Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-03-27
2001-04-03
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S06700R, C384S100000, C384S107000, C384S112000, C384S113000, C360S098080, C360S099080, C360S099040
Reexamination Certificate
active
06211592
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to storage-disk drive motors for spinning for example hard disks and like storage disks, wherein the motors have dynamic-pressure bearings for supporting the storage disk rotation. In particular the present invention relates to storage-disk drive motors having dynamic-pressure bearings for supporting rotation of storage disks of small outside-diameter, such as 1-inch.
2. Description of Related Art
Miniature and thin storage-disk drive motors for driving hard disks and like storage disks are known. Such an example is the motor disclosed in Japanese Laid-Open Patent Application No. 09-46938. This conventional storage-disk drive motor is provided with a bracket, a rotor hub outer-circumferentially carrying a storage disk and supported by a pair of ball bearings so as to be rotatable relative to the bracket; a rotor magnet fixedly fitted to the rotor hub; and a stator disposed so as to radially oppose the rotor magnet.
Nevertheless, in motors thus employing ball bearings to support rotation of the rotor hub, bearing rigidity is largely due to the diameter of the balls used. In driving for example 1-inch outside-diameter storage disks, however, the diameter of the mounting hole formed in the center of the storage disk for mounting it on the rotor hub will only be approximately 6 mm. This not only restrains the dimension of the balls that may be used for the ball bearings to a diameter that leaves rotation of the rotor hub unstable, but also compels miniaturizing the shaft and making other structural parts thin-walled, such that it is difficult to maintain sufficient mechanical strength in the motor.
There are, furthermore, storage-disk drive motors wherein instead of the ball bearings as described above, dynamic-pressure bearings are used for supporting rotation of the rotor hub. Such an example is the motor disclosed in Japanese Laid-Open Patent Application No. 09-166145. This conventional motor has a pair of radial bearings as means that support radial loads; and further a pair of thrust bearings as means that support axial loads. The radial bearings retain a lubricant in a micro-gap defined between the shaft and the inner circumferential surface of a sleeve member that radially opposes the outer circumferential surface of the shaft. Dynamic pressure-generating grooves consisting of herringbone striations are formed on the outer circumferential surface of the shaft so as to generate dynamic pressure in the lubricant during rotation of the rotor hub.
Likewise, the thrust bearings retain a lubricant in a micro-gap defined between a disk-shaped thrust plate fastened to the end of the shaft, and the end face of the sleeve member and the upper face of the thrust cover, which axially oppose the top/bottom faces of the thrust plate. Dynamic pressure-generating grooves consisting of spiral striations formed on the top/bottom faces of the thrust plate generate dynamic pressure in the lubricant during rotation of the rotor hub.
Nevertheless, personal computers using storage-disk drive devices continue to be made smaller and thinner. What is more, storage-disk drive devices have come to be used in compact equipment such as digital cameras. This calls for miniaturizing and making thinner the storage-disk drive motor itself.
Employing dynamic-pressure bearings instead of ball bearings has done away with the effects of the ball diameter, and has made it possible stably to sustain rotation of the rotor hub. With there being a pair of radial bearings, however, it is very difficult to miniaturize the motor and make it thinner overall while maintaining satisfactory assembly precision, and joint strength in the shaft and thrust plate joint.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a smaller, thinner storage-disk drive motor.
An additional object of the invention is to provide a storage-disk drive motor wherein the motor has been miniaturized and made thinner, and that further enables precision driving of storage disks diametrically small in outside diameter.
A yet further object of the invention is to provide a storage-disk drive motor that is of simple and inexpensive construction without using a thrust plate on thrust bearing.
A additional object of the present invention is to provide a storage-disk drive motor that is miniaturized, made thinner, and at the same time is inexpensive and moreover readily manufactured and assembled.
A still further object of the invention is to provide a smaller, thinner storage-disk drive motor that meanwhile has high bearing rigidity.
Another object of the present invention is to provide a storage-disk drive motor that does not have a thrust plate on the thrust bearing, is miniaturized as well as made thinner, and meanwhile is inexpensive, and readily manufactured and assembled.
A still further object of the present invention is to provide a storage-disk drive motor that is minimized as well as thinner without reducing motor reliability and rigidity.
A storage-disk driving motor according to the present invention includes a radial bearing portion and a thrust bearing portion for supporting rotation of the rotor hub, from the outer circumference of which a flange extends such that a storage disk can be mounted thereon. The radial bearing portion is constituted by the inner peripheral surface of a cylindrical through-hole formed in the central portion of the rotor hub, and the outer peripheral surface of the shaft. The thrust bearing portion is constituted between the lower end-face of the rotor hub and the upper face of the bracket. Furthermore, the rotor hub is biased in the axial direction by magnetic force.
The thrust bearing in a storage-disk drive motor of the present invention is formed between lower end-face of rotor hub having the cylindrical through-hole through which the shaft is inserted, and the upper face of the bracket. Thus the conventional thrust plate is unnecessary, and the motor is therefore miniaturized and made thinner.
Furthermore, since a thrust plate is not employed, there is no need for concern that rotational precision will be out of true due to error in precision and insufficient strength of the thrust plate and the shaft joint. This improves productivity in facilitating manufacture as well as assembly of the motors, and at the same time contributes to motor cost reduction.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description in conjunction with the accompanying drawings.
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patent: 4998033 (1991-03-01), Hisabe et al.
patent: 5052822 (1991-10-01), Van Beek
patent: 5193084 (1993-03-01), Christiaens
patent: 5358339 (1994-10-01), Konno et al.
patent: 5504637 (1996-04-01), Asada et al.
patent: 5543984 (1996-08-01), Itoh
patent: 5810479 (1998-09-01), Miyasaka et al.
patent: 6033118 (2000-03-01), Asai et al.
patent: 6074098 (2000-06-01), Asai et al.
patent: 6-221324 (1994-08-01), None
patent: 6-284631 (1994-10-01), None
patent: 8-331796 (1996-12-01), None
patent: 9-46938 (1997-02-01), None
patent: 9-166145 (1997-06-01), None
patent: 10-9250 (1998-01-01), None
Nguyen Tran
Nidec Corporation
Shinjyu Intellectual Property Firm
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