JPH0435860B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a high frequency oscillation type proximity switch used for detecting whether an object passes or not and controlling the position of an object.

BACKGROUND OF THE INVENTION Proximity switches that detect the proximity of objects have been put into practical use in various shapes depending on their uses. Figures 1a-g are perspective views showing various conventional proximity switches. Figure 1 a~
The left end face of each proximity switch in e, and f, g in Figure 1.
The "+" symbol shown on the top surface of the proximity switch is the object detection surface, and in the case of a high frequency oscillation type proximity switch, a detection coil is embedded inside. These proximity switches are attached to conveyor lines and various control devices depending on their shape.
For example, the proximity switch shown in FIG. 1a is attached to a desired position using a band 1 that covers the outer periphery of the proximity switch as shown in FIG. 2a, and the proximity switch shown in FIGS.
The proximity switch g is fixed to the installation stand 2 with bolts as shown in FIG. 2b. Also, Figure 1c,
For proximity switches such as d, L as shown in Figure 2c.
It is fixed to the installation base 2 with bolts via the letter-shaped metal fittings 3. Furthermore, in the case of a proximity switch in which a thread groove is cut on the outer periphery of the cylindrical case of the proximity switch as shown in FIG. , and tighten it with a nut from at least one side to pass through the metal plate 4 and fix it. In addition, if the case has threaded grooves on the entire surface, it may be installed by being embedded in the metal body 5 as shown in Fig. 2 f, or it may be installed by penetrating the metal plate 4 as shown in Fig. 2 g. You can also install it by letting it slide.

However, as described above, all of the conventional proximity switches require fixing screws, mounting plates, fixing nuts, etc., and therefore have the problem of being time-consuming and requiring installation tools. Furthermore, when using a proximity switch inside a device such as a copying machine or a vending machine, there is often not enough installation space for the detection sensor, or the wire for signal transmission cannot be extended very long. . In such cases, conventional proximity switches have the problem of being difficult to use.

Therefore, the inventors installed a detection coil on a lead frame, integrated the detection circuit part into an IC, placed it on the lead frame, and integrated them by resin molding to create a proximity switch that was configured in a shape similar to an integrated circuit. is proposed. However, when the sensing coil is mounted directly on the lead frame,
When the detection coil is used as an oscillation circuit element and is caused to oscillate, an eddy current flows through the lead frame. Therefore, the same situation will occur if a metal object approaches the detection coil.
The oscillation level may drop or oscillation may stop, affecting object detection.

OBJECTS OF THE INVENTION The present invention solves the problems of such proximity switches, and aims to provide a proximity switch that is not affected by the lead frame even when the detection coil is configured on the lead frame. purpose.

Structure and Effects of the Invention The present invention is a high frequency oscillation type proximity switch for detecting the proximity of an object, which has a switch circuit section including a detection coil and an oscillation circuit using the detection coil as an oscillation circuit element. It is characterized by being arranged on the lead frame via a shield plate made of a high magnetic permeability polar material, and at the same time, the switch circuit section is miniaturized and arranged on the lead frame, and is integrally formed by resin molding. It is something.

According to the present invention having such features, since the detection coil is provided on the lead frame via the shield plate, the influence of the lead frame constituting the proximity switch is eliminated. Therefore, the proximity switch, including the detection coil, can be arranged on a lead frame and configured in the same manner as an integrated circuit, making it possible to make it extremely compact. Therefore, it becomes possible to provide a proximity switch and detect objects even in a narrow space.

DESCRIPTION OF THE EMBODIMENTS FIG. 3 is a block diagram showing the configuration of a general high frequency oscillation type proximity switch. As shown in this figure, the high-frequency oscillation type proximity switch uses a detection coil L as a detection element, and an oscillation circuit 10 is connected to this detection coil L, and an oscillation state detection circuit 11 is further connected to the detection coil L. The oscillation circuit 10 continues to oscillate at a constant frequency, and its oscillation state is constantly checked by the oscillation state detection circuit 11. When an object approaches, the oscillation state changes, so an output is output from the output circuit 12 to detect the proximity of the object. Additionally, many proximity switches are provided with an operation indicator light 13 for confirming their operation.

FIG. 4 is a perspective view showing the assembled state of the high frequency oscillation type proximity switch, which is the premise of the present invention. This high-frequency oscillation type proximity switch uses a printed coil that has recently been put into practical use. A printed coil is a small, ultra-thin coil made by laminating copper foil with a coil pattern formed on it.Here, four printed coils L1, L2, L3, and L4 are connected in series to increase the inductance. The detection coil L is used as the detection coil L. Next, the circuit section shown in Fig. 4,
That is, an IC chip 20 dedicated to the proximity switch is used, in which the oscillation circuit 10, the oscillation state detection circuit 11, and the output circuit 12 are integrated into a single chip.
Then, the detection coil L and IC chip 20 are arranged on a lead frame 21 in the same manner as when manufacturing a normal IC. The lead frames 21a and 21e are connected to the lead wires of the detection coil L, and the IC chip 20 is tie-bonded onto the lead frame 21c. and other lead frame 2
1b, 21d, 21e, and 21g by wire bonding to achieve a predetermined function. Furthermore, a light emitting diode chip 22 is fixed on the lead frame 21h as an operation indicator of the proximity switch, and is connected by wire bonding.
It is connected to the IC chip 20. The other lead frame 21f is not electrically connected to the IC chip, etc., but it is provided as appropriate so that the distance between adjacent terminals is 1/10 inch, that is, 2.54 mm, as in a normal IC, and the lead frame 21f is connected to the printed circuit board. Used when implementing. After forming the central portion of the lead frame in this manner, it is molded at low pressure using a resin mold, unnecessary portions of the lead frame are cut off, and the lead frame is integrally molded. At this time, only the upper part of the chip 22 is molded from transparent resin as a light guide 23 so that the light emitted from the light emitting diode chip can be detected after resin molding. Thereafter, each terminal of the lead frame is bent so as to form a dual-in-line type, thereby forming a dual-in-line type proximity switch S.

In the present invention, in order to eliminate the influence of the sensing coil L on the lead frame 21, a shield plate made of a magnetic material with high magnetic permeability is placed on the lead frame 21 between the sensing coil L and the lead frame as shown in FIG. 6a. For example, a ferrite plate 25 is connected by adhesive, and a detection coil L made of a printed coil is fixed thereon by adhesive, press-fitting, or the like. As shown in the figure, the ferrite plate 25 has an outer shape slightly larger than the detection coil L.
Then, the ends 26a and 26b of the detection coil are connected to the lead frames 21a and 21e by wire bonding. After configuring the sensing coil L on the lead frame through the ferrite plate 25 in this way, by low-pressure molding with resin molding, the sensing surface of the sensing coil L can be formed as shown in FIG. 5 without being affected by the lead frame. It can be used as the top surface of the package. FIG. 6b shows an arrangement in which a normal coil rather than a printed coil is used as the detection coil L. That is, the detection coil L is constructed by inserting a coil portion 27 wound with a coated copper wire into a core 28 made of a high permeability magnetic material such as ferrite. When such a detection coil L is used, it is disposed on the ferrite plate 25, connected to the switch circuit section by wire bonding, etc., and integrally molded with resin, as in the case described above.

FIG. 7 is a perspective view showing another embodiment of the proximity switch according to the present invention. In this embodiment, a printed coil, which is a detection coil, is arranged perpendicularly to the surface of the lead frame before bending, the lead wires of the detection coil are connected, and the seventh coil is formed by low-pressure resin molding as in the previous embodiment. As shown in the figure, it is molded into a flat package. Then, as shown in the figure, the proximity switch S of the dual in-line package with the sensing surface 24 on the side
It can be set to 1. When the proximity switch S1 having such a structure is mounted on the edge of a printed circuit board, it is possible to detect the passage of an object such as a metal coin that moves along the side of the printed circuit board in a narrow space. can.

[Brief explanation of drawings]

Figures 1a-g are perspective views showing the appearance of various conventional proximity switches, Figures 2a-g are views showing how these proximity switches are installed, and Figure 3 is a general high-frequency oscillation type proximity switch. 4 is a diagram showing the assembled state of the proximity switch, which is the premise of the present invention, FIG. 5 is a perspective view showing its external appearance, and FIGS. FIG. 7 is a partially enlarged view showing the configuration of the detection coil portion of the switch, and is a perspective view of a proximity switch showing another embodiment of the present invention. L...detection coil, L1-L4...printed coil, 10...oscillation circuit, 11...oscillation state detection circuit,
12...Output circuit, 13...Operation indicator, 20...IC
Chip, 21a to 21h...Lead frame, 22
...Light emitting diode chip, 23...Light guide,
24...Detection surface, 25...Ferrite plate.

Claims (1)

[Scope of Claims] 1. A high-frequency oscillation type proximity switch for detecting the proximity of an object, which has a switch circuit section including a detection coil and an oscillation circuit using the detection coil as an oscillation circuit element, wherein the detection coil has a high transparency. The switch circuit is arranged on a lead frame through a shield plate made of a magnetic material, and the switch circuit section is miniaturized and arranged on the lead frame, and is integrally formed by resin molding. Switch. 2. The proximity switch according to claim 1, wherein the shield plate is a ferrite plate. 3. The proximity switch according to claim 1, wherein the switch circuit section is an integrated circuit. 4. The proximity switch according to claim 1, wherein the detection coil is a printed coil formed by laminating copper foil on which a coil pattern is formed.