JP2001258093A - Electroacoustic transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electroacoustic transducer, having a thin and long shape that can prevent characteristic deterioration due to compliance load, in the air chamber behind a diaphragm. SOLUTION: A thin and long magnet 12 and a pole piece 13 are placed in the inside of a thin and long yoke 11 to configure a magnetic circuit using the magnet 12, the pole piece 13 and the yoke 11 for a magnetic path, the internal space of the magnetic circuit is configured as an air chamber 15 in the magnetic circuit, a diaphragm 16 is formed so as to plug the an upper part of the yoke 11, and the air chamber 17 behind the diaphragm is configured to the rear side of the diaphragm 16 in the electroacoustic transducer. Both ends of a dome part 16a of the diaphragm 16 in the length direction are provided with both ends of the diaphragm in the length direction, that are projected outwardly from both ends of the yoke 11 in the length direction and a side face of the yoke 11 in its short-hand direction, placed at its both ends in the length direction, in used as an opening 21 so as to constitute an air communicating path 20 for making the air chamber 17 behind the diaphragm externally communicate with the external.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inner-magnet type electro-acoustic transducer in which a magnet is arranged inside a yoke, and more particularly to a technique for preventing characteristic deterioration due to a compliance load by an air chamber behind a diaphragm. Related to

[0002]

2. Description of the Related Art A so-called inner magnet type electroacoustic transducer is
As shown in FIG. 4, a space having an open side is provided inside the yoke 1, and a magnet 2 is provided in this space.
And the pole piece 3 are arranged. Then, a magnetic circuit is configured in which the magnet 2, the pole piece 3, and the yoke 1 are used as a magnetic path, and the opening of the space is used as a magnetic gap 4 of the magnetic path. The internal space of the magnetic circuit is configured as a magnetic circuit air chamber 5 surrounded by the magnet 2 and the yoke 1.

A diaphragm 6 is provided on the upper surface side of the yoke 1 so as to close the opening of the space, and the back surface of the diaphragm 6 is configured as a diaphragm back air chamber 7. The air chamber 7 behind the diaphragm is provided in the air chamber 5 in the magnetic circuit.
Are communicated through. A drive coil 8 is fixed to the lower surface of the diaphragm 6, and the drive coil 8 is disposed in the magnetic gap 4.

In the above configuration, when a predetermined drive current is applied to the drive coil 8, an electromagnetic force corresponding to the applied current is generated in the drive coil 8, and the diaphragm 6 is vibrated by the electromagnetic force.

Here, F: driving force, m: weight of diaphragm 6, Cm: compliance of vibration system, Rm: mechanical resistance of vibration system, C1: compliance of air chamber 7 behind diaphragm, C2: inside magnetic circuit Compliance of air chamber 5, R
Assuming that 2: the viscous resistance of the magnetic gap 4 and S: the area of the diaphragm 6, the equivalent circuit of the inner magnet type electroacoustic transducer is shown in FIG.
The mechanical-acoustic conversion model is as shown in FIG.

As is apparent from FIGS. 5 and 6, if the load on the compliance C1 due to the diaphragm back air chamber 7 is large, the characteristics are deteriorated. Therefore, reducing the compliance C1 is effective for improving the characteristics. . FIG. 7 shows a conventional electroacoustic transducer to which means for reducing compliance C1 is added.

In FIG. 7, the electroacoustic transducer has a circular shape, and the yoke 1 has a plane circular shape, in which a circular space having an open upper surface is provided.
The planar circular magnet 2 and the pole piece 3 are arranged in this space, and a magnetic gap 4 is formed between the outer peripheral surface of the pole piece 3 and the inner peripheral surface of the yoke 1. Although not shown, a diaphragm is arranged on the upper surface side of the yoke 1 so as to close the space, and an air chamber behind the diaphragm is formed on the back surface side of the diaphragm. Further, a through hole 9 communicating the air chamber behind the diaphragm with the outside is provided over the pole piece 3, the magnet 2, and the yoke 1. That is, the compliance C1 is reduced by allowing the air in the air chamber behind the diaphragm to easily flow in and out through the through holes 9.

On the other hand, as the inner magnet type electroacoustic transducer, there is also an elongated one represented by an elliptical shape as shown in FIG. 8 in addition to the above-mentioned circular shape. In FIG. 8, the yoke 11 has an elongated shape in one direction, and a space having an open upper surface is provided in the longitudinal direction. That is, the space is made up of a pair of longitudinal side surfaces 11a, 11a, a pair of lateral arcuate side surfaces 11b, 11b, and a bottom surface 1
1c. In the center of this space, a magnet 12 and a pole piece 13 which are elongated in one direction are arranged. A magnetic circuit as the magnetic gap 14 is configured. The internal space of the magnetic circuit is configured as an air chamber 15 in the magnetic circuit surrounded by the magnet 12 and the yoke 11. On the upper surface side of the yoke 11, an elongated diaphragm 16 is provided in one direction so as to close the opening of the space.
6a and the flat portion 1 connected to the periphery of the dome portion 16a
6b. Dome 16 of diaphragm 16
The rear surface side of “a” is configured as a diaphragm rear air chamber 17. The air chamber 17 behind the diaphragm is provided in the air chamber 15 in the magnetic circuit.
Through a magnetic gap 14. A drive coil 18 is fixed to the lower surface of the diaphragm 16, and the drive coil 18 is disposed in the magnetic gap 14.

In the above configuration, when a predetermined drive current is applied to the drive coil 18, an electromagnetic force corresponding to the applied current is generated in the drive coil 18, and the vibration plate 16 is vibrated by the electromagnetic force.

[0010]

However, recent AV
(Audio / Visual) With the downsizing of the equipment, the downsizing of the inner magnet type electroacoustic transducer to be equipped is also required. When the elongated electroacoustic transducer as shown in FIG. 8 is miniaturized, the width of the components such as the magnet 12 is correspondingly reduced, so that the means for reducing the compliance C1 as shown in FIG. Cannot be applied to converters. That is, it is extremely difficult to provide an opening in the magnet 12 or the like for securing a sufficient air flow.

The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide an elongated device.
It is an object of the present invention to provide an electroacoustic transducer capable of preventing characteristic deterioration due to a compliance load of an air chamber behind a diaphragm.

[0012]

According to the first aspect of the present invention, a space having an open surface on one side is provided inside an elongated yoke,
An elongated magnet and a pole piece are arranged in this space, a magnetic circuit is formed by using the magnet, the pole piece, and the yoke as a magnetic path, and an opening of the space is used as a magnetic gap of the magnetic path, The internal space of the magnetic circuit is configured as an air chamber in the magnetic circuit surrounded by the magnet and the yoke, and a diaphragm is provided so as to close an opening of the space of the yoke, and the magnetic circuit is provided on the back side of the diaphragm. An electroacoustic system in which a diaphragm-back air chamber communicating with the inner air chamber via the magnetic gap is formed, and the diaphragm is vibrated by an electromagnetic force generated in response to a current supplied to a drive coil disposed in the magnetic gap. In the converter, an air communication passage is provided at both ends in the longitudinal direction of the diaphragm to communicate the air chamber behind the diaphragm with the outside.

According to a second aspect of the present invention, in the electroacoustic transducer according to the first aspect, the air communication passage is formed by connecting both ends of the dome portion of the diaphragm in the longitudinal direction to both ends of the pole piece in the longitudinal direction. The yoke is configured so as to protrude outward from the portion, and the side surfaces in the short direction located at both ends in the longitudinal direction of the yoke are formed as openings.

According to a third aspect of the present invention, there is provided an elongated yoke having a space open on one side, an elongated magnet and a pole piece provided in this space, and the magnet, the pole piece and the yoke are used as magnetic paths. ,and,
A magnetic circuit having an opening of the space as a magnetic gap of the magnetic path constitutes a magnetic circuit, and an internal space of the magnetic circuit constitutes an air chamber in a magnetic circuit surrounded by the magnet and the yoke. A diaphragm is provided so as to close the opening, and a diaphragm back air chamber is formed on the back side of the diaphragm to communicate with the air chamber in the magnetic circuit via the magnetic gap, and a drive coil disposed in the magnetic gap An electro-acoustic transducer that vibrates the diaphragm with an electromagnetic force generated in accordance with energization of the diaphragm, wherein the pole piece and the magnet communicate with the air chamber behind the diaphragm and the air chamber in the magnetic circuit. An internal air communication passage is provided, and the yoke is provided with an external air communication passage for communicating the air chamber in the magnetic circuit with the outside.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

1 (A) to 1 (D) show a first embodiment of the present invention. FIG. 1 (A) is a plan view of an elongated electro-acoustic transducer of an inner magnet type, and FIG. Side view, Fig. 1 (C)
1A is a sectional view taken along line ee in FIG. 1A, and FIG. 1D is a sectional view taken along line ff in FIG. FIG. 1 (A) ~
In (D), in the first embodiment, the same components as those in the conventional example of FIG. 8 are denoted by the same reference numerals in the drawings, and the description thereof will be omitted, and only different components will be described.

That is, at both ends in the longitudinal direction of the diaphragm 16, there are provided air communication passages 20 for communicating the air chamber 17 behind the diaphragm with the outside of the apparatus. The air communication passage 20 is set to be long so that the longitudinal direction of the dome portion 16a in the longitudinal direction of the diaphragm 16 protrudes outward beyond both end portions in the longitudinal direction of the yoke 11 as well as the pole piece 13. The bottom surface of both ends of the portion 16a is open to the outside, and the lateral side portions (11b in FIG. 8) located at both ends in the longitudinal direction of the yoke 11 are removed to form the opening 2
It is formed by being set to 1.

According to the above configuration, when a predetermined drive current is applied to the drive coil 18, an electromagnetic force corresponding to the applied current is generated in the drive coil 18, and the diaphragm 16 is vibrated by the electromagnetic force. Although the volume of the diaphragm back air chamber 17 fluctuates according to the vibration of the diaphragm 16, air flows into and out of the diaphragm back air chamber 17 through the air communication passage 20.
6 is reduced. That is, the air chamber 1 behind the diaphragm
Since the air communication passage 20 secures a sufficient flow of air between the device 7 and the outside, it is possible to prevent characteristic deterioration due to the compliance load of the diaphragm back air chamber 17 in an elongated device.

In the first embodiment, the length of the drive coil 18 in the longitudinal direction together with the dome portion 16a of the diaphragm 16 is similarly set to be longer than the both ends of the yoke 11 in the longitudinal direction. Therefore, it is possible to prevent the driving force due to the electromagnetic force from being reduced.

Further, in the first embodiment, since the air in the air chamber 15 in the magnetic circuit can also freely flow with the outside air through the opening 21 of the air communication passage 20, the air in the air chamber 15 in the magnetic circuit It is also possible to prevent characteristic deterioration due to compliance.

2 (A) to 2 (D) show a second embodiment of the present invention. FIG. 2 (A) is a plan view of an elongated electroacoustic transducer of an inner magnet type, and FIG. Side view, FIG. 2 (C)
2A is a cross-sectional view along the line gg in FIG. 2A, and FIG. 2D is a cross-sectional view along the line hh in FIG. 2A. FIG.
In (D), in the second embodiment, the same components as those in the conventional example of FIG. 8 are denoted by the same reference numerals in the drawings, and the description thereof will be omitted. Only different components will be described.

That is, the magnet 12 and the pole piece 13
Is provided with an internal air communication passage 22 for communicating the air chamber 17 behind the diaphragm with the air chamber 15 in the magnetic circuit. The internal air communication passage 22 is configured as divided members 12a and 13a in which the magnet 12 and the pole piece 13 are divided at a center position and arranged at intervals.
The space is formed by a space formed between the pair of divided members 12a and 13a. Further, the yoke 11 is provided with an external air communication passage 23 which communicates the air chamber 15 in the magnetic circuit with the outside of the apparatus. The external air communication passage 23 is provided at a position of the side surface 11 a corresponding to the position of the internal air communication passage 22.

According to the above configuration, when a predetermined drive current is applied to the drive coil 18, an electromagnetic force corresponding to the applied current is generated in the drive coil 18, and the diaphragm 16 is vibrated by the electromagnetic force. The volume of the diaphragm rear air chamber 17 fluctuates in accordance with the vibration of the diaphragm 16, and external air is supplied to the diaphragm rear air chamber 17 via the internal air communication passage 22 and the external air communication passage 23. Because of the inflow and outflow, the vibration load on the diaphragm 16 is reduced. In other words, a sufficient air flow between the diaphragm rear air chamber 17 and the outside is ensured by the internal air communication passage 22 and the external air communication passage 23. 17 can prevent characteristic deterioration due to the compliance load.

In the second embodiment, since the air in the air chamber 15 in the magnetic circuit can freely flow with the external air through the external air communication passage 23, the compliance of the air chamber 15 in the magnetic circuit can be improved. The characteristic deterioration caused by the load can be prevented.

In the second embodiment, since the external air flow passage 23 is provided at a position corresponding to the internal air flow passage 22, the air flow between the diaphragm back air chamber 17 and the outside is smooth. There is an advantage that is done.

3 (A) to 3 (D) show a third embodiment of the present invention. FIG. 3 (A) is a plan view of an elongated electroacoustic transducer of an inner magnet type, and FIG. Side view, FIG. 3 (C)
3A is a sectional view taken along line ii of FIG. 3A, and FIG. 3D is a sectional view taken along line JJ of FIG. FIG.
In (D), in the third embodiment, the second
The same components as those of the embodiment are denoted by the same reference numerals in the drawings, and the description thereof will be omitted. Only different components will be described.

That is, the external air flow passage 23 is connected to the yoke 11
Are formed by a plurality of through holes provided in the bottom surface portion 11c. According to the third embodiment, similarly to the second embodiment, sufficient air circulation between the diaphragm rear air chamber 17 and the outside can be ensured, and the characteristic deterioration due to the compliance load of the diaphragm rear air chamber 17 is prevented. Can be prevented. In addition, the air in the air chamber 15 in the magnetic circuit is also a through-hole.
Since it is free to flow with the outside air through 3, it is possible to prevent the characteristic deterioration due to the compliance load of the air chamber 15 in the magnetic circuit.

In the first embodiment, the air communication passage 2
0 is set so that the longitudinal direction of the dome portion 16a of the diaphragm 16 protrudes outward beyond both ends in the longitudinal direction of the yoke 11 as well as the pole piece 13, and the dome portion 16a
The bottom surfaces of both ends of the yoke 11 are opened to the outside and the yoke 11
Is formed by making the side portions in the lateral direction located at both ends in the longitudinal direction of the diaphragm 16 into the openings 21.
The dome portion 16a may be configured such that the longitudinal direction of the dome portion 16a is set to be longer than both ends in the longitudinal direction of the yoke 11 so as to protrude outward, and only the bottom surfaces of both ends of the dome portion 16a are opened to the outside. good. That is, the side portions in the short direction located at both ends in the longitudinal direction of the yoke 11 are not the openings 21. In addition, the longitudinal direction of the dome portion 16a of the diaphragm 16 is set to be longer than both longitudinal ends of the pole piece 13, and the bottom surface of the both ends of the dome portion 16a is
The yoke 11 may be configured by forming the opening 21 on the side surface in the short direction located at both ends in the longitudinal direction of the yoke 11. However, the configuration as in the first embodiment can configure the large air communication passage 20, and thus is excellent in air circulation.

The apparatus of the first embodiment is provided with the second
The internal air flow passage 22 of the embodiment may be added.
Further, the internal air flow passage 22 and the external air flow passage 23 of the second embodiment may be added. Further, an internal air flow passage 22 and an external air flow passage 23 which is an opening may be added in the third embodiment. With this configuration, the air flow between the diaphragm back air chamber 17 and the outside is further improved, so that the characteristic deterioration due to the compliance load of the diaphragm back air chamber 17 can be more effectively prevented.

In the second and third embodiments, the internal air flow passage 22 is formed by the magnet 12 and the pole piece 1.
3 is divided into two parts, but it may be composed of three or more divided members, or a notch may be provided in a part of the magnet 12 and the pole piece 13. The piece 13 may be used as a dividing member, but the magnet 12 may not be used as a dividing member and a concave portion may be provided on the pole piece side of the magnet 12.

[0031]

As described above, according to the first aspect of the present invention, the magnet is arranged inside the yoke, and the internal space of the magnet and the magnetic circuit such as the yoke is constituted as an air chamber in the magnetic circuit. In the electroacoustic transducer that forms the air chamber in the magnetic circuit on the back side of the diaphragm, air communication passages that communicate the air chamber behind the diaphragm and the outside are provided at both ends in the longitudinal direction of the diaphragm. In addition, since sufficient air circulation between the air chamber behind the diaphragm and the outside is ensured, it is possible to prevent characteristic deterioration due to the compliance load of the air chamber behind the diaphragm in an elongated device.

According to a second aspect of the present invention, in the electroacoustic transducer according to the first aspect, the air communication passage is formed by connecting both ends of the dome portion of the diaphragm in the longitudinal direction with respect to the longitudinal direction of the pole piece. The present invention is characterized in that the length of the yoke is set to protrude outward from both ends, and the lateral side portions located at both ends in the longitudinal direction of the yoke are formed as openings. In addition to the effect, a sufficiently wide air communication path can be configured without reducing the electromagnetic force for vibrating the diaphragm. Also, since the air in the air chamber in the magnetic circuit can freely flow with the outside air through the opening of the yoke,
It is also possible to prevent the characteristic deterioration due to the compliance load of the air chamber in the magnetic circuit.

According to the third aspect of the present invention, the magnet and the pole piece are arranged inside the yoke, and the internal space of the magnetic circuit such as the magnet, the pole piece and the yoke is configured as an air chamber in the magnetic circuit. In the electroacoustic transducer that forms an air chamber in the magnetic circuit on the side, the pole piece and the magnet are provided with an internal air communication passage that communicates the air chamber behind the diaphragm and the air chamber in the magnetic circuit. Since the yoke is provided with an external air communication passage communicating the air chamber in the magnetic circuit with the outside, sufficient air communication between the diaphragm back air chamber and the outside can be achieved via the internal air communication passage and the external air communication passage. As a result, it is possible to prevent the deterioration of characteristics due to the compliance load of the air chamber behind the diaphragm in an elongated device. In addition, since the air in the air chamber in the magnetic circuit can freely flow with the outside air through the external air communication passage, it is possible to prevent the characteristic deterioration due to the compliance load of the air chamber in the magnetic circuit.

[Brief description of the drawings]

1A and 1B show a first embodiment of the present invention, wherein FIG. 1A is a plan view of an inner-magnet-type elongated electroacoustic transducer, FIG. 1B is a side view thereof, and FIG. Sectional view along the ee line of FIG.
FIG. 1D is a cross-sectional view along the line ff in FIG.

FIGS. 2A and 2B show a second embodiment of the present invention, wherein FIG. 2A is a plan view of an elongated electroacoustic transducer of an inner magnet type, FIG. 2B is a side view thereof, and FIG. Sectional view along the line gg
FIG. 2D is a cross-sectional view taken along the line hh in FIG.

3A and 3B show a third embodiment of the present invention, wherein FIG. 3A is a plan view of an elongated electroacoustic transducer of an inner magnet type, FIG. 3B is a side view thereof, and FIG. Sectional view along line ii of
FIG. 3D is a sectional view taken along the line JJ in FIG.

FIG. 4 is a configuration diagram of a general inner magnet type electroacoustic transducer.

FIG. 5 is an equivalent circuit of an inner magnet type electroacoustic transducer.

FIG. 6 is a mechanical-acoustic conversion model of an inner magnet type electro-acoustic converter.

7A is a plan view of an inner magnet type circular electroacoustic transducer, and FIG. 7B is a cross-sectional view thereof.

FIG. 8 shows a conventional inner magnet type elongated shape, and FIG.
Is a plan view of the electroacoustic transducer, (B) is a side view thereof, (C) is a cross-sectional view taken along the line kk of FIG.
FIG. 9D is a sectional view taken along the line II of FIG.

[Explanation of symbols]

 Reference Signs List 11 yoke 12 magnet 13 pole piece 14 magnetic gap 15 air chamber in magnetic circuit 16 diaphragm 16a dome portion 17 diaphragm rear air chamber 18 drive coil 20 air communication path 21 opening 22 internal air communication path 23 external air communication path

Claims (3)

[Claims] An elongated yoke is provided with a space having an open surface on one side, an elongated magnet and a pole piece are disposed in the space, and the magnet, the pole piece, and the yoke are used as a magnetic path. A magnetic circuit having an opening portion of the space as a magnetic gap of the magnetic path, and an internal space of the magnetic circuit configured as an air chamber in the magnetic circuit surrounded by the magnet and the yoke; A diaphragm is provided so as to close the diaphragm, and a diaphragm back air chamber communicating with the air chamber in the magnetic circuit through the magnetic gap is formed on the back side of the diaphragm, and a drive coil arranged in the magnetic gap is formed. An electro-acoustic transducer that vibrates the diaphragm with an electromagnetic force generated in response to the energization of the diaphragm, wherein the opposite sides of the diaphragm are provided at both ends in the longitudinal direction of the diaphragm. Electroacoustic transducer, characterized in that a air communicating passage communicating the air chamber and the outside. 2. The electro-acoustic transducer according to claim 1, wherein the air communication path is such that both ends of the dome portion of the diaphragm in the longitudinal direction are more outward than both ends of the pole piece in the longitudinal direction. The electro-acoustic transducer is characterized in that it is configured to be long so as to protrude from the yoke, and to have openings in the short side surfaces located at both ends in the longitudinal direction of the yoke. 3. An elongate yoke is provided with a space having an open surface on one side, an elongate magnet and a pole piece are provided in the space, and the magnet, the pole piece and the yoke are used as a magnetic path. An opening portion constitutes a magnetic circuit having a magnetic gap of the magnetic path, and an internal space of the magnetic circuit forms an air chamber in a magnetic circuit surrounded by the magnet and the yoke, and closes an opening of the space of the yoke. A diaphragm air chamber is provided on the back side of the diaphragm so as to communicate with the air chamber in the magnetic circuit through the magnetic gap on the back side of the diaphragm, and power is supplied to a drive coil disposed in the magnetic gap. An electro-acoustic transducer that vibrates the diaphragm with an electromagnetic force generated according to the above, wherein the pole piece and the magnet are provided in the air chamber behind the diaphragm. An electroacoustic transducer, wherein an internal air communication passage communicating with the air chamber in the magnetic circuit is provided, and an external air communication passage communicating the air chamber in the magnetic circuit with the outside is provided in the yoke. .