JPS6326745Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a capacitive pressure sensor mainly used for measuring minute fluid pressure.

Generally, as a measuring device for measuring fluid pressure, one side of the pressure introduction chamber into which the fluid to be measured is introduced is configured with a flat diaphragm, and an electrode plate is placed opposite the surface of the flat diaphragm. Using a capacitance pressure sensor with electrodes deposited on the surface facing the flat diaphragm, the internal pressure of the pressure introduction chamber is determined by measuring the capacitance between the two electrodes, which changes as the flat diaphragm deforms. There are known devices that measure changes.

Among this type of measuring instruments, especially capacitance type pressure detectors that measure minute pressures, as shown in FIG. A capacitor is known in which the flat diaphragm 3 is closed and an electrode plate 4 is provided opposite the central portion of the diaphragm, and a capacitor is formed by the facing surfaces of the flat diaphragm 3 and the electrode plate 4.

In this type of capacitive pressure sensor, the peripheral edge of the flat diaphragm 3 is supported by the detector body 1, and the electrode plate 4 is fixed to the detector body 1 separately from the flat diaphragm 3. Therefore, it required a high degree of skill to form a desired minute gap between the electrodes, and the processing was difficult.

In addition, the gap between the electrodes must be unaffected by changes in temperature, but it is difficult to use a material with a small coefficient of thermal expansion, such as ceramic, for the detector body itself, and conventional In this type, the thermal deformation of the detector body directly affects the gap between the electrodes, resulting in problems such as the measured value changing greatly depending on the temperature.

The purpose of this invention is to solve the above-mentioned problems, and its gist is as follows:
One surface of the pressure introduction chamber is constituted by a flat diaphragm, and electrodes are provided on either the front or back surface of the flat diaphragm and the opposing surface of an electrode plate provided opposite thereto, and the flat diaphragm In a capacitive pressure sensor configured to detect a change in capacitance between both electrodes due to deflection, the center portion of the flat diaphragm is supported by a protrusion provided on the detector body, and the flat diaphragm is Only the center portion of the electrode plate is fixed to the center portion of the electrode plate via a spacer, and the portions other than the center portion of the electrode plate are arranged at predetermined intervals with respect to the flat diaphragm and the detector body, respectively. The method consists in covering the outside of the flat diaphragm and the electrode plate with a cover and adjusting the pressure inside the cover.

Next, a first embodiment of the present invention will be described with reference to FIG.

In the figure, 10 is a detector body. The detector body 10 has a pressure introduction chamber 1 arranged in a ring shape on its upper surface.
1 is recessed and its outer surface is closed with a metal flat diaphragm 12. The periphery of the flat diaphragm 12 is held between the retaining ring 13 and the detector body 10, and the O-ring 1
4 and 14, it is airtightly sealed. Further, the center portion of the flat diaphragm 12 is supported by a protrusion 15.

On the other hand, electrode plates 16 are provided at intervals to face the outer surface of the flat diaphragm 12. This electrode plate 16 is a flat diaphragm 12
A bolt 18 is passed through the center of the flat diaphragm 12 with a spacer 17 in between, and the bolt 18 is screwed onto the protrusion 15 of the detector body 10, thereby connecting the center of the flat diaphragm 12 to the detector body. 10, the center of the electrode plate 16 is supported, and the electrode plate 1
The portions other than the central portion of the sensor 6 are arranged at predetermined intervals from the flat diaphragm 12 and the detector body 10, respectively.

A capacitor is formed between the electrode 17a deposited on the electrode plate 16 and the diaphragm 12 on the facing surface of the diaphragm 12 and the electrode plate 16 arranged in this way.
Lead wires 18a and 18b are led out from this.

When using the capacitive pressure sensor configured in this manner, the measurement pressure introduction hole 19 is communicated with a flow path or tank of the fluid to be measured, and measurement pressure is introduced into the pressure introduction chamber 11. As a result, the flat diaphragm 12 expands outward or recesses inward, the distance between the electrodes 17a and 12a between the electrode plate 16 and the diaphragm 12 changes, and the capacitance between the electrodes changes. . This change in capacitance is read using a bridge circuit, and pressure is thereby measured.

In the above embodiment, the outside of the flat diaphragm 12 is dissolved in atmospheric pressure, but as shown in FIG. However, by creating a vacuum inside the cover 20, it can be used for absolute pressure measurement, and by adjusting the pressure inside the cover 20 to introduce a reference pressure, it can be used for comparison measurement with the reference pressure. You can also do that.

Furthermore, a flat diaphragm 12 and an electrode plate 16
In addition to the above-mentioned support, as shown in Fig. 4, the cover 2
Alternatively, the spacer 17 and the electrode plate 16 may be superimposed and attached to the projection 21 at the center of the diaphragm 12, and then pressed against the center portion of the flat diaphragm 12.

The capacitive pressure sensor of the present invention is constructed as described above, with only the center part of the flat diaphragm supported by a protrusion provided on the detector body, and an electrode plate stacked on the center part via a spacer. By supporting the electrode plate at the center of the flat diaphragm and arranging the parts other than the center at a predetermined distance from the flat diaphragm and the detector body, the flat diaphragm and the electrode plate can be separated. Even if the gap between the electrode plate and the flat diaphragm is manufactured with an error of less than a few microns, it can be achieved by precisely manufacturing a single spacer in the center of the flat diaphragm. It has become easier to keep it constant.

In addition, the electrode plate is stacked on the center of the flat diaphragm via a spacer, and only the center part is supported by the detector body, resulting in a mechanically stable structure, stable capacitance, and temperature characteristics. As a result, a capacitance type pressure sensor with good quality can be obtained. Furthermore, since only the center portion of the flat diaphragm, which has a small area compared to its entire area, is supported by the protrusion provided on the detector body, it is sensitive to changes in the pressure in the pressure introduction chamber.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional capacitance type pressure sensor, Fig. 2 is a sectional view of a capacitance type pressure sensor as an example of the implementation of the present invention, and Figs. FIG. 7 is a sectional view showing another embodiment of the invention. 10...Detector body, 11...Pressure introduction chamber,
12... Flat diaphragm, 16... Electrode plate, 17... Spacer.

Claims (1)

[Scope of utility model registration request] One surface of the pressure introduction chamber is constituted by a flat diaphragm, and electrodes are provided on either the front or back surface of the flat diaphragm and the opposing surface of an electrode plate provided opposite thereto, and the flat diaphragm In a capacitive pressure sensor configured to detect a change in capacitance between both electrodes due to deflection, the center portion of the flat diaphragm is supported by a protrusion provided on the detector body, and the flat diaphragm is Only the center portion of the electrode plate is fixed to the center portion of the electrode plate via a spacer, and the portions other than the center portion of the electrode plate are arranged at predetermined intervals with respect to the flat diaphragm and the detector body, respectively. A capacitance type pressure sensor characterized in that a flat diaphragm and the electrode plate are covered with a cover, and the pressure inside the cover is adjusted.