JPS60214198A - Speaker - Google Patents

Abstract

PURPOSE:To decrease the magnetic effect on the peripheral device of a speaker by assembling a demagnetizing coil to the speaker so as to allow other demagnetizing coil to cancel the magnetic field generated in the voice coil in impressing an input to the speaker. CONSTITUTION:The part applied with a coil 6 of a bobbin 7 on which the voice coil 5 and the demagnetizing coil 6 are wound is connected to the center of a diaphragm 4 so as to be projected in front of the diaphragm 4 and the coil 6 is fitted to the bobbin 7 and bonded thereto. The lead wire to the coil 5 and the lead wire to the coil 6 are wound in a way flowing electrically opposite current flows. The direction of the current flowing to the coil 5 and the direction of the current flowing to the coil 6 are made opposite and since the magnetic flux A generated by the coil 5 and the magnetic flux B generated by the coil 6 are opposite and cancelled so as to reduce the magnetic flux as a whole.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is applicable to devices using magnetic recording media such as magnetic tapes and floppy disks, typified by televisions, cathode ray tube displays, and video and tape recorders. This article relates to a speaker that can be used in these devices even when a magnetic field exists nearby.

(Conventional structure and its problems) Figure 1 shows an example of the structure of a conventional speaker that can be used even when a magnetic field exists nearby. The input lead wire 3 to the speaker terminal 2 was wound around to cancel the magnetic field generated in the voice coil. However, with this method, the input lead wire 3
Zero winding causes various problems such as variations in position, number of windings, etc. during work, poor reliability, lengthening of the input lead wire 3, and complicated work management.

(Objective of the Invention) The present invention solves these conventional problems by incorporating a demagnetizing coil into a speaker, and canceling the magnetic field generated in the voice coil when input is applied to the speaker. The purpose is to reduce the magnetic influence on peripheral devices.

(Structure of the Invention) The present invention provides an electrodynamic speaker having a voice coil for acoustic conversion in a magnetic gear. By configuring the demagnetizing coil to be located outside the gap so that the magnetic flux generated by the voice coil is canceled out by the magnetic flux generated by the demagnetizing coil, problems will not occur even if there is a magnetic field near the speaker. This is what I did.

(Description of Embodiment) Fig. 2 shows a sectional view of an embodiment of the speaker of the present invention, in which 4 is a diaphragm, 5 is a voice coil, 6 is a demagnetizing coil, 7 is a bobbin, and 8 is a center pole. , 9 is a magnet,
10 is an upper plate, 11 dampers, 12 frames, 13 gaskets, 14 dust cages, and 15 input lines.

A discoil 5 and a demagnetizing coil 6 are installed in the center of the diaphragm 4.
The part of the bobbin 7 wound with the demagnetizing coil 6 is connected so as to protrude from the front surface of the diaphragm 4, and the demagnetizing coil 6 is fitted onto the bobbin 7 and bonded. Further, the lead wire of the voice coil 5 and the lead wire of the demagnetizing coil 6 are connected so that magnetic fluxes in opposite directions are generated and currents in opposite directions flow electrically.

FIG. 3 is a cross-sectional view showing the detailed structure of the coil section used in the present invention, in which a bobbin 7 provided at the center of the diaphragm 4 is shown.
2 shows a state in which a voice coil 5 and a demagnetizing coil 6 are installed so as not to generate magnetic fields in opposite directions.

FIG. 4 shows a sectional view of the image coil for explaining the actions of the voice coil 5 and the demagnetizing coil 6.

In this figure, the direction of the current flowing through the voice coil 5,
The directions of the current flowing through the demagnetizing coil 6 are opposite to each other, and since the magnetic flux A generated by the voice coil 5 and the magnetic flux B generated by the demagnetizing coil 6 are in opposite directions, they cancel each other out and reduce the magnetic flux as a whole. Acts to reduce

5 and 6 are cross-sectional views of other embodiments of the present invention, in which a voice coil 5 and a demagnetizing coil 6 are wound on the same bobbin, but FIG. For comparison, in the case shown in FIG. 2, the demagnetizing coil 6 is provided so as to protrude from the front of the diaphragm 4, whereas in both FIGS. 5 and 6, it is provided on the back side of the diaphragm 4. The difference is that it is

The winding directions of the demagnetizing coil 5 and the demagnetizing coil 6 in FIGS. 5 and 6 may be the same or opposite, but they are connected so that current flows in opposite directions to generate magnetic flux in opposite directions. It is configured to do so.

FIGS. 7 and 8 show assembled states of the voice coil 5 and demagnetizing coil 6 used in the speakers shown in FIGS. 5 and 6, respectively.

FIG. 9 is a sectional view of another embodiment of the speaker according to the present invention in which the center pole 8 is lengthened.

This means that the speakers shown in FIGS. 2, 5, and 6 are
Because the demagnetizing coil 6 does not have an iron core, the generated magnetic flux is too small to demagnetize sufficiently, or when you want to improve heat dissipation to prevent the coil from burning out due to the noll heat of the current flowing through the demagnetizing coil 6. This shows an example of its use, and by having the voice coil 5 and the demagnetizing coil 6 share the iron core formed by the center pole 8, the demagnetizing effect is greatly improved.

FIG. 10 is an explanatory diagram of the results of measuring magnetic flux density outside the speaker using the speaker shown in FIG. 9.

The measurement conditions were a speaker surface diameter of 124φ and a thickness of 62mm.
6. The distance from the bottom of the speaker to measurement point a is 75 (in WrIn), and the following results were confirmed. Only the alternating current magnetic fields generated in the coil 5 and the demagnetizing coil 6 were treated. The voice coil 5 and the demagnetizing coil 6 were the same, with a coil wire diameter of 0.18φ and a DC resistance of 76Ω. The input signal has a frequency of 40
We are dealing with a 0 Hz sine wave. First, when a current of 632A is passed through only the disc coil 5, the magnetic flux density at the measurement point is 12G.
It was auss. Next, voice coil 5 and demagnetizing coil 6
When a current of 6.32 A was passed through both, the magnetic flux density at measurement point a decreased to 0.32 Gauss.

(Effects of the Invention) As explained above, the present invention can significantly reduce leakage magnetic flux to the outside by providing a demagnetizing coil that cancels the magnetic flux generated by the voice coil of the speaker. In particular, even if a large input is applied to the speaker, it can be canceled out, so for example, it can reduce the distortion of images on TV receivers, etc.
It is possible to obtain a speaker that does not cause color shift, etc., and its practical effects are significant.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a conventional speaker that can be used even when a magnetic field exists nearby, FIG. 2 is a cross-sectional view of an embodiment of the speaker of the present invention, and FIG. FIG. 4 is a sectional view showing the detailed structure of the coil section used, FIG. 4 is a sectional view of both the voice coil and the demagnetizing coil, and FIGS. 5 and 6 are views showing other embodiments of the present invention. The sectional view of the example, FIGS. 7 and 8, is a diagram showing the assembled state of the voice coil and demagnetizing coil used in the speakers of FIGS. 5 and 6, respectively, and FIG. FIG. 10, which is a sectional view of another embodiment in which the pole is lengthened, is an explanatory diagram of the results of measuring magnetic flux density outside the speaker using the speaker shown in FIG. 9. DESCRIPTION OF SYMBOLS 1... Field part, 2... Speaker terminal, 3... Input lead wire, 4... Vibration plate, 5... Voice coil, 6
... Demagnetizing coil, 7... Bobbin, 8... Center pole, 9... Magneto 7), 10... Upper grate, 1
1... Danno e-112... Frame, 13...
Gasket, 14...Dust cap, 15...Input line. Figure 1 Figure 2 13° Figure 3 Figure 4 Figure 5 Figure 7 Figure 8 Figure 9 Figure 1o

Claims (3)

[Claims] (1) An electrodynamic speaker having a voice coil for acoustic conversion in a magnetic gap, having a demagnetizing coil outside the magnetic gap consisting of another coil through which a current flows in a direction opposite to that of the voice coil; A speaker characterized in that the magnetic flux generated by the voice coil is canceled by the magnetic flux generated by the demagnetizing coil. (2) The speaker according to claim (1), characterized in that separate bobbins are used for the coil demagnetizing coil. (3) The speaker according to claim (1), wherein the same bobbin is used for the voice coil and the demagnetizing coil.