JPH03131733A - Pressure sensor - Google Patents

Abstract

PURPOSE:To improve sensitivity and to suppress the variation of an output voltage by directly arranging a coil on an amorphous magnetic alloy. CONSTITUTION:Pressure is transmitted to a pressure chamber 3 from a pressure introducing port 2 and expands the chamber 3. As a result, a deformed part 4 is varied and the amorphous magnetic alloy 7 fixed on the surface of the part 4 is deformed. Thus, the magnetic permeability of the alloy 7 is changed, which is detected as the change of inductance by a pressure detection coil 8 and the difference between a differential coil 9 and the coil 8 is obtained by a detection circuit 13, thereby obtaining the pressure. Then, the sensitivity is improved and the variation of the output voltage caused by a heat cycle is suppressed.

Description

[Detailed description of the invention] Industrial application field The present invention is amorphous! The present invention relates to a pressure sensor using the strain effect of a fl alloy.

BACKGROUND OF THE INVENTION In recent years, pressure sensors using the magnetostrictive effect of amorphous magnetic alloys have been proposed. FIG. 3 is a cross-sectional view schematically showing an example of such a pressure sensor. 21 is a cylindrical main body, 22
2 is a pressure introduction port, and 23 is a pressure chamber for transmitting pressure. 24
25 is a deformed portion made by thinning a part of the main body 21, and a non-deformed portion 25 is made to be free from distortion due to pressure. The inside of the non-deformable part 25 has a hollow part 26 of the same size as the pressure chamber 23, 27 is on the outer periphery of the main body 21, and the deformable part 24
and an amorphous magnetic alloy adhered onto the non-deformable portion 25. Reference numeral 28 denotes a pressure detection coil, which is disposed via a bobbin 30 on the outside of the amorphous magnetic alloy 27 adhered on the outer periphery of the deformable portion 24 . Reference numeral 29 denotes a differential coil having the same configuration as the pressure detection coil 28, and is arranged outside the amorphous magnetic alloy 27 bonded on the outer periphery of the non-deformable portion 25 via a bobbin 30. 3
A yoke 1 is attached to the outer circumference of the bobbin 30. 32 is a screw portion for fixing the main body 21, and 33 is a detection circuit.

The pressure is transmitted from the pressure introduction port 22 to the pressure chamber 23, and applies stress in the direction of expanding the pressure chamber 23. As a result, the deformed portion 24 changes, and the magnetic permeability of the amorphous magnetic alloy 27 bonded to its surface changes.

This change in magnetic permeability is detected as a change in inductance by the pressure detection coil 2, and the change in pressure is obtained from the differential output with the differential coil 29.

Problems to be Solved by the Invention The sensitivity of the pressure sensor configured as described above, that is, the width of change in output voltage due to pressure relative to the absolute value of the output voltage was as small as about 6%. This is because the magnetic field is weakened by the bobbin gap between the amorphous magnetic alloy and the coil. Furthermore, when the same sensor was subjected to a thermal cycle, the absolute value of the output voltage varied by a maximum of about 2 mV even after returning to the same temperature. This is because the relative positions of the coil and the amorphous magnetic alloy shift due to expansion of the bobbin due to heat.

From the above, the configuration of the pressure sensor has a problem of low sensitivity and large fluctuations in output voltage due to thermal cycles.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention has a deformable portion having a pressure introduction port, a pressure chamber that is distorted by the pressure introduced from the pressure introduction port, and a non-deformable portion that does not undergo distortion due to pressure. an amorphous magnetic alloy having magnetostriction is fixed to the deformable part and the non-deformable part, and coils are respectively attached to the deformable part and the non-deformable part so as to form a magnetic circuit with the amorphous magnetic alloy. The coil is arranged so as to be in direct contact with the amorphous magnetic alloy, and the pressure is detected from the difference in inductance between the two coils as pressure is applied.

Effects According to the above configuration, since there is no bobbin part, there is no gap caused by the bobbin and sensitivity can be increased.
Furthermore, fluctuations in output voltage caused by thermal expansion of the bobbin can be suppressed.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view schematically showing a pressure sensor according to an embodiment of the present invention. l is made of titanium with a diameter of 10 and a height of 70
The cylindrical main body of the bolt, 2 is a pressure introduction port with a diameter of 6 mm, and 3 is a pressure chamber for transmitting pressure.

4 is a part deformed by pressure, and a part of the main body 1 has a wall thickness of 2 m.
It has been processed into m. Reference numeral 5 denotes a non-deformable portion which is not distorted by pressure, and a hollow portion 6 having the same size as the pressure chamber 3 is provided inside the portion. 7 is heated at 250°C with Epoquin resin so as to cover the deformed part 4 and non-deformed part 5 of the main body L.
This is an Fe-3i-B-Cr amorphous magnetic alloy that was fixed in 2 hours.

8 is a pressure detection coil formed by winding the coil 100 times so as to be in direct contact with the amorphous magnetic alloy 7, and 9 is a differential coil having the same configuration as the pressure detection coil 8. IO is a spacer for positioning the pressure detection coil 8 and the differential coil 9. Reference numeral 11 denotes a yoke made of 45% Ni--Fe alloy, which is attached to the outer periphery of the pressure detection coil 8 and the differential coil 9. 12 is the screw part for fixing the main body, PF3/8
It is processed in a pinch. 13 is a detection circuit.

The operation of the above-mentioned pressure sensor will be explained below.

The pressure is transmitted from the pressure introduction port 2 to the pressure chamber 3, and applies stress in the direction of inflating the pressure chamber 3. As a result, the deformed part 4
changes, and the amorphous magnetic alloy 7 fixed to its surface is deformed. This deformation causes the amorphous magnetic alloy 7 to form due to the inverse magnetostriction effect.
magnetic permeability changes.

This change is detected as a change in inductance by the pressure detection coil 8, and the pressure is obtained by detecting the difference with the differential coil 9 by the detection circuit 13.

FIG. 2 shows an example of the output of the pressure sensor with this configuration. Second
In the figure, the solid line represents the output characteristics of the pressure sensor with this configuration.
The dotted lines each indicate the output characteristics of the conventional pressure sensor.

In addition, the output characteristics are normalized with the sensitivity width of the conventional example as 1. From Figure 2, the sensitivity is approximately 20% compared to the conventional pressure sensor.
You can see that it has risen. Furthermore, when the same sensor was subjected to a thermal cycle, when the temperature was returned to the same temperature, the fluctuation range of the absolute value of the output voltage was approximately 1 mV at maximum, which was halved compared to the conventional pressure sensor.

With the above configuration and operation, it was possible to obtain a pressure sensor that has higher sensitivity than conventional pressure sensors and has less variation in output voltage due to thermal cycles.

Effects of the Invention As is clear from the above explanation, the present invention provides a pressure sensor with a higher window density than conventional ones and less variation in output voltage due to thermal cycles by disposing a coil directly on an amorphous magnetic alloy. It is possible to configure

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a pressure sensor according to an embodiment of the present invention, and FIG.
The figure shows the output characteristics of the same sensor and a conventional pressure sensor.
FIG. 3 is a sectional view of a conventional pressure sensor. 1.21...Main body, 2,22...Pressure inlet, 3.23...Pressure chamber, 4.24...
...Deformed part, 5゜25...Non-deformed part, 6
．． 26...Hollow part, 7°27...Amorphous magnetic alloy, 8.28...Pressure detection coil,
9.29...Differential coil, lO...
Spacer, 11.31...Yoke, 12.3
2...Fixing screw, 13.33...Detection circuit, 30...Bobbin. [Use] 4th figure, power kunipu/crn2J 3 pressure f) room 7 well & award 1 favor dedication

Claims (1)

[Claims] The non-deformable part has a pressure introduction port, a deformable part having a pressure chamber that is distorted by the pressure introduced from the pressure introduction port, and a non-deformable part that is not distorted by pressure, and the deformable part and the non-deformable part have magnetostriction. A crystalline magnetic alloy is fixed, and coils are arranged in the deformable portion and the non-deformable portion so as to be in direct contact with the amorphous magnetic alloy so as to form a magnetic circuit with the amorphous magnetic alloy. . A pressure sensor, characterized in that pressure is detected from an inductance difference between the two coils as pressure is applied.