JPH0221232A - Pressure sensor - Google Patents

Abstract

PURPOSE:To enhance detection accuracy and to obtain stable linear output even when a temp. change is generated by applying internal stress to an amorphous magnetic alloy at the time of fixing and keeping the same in a measuring state. CONSTITUTION:Pressure to be detected is applied to the interior of a round pipe 1 composed of a titanium alloy from one end part thereof through a pressure introducing part 2. The other end of the round pipe is closed and a rectangular ferrous amorphous magnetic alloy 3 having positive magnetostriction is wound around the outside central part of the round pipe and fixed thereto at temp. higher than sensor using temp. In-plane compression stress is always applied to the amorphous magnetic alloy thin strip in a sensor using temp. region. A coil 4 is wound around the round pipe 1 in a concentric circular state and, when pressure to be applied is changed, an inductance change is generated in the coil 4.

Description

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

2. Description of the Related Art Mechanical quantity sensors that use the so-called stress-magnetic effect, which has the property that when stress is externally applied to an amorphous magnetic alloy with magnetostriction, changes its magnetic permeability, are attracting attention. For example, a pressure sensor using this principle was proposed in a patent application filed in 1984.
No. 21, No. 58-195239, etc.

FIG. 4 is a sectional view schematically showing an embodiment in the latter application. 11 is a cylindrical soft magnetic material provided with an annular groove; 12 is an amorphous magnetic alloy having magnetostriction; 13 is a coil wound around the groove of the soft magnetic material 11;・A non-magnetic ring that is in contact with the bottom and whose other end is flush with the opening surface of the soft magnetic material, 15 is a container for storing these, and 16 is a lid having a through hole 17 for transmitting pressure to the amorphous magnetic alloy. be.

Next, the operation of the above-mentioned prior art will be explained.

When pressure is applied to the hydraulic pressure introduction part 18, pressure is applied to the amorphous magnetic alloy disk 12 through the through hole 17, pushing it down in the soft magnetic groove, and stress is generated in the amorphous magnetic alloy disk. do. Due to the generation of this internal stress, the magnetic permeability of the amorphous magnetic alloy decreases due to the stress-magnetic effect. This change is detected in the form of inductance using a coil 13, which is one of the electromagnetic means, and the pressure is measured.

Problems to be Solved by the Invention In the conventional sensor configured as described above, the amorphous magnetic alloy disk 12, which is the pressure detection material, is pressed and fixed in the thickness direction of the disk by the sensor component members on both sides. has been done.

In such pressure sensors, it is difficult to maintain a uniform contact pressure state of the amorphous magnetic alloy disc under the operating conditions;
In particular, when a temperature change occurs, the sensor output changes, reducing detection accuracy. Further, the output of this sensor is non-linear, and the sensitivity changes depending on the detection pressure region.

In view of the problems of conventional pressure sensors as described above, the present invention
It is an object of the present invention to provide a pressure sensor that has high detection accuracy, has a linear output, and has a stable output even when temperature changes occur.

Means for Solving the Problems The present invention has a pressure introduction port and at least a deformed portion where distortion occurs due to the pressure, an amorphous magnetic alloy having magnetostriction is fixed to at least the deformed portion, and the amorphous In a pressure sensor that has electric and magnetic means for measuring the magnetic permeability of an amorphous magnetic alloy so as to form a magnetic circuit with the amorphous magnetic alloy, and detects pressure from the output of the electromagnetic means as pressure is applied, Under the measurement conditions of the sensor, if the amorphous magnetic alloy fixed to the deformed part has a positive saturation magnetostriction constant, it is always under in-plane compressive stress, and if it has a negative saturation magnetostriction constant, it is always under in-plane compressive stress. The pressure sensor has a structure that is maintained under internal tensile stress.

Function Since the present invention has the above-described configuration, the spontaneous magnetization within the amorphous magnetic alloy is basically caused by the stress constantly applied to the amorphous magnetic alloy from the deformed part of the sensor body under measurement conditions. The direction is perpendicular to the amorphous magnetic alloy surface, that is, the thickness direction, and is orthogonal to the measurement magnetic field. This makes it possible to realize a pressure sensor with high detection accuracy, linear output, and stable output even when temperature changes occur.

EXAMPLES Below, the present invention will be explained in detail based on drawings showing examples thereof.

Embodiment 1 FIG. 1 is a sectional view of an embodiment of a pressure sensor according to the present invention. 1 is made of titanium alloy and has an outer diameter of 10 mm5
It is a circular tube with an inner diameter of 9.7 mm, and the pressure to be detected can be applied to the inside of the circular tube from one end of the circular tube through a pressure introduction port 2. The other end has a closed structure, and a rectangular iron-based amorphous magnetic alloy 3 having a positive magnetostriction with a saturation magnetostriction constant of 20X10-6 is placed at the outer center of the circular tube. It is wound around the shaft and is fixed at temperatures higher than the sensor operating temperature. At this time, the difference in linear thermal expansion coefficient between the iron-based amorphous magnetic alloy and the titanium alloy constituting the cylindrical tube 1 is lXl0-6, and the titanium alloy is slightly larger. Therefore, in the sensor operating temperature range, in-plane compressive stress is always applied to the amorphous magnetic alloy ribbon. 4 is a coil wound concentrically around the metal circular tube 1.

Furthermore, a container 5 made of 48% Ni--Fe is provided outside the coil. 6 is a sensor output circuit, 7 is an output terminal, and 8 is a sensor mounting screw.

When the applied pressure is changed, an inductance change occurs in the coil 4. The results are shown in Figure 2. The measurement frequency is 30
The k Hz applied magnetic field is 180 A/m. The vertical axis shows the ratio of the inductance value at each pressure to the inductance value L9 when atmospheric pressure is Okgf/cm2. The pressure on the horizontal axis indicates the differential pressure with atmospheric pressure, that is, the relative pressure with atmospheric pressure. Inductance changes linearly with pressure up to a pressure of 10 kgf/cm2. In addition, a substantially linear senna was obtained in the output range of 130 to 120°C, and pressure hysteresis during pressurization and depressurization was less than 1% of the full scale, and hardly occurred. Furthermore, even when there was a change in the temperature of the atmosphere, the sensor output was extremely stable with a change of less than 5% of the full scale in the range of -30 to 120''C.

Example 2 A pressure sensor having a structure similar to that of Example 1 was fabricated.

The conditions for fixing the amorphous magnetic alloy were also the same as in Example 1. 1 in Figure 1 is made of nickel-iron alloy with an outer diameter of 10 mm.
1 A circular tube with an inner diameter of 9.4 mm was used. Further, for No. 3, a cobalt-based amorphous magnetic alloy having negative magnetostriction with a saturation magnetostriction constant of -4×10 −6 was used. Other constituent materials are also the same as in Example 1.

At this time, the difference in linear thermal expansion coefficient between the cobalt-based amorphous magnetic alloy 3 and the nickel-iron alloy cylindrical tube 1 is 1.2×10 −6 , and the cobalt-based amorphous magnetic alloy is slightly larger. Therefore, in the sensor operating temperature range, in-plane tensile stress is always applied to the amorphous magnetic alloy ribbon.

Figure 3 shows the output of this sensor. Measurement frequency is 50k
The HZN applied magnetic field is designed to be approximately 100 A/m.

As in Example 1, the pressure is relative to atmospheric pressure. The output changes linearly with pressure up to a pressure of 20 kgf/cm2. Also, as in Example 1, the output was 130 to 120.
It was almost linear in the range of "C", and the pressure hysteresis during pressurization and depressurization was less than 1% of the full scale, which was almost non-existent.Also, even when there was a change in the temperature of the atmosphere, it was -30 to 1
In the range of 20'C, the sensor output was extremely stable with a change of less than 5% of full scale.

As described above, the pressure sensor according to the present invention has high detection accuracy and linear output, and can provide a pressure sensor with stable output even if the temperature changes by 1 degree.

In the embodiments of the present invention, an appropriate temperature is formed inside the amorphous magnetic alloy based on the difference in linear thermal expansion coefficient between the fixed amorphous magnetic alloy and the material forming at least the fixed deformed part that is strained by the pressure and the fixing conditions. I mentioned that it creates a stress state. In particular, when the difference in linear thermal expansion coefficient of this material was 2X10-6 or less, a linear output with high accuracy and good sensitivity was obtained, but when the difference in linear thermal expansion coefficient became larger than this value,
The output sensitivity to pressure is greatly reduced, resulting in a reduction in accuracy.

Effects of the Invention As described above, the pressure sensor of the present invention applies internal stress to the amorphous magnetic alloy when it is fixed and maintains this in the measurement state, so it has high detection accuracy, a linear output, and is sensitive to temperature changes. This has the effect of stabilizing the output even if this occurs.

Furthermore, since this pressure sensor has a simple structure, it can be supplied at low cost and has the above-mentioned effects, so it can be used as a control device for automobiles, etc.
The application is appropriate for your field.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of an embodiment of the pressure sensor of the present invention, Fig. 2 is a diagram showing changes in inductance value due to pressure of the coil of the same embodiment, and Fig. 3 is a diagram of a pressure sensor according to another embodiment. FIG. 4, which is a diagram showing the output results, is a sectional view showing an outline of a conventional pressure sensor. DESCRIPTION OF SYMBOLS 1... Titanium alloy cylindrical tube, 2... Pressure introduction port, 3... Iron-based amorphous magnetic alloy having magnetostriction, 4...
Coil, 5... Container, 6... Sensor output circuit, 7
... Output terminal, 8... Screw for sensor installation, 11
. . . Cylindrical soft magnetic material, 12 . . . is an amorphous magnetic alloy having strain, 13 . . . Coil wound in the groove of the soft magnetic material, 14 .・・Container, 1
6... Through hole, 17... Lid part, 18... Hydraulic pressure introduction part. Name of agent Patent attorney Shigetaka Awano (1 person) Figure Cylindrical pipe pressure 1 Population Amorphous alloy coil Figure Pressure (Kgf/cm2) (kg%m2')

Claims (1)

[Claims] A non-crystalline magnetic alloy having a pressure introduction port and at least a deformed portion that is strained by the pressure, an amorphous magnetic alloy having magnetostriction fixed to at least the deformed portion, and forming a magnetic circuit with the amorphous magnetic alloy. In a pressure sensor that has an electromagnetic means for measuring the magnetic permeability of a crystalline magnetic alloy and detects pressure from the output of the electromagnetic means as pressure is applied, the pressure sensor is fixed to at least the deformed portion under measurement conditions of the sensor. When an amorphous magnetic alloy has a positive saturation magnetostriction constant, it is always under in-plane compressive stress, and when it has a negative saturation magnetostriction constant, it is always under in-plane tensile stress. Features of pressure sensor.