Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-10-27
2001-08-28
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S06700R, C360S098070, C360S099040, C360S099050, C360S099080
Reexamination Certificate
active
06281608
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a spindle motor adapted to rotate a data record disk (hereinafter referred to merely as “a disk”, when applicable) such as CD, DVD, CD-ROM and DVD-ROM, and more particularly to a spindle motor which suppresses the swing or vibration of the shaft which attributes to the eccentric gravity center during rotation.
2. Related Art
In general, in a spindle motor adapted to turn a disk, a turn table is fitted on one end of the shaft, and a disk is mounted on the turn table. The turn table has a circular-truncated-cone-shaped or semi-spherical protrusion at the center, while the disk has a central hole. With the protrusion engaged with the central hole of the disk, the central position is determined.
When the turn table is turned by the spindle motor, the disk is also turned together with the turn table, so that the signals recorded on the recording track of the disk are read by a reading section such as an optical pickup. In the case of a rewritable or writable disk, data signals can be rewritten or written in the disk. As in the case of a recent CD-ROM drive unit, in order to increase the data reading and writing speed there is a tendency to increase the speed of rotation of the disk. Accordingly, there has been a strong demand for the provision of a spindle motor which can turn the disk at higher speed.
However, if the speed of rotation of the disk is increased, then the unbalance of the centrifugal force is increased which occurs during the rotation of the disk, as a result of which the shaft is rotated while swinging. When the shaft turns while swinging, and its vibration is increased, then it is difficult for the reading section to accurately read data signals recorded on the disk, or it is difficult for the writing section to accurately write data signals on the disk.
In general, the centrifugal force attributing to the eccentric gravity center of a disk is proportional to the square of the speed of rotation, and as the speed of rotation increases, the swinging and vibrating of the shaft is extremely increased. Accordingly, the swinging and vibrating of the shaft, which attribute to the eccentric gravity center, are serious problems when it is required to increased the speed of rotation of the disk.
SUMMARY OF THE INVENTION
Accordingly, an object of the invention is to eliminate the above-described difficulties accompanying a conventional spindle motor. More specifically, an object of the invention is to provide a spindle motor in which during rotation of the disk the unbalance of the centrifugal force which attributes to the eccentric gravity center is canceled out, whereby even when the disk is turned at high speed, the swinging of the shaft can be suppressed, and the vibration of the same is also suppressed, which makes it possible to read data signals from the disk or to write data signals on the disk.
According to an aspect of the present invention, there is provided a spindle motor including a shaft rotatably supported, a rotor casing turned together with said shaft, a turn table fixedly mounted on one end portion of said shaft and rotated with a disk mounted thereon,an eccentric member loosely mounted on the part of said shaft which is located between said rotor casing and said turn table, and which is turned with the rotation of said rotor casing.
In the spindle motor of the invention, the eccentric member or the ball are provided as the movable balance member. This feature makes it possible to cancel out the unbalanced centrifugal force which attributes to the eccentric gravity center of the disk, and to suppress, even when the disk is turned at high speed, the swinging of the shaft or turn table; that is, to decrease the vibration thereof. As a result, data signals can be accurately read from the disk, and can be accurately written in the latter.
REFERENCES:
patent: Re. 7455 (1877-01-01), Fesca
patent: 3751044 (1973-08-01), Sawada
patent: 4730299 (1988-03-01), Kamoshita et al.
patent: 4874976 (1989-10-01), Ohsawa et al.
patent: 5748406 (1998-05-01), Morimoto et al.
patent: 5757762 (1998-05-01), Lee
patent: 5883454 (1999-03-01), Hones et al.
patent: 6016238 (2000-01-01), Yoshikawa et al.
Kabushiki Kaisha Sankyo Seiki Seisakusho
Nguyen Tran
Sughrue Mion Zinn Macpeak & Seas, PLLC
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