JPH06275182A - Proximity switch and its manufacture - Google Patents

Abstract

PURPOSE:To safely and quickly manufacture a detection switch which is stabilized in quality, excellent in the sealing property of a detecting circuit, and highly reliable by using no hardening resin. CONSTITUTION:An inner packing body 2 in which a detecting circuit is sealed is formed by injection-molding a thermoplastic resin. The inner packing body 2 is held in the neutral position within a molding die for forming a sheath layer 1 by a number of tapered projections 20 provided in a plurality of positions on its outer surface, and the sheath layer 1 is formed by injection- molding the thermoplastic resin to manufacture a proximity switch S.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a proximity switch for detecting the approach of an object without contact and opening / closing the contact, and a method for manufacturing the proximity switch.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 7, the proximity switch has a detection coil 91.
In addition, a printed circuit board 92 on which parts constituting a detection circuit are mounted at a predetermined position is provided with polybutylene terephthalate (PBT) or polytetrafluoroethylene (PTFE
It is placed at a predetermined position in a case 93 made of a heat-resistant thermoplastic resin such as fluororesin), and a curable resin such as an epoxy resin is used as a sealing agent to protect the circuit from water and heat. 94 is injected and before the curable resin 94 is cured,
It is manufactured by sealing the case 93 with a lid 95 also made of a heat-resistant thermoplastic resin at any stage during or after curing.

However, in the above manufacturing method, when an epoxy resin is used, bubbles are likely to be generated due to its high viscosity, which may cause variations in the circuit protection effect, resulting in a decrease in reliability. When used, the viscosity is high and it cannot be poured into every corner in a complicated shape, and the shape is restricted.The curable resin contains toxic substances such as curing agents and organic solvents, and also has a strong odor. , May impair the health of workers (eczema, rough skin, respiratory illness, etc.) or adversely affect the environment (air pollution or offensive odor due to toxic gas, soil or water pollution due to waste liquid, etc.), It takes a long time (1 day or more) to completely cure,
During that time, there is a problem that productivity is poor because the product must be stored and placed.

The present invention has been made in view of the above circumstances, and provides a proximity switch which can be manufactured without using a curable resin having the various drawbacks described above, and a manufacturing method thereof. It is an object.

[0005]

The proximity switch of the present invention for solving the above-mentioned problems is an interior body in which a detection circuit including at least a detection coil is enclosed in a thermoplastic resin, and a state in which the interior body is inserted. And an outer shell layer made of a thermoplastic resin that covers the outer surface of the interior body injection-molded with
It is characterized in that the inner body is formed with a projection having a sharp tip for holding the inner body at a neutral position of a mold during injection molding of the outer shell layer.

The proximity switch manufacturing method of the present invention is
A thermoplastic resin is filled into the first molding die by injection molding while a detection circuit including at least a detection coil is held at a predetermined position in the first molding die for forming the inner body. Then, after forming an inner body having projections with sharp tips at a plurality of positions on the outer surface, the inner body is held in a neutral position in the second molding die for molding the outer shell layer by the projections. , By injection molding, into the second mold,
It is characterized in that it is filled with a thermoplastic resin to form an outer shell layer.

[0007]

In the proximity switch of the present invention having the above structure, since the detection circuit such as the detection coil is enclosed in the interior body formed by injection molding of thermoplastic resin, it is possible to use a curable resin such as epoxy resin. As in the case of sealing, there is no variation in protection effect due to generation of bubbles or the like. Moreover, since the outer shell layer is formed by injection molding in a state where the inner body is held at the neutral position in the second molding die for molding the outer shell layer by the projections formed at a plurality of positions on the outer surface of the inner shell, The inner body and outer shell layer are integrated, and the inner body is evenly covered by the outer shell layer. Therefore, the proximity switch of the present invention has stable quality and excellent sealing property of the detection coil and the like, and is highly reliable. In particular, the reliability can be further improved by forming the outer shell layer from a thermoplastic resin having excellent heat resistance and oil resistance. Moreover, the proximity switch of the present invention is not limited in shape because both the inner body and the outer shell layer are formed by injection molding of thermoplastic resin, and various shapes according to needs can be produced.

Further, according to the manufacturing method of the present invention, the interior body and the outer shell layer are both formed by injection molding of a thermoplastic resin, and since no harmful curable resin is used, safety and environmental protection are ensured. Excellent in points. Moreover, in the manufacturing method of the present invention, unlike the curable resin, curing for a long time is not necessary at all, and since injection molding for only about 1 minute needs to be performed twice, the production efficiency of the proximity switch is significantly improved.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing embodiments. FIG. 1 is a perspective view showing an embodiment of a proximity switch of the present invention with a part cut away so that the inside can be seen. FIGS. 2 (a) to 2 (c) are side views of the proximity switch of the above embodiment. FIG. 3 is a three-view drawing showing a front surface and another side surface.

As shown in these figures, the proximity switch S of the embodiment is provided with a main body S1 which has a substantially rectangular parallelepiped shape and a part of which is formed thinly to serve as a mounting portion S5 to other members. . The front surface S1a of the main body S1 is provided with a detection portion S3 having a detection portion mark S2 indicating the center position of the detection coil (which will be described later) built in the main body S1 and slightly protruding forward from the front surface S1a. There is. Also, the front surface S1
A transparent window S4 for guiding the light of a light emitting element (described later) built in the main body S1 for confirming the operation of the proximity switch S is arranged at a position a slightly away from the detection unit S3. Further, a mounting hole S6 into which a screw or the like for mounting is inserted is formed in the mounting portion S5. Further, from the lower surface of the main body S1, a connection cord 34 for connecting a detection circuit described later to the outside is projected.

The proximity switch S has an outer shell layer 1 forming the above-mentioned outer shape, as can be seen from the cutout portion of FIG.
And the interior body 2 inside thereof. Outer shell layer 1
As will be described later, the inner body 2 previously formed is provided with a large number of projections 20 formed at a plurality of locations on the outer surface thereof.
It is formed by injection molding of a thermoplastic resin, that is, so-called insert molding, in a state of being held at a neutral position in a second molding die corresponding to the outer shape of the proximity switch S.

As the thermoplastic resin forming the outer shell layer 1, nylon polyamide (PA), polyacetal (POM), polybutylene terephthalate (PB) is used.
T), polyphenylene sulfide (PPS), tetrafluoroethylene-ethylene copolymer (ETFE) and other fluororesins, and so-called engineering plastics having excellent heat resistance and oil resistance are preferably used. The outer shell layer 1 may be reinforced with reinforcing fibers such as glass fibers, or may be colored with various colors such as pigments and dyes.

As shown in FIGS. 3 (a) to 3 (d), the inner body 2 includes a main body 21 formed in a shape in which a part of a rectangular parallelepiped is cut out so as to avoid the mounting portion S5, The detection circuit 3 including the detection coil 30 is enclosed therein. The detection circuit 3 enclosed in the inner body 2 is shown in FIG.
As shown in (a) and (b), the detection coil 30, the light emitting element 31, and other electronic components 32 are mounted at predetermined positions on the printed board 33, and the connection cord 34 to the outside is attached to the printed board 33. It is configured by connecting to a predetermined position.

On the front surface 21a of the main body 21 corresponding to the front surface S1a of the proximity switch S, a thick disk-shaped coil cover 22 is provided in order to cover the detection coil 30 which is thicker than the main body 21. At a position slightly apart from the cover 22 (a position corresponding to the light emitting element 31 of the enclosed detection circuit 3), a cylindrical projection 23 that constitutes the window S4 is provided. A plurality of protrusions 20 having sharp tips are formed on the outer surfaces of the main body 21 and the coil cover 22 at a plurality of locations. A hole 22a is formed in the center of the coil cover 22. Further, a connection cord 34 is projected from the lower surface of the main body 21.

As will be described later, the inner body 2 constitutes a detection circuit 3 at a predetermined position in a first molding die for integrally molding the main body 21, the protrusion 20, the coil cover 22 and the protrusion 23. It is formed by injection molding of a thermoplastic resin, that is, so-called insert molding, while holding each of the above-mentioned members. In addition, in the embodiment, the inner body 2 is integrally formed with the projection 23 which becomes the window S4 for guiding the light of the light emitting element 31 to the outside as described above, and thus is entirely formed of the transparent thermoplastic resin. As the transparent thermoplastic resin for forming the inner body 2, a transparent grade of the various engineering plastics is preferably used.

Further, in the inner body 2 of the embodiment, a part of the printed circuit board 33 constituting the detection circuit 3 has a notch portion of the main body 21 which avoids the above-mentioned mounting portion S5 and a notch on the back side of the coil cover 22. It is exposed at two places of the portion 21b. The former exposed portion is after the printed board 33 is clamped by the molding die so as to hold the printed circuit board 33 at a predetermined position in the first molding die when the inner body 2 is molded, and the latter exposed portion is This is because a resistor for adjusting the sensitivity of the detection coil 30 is attached.

The proximity switch S of this embodiment, which is composed of the above-mentioned respective parts, is manufactured by the following procedure according to the manufacturing method of the present invention. First, as shown in FIGS. 4A and 4B, the detection coil 30
3 (a) to 3 (a), the detection circuit 3 configured by mounting components such as the above at predetermined positions on the printed circuit board 33 and connecting the external connection cord 34 to the predetermined positions on the printed circuit board 33.
The transparent thermoplastic resin described above is injected into the molding die by injection molding while being held at a predetermined position in the first molding die for forming the inner body 2 having the outer shape shown in (d). At this time, as shown in FIG. 5 (a), the first mold M1
The molten thermoplastic resin P1 is also filled in the concave portion M1a for forming the protrusion 20.

Then, when the first molding die M1 is opened when the thermoplastic resin P1 is cooled, the detection circuit 3 is enclosed inside, and the recesses M1a are provided at a plurality of locations on the outer surface thereof. The inner body 2 (FIGS. 3 (a) to 3 (d)) having the projection 20 having a sharp tip is obtained. Next, the inner body 2 is set in a second molding die corresponding to the outer shape of the proximity switch S shown in FIGS. 1 and 2A to 2C. At this time, as shown in FIG. 6 (a), the tip of the protrusion 20 abuts on the inner surface of the second molding die M2, so that the inner body 2 has a large number of protrusions 20 formed at a plurality of positions on the outer surface. It is held in the neutral position in the second mold M2.

In this state, the void C in the second molding die M2
Then, the molten thermoplastic resin P2 is filled by injection molding (FIG. 6 (b)), and the second molding die M2 is opened when the filled thermoplastic resin P2 is cooled. The proximity switch S of the embodiment shown in FIGS. 1 and 2 (a)-(c) is completed, the outer surface of which is covered by the outer shell layer 1 which forms the outer shape of the proximity switch S.

When molding the outer shell layer 1, as shown in FIG.
As indicated by the black arrow in (b), the pressure of the molten resin injected into the mold is equal not only on the inner surface of the second mold M2 and the surface of the inner body 2 but also on the tip of the protrusion 20. To join
The molten resin also penetrates into the contact points between the tips of the protrusions 20 and the molding die M2, and the completed proximity switch S has the advantage that almost no trace of the protrusions 20 remains on the appearance.

The configuration of the proximity switch and the manufacturing method thereof according to the present invention is not limited to the embodiments described above. For example, in the above embodiment, the light emitting element 3
In order to transmit the light from the outside 1 to the outside, a projection 23 to be a window portion S4 is provided in a part of the inner body 2 and the whole inner body 2 is formed of a transparent thermoplastic resin. Layer 1
In addition, both of the molding dies for molding the inner body 2 are provided with movable pins that project at the time of molding and come into contact with the tip of the light emitting element so that both the outer shell layer 1 and the inner body 2 reach the light emitting element. By providing the holes, it is not necessary to form the inner body 2 with a transparent thermoplastic resin. Further, in the case of a proximity switch of the type that does not include the light emitting element, the above consideration is not necessary at all.

The shape of the proximity switch S, that is, the outer shell layer 1
The shape of the inner body 2 is not limited to that of the illustrated embodiment. As described above, in the present invention, the outer shell layer 1
Since both the inner body 2 and the inner body 2 are formed by injection molding of a thermoplastic resin, there is no limitation on the shape that can be manufactured, and the proximity switch S having various shapes according to needs can be manufactured.

In addition, various design changes can be made without changing the gist of the present invention.

[0024]

As described in detail above, in the proximity switch S of the present invention, the detection circuit such as the detection coil is enclosed in the interior body formed by injection molding of thermoplastic resin, and the interior body is It is covered with an outer shell layer also formed by injection molding of a thermoplastic resin while being held in a neutral position in a second mold for molding the outer shell layer by projections formed at a plurality of points on the outer surface. Since no curable resin such as epoxy resin is used, there is no variation in the protective effect due to the occurrence of bubbles, etc., the quality is stable, and the above-mentioned detection coil etc. is excellent in hermeticity. Is high. In particular, the reliability can be further improved by forming the outer shell layer from a thermoplastic resin having excellent heat resistance and oil resistance. Moreover, the proximity switch of the present invention is not limited in shape because both the inner body and the outer shell layer are formed by injection molding of thermoplastic resin, and various shapes according to needs can be produced.

Further, according to the manufacturing method of the present invention, the interior body and the outer shell layer are both formed by injection molding of a thermoplastic resin, and since no harmful curable resin is used at all, safety and environmental protection are ensured. Excellent in points. Moreover, in the manufacturing method of the present invention, unlike the curable resin, curing for a long time is not necessary at all, and since injection molding for only about 1 minute needs to be performed twice, the production efficiency of the proximity switch is significantly improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a proximity switch of the present invention with a part cut away so that the inside can be seen.

2A is a side view of the proximity switch of the above embodiment, FIG. 2B is a front view, and FIG. 2C is another side view.

FIG. 3 (a) is a rear view of an interior body that constitutes the inside of the proximity switch of the above embodiment, FIG. 3 (b) is a side view, and FIG.
(c) is a front view and (d) is another side view.

FIG. 4 (a) is a side view of a detection circuit including a detection coil, which is enclosed in the interior body, and FIG. 4 (a) is a front view.

FIG. 5 (a) is an enlarged cross-sectional view showing a state where a thermoplastic resin is filled in a first molding die for molding an inner body by injection molding, and FIG. 5 (b) is molded. The interior body, the first
FIG. 3 is an enlarged cross-sectional view showing a state taken out from the molding die of FIG.

FIG. 6 (a) is an enlarged cross-sectional view showing a state in which the inner body is held at a neutral position in a second molding die for molding the outer shell layer by projections formed at a plurality of positions on the outer surface, Figure (b) shows
It is an expanded sectional view showing the state where thermoplastic resin was filled up in the 2nd mold of the above-mentioned state by injection molding.

FIG. 7 is a cross-sectional view showing a conventional method of manufacturing a proximity switch using a curable resin such as an epoxy resin as a sealing agent for circuit protection.

[Explanation of symbols]

 S Proximity switch 1 Outer shell layer 2 Inner body 20 Protrusion 3 Detection circuit 30 Detection coil M1 First molding die M2 Second molding die P1 Thermoplastic resin P2 Thermoplastic resin

Claims (2)

[Claims] 1. An interior body in which a detection circuit including at least a detection coil is enclosed in a thermoplastic resin, and a thermoplastic resin covering the outer surface of the interior body, which is injection molded with the interior body inserted. An outer shell layer, and the above-mentioned interior body,
A proximity switch characterized in that a projection having a sharp tip is formed to hold the inner body at a neutral position of the mold during injection molding of the outer shell layer. 2. A first molding die for forming an interior body, wherein a detection circuit including at least a detection coil is held at a predetermined position in the first molding die by injection molding. After filling the thermoplastic resin to form an inner body having projections having sharp tips at a plurality of points on the outer surface, the inner body is formed by the projections at a neutral position in the second molding die for molding the outer shell layer. In the state of being held at
A method for manufacturing a proximity switch, characterized in that a molding resin is filled with a thermoplastic resin to form an outer shell layer.