JP2012104865A - Electromagnetic transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive electromagnetic transducer that has high rigidity of a diaphragm and satisfactory performance.SOLUTION: In a frame 15, a plurality of strip-shaped permanent magnets 13 having different polarities at obverse and reverse surfaces are fixed at predetermined intervals with the polarities alternated. Iron plates 16 are bonded to end surfaces of the permanent magnets 13 opposite to the surfaces fixed to the frame 15. A diaphragm 11 is mounted on the frame 15 so as to cover the permanent magnets 13 and the iron plates 16. The diaphragm 11 has an uneven shape corresponding to an uneven structure comprising the plurality of permanent magnets 13 fixed at the predetermined intervals, and diaphragm reference surfaces 11d defining concaving portions of the uneven shape are in the same height position as the iron plates 16, that is, in a high magnetic flux density position, and has a voice coil 11b formed thereon. Furthermore, a diaphragm surface material 17 is attached to a surface side of diaphragm protruding portions 11c to provide improved rigidity.

Description

  The present invention relates to an electromagnetic transducer that reproduces sound from an audio signal by combining a permanent magnet and a diaphragm.

  A conventional electromagnetic transducer is disposed so that a permanent magnet plate and a diaphragm are opposed to each other and covered so as to be sandwiched between members such as a frame, and is attached to, for example, a speaker housing.

The permanent magnet plate has strip-shaped magnet portions (also referred to as a multipolar magnetized pattern) alternately having different polarities at regular intervals. The diaphragm is formed by forming a meandering coil pattern at a position opposite to an interval at a boundary of different polarity of the permanent magnet plate, that is, a so-called magnetized neutral zone. When the current of the audio signal flows through the serpentine coil pattern formed on the diaphragm, the serpentine coil pattern and the multipolar magnetization pattern of the permanent magnet are electromagnetically coupled, and the current is applied to the serpentine coil pattern by Fleming's law. The diaphragm vibrates by acting. Sound waves generated by this vibration are radiated to the outside through sound emission holes drilled in the permanent magnet plate and the frame, and audio reproduction is performed (see, for example, Patent Document 1).
Further, the diaphragm is reinforced with a rigidity imparting member for the purpose of preventing the conductor coil of the meandering coil pattern formed on the diaphragm due to this vibration from being disconnected due to metal fatigue (for example, see Patent Document 2). .

Conventionally, there is a thin speaker called “gummazon type” having a configuration similar to that of the above-described electromagnetic transducer and configured by a long bar-shaped magnet instead of the permanent magnet plate. The Gamson-type thin speaker has a configuration in which the front and back of the diaphragm are sandwiched between bar magnets with alternately arranged bar magnets, and the poles of the bar magnets facing each other across the diaphragm are the same. This member is composed of the same member as the electromagnetic transducer.
Such a thin speaker has a diaphragm formed by attaching copper or aluminum foil to a thin film made of polyester or polyimide and etching a voice coil pattern (see, for example, Non-Patent Document 1). The thin speaker having this configuration also has the same sound wave generation operation for audio reproduction as the electromagnetic transducer.

Japanese Patent No. 3192372 International Publication No. 2003/073787

Edited by Takeo Yamamoto, Speaker System, Radio Technology, July 1977

Since conventional electromagnetic transducers are configured as described above, if a permanent magnet plate is placed only on one surface of the diaphragm to obtain an inexpensive speaker, the vicinity of the voice coil on the side without the permanent magnet plate There is a problem that the sound pressure level is also reduced because the magnetic flux density is reduced.
Further, since the diaphragm base material has a flat thin film structure of several tens of microns, the mechanical strength is small, and natural resonance occurs even at a low frequency. When resonance occurs, there is a problem that abnormal noise due to abnormal vibration of the diaphragm and noise per diaphragm magnet due to increase in amplitude of the diaphragm are generated.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain a low-cost electromagnetic transducer in which the vibration plate has high rigidity and excellent performance.

  The electromagnetic transducer according to the present invention includes a frame in which a plurality of strip-shaped permanent magnets having different polarities on the front and back sides are fixed at predetermined intervals with alternating polarities, and an end surface opposite to the surface fixed to the frame of the permanent magnet Is an uneven shape corresponding to an uneven structure composed of a plurality of permanent magnets attached to a frame so as to cover the permanent magnet and the iron plate, and fixed at a predetermined interval. And a diaphragm in which a meandering coil pattern is formed at the same height position.

  According to this invention, the sound pressure level can be increased by adhering the iron plate to the end face of the permanent magnet to concentrate the magnetic flux, and arranging the meandering coil pattern at the high magnetic flux density position where the magnetic flux is concentrated, and the permanent magnet It is possible to reduce the cost by disposing only on one side of the diaphragm. Moreover, the rigidity of the diaphragm can be increased by providing the diaphragm with a three-dimensional structure having an uneven shape. As a result, it is possible to obtain a low-cost electromagnetic transducer having high vibration plate rigidity and excellent performance.

It is an external appearance perspective view which shows the structure of the electromagnetic transducer which concerns on Embodiment 1 of this invention, Fig.1 (a) shows the surface, FIG.1 (b) shows a back surface. It is sectional drawing which cut | disconnected the electromagnetic transducer which concerns on Embodiment 1 of this invention along the AA line shown to Fig.1 (a). It is a perspective view which shows the structure of the back surface of the diaphragm in the electromagnetic transducer which concerns on Embodiment 1 of this invention. It is the figure which expanded a part of sectional drawing which cut | disconnected the electromagnetic transducer which concerns on Embodiment 1 of this invention along the AA line shown to Fig.1 (a), and shows a magnetic circuit.

Embodiment 1 FIG.
1A and 1B are external perspective views showing the configuration of an electromagnetic transducer 10 according to Embodiment 1 of the present invention, in which FIG. 1A shows the front surface and FIG. 1B shows the back surface. 2 is a cross-sectional view of the electromagnetic transducer 10 cut along the line AA shown in FIG. 1A, and FIG. 3 is a perspective view showing the configuration of the diaphragm 11 as seen from the back surface direction. FIG. 4 is an enlarged sectional view of only a main part constituting the magnetic circuit. 1 to 4 are exaggerated and enlarged for the sake of simplicity, and are different from the actual scale. Here, for convenience of explanation, the front and back surfaces of the electromagnetic transducer 10 are specified as shown in FIGS. 1A and 1B, but any direction may be used as the front and back surfaces.

  The electromagnetic transducer 10 includes a diaphragm 11, a permanent magnet 13, a frame 15, an iron plate 16, and a diaphragm surface material 17. A diaphragm support 12 is connected to the periphery of the diaphragm 11, and the outer periphery of the diaphragm support 12 is fixed to the opening surface periphery of the frame 15. By providing the diaphragm support 12 in this manner, the diaphragm 11 covering the opening surface of the frame 15 can be displaced in the vertical direction.

  On the inner wall surface of the frame 15, a plurality of strip-shaped permanent magnets 13 are fixed in parallel with predetermined gaps so that alternate polarities are directed to the diaphragm 11. A band-shaped iron plate 16 is bonded to the end surface of the permanent magnet 13 facing the diaphragm 11. In addition, air vent holes 14 opened to the outside are provided at regular intervals in portions of the frame 15 where the permanent magnets 13 are not fixed.

  The diaphragm base 11a that is the base of the diaphragm 11 is made of a thermoplastic film such as polyetherimide (PEI), polyethylene terephthalate (PET), or polyethylene naphthalate (PEN). Voice coils 11b made of copper, aluminum foil or the like are formed in a meandering shape on the front and back surfaces of the diaphragm base 11a. The diaphragm base 11a is provided with a convex diaphragm convex portion 11c protruding from the diaphragm reference surface 11d when the portion where the voice coil 11b is formed is a diaphragm reference surface 11d. Thus, by making the diaphragm 11 into a three-dimensional structure in an uneven shape, the rigidity of the diaphragm 11 can be improved and the occurrence of resonance can be suppressed. The diaphragm reference surface 11d is aligned so as to be at the same height as the iron plate 16 when the electromagnetic transducer 10 is assembled.

  Further, a diaphragm surface material 17 made of a lightweight and rigid member such as aluminum or a polymer material is attached to the surface of the diaphragm 11 on the diaphragm convex portion 11c side. By using the uneven diaphragm 11 as a honeycomb core material and pasting the diaphragm surface material 17 thereon to form a substantially honeycomb panel, the highly rigid diaphragm 11 can be obtained and the occurrence of resonance can be suppressed. Can do. The diaphragm 11 may be used alone without attaching the diaphragm surface material 17.

  Here, a method for forming the diaphragm 11 will be described. First, the voice coil 11b is formed by pasting or etching copper, aluminum foil or the like in a meandering shape on the front and back surfaces of the planar diaphragm base 11a. And the diaphragm convex part 11c is formed in the diaphragm base material 11a by hot press, vacuum forming, etc. on the basis of the attachment location of the voice coil 11b. That is, the reference portion is directly the diaphragm reference surface 11d, and the portion where the voice coil 11b is not attached projects to form the diaphragm convex portion 11c. Therefore, although the voice coil 11b and the diaphragm base material 11a having different elongation rates are bonded together, the voice coil 11b and the diaphragm base material 11a can be molded integrally, and the diaphragm base material 11a is not broken. The protruding height of the diaphragm convex portion 11c from the diaphragm reference surface 11d is such that the diaphragm 11 supported by the diaphragm support portion 12 does not come into contact with the permanent magnet 13 when the diaphragm 11 vibrates up and down. .

  Next, the operation principle of the electromagnetic transducer 10 will be described. In the vicinity of the voice coil 11 b of the diaphragm 11, the magnetic flux emitted from the N pole of the permanent magnet 13 to which the iron plate 16 is bonded crosses the voice coil 11 b and reaches the S pole of a different permanent magnet 13. When a current (audio signal) is supplied from the outside to the voice coil 11b of the diaphragm 11, the current flowing through the voice coil 11b and the magnetization pattern (magnetic flux density) of the permanent magnet 13 are electromagnetically coupled, and according to Fleming's law. Driving force is generated. The generated driving force vibrates the diaphragm 11 that is supported by the diaphragm supporter 12 so as to be displaceable. Since the iron plate 16 is bonded to the end face of the permanent magnet 13, the iron plate 16 forms a magnetic pole, and the magnetic flux density is concentrated on the portion (B line shown in FIG. 4) that linearly advances from the N pole to the S pole. In the present embodiment, since the voice coil 11b is disposed at the height position (high magnetic flux density position) of the B line where the magnetic flux density becomes maximum in the magnetic gap between the permanent magnets, the magnetic flux crossing the voice coil 11b increases. Sound pressure level can be improved.

As described above, according to the first embodiment, since the diaphragm 11 is formed in the concavo-convex shape by forming the diaphragm convex portion 11c, the rigidity is improved and the occurrence of resonance can be suppressed. Further, since the diaphragm surface material 17 is attached to the surface of the diaphragm convex portion 11c of the diaphragm 11 to form a substantially honeycomb panel shape, the rigidity can be further improved while maintaining the light weight.
Further, since the diaphragm 11 is three-dimensionally formed into a concavo-convex shape based on the diaphragm reference surface 11d on which the voice coil 11b is molded, the diaphragm base is formed regardless of the difference in elongation between the diaphragm base 11a and the voice coil 11b. The material 11a is not broken and high-precision molding can be realized.

  Further, the sound pressure level can be increased by adhering the iron plate 16 to the end face of the permanent magnet 13 to concentrate the magnetic flux and disposing the voice coil 11b at the high magnetic flux density position where the magnetic flux is concentrated. Since the sound pressure level is improved, it is possible to reduce the number of permanent magnets by halving the number of permanent magnets 13 by arranging the permanent magnets 13 only on one surface of the diaphragm 11, thereby reducing the cost.

  DESCRIPTION OF SYMBOLS 10 Electromagnetic transducer, 11 Diaphragm, 11a Diaphragm base material, 11b Voice coil, 11c Diaphragm convex part, 11d Diaphragm reference surface, 12 Diaphragm support part, 13 Permanent magnet, 14 Air vent hole, 15 Frame, 16 Iron plate 17 Surface material of diaphragm.

Claims (3)

A plurality of strip-shaped permanent magnets with different polarities on the front and back, a frame in which the polarities are alternately fixed and fixed at predetermined intervals,
An iron plate bonded to the end surface opposite to the surface fixed to the frame of the permanent magnet;
The concavo-convex shape is a concavo-convex shape corresponding to the concavo-convex structure composed of the plurality of permanent magnets attached to the frame so as to cover the permanent magnet and the iron plate, and the concavo-convex concave portion is the iron plate And a diaphragm in which a meandering coil pattern is formed at the same height position.   The vibration plate has a concavo-convex shape formed by forming a convex portion of a planar diaphragm base material on which a meandering coil pattern is formed with reference to a portion on which the meandering coil pattern is formed. The electromagnetic transducer according to 1.   The electromagnetic transducer according to claim 1, wherein the diaphragm includes a surface material attached to the surface of the convex and concave portion.

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