JPS63268397A - Magnetic circuit with low leakage - Google Patents

Abstract

PURPOSE:To reduce leakage flux, by joining a magnetic flux focusing plate between a frame and an upper plate. CONSTITUTION:A remarkable effect can be given on leakage in the neighborhood of the frame by adding the plate 11 between the frame 6 and the upper plate 1. The magnetic flux to the frame 6 can be reduced and the leakage in the neighborhood of the frame can be reduced by focusing the magnetic flux emitted from the ball part of the upper plate to the plate 11.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention has the following advantages: 1.
This invention relates to a low-leakage magnetic circuit that effectively utilizes magnets.

2. Description of the Related Art Generally speaking, it is desirable that magnetic leakage of a speaker be small, but speakers for color television receivers in particular need to have particularly low magnetic leakage. In color televisions, speakers are generally placed at the bottom or side of the cathode ray tube, but in such a configuration, if a large amount of magnetic leakage is emitted from the speakers, the electron beams of the cathode ray tube will not be focused on one point on the fluorescent surface, resulting in color shift. This causes a problem where the screen color changes. To solve this problem, a magnetic circuit using two magnets as shown in FIG. 3 has conventionally been used. In the figure, 1 is the upper plate;
2 is a permanent magnet, 3 is a lower plate, and 4 is a permanent magnet, which is magnetized with the opposite polarity to the permanent magnet 2. 5 is a shield cover, 6 is a frame, 7 is a cone, 8 is a dust cap, 9
is a voice coil, and 10 is a damper.

Problems to be Solved by the Invention However, in the configuration shown in FIG. 3, as shown in the state diagram of magnetic flux flow in FIG. 3
It passes through the bottom of the pole part, passes through the magnetic gap between the upper plate 1 and the S pole of the magnet 2. As shown above, the magnetic flux from the canceling magnet 4 enters the S pole from the N pole through the bottom of the lower plate 3 → the pole part → the shield cover 5. There are countless other magnetic flux flows, but the one that particularly affects the cathode ray tube is the magnetic flux that flows from the pole portion to the frame e and flows to the upper plate 1, as shown in D. The magnetic flux flows through the frame 6 to the upper plate 1, but since the frame 6 is generally thin, about 0.6 to 1 mm thick, magnetic saturation occurs in the frame 6, and a portion of it leaks outside and affects the cathode ray tube.

The present invention aims to provide a low leakage magnetic circuit that can solve this problem.

Means for Solving the Problems The present invention provides an annular permanent magnet arranged between an upper plate joined to a frame and a lower plate having a pole piece, and a ring-shaped permanent magnet arranged under the lower plate with a polarity opposite to that of the permanent magnet. In a magnetic circuit consisting of magnetized annular permanent magnets joined together and surrounded by a magnetic shield cover,
The present invention is a low-leakage magnetic circuit characterized in that a magnetic flux focusing plate is joined between the frame and the upper plate.

Function: A part of the magnetic flux leaking from the upper plate is focused by the magnetic flux focusing plate.

Embodiment FIG. 1 is a structural sectional view of a low leakage magnetic circuit according to an embodiment of the present invention. In this figure, the same numbers as in FIG. 3 indicate the same parts, and 11 is a magnetic flux concentrating plate. That is, the plate 1 is placed between the frames and the upper plate 1.
1 is added, and it has a great effect on leakage especially around the frame. By concentrating the magnetic flux exiting from the pole portion of the upper plate onto the plate 11, the magnetic flux flowing to the frame 6 can be reduced and leakage to the surroundings of the frame can be reduced.

FIG. 2 is a state diagram showing the flow of the magnet. As is clear from the figure, according to this embodiment, the frame e is lower than the pole part.
A part of the magnetic flux G flowing through the upper plate 1 flows to the upper plate 1, and leakage magnetic flux can be reduced compared to the conventional example.

In addition to the effects of the invention, the present invention can provide a magnetic circuit that can reduce leakage magnetic flux with a simple configuration.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the structure of the low leakage magnetic circuit of the present invention, FIG. 2 is a state diagram of the flow of magnetic flux in the low leakage magnetic circuit of the present invention, and FIG.
The figure is a structural sectional view of a conventional low leakage magnetic circuit for a speaker, and FIG. 4 is a state diagram of the flow of magnetic flux in the conventional low leakage magnetic circuit. 11... Magnetic flux concentrating plate. Name of agent: Patent attorney Toshio Nakao and 1 other person 7l
-4a end focusing port Fig. 1 Fig. 2

Claims (1)

[Claims] An annular permanent magnet is arranged between an upper plate joined to the frame and a lower plate having a pole piece, and an annular permanent magnet magnetized with a polarity opposite to that of the permanent magnet is joined to the lower side of the lower plate, A low-leakage magnetic circuit comprising a magnetic circuit whose periphery is covered with a magnetic shield cover, wherein a magnetic flux concentrating plate is joined between the frame and the upper plate.