JPS5931106Y2 - Magnetic circuit for electrodynamic speaker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic circuit for an electrodynamic speaker, and particularly to means for reducing current distortion.

This type of magnetic circuit generally causes distortion in the driving force.

One cause of current distortion is the hysteresis of the iron material in the magnetic circuit.

In other words, when a voice current flows through the voice coil, the pole piece is magnetized, and the magnetization curve at this time draws a so-called minor loop.

Therefore, the operating point always changes.

This reaction distorts the current flowing through the voice coil.

This distortion includes many third harmonics.

Such distortion can be alleviated by generating an induced current with alternating current magnetic flux from the voice coil and canceling out the alternating magnetic flux with the magnetic flux of this induced current.

The canceling means usually involves fitting a cap or shorting ring of good conductivity to the magnetic gap side of the pole piece or top plate, resulting in an increase in magnetic resistance.

Therefore, conventional common solutions have not been effective.

The present invention is intended to solve the above-mentioned drawbacks of the conventional example, and its purpose is to develop a means that does not narrow the magnetic gap and to reduce the resistance of the shorting conductor corresponding to the shorting ring. The point is to enhance the effect as a short ring.

For this purpose, the present invention takes measures such as dividing the inner circumferential surface of the top plate into a plurality of sections and arranging shorting conductors independently from each other in each section.

Hereinafter, the present invention will be specifically explained based on an embodiment shown in the drawings.

The magnetic circuit for an electrodynamic speaker, which is the premise of the present invention, has an annular magnet 3 such as a ferrite magnet sandwiched between a pole piece 1 and an annular top plate 2. A magnetic gap 4 for a DC magnetic field is formed with the inner circumferential surface of 2.

In the present invention, the inner circumferential surface of the top plate 2 is divided into a plurality of sections, for example, four sections, and a short-circuiting conductor 5 made of a good conductor is arranged independently of each other in each of the four section sections. be.

Here, the shorting conductor 5 crosses the thickness direction, that is, the front and back directions, at a groove 6 formed in the generatrix direction on the inner circumferential surface of the top plate 2, and communicates with the front and back surfaces of the top plate 2.

Therefore, the shorting conductor 5a in the magnetic gap 4 does not substantially narrow the distance between the magnetic gaps 4.

In order to make these four short-circuiting conductors 5 independent, appropriate spacing is provided at adjacent positions, or if necessary, an insulator or the like is interposed between the four short-circuiting conductors 5 to separate them.

Now, when a voice current flows through the voice coil T during operation, an alternating magnetic field caused by the current tends to magnetize the top plate 2, particularly the inner peripheral surface of the magnetic gap 4.

However, at this time, an induced current is generated in the short-circuited conductor 5, and the magnetic flux of this induced current acts to cancel out the alternating current magnetic field, so that changes due to the operating point due to the hysteresis characteristic of the magnetic circuit are reduced.

Especially in this case, since the plurality of short circuit conductors 5 are independent,
The resistance of the induced current flowing through each shorting conductor 5 is smaller than that of a conventional show FIJ song for the entire length of the annular magnetic gap 4.

Therefore, an induced current is reliably generated and the alternating current magnetic flux is effectively canceled out.

Furthermore, since a portion of the shorting conductor 5 is inserted into the groove 6 on the inner peripheral surface of the top plate 2, the gap in the magnetic gap 4 is not narrowed by the presence of the shorting conductor 5.

Therefore, the DC magnetic flux of the magnetic gap 4 can be used effectively, and the inner circumferential surface of the top plate 2 is no longer opposed to the pole piece 1 only by the plurality of grooves 6, so that the relationship between the pole piece 1 and the top plate 2 is It is also possible to make the magnetic resistance of the magnetic gap 4 as small as possible.

Although it is advantageous if the annular conductor 5 is made of a thin plate-like material, it may be made of a coil-like material.

According to the present invention, since the short-circuit conductor is divided into a plurality of parts, the current resistance of each short-circuit conductor is small, so that an induced current is reliably generated and effectively cancels the alternating magnetic flux, and the short-circuit conductor Since it only partially crosses the magnetic gap, the magnetic gap does not become particularly narrow, and the magnetic resistance of the magnetic gap does not decrease.

In particular, the above effect is suitable for reducing third harmonic distortion when using a long voice coil.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the magnetic circuit for an electrodynamic speaker of the present invention.
FIG. 2 is a plan view thereof, and FIG. 3 is a partially cutaway perspective view showing the combination relationship between the top plate and the short-circuit conductor. 1... Pole piece, 2... Top plate, 3... Magnet, 4... Magnetic gap, 5... Short circuit conductor, 6・・・・・・
Groove, 7...Voice coil.

Claims (1)

[Scope of utility model registration request] In the magnetic circuit C for an electric speaker, a magnet is interposed between a pole piece and an annular top plate, and a magnetic gap of a DC magnetic field is formed between the outer circumferential surface of the pole piece and the inner circumferential surface of the top plate. A magnetic circuit for an electrodynamic speaker, characterized in that the magnetic gap side of the top plate is divided into a plurality of sections, and a short-circuit conductor made of a good conductor is independently arranged for each section.