WO2010100680A1

WO2010100680A1 - Electromagnetic converter

Info

Publication number: WO2010100680A1
Application number: PCT/JP2009/001917
Authority: WO
Inventors: 吉田俊治
Original assignee: 三菱電機エンジニアリング株式会社
Priority date: 2009-03-04
Filing date: 2009-04-27
Publication date: 2010-09-10

Abstract

On a frame (15), a plurality of strip-like permanent magnets (13), each of which has different polarities at the front and rear, are fixed at prescribed intervals with polarities alternately arranged. On an end surface opposite to the surface fixed to the frame (15) of the magnets (13), an iron plate (16) is bonded. A vibrating plate (11) is attached to the frame (15) to cover the permanent magnets (13) and the iron plate (16). The vibrating plate (11) has an uneven shape which corresponds to an uneven structure composed of the permanent magnets (13) fixed at the prescribed intervals, and a vibrating plate reference surface (11d) to be a recessed section of the uneven shape is at a position at the same height as the iron plate (16), namely, at a high magnetic flux density position, and a voice coil (11b) is formed on the vibrating plate. Furthermore, on the front side of the protruding section (11c) of the vibrating plate, a vibrating plate front side material (17) is bonded to improve rigidity.

Description

Electromagnetic transducer

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 such 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 polarities of the permanent magnet plate, 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 to perform audio reproduction (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 (see, for example, 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

Since the conventional electromagnetic transducer is configured as described above, after magnetizing the permanent magnets constituting the electromagnetic transducer one by one, the magnets must be assembled alternately with different polarities. There is a problem that the cost is higher than that of a cone type speaker that can magnetize all the magnets by the magnetizing operation. Moreover, the assembly operation of the electromagnetic transducer has to be performed in a state where the permanent magnet is magnetized, and there is a problem that iron powder or the like is mixed during the assembly.
On the other hand, when a permanent magnet plate is disposed only on one surface of the diaphragm in order to obtain an inexpensive speaker, the sound pressure level also decreases because the magnetic flux density near the voice coil on the side without the permanent magnet plate decreases. There was a problem. Moreover, the fluctuation | variation of the magnetic flux distribution produced in a diaphragm front and back direction becomes large, and there existed a subject which distortion generate | occur | produced.
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 having a diaphragm having 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 an 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.

The electromagnetic transducer according to the present invention is fixed in a staggered arrangement alternately on a pair of inner wall surfaces of a hollow frame having sound radiation holes on the surface, and opposite to the fixed surface. Concavities and convexities composed of a plurality of permanent magnets having opposite polarities alternately opposed to each other, iron plates fixed to the opposite end surfaces of the staggered permanent magnets, and opposite end surfaces of the staggered permanent magnets Concave and convex shape corresponding to the structure, having a reference plane parallel to the concave and convex portions at the same height as the iron plate at the boundary between the concave and convex portions of the concave and convex shapes, and a meandering coil pattern on the reference plane Is provided with a molded diaphragm.

According to the present invention, a plurality of permanent magnets are alternately fixed to the pair of inner wall surfaces of the frame in a staggered arrangement, and opposite end surfaces opposite to each other and having opposite polarities. Thus, after permanent magnets that are not magnetized are attached to the frame and the electromagnetic transducer is assembled, all the permanent magnets can be magnetized together. 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. The structure of the electromagnetic transducer based on Embodiment 2 of this invention is shown, Fig.5 (a) is an external appearance perspective view, FIG.5 (b) is an exploded perspective view. It is sectional drawing which cut | disconnected the electromagnetic transducer which concerns on Embodiment 2 of this invention along CC line shown in FIG. It is the figure which expanded a part of sectional drawing which cut | disconnected the electromagnetic transducer which concerns on Embodiment 2 of this invention along CC line shown in FIG. 5, and shows a magnetic circuit.

Hereinafter, in order to describe the present invention in more detail, modes for carrying out the present invention will be described with reference to the accompanying drawings.
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 cross-sectional view of only the 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.

A plurality of strip-shaped permanent magnets 13 are fixed to the inner wall surface of the frame 15 in parallel with gaps of a predetermined interval so that the polarities of the diaphragms 11 are alternate. 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 material 11a serving as the base material 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.

Embodiment 2. FIG.
5A and 5B show a configuration of an electromagnetic transducer 20 according to Embodiment 2 of the present invention. FIG. 5A is an external perspective view, and FIG. 5B is an exploded perspective view. 6 is a cross-sectional view of the electromagnetic transducer 20 cut along the line CC shown in FIG. 5, and FIG. 7 is an enlarged cross-sectional view of a part thereof. 5 to 7 are exaggerated and enlarged for the sake of simplicity, and are different from the actual scale.

The electromagnetic transducer 20 includes a diaphragm 21,

permanent magnets

22 and 23, an upper frame 26, a lower frame 27, and an iron plate 28. The frame formed by superposing the upper frame 26 and the lower frame 27 has a hollow casing structure. Here, for convenience, they are referred to as an upper frame and a lower frame, but they may be turned upside down.

A permanent magnet 22 is fixed to the inner wall surface of the upper frame 26, that is, the surface facing the diaphragm 21 at a predetermined interval. A plurality of rows of permanent magnets 23 are fixed to a position corresponding to a gap between the permanent magnets 22 on the inner wall surface of the lower frame 27, that is, the surface facing the diaphragm 21. Therefore, as shown in FIG. 6, the

permanent magnets

22 and 23 are staggered and fixed to the upper frame 26 and the lower frame 27 alternately.

As shown in FIG. 6, the permanent magnet 22 fixed to the upper frame 26 has an N pole on the end face fixed to the upper frame 26 and an S pole on the end face facing the diaphragm 21. On the other hand, the permanent magnet 23 fixed to the lower frame 27 has an end surface fixed to the lower frame 27 as an S pole and an end surface facing the diaphragm 21 as an N pole. Therefore, the

permanent magnets

22 and 23 have a configuration in which end faces facing each other on the side opposite to the fixed face have different polarities.

In the portions of the upper frame 26 and the lower frame 27 where the

permanent magnets

22 and 23 are not fixed, sound radiation holes 25 opened to the outside are provided at regular intervals. Further, an iron plate 28 is bonded to the end surfaces of the

permanent magnets

22 and 23 facing the vibration plate 21.

The diaphragm substrate 21a that is the substrate of the diaphragm 21 is made of a thermoplastic film such as polyetherimide (PEI), polyethylene terephthalate (PET), or polyethylene naphthalate (PEN). Voice coils 21b made of copper, aluminum foil or the like are formed in a meandering shape on the front and back surfaces of the diaphragm base 21a. Moreover, the diaphragm base 21a is formed with a diaphragm protrusion 21c protruding toward the upper frame 26 and a diaphragm recess 21d protruding toward the lower frame 27. A diaphragm reference surface 21f for arranging the voice coil 21b is provided at a boundary portion between the diaphragm convex portion 21c and the diaphragm concave portion 21d. The diaphragm convex portion 21c, the diaphragm concave portion 21d, and the diaphragm reference surface 21f have surfaces parallel to each other.

Further, each of the diaphragm convex portion 21c and the diaphragm concave portion 21d is provided with a diaphragm rib portion 21e having an uneven structure or a rib structure for improving the rigidity of the diaphragm 21. However, since the rigidity of the diaphragm 21 is improved by the uneven shape including the diaphragm convex part 21c and the diaphragm concave part 21d, the diaphragm rib part 21e may not be provided. Further, the diaphragm rib portion 21e may be provided only on a part of the diaphragm convex part 21c and the diaphragm concave part 21d.

A diaphragm support 24 is fixed to the outer periphery of the diaphragm 21, and the diaphragm 21 is fixed to the inner periphery of the upper frame 26 or the lower frame 27 so that the diaphragm 21 can be displaced vertically. Is done. As shown in FIG. 6, the diaphragm support member 24 fixes the diaphragm 21 to the frame. At this time, the diaphragm reference surface 21 f on which the voice coil 21 b is disposed is positioned at the same height as the iron plate 28. Aligned.

Here, a method for forming the diaphragm 21 will be described. First, the voice coil 21b 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 21a. Then, the diaphragm convex portion 21c and the diaphragm concave portion 21d are formed on the diaphragm base material 21a by hot pressing, vacuum forming, or the like with reference to the location where the voice coil 21b is attached. That is, the reference portion is directly the diaphragm reference surface 21f, and the portions where the voice coil 21b is not attached are the diaphragm convex portion 21c and the diaphragm concave portion 21d. Therefore, although the voice coil 21b and the diaphragm base material 21a having different elongation rates are bonded together, the voice coil 21b and the diaphragm base material 21a can be integrally molded, and the diaphragm base material 21a is not broken. The protruding height of the diaphragm convex portion 21c and the diaphragm concave portion 21d from the diaphragm reference surface 21f is such that when the diaphragm 21 supported by the diaphragm support member 24 vibrates and is displaced up and down, 23 to the extent that it does not touch.

Next, a method for magnetizing the

permanent magnets

22 and 23 will be described. First, the permanent magnet 22 is fixed to the upper frame 26 and the permanent magnet 23 is fixed to the lower frame 27 in a staggered arrangement, and the electromagnetic transducer 20 is assembled with the diaphragm 21 sandwiched therebetween. Thereafter, the assembled electromagnetic transducer 20 is uniformly magnetized in a direction perpendicular to the upper frame 26 and the lower frame 27, whereby the

permanent magnets

22 and 23 are magnetized in the same magnetic pole direction. Therefore, the end surfaces of the

permanent magnets

22 and 23 facing each other have alternating strip-like polarities.

Next, the operating principle of the electromagnetic transducer 20 will be described. As shown in FIG. 7, in the vicinity of the voice coil 21 b of the diaphragm 21, the magnetic flux emitted from the N pole of the permanent magnet 23 to which the iron plate 28 is bonded crosses the voice coil 21 b and reaches the S pole of a different permanent magnet 22. When a current (audio signal) is supplied to the voice coil 21b of the diaphragm 21 from the outside, the current flowing through the voice coil 21b and the magnetization patterns (magnetic flux density) of the

permanent magnets

22 and 23 are electromagnetically coupled to each other. A driving force is generated according to the law. Due to the generated driving force, the diaphragm 21 supported so as to be displaceable by the diaphragm support portion 24 vibrates. This vibration is radiated from the sound radiation hole 25 as audio reproduction sound. Since the iron plate 28 is bonded to one end of the

permanent magnets

22 and 23 of the electromagnetic transducer 20, the iron plate 28 forms a magnetic pole and linearly travels from the N pole to the S pole (indicated by an arrow D in FIG. 7). The magnetic flux density is concentrated on. In this embodiment, since the voice coil 21b is disposed at the height of the arrow D where the magnetic flux density is maximized in the magnetic gap between the permanent magnets, the magnetic flux crossing the voice coil 21b is increased, and the sound pressure level is improved. be able to.

As described above, according to the second embodiment, since the diaphragm 21 is formed into a concavo-convex shape by forming the diaphragm convex portion 21c and the diaphragm concave portion 21d, the rigidity is improved and the occurrence of resonance is suppressed. it can. Further, since the diaphragm rib portion 21e is formed in the diaphragm convex portion 21c and / or the diaphragm concave portion 21d, the rigidity can be further improved.
Furthermore, since the voice coil 21b is formed on the diaphragm reference surface 21f, when the diaphragm 21 is three-dimensionally formed into a concavo-convex shape, vibrations occur even though the elongation rates of the diaphragm base material 21a and the voice coil 21b are different. The plate base material 21a is not broken and high-precision molding can be realized.

In addition, since the diaphragm 21 has an uneven shape and the

permanent magnets

22 and 23 are arranged in a staggered arrangement so that the magnetic pole direction of the permanent magnet 22 and the magnetic pole direction of the permanent magnet 23 are the same, the electromagnetic transducer 20 After assembling, the

permanent magnets

22 and 23 can be magnetized together. Therefore, foreign matters such as iron powder do not enter during assembly work. Therefore, it is possible to prevent an abnormal noise from being generated in the electromagnetic transducer 20 and prevent the initial performance from being produced, and to easily manufacture the electromagnetic transducer 20 having excellent performance.

Moreover, since the

permanent magnets

22 and 23 are arranged in an alternating staggered arrangement, the number of magnets can be halved, and a low-cost electromagnetic transducer 20 can be obtained. Conventionally, if a permanent magnet is arranged only on one side of the diaphragm for the purpose of halving the number of magnets, the magnetic flux distribution fluctuates in the front and back directions of the diaphragm. However, in this embodiment, even if the number of magnets is halved, the diaphragm 21 Since it is arranged in the front and back direction, the magnetic flux distribution in the front and back direction can be made uniform by the front and back magnetic circuits of the diaphragm 21. As a result, the occurrence of distortion can be prevented.

As described above, in the electromagnetic transducer according to the present invention, the diaphragm has a three-dimensional structure that matches the uneven shape of the permanent magnet fixed to the frame, and the meandering coil pattern is disposed at a high magnetic flux density position where the magnetic flux is concentrated. By doing so, the diaphragm has a high rigidity and a low-performance electromagnetic transducer with excellent performance, and is suitable for use in a thin speaker or the like.

Claims

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.
2. The electromagnetic transducer according to claim 1, wherein the diaphragm includes a surface material attached to the surface of the convex and concave portion.
A hollow frame with sound radiation holes on the surface;
A plurality of permanent magnets alternately fixed to a pair of inner wall surfaces of the frame in a staggered arrangement, opposite to the fixed surface, and opposite end surfaces opposite to each other, having different polarities,
An iron plate fixed to the end faces facing each other of the permanent magnets arranged in a staggered manner;
It is a concavo-convex shape corresponding to the concavo-convex structure constituted by the end surfaces facing each other of the permanent magnets arranged in a staggered manner, and is a boundary portion between the concave and convex portions of the concavo-convex shape and the same height position as the iron plate And a diaphragm having a reference plane parallel to the concave portion and the convex portion and having a meandering coil pattern formed on the reference plane.
The diaphragm is characterized in that it has a concave and convex shape formed by forming a concave and convex portion on a planar diaphragm base material on which a meandering coil pattern is formed, with reference to the portion on which the meandering coil pattern is formed. The electromagnetic transducer according to claim 4.
5. The electromagnetic transducer according to claim 4, wherein a rib structure or a concavo-convex structure for reinforcement is formed in a concave portion and / or a convex portion of the diaphragm.
Fixed to a hollow frame having sound emission holes on the surface, a plurality of permanent magnets alternately fixed to a pair of inner wall surfaces of the frame in a staggered manner, and end faces facing each other of the permanent magnets arranged in a staggered manner And a concavo-convex shape corresponding to the concavo-convex structure composed of the end faces of the permanent magnets opposed to each other in a staggered manner, and is a boundary portion between the concave and convex portions of the concavo-convex shape, and the iron plate After assembling an electromagnetic transducer having a reference plane parallel to the concave portion and the convex portion at the same height position and having a meandering coil pattern formed on the reference plane, An electromagnetic transducer in which the end surfaces facing each other of the permanent magnets arranged in a staggered manner have different polarities by magnetizing in a direction perpendicular to a pair of inner wall surfaces.