JPS5911255B2 - How to manufacture magnetic poles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a magnetic pole used in a magnetic circuit such as a DC thermomotor having a moving coil that moves linearly through a magnetic pole gap.

This type of moving coil motor has good response characteristics, so it is used in dynamic speakers, etc. When this moving coil motor is used as a servo motor to drive the moving magnetic head of a magnetic disk drive, it is possible to achieve high-speed access times and high-density recording. can be obtained.

By the way, when used in such a magnetic disk device, as shown in FIG. (as soon as it is installed)
A permanent magnet 8 is attached to the periphery via a magnetic pole 7 to form a magnetic circuit.The above-mentioned coil 3 is inserted into the magnetic gap between the iron core 6 and the magnetic pole 7, and a current is applied to the coil 3. By flowing, the carriage 2 and the front and back 1 are moved back and forth.

In this case, in order to increase the output, a ferromagnetic material such as the magnetic pole 7 is arranged around the coil in order to increase the magnetic flux density in the air gap where the coil 3 is present, and the number of turns of the coil 3 is also increased.

Therefore, the inductance inevitably has a large value, resulting in a problem of poor response.

To solve this problem, as shown in Figure 2, the magnetic pole 7
It is known that a structure in which ferromagnetic plates 9 and nonmagnetic conductive plates 10 are alternately arranged is effective.

In this method, when a ferromagnetic plate 9 and a non-magnetic conductive plate 10 are arranged at an appropriate ratio, an eddy current flows through the conductive plate 10 and acts to short-circuit the coil secondary circuit, reducing the self-inductance. By doing so, the coil inductance can be significantly lowered without reducing the magnetic flux density in the air gap.

Although this has no effect when the current flowing through the coil 3 is a steady direct current, it has a significant effect in the actual drive current frequency range.

Furthermore, by applying the above-mentioned means not only to the above-mentioned embodiment but also to a dynamic acoustic speaker, the responsiveness can be similarly improved, the fidelity of the sound reproduced by the speaker can be increased, and a speaker with less distortion can be obtained.

Next, a method generally used at present when actually manufacturing such a magnetic pole 7 will be explained. As shown in a and b of FIG. 3, a ferromagnetic plate 9 and a non-magnetic conductive plate 10 are
are punched into a predetermined shape using a press, stacked alternately at an appropriate ratio, and then tightened with bolts 11 and nuts 12 to integrate.

In this example, a shows an example of a structure in which a flat magnet is arranged on the outside of the magnetic pole, and b shows a structure in which a segment magnet is arranged.

The magnetic pole 7 manufactured and assembled in this way is of course fully satisfactory in terms of magnetic circuit and electric circuit performance, but the dimensional accuracy after assembly is poor, and the number of assembly steps required makes it extremely valuable as a magnetic pole. Since it is manufactured without pressing, there is a concern that particles such as Paris will become garbage during use.

Regarding dimensional accuracy, since the coil moves in a narrow air gap, dimensional accuracy is required on the inner surface of the inner cylinder, and poor dimensional accuracy on the outer periphery increases magnetic resistance and causes a decrease in air gap magnetic flux density. There are cases.

Regarding the price, ferromagnetic plate 9 and non-magnetic conductive plate 10
For example, they are made by punching out cold-rolled steel sheets or soft aluminum sheets, and the number of man-hours involved in laminating them is large, making them the most expensive of the magnetic circuit structural components.

The present invention has been made in view of the above circumstances, and provides a magnetic circuit in which magnetic poles made of alternating ferromagnetic materials and non-magnetic conductive materials can be manufactured with high accuracy at a cost advantage and with a small number of man-hours. A method of manufacturing a magnetic pole is provided.

The manufacturing method according to the present invention will be specifically explained below.

First, aluminum was selected as a non-magnetic conductor due to its cost and advantages in casting, and in order to metallurgically bond the molten aluminum to the solid ferromagnetic plate, the surface of the ferromagnetic plate was pre-coated. Conventionally well-known technology (Special Public Interest Publication 1974
No. 1481) to apply aluminum dip plating and cool.

After that, a predetermined number of plated ferromagnetic plates are placed in a mold by arranging them at a predetermined interval using a jig, and molten aluminum casting alloy is injected between each ferromagnetic plate and solidified by cooling. .

Then, the ferromagnetic plate and the aluminum material are firmly and integrally bonded, and such an integrated product is taken out from the mold and machined into a predetermined size and shape to manufacture a magnetic pole.

In addition, non-magnetic conductors include copper, silver, etc.

As a result, as shown in FIG. 4, an integrated magnetic pole 7 is formed by alternately arranging the ferromagnetic plate 9 and the non-magnetic conductive aluminum material 13 without using fasteners such as bolts and nuts. .

, Incidentally, in this embodiment, the spacing between the ferromagnetic plates 9 is not equal, and the magnetic poles are wide at the center and narrow at both ends. In this case, there is an effect that the distribution of magnetic flux density in the gap becomes even.

According to the present invention, the magnetic circuit magnetic poles are manufactured by casting, which reduces the number of man-hours compared to the conventional laminated type, and the final shape is finished in one step by machining, resulting in extremely high dimensional accuracy. become.

Furthermore, since no debris such as flakes is generated during press punching as in the conventional method, the number of dust generation factors is reduced.

[Brief explanation of the drawing]

FIG. 1 is a side view showing a direct current linear servo motor applied to a magnetic disk drive, FIG. 2 is a view showing magnetic circuit magnetic poles thereof, and FIGS. 3 a and b are perspective views of magnetic poles manufactured by a conventional method. FIG. 4 is a perspective view showing a magnetic pole manufactured by the method of the present invention. 1...head, 2...carriage, 3
... Coil, 4 ... Direct current servo motor, 5 ... Yoke, 6 ... Iron core, 7.
...Magnetic pole, 8...Permanent magnet, 9...
...Ferromagnetic plate, 10...Nonmagnetic conductor plate, 1
1...Bolt, 12...Nut, 13
...Aluminum material.

Claims (1)

[Claims] 1 A plurality of ferromagnetic plates coated with aluminum in advance are arranged in parallel at predetermined intervals and integrated into a mold, and then molten aluminum is injected between the ferromagnetic plates and solidified to form an integral bond. A method for manufacturing a magnetic pole, comprising manufacturing a magnetic pole by processing an integrated product of the ferromagnetic plate and aluminum into an arbitrary shape.