JPH0422637Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a magnetic circuit for an electrodynamic speaker used in audio equipment, and is designed to obtain a sufficient magnetic flux density in the gap and achieve good speaker drive even when there are dimensional restrictions. This is what I did.

Conventionally, a speaker 1 having a so-called internal magnetic type magnetic circuit
For example, there was something like the one shown in Figure 1. In this Fig. 1, 2 indicates a yoke made of pure iron,
A magnet 3 is provided within the yoke 2. This magnet 3 is made of alnico and has a cylindrical shape, and is magnetized in the axial direction of the magnet 3, and the entire circular plane 3a at the end on the S pole side is connected to the yoke 2.
They are abutted and fixed to the bottom inner surface 2a of the base 2a, aligned with each other along their central axes. On the circular plane of the N-pole side end of the magnet 3, set the diameter of the bottom surface 4a to the length of the opening of the yoke 2 minus the width required for the magnetic gap 5, and set the thickness of the yoke 2. Disc-shaped top plate 4 with the same thickness as the wall thickness
is provided. A magnetic circuit is constituted by the magnet 3, yoke 2, magnetic gap 5, and top plate 4, and the diaphragm 7 moves in the same direction as the magnetization direction of the magnet 3 according to the current flowing through the voice coil 6 in the magnetic gap 5. It vibrates back and forth to produce sound. In order to increase the magnetic flux density within the magnetic gap 5 in the speaker 1 having such an internal magnet type magnetic circuit, the diameter of the magnet 3 must be increased to increase its size. When increasing the size, it becomes necessary to introduce a center pole 10 in order to concentrate the magnetic flux, but since the magnetic flux utilization rate decreases due to the leakage of magnetic flux related to the center pole 10, it is necessary to compensate for this leakage of magnetic flux. So it was necessary to make the magnet 3 larger. Therefore, in order to achieve a high magnetic flux density inside the magnetic gap 5, it is necessary to increase the size of the speaker's magnetic circuit in the width and depth directions, and if there are dimensional restrictions on the width or depth of such a magnetic circuit. The structure had a drawback in that it was sometimes impossible to obtain a desired and sufficient magnetic flux density within the magnetic gap 5. Furthermore, since the magnet 3 is made of expensive alnico material, there is also the disadvantage that the larger speaker becomes very expensive.

Furthermore, a speaker 11 having an external magnet type magnetic circuit as shown in FIG. 3 has been proposed. In the speaker 1 having this external magnet type magnetic circuit, a magnetic circuit is constituted by a cylindrical center pole 12, a pair of plates 4a and 4b, a magnetic gap 5, and a magnet 3, and a ring-shaped magnetic circuit is formed in the same direction as the magnetization direction of the magnet 3. A magnetic gap 5 is formed so that the diaphragm 7 of the speaker 11 vibrates back and forth in the same direction to obtain desired sound. In order to increase the magnetic flux density in the gap in the speaker 11 having this outer magnetic type magnetic circuit, the magnet cannot be extended in the inner diameter direction of the outer magnet 3, and the only way is to extend the outer diameter of the magnet 3. When the magnetic flux becomes large, the magnetic flux utilization rate decreases, and the outer diameter must be increased while compensating for this, and as shown in FIG. 4, it is necessary to increase the size of the magnetic circuit in the width direction and the depth direction. Therefore, if there is a dimensional restriction on the width or depth of the magnetic circuit, it is structurally impossible to obtain a speaker 11 having a high-quality external magnet type magnetic circuit with a desired and sufficient in-gap magnetic flux density. There were some shortcomings. Also,
Even if it could be manufactured within the dimensional constraints, the increased outer diameter would make the manufacturing of each member constituting the magnetic circuit expensive, resulting in an expensive product.

In view of this, the present invention aims to provide a magnetic circuit for an electrodynamic speaker that can obtain a sufficient magnetic flux density within the gap 5 even if there are dimensional restrictions.

Hereinafter, one embodiment of the speaker of the present invention will be described with reference to FIGS. 5 and 6. In FIGS. 5 and 6, parts corresponding to those in FIGS. 1 and 3 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

In FIG. 5, 13 indicates a plate-shaped magnet made of Alnico, for example, and the magnetization direction is on the top side 1 in FIG.
3a is the north pole, and the lower surface side 13b is the south pole in a direction perpendicular to both planes. 14 and 15 respectively indicate first and second yokes made of pure iron and formed separately;
These yokes 14 and 15 are in contact with substantially the entire upper and lower surfaces of the plate magnet, respectively.
It has a sandwich structure in which the plate magnet 13 is sandwiched between the magnets 15 and 15. Further, 16 indicates a plate made of pure iron, for example, and this plate 16 has a gap 5.
A circular hole for the pole piece 17 is punched out at a predetermined position in a direction perpendicular to the magnetization direction of the magnet 13, and the magnetic gap 5 is inserted into the magnet 3.
It is formed into a ring shape in a direction perpendicular to the direction of magnetization. Here, the dimensions in the X-axis direction (width) and Y-axis direction (depth) shown in FIG. 6 are determined at the design stage in accordance with required dimensional constraints. Note that the other parts are configured in the same manner as the conventional speaker.

Furthermore, when the magnetic circuit of a speaker is subject to dimensional constraints in the width direction, a magnetic circuit such as the one shown in FIG. When the magnetic circuit is subject to dimensional constraints in the depth direction, a magnetic circuit as shown in FIG. 8 can be obtained by widening the width in the width direction and providing a desired magnetic flux density within the magnetic gap 5. Note that in FIGS. 7 and 8, parts corresponding to those in FIG. 5 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

According to this embodiment configured in this way, the desired sound can be obtained as in the conventional case, and the magnetic circuit is determined by the length (width) in the X-axis direction and the length (depth) in the Y-axis direction of the magnet 13. Since a desired magnetic flux density can be obtained depending on the area, there is an advantage that a high-quality speaker with a required high magnetic flux density within the magnetic gap 5 can be obtained even if there are dimensional restrictions. Further, since magnetic flux leakage is extremely small and magnetic flux utilization rate is high, there is an advantage that such a speaker can be obtained at a low cost.

Further, FIG. 9 shows a magnetic circuit portion of another embodiment of the present invention. In FIG. 9, parts corresponding to those in FIG. 5 are given the same reference numerals, and detailed explanation thereof will be omitted. This magnetic circuit is an example in which the present invention is applied to a two-point drive speaker.
It is designed so that two are provided. In this example, in addition to obtaining the same effects as the example in FIG.
There is an advantage that a small two-point drive type speaker can be obtained at low cost. It is also possible to arrange two of these two-point drive type speakers and apply them, for example, as shown in FIG. 10, or to use an integrated unit of tweeter 18 and woofer 19 as shown in FIG. 11.

Moreover, FIG. 12 shows still another embodiment of the present invention. In FIG. 12, parts corresponding to those in FIG. 5 are given the same reference numerals, and detailed explanation thereof will be omitted.
This example in Figure 12 is the first example in which the present invention is applied to a speaker with an ultra-slim magnetic circuit and a flat diaphragm.
As shown in Fig. 3, four magnetic gaps 5 are provided. It is easy to understand that the effects of the above-mentioned embodiments can also be obtained in this example. Furthermore, an embodiment in which the plate-shaped magnet 13 is made into a disc-shaped one to form an omnidirectional speaker as shown in FIG. 14 is also possible.

Furthermore, if the first and second yokes 14 and 15 and the magnet 13 are integrated into a unit, there is the advantage that various dimensional constraints can be easily met by simply changing the plate 16 and the pole piece 17.

It goes without saying that the present invention is not limited to the above-described embodiments, and that various other configurations may be adopted without departing from the gist of the present invention.

[Brief explanation of the drawing]

1 and 3 are cross-sectional views showing examples of conventional speakers, FIGS. 2 and 4 are cross-sectional views showing main parts of the examples shown in FIGS. 1 and 3, respectively, and FIG. A sectional view showing an embodiment of the magnetic circuit of the electrodynamic speaker of the invention, FIG. 6 is an exploded perspective view showing an example of the main parts of an embodiment of the invention, and FIGS. FIG. 9 is a perspective view showing an example of the main part of one embodiment, FIG. 9 is a perspective view showing an example of the main part of another embodiment of the present invention, and FIGS. 10 to 12 are other embodiments of the present invention. FIG. 13 is a diagram showing an example of the essential parts of the example shown in FIG. 12, and FIG. 14 is a perspective view showing still another embodiment of the present invention. 5 is a magnetic gap, 6 is a voice coil, 7 is a diaphragm, 13 is a plate magnet, 14 and 15 are first and second yokes, respectively, 16 is a plate, 1
7 is the pole piece.

Claims (1)

[Claims for Utility Model Registration] A plate-shaped magnet, which is attached to each magnetic pole face of the plate-shaped magnet so as to sandwich the plate-shaped magnet, and whose thickness in the magnetization direction is equal to the plate-shaped magnet. first and second yokes smaller than the magnet; a pole piece attached to a surface of the first yoke opposite to the surface that comes into contact with the plate magnet; and a pole piece attached to one end of the second yoke. and a plate having a circular hole in which a ring-shaped magnetic gap is formed in a direction perpendicular to the magnetization direction of the plate-shaped magnet between the plate and the pole piece to be inserted. Magnetic circuit of type speaker.