JP5449002B2 - Acoustic electrodynamic transducer - Google Patents

Description

  The present invention relates to an acoustic electrodynamic transducer including a diaphragm having a voice coil and a magnetic circuit unit having a magnetic gap in which the voice coil is arranged to vibrate. More specifically, the magnetic gap is formed. It relates to magnetic poles.

  In the electrodynamic (dynamic) unit, as schematically shown in FIG. 7, a pole piece 2 provided on one pole side of the permanent magnet 1 and a ring yoke 3 provided on the other pole side of the permanent magnet 1. The voice coil 6 attached to the diaphragm 5 is disposed in the magnetic gap 4 formed by each magnetic pole.

  In the microphone, the vibration speed of the voice coil 6 that vibrates due to the sound wave becomes a signal output, and in the headphone or the speaker, a driving force that vibrates the diaphragm is generated by the current passed through the voice coil 6.

  Since FIG. 7 is a schematic diagram, the magnetic gap 4 is drawn widely. Actually, however, the gap between the voice coil 6 and the pole piece 2 is, for example, about 0.12 mm, and the voice coil 6 and the ring yoke 3. For example, a relatively large acoustic impedance (acoustic mass and acoustic resistance) exists between the magnetic poles (pole piece 2 and ring yoke 3) and the voice coil 6 because the gap between them is as narrow as about 0.18 mm. To do.

  This relatively large acoustic impedance degrades the directional frequency response in microphones and the frequency response in headphones or speakers. Non-Patent Document 1 describes a first method and a second method for solving this.

  The first method is a method of increasing the equivalent resistance of the acoustic impedance Z4a between the voice coil 6 and the pole piece 2 and the acoustic impedance Z4b between the voice coil 6 and the ring yoke 3.

  In the second method, the air chamber on the back side of the diaphragm 5 divided by the voice coil 6, that is, the back air chamber P on the center dome 5 a side and the back air chamber Q on the sub dome 5 b side have low impedance. This is a method of short-circuiting with an equivalent circuit element. This includes a method of providing a vent hole at a bonding portion between the diaphragm 5 and the voice coil 6 and a part of the pole piece 2 and the ring yoke 3 as magnetic poles. There is a method of forming a vent hole.

“Design and Trial Production of Unidirectional Moving Coil Microphone” NHK Technology Research, Vol. 19, No. 1, pp. 7-8 (Showa 42)

  However, in the first method, since the gap between the magnetic poles 2 and 3 and the voice coil 6 must be extremely narrow, the magnetic poles 2 and 3 and the voice coil 6 may come into contact with each other. It can not be said.

  Therefore, the second method is preferable. However, when vent holes are provided at several locations in the bonding portion between the diaphragm 5 and the voice coil 6, the stiffness of the sub dome 5b changes, and the directivity frequency is increased due to abnormal resonance of the sub dome 5b. Response may be impaired.

  Further, when the vent piece is formed by cutting a part of the pole piece 2 and the ring yoke 3 which are magnetic poles, another problem arises that the sensitivity is lowered accordingly.

  Therefore, an object of the present invention is to reduce the acoustic impedance between the magnetic pole and the voice coil without causing abnormal resonance in the sub-dome of the diaphragm and without reducing the sensitivity.

  In order to solve the above problems, the present invention provides a diaphragm having a voice coil, a pole piece connected to one pole side of a permanent magnet, and a pole piece connected to the other pole side of the permanent magnet. A magnetic circuit portion having a ring yoke to be arranged, a magnetic gap having a predetermined width is formed between the pole piece and the ring yoke, and the voice coil of the diaphragm is arranged to vibrate within the magnetic gap. In the acoustic electrodynamic converter, the pole piece is substantially C-shaped, and a plurality of pole piece members are laminated in which the outer peripheral surface is the magnetic gap forming surface and the air passage is formed in part. A plurality of ring yoke members comprising a body, wherein the ring yoke is substantially C-shaped, and an inner peripheral surface is the magnetic gap forming surface and a ventilation path is formed in part. Made from the laminate, the pole piece members and the ring yoke member is characterized in that it is laminated, respectively, as described above ventilation path member between adjacent do not overlap.

  According to a preferred aspect of the present invention, each of the pole piece members and each of the ring yoke members has the same configuration, and adjacent members are stacked while being shifted by a predetermined angle in the circumferential direction.

  Moreover, it is preferable that the pole piece member and the ring yoke member are arranged so that their ventilation paths do not face each other.

  Moreover, it is preferable that a groove is formed on the outer peripheral surface side of each ring yoke member at a position overlapping with the air passage of the other ring yoke member.

  According to the present invention, each magnetic pole (pole piece and ring yoke) maintains a cylindrical surface that forms a magnetic gap, while the magnetic gap forming surface has a ventilation hole formed by an air passage provided in each member. Therefore, without causing abnormal resonance in the sub dome of the diaphragm, and without lowering the sensitivity, the acoustic impedance between the magnetic pole and the voice coil is reduced, and the directional frequency response is deteriorated in the microphone. With headphones or speakers, it is possible to prevent the frequency response from being degraded.

Sectional drawing which shows the dynamic microphone unit which concerns on one Embodiment of this invention. The top view which shows the pole piece member which comprises a pole piece. The top view which shows the ring yoke member which comprises a ring yoke. (A)-(d) The perspective view for demonstrating the lamination | stacking order of the said pole piece member. (A)-(d) The perspective view for demonstrating the lamination | stacking order of the said ring yoke member. Sectional drawing which shows the dynamic microphone unit which concerns on other embodiment of this invention. The schematic diagram which shows the basic form of the electrodynamic transducer for acoustic.

  Next, an embodiment of the present invention will be described with reference to FIGS. 1 to 6, but the present invention is not limited to this. The present invention can be applied to headphone and speaker drive units, but the embodiment described here is for a dynamic microphone unit.

  Referring to FIG. 1, a dynamic microphone unit (hereinafter sometimes referred to as “microphone unit”) according to this embodiment basically includes a diaphragm 10, a magnetic circuit unit 20, and a unit holder. 30 and a resonator 40.

  The diaphragm 10 has a center dome 11 and a sub dome 12 integrally connected around the center dome 11, and a voice coil 13 is fixed to the boundary portion between the center dome 11 and the sub dome 12 with an adhesive or the like. ing. The sub dome 12 is sometimes called an edge.

  The magnetic circuit unit 20 is formed in a disk shape, and is composed of a permanent magnet 21 magnetized in the thickness direction, a pole piece 22 magnetically connected to one pole side of the permanent magnet 21, and the permanent magnet 21. A pole-shaped yoke body 23 magnetically connected to the other pole side, and a ring yoke 24 provided on the opening side of the yoke body 23 and disposed around the pole piece 22. The ring yoke 24 serves as a magnetic pole, and a magnetic gap 25 is formed between them.

  The unit holder 30 is formed of a cylindrical body, and supports the yoke body 23 side of the magnetic circuit unit 20 on one end side (the upper end side in FIG. 1). The unit holder 30 includes a rear air chamber 31 having a predetermined volume on the rear end side (lower end side in FIG. 1).

  Further, an enlarged flange portion 33 is provided on one end side of the unit holder 30, and the peripheral portion of the sub dome 12 of the diaphragm 10 is supported by the flange portion 33. As a result, the voice coil 13 is disposed in the magnetic gap 25 so as to vibrate. Since this microphone unit is unidirectional, a rear acoustic terminal 32 is formed on the flange portion 33.

  The resonator 40 is placed on the flange portion 33 of the unit holder 30 so as to cover the front side of the diaphragm 10. The resonator 40 includes a front acoustic terminal 41.

  According to the present invention, both the pole piece 22 and the ring yoke 24 are composed of a laminate of a plurality of magnetic metal plates. 2 and 3 show a pole piece member 220 and a ring yoke member 240 as laminate elements used in this embodiment.

  Referring to FIG. 2, the pole piece member 220 includes a washer-like perforated disc body 221 made of a magnetic material having a circular opening 222 at the center portion, and a part of the disc body 221 is arranged in a radial direction. A single air passage 223 is formed along the substantially C shape.

  Referring to FIG. 3, ring yoke member 240 is similarly provided with a washer-like perforated disk body 241 made of a magnetic material having a circular opening 242 in the center, and a radius is formed in a part of this disk body 241. A single air passage 243 is formed along the direction to form a substantially C-shape, but the inner diameter of the opening 242 is arranged so that a predetermined magnetic gap is formed, and the pole piece member 220 is disposed inside the opening 242. Is the size to be.

  In this embodiment, since the pole piece 22 and the ring yoke 24 are both a four-layer (four-piece structure) laminate, the inner peripheral surface of the opening 222 of the pole piece member 220 is located from the position of the air passage 223. Three grooves 224a, 224b, and 224c are formed at intervals of 90 degrees around the counterclockwise direction.

  On the other hand, on the outer peripheral surface of the ring yoke member 240, three grooves 244a, 244b, and 244c are formed at intervals of 90 degrees clockwise from the position of the air passage 243.

  Next, an example of a method of stacking the pole piece members 220 will be described with reference to FIG. Although four pole piece members 220 are laminated, the same one may be used for each pole piece member 220. Therefore, description will be made with FIG. 4 (a) as the first layer and FIG. 4 (d) as the fourth layer. For convenience, the pole piece members of the first to fourth layers are designated as 220a, 220b, 220c, and 220d.

  Basically, the ventilation paths 223 of adjacent pole piece members 220 do not overlap each other. Therefore, in this embodiment, if the ventilation path 223 of the first-layer pole piece member 220a in FIG. 4A is directed to the right in the drawing, the ventilation path 223 of the second-layer pole piece member 220b in FIG. Is shifted upward by 90 degrees counterclockwise from the first layer air passage 223 and is upward in the figure.

  Similarly, the ventilation path 223 of the third-layer pole piece member 220c in FIG. 4C is further shifted 90 degrees counterclockwise from the second-layer ventilation path 223 to the left in the figure, and FIG. The air passage 223 of the fourth layer pole piece member 220d is further shifted 90 degrees counterclockwise from the air passage 223 of the third layer and is downward in the drawing.

  By laminating in this way, the laminated pole piece 22 is provided with four ventilation holes by the ventilation path 223 at positions shifted by 90 degrees for each layer, and the four ventilation holes by these ventilation paths 223 and The opening 222 reduces the acoustic impedance (acoustic mass and acoustic resistance) between the gap between the voice coil 13 and the pole piece 22 and the back air chamber P of the center dome 11.

  Next, an example of how the ring yoke members 240 are stacked will be described with reference to FIG. Four ring yoke members 240 are laminated. Since the same members may be used for each ring yoke member 240, FIG. 5 (a) is the first layer and FIG. 5 (d) is the fourth layer. For convenience, the ring yoke members of the first to fourth layers are designated as 240a, 240b, 240c, and 240d.

  Basically, the air passages 243 of adjacent ring yoke members 240 do not overlap each other, and the air passages 243 of the ring yoke members 240 do not face the air passages 223 on the pole piece member 220 side of the same layer. To do.

  Therefore, in this embodiment, the ventilation path 243 of the first layer ring yoke member 240a in FIG. 5A is directed leftward in the drawing, and the ventilation path 243 of the second layer ring yoke member 240b in FIG. The first-layer air passage 243 is shifted 90 degrees counterclockwise and is directed downward in the figure.

  Similarly, the air passage 243 of the third-layer ring yoke member 240c in FIG. 5C is further shifted 90 degrees counterclockwise from the second air passage 243 so as to face right in the drawing, and FIG. The air passage 243 of the fifth layer ring yoke member 240d is further shifted 90 degrees counterclockwise from the air passage 223 of the third layer and is upward in the drawing.

  By laminating in this way, the laminated ring yoke 24 is provided with four ventilation holes by the ventilation path 243 at positions shifted by 90 degrees for each layer.

  Further, on the outer peripheral surface side of the ring yoke 24, for example, the second layer groove 224a, the third layer 224b, and the fourth layer 244c are overlapped at the position of the first layer ventilation path 243, and the second layer ventilation is performed. At the position of the channel 243, the first layer groove 224c, the third layer 224a, and the fourth layer 244b overlap each other, and the other three layers of grooves overlap the one layer air passage 243. Thus, a series of ventilation grooves are formed.

  Due to the four vent holes formed by the vent passage 243 formed as described above and the vent groove on the outer peripheral surface side of the ring yoke 24, the gap between the voice coil 13 and the ring yoke 24 and the back air of the sub dome 12 can be obtained. The acoustic impedance (acoustic mass and acoustic resistance) between the chambers Q is lowered.

  As described above, according to the present invention, the acoustic impedance between the magnetic poles (the pole piece 22 and the ring yoke 24) and the voice coil 13 is reduced, so that it is possible to prevent the directional frequency response from being deteriorated.

  Further, the air passages in the adjacent layers do not overlap on both the pole piece 22 side and the ring yoke 24 side, and the air passages in the same layer do not face each other on the pole piece 22 side and the ring yoke 24 side. By doing so, the sensitivity is not lowered.

  Further, unlike the prior art described above, it is not necessary to provide a vent hole in the bonding portion between the diaphragm 10 and the voice coil 13, so that no abnormal resonance occurs in the sub dome 12.

  Furthermore, since both the pole piece member 220 and the ring yoke member 240 can be produced at low cost by pressing a magnetic metal plate, it can be easily replaced with the pole piece and ring yoke of an existing unit.

  In the above embodiment, both the pole piece member 220 and the ring yoke member 240 are configured such that the air passages 223 and 243 are shifted by 90 degrees. However, as shown in FIG. The air passages 223 and 243 of the eyes may be in the same direction.

DESCRIPTION OF SYMBOLS 10 Diaphragm 11 Center dome 12 Sub dome 13 Voice coil 20 Magnetic circuit part 21 Permanent magnet 22 Pole piece 220 (220a-220d) Pole piece member 221 Perforated disk body 222 Opening part 223 Air passage 24 Ring yoke 240 (240a-240d) ) Ring yoke member 241 Perforated disk body 242 Opening 243 Air passage 244a to 244c Groove 30 Unit holder 31 Rear air chamber 32 Rear acoustic terminal 33 Flange portion 40 Resonator 41 Front acoustic terminal P Back air chamber of center dome Q Sub dome Back air chamber

Claims (4)

A diaphragm having a voice coil, a pole piece connected to one pole side of a permanent magnet, and a magnetic circuit unit having a ring yoke connected to the other pole side of the permanent magnet and disposed around the pole piece An acoustic electrodynamic converter in which a magnetic gap having a predetermined width is formed between the pole piece and the ring yoke, and a voice coil of the diaphragm is arranged to vibrate within the magnetic gap. ,
The pole piece is substantially C-shaped, and is composed of a laminate of a plurality of pole piece members, the outer peripheral surface of which is the magnetic gap forming surface and a part of which is formed with an air passage. The ring yoke is substantially C-shaped. The inner circumferential surface is a laminated body of a plurality of ring yoke members in which the air gap is formed in part with the magnetic gap forming surface,
An acoustic electrodynamic transducer, wherein the pole piece member and the ring yoke member are laminated so that the air passages between adjacent members do not overlap each other.   2. The acoustic motion according to claim 1, wherein each of the pole piece members and each of the ring yoke members has the same configuration, and adjacent members are stacked while being shifted by a predetermined angle in the circumferential direction. Electric type converter.   3. The acoustic electrodynamic converter according to claim 1, wherein the pole piece member and the ring yoke member are arranged so that their ventilation paths do not face each other. 4. The acoustic motion according to claim 1, wherein a groove is formed on an outer peripheral surface side of each ring yoke member at a position overlapping with the air passage of the other ring yoke member. Electric type converter.

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