JP2014199991A - Speaker device and design method therefor - Google Patents

Abstract

A speaker device capable of functioning as a sounding body by attaching electric field driven polymer films to each other without using a diaphragm is provided. A speaker device according to the present invention includes a circular electric field driven polymer film (12, 13), a conductor (13, 23) along a circumference of the electric field driven polymer film, and the electric field. Two sound generating units (10, 20) having a driving polymer film and a frame (11, 21) for sandwiching the conducting wire, the two sound generating units (10, 20) being arranged to face each other, The two sound generating units are supported by a spacer 30 and the center portions of the electric field driven polymer films (12, 22) of the two sound generating units (10, 20) are bonded together to form a joint 40. . [Selection] Figure 1

Description

  The present invention relates to a speaker device and a method for designing the speaker device, and more particularly to a speaker device using an electric field driven polymer and a method for designing the speaker device.

  Currently, the development of sound field reproduction technology is being promoted internationally as one of the next generation acoustic technologies. The purpose of sound field reproduction technology is to reproduce the sound field recorded in a space such as a concert hall in a completely different space such as a home and provide the listener with a sense of presence as if they were there. It is said. So far, sound field reproduction technologies based on various theoretical backgrounds such as multi-channel sound, boundary sound field control, wavefront synthesis, and higher-order ambisonics have been proposed, and there are a wide range of groups involved in development (non- Patent Document 1).

  In general, it is a major premise that an acoustic signal generated by a sound field reproduction technique is finally radiated into the air via a speaker. The sound field reproduction technique is based on the principle that the number of sound generation points increases with the advancement of processing, and requires a large number of speakers. However, the most commonly used loudspeaker is the electrodynamic type that has been used for more than a century since the invention of the principle, and as long as this structure consisting of coils and magnets is used, the increase in the weight and depth of the loudspeaker should be avoided. I can't. Sound generators using piezoelectric materials such as piezoelectric ceramics are suitable for miniaturization, but because the reproduction frequency band is narrow and the harmonic distortion rate is high, sound field reproduction technology that requires high-quality reproduction sound is not suitable. It is unsuitable.

  By the way, in order to realize a flexible actuator, an electric field driven polymer having electric field response has been actively studied in recent years (Non-patent Document 2). The characteristic of the electric field driven polymer is the deformation of the material due to the application of voltage, but using the electric field driven polymer as a sounding body pays attention to the possibility of realizing a speaker that greatly overturns the conventional speaker concept (Non-Patent Document 3). In addition, when an electric field driving polymer is used for a speaker, it is becoming clear that a high-quality reproduced sound can be obtained by using a push-pull type (Non-patent Document 4).

  Development of a speaker using an electric field driven polymer is also progressing (Non-Patent Document 5). The speaker using the electric field drive type elastomer described in Non-Patent Document 5 includes two units in which a diaphragm is arranged at the center of the electric field drive type elastomer surrounded by a circular frame, with the two units facing each other. A push-pull structure is realized by bonding the diaphragms together and inserting spacers between the frames. When a normal phase / reverse phase acoustic signal is applied to each electric field driven elastomer, each electric field driven elastomer expands and contracts, the diaphragm vibrates, and sound is emitted into the air.

Ando, `` High Realistic Acoustic Technology and Its Theory '', IEICE Fundamentals Review, Vol.3, No.4, pp.33-46, April 2010. Nagata, `` Frontier of Soft Actuator Development '', NTS, October 2004. T. Sugimoto, K. Ono, A. Ando, Y. Morita, K. Hosoda, and D. Ishii, “Semicylindrical acoustic transducer from a dielectric elastomer film with compliant electrodes, 'J. Acoust. Soc. Am., Vol. 130, No.2, pp. 744-752, 2011. T.Sugimoto, K.Ono., A.Ando, S.Chiba, M.Waki, and K.Kurozumi, “Sound generator structure for low-elastic electroactive polymer, 'Acoust. Sci. & Tech., Vol. 31, No.6, pp.411-413, 2010. Sugimoto, “Push-pull type sounding body using electric field driven elastomer”, Acoustical Society of Japan, 1-5-19, pp.697-698, March 2010 Kawamura, "Introduction to Electroacoustic Engineering", Shosodo, 1971 R.M.Aarts and A.J.E.M.Janssen, “Approximation of the Struve function H1 occurring in impedance calculations,” J.Acoust.Soc.Am. 113, 2635-2637, 2003.

  Here, since the speaker described in Non-Patent Document 5 is provided with a diaphragm made of a material different from the electric field driven elastomer at the center of the electric field driven elastomer, a high voltage / current is required for driving due to the weight of the diaphragm. There was a problem.

  Accordingly, an object of the present invention made in view of such a point is to provide a speaker device capable of sound generation by an electric field driven polymer without using a diaphragm and a design method thereof.

  In order to solve the above-mentioned problems, a speaker device according to the present invention includes a circular electric field driving polymer film, a conductor along the circumference of the electric field driving polymer film, and the electric field driving polymer film. And two sounding units having a frame for sandwiching the conducting wire, the two sounding units are arranged to face each other, and are supported by a spacer between the two sounding units. The center portion of the electric field driven polymer film is bonded to form a joint portion.

  In addition, the speaker device design method according to the present invention uses the material constant of the electric field driven polymer film, the radius of the speaker device, which is the size of the speaker device, and the radius of the joint as parameters. The speaker device that achieves desired sound pressure / frequency characteristics is designed by a model function of sound pressure.

  In the model function, it is preferable that a material constant of the electric field driving polymer film and a radius and a depth of the speaker device are fixed and a radius of the joint that realizes the desired sound pressure is obtained.

  Moreover, it is preferable that the said model function is what made the thickness of the said electric field drive type polymer film uniform at the time of a drive.

  Moreover, it is preferable that the said model function is what fixed the angle which the said electric field drive type polymer film and the said junction part make at the time of a drive.

  According to the speaker device and the design method according to the present invention, it is possible to provide a speaker device that can produce sound using an electric field driven polymer without using a diaphragm.

It is a figure which shows the structure of the speaker apparatus which concerns on one Embodiment of this invention. It is a figure which shows the exploded view of the unit which comprises a speaker apparatus. It is sectional drawing for demonstrating the sound emission operation | movement of a speaker apparatus. It is an enlarged view of an electric field drive type polymer film. It is a figure which shows the simulation result of the change of the frequency characteristic by this invention.

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

  FIG. 1 is a diagram showing a structure of a speaker device according to an embodiment of the present invention. The speaker device includes two sounding units (the sounding unit 10 and the sounding unit 20). The sounding unit 10 is configured to surround the electric field driving polymer film 12 with a frame 11, and the sounding unit 20 includes an electric field driving polymer film 22 as a frame. 21. For convenience of explanation, the sound generation unit 10 and the sound generation unit 20 are denoted by different reference numerals, but the sound generation unit 10 and the sound generation unit 20 have the same configuration, and the frame 11 and the frame 21, the electric field driven polymer. The film 12 and the electric field driven polymer film 22 are each made of the same material. The sound generation unit 10 and the sound generation unit 20 are arranged to face each other, and the space between the sound generation unit 10 and the sound generation unit 20 is supported by a spacer 30. The central portions of the electric field drive type polymer film 12 of the sound generation unit 10 and the electric field drive type polymer film 22 of the sound generation unit 20 are bonded together with an adhesive or the like to form a joint 40.

  FIG. 2 is an exploded view of the sound generation unit constituting the speaker device. Note that FIG. 2 shows an exploded view of the sounding unit 10, but the sounding unit 10 and the sounding unit 20 have the same configuration as described above. The sound generation unit 10 includes a circular electric field driving polymer film 12, and an upper conductor 13a and a lower conductor 13b along the circumference of the electric field driving polymer film 12 (hereinafter referred to as an upper conductor 13a and a lower conductor 13b). Collectively referred to as “conductive wire 13” as appropriate), and an electric field driven polymer film 12 and an upper frame 11a and a lower frame 11b forming a frame 11 for sandwiching the conductive wire 13. The conducting wire 13 is formed in a shape along the circumference of the electric field driving polymer film 12 so that a driving signal is evenly applied to the electric field driving polymer film 12. The sounding unit 10 is formed by sandwiching an electric field driven polymer film 12 in which the upper conductor 13a and the lower conductor 13b are vertically stacked between the upper frame 11a and the lower frame 11b.

  Here, as a polymer material used as an electric field driving type polymer film, the smaller the volume change accompanying the shape change, the better. For example, the Poisson's ratio of the material used is preferably closer to 0.5. Examples of the polymer material include elastomers such as polyurethane, acrylic, silicon, and polypropylene.

  FIG. 3 is a cross-sectional view for explaining the sound generation operation of the speaker device. A normal phase / reverse phase drive signal is applied to the sound generation unit 10 and the sound generation unit 20 facing each other. In the case of FIG. 3, a positive phase drive signal is applied to the electric field driven polymer film 12 of the sound generation unit 10 through the conductive wire 13, and a reverse phase is applied to the electric field drive polymer film 22 of the sound generation unit 20 through the conductive wire 23. The drive signal is applied. When a driving signal is applied, the electric field driving polymer film 12 and the electric field driving polymer film 22 expand and contract, and the electric field driving polymer film 12 and the electric field driving polymer film 22 are bonded to each other. The joint 40 vibrates in the vertical direction. Sound is emitted into the air by such vibration, and the speaker device functions as a push-pull type speaker device.

  As described above, according to the present embodiment, two sounding units each having an electric field driven polymer film are arranged to face each other, and the center portion of each electric field driven polymer film is bonded to form a joint portion. The speaker device can function as a push-pull type sounding body without using a diaphragm made of a material different from that of the electric field driven polymer film. Further, by forming the conducting wire 13 in a shape along the circumference of the electric field driving polymer film 12, it becomes possible to apply a driving signal to the electric field driving polymer film 12 evenly.

  Here, the examination about the design method of the speaker apparatus using the above electric field drive type polymer films has not been performed yet. For practical use, for example, a design method for realizing a desired sound pressure is required in a speaker device of a prescribed size. Hereinafter, a method for designing a speaker device using an electric field driven polymer film will be described in detail.

First, from FIG. 3, the elongation Δr of the electric field driven polymer film in the radial direction of the speaker device is expressed by the equation (1), where θ is the angle formed by the electric field driven polymer film and the joint. The angle θ is defined by the radius R + r of the speaker device (the inner periphery of the frame), which is the size of the speaker device, the depth (r · tan θ: half of the spacer length in FIG. 3), and the radius r of the joint. is there.

FIG. 4 is an enlarged view of the electric field driven polymer film, and the central angle is α. If the tension is F _α , and the Young's modulus of the electric field driven polymer is Y, Δr is expressed by equation (2).

Here, d is the initial value of the thickness of the electric field driven polymer film, x is the length in the radial direction of the electric field driven polymer film excluding the joint, and A (x) is a cross-sectional area given by dα (R + x). It is. Here, the entire value F _T of tension along the major axis direction of the speaker device is represented by the formula (3).

From the above, the stiffness s of the push-pull type speaker device is expressed by Expression (4).

Next, for the sake of simplicity, in the push-pull type speaker device, it is assumed that the thickness d _pp of the electric field driven polymer film during driving is uniform, and d _pp = d · cos θ is set. Here, when the change u along the radial direction of the electric field driven polymer film is expressed by the applied voltage V, it is expressed by Equation (5) (see Non-Patent Document 3).

Here, ε ₀ is the dielectric constant of vacuum, and ε _r is the relative dielectric constant of the electric field driven polymer. As a result, the displacement of the push-pull type speaker device with respect to the applied voltage V can be expressed as u · sin θ. Note that θ changes as the speaker device is driven, but since the change is minute, it can be assumed that the angle θ during driving of the speaker device is constant. Further, the driving force G of the push-pull type speaker device by the applied voltage V is expressed by Expression (6).

Here, V _dc is a DC bias voltage, and V _ac is an AC signal, that is, an acoustic signal.

Next, paying attention to the component G _fr linear with respect to the input in the driving force G, this is a term related to the fundamental frequency component of the push-pull type speaker device, and is expressed by Expression (7).

Next, following a general analysis method of a direct radiation speaker (see Non-Patent Document 6), the sound pressure P at the position of the distance l on the main axis is expressed by Expression (8).

Here, _{Z m} is the mechanical impedance represented by _{r m + j (ωm-s} / ω), r m is the mechanical resistance, m is the mass of the joint, omega is the angular frequency. _Zs is a radiation resistance when the joint is regarded as a diaphragm (see Non-Patent Document 6), and is represented by Expression (9).

Here, ρ is the density of air, c is the speed of sound, k is the wave number, J ₁ is a first-order first-type Bessel function, and H ₁ is a first-type Struve function. The Struve function uses the approximate expression of Expression (10) (see Non-Patent Document 7).

When the sound pressure P is obtained from the above equation, the sound pressure P can be expressed by equation (11).

  From the above derivation, the acoustic characteristics of the push-pull type speaker device are based on the parameters of the material constant of the electric field driven polymer and the size of the speaker device (speaker device radius R + r, depth r · tan θ, joint radius r). It can be expressed by a model function of sound pressure. That is, the model function shown in Equation (11) enables the design of a speaker device that achieves a desired sound pressure.

  Note that the above design method is not limited to the speaker device according to the present invention, and instead of the joint portion to which the electric field driving polymer film is bonded, the speaker device that vibrates a diaphragm made of a material different from the electric field driving polymer film. Note that this is also applicable. In this case, the above-described joint portion is appropriately read as a diaphragm.

  Here, when designing a speaker device based on the model function of Equation (11), the requirements for the speaker device used in a home multi-channel acoustic system are limited by the space where it can be installed, as well as the acoustic characteristics. Is in size. Therefore, it is preferable that the size of the speaker device is defined in advance by area (radius) and depth, and a desired frequency characteristic is obtained by changing a parameter having a high degree of freedom (for example, the radius of the joint).

FIG. 5 is a diagram showing a change in frequency characteristics of sound pressure when the material constant and the size of the speaker device are fixed and the radius of the joint is changed. In this case, as the size of the speaker device, the radius (R + r) and the depth (r · tan θ) of the speaker device are fixed conditions. The calculation of formula (11) was performed under the following conditions. Incidentally, assuming that r _m is sufficiently small, the calculation is set to zero.
R + r = 8 cm (speaker device radius)
r · tan θ = 2cm (depth of the speaker device)
d = 100 μm (material constant of electric field driven polymer)
Y = 2.6 MPa (material constant of electric field driven polymer)
ε _r = 7.8 (material constant of electric field driven polymer)
V _dc = 500V
V _ac = 70.7 V (rms)
l = 1m

  Referring to the results of FIG. 5, even if the material constant of the electric field driven polymer and the radius and depth of the speaker device are constant, the radiation sound pressure and the reproduction frequency band change by changing the radius r of the joint. You can see that That is, according to the present invention, it is possible to change the radiated sound pressure and the reproduction frequency band of the speaker device without changing the radius and depth of the speaker device at a material constant of an electric field driven polymer, and the characteristics of the acoustic system It is possible to design a speaker suitable for the above.

  As described above, according to the present embodiment, the sound pressure model function having the parameters of the material constant of the electric field driven polymer film and the radius and depth of the speaker device, which is the size of the speaker device, and the radius of the joint. Thus, a speaker device that realizes desired sound pressure / frequency characteristics is designed. For this reason, even if the size of the speaker device is defined in advance, it is possible to realize a speaker device that realizes a desired sound pressure.

  Further, in the model function shown in Equation (11), the material constant of the electric field driven polymer film and the radius and depth of the speaker device are fixed, and the radius of the joint that achieves the desired sound pressure is obtained, thereby installing Desired sound pressure / frequency characteristics can be realized in a speaker device having a size according to environmental requirements (size specifications).

  In addition, the model function has a uniform thickness of the electric field drive type polymer film at the time of driving with a particularly small change, and the calculation load can be reduced without impairing the model accuracy. In addition, since the model function maintains a constant angle between the electric field driven polymer film and the joint during driving that is particularly small, the calculation load can be reduced without impairing the model accuracy.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention. For example, functions included in each member, each means, each step, etc. can be rearranged so as not to be logically contradictory, and a plurality of means, steps, etc. can be combined or divided into one. Is possible.

10, 20 Sound generation unit 11, 21 Frame 12, 22 Electric field driven polymer film 13, 23 Conductor 30 Spacer 40 Joint

Claims (5)

A circular electric field-driven polymer film;
A conductor along the circumference of the electric field driven polymer film;
Two sounding units having the electric field driven polymer film and a frame for sandwiching the conducting wire,
The two sounding units are arranged opposite to each other,
A space between the two sounding units is supported by a spacer,
A speaker device in which a central portion of each electric field driven polymer film of the two sounding units is bonded to form a joint. A method for designing a speaker device according to claim 1,
Material constants of the electric field driven polymer film,
A design method for designing the speaker device that realizes a desired sound pressure by using a model function of sound pressure using parameters of the speaker device radius and depth, which are the size of the speaker device, and the radius of the joint.   The said model function WHEREIN: The material constant of the said electric field drive type polymer film and the radius and depth of the said speaker apparatus are fixed, and the radius of the said junction part which implement | achieves the said desired sound pressure is calculated | required. Design method.   The design method according to claim 2 or 3, wherein the model function is a uniform thickness of the electric field driven polymer film during driving. 5. The design method according to claim 2, wherein the model function is a constant angle formed by the electric field driving polymer film and the joint during driving.

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