JP2567822Y2 - Magnetic circuit for speaker - Google Patents

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 loudspeaker which can be suitably used, for example, for a small oval loudspeaker.

[0002]

2. Description of the Related Art As a magnetic circuit for a speaker of this type,
In order to reduce the diameter of the magnetic circuit, an inner magnetic circuit composed of a center pole 20, a permanent magnet piece 21 and a yoke 22 is generally used as shown in FIG. However, in such a magnetic circuit, the lateral width of the magnetic circuit is limited by the outer width of the yoke 22. In order to further reduce the width of the magnetic circuit, it is necessary to reduce the diameter of the permanent magnet piece 21, but in that case, the magnetic flux density in the magnetic gap 23 is reduced, and the magnetic driving force is reduced. Therefore, in the conventional example using a single permanent magnet piece 21, it is difficult to obtain a desired total magnetic flux density when used in a magnetic circuit such as a small elliptical speaker.

In order to solve this problem, an elliptical or rectangular magnetic circuit in which the permanent magnet pieces are separated and the permanent magnet pieces are arranged on both sides of the center pole 20 is considered. In this way, even if the diameter of the permanent magnet piece is reduced, a total magnetic flux density that is twice as large can be obtained, and the width of the magnetic circuit can be reduced by that much without lowering the magnetic driving force. .

[0004]

However, in this case, the magnetic flux density on the short axis side in the magnetic air gap is lower than that on the long axis side. Therefore, the magnetic drive force does not act uniformly in the circumferential direction of the voice coil, and the voice coil receives a mechanical load twisted to the short axis side, and is not driven smoothly, which causes a new problem that sound quality is deteriorated. Occurs. An object of the present invention is to provide a magnetic circuit for a speaker that can solve the above problem.

[0005]

In order to achieve the above object, the present invention is characterized by a back plate,
A center pole erected at the center of the back plate, a front plate forming a ring-shaped magnetic gap between the center pole and the back plate and the center pole are housed, and the upper end is in contact with the front plate. A plurality of first permanent magnet pieces, each having the same polarity, are interposed between the back plate and the front plate, and the first permanent magnet pieces include an axis of the center pole. With respect to one plane, it is arranged on both sides to form a first magnetic flux path passing through a magnetic gap in a direction perpendicular to the one plane, and a back-plate and a field cover have a polarity opposite to that of the first permanent magnet piece. This is a point that a second magnetic flux path that passes through the magnetic gap in a direction perpendicular to the first magnetic flux path is formed with the second permanent magnet piece interposed.

Further, the present invention is characterized in that a back plate, a center pole erected at the center of the back plate, and an oval or rectangular oval which forms a ring-shaped magnetic gap between the center pole and the center pole. A front plate,
A field cover that houses the back plate and the center pole and has an upper end portion abutted on the front plate, and between the back plate and the front plate, two first permanent magnets each having the same polarity; Magnet pieces are interposed, and these first permanent magnet pieces are arranged on both sides of the center pole in the major axis direction of the front plate to form a first magnetic flux path passing through the magnetic gap in the major axis direction. A second permanent magnet piece having a polarity opposite to that of the first permanent magnet piece is interposed between the back plate and the field cover;
A second magnetic flux path that passes through the magnetic gap in a direction perpendicular to the first magnetic flux path is formed. The field cover includes an oval or rectangular bottom portion, and a central portion in the major axis direction of the bottom portion and side portions extending upward from both ends in the short axis direction and contacting both ends in the short axis direction of the front plate. In some cases. Further, the front plate may have four corners cut out.

[0007]

According to the present invention, a plurality of first permanent magnet pieces, each magnetized in the same polarity, are interposed between the back plate and the front plate, and these first permanent magnet pieces are connected to the axis of the center pole. Are arranged on both sides with respect to one plane including. Therefore, the first permanent magnet piece forms a first magnetic flux path that passes through the magnetic gap in a direction perpendicular to the one plane. On the other hand, between the back plate and the field cover,
A second permanent magnet piece having a polarity opposite to that of the first permanent magnet piece is interposed. The main magnetic flux path created by the second permanent magnet piece is in the direction of low magnetic resistance (Y direction in FIG. 2). Therefore, the second permanent magnet piece forms a second magnetic flux path that passes through the magnetic gap in a direction perpendicular to the first magnetic flux path. As a result, the second magnetic flux path functions to compensate for the magnetic flux density in the direction perpendicular to the direction of passage of the first magnetic flux path with respect to the magnetic air gap. Therefore, the magnetic flux density in the magnetic gap can be made uniform in the circumferential direction by appropriately selecting a combination in consideration of the magnetic flux density for the first permanent magnet piece and the second permanent magnet piece.

[0008]

1 is a longitudinal sectional view of an embodiment of the present invention.
FIG. 2 is a plan view, and FIG. 3 is a sectional view taken along line AA of FIG. In FIGS. 2 and 3, the housing is omitted. The speaker magnetic circuit 1 includes a back plate 2, a center pole 3 erected at the center of the back plate 2, a rectangular front plate 5 forming a ring-shaped magnetic gap 4 between the center pole 3,
It has a bottomed rectangular cylindrical field cover 6 that houses the back plate 2 and the center pole 3 and has an upper end abutting on the front plate 5. The field cover 6 is housed in a housing 7, and a voice coil 8 is inserted in the magnetic gap 4. In the figure, 9 is a dust cap,
Reference numeral 10 denotes a diaphragm.

Two cylindrical first permanent magnet pieces 11A and 11B are interposed between the back plate 2 and the front plate 5. The first permanent magnet piece 11A and the first permanent magnet piece 11B are arranged symmetrically with respect to the center pole 3 in the major axis (long side) direction X (the left-right direction in FIG. 2) of the front plate 5. Each first permanent magnet piece 11A, 11B
Is magnetized in the thickness direction (vertical direction in FIG. 1), one magnetic pole surface (upper surface in FIG. 1) is magnetized to the S pole, and the other magnetic pole surface (lower surface in FIG. 1) is magnetized to the N pole. I have. Therefore, the first magnetic flux path of the main magnetic flux Φ1 with respect to the first permanent magnet pieces 11A and 11B is the N pole of the first permanent magnet pieces 11A and 11B → the back plate 2 → the center pole 3 → the magnetic gap 4 → the front plate 5 → the Follow the S pole of one permanent magnet piece 11A, 11B. That is, the first magnetic flux path of the magnetic flux Φ1 forms a magnetic field in the major axis direction X in the magnetic gap 4.

One cylindrical second permanent magnet piece 12 is interposed between the back plate 2 and the field cover 6 and below the center pole 3.
The permanent magnet pieces 12 are the first permanent magnet pieces 11A and 11B.
It is magnetized to the opposite polarity. That is, the second permanent magnet piece 12
Is magnetized in the thickness direction, and one magnetic pole surface (upper surface in FIG. 1) is magnetized to the N pole, and the other magnetic pole surface (lower surface in FIG. 1) is magnetized to the S pole. Therefore, the second magnetic flux path of the main magnetic flux Φ2 with respect to the second permanent magnet piece 12
N pole → back plate 2 → center pole 3 → magnetic gap 4 → front plate 5 → field cover 6 → second
The S pole of the permanent magnet piece 12 is traced. That is, the second magnetic flux path of the magnetic flux Φ2 forms a magnetic field in the magnetic gap 4 in the short axis (short side) direction Y of the front plate 5.

Thus, the first permanent magnet pieces 11A,
11B alone, the magnetic flux density in the short axis direction Y in the magnetic gap 4 is extremely small as compared with the magnetic flux density in the long axis direction X. However, by providing the second permanent magnet piece 12, the short axis The magnetic flux density in the direction Y can be compensated for in the direction of increasing, and the first permanent magnet pieces 11A, 11B can be compensated.
The magnetic flux density in the magnetic gap 4 can be made uniform in the circumferential direction by appropriately selecting a combination in consideration of the magnetic flux density for the second permanent magnet piece 12. Therefore, the magnetic driving force acting on the voice coil 8 can be made uniform in the circumferential direction, and the voice coil 8 can be driven smoothly.

Also, the first permanent magnet pieces 11A and 11B and the second
Since the permanent magnet piece 12 is magnetized in the opposite polarity, a magnetic dipole is formed at the bottom of the field cover 6 as shown in FIG. Therefore, external leakage magnetic flux is reduced. FIG. 4 is a perspective view of another embodiment of the field cover. This field cover 15 has a rectangular bottom 15
A and bottom portions 15A, 15B and 15C extending upward from both ends in the short axis direction at the center portion in the long axis direction and contacting both ends in the short axis direction of the front plate 5 respectively. With such a configuration, a magnetic gap is formed in a portion of the magnetic flux path formed by the second permanent magnet piece 12 excluding the path of the main magnetic flux Φ2. It is extremely large as compared with the embodiment.
Therefore, since the magnetic flux converges on the portion where the magnetic resistance is small, the magnetic flux density in the path of the magnetic flux Φ2 becomes extremely large as compared with the above-described embodiment. Therefore, the first permanent magnet piece 1
In relation to 1A and 11B, when making the magnetic flux density in the magnetic air gap 4 uniform in the circumferential direction, the second permanent magnet piece 12 having a relatively small magnetic flux density can be used. FIG. 5 is a perspective view of another embodiment of the front plate. The front plate 17 has four corners cut out. With such a configuration, the field cover 15 shown in FIG.
As in the case of (1), the magnetic flux density in the path of the magnetic flux Φ2 can be increased. In the above embodiment, the speaker magnetic circuit is rectangular, but may be oval. By applying the present invention to such an elliptical or rectangular magnetic circuit, the total magnetic flux density is large, and
An elliptical speaker with a reduced width can be realized. Further, the magnetic circuit for a speaker according to the present invention can be used not only for an elliptical or rectangular magnetic circuit but also for a circular magnetic circuit for a speaker.

[0013]

[Effect of the Invention] As described in detail above, according to the present invention,
By providing the first permanent magnet piece and the second permanent magnet piece, the magnetic flux density in the magnetic gap can be made uniform in the circumferential direction. Therefore, the magnetic driving force acting on the voice coil can be made uniform in the circumferential direction, and the voice coil can be driven smoothly. In addition, a magnetic dipole is formed at the bottom of the field cover, so that external leakage magnetic flux can be improved. According to the second aspect of the present invention, by arranging the first permanent magnet pieces on both sides of the center pole, it is possible to realize a magnetic circuit for an oval speaker having a large total magnetic flux density and a narrow width. . According to the third or fourth aspect, the magnetic flux density of the second magnetic flux path can be increased. Therefore, in making the magnetic flux density in the magnetic gap uniform in the circumferential direction in relation to the first permanent magnet piece, it is possible to use the second permanent magnet piece having a relatively small magnetic flux density.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of one embodiment of the present invention.

FIG. 2 is a plan view of one embodiment of the present invention.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a perspective view of another embodiment of the field cover.

FIG. 5 is a perspective view of another embodiment of the front plate.

FIG. 6 is a longitudinal sectional view of a conventional magnetic circuit for a speaker.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Speaker magnetic circuit, 2 ... Back plate, 3 ... Center pole, 4 ... Magnetic gap, 5, 17 ... Front plate, 6, 15 ... Field cover, 8 ... Voice coil, 11A, 11B ... 1st permanent magnet piece , 12: second permanent magnet piece, X: long axis direction, Y: short axis direction, Φ1: magnetic flux of the first permanent magnet piece, Φ2: magnetic flux of the second permanent magnet piece.

Claims (4)

(57) [Scope of request for utility model registration] A back plate, a center pole erected at the center of the back plate, and a front plate forming a ring-shaped magnetic gap between the center pole and the center pole.
A plurality of first permanent magnets, each of which is magnetized to have the same polarity, between the back plate and the front plate, the first permanent magnet having a field cover that houses the back plate and the center pole and has an upper end abutted on the front plate; Pieces are interposed, and these first permanent magnet pieces are arranged on both sides with respect to a plane including the axis of the center pole to form a first magnetic flux path passing through a magnetic gap in a direction perpendicular to the plane. A second permanent magnet piece having a polarity opposite to that of the first permanent magnet piece is interposed between the back plate and the field cover, and a second magnetic flux path passing through a magnetic gap in a direction perpendicular to the first magnetic flux path. A magnetic circuit for a speaker, comprising: 2. A back plate, a center pole erected in the center of the back plate, an oblong or rectangular front plate forming a ring-shaped magnetic gap between the center pole, a back plate and a center pole. And a field cover whose upper end is in contact with the front plate. Between the back plate and the front plate, two first permanent magnet pieces, each magnetized to the same polarity, are interposed. , These first permanent magnet pieces are arranged in the longitudinal direction of the front plate,
A first magnetic flux path is disposed on both sides of the center pole and passes through the magnetic gap in the longitudinal direction. A second magnetic flux path opposite to the first permanent magnet piece is provided between the back plate and the field cover. A magnetic circuit for a loudspeaker, wherein a permanent magnet piece is interposed to form a second magnetic flux path passing through a magnetic gap in a direction perpendicular to the first magnetic flux path. 3. The field cover has an oval or rectangular bottom portion and side portions extending upward from both ends of the bottom portion in the long axis direction and both ends in the short axis direction and contacting both ends of the front plate in the short axis direction. The speaker magnetic circuit according to claim 2, comprising: 4. The magnetic circuit for a speaker according to claim 2, wherein the four corners of the front plate are cut out.