JPS63121726A - Pressure sensor - Google Patents

Abstract

PURPOSE:To attain stable and highly accurate pressure detection by setting up the diameter of the part of a magnetic circuit formed on a magnetic alloy plate so as to be larger than the outer diameter of a circular ring on a groove part of the soft magnetic body and smaller than the inner diameter of an O-ring. CONSTITUTION:An amorphous magnetic alloy disk 5 having magnetic distortion and a non-magnetic disk 6 are laminated on the upper surface 1a of the soft magnetic body 1 having the groove part 2 through a spacer 4. The circular ring-like slit 12 having a diameter larger than the outer diameter of the circular ring on the groove part 2 of the soft magnetic body 1 and smaller than the inner diameter of the O-ring 11. Thereby, the part of the magnetic circuit formed on the disk 5 is constituted so as not to be affected by the pressure of the O-ring. In case of detecting a change in magnetic permeability due to hydraulic pressure, magnetic flux can detect pressure stable and highly accurately without receiving the pressure variation of the O-ring.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a pressure sensor that utilizes magnetostriction of a magnetic alloy.

BACKGROUND OF THE INVENTION In recent years, pressure sensors that utilize the magnetostrictive effect of amorphous magnetic alloys and the like have been developed. The pressure sensor is constructed as shown in FIG. 4, for example.

An annular groove 2 on the upper surface 21a side of the cylindrical soft magnetic body 21
2 is provided, a coil 23 is wound around the groove 22,
and an upper surface 21a of the soft magnetic body 21 in which the groove portion 22 is opened.
A non-magnetic disk-shaped spacer 24 with a slit provided in a portion corresponding to the groove 22 is placed on the spacer 24, and an amorphous magnetic alloy disk 25 having magnetostriction is placed on top of the spacer 24. Nonmagnetic discs 26 are stacked on top of each other. These soft magnetic materials 21 and the like are housed in a container 28 with a non-magnetic metal bottom plate 27 interposed at the bottom. A lid portion 29 is disposed on the upper surface of the non-magnetic disk 26, and this lid portion 29 is provided with a through hole 30 for transmitting hydraulic pressure, and pressure is maintained between the lid portion 29 and the non-magnetic disk 26. An O-ring 31 is attached to prevent leakage of the transmission medium. A detection circuit 32 is connected to the coil 23.

In the pressure sensor configured as described above, when hydraulic pressure is applied to the hydraulic pressure inlet 33, pressure is applied to the magnetic alloy disc 25 through the through hole 30, and this is pushed down in the groove 22, causing the magnetic alloy disc 25 to be pressed down. Stress is generated inside. The magnetic permeability of the magnetic alloy disk 25 decreases due to the magnetostrictive effect caused by this internal stress. This change is detected by the detection circuit 32 in the form of inductance using the coil 23, and the oil pressure is measured.

Problems to be Solved by the Invention In the pressure sensor configured as described above, as shown in FIG.
A ring 31 is used to press the container 28 and the lid part 29 from the outside and mechanically fix them. Therefore, in addition to the pressure caused by the pressure transmission medium, the magnetic alloy disk 25
It will also receive pressure from the ring 31. Since the part receiving this pressure forms a part of the magnetic circuit as shown in FIG. The magnetic permeability of the magnetic alloy disc 25 is affected not only by the oil pressure but also by the pressure of the O-ring 31. There is no problem if the pressure of the O-ring 31 is only a certain amount, but there is a fluctuation in the force that fixes the container 28 and the lid part 29, and therefore the pressure caused by the O-ring 31 also fluctuates.

Due to the fluctuation of the pressure of the O-ring 31, the inductance value detected by the magnetostrictive effect fluctuates by up to 20%, which is becoming a problem as sensors become more precise.

The present invention solves the above-mentioned problems, and the magnetic alloy disc forming the magnetic circuit is not affected by the pressure of the O-ring, and the pressure is such that stable measurement values can be obtained. The purpose is to provide a sensor.

Means for Solving the Problems The pressure sensor of the present invention for solving the above problems includes:
A columnar soft magnetic body provided with an annular groove, a plurality of non-magnetic plates arranged on the opening surface of the groove of the soft magnetic body, and at least one of the non-magnetic plates sandwiched between two of the non-magnetic plates. A magnetic alloy plate having magnetostriction, a coil wound around the groove of the soft magnetic material, a container holding the soft magnetic material, and a surface of the non-magnetic alloy plate opposite to the soft magnetic material side. The soft magnetic material and the magnetic alloy plate are provided with a lid portion having a through hole through which a pressure transmission medium passes, an O-ring attached to the lid portion for sealing the pressure transmission medium, and a detection circuit connected to the coil. The diameter of the magnetic alloy plate portion of the magnetic circuit formed by
The outer diameter of the groove of the soft magnetic material is larger than the outer diameter of the annular ring, and the inner diameter of the O-ring is smaller than the inner diameter of the O-ring.

Effect With the above configuration, the part of the magnetostrictive magnetic alloy plate that forms the magnetic circuit with the soft magnetic material is larger than the outer diameter of the groove provided in the soft magnetic material and smaller than the -5=inner diameter of the O-ring. , the magnetic flux of the magnetic circuit does not pass below the O-ring, which means that the magnetic alloy plate part of the magnetic circuit that is formed is not affected by the fluctuating pressure of the O-ring, and as a result, the sensor output becomes stable. , it becomes possible to perform highly accurate measurements.

Example ° Hereinafter, embodiments of the present invention will be described based on the drawings.

FIG. 1 is a side sectional view of a pressure sensor according to an embodiment of the present invention. An annular groove 2 on the upper surface 1a side of the cylindrical soft magnetic body 1
is provided, and a coil 3 is wound around the groove 2.

A spacer 4 made of a non-magnetic disk is arranged on the upper surface 1a of the soft magnetic material 1 where the groove 2 is provided.
A thin slit 4a is provided in a portion corresponding to the groove portion 2. Further, an amorphous magnetic alloy disk 5 having magnetostriction is arranged on the spacer 4, and a non-magnetic disk 6 is further stacked on top of the disk 5. The soft magnetic body 1, spacer 4, magnetic alloy disc 5, and nonmagnetic disc 6 arranged as described above are attached to the bottom of the soft magnetic body 1 with a nonmagnetic metal bottom plate 7.
It is housed in a container 8 with a . A lid part 9 is disposed on the upper surface of the non-magnetic disc 6, a through hole 10 for transmitting hydraulic pressure is provided in the lid part 9, and a gap between the lid part 9 and the non-magnetic disc 6 is provided. An O-ring 11 is attached to the inner wall of the container 8 to prevent leakage of the pressure transmission medium. The magnetic alloy disc 5 is provided with an annular slit 12 having a diameter larger than the outer diameter of the annular ring of the groove 2 provided in the soft magnetic body 1 and smaller than the inner diameter of the O-ring 11. A magnetic circuit is formed between the inner portion 5a of the magnetic alloy disk 5 surrounded by the annular slit 12 and the soft magnetic body 1,
The annular portion 5b that is outside the slit 12 and receives the pressure of the O-ring 11 is configured so that no magnetic flux passes through it. The coil 3 is used to measure the inductance of the magnetic circuit, and is connected to the detection circuit 13 via the soft magnetic body 1, the nonmagnetic metal plate 7, and the bottom of the container 8.

In the pressure sensor configured as described above, when hydraulic pressure is applied from the hydraulic pressure inlet 14, the hydraulic pressure is applied to the inner portion 5a of the magnetic alloy disk 5 through the through hole 10, and the inner portion 5a
The portion of the soft magnetic body 1 corresponding to the groove 2 is pushed down. This generates stress inside the inner portion 5a of the magnetic alloy disk 5, and this internal stress reduces the magnetic permeability of the magnetic alloy due to the magnetostrictive effect. This change in magnetic permeability is measured by the magnetic alloy disk 5.
At the same time, the oil pressure can be measured by detecting in the form of inductance using a coil 3 wound around a soft magnetic material 1 constituting a magnetic circuit.

As described above, in order to detect the internal stress generated in the magnetic alloy disk by hydraulic pressure in the form of a change in inductance value, the magnetic alloy disk is If stress other than hydraulic pressure is generated, such as due to O-ring pressure, measurement accuracy will decrease. however,
In the pressure sensor having the configuration of the above embodiment, as shown in the schematic diagram of the main part of the magnetic circuit in FIG.
Since the magnetic flux M in the magnetic circuit does not pass through the annular part 5b which is formed only at the inner part 5a and receives the pressure of the O-ring 11, the change in the internal stress of the magnetic alloy disk 5 due to the hydraulic pressure is
Stable and highly accurate pressure detection is possible without being affected by the pressure of the ring 11 at all.

FIG. 3 is a schematic diagram of essential parts regarding a magnetic circuit in another embodiment of the present invention. In the embodiment shown in FIG. 3, the outer peripheral edge of the soft magnetic body 1 up to the portion where the O-ring 11 presses is replaced with a non-magnetic metal body 15 similar to the non-magnetic metal plate 7. With this configuration, the magnetic flux M of the magnetic circuit is not subjected to the pressure of the O-ring 11. Since the density is more uniform compared to the embodiments shown in Figures 1 and 2, more accurate oil pressure detection is possible, and the force applied to the soft magnetic body 1 is reduced, so higher pressure can be achieved. It becomes possible to measure up to

Effects of the Invention The present invention is characterized in that the diameter of the magnetic alloy plate portion of the magnetic circuit formed by the magnetostrictive magnetic alloy plate and the soft magnetic material is made larger than the outer diameter of the groove and smaller than the inner diameter of the O-ring. As a result, the magnetic flux in the magnetic circuit does not pass through the pressure-sensitive part of the O-ring, so even if the force that fixes the container and lid varies and the O-ring pressure fluctuates, it is completely irrelevant. This makes it possible to realize an excellent pressure sensor that can perform stable and highly accurate measurements.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a pressure sensor according to an embodiment of the present invention, FIG. 2 is a schematic diagram of the main part related to the magnetic circuit in the pressure sensor according to the embodiment of FIG. 1, and FIG. 3 is a pressure sensor according to another embodiment. FIG. 4 is a side sectional view of a conventional pressure sensor, and FIG. 5 is a schematic diagram of a principal part of the magnetic circuit in the conventional pressure sensor shown in FIG. 4. DESCRIPTION OF SYMBOLS 1... Soft magnetic material, 2... Groove part, 3... Coil, 4
... Spacer, 5... Magnetic alloy disk, 5a... Inner part, 5b... Annular part, 6... Non-magnetic disk, 7
・・・Non-magnetic metal bottom plate, 8... Container, 9... Lid part,
DESCRIPTION OF SYMBOLS 10...Through hole, 11...O ring, 12...Slit, 13...Detection circuit, 15...Nonmagnetic metal body. Agent Yoshihiro Morimoto Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Scope of Claims] 1. A columnar soft magnetic body provided with an annular groove, a plurality of nonmagnetic plates arranged on the opening surface of the groove of the soft magnetic body, and two of the nonmagnetic plates. at least one magnetic alloy plate having magnetostriction placed between them, a coil wound around the groove of the soft magnetic material, and a container holding the soft magnetic material;
a lid portion that is in contact with the surface of the non-magnetic alloy plate opposite to the soft magnetic material side and has a through hole through which a pressure transmission medium passes; an O-ring attached to the lid portion that seals the pressure transmission medium; and a lid portion that is connected to the coil. of the magnetic circuit formed by the soft magnetic material and the magnetic alloy plate, the diameter of the portion of the magnetic alloy plate is larger than the outer diameter of the ring of the groove of the soft magnetic material, and A pressure sensor that is smaller than the inner diameter of the ring. 2. The pressure sensor according to claim 1, wherein the magnetic alloy plate is an amorphous alloy plate. 3. The pressure sensor according to claim 1 or 2, wherein the columnar soft magnetic body has a nonmagnetic layer on the side surface.