JPS6293625A - Pressure sensor - Google Patents

Abstract

PURPOSE:To attain stabilization of a magnetic circuit and to stabilize magnetic circuit and to stabilize the inductance value of a sensor, by bonding an amorphous magnetic alloy disc fixed at the circumferential part thereof by a metal ring to a soft magnetic body by interposing a spacer consisting of a non- magnetic disc between both of them. CONSTITUTION:When pressure is applied from a pressure introducing port 11, said pressure is applied to an amorphous magnetic alloy disc 2, of which the circumferential part is fixed by a metal ring 4, through a through-hole 6 to downwardly push the amorphous magnetic alloy disc 2 at the part of the groove 1a of a soft magnetic body 1. By this method, stress is generated in the amorphous magnetic alloy disc 2 and the magnetic permeability of the amorphous magnetic alloy disc is reduced by magnetostriction effect based on said internal stress and this reduction is detected in an inductance form using a coil 9 to detect pressure. At this time, because a spacer consisting of a non-magnetic disc 3 is used between the soft magnetic body 1 and the amorphous magnetic alloy disc 2, the stabilization of a magnetic circuit is attained and, because the inductance value becomes stable, highly accurate measurement can be performed.

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 A pressure sensor has been proposed that uses the magnetostrictive effect of an amorphous magnetic alloy as a pressure-receiving diaphragm.

Among these, there is one that uses soldering to fix the crystalline magnetic alloy diaphragm. For example, JP-A-57-152191
It is shown in the publication No. FIG. 3 is a schematic diagram showing the soldering part of the embodiment.

31 is a cylindrical soft magnetic body provided with an annular groove;
2 is an amorphous magnetic alloy disk having magnetostriction. Reference numeral 33 indicates a solder layer provided to fix the soft magnetic material 31 and the amorphous magnetic alloy 32 together. Pressure is applied from above. By adopting such a configuration, the diaphragm of the amorphous magnetic alloy disc 32 is securely fixed to the soft magnetic body 31, and mechanical backlash due to deformation due to pressure does not occur. This allows accurate measurement of pressure.

Problems to be Solved by the Invention In the sensor configured as described above, since a soft magnetic material and an amorphous magnetic alloy disk having magnetostriction are soldered, a spacer for stabilizing the magnetic circuit is made of soft magnetic material. and an amorphous magnetic alloy disc. Therefore, for example, the fifth
As shown in the figure, the variation in the sensor inductance value when the magnetic circuit stabilizing spacer is not inserted,
The magnetic flux state changes due to the effect of a slight change in the air gap, and the inductance value fluctuates by 30%, making it unstable.

Furthermore, since the soft magnetic material and the amorphous magnetic alloy disk are completely fixed with solder, it is necessary to use materials with similar coefficients of thermal expansion. It is quite difficult to find a combination of materials that satisfies this condition, and even a desirable combination of properties does not necessarily satisfy this condition.

Means for Solving the Problems: An amorphous magnetic alloy disk is fixed near its circumference to a metal ring with a similar coefficient of thermal expansion, and this is used as a pressure receiving diaphragm. This amorphous magnetic alloy disk and the soft magnetic material are coupled with a spacer made of a non-magnetic disk interposed between them.

Since the circumference of the working amorphous magnetic alloy disk is fixed with a metal ring, mechanical backlash of the pressure receiving diaphragm does not occur (
The output becomes stable. In addition, since the soft magnetic material and the amorphous magnetic alloy disk are not directly fixed, even if there is a difference in thermal expansion coefficient between the two, the output will not be affected. By providing a spacer made of a non-magnetic disk in the magnetic circuit, the magnetic circuit is stabilized, and the inductance value of the sensor becomes stable.

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

1 is a cylindrical soft magnetic body provided with an annular groove 1a;
2 is an amorphous magnetic alloy disk having magnetostriction, and 3 is a non-magnetic disk (constituting a spacer) placed between the soft magnetic material and the amorphous magnetic alloy disk, which corresponds to the groove 1a of the soft magnetic material 1. It has an elongated groove 3b in the part where it is located. These three members constitute one closed magnetic path. 4 is a metal ring soldered near the circumference of the amorphous magnetic alloy disk 2 to fix the amorphous magnetic alloy disk 2. This fixing is not limited to soldering, but may be performed by welding or other methods. 5 is an O-ring 7 having a through hole 6 for transmitting pressure and blocking a pressure transmitting medium.
This is the lid part with the . Reference numeral 8 denotes a container which houses and holds the above-mentioned magnetic circuit together with the lid part 5. A coil 9 is provided in the soft magnetic groove and is used to measure the inductance of the magnetic circuit described above. 10 is a detection circuit.

When pressure is applied from the pressure introduction port 11, the pressure is applied to the amorphous magnetic alloy disk 2 through the through hole 6, and the amorphous magnetic alloy disk 2 is pushed down by the groove 1a of the soft magnetic material 1. . This generates stress within the amorphous magnetic alloy disk 2, 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 a coil 9 to measure pressure.

This can be understood from the above detection principle. As such, this sensor detects pressure in the form of a change in inductance value, and for this reason the stability of the magnetic circuit is necessary for high-precision measurements.

Therefore, a spacer of a non-magnetic disk 3 is used between the soft magnetic material 1 and the amorphous magnetic alloy disk 2.

FIG. 2 is a schematic diagram showing the amorphous magnetic alloy disk 2 and the metal ring 4, in which 21 indicates a solder layer fixing the two. The metal ring 4 prevents mechanical backlash from occurring even when the amorphous magnetic alloy disk 2 is deformed as a diaphragm. If the amorphous magnetic alloy disk 2 is not fixed properly, it will deform downward in the groove of the soft magnetic material 1 as shown in Figure 4 when pressure is applied, and the amorphous magnetic alloy will deform as shown by the arrow in the figure. The disc 2 is drawn into the groove. When this happens, the sensor output has hysteresis with respect to pressure. In the conventional example described above, the soft magnetic material and the amorphous magnetic alloy disk were fixed by soldering, but as mentioned earlier, it is necessary to insert a spacer in consideration of the stability of the magnetic circuit.

Therefore, in the present invention, the diaphragm of the amorphous magnetic alloy disk is fixed by soldering or fixing the circumferential portion to a metal ring.

FIG. 6 shows the variation in inductance value in this embodiment of FIG. 1, which is about 1.5%, one-twentieth of the variation of about 30% in the conventional case. Therefore, it can be seen that pressure detection can be performed with high accuracy. This is because the air gap in the magnetic circuit was precisely controlled by the spacer.

FIG. 7 shows the change in inductance with respect to pressure in the embodiment shown in FIG. Ferrite was used as the soft magnetic material, and an iron-based amorphous magnetic alloy was used as the amorphous magnetic alloy. Although there is a difference of about 1 ppm in the thermal expansion coefficient between the two, there is no hysteresis in the output and the output is stable.

Effects of the Invention According to the present invention, the amorphous magnetic alloy disc constituting the diaphragm can be fixed to prevent the occurrence of backlash, and the magnetic circuit can be stabilized between the soft magnetic material and the amorphous magnetic alloy disc. A structure in which spacers can be inserted can be realized.

[Brief explanation of drawings]

FIG. 1 is a sectional view of one embodiment of the pressure sensor of the present invention, and FIG.
The figure is a perspective view showing the main part of Fig. 1, Fig. 3 is a perspective view showing the method of fixing the conventional pressure sensor amorphous magnetic alloy disk and soft magnetic material, and Fig. 4 is A cross-sectional view showing the deformation of a magnetic alloy disc diaphragm, FIG. 5 is a graph showing variations in inductance values of conventional sensors, FIG. 6 is a graph showing variations in inductance values of the pressure sensor of the present invention, and FIG. The figure is a graph showing the output characteristics of the pressure sensor of the present invention. 1-m-soft magnetic material, 2-11 amorphous magnetic alloy disk, 3-
11-non-magnetic disk, 4-m-metal ring, 5-m-lid part,
6--through hole, 7--0 ring, 8--one container, 9-
11 Coil, 10--1 Detection circuit, 11-11 Pressure introduction Ro Moria's agent's name: Patent attorney Toshio Nakao and one other person Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 "Hin Asanfu" 10 20 Jθ Stone stepping force (K1/missing)

Claims (3)

[Claims] (1) A cylindrical soft magnetic body provided with an annular groove, a non-magnetic disc in contact with the surface of the soft magnetic body having the groove, and a non-magnetic circular plate on the side opposite to the soft magnetic body. at least one magnetostrictive amorphous magnetic alloy disk having a circumferential portion in contact with the plate and fixed to a metal ring, a coil wound in the soft magnetic groove, and a container holding these; A pressure control device comprising: a lid portion that is in contact with the amorphous magnetic alloy and has means for preventing the pressure transmission medium from flowing out; and a lid portion that corresponds to the soft magnetic groove portion and has a means for transmitting pressure to the amorphous magnetic alloy disc. sensor. (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. (3) The pressure sensor according to claim 1, wherein the amorphous magnetic alloy disk is fixed to the metal ring by soldering or welding.