JP5467530B2 - Electroacoustic transducer - Google Patents

Description

  The present invention relates to an electroacoustic transducer, and more particularly to an electroacoustic transducer capable of obtaining excellent frequency reproduction characteristics.

  Conventionally, as an electroacoustic transducer, a balance armature (BA) that transmits the vibration of an armature (movable iron piece) indirectly to a diaphragm via a transmission member called a drive rod, thereby vibrating the diaphragm. The thing of a type | mold is known (for example, patent document 1).

  Here, the BA-type electroacoustic transducer is widely used as a hearing aid because it has a high resolution in the middle and high sound range and can be easily downsized.

JP-T-2002-541749

  However, although the BA-type electroacoustic transducer is useful as a hearing aid due to its small size, the reproduced sound pressure in the low frequency range is small, and there is room for improvement for headphones for listening to music.

  In Patent Document 1, an aluminum sheet is used as a vibration plate. However, a metal material such as aluminum cannot be used to expand the bass reproduction limit, and the internal loss is as small as 0.002 to 0.005. For this reason, standing waves are likely to be generated on the surface of the diaphragm due to the occurrence of resonance.

  On the other hand, when a general paper sheet or resin film is used as the material for the diaphragm, the transient characteristics and resolution at the rise and fall of the reproduced sound are poor due to the low sound wave propagation speed. Become.

  The present invention has been made in view of the circumstances as described above, and its main purpose is an electroacoustic transducer, which improves the reproduction sound quality in the low frequency range while improving the resolution of the mid and high frequency ranges, and the reproduction frequency band. Is to obtain a wide and high-quality playback sound.

In order to achieve the above object, the present invention provides an electroacoustic transducer as described below.
(1) a housing 1 having a sound emitting hole 12a for radiating sound waves to the outside;
A vibration plate 3 having a structure including a layer made of a wood sheet 31 and provided in the housing 1 with the fiber direction of the wood sheet 31 facing the axial direction L of the sound emitting hole 12a;
E Bei a, a driving section 4 for vibrating the vibration plate 3,
The inside of the housing 1 is partitioned by the diaphragm 3 into a first space S1 that communicates with the outside through the sound emission hole 12a and a second space S2 in which the drive unit 4 is built. ,
A sheet member 7 is attached to the inner surface portion of the casing 1 forming the first space S1 so as to face the diaphragm 3, and the fiber direction of the sheet member 7 is also the sound emitting hole 12a. An electroacoustic transducer having a wood sheet 71 oriented in the axial direction .
(2) pre-Symbol diaphragm 3, the timber sheet 31 as a surface layer, an electroacoustic transducer of the above (1), wherein that the timber sheet 31 is directed to the first space S1 side.
(3) having a nozzle 2 that communicates with the sound emitting hole 12a and is inserted into a user's ear hole;
The electroacoustic conversion according to (1) or (2), wherein the sheet member 7 having the wood sheet 71 is attached to an inner surface portion of the nozzle 2 and an outer surface portion of the housing 1. vessel.
(4) The diaphragm 3 is a laminate of the wood sheet 31 and the paper sheet 32 or a laminate of the wood sheet 31, the paper sheet 32, and the resin film 33 according to the above (1) to (3). The electroacoustic transducer in any one.
(5) The sheet member 7 is a laminate of the wood sheet 71 and the paper sheet 72 or a laminate of the wood sheet 71, the paper sheet 72, and the resin film 73 according to the above (1) to (4). The electroacoustic transducer in any one .

  According to the electroacoustic transducer of the present invention, it is possible to improve the reproduction sound quality in the low sound range while increasing the resolution in the middle and high sound range, and obtain a reproduction sound having a wide reproduction frequency band and high sound quality.

The perspective view which shows one of the embodiment of the electroacoustic transducer which concerns on this invention. The perspective perspective view which shows the basic form inside one of the embodiment of the electroacoustic transducer which concerns on this invention . The longitudinal cross-sectional view of one basic form of embodiment of the electroacoustic transducer based on this invention Explanatory drawing which shows the arrangement | positioning aspect of a diaphragm Partial enlarged sectional view of diaphragm Enlarged sectional view showing the edge of the diaphragm 1 is a longitudinal sectional view of an embodiment of an electroacoustic transducer according to the present invention. Partial enlarged sectional view of a sheet member The longitudinal cross-sectional view which shows other embodiment of the electroacoustic transducer based on this invention

Hereinafter, an embodiment in which the electroacoustic transducer of the present invention is used for headphones will be described in detail with reference to the drawings. First, one basic form of embodiment of this invention is demonstrated based on FIGS. In FIG. 1 to FIG. 3, reference numeral 1 denotes a casing that forms the exterior of the electroacoustic transducer according to the present invention. The casing 1 is fitted into a box-shaped case body 11 and an upper end opening of the case body 11. It is comprised by the lid | cover 12 with which it mounted | wore. Further, the nozzle 2 is fixed to one end surface of the housing 1 across the joint portion between the case main body 11 and the lid 12. The nozzle 2 is a portion that is inserted directly into the user's ear canal or via an earplug (not shown), and is configured to emit sound waves (audible sound) into the ear canal through the nozzle 2.

  As apparent from FIGS. 2 and 3, a planar diaphragm 3 is provided between the case main body 11 and the lid 12 in the casing 1, and the inside of the casing 1 is formed by the diaphragm 3. It is partitioned into a first space S1 located on the lid 12 side and a second space S2 located on the case body 11 side. The lid 12 is formed with a sound emitting hole 12a in a portion covered with the nozzle 2, and the first space S1 is communicated with the outside through the sound emitting hole 12a. Sound waves are emitted to the outside of the housing 1 through the sound emission holes 12a. The first space S1 and the second space S2 do not have to be completely partitioned.

  On the other hand, in the second space S <b> 2 in the housing 1, a drive unit 4 for vibrating the diaphragm 3 is incorporated. The drive unit 4 includes a pair of magnets 41 constituting a magnetic circuit, a magnet housing 42 (yoke) that holds the magnets 41, a coil 43, and an armature 44.

  Among these, the magnet housing 42 has a rectangular tube shape made of a magnetic material, and a pair of magnets 41 are fixed to the opposing inner wall surfaces. The pair of magnets 41 are flat plate-like permanent magnets, which are fixed with their different magnetic poles facing each other, and a magnetic gap G that generates a DC magnetic field is formed between the two magnets.

  The coil 43 has a configuration in which a winding 43b through which an audio signal current flows is provided on the outer periphery of a bobbin 43a formed of a synthetic resin or the like, and both ends of the winding 43a are drawn to the outside of the housing 1 to input signals. Connected to terminal 5. The coil 43 is fixed to the case main body 11 in a state where the inside of the bobbin 43a is continuous with the magnetic gap G, and generates an alternating magnetic field that changes the magnetism of one end of the armature 44 placed in the magnetic gap G. .

  The armature 44 is formed by bending a metal plate of a soft magnetic material into a U shape as in the example shown in FIG. 3, and one end side thereof is fixed to the outer wall surface of the magnet housing 42 as a fixed end portion 44a. One end side of the coil passes through the inside of the coil bobbin 43a and the magnetic gap G as the vibration generating portion 44b. In particular, the tip of the vibration generating part 44 b protrudes from the magnetic gap G and is connected to the diaphragm 3 via the drive rod 45.

  The drive rod 45 is a hard transmission member that transmits the vibration of the armature 44 (vibration portion 44b) to the diaphragm 3, and one end of the drive rod 45 is fixed to the tip of the armature perpendicular to the vibration portion 44b of the armature. The other end of the rod 45 is fixed to the diaphragm 3 with an adhesive or the like.

  The diaphragm 3 is fixed to the frame body 6 via, for example, a roll-shaped edge portion 3 a formed in a semicircular cross section, and the frame body 6 is sandwiched between the case body 11 and the lid 12. It is held so that it can vibrate. As shown in FIGS. 3 and 4, the diaphragm 3 is formed with a through hole 3b for adjusting the differential pressure of the internal air pressure between the first space S1 and the second space S2. Note that the hatching shown in FIG. 4 is intended to clearly show the edge portion 3a of the diaphragm 3 and its inner region (radiation portion), and does not represent a cross section.

  In the present invention, the diaphragm 3 has a laminated structure using the wood sheet 31 as a base material. For example, as shown in FIG. 5A, the diaphragm 3 has a two-layer structure in which a wood sheet 31 and a paper sheet 32 are bonded together.

  Wood has anisotropy that physical properties differ between the fiber direction and its orthogonal direction, and the propagation velocity (sound speed) of sound waves in the fiber direction is as high as 4 to 6 km / sec, comparable to metal. Moreover, the internal loss is as high as 0.02 to 0.04, which is comparable to paper and resin. For this reason, according to the diaphragm 3 using the wood sheet 31 as a base material, it is possible to obtain a high-resolution reproduced sound free from modulation distortion caused by the occurrence of standing waves. In addition, the diaphragm 3 based on the wood sheet 31 is softer, lighter (low specific gravity) and lower in the minimum resonance frequency than the metal diaphragm, so that the bass reproduction capability is improved compared to the metal diaphragm. The reproduction frequency band can be expanded.

  The raw material of the wood sheet 31 is a tree species having a high acoustic wave propagation speed and a large internal loss among wood such as hippopotamus, cherry, pear, beech, oak, walnut, maple, maple, spruce, mahogany, or rosewood. Preferably used. Conversely, tropical tree species such as Lauan are not suitable as raw materials for the wood sheet 31 because of their low strength and low anisotropy.

  Here, the overall weight of the diaphragm 3 is a very important factor in terms of vibration performance, and an electroacoustic transducer having only a magnetic circuit with a small driving force such as headphones, particularly a balanced armature (BA When the wood sheet 31 is used as the) type diaphragm 3, it is required to reduce the thickness and weight. For this reason, the wood sheet 31 has a thickness of 0.1 mm or less, preferably 10 to 80 μm, using a fine wood sap material portion that can be processed extremely thinly. For this, an ultra-finish dredge device capable of ultra-thin smoothing of wood is preferably used.

  In the wood sheet 31 having a thickness of 10 to 80 μm, a slight force is applied in a direction orthogonal to the fiber direction, and a tear is likely to occur in the fiber direction. For this reason, it is preferable that the diaphragm 3 according to the present invention is not a single-layer structure of the wood sheet 31 but a laminated structure in which the paper sheet 32 as described above is bonded to reinforce the wood sheet 31. As the paper sheet 32, a thin Japanese paper having a high strength and a Gampi paper having a high strength while being a thin fiber are preferably used. Furthermore, the thickness of the paper sheet 32 is preferably 5 to 20 μm.

The paper sheet 32 may be laminated with the wood sheet 31 at the same time as the cutting of the wood sheet 31, or after the cutting processing of the wood sheet 31, the paper sheet 32 may be carefully handled and laminated with the paper sheet 32. Anyway. The wood sheet 31 and the paper sheet 32 are joined and integrated by, for example, hot pressing after lamination. In this case, the paper sheet 32 is impregnated with a thermosetting resin in advance in order to ensure the shape retention of the diaphragm 3. It is good to keep. As the thermosetting resin, an acrylic resin or the like can be used in addition to the resol type phenol resin. Since the curing temperature of the phenol resin is about 150 ° C. to 180 ° C., the temperature of the hot press is higher than that, and the press pressure is 5 to 40 kg / mm ^{2 at} which the cell gaps and cell walls of the wood sheet 31 are compressed. Is set. At this time, the thermosetting resin also permeates the wood sheet 31 side, and the laminate is integrated.
Incidentally, a wood sheet 31 having a thickness of 20 μm was stacked on a paper sheet 32 having a thickness of 10 μm and hot-pressed at a pressure of 20 kg / mm ^2. The thickness of the diaphragm 3 thus obtained was 10 μm. .

  Here, the peripheral edge portion of the diaphragm 3 is an edge portion 3a capable of increasing the amplitude of the radiating portion, but the edge portion 3a is limited to a roll shape having a semicircular cross section as described above. It may be a corrugation type or a thin flat plate type. However, it is desirable to form such an edge portion 3 a on a laminated member excluding the wood sheet 31.

  For example, when the diaphragm 3 has a two-layer structure of a wood sheet 31 and a paper sheet 32 as shown in FIG. 5A, the paper sheet 32 that is more flexible and easier to form than the wood sheet 31 is used. The edge portion 3a is formed on the periphery of the paper sheet 32 which is made slightly larger and protrudes from the periphery of the wood sheet 31 as shown in FIG.

  The diaphragm 3 is not limited to the two-layer structure of the wood sheet 31 and the paper sheet 32, but may be a three-layer structure including the resin film 33 as shown in FIG. 5B. In this case, only the resin film 33 is used. The edge 3a can be formed on the periphery of the edge 3a. As the resin film 33, a polyester resin film such as polyethylene terephthalate or polyethylene naphthalate can be used, and the thickness is preferably 2 to 10 μm. In addition, when the diaphragm 3 has three or more layers, the wood sheet 31 should not be interposed between two layers, but should be a surface layer, that is, the wood sheet 31 may appear on either surface of the diaphragm 3. preferable.

  Thus, the diaphragm 3 is provided in the housing 1 so as to be vibrated by sandwiching the frame body 6 between the case body 11 and the lid 12 as described above. That is, it is desirable to arrange it toward the first space S1 side. In particular, as shown in FIG. 4, the fiber direction of the wood sheet 31 is the axial direction L of the sound emitting hole 12a (the direction along the straight line passing through the center of the sound emitting hole 12a and orthogonal to the sound emitting surface of the sound emitting hole 12a). Toward (to be along). According to this, due to the high propagation speed of the sound wave in the fiber direction of the wood sheet 31, the sound quality of the reproduced sound radiated to the outside from the sound emitting hole 12a through the nozzle 2 can be improved. Although it is desirable that the fiber direction of the wood sheet 31 and the axial direction L of the sound emission hole 12a are perfectly matched, it is practically difficult to achieve perfect matching, and is about 10 degrees from the viewpoint of acoustic characteristics. The deviation is within an acceptable range. If the deviation is about 10 degrees, an effect of improving sound quality can be exhibited.

  As described above, since the wood sheet 31 is used for the diaphragm 3 in the present invention, the bass reproduction capability is improved and the reproduction frequency band is improved as compared with an electroacoustic transducer using a metal diaphragm made of aluminum or the like. Can be expanded. Further, since the wood sheet 31 has a large internal loss, generation of standing waves on the surface of the diaphragm 3 can be suppressed, and the fiber direction of the wood sheet 31 is oriented in the axial direction of the sound emitting hole 12a. It is possible to draw out high quality sound with excellent transient characteristics and resolution at the rise and fall of the reproduced sound. Further, in the configuration in which the wood sheet 31 is a surface layer and the wood sheet 31 is directed to the first space S1 communicating with the outside through the sound emission hole 12a, the positive influence on the reproduced sound by the wood sheet 31 is enhanced. The sound quality can be further improved.

Incidentally, in addition to the configuration described above, in one embodiment of the electroacoustic transducer according to the present invention, the housing 1 (the lid 12 which forms a first space S1 opposite to the vibration plate 3 as shown in FIG. 7 The sheet member 7 is adhered to the inner surface portion of). Here, the sheet member 7 is basically configured similarly to the diaphragm 3. That is, the sheet member 7 is also a laminate of the wood sheet 71 and the paper sheet 72 or a laminate of the wood sheet 71, the paper sheet 72, and the resin film 73, as shown in FIG. Wood is a material that has ideal characteristics as an acoustic diaphragm with high sound speed and large internal loss, so it has high sound reproduction capability and excellent transient characteristics and resolution in addition to expansion of the reproduction frequency band. The sound quality can be improved by including the wood sheet 71 in the sheet member 7 in order to reproduce the sound.

The sheet member 7 is also directed to the wood sheet 71 to the first space S1 side, and you place towards the fiber direction in the axial direction L of the sound release hole 12a. As described above, the wood sheet 71 having ideal characteristics as an acoustic diaphragm having high sound speed and large internal loss on the outermost surface leads to the first space S1 by directing the wood sheet 71 toward the first space S1. Since the excellent reproduced sound is propagated to the sound emitting hole 12a and further to the nozzle 2, the sound quality can be further improved.

  Furthermore, if the fiber direction of the wood sheet 71 is arranged toward the axial direction L of the sound emission hole 12a, the wood sheet uses a direction having excellent acoustic characteristics such as high sound velocity, and has excellent frequency band reproduction capability. Since the reproduced sound having excellent transient characteristics is propagated to the sound emitting hole 12a which is the extraction hole, the sound quality can be further improved.

  Even with an electroacoustic transducer as shown in FIG. 7, it is possible to extract reproduced sound having a wide reproduction frequency band and excellent acoustic characteristics.

  That is, in the configuration in which the sheet member 7 including the wood sheet 71 is attached to the inner surface portion of the housing 1 that forms the first space S <b> 1 so as to face the diaphragm 3, noise is generated due to resonance of the housing 1. It can be suppressed and the playback sound quality can be further improved. In addition, in the configuration in which the diaphragm 3 and the sheet member 7 are a laminate of the wood sheet 71 and the paper sheet 72 or a laminate of the wood sheet 71, the paper sheet 72, and the resin film 73, the electroacoustic transducer It is possible to prevent the wood sheet 71 from being broken during manufacture and use.

  Although it is desirable that the fiber direction of the wood sheet 71 and the axial direction L of the sound emitting hole 12a are completely matched, it is practically difficult to match completely, and it is about 10 degrees from the viewpoint of acoustic characteristics. The deviation is within an acceptable range. If the deviation is about 10 degrees, an effect of improving sound quality can be exhibited.

  In addition, as shown in FIG. 9, the sheet member 7 may be attached not only to the inner surface portion of the lid 12 but also to the inner surface portion of the nozzle 2, the outer surface portion of the lid 12, and the outer surface portion of the case body 11. According to this, it becomes possible to suppress the vibration of the housing 1 and prevent the generation of noise due to this.

  As mentioned above, although the embodiment of the present invention has been described, the electroacoustic transducer has a pair of left and right ear pads connected not only as an inner ear type headphone that is used by inserting the nozzle 2 into the ear hole, but also by a headband. The housing 1 can be fixed in the housing to provide a sealed headphone, and a microphone (not shown) can be connected to the signal input terminal 5 to be used as a hearing aid. Further, it can be used for various other devices.

DESCRIPTION OF SYMBOLS 1 Case 12a Sound emission hole 3 Diaphragm 31 Wood sheet 32 Paper sheet 33 Resin film 4 Drive part 41 Magnet 42 Magnet housing 43 Coil 44 Armature 45 Drive rod S1 1st space S2 2nd space 7 Sheet member 71 Wood sheet 72 Paper Sheet 73 Resin film

Claims (5)

A housing having a sound emitting hole for radiating sound waves to the outside;
A diaphragm including a layer made of a wood sheet, the diaphragm provided in the casing with the fiber direction of the wood sheet facing the axial direction of the sound emitting hole,
A drive unit for vibrating the diaphragm ,
The inside of the housing is partitioned by the diaphragm into a first space that communicates with the outside through the sound emission hole, and a second space in which the driving unit is incorporated,
A sheet member is attached to the inner surface portion of the casing forming the first space so as to face the diaphragm, and the fiber direction of the sheet member is also directed to the axial direction of the sound emitting hole. An electroacoustic transducer comprising a wood sheet . Before SL diaphragm the wood sheet as a surface layer, electro-acoustic transducer according to claim 1, wherein that the wood sheet is directed to the first space side. Having a nozzle in communication with the sound emitting hole and inserted into the ear hole of the user;
The electroacoustic transducer according to claim 1 or 2, wherein the sheet member having the wood sheet is attached to an inner surface portion of the nozzle and an outer surface portion of the housing . The electroacoustic transducer according to any one of claims 1 to 3, wherein the diaphragm is a laminate of the wood sheet and a paper sheet, or a laminate of the wood sheet, a paper sheet, and a resin film. The electroacoustic transducer according to any one of claims 1 to 4, wherein the sheet member is a laminate of the wood sheet and a paper sheet, or a laminate of the wood sheet, a paper sheet, and a resin film.

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