JP2012098154A - Magnetostriction force sensor, manufacturing method of plate like member for the magnetostriction force sensor, ring like member for magnetostriction force sensor, and manufacturing method of ring like member for magnetostriction force sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetostriction force sensor having a sufficient sensitivity, a manufacturing method of a plate like member for the magnetostriction force sensor, a ring like member for the magnetostriction force sensor, and a manufacturing method of the ring like member for the magnetostriction force sensor.SOLUTION: The magnetostriction force sensor includes a magnetostrictive material in which a magnitude of magnetostriction in a specific direction is larger than a magnitude of magnetostriction in a direction perpendicular to the specific direction. In the manufacturing method of the plate like member for the magnetostriction force sensor, when manufacturing the plate like member composed of the magnetostrictive material in which a magnitude of magnetostriction in its length direction is larger than a magnitude of magnetostriction in a direction perpendicular to the length direction, the plate like member is cut out in a columnar crystal direction from a coagulated member or a cast member in which a columnar crystal structure is formed in a direction.

Description

The present invention relates to a magnetostrictive force sensor, a method for manufacturing a magnetostrictive force sensor plate member, a magnetostrictive force sensor ring member, and a magnetostrictive force sensor ring member.
More specifically, the present invention relates to a magnetostrictive force sensor provided with a predetermined magnetostrictive material, a method of manufacturing a plate member for a magnetostrictive force sensor used therefor, a ring member for a magnetostrictive force sensor, and a ring member for a magnetostrictive force sensor. It relates to a manufacturing method.

In the field of vehicle control, development of an inexpensive and small force sensor is desired, and research and development of a force sensor is being conducted. For example, if the braking force can be detected, comprehensive control of the vehicle is possible, and a fuel-saving vehicle can be realized.
Development of a torque sensor is also desired. For example, a torque sensor is indispensable for electric power steering, and a displacement type torque sensor is adopted. However, there is a demand for a reduction in price, and research and development of a magnetostrictive type torque sensor has been made. Furthermore, there is a demand for an inexpensive torque sensor in the steer-by-wire, which is the next generation of steering.
On the other hand, a magnetostrictive force sensor excellent in sensor sensitivity and a magnetostrictive force sensor capable of accurately detecting stress have been proposed (see Patent Document 1 and Patent Document 2).

JP 2008-26210 A JP 2008-268175 A

  However, the magnetostrictive force sensors described in Patent Document 1 and Patent Document 2 also have room for improvement in sensitivity as a practical sensor.

  The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide a magnetostrictive force sensor having sufficient sensitivity and a method for manufacturing a plate member for a magnetostrictive force sensor used therefor. Another object is to provide a ring-shaped member for a magnetostrictive force sensor and a method for manufacturing the ring-shaped member for a magnetostrictive force sensor.

  The inventors of the present invention have made extensive studies in order to achieve the above object. As a result, it has been found that the above object can be achieved by providing a predetermined magnetostrictive material, and the present invention has been completed.

  The magnetostrictive force sensor of the present invention includes a magnetostrictive material in which the magnitude of magnetostriction in a specific direction is larger than the magnitude of magnetostriction in a direction orthogonal to the direction.

  The method for manufacturing a magnetostrictive force sensor plate member according to the present invention provides a magnetostrictive force sensor plate member made of a magnetostrictive material having a magnetostriction in the longitudinal direction larger than the magnetostriction in a direction perpendicular to the direction. The plate-shaped member is cut out in the direction of the columnar crystal from the solidified member or cast member in which the columnar crystal structure is formed in one direction.

  The ring-shaped member for a magnetostrictive force sensor of the present invention is a ring-shaped member made of a magnetostrictive material in which the magnitude of magnetostriction in the circumferential direction is larger than the magnitude of magnetostriction in the axial direction perpendicular to the direction, and the columnar crystal structure is a ring shape. It is characterized by being directed in the radial direction of the member.

  The method for producing a ring-shaped member for a magnetostrictive force sensor according to the present invention is a ring-shaped member made of a magnetostrictive material having a magnetostriction in the circumferential direction larger than the magnetostriction in the axial direction orthogonal to the direction, and having a columnar crystal structure When manufacturing a ring-shaped member for a magnetostrictive force sensor whose diameter is directed in the radial direction of the ring-shaped member, the ring-shaped member is cut out from a cast member in which columnar crystals are formed in the radial direction.

  According to the present invention, a magnetostrictive force sensor having sufficient sensitivity is provided by using a magnetostrictive material in which the magnitude of magnetostriction in a specific direction is larger than the magnitude of magnetostriction in a direction perpendicular to the direction, and the magnetostrictive force sensor is used for this. The manufacturing method of the magnetostrictive force sensor plate-shaped member, the magnetostrictive force sensor ring-shaped member, and the magnetostrictive force sensor ring-shaped member can be provided.

It is typical explanatory drawing of the conventional magnetostrictive force sensor. It is typical explanatory drawing of the other conventional magnetostrictive force sensor. It is explanatory drawing of the plate-shaped member used for the magnetostrictive force sensor which concerns on one Embodiment of this invention. It is explanatory drawing of the heat processing under stress in the manufacturing method of the plate-shaped member for magnetostrictive force sensors which concerns on one Embodiment of this invention. It is explanatory drawing of the magnetostrictive force sensor which concerns on one Embodiment of this invention. It is typical sectional explanatory drawing of the cast member in the manufacturing method of the ring-shaped member for magnetostrictive force sensors which concerns on one Embodiment of this invention. It is typical explanatory drawing of the ring-shaped member for magnetostrictive force sensors which concerns on other embodiment of this invention. It is explanatory drawing of the heat treatment under stress in the manufacturing method of the ring-shaped member for magnetostrictive force sensors which concerns on other embodiment of this invention. It is explanatory drawing of the diameter expansion deformation | transformation in the manufacturing method of the ring-shaped member for magnetostrictive force sensors which concerns on other embodiment of this invention. It is typical explanatory drawing of the ring-shaped member for magnetostrictive force sensors which concerns on other embodiment of this invention. It is a graph which shows the magnetostriction measurement result in the ring-shaped member for magnetostrictive force sensors in Example 6.

  Hereinafter, the magnetostrictive force sensor, the method for producing a magnetostrictive force sensor plate-like member, the magnetostrictive force sensor ring-like member, and the magnetostrictive force sensor ring-like member of the present invention will be described in detail.

First, the configuration of the magnetostrictive force sensor will be described using a conventional example.
FIG. 1 is an explanatory diagram of a conventional magnetostrictive force sensor. FIG. 20 is a diagram corresponding to FIGS. 18 and 19 of Patent Document 2. As shown in the figure, a permanent magnet is disposed on one side of the magnetostrictive plate, and a Hall IC is disposed on the opposite side (see FIG. 1A). The leakage flux of the permanent magnet is detected by the Hall IC. When a compressive force indicated by an arrow acts on the magnetostrictive plate, the leakage magnetic flux increases, so that the stress can be detected (see FIG. 1B).
FIG. 2 is an explanatory diagram of another conventional magnetostrictive force sensor. It is a figure equivalent to Drawing 14 and Drawing 2 of patent documents 1. As shown in the drawing, a magnetostrictive ring is fitted to the shaft and magnetized in the circumferential direction. When torque is applied, leakage magnetic flux is generated from the ring, and can be detected by the Hall IC arranged as shown (see FIG. 2A). Then, a signal corresponding to the direction of the applied torque is obtained (see FIG. 2B). Since the magnetostrictive ring fitted to the shaft is subjected to tensile stress in the circumferential direction, more magnetized components remain in the circumferential direction. That is, the stress-induced magnetic anisotropy is utilized.

Next, the magnetostrictive force sensor of the present invention will be described taking as an example the case where the magnetostrictive material is a plate-like member. In the case of a cubic metal, columnar crystals extend in the direction of heat flow during solidification, and therefore can be suitably used. In particular, in the case of Fe ₄₉ Co ₄₉ V ₂ , Fe ₈₀ Ga ₁₅ Al ₅ , (Fe ₈₀ Ga ₁₅ Al ₅ ) ₉₉ Zr _0.5 C _0.5 , the columnar crystals in the <100> direction are directions of heat flow. It is suitable because it stretches. These magnetostrictive alloys are alloys having a body-centered cubic (BCC) crystal structure, and the direction of easy magnetization is <100>.
Here, a plate-like member is cut out from the solidified member (see FIG. 3). Of course, you may cut out from a cast member. For example, the alloy composition is (Fe ₈₀ Ga ₁₅ Al ₅ ) ₉₉ Zr _0.5 C _0.5 , the crystal grain size is about 50 μm, and the direction of the columnar crystals is the direction indicated by the arrows in FIG. After cutting out a plate-like member having a width of 8 mm, a length of 12 mm, and a thickness of 1 mm (after machining), heat treatment is performed at 550 ° C. for 2.5 hours, and the magnetostriction in the plate longitudinal direction is measured to be 100 ppm. On the other hand, when a plate-like member of the same size is cut out from the equiaxed crystal part of the solidified member and heat-treated at 550 ° C. for 2.5 hours and the magnetostriction in the plate longitudinal direction is measured, it becomes 50 ppm.
Higher sensitivity is advantageous from the viewpoint that the signal processing cost of the sensor can be reduced, and in particular, it is easy to ensure temperature characteristics.
Now, a method for measuring magnetostriction will be defined. The magnetostriction in the plate longitudinal direction is a magnetostriction measured by applying a strain gauge in the plate longitudinal direction and applying a magnetic field in the plate longitudinal direction. The material used here is stretched because the magnetostriction is positive (as will be described later, if the direction in which the magnetic field is applied to the strain gauge is orthogonal to the strain gauge in this state, the magnetostriction will be negative (negative, shrink)). .

Next, an example is given and demonstrated about the case where it heat-processes in the state which gave the tensile stress to the plate-shaped member.
FIG. 4 is a cross-sectional explanatory view of heat treatment under stress in the method of manufacturing a plate member for a magnetostrictive force sensor. The frame-shaped sample has a thin plate shape (width 8 mm, thickness 1 mm) on both sides. A frame-shaped sample is cut out from, for example, a solidified member so that the direction of the arrow in the figure is the direction of the columnar crystal structure. Moreover, the block-shaped member which enters into a frame-shaped sample in a cold fitting state is cut out from the same material. In addition, the structure state of a block-shaped member in particular is not ask | required. The length of the block-like member is determined so that the magnitude of the tensile stress in the plate-like portions on both sides of the frame-like member is about 200 MPa (about 20 μm about the inner length of the frame-like sample is blocked. This can be realized by lengthening the shaped member.) It is cold-fitted at room temperature and heat-treated at 640 ° C. for 2 hours in a vacuum.
The heat treatment temperature is preferably equal to or higher than the order phase appearance temperature. In this FeGa-based composition alloy, it is known that the Fe ₃ Al type ordered phase (BCC) appears at about 500 ° C. or less.
After the heat treatment, a plate-like sample having a length of 12 mm was cut out from the thin plate-like portion of the frame-like sample by wire cutting, and the magnetostriction in the longitudinal direction was measured. As a result, the magnetostriction was 30 ppm. Will be significantly less than the ones. On the other hand, the magnetostriction measured by applying a magnetic field in the direction of width 8 mm is −110 ppm. For comparison, when the magnetostriction in the same magnetic field application mode is measured on a plate-like member having a columnar crystal structure that has not been subjected to the heat treatment under stress again, the magnetostriction is -90 ppm. Therefore, the magnitude of magnetostriction in the columnar crystal direction increases by about 22% by heat treatment under stress. That is, it can be interpreted that the ratio of the magnetic domains facing the columnar crystal direction is greatly increased.

  FIG. 5 is an explanatory diagram of a magnetostrictive force sensor according to an embodiment of the present invention, and is a diagram illustrating a usage state as a stress sensor. For example, a base member made of SUS303 or SUS304 is brazed to the measurement member (member whose stress is to be detected). A plate member (magnetostrictive plate) made of a magnetostrictive material is accommodated in the base member. Permanent magnets and Hall ICs are arranged on both sides of the magnetostrictive plate. When a force as shown in the figure is applied to the measurement member, a compressive force is applied to the magnetostrictive plate, so that the leakage flux increases and the force can be detected. The sensitivity of the stress sensor increases as the magnetostriction becomes anisotropic in the longitudinal direction of the plate.

Next, the magnetostrictive force sensor of the present invention will be described taking as an example the case where the magnetostrictive material is a ring-shaped member. For _example, a _{(Fe 80 Ga 15 Al 5)} 99 Zr 0.5 C 0.5 alloy cast into copper mold, obtaining cylindrical cast member. FIG. 6 shows a vertical cross section near the center in the axial direction of the cylindrical cast member. Since heat is absorbed by the copper mold, columnar crystals are formed in the radial direction. When a ring is cut out along a two-dot chain line in FIG. 6, a ring-shaped member (see FIG. 7A) in which columnar crystals penetrate in the radial direction can be obtained. A vertical section of columnar crystals appears on the surface of the ring-shaped member, and the particle size is substantially circular (see FIG. 7B). The grain size is about 50 μm. When the magnetostriction is measured by performing a heat treatment at 550 ° C. for 2.5 hours and applying a magnetic field in the axial direction, the magnitude of magnetostriction is 60 ppm. On the other hand, a ring-shaped member prepared in the same manner (without heat treatment) was cooled and fitted to a shaft member made of an alloy of the same composition (see FIG. 8), and the circumferential tensile stress in the ring-shaped member was set to 200 MPa (about approximately When the heat treatment is performed at 640 ° C. for 2 hours in a vacuum, the magnetostriction in the axial direction after the heat treatment increases to 70 ppm (increase of about 17%).
The direction of the strain gauge is the axial direction. Further, in the case of a ring, there is a circumstance that a magnetic field can be applied only in the axial direction.

  The torsional sensitivity when such a ring-shaped member is a magnetostrictive force sensor will be described. The ring is fitted to a SUS shaft with a 10 μm cold fit. The shaft is magnetized in the circumferential direction by energizing about 8500 A. When measured at +/− 5 Nm, the torsional sensitivities are 0.5 G / Nm and 0.6 G / Nm, respectively, and the degree of increase almost coincides with the rate of increase in magnetostriction.

Next, taking the case of (Fe ₈₀ Ga ₁₅ Al ₅ ) ₉₉ Zr _0.5 C _0.5 alloy as an example, the anisotropic operation in the circumferential direction will be described. FIG. 9 is an explanatory diagram of a jig or the like for expanding the diameter of the ring-shaped member. First, a ring-shaped member as shown in FIG. 7 is produced. And it sets as shown in FIG. For example, when using a hot press apparatus, it is convenient to set in the apparatus. After holding at 700 ° C. for a predetermined time (for example, 30 minutes), the punch is pressed to plastically deform the ring-shaped member. In addition, 700 degreeC is a state higher temperature than the temperature which an ordered phase appears in the alloy of a FeGa type composition. The punch and pedestal are produced by machining Hitachi Metals maraging steel YAG300, and can be used as they are without being subjected to an aging treatment or the like. If the outer diameter of the punch is made 20% larger than the inner diameter of the ring, the diameter can be expanded by 20%. By such plastic deformation, the shape of the crystal grains on the surface of the ring-shaped member becomes a shape extending in the circumferential direction as shown in FIG. In this case, the flatness (ratio of the difference between the major axis and the minor axis of the ellipse to the minor axis) is about 20%.
In addition, when additional machining is performed to adjust the shape of the ring-shaped member, it is preferable to perform additional heat treatment. A heat treatment at 550 ° C. for 2.5 hours is preferred. Further, the heat treatment may be performed in a state where the tensile stress described above is applied.
In addition, when it can employ | adopt as a ring-shaped member as it is after diameter expansion deformation | transformation, it can replace with heat processing by hold | maintaining for 1 hour with pushing a punch. In that case, it is possible to obtain the same effect as when the heat treatment is performed in a state where a tensile stress is applied.
For example, a ring-shaped member is cut out from a cylindrical cast member, and after 20% diameter expansion deformation at 700 ° C., the furnace is immediately cooled. Next, when the taken-out ring-shaped member (only the ring-shaped member) is subjected to heat treatment at 550 ° C. for 2.5 hours, the magnitude of the magnetostriction in the axial direction of the ring-shaped member is 80 ppm, compared with the case where no diameter expansion deformation occurs. Greatly increased.
When the ring-shaped member in this state is further subjected to heat treatment under tensile stress (tensile stress: 200 MPa, atmosphere: vacuum, time: 2 hours, temperature: 640 ° C.), the magnetostriction in the axial direction of the ring-shaped member The magnitude of becomes 95 ppm and further increases.
On the other hand, after the diameter expansion deformation at 700 ° C., the punch was pushed in and held for an additional hour, and then cooled in the furnace. The magnitude of magnetostriction in the axial direction of the extracted ring-shaped member was about 95 ppm, and the tensile stress The same level as in the case of the lower heat treatment.

  EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.

Example 1
A plate-like member having a columnar crystal structure as shown in FIG. 3 from a solidified member of (Fe ₈₀ Ga ₁₅ Al ₅ ) ₉₉ Zr _0.5 C _0.5 alloy (width: 8 mm, length: 12 mm, thickness: 1 mm) , Crystal grain size: about 50 μm). For comparison, a plate member of the same size was cut out from the equiaxed crystal portion of the solidified member. These plate members were heat-treated at 550 ° C. for 2.5 hours to obtain a magnetostrictive force sensor plate member (magnetostrictive plate) used in this example. When the magnetostriction in the longitudinal direction of the plate-like member was measured, the plate-like member having an equiaxed crystal structure had a magnetostriction magnitude of 50 ppm, whereas the plate-like member having a columnar crystal structure had a magnetostriction magnitude of 100 ppm. .
In addition, an SmCo magnet having a diameter of 6 mm and a thickness of 1.6 mm was prepared as a permanent magnet. The magnetic flux density at the end face of the magnet alone was about 2.1 kG. In addition, a Hall IC was prepared as a magnetic pickup.
Using these, the magnetostrictive force sensor of this example shown in FIG. 5 was produced. The permanent magnet was attached with a 0.1 mm gap between it and the plate member. The Hall IC detects a magnetic flux at a position of about 0.5 mm from the plate-like member.
In the case of a plate-like member having a columnar crystal structure, the sensitivity of this magnetostrictive force sensor was measured, and converted to the stress value at the magnetostrictive plate, the sensitivity was approximately 1 G / MPa (corresponding to the slope in FIG. 1B). It was a linear characteristic in the range of 50MPa of compressive stress. Further, the sensitivity of the plate member having the equiaxed crystal structure was about half.

(Example 2)
The same material block member is cooled to a frame-shaped sample (both sides are thin plate-like) of (Fe ₈₀ Ga ₁₅ Al ₅ ) ₉₉ Zr _0.5 C _0.5 alloy as shown in FIG. Fitted. At this time, the length of the block-like member was determined so that the magnitude of the tensile stress in the plate-like portions on both sides was about 200 MPa (the length of the block-like member was reduced to the inner length of the sample. It was about 20 μm longer.) This sample was heat-treated in vacuum at 640 ° C. for 2 hours. A plate-like member having a columnar crystal structure as shown in FIG. 4 (width: 8 mm, length: 12 mm, thickness: 1 mm) is cut out from the plate-like portions on both sides, and a plate for a magnetostrictive force sensor used in this example. A member (magnetostrictive plate) was obtained. A magnetostrictive force sensor of this example was produced by repeating the same operation as in Example 1 except that the plate member for the magnetostrictive force sensor obtained in this example was used.
When the sensitivity of the magnetostrictive force sensor was measured, the sensitivity was about 1.2 G / MPa when converted to the stress value at the magnetostrictive plate.

(Example 3)
A plate-like member (width: 8 mm, length: 12 mm, thickness: 1 mm, crystal grain size: about 400 μm) having a columnar crystal structure as shown in FIG. 3 was cut out from a solidified member of Fe ₈₀ Ga ₁₅ Al ₅ alloy. . It can be seen that the crystal grain size is larger than that used in the above examples. The plate member was heat treated at 550 ° C. for 2.5 hours to obtain a plate member (magnetostrictive plate) for a magnetostrictive force sensor used in this example. A magnetostrictive force sensor of this example was produced by repeating the same operation as in Example 1 except that the plate member for the magnetostrictive force sensor obtained in this example was used.
When the sensitivity of the magnetostrictive force sensor was measured, the sensitivity was about 1.5 G / MPa in terms of the stress value at the magnetostrictive plate. In the case of this alloy, the compressive stress range of linear characteristics was as narrow as 30 MPa. This is considered to reflect the low mechanical strength of this alloy.

Example 4
(Fe ₈₀ Ga ₁₅ Al ₅ ) ₉₉ Zr _0.5 C _0.5 alloy was cast into a copper mold to obtain a cylindrical cast member. FIG. 6 shows a vertical cross section near the center in the axial direction of the cylindrical cast member. Since heat was absorbed by the copper mold, columnar crystals were formed in the radial direction. Next, a ring-shaped member (inner diameter: 12.6 mm, outer diameter: 14.2 mm, length: 13 mm) was cut out along the two-dot chain line in FIG. In addition, the columnar crystals penetrated in the radial direction (see FIG. 7A). In addition, a vertical section of columnar crystals appeared on the surface of the ring-shaped member, and the particle size was almost circular (see FIG. (B)). The crystal grain size was about 50 μm. This ring-shaped member was heat-treated at 550 ° C. for 2.5 hours to obtain a ring-shaped member for a magnetostrictive force sensor used in this example. When magnetostriction was measured by applying a magnetic field in the axial direction, the magnitude of magnetostriction was 60 ppm.
On the other hand, a ring-shaped member produced in the same manner (no heat treatment) was cooled and fitted to an alloy shaft having the same composition (see FIG. 8). The circumferential tensile stress in the ring-shaped member was 200 MPa (can be achieved with a cold fit of about 20 μm). In this state, heat treatment was performed in vacuum at 640 ° C. for 2 hours to obtain a ring-shaped member for a magnetostrictive force sensor used in this example. The magnetostriction in the axial direction after the heat treatment increased to 70 ppm (an increase of about 17%).
Using these, a magnetostrictive force sensor of this example as shown in FIG. 2 was produced. The ring-shaped member for the magnetostrictive force sensor was magnetized in the circumferential direction by fitting with a shaft made of SUS303 (shaft diameter: 12.6 mm) with a cold fit of 10 μm and applying about 8500 A to the shaft.
When the torsional sensitivity of these magnetostrictive force sensors was measured at +/− 5 Nm, they were 0.5 G / Nm and 0.6 G / Nm, respectively, and the degree of increase almost coincided with the rate of increase in magnetostriction. It was.

(Example 5)
In the same manner as in Example 4, a ring-shaped member (inner diameter: 10 mm, outer diameter: 13 mm, length: 15 mm) was produced from the same alloy. Next, 20% diameter expansion deformation was performed using a punch and pedestal made of maraging steel made by Hitachi Metals. Thereafter, it was machined to obtain a ring-shaped member having an inner diameter of 12.6 mm, an outer diameter of 14.2 mm, and a length of 13 mm. This ring-shaped member was heat-treated at 550 ° C. for 2.5 hours to obtain a ring-shaped member for a magnetostrictive force sensor used in this example. The crystal grain size on the surface of the ring-shaped member was about 50 μm, and had a shape extending about 20% in the circumferential direction (that is, a flat oval shape).
On the other hand, a separately prepared ring-shaped member after machining is cold-fitted to a shaft member of the same composition, and the circumferential tensile stress in the ring member is 200 MPa (can be achieved with a cold-fitting of about 20 μm). Then, heat treatment was performed at 640 ° C. in vacuum for 2 hours to obtain a ring-shaped member for a magnetostrictive force sensor used in this example.
Using this, a magnetostrictive force sensor of this example as shown in FIG. 2 was produced. The ring-shaped member for the magnetostrictive force sensor was magnetized in the circumferential direction by fitting a shaft made of SUS303 (shaft diameter: 12.6 mm) with a cold fit of 10 μm and applying about 8500 A to the shaft.
When the torsional sensitivity of these magnetostrictive force sensors was measured at +/− 5 Nm, they were 0.7 G / Nm and 0.8 G / Nm, respectively. See Example 4.)

(Example 6)
An Fe ₄₉ Co ₄₉ V ₂ alloy was cast into a copper mold to obtain a cylindrical cast member. FIG. 6 shows a vertical cross section near the center in the axial direction of the cylindrical cast member. Since heat was absorbed by the copper mold, columnar crystals were formed in the radial direction. Next, a ring-shaped member (inner diameter: 12.6 mm, outer diameter: 14.2 mm, length: 13 mm) was cut out along the two-dot chain line in FIG. In addition, the columnar crystals penetrated in the radial direction (see FIG. 7A). In addition, a vertical section of columnar crystals appeared on the surface of the ring-shaped member, and the particle size was almost circular (see FIG. 7B). The crystal grain size was about 40 μm. This ring-shaped member was heat-treated at 850 ° C. for 3 hours to obtain a ring-shaped member for a magnetostrictive force sensor used in this example. The magnitude of axial magnetostriction after the heat treatment was 70 ppm.
On the other hand, a ring-shaped member produced in the same manner (no heat treatment) was cooled and fitted to an alloy shaft having the same composition (see FIG. 8). The circumferential tensile stress in the ring-shaped member was 100 MPa (can be achieved with a cold fit of about 10 μm). In this state, heat treatment was performed at 850 ° C. for 3 hours to obtain a ring-shaped member for a magnetostrictive force sensor used in this example. In the case of the Fe ₄₉ Co ₄₉ V ₂ alloy, it is known that the ordered phase FeCo appears at 730 ° C. Therefore, the heat treatment temperature is higher than the order phase appearance temperature. The axial magnetostriction data is shown in FIG. The horizontal axis is plotted by the current passed through the electromagnet for applying the magnetic field, but it can be regarded as a magnetic field. A magnetic field of +/− 8 kOe is applied. The direction of application of the magnetic field (H) was the ring axis direction. The value of the strain gauge attached in the axial direction is the axial magnetostriction (series 1 data). The magnetostriction of the strain gauge attached perpendicular to the magnetic field is-(series 2 data). As shown in FIG. 11, the magnetostriction in the axial direction is about 90 ppm, and it can be seen that it increases by about 28% compared to the case where the heat treatment is not performed under stress.
Using these, a magnetostrictive force sensor of this example as shown in FIG. 2 was produced. The ring-shaped member for the magnetostrictive force sensor was magnetized in the circumferential direction by fitting with a shaft made of SUS303 (shaft diameter: 12.6 mm) with a cold fit of 10 μm and applying about 8500 A to the shaft.
When the torsional sensitivity of these magnetostrictive force sensors was measured at +/− 5 Nm, the torsional sensitivity was 1.0 G / Nm and 1.3 G / Nm, respectively. When heat-treated under stress, the torsional sensitivity was improved by about 30%.

(Example 7)
An Fe ₄₉ Co ₄₉ V ₂ alloy was cast into a copper mold to obtain a cylindrical cast member. FIG. 6 shows a vertical cross section near the center in the axial direction of the cylindrical cast member. Since heat was absorbed by the copper mold, columnar crystals were formed in the radial direction. Next, a ring-shaped member (inner diameter: 10 mm, outer diameter: 13 mm, length: 15 mm) was cut out along the two-dot chain line in FIG. Subsequently, 20% diameter expansion deformation was performed at 800 ° C. using a punch and a base made of maraging steel made by Hitachi Metals. Thereafter, in the case of the Fe ₄₉ Co ₄₉ V ₂ alloy, an ordered phase appeared at 730 ° C., but since it was higher than this temperature, it could be deformed without cracking. Thereafter, it was machined to obtain a ring-shaped member having an inner diameter of 12.6 mm, an outer diameter of 14.2 mm, and a length of 13 mm. This ring-shaped member was heat-treated at 800 ° C. for 3 hours to obtain a ring-shaped member for a magnetostrictive force sensor used in this example. When the crystal grains on the ring surface were observed, the grain size expanded about 20% in the circumferential direction (flattening rate about 20%).
On the other hand, a ring-shaped member produced in the same manner (no heat treatment) was cooled and fitted to an alloy shaft having the same composition (see FIG. 8). The circumferential tensile stress in the ring-shaped member was 100 MPa (can be achieved with a cold fit of about 10 μm). In this state, heat treatment was performed at 800 ° C. for 3 hours to obtain a ring-shaped member for a magnetostrictive force sensor used in this example.
The axial magnetostriction of the ring-shaped member was about 95 ppm without heat treatment under stress and about 110 ppm with heat treatment under stress (an increase of about 16%).
Using these, a magnetostrictive force sensor of this example as shown in FIG. 2 was produced. The ring-shaped member for the magnetostrictive force sensor was magnetized in the circumferential direction by fitting with a shaft made of SUS303 (shaft diameter: 12.6 mm) with a cold fit of 10 μm and applying about 8500 A to the shaft.
When the torsional sensitivity of these magnetostrictive force sensors was measured at +/− 5 Nm, the torsional sensitivity was 1.4 G / Nm and 1.7 G / Nm, respectively. When heat-treated under stress, the torsional sensitivity was improved by about 20%.

  As mentioned above, although this invention was demonstrated with some embodiment and an Example, this invention is not limited to these, A various deformation | transformation is possible within the range of the summary of this invention.

For example, only the Hall IC has been described as an example of the sensor of the magnetic detection unit, but in the present invention, a GMR or MI sensor that is power-saving and small can be applied.

Claims (20)

  A magnetostrictive force sensor comprising a magnetostrictive material having a magnitude of magnetostriction in a specific direction larger than that in a direction orthogonal to the direction.   The magnetostrictive force sensor according to claim 1, wherein the magnetostrictive material is an alloy having a cubic crystal structure.   3. The magnetostrictive force sensor according to claim 1, wherein the magnetostrictive material is an alloy having a body-centered cubic crystal structure.   The magnetostrictive force sensor according to any one of claims 1 to 3, wherein the magnetostrictive material is an FeGaAl alloy or an FeCoV alloy.   The magnetostrictive force sensor according to claim 1, wherein the magnetostrictive material is a plate-like member, and a longitudinal direction of the plate-like member is the specific direction. A permanent magnet is disposed on one surface of the plate member made of the magnetostrictive material, and a magnetic detection unit is disposed on the other surface,
6. The magnetostrictive force sensor according to claim 5, wherein a stress acting on the plate member is detected by detecting an increase in leakage magnetic flux when a compressive force is applied in the longitudinal direction of the plate member.   When manufacturing a plate member for a magnetostrictive force sensor made of a magnetostrictive material having a magnetostriction in the longitudinal direction larger than the magnetostriction in a direction perpendicular to the direction, a solidified member or cast member in which a columnar crystal structure is formed in one direction A plate-shaped member for a magnetostrictive force sensor, wherein the plate-shaped member is cut out in the direction of a columnar crystal.   The method for manufacturing a plate member for a magnetostrictive force sensor according to claim 7, wherein when the plate member is manufactured, heat treatment is performed in a state in which a tensile stress is applied in a columnar crystal direction.   The method for producing a plate member for a magnetostrictive force sensor according to claim 8, wherein the temperature of the heat treatment is equal to or higher than a regular phase appearance temperature.   The magnetostrictive force sensor according to claim 1, wherein the magnetostrictive material is a ring-shaped member, and a circumferential direction of the ring-shaped member is the specific direction. A shaft, a ring-shaped member made of the magnetostrictive material, and a magnetic detector;
The ring-shaped member is disposed so as to be fitted to the shaft, the magnetic detection unit is disposed in proximity to the ring-shaped member,
The ring-shaped member is magnetized in the circumferential direction,
The non-contact type magnetostrictive torque sensor for detecting the magnitude of magnetic flux leakage from the ring-shaped member by the magnetic detection unit when torque is applied to the shaft. Magnetostrictive force sensor.   The magnetostriction according to claim 11, wherein the magnitude of magnetostriction in the axial direction measured by applying a magnetic field in the axial direction of the ring-shaped member is larger than that when no anisotropy is imparted. Force sensor.   13. The magnetostrictive force sensor according to claim 12, wherein the magnitude of the axial magnetostriction is 10% or more.   A ring-shaped member made of a magnetostrictive material whose magnetostriction in the circumferential direction is larger than the magnetostriction in the axial direction perpendicular to the direction, wherein the columnar crystal structure is oriented in the radial direction of the ring-shaped member. A ring-shaped member for a magnetostrictive force sensor.   The ring-shaped member for a magnetostrictive force sensor according to claim 14, wherein the shape of crystal grains in a vertical section of the columnar crystal is a shape extending in a circumferential direction of the ring-shaped member.   The ring-shaped member for a magnetostrictive force sensor according to claim 15, wherein the flatness of the columnar crystals is 10% or more.   For a magnetostrictive force sensor in which the magnetostriction in the circumferential direction is made of a magnetostrictive material larger than the magnetostriction in the axial direction perpendicular to the direction, and the columnar crystal structure is oriented in the radial direction of the ring-like member A method for manufacturing a ring-shaped member for a magnetostrictive force sensor, comprising: cutting a ring-shaped member from a cast member in which columnar crystals are formed in a radial direction when the ring-shaped member is manufactured.   A ring-shaped member made of a magnetostrictive material whose magnetostriction in the circumferential direction is larger than the magnetostriction in the axial direction perpendicular to the direction, the columnar crystal structure being oriented in the radial direction of the ring-shaped member, and the columnar crystal When producing a ring-shaped member for a magnetostrictive force sensor in which the shape of crystal grains in the vertical cross section of the ring-shaped member extends in the circumferential direction, the ring-shaped member is cut out from a cast member in which columnar crystals are formed in the radial direction. A method for producing a ring-shaped member for a magnetostrictive force sensor, wherein plastic deformation is performed in a temperature range equal to or higher than a regular phase appearance temperature.   The method for manufacturing a ring-shaped member for a magnetostrictive force sensor according to claim 17 or 18, wherein when the ring-shaped member is manufactured, heat treatment is performed in a state where tensile stress is applied in a circumferential direction. The method for producing a ring-shaped member for a magnetostrictive force sensor according to claim 19, wherein the temperature of the heat treatment is equal to or higher than a regular phase appearance temperature.

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