JPH0221233A - Pressure sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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 having 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. 5 is a sectional view schematically showing a pressure sensor disclosed in the latter publication. 31 is a cylindrical soft magnetic material provided with an annular groove; 32 is an amorphous magnetic alloy having magnetostriction;
3 is a coil wound around the groove of the soft magnetic material 31; 34;
3 is a non-magnetic ring having one end in contact with the bottom of the groove and the other end facing the opening surface of the soft magnetic material; 35 is a container for storing these;
6 is a lid portion having a through hole 37 for transmitting pressure to the amorphous magnetic alloy.

When pressure is applied to the hydraulic pressure introducing portion 38, pressure is applied to the amorphous magnetic alloy disk 32 through the through hole 37, pushing it down in the soft magnetic groove and generating stress within the amorphous magnetic alloy disk. 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 33, which is one of the electromagnetic means, and the pressure is measured.

However, in the conventional pressure sensor configured as described above, the output characteristics of the sensor are determined by the pressure applied to the amorphous magnetic alloy disk 32 through the through hole 37 and the coil 33. is determined based on the pressure difference in the soft magnetic groove in which it is located. That is, since the atmosphere exists in the magnetic groove, the detection output of the sensor detects the differential pressure between the atmospheric pressure and the measured pressure. For example, atmospheric pressure can be less than 1/2 atmosphere (1/2 kgf/cm2) in spaces where aircraft and rockets fly at high altitudes, and it varies depending on the measurement location and measurement time. This indicates that in the conventional sensor as described above, errors occur depending on the measurement location and measurement time. Especially in the case of a pressure sensor with a low measurement pressure, for example in the range of several atmospheres,
This error becomes extremely large, making it unsuitable for low-pressure pressure measurement.

In addition, in the conventional sensor described above, the measurement pressure medium oil and the atmosphere come into direct contact with the front and back surfaces of the amorphous magnetic alloy disc, respectively, so if it is exposed to an oxidizing atmosphere, the amorphous magnetic alloy will corrode. Sensor output changes over time. Additionally, when the sensor receives thermal radiation from the outside world, the sensor components that come into contact with the amorphous magnetic alloy and the amorphous magnetic alloy itself thermally expand, creating thermal stress, which causes errors in the sensor output. . As described above, conventional sensors cannot be expected to have high output accuracy.

In view of the problems of conventional pressure sensors, the present invention
The purpose of the present invention is to provide a pressure sensor capable of measuring absolute pressure with high output accuracy.

Means for Solving the Problems The present invention as claimed in claim 1 includes a pressure introduction port and at least a deformed portion that is distorted by the pressure, and an amorphous magnetic alloy having magnetostriction is fixed to at least the deformed portion. , a pressure sensor comprising electromagnetic means for measuring the magnetic permeability of the amorphous magnetic alloy so as to form a magnetic circuit with the amorphous magnetic alloy, and detecting pressure from the output of the electromagnetic means as pressure is applied. The pressure sensor has a structure in which at least the non-fixed surface portion of the amorphous magnetic alloy fixed to the deformed portion is exposed to a vacuum atmosphere.

The present invention according to claim 2 has a pressure introduction port, a deformable portion that is strained by the pressure, and a non-deformable portion that is not strained by the pressure, and the deformable portion and the non-deformable portion are each or both of the deformable portion and the non-deformable portion. An electromagnetic means for fixing a continuous amorphous magnetic alloy having magnetostriction and measuring the magnetic permeability of the amorphous magnetic alloy in a deformed part and a non-deformed part so as to form a magnetic circuit with the amorphous magnetic alloy. and detects pressure from the output difference between the two electromagnetic means upon application of pressure, in which at least a non-fixed surface portion of the amorphous magnetic alloy fixed to the deformed portion is exposed to a vacuum atmosphere. It is a pressure sensor with a structure.

Function: With the above-described structure, the stress applied to the amorphous magnetic alloy fixed to the deformed portion that undergoes deformation due to the measured pressure always depends only on the measured pressure. Therefore, the magnetic permeability of the amorphous magnetic alloy changes, and by detecting this change using electromagnetic means, it becomes possible to measure the difference between the vacuum pressure and the measured pressure, that is, the absolute pressure.

In addition, even if the sensor receives heat radiation from the outside world, heat transfer to the non-quality magnetic alloy is suppressed from the vacuum part, so it is only necessary to control the heat transfer and thermal stress from the deformed part, which improves sensor accuracy. Improvements can be made. Furthermore, since the amorphous magnetic alloy does not come into direct contact with the oil of the measurement pressure medium or the ambient air, the amorphous magnetic alloy will not be corroded even if the sensor is exposed to an oxidizing atmosphere. Therefore, the sensor output does not change over time.

As described above, the pressure sensor of the present invention is capable of highly accurate pressure measurement that is insensitive to atmospheric pressure at the time of measurement, reduces the influence of changes in the measurement environment such as temperature on the sensor output, and does not change over time.

Example The present invention will be explained in detail using the following examples.

Embodiment 1 FIG. 1 is a sectional view of an embodiment of the pressure sensor of the present invention. 1 is made of titanium alloy and has an outer diameter of 10 m rl'h
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. In addition, the other end has a closed structure, and a rectangular iron-based amorphous magnetic alloy 3 having magnetostriction is wound around the axis at the outer center of the circular tube, and is heated to a temperature higher than the sensor operating temperature. It is firmly fixed. 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. Here, the space 9 formed by the container 5 and the titanium alloy circular tube 1 to which the amorphous magnetic alloy is fixed is 5X.
1 (13 Torr) and isolated from the outside.

When the applied pressure is changed, an inductance change occurs in the coil. The results are shown in FIG.

The measurement frequency was 30 kHz, and the applied magnetic field was 160 A/m. The vertical axis represents the inductance value at absolute pressure Okgf/cm2 and the ratio of the inductance value at each pressure to 9. Inductance changes linearly with pressure up to a pressure of 10 kgf/am2 (absolute pressure). In addition, a nearly linear sensor was obtained with an output in the range of 130 to 120"C, and the pressure hysteresis during pressurization and depressurization was less than 1% of the full scale, which was almost non-existent. The sensor output was stable even when there was a temperature change. This is because the heat transfer to the transducer is mainly from the body, which has a large heat capacity and is difficult to change temperature. The example sensor showed longer output stability than a sensor with a structure without a vacuum section.This was especially noticeable when epoxy adhesive was used as the adhesive.Sensor output changes over time Possible causes include reactions of the adhesive with water in the atmosphere, and oxidation of the amorphous magnetic alloy by the atmosphere.

Embodiment 2 FIG. 3 is a sectional view of another embodiment of the pressure sensor of the present invention. 11 is a cylinder made of titanium alloy with an outer diameter of 10 mm, and inside the cylinder there is a circular tube part 12 with an inner diameter of 9.5 mm.
The pressure to be detected can be applied into the circular tube from one end of the circular tube through the pressure introduction port 13, and a deformed portion 14 due to pressure is formed. Further, the other end has a closed structure without holes, and is provided with a non-deformable portion 15 that does not deform even under pressure. A magnetostrictive iron-based amorphous magnetic alloy 16 is wound around the outer central part of the circular tube so as to cover the outer side of the cylinder of the deformed and non-deformed portions, and is fixed at a temperature higher than the sensor operating temperature. In this method, in-plane compressive stress is generated on the surface of an amorphous magnetic alloy ribbon. At this time, the difference in linear thermal expansion coefficient between the iron-based amorphous magnetic alloy and the titanium alloy forming the cylinder 11 is lX10-6, and the titanium alloy is slightly larger. Further, a cylindrical bobbin 17 is provided outside the deformed and non-deformed portions, and coils 18 wound concentrically thereon are respectively arranged. Furthermore, a container 19 made of 48% Ni-Fe, which is a magnetic material with high magnetic permeability, is provided outside the coil to constitute the magnetic circuit of the sensor and to serve as a magnetic shield strong against external magnetic disturbances. There is. 20 is a sensor output circuit, and 21 is a sensor mounting screw. Here, the space 22 formed by the container 19 and the titanium alloy cylinder 11 to which the amorphous magnetic alloy is fixed is lXl0-2Tor.
It is isolated from the outside with a vacuum degree of r.

When the applied pressure is changed, the inductance mainly changes in the coil in the deformed part, and the inductance of the coil in the non-deformed part hardly changes.

A circuit that detects the difference between these two inductance values enables highly accurate measurement with an accuracy of 4% or less of full scale in the temperature range of -30 to 120°C. Figure 4 shows the output results of the sensor. The measurement frequency is 50 kHz,
The applied magnetic field is designed to be approximately 100 A/m. pressure is 2
Output changes linearly with pressure up to 0 kgf/cm2 (absolute pressure). The output of the sensor of this example was basically the same as in Example 1, with high accuracy and little change over time, but by measuring the inductance difference, it became possible to measure with higher accuracy.

In the case of this embodiment, the amorphous magnetic alloy fixed to the non-deformed portion receives pressure from the non-fixed portion. It is preferable that this non-fixed part also be in a vacuum, but in general, changes in the magnetic permeability of the amorphous magnetic alloy due to pressure changes in this part are small and can be ignored under normal measurement conditions. Therefore, the non-fixed part of the amorphous magnetic alloy fixed to the non-deformed part does not need to be in a vacuum atmosphere.

As described above, the pressure sensor of the present invention enables highly accurate and stable measurement of the difference between vacuum pressure and measured pressure, that is, absolute pressure.

In the embodiments of the present invention, an example was described in which the non-fixed surface portion of the fixed amorphous lf1@ alloy was in a vacuum atmosphere with a value of LX 10-2 Torr or less, but
As long as the vacuum is at a high vacuum below the value of o r r , the same effects as in the embodiment can be expected. In a low vacuum region above this value, if the volume of the vacuum portion becomes small, the measurement accuracy will decrease.

Effects of the Invention As described above, the pressure sensor according to the present invention has a structure in which at least the non-fixed surface portion of the amorphous magnetic alloy fixed to the deformed portion due to the applied pressure is exposed to the vacuum atmosphere, so that it can measure absolute pressure. It is stable against ambient temperature changes over a wide measurement temperature range, has high precision, output linearity, and maintains stable output for a long time. Furthermore, since this pressure sensor has a simple structure, it can be supplied at low cost, and has the above-mentioned effects, so it is suitable for the control field of automobiles, aircraft, rockets, and various machines.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a pressure sensor according to an embodiment 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 cross-sectional view of another embodiment of the present invention. Figure 4 shows the output results of the sensor of the same example, Figure 5 shows the output results of the sensor of the same example.
The figure is a cross-sectional view schematically showing 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...sensor mounting screw, 9.
...Vacuum space, 11...Titanium alloy cylinder, 12...Cylindrical tube part 1
2.13... Pressure introduction port, 14... Deformed part due to pressure, 15... Non-deformable part that does not deform even under pressure, 16... Iron-based amorphous magnetic alloy having magnetostriction, 1
7...Bobbin, 18...Coil, 19...4
8% Ni-Fe container, 20... sensor output circuit,
21...Sensor mounting screw, 22...Vacuum space, 31...Cylindrical soft magnetic material, 32...Amorphous magnetic alloy having magnetostriction, 33...Soft magnetic material Coil wound around the groove, 34... Non-magnetic ring, 35... Container, 36... Through hole, 37... Lid, 38... Hydraulic pressure introduction part. Name of agent: Patent attorney Shigetaka Awano (1 person) Fig. Cylindrical pipe pressure inlet Amorphous cylindrical alloy coil Fig. 3 Fig. 2 Extinct! Bri force (Kgf/cm”) Absolute pressure (Kgf/Cm2)

Claims (3)

[Claims] (1) It has a pressure introduction port and at least a deformed part where distortion occurs due to the pressure, and an amorphous magnetic alloy having magnetostriction is fixed to at least the deformed part to form a magnetic circuit with the amorphous magnetic alloy. In a pressure sensor that has an electromagnetic means for measuring the magnetic permeability of an amorphous magnetic alloy and detects pressure from the output of the electromagnetic means as pressure is applied,
A pressure sensor having a structure in which at least a non-fixed surface portion of the amorphous magnetic alloy fixed to the deformed portion is exposed to a vacuum atmosphere. (2) It has a pressure inlet, a deformed part that is strained by the pressure, and a non-deformed part that is not strained by the pressure, and has magnetostriction that is continuous to each or both of the deformed part and the non-deformed part. An amorphous magnetic alloy is fixed thereon, and an electromagnetic means for measuring the magnetic permeability of the amorphous magnetic alloy is provided in a deformed portion and a non-deformed portion, respectively, to form a magnetic circuit with the amorphous magnetic alloy. In a pressure sensor that detects pressure from the output difference between the two electromagnetic means as a result of application, it is preferable that at least a non-fixed surface portion of the amorphous magnetic alloy fixed to the deformed portion is exposed to a vacuum atmosphere. Features of pressure sensor. (3) The vacuum atmosphere according to claim 1 or 2 is 10^
A pressure sensor characterized by a pressure of -^1 Torr or less.