JPS6016730B2 - magnetic circuit device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic circuit device, and particularly to an improvement in a magnetic circuit device that generates a magnetic field with high magnetic flux density in a specific gap in a magnetic path.

A generalized conventional magnetic circuit device widely used in speaker magnetic circuits and other applications is shown in FIG.

In the figure, a permanent magnet 10 is magnetized in the vertical direction of the figure, and a pole piece 12 and a yoke plate 14 are closely connected to both ends of the permanent magnet 10, and the minimum distance between the pole piece 12 and the yoke plate 14 is A magnetic gap 16 is formed in the portion. The joint surfaces between the permanent magnet 10, the pole piece 12, and the yoke plate 14 are usually formed of a flat surface or a relatively monotonous surface such as a spherical or cylindrical surface with a large radius of curvature. Next, the operation of the conventional device will be explained.

In general, a permanent magnet in a magnetic circuit has an operating point determined by the permeance coefficient, that is, the product of the magnetic flux density d and the area of the magnetic pole surface at the intersection D of the demagnetization curve in Figure 2 and the operating point where the permeance coefficient becomes a nuisance. A large amount of magnetic flux is generated, most of which is guided to the magnetic air gap 16 through the pole piece 12 and the yoke plate 14, but a considerable amount of leakage magnetic flux is also generated through other paths. The air gap magnetic flux density is the value obtained by subtracting the leakage magnetic flux from the magnetic flux generated by the permanent magnet 10, divided by the cross-sectional area of the magnetic air gap 16. In order to increase the air gap magnetic flux density, the magnetic pole area of the permanent magnet and the magnetic air gap are The ratio to the cross-sectional area must be much larger than the ratio between the air gap magnetic flux density and the permanent magnet pole surface magnetic flux density. Figure 3 shows the demagnetizing characteristics of typical permanent magnets.

The permanent magnets mainly used in the past are anisotropic alnico magnets and anisotropic ferrite magnets. In order to use a permanent magnet most efficiently, it is necessary to set its operating point at the point where the energy product, which is the product of demagnetizing force and magnetic flux density, is maximum. In this case, it needs to be about 20 [G/○e], and in the case of an anisotropic ferrite magnet, it needs to be about 2 [G/∊]. however,
In a subordinate magnetic circuit device in which the joining interface between the magnetic pole of the permanent magnet and the pole piece and yoke plate is a flat surface or a similar curved surface with a large radius of curvature, the permeance coefficient at the operating point of the permanent magnet is If the magnetic pole area of a permanent magnet is increased and its thickness is decreased in order to reduce the size, there is a disadvantage that the leakage magnetic flux at the outer circumference of the permanent magnet increases, and when it is difficult to increase the magnetic pole area itself due to restrictions on external dimensions. The problem was that there were a lot of

Therefore, the rare cobalt magnet shown in Fig. 3 or the flexible magnet made by mixing its powder with a suitable resin has a permeance coefficient of 1 that provides the maximum energy product because the material is expensive.
It is necessary to operate near [G/0e],
Also, consider that rubber magnets made by mixing ferrite magnet powder with rubber are inexpensive, but in order to operate most efficiently with a small maximum energy product, the permeance coefficient needs to be around 1 [G/㈊]. As a result, it was difficult to use these in a secondary magnetic circuit.

The above conventional problems will be specifically explained below regarding a speaker magnetic circuit.

FIG. 4 shows typical magnetic circuit configurations of the external magnetic type, and FIG. 5 shows typical magnetic circuit configurations of the internal magnetic type. Permanent magnet 10 and pole piece 1
2 and the yoke plate 14 are usually fixed using an adhesive, but in the internal magnet type shown in FIG. many. In the external magnet type, a structure in which the permeance coefficient at the operating point of the permanent magnet is reduced is shown in FIG. As is clear from the figure, as a result of the permanent magnet 10 becoming striped and flat, its thickness decreases, but on the other hand, its external shape increases. In a speaker, the purpose is to move the voice coil in the vertical direction in the figure in the magnetic gap 16.
Particularly in speakers for bass reproduction with large amplitudes, as shown in Fig. 7, even if the permanent magnet 10 becomes thinner, the height of the pole piece 12 must be at least equal to the movement of the voice coil. , it is not possible to obtain the effect of reducing the thickness, and only the disadvantage of increasing the external size remains. In addition, as shown in Figure 8, in the case of the internal magnet type, although there is an effect of reducing the thickness, the degree of increase in size due to increase in the radial direction is large, and this is because the permeance coefficient is usually 20 [G
/06], and is already impractical for ferrite magnets with an appropriate permeance coefficient of 2 to 3 [G/■], and if the permeance coefficient becomes even smaller, it will become even more impractical. It turns out. FIG. 9 shows a simplified conventional internal magnetic circuit used in small, low-cost speakers. Permanent magnet 10
The cross-sectional area of the pole piece 12 must be smaller than the cross-sectional area of the pole piece 12, and the permeance coefficient at the operating point of the permanent magnet 10 must be quite large, so that the use of permanent magnets with a low permeance coefficient is not possible. . The present invention has been made in view of the above-mentioned problems, and its purpose is to create a structure in which the joint surfaces of the permanent magnet, the pole piece, and the yoke plate are interwoven with each other, and to reduce the effective cross-sectional area of the permanent magnet. The object of the present invention is to provide a magnetic circuit in which a permanent magnet can be used at an operating point with a low permeance coefficient without increasing the external size.

Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 10 shows a generalized first embodiment of the present invention corresponding to the conventional device of FIG.

Isotropic permanent magnet 10 capable of operating with low permeance coefficient
consists of a shell-like structure with a constant thickness, and its curved shape increases its magnetic pole area. The pole piece 12 and the yoke plate 14 have a joint surface shape corresponding to the bent shape of the permanent magnet 10, and are held in close contact with each other when they are alternately joined together. Furthermore, FIG. 11 shows the second embodiment of the present invention in the external magnetic type speaker magnetic circuit corresponding to the conventional device shown in FIG.
This is an embodiment, and the permanent magnet 101 is made of a rare earth cobalt magnet formed into the shell shape shown in the figure by sintering.

As in the first embodiment, the pole piece 12 and the yoke plate 14 have joint surfaces processed into a shape compatible with the permanent magnet 10. In the magnetic circuit according to the present invention configured as described above, unless there is a special part where the cross-sectional area is small and the magnetic east density is abnormally high in the intricate part of the pole piece 12 and the yoke plate 14, the pole For both the piece 12 and the yoke plate 14, the difference in magnetic potential depending on the position of the part where they are joined to the permanent magnet 10 can be ignored, and the permanent magnet magnetic pole area is substantially larger, and in the case of a fan-flat shape with an equivalent magnetic pole area. Similarly, the permeance coefficient at the operating point of the permanent magnet can be made small.

In the second embodiment shown in FIG. 11, a rare earth cobalt magnet is used as the permanent magnet, but a phantom magnet or a rubber magnet may also be used.

Although the magnetic properties of these magnets deteriorate, even if the machining accuracy of the pole piece 12 and yoke plate 14 becomes rough, it is absorbed by partial deformation of the permanent magnet 10, and the overall assembly requires less force. Even if the magnet 10 is added, it can be easily carried out without causing the magnet 10 to break. Furthermore, if a certain degree of compressive stress remains in the magnet part when the permanent magnet 10, pole piece 12, and yoke plate 14 are aligned, the magnetic circuit will be fixed by the frictional force at the interface, and the adhesive will The advantage is that it is not necessary. FIG. 12 shows an example of the present invention in which the permanent magnet 10 in an external magnet type speaker magnetic circuit is divided into a plurality of pieces and has a simple shape, and is particularly suitable for rare cobalt magnets.

FIG. 13 shows the case of an external magnet type speaker magnetic circuit that uses a movable magnet or a rubber magnet as the permanent magnet 10, and the pole piece 12 and yoke plate 14 are assembled in advance.
As shown on the left side of the figure, a third embodiment of the present invention is constructed by inserting a stopper 20 into the magnetic gap 16 and injecting fluidized permanent magnet material through an injection port 22 provided on the outer periphery of the magnetic circuit to form a magnetic circuit. Give an example.

According to this embodiment, there is no need to mold the permanent magnet in advance, which simplifies the assembly work, and
By applying a magnetic field to adjust the magnetic moment of fine permanent magnet particles in a certain direction during the process in which the magnet material solidifies from a fluid state, it is possible to improve the characteristics in the magnetic circuit used. FIG. 14 shows a fourth embodiment in which the present invention is applied to an internal magnet type speaker magnetic circuit, and compared to the conventional internal magnet type magnetic circuit shown in FIG. 5, the thickness is reduced without increasing the outer diameter. Understand what is possible. FIG. 15 shows a fifth embodiment in which the present invention is applied to an internal magnet type magnetic circuit for a small speaker configured in correspondence with the conventional device shown in FIG. For applications where the amplitude is not very large, it is possible to use ferrite magnets, which are cheaper than conventional alnico magnets.

Each of the above embodiments is a case where the present invention is applied to a speaker magnetic circuit, but FIG. 16 shows a sixth embodiment in which the present invention is applied to a magnetic circuit of a moving coil type instrument, and a corresponding conventional Figure 17 shows the magnetic circuit of the shape.

Both permanent magnets are magnetized in the left-right direction in the horizontal direction, and a magnetic gap 16 is formed between the magnetic pole pieces 24 and 26 and the core 28. The permanent magnet 10 in FIG. 17 is made of alnico, and in the embodiment shown in FIG. 16, it is replaced with a ferrite type, which makes it possible to lower the price or improve performance by replacing it with a rare earth cobalt type. . As described above, according to the present invention, in a magnetic circuit device, the magnetic pole area of the permanent magnet can be increased and the thickness of the magnetic pole can be reduced without increasing the outer diameter, so that the generation of leakage magnetic flux can be suppressed. Therefore, it is possible to reduce the permeance coefficient at the operating point of the permanent magnet to a value that provides maximum efficiency.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional side view of a generalized conventional magnetic circuit device.
Fig. 2 is an explanatory diagram of the permanent magnet operating point, Fig. 3 is a demagnetization characteristic diagram of various permanent magnet materials, and Figs. 4 and 5 are cross sections of conventional external magnet type and internal magnet type speaker magnetic circuit devices. Side view, No. 6
Figure 7 is a cross-sectional side view of a conventional external magnetic type speaker magnetic circuit device with a small permeance coefficient at the operating point of the permanent magnet, and Figure 8 is a cross-sectional side view of a conventional internal magnetic type magnetic circuit device with a small permeance coefficient. 9 is a sectional side view of a conventional internal magnetic circuit device for a small speaker, FIG. 10 is a sectional side view of a first embodiment of a magnetic circuit device according to the present invention, and FIG. A cross-sectional side view showing an external magnet type speaker device according to a second embodiment of the invention, FIG. 12 is a diagram showing a state in which the permanent magnet is divided into a plurality of pieces in the external magnet type speaker magnetic circuit, and FIG. FIGS. 14 and 15 are cross-sectional side views of the Gaishi type speaker device showing the third embodiment, and FIGS.
, FIG. 16 is a sectional side view of a magnetic circuit in a moving coil type instrument showing a sixth embodiment of the present invention, and FIG. 17 is a sectional side view of a conventional moving coil type speaker device showing a fifth embodiment. FIG. 3 is a cross-sectional view of the magnetic circuit of the meter. The same members are given the same reference numerals throughout each figure, 10 is a permanent magnet, 12 is a pole piece, 14 is a yoke plate, 16 is
Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. T Fig. 8 Fig. 9 Fig. 10 Fig. 11 Fig. 13 Fig. 14 Fig. 1 Figure 17

Claims (1)

[Claims] 1. In a magnetic circuit device that includes a permanent magnet as a magnetic flux source and generates a magnetic field with high magnetic flux density in a specific magnetic gap, the permanent magnet has a constant thickness and a three-dimensionally bent shape. 1. A magnetic circuit device comprising: a permanent magnet having an increased substantial magnetic pole area. 2. The magnetic circuit device according to claim 1, wherein the permanent magnet has a single shell shape. 3. A magnetic circuit device according to claim 1, wherein the permanent magnet is a flexible magnet such as a flexible magnet or a rubber magnet. 4. A magnetic circuit device according to claim 3, wherein the permanent magnet is formed by pouring a fluidized permanent magnet material into a mold provided during the device assembly process and solidifying it.