JPH03225719A - Non-contact switch - Google Patents

Abstract

PURPOSE:To sense approach of a body with high sensitivity by arranging a plate-like approach sensitizer with a high specific dielectric constant in non- contact with a sensor at the side where the sensor detects a neighboring body. CONSTITUTION:A protection cover 2 made up of a plastic molding and a plate- like approach sensitizer 2a with a high specific dielectric constant is arranged at a side where a sensor 1 detects a neighboring body 4 such that they do not come into contact with each other. The sensitizer 2a is mainly composed of barium titanic acid and covers an electrode plate 1b; and this the size of the sensitizer is such that the sensitizer does not cover an electrode plate 1a, and it is fitted in a film 2. When a pulse voltage is intermittently imposed on the electrode plate 1a, a pulse voltage is outputted from the electrode plate 1b. When the body approaches, a part of input pulse voltage is dispersed to reduce an output pulse, but a large electrostatic capacity is formed between the electrode plates 1a, 1b, so that the reduced width increases. It is therefore possible to sense approach of a body with high sensitivity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a non-contact switch that senses the presence or absence of a nearby object with high sensitivity based on changes in capacitance.

[Conventional technology]

BACKGROUND ART Conventionally, a proximity detection device of International Application No. PCT/AU 8610043 has been known as a non-contact switch that detects the presence or absence of a nearby object based on capacitance.

As shown in FIG. 3, this proximity detection device is equipped with a sensor 1 in which a pair of electrode plates 1a and lb are arranged on substantially the same plane. Therefore, a protective cover 2 made of plastic is placed on top of the sensor 1 without contacting the sensor 1.

As shown in FIG. 4, the sensor 1 has one electrode plate 1a spaced apart from the other electrode plate 1b, and is formed in an annular shape surrounding the electrode plate 1b. It forms a capacitor of the shape.

As shown in FIG. 7, on one electrode plate 1a of the sensor 1,
A pulse voltage is intermittently inputted at regular intervals, and a switch circuit (not shown) for detecting the output pulse voltage is connected to the other electrode plate 1b.

When no nearby object approaches the sensor 1, as shown in FIG. 5, the bipolar plate 1a.

Since the capacitor is formed only by lb, a relatively large output pulse voltage can be obtained from the electrode plate 1b.

On the other hand, as shown in FIG. 6, when a finger as the proximate object 4 approaches, the finger functions as a third electrode, and each electrode plate 1a
, 1b and the finger, a part of the potential of the input pulse is absorbed by the finger, and the output pulse voltage from the electrode plate 1b decreases.

Therefore, if a change in the output pulse voltage is detected, the binary output corresponding to the presence or absence of the nearby object 4 can be changed.

In order to obtain such a binary output, first, the voltage of the output pulse when the power is turned on is memorized as a reference level, and the difference between the sequentially obtained output pulse voltage and the reference level exceeds a predetermined value. In this case, it is only necessary to determine that the nearby object 4 is present and send an ON output.

[Problem to be solved by the invention]

However, the non-contact switch of the prior art has a problem in that the difference between the two outputs depending on the presence or absence of the proximity object is not large enough, and the switch often misjudges the presence or absence of the proximity object.

The present invention has been made in view of the problems of the prior art described above, and its purpose is to provide a non-contact switch that is highly sensitive to the proximity of a nearby object.

[Means to solve the problem]

The non-contact switch of the present invention includes a sensor in which a pair of electrode plates are spaced apart and arranged on substantially the same plane to detect a nearby object;
The device is characterized in that it has a plate-shaped proximity intensifying piece with a high dielectric constant, and the proximity intensifying piece is arranged on the side of the sensor that detects a nearby object without contacting the sensor.

[Effect]

As shown in FIG. 1, the non-contact switch of the present invention has a sensor 1 in which a pair of electrode plates 1a and 1b are spaced apart and arranged on substantially the same plane, and detects an object 4 near the sensor 1. Since a plate-shaped proximity aggravating piece 2a with a high dielectric constant is placed on the side without contacting the sensor 1, when a nearby object 4 approaches the sensor 1, the electrode plate 1a, A high capacitance capacitor is formed between 1b and the nearby object 4.

That is, in the electric field around the sensor 1, the bipolar plate 1
Capacitors with capacitances CA and CB are formed between a and lb and the nearby object 4, and as a result, as shown in FIG. 7, an equivalent circuit including these capacitances CA and CB is formed. .

Thus, the pulse voltage intermittently applied to one electrode plate 1a of the pair of electrode plates 1a, lb is applied to the electrode plate and the nearby object 4.
The output pulse voltage from the electrode plate 1b is reduced in a dispersed manner by the high capacitance capacitor formed between the electrode plate 1b.

Note that in order to increase the drop in the output pulse voltage from the electrode plate 1b as much as possible, it is desirable to make the capacitance CB shown in FIGS. 6 and 7 as large as possible.

〔Example〕

An embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2.

Reference numeral 1 denotes a sensor, and as described in the prior art section, a pair of electrode plates 1a and 1b are arranged on the same plane of a substrate 3. This is formed by etching a printed circuit board.

Reference numeral 2 denotes a protective cover, which is disposed on the proximity detection side of the nearby object 4 of the sensor 1 without contacting the sensor 1, and includes a protective plate 2b made of a plastic molded product and a plate-shaped proximity aggravating piece 2a with a high dielectric constant. It is composed of.

The proximity sensitizer 2a is mainly composed of barium titanate, and is disposed so as to be embedded in the protection plate 2b. Further, its size is large enough to cover the electrode plate 1b, but not large enough to cover the electrode plate 1a.

In this embodiment, when a pulse voltage is intermittently applied to one electrode plate 1a with the above configuration,
When no nearby object approaches, a capacitor is formed only by the electrode plates 1a and lb, and a relatively large pulse voltage is output from the electrode plate 1b.

As shown in FIG. 2, when a finger approaches as the proximal object 4, a capacitor is also formed between the finger and each electrode plate 1a, and a part of the potential of the input pulse voltage is dispersed.

Between the sensor 1 and the finger, there is a proximity intensifying piece 2 with a high relative dielectric constant.
a is arranged, a high capacitance capacitor is formed between the electrode plates 1a, 1b and the finger, and the reduction in output pulse voltage caused by the finger increases, resulting in high sensitivity to the approach of the finger. Be sensitive.

Here, the size of the proximity sensitizing piece 2a is such that it covers the electrode plate 1b but does not cover the electrode plate 1a.
This is to make the capacitance CB shown in the sixth and FIG. 7 as large as possible, and to make the drop in the output pulse voltage from the electrode plate 1b as large as possible.

(Effects of the Invention) According to the non-contact sinch of the present invention, since the proximity sensitizer is disposed between the electrode plate and the nearby object, the high capacitance capacitor formed by the proximity of the nearby object is , by dispersing the potential of the pulse voltage that is intermittently applied to one of the pair of electrode plates, and increasing the reduction in the output of the pulse voltage from the other electrode plate, thereby achieving high sensitivity to the proximity of nearby objects. It produces an effect that can be sensed.

[Brief explanation of drawings]

FIG. 1 is a cutaway perspective view of one embodiment of the present invention, and FIG. 2 is a
3 is a sectional view of the conventional example, FIG. 4 is a front view of the sensor (common to the present invention and the conventional example), and FIG. 5 is a capacitance distribution diagram in its normal state (this common to the invention and conventional examples),
FIG. 6 is a capacitance distribution diagram when the nearby object approaches (common to the present invention and the conventional example), and FIG. 7 is an equivalent circuit diagram of the sensor (common to the present invention and the conventional example). ■-sensor, 1a, lb-electrode plate, 2-protective cover, 2a-proximity sensitizer, 2b-protective plate, 3-substrate, 4-
Close object.

Claims (1)

[Claims] (1) It has a sensor in which a pair of electrode plates are spaced apart and arranged on substantially the same plane to detect a nearby object, and a plate-shaped proximity sensitizer with a high relative dielectric constant. A non-contact switch characterized by being disposed on the side of the sensor that detects a nearby object without contacting the sensor.