JP2017130704A - Flat type electro-acoustic transducer and headphone - Google Patents

Abstract

PROBLEM TO BE SOLVED: To put a break on a flat diaphragm plate without reducing a high sound area.SOLUTION: A flat type electro-acoustic transducer includes: a flat diaphragm plate 10 having a coil 11; a pair of yolks 20a and 20b arranged in parallel to both surfaces with a predetermined interval. Each of yokes is alternately arranged while oppositely facing in a direction of a magnetic pole in a plurality of permanent magnets 30 so that a magnetic flux is linked to the coil 11, and permanent magnets 30a1 to 30a6 of one yoke 20a side and permanent magnets 30b1 to 30b6 of the other yoke 20b side are arranged so as to be faced as the same pole. In the flat type electro-acoustic transducer in which a sound radiation hole 21 is formed in at lest one yoke, porous resistance cards 50a and 50b (thin air layer applying means) is attached along each magnetic pole surface 31 of the permanent magnets 30a1 to 30a6 on the yoke 20a side and each magnetic pole surface 31 of permanent magnets 30b1 to 30b6 of the yoke 20b side. Thereby a thin air layer 60 mechanically putting a brake the flat diaphragm plate 10 between flat diaphragm plates 10.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a planar electroacoustic transducer and headphones, and more particularly to a technique for braking a planar diaphragm without attenuating the high frequency range.

  As described in Patent Document 1, according to a planar electroacoustic transducer (for example, a dynamic headphone element) using a planar diaphragm on which a coil is formed as a sound source, the entire diaphragm is driven. The frequency response of the output sound pressure has little unevenness due to the divided vibration, but it is necessary to control the resonance sharpness at a low resonance frequency.

  According to the magnetic circuit using a normal cylindrical voice coil, the magnetic flux density in the magnetic gap in which the voice coil is arranged can be designed to be high, so that appropriate electromagnetic braking can be applied to the diaphragm.

  However, in the case of a dynamic headphone element in which a coil is formed on a flat diaphragm, it is necessary to design the gap between the opposing magnetic poles of the permanent magnets arranged on both sides of the diaphragm wider than the vibration amplitude of the diaphragm. The sufficient magnetic flux density required cannot be ensured.

  Therefore, in the invention described in Patent Document 2, a planar diaphragm having a coil, a plurality of magnetic poles arranged opposite to each other with a slight gap on both sides of the planar diaphragm, and supporting these magnetic poles In addition, in a full drive speaker including a pair of yoke plates provided with sound emission holes between adjacent magnetic poles, a braking member made of urethane foam or the like is provided in a sound wave path from the flat diaphragm to the sound emission holes. It is packed and emits sound waves through the braking member.

  However, a braking member made of this type of urethane foam or the like has a problem that it operates as a low-pass filter because it includes an air chamber corresponding to its volume, and particularly attenuates the high frequency range.

JP-A-52-89911 No. 7-3757

  Accordingly, an object of the present invention is to brake a planar diaphragm without attenuating a high frequency range in a planar electroacoustic transducer.

  In order to solve the above-described problems, the present invention includes a planar diaphragm having a coil and a pair of yokes in the form of a plate arranged in parallel at a predetermined interval on both sides of the planar diaphragm, and each of the yokes In this case, a plurality of permanent magnets are alternately arranged so that the magnetic poles are opposite to each other so that the magnetic flux intersects the coil, and the permanent magnet on the one yoke side and the permanent magnet on the other yoke side are the same. In a planar electroacoustic transducer that is disposed so as to face each other and at least one of the yokes has a sound emitting hole, the planar diaphragm is mechanically braked against the planar diaphragm. It is characterized by comprising a thin air layer applying means for applying a thin air layer for the purpose.

  According to a preferred aspect of the present invention, the thin air layer applying means includes a non-magnetic resistance plate disposed along a magnetic pole surface facing the planar vibration plate of each permanent magnet and having a plurality of openings. The thin air layer is formed between the resistance plate and the planar diaphragm.

  A metal sheet or a resin sheet may be used as the resistance plate. When using a flexible resin sheet, a predetermined tension may be applied so as not to bend by the sound pressure of the diaphragm.

  It is preferable that the coil is a planar coil formed in a zigzag shape including a plurality of linear wiring portions interlinking with the magnetic flux of the permanent magnet.

  The present invention includes a headphone having the above-described planar electroacoustic transducer as the headphone element.

  According to the present invention, the planar diaphragm can be mechanically braked by the thin air layers existing on both sides thereof. Further, since the volume of the air chamber formed by the thin air layer is small, the cutoff frequency of the low-pass filter formed by the air chamber and the resistance can be set to a high frequency, thereby preventing the attenuation of the high sound range.

Sectional drawing which shows the internal structure of one Embodiment of the planar electroacoustic transducer by this invention. The disassembled perspective view which shows the said planar electroacoustic transducer. The top view which shows the plane diaphragm with which the said planar electroacoustic transducer is provided. AA line sectional view of Drawing 3.

  Next, an embodiment of the present invention will be described with reference to FIGS. 1 to 4, but the present invention is not limited to this.

  First, referring to FIG. 1 and FIG. 2, a planar electroacoustic transducer 1 according to this embodiment has a basic configuration in which a planar diaphragm 10 is parallel to both sides of the planar diaphragm 10 with a predetermined interval. And a pair of yokes 20a, 20b made of a plate-like magnetic body. Note that the yokes 20a and 20b have the same configuration and are collectively referred to as the yoke 20 when it is not necessary to distinguish them.

  Each yoke 20 is provided with a plurality of permanent magnets 30 on one surface side. In this embodiment, six permanent magnets 30 (30a1 to 30a6) are provided on one yoke 20a side, and six permanent magnets 30 (30b1 to 30b6) are also provided on the other yoke 20a side. ing.

  Each permanent magnet 30 is composed of prisms having the same size, and the N and S magnetization directions are perpendicular to the plate surface of the yoke 20. In each yoke 20, the magnetic poles of adjacent permanent magnets 30 are the same. And the permanent magnet 30 on the one yoke 20a side and the permanent magnet 30 on the other yoke 20b side are disposed so as to face each other with the same polarity.

  That is, in this embodiment, out of the six permanent magnets 30a1 to 30a6 provided in one yoke 20a, the odd-numbered permanent magnets 30a1, 30a3, and 30a5 are configured such that the N pole faces the planar diaphragm 10, respectively. In contrast, the even-numbered permanent magnets 30 a 2, 30 a 4, and 30 a 6 are oriented so that the south pole faces the planar diaphragm 10.

  Similarly, out of the six permanent magnets 30b1 to 30b6 provided on the other yoke 20b, the odd-numbered permanent magnets 30b1, 30b3, and 30b5 are each oriented so that the north pole faces the planar diaphragm 10. On the other hand, the even-numbered permanent magnets 30 b 2, 30 b 4, and 30 b 6 are oriented so that the south pole faces the planar diaphragm 10. The surface of each permanent magnet 30 that faces the planar diaphragm 10 is referred to as a magnetic pole surface 31.

  The permanent magnets 30a1 and 30b1 (both N poles), 30a2 and 30b2 (both S poles), 30a3 and 30b3 (both N poles), 30a4 and 30b4 (both S poles), 30a5 and 30b5 (both N poles), and 30a6 And 30b6 (both S poles) face each other as the same poles.

  Further, in each yoke 20 (20a, 20b), a plurality of sound emitting holes 21 are formed between adjacent permanent magnets 30, 30 for emitting sound waves generated by the planar diaphragm 10 to the outside. Yes. The sound emitting hole 21 may be, for example, an elongated slit hole other than the round hole. In this embodiment, the sound emission holes 21 are provided in both the yokes 20 a and 20 b, but may be provided only in one of the yokes 20.

  Referring also to FIG. 3, the planar diaphragm 10 is preferably made of an electrically insulating resin film, and includes planar coils 11 (11 a and 11 b) on at least one surface, in this embodiment, both surfaces.

  In this embodiment, the planar coil 11 is formed as a preferred pattern as a zigzag pattern including a plurality of linear wiring portions 12 interlinking with the magnetic flux (lines of magnetic force) generated by the permanent magnet 30.

  That is, the straight wiring portion 12 is formed between the permanent magnets 30a1 and 30a2; 30b1 and 30b2, 30a2 and 30a3; 30b2 and 30b3, 30a3 and 30a4; 30b3 and 30b4, 30a4 and 30a5; 30b4 and 30b5. And 30a5 and 30a6; 30b5 and 30b6.

  The planar coil 11a on the one surface side and the planar coil 11b on the other surface side are formed so as to be overlapped in the same pattern, and the direction in which the drive current flows is the same. According to this embodiment, as shown in FIG. 3, the planar coil 11 is drawn as a single wide conductor, but the planar coil 11 includes a plurality of conductors wired in parallel to each other. May be.

  The planar diaphragm 10 has a predetermined gap between the permanent magnet 30 and the magnetic pole surface 31 in a state where the peripheral edge portion is sandwiched between the square frame spacers 40a and 40b (see FIG. 2). Are incorporated into the yokes 20a and 20b. Although not shown, an edge portion that easily deforms may be formed in a peripheral portion along the inner circumference of the spacers 40a and 40b of the planar diaphragm 10.

  In the flat electroacoustic transducer, since it is necessary to make the interval between the opposing magnetic pole surfaces 31 and 31 wider than the vibration amplitude of the flat diaphragm 10, a sufficient magnetic flux required for electromagnetically braking the flat diaphragm 10. The density cannot be secured. Therefore, in the present invention, a thin air layer applying means is provided, and a thin air layer is applied to the flat diaphragm 10 by the thin air layer applying means so that the flat diaphragm 10 is mechanically braked. ing.

  In this embodiment, a resistance plate 50a functioning as a thin air layer applying means is attached along each magnetic pole surface 31 of the permanent magnets 30a1 to 30a6 on the yoke 20a side, and each magnetic pole surface of the permanent magnets 30b1 to 30b6 on the yoke 20b side. The resistor plate 50b is attached along the line 31, and the thin air layer 60 is formed between the resistor plate 50a and the planar diaphragm 10, and between the resistor plate 50b and the planar diaphragm 10, respectively. When it is not necessary to distinguish between the resistance plates 50a and 50b, they are collectively referred to as the resistance plate 50.

  The resistance plate 50 is a non-magnetic material. For example, a metal sheet such as SUS304 having a thickness of about 0.2 mm and a large number of openings (through holes) formed by edging is preferably used. Thus, since the resistance plate 50 is thin and non-magnetic, the magnetic flux applied to the planar coil 11 is hardly reduced. In addition, the distance between the resistance plate 50 and the planar diaphragm 10 is less than the maximum amplitude of the planar diaphragm 10. What is necessary is just to design about several mm large.

  Since the air chamber of the thin air layer 60 formed between the resistance plate 50 and the flat diaphragm 10 is small, the cutoff frequency of the low-pass filter formed by the air chamber and the resistance can be increased. . For this reason, attenuation of a high sound range can be prevented. Further, the resistance (acoustic resistance) due to the thin air layer can be arbitrarily designed according to the size of the opening opened in the resistance plate 50.

  As the resistance plate 50, a porous resin sheet having a plurality of openings may be used. In the case of a flexible resin sheet, it is affixed to each magnetic pole surface 31 of the permanent magnet 30 with an adhesive or the like in a state where a predetermined tension is applied so as not to bend by the sound pressure due to the vibration of the flat diaphragm 10. Just wear it.

  As described above, according to the present invention, the thin diaphragm 60 is formed on both sides of the planar diaphragm 10 by the resistor plates 50 (50a, 50b), so that the planar diaphragm 10 is not attenuated in the high frequency range. Mechanical braking can be applied.

  In addition, in the said embodiment, although the planar electroacoustic transducer 1 is made into the rectangular shape, it can also be formed in circular (disk) shape. The planar electroacoustic transducer 1 of the present invention is preferably applied to headphones as a headphone element.

DESCRIPTION OF SYMBOLS 1 Plane type electroacoustic transducer 10 Plane diaphragm 11 (11a, 11b) Plane coil 12 Linear wiring part 20 (20a, 20b) Yoke 21 Sound emission hole 30 (30a1-30a6, 30b1-30b6) Permanent magnet 31 Magnetic pole surface 40 (40a, 40b) Spacer 50 (50a, 50b) Resistance plate (thin air layer applying means)
60 thin air layer

Claims (7)

A planar diaphragm having a coil and a pair of yokes arranged in parallel with a predetermined interval on both sides of the planar diaphragm, each of which has a magnetic flux linked to the coil. The plurality of permanent magnets are alternately arranged with the directions of the magnetic poles opposite to each other, and the permanent magnets on the one yoke side and the permanent magnets on the other yoke side are arranged so as to face each other as the same poles. In a planar electroacoustic transducer in which a sound emitting hole is formed in at least one of the yokes,
A flat electroacoustic transducer comprising thin air layer applying means for applying a thin air layer for mechanically braking the flat diaphragm to the flat diaphragm.   The thin air layer applying means includes a non-magnetic resistance plate arranged along a magnetic pole surface facing the planar vibration plate of each permanent magnet, and having a plurality of openings. The flat electroacoustic transducer according to claim 1, wherein the thin air layer is formed between the two.   The flat electroacoustic transducer according to claim 2, wherein a metal sheet is used as the resistance plate.   The flat electroacoustic transducer according to claim 2, wherein a resin sheet is used as the resistance plate.   5. The planar electroacoustic conversion according to claim 1, wherein the coil is formed in a zigzag shape including a plurality of linear wiring portions interlinking with the magnetic flux of the permanent magnet. vessel.   6. The flat electroacoustic transducer according to claim 1, wherein a sound emitting hole is also formed in the other yoke.   A headphone having the planar electroacoustic transducer according to any one of claims 1 to 6 as a headphone element.

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