Dynamic magnetic information storage or retrieval – Head mounting – For shifting head between tracks
Utility Patent
1999-05-17
2001-01-02
Klimowicz, William (Department: 2754)
Dynamic magnetic information storage or retrieval
Head mounting
For shifting head between tracks
C310S049030, C310S254100
Utility Patent
active
06169644
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a read/write device which has a removable disk-shaped recording medium and writes data on the medium or reads data recorded on the medium and, more particularly, to such a read/write device equipped with a stepper motor.
2. Description of the Background Art
A former read/write device (not shown) is equipped with a claw-poll type stepper motor (not shown) such as that described in Japanese Patent Application Laid-open No. 9-154271. In general, the claw-poll stepper motor comprises a stator made of a metal plate and a rotor provided in the stator. The stator is formed so as to enclose the outside of a ring-shaped drive coil and have spin-shaped teeth inserted from both side of the openings of the drive coil and fitted inside the same. The rotor is provided in an annular space formed in the spine-shaped teeth of the stator.
In a claw-poll stepper motor provided in a former read/write device, spine-shaped teeth of the stator require a high degree of profile precision, and a high degree of mounting precision is required when the teeth are placed in the motor. Therefore, machining of spine-shaped teeth requires a high-precision drawing technique, and predetermined enough strength is required for retaining the profile precision of the spine-shaped teeth.
With recent miniaturization of and a reduction in weight of a read/write device, there exists a demand for a more compact and light-weight stepper motor. When the state is made thinner and reduced in weight in order to realize such a stepper motor, the stator and the spine-shaped teeth thereof decrease in strength, thereby making it difficult to hold the profile precision of the spine-shaped teeth. As a result, variations arise in the precision of step feed, which in turn causes variations in the accuracy of positioning of a head. Consequently, the reliability of the read/write device is deteriorated. Further, since the stator and the spine-shaped teeth thereof decrease in strength, the profile precision of the stator and its spine-shaped teeth is difficult to maintain during the processes of manufacturing a stepper motor. Such a problem causes a decrease in the productivity of a stepper motor and by extension a decrease in the productivity of a read/write device. A stepper motor is mounted on the main unit through use of screws. When the position of the head is adjusted (such an adjustment will be hereinafter referred to as an “alignment adjustment”), there are involved laborious operations such as loosening of the screws, rotation of the stepper motor in the direction in which the rotor rotates, and re-fastening of the screws.
SUMMARY OF THE INVENTION
The present invention has been conceived to solve the previously-mentioned problems, and a general object of the present invention is to provide a novel and useful read/write device.
A more specific object of the present invention is to provide a read/write device which is equipped with a stepper motor employing a new structure in place of a claw-poll structure and which enables miniaturization, a reduction in weight, and an improvement in reliability such as an improvement in the accuracy of step feed.
Above object of the present invention is achieved by a read/write device described below. The device includes heads for writing data on and reading data recorded on a disk-shaped recording medium. The device also includes a carriage which is equipped with the heads and is supported to as to be able to move in the radial direction of the recording medium. The device further includes a stepper motor for moving the carriage stepwise. The device moreover includes a medium drive motor for spinning the recording medium. The stepper motor comprises a rotor which has an annular magnet alternately magnetized with different polarities in a circumferential direction and has a rotary shaft on which is formed a spiral portion engaging the carriage; a first stator which is formed from multilayer magnetic material and is fixedly positioned so as to surround the rotor; a second stator which is formed in substantially the same way as the first stator and is fixedly positioned so as to surround the rotor; and a holder which rotatably retains the rotor and houses the first and second stators. Each of the first and second stators comprises a plurality of teeth which protrude toward the magnet and are arranged at regular intervals around the magnet; a joint section which joins together the base ends of the teeth and has gap angle limitation sections for limiting the angle formed between adjacent teeth; and a coil including drive coils formed on the individual teeth and a cross-over line for electrically connecting the drive coils. The first and second stators are fixedly positioned such that they are spaced a predetermined distance away from each other along the rotary shaft of the rotor and such that they are offset from each other by a predetermined angle in a rotation direction.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.
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Akutsu Satoru
Ito Hiroshi
Miyake Nobuaki
Sato Masakatsu
Yamaoka Yusuke
Klimowicz William
Mitsushita Denki Kabushiki Kaisha
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