is the purpose.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an oscillation coil,
In a proximity switch integrally constructed by covering a printed wiring board and a cable end with molded resin, the oscillation coil and the printed wiring board are held in one holder, the surroundings thereof are covered with molded resin, and at the same time, The oscillation coil holding portion of the holder is made to protrude from the detection surface of the oscillation coil by a predetermined height, and the thickness of the molded resin coating on the detection surface is regulated by the height.

[For use]

The oscillation coil and the printed wiring board are incorporated into one holder, and the oscillation coil holding portion of the holder projects a predetermined height from the detection surface of the oscillation coil. Therefore, by bringing the front surface of the oscillation coil holding part into close contact with the mold during molding, the molding resin will only cover the oscillation coil detection surface by the protruding height of the oscillation coil holding part, and the thickness of the resin coating will be proportional to that height. regulated and constant. Furthermore, since the oscillation coil is held by the holder, it will not shift position even if it receives injection pressure of the molded resin. Although the end face of the oscillation coil holding portion is exposed on the surface of the molded resin, it can be used as a detection surface mark indicating the detection surface of the oscillation coil.

【Example】

1 to 3 show an embodiment of the present invention, FIG. 1 is a joint cross-sectional view, FIG. 2 is a perspective view showing its appearance, and FIG. 3 is a holder holding an oscillation coil and a printed wiring board. FIG. Note that the same parts as those in the conventional example are denoted by the same reference numerals, and the explanation thereof will be omitted. First, in FIG. 3, the holder 7 is the oscillation coil holder 8.
and a printed wiring board holder 9, and these image parts are integrally formed using molded resin. The oscillation coil holding portion 8 is a cylindrical body whose lower surface is open. Also,
There is a cross-shaped rib 8a at the upper end of the oscillation coil holding portion 8, and the upper surface is open except for this portion. This rib 8
A regulates the thickness of the resin coating on the detection surface of the oscillation coil, as will be described later. The printed wiring board holding section 9 consists of left and right side walls 9a extending back and forth, and these side walls 9a are connected by the oscillation coil holding section 8. To make the holder 7 hold the oscillation coil 1 and the printed wiring board 2, after wiring the printed wiring board 2, the oscillation coil 1, and the cable 4, first press-fit the oscillation coil l into the oscillation coil holding part 8 from below. and the detection surface 1a is connected to the rib 8
Hit against a. Next, the printed wiring board 2 on which the LED 3 is mounted is press-fitted between the side walls 9a of the printed wiring board holding part 9 as shown in FIG. The holder 7 holding the oscillation coil l and the printed wiring board 2 in this way is positioned in a mold (not shown) with the front side of the rib 8a in close contact with the mold, and the back side of the holder (opposite to the rib 8a) The molding resin is cast by applying injection pressure from the side) and molded as shown in FIGS. 1 and 2. During molding, the front surface of the rib 8a of the holder 7 is pressed against the mold by the injection pressure of the resin and comes into close contact with the mold surface. As a result, the resin on the detection surface 1a side of the oscillation coil 1 is injected only into the fan-shaped space between the ribs 8a, and the coating thickness is regulated by the height t of the ribs 8a. Furthermore, since the oscillation coil 1 is held by the holder 7, it will not be displaced due to resin injection pressure. After resin molding, the end face of the oscillation coil holding part 8 (the front surface of the rib 8a) is exposed flush with the resin molded surface as shown in FIG. ) can be used as a mark indicating the detection surface of the oscillation coil. Note that the means for configuring the protrusion height t of the oscillation coil holder 8 is not limited to the rib 8a of the embodiment, but may include protruding leg pieces between the ends of the oscillation coil holder 8, or a cylindrical oscillation coil holder. Various modifications can be considered, such as allowing the portion 8 to protrude as it is and forming a notch in the side surface of the protruding portion for allowing resin to flow therein.

【Effect of the invention】

According to this invention, the thickness of the resin coating on the detection surface of the oscillation coil becomes constant, and the positional deviation of the oscillation coil is eliminated, so that the detection distance accuracy of the integrally molded proximity switch is improved. Furthermore, by changing the height of the oscillation coil holding portion protruding from the detection surface, the thickness of the resin coating can be set arbitrarily. Another advantage is that the end face of the oscillation coil holding portion exposed from the surface of the molded resin can be used as a detection surface mark.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention, FIG. 2 is a perspective view showing the external appearance of the proximity switch shown in FIG. 1, and FIG. 3 is a holder shown in FIG. 1 holding an oscillation coil and a printed wiring board. FIG. 4 is a vertical sectional view of the conventional example. ■...Oscillation coil, 2...Printed wiring board, 3.
... LED for operation display, 4 ... Cable, 6 ... Molded resin, 7 ... Holder, 8 ... Oscillation coil holding part,
9...Printed wiring board holding section.

Claims (1)

[Claims] 1) In a proximity switch that is integrally constructed by covering the oscillation coil, printed wiring board, and cable terminal with molded resin, the oscillation coil and printed wiring board are held in one holder, and the surrounding area is covered with molded resin. With,
In this case, the oscillation coil holding part of the holder is made to protrude from the detection surface of the oscillation coil by a predetermined height, and the thickness of the molded resin coating on the detection surface is regulated by the height.