JP5120730B2 - Center cap for speaker and speaker unit with cap - Google Patents

Description

  The present invention relates to a speaker center cap attached to the center of a diaphragm and a speaker unit including the center cap.

  Conventionally, a speaker unit in which a center cap is attached to the center of a diaphragm joined to the tip of a voice coil is generally widely known (for example, Patent Document 1).

Japanese Utility Model Publication No. 5-18197

  The speaker center cap as described above is a dome-shaped member that covers the center hole of the cone-shaped diaphragm communicating with the voice coil, and serves to prevent dust from entering the magnetic circuit that drives the diaphragm. In addition, it contributes to the reproduction of high frequencies as part of the diaphragm.

  Ideally, the diaphragm should be lightweight, rigid and have high internal loss, but the center cap attached to the center of the diaphragm will also vibrate with the diaphragm and affect the acoustic characteristics of the speaker. As with the diaphragm, it is desired to be light, rigid and have high internal loss.

  If the center cap is light, the movement of the diaphragm is not hindered and it reacts with high sensitivity to the driving force, so that an effect such as improvement in sound pressure of reproduced sound can be obtained. If the rigidity (Young's modulus) is high, the center cap vibrates while maintaining a fixed shape, so that a clear sound with little distortion can be reproduced, and the propagation speed of sound waves (Young's modulus E / density ρ) is correlated. Since the square root of) increases, the reproduction band can be expanded. On the other hand, the internal loss represents a damping performance that absorbs vibration energy from the outside, and if this is large, it is difficult to generate reverberation because it can absorb divided vibration that degrades sound quality, and sound quality can be improved. .

  However, since many of the center caps for speakers have been molded from metallic materials for the purpose of extending the high frequency range, the high frequency characteristics are improved, but the metal center cap has low internal loss. As a result, there is a problem that unpleasant noise and reverberation are likely to occur due to resonance in the high frequency range.

  In this respect, when a paper sheet is attached to the back surface of the metal center cap as in Patent Document 1, the occurrence of resonance in the high sound range can be suppressed, but the high frequency limit frequency is lowered and the high frequency characteristic is reduced. Cause deterioration. In addition to metal, various materials are used for the center cap. However, in the center cap made of metal or other uniform material, the propagation speed of sound waves is equal in all directions (up, down, left, and right). Therefore, it is easy to generate a standing wave that causes deterioration in sound quality, and it is difficult to create a large sound field space due to poor sound spread at high frequencies.

  The present invention has been made in view of the circumstances as described above, and an object of the present invention is to provide a speaker center cap capable of improving sound quality at a high frequency and expanding directivity and a speaker unit including the same. There is to do.

  In order to achieve the above object, the speaker center cap 7 according to the present invention covers the central hole 5a of the diaphragm 5 having the propagation speed of the first sound wave and the first internal loss and having the central hole 5a. A cap body 71, a second sound wave propagation speed lower than the first sound wave propagation speed, and a second internal loss larger than the first internal loss; And a thin film member 72 having a cutout portion 72c partially cut out so as to spread radially from the outer periphery to the outer peripheral portion and affixed to the back surface of the cap main body 71.

Moreover, the speaker unit with a cap according to the present invention is:
A voice coil 3 having a conductive wire wound around the outer periphery of the coil bobbin 3; a diaphragm 5 having a central hole 5a communicating with the voice coil 3; and a center cap 7 attached to the center of the diaphragm 5; The center cap 7 has a propagation speed of the first sound wave and a first internal loss, the cap body 71 covering the center hole 5a, and the propagation of the second sound wave lower than the propagation speed of the first sound wave. It has a second internal loss greater than the speed and the first internal loss, and has a cutout portion 72c partially cut out so as to spread radially from the inner peripheral portion of the cap body 71 toward the outer peripheral portion. And a thin film member 72 affixed to the back surface of the cap main body 71.

  According to the center cap of the present invention, a thin film-like member having a lower propagation velocity of sound waves and a larger internal loss is attached to the cap body that covers the center hole of the diaphragm, so that the treble range is extended. It is possible to suppress the occurrence of abnormal sounds and reverberations in the high range while reproducing clear sounds.

  In addition, the thin film-like member has cutouts that radiate from the inner periphery to the outer periphery of the cap body, thus expanding the treble range to improve directivity and enhance the sense of sound field. In addition, since the anisotropy occurs in the propagation speed of the sound wave in the entire cap, it is possible to improve the sound quality by suppressing resonance (coloration) due to standing waves in the high sound range.

Sectional drawing which shows one Embodiment of the speaker unit with a cap concerning this invention The expanded sectional view which shows the mounting part of the center cap of one embodiment Rear view showing the center cap Perspective view of the center cap seen from the back side Explanatory drawing which shows the modification of a thin film-like member

  Hereinafter, the present invention will be described in detail with reference to the drawings. First, referring to FIG. 1, an embodiment of a speaker unit with a cap according to the present invention will be described. The speaker unit is of an electrodynamic type (dynamic type), and can output the entire band from high to low. This is a full-range speaker. Reference numeral 1 denotes a frame of a speaker unit, and a magnetic circuit 2 (an outer magnet type in the illustrated example) is attached to the frame 1.

  The magnetic circuit 2 includes a ring-shaped magnet 21 magnetized in the thickness direction, a ring-shaped top plate 22 mounted on one magnetic pole of the magnet 21, and the other magnetic pole of the magnet 21. The back plate 23 and the pole piece 24 provided at the center of the back plate 23 are formed. A magnetic gap G on which the magnetic flux of the magnet 21 acts is formed between the pole piece 24 and the top plate 22. Has been.

  The top plate 22, the back plate 23, and the pole piece 24 serve as a yoke that collects the magnetic flux of the magnet 21 in the magnetic gap G, and the voice coil 3 is inserted into the magnetic gap G. Note that the back plate 23 and the pole piece 24 may be formed as a single unit.

  The voice coil 3 is formed by winding a conductive wire such as copper or aluminum coated with an insulating film around the outer periphery of a non-conductive coil bobbin 31 made of paper or the like (a non-magnetic material such as aluminum may be used). The tip end of the pole piece 24 is inserted into the inner periphery thereof, and the inner peripheral surface of the top plate 22 faces the outer winding portion 32. The voice coil 3 is attached to the frame 1 via a damper 4, and is supported by the damper 4 so as to be movable in the front-rear direction (the direction of the axis passing through the center of the voice coil 3 and the vertical direction in FIG. 1). The tip is joined to the cone-shaped diaphragm 5.

  The diaphragm 5 is a cone-shaped radiator formed of paper, wood, synthetic resin such as polypropylene or polyester, aluminum or other metal, or chemical fiber. A circular center hole 5a communicating with the frame 5 is formed, and the outer periphery on the large diameter side is supported by the frame 1 via an edge 6 that allows the diaphragm 5 to move in the front-rear direction.

  A center cap 7 covering the center hole 5a is attached to the center of the diaphragm 5. The center cap 7 is a dome-shaped member larger than the center hole 5 a of the diaphragm 5, and its outer periphery is fixed to the diaphragm 5 with an adhesive, and the tip of the voice coil 3 is also joined to the center cap 7. Has been.

  According to the speaker unit configured as described above, it is well known that an audio current is passed through the voice coil 3 (more precisely, the winding portion 32) perpendicular to the magnetic field lines of the DC magnetic field generated in the magnetic gap G. As described above, the voice coil 3 vibrates by obtaining an axial excitation force, and the vibration is converted into air vibration via the diaphragm 5, so that sound can be reproduced. Although the center cap 7 has a dustproof function for preventing dust from entering the magnetic circuit 2, the center cap 7 itself vibrates with the diaphragm 5, so that the acoustic characteristics are affected.

  Here, the configuration of the center cap 7 according to an embodiment will be described. The center cap 7 includes a dome-shaped cap body 71 that is bonded and fixed to the diaphragm 5 as is apparent from FIG. It is comprised by the thin film-like member 72 affixed on.

  The cap body 7 is formed of a metal having a high sound wave propagation speed (hereinafter referred to as sound speed) and a small internal loss, particularly a lightweight metal such as aluminum or magnesium, and its back surface (surface on the voice coil 3 side). The thin film-like member 72 is attached.

  On the other hand, the thin film-like member 72 is a thin piece having a thickness of 10 μm to 150 μm formed of a member having a lower sound speed than the sound speed of the cap body 71 and having a larger internal loss than the cap body 71 has. It is fixed to the back surface of 71 with an adhesive. In other words, a member having a higher sound speed than the thin film member 72 and having a small internal loss is selected as the cap body 71. If the thickness of the thin film member 72 is 10 μm or less, molding and sticking become difficult. If the thickness is 150 μm or more, the weight increases and the efficiency decreases.

Further, the sound velocity (Young's modulus E / square root of density ρ) and internal loss (tan δ) are indexes for evaluating acoustic performance, and these numerical values differ depending on the material. For example, as shown in the table below,
For paper, the speed of sound is 500-2500 m / s, and the internal loss is 0.025-0.055. For wood (solid birch), the speed of sound is 5039 m / s, internal loss is 0.022, for wood (solid wood). The speed of sound is 4896 m / s, the internal loss is 0.019, the speed of sound is 4736 m / s for wood (solid beech), the internal loss is 0.025, the speed of sound is 3000 m / s for polyamide resin, and the internal loss is 0.018. Polyphenylene sulfide resin (PPS) has a sound velocity of 2740 m / s and internal loss of 0.017, polypropylene resin has a sound velocity of 1000 m / s and an internal loss of 0.08, and polypropylene resin (containing 20% by weight of carbon fiber) has a sound velocity of 2150 m. / S, internal loss is 0.048, the speed of sound is 5114 m / s for aluminum, the internal loss is 0.002, and the speed of sound is 5068 m for magnesium. s, internal loss 0.005, copper in the sound velocity 3800 m / s, internal loss 0.001, the titanium sound speed is 5145m / s, internal loss 0.003.

従って、キャップ本体７１の素材として、金属が用いられる場合、薄膜状部材７２の素材には、カバやブナといった木材、又はポリプロピレン樹脂などの合成樹脂フィルムのほか、紙や不織布が好適に用いられる。特に、センターキャップ７２は、振動板５の一部として高音域の再生に寄与するところ、各種素材の中でも音速の高い金属をキャップ本体７１の素材として絶対的に用いることが好ましく、これに対して薄膜状部材７１に音速が低く且つ内部損失の大きい素材を用いれば高音域での共鳴を抑制することが可能となる。

Therefore, when a metal is used as the material of the cap body 71, paper or non-woven fabric is suitably used as the material of the thin film-like member 72, in addition to wood such as birch and beech, or synthetic resin film such as polypropylene resin. In particular, the center cap 72 contributes to the reproduction of the high sound range as a part of the diaphragm 5, and therefore it is preferable to use a metal having a high sound speed as a material of the cap body 71 among various materials. If a material having a low sound velocity and a large internal loss is used for the thin film member 71, resonance in a high sound range can be suppressed.

  3 and 4, the thin film-like member 72 is smaller than the cap body 71 and has a shape anisotropy that does not cover the entire back surface of the cap body 71. Specifically, an annular portion 72a having a smaller diameter than the cap body 71 and a plurality of projecting piece portions 72b extending from the inner peripheral edge of the annular portion 72a toward the center thereof are provided. The annular portion 72a is fixed concentrically with respect to the cap body 71, and functions to prevent reverberation by absorbing the vibration of the cap body 71 together with the projecting piece 72b. As is clear from FIGS. 3 and 4, the thin film member 72 has a cutout portion 72 c formed by partially cutting out a circular member. The cutout portion 72c is formed inside the annular portion 72a and between the projecting piece portions 72b. The cutout portion 72c extends radially from the inner peripheral portion to the outer peripheral portion of the cap body 71, and is concentric with the annular portion 72a. The arc portion 72d is continuously formed. The cutout portions 72c serve to give the cap body 71 anisotropy of sound wave propagation so that the high sound range component is not disturbed by the cap body 71 and is emitted vertically and horizontally. .

  Here, according to the center cap 7 having the thin film-like member 72 as described above, since anisotropy occurs in the sound speed, resonance (coloration) due to standing waves in the high sound range is suppressed to improve sound quality. However, the directivity can be improved by widening the high frequency range by the action of the cutout portion 72 c, and the acoustic characteristics can be easily controlled by the form of the thin film member 72.

  In addition, as the center cap 7 of one embodiment, a polypropylene thin film member 72 (thickness of 100 μm and a cutout portion 72c in the vertical and horizontal directions) is formed on the back surface of a titanium cap body 71 as shown in FIG. When the speaker unit with the orientation) is attached to the center of the diaphragm is driven, the sound quality is clearly improved and the directivity is improved compared to the speaker unit with the conventional cap without the thin film member 72. Improvement (expansion of sound field) was also observed.

  The preferred embodiment of the present invention has been described above. However, the thin film-like member 72 is not limited to the form as shown in FIGS. 3 and 4, and may be as shown in FIGS. 5 (a) to 5 (e). .

3 Voice coil 31 Coil bobbin 32 Winding part 5 Diaphragm 5a Center hole 7 Center cap 71 Cap body 72 Thin film member 72c Cutout part

Claims (2)

A cap body having a propagation speed of a first sound wave and a first internal loss, and covering the center hole of the diaphragm having the center hole;
The second sound wave has a propagation speed that is lower than the propagation speed of the first sound wave and a second internal loss that is greater than the first internal loss, and extends from the inner periphery to the outer periphery of the cap body. A thin film-like member attached to the back surface of the cap body having a cutout portion partially cut out so as to spread radially;
A speaker center cap. A voice coil in which a conductive wire is wound around the outer periphery of the coil bobbin;
A diaphragm having a central hole communicating with the voice coil;
A center cap mounted at the center of the diaphragm,
The center cap is
A cap body having a propagation velocity of a first sound wave and a first internal loss and covering the central hole;
The second sound wave has a propagation speed that is lower than the propagation speed of the first sound wave and a second internal loss that is greater than the first internal loss, and extends from the inner periphery to the outer periphery of the cap body. A thin film-like member attached to the back surface of the cap body having a cutout portion partially cut out so as to spread radially;
The speaker unit with a cap characterized by having.

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