JP3647510B2 - Index generator - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an index generation device for a floppy disk device used in a personal computer or the like.
[0002]
[Prior art]
In the floppy disk device, an index generating device for detecting the rotational position of the recording medium is provided for initialization and writing of the recording medium (floppy disk), correction of the reading position, and the like. As described in Japanese Utility Model Publication Nos. 4-37338 and 4-134178, this index generation apparatus includes an index magnet and a coil, a hall element, etc. for detecting a change in magnetic flux of the index magnet. In combination with the magnetic detection element, an index signal for detecting the rotational position of the recording medium is generated.
[0003]
[Problems to be solved by the invention]
However, in the conventional index generation device, in order to obtain a sufficient change in the magnetic flux from the index magnet, it is necessary to use a powerful index magnet. Normally, in a floppy disk device, writing of a recording medium, Since the magnetic head for reading is arranged on the side of the chucking head that positions and rotates the recording medium, if a strong index magnet is placed near the chucking head, the reading will occur due to the leakage flux of the index magnet. Margin decreases and reliability decreases. For this reason, the index generation device cannot be disposed near the chucking head, and the rotor yoke and the chucking head are separated, which causes a problem of increasing costs.
[0004]
The present invention solves such a conventional problem, and an object thereof is to provide a low-cost and highly reliable index generation apparatus.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides an iron rotor yoke having a chucking head for positioning and rotating a recording medium at an upper portion, and an index magnet provided on an outer peripheral portion of the rotor yoke and fixed to a lower surface portion. When the index magnet substantially equal to or slightly larger eaves-like cut-and-raised portion is automatically aligned by setting either side of the front and rear on the lower surface portion of the cut-and-raised portion is magnetized in Table back two poles And an index coil having a coil that is disposed below the index magnet and wound around a soft magnetic core, and indexes the change in the magnetic flux of the index coil by the index magnet that occurs every rotation as the rotor yoke rotates. It is a signal.
[0006]
[Action]
Therefore, according to the present invention, the chucking head is provided on the rotor yoke, and the index magnet is fixed to the hook-shaped cut and raised portion provided on the outer peripheral portion of the rotor yoke. Since the shield can be shielded by the cut-and-raised part, a low-cost and highly reliable index generation device can be realized.
[0007]
【Example】
FIG. 1 is an exploded perspective view of the entire floppy disk device in one embodiment of the present invention. In FIG. 1, reference numeral 101 denotes a base plate, and each component is attached to form a floppy disk device. Reference numeral 102 denotes a head carriage to which a magnetic head for writing to and reading from a recording medium is attached. The head carriage is guided by a guide rod 103 and moved to a predetermined track by the action of a lead screw 105 provided in a step motor 104. And positioning. A spindle motor 106 rotates the recording medium. Reference numeral 107 denotes a front panel, 108 denotes a push button, 109 denotes a shield cover, and 110 and 111 denote eject levers and holders constituting a recording medium setting / ejecting mechanism.
[0008]
FIG. 2 is an enlarged view of a portion of the spindle motor 106 in the floppy disk device, and corresponds to the index generation device of the present invention. Reference numeral 1 denotes a rotor yoke of a spindle motor, which is formed of a zinc-treated steel plate having a thickness of 1 mm. A flange-like cut-and-raised portion 2 is formed on the outer peripheral portion of the rotor yoke 1, and an index magnet 3 formed of a rare earth samarium-cobalt sintered magnet is fixed to the lower surface of the cut-and-raised portion 2 with an adhesive or the like. Has been. In the present embodiment, the index magnet 3 is a magnet having a length of 2 mm, a width of 2 mm, and a height of 1 mm, and an S pole is magnetized on the front surface and an N pole is magnetized on the back surface. Reference numeral 4 denotes an index coil core. Ferrite is used, and an index coil 6 is formed by winding a coil 5 thereon. Reference numeral 7 denotes a printed wiring board on which necessary electronic circuits and electronic components (not shown) are mounted. 8 is a chucking head for 3.5 inch type provided on the upper portion of the rotor yoke 1, and a spindle shaft 9 serving as a center of rotation of the spindle motor, a hub magnet 10 for attracting the recording medium, and a recording medium being driven to rotate. Drive pins 11 and a tetrafluoroethylene sheet 12. In the spindle motor in this embodiment, the spindle shaft 9 is directly fixed to the rotor yoke 1, and rotational torque is generated by a drive magnet provided on the inner peripheral surface of the rotor yoke 1, a stator and a stator winding (both not shown). This is a so-called circumferentially opposed motor that is generated.
[0009]
FIG. 3 is an enlarged view of the bowl-shaped cut and raised portion 2, the index magnet 3, the index coil core 4 and the coil 5 of FIG. 2 as viewed from the A direction. B is a tangential direction of the index magnet 3 (rotational direction of the rotor yoke 1). FIG. 4 is an enlarged view of the index coil core 4, in which a prism is sandwiched between two upper and lower plates, and the size of the upper plate facing the index magnet 3 is the length in the direction of arrow A. The length of 3 mm × tangential direction B is set to 4 mm, which is larger than the index magnet 3.
[0010]
Next, the operation of the above embodiment will be described. In FIG. 2, a magnetic flux change once per rotation occurs in the thickness direction of the index coil core 4 as the spindle motor rotates. This change in magnetic flux causes an induced voltage to be generated at both ends of the coil 5 wound outside the index coil core 4 in accordance with Fleming's right-hand rule. This induced voltage is output in proportion to the product of the number of turns of the coil 5 and the magnetic flux change linked to the core 4 (more precisely, the coil 5) per unit time, that is, the time derivative of Φ. In this example, when the length in the tangential direction B of the index magnet 3 was measured from 2 mm to 1 mm, which was half, an output waveform almost the same as that in the case of 2 mm was obtained. It was also confirmed that it was almost proportional to the rotational speed of the rotor yoke 1 (time derivative of magnetic flux change). This indicates the relationship V = −L × (dΦ / dt) where V is the output voltage, Φ is the magnetic flux, L is the inductance, and t is the time (Faraday's law). Then, the output V is output from the index generation device as an index pulse using a comparator or a Schmitt trigger.
[0011]
FIG. 5 shows a state in which the voltage generated at both ends of the coil 5 as the rotor yoke 1 rotates changes depending on the arrangement of the index coil core 4. 5A shows an output voltage waveform when the long side of the core 4 is arranged in the tangential direction B with respect to the rotation direction of the rotor yoke 1, and FIG. 5B shows the output voltage waveform when the short side of the core 4 is tangent. It is an output waveform when it arrange | positions so that it may become the direction B, (c) is an output waveform when it arrange | positions so that the long side of the core 4 may incline about 45 degrees with the tangential direction B. FIG. The rotational speed of the rotor yoke 1 is constant at 300 rpm. It can be seen that each output waveform may be appropriately selected depending on the comparator to be used, a Schmitt trigger, or the like.
[0012]
In this embodiment, as shown in FIG. 2, the bowl-shaped cut-and-raised portion 2 provided on the outer peripheral portion of the rotor yoke 1 serves as a back yoke by magnetically shorting one surface of the index magnet 3, and the plate The thickness is 1 mm, the leakage magnetic flux with respect to the recording medium and the head carriage can be suppressed to as low as about 10 and several gausses, and the data reading margin is not reduced.
[0013]
In the present embodiment, the cut-and-raised portion 2 of the rotor yoke 1 has the same dimensions (2 mm × 2 mm) as the index magnet 3, so that the index magnet 3 can be separated from the cut-and-raised portion 2 by its own attractive force. Can be automatically aligned so that the reluctance is minimized. Even if the cut-and-raised portion 2 is formed slightly larger than the index magnet 3, the same effect is obtained. On the other hand, when it is formed slightly smaller, the reluctance is minimized, but since the leakage magnetic flux increases, the reliability as the floppy disk device is lowered. For this reason, the cut-and-raised portion 2 is set to the same size or slightly larger than the index magnet 3. As a result, when the index magnet 3 is set to the cut and raised portion 2, it is automatically aligned as described above. Therefore, if it is fixed with an adhesive or the like thereafter, operations such as alignment can be omitted.
[0014]
Further, in this embodiment, a samarium-cobalt sintered magnet having a rare earth saturation magnetic flux density of about 11 k gauss is used for the index magnet 3, so that a sufficient output voltage can be obtained and the cut-and-raised portion 2 serves as a shield. Since it functions as a yoke, high reliability can be obtained as a floppy disk device. In addition, the saturation magnetic flux density of this index magnet 3 should just be 5k gauss or more.
[0015]
As mentioned above, although this invention was demonstrated based on the said Example, the change and improvement using the idea of this invention can be made | formed variously.
[0016]
【The invention's effect】
As is clear from the above embodiment, the present invention is provided with a hook-like cut-and-raised portion on the outer peripheral portion of the rotor yoke having the catching head at the upper portion, and an index magnet is fixed to the lower portion of the cut-and-raised portion. Since an index coil in which a coil is wound around a soft magnetic core is disposed below the magnet, an index signal is generated by using a voltage generated in the coil to change a magnetic flux that changes with each rotation of the rotor yoke. Can be generated as In addition, since the hook-like cut-and-raised part at the top of the index magnet acts as a back yoke, unnecessary leakage magnetic flux can be reduced and the influence on the head carriage can be kept low. It is possible to improve the reliability by preventing the occurrence of. Further, since the chucking head can be arranged on the upper portion of the rotor yoke, the manufacturing cost can be reduced as compared with the conventional apparatus in which the rotor yoke and the chucking head are separately configured.
[0017]
In addition, by forming the bowl-shaped cut-and-raised portion to be the same as or slightly larger than the index magnet, unnecessary leakage magnetic flux can be sufficiently reduced, and the index magnet itself is automatically positioned to minimize reluctance. This eliminates the need for expensive jigs and tools for alignment, and reduces equipment costs and work costs. Furthermore, by using a rare earth index magnet, it is possible to realize a highly reliable index generating apparatus with a good SN ratio.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing the overall configuration of a floppy disk device according to an embodiment of the present invention. FIG. 2 is an enlarged view of the spindle motor portion of FIG. FIG. 3 is a schematic view seen from the direction A in FIG. 2. FIG. 4 is a perspective view of the core in the embodiment. FIG. 5 is a schematic diagram showing different arrangements of the core and output waveforms in the embodiment. Description】
DESCRIPTION OF SYMBOLS 1 Rotor yoke 2 Corrugated cut and raised part 3 Index magnet 4 Core 5 Coil 6 Index coil 7 Printed wiring board 8 Chucking head 9 Spindle shaft 10 Hub magnet 11 Drive pin 12 4 Fluoroethylene sheet 101 Base 102 Head carriage 103 Guide rod 104 Step motor 105 Lead screw 106 Spindle motor 107 Front panel 108 Push button 109 Shield cover 110 Eject lever 111 Holder

Claims (3)

An iron rotor yoke having a chucking head for positioning and rotating the recording medium on the top, and a bowl-shaped cut and raised substantially the same as or slightly larger than the index magnet provided on the outer periphery of the rotor yoke and fixed to the lower surface and parts, are arranged and the index magnet is automatically aligned by setting either side of the front and back are magnetized in Table back two-pole on the lower surface portion of the cut-and-raised portion, below the index magnet An index generator having an index coil having a coil wound around a soft magnetic core, and using the change in the magnetic flux of the index coil by the index magnet generated every rotation as the rotor yoke rotates as an index signal. 2. The index generation device according to claim 1, wherein an upper surface of the soft magnetic core is larger than an area of the index magnet facing each other . A floppy disk device comprising the index generation device according to claim 1.

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