JP4040029B2 - Giant magnetostriction unit - Google Patents

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 disposed in the radial direction thereof. Therefore, if the giant magnetostrictive element is displaced by flowing 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 disposed in a radial direction of the giant magnetostrictive element, and a yoke, and the yoke is provided between the giant magnetostrictive element and the coil. It has a first portion, a second portion arranged on the outer side in the radial direction of the coil, and a third portion connecting the first portion and the second portion. To do. According to such a configuration, the uniformity of the magnetic flux density in the giant magnetostrictive element is increased, so that the output distortion of the giant magnetostrictive unit can be effectively reduced.

  In the present invention, it is preferable that an inner diameter of the first portion of the yoke is 1/5 or less of a length in the axial direction of the giant magnetostrictive element. With this setting, the magnetic flux density in the giant magnetostrictive element can be made more uniform.

  The yoke further includes a fourth portion arranged in the axial direction of the giant magnetostrictive element, and a gap is provided between the third portion and the fourth portion of the yoke. It is preferable that According to this, it is possible to suppress a decrease in magnetic flux density at the end of the giant magnetostrictive element.

  The giant magnetostrictive unit according to the present invention preferably further comprises a permanent magnet disposed 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.

  In the present invention, it is preferable that the length of the giant magnetostrictive element in the axial direction is equal to or shorter than the length of the yoke in the axial direction. According to this, the magnetic flux density in the giant magnetostrictive element can be made uniform, and the output distortion of the giant magnetostrictive unit can be effectively reduced.

  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, a giant magnetostrictive element 11, and a coil. 12, a yoke 13 (13 a to 13 d) provided so as to surround 12, and a permanent magnet 14 disposed in the axial direction of the giant magnetostrictive element 11. 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. 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 accordance with 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 length of the giant magnetostrictive element 11 in the axial direction is preferably equal to or shorter than the length of the yoke 13 in the axial direction. This is because if the length of the giant magnetostrictive element 11 in the axial direction is longer than the length of the yoke 13 in the axial direction, the magnetic flux hardly passes through the end of the giant magnetostrictive element 11, and as a result, the magnetic flux at the end This is because density uniformity cannot be obtained.

  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 taken out from the input / output rod 15. be able to. That is, in this case, the giant magnetostrictive unit 10 functions as an actuator. On the contrary, when the magnetostrictive element 11 expands and contracts due to an external force applied to the input / output rod 15 and the permeability of the super magnetostrictive element 11 changes thereby, the coil 12 supplies a current generated thereby to a detection circuit (not shown). . 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. However, in the present invention, it is not essential to substantially match the length of the giant magnetostrictive element 11 in the axial direction with the length of the coil 12 in the axial direction.

  As shown in FIG. 1, the yoke 13 includes a first portion 13 a provided between the giant magnetostrictive element 11 and the coil 12, a second portion 13 b disposed on the radially outer side of the coil 12, and a coil 12 has a third portion 13c that is provided in the axial direction and connects the first portion 13a and the second portion 13b, and a fourth portion 13d that is disposed in the axial direction of the giant magnetostrictive element 11. Yes. Thus, the yoke 13 is arranged so as to surround the giant magnetostrictive element 11 and the coil 12. However, this does not mean that the giant magnetostrictive element 11 and the coil 12 need to be sealed by the yoke 13, but the first portion 13a and the second portion 13b are formed by the third portion 13c. As long as it is connected, the first to third portions 13a to 13c themselves may have a gap. With such a configuration, it is possible to configure a good closed magnetic circuit in the giant magnetostrictive unit 10 according to the present embodiment.

In the present embodiment, when the inner diameter of the first portion 13a of the yoke 13 is a and the length in the axial direction of the giant magnetostrictive element 11 is b,
a / b ≦ 1/5
Is set to In the present invention, it is not essential to set the relationship between the inner diameter a of the first portion 13a of the yoke 13 and the length b in the axial direction of the giant magnetostrictive element 11 within the above range, but the value of a / b is The smaller it is, the higher the effect of making the magnetic flux density uniform. Therefore, as in this embodiment, the ratio between the inner diameter a of the first portion 13a of the yoke 13 and the length b in the axial direction of the giant magnetostrictive element 11 is a / b ≦ 1/5.
Is set, the magnetic flux density in the giant magnetostrictive element 11 becomes very uniform. As a result, the output distortion of the giant magnetostrictive unit 10 can be made very small. Specifically, the difference between the magnetic flux density at the end of the giant magnetostrictive element 11 and the magnetic flux density at the center can be made 20% or less.

More preferably, the ratio between the inner diameter a of the first portion 13a of the yoke 13 and the length b in the axial direction of the giant magnetostrictive element 11 is a / b ≦ 1/10.
And it is sufficient. If set in such a range, the magnetic flux density in the giant magnetostrictive element 11 becomes extremely uniform. Specifically, the difference between the magnetic flux density at the end of the giant magnetostrictive element 11 and the magnetic flux density at the central part is 2% or less. It becomes possible.

  Further, in the present embodiment, the gap 16 is provided between the third portion 13c and the fourth portion 13d of the yoke 13, so that they are not in direct contact with each other. In the present invention, it is not essential that the yoke 13 has the fourth portion 13d. However, by providing this, it is possible to suppress a decrease in magnetic flux density at the end of the super magnetostrictive element 11. Further, if the third portion 13c and the fourth portion 13d of the yoke 13 are in direct contact with each other, the magnetic flux density at the end of the giant magnetostrictive element 11 may become excessively high. In order to suppress an excessive rise in the magnetic flux density at the end of the magnetostrictive element 11, a gap 16 is provided between the third portion 13c and the fourth portion 13d of the yoke 13 as in the present embodiment. It is preferable. The strength of the magnetic flux at the end of the giant magnetostrictive element 11 can be adjusted by the width of the gap 16, and the narrower the gap 16, the higher the magnetic flux density at the end of the giant magnetostrictive element 11.

  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 magnets 14 are disposed on both sides in the axial direction of the giant magnetostrictive element 11 and play 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, since the yoke 13 includes the first to third portions 13a to 13c, the giant magnetostrictive unit 10 having the above configuration can configure a good closed magnetic circuit. 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. Note that the first portion 13 a and the third portion 13 c of the yoke 13 can also serve as a so-called bobbin of the coil 12.

Moreover, in the present embodiment, when the inner diameter of the first portion 13a of the yoke 13 is a, and the axial length of the giant magnetostrictive element 11 is b,
a / b ≦ 1/5
Therefore, the magnetic flux density in the giant magnetostrictive element 11 can be made more uniform. In the present embodiment, since the yoke 13 includes the fourth portion 13d and the gap 16 is provided between the third portion 13c and the fourth portion 13d, the giant magnetostrictive element 11 is provided. It is possible to suppress a decrease in magnetic flux density at the end of the.

  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. 2, 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 b in the axial direction was 20 mm, and the diameter was 2 mm. The length of the coil 12 in the axial direction was 20 mm, and the inner diameter and outer diameter were 6 mm and 10 mm, respectively. The yoke 13 had a magnetic permeability (μ) of 1000, a thickness of 1 mm, an axial length of 22 mm, an inner diameter a of 2 mm, and an outer diameter c of 12 mm. In Example 1,
a / b = 1/10
It is.

  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. 3, 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 at the central portion. It was confirmed that the difference from the magnetic flux density (absolute value, the same applies hereinafter) was about 1.9%.

  [Comparative Example 1]

  As shown in FIG. 4, assuming a giant magnetostrictive unit having a configuration in which the first portion 13 a of the yoke 13 is deleted from the giant magnetostrictive unit shown in FIG. 2, a simulation of the magnetic flux density along the central axis 11 a was performed.

  The result of the simulation is also shown in FIG. As shown in FIG. 3, in the structure of Comparative Example 1, it was confirmed that the flatness of the magnetic flux density was slightly lowered as compared with Example 1.

  [Comparative Example 2]

  As shown in FIG. 5, assuming a giant magnetostrictive unit having a configuration in which the second portion 13b of the yoke 13 is deleted from the giant magnetostrictive unit shown in FIG. 2, 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. 3, in the structure of Comparative Example 2, only a very low magnetic flux density was obtained.

  [Comparative Example 3]

  As shown in FIG. 6, assuming a giant magnetostrictive unit having a configuration in which the third portion 13c of the yoke 13 is deleted from the giant magnetostrictive unit shown in FIG. 2, the magnetic flux density along the central axis 11a was simulated.

  The result of the simulation is also shown in FIG. As shown in FIG. 3, even in the structure of Comparative Example 3, only a very low magnetic flux density was obtained.

  [Example 2]

Assuming a giant magnetostrictive unit having the cross section shown in FIG. 7, the inner diameter a of the yoke 13 is 3 mm, the outer diameter c is 13 mm, and the inner diameter and the outer diameter of the coil 12 are 7 mm and 11 mm, respectively. The magnetic flux density along the central axis 11a was simulated under the same conditions as in Example 1. In Example 2,
a / b = 3/20
It is. The result of the simulation is shown in FIG. In FIG. 8, the results of Example 1 are also shown. As shown in FIG. 8, the magnetic flux density was relatively uniform. However, the magnetic flux density was generally lower than that of Example 1, and the magnetic flux density slightly decreased at the end of the giant magnetostrictive element 11. confirmed. Specifically, the difference between the magnetic flux density at the end portion and the magnetic flux density at the central portion was about 14.5%.

  [Example 3]

The inner diameter a of the yoke 13 was 4 mm, the outer diameter c was 14 mm, and the inner diameter and outer diameter of the coil 12 were adjusted to 8 mm and 12 mm, respectively. The magnetic flux density was simulated. In Example 3,
a / b = 1/5
It is. The result of the simulation is also shown in FIG. As shown in FIG. 8, the magnetic flux density was relatively uniform, but the magnetic flux density was lower overall than in Example 2, and the magnetic flux density further decreased at the end 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 19.8%.

  [Example 4]

The inner diameter a of the yoke 13 is 6 mm, the outer diameter c is 16 mm, and the inner diameter and the outer diameter of the coil 12 are 10 mm and 14 mm, respectively. The magnetic flux density was simulated. In Example 4,
a / b = 3/10
It is. The result of the simulation is also shown in FIG. As shown in FIG. 8, in the structure of Example 4, the overall magnetic flux density was lower than in Example 3, and the magnetic flux density further decreased at the end 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 22.8%.

  [Example 5]

The inner diameter a of the yoke 13 was 8 mm, the outer diameter c was 18 mm, and the inner diameter and outer diameter of the coil 12 were set to 12 mm and 16 mm, respectively. The magnetic flux density was simulated. In Example 5,
a / b = 2/5
It is. The result of the simulation is also shown in FIG. As shown in FIG. 8, in the structure of Example 5, the magnetic flux density was lower overall than in Example 4, and the magnetic flux density further decreased at the end 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 23.8%.

  [Example 6]

The inner diameter a of the yoke 13 is 10 mm, the outer diameter c is 20 mm, and the inner diameter and the outer diameter of the coil 12 are 14 mm and 18 mm, respectively. The magnetic flux density was simulated. In Example 6,
a / b = 1/2
It is. The result of the simulation is also shown in FIG. As shown in FIG. 8, in the structure of Example 6, the magnetic flux density was generally lower than that of Example 5, and the magnetic flux density further decreased at the end 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 24.1%.

  [Example 7]

  While maintaining the inner diameter a of the yoke 13 at 2 mm, the outer diameter c is set to 16 mm, and the inner diameter and outer diameter of the coil 12 are set to 10 mm and 14 mm, respectively. The magnetic flux density along the line was simulated. As a result of the simulation, the magnetic flux density distribution was not substantially different from that of Example 1.

  [Example 8]

  While maintaining the inner diameter a of the yoke 13 at 2 mm, the outer diameter c is set to 20 mm, and the inner diameter and outer diameter of the coil 12 are set to 14 mm and 18 mm, respectively. The magnetic flux density along the line was simulated. As a result of the simulation, the magnetic flux density distribution was not substantially different from that of Example 1.

  [Example 9]

  While maintaining the inner diameter a of the yoke 13 at 2 mm, the outer diameter c is set to 24 mm, and the inner diameter and outer diameter of the coil 12 are set to 18 mm and 22 mm, respectively. The magnetic flux density along the line was simulated. As a result of the simulation, the magnetic flux density distribution was not substantially different from that of Example 1.

  [Example 10]

  Assuming a giant magnetostrictive unit having a cross section shown in FIG. 9, the inner diameter a of the yoke 13 is 2 mm, the outer diameter c is 24 mm, and the inner diameter and the outer diameter of the coil 12 are 4 mm and 8 mm, respectively. The magnetic flux density along the central axis 11a was simulated under the same conditions. As a result of the simulation, the magnetic flux density distribution was not substantially different from that of Example 1.

  [Example 11]

  Assuming the giant magnetostrictive unit having the cross section shown in FIG. 10, the inner diameter a of the yoke 13 is 2 mm, the outer diameter c is 24 mm, the length of the coil 12 in the axial direction is 4 mm, and the inner diameter and outer diameter of the coil 12 are respectively The simulation of the magnetic flux density along the central axis 11a was performed under the same conditions as in Example 1 except that the thickness was set to 8 mm and 16 mm. As a result of the simulation, the magnetic flux density distribution was not substantially different from that of Example 1.

  [Example 12]

  Assuming the giant magnetostrictive unit having the cross section shown in FIG. 11, the magnetic flux along the central axis 11a is the same as in the second embodiment (see FIG. 7) except that the length of the yoke 13 in the axial direction is 26 mm. A density simulation was performed. The result of the simulation is shown in FIG. FIG. 12 also shows the results of Example 2. As shown in FIG. 12, the uniformity of the magnetic flux density was almost the same as in Example 2, but the magnetic flux density was lowered overall.

  [Example 13]

  The simulation of the magnetic flux density along the central axis 11a was performed under the same conditions as in Example 12 except that the length of the yoke 13 in the axial direction was 30 mm. The result of the simulation is also shown in FIG. As shown in FIG. 12, it was confirmed that when the distance between the third portion 13c of the yoke 13 and the coil 12 is increased in the axial direction, the magnetic flux density is further lowered as a whole. However, the uniformity of the magnetic flux density was almost the same as in Example 2.

  [Example 14]

  Assuming the giant magnetostrictive unit having the cross section shown in FIG. 13, the fourth portion 13d of the yoke 13 is provided in the axial direction of the giant magnetostrictive element 11, and the third portion 13c and the fourth portion 13d of the yoke 13 are provided. A simulation of the magnetic flux density along the central axis 11a was performed under the same conditions as in Example 2 (see FIG. 7) except that the gap between them was 0.1 mm. The simulation results are shown in FIG. FIG. 14 also shows the result of Example 2 that does not have the fourth portion 13d. As shown in FIG. 14, when the fourth portion 13d of the yoke 13 is provided in the axial direction of the giant magnetostrictive element 11, the decrease in magnetic flux density at the end of the giant magnetostrictive element 11 is suppressed, and the uniformity is further improved. confirmed.

  [Example 15]

  A simulation of the magnetic flux density along the central axis 11a was performed under the same conditions as in Example 14 except that the gap between the third portion 13c and the fourth portion 13d of the yoke 13 was set to 0.2 mm. The result of the simulation is also shown in FIG. As shown in FIG. 14, the magnetic flux density at the end of the giant magnetostrictive element 11 is slightly lower than that in Example 14. Thus, it can be seen that the magnetic flux density at the end of the giant magnetostrictive element 11 can be adjusted by the width of the gap.

  [Example 16]

  A simulation of the magnetic flux density along the central axis 11a was performed under the same conditions as in Example 14 except that the gap between the third portion 13c and the fourth portion 13d of the yoke 13 was 0.5 mm. The result of the simulation is also shown in FIG. As shown in FIG. 14, the magnetic flux density at the end of the giant magnetostrictive element 11 is slightly lower than that in the fifteenth embodiment. Thus, it can be seen that the magnetic flux density at the end of the giant magnetostrictive element 11 can be adjusted by the width of the gap.

  [Example 17]

  A simulation of the magnetic flux density along the central axis 11a was performed under the same conditions as in Example 14 except that the gap between the third portion 13c and the fourth portion 13d of the yoke 13 was set to zero. The result of the simulation is also shown in FIG. As shown in FIG. 14, when the gap was zero, the magnetic flux density increased at the end of the giant magnetostrictive element 11. This also shows that the magnetic flux density at the end of the giant magnetostrictive element 11 can be adjusted by the width of the gap.

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. It is the cross-sectional structure of the giant magnetostriction unit assumed in the static magnetic field simulation of Example 1 and 7-9. It is a graph which shows the simulation result of Example 1 and Comparative Examples 1-3. 3 is a cross-sectional structure of a giant magnetostrictive unit assumed in a static magnetic field simulation of Comparative Example 1. 3 is a cross-sectional structure of a giant magnetostrictive unit assumed in a static magnetic field simulation of Comparative Example 2. 10 is a cross-sectional structure of a giant magnetostrictive unit assumed in a static magnetic field simulation of Comparative Example 3. It is the cross-sectional structure of the giant magnetostriction unit assumed in the static magnetic field simulation of Examples 2-6. It is a graph which shows the simulation result of Examples 1-6. 10 is a cross-sectional structure of a giant magnetostrictive unit assumed in a static magnetic field simulation of Example 10. 12 is a cross-sectional structure of a giant magnetostrictive unit assumed in a static magnetic field simulation of Example 11. It is the cross-sectional structure of the giant magnetostriction unit assumed in the static magnetic field simulation of Examples 12 and 13. It is a graph which shows the simulation result of Example 2, 12, and 13. FIG. It is the cross-sectional structure of the giant magnetostriction unit assumed in the static magnetic field simulation of Examples 14-17. It is a graph which shows the simulation result of Example 2, 14-17.

Explanation of symbols

10 Giant Magnetostrictive Unit 11 Giant Magnetostrictive Element 11a Center Axis 12 Coil 13 Yoke 13a Yoke First Part 13b Yoke Second Part 13c Yoke Third Part 13d Yoke Fourth Part 14 Permanent Magnet 15 I / O Rod 16 Gap a Inner diameter b of the first part of the yoke b Length in the axial direction of the giant magnetostrictive element c Outer diameter of the second part of the yoke

Claims (7)

  A giant magnetostrictive element, a coil disposed in a radial direction of the giant magnetostrictive element, and a yoke, the yoke including a first portion provided between the giant magnetostrictive element and the coil, and the coil A giant magnetostrictive unit comprising: a second portion disposed radially outward of the first portion; and a third portion connecting the first portion and the second portion.   2. The giant magnetostrictive unit according to claim 1, wherein an inner diameter of the first portion of the yoke is 1/5 or less of an axial length of the giant magnetostrictive element.   The yoke further includes a fourth portion disposed in the axial direction of the giant magnetostrictive element, and a gap is provided between the third portion and the fourth portion of the yoke. The giant magnetostrictive unit according to claim 1, wherein the unit is a giant magnetostrictive unit.   The giant magnetostrictive unit according to any one of claims 1 to 3, further comprising a permanent magnet disposed in an axial direction of the giant magnetostrictive element.   The giant magnetostrictive unit according to any one of claims 1 to 4, wherein the yoke has a magnetic permeability of 100 or more.   6. The giant magnetostrictive unit according to claim 5, wherein the magnetic permeability of the yoke is 1000 or more. The giant magnetostrictive unit according to any one of claims 1 to 6, wherein a length of the giant magnetostrictive element in the axial direction is equal to or shorter than a length of the yoke in the axial direction.

Images