JP2005283126A - Pressure sensor and its magnetic hysteresis reduction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure sensor capable of miniaturizing in size, effectively reducing magnetic hysteresis and of detecting the variation of pressure with high degree of accuracy, and to provide a method for reducing its magnetic hysteresis. <P>SOLUTION: The pressure sensor 10 is constituted of: a first ultra magnetostriction member 28 and the detection coil 30 for detecting the magnetic permeability or the amount of the remanent magnetization of the first ultra magnetostriction member 28; a sensor part 16 capable of detecting the variation of the pressure as the variation of the magnetic permeability or the variation of the amount of the remanent magnetization based on the deformation of the first ultra magnetostriction member 28; and the driving part 14 equipped with a second ultra magnetostriction member 20 and the driving coil 22 capable of driving the second ultra magnetostriction member 20 in longitudinal vibration. The driving part 14 is constituted so that it can impress a prescribed force on the first ultra magnetostriction member 28 of the sensor part 16 by making an impulse current flow through the driving coil 22. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pressure sensor using a magnetostrictive member and a magnetic hysteresis reducing method thereof.

  2. Description of the Related Art Conventionally, pressure sensors that can detect a change in pressure using the stress magnetic effect of a magnetostrictive member are widely known. This conventionally known pressure sensor can detect a change in pressure by detecting a change in permeability based on deformation of a magnetostrictive member as a change in inductance value of a coil.

  Incidentally, the relationship between the pressure and the inductance value in such a pressure sensor generally shows a magnetic hysteresis characteristic as shown in FIG. 6, and a difference occurs between the pressure and the inductance value depending on the direction of change. As a result, there is a problem that the inductance values for the same pressure do not match in the increasing direction and decreasing direction of the pressure.

  As a means for solving such a problem, a pressure sensor 1 as shown in FIG. 7 has been proposed.

  The pressure sensor 1 includes a substantially rod-shaped giant magnetostrictive element 2, a first coil 3 for flowing an LC oscillation current, and a second coil 4 for flowing an impulse current. First and second coils 3 and 4 are wound twice so as to surround 2. The pressure sensor 1 attempts to reduce magnetic hysteresis by causing an impulse current to flow through the second coil 4 at a predetermined timing.

JP 2003-156382 A

  However, in this pressure sensor 1, since it is necessary to flow a large impulse current, the detection error accompanying the temperature rise of the giant magnetostrictive element 2 and the first and second coils 3 and 4 is large, and the detection accuracy is reduced. There was a problem.

  In addition, the first and second coils 3 and 4 are wound around the outer periphery of the giant magnetostrictive element 2 in addition to a structure in which the wire diameter of the second coil 3 is required to be as large as possible in order to pass an impulse current. There is also a problem that the apparatus is enlarged (in particular, enlarged in the radial direction of the giant magnetostrictive element 2).

  The present invention has been made to solve such problems, and while being able to reduce the size, it is possible to effectively reduce magnetic hysteresis and detect a change in pressure with high accuracy. It is an object of the present invention to provide a pressure sensor capable of performing the above and a method for reducing the magnetic hysteresis thereof.

  As a result of earnest research, the inventor of the present invention has a pressure sensor capable of effectively reducing magnetic hysteresis and detecting a change in pressure with high accuracy while reducing the size and reducing the magnetic hysteresis. I found a way.

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

  (1) A first magnetostrictive member and detection means for detecting a change in the magnetic permeability or residual magnetization amount of the first magnetostrictive member are provided, and the change in pressure is determined based on the deformation of the first magnetostrictive member. A sensor unit that can be detected as a change in quantity, and a drive unit that includes a second magnetostrictive member and a drive coil that can extend and contract the second magnetostrictive member, and the drive unit impulses the drive coil. A pressure sensor characterized in that a predetermined stress can be applied to the first magnetostrictive member in the sensor section by flowing a current of a shape.

  (2) The magnetic member is disposed between the first magnetostrictive member and the detection means in the sensor unit and the second magnetostrictive member and the drive coil in the drive unit. The pressure sensor described.

  (3) The pressure sensor according to (2), wherein the first magnetostrictive member in the sensor unit and the second magnetostrictive member in the drive unit are fixed to the magnetic member.

  (4) The pressure sensor according to any one of (1) to (3), wherein a predetermined preload is applied to the first magnetostrictive member in the sensor section.

  (5) The detection means in the sensor unit includes a detection coil disposed so as to surround the outer periphery of the first magnetostrictive member, and changes in the permeability or residual magnetization of the first magnetostrictive member are detected in the detection coil. The pressure sensor according to any one of (1) to (4), wherein the pressure sensor is detected as a change in inductance value.

  (6) The detection means in the sensor section includes a Hall element, and a change in the magnetic permeability or residual magnetization amount of the first magnetostrictive member is detected as a change in electromotive force of the Hall element. The pressure sensor according to any one of 1) to (4).

  (7) The detection means in the sensor unit includes a magnetoresistive effect element, and detects a change in permeability or residual magnetization amount of the first magnetostrictive member as a change in electromotive force of the magnetoresistive effect element. The pressure sensor according to any one of (1) to (4).

  (8) At least one of the first magnetostrictive member in the sensor unit and the second magnetostrictive member in the drive unit is composed of a giant magnetostrictive member made of a giant magnetostrictive element. The pressure sensor according to any one of the above.

  (9) A method for reducing magnetic hysteresis of a pressure sensor capable of detecting a change in pressure by a change in permeability or residual magnetization based on deformation of a magnetostrictive member, wherein a predetermined stress is applied to the magnetostrictive member, A method for reducing magnetic hysteresis of a pressure sensor, comprising removing residual magnetism of a magnetostrictive member.

  According to the pressure sensor and the method for reducing the magnetic hysteresis according to the present invention, it is possible to reduce the size of the sensor while effectively reducing the magnetic hysteresis and detecting a change in pressure with high accuracy. Has an effect.

  The pressure sensor according to the present invention includes a first magnetostrictive member and detection means for detecting a change in permeability or residual magnetization of the first magnetostrictive member, and the change in pressure is based on deformation of the first magnetostrictive member. A sensor unit that can be detected as a change in magnetic permeability or residual magnetization amount, and a drive unit that includes a second magnetostrictive member and a drive coil that can expand and contract the second magnetostrictive member. By applying an impulse-like current to the drive coil, a predetermined stress can be applied to the first magnetostrictive member in the sensor unit, thereby solving the above-described problem.

  The method for reducing magnetic hysteresis of a pressure sensor according to the present invention is a method for reducing magnetic hysteresis of a pressure sensor capable of detecting a change in pressure based on a change in permeability or residual magnetization based on deformation of a magnetostrictive member. By applying a predetermined stress to the member, the residual magnetism of the magnetostrictive member is removed, thereby solving the above problem.

  Hereinafter, the pressure sensor according to the first embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2.

  As shown in the figure, the pressure sensor 10 according to the first embodiment of the present invention includes a substantially cylindrical casing 12, and a drive unit 14 and a sensor unit 16 are accommodated in the casing 12. .

  The drive unit 14 includes a first magnetic yoke 18 made of a substantially disk-shaped magnetic member fixed to the bottom of the casing 12, and a substantially rod-shaped second supermagnetostrictive member 20 fixed on the first magnetic yoke 18. A drive coil 22 disposed around the second giant magnetostrictive member 20 and capable of extending and contracting the second giant magnetostrictive rod 20 in the axial direction, and arranged so as to cover the second giant magnetostrictive member 20 and the drive coil 22 from above. And a second magnetic yoke 24 formed of a bottomed cylindrical magnetic member. In this example, the first and second magnetic yokes 18 and 24 are made of MnZn ferrite material.

  The second giant magnetostrictive member 20 has one end fixed to the first magnetic yoke 18 and the other end fixed to the second magnetic yoke 24. The second giant magnetostrictive member 20 is made of a giant magnetostrictive element. 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 (for example, terbium, dysprosium, iron, etc.). Say. This magnetostrictive element has a property of causing a large displacement when a magnetic field is applied from the outside (Joule effect), and a property of causing a large change in magnetic permeability or residual magnetization when deformed by an external stress. doing.

  The lower end of the second magnetic yoke 24 is fixed to the first magnetic yoke 18 via a rubber 26, and the second magnetic yoke 24 can move up and down as the second giant magnetostrictive member 20 expands and contracts in the axial direction. It is configured.

  On the other hand, the sensor unit 16 disposed above the drive unit 14 is disposed coaxially with the second giant magnetostrictive member 20 and is fixed on the second magnetic yoke 24 of the drive unit 14 in a substantially rod-shaped first superstructure. A third magnetic material comprising a magnetostrictive member 28, a detection coil (detection means) 30 disposed around the first giant magnetostrictive member 28, and a substantially columnar magnetic member fixed to the upper end of the first giant magnetostrictive member 28. The yoke 32 is configured to include a transmission rod 36 disposed on the third magnetic yoke 32 via a spherical axis aligning tool 34.

  The first giant magnetostrictive member 28 is made of the same giant magnetostrictive element as the second giant magnetostrictive member 20 of the drive unit 14.

  The detection coil 30 can detect a change in the magnetic permeability or residual magnetization of the first giant magnetostrictive member 28 based on the displacement of the first giant magnetostrictive member 28 as a change in inductance value.

  The transmission rod 36 includes a substantially disc-shaped flange portion 36A located on the upper end side of the first giant magnetostrictive member 28, and a rod portion extending along the axial direction of the first giant magnetostrictive member 28 with the flange portion 36A as a base end. 36B. A disc spring 38 is contracted between the flange portion 36 </ b> A and the casing 12, the transmission rod 36 is biased toward the first super magnetostrictive member 28, and the first super magnetostrictive member 28 has a shaft. A predetermined preload is applied in the direction. Furthermore, the tip of the rod portion 36B protrudes outside the casing 12, and has a structure in which external pressure can be applied to the first giant magnetostrictive member 28 via the rod portion 36B.

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

  When pressure is applied to the transmission rod 36 from the outside and axial stress is applied to the first super magnetostrictive member 28 via the spherical axis aligning tool 34 and the third magnetic yoke 32, the first super magnetostrictive member 28 is deformed. Occurs. Then, the permeability or residual magnetic susceptibility of the first super magnetostrictive member 28 changes due to the deformation of the first super magnetostrictive member 28. Accordingly, a change in pressure can be detected by detecting a change in the magnetic permeability or residual magnetic susceptibility of the first super magnetostrictive member 28 as a change in the inductance value of the detection coil 30.

  Further, in this pressure sensor 10, a predetermined stress is applied to the first giant magnetostrictive member 28 of the sensor unit 16 via the second magnetic yoke 24 by passing an impulse current through the drive coil 22 of the drive unit 14. It has come to be.

  The inventor of the present invention collected data on the relationship between the pressure applied to the pressure sensor 10 according to the first embodiment and the voltage in the detection coil 30 through experiments. In this experiment, the drive unit 14 includes a second giant magnetostrictive member 20 having a shaft diameter of 7.4 mm and a shaft length of 8 mm, a drive having a wire diameter of 0.2 mm, a wire type UEW, a winding number of 600 turns, and a coil length of 7 mm. The coil 22 was applied, and an impulse current having a maximum value of 0.3 A was passed through the drive coil 22. Further, the sensor section 16 is applied with a first giant magnetostrictive member 28 having an axial diameter of 7.4 mm and an axial length of 6 mm, and a detection coil 30 having a wire diameter of 0.2 mm, a wire type UEW, a number of turns of 300 turns, and a coil length of 3 mm. .

  As a comparative example, the same pressure sensor 10 is used and the magnetic hysteresis reducing method according to the present invention is not applied (when no stress is applied to the first giant magnetostrictive member 28 of the sensor unit 16). Data was collected.

As a result, as shown in FIG. 3, in the pressure sensor 10 according to the first embodiment indicated by the solid line, the pressure of the experiment was 0 (kgf / cm ² ) compared to the pressure sensor of the comparative example indicated by the dotted line. It was confirmed that the magnetic hysteresis was reduced in the entire range of ˜about 500 (kgf / cm ² ). The maximum width of the magnetic hysteresis of the pressure sensor of the comparative example was 12.308 (v), whereas the maximum width of the magnetic hysteresis of the pressure sensor 10 according to the first embodiment was 7.143 (v). Thus, the magnetic hysteresis decreased by about 41.964% (= (1−7.143 / 12.308) × 100). This means that by applying a predetermined stress to the first giant magnetostrictive member 28 of the sensor unit 16 by the drive unit 14, the residual magnetism of the first giant magnetostrictive member 28 is removed and the magnetic hysteresis is reduced. doing.

  The pressure sensor 10 according to the first embodiment includes the first giant magnetostrictive member 28 and a detection coil (detection means) 30 for detecting a change in the permeability or residual magnetization amount of the first giant magnetostrictive member 28. The sensor unit 16 capable of detecting a change in pressure as a change in permeability or residual magnetization based on the deformation of the first giant magnetostrictive member 28, the second giant magnetostrictive member 20, and the second giant magnetostrictive member 20 can be expanded and contracted. And a drive unit 14 including a drive coil 22, and the drive unit 14 causes an impulse current to flow through the drive coil 22, thereby applying a predetermined stress to the first giant magnetostrictive member 28 of the sensor unit 16. Therefore, by removing the residual magnetism of the first giant magnetostrictive member 28, the magnetic hysteresis can be effectively reduced, and the change in pressure can be detected with high accuracy. Further, the apparatus does not increase in size in the radial direction as in the conventional pressure sensor, and can be reduced in size as compared with the conventional pressure sensor.

  In particular, since the first giant magnetostrictive member 28 made of a giant magnetostrictive element is used, the pressure change detection sensitivity can be further enhanced.

  A second magnetic yoke (magnetic member) 24 is disposed between the first giant magnetostrictive member 28 and the detection coil 30 in the sensor unit 16 and the second giant magnetostrictive member 20 and the drive coil 22 in the drive unit 14. Therefore, it is possible to prevent the magnetic noise and heat generated from the drive unit 14 from reaching the sensor unit 16, and to prevent the occurrence of detection errors due to the magnetic noise and heat.

  Furthermore, since the first giant magnetostrictive member 28 in the sensor unit 16 and the second giant magnetostrictive member 20 in the drive unit 14 are fixed to the second magnetic yoke (magnetic member) 24, the first giant magnetostrictive member 28 is fixed by the repetitive stress generated between the members. The breakage of the first and second giant magnetostrictive members 20 and 28 can be prevented in advance.

  In addition, since a predetermined preload is applied to the first giant magnetostrictive member 28 in the sensor unit 16 by the disc spring 38, the detection sensitivity of the pressure change is enhanced also in this respect.

  Note that first and second magnetic yokes 18 and 24 are disposed on both sides in the axial direction of the drive coil 22, and the magnetic field of the drive coil 22 is efficiently applied to the second giant magnetostrictive member 28. Can do. Further, second and third magnetic yokes 24 and 32 are disposed on both sides in the axial direction of the detection coil 30, and the detection coil 30 efficiently changes the permeability or residual magnetization amount of the first super magnetostrictive member 28. Can be detected automatically.

  The inventor of the present invention applies a drive coil 22 having a wire diameter of 1.0 mm, a wire type UEW, a winding number of 20 turns, and a coil length of 7 mm instead of the drive coil 22 of the pressure sensor 10 according to the first embodiment. An impulse-like current having a maximum value of 5.0 A was passed through the drive coil 22 and the same experiment as in Example 1 was performed.

As a result, as shown in FIG. 4, in the pressure sensor 40 according to the second embodiment indicated by the solid line, the pressure of the experiment was 0 (kgf / cm ² ) compared to the pressure sensor of the comparative example indicated by the dotted line. It was confirmed that the magnetic hysteresis was reduced in the entire range of ˜about 500 (kgf / cm ² ). The maximum width of the magnetic hysteresis of the pressure sensor of the comparative example was 12.308 (v), whereas the maximum width of the magnetic hysteresis of the pressure sensor 40 according to the second embodiment was 8.955 (v). Thus, the magnetic hysteresis decreased by about 27.239% (= (1−8.955 / 12.308) × 100). This means that by applying a predetermined stress to the first giant magnetostrictive member 28 of the sensor unit 16 by the drive unit 14, the residual magnetism of the first giant magnetostrictive member 28 is removed and the magnetic hysteresis is reduced. doing.

  As described above, the pressure sensor 40 according to the second embodiment can be reduced in size as well as the pressure sensor 10 according to the first embodiment, and at the same time, the magnetic hysteresis is effectively reduced, and the pressure change. Can be detected with high accuracy. Also, by changing the specifications (wire diameter, number of turns, etc.) of the drive coil 22, the characteristics of the pressure sensor can be changed while reducing the magnetic hysteresis.

  The pressure sensor according to the present invention is not limited to the shape and structure of the pressure sensor 10 (40) according to the first and second embodiments.

  Therefore, for example, in the first and second embodiments, the detection coil 30 is applied as detection means for detecting a change in pressure. However, the present invention is not limited to this, and the pressure shown in FIG. Like the sensor 50, the Hall element 52 (or magnetoresistive effect element such as MR or GMR) is applied as a detecting means for detecting a change in pressure, and the permeability or residual magnetization amount of the first super magnetostrictive member 28 is determined. The change may be detected as a change in electromotive force of the Hall element 52 (or magnetoresistive element).

  In addition, when the detection sensitivity of the pressure sensor is sufficiently obtained, it is not always necessary to apply a preload to the first giant magnetostrictive member 28, and instead of the giant magnetostrictive member, a magnetostrictive member made of a magnetostrictive element is used. You may apply.

  That is, the pressure sensor according to the present invention includes a first magnetostrictive member and detection means for detecting a change in the magnetic permeability or residual magnetization amount of the first magnetostrictive member, and changes in the pressure are deformed by the first magnetostrictive member. A sensor unit that can be detected as a change in magnetic permeability or residual magnetization based on the second magnetostrictive member, and a drive unit that includes a second magnetostrictive member and a drive coil that can extend and contract the second magnetostrictive member. May be configured such that a predetermined stress can be applied to the first magnetostrictive member in the sensor unit by flowing an impulse-like current through the drive coil.

1 is a schematic side sectional view of a pressure sensor according to a first embodiment of the present invention. Schematic sectional view taken along line II-II in FIG. The graph which showed the relationship between the pressure applied to the pressure sensor which concerns on Example 1 of this invention, and the voltage in a detection coil. The graph which showed the relationship between the pressure applied to the pressure sensor which concerns on Example 2 of this invention, and the voltage in a detection coil. Schematic sectional view showing an example in which a Hall element is applied as detection means of a pressure sensor according to Embodiment 1 of the present invention A graph showing the relationship between pressure and inductance in a typical pressure sensor Schematic side sectional view of a conventional pressure sensor

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 10, 40, 50 ... Pressure sensor 2 ... Giant magnetostrictive element 3 ... 1st coil 4 ... 2nd coil 12 ... Casing 14 ... Drive part 16 ... Sensor part 18 ... 1st magnetic yoke 20 ... 2nd giant magnetostrictive member 22 ... Drive coil 24 ... Second magnetic yoke 26 ... Rubber 28 ... First giant magnetostrictive member 30 ... Detection coil 32 ... Third magnetic yoke 36 ... Transmission rod 38 ... Belleville spring 52 ... Hall element

Claims (9)

  A first magnetostrictive member and detection means for detecting a change in the magnetic permeability or residual magnetization amount of the first magnetostrictive member are provided, and the change in the pressure or the residual magnetization amount based on the deformation of the first magnetostrictive member is provided. And a drive unit having a second magnetostrictive member and a drive coil capable of expanding and contracting the second magnetostrictive member, and the drive unit has an impulse current in the drive coil. The pressure sensor is configured so that a predetermined stress can be applied to the first magnetostrictive member in the sensor unit by flowing a flow of gas. In claim 1,
A pressure sensor, wherein a magnetic member is disposed between a first magnetostrictive member and detection means in the sensor unit and a second magnetostrictive member and drive coil in the drive unit. In claim 2,
The pressure sensor, wherein the first magnetostrictive member in the sensor unit and the second magnetostrictive member in the drive unit are fixed to the magnetic member. In any one of Claims 1 thru | or 3,
A pressure sensor, wherein a predetermined preload is applied to the first magnetostrictive member in the sensor section. In any one of Claims 1 thru | or 4,
The detection means in the sensor unit includes a detection coil disposed so as to surround the outer periphery of the first magnetostrictive member, and a change in the magnetic permeability or residual magnetization of the first magnetostrictive member is calculated as an inductance value of the detection coil. A pressure sensor characterized by being detected as a change. In any one of Claims 1 thru | or 4,
The detection means in the sensor section includes a Hall element, and a change in the magnetic permeability or residual magnetization amount of the first magnetostrictive member is detected as a change in electromotive force of the Hall element. In any one of Claims 1 thru | or 4,
The detecting means in the sensor unit includes a magnetoresistive effect element, and detects a change in permeability or residual magnetization amount of the first magnetostrictive member as a change in electromotive force of the magnetoresistive effect element. Sensor. In any one of Claims 1 thru | or 7,
At least one of the first magnetostrictive member in the sensor unit and the second magnetostrictive member in the drive unit is composed of a giant magnetostrictive member made of a giant magnetostrictive element.   A method for reducing magnetic hysteresis of a pressure sensor capable of detecting a change in pressure by a change in permeability or residual magnetization based on deformation of a magnetostrictive member, wherein a predetermined stress is applied to the magnetostrictive member, A method for reducing magnetic hysteresis of a pressure sensor, characterized by removing residual magnetism.

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