JP2008141274A - Electroacoustic transducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize more an electroacoustic transducer excellent in acoustic characteristics. <P>SOLUTION: The electroacoustic transducer includes: an inner magnetic type magnetic circuit 2 composed of a planar magnet 4 and a top plate 5 successively layered on the upper part of a yoke 3; a voice coil 7 disposed inside a magnetic gap 6 formed between the side wall of the yoke 3 and the top plate 5; a diaphragm 9 for holding the voice coil 7; and a frame 1 in a rectangular shape for holding the inner magnetic type magnetic circuit 2 and the diaphragm 9. A ventilation part 8 passing through from an upper surface to a lower surface at the center part of the top plate 5, the magnet 4, and the yoke 3 is formed. The ventilation part 8 formed at the magnet 4 constituting the inner magnetic type magnetic circuit 2 is a ventilation hole 4a disposed at the center part of the planar magnet 4 or a ventilation slit (4b) in which end faces of two planar magnets (4A and 4B) are disposed facing each other and which is set to a desired clearance t. The size in the width direction of the magnet can be set regardless of the size of a hole diameter. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electroacoustic transducer that is incorporated in a mobile communication device such as a mobile phone or a PDA, and notifies an incoming call by vibrating a panel, a casing of a telephone, or the like.

2. Description of the Related Art Conventionally, there is a narrow rectangular electroacoustic transducer in which a rectangular inner magnet type magnetic circuit and a diaphragm to which a rectangular voice coil driven by the magnetic circuit is fixed are held in a rectangular frame. This electroacoustic transducer has a rectangular inner magnet type composed of a rectangular yoke held on a frame, a rectangular plate-shaped magnet joined to the bottom surface of the yoke, and a rectangular plate-shaped top plate joined to the upper surface of the magnet. A magnetic circuit is configured, and a rectangular magnetic gap into which a rectangular voice coil is fitted is formed between the inner surface of the yoke and the outer surface of the top plate. When a sound signal current is supplied to the voice coil, the diaphragm that fixes the voice coil vibrates and generates sound and sound due to electromagnetic action with the magnetic field of the magnetic gap. In contrast to the above-described inner magnet type magnetic circuit, there is an outer magnet type magnetic circuit in which a magnet is disposed outside a magnetic gap. (For example, see Patent Document 1)
Japanese Patent Laying-Open No. 2005-260561 (pages 4-6, FIGS. 4 and 5)

  The structure of the electroacoustic transducer disclosed in Patent Document 1 is shown in FIG. In FIG. 7, reference numeral 21 denotes a resin-made rectangular frame having insulating properties, and elongated plate-like terminals 22 are insert-molded at both ends. A circular outer magnet type magnetic circuit 23 is held in the rectangular recess of the frame 21. The configuration of the outer magnet type magnetic circuit 23 includes a yoke 24 made of a magnetic material provided with a rectangular flange 24b at one end of a cylindrical center pole 24a, a rectangular plate-like magnet 25 having substantially the same shape as the yoke 24. An annular pole piece 26 is laminated on the upper surface of the magnet 25. Here, the magnet 25 has a split structure in which the magnet 25 is divided into two at a substantially central portion in the longitudinal direction, and the dimension in the short direction of the magnet 25 is a circle normally used for the circular outer magnet type magnetic circuit 23. The outer diameter of the annular magnet may be smaller, and the electroacoustic transducer can be reduced in size.

  A circular magnetic gap 27 for generating a magnetic field is formed between the outer peripheral surface of the tip of the center pole 24 a of the yoke 24 and the inner peripheral surface of the pole piece 26 in the outer magnet type magnetic circuit 23. A diaphragm 28 made of a resin film is mounted and held on the upper surface of the frame 21 in which the magnetic gap 27 is opened. One end of a circular voice coil 29 is joined to the center of the lower surface of the diaphragm 28 with an adhesive, and the tip portion is fitted into the circular magnetic gap 27.

  A sheet metal protector 30 is mounted on the upper surface of the frame 21 so as to cover the vibration plate 28, and the vibration plate 28 is protected by the protector 30. The protector 30 is formed with a plurality of sound emitting holes 30a. Further, a compensation cloth 31 having substantially the same shape as the frame 21 is attached to the upper surface of the frame 21 with an adhesive or a double-sided adhesive tape from above the protector 30 so as to cover the entire surface. This compensation cloth 31 covers the sound emitting hole 30a and exhibits a control function for improving acoustic characteristics by preventing excessive vibration and excessive air leakage of the diaphragm 28, and at the same time exhibits a dustproof function.

  In addition, the frame 21 on the lower surface side of the diaphragm 28 is provided with two vertical back holes 32 penetrating from the upper surface to the lower surface. The backhaul 32 is provided on both the left and right sides of the recess for housing the circular outer magnet type magnetic circuit 23. The opened back hole 32 has a ventilation function. Compensation cloths 33 may be attached at two locations so as to cover the backhaul 32. The compensation cloth 33 exhibits a dustproof function and a control function for improving acoustic characteristics.

  The problem to be solved is that in the electroacoustic transducer equipped with the outer magnet type magnetic circuit having the above-described structure, the shape of the magnet is plate-like in the inner magnet type and it is easy to ensure the strength, whereas in the outer magnet type, Since it is annular, it is difficult to ensure strength. In addition, the backhaul provided at two locations of the frame has an air circulation function, but since it is provided at the outer frame of the outer magnet type magnetic circuit, it is difficult for sound to propagate efficiently. In addition, since it is formed in a narrow portion between the left and right leg portions and the concave portion on the lower surface of the frame, there is a problem that processing is difficult.

  The present invention eliminates the above-mentioned drawbacks, and an object of the present invention is to provide a ventilation portion at the center of the inner magnet type magnetic circuit. That is, by forming a ventilation part that penetrates from the upper surface to the lower surface at the center of the top plate, magnet, and yoke constituting the inner magnet type magnetic circuit, sound can be efficiently transmitted without being disturbed by the magnet, and the acoustic characteristics can be improved. At the same time, it is an object of the present invention to provide an electroacoustic transducer in which the short direction of the magnet can be reduced regardless of the size of the air hole, and the size can be further reduced.

  In order to achieve the above object, an electroacoustic transducer according to the present invention includes a yoke, a magnetic circuit unit composed of a plate-like magnet and a top plate that are sequentially stacked on the yoke, and a magnetic circuit unit. A voice coil disposed in a magnetic gap formed between the side wall of the yoke and the top plate, a diaphragm for holding the voice coil, the magnetic circuit unit and the diaphragm in a rectangular frame In the electroacoustic transducer to be held, the magnetic circuit unit is an internal magnet type in which a magnet is disposed inside a magnetic gap, and a ventilation portion penetrating from the upper surface to the lower surface is formed at the center of the top plate, the magnet and the yoke. It is characterized by this.

  Further, the ventilation portion formed in the magnet constituting the magnetic circuit portion is a ventilation hole disposed in the central portion of the plate-like magnet.

  Further, the ventilation part formed in the magnet constituting the magnetic circuit part is a ventilation slit in which end faces of two plate magnets are arranged to face each other and set to a desired gap.

  The electroacoustic transducer of the present invention is provided with a ventilation portion having a function of improving acoustic characteristics penetrating from the upper surface to the lower surface at the center of the top plate, magnet, and yoke constituting the inner magnet type magnetic circuit. In particular, in the case of a plate-shaped magnet, if a vent hole is provided in the center, or the size in the width (short) direction of the magnet is required to be a processing limit of the vent hole, for example, 2.0 mmφ or less, 2 Ventilation slits are provided with the end faces of the plate magnets facing each other and set at a desired gap. By forming a ventilation part in the center part of the inner magnet type magnetic circuit, sound can be efficiently transmitted without being obstructed by the magnet. Moreover, further miniaturization of the electroacoustic transducer can be realized. Further, the assembly of the inner magnet type magnetic circuit has a great effect such as being able to work accurately with reference to the ventilation part formed in the center part of the top plate, the magnet and the yoke.

  The electric vibration converter of the present invention will be described with reference to the drawings.

  1 to 3 relate to a first embodiment of the present invention, FIG. 1 is a cross-sectional view of an electroacoustic transducer, FIG. 2 is a cross-sectional view of an internal magnetic circuit of FIG. 1, and FIG. FIG. 1 to 3, the frame 1 is a resin frame and is formed in a rectangular shape. An inner magnet type magnetic circuit 2 is held in a rectangular recess of the frame 1. The internal magnetic circuit 2 includes a flat magnet 4 and a top plate 5 that are sequentially stacked inside a yoke 3 having a substantially bowl-shaped cross section. A voice coil 7 is arranged in a gap (magnetic gap) 6 formed between the inner magnetic type magnetic circuit 2 and the inner peripheral portion of the side wall of the yoke 3 and the outer peripheral portion of the flat top plate 5. . A vent hole 5a is formed at the center of the top plate 5, a vent hole 4a is formed at the center of the magnet 4, and a vent hole 3a is formed at the center of the yoke 3. A ventilation portion 8 that penetrates from the upper surface to the lower surface is formed at the center of the magnetic circuit 2.

  A diaphragm 9 made of a resin film is mounted and held on the upper surface of the frame 1 in which the magnetic gap 6 is opened. One end of the voice coil 7 described above is joined to the center of the lower surface of the diaphragm 9 with an adhesive, and the tip portion is fitted into the magnetic gap 6.

  A sheet metal protector 10 is mounted on the upper surface of the frame 1 so as to cover the diaphragm 9, and the diaphragm 9 is protected by the protector 10. A mesh 11 is attached to the lower surface of the yoke 3 with an adhesive or a double-sided adhesive tape so as to close the ventilation portion 8. The mesh 11 plays a role of dust prevention and also exhibits a control function for improving acoustic characteristics.

  The operation and effect of the electroacoustic transducer having the above-described configuration will be described. In the electroacoustic transducer of the present invention, a vent is formed in the center of each of the top plate, the magnet, and the yoke in the center of the inner magnet type magnetic circuit, and the vent is configured to communicate from the upper surface to the lower surface. Therefore, sound propagates efficiently without being disturbed by the magnet. In addition, the mesh attached to the lower surface of the yoke serves to prevent dust and contributes to improvement of acoustic characteristics. Furthermore, when assembling the inner magnet type magnetic circuit, it is possible to work accurately with reference to the vent hole formed in the central portion of the top plate, the magnet and the yoke.

  4 to 6 relate to a second embodiment of the present invention, FIG. 4 is a cross-sectional view of an internal magnetic circuit, FIG. 5 is a developed plan view of FIG. 4, and FIG. 6 is a divided yoke of FIG. It is a development top view of a state. 4 and 5, the difference from Example 1 described above is that when the size in the width (short) direction of the magnet 4 is required to be a processing limit of the air hole, for example, 2.0 mmφ or less, 1 is required. Since the air hole cannot be formed with a single plate-shaped magnet, the desired clearance t is set regardless of the size in the width direction of the magnet by arranging the end surfaces of the two plate-shaped magnets 4A and 4B to face each other. The ventilation slit 4b is formed.

  As shown in FIG. 6, when a vent hole is to be set in the top plate 5, the top plate 5 is divided into two if a defect such as a crack occurs due to the relationship between the size in the width direction and the hole diameter. The ventilation slit 5b may be formed by arranging the end surfaces of the divided top plates 5A and 5B to face each other.

  The operation and effect of the electroacoustic transducer having the above-described configuration will be described. In the electroacoustic transducer of the present invention, the ventilation slit is set regardless of the size of the hole diameter in the width direction of the magnet (if necessary, the top plate). In particular, it is effective when the size in the width (short) direction of the magnet is required to be a processing limit of the air hole, for example, 2.0 mmφ or less, and further miniaturization of the electroacoustic transducer can be realized. As in the first embodiment, by forming a ventilation portion at the center of the inner magnet type magnetic circuit, the distortion rate in the high frequency region of the electroacoustic transducer is improved, and sound is efficiently transmitted without being obstructed by the magnet. However, this contributes to improvement of acoustic characteristics. Furthermore, when assembling the inner magnet type magnetic circuit, it is possible to work accurately with reference to the ventilation portion formed in the central portion of the top plate, the magnet and the yoke.

It is sectional drawing of the electroacoustic transducer concerning Example 1 of this invention. FIG. 2 is a cross-sectional view of the inner magnet type magnetic circuit of FIG. 1. FIG. 3 is a plan view of FIG. 2. It is sectional drawing of the internal magnet type | mold magnetic circuit concerning Example 2 of this invention. FIG. 5 is a developed plan view of FIG. 4. It is a top view of the state which divided | segmented the yoke of FIG. It is sectional drawing of the conventional electroacoustic transducer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Frame 2 Inner magnet type magnetic circuit 3 Yoke 3a, 4a, 5a Vent hole 4, 4A, 4B Magnet 4b, 5b Vent slit 5 Top plate 6 Magnetic gap 7 Voice coil 8 Ventilation part 9 Diaphragm 10 Protector 11 Mesh

Claims (3)

  Within a magnetic gap formed between a yoke, a magnetic circuit portion composed of a plate-like magnet and a top plate sequentially stacked on the top of the yoke, and a side wall of the yoke of the magnetic circuit portion and the top plate An electroacoustic transducer that holds a voice coil to be arranged, a diaphragm that holds the voice coil, and the magnetic circuit unit and the diaphragm in a rectangular frame, wherein the magnetic circuit unit is located inside a magnetic gap. An electroacoustic transducer characterized in that an inner magnet type in which a magnet is disposed on the top plate, and a ventilation portion penetrating from the upper surface to the lower surface is formed at a central portion of the top rate, magnet and yoke.   The electroacoustic transducer according to claim 1, wherein the ventilation portion formed in the magnet constituting the magnetic circuit portion is a ventilation hole disposed in a central portion of the plate-like magnet. 2. The electroacoustic according to claim 1, wherein the ventilation portion formed in the magnet constituting the magnetic circuit portion is a ventilation slit which is set at a desired gap by arranging the end faces of the two plate magnets to face each other. converter.

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