JPS59184831A - Electrostatic capacity type pressure detector - Google Patents

Abstract

PURPOSE:To raise the overload pressure resistance of a sensor diaphragm by constituting a thickness of a thin movable part of the sensor diaphragm of an electrostatic capacity type pressure detector so that the part which is close to a thick fixed part of the outside circumference is larger. CONSTITUTION:A thick ridge 12C is provided on a thin movable part 12B of a sensor diaphragm 12. The thin movable part 12B of the sensor diaphragm 12 is pressed against a sensor base 18 as shown by a dotted line by an overload pressure P. In that case, the ridge 12C provided near a thick fixed part 12A is also brought into contact with the sensor base 18. In this case, excessive deformation of the boundary surface of the thick fixed part 12A and the thin movable part 12B is suppressed, therefore, the overload pressure resistance is raised. When a position of the annular ridge 12C is set to b/a=0.5, it is most effective. The smaller a gap G is, the larger the pressure resistance becomes.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to a capacitive pressure sensor that detects pressure and differential pressure as changes in capacitance, and particularly relates to a capacitive pressure sensor that detects pressure and differential pressure as changes in capacitance. Regarding capacitive pressure detectors.

- [Background of the Invention] A capacitive pressure sensor using silicon as a sensor diaphragm is disclosed in, for example, Japanese Patent Application Laid-open No. 16228/1983.

The sensor diaphragm has the role of a movable electrode that responds to pressure, and is installed with a predetermined gap between it and a fixed electrode provided on the sensor stand.

Conventionally, this gap has been secured by machining the sensor stand into a spherical surface, but since this involves machining an insulating material such as ceramic into a spherical surface, it cannot be said to be excellent in manufacturability. On the other hand, if the sensor diaphragm is made of silicon, silicon has excellent machinability through etching, etc., so it is possible to form a recessed part in the sensor diaphragm by etching and secure a gap, which greatly improves manufacturing efficiency. .

However, silicon sensor diaphragms have a drawback of having a lower overload withstand voltage than metal sensor diaphragms such as iron-nickel alloys. For this reason, it can be used at comparatively low pressures (for example, it can be handled by reducing the gap up to about IMPH), but
To be used as a detector for industrial measurement, an overload withstand voltage of 10 MPH or more is required, and it is necessary to improve the overload withstand voltage.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide a capacitive pressure sensor with excellent overload resistance. 7 [Summary of the Invention] The sensor diaphragm has four parts formed at its center by etching or the like, and is separated into a thick fixed part on the outer periphery and a thin movable part in the center. When overload pressure acts on such a sensor diaphragm, the thin movable part in the center comes into contact with the sensor stand, but at this time, a large concentrated stress is generated at the interface between the thin movable part and the thick fixed part, improving overload resistance. It is a hindrance to For this reason, the present invention makes the wall thickness of the thin movable part larger at the outer periphery, for example, by forming a ridge or the like on the outer periphery, and before a large concentrated stress is generated at the interface, the ridge is brought into contact with the sensor stand. [Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described based on the drawings.

FIG. 1 shows a cross-sectional view of the overall structure of a capacitive pressure sensor, in which 10 is the pressure receiving part main body, 12 is a sensor diaphragm made of silicon single crystal, and 14 is a sensor diaphragm 1.
2 is a lead wire that takes out an output, 16 is an airtight terminal that takes out an electric signal to the outside, 18.2 (1: The sensor diaphragm 12 is held in its periphery so as to sandwich the sensor diaphragm 12.
The senna base is made of an insulating material such as borosilicate glass, which is airtightly bonded to the
ll -Si eutectic alloy bonding method is used. 22 is an outer chamber constructed around the sensor stand 18, 20, and between the two outer seal diaphragms 24, 26 and the pressure receiving part main body 10 is sealed oil. # is included. 28.30 is an electrode deposited on the flat surface of the sensor stand 18.20;
The Riet wire is passed through the metal coating 36.38 provided on the inner surface of the pressure conduction path 32.34 provided at the center of the pressure receiving section 20, and the metal pipe 44.46 of the airtight terminal 40.42 provided on a part of the pressure receiving section main body 1o. Airtight terminal 4 connected to 48.50
0.42 metal pipes 44 and 46 are sensor stands 18 and 20
The electrodes 2-8 and 30 are fitted with pressure guide paths 32 and 34 and bonded using low-temperature solder K to maintain electrical continuity and airtightness with the electrodes 2-8 and 30.

A holding plate 52.54 Ky-ru diaphragm 56.5i9 for holding down the sensor stand 18.20 is provided on the outside of the pressure-receiving part main body 10, and is hermetically welded circumferentially near the outer periphery, so that sealed oil is kept between it and the sensor diaphragm 12. Enclosed 1st. A second pressure receiving chamber 60,62 is formed. Reference numerals 64 and 66 are flanges that clamp the pressure receiving part main body 1o, and a pressure guiding port 68,
70 are provided.

As shown in FIG. 2, the sensor diaphragm 12 is composed of a thick fixed part 12A on the outer periphery and a thin movable part 12B in the center, and a ring-shaped ridge 12C is formed near the outer periphery of the thin movable part 12B. The sensor diaphragm 12 having such a shape can be fabricated with high precision by etching using photolithography technology if it is made of silicon, or by pressing or the like if it is made of metal. The sensor stand 18.20 is electrostatically bonded to the thick-walled fixing part 12A,
The first. Second measurement chamber 72.7
4 is formed. Sensor diaphragm J2 and sensor stand 1
8.20 is preferably selected such that the coefficient of thermal expansion is larger than that of the sensor stand, so that tension due to the difference in thermal expansion s number is applied to the sensor diaphragm after electrostatic bonding.

With the above configuration, it works as follows. Pressure guiding port 68.7
The fluid pressure derived from 0 is the seal diaphragm 56,
58 acts on the sensor diaphragm 12 via the sealed liquid, and the sensor diaphragm 12 is displaced to one side due to the differential pressure. As a result, the sensor diaphragm 12, which is a movable electrode,
The capacitance between and one electrode decreases, and the capacitance between and the other electrode increases. These electrical signals are transmitted through lead wires 48 and 50.
° As shown in FIG. 2, when overload pressure acts on the sensor diaphragm 12, the thin movable portion 12B of the sensor diaphragm 12 changes as shown by the dotted line. It is pressed against the sensor stand 18. At this time, the ridge 12C provided near the thick fixed leg part 12A also comes into contact with the sensor stand 18, and the thick fixed part 12A
Excessive deformation of the interface between the thin-walled movable portion 12B and the thin-walled movable portion 12B is suppressed. As a result, the stress applied to the interface is alleviated, and a larger overload pressure can be withstood. The overload pressure of the sensor diaphragm 12 is determined by the gap G as shown in FIG.
It is also related to the size of , A shows the case without a ridge, B shows the case with a ridge, and the gap G
Although the breakdown voltage can be improved by reducing the ridge, the breakdown voltage is further improved by providing a ridge. ,,It also depends on the position of the ridge, with the middle part being the most effective.

As mentioned above, the pressure sensor is connected to the pressure inlet 68.70 to 100
A high static pressure close to Kg/lri is introduced, and the differential pressure between the two is I
K9/cF7! The sealed oil in the first measurement chamber 72 and second measurement chamber 74 is 1ooK9/crI.
The pressure is close to K. In a structure where the outer periphery of the sensor stand 18.20 is exposed to atmospheric pressure, this pressure sensor stand 18.20
The sensor diaphragm 12 is deformed in the radial direction, and the tension of the sensor diaphragm 12 is changed, which has the adverse effect of modulating the ease of deformation due to pressure (sensitivity). For this reason, the seal diaphragm 56
, 58 in the outer diameter direction of the outer seal diaphragms 24 , 2
6 ktt, '/"j An outer chamber 22 is provided between the sensor stand 18, 20 and the pressure receiving part main body 10, and this is filled with sealed oil. The structure applies the same static pressure to the entire sensor to prevent uneven deformation of the sensor.Also, since the sensor diaphragm 12 and the sensor stand 18.20 have almost the same rigidity +i'Th, they can be easily applied under high static pressure. No deformation occurs and there is no negative effect on capacitance changes.

Further, even if the ambient temperature changes, the thermal expansion of the sensor diameter 7 and the sensor base 18, 20 are almost the same, so thermal deformation does not occur and there is no adverse effect on the capacitance change.

FIGS. 4(A) to 4(F) show other examples of sensor diaphragms, and FIG. 4(A) has double ring-shaped ridges, and the thickness of the inner ridge is reduced.

(b) has a ridge divided into multiple parts, e9 has a plurality of circular protrusions, and (b) has a radially elongated trapezoidal thick part, all of which extend in the circumferential direction. It is possible to give elongation and improve followability to pressure. (E)
1 shows an example in which the thin movable part is made thicker in stages toward the thicker fixed part, and (f) shows an example in which the thickness is further increased continuously.

Figure 5 shows a case where the present invention is applied to a pressure detector that measures the difference between atmospheric pressure and atmospheric pressure, with one fluid being the atmosphere.The configuration is one half of the pressure detector shown in Figure 1. Although the detailed explanation is omitted because it corresponds to
Atmospheric pressure is introduced into the measurement chamber 72 between the sensor diaphragm 12 and the sensor stand 18 via the sensor diaphragm 12, and the sensor diaphragm 12 detects the differential pressure between this atmospheric pressure and the measured fluid pressure P. A vacuum gauge can be constructed by eliminating the pressure guiding port 32 and creating a vacuum inside the measurement chamber 72.

〔Effect of the invention〕

As described above, according to the present invention, by configuring the wall thickness of the thin-walled movable portion of the sensor diaphragm to be larger near the thick-walled fixed portion on the outer periphery, when overload pressure is applied to the sensor diaphragm, the thin-walled movable portion This makes it possible to alleviate stress on the interface with the thick-walled fixing part, and improve the overload withstand pressure of the sensor diaphragm.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of the overall structure of a capacitive pressure sensor according to an embodiment of the present invention, Fig. 2 is a partial detailed view of the sensor diaphragm, and Fig. 3 shows the relationship between the withstand pressure and clearance of the sensor diaphragm. FIG. 4 is a diagram showing another example of the sensor diaphragm, and FIG. 5 is a sectional view when applied to another pressure detector. 12...Sensor diaphragm, 12...Thick wall fixed part, 12B...Thin wall moving part, 12C...Ridge, 1
8゜￥ 1 Figure 72 Figure 4m (2l star 4 figure (4) r mouth (hano)

Claims (1)

[Claims] 1. A sensor diaphragm consisting of a thin movable part and a thick fixed part surrounding it; a sensor stand made of an insulator joined to the thick fixed part and forming a gap between it and the thin movable part; an electrode provided on a surface facing the thin-walled movable section, and the capacitance-type pressure detection is characterized in that the wall thickness of the thin-walled movable section is formed to be larger near the thick-walled fixed section. vessel.