JPH11153470A - Sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely hold a detecting position with a proper rigidity, reduce the diameter, and dispense with cut stripping by combining a highly rigid conductive rod with a highly rigid conductive pipe. SOLUTION: An electrode is formed of a conductive rod 1, two insulating tubes 2 and two conductive pipes 3, and the tip part 1a of the conductive rod 1 and the tip part 3a of each conductive pipe 3 are exposed from the insulating tubes 2 with respective spaces. When each tip part 1a, 3a makes contact with a conductive material to be detected, the conductive rod 1 is conducted to each conductive pipe 3 to detect the presence of the material to be detected in multiple point. Since the highly rigid conductive rod 1 and conductive pipe 3 are used, the detecting position can be precisely held, and the diameter can be reduced, so that this sensor can be mounted in a narrow place. Further, since the rod, tubes and pipes of prescribed dimensions are combined together, a cut stripping work as in a coaxial cable is dispensed with, and the work is facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor for detecting the presence of a conductive substance, and more particularly to a sensor having rigidity, easy positioning, and suitable for detecting a liquid such as water. is there.

[0002]

2. Description of the Related Art Conventionally, as a liquid detection sensor such as a liquid level sensor, there has been generally used a liquid detection sensor in which metal electrodes are opposed to each other and the presence of liquid makes the two electrodes conductive. With this sensor, water droplets and bubbles remain between the electrodes, causing malfunction. For this reason, the distance between the electrodes is increased so that water droplets and bubbles do not remain. However, the size of the sensor is increased, and it is difficult to use the sensor in a narrow place. Furthermore, there is also a problem that the service life is short because the metal electrode is easily corroded.

In order to solve such a problem, the present applicant uses a coaxial cable in which an inner conductor and an outer conductor are first provided via an inner insulating layer, and the outer periphery is covered with the outer insulating layer. (Japanese Unexamined Patent Publication No. 7-32505)
No. 6).

However, since this sensor uses a coaxial cable, it is too flexible and easily bends. When inserted into a medium to be detected, the sensor bends or its installation position shifts during use. Thus, it has been found that there is a problem that the detection position cannot be accurately maintained. In addition, when the sensor diameter is reduced in order to install the sensor in a narrow space, the above tendency is further promoted, and the sensor is downsized (smaller diameter).
There was a limit to doing it.

In the coaxial cable type sensor described above, it is necessary to peel off the outer insulating layer with a cut-strip machine in order to expose the outer conductor, and this operation is complicated. It can be peeled off only about 80 mm in length, and when exposing the external conductor over this length, it was necessary to peel off by hand using a cutter or the like.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention solves the above-mentioned problems of the prior art, has an appropriate rigidity, can accurately hold the detection position, and can reduce the diameter. It is another object of the present invention to provide a sensor which does not require a cut strip.

[0007]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, have conceived of combining a conductive rod having high rigidity with a conductive pipe. It was completed.

That is, according to the present invention, (1) an insulating tube and a conductive pipe are provided in this order on the outer periphery of the conductive rod, and the tip of the conductive rod is spaced from the tip of the conductive pipe. And (2) the outer periphery of the conductive pipe is covered with an insulating tube, and the tip is exposed from the insulating tube. The sensor described in 1) and (3) one or two or more insulating tubes and conductive pipes are further provided in this order on the outer circumference of the conductive pipe, and the tip of each conductive pipe is spaced apart from each other. The outer periphery of the outermost layer of the sensor described in (1) and (4) the conductive pipe, which is exposed from the tube, is covered with an insulating tube, and the tip of the sensor is insulated. (5) The sensor according to the above (3), characterized in that the exposed tip is covered with a conductive resin at intervals. The sensor according to any one of (1) to (4).

According to the sensor of the present invention, since the tip of the conductive rod at the center is exposed at an interval from the tip of each conductive pipe, the conductive rod and each conductive pipe are exposed. When the tip of the probe comes in contact with a conductive substance to be detected (for example, liquid such as water), the conductive rod and each conductive pipe conduct through the substance to be detected, and the presence of the substance to be detected is detected at multiple points. can do.

Further, in the present invention, since the conductive rod having high rigidity and the conductive pipe are used, the detection position can be accurately maintained. In addition, since a thin conductive pipe with high rigidity is used and the diameter can be reduced, it can be mounted in a narrow place.

Further, if the exposed end portions of the conductive rod and the conductive pipe are coated with a conductive resin, the metal of the rod and the pipe does not come into direct contact with the substance to be detected, thereby preventing corrosion. Can be. In addition, since rods, tubes, and pipes of predetermined dimensions are combined, a cut strip operation such as a coaxial cable is not required, and processing is easy.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing an example of the sensor of the present invention. This is a sensor having three electrodes composed of a conductive rod-shaped body, two insulating tubes, and two conductive pipes 3. Tip 1 of conductive rod 1
a and the distal end portion 3a of each conductive pipe 3 are exposed from the insulating tube 2 at intervals.

The dimensions of the conductive rod 1 are φ0.5 to φ5 m.
m is preferable, and φ1 can secure sufficient strength with a small diameter.
φ2 mm is particularly preferred. The material of the conductive rod 1 is hard iron, aluminum, brass, phosphor bronze, copper, silver, SUS, titanium, hastelloy,
Metals such as gold, tin, nickel, and platinum are preferable, and SUS, titanium, and Hastelloy, which have excellent corrosion resistance, are particularly preferable.

The material of the conductive pipe 3 is preferably the same as the material of the conductive rod 1. The thickness is preferably about 0.2 mm to 1 mm.

Next, as the material of the insulating tube 2, the following various polymers are used. Such polymers include, for example, general-purpose polymers such as polyvinyl chloride, polyethylene, polypropylene, and polyurethane, polyamides,
Polycarbonate, polysulfone, polyimide, polyamideimide, polyetherimide, polyarylate,
Polyethersulfone, polyetheretherketone, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkylvinylether copolymer, ethylene-tetrafluoroethylene copolymer,
Examples include engineering plastic polymers such as polyvinylidene fluoride, and thermosetting polymers such as phenolic resins, epoxy resins, and silicone resins.

In addition, synthetic rubbers such as silicone rubber, ethylene propylene rubber, acrylic rubber, and fluorine rubber, and various thermoplastic elastomers such as vinyl chloride, urethane, and fluorine can be used.

Among them, polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, ethylene-tetra Fluororesins such as fluoroethylene copolymers are preferably used, and particularly, tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and ethylene-tetrafluoroethylene copolymer having excellent processability are used. Polymers are preferably used.

The thickness of the insulating tube 2 is 0.2 mm.
Approximately 1 mm is preferable. Here, in the case of using in an environment where the metal is further corroded, as shown in FIG.
The conductive rod-shaped body 1 and the exposed tip portions 1a and 3a of the conductive pipe 3 are coated with a conductive resin 4 having corrosion resistance.
What is necessary is just to cover with. As the conductive resin 4, those obtained by adding various conductive fillers to the various polymers described above are used.

Examples of the conductive filler include carbon black such as acetylene black, Ketjen black and graphite, carbon fiber, particles or fibers made of metal such as silver, copper and nickel, and metal oxides such as tin oxide. No. These conductive fillers
The volume resistivity of the obtained conductive resin is 10 ⁻³ to 10 ⁹ Ωc.
It is preferable to add an amount of m. In addition, conjugated polymers such as polyacetylene, polyaniline, polythiophene, and polypyrrole can be used as a conductive resin without adding a conductive filler.

Further, the conductive rod 1 and the conductive pipe 3
And between the conductive pipes 3 are preferably at least 5 mm apart from each other in order to prevent malfunctions due to pools or bubbles. Here, in order to prevent corrosion and oxidation of the electrode, the outer periphery of the outermost conductive pipe 3 may be further covered with an insulator such as the insulating tube 2 except for the tip 3a.
As described above, the example of the sensor having three electrodes has been described, but an arbitrary multipoint detection sensor can be realized by adding the insulating tube 2 and the conductive pipe 3 according to the number of locations to be detected.

Next, in order to manufacture the sensor of the present invention, the insulating tube 2 is heat-sealed or bonded with an adhesive so that the leading end 1a of the conductive rod 1 as the center is exposed. Fix to body 1. Alternatively, a physical method such as caulking, press-fitting or a binding member may be used.

Next, the conductive pipe 3 is fixed to the insulating tube 2 at a position separated from the conductive rod 1 by a predetermined distance in the same manner. Hereinafter, the insulating tube 2 and the conductive pipe 3 are fixed in the same manner. Here, it is preferable that the inner surface of the insulating tube 2 is subjected to a surface treatment such as a chemical treatment in advance, so that stronger adhesion can be obtained.

Next, as shown in FIG.
When a is coated with the conductive resin 4, the processed sensor is set in an injection mold, and the conductive resin 4 is injection-molded around the conductive rod 1 and the conductive pipe 3. The conductive rod 1 and the conductive pipe 3 may be integrated. In addition, an arbitrary method such as melting and applying a conductive resin can be used.

Further, a flange-like mounting stay 5 can be bonded, welded, or soldered to the outermost conductive pipe 3 (or the insulating tube 2) to facilitate mounting of the sensor. Also, as shown in FIG. 2, the electrode terminal 6 is attached to the end of the conductive rod 1 or the conductive pipe 3 on the side opposite to the detection side by spot welding, soldering, bonding or press fitting. Good. In FIG. 2, the same parts as those in FIG.

In the sensor of the present invention, the other end of the sensor can be connected to a buzzer, a display device or the like to notify the presence of the substance to be detected, and further connected to a control circuit to control the liquid level. Can also.

The sensor of the present invention is useful as a level sensor for detecting a conductive liquid such as water at multiple points, but can also be used for detecting other conductive substances.

[0027]

According to the present invention, it is possible to provide a multi-point detection sensor that is compact, rigid, easy to position, and does not require a cut strip.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an example of a sensor of the present invention.

FIG. 2 is a longitudinal sectional view showing another example of the sensor of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 conductive rod 1a tip of conductive rod 2 insulating tube 3 conductive pipe 3a tip of conductive pipe 4 conductive resin 5 mounting stay 6 electrode terminal

Claims (5)

[Claims] 1. An insulating tube and a conductive pipe are provided in this order on the outer periphery of a conductive rod-shaped body, and the tip of the conductive rod-shaped body is spaced apart from the tip of the conductive pipe. A sensor exposed from an insulating tube. 2. The sensor according to claim 1, wherein an outer periphery of the conductive pipe is covered with an insulating tube, and a tip end thereof is exposed from the insulating tube. 3. One or more insulating tubes and conductive pipes are further provided in this order on the outer periphery of the conductive pipe, and the distal ends of the conductive pipes are spaced from each other by an insulating tube. The sensor according to claim 1, wherein the sensor is exposed from the surface. 4. The sensor according to claim 3, wherein the outer periphery of the outermost layer of the conductive pipes is covered with an insulating tube, and a tip end of the outer tube is exposed from the insulating tube. 5. The method according to claim 1, wherein each of the exposed front ends is covered with a conductive resin at intervals.
5. The sensor according to any one of 4).