JPH02128131A - pressure sensor - Google Patents

Abstract

PURPOSE:To realize a smaller size and a lower cost along with a higher accuracy by outputting an inductance difference between two elements as pressure value using a detection circuit containing an AC differential circuit or a DC differential circuit. CONSTITUTION:A pressure is transmitted to a pressure chamber 3 from a pressure introduction port 2. As a result, a deformed part 4 varies and an amorphous magnetic alloy 6 bonded on the surface thereof is deformed to change a magnetic permeability thereof. This change is detected with a pressure detection coil 7 as change in inductance to be inputted into an AC differential circuit. On the other hand, an output of a differential coil 8 is inputted into an AC differential circuit simultaneously. A difference between the two outputs is obtained within the AC differential circuit and rectified to produce an output. With such an arrangement, as compared with a strain gauge type pressure sensor, sensitivity of this sensor is higher more than several hundred times, which requires no complicated and precise circuitry as detection circuit thereby allowing significant simplification thereof. This enables the suppression of costs with a smaller size of this pressure sensor thereby achieving a smaller size and a lower cost maintaining a high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a pressure sensor using the magnetostrictive effect of an amorphous magnetic alloy.

2. Description of the Related Art Conventionally, pressure sensors using strain gauges have been proposed as means for converting pressure changes into electrical changes (for example, Japanese Patent Laid-Open No. 62-235536). FIG. 5 is a cross-sectional view schematically showing an example of such a pressure sensor. 21 is a cylindrical main body, 22 is a pressure introduction port, and 23 is a pressure chamber for transmitting pressure.

24 is a diaphragm fixed within the main body 21. 25
is a strain gauge glued to the top of the diaphragm 24,
26 is a relay plate that connects the strain gauge 25 and the detection circuit 27.

The pressure is transmitted from the pressure introduction port 22 to the pressure chamber 23, and applies stress in the direction of pushing up the diaphragm 24. As a result, the diaphragm 24 is distorted, and the resistance of the strain gauge 25 bonded to the upper surface of the diaphragm 24 changes. The detection circuit 27 outputs this resistance change as a pressure change.

A block diagram of the detection circuit 27 is shown in FIG. From FIG. 6, it can be seen that the output is obtained by using various detection and cancellation circuits.

FIG. 7 shows the output characteristics of the pressure sensor configured as described above. It can be seen that the output voltage changes linearly with pressure.

Problems to be Solved by the Invention In the pressure sensor that uses the strain gauge described above to measure changes in pressure, the change in resistance due to the pressure of the strain gauge is very small, and the output voltage when the amount of strain is several thousand x 10-6 is very small. However, several mV/VL cannot be obtained. For this reason, the seventh
As shown in the figure, accuracy is high (in order to obtain the characteristics of pressure changes, it is necessary to use a complex and highly accurate circuit configuration in the detection circuit as shown in Figure 6, making it difficult to miniaturize and lower the price of the pressure sensor. There was an issue.

Means for Solving the Problems The present invention has a pressure introduction port, a deformable portion that is distorted by the pressure introduced from the pressure introduction port, and a non-deformable portion that is not distorted by the pressure, the deformable portion and the non-deformable portion. An amorphous magnetic alloy having magnetostriction is fixed to the amorphous magnetic alloy, and an element for detecting magnetic permeability and rate is provided in the deformed part and the non-deformed part to form a magnetic circuit with the amorphous magnetic alloy, and the permeability increases as pressure is applied. In a pressure sensor that detects a change in magnetic property as a change in inductance in the two elements, the two elements
The configuration is such that the difference in inductance between the elements is output as a pressure value using a detection circuit including an AC differential circuit or a DC differential circuit.

Effects According to the above-mentioned configuration, since the change in magnetic permeability due to pressure is several hundred times larger than the change in resistance of the strain gauge, a simple circuit configuration can be achieved, making it possible to achieve high accuracy, miniaturization, and cost reduction.

Embodiments Embodiment 1 FIG. 1 is a sectional view schematically showing a pressure sensor according to an embodiment of the present invention. 1 is a cylindrical body made of titanium with a diameter of 1 cIl and a height of 7 cya, 2 is a pressure introduction lower 3 with a diameter of 0°6 cm, and is a pressure chamber for transmitting pressure. Reference numeral 4 denotes a portion deformed by pressure, which is a part of the main body 1 processed to have a wall thickness of 0.2c+a. 5 is a non-deformed portion to prevent distortion due to pressure. 6 is heated at 250°C with epoxy resin so as to cover the deformed part 4 and non-deformed part 5 of the main body 1.
This is an amorphous magnetic alloy with positive magnetostriction based on Fe-8i-B-Cr that adheres over time. At this time, the coefficient of thermal expansion of the amorphous magnetic alloy 6 is 7.8X10-6, which is smaller than that of the main body 1, 9X10-'. Compressive stress is applied to the magnetic alloy 6, and the direction of spontaneous magnetization of the amorphous magnetic alloy 6 can be aligned in the thickness direction, increasing sensitivity. 7 is a pressure detection coil formed by winding a coil 63 times around a Teflon bobbin 9, and 8 is a differential coil having the same configuration as the pressure detection coil.

Both coils correspond to the oscillation circuit 13 and filter circuit 14 in the detailed block diagram of the detection circuit 12 shown in FIG.
．． It is excited by the amplifier circuit 15 to a magnetic field of about 10e.

A bobbin 9 with these coils 7.8 is mounted on the outer periphery of the amorphous magnetic alloy 6. Reference numeral 10 denotes a yoke made of 45% Ni--Fe alloy, which is attached to the outer periphery of the bobbin 9. 11
is the screw part for fixing the main body, which is machined to a pitch of PF3/8. 12 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 6 bonded to its surface is deformed. This deformation causes the amorphous magnetic alloy 6 to form due to the inverse magnetostriction effect.
magnetic permeability changes. This change is detected by the pressure detection coil 7 as a change in inductance. This output is the second
It is input to the AC differential circuit in the figure. On the other hand, the output of the differential coil 8 is also input to the AC differential circuit at the same time. The difference between the two is taken in the AC differential circuit 16, rectified by the rectifier circuit 17, and output.

FIG. 3 shows an output characteristic diagram of the pressure sensor with this configuration.

In FIG. 3, it can be seen that the output voltage changes linearly as the pressure increases.

Also, when compared with FIG. 7, which is the output characteristic diagram of the conventional example,
High accuracy characteristics equivalent to those of Habo were obtained. On the other hand, since the pressure sensor of this configuration has a sensitivity several hundred times higher than that of the conventional strain gauge type pressure sensor, the detection circuit 12 is as shown in FIG. The pressure sensor can be significantly simplified without requiring a complex and precise circuit configuration like the detection circuit of
We were able to reduce the size by 0% and reduce the cost to about one-tenth.

With the above configuration and operation, a pressure sensor that can be made smaller and cheaper while maintaining high accuracy compared to the conventional example has been obtained.

Embodiment 2 FIG. 4 shows a block diagram of a detection circuit for a pressure sensor according to a second embodiment of the present invention. The pressure sensor of this embodiment has the same configuration as the pressure sensor of the first embodiment shown in FIG. 1, so the drawings and detailed description of this embodiment will be omitted.

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 6 bonded to its surface is deformed. This deformation causes the amorphous magnetic alloy 6 to form due to the inverse magnetostriction effect.
magnetic permeability changes. This change is detected by the pressure detection coil 7 as a change in inductance. This output is input to the rectifier circuit 18a in FIG. 4, where it is converted to DC and then input to the DC differential circuit 19. On the other hand, the output of the differential coil 8 is also input to the rectifier circuit 18b in FIG. 4, converted into DC, and then input to the DC differential circuit 19. The difference between the two is taken within the DC differential circuit 19 and is used as an output.

The output characteristics of the pressure sensor with this configuration were similar to those in the first embodiment shown in FIG. In addition, since the detection circuit itself has almost the same configuration as the first embodiment, it can be miniaturized and
As in the first embodiment, it is possible to reduce the price. In addition,
As shown in FIG. 4, by using a DC differential as the differential circuit, it was possible to reduce the output error due to the phase difference between the two coils.

With the above configuration and operation, a pressure sensor that can be made smaller and cheaper while maintaining high accuracy compared to the conventional example has been obtained.

Effects of the Invention According to the present invention, by using changes in magnetic permeability of an amorphous magnetic alloy as pressure detection means, the detection circuit can be simplified, and the pressure sensor can be made smaller and lower in price. It has the effect of being.

[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 is a detection circuit block diagram of the same pressure sensor, Figure 3 is an output characteristic diagram of the same pressure sensor, Figure 4 is a detection circuit block diagram of the same pressure sensor, and Figure 5 is a sectional view of a conventional pressure sensor.
FIG. 6 is a detection circuit block diagram of the same pressure sensor, and FIG. 7 is an output characteristic diagram of the same pressure sensor. 1.21... Main body, 2.22... Pressure introduction port, 3.
23... Pressure chamber, 4... Deformed portion, 5... Non-deformed portion, 6... Amorphous magnetic alloy, 7... Pressure detection coil, 8... Differential coil, 9 ...Bobbin, 10...
- Yoke, 11... Fixing screw, 12.27... Detection circuit, 24... Diaphragm, 25... Strain gauge, 26... Relay plate. Name of agent: Patent attorney Shigetaka Awano and one other person

Claims (1)

[Claims] An amorphous material having a pressure introduction port, a deformable part that is distorted by the pressure introduced from the pressure introduction port, and a non-deformable part that is not distorted by the pressure, and has magnetostriction in the deformable part and the non-deformable part. A magnetic alloy is fixed, and an element for detecting magnetic permeability is provided in each of the deformed part and the non-deformed part so as to form a magnetic circuit with the amorphous magnetic alloy, and changes in magnetic permeability due to pressure application are detected by the two elements. In a pressure sensor that detects a change in inductance in the pressure sensor, the difference in inductance between the two elements is output as a pressure value using a detection circuit including an AC differential circuit or a DC differential circuit. sensor.