JP2005236115A - Super-magnetostriction unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make more uniform magnetic flux density in a super-magnetostriction element and to reduce the output distortion of a super-magnetostriction unit. <P>SOLUTION: There are provided a super-magnetostriction element 11, a coil 12 disposed in the direction of a diameter of the super-magnetostriction element 11, and a yoke 13 disposed in the direction of an axis of the super-magnetostriction element 11. The length of the super-magnetostriction element 11 in the axial direction is substantially matched with the length of the coil 12 in the axial direction, and the diameter X1 of the yoke 13 is set greater than the inner diameter X3 of the coil 12. Thus, the uniformity of the magnetic flux density in the super-magnetostriction element 11 is improved, thereby effectively reducing the output distortion of a super-magnetostriction unit 10. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a giant magnetostrictive unit such as an actuator or a pressure sensor using a giant magnetostrictive element.

  Magnetostrictive elements that expand and contract in response to the application of a magnetic field have been known for a long time, but conventional magnetostrictive elements have a small displacement, and thus have been rarely used practically. However, in recent years, magnetostrictive elements (giant magnetostrictive elements) having a very large displacement of 1500 ppm to 2000 ppm have been known, and various usage forms thereof have been proposed. For example, paying attention to the high responsiveness and the magnitude of the driving force of the giant magnetostrictive element, a proposal to use it as an actuator (see Patent Documents 1 and 2) and a proposal to use as a pressure sensor (Patent Document) 3-6)).

Such a giant magnetostrictive unit basically includes a giant magnetostrictive element and a coil arranged in the radial direction thereof. Therefore, if the giant magnetostrictive element is displaced by passing a predetermined current through the coil, it can be used as an actuator. Conversely, if the displacement of the giant magnetostrictive element due to an external force is detected as a change in the coil current. This can be used as a pressure sensor.
JP-A-10-145892 Japanese Patent No. 2523027 Japanese Patent Publication No. 7-54282 Japanese Patent Laid-Open No. 11-139270 Japanese Patent Laid-Open No. 11-241955 JP 2000-114615 A

  However, the giant magnetostrictive material generally has a low magnetic permeability (about μ = 6 to 10), so that there is a problem that the magnetic flux density in the giant magnetostrictive element tends to be uneven depending on the design of the magnetic circuit. If the magnetic flux density in the giant magnetostrictive element is not uniform, the linearity between the displacement of the giant magnetostrictive element and the coil current is reduced, resulting in distortion in the output of the giant magnetostrictive unit. It is desirable that the magnetic flux density in the element be as uniform as possible.

  Accordingly, an object of the present invention is to make the magnetic flux density in the giant magnetostrictive element more uniform, thereby reducing the output distortion of the giant magnetostrictive unit.

  A giant magnetostrictive unit according to the present invention includes a giant magnetostrictive element, a coil arranged in a radial direction of the giant magnetostrictive element, and a yoke arranged in the axial direction of the giant magnetostrictive element, and the axial direction of the giant magnetostrictive element. And the length in the axial direction of the coil substantially coincide with each other, and the diameter of the yoke is larger than the inner diameter of the coil. According to the present invention, since the uniformity of the magnetic flux density in the giant magnetostrictive element is high, the output distortion of the giant magnetostrictive unit can be effectively reduced.

  In the present invention, the diameter of the yoke is preferably equal to or larger than the outer diameter of the coil. According to this, it becomes possible to make the magnetic flux density in the giant magnetostrictive element more uniform.

  In the present invention, the yoke includes a first and second portion provided in the axial direction of the giant magnetostrictive element, and a third portion provided in the radial direction of the giant magnetostrictive element and connecting the first and second portions. It is preferable that the portion is included. According to this, the magnetic flux density in the giant magnetostrictive element can be made uniform and higher.

  The giant magnetostrictive unit according to the present invention preferably further comprises a permanent magnet, which can be arranged in the radial direction of the coil or in the axial direction of the giant magnetostrictive element. By providing a permanent magnet, a magnetic bias can be applied to the giant magnetostrictive unit.

  In the present invention, the magnetic permeability of the yoke is preferably 100 or more, and more preferably 1000 or more. This is because the higher the magnetic permeability of the yoke, the lower the magnetic flux density at the end of the giant magnetostrictive element can be suppressed, and as a result, the magnetic flux density is made more uniform.

  As described above, since the giant magnetostrictive unit according to the present invention has high uniformity of magnetic flux density in the giant magnetostrictive element, the output strain can be reduced when the actuator is used as an actuator or as a pressure sensor. It can be greatly reduced.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic cross-sectional view showing the structure of a giant magnetostrictive unit 10 according to a preferred embodiment of the present invention.

  As shown in FIG. 1, the giant magnetostrictive unit 10 according to the present embodiment includes a cylindrical giant magnetostrictive element 11, a cylindrical coil 12 arranged in the radial direction of the giant magnetostrictive element 11, and the axis of the giant magnetostrictive element 11. A disk-shaped yoke 13 arranged in the direction and a cylindrical permanent magnet 14 arranged in the radial direction of the coil 12 are provided. The giant magnetostrictive unit 10 according to the present embodiment can be used as an actuator for displacing the giant magnetostrictive element 11 by causing a predetermined current to flow through the coil 12, and further, the displacement of the giant magnetostrictive element 11 due to an external force can be used as a coil current. It is also possible to use it as a pressure sensor that detects the change in the pressure.

The giant magnetostrictive element 11 is a cylindrical element made of a giant magnetostrictive material that is displaced in response to application of a magnetic field and whose permeability changes in accordance with displacement due to an external force. The giant magnetostrictive material to be used is not particularly limited, and a giant magnetostrictive material having a central composition of Tb _0.34 -Dy _0.66 -Fe _1.90 can be used. The size of the giant magnetostrictive element 11 may be appropriately selected according to the intended use and output of the giant magnetostrictive unit 10.

  The coil 12 has a giant magnetostrictive element 11 inserted in a hollow portion thereof, and is used as electromagnetic conversion means that is magnetically coupled to the giant magnetostrictive element 11. Therefore, when a predetermined current is supplied to the coil 12 from a drive circuit (not shown), the coil 12 applies a magnetic field based on this to the giant magnetostrictive element 11, and the displacement of the giant magnetostrictive element 11 obtained thereby is the first of the yoke 13. It can be taken out from the part 13a. That is, in this case, the giant magnetostrictive unit 10 functions as an actuator. Conversely, when the magnetostrictive element 11 expands and contracts due to an external force applied to the first portion 13a of the yoke 13 and the permeability of the super magnetostrictive element 11 changes thereby, the coil 12 detects a current generated thereby by a detection circuit (not shown). To supply. That is, in this case, the giant magnetostrictive unit 10 functions as a pressure sensor.

  As shown in FIG. 1, in the giant magnetostrictive unit 10 according to the present embodiment, the length in the axial direction of the giant magnetostrictive element 11 and the length in the axial direction of the coil 12 substantially coincide. This is to make the magnetic flux density in the giant magnetostrictive element 11 uniform, and the output distortion of the giant magnetostrictive unit 10 is reduced by this configuration. That is, when the length in the axial direction of the giant magnetostrictive element 11 is shorter than the length in the axial direction of the coil 12, the magnetic flux density at the end of the giant magnetostrictive element 11 is higher than that in the central portion, while the giant magnetostrictive element 11. When the length in the axial direction of the coil 12 is longer than the length in the axial direction of the coil 12, the magnetic flux density at the end of the giant magnetostrictive element 11 is lower than that in the central portion. On the other hand, if the lengths in these axial directions are made substantially the same, the magnetic flux density in the giant magnetostrictive element 11 becomes substantially uniform from the end to the center, and specifically, the magnetic flux at the end. The difference between the density and the magnetic flux density at the center can be made 10% or less.

  As shown in FIG. 1, the yoke 13 is composed of a first portion 13a provided on one end side of the giant magnetostrictive element 11 and a second portion 13b provided on the other end side. Yes. The first portion 13a of the yoke 13 functions as an input / output unit that extracts the displacement of the giant magnetostrictive element 11 or transmits an external force to the giant magnetostrictive element 11, and the second portion 13b of the yoke 13 is substantially fixed. The

  In the present embodiment, the diameter X1 of the yoke 13 is set larger than the outer diameter X2 of the coil 12. In the present invention, it is not essential that the diameter X1 of the yoke 13 is larger than the outer diameter X2 of the coil 12, but at least the diameter X1 of the yoke 13 needs to be larger than the inner diameter X3 of the coil 12. This is because as the diameter X1 of the yoke 13 is larger than that of the coil 12, the effect of making the magnetic flux density uniform becomes higher. As in this embodiment, the diameter X1 of the yoke 13 is set to the outer diameter X2 of the coil 12. If it is set larger than this, the output distortion of the giant magnetostrictive unit 10 can be made very small. On the other hand, if the diameter X1 of the yoke 13 is equal to or smaller than the inner diameter X3 of the coil 12, the difference between the magnetic flux density at the end and the magnetic flux density at the central portion exceeds 10%, and output distortion increases.

  As the material of the yoke 13, it is preferable to use a material having as high a permeability as possible. Specifically, the permeability (μ) is preferably 100 or more, and more preferably 1000 or more. This is because the higher the magnetic permeability of the yoke 13, the higher the effect of suppressing the decrease in magnetic flux density at the end of the super magnetostrictive element 11, and a material having a magnetic permeability of 100 or more is used as the material of the yoke 13. Thus, in combination with the configuration of the present embodiment, the magnetic flux density can be made more uniform. In particular, if a material having a magnetic permeability of 1000 or more is used as the material of the yoke 13, the magnetic flux density can be made substantially uniform in combination with the configuration of the present embodiment. Preferred specific materials include pure iron (μ = 5000 or more), silicon iron (μ = 6000 or more), electromagnetic stainless steel (μ = 4000 or more), permalloy (μ = 30000 or more), ferrite (μ = 1000 or more). And the like.

  The permanent magnet 14 is a cylindrical body that surrounds the outside of the coil 12 and plays a role of applying a magnetic bias to the giant magnetostrictive element 11. This is because in the state where there is no magnetic bias, the displacement of the giant magnetostrictive element 11 is not directional with respect to the direction of the magnetic field.

  As described above, the giant magnetostrictive unit 10 having the above-described configuration has the length of the giant magnetostrictive element 11 in the axial direction substantially equal to the length of the coil 12 in the axial direction, and the diameter X1 of the yoke 13 is equal to the coil. Therefore, the uniformity of the magnetic flux density in the giant magnetostrictive element 11 becomes very high. As a result, the output distortion can be greatly reduced when the giant magnetostrictive unit 10 of the present embodiment is used as an actuator or as a pressure sensor.

  The “length in the axial direction of the coil” means the length of only the main body portion constituted by the windings, excluding the length of a portion having no electromagnetic conversion function such as a bobbin. Therefore, when the coil 12 is wound around the bobbin, as shown in FIG. 2, if the concave portion 15 corresponding to the thickness of the bobbin 12a is provided in the yoke 13, the length of the giant magnetostrictive element 11 in the axial direction is increased. The bobbin 12a can be held by the yoke 13 while substantially matching the length of the coil 12 in the axial direction.

  FIG. 3 is a schematic cross-sectional view showing the structure of a giant magnetostrictive unit 20 according to another preferred embodiment of the present invention.

  In the giant magnetostrictive unit 20 according to the present embodiment, the yoke 13 further includes a third portion 13c provided on the outer side in the radial direction of the coil 12, whereby the first portion 13a and the second portion 13b are connected. In addition, the present embodiment is different from the above embodiment in that the permanent magnet 21 is disposed in the axial direction of the giant magnetostrictive element 11. With this structure, in the present embodiment, a closed magnetic path is formed by the giant magnetostrictive element 11 and the yoke 13 (first, second and third portions 13a, 13b, 13c). In the present embodiment, since the yoke 13 is integrated, the displacement of the giant magnetostrictive element 11 is directly taken out from the first portion 13a, or an external force is directly applied to the giant magnetostrictive element 11 through the first portion 13a. I can't tell you. Therefore, in the present embodiment, a through hole is provided in the first portion 13a of the yoke 13, and the input / output rod 22 is disposed here. Therefore, in the present embodiment, the displacement of the giant magnetostrictive element 11 is taken out via the input / output rod 22 or an external force is transmitted to the giant magnetostrictive element 11 via the input / output rod 22. In the input / output rod 22, at least a region surrounded by the first portion 13a is preferably made of a yoke material. In this case, the entire input / output rod 22 may be made of the yoke material, or only the region surrounded by the first portion 13a may be made of the yoke material. According to this, a closed magnetic circuit can be formed more reliably.

  As long as the magnetic coupling is dense, the yoke 13 composed of the first, second, and third portions 13a, 13b, and 13c does not need to be integrated, and some or all of them are separate parts. It doesn't matter.

  Also in this embodiment, the length in the axial direction of the giant magnetostrictive element 11 and the length in the axial direction of the coil 12 are substantially the same, and the diameter X1 of the yoke 13 is larger than the outer diameter X2 of the coil 12. Is set. As a result, as in the above embodiment, the magnetic flux density in the giant magnetostrictive element 11 can be made substantially uniform. In the present embodiment, since the permanent magnet 21 is disposed in the axial direction of the giant magnetostrictive element 11, as shown in FIG. 3, a recess 23 corresponding to the thickness of the permanent magnet 21 is provided in the yoke 13. The coil 12 can be held by the yoke 13 while substantially matching the length in the axial direction of the giant magnetostrictive element 11 and the length in the axial direction of the coil 12.

  Further, as shown in FIG. 4, when the coil 12 is wound around the bobbin 12 a, the depth of the recess 23 may be set to a depth obtained by subtracting the thickness of the bobbin 12 a from the thickness of the permanent magnet 21. Although not shown, when the thickness of the bobbin 12a is thicker than the thickness of the permanent magnet 21, conversely, a protrusion is provided on the yoke 13, and the height of the permanent magnet 21 is changed from the thickness of the bobbin 12a. You can set it to a reduced height.

  In addition to the effect of the giant magnetostrictive unit 10 according to the above embodiment, the giant magnetostrictive unit 20 according to the present embodiment is connected to the first portion 13a and the second portion 13b by the third portion 13c of the yoke 13. Not only is the magnetic flux density in the giant magnetostrictive element 11 uniform, but the magnetic flux density itself can be increased. Thereby, compared with the giant magnetostriction unit 10 by the said embodiment, it becomes possible to obtain higher electromagnetic conversion efficiency.

  The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the invention described in the claims, and these are also included in the scope of the present invention. Needless to say.

  Hereinafter, the results of a static magnetic field simulation using a static magnetic field analyzer will be described in order to verify the effects of the present invention.

  [Example 1]

  First, assuming a giant magnetostrictive unit having a cross section shown in FIG. 5, the magnetic flux density along the central axis 11a of the giant magnetostrictive element 11 was simulated. The magnetic permeability (μ) of the giant magnetostrictive element 11 was 6, the length in the axial direction was 20 mm, and the diameter was 2 mm. The length of the coil 12 in the axial direction was also 20 mm, and the inner diameter and the outer diameter were 4 mm and 8 mm, respectively. The magnetic permeability (μ) of the yoke 13 was set to 1000, and its diameter was matched with the outer diameter of the coil 12 (8 mm).

  And the magnetic flux density along the central axis 11a when the electric current whose product of a coil electric current (A: ampere) and a coil turn number (T: turn number) is 500A * T was sent to the coil 12 was simulated. The result of the simulation is shown in FIG.

  As shown in FIG. 6, the magnetic flux density along the central axis 11a is substantially uniform in the axial direction of the giant magnetostrictive element 11, and the magnetic flux density at the end portion (about 2 mm from the end, the same applies hereinafter) and the central portion. It was confirmed that the difference from the magnetic flux density (absolute value, the same applies hereinafter) was about 6.2%.

  [Comparative Example 1]

  Assuming the giant magnetostrictive unit having the cross section shown in FIG. 7, the length of the coil 12 in the axial direction is 18 mm, and the sectional shape of the yoke 13 is U-shaped. The end of the coil 12 was brought into contact with the yoke 13. The other conditions were the same as in Example 1, and a simulation of the magnetic flux density along the central axis 11a was performed.

  The result of the simulation is shown in FIG. As shown in FIG. 6, in the structure of Comparative Example 1, it was confirmed that a decrease in magnetic flux density was observed at the end of the super magnetostrictive element 11, and as a result, the magnetic flux density became non-uniform in the axial direction of the super magnetostrictive element 11. It was. Specifically, the difference between the magnetic flux density at the end portion and the magnetic flux density at the central portion was about 12.8%.

  [Comparative Example 2]

  The magnetic flux density was simulated under the same conditions as in Comparative Example 1 except that the length of the coil 12 in the axial direction was set to 16 mm and the shape of the yoke 13 was adjusted to this. The result of the simulation is shown in FIG. 6, and it was confirmed that the magnetic flux density at the end of the giant magnetostrictive element 11 is significantly reduced in the structure of Comparative Example 2. Specifically, the difference between the magnetic flux density at the end portion and the magnetic flux density at the central portion was about 14.7%.

  [Comparative Example 3]

  Assuming the giant magnetostrictive unit having the cross section shown in FIG. 8, the length of the coil 12 in the axial direction is 22 mm, and the sectional shape of the yoke 13 is T-shaped. 12 ends were brought into contact with the yoke 13. The other conditions were the same as in Example 1, and a simulation of the magnetic flux density along the central axis 11a was performed.

  The result of the simulation is also shown in FIG. As shown in FIG. 6, in the structure of Comparative Example 3, it was confirmed that a rise in the magnetic flux density was observed at the end of the super magnetostrictive element 11, and as a result, the magnetic flux density became non-uniform in the axial direction of the super magnetostrictive element 11. It was. Specifically, the difference between the magnetic flux density at the end portion and the magnetic flux density at the central portion was about 11.7%.

  [Comparative Example 4]

  The magnetic flux density was simulated under the same conditions as in Comparative Example 3 except that the length of the coil 12 in the axial direction was set to 24 mm and the shape of the yoke 13 was adjusted to this. The result of the simulation is shown in FIG. 6, and it was confirmed that the rise of the magnetic flux density at the end of the giant magnetostrictive element 11 becomes more remarkable in the structure of Comparative Example 4. Specifically, the difference between the magnetic flux density at the end portion and the magnetic flux density at the central portion was about 46.3%.

  [Example 2]

  The magnetic flux density simulation was performed under the same conditions as in Example 1 except that the diameter of the yoke 13 was set to 12 mm (1.5 times the outer diameter of the coil 12) with the central axes of the giant magnetostrictive element 11 and the yoke 13 aligned. Went. The result of the simulation is shown in FIG. FIG. 9 also shows the results of Example 1. As shown in FIG. 9, it is confirmed that when the diameter of the yoke 13 is increased to 1.5 times the outer diameter of the coil 12, the magnetic flux density along the central axis 11a becomes more uniform and the magnetic flux density itself increases. It was. The difference between the magnetic flux density at the end portion and the magnetic flux density at the central portion was about 2.5%.

  [Example 3]

  Simulation of magnetic flux density under the same conditions as in Example 1 except that the diameter of the yoke 13 is set to 20 mm (2.5 times the outer diameter of the coil 12) while the central axes of the giant magnetostrictive element 11 and the yoke 13 are aligned. Went. The result of the simulation is also shown in FIG. 9. When the diameter of the yoke 13 is increased to 2.5 times the outer diameter of the coil 12, the magnetic flux density along the central axis 11a becomes more uniform, and the magnetic flux density itself. It was confirmed that the price would be higher. The difference between the magnetic flux density at the end and the magnetic flux density at the center was about 0.5%.

  [Example 4]

  The magnetic flux density was simulated under the same conditions as in Example 1 except that the diameter of the yoke 13 was set to 40 mm (5 times the outer diameter of the coil 12) while the central axes of the giant magnetostrictive element 11 and the yoke 13 were aligned. It was. The result of the simulation is also shown in FIG. 9. When the diameter of the yoke 13 is increased to five times the outer diameter of the coil 12, the magnetic flux density along the central axis 11a becomes even more uniform, and the magnetic flux density itself is also increased. It was confirmed that it would be higher. The difference between the magnetic flux density at the end and the magnetic flux density at the center was about 0.1%.

  [Example 5]

  The magnetic flux density simulation was performed under the same conditions as in Example 1 except that the diameter of the yoke 13 was set to 6 mm (the intermediate value between the outer diameter and the inner diameter of the coil 12) while the central axes of the giant magnetostrictive element 11 and the yoke 13 were aligned. Went. The result of the simulation is also shown in FIG. 9, and when the diameter of the yoke 13 is set to an intermediate value between the outer diameter and the inner diameter of the coil 12, the magnetic flux density along the central axis 11a is inferior to that of the first embodiment. The difference between the magnetic flux density at the end and the magnetic flux density at the center was only about 9.6%.

  [Comparative Example 5]

  The magnetic flux density was simulated under the same conditions as in Example 1 except that the diameter of the yoke 13 was changed to 4 mm (matching the inner diameter of the coil 12) while the central axes of the giant magnetostrictive element 11 and the yoke 13 were matched. The result of the simulation is also shown in FIG. 9, and when the diameter of the yoke 13 is set to the same value as the inner diameter of the coil 12, a decrease in the magnetic flux density is observed at the end of the giant magnetostrictive element 11, and as a result, the magnetic flux density Has been confirmed to be slightly non-uniform in the axial direction of the giant magnetostrictive element 11. Specifically, the difference between the magnetic flux density at the end portion and the magnetic flux density at the central portion was about 13.6%.

  [Comparative Example 6]

  The magnetic flux density was simulated under the same conditions as in Example 1 except that the diameter of the yoke 13 was set to 2 mm (matching the diameter of the giant magnetostrictive element 11) while keeping the central axes of the giant magnetostrictive element 11 and the yoke 13 aligned. It was. The result of the simulation is also shown in FIG. 9, and it is confirmed that when the diameter of the yoke 13 is set to the same value as the diameter of the giant magnetostrictive element 11, the decrease in the magnetic flux density at the end of the giant magnetostrictive element 11 becomes more significant. It was. Specifically, the difference between the magnetic flux density at the end and the magnetic flux density at the center was about 18.2%.

  [Comparative Example 7]

  The magnetic flux density was simulated under the same conditions as in Example 1 except that the yoke 13 was omitted. The result of the simulation is also shown in FIG. 9, and it was confirmed that when the yoke 13 was deleted, the magnetic flux density at the end of the giant magnetostrictive element 11 was further reduced significantly. Specifically, the difference between the magnetic flux density at the end portion and the magnetic flux density at the central portion was about 26.4%.

  [Example 6]

  The magnetic flux density was simulated under the same conditions as in Example 1 except that the yokes 13 at both ends were connected and the cross-sectional structure shown in FIG. 10 was assumed. The result of the simulation is also shown in FIG. 9, and it is confirmed that when the yokes 13 at both ends are connected, the magnetic flux density along the central axis 11a becomes even more uniform and the magnetic flux density itself becomes very high. . The difference between the magnetic flux density at the end and the magnetic flux density at the center was about 0.1%.

  [Example 7]

  The magnetic flux density was simulated under the same conditions as in Example 6 except that the magnetic permeability (μ) of the yoke 13 was set to 100. The result of the simulation is shown in FIG. In addition, the result of Example 6 is also shown by FIG. As shown in FIG. 11, when the magnetic permeability (μ) of the yoke 13 is 100, the magnetic flux density along the central axis 11a is slightly inferior to that of the sixth embodiment, but the magnetic flux density at the end portion and the magnetic flux density at the central portion. The difference was only 1.1%.

  [Example 8]

  The magnetic flux density was simulated under the same conditions as in Example 6 except that the permeability (μ) of the yoke 13 was set to 10. The result of the simulation is also shown in FIG. 11. When the magnetic permeability (μ) of the yoke 13 is 10, the magnetic flux density along the central axis 11a is inferior to that of the seventh embodiment. The difference from the magnetic flux density at the center was only about 8.3%.

1 is a schematic cross-sectional view showing the structure of a giant magnetostrictive unit 10 according to a preferred embodiment of the present invention. In the giant magnetostriction unit 10 shown in FIG. 1, it is a schematic sectional drawing which shows a structure when the coil 12 is wound around the bobbin 12a. It is a schematic sectional drawing which shows the structure of the giant magnetostriction unit 20 by other preferable embodiment of this invention. In the giant magnetostrictive unit 20 shown in FIG. 3, it is a schematic sectional drawing which shows a structure when the coil 12 is wound around the bobbin 12a. 2 is a cross-sectional structure of a giant magnetostrictive unit assumed in the static magnetic field simulation of the first embodiment. It is a graph which shows the simulation result of Example 1 and Comparative Examples 1-4. It is the cross-sectional structure of the giant magnetostriction unit assumed in the static magnetic field simulation of Comparative Examples 1 and 2. It is the cross-sectional structure of the giant magnetostrictive unit assumed in the static magnetic field simulation of Comparative Examples 3 and 4. It is a graph which shows the simulation result of Examples 1-6 and Comparative Examples 5-7. It is the cross-sectional structure of the giant magnetostriction unit assumed in the static magnetic field simulation of Examples 6-8. It is a graph which shows the simulation result of Examples 6-8.

Explanation of symbols

10, 20 Giant magnetostrictive unit 11 Giant magnetostrictive element 11a Central axis 12 Coil 12a Bobbin 13 Yoke 13a First portion 13b Yoke second portion 13c Yoke third portion 14, 21 Permanent magnets 15, 23 Recessed portion 22 I / O rod X1 Yoke diameter X2 Coil outer diameter X3 Coil inner diameter

Claims (7)

  A giant magnetostrictive element, a coil arranged in the radial direction of the giant magnetostrictive element, and a yoke arranged in the axial direction of the giant magnetostrictive element, the axial length of the giant magnetostrictive element and the axial direction of the coil The giant magnetostrictive unit is characterized in that the lengths of the yokes are substantially the same, and the diameter of the yoke is larger than the inner diameter of the coil.   The giant magnetostrictive unit according to claim 1, wherein a diameter of the yoke is equal to or larger than an outer diameter of the coil.   The giant magnetostrictive unit according to claim 1, further comprising a permanent magnet disposed in a radial direction of the coil.   The yoke includes first and second parts provided in the axial direction of the giant magnetostrictive element, and a third part provided in the radial direction of the giant magnetostrictive element and connecting the first and second parts. The giant magnetostrictive unit according to claim 1, wherein the giant magnetostrictive unit is included.   The giant magnetostrictive unit according to claim 4, further comprising a permanent magnet disposed in an axial direction of the giant magnetostrictive element.   6. The giant magnetostrictive unit according to claim 1, wherein the yoke has a magnetic permeability of 100 or more. The giant magnetostrictive unit according to claim 6, wherein the yoke has a magnetic permeability of 1000 or more.

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