JP2005241567A - Pressure sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure sensor capable of detecting pressure variation at high sensitivity, while realizing price reduction which results from reduction of parts count, miniaturization and enhancement in reliability. <P>SOLUTION: This pressure sensor 10 is located in a casing 12, filled with a fluid 14, such as liquid and a gas, and also comprises a super-magnetostrictive member 16 having an anisotropic shape and a detection coil 18 detecting pressure variation of the fluid 14 as a variation of permeability of the super-magnetostrictive member 16 or of the residual magnetization, based on the deformation of the super-magnetostriction member 16. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pressure sensor using a magnetostrictive member.

  Conventionally, a pressure sensor using a magnetostrictive member is widely known as one of pressure sensors that can detect a pressure change of a fluid such as liquid or gas.

  For example, a conventionally known pressure sensor 1 shown in FIG. 11 has a giant magnetostrictive member 3 that receives a compressive force from the outside via a push rod 2 and a coil 4 disposed around the giant magnetostrictive member 3. Configured.

  In the pressure sensor 1, the pressure applied to the push rod 2 is detected by detecting a change in the magnetic permeability of the giant magnetostrictive member 3 by the coil 4.

JP-A-11-287725

  However, in this conventionally known pressure sensor 1, since external pressure is applied to the giant magnetostrictive member 3 via the push rod 2, it is difficult to detect a minute change in pressure, and the detection sensitivity is high. There was a problem that it became low.

  Moreover, since the giant magnetostrictive member 3 is made of a rod-like member and receives a compressive force from the push rod 2 only at its axial end face, the contact area between the push rod 2 and the giant magnetostrictive member 3 is unstable. Thus, there was a problem in the repetition characteristics.

  The present invention has been made in order to solve such problems, and at the same time, it achieves cost reduction, reduction in size, improvement in reliability, etc. by reducing the number of parts, and at the same time, pressure change with high sensitivity. An object of the present invention is to provide a pressure sensor capable of detecting the above.

  As a result of earnest research, the inventor of the present invention has realized a reduction in cost by reducing the number of parts, a reduction in size, an improvement in reliability, etc., and at the same time, a pressure sensor capable of detecting a pressure change with high sensitivity. I found.

  That is, the above-described object can be achieved by the following present invention.

  (1) A magnetostrictive member disposed in a casing filled with a fluid such as liquid or gas with a gap and having an anisotropic shape, and a pressure change of the fluid based on deformation of the magnetostrictive member. And a detecting means for detecting a change in magnetic permeability or residual magnetization amount of the magnetostrictive member.

  (2) The pressure sensor according to (1), wherein the magnetostrictive member is formed of a substantially rod-shaped body.

  (3) The pressure sensor according to (2), wherein the surface area of the outer circumferential surface in the radial direction of the magnetostrictive member is at least three times the surface area of both end surfaces in the axial direction.

  (4) The detection means includes a detection coil, and detects a change in permeability or residual magnetization of the magnetostrictive member as a change in inductance value of the detection coil. The pressure sensor according to any one of 3).

  (5) The pressure sensor according to (4), wherein the detection coil is wound around the casing so as to surround the magnetostrictive member.

  (6) The pressure sensor according to (4), wherein the detection coil is wound around the magnetostrictive member.

  (7) The detection means (1) to (3) are characterized in that the detection means includes a Hall element, and a change in permeability or residual magnetization of the magnetostrictive member is detected as a change in electromotive force of the Hall element. ).

  (8) The detection unit includes a magnetoresistive effect element, and detects a change in magnetic permeability or residual magnetization of the magnetostrictive member as a change in electromotive force of the magnetoresistive effect element. The pressure sensor according to any one of (3) to (3).

  (9) The pressure sensor according to any one of (1) to (8), further including a fixing member that is fixed to the inner peripheral surface of the casing while holding the magnetostrictive member.

  (10) Any of (1) to (8) above, further comprising a fixed spring that is contracted in a gap between the casing inner peripheral surface and the magnetostrictive member and restricts movement of the magnetostrictive member. A pressure sensor according to claim 1.

  (11) The pressure sensor according to any one of (1) to (8), wherein the magnetostrictive member can be accommodated and includes a net suspended in the casing.

  (12) The pressure sensor according to any one of (1) to (11), wherein the magnetostrictive member is a giant magnetostrictive member made of a giant magnetostrictive element.

  According to the pressure sensor of the present invention, it is possible to detect a change in pressure with high sensitivity at the same time while realizing cost reduction, downsizing, and improvement in reliability by reducing the number of parts. Have

  The pressure sensor according to the present invention includes a magnetostrictive member disposed in a casing filled with a fluid such as liquid or gas with a gap and having an anisotropic shape, and a change in pressure of the fluid in the magnetostrictive member. And detecting means for detecting the change in the magnetic permeability or the residual magnetization amount of the magnetostrictive member based on the deformation of the magnetostrictive member.

  The “anisotropic shape” in the present invention means a shape having anisotropy, and includes, for example, a rod-like body and a plate-like body.

  Hereinafter, the pressure sensors according to the first and second embodiments of the present invention will be described in detail with reference to the drawings.

  As shown in FIGS. 1 and 2, the pressure sensor 10 according to the first embodiment of the present invention has a gap between the pressure sensor 10 and the casing 12 in a substantially cylindrical casing 12 filled with a fluid 14 such as liquid or gas. The substantially bar-shaped super magnetostrictive member 16 and a detection coil (detection) for detecting a change in pressure of the fluid 14 as a change in the permeability or residual magnetization of the super magnetostrictive member 16 based on the deformation of the super magnetostrictive member 16. Means) 18.

  A substantially disc-shaped punching metal (fixing member) 24 that is fixed to the inner peripheral surface of the casing 12 while holding the giant magnetostrictive member 16 is disposed at the axially central portion in the casing 12. The punching metal 24 is formed with a plurality of through holes in the axial direction so that the fluid 14 can flow through the casing 12. Note that mounting flanges 22A and 22B that can be connected to the external members 20A and 20B are formed at both ends of the casing 12 in the axial direction.

  The substantially bar-shaped giant magnetostrictive member 16 uses a giant magnetostrictive element as a material. Here, the “super magnetostrictive element” is a magnetostrictive element made of a powder sintered alloy or a single crystal alloy containing a rare earth element and / or a specific transition metal as a main component (eg, terbium, dysprosium, iron, etc.). When deformed by external stress, it has the property of causing a large change in magnetic permeability or amount of remaining magnetization.

The giant magnetostrictive member 16 in Example 1 is a rod-shaped body having an axial diameter of 3 mm and an axial length of 10 mm, the surface area of the radially outer peripheral surface is 30πmm ² (= 10 mm × 3 mm × π), and the surface areas of both axial end surfaces. Is 4.5πmm ² (= π × 1.5 mm × 1.5 mm × 2 surfaces). Therefore, the surface area of the outer circumferential surface in the radial direction of the giant magnetostrictive member 16 is designed to be three times or more than the surface area of both end surfaces in the axial direction.

  The detection coil 18 is wound around the casing 12 so as to surround the giant magnetostrictive member 16, and can detect a change in permeability or residual magnetic susceptibility of the giant magnetostrictive member 16 as a change in inductance value.

  Next, the operation of the pressure sensor 10 according to the first embodiment will be described.

  When the pressure of the fluid 14 changes, the external stress applied to the giant magnetostrictive member 16 changes and the giant magnetostrictive member 16 is deformed. For example, when the pressure of the fluid 14 increases, the giant magnetostrictive member 16 has a larger external stress applied to the radially outer circumferential surface having a large surface area than an external stress applied to both axial end surfaces having a small surface area. The giant magnetostrictive member 16 shrinks more in the radial direction than in the axial direction. Then, the permeability or residual magnetic susceptibility of the super magnetostrictive member 16 changes due to the deformation of the super magnetostrictive member 16. Therefore, the pressure change of the fluid 14 can be detected by detecting the change of the magnetic permeability or the residual magnetic susceptibility as the change of the inductance value of the detection coil 18.

  According to the pressure sensor 10 according to the first embodiment, the giant magnetostrictive member 16 disposed in the casing 12 filled with the fluid 14 such as liquid or gas and having an anisotropic shape, and the pressure change of the fluid 14. And a detection coil (detection means) 18 for detecting a change in permeability or residual magnetization amount of the giant magnetostrictive member 16 based on the deformation of the giant magnetostrictive member 16, so that the pressure from the fluid 14 can be changed. It is possible to transmit directly to the giant magnetostrictive member 16 without going through any member. Therefore, it is possible to detect a change in pressure with high sensitivity while realizing cost reduction, downsizing, improvement in reliability, etc. by reducing the number of parts.

  In particular, since the giant magnetostrictive member 16 uses a giant magnetostrictive element as a material, the detection sensitivity can be further improved.

  Also, since the giant magnetostrictive member 16 is a substantially rod-like body having a surface area of the radially outer peripheral surface that is three times or more of the surface area of both axial end faces, the giant magnetostrictive member 16 is greatly deformed, It is possible to increase the change of the magnetic permeability or the residual magnetization amount, and the detection sensitivity is improved also in this respect.

  Hereinafter, the pressure sensor according to the second embodiment of the present invention will be described in detail with reference to FIGS. 3 and 4.

  As shown in the figure, in the pressure sensor 30 according to the second embodiment of the present invention, the detection coil 18 is wound around the giant magnetostrictive member 16, the detection coil 18 is molded with a resin 31, and the giant magnetostrictive member 16. Is fixed to the casing 12 by fixing springs 32A and 32B. Since the other structure is the same as that of the pressure sensor 10 according to the first embodiment, the same portions are denoted by the same reference numerals in the drawing and the description thereof is omitted.

  The fixed springs 32 </ b> A and 32 </ b> B are contracted in the gap between the inner peripheral surface of the casing 12 and the giant magnetostrictive member 16 to restrict the movement of the giant magnetostrictive member 16.

  According to the pressure sensor 30 according to the second embodiment, since the detection coil 18 is wound around the giant magnetostrictive member 16, the detection sensitivity can be further improved and the detection coil 18 is accommodated in the casing 12. Therefore, further downsizing can be realized.

  The pressure sensor according to the present invention is not limited to the shape and structure of the pressure sensors 10 and 30 according to the first and second embodiments.

  Therefore, for example, the giant magnetostrictive member 16 is not limited to a substantially rod-like body, and a giant magnetostrictive member 42 made of a substantially plate-like body, such as the pressure sensor 40 shown in FIGS. Good. Of course, it goes without saying that the giant magnetostrictive member 16 is not limited to a substantially rod-like body having a surface area of the radially outer peripheral surface that is three times or more the surface area of both axial end surfaces.

  Further, the detection means for detecting the change in the magnetic permeability or the residual magnetization amount of the giant magnetostrictive member 16 is not limited to the detection coil 18, for example, like the pressure sensor 50 shown in FIGS. 7 and 8. In addition, a Hall element 52 (or a magnetoresistive effect element such as MR or GMR) is used as a detecting means, and a change in the magnetic permeability or residual magnetization amount of the giant magnetostrictive member 16 is detected by an electromotive force of the Hall element 52 (or magnetoresistive effect element). You may make it detect as a change. In this example, in order to improve the detection sensitivity of the Hall element 52, the Hall element 52, a pair of yokes 54 disposed near the end of the giant magnetostrictive member 16, and the pair of yokes 54 are interposed. A magnetic circuit is constituted by the arranged magnets 56.

  In the first embodiment and the second embodiment, the giant magnetostrictive member 16 is fixed to the casing 12 by the punching metal 24 and the fixing springs 32A and 32B. However, the present invention is not limited to this, for example, FIG. As in the pressure sensor 60 shown in FIG. 10, a net 62 that can accommodate the giant magnetostrictive member 16 and is suspended in the casing 12 may be used. The giant magnetostrictive member 16 does not necessarily have to be fixed to the casing 12 as long as the giant magnetostrictive member 16 can be held in the casing 12.

  In addition, when the sensitivity of the pressure sensor 10 is sufficiently obtained, a magnetostrictive rod made of a magnetostrictive member may be applied instead of the super magnetostrictive member 16.

  That is, the pressure sensor according to the present invention is arranged in a casing filled with a fluid such as liquid or gas with a gap between the casing and a magnetostrictive member having an anisotropic shape, and changes in pressure of the fluid. Any detection means for detecting as a change in the magnetic permeability or residual magnetization amount of the magnetostrictive member based on the deformation of the magnetostrictive member may be used.

1 is a schematic side sectional view of a pressure sensor according to a first embodiment of the present invention. Sectional view along line II-II in Fig. 1 Schematic side sectional view of a pressure sensor according to a second embodiment of the present invention Sectional view along line IV-IV in FIG. Schematic side sectional view of a pressure sensor to which a substantially plate-like giant magnetostrictive member is applied Sectional view along line VI-VI in FIG. Schematic side sectional view of a pressure sensor using a Hall element as a detection means Sectional view along line VIII-VIII in FIG. Schematic side sectional view of a pressure sensor with a giant magnetostrictive member fixed by a net Sectional view along line XX in FIG. Schematic side sectional view of a conventional pressure sensor

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 10, 30, 40, 50, 60 ... Pressure sensor 2 ... Push rod 3, 16, 42 ... Giant magnetostrictive member 4 ... Coil 12 ... Casing 14 ... Fluid 18 ... Detection coil 20A, 20B ... External member 22A, 22B ... Flange 24 ... Punching metal 31 ... Resin 32A, 32B ... Fixing spring 52 ... Hall element 62 ... Net

Claims (12)

  A magnetostrictive member disposed in a casing filled with a fluid such as liquid or gas with a gap and having an anisotropic shape, and a change in pressure of the fluid based on deformation of the magnetostrictive member. And a detecting means for detecting as a change in magnetic permeability or residual magnetization amount. In claim 1,
The pressure sensor according to claim 1, wherein the magnetostrictive member comprises a substantially rod-shaped body. In claim 2,
The pressure sensor according to claim 1, wherein a surface area of a radially outer peripheral surface of the magnetostrictive member is at least three times a surface area of both axial end surfaces. In any one of Claims 1 thru | or 3,
The pressure sensor according to claim 1, wherein the detection means includes a detection coil, and detects a change in permeability or residual magnetization of the magnetostrictive member as a change in inductance value of the detection coil. In claim 4,
The pressure sensor, wherein the detection coil is wound around the casing so as to surround the magnetostrictive member. In claim 4,
The pressure sensor, wherein the detection coil is wound around the magnetostrictive member. In any one of Claims 1 thru | or 3,
The pressure sensor according to claim 1, wherein the detection means includes a Hall element and detects a change in magnetic permeability or residual magnetization of the magnetostrictive member as a change in electromotive force of the Hall element. In any one of Claims 1 thru | or 3,
The pressure sensor according to claim 1, wherein the detecting means includes a magnetoresistive effect element, and detects a change in magnetic permeability or residual magnetization of the magnetostrictive member as a change in electromotive force of the magnetoresistive effect element. In any one of Claims 1 thru | or 8.
A pressure sensor, comprising: a fixing member that is fixed to the inner peripheral surface of the casing while holding the magnetostrictive member. In any one of Claims 1 thru | or 8.
A pressure sensor, comprising: a fixed spring that is contracted in a gap between the inner peripheral surface of the casing and the magnetostrictive member and restricts movement of the magnetostrictive member. In any one of Claims 1 thru | or 8.
A pressure sensor characterized by comprising a net capable of accommodating the magnetostrictive member and suspended in the casing. In any one of Claims 1 thru | or 11,
The pressure sensor, wherein the magnetostrictive member is a giant magnetostrictive member made of a giant magnetostrictive element.

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