JP6814388B2 - Proximity sensor - Google Patents

Description

The present invention relates to a proximity sensor.

Conventionally, a capacitance type proximity sensor that detects a change in capacitance is known. The capacitance type proximity sensor detects the proximity of an object by detecting a change in capacitance caused by an object (for example, a finger) such as a human body.

FIG. 5 shows the proximity sensor 100 of Patent Document 1. The proximity sensor 100 has a first detection electrode 101, a second detection electrode 102, and a shielding electrode 103. The first detection electrode 101 and the second detection electrode 102 are arranged so as to have a predetermined distance difference Δh'with respect to the detection direction, and the shielding electrode 103 holds the first and second detection electrodes 101 and 102. It is formed so as to surround it and selectively shield a direction other than the detection direction.

The proximity sensor 100 detects the capacitances Ca and Cb formed between the object 104 and the first and second detection electrodes 101 and 102 when the object (detected body) 104 is in close proximity, and static electricity thereof. Proximity is detected from the difference between the capacitances Ca and Cb. Changes in capacitance due to airborne substances such as raindrops and fog appear in the same way on each of the first detection electrode 101 and the second detection electrode 102, so by detecting proximity from the difference in capacitance, , It is possible to avoid detection malfunction due to airborne objects such as raindrops and fog.

Japanese Patent No. 4578980

In the proximity sensor 100, the first and second detection electrodes 101 and 102 and the shielding electrode 103 are independent electrodes, and these electrodes must be insulated from each other. However, it is not easy to manufacture the first and second detection electrodes 101 and 102 so that the shielding electrodes 103 and the shielding electrodes 103 are insulated from each other, and the mass productivity is not excellent. Especially when manufacturing a long proximity sensor or a small diameter proximity sensor, it has not been particularly easy.

Therefore, an object of the present invention is to provide a proximity sensor which is excellent in mass productivity and can avoid detection malfunction due to airborne substances such as raindrops and fog.

The present invention, which was devised to achieve this object, comprises a first and second electrode wires provided in parallel, an insulator that collectively covers the first and second electrode wires, and the insulator. The sensor cable includes a sensor cable having a coating covering the sensor and a shield having an opening and partially covering the periphery of the sensor cable, and the sensor cable has the first and second electrode lines. A first capacitance detected by the first electrode line and a second capacitance detected by the second electrode line, which are fixed to the shield so as to have a distance difference with respect to the opening. It is a proximity sensor that detects the proximity of the object to be detected by the difference from the capacitance.

According to the present invention, it is possible to provide a proximity sensor which is excellent in mass productivity and can avoid detection malfunction due to airborne substances such as raindrops and fog.

It is a perspective view of the proximity sensor which concerns on embodiment of this invention. It is a schematic diagram of the proximity sensor which concerns on embodiment of this invention. It is sectional drawing of the proximity sensor which concerns on embodiment of this invention. It is sectional drawing of the proximity sensor which concerns on the modification of this invention. It is a schematic diagram which shows the conventional proximity sensor.

[Embodiment]
FIG. 1 is a perspective view of a proximity sensor according to an embodiment of the present invention.

As shown in FIG. 1, the proximity sensor 1 according to the embodiment of the present invention collectively includes the first and second electrode lines 21 and 22 and the first and second electrode lines 21 and 22 provided in parallel. A sensor cable 2 having an insulator 23 covering the insulator 23 and a coating 24 covering the insulator 23, and a shield 3 having an opening 31 and partially covering the periphery of the sensor cable 2 for a sensor. The cable 2 is fixed to the shield 3 so that the first and second electrode wires 21 and 22 have a distance difference ΔL with respect to the opening 31, and the first capacitance C1 detected by the first electrode wire 21. The proximity of the object to be detected 4 is detected by the difference between the force and the second capacitance C2 detected by the second electrode wire 22. The proximity sensor 1 according to the embodiment of the present invention can be attached to, for example, an electric opening / closing member such as an electric door of an automobile or a railroad vehicle, and can be used as a detection device for detecting pinching of a human body or the like.

(Sensor cable 2)
The sensor cable 2 includes first and second electrode wires 21, 22 and an insulator 23 and a coating 24. The first electrode wire 21 and the second electrode wire 22 are provided in parallel along the longitudinal direction (z-axis direction in FIG. 1) without being twisted. The first electrode wire 21 and the second electrode wire 22 are provided apart from each other, and a fixed interval d1 is formed between them. Here, the fixed interval d1 means the shortest distance connecting the surfaces of the first electrode wire 21 and the second electrode wire.

The first electrode wire 21 has a first conductor wire 21a made of metal and a first conductive layer 21b covering the first conductor wire 21a, and the second electrode wire 22 has a second conductor wire 22a and a second conductor wire 22a made of metal. It has a second conductive layer 22b that covers the conducting wire 22a. The first lead wire 21a and the second lead wire 22a are, for example, stranded wires of 26 to 30 AWG silver-plated annealed copper wire. The first conductive layer 21b and the second conductive layer 22b are conductive rubber or conductive plastic, and for example, EPDM (ethylene propylene / diene rubber) or silicone rubber is mixed with a conductive filler such as carbon black. Can be used. Further, as the first conductive layer 21b and the second conductive layer 22b, those obtained by blending a thermoplastic elastomer (for example, a styrene-based thermoplastic elastomer) with a conductive filler such as carbon black can also be used. By using the thermoplastic elastomer, the cross-linking step at the time of molding becomes unnecessary, so that the manufacturing steps of the conductive layers 21b and 22b can be simplified and the manufacturing cost can be reduced.

The insulator 23 is formed so as to collectively cover the first and second electrode wires 21 and 22. The positions of the first electrode wire 21 and the second electrode wire 22 are fixed by the insulator 23 in a state of being parallel to each other. That is, a fixed interval d1 is formed between the first electrode wire 21 and the second electrode wire 22.

In this embodiment, the hollow portion 25 is formed between the first electrode wire 21 and the second electrode wire 22. The surface of the first electrode wire 21 facing the second electrode wire 22 is exposed by the hollow portion 25, and the surface of the second electrode wire 22 facing the first electrode wire 21 is the hollow portion 25. Is exposed by. That is, the hollow portions 25 expose the surfaces of the conductive layers 21b and 22b that face each other.

By forming the hollow portion 25, when the object to be detected 4 comes into contact with the sensor cable 2 and the sensor cable 2 is deformed, the first electrode wire 21 and the second electrode wire 22 come into contact with each other and become conductive. Will be. By detecting this continuity, it is possible to detect the contact of the detected body 4 with the sensor cable 2. Therefore, by forming the hollow portion 25, the function of the contact sensor can be added in addition to the function as the proximity sensor (that is, the non-contact sensor).

(Shield 3)
The shield 3 has an opening 31 in the detection direction of the proximity sensor 1 (the y-axis direction in FIG. 1), and covers the periphery of the sensor cable 2 except for the detection direction. The shield 3 is formed by bending a thin plate made of metal, for example. In the present embodiment, the shield 3 is formed so as to have a U-shape whose cross section is bent at a right angle.

(Fixing of sensor cable 2 and shield 3)
The sensor cable 2 is fixed to the shield 3 so that the first and second electrode wires 21 and 22 have a distance difference with respect to the opening 31. The opening 31 of the shield 3 is formed so as to have an opening surface parallel to the xz plane of FIG. 1, and the distance between the first and second electrode lines 21 and 22 and the opening 31 is perpendicular to the opening surface. It means the distance between the opening 31 and the surfaces of the first and second electrode lines 21 and 22 in a direction (y-axis direction in FIG. 1). As shown in FIG. 2, the distances between the opening 31 and the first and second electrode lines 21 and 22, respectively, are L1 and L2, and L1 and L2 have a distance difference ΔL. L1 and L2 can be adjusted by rotating the sensor cable 2. Therefore, the distance difference ΔL can be adjusted by rotating the sensor cable 2.

The sensor cable 2 can be fixed to the shield 3 with an adhesive or double-sided tape. Further, by forming the width of the shield 3 (the inner length in the x-axis direction of FIG. 1) slightly smaller than the diameter of the sensor cable 2, the sensor cable 2 becomes the shield 3 due to the elasticity of the sensor cable 2. It can also be fixed.

(Detection circuit 5 and detection method)
As shown in FIG. 2, a detection circuit 5 is connected to the proximity sensor 1. The detection circuit 5 is a capacitance detection unit 51 that detects the capacitance C1 between the first electrode wire 21 and the detected body 4, and the capacitance between the second electrode wire 22 and the detected body 4. The second capacitance detection unit 52 that detects the capacitance C2, the shielding voltage application unit 53 that applies the shielding voltage so that the shield 3 has the same potential as the first electrode wire 21 and the second electrode wire 22, and the first capacitance detection. A control unit 54 that synchronizes the timing at which the unit 51 and the second capacitance detection unit 52 detect the capacitance with the timing at which the shielding voltage application unit 53 applies the shielding voltage to the shield 3, and the capacitance C1 and the capacitance C2. It is provided with a differential output unit 55 that outputs a difference.

First, the shielding voltage application unit 53 applies a shielding voltage to the shield 3 so that the shield 3 has the same potential as the first electrode wire 21, and the first capacitance detecting unit 51 detects the capacitance C1 in that state. Next, the shielding voltage application unit 53 applies the shielding voltage to the shield 3 so that the shield 3 has the same potential as the second electrode wire 22, and the second capacitance detecting unit 52 detects the capacitance C2 in that state. .. These operations are controlled by the control unit 54. Then, the differential output unit 55 outputs the difference ΔC between the capacitances C1 and C2, and determines the proximity of the detected body 4 based on the magnitude of the output ΔC. For example, a threshold value is set in advance, and when ΔC is smaller than the threshold value, it is determined that there is no proximity of the detected body 4, and when it is larger than the threshold value, it is determined that there is proximity of the detected body 4.

(Example)
An embodiment of the present invention shown in FIG. 3 will be described.

(1) First electrode wire 21 and second electrode wire 22
The first conductor 21a and the second conductor 22a, which are made of stranded silver-plated annealed copper wire and have an outer diameter of 0.3 mm (28 AWG), are prepared, and the surfaces of the first conductor 21a and the second conductor 22a are made of conductive rubber. The first conductive layer 21b and the second conductive layer 22b are coated. The first conductive layer 21b and the second conductive layer 22b are made by blending EPDM with carbon black and adjusting the conductivity to 50 Ω / cm. The outer diameters of the first electrode wire 21 and the second electrode wire 22 are 0.77 mm.

(2) Sensor cable 2
In addition to the first lead wire 21a and the second lead wire 22a, a linear spacer (not shown) is prepared. The spacer is for forming the hollow portion 25, and is unnecessary when the hollow portion 25 is not formed. There is also a method of forming the hollow portion 25 by devising the shape of the die when the insulator 23 is extruded without using a spacer.

First, one spacer having a diameter of 1.1 mm is arranged at the center, and two spacers having a diameter of 0.77 mm, a first lead wire 21a, two spacers having a diameter of 0.77 mm, and a second spacer are arranged around the spacer. The conductors 22a are arranged in this order. The spacer consists of an ethylene tetrafluoride ethylene (ETFE) coated wire. Next, while holding the first lead wire 21a and the second lead wire 22a and the spacer so as not to form a gap, an insulator 23 made of TPE (thermoplastic elastomer) is coated around them by extrusion molding to insulate them. A coating 24 made of a styrene-based thermoplastic elastomer is further coated around the body 23.

The sensor cable 2 (including the spacer) produced in this manner is cut into 1100 mm pieces, and the five spacers are pulled out to produce the sensor cable 2. When pulling out the spacer, it is possible to facilitate the pulling out of the spacer by injecting air between the insulator 23 and the spacer. Further, since the first and second conductors 21a and 22a and the spacer are not twisted, the spacer can be easily pulled out.

(Shield 3)
A thin copper plate having a thickness of 0.3 mm is prepared and bent at two places along the longitudinal direction to form a shield 3 having an opening 31. The shield 3 has a height of 4.0 mm and a width of 4.0 mm.

Next, the sensor cable 2 is attached to the shield 3. At this time, the first electrode wire 21 and the second electrode wire 22 are attached so as to have a distance difference ΔL with respect to the opening 31 of the shield 3. Finally, the detection circuit 5 is connected to the first electrode wire 21 and the second electrode wire 22 from the end of the sensor cable 2, and the proximity sensor 1 is manufactured. An experiment was conducted using the manufactured proximity sensor 1, and it was confirmed that the detection was possible at a position of 1 mm. The detectable position can be adjusted by adjusting the threshold value.

(Action and effect of embodiment)
As described above, the proximity sensor 1 according to the embodiment of the present invention collectively covers the first and second electrode lines 21 and 22 provided in parallel and the first and second electrode lines 21 and 22. The sensor cable 2 includes an insulator 23, a sensor cable 2 having a coating 24 covering the insulator 23, and a shield 3 having an opening 31 and partially covering the periphery of the sensor cable 2. Is fixed to the shield 3 so that the first and second electrode wires 21 and 22 have a distance difference ΔL with respect to the opening 31, and the first capacitance C1 and the first capacitance C1 detected by the first electrode wire 21 The proximity of the object to be detected 4 is detected by the difference from the second capacitance C2 detected by the two electrode wires 22.

With this configuration, in the sensor cable 2, the first electrode wire 21 and the second electrode wire 22 are collectively covered with the insulator 23 and are maintained in a parallel state with each other. Therefore, when the sensor cable 2 is attached to the shield 3, the detection circuit 5 is simply provided so that the first electrode wire 21 and the second electrode wire 22 have a distance difference ΔL with respect to the opening 31 of the shield 3. It is possible to manufacture the proximity sensor 1 excluding the above. Further, the distance difference ΔL can be adjusted only by rotating the sensor cable 2. Further, since the sensor cable 2 is manufactured by a cable manufacturing process, it is possible to easily manufacture a long cable having a diameter of several hundred meters and a cable having a diameter of 10 mm or less. Therefore, according to the present invention, it is possible to realize the proximity sensor 1 having excellent mass productivity.

Further, in order to detect the proximity of the object to be detected 4 by the difference between the first capacitance C1 detected by the first electrode wire 21 and the second capacitance C2 detected by the second electrode wire 22. It is possible to avoid detection malfunction due to airborne objects such as raindrops and fog.

Although the embodiments of the present invention have been described above, the embodiments described above do not limit the invention according to the claims. It should also be noted that not all combinations of features described in the embodiments are essential to the means for solving the problems of the invention. For example, in the above embodiment, the shield 3 using a thin metal plate has been described, but the shield 32 in which the metal conductive film 32b is formed on the surface of the resin shield main body 32a as shown in FIG. Can be used. It is also possible to provide the opening 31 so as to expose a part of the sensor cable 2.

The present invention can be appropriately modified and implemented without departing from the spirit of the present invention.

1 Proximity sensor 2 Sensor cable 3 Shield 4 Detected object 5 Detection circuit 21 1st electrode wire 21a Conductor 21b Conductive layer 22 2nd electrode wire 22a Conductor 22b Conductive layer 23 Insulator 24 Coating 25 Hollow part 31 Opening 51 1st Capacity detection unit 52 Second capacity detection unit 53 Shielding voltage application unit 54 Control unit 55 Differential output unit 100 Proximity sensor 101 First detection electrode 102 Second detection electrode 103 Shielding electrode 104 Object (detected object)

Claims (4)

Possess first and second electrode lines provided in parallel, an insulator collectively covering the first and second electrode lines, and a cover covering the insulator, the sensor cross-section is circular Cable and
A shield that has an opening and partially covers the periphery of the sensor cable,
With
The sensor cable is fixed to the shield so that the first and second electrode wires have a distance difference with respect to the opening.
A proximity sensor that detects the proximity of the object to be detected by the difference between the first capacitance detected by the first electrode wire and the second capacitance detected by the second electrode wire .
The shield is bent in two places so that a thin metal plate is bent along the longitudinal direction so that the cross section is at a right angle.
The sensor cable is a proximity sensor fixed to the shield so that spaces are formed between the two bent portions of the shield. The proximity sensor according to claim 1, wherein the insulator has a hollow portion formed between the first electrode wire and the second electrode wire. The proximity sensor according to claim 1 or 2, wherein the first and second electrode wires have a conducting wire made of metal and a conductive layer made of conductive rubber or conductive plastic covering the conducting wire. The proximity sensor according to any one of claims 1 to 3, wherein the insulator is made of a thermoplastic elastomer, and the coating is made of a styrene-based thermoplastic elastomer .

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