Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-07-11
2002-05-07
Mullins, Burton S. (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C360S137000, C310S07500D, C310S156010
Reexamination Certificate
active
06384502
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a permanent magnet generator, and more particularly to a permanent magnet generator that can be incorporated in a diskette designed to be used by inserting into a floppy disk drive, and when a memory, such as a magnetic card, is installed in the diskette, serves as a power source for the memory to write and read data in the memory.
2. Description of the Related Art
Medical information, such as personal medical checkup results, is stored in an IC card, from which medical institutions can retrieve such information for use in the treatment of a patient, and can store in the card the contents of his case records after some medical treatments. Plans are also now under way to use IC cards as electronic money. Under the plans, data on a customer's bank account, password, and the balance of his account, if necessary, are stored in an IC card, by means of which payment is made on-line every time the card holder spends money.
It has been proposed that an enormous amount of video information handled by a digital camera be stored in a flash memory that has a capacity as large as several megabytes to 10 megabytes. A flash memory containing the video information taken by a digital camera can be connected to a personal computer for subsequent video processing. The use of a flash memory to record the video information taken by a digital camera may eliminate an additional external memory unit, such as MOs.
The widespread use of IC cards or flash memories, however, has been deterred by the need for special input/output (I/O) devices dedicated for such media. Since most commonly used I/O devices for personal computers are floppy disk drives, particularly 3.5″ floppy disk drives, the use of 3.5″ floppy disks as an I/O device for IC cards and flash memories could spur their proliferation. In fact, methods for writing and reading data into and from an IC card or flash memory are being studied, and adapters that can be inserted or incorporated in 3.5″ floppy disk drives have already been proposed. A conventional type of 3.5″ floppy disk drive has a magnetic head to read and write information from and into a 3.5″ diskette, and a drive shaft to cause the diskette to rotate at 300 rpm, but it has no power feeding terminals. In diskette-shaped adapters, a button battery is incorporated to power the built-in CPU. A battery, which depletes as it is used, has to be replaced with a new one every four to five months at the longest.
Introduction of a 3.5″ floppy disk in which a generator is incorporated and driven by the rotation of the drive shaft of a 3.5″ floppy disk drive would prove very useful, giving momentum to the proliferation of IC cards and similar media. In fact, the concept of incorporating a generator in a 3.5″ diskette has already been proposed in U.S. Pat. No. 5,159,182 SMART DATA STORAGE DEVICE, issued Oct. 27, 1992 to Raymund H. Eisele and Tokuhyo Hei-7(1995)-500238, a published Japanese translation of PCT international publication for patent application.
U.S. Pat. No. 5,159,182 discloses that a generator is incorporated in a 3.5″ diskette, and that the generator has a rotor, a stator and a regulator, but its detailed construction is not disclosed. Tokuhyo Hei-7(1995)-500238 discloses a generator incorporated in a 3.5″ diskette having a permanent magnet that rotates with a hub, which is caused to rotate by the drive shaft of a floppy disc drive. This permanent magnet is of a cylindrical shape, magnetized in the axial direction so that multiple magnetic poles are provided on the both end faces of the cylinder. The magnetic poles of a stator yoke are disposed in such a manner as to sandwich the cylindrical permanent magnet, and a stator coil is provided between the stator yokes on both sides of the cylindrical permanent magnet. Another example is also disclosed in which magnetic poles are provided on the circumferential surface of the cylindrical permanent magnet. In this example, the magnetic poles of the stator yoke are of a claw pole shape.
Now, let us consider a permanent magnet generator of a size that can be incorporated in a 3.5″ floppy disk, as disclosed in Tokuhyo Hei-7(1995)500238, where the cylindrical permanent magnet is magnetized in the direction of the rotating shaft of the rotating permanent magnet in such a manner that multiple magnetic poles are provided on the both end faces of the cylinder. In this case, stator magnetic poles are disposed on both sides of the cylinder end face with small magnetic gaps. Since the allowable thickness of a generator in a diskette is 2.0 to 2.5 mm, the permanent magnet is allowed to have a thickness of only 0.5 to 0.8 mm at most. Even when a material having a large coercive force is used for a magnet with such a short distance between magnetic poles, only a small magnetomotive force could be expected. Even if magnetomotive force is increased by increasing the thickness of the magnet, the allowable thickness of the stator magnetic poles is reduced, making it difficult to pass a sufficient amount of magnetic flux in them.
In a permanent magnet generator where magnetic poles are provided on the circumferential surface of the cylindrical permanent magnet and the claw pole type stator yoke is provided, as disclosed in Tokuhyo Hei-7(1995)-500238, the end yokes of both claw pole type magnetic poles are provided facing each other within the thickness of 2.0 to 2.5 mm allowed for the generator, and a stator winding is provided between the end yokes. Since a sufficient number of winding turns cannot be provided within the thickness of no more than 1 mm allowed for the stator winding, a generator having a low output voltage would inevitably result.
In order to realize a generator having as high an output as possible and the lowest possible distortion, it is necessary to dispose rotor magnetic poles on the circumferential surface of the cylindrical permanent magnet at equal angular intervals, and make the number of magnetic poles of the stator yokes equal to the number of magnetic poles of the rotor permanent magnet, so that the stator magnetic poles can face the permanent magnet magnetic poles.
In order to implement a diskette which serves as an information I/O device in conjunction with a memory card having magnetic stripes, such as an IC card, a space for housing a memory card must be provided in the diskette. The typical size of a standard memory card is 85 mm in length, 54 mm in width, and 0.8 mm in thickness. Since the thickness given above ignores the embossed part for raised letters of the memory card, its actual thickness is a little bit thicker. To provide a space for a memory card and a permanent magnet type generator in a 3.5″ diskette having a thickness of 3.5 mm and two 0.2 mm-thick covers on both sides, the thickness of the generator must be not more than 2.0 mm, allowing for the thickness of the memory card of 0.8 mm and some clearance for loading and unloading the card.
One of the present assignees has already filed a U.S. patent application for a diskette having a permanent magnet type generator, Ser. No. 09/369,420, filed Aug. 6, 1999. The diskette according to the patent application is shown in
FIG. 19. A
diskette
9
shown in the figure incorporates a permanent magnet generator
90
around a hub
911
disposed at the center thereof in such a manner that a ring-shaped permanent magnet
912
having magnetic poles on the outer circumferential surface thereof can be rotated together with the hub. A generator stator
92
is provided inside the diskette on the outer periphery of a permanent magnet
912
of a rotor
91
, with a magnetic gap between the magnetic poles on the outer circumferential surface of the permanent magnet
912
. The diskette
9
, which is designed to be used as an I/O device for IC card or memory card, has a space
95
for accommodating a memory card, and a card contact terminal
96
used for exchanging information with the memory card. An I/O te
Kimura Fumio
Kitta Kenichi
Masuzawa Masahiro
Mita Masahiro
Takahashi Takehiro
Hitachi Metals Ltd.
Mullins Burton S.
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