JPH07322391A - Magnetic circuit for speaker - Google Patents

Abstract

PURPOSE:To provide a magnetic circuit for speaker realizing a speaker with high sound quality and high reliability. CONSTITUTION:This circuit is provided with a yoke 1 provided with a pole 1p provided projectingly in a cylindrical shape at the center part of a disk shaped based end part 1b and a non-magnetic member 3 having elasticity on its inner peripheral surface. The circuit is provided with a ring-shaped ferritic magnet 2 to be arranged on the base end part 1b of the yoke 1 so that this inner peripheral surface may be opposed to the outer peripheral surface of the pole 1p of the yoke 1 and a ring-shaped top plate 4 to be arranged on the ferritic magnet 2 so that the inner peripheral surface may be opposed to the outer peripheral surface of the pole 1p.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic circuit for a speaker suitable for use in a dynamic type speaker, and more particularly to a magnetic circuit for a speaker that outputs audio efficiently from the speaker.

[0002]

2. Description of the Related Art Today, various audio equipments such as a disc reproducing apparatus, a video tape reproducing apparatus, an audio tape reproducing apparatus, a radio receiving apparatus and the like for outputting sound have been widely used.

In this audio equipment, the speaker for outputting the sound is based on the current supplied to the voice coil.
The most commonly used is a dynamic speaker that produces an electromagnetic force in the voice coil and outputs a voice by the electromagnetic force.

This dynamic type speaker includes a magnetic circuit in which a magnetic flux is formed in a magnetic air gap, a voice coil wound in the magnetic air gap, and a diaphragm which is integrally combined with the voice coil in an interlockable manner. Have

The magnetic circuit 18 is, as shown in FIG.
A yoke 21 provided with a cylindrical pole 21p protruding from the central portion of a disk-shaped base end portion 21b, and the yoke 21.
Has a ring-shaped ferrite magnet 22 provided at the base end portion 21b thereof and a ring-shaped top plate 24 provided on the ferrite magnet 22.
A magnetic gap G is formed between the outer peripheral surface of the pole 21p of the yoke 21 and the inner peripheral surface of the top plate 24 facing the outer peripheral surface.
Is formed.

The polarity of the ferrite magnet 22 arranged so as to be sandwiched between the yoke 21 and the top plate 24 is such that the base end 21b side of the yoke 21 is the N pole and the top plate 24 side is the S pole. Indicates.

The magnetic circuit 18 is connected from the N pole of the ferrite magnet 22 to the base end 21b of the yoke 21,
The base end portion 21b of the yoke 21 is connected to the tip side of the pole 21p, the tip side of the pole 21p of the yoke 21 is connected to the magnetic gap G, and the magnetic gap G is connected to the top plate 24. 24 forms a closed loop magnetic path which is connected to the S pole of the ferrite magnet 22 and is connected from the S pole of the ferrite magnet 22 to the N pole, and a magnetic flux Φ ₃ is generated in the magnetic gap G.

In the speaker using the magnetic circuit 18, a voice coil is wound movably along the outer peripheral surface of the pole 21p facing the inner peripheral surface of the top plate 24, and is integrated integrally with the voice coil. A diaphragm is provided in combination.

In the speaker having the above structure, the wound voice coil is supplied with an audio signal in the frequency band of the audio, and based on the current generated by the audio signal,
Electromagnetic force is generated according to Fleming's left-hand rule.

In this speaker, the electromagnetic force causes the voice coil to vibrate along the longitudinal direction of the pole 21p, and the diaphragm vibrates in conjunction with the voice coil. To output a voice.

The speaker magnetic circuit 18 of this speaker
Is to vibrate the voice coil faithfully to the supplied voice signal and output the voice faithfully based on the voice signal so that the magnetic gap does not cause a magnetic flux loss such as a leakage magnetic flux in the magnetic path. It is required to efficiently generate a magnetic flux in G.

[0012]

In the conventional speaker magnetic circuit 18, the inner diameter E of the ferrite magnet 22 is considerably larger than the inner diameter F of the top plate 24 as shown in FIG. A non-polymerized portion J that does not overlap with the ferrite magnet 22 is formed on the bottom surface of the.

Therefore, in the magnetic circuit 18, a leakage magnetic flux Φ _L3 is formed at the base end portion 21b side of the yoke 21 and the non-overlapping portion J of the top plate 24, and the magnetic flux Φ ₃ of the magnetic gap G is disturbed. Since the loss occurs, there is a problem that the sound quality is deteriorated.

The leakage flux Φ _L3 of the non-overlapping portion J is shown in FIG.
As shown in, by forming the speaker magnetic circuit 19 by setting the inner diameter H of the ferrite magnet 25 and the inner diameter I of the top plate 24 to be the same or substantially the same, it is possible to cause almost no occurrence.

In this magnetic circuit 19, since the inner diameter H of the ferrite magnet 25 is the same as or substantially the same as the inner diameter I of the top plate 24, from the outer peripheral surface of the yoke 21 on the base end 21b side to the inner peripheral surface of the ferrite magnet 25. without causing almost no leakage flux [Phi _L4 like on the side or the like, a magnetic flux [Phi ₄ in the magnetic gap G between the inner circumferential surface of the top plate 24 facing the outer peripheral surface and the outer peripheral surface of the pole 21p of the yoke 21
To form.

However, since the inner peripheral surface of the ferrite magnet 25 of the magnetic circuit 19 is extremely fragile, it is easily cracked by a small impact or the like and is likely to be chipped. Fragments due to this chipping adhere to the inner peripheral surface of the top plate 24 and the tip end side of the pole 21p of the yoke 21 facing the inner peripheral surface, and thus disturb the magnetic field of the magnetic flux Φ ₄ in the magnetic gap G, The voice coil is prevented from moving smoothly along the longitudinal direction of the pole 21p.

For this reason, the magnetic circuit 19 causes a problem that reliability is deteriorated such that abnormal sound is generated in the speaker due to unnecessary vibration to deteriorate sound quality.

In view of the above problems, it is an object of the present invention to provide a speaker magnetic circuit for realizing a speaker with high sound quality and high reliability.

[0019]

A magnetic circuit for a speaker according to the present invention has a yoke provided with a columnar projecting pole at the center of a disk-shaped base end, and an inner peripheral surface having elasticity. A non-magnetic member is provided, and a ring-shaped ferrite magnet is provided on the base end portion of the yoke so that the inner peripheral surface faces the outer peripheral surface of the yoke pole, and the inner peripheral surface has the yoke. And a ring-shaped top plate disposed on the ferrite magnet so as to face the outer peripheral surface of the pole.

Further, the inner diameter of the ferrite magnet provided with the non-magnetic member and the inner diameter of the top plate are the same or substantially the same.

Further, a yoke provided with a columnar protruding pole at the center of the disk-shaped base end portion and at least the inner peripheral surface are coated with a resin protective film. A ring-shaped ferrite magnet disposed on the base end portion of the yoke so that the peripheral surface faces the outer peripheral surface of the pole of the yoke, and the inner diameter of the ferrite magnet coated with the resin protective film, the same.
Alternatively, a ring-shaped top plate is provided on the ferrite magnet so that the substantially same inner peripheral surface faces the outer peripheral surface of the pole of the yoke.

[0022]

In the speaker magnetic circuit according to the present invention, the non-magnetic member having elasticity is provided on the inner peripheral surface of the ferrite magnet to reduce the leakage magnetic flux from the yoke.
In addition, it is possible to improve the brittleness of the inner peripheral surface.

The inner diameter of the ferrite magnet provided with the non-magnetic member is closer to the inner diameter of the top plate to reduce the leakage flux.

Further, by coating a resin protective film on at least the inner peripheral surface of the ferrite magnet so that the inner diameter of the top plate is the same or almost the same, almost no magnetic flux loss occurs between the yoke and the top plate. In addition, it is possible to improve the brittleness of the inner peripheral surface.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the speaker magnetic circuit according to the present invention will be described below with reference to FIGS.

A speaker magnetic circuit 15 according to the present invention shown in FIG. 1 has a yoke 1 provided with a cylindrical pole 1p protruding from the center of a disk-shaped base end 1b, and a yoke 1 of this yoke 1. A ring-shaped ferrite magnet 2 provided on the base end portion 1b, a ring-shaped non-magnetic member 3 provided on the inner circumference of the ferrite magnet 2, and a ferrite magnet 2 provided with the non-magnetic member 3 And a ring-shaped top plate 4.

The thickness and diameter of the base end portion 1b of the yoke 1 are set so that the magnetic flux is efficiently formed in the yoke 1 and the mechanical strength is sufficient. The diameter of the pole 1p is set so that an electromagnetic force is efficiently generated in the voice coil wound around the pole 1p and the voice coil is movable in the longitudinal direction of the pole 1p by the electromagnetic force. . The height of the pole 1p is set so that the outer peripheral surface of the tip of the pole 1p can face the inner peripheral surface of the top plate 4.

The ferrite magnet 2 has its inner peripheral surface facing the outer peripheral surface of the pole 1p of the yoke 1.
Is disposed on the base end portion 1b of the. The ferrite magnet 2 and the yoke 1 are closely fixed by an adhesive.

The ferrite magnet 2 is a permanent magnet made of a ferrite material, and shows the case where the base end portion 1b side of the yoke 1 is the N pole and the top plate 4 side is the S pole.

The non-magnetic member 3 is a butyl-based material having elasticity.
Alternatively, the ring shape is made of synthetic rubber such as nitrile-butadiene type and has a thickness of about 0.3 to 0.5 mm, and the outer peripheral surface is closely fixed to the inner peripheral surface of the ferrite magnet 2 with an adhesive.

The inner diameter A of the ferrite magnet 2 provided with the non-magnetic member 3 is the same as or substantially the same as the inner diameter B of the top plate 4.

The top plate 4 is arranged on the ferrite magnet 2 provided with the non-magnetic member 3 so that the inner peripheral surface faces the outer peripheral surface of the pole 1p of the yoke 1. The top plate 4 and the ferrite magnet 2 provided with the non-magnetic member 3 are closely fixed by an adhesive.

In the magnetic circuit 15, a magnetic gap G is formed between the inner peripheral surface of the top plate 4 and the outer peripheral surface of the pole 1p of the yoke 1 facing the inner peripheral surface. In this top plate 4, the voice coil wound around the pole 1p of the yoke 1 is located in the magnetic gap G, and the voice coil is movable in the longitudinal direction of the pole 1p.
The dimensions of the inner diameter B and the height are set.

The magnetic circuit 15 having the above construction is connected from the N pole of the ferrite magnet 2 to the base end portion 1b of the yoke 1, and is connected from the base end portion 1b of the yoke 1 to the tip side of the pole 1p. The magnetic pole G of the first pole 1p is connected to the magnetic gap G, the magnetic gap G is connected to the top plate 4, and the top plate 4 is connected to the S pole of the ferrite magnet 2.
Forms a closed loop magnetic path connecting the S pole to the N pole, and a magnetic flux Φ ₁ is generated in the magnetic gap G.

As shown in FIG. 2, the non-magnetic member 3 provided on the inner peripheral surface of the ferrite magnet 2 leaks magnetic flux Φ from the outer peripheral surface of the yoke 1 on the base end 1b side in the magnetic path.
It prevents _L1 from occurring. Therefore, the magnetic circuit 15
, The magnetic flux Φ ₁ is efficiently formed in the magnetic gap G with almost no magnetic flux loss.

The inner diameter A of the ferrite magnet 2 provided with the non-magnetic member 3 is equal to that of the top plate 4
The closer it is to the inner diameter B, the smaller the magnetic flux loss in the magnetic path.

Further, since the non-magnetic member 3 is not brittle, the ferrite magnet 2 is not chipped or broken in the magnetic circuit 15.

Therefore, the magnetic circuit 15 is formed so as to improve the sound quality and the reliability of the speaker.

Next, a second embodiment of the present invention will be described with reference to FIG. In the second embodiment, the same members as those in the first embodiment are designated by the same reference numerals, and the description of the configuration will be omitted.

In the magnetic circuit 16 of this embodiment, as shown in FIG. 3, the entire surface of the ferrite magnet 5 is coated with a non-fragile resin protective film 6 made of urethane or the like, and the coated ferrite magnet 5 is coated. The inner diameter C of the upper plate 4 is the same as or substantially the same as the inner diameter D of the top plate 4.

In this magnetic circuit 16, the inner diameter C of the ferrite magnet 5 and the inner diameter D of the top plate 4 are the same or
Since they are almost the same, the leakage flux Φ from the outer peripheral surface of the yoke 1 on the base end portion 1b side to the inner peripheral surface side of the ferrite magnet 5 or the like.
Pole 1p of yoke 1 with almost no _L2
A magnetic flux Φ ₂ is formed in the magnetic gap G between the outer peripheral surface of and the inner peripheral surface of the top plate 4 facing the outer peripheral surface.

Further, the coated resin protective film 6 protects the ferrite magnet 2 from an impact and is less likely to be chipped.

Therefore, the speaker magnetic circuit 16 for improving the sound quality and the reliability of the speaker is formed.

Next, an example of the case where the speaker 17 is configured by using the magnetic circuit 15 described with reference to FIGS. 1 and 2 will be described with reference to FIG.

The speaker 17 shown in FIG. 4 is located in the magnetic circuit 15 and a magnetic gap G between the outer peripheral surface of the pole 1p of the yoke 1 of the magnetic circuit 15 and the inner peripheral surface of the top plate 4. The voice coil 7 is wound movably along the longitudinal direction of 1p, and has a cone-shaped large-diameter open end and a small-diameter open end, and the voice coil 7 is interlocked with the small-diameter open end. Diaphragm 8 that can be combined together as possible
A frame 9 having an upper end and a lower end, the upper end and the lower end supporting the diaphragm 8 on the top plate 4, and the voice coil 7 inside the magnetic gap G. 1 for holding the small-diameter open end of the diaphragm 8 via the lower end of the frame 9 so as to be located at
0, an edge 11 supporting the large-diameter opening end of the diaphragm 8 through the upper end of the frame 9 so that the diaphragm 8 vibrates in conjunction with the voice coil 7, and a dust-proof passage. And a cap 12 that is provided with pores and closes the small-diameter open end of the diaphragm 8.

In the speaker 17, the voice coil 7 wound around the pole 1p of the yoke 1 is supplied with the voice signal in the frequency band in the voice range, and the current generated by this voice signal causes
According to Fleming's left-hand rule, the voice coil 7 vibrates along the longitudinal direction of the pole 1p, and the diaphragm 8 interlocks with the voice coil 7 to vibrate.

In the speaker having the above-described structure, a magnetic flux is formed in the magnetic gap G of the speaker magnetic circuit with almost no leakage magnetic flux, and the voice coil is vibrated faithfully based on the audio signal to obtain a high sound quality. Sound is output.

In this embodiment, as an example of the speaker, the case of the direct radiation system in which the sound is directly radiated from the diaphragm to the space is shown, but the present invention is limited to the case of the direct radiation system speaker. However, the present invention can be applied to an indirect radiation type speaker in the same manner.

As an example of the polarity of the ferrite magnet, the case where the base end side of the yoke is the N pole and the top plate side is the S pole is shown, but the present invention is limited to the polarity of the ferrite magnet. However, the present invention is also applicable to the case where the base end side of the yoke of the ferrite magnet is the S pole and the top plate side is the N pole.

Also, an example has been shown in which a resin protective film is coated on the entire surface of the ferrite magnet to make it brittle, but the present invention is not limited to the case of coating the entire surface. By coating a resin protective film on at least the inner peripheral surface of the ferrite magnet, the ferrite magnet is not chipped on the inner side of the magnetic circuit, and thus the same application is possible.

Further, as an example of the speaker, the case where the magnetic circuit in which the non-magnetic member is provided on the inner peripheral surface of the ferrite magnet is used is shown, but the resin protective film is formed on at least the inner peripheral surface of the ferrite magnet according to the present invention. The same can be applied to the case where a magnetic circuit using a ferrite magnet coated with is used.

[0052]

As described above in detail, according to the speaker magnetic circuit of the present invention, it is possible to improve the brittleness of the inner peripheral surface of the ferrite magnet with almost no leakage magnetic flux from the yoke. It is possible.

Further, it is possible to form the magnetic flux between the yoke and the top plate and to improve the brittleness of the inner peripheral surface of the ferrite magnet without causing the loss of the magnetic flux in the magnetic circuit.

Therefore, it is possible to provide a speaker magnetic circuit that realizes a speaker with high sound quality and high reliability.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a magnetic circuit for a speaker according to the present invention.

FIG. 2 is a cross-sectional view of a main part of the speaker magnetic circuit.

FIG. 3 is a schematic cross-sectional view of another speaker magnetic circuit according to the present invention.

FIG. 4 is a schematic cross-sectional view of a speaker using the speaker magnetic circuit according to the present invention.

FIG. 5 is a schematic cross-sectional view of a conventional speaker magnetic circuit.

FIG. 6 is a cross-sectional view of a main part of the speaker magnetic circuit.

FIG. 7 is a schematic cross-sectional view of another conventional speaker magnetic circuit.

[Explanation of symbols]

 1 yoke 1b yoke base end 1p yoke pole 2, 5 ferrite magnet 3 non-magnetic member 4 top plate 6 resin protective film

Claims (3)

[Claims] 1. A yoke having a columnar projecting pole provided at the center of a disk-shaped base end portion, and a non-magnetic member having elasticity on an inner peripheral surface, the inner peripheral surface being the yoke. Ring-shaped ferrite magnet disposed on the base end portion of the yoke so as to face the outer peripheral surface of the pole, and the ferrite magnet so that the inner peripheral surface faces the outer peripheral surface of the yoke pole. A magnetic circuit for a speaker, comprising a ring-shaped top plate disposed on the top. 2. The magnetic circuit for a speaker according to claim 1, wherein the inner diameter of the ferrite magnet provided with the non-magnetic member and the inner diameter of the top plate are the same or substantially the same. 3. A yoke having a columnar projecting pole provided at the center of a disk-shaped base end, and at least an inner peripheral surface of which is coated with a resin protective film, and which is coated with this resin protective film. A ring-shaped ferrite magnet disposed on the base end portion of the yoke so that its peripheral surface faces the outer peripheral surface of the pole of the yoke, and the same inner diameter as the ferrite magnet coated with the resin protective film, Alternatively, a magnetic circuit for a speaker, comprising: a ring-shaped top plate disposed on the ferrite magnet such that an inner peripheral surface that is substantially the same as the outer peripheral surface of the pole of the yoke faces.