Dynamic magnetic information storage or retrieval – Record medium – In container
Reexamination Certificate
1999-08-06
2002-10-08
Renner, Craig A. (Department: 2652)
Dynamic magnetic information storage or retrieval
Record medium
In container
C360S137000
Reexamination Certificate
active
06462907
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a diskette incorporating a permanent magnet generator, and more particularly to a diskette incorporating a permanent magnet generator, and a permanent magnet generator that is incorporated in a diskette used by inserting into a floppy disk drive, and when a memory is installed in the diskette, serves as a power source for the memory to input and output data in the memory.
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 the patient, and can store the contents of his case records in the card. Plans are also now under way to use IC cards as electronic cash. Under the plans, data on a customer's bank account, password, and his bank balance, if necessary, are stored in an IC card, by means of which payment is made on-line every time the customer buys a product.
It has been proposed that an enormous amount of video information handled by a digital camera should be stored in a flash memory that has a capacity as large as a couple of megabytes to 10 megabytes. A flash memory in which the video information is 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, as discussed above, 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, 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 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, as discussed above, a button battery is incorporated as a power source for 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 the 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 Published Examined Japanese Patent Application No. Hei-7(1995)-86912 and Tokuhyo Hei-7(1995)-500238, the published Japanese translation of PCT international publication for patent application.
Published Examined Japanese Patent Application No. Hei-7(1995)-86912 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 disk drive. This permanent magnet is of a cylindrical shape, magnetized in the axial direction so that multiple magnetic poles are provided on the end face 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.
In this way, these documents state a permanent magnet type generator incorporated in a 3.5″ diskette, but it is unknown how much output can be produced with such a generator because they do not disclose the material of permanent magnet suitable for use in such a generator, and the detailed construction of the rotor and stator.
Now, let us consider a permanent magnet generator of a size that can be incorporate in a 3.5″ floppy disk, as disclosed in Tokuhyo Hei-7(1995)500238, where the cylindrical permanent magnet is magnetized in such a manner that multiple magnetic poles are provided on the end face of the cylinder. In this case, stator magnetic poles are disposed on both sides of the cylinder end face via small magnetic gaps. Since the allowable thickness of a generator in a diskette is 2.0 to 2.5 mm, the thickness of the permanent magnet is 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 can 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 sufficient 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 yoke of both claw pole type magnetic poles is provided facing each other within the allowable thickness of 2.0 to 2.5 mm for the generator, and a stator winding is provided between the end yoke. Since a sufficient number of winding turns cannot be provided within the allowable length of no more than 1 mm for the stator winding. Thus, a generator having a low output voltage would result.
In order to realize a generator having as high an output as possible and as low distortion as possible, it is necessary to dispose rotor magnetic poles on the circumferential surface of the cylindrical permanent magnet at equal angular intervals, make the number of magnetic poles of the stator yokes equal to the number of magnetic poles of the rotor permanent magnet, and dispose the stator magnetic poles facing the permanent magnet magnetic poles via magnetic gaps of substantially the same size. If a generator of such a construction is to be incorporated in a thin 3.5″ diskette, the teeth of the stator magnetic poles must be extended outward in the radial direction from the stator magnetic poles. When the number of magnetic poles is 12 to 24 and the inside diameter of the stator yoke is 30 mm, the inner circumferential dimensions of the stator yoke given to one magnetic pole is as small as 8 to 4 mm. If stator magnetic poles of a 4-mm width are used, the gaps between the stator magnetic poles is not more than 4 mm. The gaps between the magnetic pole teeth, however, become considerably larger along the outer circumference of the stator magnetic poles, beyond which the teeth of the stator magnetic poles extend outward in the radial direction.
Since the allowable thickness of a generator is 2.0 to 2.5 mm, as described above, the allowable thickness of the stator coil is 0.6 to 0.8 mm on one side if the thickness of the stator magnetic poles is 0.8 mm. No matter how densely a coil is wound on this thin allowable coil thickness, the number of turns of coil cannot be increased too much. On the outer circumference of the stator magnetic pole where the gaps between the magnetic pole teeth are large, the gaps between the coils will have to be increased, producing a large dead space around them. This is contrary to the purpose of the present invention to reduce space as much as possible when a permanent magnet generator is incorporated in a small diskette.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a diskette incorporating a thin permanent magnet gen
Kimura Fumio
Masuzawa Masahiro
Mita Masahiro
Takahashi Toshiko
Hitachi Metals Ltd.
Renner Craig A.
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