JPH0638558Y2 - Magnetic circuit of speaker unit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to an improvement of a magnetic circuit of a speaker unit.

[Conventional technology]

FIG. 7 is a sectional view showing the right half of the magnetic circuit of the conventional speaker unit. In the figure, (1) is a bottom plate integrally having a center pole (1a), and (2) is on the bottom plate (1). It is a ring-shaped magnet adhered to the outer surface of which the positioning projections (2a) are formed on both sides in the thickness direction, and the bottom plate (1a) is formed on the inner surface of the lower projection (2a). ) Is fitted on the outer peripheral surface.
(3) is fitted on the inner surface of the convex portion (2a) on the magnet (2) so as to maintain a predetermined magnetic gear (4) with respect to the outer peripheral surface of the center pole (1a). Is a top plate that is placed and adhered to form a magnetic circuit.

In the above configuration, since the upper and lower surfaces of the magnet (2) contacting the bottom plate (1) and the top plate (3) are flat, the magnet (2) is misaligned before being fixed by an adhesive. There is.
Therefore, as a countermeasure against this, as shown in FIG. 7, a convex portion (2a) is formed on the outer periphery of the magnet (2) for positioning.

[Problems to be solved by the invention]

Since the magnetic circuit of the conventional speaker unit is configured as described above, the projection (2) provided on the magnet (2)
The outer diameters of the upper and lower end portions of a) are increased by that amount, so that a large amount of ineffective magnetic flux is generated, the effective magnetic flux passing through the magnetic gear (4) is reduced, and the magnetic flux density of that portion is reduced. It was

This invention improves the shape of the convex portion formed on the outer periphery of the magnet so as to solve the above problems.

[Means for solving problems]

In the magnetic circuit of the speaker unit according to the present invention, the outer diameter of the central portion of the convex portion (2a) formed on the outer periphery of the magnet (2) in the thickness direction of the magnet is set to the maximum, and both are arranged in the thickness direction. It is designed to be smaller toward the end.

[Action]

In the case of the present invention, since the magnet is formed with the convex portion configured as described above, the amount of effective magnetic flux generated at the end of the convex portion is small and the amount of effective magnetic flux passing through the magnetic gear is large.

〔Example〕

An embodiment of the present invention will be described below. That is, in FIG. 1, the same parts as those of the conventional one shown in FIG. 7 are designated by the same reference numerals and their duplicate description will be omitted. However, in the case of the present invention, the convex portion (2a) of the ring-shaped magnet (2) The outer circumference of the magnet is designed so that the outer diameter at both end portions in the thickness direction of the magnet becomes smaller than the outer diameter at the center portion in the thickness direction as it passes through the inflection point (2b). Further, it is characterized in that it is composed of an injection-moldable rare earth plastic magnet material or an Nd-FeB-based magnet material excellent in machinability.

2 and 3 show another embodiment of the present invention. In the case of FIG. 2, the outer peripheral surface of the convex portion (2a) is flush with the vertical direction, and in the case of FIG. Are different in that they are convex arc surfaces.

Next, the results of analyzing the magnetic flux density of the magnetic gap by the finite element method due to the difference in the shape of the convex portion (2a) formed on the outer circumference of the magnet (2) are shown in the following table.

In these cases, the center pole (1a) and the top plate (3) have the same dimensions, and the outer diameter of the magnet (2) is the same as that in FIG.
The outer diameters of those in FIG. 2 are the same.

On the other hand, FIG. 4, FIG. 5 and FIG. 6 are the actual measurement results showing the distribution state of the magnetic field lines. Similar to the above analysis results, the case of the present invention shows that the ineffective magnetic flux is reduced. Is clear from the figure.

In the above embodiment, the projection (2a) of the magnet (2) is abutted against both the center pole (1a) and the top plate (3) to perform the positioning. Any one of the convex portions (2a) may be provided. Further, the outer peripheral surface of the convex portion (2a) may be formed in a convex arc shape as shown in another embodiment of FIG.

[Effect of device]

In the magnetic circuit of the speaker unit according to the present invention, the shape of the outer peripheral surface having the convex portion having the positioning function of the magnet is formed as described above, so that the ineffective magnetic flux can be reduced and the magnetic flux density of the magnetic gear can be increased. Not only is it possible, but there is also the effect that a magnet for a magnetic circuit having a predetermined shape with high accuracy, stable quality, and good workability can be easily obtained by the desired selection of the material of the magnet.

[Brief description of drawings]

FIG. 1 is a sectional view showing a half of a magnetic circuit of a speaker unit of the present invention, FIGS. 2 and 3 are similar sectional views showing other embodiments of the present invention, FIGS. 4, 5 and 6
FIG. 7 is a distribution diagram of magnetic force lines, and FIG. 7 is a sectional view showing a half of a magnetic circuit of a conventional speaker unit. In the figure, (1) is a bottom plate, (1a) is a center pole, (2) is a magnet, (2a) is a convex portion, (2b) is an inflection point, and (3) is a top plate. In other figures, the same reference numerals indicate the same parts.

Claims (5)

[Scope of utility model registration request] Claims: 1. A ring-shaped magnet sandwiched between a bottom plate having a center pole and a top plate is provided with a convex portion in the thickness direction of the magnet, the convex portion preventing displacement of the position facing the center pole. In the case where the outer peripheral surfaces of the bottom plate and the top plate are fitted so as to protrude on both sides, the outer diameter of the magnet at both end portions in the thickness direction of the protrusion is the outer diameter of the center portion in the thickness direction of the magnet. The magnetic circuit of the speaker unit characterized by being made smaller. 2. One or more deviations on the outer peripheral surface of the magnet in which the convex portion is formed, the outer diameter of which gradually decreases from the outer diameter of the central portion in the thickness direction of the magnet toward both end portions in the thickness direction. The magnetic circuit of the speaker unit according to claim 1, wherein the utility model registration has a bending point. 3. The magnetic circuit of a speaker unit according to claim 1, wherein the outer peripheral surface of the magnet, on which the convex portion is formed, is formed in a convex arc shape. 4. The magnetic circuit of a speaker unit according to claim 1, wherein the magnet is an injection molded body of a rare earth plastic magnet material. 5. The magnetic circuit of the speaker unit according to claim 1, wherein the magnet is composed of a machined body of Nd-FeB magnet material.