JP2017158038A - Unidirectional dynamic microphone - Google Patents

Abstract

A unidirectional dynamic microphone capable of easily reducing the volume of the space on the back side of a diaphragm, having no irregularities in the frequency response of the main sound collection band, and capable of obtaining a stable directional frequency response is obtained. . A magnetic gap formed in a magnetic circuit, a diaphragm that vibrates in response to a sound wave, and a voice that is fixed to the diaphragm and is located in the magnetic gap and vibrates integrally with the diaphragm. A coil 6, a communication path 30 that connects the space on the back side of the diaphragm 5 and the external space, and a thin space that is disposed in the space on the back side of the diaphragm 5 and spaced from the opening on one end side of the communication path 30. And an air layer forming member 10. [Selection] Figure 1

Description

  The present invention relates to a unidirectional dynamic microphone.

  Unidirectional dynamic microphones obtain unidirectionality by combining an omnidirectional component and a bidirectional component. The omnidirectional component depends on resistance control, and the bidirectional component depends on mass control. In order to realize unidirectionality, it is necessary to flatten the frequency response of the resistance component, and the acoustic resistance is disposed near the back surface of the diaphragm.

  A voice coil is fixed to the rear surface of the diaphragm along the boundary between the center dome and the sub dome, and the air chamber on the rear side of the diaphragm is divided into the center dome side and the sub dome side by the voice coil. The voice coil is located in a magnetic gap formed between the magnetic poles, and the acoustic mass and acoustic resistance between the magnetic poles are divided by the voice coil. The acoustic mass and acoustic resistance are divided into an acoustic mass and acoustic resistance on the inner circumference side of the voice coil, and an acoustic mass and acoustic resistance on the outer circumference side of the voice coil, and these acoustic mass and acoustic resistance connect the air chamber. It is equivalent to

  The acoustic mass and acoustic resistance of the air chamber resonate, making the frequency response uneven by resonance and deteriorating acoustic characteristics. In order to eliminate such an adverse effect due to resonance, as described in Japanese Patent Application Laid-Open No. H10-228707, there is a device designed to make the volume of the air chamber on the back side of the voice coil as small as possible. When the volume of the air chamber on the back side of the diaphragm is reduced as in the invention described in Patent Document 1, the stiffness of the air chamber is increased, so that the resonance frequency can be increased. By making the resonance frequency higher than the main sound collection band, unevenness in the frequency response of the main sound collection band can be prevented.

  In the invention described in Patent Document 1, a thin plate-like acoustic resistance which includes a rear air chamber behind the voice coil and a second air chamber communicating with the rear air chamber, restricts the volume of the second air chamber and has an elastic force. The body is in place. The acoustic resistor is provided with tension at a position where the voice coil can be contacted within the maximum displacement, thereby reducing the impact sound generated when the diaphragm is greatly displaced. Yes.

  Patent Document 2 describes a dynamic microphone that can avoid resonance due to the presence of an air chamber on the back side of a voice coil. The dynamic microphone described in Patent Document 2 is obtained by connecting the first air chamber on the back side of the voice coil where the acoustic resistance is arranged and the second air chamber on the back side of the voice coil by a sound wave communication path. . The communication path causes the acoustic mass of the magnetic gap portion to be short-circuited, so that the acoustic mass is substantially ineffective, the resonance between the acoustic capacity of the second air chamber and the acoustic mass is prevented, and a good frequency response is achieved. Can be obtained.

  FIG. 8 shows an example of a conventional unidirectional dynamic microphone. In FIG. 8, reference numeral 1 denotes a unit case, 2 denotes a yoke, 3 denotes a magnet, 4 denotes an outer yoke, 5 denotes a diaphragm, 6 denotes a voice coil, and 8 denotes a pole piece. The yoke 2, the magnet 3, the outer yoke 4, and the pole piece 8 constitute a magnetic circuit, and a magnetic gap is formed between the inner peripheral surface of the outer yoke 4 and the outer peripheral surface of the pole piece 8.

  The diaphragm 5 includes a center dome 51 and a sub dome 52 around the center dome 51, and one end of a cylindrical voice coil 6 is fixed to the back side of the diaphragm 5 along the boundary between the center dome 51 and the sub dome 52. ing. The voice coil 6 is disposed through the magnetic gap. When the diaphragm 5 receives a sound wave and vibrates, the voice coil 6 also vibrates integrally with the diaphragm 5, and the voice coil 6 crosses the magnetic flux in the magnetic gap, so that the voice coil 6 outputs a sound signal corresponding to the sound wave. Output.

  In the conventional example shown in FIG. 8, in order to obtain unidirectionality, a communication path 30 that connects the back side space of the diaphragm 5 (sub dome 52) and the external space is formed in the upper part on the outer peripheral side of the unit case 1. Yes. The communication path 30 has a rear acoustic terminal that is a position of air that effectively applies sound pressure to the diaphragm 5, that is, a center position of air that moves simultaneously with the diaphragm.

  An acoustic resistance 20 made of sponge or cloth is disposed in a part of the communication path 30. The sound wave taken from the rear acoustic terminal is guided to the back side of the diaphragm 5 (sub dome 52) through the acoustic mass of the communication path 30 and the acoustic resistance 20. In order to brake the low frequency resonance of the diaphragm 5 and adjust the directivity frequency response, it is equivalent to connecting the acoustic resistance 20 in series with the acoustic mass in the above configuration.

  The closer to the diaphragm 5, the more effective the acoustic resistance 20 is. The closer the acoustic resistance 20 is to the diaphragm 5, the smaller the volume of the air chamber on the back side of the diaphragm 5, and the sound wave taken from the rear acoustic terminal is applied to the diaphragm 5 at a position close to the diaphragm 5. As a result, the resonance frequency becomes high, and as described above, the resonance frequency can be made higher than the main sound collection band to prevent unevenness in the frequency response of the main sound collection band.

JP 2013-55466 A JP2013-55397A

  The present invention further improves the prior art, makes it easy to reduce the volume of the space on the back side of the diaphragm, has no irregularities in the frequency response of the main sound collection band, and can obtain a stable directional frequency response. The purpose is to obtain a unidirectional dynamic microphone.

The unidirectional dynamic microphone according to the present invention is
A magnetic gap formed in the magnetic circuit;
A diaphragm that vibrates in response to sound waves;
A voice coil that is fixed to the diaphragm and is located in the magnetic gap and vibrates integrally with the diaphragm;
A communication path connecting the space on the back side of the diaphragm and the external space;
A thin air layer forming member disposed in a space on the back side of the diaphragm and spaced from an opening at one end of the communication path;
It has the most important feature.

  Since the thin air layer forming member is in the space on the back side of the diaphragm, the volume of the space on the back side of the diaphragm is limited, the resonance frequency becomes higher than the main sound collection band, and the frequency response of the main sound collection band Can prevent unevenness. The thin air layer forming member restricts the space from the space on the back side of the diaphragm to the opening on the one end side of the communication path, and functions as an acoustic resistance.

It is a longitudinal cross-sectional view which shows the Example of the unidirectional dynamic microphone which concerns on this invention. It is a longitudinal cross-sectional view which shows the thin air layer formation member in the said Example. It is an expanded longitudinal cross-sectional view which shows the principal part of the said Example. It is an expanded longitudinal cross-sectional view which shows the principal part of another Example of this invention. It is an expanded longitudinal cross-sectional view which shows the principal part of another Example of this invention. It is an expanded longitudinal cross-sectional view which shows the principal part of another Example of this invention. It is a top view of the unit holder used for each Example of the present invention. It is a longitudinal cross-sectional view which shows the example of the conventional unidirectional dynamic microphone.

  Embodiments of a unidirectional dynamic microphone according to the present invention will be described below with reference to the drawings. The same components as those in the conventional example shown in FIG.

[Example 1]
In FIG. 1, the unidirectional dynamic microphone according to the present embodiment has each member assembled based on a unit case 1. The unit case 1 has a substantially cylindrical shape, and an inner cylinder 7 is fitted and fixed inside the lower half of the unit case 1. On the inner periphery of the unit case 1, a stepped portion 12 is formed by expanding the diameter above the inner cylinder 7. A circuit component member is fitted, and the yoke 2 is in contact with the stepped portion 12.

  The yoke 2 is a dish-like member having a peripheral wall, and a flat plate-like magnet 3 is fixed to the inner central portion at a distance from the peripheral wall. On the magnet 3, a flat pole piece 8 is stacked and fixed. A ring-shaped outer yoke 4 is stacked and fixed on the upper surface of the peripheral wall of the yoke 2. The outer peripheral surface of the yoke 2 and the outer peripheral surface of the outer yoke 4 are on a common cylindrical surface. The outer yoke 4 and the pole piece 8 have their upper and lower surfaces on a common plane.

  The magnet 3 is magnetized in the thickness direction, that is, in the vertical direction in FIG. 1, and the N pole and the S pole are separated in the vertical direction. A cylindrical space is formed at an appropriate interval between the inner peripheral surface of the outer yoke 4 and the outer peripheral surface of the pole piece 8. This cylindrical space is a magnetic gap, and the magnetic flux emitted from the magnet 3 passes through the magnetic gap with a uniform density.

  A jetty 15 is formed on the outer peripheral edge of the upper end of the unit case 1, and a step portion 14 is formed on the inner peripheral side of the jetty 15 at a position lower than the upper surface of the jetty 15. The outer peripheral edge of the diaphragm 5 is fixed to the stepped portion 14. The diaphragm 5 has a center dome 51 in which a part of a spherical surface is cut off, a sub dome 52 having an arcuate vertical cross-sectional shape that follows the outer periphery of the center dome 51, and a flat outer peripheral edge that continues to the outer periphery of the sub dome 52. . The outer peripheral edge of the diaphragm 5 is bonded to the step 14 of the unit case 1. When the diaphragm 5 receives sound waves, the center dome 51 and the sub dome 52 vibrate in the front-rear direction according to the sound waves.

  One end of a voice coil 5 formed by winding a thin wire in a cylindrical shape along the boundary between the center dome 51 and the sub dome 52 is fixed to the back side of the diaphragm 5 (the lower surface side in FIG. 1). Yes. The voice coil 5 penetrates the magnetic gap. The voice coil 5 is separated from both the outer yoke 4 and the pole piece 8. As is well known, when the diaphragm 5 receives a sound wave, the voice coil 5 vibrates integrally with the diaphragm 5, and the voice coil 5 responds to the sound wave by an electromagnetic conversion action between the magnetic flux passing through the magnetic gap and the voice coil 5. An audio signal to be generated is generated.

  The outer peripheral portion of the lower end of the equalizer 22 is fixed to the jetty 15 of the unit case 1. The equalizer 22 has a hole for guiding sound waves from the outside to the diaphragm 5. This hole constitutes the front acoustic terminal. The equalizer 22 also serves as a protective member for the diaphragm 5. The center portion on the lower surface side of the equalizer 22 is formed in a dome shape in accordance with the shape of the center dome 51 of the diaphragm 5, and a gap with a constant interval is maintained between the center dome 51.

  The magnetic gap communicates a space 40 formed between the space on the back side of the diaphragm 5 and the outer peripheral surface of the magnet 3 and the inner peripheral surface of the peripheral wall of the yoke 2. The space 40 communicates with the internal space of the inner cylinder 7 through an appropriate number of holes opened at the bottom of the yoke 2.

  As shown in FIG. 7, the unit case 1 is formed with a plurality of communication passages 30 along the circular arc centered on the central axis of the unit case 1 at equal intervals in the circumferential direction. The communication path 30 is located at a position corresponding to the sub dome 52 of the diaphragm 5 and is formed in the central axis direction of the unit case 1. In the unit case 1, the lower part of the communication path 30 is open to the external space. Therefore, the communication path 30 connects the space on the back side of the diaphragm 5 and the external space. The communication path 30 includes a rear acoustic terminal that is a position of air that effectively applies sound pressure to the diaphragm 5, that is, a center position of air that moves simultaneously with the diaphragm. By having the rear acoustic terminal, the directivity of the microphone according to the present embodiment is unidirectional.

  The thin air layer forming member 10 is fixed to the unit case 1 so as to overlap an opening on one end side (the upper end side in FIG. 1) of the communication path 30. As shown in FIG. 2, the thin air layer forming member 10 is a ring-shaped member in which an outer peripheral edge portion is bent downward to form an extremely low peripheral wall 101 and a center hole 102 is formed.

  As shown in FIG. 3, the second step portion is located on the inner periphery side of the step portion 14 of the unit case 1 to which the outer peripheral edge portion of the diaphragm 5 is fixed and at a position lower than the step portion 14. . This second step is flush with the top surface of the pole piece 8. A peripheral wall 101 of the thin air layer forming member 10 is engaged and fixed to the second step portion. The diameter of the central hole 102 of the thin air layer forming member 10 is larger than the outer diameter of the voice coil 6, and the radial width of the thin air layer forming member 10 is smaller than the radial width of the sub dome 52 of the diaphragm 5. .

  The thin air layer forming member 10 is disposed on the back side of the sub dome 52 of the diaphragm 5 at a position overlapping the sub dome 52 and is set to a size that does not contact the sub dome 52. The thin air layer forming member 10 has a peripheral wall 101 fixed to the second step portion of the unit case 1 as described above, so that the thin air layer forming member 10 is in the space on the back side of the diaphragm 5 (sub dome 52) and is connected to the communication path. 30 is spaced apart from the one end side opening 30A. A thin air layer is formed by a gap between the thin air layer forming member 10 and the magnetic circuit.

  Since the radial width of the thin air layer forming member 10 is smaller than the radial width of the sub dome 52 of the diaphragm 5 as described above, the space on the back side of the sub dome 52 is formed between the thin air layer and the communication path 30. It is connected to the external space through a path passing through the one end side opening 30 </ b> A and the communication path 30. Specifically, the thin air layer forming member 10 is formed to extend inward from the one end side opening 30 </ b> A with a predetermined interval between the thin air layer forming member 10 and the outer yoke 4.

  The degree of separation of the thin air layer forming member 10 from the one end side opening of the communication passage 30 depends on the height of the peripheral wall 101 of the thin air layer forming member 10. Since the height of the peripheral wall 101 is low, the degree of separation of the thin air layer forming member 10 from the one end side opening of the communication path 30 is small, and the space connecting the back side space of the diaphragm 5 and the communication path 30 is narrow.

  The volume limiting member 18 is also disposed in the back side space of the center dome 51 of the diaphragm 5, and the volume of the back side space of the center dome 51 is also limited. The volume limiting member 18 also has a shape obtained by cutting a part of a sphere. The flat surface is fixed to the upper surface of the pole piece 8, and the spherical surface faces the back surface of the center dome 51. A gap is maintained at a constant interval between the spherical surface of the volume limiting member 18 and the back surface of the center dome 51.

  In the embodiment of the unidirectional dynamic microphone described above, the volume of the back side space of the sub dome 52 is reduced by the presence of the thin air layer forming member 10 in the back side space of the sub dome 52 of the diaphragm 5. . Further, due to the presence of the thin air layer forming member 10, a sound wave taken from the rear acoustic terminal is applied in the immediate vicinity of the back surface of the diaphragm 5 by the resistance of the thin air layer. By reducing the volume of the back side space of the sub dome 52, the resonance frequency can be made higher than the main sound collection band, and unevenness in the frequency response of the main sound collection band can be prevented.

  The presence of the thin air layer forming member 10 allows the thin air layer forming member 10 to function as acoustic resistance. When a hygroscopic material such as cloth or non-woven fabric is used as an acoustic resistance as in the past, acoustic characteristics such as frequency response are likely to fluctuate due to changes in humidity. However, according to the Example of this invention, since the thin air layer by the thin air layer formation member 10 is utilized as acoustic resistance, the stable acoustic characteristic which is not influenced by the humidity change etc. can be acquired.

  Next, a thin air layer forming member, which is a main part of the unidirectional dynamic microphone according to the present invention, and various modifications around it will be described.

[Example 2]
FIG. 4 shows a second embodiment. In the second embodiment, the thin air layer forming member 50 having a smaller radial width than the thin air layer forming member 10 in the first embodiment is used. Other configurations of the unit case 1, the outer yoke 4, the diaphragm 5, the communication path 30, and the like are the same as those in the first embodiment. Compared to the case of the first embodiment, the length of the thin air layer from the back side space of the sub dome 52 of the diaphragm 5 to the communication path 30 is shorter, and the acoustic resistance is reduced. Further, the volume of the back side space of the sub dome 52 is larger than that of the first embodiment, and the resonance frequency is lower than that of the first embodiment. How to set the size of the thin air layer forming member 50 in the radial direction may be set in accordance with the required acoustic characteristics.

[Example 3]
FIG. 5 shows a third embodiment. The third embodiment uses a thin air layer forming member 60 whose upper surface corresponds to the arc of the sub dome 52 of the diaphragm 5 and whose cross-sectional shape is formed in an arc shape. Although the radial width of the thin air layer forming member 60 is arbitrary, the radial width of the thin air layer forming member 60 in the third embodiment shown in FIG. 5 is the same as that of the thin air layer forming member 10 of the first embodiment. It is almost the same. According to the third embodiment, the thin air layer forming member 60 further reduces the spatial volume on the back side of the sub dome 52 of the diaphragm 5, further increases the resonance frequency, and prevents unevenness in the frequency response of the main sound collection band. It becomes easy.

[Example 4]
FIG. 6 shows a fourth embodiment. In Example 4, the thin air layer forming member 10 having the same configuration as that of the thin air layer forming member 10 of Example 1 is used, but the structure of the fixing portion is different. As shown in FIG. 6, the second step portion 16 that fixes the peripheral wall 101 of the thin air layer forming member 10 to the step portion 14 that is a fixing portion of the outer peripheral edge of the diaphragm 5 has been described so far. It is formed with a large step compared to the example. The second step portion 16 is provided on the inner peripheral side of the step portion 14, and the second step portion 16 is provided below the step portion 14.

  According to the fourth embodiment shown in FIG. 6, the diaphragm 5 and the peripheral wall 101 of the thin air layer forming member 10 can be separated from each other, so that the adhesive attached to the peripheral portion of the diaphragm 5 forms the thin air layer. It is possible to prevent penetration into the gap with the member 10. Thereby, the malfunction that the vibration by the sound wave of the diaphragm 5 is inhibited can be prevented.

DESCRIPTION OF SYMBOLS 1 Unit case 2 Yoke 3 Magnet 4 Outer yoke 5 Diaphragm 6 Voice coil 7 Inner cylinder 8 Pole piece 10 Thin air layer formation member 14 Step part 16 Step part 18 Volume restriction member 30 Communication path

Claims (6)

A magnetic gap formed in the magnetic circuit;
A diaphragm that vibrates in response to sound waves;
A voice coil that is fixed to the diaphragm and is located in the magnetic gap and vibrates integrally with the diaphragm;
A communication path connecting the space on the back side of the diaphragm and the external space;
A thin air layer forming member disposed in a space on the back side of the diaphragm and spaced from an opening at one end of the communication path;
A unidirectional dynamic microphone.   2. The unidirectional dynamic according to claim 1, wherein the communication path is formed in an appropriate number along a circular arc, and the thin air layer forming member is a ring-shaped member overlapping the communication path formed along the circular arc. Microphone.   The unidirectional dynamic microphone according to claim 1, wherein the diaphragm has a center dome and a sub dome around the center dome, and the communication path and the thin air layer forming member are on a back side of the sub dome.   4. The unidirectional dynamic microphone according to claim 1, wherein the magnetic circuit is composed of a magnetic circuit constituent member including a yoke, a magnet, and a pole piece, and the magnetic circuit constituent member is attached to a unit case.   The unidirectional dynamic microphone according to claim 4, wherein the communication path is provided in the unit case, and the thin air layer forming member is attached to the unit case. 6. The unidirectional dynamic microphone according to claim 3, wherein the thin air layer forming member has an arcuate cross section corresponding to the curved surface of the sub dome at a surface facing the sub dome. 7. .

Images