JP2012165537A - Magnetic circuit and actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an actuator using a magnetic circuit compactly capable of generating a strong magnetic field in a simple configuration.SOLUTION: The magnetic circuit includes: a yoke 1 having loop sections 2 capable of forming a magnetic field in a loop; stationary magnetic field application means 4 for applying a stationary magnetic field to the loop sections; and variable magnetic field application means 7 capable of applying a variable strength magnetic field to the loop sections, and the loop sections have a magnetic field concentration section 3 narrower than the other portions. The actuator includes the magnetic circuit, and a magnetostrictive material 9 arranged in the magnetic field concentration section of the magnetic circuit.

Description

  The present invention relates to a magnetic circuit and an actuator including the magnetic circuit and a magnetostrictive material.

  Conventionally, piezoelectric elements have been used for vibrators and small actuators. However, the piezoelectric element has problems such as weak mechanical strength and brittleness. In response to such problems, actuators using magnetostriction of magnetic metals have been developed. Magnetostriction is a phenomenon in which a magnetic metal is distorted in a magnetic field and the magnetic metal expands and contracts.

  For example, Patent Document 1 discloses a technique related to an actuator or a motor using a magnetostrictive material. Patent Document 2 discloses a technique related to a method of applying an optimum magnetic field to a magnetostrictive material.

  In a magnetostrictive material such as an FeGa-based alloy described in Patent Document 1 or the like, a magnetostriction of about several tens of ppm at maximum can be generated by applying a magnetic field having a predetermined magnitude. On the other hand, A. E. Terfenol-D (registered trademark), which is an alloy of Fe and rare earth elements Dy and Tb developed by Clark et al., Can generate magnetostriction of 2000 ppm at the maximum. An alloy that generates such a large magnetostriction is called a giant magnetostrictive material. Giant magnetostrictive materials have an extremely large displacement due to magnetostriction compared to piezo-electric elements, and when super-magnetostrictive materials are used in actuators, a very large mechanical output can be obtained compared to piezo-electric elements. . In addition, the giant magnetostrictive material has an advantage that the response speed of the magnetostriction with respect to the alternating magnetic field is faster than that of the piezoelectric element. Furthermore, the giant magnetostrictive material has advantages such as being easy to process as compared to the piezoelectric element, being able to be incorporated into a device having a simple structure, having a high degree of freedom in shape, and having a wide usable temperature range.

JP 2009-130988 A JP-A-9-168197

  In order to cause magnetostriction in the giant magnetostrictive material, it is necessary to apply a stronger magnetic field than in the case where magnetostriction is caused in the FeGa alloy disclosed in Patent Document 1. For example, when Terfenol-D (registered trademark) is used as an actuator, a strong magnetic field of about several thousand Oersted to about 1 Tesla is required. Therefore, in order to apply the giant magnetostrictive material to the actuator, a magnetic circuit capable of generating a strong magnetic field is required. However, in the prior art, it is difficult to produce a magnetic circuit that can generate a small and strong magnetic field, and it is difficult to reduce the size of an actuator using a giant magnetostrictive material.

  Accordingly, an object of the present invention is to provide a magnetic circuit that can generate a strong magnetic field with a simple configuration and can be miniaturized, and an actuator using the magnetic circuit.

The present invention will be described below.
The first aspect of the present invention includes a yoke having an annular portion formed in an annular shape, a stationary magnetic field applying means for applying a steady magnetic field to the annular portion, and a variable magnetic field applying means capable of applying a magnetic field whose intensity can be changed to the annular portion. And the annular portion includes a magnetic field concentration portion formed narrower than other portions.

  Here, “annularly formed” means that it is formed in a form that can form an annular magnetic field when a magnetic field is applied, and is limited to being formed in a complete annular form. Not a concept. That is, the annular part may be in a form in which a part is notched as will be described later.

  In the magnetic circuit of the first aspect of the present invention, it is preferable that a part of the magnetic field concentration portion is cut away. By adopting such a configuration, a magnetostrictive material is arranged in the notched gap, and the magnetic circuit of the first invention can be suitably used for the actuator of the second invention described later.

  In the magnetic circuit of the first aspect of the present invention, the yoke has a plurality of annular portions, and the plurality of annular portions are arranged so that the magnetic field concentration portions respectively provided in the plurality of annular portions are concentrated at one point. preferable. By adopting such a form, it becomes easy to generate a large magnetic field in the magnetic field concentration part.

  The second aspect of the present invention is an actuator comprising the magnetic circuit of the first aspect of the present invention and a magnetostrictive material disposed in a magnetic field concentration portion of the magnetic circuit.

  In the actuator according to the second aspect of the present invention, the magnetostrictive material disposed in the magnetic field concentration portion is preferably a TbDyFe-based alloy.

  According to the first aspect of the present invention, it is possible to provide a magnetic circuit that can generate a strong magnetic field with a simple configuration and can be miniaturized. The magnetic circuit of the first aspect of the present invention can generate a strong magnetic field in a micro space on the order of millimeters by downsizing. Further, according to the second aspect of the present invention, an actuator that can be miniaturized can be provided by using the magnetic circuit of the first aspect of the present invention.

1 is a plan view schematically showing a magnetic circuit of the present invention according to one embodiment. FIG. 2 is a plan view schematically showing a yoke in the magnetic circuit shown in FIG. 1. FIG. 3 is an enlarged view of a portion III of the yoke shown in FIG. 2. It is the top view which showed schematically the yoke among the magnetic circuits of this invention concerning other embodiment. It is the top view which showed schematically the yoke among the magnetic circuits of this invention concerning other embodiment. It is the perspective view which showed schematically the yoke among the magnetic circuits of this invention concerning other embodiment. 1 is a plan view schematically showing an actuator of the present invention according to one embodiment. It is the figure which showed roughly the structure of the apparatus used for the calibration test. It is the figure which showed the result of the calibration test. It is a figure which shows the relationship between the magnetic field applied to the magnetostrictive material, and the magnetostriction which arose in the magnetostrictive material. It is the top view which showed roughly the apparatus for experiment produced in the Example. It is a figure (upper stage) which shows the relationship between the output voltage from the speaker terminal of an audio amplifier, and time (upper stage), and the figure (lower stage) which shows the relationship between the displacement of magnetostrictive material, and time.

  The above-described operation and gain of the present invention will be clarified from embodiments for carrying out the invention described below. Hereinafter, the present invention will be described based on embodiments shown in the drawings. However, the present invention is not limited to these embodiments.

<Magnetic circuit>
FIG. 1 is a plan view schematically showing a magnetic circuit 10 of the present invention according to one embodiment. FIG. 2 is a plan view schematically showing the yoke 1 in the magnetic circuit 10 shown in FIG. FIG. 3 is an enlarged view of a portion III of the yoke 1 shown in FIG. The magnetic circuit 10 shown in FIG. 1 includes a yoke 1, steady magnetic field applying means 4 and 4, and variable magnetic field applying means 7 and 7.

(yoke)
As shown in FIG. 1, the yoke 1 includes two annular portions 2. A magnetic field is applied to the two annular portions 2 by a stationary magnetic field applying unit 4 and a variable magnetic field applying unit 7 which will be described later. 1 indicate the direction of the magnetic field formed in the annular part 2, and as indicated by the arrows M, M,..., An annular magnetic field is formed in the annular part 2. Has been. The annular portion 2 includes a portion 3 that is formed thinner than other portions and partially cut away. As will be described later, the part 3 is a part where a magnetic field can be concentrated, and is hereinafter referred to as a magnetic field concentration unit 3. Each of the two annular portions 2 includes a magnetic field concentrating portion 3, and the two annular portions 2 are arranged so that the magnetic field concentrating portions 3 included therein are concentrated at one point. Therefore, one magnetic field concentration part 3 appears in FIG.

  Further, as shown in FIG. 2, the annular portion 2 includes a notch 4 a in which a stationary magnetic field applying means 4 to be described in detail later can be disposed. As shown in FIG. 1, by placing the stationary magnetic field applying means 4 in the notch 4a, a stationary magnetic field is applied to the annular portion 2 by the stationary magnetic field applying means 4, and as indicated by arrows M, M,. An annular magnetic field can be formed in the annular portion 2. In the embodiment shown in FIG. 1, the notch 4a is provided in the annular portion 2, and the stationary magnetic field applying means 4 is arranged in the notch 4a. However, the present invention is not limited to such an embodiment. The stationary magnetic field applying means may be arranged in a state where a stationary magnetic field can be applied to the annular portion. That is, the form which mounted the stationary magnetic field application means on the annular part, without providing a notch in an annular part may be sufficient.

  The annular portion 2 is disposed so as to pass through the hollow portion of the cylindrical coil 5 provided in the variable magnetic field applying means 7 described in detail later. Therefore, by supplying a current of an arbitrary magnitude to the coil 5, a magnetic field of an arbitrary intensity is applied from the coil 5 to the annular portion 2, and an annular magnetic field as indicated by arrows M, M,. An annular portion 2 can be formed.

  When an annular magnetic field is applied to the annular portion 2 as described above, the magnetic field concentrating portion 3 is formed thinner than other portions of the annular portion 2, so that the density of magnetic lines of force of the magnetic field concentrating portion 3 is the annular portion 2. It becomes higher than other parts. That is, the magnetic field in the vicinity of the magnetic field concentration part 3 becomes strong. For example, the width of the end of the annular portion 2 (W1 shown in FIG. 3) in the magnetic field concentrating portion 3 and the width of the portion to which the alternating magnetic field is applied (the portion where the coil 5 is provided) (W2 shown in FIG. 2). Is preferably in the range of W2: W1 = 10: 5 to 10: 2. If the ratio is larger than 10: 2, the magnetic field concentrating part 3 becomes too small to be practical, and the magnetization of the yoke 1 near the magnetic field concentrating part 3 is saturated, resulting in a voltage applied to the coil 5. There is a possibility that a magnetic field proportional to the frequency will not be generated in the magnetic field concentration part 3.

  In addition, a narrower interval (D shown in FIG. 3) between the notch portions provided in the magnetic field concentration portion 3 is advantageous because a spatially uniform magnetic field can be generated in the notch portion. . The ratio of the notch spacing (D) to the width (W1) of the end of the annular portion 2 in the magnetic field concentrating portion 3 is preferably about D: W1 = 2: 1. If the gap (D) is made larger than this ratio, the leakage of the magnetic field becomes large, and the effect of concentrating the magnetic field on the magnetic field concentrating part 3 may be reduced.

  When a ferromagnetic magnetic material or a giant magnetostrictive material is installed in the notch portion of the magnetic field concentration portion 3, the magnetic field lines pass through the material due to the ferromagnetism of the material itself. Thus, the uniformity of the magnetic field in the magnetic field concentration unit 3 is increased.

  In order to make the magnetic flux passing through the annular portion 2 easy to concentrate at the magnetic field concentrating portion 3, as shown in FIG. 1, the annular portion 2 is formed so as not to have an acute angle, and the flow of magnetic lines of force is made smooth. Is preferred.

  Furthermore, in order to make it easier to increase the magnetic field in the magnetic field concentration part, it is preferable to form a substantially vertical and laterally symmetric shape like the yoke 1 shown in FIG. This is because a smooth flow of magnetic lines of force with no magnetic field bias is generated, and the magnetic field of the magnetic field concentration portion can be easily increased.

  The magnitude of the magnetic field generated in the magnetic field concentration unit 3 can be appropriately adjusted by adjusting the magnitude of the magnetic field applied to the annular part 2 by the steady magnetic field application unit 4 and the variable magnetic field application unit 7. It is preferable that the maximum magnetic field generated in the magnetic field concentration unit 3 is, for example, not less than 0.2T and not more than 2T. As described above, it is necessary to apply a strong magnetic field in order to cause magnetostriction in the giant magnetostrictive material. By setting the magnetic field generated in the magnetic field concentrating part 3 within the above range, when a super magnetostrictive material is arranged in the magnetic field concentrating part 3, it is easy to cause a large magnetostriction in the super magnetostrictive material.

  In the description of the magnetic circuit 10 so far, as shown in FIG. 1, the yoke 1 includes two annular portions 2, each of which is formed to be thinner than other portions and partly cut away. An example in which two annular portions 2 are arranged so that the magnetic field concentration portions 3 are provided and the magnetic field concentration portions 3 are concentrated at one point is illustrated. However, the present invention is not limited to such a form. FIG. 4 is a plan view schematically showing a yoke in a magnetic circuit of the present invention according to another embodiment. FIG. 5 is a plan view schematically showing a yoke in a magnetic circuit according to another embodiment of the present invention. FIG. 6 is a perspective view schematically showing a yoke in a magnetic circuit according to another embodiment of the present invention.

  The yoke provided in the magnetic circuit of the present invention may include an annular portion formed in an annular shape, and the annular portion may include a magnetic field concentration portion formed narrower than other portions. Therefore, like the yoke 1a shown in FIG. 4, the magnetic field concentration part 3a having no notch may be formed by simply making it thinner than other parts. Even in this form, the magnetic flux density in the magnetic field concentrating part 3a is higher than in other parts, and a strong magnetic field can be generated in the magnetic field concentrating part 3a. However, as will be described later, when a magnetostrictive material is disposed in a magnetic field concentration portion and a magnetic field is applied to the magnetostrictive material, a part of the magnetic field concentration portion is notched as in the magnetic field concentration portion 3 shown in FIG. However, it becomes easier to apply a strong magnetic field to the magnetostrictive material by disposing the magnetostrictive material in the gap of the notch.

  Further, the yoke provided in the magnetic circuit of the present invention only needs to have an annular portion formed in an annular shape, and the number of the annular portions is not particularly limited. Therefore, it may be configured to have only one annular portion 2b as in the yoke 1b shown in FIG. 5, and three or more annular portions 2c (as shown in FIG. 6) as in the yoke 1c shown in FIG. 4 may be provided). However, when the yoke has a plurality of annular portions, the plurality of annular portions are arranged so that the magnetic field concentration portions respectively provided in the plurality of annular portions are concentrated at one point, such as the yokes 1, 1a, and 1c. Form. This is because the magnetic field formed in each annular portion is concentrated at one point (magnetic field concentration portion).

  As described above, the number of the annular portions of the yoke provided in the magnetic circuit of the present invention is not particularly limited. However, it is easier to increase the magnetic flux density of the magnetic field concentrating portion if the configuration includes a plurality of annular portions. Moreover, when a yoke is provided with two or more annular parts, the form provided with an annular part on the same plane like the yokes 1 and 1a from a viewpoint that manufacture is easy is preferable. If it is set as the form which forms a some annular part on the same plane, a yoke can be easily produced from one board | plate material.

  4 to 6 do not show notches for arranging the stationary magnetic field applying means. However, like the yoke 1 shown in FIG. 1, in order to arrange the stationary magnetic field applying means, the yokes 1a and 1b are arranged. , And 1c can also be arranged with a part cut away.

  Such a yoke can be made of a highly permeable material or a magnetic material. Examples of the material constituting the yoke include iron, stainless steel, and nickel.

(Stationary magnetic field application means)
The magnetic circuit 10 shown in FIG. 1 includes two stationary magnetic field applying means 4. The stationary magnetic field applying unit 4 is a unit that applies a stationary magnetic field having a predetermined strength to the annular portion 2. As a specific example of the stationary magnetic field applying means 4, a permanent magnet can be mentioned. In the form shown in FIG. 1, it is assumed that a permanent magnet is used as the stationary magnetic field application unit 4. Therefore, in the following description, the stationary magnetic field application unit 4 is described as a permanent magnet 4. Examples of permanent magnets that can be used include ferrite magnets and samarium cobalt magnets. However, the present invention is not limited to such a form, and a coil or the like supplied with a direct current can also be used as the stationary magnetic field applying means. According to the permanent magnet, it is easy to apply a steady magnetic field having a predetermined strength to the annular portion. Therefore, in the present embodiment, an example in which a permanent magnet is used as the stationary magnetic field applying unit is illustrated.

  In the form shown in FIG. 1, the permanent magnet 4 is arranged by cutting out a part of the annular portion 2. However, as described above, the installation position of the permanent magnet is not limited to this form in the present invention. The permanent magnet only needs to be installed so that a steady magnetic field can be applied to the annular portion, and the permanent magnet may be placed on the annular portion. However, in order to make it easy to apply a steady magnetic field to the annular portion, it is preferable to insert a permanent magnet by cutting out a part of the annular portion. Moreover, it is preferable to arrange | position a permanent magnet so that an annular part may be contact | connected. By setting it as this form, it becomes easy to apply a magnetic field from a permanent magnet to an annular part.

  The strength of the stationary magnetic field applied to the annular portion by the permanent magnet can be adjusted by adjusting the installation position of the permanent magnet, the material constituting the permanent magnet, and the number of permanent magnets installed.

(Variable magnetic field supply means)
The magnetic circuit 10 shown in FIG. 1 includes two variable magnetic field supply means 7. The variable magnetic field supply means 7 is a means that can apply a magnetic field of arbitrary strength to the annular portion 2. The form of the variable magnetic field supply means 7 is not particularly limited as long as it is a means that can form a magnetic field of arbitrary strength in the annular portion 2 in the same direction as the magnetic field formed by the permanent magnet 4 in the annular portion 2. As a specific example of the variable magnetic field supply means 7, as shown in FIG. 1, an electromagnet including a coil 5 and a power source 6 that supplies power to the coil 5 can be cited. In the form shown in FIG. 1, it is assumed that an electromagnet is used as the variable magnetic field supply unit 7. Therefore, in the following description, the variable magnetic field supply unit 7 is described as an electromagnet 7. According to the electromagnet, it is easy to apply a magnetic field having an arbitrary strength to the annular portion. Therefore, in the present embodiment, an example in which an electromagnet is used as the variable magnetic field supply unit is illustrated.

  As described above, it is necessary to apply a strong magnetic field in order to cause magnetostriction in the giant magnetostrictive material. In order to adjust the degree of magnetostriction generated in the giant magnetostrictive material, the strength of the magnetic field applied to the giant magnetostrictive material must be adjusted. That is, in order to change the degree of magnetostriction generated in the giant magnetostrictive material, it is necessary to change the strength of the magnetic field applied to the giant magnetostrictive material within a strong range that causes magnetostriction in the giant magnetostrictive material. In this way, it is difficult to change the magnetic field with only a permanent magnet or only an electromagnet. According to the magnetic circuit 10, it is possible to change the strength of the magnetic field generated in the magnetic field concentration unit 3 by the electromagnet 7 while generating a stationary magnetic field having a predetermined strength in the magnetic field concentration unit 3 by the permanent magnet 4. Further, as described above, a strong magnetic field can be generated in the magnetic field concentration unit 3. That is, according to the magnetic circuit 10, the magnetic field generated in the magnetic field concentrating part 3 can be changed within a strong range that causes magnetostriction in the giant magnetostrictive material. Therefore, if a giant magnetostrictive material is disposed in the magnetic field concentrating portion 3, it becomes easy to adjust the degree of magnetostriction generated in the giant magnetostrictive material.

  According to the magnetic circuit 10, an oscillating magnetic field having an arbitrary frequency (for example, 1 kHz or more) is generated by changing the frequency of the current supplied from the AC power source to the coil 5 by using the power source 6 as an AC power source. 3 can also be generated. However, the power source 6 may be a DC power source. By adjusting the strength of the current supplied from the DC power supply to the coil 5, the strength of the magnetic field generated in the magnetic field concentrating unit 3 can be set to an arbitrary strength.

(Use)
The magnetic circuit of the present invention can generate a strong magnetic field in the magnetic field concentration part. Therefore, when a giant magnetostrictive material that cannot generate magnetostriction unless a strong magnetic field is applied as described above is installed in the magnetic field concentration portion, magnetostriction can be caused in the giant magnetostrictive material. Therefore, the magnetic circuit of the present invention can be applied to an actuator using a giant magnetostrictive material, as will be described later. Further, since the magnetic circuit of the present invention has a simple configuration as described above, it can be easily downsized. Therefore, the magnetic circuit of the present invention can be incorporated in a small device and can be used as a magnetic circuit for generating a strong magnetic field in a micro space of millimeter order. Furthermore, according to the magnetic circuit of the present invention, a vibration phenomenon caused by a magnetic force is caused by bringing a magnetic needle such as a magnetic body or a azimuth magnet or another permanent magnet close to the yoke while an alternating current is applied to the yoke to generate an alternating magnetic field. Can be observed. Therefore, the magnetic circuit of the present invention can also be used as an electromagnetic science experiment teaching material for elementary school to high school students. The magnetic circuit of the present invention can be made of a material that is inexpensive and easy to process. For this reason, by replacing the conventional magnetic circuit with the magnetic circuit of the present invention, it is possible to reduce the cost of a device including the magnetic circuit.

<Actuator>
Next, the actuator of the present invention will be described. The actuator of the present invention includes the above-described magnetic circuit of the present invention and a magnetostrictive material disposed in the magnetic field concentration portion of the magnetic circuit. FIG. 7 is a plan view schematically showing the actuator 100 of the present invention according to one embodiment. The actuator 100 shown in FIG. 7 includes a magnetic circuit 10 and a magnetostrictive material 9 disposed in the magnetic field concentration portion 3 of the magnetic circuit 10. In FIG. 7, the same components as those shown in FIG.

As described above, the magnetic circuit 10 can generate a strong magnetic field in the magnetic field concentration unit 3. Therefore, a strong magnetic field can be applied to the magnetostrictive material 9 by disposing the magnetostrictive material 9 in the magnetic field concentration portion 3. Therefore, even when a giant magnetostrictive material is used as the magnetostrictive material 9, magnetostriction can be generated in the giant magnetostrictive material. As the magnetostrictive material 9, for example, a giant magnetostrictive material such as a TbFe alloy or a TbDyFe alloy can be used. An example of the TbDyFe-based alloy is Teffenol-D (registered trademark) having a composition of Tb _0.27 Dy _0.73 Fe _1.9 .

  Giant magnetostrictive material is small in displacement only by applying an alternating magnetic field near zero magnetic field. However, the displacement increases around several thousand oersteds. As described above, the magnetic circuit of the present invention applies a steady magnetic field having a predetermined strength by the stationary magnetic field applying unit and then applies a magnetic field serving as a bias by the variable magnetic field applying unit, thereby centering the predetermined strength. As described above, a magnetic field whose strength changes within a predetermined range can be generated in the magnetic field concentration portion. Therefore, by arranging the giant magnetostrictive material in the magnetic field concentration portion, the giant magnetostrictive material can be displaced more than the alternating magnetic field alone.

  Further, by controlling the output of the oscillator provided in the power source of the variable magnetic field applying means in the order of mV, the displacement of the giant magnetostrictive material can be controlled with an accuracy of about 10 nm. Therefore, the actuator of the present invention can be used as a positioning means for an apparatus that requires high-precision positioning such as an atomic force microscope.

  In addition, since the magnetic circuit of the present invention can be easily downsized, the actuator of the present invention can also be easily downsized. The actuator of the present invention can be applied to medical devices, small electronic devices, and the like by downsizing.

  As an example of application of the actuator of the present invention to a medical device, an example of application to a microcatheter is given. In the medical field, a microcatheter having an outer diameter of about 1.5 mm is used. By miniaturizing the actuator of the present invention provided with a giant magnetostrictive material and inserting it into such a microcatheter, it becomes possible to remove waste products in tumors and blood vessels.

  As an application example of the actuator of the present invention to a small electronic device, an example of application to a microswitch or a micro vibrator is given. The actuator of the present invention can also be applied as a switch of 1 mm size, and can be used as a switch for a micromachine or a small electronic board. Since the magnetostrictive material is a metal and can pass a current through itself, the actuator of the present invention can also be used as an electric switch.

  Furthermore, it is considered that the actuator of the present invention can be applied to a speaker or the like.

  In the description of the actuator of the present invention so far, the mode including the magnetic circuit 10 has been illustrated, but the magnetic circuit included in the actuator of the present invention is not limited to such a mode. The actuator of the present invention only needs to include the magnetic circuit of the present invention and a magnetostrictive material. That is, the actuator of the present invention may include another form of the magnetic circuit of the present invention instead of the magnetic circuit 10. Further, when the magnetic field concentration portion has a notch as in the magnetic circuit 10, a strong magnetic field can be applied to the magnetostrictive material by disposing the magnetostrictive material in the gap of the notch. On the other hand, when using a magnetic circuit without a notch in the magnetic field concentration portion, a strong magnetic field can be applied to the magnetostrictive material by placing the magnetostrictive material on the magnetic field concentration portion.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the examples.

(Calibration test)
In evaluating the performance of the magnetic circuit of the present invention, first, the relationship between the strength of the magnetic field applied to the magnetostrictive material (Terfenol-D (registered trademark)) by the calibration test described below and the magnitude of the magnetostriction generated in the magnetostrictive material. I investigated. FIG. 8 is a diagram schematically showing the configuration of the apparatus used for the calibration test.

  Water-cooled pulse magnet 71 (pulse strong magnetic field magnet formed by stacking 30 bitter plates (disk shape) having a thickness of 3.0 mm) and pulse magnetic field power source 72 for supplying power to the pulse magnet 71 (Nichicon Corporation) A capacitor bank (40 A4 size capacitors), a maximum of 5 kV, C = 8 mF, E = 100 kJ) was prepared, and electric charges were stored in the pulse magnetic field power source 72 to form a pulse magnetic field. In the case of a 200 Hz water-cooled pulse magnet, the charging pressure was set at 1 kV and 7T. For example, if it is 0.20 kV, it becomes 1.4T. The pulse magnetic field thus formed was applied to the sample (magnetostrictive material) 9.

The magnetostriction generated in the magnetostrictive material 9, that is, the amount of strain, was measured by a capacitance method. A pair of electrodes (copper-clad shield tape) 73a and 73b is prepared, and one electrode 73a is attached to the end surface of the magnetostrictive material 9 (one end surface in the direction of expansion and contraction by magnetostriction), and the other electrode 73b is the electrode 73a. And fixed at a predetermined distance. At this time, the distance between the electrode 73a (the end face of the magnetostrictive material 9) and the electrode 73b was set by fixing the magnetostrictive material 9 and the electrode 73b using a bakelite plate. The pair of electrodes 73a and 73b constitute a capacitor of about C ₀ = 1.5 pF. Both ends of this capacitor were connected to a capacitance bridge 74 (“1615A” manufactured by Quadtech) for measuring capacitance. The capacitance bridge 74 was operated by an oscillator 75 (“WF1945” manufactured by NF Circuit Design Block Co., Ltd.). The capacitance bridge 74 is provided with an AC bridge circuit of variable capacitance, and the AC output from the bridge circuit is a lock-in amplifier 76 ("LI5640" manufactured by NF Circuit Design Block Co., Ltd., equivalent to an AC voltmeter). It detected and analyzed with the digital oscilloscope 77 ("BRINGO DS-8814" by Iwasaki Tsushinki Co., Ltd.).

First, the capacitance C ₀ in a zero magnetic field (a state in which no magnetic field is applied to the magnetostrictive material 9) is measured by turning the knob of the capacitance bridge 74, and then the output of the capacitance bridge 74 is digitally applied when a pulse magnetic field is applied. The signal was input to an oscilloscope (“TDS460A” manufactured by TFF Co., Ltd.) to detect the magnetostrictive signal voltage. The magnitude of the voltage of this signal is proportional to the capacitance change amount ΔC. Before applying a magnetic field to the magnetostrictive material 9, the distance d ₀ between the electrodes 73a and the electrodes 73b by leaving measured with a micrometer, the amount of change in electrostatic capacitance when a magnetic field is applied to the magnetostrictive material 9 [Delta] C Is proportional to the amount of change Δd in the distance between the electrodes 73 a and 73 b, Δd can be obtained from C ₀ , d ₀ and ΔC, and this Δd becomes the magnetostriction amount of the magnetostrictive material 9.

  The results of the calibration test are shown in FIGS. FIG. 9 shows the result of measuring the magnetostriction generated in the magnetostrictive material 9 in a pulse magnetic field of 200 Hz with a period τ = 2.6 ms and a frequency. The calibration test was performed at room temperature (297 K, 23 ° C.). As shown in FIG. 9, the pulse magnetic field strength applied to the magnetostrictive material 9 was 1.4 T at the maximum as read on the horizontal axis. The magnetostriction generated in the magnetostrictive material 9 is shown to be 10% multiplied by%, and was 0.22% (2200 ppm) at the maximum. The output voltage from the lock-in amplifier 76 is proportional to the amount of magnetostriction generated in the magnetostrictive material 9. It can be considered that the vibration of magnetostriction after the pulse magnetic field returns to zero is the vibration caused by the double-sided tape used for fixing the magnetostrictive material 9 to the bakelite fixing base.

  The graph of FIG. 10 is a magnetic field-magnetostriction calibration curve as a result of an experiment using the apparatus system of FIG. The horizontal axis represents the strength of the maximum magnetic field applied to the magnetostrictive material 9, and the vertical axis represents the magnitude of the magnetostriction (displacement amount) generated in the magnetostrictive material 9. As can be seen from FIG. 10, a magnetic field of up to about 1.4 T could be applied to the magnetostrictive material 9 by the pulse magnet 71. In addition, even when the frequency of the alternating magnetic field applied to the magnetostrictive material 9 by the pulse magnet 71 is 80 Hz or 200 Hz, the displacement amount of the magnetostrictive material 9 is changed with respect to the change in the magnitude of the magnetic field applied to the magnetostrictive material 9. It can be seen that there is a range where the inclination increases. As described above, the magnetostrictive material 9 has a range of the strength of the magnetic field that can increase the amount of displacement. Therefore, by varying the strength of the magnetic field applied to the magnetostrictive material 9 in this range, the magnetostrictive material 9 is changed. It can be seen that the change in the amount of displacement can be increased. Therefore, the magnetic circuit of the present invention can be suitably used as an actuator by adopting a form in which a magnetic field having a strength in such a range can be applied to the magnetostrictive material. The magnetic circuit of the present invention can generate a magnetic field in the magnetic field concentration portion by the stationary magnetic field applying means and the variable magnetic field applying means. Therefore, for example, a stationary magnetic field having a lower limit strength of a magnetic field range in which the gradient of the displacement amount of the magnetostrictive material is increased by the stationary magnetic field application unit is generated in the magnetic field concentration portion, and the displacement gradient of the magnetostrictive material is changed by the variable magnetic field application unit. The amount of displacement of the magnetostrictive material arranged in the magnetic field concentration part can be easily fine-tuned by changing the strength of the magnetic field generated in the magnetic field concentration part within the range in which the magnetic field is large. It can be used suitably.

  By confirming the relationship between the strength of the magnetic field applied to the magnetostrictive material 9 by the calibration test and the magnitude of the magnetostriction generated in the magnetostrictive material 9, the magnitude of the magnetostriction generated in the magnetostrictive material 9 is changed to the magnetostrictive material 9. The strength of the applied magnetic field can be estimated. That is, the magnetic field applied to the magnetostrictive material 9 (the magnetic field of the magnetic circuit 10) is calculated from the magnitude of magnetostriction generated in the magnetostrictive material 9 when a magnetic field is applied to the magnetostrictive material 9 by the magnetic circuit 10 as described below. The strength of the magnetic field generated in the concentrated portion can be estimated.

(Performance evaluation of the magnetic circuit of the present invention)
An experimental apparatus 101 having the configuration shown in FIG. 11 was produced, and the performance of the magnetic circuit of the present invention was evaluated. In FIG. 11, the same components as those in FIG.

  The yoke 1 was made of a pure iron plate having a thickness of 2 mm. As for the dimensions of the yoke 1, the length in the vertical direction (L1 shown in FIG. 2) and the length in the left-right direction (L2 shown in FIG. 2) were each 100 mm. In the cutout portion formed in the magnetic field concentration portion 3, the width of the end portion of the yoke 1 (W1 shown in FIG. 3) is 3.0 mm, and the interval between the cutout portions (D shown in FIG. 3) is 6. 0.0 mm. The width of the portion where the coil 5 is provided (W2 shown in FIG. 2) was 10 mm. At the center of the notch portion formed in the magnetic field concentration portion 3, the magnetostrictive material 9 is 2 mm × 2 mm × length (length in the direction of expansion / contraction due to magnetostriction when no magnetic field is applied) 5.8 mm. The size of Terfenol-D (registered trademark) was installed. As the permanent magnet 4, a disk-type ferrite magnet having a thickness of 5 mm was used. In the experimental apparatus 101, two permanent magnets 4 were installed in the same manner as the actuator 100, and two similar permanent magnets 4 were placed on the annular portion 2 as shown in FIG. 10. With these four permanent magnets 4, a 0.3 T steady magnetic field could be generated in the magnetic field concentrating part 3. As the coil 5, a coil having a winding number of 10 using a polyester-coated copper wire having an outer diameter of 0.20 mm was used. As the power source 6 of the coil 5, an oscillator (manufactured by NF Circuit Block, WF1945) and an audio amplifier (manufactured by Marantz, PM5003) were used.

  The experimental apparatus 101 was produced as described above, and the magnetostriction generated in the magnetostrictive material 9 was measured. Magnetostriction is measured using strain gauge (manufactured by Kyowa Denki Co., Ltd.), strain gauge bridge (self-made, bridge power supply is 3.0V (two AA batteries in series)), amplifier for bridge circuit output amplification (Iwasaki Tsushinki Co., Ltd. "DA-2B" manufactured, the bridge output voltage was amplified 1000 times, and a digital oscilloscope ("BRINGO DS-8814" manufactured by Iwasaki Tsushinki Co., Ltd.) was used. The results are shown in FIG.

  In the upper graph of FIG. 12, the horizontal axis represents the time when the magnetic field is applied to the magnetostrictive material 9, and the vertical axis represents the output voltage from the speaker terminal of the audio amplifier. In the lower graph of FIG. 12, the horizontal axis represents the time during which a magnetic field is applied to the magnetostrictive material 9, and the vertical axis represents the magnitude of magnetostriction generated in the magnetostrictive material 9.

  As can be seen from FIG. 12, the magnetostriction of the magnetostrictive material 9 depends on the frequency of the alternating magnetic field applied to the magnetostrictive material 9, and can be displaced by about 680 ppm at the maximum. Since the magnetostrictive material 9 having a length of 6 mm was used in this experiment, the maximum displacement amount of the magnetostrictive material 9 was about 4.0 μm. Thus, if the magnetic circuit of the present invention was used, a large magnetostriction could be easily generated in the giant magnetostrictive material.

1, 1a, 1b, 1c Yoke 2, 2a, 2b, 2c Annular part 3, 3a, 3b, 3c Magnetic field concentrating part 4 Permanent magnet (stationary magnetic field applying means)
5 Coil 6 Power supply 7 Electromagnet (variable magnetic field application means)
9 Magnetostrictive material 10, 10a, 10b Magnetic circuit 100 Actuator 101 Experimental device

Claims (5)

A yoke having an annular portion formed in an annular shape, a stationary magnetic field applying means for applying a stationary magnetic field to the annular portion, and a variable magnetic field applying means capable of applying a magnetic field whose intensity can be changed to the annular portion,
A magnetic circuit, wherein the annular portion includes a magnetic field concentration portion formed narrower than other portions.   The magnetic circuit according to claim 1, wherein a part of the magnetic field concentration portion is cut out. The yoke includes a plurality of the annular portions;
3. The magnetic circuit according to claim 1, wherein the plurality of annular portions are arranged so that the magnetic field concentration portions provided in the plurality of annular portions are concentrated at one point. A magnetic circuit according to any one of claims 1 to 3,
And a magnetostrictive material disposed in the magnetic field concentration portion of the magnetic circuit.   The actuator according to claim 4, wherein the magnetostrictive material is a TbDyFe-based alloy.

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