JPH06339196A - Electroacoustic transducer - Google Patents

Abstract

PURPOSE:To provide an electroacoustic transducer in which positioning of a magnet is simplified, the positioning accuracy is improved and a degree of freedom of a back surface space is enhanced. CONSTITUTION:The transducer is provided with a main body case 2A incorporating a magnetic drive section 8 transducing an electric signal into magnetic vibration and imparting vibration to a diaphragm 6 and forming a back surface space 10 for the diaphragm, a case piece 2B covering an opening part of a front surface side of the main body case to form a front surface space (resonance chamber 22) on the front surface side of the diaphragm and plural projections 30 formed on an inner wall surface of the main body case toward the height direction of the main body case and the magnet of the magnetic drive section is positioned by using the projections.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroacoustic transducer used in a buzzer or the like for converting an electric signal into sound.

[0002]

2. Description of the Related Art Conventionally, an electromagnetic electroacoustic transducer is shown in FIG.
As shown in FIG. 3, the exterior case 2 is made of synthetic resin, and the exterior case 2 is divided into two case portions, a main body case 2A and a case piece 2B. The two-part configuration is based on the requirements of the internal structure and the ease of assembly.

A vibrating plate 6 is supported on the main body case 2A by a supporting step portion 4, and a magnetic drive unit 8 for applying magnetic vibration to the vibrating plate 6 is installed on the back side of the vibrating plate 6 and vibrates. A back space 10 for the plate 6 is formed. A base 12 and a substrate 14 forming a part of the magnetic drive unit 8 are installed on the back surface of the main body case 2A, and the back space 10 is closed by the base 12 and the substrate 14 to form a closed space. Therefore, the back space 10 is an element that is closely related to the vibration of the diaphragm 6 and affects the sound pressure characteristics. That is, if the back space 10 is set large, the resonance frequency, which is a natural value, can be lowered, and the sound pressure on the low frequency side can be enhanced. The vibrating plate 6 has its own resonance frequency, but since it is formed of a thin metal plate, the magnetic piece 7 is provided at the center thereof as a means for increasing the mass.
Is attached.

The magnetic drive unit 8 is provided with a columnar iron core 16 projecting from the base 12, and a coil 18 is wound around the iron core 16. The coil 18 is excited by an AC input applied from the outside through an input terminal. A ring-shaped magnet 20 is installed around the coil 18 in order to form a bias magnetic field acting on the diaphragm 6.

A case piece 2B is attached to the front side of the body case 2A to cover its opening. That is, the case 2 </ b> B forms the resonance chamber 22 as a front space for the diaphragm 6. In order to open the resonance chamber 22 to the outside air, the sound emitting tube 2 is provided on the ceiling of the case piece 2B.
4 are formed. The resonance vibration of the resonance chamber 22 is emitted to the outside through the sound output hole 26.

[0006]

By the way, in this electroacoustic transducer, the outer case 2 is flattened and the rear space 10 on the main body case 2A side is enlarged. When the back space 10 is enlarged, the inner diameter of the main body case 2A becomes large, and thus the positioning of the magnet 20 installed therein becomes a problem. Therefore, as a means for positioning the magnet 20 on the inner wall portion of the main body case 2A, an annular protrusion 28 that forms a horizontal plane in the circumferential direction is formed. Such a ridge 28 projects toward the center of the main body case 2A and forms a plane parallel to the diaphragm 6. In other words, the ridge 28 narrows the diameter of the back space 10. Such protrusions 28 act as a resistance component to acoustic vibration, reduce the function of the back space 10, and cause the sound pressure characteristics in the low sound range to deteriorate.

In the assembly of such an electroacoustic transducer, for example, the base 12 having the iron core 16 protruding and the coil 18 attached is attached to the main body case 2A, and then the magnet 20 is attached to the main body case 2A. Then, a stepwise assembling method of subsequently installing the diaphragm 6 is adopted. The magnet 20 needs to be installed in a horizontal state so that its center is aligned with the center of the diaphragm 6 and is parallel to the diaphragm 6.

However, if the ridge 28 is used as the positioning means, as shown in FIG. 4, a part of the magnet 20 rides on the ridge 28 and is in a biased state. That is, the balance with the diaphragm 6 is impaired.
Such a bias of the magnet 20 impairs the sound pressure characteristic of the product, resulting in a defective product. Therefore, the operator needs to pay attention to the mounting of the magnet 20 and individually inspect the installation state. That is, the ridge 2 as the positioning means
The presence of 8 causes defective products, and the improvement thereof has been demanded.

Therefore, an object of the present invention is to provide an electroacoustic transducer which simplifies the positioning of the magnet, improves the positioning accuracy, and enhances the degree of freedom of the back space.

[0010]

The electro-acoustic transducer of the present invention, as illustrated in FIG. 1, is a magnetic drive section (8) for converting an electric signal into magnetic vibration and vibrating the diaphragm (6). And a back space (10) for the diaphragm.
A main body case (2A) that forms a front space (resonance chamber 22) on the front side of the diaphragm that covers the front opening of the main body case; A plurality of protrusions (30) formed in the height direction of the main body case are provided on an inner wall surface, and the magnets (20) of the magnetic drive unit are positioned by the protrusions. And

The electroacoustic transducer of the present invention is characterized in that the projecting piece has a guide surface (32) for guiding the insertion of the magnet installed in the main body case.

[0012]

In the electroacoustic transducer of the present invention, a plurality of protrusions are formed as the magnet positioning means. The protruding piece is formed in the height direction of the main body case, has no mounting surface unlike the conventional protruding strip, and the magnet is installed on the tip end side of the protruding piece. As a result, the bias of the magnet is surely prevented.

Further, since the projecting piece which constitutes such positioning means can be formed thin and can be aligned with the axial direction of the back space, the volume of the back space can be expanded and the space efficiency is not deteriorated. There are advantages.

If the guide surface is formed on the projecting piece, the insertion of the magnet becomes easier, and the guide surface reduces the projecting piece, which contributes to the expansion of the volume of the rear space.

[0015]

The present invention will be described in detail below with reference to the embodiments shown in the drawings.

FIG. 1 shows one embodiment of the electroacoustic transducer of the present invention. The outer case 2 is formed by being divided into a main body case 2A and a case piece 2B, and is molded using a synthetic resin as a molding material like the conventional electroacoustic transducer.

A support step portion 4 is formed on an inner wall portion of the main body case 2A, and a diaphragm 6 is installed on the support step portion 4. A magnetic piece 7 is attached to the center of the vibration plate 6 as a means for increasing the mass. On the back side of the diaphragm 6, a magnetic drive unit 8 is installed as a means for applying magnetic vibration to the diaphragm 6, and a back space 10 for housing the magnetic drive unit 8 is formed. That is, the main body case 2A is a means for supporting the diaphragm 6 and a means for forming the back space 10. A base 12 forming a part of the magnetic drive unit 8 is installed on the back surface of the main body case 2A. A substrate 14 is laminated on the base 12. That is, the back surface of the body case 2A is closed by the base 12 and the substrate 14, and as a result, the back space 10 forms a closed space.

The base 12 is made of a magnetic material that can be magnetized, and constitutes a part of a magnetic circuit that forms a closed magnetic circuit together with the diaphragm 6, the magnetic piece 7, and the magnetic drive unit 8. Also, the substrate 1
Reference numeral 4 is an electrode terminal or means for making an electrical connection, which is made of an insulating material such as synthetic resin for electrical insulation. External input is applied to the magnetic drive unit 8 through terminals provided on the substrate 14. This external input is an AC input for generating an alternating magnetic field in the magnetic drive unit 8.

The magnetic drive unit 8 is provided with a columnar iron core 16 protruding from the base 12, and a coil 18 is wound around the iron core 16. This coil 18 is excited by an external input. A magnet 20 is installed around the coil 18, and the magnetic field generated by the magnet 20 acts on the diaphragm 6 as a bias magnetic field. As the magnet 20, an annular magnet is used in order to apply a uniform cylindrical magnetic field to the diaphragm 6.

The back space 10 formed by the main body case 2A is also the installation space for the magnet 20. Due to the function of the magnet 20, the central axis of the diaphragm 6 and the central axis of the magnet 20 need to be aligned. As the positioning means, a plurality of projecting pieces 30 are formed on the inner wall portion of the main body case 2A. This protrusion 30 is
It can be formed integrally with the body case 2A or as a separate member. When the main body case 2A is molded with synthetic resin, the respective projecting pieces 30 can be easily integrally molded. When the projecting piece 30 is formed by a member different from the body case 2A, the projecting piece 30 is fixed to the body case 2A with an adhesive or the like in a post-treatment, so that the body case 2A and the projecting piece 30 are integrated. be able to.

Each protrusion 30 is formed in the height direction of the main body case 2A. The ridge in the conventional electroacoustic transducer is formed in the circumferential direction, but is formed in parallel with the central axis of the magnet 20. That is, FIG.
As shown in, a plurality of protrusions 30 forming a surface parallel to the outer wall surface of the magnet 20 are formed at intervals of 60 degrees.

A guide surface 32 for guiding the insertion of the magnet 20 is formed on each protrusion 30. As shown in FIG. 3, the guide surface 32 of this embodiment has an inclined surface of about 45 to 60 degrees in the middle of the protrusion 30. Further, in order to facilitate insertion of the magnet 20, the spacing between the diametrical protrusions 30 of the main body case 2A is set to
It is set to be slightly larger than the outer diameter of the above so as to form the gap 34.

A case piece 2B is attached to the front surface side of the main body case 2A so as to cover the opening thereof, and a resonance chamber 22 which is a resonance portion as a front space of the diaphragm 6 is formed. A sound emitting cylinder 24 is formed in the case piece 2B, the resonance chamber 22 communicates with the outside through the sound emitting hole 26, and acoustic vibrations are emitted to the outside from the sound emitting hole 26.

The case piece 2B is formed with a plurality of columnar protrusions 36 protruding toward the main body case 2A. Each columnar protrusion 36 is inserted into the main body case 2A, and its end face faces the upper surface of the diaphragm 6. That is, each columnar projection 36 serves as a positioning means for positioning the case piece 2B with respect to the main body case 2A, and also as a movement restricting means for preventing the diaphragm 6 from moving more than necessary toward the resonance chamber 22 side.

In the electroacoustic transducer thus configured, after the base 12 is attached to the main body case 2A,
When the magnet 20 is installed, the magnet 20 is positioned at a predetermined position with the protrusion 30. In addition, since the protruding piece 30 is formed with the guide surface 32 that is an inclined surface, the magnet 20 slides on the guide surface 32, moves to a predetermined position, and is automatically positioned.

Further, since such a protruding piece 30 does not have a mounting surface unlike a conventional protruding strip, the magnet 20 does not ride on it and the magnet 20 does not deviate.

Since the protrusion 30 can be formed thin and small only for the purpose of positioning the magnet 20,
The proportion of the protruding piece 30 in the back space 10 is small, and the volume of the back space 10 is not reduced. In other words, the degree of freedom in setting the volume of the back space 10 can be increased.
Further, in the formation of the guide surface 32, the volume of the projecting piece 30 is reduced accordingly, and the volume ratio of the projecting piece 30 in the back space 10 is reduced, so that the volume efficiency of the back space 10 is increased. Therefore, it is possible to increase the volume of the back space 10, and as a result, it is possible to enhance the sound pressure in the low frequency range and obtain a mellow sound output. Also, the same body case 2
Since the back space 10 can be increased by A, the main body case 2A can be flattened or downsized, and the electroacoustic transducer can be downsized.

Each protrusion 3 facing the peripheral surface of the magnet 20.
If the side surface of 0 is a curvature surface that matches the curvature of the peripheral surface of the magnet 20, the stability of the magnet 20 can be further enhanced.

Next, FIG. 4 shows sound pressure frequency characteristics showing the influence of the back space in this electroacoustic transducer.
Characteristic a is a large back space, and characteristic b is a small back space. As is clear from the comparison between the characteristics a and b, when the back space is large, the sound pressure in the bass range is enhanced. As a result, it is possible to obtain a mellow sound output.

Next, modifications of the electroacoustic transducer of the present invention will be listed below. a. The protrusion 30 may be formed in a spiral shape. b. The number of the protruding pieces 30 to be installed may be two or more, and when the width thereof is increased, positioning can be performed by forming the surface in contact with the magnet 20 with a curved surface. c. The shape of the guide surface 32 of the protruding piece 30 may be a curved surface as well as a tapered surface, and may be selectively formed for a plurality of protruding pieces 30.

[0031]

As described above, according to the present invention,
The following effects can be obtained. a. Since the positioning of the magnet with respect to the main body case can be facilitated and the work can be simplified, the deviation of the magnet can be prevented and the yield can be improved. b. The degree of freedom in setting the volume of the back space is expanded, and the sound pressure characteristic can be improved. c. The guide surface can guide the magnet to a predetermined position of the main body case, and can be automatically positioned at the predetermined position of the main body case.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of the electroacoustic transducer of the present invention.

FIG. 2 is a plan view showing the electroacoustic transducer before attaching the case piece and the diaphragm.

FIG. 3 is an enlarged cross-sectional view showing a protruding piece portion of the electroacoustic transducer.

FIG. 4 is a sound pressure frequency characteristic showing the influence of the back space.

FIG. 5 is a vertical sectional view showing a conventional electroacoustic transducer.

[Explanation of symbols]

 2A Main body case 2B Case piece 6 Vibration plate 8 Magnetic drive unit 10 Back space 20 Magnet 22 Resonance chamber (front space) 30 Projection piece 32 Guide surface

Claims (2)

[Claims] 1. A main body case that incorporates a magnetic drive unit that converts an electric signal into a magnetic vibration to vibrate the vibration plate, forms a rear space with respect to the vibration plate, and an opening of the main body case. The protrusion includes: a case piece that is closed to form a front space on the front side of the diaphragm; and a plurality of protrusions formed on the inner wall surface of the body case in the height direction of the body case. An electroacoustic transducer characterized in that the magnet of the magnetic drive unit is positioned by one piece. 2. The electroacoustic transducer according to claim 1, wherein the protrusion has a guide surface that guides insertion of the magnet installed in the main body case.