JPS62162936A - Pressure sensor - Google Patents

Abstract

PURPOSE:To reduce variance at the time of manufacture and to increase pressure detection accuracy by forming a closed magnetic path of a columnar soft magnetic body, a nonmagnetic disk which has grooves corresponding to the groove part of the body 1 and many small holes 3a, and one amorphous alloy disk which has magnetic strain. CONSTITUTION:The closed magnetic path consists of the soft magnetic body 1, the nonmagnetic disk 3 having grooves 3 at parts corresponding to its groove parts and numbers of small holes 3a, and the amorphous magnetic alloy disk 2 having magnetic strain. The disk 2 is pressed down at groove parts 3b and small holes 3a with pressure from a pressure intake 4a to generate internal stress in the disk 2, the alloy 2 decreases in magnetic permeability owing to its magnetostrictive effect, and this variation is detected by a coil 8 in the form of inductance. Therefore, a magnetic circuit is stabilized by the spacer 3 of the nonmagnetic disk to reduce variance at the time of manufacture and improve the detection accuracy of pressure.

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.

BACKGROUND OF THE INVENTION In recent years, pressure sensors using the magnetostrictive effect of amorphous magnetic alloys have been proposed. For example, those described in JP-A-58-195239, JP-A-58-195240, etc.

FIG. 3 shows the former embodiment. 31 is a cylindrical soft magnetic body provided with an annular groove 31a, and 32 is an amorphous magnetic alloy disk having magnetostriction disposed above it. A coil 33 is wound around the groove 31 a of the soft magnetic material 31 . 34 is a non-magnetic ring arranged so that one end is in contact with the bottom of the groove and the other end is flush with the opening surface of the soft magnetic material. These are stored in a container 35. Container 35
A lid portion 37 having a through hole 36 for transmitting pressure to the amorphous magnetic alloy 32 is coupled to the top of the amorphous magnetic alloy 32 to form a pressure introduction port 38 . When pressure is applied to the pressure inlet 38, the through hole 36
Pressure is applied through the amorphous magnetic alloy disk 32, pushing it down in the soft magnetic groove and creating 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 magnetostrictive effect.

This change is detected in the form of inductance using a coil 33 to measure pressure.

Problems to be Solved by the Invention In a sensor configured as described above, in a magnetic circuit made of a soft magnetic material and an amorphous magnetic alloy disk having magnetostriction, the magnetic resistance is greatly affected by the air gap between the two. receive.

For example, Figure 4 shows the variation in the inductance value of a conventional sensor, and it shows that the air gap varies slightly (as a result, the magnetic flux state changes and the inductance value fluctuates by about 30%, making it unstable. To solve this problem, a spacer can be installed between the soft magnetic material and the magnetostrictive amorphous magnetic alloy disc, but simply inserting the spacer increases the stability of the magnetic circuit, but at the same time The sensitivity as a sensor also decreases, making it impractical.

Means for Solving the Problem A non-magnetic disc spacer having small holes over its entire surface is inserted between the soft magnetic material and the amorphous magnetic alloy disc.

By providing a non-magnetic spacer with a small hole between the working soft magnetic material and the amorphous magnetic alloy disc, the magnetic circuit is stabilized and the inductance value of the sensor becomes stable. At the same time, the amorphous magnetic alloy disk is deformed by pressure in the spacer small hole portion, internal stress is generated, the magnetic permeability decreases in this portion, and the output as a sensor increases. When the non-magnetic spacer is made of metal, the alternating magnetic field detected by inductance is attenuated due to the skin effect, but if a small hole is provided, this skin effect can be avoided and the output can be increased.

Example FIG. 1 is a sectional view of an embodiment of the present invention.

1 is a cylindrical soft magnetic material provided with an annular groove, 2 is an amorphous magnetic alloy disc with magnetostriction, and 3 is a nonmagnetic material placed between the soft magnetic material and the amorphous magnetic alloy disc. A spacer made of a disk. The details of the shape of this spacer 3 are shown in FIG. There are small holes 3a over the entire surface, and elongated grooves 3b in portions corresponding to the soft magnetic grooves. These three members constitute one closed magnetic path. Reference numeral 4 designates a lid portion having a through hole 6 for transmitting pressure and having an O-ring 5 for blocking oil, the upper part of which is a pressure introduction port 4a. Reference numeral 7 denotes a container which, together with the lid 4, houses and holds the members constituting the above-mentioned magnetic circuit. A coil 8 is provided in the groove of the soft magnetic material 1 and is used to measure the inductance of the magnetic circuit described above. 9 is a detection circuit.

When pressure is applied from the pressure introduction port 4a, the pressure is applied to the amorphous magnetic alloy through the through hole 6, and the amorphous magnetic alloy is pushed down by the soft magnetic groove and the small hole of the spacer. This generates stress within the amorphous magnetic alloy disc, and this internal stress reduces the magnetic permeability of the amorphous magnetic alloy due to the magnetostrictive effect.

This change is detected in the form of inductance using the coil 9, and the pressure is measured.

Figure 5 shows the variation in inductance value between samples in the embodiment shown in Figure 1, which is about 30% of the conventional value.
This is approximately 1.5%, which is one-twentieth of the variation in .

As can be seen from the above-mentioned detection principle, since this sensor detects changes in magnetic permeability of the amorphous magnetic alloy due to pressure, improving the stability of the magnetic circuit significantly improves pressure detection accuracy.

Furthermore, in addition to the internal stress in the conventional soft magnetic groove, the amorphous magnetic alloy is deformed downward by pressure in the small hole portion of the spacer, generating internal stress, thereby increasing the sensor output.

FIG. 6 shows the results of actually measuring the characteristics of the pressure-inductance conversion section of the sensor using the metal spacer with a small hole and the metal spacer without a small hole in the embodiment shown in FIG. It can be seen that the change in inductance of the converter using a spacer with small holes on its entire surface increases. This result is also due to the fact that the skin effect of the metal is avoided.

In the embodiment shown in FIG. 1, the non-magnetic spacer 3 is provided with a long and narrow groove, but since there is no support from below in the soft magnetic groove of the non-magnetic spacer, the same effect can be obtained even if the non-magnetic spacer does not have a long and thin groove. Effects of the Invention According to the present invention, the magnetic circuit is stabilized by the non-magnetic disk spacer having small holes, and variations during manufacturing are extremely minimized. This makes it possible to improve pressure detection accuracy.Moreover, the amount of amorphous magnetic alloy that deforms due to pressure increases, and the output of the sensor also increases.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a pressure sensor according to an embodiment of the present invention, FIG. 2 is a plan view showing details of the non-magnetic disk shown in FIG. 1, and FIG.
Figure 4 is a cross-sectional view of a conventional sensor, Figure 4 is a diagram showing the variation in inductance value of the conventional sensor, Figure 5 is a diagram showing the variation in inductance value of the sensor of the present invention, and Figure 6 is a diagram showing the variation in inductance value of the sensor of the present invention. It is a graph showing the characteristics of the pressure-inductance conversion section of a sensor employing a spacer with a hole and a spacer without a hole. 1...Soft magnetic material, 2...Amorphous magnetic alloy disk having magnetostriction, 3...Nonmagnetic disk, 3a...Small hole, 3b...
... Groove, 4... Lid, 4a... Pressure introduction port, 6...
- Through hole, 7... Container, 8... Coil, 9... Detection circuit. Name of agent: Patent attorney Toshio Nakao (1 person) Figure 1 Figure 2 Figure 3b groove Figure 4 Figure 4

Claims (2)

[Claims] (1) A cylindrical soft magnetic body provided with an annular groove,
a non-magnetic disk that is in contact with a surface having grooves of the soft magnetic material and has small holes over the entire surface; and at least one amorphous magnetic material that has magnetostriction and that is in contact with the non-magnetic disk on a side opposite to the soft magnetic material. an alloy disc, a coil wound around the soft magnetic groove, a container for holding these, a means for contacting the amorphous magnetic alloy to prevent the pressure transmission medium from flowing out, and a coil wound in the soft magnetic groove. A pressure sensor comprising: a lid portion having a means for transmitting pressure to the amorphous magnetic alloy disk at a corresponding position. (2) The pressure sensor according to claim 1, wherein the non-magnetic disc has an elongated groove in a portion corresponding to the soft magnetic groove.