JPH024097A - Magnetic circuit for double-sided speaker - Google Patents

Abstract

PURPOSE:To make a circuit light and thin by using a rare earth magnet which is manufactured by melting and casting alloy whose basic components are a rare earth element, transition metal and boron, and next, covering a cast ingot with soft magnetic material, and subjecting to hot working at over 500 deg.C, and heat-treating it at over 250 deg.C as a permanent magnet. CONSTITUTION:The rare earth magnet is used as the permanent magnet. The manufacture of said rare earth magnet is as follows. The alloy whose basic components are the rare earth element (provided it contains yttrium), the transition metal and the boron is melted and is cast into a cylindrical mold. Next, the soft magnetic material is arranged so as to cover the inner diameter side and the outer diameter side of the cylindrical cast ingot, and hot extruding work to give pressure from an outer periphery toward a center is performed at over 500 deg.C, and afterward, it is heat-treated at over 250 deg.C. This radially anisotropic rare earth permanent magnet 101 is worked so as to be cut into a round slice together with the soft magnetic material covering it, and the soft magnetic material is used as an outer side magnetic member 102 and an inner side magnetic member 103 by magnetizing it as being joined to the permanent magnet 101.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a double-sided speaker, which is used in audio equipment, etc., in which a diaphragm is placed on both sides of a permanent magnet in a speaker magnetic circuit made of a permanent magnet and a soft magnetic material. related to magnetic circuits for use.

[Prior Art] A conventional magnetic circuit for a speaker uses a ferrite magnet or an alnico magnet as a permanent magnet, and a soft magnetic material with a high saturation magnetic flux density such as pure iron as a magnetic circuit material. The magnetic circuit had a structure as shown in the cross-sectional view, and these magnetic circuits were arranged back to back to form a magnetic circuit for double-sided speakers.

First, in the method using a permanent magnet having the shape shown in FIG.
A ferrite magnet 201 was installed so as to be sandwiched between the gap 2 and the yoke 203 to form a magnetic circuit using magnetic flux generated in the gap 204.

In addition, in FIG. 3, a magnetic member 30 made of a soft magnetic material is attached to a cylindrical alnico magnet 301 that has magnetic anisotropy in the axial direction.
2 is fixed, and a cup-shaped yoke 3 made of soft magnetic material is fixed.
03, a voice coil was inserted between the inner edge of the yoke 303 and the magnetic member 302, and the magnetic flux generated in the gap 304 was used as a speaker.

[Problem to be solved by the invention] However, ferrite magnets have poor magnetic properties and the only way to extract the required amount of magnetic flux is to increase the volume of the permanent magnet. The problem was that it was very heavy and thick.

Furthermore, alnico magnets have magnetic properties such that when the operating point of the permanent magnet is high, a very large amount of magnetic flux can be extracted, but when the operating point is even slightly lower, the amount of magnetic flux that can be extracted becomes extremely low.

Therefore, the operating point had to be set high before use, and a permanent magnet that was thick in the axial direction had to be used, resulting in a thick magnetic circuit.

The magnetic circuit for the double-sided speaker, in which the six individual magnetic circuits are arranged back to back, has the problem of being extremely thick.

The present invention solves the problems of the prior art as described above, and its purpose is to provide a light and thin magnetic circuit for a double-sided speaker.

[Means for Solving the Problems] The magnetic circuit for a double-sided speaker made of a permanent magnet and a soft magnetic material of the present invention uses an alloy whose basic components are a rare earth element (including yttrium), a transition metal, and boron as a permanent magnet. melting and casting, and then covering the cast ingot with a soft magnetic material, or melting and casting an alloy consisting of at least the above basic components into a mold made of a soft magnetic material, and then covering the cast ingot with a soft magnetic material; 500°C for each mold
The present invention is characterized in that a rare earth magnet produced by hot working as described above and then heat treatment at a temperature of 250° C. or higher is used.

[Example] Embodiments of the present invention will be described below based on the drawings.

[Example 1] In the cross-sectional view of FIG. 1, the magnetic circuit for a double-sided speaker is as follows:
Rare earth elements (including yttrium) as permanent magnets
and transition metals, and alloys whose basic components are boron,
It was cast into a cylindrical mold, and then a soft magnetic material was placed so as to cover the inner diameter side and the outer diameter side of the cylindrical cast ingot.
A rare earth magnet was used that was manufactured by performing hot extrusion processing such that pressure is applied from the outer periphery toward the center at a temperature of 250° C. or higher, and then heat-treated at a temperature of 250° C. or higher.

In this way, during hot extrusion, the cast ingot is pressurized from the outer periphery toward the center, and the gap with the soft magnetic material that covers it is also filled and the cast ingot sticks closely to each other. It becomes a radially anisotropic rare earth permanent magnet with a radial axis of easy magnetization.

The radial anisotropic rare earth permanent magnet 101 is sliced together with the soft magnetic material covering it, and each outer magnetic member 10 is
2 and the inner magnetic member 103, it is used by being magnetized so that it has magnetic poles inside and outside while being bonded to a permanent magnet.

Above and below the outer magnetic member 102 and the inner magnetic member 103,
A ring-shaped outer yoke 104 having a convex portion on the inside and an inner yoke 105 having a convex portion on the outside were joined while controlling the gap 106 to be uniform over the entire circumference.

Note that if the bonding surfaces are not in close contact, a loss will occur in the flow of magnetic flux.6 The mutual contact surfaces were finished flat before bonding.

In the double-sided speaker magnetic circuit assembled in this way, the magnetic flux generated in each gap 106 is used for the speaker.

The double-sided speaker magnetic circuit of the present invention manufactured as described above has a total thickness of 32 mm, and when compared assuming that the magnetic flux generated in each gap is at the same level, it is different from that using conventional ferrite magnets. The thickness of the magnetic circuits back to back is 52mm, and the total thickness of the Alnico magnet is 64mm.
Because of this, it is thin and has a small volume including the magnetic circuit, making it light in weight.

[Example 2] In the cross-sectional view of FIG. 1, the magnetic outlet path for double-sided speakers is
Rare earth elements (including yttrium) as permanent magnets
An alloy containing boron, transition metal, and boron as basic components is melted and cast into a cylindrical mold made of soft magnetic material, and the cast ingot is heated at 500°C or higher with the entire mold under pressure from the outer periphery toward the center. A radial anisotropic rare earth permanent magnet having a radial axis of easy magnetization was obtained by hot extrusion processing such that the magnetization was applied, and then heat treatment at a temperature of 250°C or higher.

The radial anisotropic rare earth permanent magnet 101 is cut into rings with a flat cut surface using a mold made of soft magnetic material.
The outer magnetic member 102 and the inner magnetic member 103 are used by being magnetized to have internal and external magnetic poles while being joined to a permanent magnet.

Above and below the outer magnetic member 102 and the inner magnetic member 103,
A ring-shaped outer yoke 104 having a convex portion on the inside and an inner yoke 105 having a convex portion on the outside were joined while controlling the gap 106 to be uniform over the entire circumference.

The double-sided speaker magnetic circuit of the present invention manufactured as described above has the same total thickness as Example 1, and is thinner and magnetically thinner than conventional back-to-back magnetic circuits using ferrite magnets or alnico magnets. The volume including the circuit is small,
The weight is also lighter.

[Effects of the Invention] As described above, the magnetic circuit for a double-sided speaker made of a permanent magnet and a soft magnetic material of the present invention has rare earth elements (including yttrium), transition metals, and boron as basic components as a permanent magnet. Melting and casting an alloy and then covering the cast ingot with a soft magnetic material, or melting and casting an alloy consisting of at least the above basic components into a mold made of a soft magnetic material, and then covering the cast ingot with a soft magnetic material; Or is the whole mold subjected to hot working at 500°C or higher? &25
By using a rare earth magnet manufactured through heat treatment at a temperature of 0° C. or higher, the magnetic circuit for a double-sided speaker is thinner and lighter.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention. FIGS. 2 and 3 are cross-sectional views showing conventional examples. 101... Rare earth permanent magnet 102... Magnetic member 103
... Inner magnetic member 104 ... Outer yoke 105 ... Inner yoke 201 ... Ferrite magnet 203 ... Yoke 301 ... Alnico magnet 303 ... Yoke 106 ... Gap 202 ... Magnetic member 204 ... Gap 302 ... Magnetism Member 304... Gap 1 or more - Applicant Seiko Epson Corporation Representative Patent Attorney Kizobe Suzuki and 1 other person/ρ! Inner yaw 7 / Figure 204, af. / / Figure 2

Claims (2)

[Claims] (1) In a magnetic circuit for a speaker consisting of a permanent magnet and a soft magnetic material, an alloy whose basic components are rare earth elements (including yttrium), transition metals, and boron is melted and cast as the permanent magnet, and then a cast ingot is formed. A magnetic circuit for a double-sided speaker, characterized in that it uses a rare earth magnet manufactured by covering the magnet with a soft magnetic material, hot-processing the magnet at a temperature of 500°C or higher, and then heat-treating the magnet at a temperature of 250°C or higher. (2) In a magnetic circuit for a speaker consisting of a permanent magnet and a soft magnetic material, the permanent magnet consists of at least the basic components of a rare earth element (including yttrium), a transition metal, and a permanent magnet whose basic components are boron. The alloy is melted and cast into a mold made of soft magnetic material, and the cast ingot is then hot-worked at over 500°C along with the mold.
A magnetic circuit for a double-sided speaker, characterized in that it uses a rare earth magnet manufactured by subjecting it to heat treatment at a temperature of 250° C. or higher.