JP2000292270A - Capacitance-type load sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a capacitance-type load sensor in a simple structure for stabilizing long-term measurement accuracy and improving the measurement accuracy. SOLUTION: In the load sensor, first and second electrode bodies 11 and 12 made of a metal plate are arranged in parallel with a specific gap through a spacer 14 for supporting the outer-periphery end part, and at the same time a third electrode body 13 that is made of a printed-circuit board 13a where a metal film 13b is arranged on both surfaces is insulated for the first and second electrode bodies and is provided in parallel with a specific distance between the first and second electrode plates. Then, a third electrode body is used as a reference electrode body to which outer force applied to the first and second electrode bodies is not transferred, and at the same time each capacitor that is formed between the first and second electrode bodies is used as a common electrode to be connected in parallel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitance type load sensor for improving stability and accuracy of load measurement.

[0002]

2. Related Background Art Basically, as shown in FIG. 2A, a capacitive load sensor is opposed to a pair of electrode bodies (a first electrode body and a second electrode body) with a minute gap therebetween. ) 1,2
And two electrode bodies 1 and 2
And an annular spacer 3 interposed between the electrode bodies 1 and 2 to insulate the electrode bodies 1 and 2 from each other. Make the formed structure. Then, under the load P, for example, FIG.
As shown in FIG.
The change in the distance between the electrodes 2 and thus the change in the capacitance of the capacitor formed by the electrodes 1 and 2 is changed via the lead wires 5 and 6 connected to the electrodes 1 and 2 respectively. It works as if it were caught.

In some cases, one of the electrode bodies 1 and 2 is realized as a metal film 2b formed on a printed circuit board 2a on the side of the electrode body 2 to which no load P is applied, for example, as shown in FIG. The spacer 3 is usually made of a highly insulating plastic material, for example, using an engineering plastic such as POM (polyoxymethylene), PI (polyimide), or PEN (polyethylene naphthalate).

[0004]

When a load P is applied to one of the electrode members 1, a reaction force due to the bending of the electrode member 1 acts on the rivets 4, 4, etc., and the other electrode member 2 is bent. Sometimes In particular, a large load P of 100 kg or more
, It is easy to cause such a problem. By the way, if the other electrode body 2 bends, the warp causes a disturbance to the change in the distance between the pair of electrode bodies 1 and 2, which significantly deteriorates the measurement accuracy and makes stable measurement impossible.

[0005] Further, in this type of capacitance type load sensor, in order to ensure easy measurement and sufficient measurement accuracy,
Usually, measures are taken to increase the change in the capacitance. Specifically, a countermeasure such as using a metal material having a large deflection with respect to the load as the electrode body 1 or reducing the thickness thereof so as to be easily bent is taken. However, when the plate thickness is reduced, the metal plate forming the electrode body 1 is liable to be permanently deformed (plastically deformed), and a new problem such as a significant deterioration in measurement accuracy is liable to occur.

The present invention has been made in view of such circumstances, and has as its object to stabilize the measurement accuracy over a long period of time and to improve the measurement accuracy by using a simple-structured capacitance. It is to provide a mold load sensor.

[0007]

In order to achieve the above-mentioned object, a capacitive load sensor according to the present invention comprises a first and a second electrode body made of a metal plate, and a spacer for supporting the outer peripheral edge of the first and second electrode bodies. And a third electrode body made of a printed circuit board having the same metal plate as the first and second electrode bodies or an electrode body disposed on both sides thereof, and It is characterized in that the first and second electrode plates are provided in parallel with a predetermined distance from each other while being insulated from the first and second electrode bodies.

According to a second aspect of the present invention, the third electrode body is used as a reference electrode body to which an external force applied to the first and second electrode bodies is not transmitted. As described in above, a capacitor formed between the first and second electrode bodies is used as a common electrode for parallel connection. That is,
A third electrode body to which no external force is applied is provided between the first and second electrode bodies to which external force is applied.
For the two capacitors formed between the first electrode body and the first and second electrode bodies, the third electrode body is used as the reference electrode body or a common electrode for connecting the capacitors in parallel. It is characterized in that it is used.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A capacitance type load sensor according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing a schematic configuration of a capacitive load sensor according to this embodiment. Numerals 11 and 12 denote first and second disk-shaped electrode members made of a metal plate such as stainless steel. Reference numeral 13 denotes a third electrode body formed by forming circular metal films 13b, 13b on both sides of a central portion of a printed circuit board 13a having the same diameter as the electrode bodies 11, 12 except for an outer peripheral region having a predetermined width. . These metal films 13b, 13b
The printed circuit board 13a is electrically connected between the front and back surfaces of the printed circuit board 13a via conductive through holes 13c to function as one electrode.

The first to third electrode bodies 11, 1
The reference numerals 2 and 13 are stacked via annular spacers 14 and 14 having a predetermined thickness d with the third electrode body 13 therebetween, and are arranged in parallel with a predetermined interval d therebetween. A rivet 15 for joining and integrating the electrode bodies 11, 12, 13 and the spacers 14, 14 laminated as described above is provided on the outer peripheral portions of these electrode bodies 11, 12, 13 and the spacers 14, 14. The mounting holes to be inserted are provided, respectively, and these mounting holes are sandwiched and integrated by the rivets 15 inserted.

In particular, mounting holes formed in the third electrode body 13 and the spacers 14 and 14 respectively allow a predetermined length of cylindrical metal collar 16 to be inserted into the outer periphery of the rivet 15 so as to be inserted therethrough. Each of the electrode bodies 11, 1
2 are formed slightly larger in diameter than the mounting holes provided respectively. As described above, when the laminated body from the first electrode body 11 to the second electrode body 12 is joined and integrated by using the rivet 15, the mounting provided on the third electrode body 13 and the spacers 14 and 14 is performed. With the metal collar 16 inserted into the hole, the facing distance between the lower surface of the first electrode body 11 and the upper surface of the second electrode body 12 is defined with high precision.

The third electrode body 13 of the capacitive load sensor having a structure of being laminated and bonded and integrated via the spacers 14 and 14 is a metal film 13b and 13b of the printed board 13a. By supporting the outer peripheral surface, on which is not formed, via the spacers, they are insulated from the first and second electrode bodies 11, 12, respectively. Thus, the metal films 13b, 13b of the third electrode body 13 and the first and second electrode plates 11,
12, capacitors formed of parallel electrode plates are formed. Further, the first and second electrode plates 11, 12 arranged in parallel with the facing distance defined by the metal collar 16 are electrically connected to each other via the metal collar 16, whereby The third electrode body 13
As a common electrode, the first and second electrode plates 11,
12 are connected in parallel with each other.

The first and second electrode bodies 11, 1
The second electrode lead 17 is connected to the spacer 14 or the rivet 1.
5 and is led out to the outside.
The electrode lead 18 is connected to the metal films 13b, 13b and led out. And each of the electrode leads 1
The third electrode body 13 and the first and second electrode bodies 11, 1 are connected by connecting the first and second electrode bodies 7 and 18 to a capacitance meter (not shown).
The change in capacitance due to the loads P and Q applied between the electrode bodies 11 and 12 of the capacitors respectively formed between the electrodes 2 and 2 is detected.

Thus, according to the capacitance type load sensor having the structure as described above, the first and second electrode bodies 11 and 12 made of a metal plate can be precisely positioned between the opposing electrodes via the metal collar 16. The distance is defined, and a third electrode body 13 positioned between these electrode bodies 11 and 12 is provided.
Has a structure in which the loads P and Q applied to the electrode bodies 11 and 12 are not transmitted. Therefore, even if the electrode bodies 11 and 12 are bent under the loads P and Q, the third Electrode body 13 does not bend. In particular, the spacers 14,1
For example, if the electrodes 4 and 4 are made of the same metal material as the electrodes 11 and 12, even if large loads P and Q of 100 kg or more are applied, the loads can be reliably received by the spacers 14 and 14. Since only the first and second electrode bodies 11 and 12 can be bent, the entire structure can be made rigid without causing distortion.
As a result, the third electrode body 13 can function as a reference electrode plate to which no load is applied. Furthermore, with reference to the third electrode body 13, it is possible to stably and highly accurately measure a change in capacitance caused by bending of the first and second electrode bodies 11, 12 due to the loads P, Q. It becomes possible.

Further, since two capacitors formed respectively between the third electrode body 13 and the first and second electrode bodies 11, 12 are connected in parallel, the loads P, Q
Can double the change in capacitance due to the measurement and expand the measurement dynamic range.
Effects such as an increase in measurement accuracy for a load can be obtained.

The present invention is not limited to the above embodiment. For example, if the spacers 14 are
OM (polyoxymethylene), PI (polyimide), P
It is also possible to use an engineering plastic having high insulation properties such as EN (polyethylene naphthalate). Also, the third electrode body 13 can be realized by using the same metal plate as the first and second electrode bodies 11 and 12. In this case, for example, rivet 1
By using the above-mentioned high engineering plastic as 5 or by forming an insulating layer made of an insulative chemical conversion film such as alumina or a phosphorous oxide film on the surface of the metal collar 16, the first electrode body 13 is made of the first material. In addition, it is only necessary to ensure the insulating properties for the second electrode bodies 11 and 12.

Further, here, two capacitors formed on both surfaces of the third electrode body 13 may be connected in parallel, or only one of the two capacitors may be used. In this case, one of the electrode bodies 11 and 12 functions to cancel the reaction force of the electrode body that bends under the load P (Q) and prevents the third electrode body 13 from warping. Become. Also, instead of joining and integrating with the rivet 15,
Needless to say, the electrodes 11, 12, 13 and the spacer 14 may be joined and integrated by ultrasonic welding or the like. Furthermore, the thickness and the diameter (the size of the pressure-receiving surface) of the first and second electrode bodies 11 and 12 may be determined according to the measurement specifications such as the maximum measurement load and the measurement resolution. In addition, the present invention can be variously modified and implemented without departing from the gist thereof.

[0018]

As described above, according to the present invention, 2
By providing a third electrode body to which no external force is applied between the first and second electrode bodies made of a single metal plate, the third electrode body can be used as a standard electrode plate, Since it functions as a common electrode for connecting two capacitors formed in parallel with each other, the detection sensitivity is improved to improve the measurement accuracy, and practical load measurement can be performed over a long period of time. A great effect can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic configuration of a capacitive load sensor according to an embodiment of the present invention.

FIG. 2 is a cross-sectional configuration diagram for explaining a schematic configuration of a conventional general capacitive load sensor and a problem thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 1st electrode body (metal plate) 12 2nd electrode body (metal plate) 13 3rd electrode body 13a Printed circuit board 13b Metal film 14 Spacer 15 Rivet 16 Metal color 17, 18 Electrode lead

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ken Koyata 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Inside Furukawa Electric Co., Ltd. (72) Inventor Takayuki Enomoto 2-6-1 Marunouchi, Chiyoda-ku, Tokyo No. Furukawa Electric Co., Ltd. (72) Inventor Katsutoshi Sasaki 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (72) Inventor Hideo Morimoto 172 Ikezawa-cho, Yamatokoriyama-shi, Nara Nita shares Inside the Nara factory

Claims (3)

[Claims] 1. A first and a second electrode body made of a metal plate, and supporting the outer peripheral edges of the first and the second electrode body so that the first and the second electrode body are separated by a predetermined distance. And a printed circuit board having the same metal plate as the first and second electrode bodies or an electrode body disposed on both sides thereof, and insulated from the first and second electrode bodies. And a third electrode body supported by the spacer and arranged in parallel with a predetermined distance between the first and second electrode plates. Sensor. 2. The device according to claim 1, wherein the third electrode body is used as a reference electrode plate to which an external force applied to the first and second electrode bodies is not transmitted. Capacitive load sensor. 3. The device according to claim 1, wherein the third electrode body is used as a common electrode for connecting in parallel a capacitor formed between the first and second electrode bodies. Capacitive load sensor.