JPH06197399A - Magnetic circuit for speaker - Google Patents

Abstract

PURPOSE:To increase the amplitude of a voice coil by lifting an inner circumferential part of a top plate upward so as to increase the distance between a bottom surface of the top plate and an upper surface of a bottom plate. CONSTITUTION:A prescribed gap 5 is formed between an inner circumferential surface of a top plate 4 and an outer circumferential surface of a center pole 2 and a voice coil 6 is mounted in the gap 5. In this case, the top plate 4 is formed to have an increased distance between the bottom surface of the top plate 4 and an upper surface of a bottom plate 1 by giving a notch to a lower surface of an inner circumferential part located toward the center pole 2 rather than the inner circumferential ridge of the magnet 3 with a shear press so as to form an air gap 4a. Thus, the amplitude of the voice coil is increased and the contact of the tip of the voice coil with the bottom plate is eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic circuit of a speaker used for various audio equipments, and more particularly to an external magnet type magnetic circuit for a speaker using a rare earth cobalt magnet as a permanent magnet.

[0002]

2. Description of the Related Art Samarium Cobalt (SmCo ₅ , S
m ₂ Co ₁₇ ) and rare earth cobalt magnets such as neodymium / iron / boron have high magnetic energy (generally expressed by the maximum energy product (B × H) _max ) and have good stability against an external magnetic field. The shape to be used can be thin and has a large cross-sectional area, and is therefore used in an external magnet type magnetic circuit that constitutes a small and thin high-performance dynamic speaker.

[0003]

The rare earth cobalt magnet having the above advantages is extremely expensive as compared with the ferrite magnet and the alnico magnet and has good stability against an external magnetic field, so that it has a large cross-sectional area. It is best to use it as a thin type in terms of cost efficiency, but especially when it is used for an external magnet type magnetic circuit, the thinner the magnet, the larger the amplitude of the voice coil,
There is a problem in that the bottom of the voice coil comes into contact with the top surface of the bottom plate, and abnormal noise is easily generated, and the voice coil itself is destroyed by repeated contact.

In view of the above situation, the present invention is to provide an outer magnet type magnetic circuit using a rare earth magnet capable of sufficiently ensuring the amplitude of the voice coil even if it is thin and has a large cross-sectional area. is there.

[0005]

In order to achieve the above object, a magnetic circuit for a speaker according to the present invention comprises a thin ring-shaped magnet having a large cross-sectional area, which is sandwiched between a top plate and a bottom plate, and a rare earth element. In an outer magnet type magnetic circuit using a cobalt magnet, at least the inner peripheral portion of the top plate located closer to the center pole than the inner peripheral edge of the magnet is lifted upward to increase the distance between the top plate bottom surface and the bottom plate upper surface. It is characterized by having done.

In the speaker magnetic circuit of the present invention, basically, the inner peripheral portion of the top plate located on the side of the center pole with respect to at least the inner peripheral edge of the magnet forming the outer magnet type magnetic circuit is lifted upward. It is configured to increase the distance between the bottom surface and the top surface of the bottom plate, and as a concrete means therefor, the lower surface of the inner peripheral portion of the top plate located closer to the center pole than the inner peripheral edge of the magnet is shear-pressed. There is a means for increasing the distance from the bottom surface of the top plate by notching and forming a void below the inner peripheral portion of the top plate.

Another means is to bend the inner peripheral portion of the top plate, which is located closer to the center pole than the inner peripheral edge of the magnet, by pressing or forging, and then extend the tip end portion in parallel with the bottom plate. In this method, a gap is formed below the inner peripheral portion of the top plate to increase the distance from the top surface of the bottom plate.

Another means is to provide a ring-shaped main plate having an inner diameter larger than the inner diameter of the magnet on the upper surface of the magnet, and integrally provide a ring-shaped auxiliary plate on the main plate. As a plate,
In this method, a space is formed below the inner peripheral portion of the top plate to increase the distance from the top surface of the bottom plate.

[0009]

The magnetic circuit for a speaker of the present invention is an outer magnetic type magnetic circuit using a rare earth cobalt magnet as a magnet, and the inner peripheral portion of the top plate located at the center pole side at least from the inner peripheral edge of the magnet forming the magnetic circuit. Since the distance between the bottom surface of the top plate and the top surface of the bottom plate is increased, the amplitude of the voice coil can be increased.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a speaker magnetic circuit of the present invention will be described below in detail with reference to the accompanying drawings. Embodiment 1 In FIG. 1, 1 is a disk-shaped bottom plate made of a magnetic material integrally provided with a center pole 2 in the center, 3 is a ring-shaped magnet made of samarium cobalt, and 4 is a ring-shaped made of a magnetic material. In the top plate, a gap 5 having a predetermined interval is formed between the inner peripheral surface of the top plate 4 and the outer peripheral surface of the center pole 2, and the voice coil 6 is mounted in the gap 5. is there. In the top plate 4, the bottom surface of the top plate 4 and the bottom surface of the top plate 4 are formed by cutting the lower surface of the inner peripheral portion of the magnet 3 located closer to the center pole 2 than the inner peripheral edge of the magnet with a shearing press to form a void 4a. It is configured such that the distance from the upper surface of the plate 1 becomes large.

Embodiment 2 The embodiment shown in FIG. 2 is similar to Embodiment 1 in that the ring-shaped top plate 4 made of a magnetic material is located closer to the center pole 2 than the inner peripheral edge of the ring-shaped magnet 3 made of samarium cobalt. The inner peripheral portion of the top plate 4 is bent upward by, for example, a pressing means, and the tip end portion thereof is extended in parallel with the bottom plate 1 to form the void portion 4a. It is configured to increase the distance. The reference numerals in the figure are the same as those in the first embodiment.

The embodiment shown in [0012] Example 3 Figure 3, like the upper surface of the ring-shaped magnet 3 made of samarium cobalt, a ring-shaped main plate 4 ₁ made of a magnetic material having a larger inner diameter than the inner diameter of the magnet 3 And a ring-shaped auxiliary plate 4 ₂ which is also made of a magnetic material is integrally provided on the main plate 4 ₁ to form the top plate 4, thereby forming a space 4 a below the top plate 4. The distance between the bottom surface of the plate 4 and the upper surface of the bottom plate 1 is increased. The reference numerals in the figure are the same as those in the first embodiment.

[0013]

The speaker magnetic circuit of the present invention is an external magnet type magnetic circuit in which a thin ring-shaped magnet having a large cross-sectional area sandwiched between a top plate and a bottom plate is used as a rare earth cobalt magnet. Since the inner periphery of the top plate located on the center pole side of at least the inner peripheral edge of the magnet is lifted upward to increase the distance between the bottom surface of the top plate and the top surface of the bottom plate, increase the amplitude of the voice coil. As a result, the contact of the tip of the voice coil with the bottom plate is eliminated, and as a result, a small and thin speaker with high efficiency and high input can be provided at low cost. Particularly, in the speaker magnetic circuit of the present invention, the bottom surface of the inner peripheral portion of the top plate and the top surface of the bottom plate are formed by an extremely simple means of raising the inner peripheral portion of the top plate forming the magnetic circuit on the side of the center pole. Since the distance can be set large and the size of the expensive rare earth cobalt magnet can be used without changing from the conventional size, it does not increase the cost of the speaker, which is a great practical advantage. I have.

[Brief description of drawings]

FIG. 1 is a half sectional view showing an example of a speaker magnetic circuit of the present invention.

FIG. 2 is a half cross-sectional view showing another example of the speaker magnetic circuit of the present invention.

FIG. 3 is a half sectional view showing still another example of the speaker magnetic circuit of the present invention.

[Explanation of symbols]

 1 Bottom plate 2 Center pole 3 Magnet 4 Top plate 6 Voice coil

Claims (4)

[Claims] 1. In an outer magnet type magnetic circuit using a rare earth cobalt magnet as a thin ring-shaped magnet having a large cross-sectional area and sandwiched between a top plate and a bottom plate, a center is provided at least from an inner peripheral edge of the magnet. A magnetic circuit for a speaker, characterized in that an inner peripheral portion of a top plate located on a pole side is lifted upward to increase a distance between a bottom surface of the top plate and an upper surface of the bottom plate. 2. The speaker magnetic circuit according to claim 1,
The lower surface of the inner peripheral part of the top plate located closer to the center pole than the inner peripheral edge of the magnet is cut out by a shear press to form a gap below the inner peripheral part of the top plate to increase the distance from the bottom surface of the top plate. A magnetic circuit for a speaker, characterized in that 3. The speaker magnetic circuit according to claim 1,
Bend the inner circumference of the top plate, which is located closer to the center pole than the inner edge of the magnet, by pressing or forging, and then extend the tip in parallel with the bottom plate to lower the inner circumference of the top plate. A magnetic circuit for a loudspeaker, characterized in that it is configured so that a distance from the top surface of the bottom plate is increased by forming a void portion in the magnetic circuit. 4. The magnetic circuit for a speaker according to claim 1,
A ring-shaped main plate having an inner diameter larger than the inner diameter of the magnet is provided on the upper surface of the magnet, and a ring-shaped auxiliary plate is integrally provided on the main plate to form a top plate, and an inner peripheral portion of the top plate is provided. A magnetic circuit for a loudspeaker, characterized in that it is configured so that a distance from the upper surface of the bottom plate is increased by forming a space below the bottom plate.