JP2005177688A - Supermagnetostriction actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a supermagnetostriction actuator that is capable of realizing a broad band speaker with good low-pass properties in a speaker to vibrate the diaphram by the supermagnetostriction actuator. <P>SOLUTION: The supermanetostriction actuator is provided with a coil 37 to which the sound signal is supplied and columnar supermagnetostrictive elements 22, 23 with the mutually different diameters extensible through the magnetic field variation caused by the coil 37. The supermagnetostrictive elements 22, 23 are arranged in line on the same shaft and a movable rod 28 to vibrate the vibration plate 41 is connected with the free end of one end side. The size variation (vibration amplitude) in the low-pass can be emphasized by combining the supermagnetostrictive element 23 of small diameter of which the frequency properties of the supermagnetostriction value extends to the high region with the supermagnetostrictive element 22 of large diameter. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a giant magnetostrictive actuator used for vibrating a diaphragm to emit sound.

The giant magnetostrictive actuator uses a dimensional change (expansion / contraction) of the giant magnetostrictive element generated according to the strength of the magnetic field, and has recently attracted attention as a high speed, large displacement, high power actuator.
FIG. 6 shows an example of a conventional configuration of a speaker (a giant magnetostrictive speaker) using a giant magnetostrictive actuator as a sound vibration generation source. A coil 12 to which an audio signal is supplied into a housing 11 and a magnetic field generated by the coil 12 are shown. A columnar giant magnetostrictive element 13 that expands and contracts due to a change, a spring 14 that applies a load (prestress) in the compression direction to the giant magnetostrictive element 13, and a magnet (permanent magnet) 15 that applies a bias magnetic field to the giant magnetostrictive element 13 are housed. ing. In this example, the spring 14 is a disc spring.

A movable rod 16 is connected to the free end 13 a of the giant magnetostrictive element 13, and a diaphragm 17 is attached to the tip of the movable rod 16 protruding outside the housing 11. The movable rod 16 is displaced in accordance with the expansion and contraction of the giant magnetostrictive element 13, and accordingly, by supplying an audio signal to the coil 12, the displacement corresponding to the audio signal is transmitted to the diaphragm 17 via the movable rod 16. 17 vibrates and sound is radiated into the space. In FIG. 6, reference numeral 18 denotes a housing to which the housing 11 is fixed (see, for example, Patent Document 1).
JP-A-11-266696

By the way, although it is required that a wide range of sounds from low to high can be output evenly in a speaker, it is generally difficult to output a low-frequency sound. For this reason, a woofer is additionally used. ing. This also applies to the speaker using the above-described giant magnetostrictive actuator, and there is a problem that the low frequency characteristics are not good although the high characteristics can be obtained.
In view of this problem, an object of the present invention is to provide a giant magnetostrictive actuator for speakers capable of realizing a low reproduction characteristic and a wide reproduction frequency band.

According to the first aspect of the present invention, the giant magnetostrictive actuator used for oscillating the diaphragm to emit sound has a coil to which an audio signal is supplied and two diameters that expand and contract by a magnetic field change generated by the coil. Different columnar giant magnetostrictive elements are provided, the giant magnetostrictive elements are coaxially arranged in series, and a movable rod that vibrates the diaphragm is connected to a free end on one end side thereof.
According to the invention of claim 2, in the invention of claim 1, the compressive load is applied only to the first spring that applies a compressive load to both of the two giant magnetostrictive elements and to the one giant magnetostrictive element that has a larger diameter than the other. A second spring to be added is provided.

  In the invention of claim 3, in the invention of claim 2, the two giant magnetostrictive elements are accommodated in a case having the one giant magnetostrictive element on the bottom side and the top surface is opened, and the movable rod is placed on the top surface of the case. Between the inertia mass fixed on the inner bottom surface of the case and the one giant magnetostrictive element and between the two giant magnetostrictive elements and the other giant magnetostrictive element and the movable rod. Between the large diameter portion formed at the end, first, second and third magnets for applying a bias magnetic field to the giant magnetostrictive element are respectively interposed, and the first spring is between the large diameter portion and the lid. The second spring is sandwiched between a flange formed on the upper end of a cylindrical body mounted on the periphery of the second magnet so as to surround the other giant magnetostrictive element and a lid, and the cylindrical body And a bobbin housed in the case so as to surround one of the giant magnetostrictive elements. Serial coil is assumed to have been wound.

  In the invention of claim 4, in the invention of claim 2, the two giant magnetostrictive elements are accommodated in a case having the one giant magnetostrictive element on the bottom surface and the top surface is opened, and the movable rod is on the top surface of the case. Between the inertia mass fixed on the inner bottom surface of the case and the one giant magnetostrictive element and between the two giant magnetostrictive elements and the other giant magnetostrictive element and the movable rod. Between the large diameter portion formed at the end, first, second and third magnets for applying a bias magnetic field to the giant magnetostrictive element are respectively interposed, and the first spring is between the large diameter portion and the lid. The second spring is sandwiched between the peripheral edge of the second magnet and the lid, the first bobbin housed in the case so as to surround the one super magnetostrictive element, and the second magnet A second mounted on the second giant magnetostrictive element and positioned between the second spring; The coil is assumed to have been wound respectively on the bobbin.

In the invention of claim 5, in the invention of claim 2, the two giant magnetostrictive elements are accommodated in a case where the one giant magnetostrictive element is on the bottom side and the top surface is opened, and the movable rod is on the top surface of the case. Between the inertia mass fixed on the inner bottom surface of the case and the one giant magnetostrictive element, between the two giant magnetostrictive elements, and between the other giant magnetostrictive element and the movable rod. Between the large diameter portion formed at the end, first, second and third magnets for applying a bias magnetic field to the giant magnetostrictive element are respectively interposed, and the first spring is between the large diameter portion and the lid. And a second bobbin mounted on the periphery of the second magnet so as to surround the other giant magnetostrictive element and the first bobbin housed in the case so as to surround the one giant magnetostrictive element. The coil is wound around the bobbin, and the second spring is the second bobbin. It is those sandwiched between the upper surface and the lid of.
According to a sixth aspect of the present invention, in the third aspect of the present invention, a plurality of rods are formed at the upper end of the cylindrical body so as to surround the movable rod, and the tips of the rods are projected from the lid to the outside. The

  According to the present invention, it is possible to emphasize the vibration amplitude in the low range of the movable rod that vibrates the diaphragm, and thus it is possible to realize a wide-band speaker with good low-frequency characteristics.

The best mode for carrying out the present invention will be described by way of example with reference to the drawings.
FIG. 1 shows an embodiment of a giant magnetostrictive actuator for speakers according to the present invention. In this example, a giant magnetostrictive actuator 20 includes two cylindrical giant magnetostrictive elements 22 and 23 having different diameters in a case 21. It is supposed to be.
The case 21 has a cylindrical shape with one end open, and an inertial mass 24 is disposed on the inner bottom surface. A first magnet 25 is mounted in contact with the inertial mass 24, and super magnetostrictive elements 22 and 23 arranged in series on the same axis are mounted on the magnet 25. The giant magnetostrictive elements 22 and 23 have a large-diameter giant magnetostrictive element 22 on the bottom side of the case 21 and are positioned on the central axis of the case 21, and a second magnet is interposed between the giant magnetostrictive elements 22 and 23. The third magnet 27 is mounted on the small-diameter giant magnetostrictive element 23 located on the upper side. The inertial mass 24 has a disc shape and is fixed to the case 21 by, for example, adhesion, and the three magnets (permanent magnets) 25 to 27 for applying a bias magnetic field to the giant magnetostrictive elements 22 and 23 are also in a disc shape. Yes. The magnet 26 sandwiched between the two giant magnetostrictive elements 22 and 23 has a larger diameter than the giant magnetostrictive elements 22 and 23 as shown in FIG. 1B.

The giant magnetostrictive elements 22 and 23 arranged in series as described above have a fixed end at the lower end and a free end at the upper end, and a movable rod 28 is mounted on a magnet 27 arranged at the free end. The central axis of the movable rod 28 coincides with the central axis of the giant magnetostrictive elements 22, 23, and the tip side protrudes to the outside through a through hole 31 provided in the lid 29 that covers the open upper surface of the case 21. ing. A large-diameter portion 28a that contacts the magnet 27 is formed at the inner end of the movable rod 28, and the protruding tip portion 28b has a spherical shape in this example. In this example, the lid 29 is fixed and secured by a cap 32. The cap 32 and the case 21 are not shown in the drawing, but are fixed by, for example, screws at the cylindrical peripheral surface portion. In FIG. 1, 33 indicates an opening provided in the cap 32.
Two springs that apply a load (prestress) in the compression direction to the giant magnetostrictive elements 22 and 23 are provided, and the first spring 34 is sandwiched between the large-diameter portion 28a of the movable rod 28 and the inner surface of the lid 29. It is. The second spring 35 is disposed between the flange 36 a formed at the upper end of the cylindrical body 36 mounted on the periphery of the magnet 26 so as to surround the small-diameter giant magnetostrictive element 23 located on the upper side and the inner surface of the lid 29. In this example, the springs 34 and 35 are both constituted by compression coil springs.

By arranging the springs 34 and 35 in this way, a compressive load is applied to the large-diameter giant magnetostrictive element 22 by both the springs 34 and 35, and a compressive load is applied to the small-diameter giant magnetostrictive element 23 by one spring 34. Will be added.
A coil 37 to which an audio signal is supplied is wound around a bobbin 38 and accommodated in the case 21. The bobbin 38 is disposed so as to surround the large-diameter giant magnetostrictive element 22 and the cylindrical body 36, and the cylindrical part 38a is opposed to the giant magnetostrictive element 22 and the cylindrical body 36 with a slight gap therebetween. It has a step part 38b in the middle. The lower end surface of the bobbin 38 is mounted on the inertia mass 24 and fixed.
In the above structure, for example, PMS-1 manufactured by TDK Corporation can be used as the material of the giant magnetostrictive elements 22 and 23. The case 21, the bobbin 38, the cap 32, and the cylindrical body 36 are made of, for example, aluminum, and the movable rod 28 and the inertial mass 24 are made of, for example, brass. The lid 29 is made of, for example, resin.

Next, the characteristics of the giant magnetostrictive actuator 20 having a configuration in which the two giant magnetostrictive elements 22 and 23 having different diameters as shown in FIG. 1 are arranged in series on the same axis will be described.
FIG. 2 shows the shape dependence of the frequency characteristics of the magnetostrictive value of the giant magnetostrictive element. The horizontal axis represents the drive frequency, and the vertical axis represents the time when a magnetic field change of ± 0.5 kOe is applied to the giant magnetostrictive element. The magnetostriction value is expressed as a pp amplitude value (unit: ppm) by a dimensional change rate. The indication φ1 × 8 mm indicates that the diameter is 1 mm and the length is 8 mm.
As is apparent from FIG. 2, as the diameter of the giant magnetostrictive element is smaller, the frequency characteristic extends to a higher range, and the dimensional change rate in the lower range is independent of the diameter and length. Therefore, by combining the magnetostrictive elements having different diameters in series, it is possible to emphasize the dimensional change amount in the low range as compared with, for example, a single giant magnetostrictive element.

FIG. 3 shows the frequency characteristics of magnetostriction values when the magnetostrictive elements having different diameters are combined as described above. FIGS. 3A to 3C show φ10 × 10 mm and φ10 mm for the giant magnetostrictive element of φ6 × 20 mm, respectively. This shows a case where super magnetostrictive elements of × 20 mm and φ10 × 30 mm are combined. The vertical axis indicates the magnetostriction value when a magnetic field change of ± 0.5 kOe is given as an absolute value as a pp amplitude value (unit: μm).
As shown in FIG. 3, the amount of dimensional change in the low band can be emphasized (increased) by combining a giant magnetostrictive element having a larger diameter with one giant magnetostrictive element (φ6 × 20 mm), and By selecting the length of the large-diameter giant magnetostrictive element, it is possible to obtain a frequency characteristic in which the low frequency range is emphasized by a desired amount. In the embodiment shown in FIG. 1, the large-diameter giant magnetostrictive element 22 is φ10 × 20 mm, and the small-diameter giant magnetostrictive element 23 is φ6 × 20 mm.
According to the giant magnetostrictive actuator 20 having the above-described configuration, by supplying an audio signal to the coil 37, the giant magnetostrictive elements 22 and 23 expand and contract in accordance with the magnetic field generated by the coil 37. The movable rod 28 connected to the free ends 22 and 23 vibrates. Therefore, when the diaphragm 41 is vibrated by the movable rod 28, the diaphragm 41 emits sound into the space.

The vibration of the movable rod 28 is an addition of the dimensional changes of the two giant magnetostrictive elements 22 and 23, that is, the low-frequency amplitude is emphasized, so that the vibration of the movable rod 28 is higher than that of the speaker using the conventional giant magnetostrictive actuator shown in FIG. The amplitude of the vibration plate 41 in the low frequency range can be relatively increased. Therefore, if this giant magnetostrictive actuator 20 is used, a low-frequency characteristic and a wide-band speaker can be realized.
Although it is necessary to apply an appropriate compressive load (prestress) according to the cross-sectional area of the giant magnetostrictive elements 22 and 23, this example includes two springs 34 and 35, which are shown in FIG. Thus, the compressive load can be optimally applied to the two giant magnetostrictive elements 22 and 23, respectively.
In the giant magnetostrictive actuator 20 described above, the movable rod 28 is not fixed to the diaphragm 41, and the entire giant magnetostrictive actuator 20 is pressed against the diaphragm 41 by a pressing means (not shown), so that the movable rod 28 contacts the diaphragm 41 in a required contact. Although contact is made by pressure and vibration is transmitted, for example, the vibration plate 41 may be attached and fixed to the movable rod 28. The giant magnetostrictive actuator 20 having a structure in which the movable rod 28 is pressed and contacted with the diaphragm 41 as shown in FIG. 1 is used, for example, when an existing structure functions as a diaphragm. For example, there is a case where a hollow columnar body is used as a diaphragm and the giant magnetostrictive actuator 20 is accommodated in the columnar body.

4A and 4B show other embodiments of the giant magnetostrictive actuator according to the present invention, and the same reference numerals are given to the portions corresponding to those in FIG.
The giant magnetostrictive actuator 50 shown in FIG. 4A has two bobbins around which a coil 37 to which an audio signal is supplied is wound, and the first bobbin 51 surrounds the large-diameter giant magnetostrictive element 22. The second bobbin 52 is mounted and fixed on a magnet 26 sandwiched between the giant magnetostrictive elements 22 and 23 so as to surround the small-diameter giant magnetostrictive element 23. The spring 35 that applies a compressive load only to the large-diameter giant magnetostrictive element 22 is a compression coil spring. In this example, the spring 35 is sandwiched between the peripheral edge of the magnet 26 and the inner surface of the lid 29. A bobbin 52 around which 37 is wound is positioned between the spring 35 and the giant magnetostrictive element 23.
The giant magnetostrictive actuator 60 shown in FIG. 4B has two bobbins 51 and 52 like the giant magnetostrictive actuator 50 shown in FIG. 4A. However, the arrangement of the spring 35 is different from FIG. The structure is sandwiched between the upper end surface and the inner surface of the lid 29. In this example, the compressive load by the spring 35 is applied to the large-diameter giant magnetostrictive element 22 via the bobbin 52 and the magnet 26. The arrangement of the springs 35 is not limited to the arrangement structure shown in FIG. 1, but may be an arrangement structure as shown in FIGS. 4A and 4B. In the giant magnetostrictive actuators 50 and 60 shown in FIGS. 4A and 4B, the coil 37 for changing the magnetic field can be disposed closer to the giant magnetostrictive element 23 having a small diameter.

Next, the structure of the giant magnetostrictive actuator shown in FIG. 5 will be described.
The giant magnetostrictive actuator 70 shown in FIG. 5 is formed by projecting a rod 36b on the upper end of the cylindrical body 36 of the giant magnetostrictive actuator 20 shown in FIG. Rods 36b are formed at equiangular intervals. These rods 36 b are protruded to the outside through the through holes 71 formed in the lid 29, and the protruding tip surfaces 36 c are spherical like the movable rod 28. The protruding height of the rod 36b is set lower than the protruding height of the movable rod 28. Further, the opening 33 of the cap 32 is made larger than that in FIG. 1 so as not to prevent the protrusion of the rod 36b.

  In the giant magnetostrictive actuator 70 configured as described above, in addition to the movable rod 28 that vibrates due to the added dimensional change of the giant magnetostrictive elements 22 and 23, the rod 36b that vibrates only due to the dimensional change of the large-diameter giant magnetostrictive element 22. The vibration of the rod 36b has a large amplitude in the low range. Therefore, in addition to the vibration plate 41, for example, as shown in FIG. 5, a low frequency range vibration plate 42 is added and the vibration plate 42 is vibrated by the three rods 36b. A speaker can be realized. The diaphragm 42 is provided with a through hole 43 for the movable rod 28. The diaphragm 42 for the low sound range has a high rigidity and is thin and has a large area.

The figure which shows one Example of the giant magnetostrictive actuator by this invention, A is a top view, B is sectional drawing. The graph which shows the frequency characteristic of the magnetostriction value of a giant magnetostrictive element. Graphs showing frequency characteristics of magnetostriction values when combining giant magnetostrictive elements having different diameters, A to C show cases where the length of the giant magnetostrictive element having a large diameter (φ10 mm) is changed. A and B are sectional views showing other embodiments of the giant magnetostrictive actuator according to the present invention. The figure which shows the example which added the rod which vibrates the diaphragm for low frequencies with respect to the giant magnetostrictive actuator shown in FIG. 1, A is a top view, B is sectional drawing shown with the diaphragm. Sectional drawing which shows the structure of the speaker using the conventional giant magnetostrictive actuator.

Claims (6)

A giant magnetostrictive actuator used to radiate sound by vibrating a diaphragm,
A coil to which an audio signal is supplied;
Two columnar giant magnetostrictive elements having different diameters that expand and contract due to a magnetic field change generated by the coil;
A giant magnetostrictive actuator, wherein the giant magnetostrictive elements are arranged in series on the same axis, and a movable rod that vibrates the diaphragm is connected to a free end of the giant magnetostrictive element. The giant magnetostrictive actuator according to claim 1, wherein
A first spring that applies a compressive load to both of the two giant magnetostrictive elements and a second spring that applies a compressive load only to one giant magnetostrictive element having a larger diameter than the other are provided. Giant magnetostrictive actuator. The giant magnetostrictive actuator according to claim 2, wherein
The two giant magnetostrictive elements are housed in a case in which the one giant magnetostrictive element is on the bottom side and the top surface is opened,
The movable rod has a tip protruding outward from a lid that covers the upper surface of the case,
A large-diameter portion formed between the inertial mass fixed on the inner bottom surface of the case and the one giant magnetostrictive element, between the two giant magnetostrictive elements, and the other giant magnetostrictive element and the inner end of the movable rod; Between the first, second and third magnets for applying a bias magnetic field to the giant magnetostrictive element,
The first spring is sandwiched between the large diameter portion and the lid,
The second spring is sandwiched between a flange formed on the upper end of a cylindrical body mounted on the periphery of the second magnet so as to surround the other giant magnetostrictive element and the lid,
A giant magnetostrictive actuator, wherein the coil is wound around a bobbin accommodated in the case so as to surround the cylindrical body and one giant magnetostrictive element. The giant magnetostrictive actuator according to claim 2, wherein
The two giant magnetostrictive elements are housed in a case in which the one giant magnetostrictive element is on the bottom side and the top surface is opened,
The movable rod has a tip protruding outward from a lid that covers the upper surface of the case,
A large-diameter portion formed between the inertial mass fixed on the inner bottom surface of the case and the one giant magnetostrictive element, between the two giant magnetostrictive elements, and the other giant magnetostrictive element and the inner end of the movable rod; Between the first, second and third magnets for applying a bias magnetic field to the giant magnetostrictive element,
The first spring is sandwiched between the large diameter portion and the lid,
The second spring is sandwiched between the peripheral edge of the second magnet and the lid,
A first bobbin housed in the case so as to surround the one giant magnetostrictive element, and mounted between the second giant magnetostrictive element and the second spring mounted on the second magnet. A giant magnetostrictive actuator, wherein the coil is wound around each of the second bobbins. The giant magnetostrictive actuator according to claim 2, wherein
The two giant magnetostrictive elements are housed in a case in which the one giant magnetostrictive element is on the bottom side and the top surface is opened,
The movable rod has a tip protruding outward from a lid that covers the upper surface of the case,
A large-diameter portion formed between the inertial mass fixed on the inner bottom surface of the case and the one giant magnetostrictive element, between the two giant magnetostrictive elements, and the other giant magnetostrictive element and the inner end of the movable rod; Between the first, second and third magnets for applying a bias magnetic field to the giant magnetostrictive element,
The first spring is sandwiched between the large diameter portion and the lid,
A first bobbin housed in the case so as to surround the one giant magnetostrictive element, and a second bobbin mounted on the periphery of the second magnet so as to surround the other giant magnetostrictive element; Each of the above coils is wound on
The giant magnetostrictive actuator, wherein the second spring is sandwiched between an upper end surface of the second bobbin and the lid. The giant magnetostrictive actuator according to claim 3, wherein
At the upper end of the cylindrical body, a plurality of rods are formed so as to surround the movable rod,
A giant magnetostrictive actuator characterized in that the tips of the rods protrude outward from the lid.

Images