JP2012165129A - Electroacoustic transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple electroacoustic transducer with small size and light weight, capable of generating or storing power while listening to music, even when listening to the music under a no-vibration environment.SOLUTION: An electroacoustic transducer comprises a first diaphragm 211; a diaphragm driving portion 213 having a signal input portion 214 in which a voice signal for vibrating the diaphram 211 is input; a second diaphragm 221 vibrated due to pressure change of air generated behind the diaphragm 211 when the diaphragm 211 is vibrated; an electromagnetic induction coil 224 united with the diaphragm 221, and vibrated in the same direction together with the diaphragm 221; a power generating magnetic circuit 225 for generating a magnetic flux intersecting the vibrating direction of the electromagnetic induction coil 224, and generating electromotive force in the electromagnetic induction coil 224; and a power storing portion 44 for storing the electromotive force generated in the electromagnetic induction coil 224 as direct current power.

Description

  The present invention relates to an electroacoustic transducer used as a canal type or other in-ear headphone or a hearing aid, and more particularly to an electroacoustic transducer having a power generation / storage function for storing vibration energy of a diaphragm as electric energy.

Conventionally, as an electroacoustic transducer having both functions of a speaker and a generator,
A first mode position for extracting a back electromotive force generated when an external vibration is applied to a voice coil disposed in a magnetic gap provided in a magnetic circuit; and the first mode position is opened when listening to audio. A device including a switch including a second mode position for supplying an audio signal to a voice coil is known (for example, Patent Document 1).

JP 2004-221743 A (Claim 1, FIG. 1)

  However, the configuration of generating power by vibrating a voice coil by external vibration as in Patent Document 1 is limited to that used in a vibration system such as an automobile, and the boil coil has an amplitude of external vibration even when used in the vibration system. If it is not directed in the direction, the boil coil cannot be vibrated well.

  On the other hand, if the voice coil is arranged in the direction of the amplitude of the external vibration in order to promote the vibration of the voice coil, the external vibration acts directly on the diaphragm during audio listening, thereby degrading the reproduced sound quality.

  Patent Document 1 discloses an example in which a weight is provided to a vibration system part including a boil coil in order to promote vibration of a voice coil. There is a concern that it will not be possible to reproduce.

  The present invention has been made in view of the circumstances as described above, and its purpose is to be able to generate and store electricity while listening to music even when listening to music in an environment where the surroundings are vibration-free. It is to provide a simple electroacoustic transducer.

In order to achieve the above object, the present invention provides an electroacoustic transducer as described below.
(1) A diaphragm driving unit 213 having a first diaphragm 211, a signal input unit 214 to which an audio signal for vibrating the diaphragm 211 is input, and air generated behind the diaphragm 211 when the diaphragm 211 vibrates. A second diaphragm 221 that vibrates due to pressure fluctuation, an electromagnetic induction coil 224 that couples to the diaphragm 221 and vibrates in the same direction together with the diaphragm 221, and generates a magnetic flux that intersects the vibration direction of the electromagnetic induction coil 224 And a power storage magnetic circuit 225 for generating an electromotive force in the electromagnetic induction coil 224, and a power storage unit 44 for storing the electromotive force generated in the electromagnetic induction coil 224 as DC power. vessel.
(2) A signal processing unit 41 that processes an audio signal input to the signal input unit 214 of the diaphragm driving unit 213 is provided, and the signal processing unit 41 is connected to the power storage unit 44 as its power source. The electroacoustic transducer according to (1) above.
(3) The electroacoustic transducer according to (1) or (2), wherein the second diaphragm 221 has a lowest resonance frequency lower than that of the first diaphragm 211.
(4) It is characterized by having a communication hole 230 that communicates the air chamber C1 formed behind the first diaphragm 211 and the air chamber C2 formed behind the second diaphragm 221. The electroacoustic transducer according to any one of (1) to (3) above.

  Since the electroacoustic transducer according to the present invention generates an electromotive force in the electromagnetic induction coil, even when listening to music in a no-vibration environment, it can efficiently generate power while listening to the music. Moreover, if the power storage unit that stores the electromotive force generated in the electromagnetic induction coil as DC power is provided, the signal processing unit is applied to headphones or hearing aids that have a noise canceling function and the like, and is stored in the power storage unit. Electric power can be used as driving power for the signal processing unit. For this reason, it becomes possible to listen to high-quality reproduced sound over a long period of time while reducing the replacement frequency of the battery used as the main power source of the signal processing unit. Further, in the configuration in which the lowest resonance frequency of the second diaphragm is lower than that of the first diaphragm, the vibration load on the first diaphragm can be reduced. For this reason, it becomes possible to suppress the power consumption of the sound source device while expanding the sound reproduction band due to the vibration of the first diaphragm.

Sectional drawing which shows embodiment of the electroacoustic transducer which concerns on this invention The expanded sectional view of the drive unit which comprises the electroacoustic transducer shown in FIG. Enlarged sectional view showing an example of change of drive unit Enlarged sectional view showing another modification of the drive unit

  Hereinafter, the present invention will be described in detail with reference to the drawings. First, FIG. 1 shows an example in which the electroacoustic transducer according to the present invention is a canal type inner ear headphone.

  In FIG. 1, reference numeral 1 denotes a housing that forms an exterior of a headphone. The housing 1 includes a drive unit 2 as a main component. As can be seen from FIG. 1, the drive unit 2 has a structure in which two electrodynamic speaker units are coupled opposite each other. The drive unit 2 has a sound reproduction function and a power generation function. The specific configuration will be described later.

  A cylindrical nozzle 11 to be inserted into the ear hole is formed on one end side of the housing 1, and an earpiece 12 that is in close contact with the inner wall of the ear hole is fitted to the outer periphery of the nozzle 11. Further, between the nozzle 11 and the drive unit 2, the housing 1 has a built-in diffuser 3 that diffuses the sound wave emitted from the drive unit 2, and the sound wave diffused by the diffuser 3 passes through the inside of the nozzle 11. It is set as the structure discharge | released in.

  On the other hand, a space 14 partitioned by the circuit board 4 and the lid member 13 is formed in the housing 1 at a position opposite to the nozzle 11 with the drive unit 2 interposed therebetween. The space 14 is provided with a signal processing unit 41 (for example, a digital signal processor: DSP), and the signal processing unit 41 and the sound source device 5 (for example, a portable music player: DAP) are connected by a connection cord 42. Yes.

  The signal processing unit 41 performs processing such as sound field reproduction processing such as binaural and surround effects and noise canceling on the audio signal transmitted from the sound source device 5 through the connection cord 42, and signal output by this is performed. The input is made to the input terminal 4 a on the circuit board 4. In the configuration including such a signal processing unit 41, high-quality reproduced sound can be obtained.

  Here, in the space 14, a battery 43 (an alkaline dry battery, a nickel oxyhydroxide battery, a nickel hydride rechargeable battery, a lithium ion rechargeable battery, an air zinc battery, a silver oxide battery, etc.) is used as a main power source for driving the signal processing unit 41. However, its lifetime is short and replacement in a short period is required. For example, in the digital signal processing, the continuous reproduction time is 10 to 20 hours, and the continuous reproduction time is about 200 hours even when the noise canceling is analog. Moreover, even in the case of a hearing aid, in a high-functional digital model in which the signal processing unit 41 reduces noise, the continuous use time is only about 200 hours, and all of them require complicated battery replacement of about 1 day to 1 week. Is done.

  Therefore, in the present invention, a power storage unit 44 is provided in the space 14 as an auxiliary power source for the signal processing unit 41, and the DC power stored in the power storage unit 44 is supplied to the signal processing unit 41. The power storage unit 44 is connected to the output terminal 4 b of the circuit board 4 via the rectifier unit 45, so that the electromotive force generated in the drive unit 2 is stored in the power storage unit 44 as DC power. . Note that a secondary battery such as a capacitor, a capacitor, a lithium ion rechargeable battery, or a nickel hydride rechargeable battery is suitably used for the power storage unit 44.

  Here, referring to the configuration of the drive unit 2 based on FIG. 2, reference numerals 210 and 220 denote frames having substantially the same shape, and both the frames 210 and 220 are coupled to each other with the back surface being a joint surface 200. The peripheral edge of a dome-shaped diaphragm 211 (first diaphragm) is fixed to one frame 210 by a gasket 212, and the diaphragm 211 is moved in a predetermined direction (vertical direction in FIG. 2) by a diaphragm driving unit 213. It is configured to be vibrated.

  The diaphragm driving unit 213 includes a voice coil 214 (signal input unit) to which an audio signal is input and a magnetic circuit 215. Among these, the voice coil 214 is configured by winding a winding gland portion 214 a made of copper or aluminum around the outer periphery of the bobbin 214 b, and one end thereof is fixed to the center portion of the diaphragm 211 with an adhesive or the like. The bobbin 214b can be omitted.

  On the other hand, the magnetic circuit 215 includes a yoke 215a having a U-shaped cross section, a ring-shaped permanent magnet 215b disposed on the center of the yoke 215a, and a ring-shaped magnetic body disposed on the permanent magnet 215b. A magnetic gap G1 that generates a magnetic flux acting on the voice coil 214 is formed between the peripheral surface of the top plate 215c and the yoke 215a. And by inserting the boil coil 214 into the magnetic gap G1, an electromagnetic force acts in a direction (vertical direction in FIG. 2) orthogonal to the magnetic flux in the magnetic gap G1 and the current flowing through the voice coil 214, As a result, the diaphragm 211 to which the voice coil 214 is coupled vibrates in the same direction together with the voice coil 214.

  On the other hand, the periphery of a dome-shaped diaphragm 221 (second diaphragm) is also fixed to the frame 220 by a gasket 222. An electromagnetic induction coil 224 is coupled to the central portion of the diaphragm 221, and the electromagnetic induction coil 224 is configured to vibrate in a predetermined direction (vertical direction in FIG. 2) together with the diaphragm 221.

  The electromagnetic induction coil 224 is configured by winding a winding gland portion 224 a made of copper or aluminum around the outer periphery of the bobbin 224 b, and one end thereof is fixed to the center portion of the diaphragm 221 with an adhesive or the like. Note that the bobbin 224b of the electromagnetic induction coil 224 can be omitted.

  The frame 220 is provided with a power generation magnetic circuit 225 that generates a magnetic flux for generating an electromotive force in the electromagnetic induction coil 224 when the diaphragm 221 and the electromagnetic induction coil 224 vibrate.

  Similarly to the magnetic circuit 215, the magnetic circuit for power generation 225 includes a yoke 225a having a U-shaped cross section, a ring-shaped permanent magnet 225b disposed on the center of the yoke 225a, and a ring-shaped disposed on the permanent magnet 225b. A magnetic gap G2 that generates a magnetic flux acting on the electromagnetic induction coil 224 is formed between the peripheral surface of the top plate 225c and the yoke 225a. . An electromagnetic induction coil 224 is inserted into the magnetic gap G2, and the electromagnetic induction coil 224 vibrates in a direction crossing the magnetic flux of the magnetic gap G2, thereby generating an induced electromotive force in the electromagnetic induction coil 224. The direct current power is stored in the power storage unit 44 shown in FIG. In other words, the electromagnetic induction coil 224 is connected to the power storage unit 44 via the output terminal 4b and the rectifier unit 45 shown in FIG.

  In particular, in the present invention, the diaphragm 221 is configured to interlock with the diaphragm 211 through the air. For this purpose, in the example shown in FIG. 2, a communication hole 230 is formed at the center of the frames 210 and 220 and the yokes 215a and 225a so as to match the center holes of the permanent magnets 215b and 225b and the top plates 215c and 225c. The hole 230 allows the air chamber C1 formed behind the diaphragm 211 (on the magnetic circuit 215 side) to communicate with the air chamber C2 formed behind the diaphragm 221 (on the power generation magnetic circuit 225 side). According to this, when air pressure fluctuations occur in the air chamber C1 located behind the diaphragm 211 due to vibration, the same pressure fluctuations also occur in the air in the air chamber C2 through the communication hole 230. The diaphragms 211 and 221 can be vibrated synchronously. In short, according to the present invention, the vibration energy of the diaphragm 211 is transmitted to the diaphragm 221 while converting the electric signal (sound signal) input to the voice coil 214 into air vibration (acoustic signal) driven by the diaphragm 211. Then, power generation is performed, and this can be stored as drive power for the signal processing unit 41. Therefore, it is more preferable that the space between the diaphragm 211 and the diaphragm 221 be sealed.

  Note that the magnetic circuit 215 and the power generation magnetic circuit 225 are not limited to being configured separately, and for example, the yokes 215a and 225a of both can be configured as an integral structure.

Further, the two diaphragms 211 and 221 may be exactly the same, but the diaphragm 221 has a lowest resonance frequency (f ₀ ) lower than that of the diaphragm 211 from the viewpoint of reducing the load on the diaphragm 211. Is preferably used.

Here, f ₀ = (m / c) ^0.5 {m: mass of vibration system, c: compliance (reciprocal of stiffness s)}, so that the mass m of the diaphragm is reduced and compliance c (motion the ease) is increased, by reducing the stiffness s (hardness), the lowest resonance frequency f ₀ is lowered.

For example, by reducing the diameter of the diaphragm 221, the thickness, the density, or the diameter of the electromagnetic induction coil 224, the number of turns of the winding portion 224 a, the wire diameter, etc., and reducing the weight of the diaphragm 221, the minimum resonance frequency f ₀ can be lowered. In addition, the minimum resonance frequency f ₀ of the diaphragm 221 is lowered by reducing the thickness or Young's modulus of the diaphragm 221 or optimizing the shape of the diaphragm 221 or the edge portion to reduce the stiffness. be able to.

On the other hand, the estimation of the maximum power generation in the vibration system is calculated as a combined model of spring and dashpot by Mitcheson et al. Here, the maximum power generation amount P _max is
^{_{P max = (1/2) X 0}} 2 ω 3 m (X max / X 0) {X 0: _{displacement,} ω: 2πf, _{X max:} maximum displacement, m: mass} so represented, for example vibration If the mass m of the plate 221 is 4 mg, its displacement (amplitude) X ₀ is 1 μm, the maximum displacement X _max is 10 μm, and the frequency f is 600 Hz, P _max is about 1 mW. It should be noted that a commercially available canal type in-ear headphone having a noise canceling function consumes 20 mW or less, and a hearing aid uses 1 to 2 mW. Therefore, even a power generation amount of 1 mW is sufficient as driving auxiliary power for the signal processing unit 41.

  Next, an example of changing the drive unit will be described with reference to FIG. In FIG. 3, the drive unit 21 has permanent magnets 215b and 225b and top plates 215c and 225c formed in a non-perforated disk shape. A communication hole 230 is formed in the bottom periphery, and the air chambers C1 and C2 are communicated through the communication hole 230, which is different from the above example. In short, the drive unit 21 in FIG. 3 differs from the drive unit 2 in FIG. 2 except for the position of the communication hole 230. Also in the drive unit 21 as shown in FIG. 3, the pressure fluctuation of the air in the air chamber C1 due to the vibration of the vibration plate 211 is exerted on the air chamber C2 through the communication hole 230, thereby causing the vibration plate 221 and the electromagnetic induction coil 224 to move. While vibrating, the electromotive force generated in the electromagnetic induction coil 224 can be stored in the power storage unit 44 shown in FIG. 1 as DC power. Note that a plurality of communication holes 230 according to this modification may be provided circumferentially on the bottom periphery. Further, the communication hole 230 may be a communication hole 230 having a circular shape when viewed from the first diaphragm 211 side, or the center position of the bottom of the frames 210 and 220 and the yokes 215a and 225a. An arc-shaped communication hole 230 may be used.

  FIG. 4 shows an example in which the power generation magnetic circuit 225 is an external magnetic type. That is, in FIG. 4, the power generation magnetic circuit 225 includes a ring-shaped permanent magnet 225 b arranged on the outer periphery of a T-shaped yoke 225 a having a center piece portion cp, and a disc-like shape on the upper end surface of the center piece portion cp. The inner top plate 225c is provided, and a ring-shaped outer top plate 225d is provided on the upper end surface of the permanent magnet 225b, and a magnetic gap G2 is formed between the inner top plate 225c and the outer top plate 225d. Also in the drive unit 22 as shown in FIG. 4, when the diaphragm 211 vibrates, the air in the air chambers C1 and C2 undergoes pressure fluctuations through the communication holes 230, and thereby the electromagnetic induction coil 224 inserted into the magnetic gap G2. The electromotive force generated in the electromagnetic induction coil 224 can be stored as DC power in the power storage unit 44 shown in FIG. 1 while vibrating the diaphragm 221 to which it is coupled in the same direction.

  As described above, the first diaphragm is provided with the second diaphragm that vibrates due to air pressure fluctuation generated behind the first diaphragm, and the electromagnetic induction coil coupled to the second diaphragm is a magnetic circuit for power generation. Since the electromotive force is generated in the electromagnetic induction coil by oscillating in the direction intersecting with the magnetic flux, the power can be efficiently generated while listening to the music even when listening to the music in a no-vibration environment. it can.

  In addition, although embodiment of this invention was described, the electroacoustic transducer which concerns can be applied not only to headphones but to a hearing aid. In the above embodiments, the two diaphragms 211 and 221 are arranged on the same straight line so that their vibration directions are the same. However, the vibration directions of both diaphragms 211 and 221 cross each other. It may be a simple arrangement.

  Furthermore, the power storage unit 44 is not limited to being used as an auxiliary power source for the signal processing unit 41 that performs noise canceling or the like. For example, the power storage unit 44 may be an electroacoustic transducer to which an LED for illumination is added, and the power storage unit 44 is an LED light emitting power source. Can be used as

211 First diaphragm 213 Diaphragm driver 214 Voice coil (signal input section)
215 Magnetic circuit 221 Second diaphragm 224 Electromagnetic induction coil 225 Magnetic circuit for power generation 41 Signal processing unit 44 Power storage unit

Claims (4)

A first diaphragm;
A diaphragm driving unit having a signal input unit to which an audio signal for vibrating the first diaphragm is input;
A second diaphragm that vibrates due to air pressure fluctuations that occur behind it when the first diaphragm vibrates;
An electromagnetic induction coil that is coupled to the second diaphragm and vibrates in the same direction together with the second diaphragm;
A power generation magnetic circuit that generates a magnetic flux that intersects a vibration direction of the electromagnetic induction coil to generate an electromotive force in the electromagnetic induction coil;
A power storage unit that stores electromotive force generated in the electromagnetic induction coil as DC power;
An electroacoustic transducer comprising: A signal processing unit for processing an audio signal input to the signal input unit of the diaphragm driving unit;
The electroacoustic transducer according to claim 1, wherein the signal processing unit is connected to the power storage unit as a power source. The electroacoustic transducer according to claim 1, wherein the second diaphragm has a lowest resonance frequency lower than that of the first diaphragm. 4. A communication hole for communicating an air chamber formed behind the first diaphragm and an air chamber formed behind the second diaphragm. The electroacoustic transducer according to any one of the above.

Images