JPS5814967B2 - Manufacturing method of stress detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stress detector for detecting stress.

More specifically, the present invention relates to a stress detector that detects stress and converts it into an electrical signal.

Generally, stress is divided into dynamic stress and static stress.

Vibration meters, fluctuating force meters,
There are accelerometers, wave height meters, variable pressure gauges, impact testers, vortex flowmeters, gyros, etc.

On the other hand, pressure gauges, differential pressure gauges,
There are load cells (scales), etc.

The present invention relates to a stress detector suitable for use in these sensors.

An object of the present invention is to provide a stress detector that is robust, can be used up to a high temperature range, and has good stress detection sensitivity.

An example in which the stress detector of the present invention is used as a pressure gauge sensor will be described below.

FIG. 1 is an explanatory diagram of the configuration of an embodiment of the present invention.

In the figure, reference numeral 1 denotes a container made of a metal material and consisting of a cylindrical portion 11 and a bottom portion 12.

Reference numeral 2 denotes a disc-shaped insulator made of ceramic, one side of which is in contact with the bottom portion 12 via a brazing material 21.

Reference numeral 3 denotes a disk-shaped piezoelectric element portion in contact with the other surface of the insulator 2, and the piezoelectric element body 31, which consists of a piezoelectric element body 31, an electrode surface 32 made of conductive paste, and a lead wire 33, is made of lithium niobate in this case. (LiNb03) is used.

Reference numeral 4 denotes a fixed body made of cylindrical ceramic, one side of which is in contact with the piezoelectric element 3, and the other side's circumferential edge (this portion has been previously metallized) welded 5 to the container 1.

In this case, soldering is done.

41 is a hole through which the lead wire 33 is passed. The stress detector having the above configuration is assembled as follows.

After the brazing material is applied to the joint surface of the insulator 2 with the bottom 12 of the container 1, the insulator 2 is inserted into the container 1 until it contacts the bottom 12.

Next, the piezoelectric element part 3 is placed on the insulator 2 so that their central axes coincide with each other, and then the fixed body 4 is inserted, and the lead wire 33 is drawn out of the container through the hole 41.

Next, brazing material is applied to the circumferential edge on the upper end side in the figure where the container 1 and the fixed body 4 are in contact.

Next, the entire stress detector is heated to the brazing temperature, and once the brazing is completed, it is gradually cooled to room temperature.

The thermal expansion coefficient of the container 1 made of metal material is generally the same as that of the insulator 2 and fixed body 4 made of ceramic, and the piezoelectric element body 31, so when the temperature reaches room temperature, there is a difference in the amount of thermal contraction. container 1, insulator 2, piezoelectric element part 3
and the fixed body 4 are brought into close contact with each other by a compressive force.

In the above configuration, for example, the measurement pressure P applied to the bottom portion 12 is applied to the piezoelectric element portion 3 through the insulator 2 in the direction of the arrow P shown in the figure.

Thus, an electric charge corresponding to the received pressure is generated in the piezoelectric element portion 3.

If this amount of charge is measured using a measuring device with high input impedance, the pressure value of the measured pressure can be detected.

In this case, the container 1, the insulator 2, the piezoelectric element part 3 and the fixed body 4
Because a strong compressive force acts on each other due to the difference in the amount of thermal contraction, the efficiency of transmitting the measured pressure to the piezoelectric element part 3 is not impaired, and at a temperature below the welding temperature of the welded part 5. Since the adhesion of each part will not loosen, it can be used even in high temperature areas and is robust.

In addition, there are products that can be used up to high temperature ranges, such as those in which the piezoelectric element is insulated and sealed with glass inside a metal container.
Even if the sealing temperature of the glass is similar to the heat resistance temperature of the piezoelectric element, the deformation point (temperature at which the glass softens) is 300 to 400℃.
The pressure transmission efficiency deteriorates rapidly at 300 to 400°C.

Therefore, glass sealing systems are limited by the characteristics of each sealing glass.

This does not happen with the device of the present invention, and it can be used up to the allowable temperature limit of the piezoelectric element.

FIG. 2 is an explanatory diagram of the configuration of another embodiment of the present invention.

In this embodiment, the insulator 2 and the fixed body 4 are provided with recesses 22 and 42 into which the piezoelectric element 3 fits, so that the piezoelectric element 3 can be easily placed at a desired position. be.

FIG. 3 is a configuration explanatory diagram of another embodiment of the present invention.

In the figure, reference numeral 6 denotes a lid body made of a metal material, one side of which is brazed to the fixed body 4 and the other end of the circumferential edge welded to the container 1;
A tube 7 is made of ceramic and fitted into a hole passing through the lid 6, and a lead wire 33 passes through the tube.

In this example, since the welded portion 5 is made of metal, there is no need to pre-metallize the ceramic welded portion, unlike in the case of the example in Fig. 1 where one of the welded portions is made of ceramic. has advantages.

In the above embodiment, the insulator 2 is used, but if there is no need to insulate the piezoelectric element section 3 from the container 1, the insulator 2 may be omitted.

Furthermore, if the fixed body 4 does not require insulation, for example, if it does not come into direct contact with the electrode surface 32 of the piezoelectric element portion 4 as shown in FIG. 2, it may not be made of an insulating material.

Furthermore, in the above-mentioned embodiment, it was explained that the piezoelectric element part 3 is made of lithium niobate, but piezoelectric crystal such as lithium niobate or crystal, or zircon lead titanate (P
Ceramic piezoelectric ceramics such as ZT) or lead titanate may be used, as long as internal stress can be detected.

As explained above, the present invention involves inserting a piezoelectric element into a container, then inserting a fixed body into the container so that one side of the fixed body is in contact with the piezoelectric element, and heating the entire body. The other side was welded to a container and slowly cooled to room temperature to fabricate a stress detector.

As a result, due to the difference in thermal expansion coefficients between the container, the fixing body, and the piezoelectric element, compressive force acts on each of the components at room temperature, making it possible to obtain a stress detector that is tightly attached to each other. .

Therefore, according to the present invention, it is possible to realize a stress detector that is robust, can be used up to a high temperature range, and has good stress detection sensitivity.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the configuration of one embodiment of the present invention, and FIGS. 2-3 are explanatory diagrams of the configuration of another embodiment of the invention. 1... Container, 2... Insulator, 3...
. . . Piezoelectric element portion, 4 . . . Fixed body.

Claims (1)

[Claims] 1. A cylindrical container having a bottom, a piezoelectric element portion that is provided in close contact with one surface within the container, and one surface of which is in contact with the other surface of the piezoelectric element portion, and the opening of the container is welded to the opposite surface side. The above-mentioned welding process is performed while the entire stress detector is heated, and the container and the fixing body are compressed and tightly attached to the piezoelectric element part by utilizing the difference in the amount of thermal contraction when the stress detector returns to room temperature. A method for manufacturing a stress detector.