JPH0342344Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a metal diaphragm pressure sensor that converts pressure changes into electrical signals and outputs them.

Conventional diaphragm pressure sensors include those that use ceramic for the diaphragm, and those that use Fe-based or Cu-based metals for the diaphragm. Diaphragms made of ceramic are attached by printing a resistance paste on the surface of the diaphragm, drying it, and firing it at a temperature of about 850℃, since ceramic has excellent insulation and heat resistance. However, compared to metal diaphragms, ceramics have the disadvantage that the manufacturing process is more complicated and expensive, and the material is brittle and has low mechanical strength. be. On the other hand, diaphragms made of Fe-based or Cu-based metals have excellent mechanical strength, but on the other hand, they have the disadvantage of being easily oxidized at high temperatures and do not have the insulating properties of ceramics. When attaching a stress sensor, it is necessary to form an insulating film in advance.

However, since Fe-based or Cu-based metal diaphragms are easily oxidized at high temperatures, insulating films are limited to coatings that can be applied at relatively low temperatures, such as vapor deposition. As mentioned above, it has been difficult to form a stress sensor consisting of a thick film circuit that is fired at a high temperature.

The present invention was developed in view of the above circumstances, and its purpose is to form an insulating film with excellent mechanical strength and oxidation resistance at high temperatures, and with excellent heat resistance on the surface. It is an object of the present invention to provide a metal diaphragm pressure sensor to which a stress sensor consisting of a thick film circuit that requires high-temperature treatment can be easily attached.

The following is an example of the present invention shown in Figures 1 to 3.
This will be explained with reference to the figures. 1 is the diaphragm body, which is made of Fe-Cr-Al alloy material (Fe: 71%,
A plate material made of Cr: 25%, Al: 4%) was drawn using a press to form a circular container shape with a shallow bottom. After the drawing process, the diaphragm body 1 was heated at 50℃ in the atmosphere at 1160℃.
By performing high-temperature oxidation treatment for 1 minute, Al in the alloy components is selectively oxidized, and an insulating film 2 made of an alumina film with a thickness of about 1 μm is formed on the entire surface. 3 to 6 are stress sensors made of piezoresistive thick film resistors located on the insulating film 2 at the center and outer periphery of the upper surface of the diaphragm body 1, and these sensors are made of ruthenium oxide (RuO ₂ ). After printing the resistive material paste, it is formed through the following steps: drying (150°C, 10 minutes) and firing (850°C, 10 minutes). A printed conductor 7 made of a thick film conductor bridge-connects the stress sensors 3 to 6, and is formed simultaneously with the stress sensors 3 to 6 by printing, drying, and baking a conductor paste. Further, power terminal portions 7a and 7b and output terminal portions 7c and 7d, each having an enlarged area, are formed at required locations on the printed conductor 7, respectively.

Next, the operation of the above configuration will be explained. When pressure P acts upward on the lower surface side of the diaphragm body 1, tensile stress acts on the center of the diaphragm body 1 in proportion to the pressure P, and compressive stress acts on the outer circumference, causing the stress sensor 3 -6, a change in resistance value occurs in accordance with the stress, and when a constant voltage is applied between power supply terminals 7a, 7b, an output voltage is output in accordance with the change in resistance value of stress sensors 3-6.

According to the above configuration, since the diaphragm body 1 is made of a metal material, it can be easily formed into a desired shape by press working, and is easier to process than a diaphragm body 1 made of ceramic material, and is less brittle and mechanically Excellent strength. In addition, the diaphragm body 1 is made of an Fe-based alloy containing Al and has a melting point of 1500°C or higher, and the insulating film 2 is an alumina coating formed by selectively oxidizing Al contained in the diaphragm body 1. The membrane 2 has excellent adhesion to the base material and heat resistance compared to conventional structures, and the diaphragm body 1 is protected by the alumina coating on the surface and has excellent oxidation resistance at high temperatures.
Therefore, the stress sensors 3 to 6 and the printed conductor 7 can be easily attached using a thick film circuit fired at a high temperature (850 DEG C.).

The diaphragm body 1 is made of Fe-Cr as described above.
-In addition to Al alloy material, Fe-Al alloy material, Fe-Ni-Cr-
An Al alloy material, a Ni-Cr-Al alloy material, etc. can be used, and the insulating film 2 made of an alumina film can be formed by anodic oxidation treatment instead of high-temperature oxidation treatment. 6 can be formed by a thin film circuit and a semiconductor sensor in addition to a thick film circuit.

FIG. 4 shows another embodiment of the present invention, and parts different from those in FIGS. 1 to 3 will be explained. That is, 8 is an insulating material coating coated on the surface of the insulating film 2 by printing, drying, and baking a dielectric paste fired at 850°C. This is done for the purpose of improving roughness and adhesion with each stress sensor 3 to 6, and the stress sensors 3 to 6 and printed conductor 7 are formed on the surface of this insulating material coating 8.

As is clear from the above description, the present invention has excellent mechanical strength and oxidation resistance at high temperatures, and can form an insulating film with excellent heat resistance on the surface, making it possible to reduce the thickness required for high temperature treatment. A metal diaphragm pressure sensor to which a stress sensor made of a membrane circuit can be easily attached can be provided.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the present invention, in which FIG. 1 is a top view, FIG. 2 is a vertical sectional view,
FIG. 3 is an enlarged sectional view of the main part, and FIG. 4 is a view corresponding to FIG. 3 showing another embodiment of the present invention. In the drawing, 1 is a diaphragm body, 2 is an insulating film,
3 to 6 are stress sensors, 7 is a printed conductor, and 8 is an insulating film.

Claims (1)

[Claims for Utility Model Registration] 1. A diaphragm body formed by pressing an Al-containing Fe-based alloy material or Ni-based alloy material into a predetermined shape, and selectively oxidizing the Al contained in the diaphragm body. A metal diaphragm pressure sensor comprising: an insulating film made of an alumina film formed on the surface of the diaphragm body; and a stress sensor integrally attached to the insulating film. 2. The metal diaphragm pressure sensor according to claim 1, which is a registered utility model, characterized in that an insulating film is integrally interposed between the insulating film made of an alumina film and the stress sensor.