JPS6028199B2 - Magnetic circuit for planar diaphragm speakers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic circuit for a flat diaphragm speaker, and more specifically, a rectangular flat diaphragm having a rectangular flat diaphragm and a voice coil having a corresponding shape. Regarding type magnetic circuits.

The conventionally known linear magnetic circuit is a type in which the magnetic flux from the magnet is guided to the magnetic field part by a plate.It is an expanded form of a circular outer magnetic type magnetic circuit, and the magnetic flux leakage coefficient and supermagnetic loss are compared. It was costly and inefficient. Therefore, since the magnetic circuit formed along one side of the rectangular boil coil must be linear, this invention creates a magnetic circuit with a configuration suitable for this linear magnetic circuit, or in other words, an efficient magnetic circuit. For this purpose, magnets with different suitability are fixed to the inner surfaces of one end of opposing plates to form an air gap, and the pond ends of the plates are connected with a yoke. This is a characteristic feature.

- Hereinafter, embodiments of the magnetic circuit for a flat diaphragm speaker according to the present invention will be described with reference to the attached drawings.

First, the first is a rear view of a speaker unit using a rectangular planar diaphragm, in which a voice coil bobbin 2 is arranged and fixed in parallel to each side of the diaphragm 1, and a voice coil bobbin 2 is fixed at the other end of the voice coil bobbin 2. A rectangular voice coil 3 is fixed.
This voice coil 3 is located in an air gap of a magnetic circuit 4, which will be described later.

That is, in the magnetic circuit 4, a pair of long and thin plates 41 are arranged facing each other with an appropriate interval, and each of the plates 41
Magnets 42 are fixed to the inner side of one end portion in a facing state, and the magnets 42 have mutually different polarities. Further, the other parts of the plate 41 are connected by a yoke 43. The magnets 42 may be continuous and long along the elongated plate 41, but magnets 42 may be independent for each flock.

That is, when forming a large-diameter diaphragm, if the diaphragm is square, the length of one side becomes longer, and the magnet 4
The length of 2 also increases. Although it is possible to form long magnets, this requires an increase in the size of the magnetizing device, and furthermore, the obtained magnets may be damaged during storage, so it is preferable to use a large number of small magnets 42 in parallel. . Since the saturation magnetic flux density of the plate 41 differs depending on the material used, its cross-sectional area is determined in relation to the material.

When the magnetic circuit is configured in this way, unless the gap in the field part is made extremely large, the (calculated) magnetic flux leakage coefficient becomes 1, and the magnetic flux density at the magnet's operating point is directly equal to the density in the field part. This results in extremely high efficiency. According to this embodiment, the magnetic circuit is unitized, easy to assemble, and highly accurate.

Furthermore, since the plate has an extremely simple shape, it can be formed by press processing at low cost. Also, Figures 4 to 6
The embodiment shown in the figure is designed to prevent airflow generated due to the piston movement of the diaphragm 1 or the movement of the voice coil 3 from having an adverse effect on the field section.

That is, the movement of the diaphragm 1 and the voice coil 3 compresses and expands the air in the space behind them, but the viscous resistance of the air prevents this movement, resulting in distortion due to its characteristics. Therefore, a plurality of air circulation holes 44 of an appropriate size and shape are bored in the plate 41 and the yoke 43, taking into consideration that the flow of magnetic flux is not disturbed. Of course, plate 4
1. Air circulation holes 44 may be provided in both of the yokes 43. As a result of forming the air circulation holes 44, as shown in FIG. 6, the air flow generated due to the piston movement of the diaphragm 1 can be removed from the narrow field portion, and furthermore, a cooling effect can be expected.

When aiming at a large cooling effect, it is preferable to have the air circulation holes 44 facing each other. Furthermore, although air is sucked into and discharged from the magnetic circuit due to the movement of the voice coil, since the inside of the magnetic circuit is released through the air circulation holes 44, no abnormal "swishing" noise is generated due to suction. Furthermore, the circuits shown in FIGS. 7 and 8 take measures to reduce third-order harmonic distortion caused by current distortion, and the magnetic circuit in FIG.
A sheet 4 of a good conductor such as copper or aluminum is placed on the opposite surface of the
This sheet 45 is applied to either one or both of the magnets 42.

FIG. 8 shows a plate 41 in which a magnet 42 and a cap 46 made of a highly conductive material such as copper or aluminum are covered. As is clear from the above description, according to the magnetic circuit for a flat diaphragm speaker of the present invention, since the magnetic circuit is constructed by arranging magnets with different magnetic poles on a pair of plates to face each other, a highly efficient and compact device can be achieved. can get.

Further, according to the second invention, since the air circulation holes 44 are provided, the piston movement of the diaphragm is not obstructed.
According to the third invention, third harmonic distortion due to current distortion can be prevented.

[Brief explanation of the drawing]

Figure 1 is a rear view of the flat diaphragm speaker, Figure 2 is a perspective view of the lower part of Figure 1, Figure 3 is a sectional view taken along line m-m in Figure 2, Figure 4,
FIG. 5 is a sectional view of another embodiment, FIG. 6 is a sectional view showing the operation, and FIGS. 7 and 8 are sectional views of an embodiment in which harmonic distortion countermeasures are taken. 1... Vibration plate, 2... Voice coil bobbin, 3... Voice coil, 4... Magnetic circuit, 41... Pre...
42...Magnet, 43...Yoke, 44...Air circulation hole, 45...Seat, 46...Cap. But J 4 2 figures are 8 sardines 2 sardines 5 sardines are s ■ 8 sardines

Claims (1)

[Claims] 1. In a flat diaphragm speaker that includes at least a rectangular flat diaphragm and a rectangular voice coil that follows the shape of the flat diaphragm, a It has a rectangular cross-sectional shape and a certain length,
A magnetic circuit comprising magnets facing each other with different polarities, an air gap formed by these magnets, and plates connected by a yoke. 2. In a planar diaphragm speaker comprising at least a rectangular planar diaphragm and a rectangular voice coil that follows the shape of the planar diaphragm, a rectangular cross-sectional shape is provided inside a pair of parallel plates; and has a certain length,
It consists of magnets facing each other with different polarities, an air gap formed by these magnets, plates connected by a yoke, and air circulation holes provided in either or both of the plates and the yoke. A magnetic circuit featuring: 3. In a planar diaphragm speaker comprising at least a rectangular planar diaphragm and a rectangular voice coil that follows the shape of the planar diaphragm, a rectangular cross-sectional shape is provided inside a pair of parallel plates; and has a certain length,
The configuration consists of magnets facing each other with different polarities, an air gap formed by these magnets, and a yoke connecting the plates. At least one or both of the magnets is coated with a good conductor to generate third-order harmonics due to current distortion. A magnetic circuit characterized by being able to prevent wave distortion.