JP2010118852A - Electromagnetic transducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such the problem that driving forces which are generated are mutually different to cause imbalance between the driving forces since magnitudes of magnetic flux densities of positions facing gap portions between magnetic poles different each other of permanent magnets and the magnetic flux densities of the positions facing gap portions between the permanent magnets and a frame. <P>SOLUTION: In this electromagnetic transducer 10 provided with a vibrating membrane 13 arranged facing a plurality of permanent magnets 11 and 12 arranged parallel to each other, a frame 30 made of a magnetic body to hold the permanent magnets and the vibrating membrane, and conductors 13b formed as a meandering conductor pattern at positions on the vibrating membrane facing gap portions of the different magnetic poles of the permanent magnets and positions on the vibrating membrane 13 facing a gap portion between the permanent magnets arranged at both ends and the frame, out of the conductors, the number of conductors formed parallel in the longitudinal direction of the permanent magnets at a position facing longitudinal gaps of the permanent magnets differs depending on magnetic flux densities that are generated between different magnetic poles of the permanent magnets and between the permanent magnets arranged at both the ends and the frame. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electromagnetic transducer for reproducing an audio signal, for example.

Various technologies have been proposed for electromagnetic transducers combining a permanent magnet and a vibrating membrane. This type of electromagnetic transducer includes a permanent magnet plate, a vibration film disposed so as to face the permanent magnet plate, and a buffer member disposed between the permanent magnet plate and the vibration film (for example, Patent Document 1).
Permanent magnets are formed by alternately forming different belt-shaped magnetic poles at regular intervals.
In addition, a conductor made of a meandering conductor pattern is formed on the entire surface of the vibration film at a position facing a so-called neutral zone of so-called magnetization in a gap portion between different magnetic poles of the permanent magnet plate.
As a result, when a current (audio signal) flows through the conductor of the diaphragm, the conductor and the multipolar magnetization pattern of the permanent magnet plate are electromagnetically coupled, and audio vibration is generated in the diaphragm according to Fleming's law.
The permanent magnet plate, the vibration film and the buffer member are covered with a frame and attached to the speaker housing.

JP-A-9-331596

A flat speaker is an electromagnetic transducer that obtains a flat sound pressure frequency characteristic by uniformly vibrating the entire surface of the diaphragm, but in reality, the entire diaphragm will vibrate uniformly. It is known to be difficult.
In a flat speaker using rod-shaped or plate-shaped permanent magnets, different magnetic poles are alternately arranged at a fixed interval, and a meandering conductor pattern is formed at a position facing a gap portion between different magnetic poles of the permanent magnet. The vibrating membrane is arranged so that the conductor to be located is located. The permanent magnet is held on the frame together with the vibration film on which the meandering conductor pattern is formed. Here, since the magnitude of the magnetic flux density at the position facing the gap portion between the different magnetic poles of the permanent magnet is different from the magnitude of the magnetic flux density at the position facing the gap portion between the permanent magnet and the frame, the generated driving force is different. There was a problem that unbalanced driving force occurred.

  The present invention has been made in order to solve the above-described problems, and an object thereof is to obtain an electromagnetic transducer in which the driving force generated on the vibrating membrane is made substantially uniform and the vibrating membrane is made closer to the entire driving. .

  An electromagnetic transducer according to the present invention includes a vibration film disposed to face a plurality of permanent magnets arranged in parallel, a frame formed of a magnetic material and holding the permanent magnet and the vibration film, and different magnetic poles of the permanent magnets A conductor formed as a meander-shaped conductor pattern at a position on the diaphragm facing the gap between the permanent magnets at both ends and a position on the diaphragm facing the gap between the frames. In the electromagnetic transducer, the number of conductors formed in parallel to the longitudinal direction of the permanent magnets at positions opposed to the gaps in the longitudinal direction of the permanent magnets is the permanent magnets disposed between the different magnetic poles of the permanent magnets and at both ends. And the magnetic flux density generated between the frames.

  According to the present invention, among the conductors, the number of conductors formed in parallel to the longitudinal direction of the permanent magnets at positions facing the longitudinal gaps of the permanent magnets are permanent between the different magnetic poles and both ends of the permanent magnets. By configuring so as to differ depending on the magnetic flux density generated between the magnet and the frame, a uniform driving force can be obtained on the vibrating membrane, and an electromagnetic transducer having good acoustic characteristics can be obtained.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is an exploded perspective view showing a configuration of an electromagnetic converter 10 according to Embodiment 1 of the present invention, and FIG. 2 is a cross-sectional view showing a configuration of the electromagnetic converter 10 according to Embodiment 1 of the present invention. It is.

  As shown in FIG. 1, the electromagnetic transducer 10 includes an upper permanent magnet 11, a lower permanent magnet 12, a vibration film 13 and a frame 30, and a magnetic circuit is configured by the permanent magnets 11, 12 and the frame 30. The The frame 30 is formed with sound radiation holes 31a and 32a opened to the outside. Further, the upper frame 31 and the lower frame 32 of the frame 30 support the permanent magnets 11 and 12 and the vibrating membrane 13 so as to cover from above and below.

  As shown in FIG. 2, the permanent magnets 11 and 12 are a large number of rod-shaped permanent magnets magnetized with different polarities on the front and back surfaces (both sides are two-pole magnetized). 13 are arranged so that the polarities of the surfaces facing 13 are alternately different. As shown in FIG. 2, the permanent magnets 11 and 12 arranged in this way are bonded and fixed to the frame 30 with an adhesive or the like.

  The vibration film 13 includes a resin film 13a made of a thin polymer resin film and conductors 13b formed in a meandering conductor pattern on both surfaces of the resin film 13a. The conductor 13b made of a meandering conductor pattern is formed by pressing or etching a metal foil.

  The frame 30 is a magnetic body made of a metal such as iron, for example, and has a housing structure in which a cavity is formed by combining the upper frame 31 and the lower frame 32. The upper frame 31 and the lower frame 32 are joined by sandwiching part of both ends in the longitudinal direction of the vibration film 13.

  As shown in FIG. 2, circular sound radiation holes 31 a and 32 a opened to the outside are formed in the frame 30 at positions facing the conductors 13 b formed in the vibration film 13. A plurality of the sound radiation holes 31a and 32a are provided at regular intervals along a straight portion of the conductor 13b formed in parallel with the longitudinal direction of the permanent magnets 11 and 12.

FIG. 3 is a plan view of the vibrating membrane 13 showing the arrangement configuration of the conductor pattern of the conductor 13b formed on the vibrating membrane 13 of the electromagnetic transducer 10 according to Embodiment 1 of the present invention.
As shown in FIG. 3, the conductor pattern of the conductor 13 b formed on the vibration film 13 is a position facing the different magnetic poles of the permanent magnets 11 and 12 from the point A (input end) on the surface of the vibration film 13 and the permanent magnet. 11 and 12 are formed in a meandering shape so as to pass through positions facing each other. And it connects in series with the conductor 13b formed in the back surface of the diaphragm 13 in B point. The conductor 13b formed on the back surface of the vibration film 13 is formed in the same shape as the conductor 13b formed on the surface of the vibration film 13 from the point B through the dotted line portion. ).

Here, the permanent magnets 11 and 12 are arranged in parallel along the longitudinal direction of the permanent magnets 11 and 12 at positions facing the gaps between different magnetic poles of the permanent magnets 11 and 12 or positions facing the gaps between the permanent magnets 11 and 12 and the frame 30. The number of conductors 13b is referred to as the number of turns. The magnetic flux density between the permanent magnets 11 and 12 and the frame 30 is lower than the magnetic flux density between the different magnetic poles of the permanent magnets 11 and 12. Accordingly, the number of turns (number) of the conductor 13b formed at the position facing the gap between the permanent magnets 11 and 12 and the frame 30 is set to the position formed at the position facing the gap between the different magnetic poles of the permanent magnets 11 and 12. More than the number of turns (number) of 13b.
In Embodiment 1 of the present invention, assuming that the ratio of the magnetic flux density between different magnetic poles of the permanent magnets 11 and 12 and the magnetic flux density between the permanent magnets 11 and 12 and the frame 30 is 2: 1, as shown in FIG. The number of turns (number) of the conductor 13b formed at the opposing position between the different magnetic poles of the permanent magnets 11 and 12 is two, and the conductor 13b formed at the opposing position between the permanent magnets 11 and 12 and the frame 30. The number of turns (number) is four.
The electromagnetic transducer 10 according to Embodiment 1 of the present invention is configured as described above.

  In the configuration as described above, the magnetic path generated by the different magnetic poles of the permanent magnets 11 and 12 or the permanent magnets 11 and 12 and the frame in such a direction as to cross the longitudinal linear portion of the conductor 13b along the surface of the vibration film 13. The magnetic path generated by 30 passes. Therefore, when a current is supplied to the conductor 13b formed on the vibration film 13, the conductor 13b and the permanent magnets 11 and 12 are electromagnetically coupled to generate an electromagnetic force in accordance with Fleming's left-hand rule. The film 13 vibrates in the thickness direction. Sound waves generated by this vibration are emitted to the outside through the sound emission holes 31 a and 32 a formed in the permanent magnets 11 and 12 and the frame 30.

Here, one of the conductors 13b formed in parallel to the longitudinal direction of the permanent magnets 11 and 12 at different magnetic poles of the permanent magnets 11 and 12 and at a position passing through the vibration film 13 of the magnetic flux generated by the permanent magnets 11 and 12 and the frame 30. Let L be the length of the turn. Furthermore, the number of turns of the conductor 13b which is formed at a position facing the gap between different magnetic poles of the permanent magnets 11 and 12 and N _1, conductor 13b is formed at a position facing the gap between the permanent magnets 11 and 12 and the frame 30 When the number of turns of N ₂ is N ₂ , the total length L ₁ of the conductor 13 b formed at a position facing between the different magnetic poles of the permanent magnets 11, 12 and the position facing between the permanent magnets 11, 12 and the frame 30. total length L ₂ of the conductors 13b to be formed, the _{L 1 = N 1 L, L} 2 = N 2 L.
In addition, the current flowing through the conductor 13 b formed on the vibration film 13 is i, the magnetic flux density (absolute value) between different magnetic poles of the permanent magnets 11 and 12 is B _1, and between the permanent magnets 11 and 12 and the frame 30. Let B ₂ be the magnetic flux density (absolute value). Furthermore, the driving force generated in the conductor 13b which is formed at a position facing between different poles of the permanent magnets 11, 12 and F _1, the conductor 13b formed at a position facing between the permanent magnets 11 and 12 and the frame 30 Let F _{2 be} the driving force generated at.
At this time, the driving forces F ₁ and F ₂ generated in the conductors 13b formed at positions facing the respective gaps are F ₁ = B ₁ L ₁ i = B ₁ N ₁ Li, F ₂ = B ₂ L ₂ i = B ₂ N ₂ Li

Therefore, in order to correct the difference between the magnetic flux densities B ₁ and B ₂ in the conductor 13b formed at the position facing each gap, the conductor 13b formed at the position facing between the different magnetic poles of the permanent magnets 11 and 12 is used. By adjusting the number of turns (number) N ₁ or the number of turns (number) N ₂ of the conductor 13b formed at the opposing position between the permanent magnets 11 and 12 and the frame 30, the gaps are formed at the opposing positions of the gaps. In the conductor 13b, the driving forces F ₁ and F ₂ can be made equal, and a substantially uniform driving force can be obtained on the vibrating membrane 13.

  In the electromagnetic transducer 10 according to Embodiment 1 of the present invention, the ratio between the magnetic flux generated between the different magnetic poles of the permanent magnets 11 and 12 and the magnetic flux generated between the permanent magnets 11 and 12 and the frame 30 is 2. : 1, the number of turns of the conductor 13b arranged at the opposing position between the different magnetic poles of the permanent magnets 11 and 12 is 2, and the conductor 13b is arranged at the opposing position between the permanent magnets 11 and 12 and the frame 30. Although the number of turns of the conductor 13b is four, the number of turns is not limited to this, and the number of turns of the conductor 13b formed on the vibration film 13 is changed according to the magnetic flux generated in each gap.

  Further, in the electromagnetic transducer 10 according to Embodiment 1 of the present invention, two permanent magnets 11 and 12 have been described, but the present invention is not limited to this, and there are three or more permanent magnets 11 and 12. The first embodiment of the present invention can also be applied when arranged.

  Further, in the electromagnetic transducer 10 according to the first embodiment of the present invention, an example in which the magnetic flux density between different magnetic poles of the permanent magnets 11 and 12 and the magnetic flux density between the permanent magnets 11 and 12 and the frame 30 are different will be described. However, the present invention is not limited to this, and in configuring the electromagnetic transducer 10, it is not possible to use two or more types of magnets having different dimensions and strengths due to structural restrictions and the like, and the magnet arrangement interval cannot be made the same. Even when the magnetic flux density generated by the different magnetic poles of the permanent magnets 11 and 12 is different between the permanent magnets 11 and 12, the number of turns of the conductor 13b formed on the vibration film 13 of the first embodiment is also different. It is possible to apply a driving force equalization policy by adjusting the above.

  Further, in the electromagnetic transducer 10 according to Embodiment 1 of the present invention, the case where there are two types of magnetic flux density has been described, but the present invention is not limited to this, and even when the magnetic flux density differs by three or more types, the vibrating membrane The number of turns of the conductor 13b formed in 13 can be adjusted to three or more.

  Further, in the electromagnetic transducer 10 according to the first embodiment of the present invention, rod-shaped permanent magnets are used as the permanent magnets 11 and 12. However, instead of the rod-shaped permanent magnets, the polarities are set at regular intervals. It is also possible to use plate-like permanent magnets that are alternately magnetized so as to be different. Even if the electromagnetic transducer 10 is configured using a plate-like permanent magnet, the same effects as those of the first embodiment of the present invention can be obtained, and further sufficient mechanical strength can be provided.

  Further, in the electromagnetic transducer 10 according to the first embodiment of the present invention, the conductor 13b formed of the meandering conductor pattern is described as being connected in series on the front surface and the back surface of the vibration film 13, but the front surface and the back surface are described. The effect similar to that of the electromagnetic transducer according to the first embodiment of the present invention can be obtained by connecting the conductors 13b formed in parallel to each other in parallel.

  As described above, in the electromagnetic transducer 10 according to Embodiment 1 of the present invention, the driving force is substantially uniform in the vibration plane, and non-uniform vibration as in the prior art is eliminated, and good sound pressure characteristics are obtained. Is obtained.

It is a disassembled perspective view which shows the structure of the electromagnetic transducer which concerns on Embodiment 1 of this invention. It is sectional drawing of the electromagnetic transducer which concerns on Embodiment 1 of this invention. It is a figure which shows the arrangement configuration of the conductor formed in the diaphragm of the electromagnetic transducer which concerns on Embodiment 1 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Electromagnetic transducer, 11 Upper permanent magnet, 12 Lower permanent magnet, 13 Vibration film, 13a Resin film, 13b Conductor, 30 frame, 31 Upper frame, 32 Lower frame, 31a, 32a Sound radiation hole.

Claims (2)

A diaphragm disposed opposite to a plurality of permanent magnets disposed in parallel;
A frame formed of a magnetic material and holding the permanent magnet and the vibrating membrane;
A serpentine-shaped conductor pattern at a position on the vibration film facing the gap between the different magnetic poles of the permanent magnet and at a position on the vibration film facing the gap between the permanent magnet disposed at both ends and the frame. A conductor formed as
In an electromagnetic transducer with
Among the conductors, the number of the conductors formed in parallel to the longitudinal direction of the permanent magnets at positions opposed to the longitudinal gap of the permanent magnets is the permanent magnets disposed between different magnetic poles of the permanent magnets and at both ends. An electromagnetic transducer characterized by being different depending on a magnetic flux density generated between a magnet and the frame. A diaphragm disposed opposite to a plurality of permanent magnets disposed in parallel;
A frame for holding the permanent magnet and the vibrating membrane;
A conductor formed as a meander-shaped conductor pattern at a position on the vibrating membrane facing a gap portion between different magnetic poles of the permanent magnet;
In an electromagnetic transducer with
Among the conductors, the number of the conductors formed in parallel to the longitudinal direction of the permanent magnets at opposite positions of the longitudinal gap of the permanent magnets varies depending on the magnetic flux density generated between the different magnetic poles of the permanent magnets. An electromagnetic transducer characterized by that.

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