JPS62132499A - Loudspeaker - Google Patents

Abstract

PURPOSE:To reduce magnetic fluxes leaking out from a magnetic circuit, by forming a polarity which is opposite to that of a main magnetic pole at the outer margin section having an appropriate width on at least one side of the outer peripheral surface of a rectangular magnet. CONSTITUTION:Most of the magnetic fluxes coming out from the (N) pole of a main magnetic pole 25 pass through a top plate 21 and gap 30 in a magnetic circuit as shown by the dotted lines 24a and enter into the pole piece section of a facing plate 23 with pole piece. Then the magnetic fluxes enter the (S) pole of another main magnetic pole 28 after passing through the plate 23, and thus one closed magnetic path is formed. Moreover, part of the magnetic fluxes advance toward the outer margin side of the top plate 21 as shown by the dotted lines 24b and enter into the (S) pole of an auxiliary magnetic pole 26 at the outer margin section of a magnet, and thus, the other closed magnetic path is formed. Therefore, magnetic fluxes leaking out from this magnetic circuit can be reduced even when no cover is provided and the number of used parts can be reduced. As a result the cost can be reduced and assembling time can be shortened.

Description

[Detailed Description of the Invention] r? BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-leakage speaker used in audio equipment for AV and video viewing.

BACKGROUND OF THE INVENTION Conventionally, speakers used in video equipment, especially near cathode ray tubes, have leakage from the field part that makes up the magnetic circuit. As shown in Figure 3, it was found that a low number of ships had been towed.

The following description will be made with reference to FIG. 3, which is a sectional view of a low leakage speaker.

In Figure 3, 1 is a top plate, 2 is a main magnet, 3 is a plate with a pole piece, 4 is a canceling magnet, 5 is a cover for low leakage, 6 is a frame, and 7
8 is a voice coil, 8 is a damper, 9 is a diaphragm, 1o is a dust cap, and 11 is a gasket. Regarding the low leakage speaker having the grooves as described above, the low leakage magnetic circuit portion will be explained below.

Top plate 1. For a magnetic circuit formed by the magnet 2 and the plate 3 with pole pieces 61ζ without low leakage measures, the leakage magnetic flux 12b to the outside becomes as shown in Fig. 4, and has a negative effect on the cathode ray tube image. Ta. As a countermeasure to this problem, a low leakage magnetic circuit as shown in FIG. 5 has been devised and put into practical use. First, top plate 1
．． Main magnet 2 and plate with pole piece 3
In order to reduce the leakage magnetic flux 12b to the outside of the magnetic circuit formed by the groove, a canceling magnet 4 whose magnetic field direction is opposite to that of the main magnet 2, and a closed magnet 4 are used.
A low-leakage cover 6 is added to the magnetic circuit to form a low-leakage magnetic circuit hl'(l'M'). This prevents any adverse effects on the images of the cathode ray tube, etc. It has now gone into production.

Problems to be Solved by the Invention In the 11'4 configuration as shown above, the cancellation magnet 4 and the low leakage cover 6 are added, which increases the cost. Assembling the two pieces together required time and effort for positioning, etc., which had the disadvantage of limiting production numbers.

The present invention has been made in view of the above-mentioned drawbacks, and it is an object of the present invention to provide a speaker that can eliminate these drawbacks.

Means for Solving the Problems In view of the above-mentioned drawbacks, the present invention uses a method that is almost the same as that of a general speaker system, that is, it has a conventional rectangular magnetic circuit,
A suitable width of at least one side of the outer peripheral surface of the rectangular magnet of a speaker for which low leakage measures have not been taken (the side in the direction in which leakage magnetic flux is desired to be reduced) is made to have a magnetic field with a polarity opposite to the main magnetic pole at the outer edge. The circuit is configured to provide a low leakage speaker.

Effect By taking the above-mentioned measures, the magnetic flux leaking from the magnetic circuit is reduced, and it becomes possible to obtain almost the same performance as a conventional low-leakage speaker.

EXAMPLES Hereinafter, the present invention will be explained in detail with reference to the drawings. FIG. 1 shows only the magnetic circuit portion of a speaker in one embodiment of the present invention. In FIG. 1, 21 is a top plate, 22 is a magnet, and 23 is a plate with a pole piece. Figure 2 a, b, c, and d are 1 side and 2 sides, respectively.
This figure shows the magnetized state of the magnet 22, which has a polarity opposite to the main magnetic pole on the outer edge portions having appropriate widths on the third and fourth sides, as seen from the top or bottom. 32, 35.3 in Figure 2
8゜41 indicates the main magnetic pole part magnetized to N pole 33, 36
39.42 indicates a state in which the opposite sub-pole S pole is magnetized, and 34.37.40.43 indicates the neutral point of the magnetic pole.

In FIG. 1, most of the magnetic flux emitted from the N pole of the main magnetic It enters the pole piece, passes through the plate, and enters the S pole of the main magnet (box 28), forming one closed magnetic path.

A portion of the magnetic flux, as shown by 24b, heads toward the outer edge of the top plate 21 and enters the auxiliary magnetic pole S pole 26 located at the outer edge of the magnet, forming one closed magnetic path.

Below, the results of a comparative experiment with the conventional method are shown.

Experimental results (AJ leakage magnetic flux density (Gauss)) Example shown in Fig. 4 i19.6 Example shown in Fig. 5, 2.8 Present example (Fig. 1) H3.

As shown above, according to the present invention, there is an effect that leakage magnetic flux can be reduced without attaching a cover as in the conventional case.

As mentioned above, the speaker of the present invention is structurally the same as a speaker without low leakage measures, but by devising the magnetization configuration, it has achieved the conventional low 6M leakage. The cost is reduced by significantly reducing the number of parts, and the assembly time is also shortened, so the effects are significant.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a low leakage speaker having a magnetic circuit having a rectangular magnet according to the present invention, Fig. 2 is a plan view showing the M magnetic state of the magnet used in the present invention, and Fig. 3 is a conventional example. 4 is a sectional view showing the magnetic circuit of a low leakage speaker having a magnetic circuit having a rectangular magnet. FIG. 4 is a sectional view showing the magnetic circuit of a normal low leakage speaker.
The figure is a cross-sectional view showing a magnetic circuit of a conventional low-leakage speaker. 21-...Tonoffrey), 22.31...
Magnet, 23... Plate with pole piece, 2
4&...main magnetic flux, 24b...leakage/! i!
Magnetic flux, 25, 28. 32.35.38.41...Main magnetic pole, 26.29
゜33, 36, 39, 42...Sub magnetic pole,
34,37゜40.43... Name of person who hit the magnetic pole neutral point Patent attorney Toshio Nakao and one other person 2.
3---Ball Pee Person I; [Great Figure 2 Figure 3 Figure 4!

Claims (1)

[Claims] A magnetic circuit comprising a top plate, a rectangular magnet, and a plate with a pole piece is characterized in that a polarity opposite to the main magnetic pole is formed on an outer edge portion having an appropriate width of at least one side of the outer peripheral surface of the rectangular magnet. speaker.