JP2005286580A - Electromagnetic transducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-performance electromagnetic transducer which reliably prevents abnormal noise from being produced due to the mutual collision of a diaphragm and a permanent magnet plate and also those due to air flowing into exhausting through-holes of the permanent magnet plate, and lessens the sound pressure reduction in the medium- and low-pitched zones. <P>SOLUTION: The electromagnetic transducer comprises a permanent magnet plate 1 having beltlike multi-pole magnetizing patterns N, S and exhausting through-holes 1a, a diaphragm 2 having a meandering coil pattern 2a on the surface facing the multi-pole magnetizing pattern forming surface of the permanent magnet plate 1, and a buffer member 3 disposed between the diaphragm 2 and the magnet plate 1 with a packing member 6 inserted between the magnet plate 1 and the diaphragm 2 to surround the periphery of the buffer member 3. The diaphragm 2 electromagnetically couples with the magnet plate 1 during energizing of the coil pattern 2a to vibrate in the thickness direction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

  A conventional electromagnetic transducer of this type includes a permanent magnet plate having a strip-shaped multipole magnetized pattern and having many exhaust through holes, and a film-like diaphragm having a serpentine coil pattern formed on the surface thereof. Are arranged opposite to each other. In such an electromagnetic transducer, when a current (audio signal) flows through the serpentine coil pattern of the diaphragm, the serpentine coil pattern and the multipolar magnetization pattern of the permanent magnet plate are electromagnetically coupled, Audio vibration is generated on the diaphragm according to Fleming's law. As a result, the diaphragm generates a sound along with the audio signal. At this time, when the diaphragm hits the permanent magnet plate, an abnormal noise is generated. Therefore, the permanent magnet plate is provided with a buffer member that is made of a nonwoven fabric that prevents the occurrence of abnormal noise and that also functions as a suspension and has air permeability and is formed to be approximately the same size as the diaphragm. An electromagnetic transducer having a configuration in which the permanent magnet plate, the diaphragm, and the buffer member are elastically supported in the surface pressure direction by bolts and nuts, for example, at four corners is also proposed. (For example, refer to Patent Document 1).

JP-A-9-331596 (page 4, FIG. 1).

  Since the conventional electromagnetic transducer is configured as described above, collision between the permanent magnet plate and the diaphragm can be prevented by a buffer member between the two, but the buffer member is made of a non-woven fabric having air permeability. Since the peripheral edge is exposed to the outside between the permanent magnet plate and the diaphragm, the peripheral magnet plate flows into the space between the permanent magnet plate and the buffer member from many exhaust through holes of the permanent magnet plate. There was a problem in that abnormal noise was generated when air passed through the buffer member. That is, even if the shock-absorbing member can prevent the generation of noise due to the vibration plate and the permanent magnet plate being hit, there is a problem that the noise generation due to air passing through the buffer member cannot be prevented. Further, as described above, in the cushioning member having air permeability, the back surface sound of the diaphragm (vibration sound generated on the side opposite to the meandering coil pattern) cannot be completely blocked, and therefore the back surface sound is There was a problem that the sound pressure in the mid-low range decreased due to leakage to the side.

  The present invention has been made to solve the above-described problems, and it is possible to prevent the generation of abnormal noise caused by the collision between the diaphragm and the permanent magnet plate, as well as from the exhaust through hole of the permanent magnet plate. An object of the present invention is to obtain a high-performance electromagnetic transducer that can surely prevent the generation of abnormal noise due to air inflow and can suppress the reduction of sound pressure in the mid-low range.

  The electromagnetic transducer according to the present invention includes a permanent magnet plate having a strip-shaped multipole magnetized pattern and having an exhaust through-hole, and a serpentine coil pattern formed on the surface thereof. A vibration plate that is disposed to face the pattern forming surface and electromagnetically couples with the permanent magnet plate and vibrates in the thickness direction when the meandering coil pattern is energized, and is disposed between the vibration plate and the permanent magnet plate. In an electromagnetic transducer including a buffer member, a packing member surrounding an outer peripheral portion of the buffer member is interposed between the permanent magnet plate and the diaphragm.

  According to the present invention, the outer peripheral portion of the buffer member interposed between the permanent magnet plate and the diaphragm having the meandering coil pattern disposed opposite to the multipolar magnetization pattern of the permanent magnet plate is provided. Since the surrounding packing member is arranged, the gap between the permanent magnet plate and the diaphragm can be completely sealed on the outer peripheral side of both by the packing member. In addition to being able to prevent the occurrence of noise caused by the collision with the plate with the buffer member, it is possible to reliably prevent the occurrence of noise caused by the inflow of air from the exhaust through hole of the permanent magnet plate. It is possible to suppress a reduction in sound pressure in the low sound range, and there is an effect that acoustic performance is improved.

Embodiment 1 FIG.
1 is an exploded perspective view showing an electromagnetic transducer according to Embodiment 1 of the present invention, FIG. 2 is a cross-sectional view showing the assembled state of FIG. 1, and FIG. 3 is an electromagnetic mechanism portion excluding the buffer member and packing member of FIG. FIG. 4 is an exploded perspective view of FIG. 3, and FIG. 5 is a plan view of the diaphragm in FIG.
The electromagnetic transducer shown in the figure includes two permanent magnet plates 1, one diaphragm 2 disposed between these permanent magnet plates 1, and between the diaphragm 2 and the permanent magnet plate 1. Two cushioning members 3 arranged on the two sides, two packing members 6 that surround the periphery of these cushioning members 3 and are interposed between the permanent magnet plate 1 and the diaphragm 2, and both the permanent magnet plates The two high-permeability magnetic plates (hereinafter simply referred to as “magnetic plates”) 4 disposed on the outer side of 1 are laminated and integrally coupled, and the details will be described below.

  First, as shown in FIGS. 3 and 4, the permanent magnet plate 1 has strip-shaped multipolar magnetization patterns N and S made of sintered ferrite magnets formed on one side almost on the entire surface facing the diaphragm 2. The multipolar magnetization patterns N and S are parallel striped multipolar magnetization patterns in which strip-shaped N poles and S poles appear alternately, along the neutral zone nz of the magnetization. A plurality of exhaust through holes 1a are provided at a constant pitch.

  Next, the diaphragm 2 has a meandering coil pattern 2a (see FIGS. 3 to 5) formed on the surface thereof, and is disposed opposite to the formation surface of the multipolar magnetization patterns N and S on the permanent magnet plate 1. When a current (audio signal) flows through the meandering coil pattern 2a, it is electromagnetically coupled to the permanent magnet plate 1 and vibrates in the thickness direction. Here, the meandering coil pattern 2a is parallel at the same pitch as the strip-shaped magnetic poles N and S so that the straight line portion is always located at the center of the strip-shaped N-pole and S-pole of the multipolar magnetization pattern. Has been placed. Such a diaphragm 2 has a structure in which the meandering coil pattern 2a is printed on a flexible thin film resin film 2b, and the linear portion of the conductor pattern (meandering coil pattern 2a) is the permanent magnet. It is provided at a position corresponding to the neutral zone nz of the magnet plate 1. In FIG. 4, the N pole S pole of the multipolar magnetization pattern is arranged on the line of the exhaust through hole 1a. However, the N pole S pole is arranged between the lines of the exhaust through hole 1a. Also good. Further, the pitch between the exhaust through hole 1a and the N pole S pole is not necessarily the same.

  The buffer member 3 is made of a non-woven fabric having air permeability and acoustic energy permeability, and is disposed between the permanent magnet plate 1 and the diaphragm 2 as described above. While preventing it from colliding with the magnet plate 1, it plays a role as a suspension.

  The magnetic plate 4 is disposed on the surface of the permanent magnet plate 1 opposite to the surface on which the multipolar magnetization pattern is formed to prevent magnetic flux leakage. There is an exhaust through-hole 4a communicating with 1a. As such a magnetic plate 4, for example, an iron plate, a nickel / iron alloy (permalloy) plate, or the like is applied.

  The packing member 6 interposed between the permanent magnet plate 1 and the diaphragm 2 is made of polyolefin foamed polyethylene foam. The polyolefin foamed polyethylene foam is, for example, a petrochemical product in which polyethylene is the main component and foamed by mixing a foaming agent, foam stabilizer, catalyst, etc., and a structure in which polyethylene resin is foamed about 5 to 40 times. It has the performance of compressing and deforming when it is pressurized and hindering the permeation of air. As shown in FIGS. 1 and 2, the packing member 6 made of such a polyolefin foamed polyethylene foam is formed in a frame shape having almost the same size as the permanent magnet plate 1 and is fitted into the outer periphery of the buffer member 3. In this state, it is arranged between the permanent magnet plate 1 and the diaphragm 2. Therefore, the buffer member 3 is formed smaller than the permanent magnet plate 1 by the width of the wall of the packing member 6.

  In the above, the permanent magnet plate 1 and the diaphragm 2, and the buffer member 3 inserted between the permanent magnet plate 1 and the diaphragm 2 with the frame-shaped packing member 6 fitted therein, and the permanent magnet plate 1 An electromagnetic transducer is assembled by laminating the magnetic plates 4 arranged outside the substrate in the state shown in FIG. 2 and fastening the four corners with support members 5. The support member 5 includes a support bar 5a that passes through the four corners of the permanent magnet plate 1, the vibration plate 2, the buffer member 3, and the magnetic plate 4, and nuts 5b that are screwed to both ends of the support bar 5a. Thus, the permanent magnet plate 1, the diaphragm 2, the buffer member 3 and the magnetic plate 4 are firmly fixed to each other. Here, the support bar 5a allows the displacement of the diaphragm 2 in the thickness direction, but the holes 2c at the four corners of the diaphragm 2 are restricted so as to restrict the displacement of the diaphragm 2 in the in-plane direction. It penetrates slowly. The packing member 6 is compressed between the permanent magnet plate 1 and the diaphragm 2 by the tightening force of the support member 5. Therefore, the packing member 6 is formed to be thicker than the thickness of the buffer member 3 in a natural state before the support member 5 is tightened, and the outer periphery of the buffer member 3 and the permanent magnet are tightened by the support member 5. The plate 1 and the diaphragm 2 are strongly pressed against the outer peripheral facing surfaces.

Next, the operation will be described.
When a current (audio signal) flows in the meandering coil pattern 2a formed on the surface of the diaphragm 2 arranged to face the multipolar magnetization pattern forming surface of the permanent magnet plate 1, the meandering coil pattern 2a and the permanent magnet plate When the multipolar magnetization pattern of 1 is electromagnetically coupled, audio vibration is generated on the diaphragm 2 according to Fleming's law. As a result, the diaphragm 2 generates sound by audio vibration. At this time, collision between the diaphragm 2 and the permanent magnet plate 1 at the time of vibration is prevented by the buffer member 3, and the packing member 6 on the outer periphery of the buffer member 3 is between the permanent magnet plate 1 and the diaphragm 2. Therefore, the generation of abnormal noise due to air leakage can be prevented, and an audio signal in the low frequency band can be reproduced. The vibration amplitude of the diaphragm 2 This is particularly effective in reproduction in a frequency band of 300 Hz or less reflected in the above.

  According to the first embodiment described above, the strip-shaped multipolar magnetized patterns N and S are formed, the permanent magnet plate 1 having the exhaust through-hole 1a, and the meandering coil pattern 2a are formed on the surface. A frame-shaped packing member 6 surrounding the outer periphery of the diaphragm 2 disposed between the diaphragm 2 and the diaphragm 2 disposed opposite to the multipolar magnetization pattern forming surface of the permanent magnet plate 1 is disposed. Since the packing member 6 is configured to be compressed by the fastening force of the permanent magnet plate 1, the vibration plate 2, and the buffer member 3 by the support member 5, the space between the permanent magnet plate 1 and the vibration plate 2 can be reduced. The outer peripheral portion can be sealed with the packing member 6, and therefore, it is possible to reliably prevent the generation of abnormal noise due to air leakage between the permanent magnet plate 1 and the diaphragm 2. At the same time, it can play back mid- and low-band audio signals There is an effect that. In addition, since the packing member 6 is formed in a frame shape with a polyolefin foamed polyethylene foam, the packing member 6 is excellent in compression performance, and exhibits the packing performance for preventing air permeation at the time of compression. 1 and the diaphragm 2 can be completely sealed by the outer peripheral portion of the buffer member 3.

Embodiment 2. FIG.
In the first embodiment, the frame-shaped packing member 6 is formed of the polyolefin foamed polyethylene foam. The packing member 6 has the same properties as the polyolefin foamed polyethylene foam, such as polyurethane, that is, a permanent magnet plate. Any material may be used as long as the space between the diaphragm 1 and the diaphragm 2 can be sealed by the outer periphery of the buffer member 3.

Embodiment 3 FIG.
In the first embodiment, the thickness and width of the packing member 6 are not particularly mentioned, but the packing member 6 is thicker and wider, and the packing performance is improved. However, the thickness of the packing member 6 is It is desirable to set it to about 2 to 3 times the gap between the diaphragm 2 and the permanent magnet plate 1. For example, when the gap between the diaphragm 2 and the permanent magnet plate 1 is 0.5 mm, the packing member 6 has a thickness of about 1 to 2.5 mm. The width of the packing member 6 having such a thickness is efficient to take as wide as not to block the exhaust through-hole 1a of the permanent magnet plate 1, and is preferably about 2 to 5 mm. The packing member 6 is preferably coated with an adhesive material on one side in order to improve workability and alignment during assembly of the electromagnetic transducer.

It is a disassembled perspective view which shows the electromagnetic transducer by Embodiment 1 of this invention. It is sectional drawing which shows the assembly state of FIG. It is an expanded sectional view which shows the electromagnetic mechanism part except the buffer member and packing member of FIG. FIG. 4 is an exploded perspective view of FIG. 3. FIG. 5 is a plan view of the diaphragm in FIG. 4.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Permanent magnet plate, 1a Exhaust through hole, 2 Vibration plate, 2a Serpentine coil pattern, 2b Resin film, 2c hole, 3 Buffer member, 4 Magnetic plate, 4a Exhaust through hole, 5 Support member, 5a Support rod, 5b Nut, 6 packing member, N, S magnetic pole (multipolar magnetization pattern), nz neutral zone.

Claims (2)

  A permanent magnet plate having a strip-shaped multipole magnetized pattern and having an exhaust through-hole, a meandering coil pattern formed on the surface, and disposed opposite to the multipole magnetized pattern forming surface of the permanent magnet plate, In an electromagnetic transducer comprising a diaphragm that is electromagnetically coupled to the permanent magnet plate and vibrates in the thickness direction when a meandering coil pattern is energized, and a buffer member disposed between the diaphragm and the permanent magnet plate An electromagnetic converter, wherein a packing member surrounding an outer periphery of the buffer member is interposed between the permanent magnet plate and the diaphragm.   2. The electromagnetic transducer according to claim 1, wherein the packing member is made of a polyolefin foamed polyethylene foam.

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