JPH01198260A - Composite outer rotor for loading magnetic disk - Google Patents

Abstract

PURPOSE:To enable the manufacture by forming an outer rotor body on a magnetic shielding cylinder as a unit, and at the same time, by coupling in a high-fit. CONSTITUTION:A composite outer rotor 1 for loading magnetic disk is such that a magnetic shielding cylinder 3 is fitted to the inner circumferential surface of a cylindrical outer rotor body 2. The body 2 is so formed as a unit that a hot forming of a non-magnetic light metal material having a thermal expansion coefficient larger than that of the magnetic shielding cylinder 3 is made. The cylinder 3 is formed of a magnetic metal material such as magnetic stainless, and is coupled with the body 2 in a high-fit by shrinkage resulting from the cooling after forming the body 2. According to the constitution, it is not necessary to manufacture the outer rotor body 2 in advance, and is coupled with the cylinder 3 as a unit at the same time as the body 2 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magnetic disk rotation drive motor built into a magnetic disk device, and relates to an outer rotor that also serves as a hub for mounting a magnetic disk.

(Prior Art) In recent years, with the demand for smaller size and larger capacity magnetic disk drives, motors for driving rotation of magnetic disks have been developed, for example, as disclosed in Japanese Utility Model Application No. 61-476. Outer rotor type brushless DC that can be made smaller
Motors are becoming increasingly popular.

As shown in FIG. 5, the outer rotor type DC motor has a fixed shaft 32 erected on a motor board 31.
A stator 33 is provided around the rotor 2, and an outer rotor 34 is rotatably supported on the fixed shaft 32 via bearings 35, 35 so as to surround the stator 33. The outer rotor 3
4 also serves as a hub for mounting the magnetic disk 36,
It is made of a magnetic metal material such as magnetic stainless steel, and a permanent magnet 37 is attached to its inner peripheral surface. Outer rotor 3
4 is made of a magnetic metal material in order to prevent leakage magnetic flux from the permanent magnet 37 from occurring and to prevent it from affecting the magnetic disk 36 mounted on the rotor 34 .

38 is a bottom member of the outer rotor 34, on which the magnetic disk 36 is placed. The magnetic disks 36 are stacked and attached via spacers (not shown) to increase the capacity.

According to the above outer rotor type DC motor, the stator 33
can be stored inside the outer rotor 34, making it possible to reduce the size. However, since a magnetic metal material is used as the material forming the outer rotor 34, it is not possible to reduce the weight, and the motor torque is equivalent to the rotation of the outer rotor 34 itself. In turn, this has become a factor that hinders miniaturization of the motor itself.

Therefore, it was disclosed in Japanese Utility Model Application Publication No. 192669/1983,
As shown in FIG. 6, an outer rotor 34a has a magnetic shielding cylinder 42 made of a magnetic metal material attached to the inner surface of an outer rotor main body 41 made of a non-magnetic lightweight metal material such as an aluminum aluminum alloy. is now being used.

(Problem to be Solved by the Invention) However, in the outer rotor 34a having such a composite structure, the outer rotor main body 41 and the magnetic shielding cylinder 4
2 must be processed with high precision.

In particular, this type of motor is required to be smaller.
It is desired that the thickness of the side wall portion forming the magnetic disk mounting surface of the magnetic shielding cylinder 42 and the outer rotor main body 41 be approximately 1 mm or less, which is extremely difficult to process. Further, fitting the outer rotor main body 41 and the magnetic shielding cylinder 42 requires care, and requires special jigs and assembly equipment, which inevitably lowers productivity and increases processing costs.

The present invention has been made in view of such problems, and an object of the present invention is to provide a composite outer rotor for mounting a magnetic disk that is easy to manufacture regardless of the thickness of the side wall portion of the outer rotor main body.

(Means for Solving the Problems) A composite outer rotor of the present invention, which has been made to achieve the above object, is an outer rotor of a magnetic disk rotation drive motor, and the inner peripheral surface of a cylindrical outer rotor body to which a magnetic disk is mounted. In a composite outer rotor in which a magnetic shielding cylinder is attached to the outer rotor, the outer rotor body is hot-formed from a non-magnetic lightweight metal material and is tightly fitted and coupled to the magnetic shielding cylinder by shrinkage due to cooling after molding. It is a feature of the invention that

(Example) Hereinafter, the composite outer rotor for mounting a magnetic disk of the present invention will be described together with its manufacturing method.

FIG. 1 shows a composite outer rotor 1 according to the present invention, in which a magnetic shielding cylinder 3 is attached to the inner peripheral surface of a cylindrical outer rotor main body 2. As shown in FIG.

The outer rotor main body 2 is made of a non-magnetic lightweight metal material (for example, A 5056
, aluminum alloys such as A6061, titanium alloys) are integrally formed by hot forming.

On the other hand, the magnetic shielding cylinder 3 is made of magnetic stainless steel (for example, 5
The outer rotor body 2 is formed of a magnetic metal material such as US416), and is tightly fitted into the outer rotor body 2 by shrinkage as the outer rotor body 2 cools after molding.

In explaining the manufacturing method of the composite outer rotor 1,
First, the molding die will be explained.

FIGS. 2 and 3 show an example of a mold for a composite outer rotor, which is slidably fitted into an outer mold 11 and used to pressure-form the molding material stored inside the outer mold 11. Inner mold 12
A pressurizing device (not shown) applies molding pressure to both dies.

The outer mold 11 has a molding hole 13 for molding the outer circumferential surface of the outer rotor main body 2 , and a shaft-shaped bottom mold part 14 is slidably attached to the lower part of the molding hole 13 . A retaining ring 15, which can be freely divided and assembled in the radial direction, is attached to the retaining ring 15. By attaching and detaching the retaining ring 15, the bottom mold part 14 can be fixed and moved within the molding hole 13.

On the other hand, the inner mold 12 includes a base portion 16 that is slidably fitted into the upper opening of the molding hole 13, and a shaft portion 17 for mounting the magnetic shielding cylinder 3 is coupled to the base portion 16. There is.

Then, when the inner mold 12 is fitted into the outer mold 11 and the molding hole 13 of the outer mold 11 is closed, a cavity 18 for molding the outer rotor body is formed in the molding hole 13.

Incidentally, during molding, a coating is applied to the molding surfaces of both the outer mold 11 and the inner mold 12 that constitute the molding cavity 18 thereof. Further, although the outer mold 11 is provided at the bottom and the inner mold 12 is provided at the top according to the figure, the positional relationship of the molds can be freely set.

In order to manufacture the composite outer rotor l shown in FIG. 1, first, as shown in FIG.
A magnetic shielding cylinder 3 is fitted onto the outside of the cylinder 3, and then a billet 19 made of a non-magnetic lightweight metal material is placed inside the outer mold 11 from the cylinder 3. Thereafter, as shown in FIG.
After hot forming, the product is immediately taken out and cooled. Through this series of operations, the desired composite outer rotor 1 can be obtained. To take out the product, remove the retaining ring 15 from the outer mold 11 and insert the bottom mold part 14 into the molding hole 13, and the molded product will separate from the mold and can be easily taken out.

As the billet 9, an extruded material made of a non-magnetic lightweight metal ingot is usually used, and it is particularly preferable to use an extruded material made of a rapidly solidified powder thereof because it has excellent moldability. For example, an extrusion molded material of rapidly solidified aluminum powder is obtained by extruding a compression molded body of rapidly solidified aluminum powder at an extrusion ratio of 5 to 20 and an extrusion temperature of 250 to 480°C. The powder in the compact is subjected to strong shearing action during extrusion processing,
Several inert and stable Al t 03 films formed on the outer surface of the powder are fragmented and destroyed, and crystallized substances and precipitates in the N base (for example, /' J-St alloy powder) are destroyed. For example, eutectic Si, etc.) are also divided into fine grains, and these are uniformly dispersed in the N base, resulting in finer crystal grains and higher strength. For this reason, extruded molded materials have extremely good moldability and are accepted as precision molded materials.

When manufacturing a composite outer rotor using the extrusion molded material of the rapidly solidified aluminum powder, the molding temperature is 350 to 4
Carry out at 80″C and take out the molded product at 250~430°
It is best to use C. If the molding temperature is high, the take-out temperature will also be high, and since cooling is performed from a high temperature, the difference in cooling temperature will be large, and the amount of shrinkage due to cooling of the outer rotor body 2 will be excessive, which may cause cracks when forming the side wall with a thin wall. It becomes easier to enter.

The molding temperature can be easily controlled by embedding a sheathed heater or the like in the mold and installing an appropriate temperature control device. It is desirable to use preheated magnetic shielding cylinder 3 and billet 9.

Furthermore, if fine irregularities are formed on the outer circumferential surface of the magnetic shielding cylinder 3 by shot blasting or turning processing (the height of the irregularities is 0.3 degrees and below the temperature is sufficient), the magnetic shielding body 2 will be exposed to the inner surface of the outer rotor main body 2 through the irregularities. They are joined in a meshed state, which improves the joint strength. Further, as shown in FIG. 4, a recess 21 and a protrusion 22 for preventing removal may be formed on the outer peripheral surface of the magnetic shielding cylinder 3.

According to the pressure forming method explained above, the outer rotor body 2
The bonding interface between the magnetic shielding cylinder 3 and the magnetic shielding cylinder 3 has a high magnification (3000
Even when observed under an electron microscope (200% magnification), no peeled boundaries were observed and the bond was firmly bonded.

Therefore, a magnetic disk drive with a built-in outer rotor type DC motor having the composite outer rotor 1 can withstand repeated temperature changes from 0 to 70°C, which is the normal operating temperature.
Since reversible dimensional change of the composite outer rotor is possible and resonance during rotation can be prevented, tracking errors are advantageously prevented.

In addition to the above-mentioned pressure molding, the composite outer rotor of the present invention can be
It can also be manufactured by powder metallurgy.

In this case, an outer rotor composite compression molded body of a non-magnetic lightweight metal material and cold solidified powder containing a magnetic shielding cylinder is created,
Sinter under pressure using WrP (warm isostatic pressing), hot press, etc. The sintering temperature is the temperature at which the powders are metallurgically integrated (sintered).

For example, aluminum 2. In the case of cold solidified powder, 35
The temperature may be about 0 to 550°C. After sintering, if the outer rotor main body 2 is cooled in a non-pressurized state, the outer rotor main body 2, which is a sintered body, is tightly fitted into the magnetic shielding cylinder 3 due to shrinkage caused by cooling after molding.

As explained above, in the composite outer rotor of the present invention, there is no need to manufacture the outer rotor main body 2 in advance, and it can be integrally connected to the magnetic shielding cylinder 3 at the same time as molding.

Furthermore, molding is easy regardless of the wall thickness of the side wall portion of the outer rotor main body 2, resulting in excellent productivity and economical efficiency.

By the way, as a method for integrally molding the outer rotor main body with the magnetic shielding cylinder, a method can be considered in which a non-magnetic soft metal molten metal is injection molded into an outer rotor main body mold containing the magnetic shielding cylinder. In this case, since the outer rotor body is cooled from the solidification temperature to the molding temperature, the amount of shrinkage increases. Therefore, in order to prevent the occurrence of cranking on the side wall of the outer rotor main body, it is necessary to increase the wall thickness of the side wall, which increases the amount of machining required for finishing after molding.
This results in decreased productivity and increased processing costs, making it unsuitable as an industrial production method.

(Effects of the Invention) As explained above, in the composite outer rotor of the present invention, the outer rotor body formed of a non-magnetic lightweight metal material is integrally molded with the magnetic shielding cylinder, and shrinks due to cooling after molding. Since the outer rotor body is tightly fitted, there is no need to process the outer rotor body with high precision in advance, and it can be manufactured extremely easily regardless of the wall thickness of the side wall portion of the outer rotor body.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a composite outer rotor according to an embodiment, and FIG.
The figures and the third area are cross-sectional views of the pressure molding die for the composite outer rotor, with FIG. 2 showing the state before molding and FIG. 3 showing the state after molding. Figure 4 is a partially enlarged sectional view of the magnetic shielding cylinder;
Figure 5 is a cross-sectional explanatory diagram of an outer rotor type DC motor, Figure 6
The figure is a sectional view of a conventional composite outer rotor. 1-・-Composite outer rotor, 2-・Outer rotor main body,
3-Magnetic shielding cylinder. Patent applicant Kubota Iron Works Co., Ltd. Agent Patent attorney Yasu 1) Toshio 1 Tsuba I,
−. °;1. Two. Figure 2 71 Figure 3 Figure 5 Decay

Claims (2)

[Claims] (1) An outer rotor of a magnetic disk rotation drive motor, which is a composite outer rotor in which a magnetic shielding cylinder is adhered to the inner peripheral surface of a cylindrical outer rotor body to which a magnetic disk is attached, wherein the outer rotor body is non-magnetic and lightweight. A composite outer rotor for mounting a magnetic disk, characterized in that it is hot-formed from a metal material and is tightly fitted into a magnetic shielding cylindrical body by shrinkage upon cooling after molding. (2) The composite outer rotor according to claim 1, characterized in that the outer peripheral surface of the magnetic shielding cylinder is formed with unevenness for strengthening the coupling with the outer rotor main body.