JP2778095B2 - Low leakage magnetic flux type speaker - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-leakage magnetic flux type speaker used for various audio equipment and video equipment.

2. Description of the Related Art Among such conventional low-leakage magnetic flux type speakers, first, a speaker using a metal frame has a configuration as shown in FIG. That is, the main magnet 1 is connected to the upper plate 2
A frame 5 made of a magnetic metal body is connected to a magnetic circuit 4 sandwiched between the magnetic plate 4 and the lower plate 3, a diaphragm 6 is adhered to an outer peripheral portion of the frame 5, and a voice for driving the diaphragm 6 is provided. The coil 7 is held in the center by a damper 8 at the center thereof, and is joined so as to fit into the magnetic gap 9, and the joint between the diaphragm 6 and the voice coil 7 is adhered to the surface with a dust cap 10 to form a speaker. It had been. Further, a cancel magnet magnetized in a direction opposite to that of the main magnet 1 on the back surface of the lower plate 3.
11 and a shield cover covering the whole of the magnetic circuit 4
It consisted of twelve.

Next, as an example of a conventional speaker using a resin frame, there is one having a configuration as shown in FIG.

That is, the diaphragm 6 is adhered to the outer periphery of a frame 5 formed by molding a magnetic circuit 4 in which the main magnet 1 is sandwiched between the upper plate 2 and the lower plate 3 by resin, and the diaphragm 6 is driven. The voice coil 7 is held at its center by a damper 8 so as to fit in the magnetic gap 9, and a dust cap 10 is attached to the surface of the diaphragm 6 at the joint with the voice col 7.
To form a speaker. Further, a cancel magnet 11 magnetized in a direction opposite to that of the main magnet 1 on the back surface of the lower plate 3 and a shield cover 12 covering these magnetic circuits as a whole were constituted.

Problems to be Solved by the Invention However, in this kind of conventional low-leakage-flux speaker, the leakage magnetic flux from the magnetic circuit 4 is reduced by the effects of the casing magnet 11 and the shield cover 12. However, there is a problem in that video equipment which has a very strict requirement level cannot be used even if leakage measures are taken as described above.

In particular, for speakers using metal frames,
Compared with the case of the resin frame, since the frame itself is a magnetic metal body, the magnetic flux from the main magnet 1 is transmitted to the frame 5 through the upper plate 2,
, The magnetic flux leaks from the end face of the peripheral portion, which has an adverse effect on video equipment and the like.

SUMMARY OF THE INVENTION The present invention solves such a conventional problem, and provides a low-leakage-flux-type speaker having extremely excellent performance with respect to a leakage magnetic flux.

Means for Solving the Problems In order to solve the above problems, the present invention is to mix a powder made of a magnetic material such as iron powder into a resin, concentrate on a peripheral portion, integrally mold a frame with a magnetic circuit, and mold the frame. It is configured to absorb magnetic leakage from the lower plate center pole, which usually has much leakage magnetic flux, and to reduce magnetic leakage to the outside. That is, a resin frame containing a magnetic material powder is provided with a magnetic shielding effect.

Function With the above configuration, the magnetic shield effect of the conventional cancel magnet and shield cover is added, and even in the case of magnetic leakage from the center pole of the lower plate toward the front of the speaker, it is mixed into the resin frame and becomes The magnetic powder is concentrated by the concentrated magnetic material powder, and the leakage magnetic flux to the outside is greatly reduced.

Embodiment First, before describing the embodiment, an improvement example leading to the embodiment will be described with reference to FIG. Note that the same parts as those in the prior art of FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted.

According to this figure, in this improved example, the iron plate or steel 26 is simultaneously insert-molded at the time when the frame 5 made of resin is integrated with the magnetic circuit 4 and molded. A vibration system is assembled to the frame 5 in the same manner as in the related art, and a cancel magnet 11 and a shield cover 12 are further assembled.

By doing so, the magnetic leakage in the front direction of the speaker, which is generated from the center pole of the lower plate 3 which usually has a large magnetic leakage, is reduced.

Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1, which suppresses an increase in cost due to the complexity of a mold structure due to insert molding of an iron plate and steel in a resin frame according to an improved example. According to the figure, a magnetic circuit 16 composed of a main magnet 13 sandwiched between an upper plate 14 and a lower plate 15 is
A diaphragm 18 is adhered to an outer peripheral portion of a frame 17 formed by molding with a resin mixed with resin, and a voice coil 19 for driving the diaphragm 18 is damped at an intermediate portion thereof.
Mainly held at 20 and connected so as to fit into the magnetic gap 21, a dust cap 22 is adhered to the surface of the connection part of the diaphragm 18 with the voice coil 19 to form a speaker, and the back of the lower plate 15 A cancel magnet 23 magnetized in a direction opposite to that of the main magnet 13 and a shield cover 24 covering the whole of the magnetic circuit 16 are provided.

In this embodiment, in order to maximize the efficiency of the magnetic gap 21, that is, the magnetic flux density, and to minimize the generation of the leakage magnetic flux from the frame 17, the magnetic material powder 25 in the frame 17 is transferred to the magnetic circuit 16. Frame 17 at a distance from
Is formed by concentrating on the periphery.

As described above, magnetic leakage in the front direction of the loudspeaker, which is usually generated from the center pole of the lower plate 15 having a large amount of magnetic leakage, is also magnetically shielded by the magnetic material powder mixed into the periphery of the resin frame 17, The leakage magnetic flux to the outside is greatly reduced.

Effect of the Invention As described above, in addition to the magnetic shielding effect of the conventional cancel magnet and shield cover, the present invention is magnetically shielded not only by the resin frame but also by the magnetic material powder mixed therein. An extremely low magnetic leakage speaker can be provided, and its industrial value is very large.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing the structure of a low-leakage magnetic flux type speaker according to one embodiment of the present invention, FIG. 2 is a cross-sectional view of a low-leakage magnetic flux type speaker of an improved example leading to the present invention, and FIG. FIG. 4 is a sectional view of a frame type low leakage magnetic flux type speaker, and FIG. 4 is a sectional view of a conventional resin frame type low leakage magnetic flux type speaker. 13: Main magnet, 14: Upper plate, 15: Lower plate, 16: Magnetic circuit, 17: Frame, 18: Diaphragm, 19: Voice coil, 20: Damper, 21: Magnetic Gap, 22: dust cap, 23: cancel magnet, 24: shield cover, 25: powder of magnetic material, 26: iron plate or mesh.

Claims (1)

(57) [Claims] 1. A frame made of a resin in which an outer magnet type magnetic circuit constituted by sandwiching a main magnet between an upper plate and a lower plate is made of a resin in which magnetic powder such as iron powder is mixed and concentrated on the periphery. A voice coil that fits into the magnetic gap of the magnetic circuit on the diaphragm adhered to the outer periphery of the diaphragm, a cancel magnet adhered to the back surface of the lower plate, and a shield cover arranged to cover the magnetic circuit. Low leakage magnetic flux type speaker.