JP2009105532A - Loudspeaker system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a loudspeaker system capable of reducing wear in an acoustic diaphragm, and maintaining stable tone quality and a volume, even if a sound is reproduced for a long time. <P>SOLUTION: A cushion member 35 is formed in a cap shape using a material such as an ETFE (tetrafluoroethylene-ethylene copolymer) etc., of which the Durometer D is within a range of 30-75. The cushion member 35 is installed at the tip of a driving rod 31 of a magneto-striction actuator 30. The magneto-striction actuator 30 is driven, and the displacement of the driving rod 31 is delivered to the acoustic diaphragm 10. Then, the acoustic diaphragm 10 is vibrated, and the sound is reproduced. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a speaker system that reproduces sound by applying vibration to an acoustic diaphragm by a drive rod of an actuator such as a magnetostrictive actuator.

  As disclosed in Patent Document 1 (Japanese Patent Application Laid-Open No. 2007-166027), for example, a cylindrical acoustic diaphragm made of acrylic is vertically installed and attached to the base casing, and the lower end of the acoustic diaphragm is installed in the base casing. Sound is reproduced by placing an actuator driven by an audio signal on the side, bringing the tip of the actuator drive rod into contact with the lower end surface of the acoustic diaphragm, and applying vibration in the direction of the plate surface to the acoustic diaphragm A speaker system is considered.

  In this speaker system, the lower end surface of the acoustic diaphragm is excited by a longitudinal wave, but the vibrational acoustic wave propagates in the direction of the surface of the acoustic diaphragm, resulting in a mixed wave of longitudinal and transverse waves. Sound waves are radiated by transverse waves in a direction perpendicular to the plate surface of the plate, and a sound field with a sense of spread can be obtained.

  In addition, as an actuator in this case, a magnetostrictive actuator using a magnetostrictive element whose shape changes when an external magnetic field is applied can be used. The magnetostrictive element generates a large amount of stress when its shape changes, so even with a small magnetostrictive actuator, the acoustic diaphragm can be sounded at a relatively high volume, and a hard acoustic diaphragm such as an iron plate can be used. Can even sound.

  Furthermore, the magnetostrictive actuator is excellent in response speed, and the response speed of the magnetostrictive element alone is on the order of nanoseconds.

  The following Non-Patent Document 1 shows “softness” of a material called Hytrel (registered trademark) which is a kind of rubber elastic body (elastomer).

The prior art documents listed above are as follows.
JP 2007-166027 A What is Toray DuPont Co., Ltd., Product Guide, Hytrel, Hytrel? Comparison with rubber and plastic, [Search September 12, 2007], Internet <URL: http://www.td-net.co.jp/hytrel/about/comparison.html>

  However, in the above speaker system, when the acoustic diaphragm is vibrated for a long time by the actuator, the portion of the acoustic diaphragm where the drive rod of the actuator abuts is worn, and the sound quality and volume change.

  FIG. 6 shows the test results. This is because the tip of the iron drive rod of the magnetostrictive actuator is brought into contact with the lower end surface 12 of the acoustic diaphragm 10 made of acrylic, and a music signal having a peak voltage of 6 to 7 Vrms is input to the magnetostrictive actuator as a drive signal, A portion where the drive rod is in contact with the lower end surface 12 of the acoustic diaphragm 10 when the acoustic diaphragm 10 is vibrated for 1000 hours is photographed.

  The central black circular portion 12a is a concave portion of the lower end surface 12 of the acoustic diaphragm 10 that has been worn by being pushed up by the drive rod, and its depth, that is, the amount of wear, was about 10 μm.

  Therefore, the present invention is capable of reducing wear of the acoustic diaphragm and maintaining stable sound quality and volume even when sound is reproduced for a long time.

The speaker system of this invention is
An acoustic diaphragm, and an actuator that applies vibration to the acoustic diaphragm by a drive rod;
A shock-absorbing member is provided at the tip of the drive rod that contacts the acoustic diaphragm.

  According to the present invention, wear of the acoustic diaphragm can be reduced, and stable sound quality and volume can be maintained even when sound is reproduced for a long time.

[1. One Embodiment of Speaker System: FIGS. 1 to 5]
(1-1. Configuration of speaker system: FIGS. 1 to 3)
FIG. 1 shows an example of the speaker system of the present invention. FIG. 1A is a top view (viewed from above), and FIG. 1B is the line in FIG. It is the side view which made the BB part the cross section.

  The speaker system of this example includes an acoustic diaphragm 10, a base housing 20, and a magnetostrictive actuator 30.

  The acoustic diaphragm 10 is formed into a cylindrical shape having openings at both ends, for example, with acrylic, and has a thickness of 2 mm, a diameter of 10 cm, and a length (height) of 100 cm.

  The base housing 20 is formed in a disc shape having a certain height (thickness) with an outer diameter larger than the outer diameter of the acoustic diaphragm 10 by, for example, synthetic resin, and at the bottom side thereof, equiangular intervals are formed. Legs 21 are formed at three positions.

  The acoustic diaphragm 10 has a ring-shaped end surface at one end as an upper end surface 11, a ring-shaped end surface at the other end as a lower end surface 12, an axial direction thereof as a vertical direction, and a central axis as a center axis of the base casing 20. It is attached to the upper surface of the base casing 20 so as to be aligned with the central axis.

  Specifically, a damping material 42 made of silicon rubber is interposed between one end of the L-shaped angle 41 and the base casing 20 at four positions at equiangular intervals on the upper surface of the base casing 20. The screw 43 is attached to the base housing 20, and damping materials 44 and 45 made of silicon rubber are interposed inside and outside the acoustic diaphragm 10, respectively, and the other end of the L-shaped angle 41 is connected to the screw 46 and The nut 47 is attached to the lower end of the acoustic diaphragm 10.

  Thus, by attaching the acoustic diaphragm 10 to the base casing 20 via the damping members 44, 45 and 42, the vibration of the acoustic diaphragm 10 propagates to the base casing 20 and a sound image is generated on the base casing 20 side. Localization can be prevented.

  Furthermore, in the base housing 20, storage holes 23 penetrating in the vertical direction are formed at four positions at equiangular intervals between the mounting positions of the L-shaped angle 41, and magnetostriction is formed in each of the storage holes 23. The actuator 30 is inserted from the lower side with the drive rod 31 facing upward, and the leaf spring 32 at the lower end is attached to the base casing 20 with screws 33 and 34 to fix the magnetostrictive actuator 30 to the base casing 20.

  The magnetostrictive actuator 30 includes a solenoid coil for applying a control magnetic field disposed around a rod-shaped magnetostrictive element, and an iron driving rod 31 connected to one end of the magnetostrictive element, and a control current flows through the solenoid coil. Thus, a control magnetic field is generated, the control magnetic field is applied to the magnetostrictive element, the magnetostrictive element is displaced in the vertical direction, and the drive rod 31 is displaced in the vertical direction.

  Then, a buffer member 35 is provided at the tip of the drive rod 31 of the magnetostrictive actuator 30 that contacts the lower end surface 12 of the acoustic diaphragm 10.

  The buffer member 35 is formed of a material as described below, for example, in a cap shape as shown in FIG. 2, and loaded on the tip of the drive rod 31, or in a sheet shape as shown in FIG. After forming, the adhesive 36 is attached to the front end surface of the drive rod 31.

  Compared to the case where it is formed in a cap shape as shown in FIG. 2 and loaded into the drive rod 31, and the case where it is formed in a sheet shape and attached to the drive rod 31 as shown in FIG. In view of the fact that it can be easily removed from the drive rod 31, it is desirable to form the cap like the former and load the drive rod 31.

  When the thickness of the buffer member 35 is large, the sound quality is changed by the buffer member 35 coming into contact with the lower end surface 12 of the acoustic diaphragm 10, and therefore the thickness of the buffer member 35 is set to a number of commas or less.

  As shown in FIG. 1B, a damping material 13 made of silicon rubber or the like is provided between the lower end surface 12 of the acoustic diaphragm 10 and the upper surface of the base housing 20 at a position other than the position of the storage hole 23. Intervene.

  Accordingly, the degree of sealing between the acoustic diaphragm 10 and the base casing 20 can be increased, and the acoustic diaphragm 10 can function well as a resonance tube. Propagation can be prevented.

  In the speaker system having the above configuration, when an audio signal is supplied as a control current to the solenoid coil of the magnetostrictive actuator 30, the magnetostrictive elements constituting the magnetostrictive actuator 30 are displaced in the vertical direction in accordance with the audio signal, and the drive rod 31 is moved up and down. Displacement in the direction causes vibration to be applied to the lower end surface 12 of the acoustic diaphragm 10.

  The lower end surface 12 of the acoustic diaphragm 10 is excited by a longitudinal wave. However, the vibration elastic wave propagates in the direction of the surface of the acoustic diaphragm 10, so that a longitudinal wave and a transverse wave are mixed. Sound waves are radiated by transverse waves in a direction perpendicular to the plate surface, and a sound field with a sense of spread is obtained.

  It is possible to obtain omnidirectionality by driving each magnetostrictive actuator 30 with the same audio signal, but each magnetostrictive actuator 30 was obtained from an audio signal of a different channel or the same audio signal. By driving with audio signals having different levels, delay times, or frequency characteristics, it is possible to obtain a more spacious sound field.

  As shown in FIG. 1A, the central portion of the base housing 20 is an opening 25, and a speaker unit of a dynamic speaker is attached to the opening 25 with, for example, the front side of the speaker facing downward. The diaphragm 10 and the magnetostrictive actuator 30 can function as a tweeter that handles the high frequency side of the audible frequency band, and the dynamic speaker can function as a woofer that handles the low frequency side of the audible frequency band.

(1-2. Buffer member material: FIGS. 4 and 5)
The buffer member 35 may basically be formed of a material softer than the material of the drive rod 31 and the acoustic diaphragm 10 as a means for reducing the impact of the drive rod 31 on the acoustic diaphragm 10.

  However, if the buffer member 35 is too soft, the compression deflection becomes large, the transmission force of the excitation to the acoustic diaphragm 10 is reduced, and the sound pressure is reduced.

  On the contrary, even if it is softer than the material of the drive rod 31 and the acoustic diaphragm 10, if the buffer member 35 is harder than a certain value, the adhesion becomes poor, and the transmission force of excitation to the acoustic diaphragm 10 is reduced. Sound pressure drops.

  Considering the above points, as a material of the buffer member 35, as indicated by an arrow in FIG. 4, the durometer D, which is one of the measures of softness (hardness), is in the range of 30 to 75. A (hardness) material is preferred.

  A general polypropylene has a durometer D of 75 to 80 and is relatively hard and has a small compression deflection, but its adhesion is poor, and the transmission force of excitation to the acoustic diaphragm 10 is reduced, so that the sound pressure is reduced. Is not suitable as a material for the buffer member 35.

  Styrene butadiene rubber (SBR) has a durometer D of 20 to 30 and is relatively soft and has good adhesion, but has a large compression deflection, and the transmission force of excitation to the acoustic diaphragm 10 is reduced. Since sound pressure falls, it is not suitable as a material of the buffer member 35.

  On the other hand, when the durometer D is in the range of 30 to 75, the compression deflection is small and the adhesion is good.

  Examples of materials having a durometer D in the range of 30 to 75 include impact-resistant polypropylene and ETFE (tetrafluoroethylene / ethylene copolymer) which is one of fluororesins.

  The impact resistant polypropylene has a durometer D of 50 to 60 and is suitable as a material for the buffer member 35 in terms of softness. However, impact resistant polypropylene has poor heat resistance.

  On the other hand, ETFE has a durometer D of 50 to 60, has a certain degree of elasticity, is excellent in adhesion and is not brittle, and has a heat resistance temperature of about 300 ° C. and excellent heat resistance. ing. Therefore, ETFE is more suitable as the material of the buffer member 35 and is optimal.

  In addition, Hytrel (registered trademark) of Toray DuPont Co., Ltd. shown in Non-Patent Document 1 is suitable as a material for the buffer member 35 because the durometer D is 30 to 75.

  FIG. 5 shows the test results. This is because the buffer member 35 is formed into a cap shape having a thickness of 0.2 mm by ETFE, is loaded on the iron drive rod 31 of the magnetostrictive actuator 30, and contacts the lower end surface 12 of the acoustic diaphragm 10 made of acrylic. As in the test of the test result of FIG. 6, the acoustic diaphragm when the music signal having a peak voltage of 6 to 7 Vrms is input to the magnetostrictive actuator 30 as the drive signal and the acoustic diaphragm 10 is vibrated for 1000 hours. A portion where the buffer member 35 of the lower end surface 12 of 10 is in contact is photographed.

  As shown in FIG. 5, the lower end surface 12 of the acoustic diaphragm 10 did not show any dents at the place where the buffer member 35 was in contact, and no wear was observed. There was no change in sound quality.

[2. Other Embodiments]
The above example is a case where both ends of the acoustic diaphragm 10 are openings, but the upper end side of the acoustic diaphragm may be bottomed. In the case where the upper end side is a bottomed one, sound waves are also emitted from the bottom portion on the upper end side, and it is possible to further enhance the sense of spread of the sound image.

  In addition, the acoustic diaphragm is not limited to a cylindrical shape, and may be formed in a cylindrical shape such as a square or a hexagon, a flat plate shape, a spherical shape, or a conical shape.

  Further, the material of the acoustic diaphragm is not limited to acrylic, and glass or the like can be used.

  Further, the actuator is not limited to the magnetostrictive actuator using the magnetostrictive element, but may be one using other elements.

It is a figure which shows an example of the speaker system of this invention. It is a figure which shows the case where a buffer member is made into a cap shape. It is a figure which shows the case where a buffer member is made into a sheet form. It is a figure which shows the range of the softness suitable as a buffer member. It is a figure which shows the test result of an example of the speaker system of this invention. It is a figure which shows the test result of an example of the conventional speaker system.

Explanation of symbols

  Since all the main parts are described in the figure, they are omitted here.

Claims (5)

An acoustic diaphragm, and an actuator that applies vibration to the acoustic diaphragm by a drive rod;
A speaker system, wherein a buffer member is provided at a tip portion of the drive rod that contacts the acoustic diaphragm. The speaker system according to claim 1, wherein
The speaker system, wherein the buffer member is made of a material having a durometer D in the range of 30 to 75. The speaker system according to claim 1, wherein
The speaker system according to claim 1, wherein the buffer member has a cap shape and is mounted on a tip portion of the drive rod. The speaker system according to claim 1, wherein
The speaker system, wherein the drive rod applies vibrations in a direction orthogonal to an end face of the acoustic diaphragm. The speaker system according to claim 1, wherein
A speaker system, wherein the actuator is a magnetostrictive actuator.