JPH01299432A - Thin-film pressure sensor - Google Patents

Abstract

PURPOSE:To uniformize the distribution of a stress acting on a pressure detecting element and to facilitate an assembling operation, by a method wherein strain gages are provided and a restrained part restrained by a restraining fittings of a metal diaphragm of a thin-film pressure sensor is disposed at a position shifted in the axial direction in relation to the pressure detecting element. CONSTITUTION:A thin pressure detecting element 5a is provided on the top part of a metal diaphragm 5 of a thin-film pressure sensor, and an insulating film 2 and strain gages R1-R4 are fitted to this detecting element 5a. Besides, an outer peripheral part of the diaphragm 5 is fitted by restraining by means of a restraining fittings 6, and a restrained part 7 thereof is provided at a position shifting in the axial direction in relation to the detecting element 5a. An amount of this positional shift is set to be the dimension of the radius of the detecting element 5a or above, a cavity 8 to form the detecting element 5a is provided inside the diaphragm 5, a corner part on the detecting element side of the cavity 8 is shaped in a circular-arc to prevent the occurrence of the concentration of a stress. By the action of a pressure acting on the inside of the cavity part 8, the shape of the detecting element 5a changes, and the pressure is detected by the gages R1-R4 in accordance with the amount of the change in the shape thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thin film pressure sensor in which a strain gauge is provided on a metal diaphragm with an insulating film interposed therebetween.

[Conventional technology]

The thin film pressure sensor is constructed as shown in FIGS. 6 and 7, in which a silicon oxide film of about 10 μm is laminated as an insulating film 2 on a metal diaphragm 1 made of stainless steel, for example. And on top of that, polycrystalline silicon is applied from 0.4~
After laminating about 1.0 μm, patterning is performed to form strain gauges R1+R2+R3r R4, and finally, metal electrodes 3 made of, for example, an aluminum thin film are formed so as to connect each strain gauge R1 to R4 to a bridge circuit. .

Metal diaphragm 1 of a thin film pressure sensor having such a configuration
When pressure is applied to the inner cavity of the sensor, strain occurs in the pressure detection section of the sensor, and the resistance value of the strain gauge formed thereon changes, and the pressure is detected based on the amount of change.

In the conventional thin film pressure sensor, as shown in FIG.
He was detained at.

[Problem to be solved by the invention]

In the conventional thin film pressure sensor described above, the restraint position by the restraint device 4 was close to the pressure detection part in the axial direction;
Accurate pressure could not be detected due to the influence of deformation of the restraint location.

That is, as shown in FIG. 3, restraints 4a and 4b having different diameters are placed near the pressure detection section in the axial direction.
, 4c and 4d, when the pressure detection part is deformed as shown in FIG. 5, the stress distribution in this part is as shown in FIG. The stress distribution for the restraints 4d is a % b SCs d, and the stress distribution changes greatly due to the difference between the restraints 4a to 4d, and the linearity between the applied pressure and the output of the strain gauges R1 to R4 is poor. Detection values vary depending on size and shape.

This means that even if the restraint is the same, if the position of the restraint is slightly shifted in the direction perpendicular to the axis, an error will occur in the detected value.
The installation required high mechanical precision in position.

The present invention was made in consideration of the above-mentioned problems, and the present invention is a thin film that does not cause errors in detected values even if the position is slightly shifted in the direction perpendicular to the axis when mounted using a restraint device, making machining and assembly work easier. The object of the present invention is to provide a pressure sensor.

[Means to solve the problem]

In order to achieve the above object, a thin film pressure sensor according to the present invention is a thin film pressure sensor in which a strain gauge is provided in a pressure detection part of a metal diaphragm through an insulating film, in which a strain gauge is restrained by a restraining device of the metal diaphragm. The pressure detecting section is provided at a position shifted in the axial direction with respect to the pressure detecting section.

[For production]

Even if the restraint position by the restraint device shifts in the direction perpendicular to the axis, the stress distribution acting on the pressure detection section remains constant.

〔Example〕

An embodiment of the present invention will be described based on FIGS. 1 and 2.

In addition, in this embodiment, the same members as those in the above-mentioned conventional example are given the same reference numerals, and the description thereof will be omitted.

In the figure, reference numeral 5 denotes a metal diaphragm, on the top of which a thin pressure sensing portion 5a is formed, and to this pressure sensing portion 5a are attached an insulating film 2 and strain gauges R4 to R4 similar to those of the above-mentioned conventional example. This metal diaphragm 5 is attached to the fixed member by restraining its outer circumferential portion with a restraining device 6 as in the conventional case, but the restraining portion 7 is provided at a position offset in the axial direction with respect to the detection portion 5a. It is being

It is desirable that the amount of deviation be around or above the radial dimension of the detection portion 5a.

A cavity 8 is provided inside the metal diaphragm 5 to constitute the detection section 5a, but the corner of the cavity 8 on the detection section side is arcuate, and stress is concentrated in this section. It is designed to prevent this from occurring. Note that this portion may be formed into a tapered shape instead of an arc shape.

In the above configuration, a predetermined pressure is set in the cavity 8, for example, 50
When a pressure of 0 kg/c is applied, the detection portion 5a is deformed, and the pressure is detected by the strain gauges R1 to R4 according to the amount of deformation. The stress distribution acting on the detection section 5a at this time is as shown in FIG. This stress distribution does not change even if the restraint 6 is slightly displaced in the direction perpendicular to the axis, since the restraint part 7 is displaced in the axial direction with respect to the detection part 5a, and the installation of the restraint 6 does not change. It is constant regardless of position.

〔Effect of the invention〕

According to the present invention, when the restraint 6 is mounted, an error will not occur in the detected value even if the position is slightly shifted in the direction perpendicular to the axis, and the machining and assembly of the restraint part 5a of the metal diaphragm 5 and the restraint 6 can be easily performed. becomes easier. Furthermore, detection accuracy can also be improved.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the present invention, Fig. 2 is a pressure distribution diagram thereof, Fig. 3 is a sectional view showing a conventional example, Fig. 4 is a pressure distribution diagram thereof, and Fig. 5 is an action explanatory diagram. , FIG. 6, and FIG. 7 are a plan view and a sectional view showing the main parts of the thin film pressure sensor. 2 is an insulating film, 5 is a metal diaphragm, 5a is a pressure detection section, and R1-R4 are strain gauges. Figure 1 Figure 2 σ [I Figure 3 Figure 5

Claims (1)

[Claims] In a thin film pressure sensor in which strain gauges R_1, R_2, R_3, and R_4 are provided on the pressure detection part 5a of the metal diaphragm 5 via the insulating film 2, the restraint part restrained by the restraint device 6 of the metal diaphragm 5 is A thin film pressure sensor characterized in that it is provided at a position shifted in the axial direction with respect to the detection section 5a.