JPH0585194U - Magnetic circuit for speaker - Google Patents

Abstract

(57) [Summary] [Structure] The magnetic circuit 1 has a back plate 2, a center pole 3, a front plate 5 that forms a ring-shaped magnetic gap 4 between the center pole 3, and a field cover 6. . Between the back plate 2 and the front plate 5, the first permanent magnet pieces 1 each having the same polarity are magnetized.
1A and 11B are interposed, and they are arranged on both sides of the center pole 3 in the major axis direction X. Therefore, a first magnetic flux path that passes through the magnetic gap 4 in the major axis direction X is formed. on the other hand,
Between the back plate 2 and the field cover 6, a second permanent magnet piece 12 having a polarity opposite to that of the first permanent magnet pieces 11A and 11B.
Is intervened. Therefore, a second magnetic flux path that passes through the magnetic gap 4 in the short axis direction Y is formed. The second magnetic flux path serves to compensate the magnetic flux density in the direction perpendicular to the passing direction of the first magnetic flux path with respect to the magnetic gap 4. [Effect] The magnetic flux density in the magnetic gap 4 can be made uniform in the circumferential direction.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a magnetic circuit for a loudspeaker which can be suitably used for a small oval speaker or the like.

[0002]

[Prior Art]

 In order to reduce the diameter of the magnetic circuit of this type of speaker magnetic circuit, generally, as shown in FIG. 6, an inner magnet type magnetic circuit including a center pole 20, a permanent magnet piece 21, and a yoke 22 is used. Is used. 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 if this is done, the magnetic flux density in the magnetic air gap 23 will decrease and the magnetic driving force will decrease. Therefore, in the conventional example using a single piece of permanent magnet 21, it is difficult to obtain a desired total magnetic flux density when used in a magnetic circuit such as a small oval speaker.

Therefore, in order to solve such a problem, an elliptic 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 conceivable. In this way, even if the diameter of the permanent magnet piece is reduced, the total magnetic flux density can be doubled, and the width of the magnetic circuit can be narrowed by that amount without reducing the magnetic driving force. it can.

[0004]

[Problems to be solved by the device]

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

[0005]

[Means for Solving the Problems]

 In order to achieve the above object, a feature of the present invention is that a back plate, a center pole erected in a central portion of the back plate, and a front plate that forms a ring-shaped magnetic gap between the center pole and the back plate. And a field cover that accommodates the back plate and the center pole and has an upper end abutting against the front plate, and between the back plate and the front plate, a plurality of magnets each magnetized with the same polarity are provided. First permanent magnet pieces are interposed, and the first permanent magnet pieces are arranged on both sides with respect to a plane including the axis of the center pole, and pass through the magnetic gap in a direction perpendicular to the first plane. A magnetic flux path is formed, and 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 magnetic gap is formed in the first magnetic flux. In that the formation of the second magnetic flux path through in a direction perpendicular to the road.

A feature of the present invention is that a back plate, a center pole erected in the central portion of the back plate, and an elliptical or rectangular shape forming a ring-shaped magnetic gap between the center pole and the back plate. It has a front plate and a field cover that houses the back plate and the center pole and has its upper end abutted against the front plate. Two pieces are magnetized to the same polarity between the back plate and the front plate. The first permanent magnet pieces are interposed, and the first permanent magnet pieces are arranged on both sides of the front plate in the long axis direction with the center pole interposed therebetween, and the first magnetic flux passes through the magnetic gap in the long axis direction. A path is formed and 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 to form a magnetic gap. This is a point where a second magnetic flux path that passes in a direction perpendicular to the first magnetic flux path is formed. In addition, the field cover has an oval or rectangular bottom and side portions at the center in the long axis direction of the bottom and extending upward from both ends in the short axis direction and contacting both ends in the short axis direction of the front plate, respectively. It may consist of and. In addition, the front plate may be cut out at its four corners.

[0007]

[Action]

 According to the present invention, a plurality of first permanent magnet pieces, each of which is magnetized to have the same polarity, are interposed between the back plate and the front plate, and the first permanent magnet pieces include the axis line of the center pole. Located on both sides with respect to the plane. Therefore, the first permanent magnet piece forms a first magnetic flux path that passes through the magnetic gap in the direction perpendicular to the one plane. On the other hand, 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. The main magnetic flux path created by the second permanent magnet piece is in the direction of the small 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 serves as a compensation for the magnetic flux density in the direction perpendicular to the passing direction 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 which the magnetic flux density is taken into consideration for the first permanent magnet piece and the second permanent magnet piece.

[0008]

【Example】

 1 is a vertical sectional view of an embodiment of the present invention, FIG. 2 is a plan view thereof, and FIG. 3 is a sectional view taken along the line AA of FIG. The housing is omitted in FIGS. 2 and 3. The speaker magnetic circuit 1 includes a back plate 2, a center pole 3 standing upright in the center of the back plate 2, and a rectangular front plate 5 forming a ring-shaped magnetic gap 4 between the center pole 3. And a bottomed rectangular tubular field cover 6 that accommodates the back plate 2 and the center pole 3 and has an upper end abutted on the front plate 5. The field cover 6 is housed in the housing 7, and the voice coil 8 is inserted in the magnetic gap 4. In the figure, 9 is a dust cap and 10 is a diaphragm.

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

Between the back plate 2 and the field cover 6 and below the center pole 3, one columnar second permanent magnet piece 12 is interposed, and the second permanent magnet piece 12 is The first permanent magnet pieces 11A and 11B are magnetized in 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 as an N pole and the other magnetic pole surface (lower surface in FIG. 1) is magnetized as an S pole. ing. Therefore, the second magnetic flux path of the main magnetic flux Φ2 related to the second permanent magnet piece 12 is as follows: N pole of the second permanent magnet piece 12 → back plate 2 → center pole 3 → magnetic gap 4 → front plate 5 → field cover 6 → Follow the south pole of the second permanent magnet piece 12. 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, with only the first permanent magnet pieces 11A and 11B, the magnetic flux density in the minor axis direction Y in the magnetic gap 4 is extremely smaller than the magnetic flux density in the major axis direction X. By providing the second permanent magnet pieces 12, the magnetic flux density in the short axis direction Y in the magnetic gap 4 can be compensated in the direction of increasing, and the first permanent magnet pieces 11A and 11B and the second permanent magnet pieces 12 can be compensated. Therefore, the magnetic flux density in the magnetic gap 4 can be made uniform in the circumferential direction by appropriately selecting a combination in which the magnetic flux density is taken into consideration. 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 smoothly driven.

Further, since the first permanent magnet pieces 11A and 11B and the second permanent magnet piece 12 are magnetized to have opposite polarities, the bottom of the field cover 6, as shown in FIG. A pole is formed. Therefore, the external leakage magnetic flux is reduced. FIG. 4 is a perspective view of another embodiment of the field cover. The field cover 15 includes a rectangular bottom portion 15A, and side portions 15B and 15C that extend upward from both ends in the major axis direction of the bottom portion 15A and extend in both directions in the minor axis direction and contact both ends of the front plate 5 in the minor axis direction. Consists of. With such a configuration, a magnetic gap is formed in a portion of the magnetic flux path of the second permanent magnet piece 12 excluding the main magnetic flux Φ2 path, and the magnetic resistance of the portion excluding the main magnetic flux Φ2 path is as described above. It is extremely large as compared with the case of the above embodiment. Therefore, since the magnetic flux converges on a portion having a small magnetic resistance, the magnetic flux density in the path of the magnetic flux Φ2 becomes extremely large as compared with the case of the above-mentioned embodiment. Therefore, in connection with the first permanent magnet pieces 11A and 11B, when the magnetic flux density in the magnetic gap 4 is made 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. Also with such a configuration, the magnetic flux density in the path of the magnetic flux Φ2 can be increased similarly to the case of the field cover 15 in FIG. Although the speaker magnetic circuit is rectangular in the above-described embodiments, it may be oval. By applying the present invention to such an elliptical or rectangular magnetic circuit, it is possible to realize an oblong speaker having a large total magnetic flux density and a narrow width. Further, the speaker magnetic circuit according to the present invention is not limited to the oblong or rectangular magnetic circuit, and can be used for a circular speaker magnetic circuit.

[0013]

[Effect of the device]

 As described above in detail, according to the present invention, the magnetic flux density in the magnetic gap can be made uniform in the circumferential direction by providing the first permanent magnet piece and the second permanent magnet piece. Therefore, the magnetic driving force acting on the voice coil can be made uniform in the circumferential direction, and the voice coil can be smoothly driven. Further, a magnetic dipole is formed at the bottom of the field cover, so that the external leakage magnetic flux can be improved. Further, according to claim 2, 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 with a large total magnetic flux density and a narrow width. it can. According to claim 3 or 4, the magnetic flux density of the second magnetic flux path can be increased. Therefore, in the context of the first permanent magnet piece, when the magnetic flux density in the magnetic gap is made uniform in the circumferential direction, it is possible to use the second permanent magnet piece having a relatively small magnetic flux density.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an embodiment of the present invention.

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

3 is a cross-sectional view taken along the line AA of FIG.

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 vertical cross-sectional view of a conventional magnetic circuit for a speaker.

[Explanation 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 first permanent magnet piece, Φ2 ... Magnetic flux of second permanent magnet piece.

Claims (4)

[Scope of utility model registration request] 1. A back plate, a center pole erected in 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 housing a back plate and a center pole, an upper end portion of which is in contact with a front plate, and a field cover, and each of which is magnetized to have the same polarity between the back plate and the front plate. The 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 that passes through the magnetic gap in a direction perpendicular to the plane. A second magnetic flux path, which is interposed between the back plate and the field cover, has a second permanent magnet piece having a polarity opposite to that of the first permanent magnet piece and passes through a magnetic gap in a direction perpendicular to the first magnetic flux path. A magnetic circuit for a speaker, characterized in that 2. A back plate, a center pole erected in the central portion of the back plate, an oval or rectangular front plate forming a ring-shaped magnetic gap between the center pole and the back plate, the back plate and the center pole. And a field cover whose upper end is in contact with the front plate, and two first permanent magnet pieces, which are magnetized with the same polarity, are interposed between the back plate and the front plate. , These first permanent magnet pieces are arranged in the longitudinal direction of the front plate,
A first magnetic flux path is formed on both sides of the center pole to pass through the magnetic gap in the long axis direction, and a second magnetic pole having a polarity opposite to that of the first permanent magnet piece is provided between the back plate and the field cover. A magnetic circuit for a speaker, wherein a permanent magnet piece is interposed to form a second magnetic flux path that passes through the magnetic gap in a direction perpendicular to the first magnetic flux path. 3. The field cover has an oval or rectangular bottom portion, and a side portion at a center portion in the long axis direction of the bottom portion and extending upward from both end portions in the short axis direction and contacting both end portions in the short axis direction of the front plate. The magnetic circuit for a speaker 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.