JPH0383496A - Low leaked magnetic flux type loudspeaker - Google Patents

Abstract

PURPOSE:To widely reduce a leaked magnetic flux to an external part by adhering a laminated structure body composed of a cancel magnet and magnetic metal, to the upper plate front surface part of a magnetic circuit and the center pole front surface part of a lower plate. CONSTITUTION:On the front surface of an upper plate 22 in a frame 25 formed integrally with a mold forming part, the laminated structure body composed of a cancel magnet a33, which is magnetized reversely to a main magnet 21, and a magnetic metal body a34 such as a steel plate, etc., is adhered with the cancel magnet a33 as an adhering surface to the upper plate 22. Samely, on the front surface of a center pole 23a in a lower plate 23, the laminated structure body composed of a cancel magnet b35, which is magnetized in a direction against the leaked magnetic flux to be generated from the center pole 23a, and a magnetic metal body b36 such as the steel plate, etc., is adhered with the cancel magnet b35 side as an adhering face to the center pole 23a. Thus, the leaked magnetic flux to the front surface direction of a loudspeaker is widely reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a low leakage flux type speaker used in various audio equipment and video equipment.

2. Description of the Related Art A conventional low leakage magnetic flux type speaker of this type has a configuration as shown in FIG. That is, a magnetic circuit 4, which is composed of a main magnet 1 sandwiched between an upper plate 2 and a lower plate 3, is molded with resin, and a diaphragm 6 is bonded to the periphery of a frame 5 that is integrally formed. A voice coil 7 for driving the plate 6 is centrally held at its middle part by a damper 8, and a magnetic gap 9 is formed.
A dust cap 10 was bonded to the surface of the connecting portion of the diaphragm 6 and the voice coil 7 to form a speaker body. Furthermore, the lower plate 3 was composed of a Kinsel magnet 11 magnetized in the opposite direction to the main magnet 1 on the back side thereof, and a shield cover 12 that covered the side and back sides of these magnetic circuits 4.

Problems to be Solved by the Invention However, in the conventional low leakage magnetic flux type speaker of this type, the leakage magnetic flux from the magnetic circuit 4 is reduced by the effects of the canceling magnet 11 and the shield cover 12, but in this case, the shield Depending on the shape of the cover 12,
This is effective for the side and rear parts of the magnetic circuit of the speaker, but some leakage magnetic flux occurs in the front part of the speaker because there are no parts to shield leakage magnetic flux, and the required level for this leakage magnetic flux is extremely strict. This has the problem that it cannot be used for video equipment.

SUMMARY OF THE INVENTION An object of the present invention is to solve these conventional problems and provide a low-leakage flux speaker that has excellent performance against leakage flux.

Means for Solving the Problems In order to solve the above problems, the present invention provides a magnetic circuit that is attached to the front surface of the upper plate and the center pole of the lower plate in a direction opposite to that of the main magnet, which is integrally molded with the frame. A laminated structure consisting of a magnetized canceling magnet and magnetic metal is bonded with the canceling magnet side serving as the adhesive surface, and this canceling magnet prevents leakage magnetic flux toward the speaker, where a large amount of leakage magnetic flux normally occurs, and repulses the canceling magnet. Reduced by magnetic force,
Furthermore, the structure is such that magnetic flux is shielded by a magnetic metal body to reduce leakage of magnetic flux to the outside.

Effect With the above configuration, in addition to the magnetic shielding effect on the side and rear parts of the speaker magnetic circuit by the conventional canceling magnet and shield cover glued to the back part of the lower plate, leakage magnetic flux to the front part is reduced. However, magnetic shielding is provided by a laminated structure consisting of a canceling magnet and a magnetic metal body arranged in front of the upper plate and the center pole of the lower plate, and leakage of magnetic flux to the outside is significantly reduced.

EXAMPLE Hereinafter, a low leakage flux type speaker according to an example of the present invention will be described with reference to the drawings. As shown in FIG. 1, a magnetic circuit 24 consisting of a main magnet 21 sandwiched between an upper plate 22 and a lower plate 23 is molded with resin so as to be integrated, and is formed integrally with this molded part. A laminated structure consisting of a canceling magnet a33 magnetized in the opposite direction to the main magnet 21 and a magnetic metal body a34 such as an iron plate is attached to the front surface of the upper plate 22 of the frame 25. The canceling magnet a33 side is attached to the upper plate 22. Also, on the front surface of the center pole 23a of the lower plate 23, there is a laminated layer consisting of a cancellation magnet b35 magnetized in a direction to repel the leakage magnetic flux generated from the center pole 23a and a magnetic metal body b36 such as an iron plate. The canceling magnet b35 side of the structure is bonded to the center pole 23a as an adhesive surface to obtain a structure that takes measures against leakage magnetic flux. Then, a diaphragm 26 is bonded to the peripheral edge of the frame 25, a voice coil 27 for driving the diaphragm 26 is held at its center by a damper 28, and is coupled so as to fit into a magnetic gap 29. A dust cap 30 is adhered to the surface of the connecting portion of the diaphragm 26 and the voice coil 27 to form the main body of the Subino 1. Further, the lower plate 23 includes a canceling magnet 31 magnetized in the opposite direction to the main magnet 21 on the back side thereof, and a shield cover 32 covering the side and back sides of these magnetic circuits. By doing this, since there are no shielding parts, even in the front direction of the speaker, where a lot of leakage magnetic flux occurs, the cancellers bonded to the front surface of the upper plate 22 and the front surface of the center pole 23a of the lower plate 23, respectively. A repulsive magnetic force is generated by a single layer structure consisting of magnets a33 and b35 and magnetic metal bodies a36 and b36, and furthermore, since it is magnetically shielded, leakage magnetic flux toward the front of the speaker is significantly reduced.

Effects of the Invention υAs described above, the present invention has the advantage of providing magnetic shielding effects in the side and rear directions of the speaker magnetic circuit using the conventional canceling magnet and shield cover, as well as in the front direction of the upper plate and the front face of the center pole of the lower plate. Magnetic shielding in the front direction of the speaker magnetic circuit can also be performed using a canceling magnet that applies a repulsive magnetic force to the leakage magnetic flux generated in each direction, and a magnetic metal body that shields the leakage magnetic flux generated in the front of the magnetic circuit, which is unprecedented. An ultra-low leakage flux type speaker can be realized.

In addition, as a secondary effect, the laminated structure consisting of the canceling magnet and magnetic metal body bonded to the center poles of the upper and lower plates increases the volume of the entire magnetic circuit, increasing heat capacity, especially as a source of heat. Since the structure is such that a metal body is added very close to the voice coil, the heat dissipation of the voice coil is very good and high input resistance can be achieved.

As described above, the present invention can provide an ultra-low leakage magnetic flux type speaker with high input resistance, and its industrial value is extremely large.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a low leakage magnetic flux type speaker according to an embodiment of the present invention, and FIG. 2 is a sectional view of a conventional low leakage magnetic flux type speaker.

Claims (1)

[Claims] An external magnetic type magnetic circuit consisting of a main magnet sandwiched between an upper plate and a lower plate is integrally molded with the frame using resin, and a canceling magnet magnetized in the opposite direction to the main magnet is attached to the front of the upper plate. and a magnetic metal body, and the front part of the center pole of the lower plate has a cancel magnet magnetized in a direction that repels the magnetic flux generated from the center pole, and a laminated structure of a magnetic metal body. A voice coil that fits into the magnetic gap of the magnetic circuit is bonded to the diaphragm bonded to the peripheral edge of the frame, and a cancellation magnet bonded to the back surface of the lower plate and the A low leakage magnetic flux speaker having a shield cover arranged to cover a magnetic circuit.