JPS5822396Y2 - Magnetic circuit of magnetically shielded speaker - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a square yoke magnetic circuit in which a magnetic shielding cover of an extremely simple structure is attached to an ordinary square yoke magnetic circuit to effectively reduce external leakage magnetic flux.

Conventionally, in a speaker having a square yoke magnetic circuit, a cylindrical magnet disposed within the square yoke is exposed, resulting in external leakage magnetic flux.

This is particularly noticeable in the direction of both openings of the square yoke.

Therefore, when incorporated into equipment such as color television receivers that are extremely sensitive to magnetic flux leakage, speakers with a round yoke magnetic circuit that wraps around the magnet are used, but this type of speaker is extremely It has the disadvantage of being expensive.

This invention significantly reduces magnetic leakage by attaching a magnetic shielding cover to the bottom of a conventional square yoke, and the embodiment shown in FIGS. 1 and 2 will be described in more detail below.

In FIG. 1, reference numeral 1 denotes a square yoke bent into a square shape, and is usually made of a magnetic material such as iron.

A magnet 2 is arranged on one surface of the square yoke 1, a pole piece 3 is arranged on the upper surface of the magnet 2, and the visible part of the pole piece 3 is located in the center hole bored on one surface of the square yoke 1. It is located.

A magnetic gap 4 is formed between the pole piece 3 and the center hole, and a voice coil (not shown) is formed within the magnetic gap 4.
is located.

Reference numeral 5 designates a magnetic shielding cover whose center portion is in close contact with the bottom surface of the square yoke 1 and whose bent pieces formed at both ends cover the lower portions of both openings of the square yoke 1.

The magnetic shielding cover 5 can significantly reduce leakage magnetic flux in the directions of both openings of the square yoke 1.

That is, as shown in FIG. 2, the main leakage magnetic flux is the magnetic flux generated between the two poles of the magnet 2, so by configuring the opening so as to cover it as in this invention, the leakage magnetic flux can be reduced. be able to.

Therefore, the larger the ratio of the bent piece of the magnetic shielding cover 5 to the opening, the greater the magnetic shielding effect, but for the reason described later, the height of the bent piece is 1 of the height to the top of the magnet 2. .0
~0.7 times.

That is, conventionally there is a structure in which the opening is shielded over the entire surface, but with such a structure, leakage magnetic flux can be further reduced, but on the other hand, the gap between the pole piece in the yoke and the magnetic shielding cover is It was found that stray magnetic flux was generated between the two, and the magnetic flux density within the magnetic air gap was reduced.

Therefore, in this invention, the height of the bent pieces standing up at both openings is made 1.0 to 0.7 times the height to the top of the magnet 2, thereby reducing the magnetic flux density within the magnetic gap 5. Therefore, the leakage magnetic flux mainly radiated from the side surface of the magnet 2 can be effectively shielded.

As explained above, this idea is based on the yoke 1 of the magnetic circuit.
Attach a magnetic shielding cover 5 to cover the opening of the magnet, and set the height of the magnetic shielding cover 5 to 1 of the height to the top of the magnet 2.
．． By selecting 0 to 0.7 times, it has a sufficient magnetic shielding effect without reducing the magnetic flux density in the magnetic gap 4, and the structure is extremely simple, so it is practical such as low cost. It also has excellent effects.

Note that the magnetic shielding cover described above is remarkable in a square yoke magnetic circuit using a square ferrite magnet.

[Brief explanation of the drawing]

1 and 2 are a perspective view and a sectional view, respectively, of the magnetic circuit of this invention. 1 is a square yoke, 5 is a magnetic shielding cover, and 2 is a magnet.

Claims (1)

[Scope of utility model registration request] In a magnetic circuit in which a magnetic shielding cover 5 is attached to cover the lower side of the opening of the square yoke 1, the height of the magnetic shielding cover 5 is set to 1.0 of the height to the upper end of the magnet 2 arranged inside the square yoke 1. A magnetic circuit for a magnetically shielded speaker characterized by a magnetic circuit that is 0.7 times larger.