JPS62222135A - Electrostatic capacity weight detector - Google Patents

Abstract

PURPOSE:To obtain the title detector having a good temp. characteristic and a good humidity resistant characteristic, by providing a diaphragm detecting a wt. to the single surface of a base and providing a diaphragm comprising resin film absorbing the expansion and contraction of hermetically closed air to the other surface thereof. CONSTITUTION:For example, this detector is constituted of an alumina base 11 having a dimension of phi30mm, 1.0mmt, the baked electrode of phi23mm provided to the central part thereof and an alumina diaphragm 15 of phi30mm, 0.6mmt having an electrode 14 provided to the back surface thereof. If the diameter of the diaphragm 15 is phi3mm or more (or less), the temp. coefficient of wt. detection quantity comes to 50ppm/ deg.C (or 25ppm/ deg.C) or less. This corresponds to that the variations of a zero point to the change in temp. of 50 deg.C are respectively 100g or less and 50g or less in a wt. detector of a 5kg-full scale. If temp. coefficient is 50ppm/ deg.C or less, sufficient correction can be performed in a circuit side detecting electrostatic capacity. Therefore, an electrostatic capacity type wt. detector having an excellent temp. characteristic is obtained.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a capacitive weight sensor.

Conventional technology Conventionally, as shown in FIG. 4, the capacitive weight detector of this building has an electrode 2 provided at the center of the upper surface of an alumina base 1, a spacer 3 provided at the periphery of the base, and a An alumina diaphragm 5 having an electrode 4 on the back surface is fixed on the spacer,
Solder the through hole 6 provided in the base! Therefore, it was used as a capacitive weight detector.

When detecting weight, a weight is applied to the center of the diaphragm 4 and the diaphragm 5 is deflected to change the capacitance between the electrodes 2 and 4, and this change allows the applied weight to be detected. was.

Problems to be Solved by the Invention However, in the above configuration, the gap between the base 1° and the diaphragm 4 is in the 'fS closed state by sealing the K through hole, so there is a problem that the temperature characteristics are poor. I was used to it. In other words, due to temperature changes, the sealed air or gas expands and contracts, pushing the diaphragm 5 up and down and lowering it, which changes the capacitance between the electrodes 2 and 4, resulting in accurate measurement. The problem was that the weight could not be detected.

In addition, if the through hole 6 is used without being sealed, the temperature characteristics are good but the moisture resistance characteristics are poor.In other words, moisture enters through the through hole 6, water droplets are formed between the electrodes 2 and 4, and static electricity between the electrodes 2 and 4 is generated. The problem was that the capacitance could no longer be detected, resulting in malfunction.

The present invention solves these conventional problems.

It is an object of the present invention to provide a capacitive weight detector having excellent temperature characteristics and good moisture resistance characteristics.

Means for Solving the Problems The capacitive weight detector of the present invention has a diaphragm for sensing weight on one side of the base, and a diaphragm for sensing weight on the other side of the base.・Equipped with a diaphragm made of a resin film to absorb shrinkage.

Function: Since the present invention is based on the above h'll structure, the volume change due to expansion and contraction of the air in the diaphragm due to temperature change is
Since the diaphragm made of a resin film is pushed up and down through the through hole, the weight sensing diaphragm does not bend, so there is no malfunction due to temperature changes. Further, since the diaphragm is sealed with a resin film, moisture does not enter into the diaphragm.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
The figure shows a partially cutaway perspective view of an electrostatic @ large weight detector based on the present invention. In the same figure, 11 is φ3 (1m
, 1. On t alumina base, 12 is a baked electrode of φ2311I+ provided in the center of the base, 13 is a spacer made of sealing glass with a height of 50 μm provided over the circumference of the base from φ24xm to φ28■, 15 is φ30trrtx, (J,
A 5mm t alumina diaphragm is shown. 15 is sealed around the spacer 13. 16 is the base 11
A through hole provided in the.

17 is tree 11m1l! Shows a support stand for fixing the peripheral part of #18. The distance between the resin film and the alumina base is 0.
．． It was set to 1n. The thickness of the resin film was 0.05 m1+t.

As the resin film, a polyimide resin film and a fluorine resin film were used. FIG. 2 shows the temperature coefficient of capacitance of the capacitive weight sensor at 20°C to 60'C.

The vertical axis shows the temperature coefficient, and the horizontal axis shows the effective diameter of the resin membrane diaphragm. Black circles (・) indicate the results for polyimide resin films.
Multiplyed by (x) indicates the result for the fluororesin film.

From the same figure, the conventional weight detector (@oil film diaphragm diameter O
The temperature coefficient of the resin membrane diaphragm (corresponding to MW&) was 200 ppm7C, but if the diameter of the resin membrane diaphragm is φ3 mm or more, it will be 50 ppm/'C or less, and if the diameter is φ4 mm or more, it will be 25 ppm/°C or less. I understand that. This corresponds to 50° on a Kufr scale weight detector.
The zero point fluctuation of C with respect to temperature change, which was about 400f in the conventional case, corresponds to 1001 or less and 50g or less, respectively. If the temperature coefficient is 50 ppm/°C or less, sufficient correction is possible on the circuit side that detects capacitance. Therefore, the present invention can provide a static FL capacitive weight sensor with improved temperature characteristics.

Next, the humidity characteristics were evaluated and the results are shown in Figure 3.

The vertical axis shows the relative change in capacitance, and the horizontal axis shows humidity.

Dotted line A shows the results of a conventional solder seal capacitive weight sensor. The dashed line B shows the results of the capacitive weight sensor having the resin film diaphragm according to the present invention shown above. The figure shows that the characteristics are significantly improved in the high humidity region.

This is thought to be due to the water resistance of the resin film used for the diaphragm, that is, the polyimide resin film or the fluorine resin 11t'f film.

For this purpose, the surface of the capacitive weight detector having a diaphragm made of a resin film based on the present invention is coated with a water-contactable resin.
For example, it can be seen that spray coating with polyimide resin or fluororesin further improves the +m-1 humidity characteristics. The moisture resistance properties in the case where the surface is covered with a water-wettable a-1 layer such as polyimide resin or fluorine resin are also shown in FIG. 3 as a solid line C. From the figure, it can be seen that the change in capacitance was significantly improved to 10% or less even in a high humidity region of 90% or more.

As described in detail, the capacitive weight sensor of the present invention provides the following effects.

(1) Since it has a diaphragm made of a resin film, it can absorb pressure changes accompanying temperature changes, which has the effect of significantly improving temperature characteristics.

(2) Since the surface is coated with a water-wettable resin, the moisture resistance properties are significantly improved.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view of a capacitive weight detector according to an embodiment of the present invention, FIGS. 2 and 3 are characteristic diagrams of the capacitive weight detector, and FIG. 4 is a conventional capacitive weight detector. FIG. 1 is a partially cutaway perspective view of the 1'# electric weight type weight detector. 11... Base, 12.14... Electrode,
13...Spacer, 15...Diaphragm, 16...Through hole, 17...Support stand, 18...Resin film. Agent's name Masu Rishi Nakao Noboru Male Haka 1 person II
-11 group right/Z-m-electrode/3-~-subedz/4-1-i sheet 15-11 da/Yafura A 16- Penetration J(,,l Fig. 2 0.5 10 15 points rlIMll lol Gun
- Posoimito Showa Kano Moon Plate Film x -------7 Tsumuji Column W1 Kushiryo 3 Figure Oz5 50 75 100t?
- Noshi 5 and z) Chopsticks 4 Figure

Claims (3)

[Claims] (1) an alumina base, a diaphragm made of alumina whose peripheral portion is fixed to the alumina base so as to obtain a predetermined distance from the alumina base on the upper surface of the alumina base, and a lower surface of the alumina base. and a diaphragm made of a resin film whose peripheral portion is fixed to the alumina base so as to obtain a predetermined distance from the alumina base, and each diaphragm is connected to the alumina base by a through hole provided in the alumina base. A capacitive weight sensor having an electrode formed on the inner surface of a diaphragm made of alumina and the alumina base facing each other. (2) The capacitive weight sensor according to claim 1, wherein the diaphragm is made of a polyimide resin film or a fluorine resin film. (3) The capacitive weight sensor according to claim 1, the surface of which is coated with a resin.