JPH04258725A - Electrostatic capacity type level sensor - Google Patents

Abstract

PURPOSE:To facilitate handling and manufacture and permit the use on a curved surface with high precision by sealing a pair of slender electrodes consisting of flexible conductors arranged in parallel, keeping a prescribed interval, in an insulating film and constituting the liquid and a condenser arranged on the periphery. CONSTITUTION:As for film-shaped insulating layers 1 and 6, adhesive layers 1b and 6b are installed on each one-side surface of the flexible base members 1a and 6a, and a pair of condenser electrodes 2 and 3 are arranged in parallel in the lengthwise direction, keeping a prescribed interval. Each of electrodes 2, 3 is made of the flexible electric conductive material consisting of a metal foil, and each of terminal electrodes, 4, 5 connected with a lead wire of a detection circuit is installed at one edge. These members are attached by the adheresive layers 1b and 6b, and the electrodes 2 and 3 and lead wire connecting part are sealed liquidtight form in an insulating film 10a consisting of the insulating layers 1 and 6. Accordingly, this element can be attached as it is, on the outer surface of a container or can be immersed into the liquid in the container, and installation is facilitated, and the structure is made simple, and manufacture can be made easy at a low cost. Futher, since the element is flexible, it can be closely attached on a curved surface, and detection precision is improved, and the liquid quantity or liquid level can be detected.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a level sensor such as a level meter or a level switch used for detecting a liquid level, and in particular, a capacitive level sensor that detects a liquid by converting the dielectric constant of the liquid into a capacitance. It is related to sensors.

0002

[Prior Art] A pair of electrode plates is attached to the outer circumferential surface of a resin or porcelain container containing the liquid to be detected so as to sandwich the liquid in the container. A capacitive capacitor is formed, and when the amount of liquid is large, the capacitance of the capacitor is large, and when the amount of liquid is small, the capacitance is small. Devices that detect the amount or level of liquid are known.

0003

[Problems to be Solved by the Invention] Conventional level sensors are installed by separately pasting a pair of electrode plates on the outer wall of a container, which not only makes the installation process extremely troublesome; Since the material of the electrode plate was relatively hard, it could not adhere tightly to the curved wall of the container, resulting in poor detection accuracy. It is an object of the present invention to solve the above problems and provide a capacitive level sensor that is easy to handle and manufacture.

0004

[Means for Solving the Problems] Therefore, the present invention provides a pair of elongated capacitor electrodes constituted by flexible conductors made of metal foil arranged side by side on the same plane with a predetermined interval, and The connecting portion of a pair of terminal electrodes connected to the ends is sealed within a flexible insulating film, and the other portion of the terminal electrode is made to protrude outward from the insulating film. be. Further, the shape of the flexible insulating film is L-shape or T-shape, and most of the capacitor electrodes are embedded in the long side of the flexible insulating film, and the flexible insulating film is curved into a cylindrical shape. This level sensor is used as a level meter by arranging the capacitor electrode perpendicular to the liquid surface, or as a level switch by arranging it parallel to the liquid surface.

[0005]

[Operation] Since the capacitor electrode is made of a flexible conductor and is sealed within an insulating film, the capacitor electrode is attached to the outer surface of the container as it is or is kept immersed in the liquid inside the container. Since a part of the terminal connected to the capacitor electrode is exposed, connection is made to a lead wire extending from the detection circuit. As a result, a capacitor is formed by the pair of elongated capacitor electrodes and the liquid interposed between the electrodes. When the amount of liquid is large, the capacitance of the capacitor is large, and when the amount of liquid is small, the capacitance is small.Using this fact, the amount or level of liquid in the container is detected based on the magnitude of these capacitances. It becomes possible to do so. Further, by bending the flexible insulating film into a cylindrical shape, it becomes possible to arrange it along the curved surface of the container. As shown in FIG.
When attaching the capacitor to the outer wall surface of No. 9, make sure to
By installing it vertically like 0a, it becomes a level meter with a capacitance proportional to the liquid level. Moreover, by installing the capacitor horizontally like 20b, the capacitance changes sharply when the liquid level passes through the gap between the capacitor electrodes, and it operates as a level switch.

[0006]

[Example] Figures 1 and 2 show an example of the present invention. In the figures, 1 is a band-shaped film-like insulating layer, which is coated on one side of a flexible base material 1a made of synthetic resin such as polyimide. It includes an adhesive layer 1b. 2 and 3 are a pair of capacitor electrodes arranged on the adhesive layer 1b of the insulating film 1 at a predetermined interval in the longitudinal direction of the insulating film, and are made of aluminum having a wall thickness of several tens of μm to several hundred μm. It is made of metal foil such as foil or copper foil, but any flexible conductive material may be used. 4 and 5 are a pair of terminal electrodes superposed and connected to one end of each of the capacitor electrodes 2 and 3, and a lead wire L extending from a detection circuit S (FIG. 3) that detects the capacitance between the capacitor electrodes. , L, and to facilitate connection by soldering, welding, etc., use a material that is stronger than the capacitor electrode, or use the same material as the capacitor electrode but with increased thickness and diameter to increase strength. There is. Similarly to the film-like insulating layer 1, 6 is a film-like insulating layer comprising an adhesive layer 6b on one side of a flexible base material 6a, and is pasted onto the adhesive layer 1b with the adhesive layer 6b facing downward. . As a result, all of the capacitor electrodes 2 and 3 and the connecting portions between the electrodes 2 and 3 and the lead wires L and L are sealed in a liquid-tight manner within the insulating film 10a made up of the film-like insulating layers 1 and 6.

[0007] A cross section of a film capacitor having the above structure is shown in FIG. 1c. Figure 1 shows the state of the electric lines of force 22 at a certain moment when an AC voltage is applied to this capacitor electrode.
c, the liquid level is detected by utilizing the change in capacitance as the dielectric constant of the medium surrounding the capacitor changes. Capacitance detection is performed using an astable multivibrator V, a rectifier circuit F, and a smoothing circuit C as shown in Figure 3.
By combining these, it is possible to read with DC voltage. Therefore, when there is sufficient liquid in the container, that is, when the liquid level is high, the capacitance of the capacitor is large, and when the liquid level decreases due to the use of liquid, the capacitance of the capacitor is small. The liquid level in the container can be detected by detecting the magnitude of these capacitances using a detection circuit.

Next, FIGS. 4 to 6 show another embodiment of the present invention, in which a flexible insulating film 10b having an L-shape or T-shape is used, and a capacitor electrode 12 is provided on the long side of the flexible insulating film 10b.
, 13 are sealed, and a pair of terminal electrodes 14, 15 connected to one end of each of the electrodes 12, 13 are sealed on the shorter side, and a portion of the terminal electrodes protrudes from the insulating film 10b. Then, as shown in FIG. 6, the long side of the insulating film 10b is bent into a cylindrical shape, and this is attached to the inner surface of a resin mounting jig 17 having a male thread 18 on the outer periphery as shown in FIG. It is inserted and fixed. This example has the advantage that the mounting jig 17 can be attached to and detached from the female screw hole provided in the upper wall surface of the container.

In each of the above embodiments, the insulating film 10 is formed by overlapping film-like insulating layers having an adhesive layer on one side.
a, 10b, and the capacitor electrode and the terminal electrode are integrally sealed between the film-like insulating layers. They may be sandwiched and joined together by thermocompression bonding.

0010

Effects of the Invention The present invention seals a pair of elongated capacitor electrodes made of flexible conductors such as metal foil or thin metal wire in juxtaposition at a predetermined interval within an insulating film. , a capacitor is formed by the liquid interposed around the electrode, and when the amount of liquid is large, the capacitance of the capacitor is large, and when the amount of liquid is small, the capacitance is small. Since the device detects the amount or level of liquid in the container based on the capacitance, it can be simply attached to the outside of the container or immersed in the liquid inside the container. , easy to install. Also, in terms of manufacturing, since the configuration is simple as described above, it can be manufactured easily and at low cost. Furthermore, since parts such as capacitor electrodes and insulating films are made of flexible materials, they can be placed in close contact with the curved surface of the container, which not only does not reduce detection accuracy, but also allows them to be bent freely onto curved surfaces such as cylindrical shapes. There are advantages that can be achieved. Furthermore, according to the present invention, since a part of the terminal connected to the capacitor electrode is exposed, there are excellent effects such as easy connection to a lead wire extending from the detection circuit.

[Brief explanation of the drawing]

FIG. 1a is a perspective view of a level sensor showing an embodiment of the present invention.

FIG. 1b is a cross-sectional view taken along line AA in FIG. 1a.

FIG. 1c is a cross-sectional side view of the same level sensor.

FIG. 2 is a perspective view of film-like insulating layers 1 and 6 similarly used in the example.

FIG. 3 is a block diagram showing a level sensor and detection circuit of the present invention.

FIG. 4 is a longitudinal sectional side view of a level sensor showing another embodiment of the present invention.

FIG. 5: Insulating film 10 also used in this example.
It is a partially cutaway development view of b.

FIG. 6: Insulating film 10 also used in this example.
It is a perspective view of b.

FIG. 7 is a perspective view showing an example of how a level sensor is used.

[Explanation of sign]

1 Film-like insulation layer 1a Flexible base material 1b Adhesive layer 2, 3 Capacitor electrode 4,5 Terminal electrode 6 Film-like insulation layer 6a Flexible base material 6b Adhesive layer 10a, 10b Insulating film 12, 13 Capacitor electrode 14, 15 Terminal electrode 17 Mounting jig 18 Male thread L, L lead wire

Claims (4)

[Claims] 1. A pair of elongated capacitor electrodes constituted by flexible conductors made of metal foil arranged side by side on the same plane with a predetermined interval apart, and a pair of terminal electrodes connected to the ends of the electrodes. A capacitive level sensor characterized in that a connecting portion is sealed within a flexible insulating film, and the other portion of the terminal electrode is made to protrude outward from the insulating film. 2. The flexible insulating film is L-shaped or T-shaped, with most of the capacitor electrode buried in the long side thereof, and curved into a cylindrical shape. Capacitive level sensor. 3. The capacitive type according to claim 1, wherein the pair of elongated capacitor electrodes made of a flexible conductor are arranged perpendicular to the liquid level and used as a level meter. level sensor. 4. The capacitive level sensor according to claim 1, wherein the pair of elongated capacitor electrodes made of flexible conductors are arranged parallel to the liquid surface and used as a level switch. .