JPH04103073A - Magnetic disk driving device - Google Patents

Abstract

PURPOSE:To prevent the generation of an error caused by a leakage flux of an index magnet by placing a yoke for leading a magnetic flux of a magnetic sensor or a magnet to the magnetic sensor, in the vicinity of a position in which the magnet approaches a magnetic head to the utmost by a rotation angle of a rotary member. CONSTITUTION:On a Hall element 23, a yoke 24 for collecting a magnetic flux of a magnet 11 and leading it to the Hall element 23 is provided. Also, the Hall element 23 is placed so as to be opposed to an index magnet 11 in the vicinity right under magnetic heads 3a, 3b, that is, in the vicinity of a position in which the index magnet 11 approaches the magnetic heads 3a, 3b to the utmost by a rotation angle of a rotor yoke 8. Accordingly, the index magnet 11 approaches the magnetic heads 3a, 3b in a period in which read and write of data are not executed, and is separated from the magnetic head in a period in which read and write are executed. In such a way, generation of an error can be prevented surely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic disk drive device that rotates a magnetic disk and records or reproduces information using a magnetic head.

[Prior Art] A representative example of the above-mentioned magnetic disk drive device is a front disk drive device (hereinafter abbreviated as FDD) that performs recording and playback on a floppy disk as a magnetic recording medium. , so-called index detection is performed to detect a predetermined rotational position corresponding to the start point of a track on the disk.

As an index detection method in conventional FDD,
Magnetic detection methods are generally used because of their low cost and high reliability. In this case, in the case of a type in which the rotational driving force of a spindle motor that rotationally drives a disk is transmitted via a belt, an index magnet for index detection is fixed to a predetermined part of the outer circumference of the spindle motor boob on which the belt is applied. Ru. In addition, D
In the D motor type, an index magnet is fixed to a predetermined portion on the outer periphery of the rotor yoke of the motor. A magnetic sensor is provided at a position facing the index magnet according to a predetermined rotation angle of the pulley or rotor yoke, and index detection is performed by detecting the index magnet with this magnetic sensor.

[Problems to be Solved by the Invention] However, as FDDs have become smaller and thinner in recent years, the spindle motor's booster or rotor yoke is provided quite close to the magnetic head. There was a problem in that the index magnet came very close to the magnetic head due to the rotation angle of , and the leakage magnetic flux jumped into the magnetic head, causing read/write errors.

Therefore, an object of the present invention is to make it possible to prevent the above-mentioned error from occurring in this type of magnetic disk drive device.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a magnetic disk drive device that rotationally drives a magnetic disk to record or reproduce information using a magnetic head. A magnet is fixed to a rotating rotating member,
In a magnetic disk drive device that detects a predetermined rotational position corresponding to the start point of a track on a magnetic disk by detecting the magnet with a magnetic sensor, the rotation angle of the rotating member determines the position where the magnet approaches the magnetic head most. A configuration is adopted in which a yoke for guiding the magnetic flux of the magnetic sensor or the magnet to the magnetic sensor is arranged nearby.

[Operation] According to this configuration, the rotational position is detected at the timing when the magnet approaches the magnetic head closest to the rotational angle of the rotational member. Generally, no data is read or written for a predetermined period before or after the detection of the rotational position. In other words, the magnet approaches the magnetic head during the period when no data is read or written, and the magnetic head approaches the magnetic head during the period when data is read or written. will be separated from.

[Example] Hereinafter, details of embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a plan view of a direct drive motor (hereinafter simply referred to as a motor) for rotationally driving a disk of a 3.5-inch FDD according to an embodiment of the present invention, and FIG. 2 is a side sectional view.

In both figures, reference numeral 1 indicates the base of the FDD, which is made of a sheet metal such as aluminum or iron. Further, reference numeral 2 denotes a metal board that serves both as a motor frame and a circuit board. The metal substrate 2 usually uses an iron plate or a silicon steel plate as a base material,
An insulating coating is applied on top of that, and then a circuit wiring pattern is printed on top of that. Electronic components (not shown) constituting a drive control circuit for driving the motor are soldered onto the board 2 .

The substrate 2 has fixed reference surfaces 1a and 1b formed by raising the bottom of the base 1 by half punching or drawing.

It is fixed to the back side of lc and 1d with screws 16. By doing this, the board 2 can be attached without protruding from the bottom surface of the base 1. Further, when the convex portions 2a and 2b formed on the substrate 2 are attached to the base 1 in the lateral direction, the convex portions 2a and 2b formed on the substrate 2 are located between the reference surfaces 1e and le', and between the reference surfaces 1e and 1f,
If', the substrate 2 is positioned laterally.

In the base 1, reference numerals 1a' and lb'lc' are retainers for removing the rotor yoke 8 of the motor, which are formed by bending a part of the base 1, and each upper surface has a floppy disk (not shown) attached to the rotor yoke. It has a disc holder to prevent it from rubbing against the 8.

Next, in FIG. 2 and FIG. 3, which is an enlarged sectional view of the main parts of the motor, reference numeral 4 is a spindle shaft which is the rotation axis of the motor, and the rotation center of the rotor yoke 8 is the rotation center of the center hub 15 of the floppy disk. Become.

The spindle shaft 4 is a ball bear nong (hereinafter referred to as
It is rotatably supported by a bearing (abbreviated as bearing) 5.5'.

The bearing 5.5° is fitted into the housing 6, and the respective outer rings 5a and 5a' are fixed to the housing 6 by push-in adhesive or the like, and the ring-shaped protrusion 6C formed on the inner peripheral surface of the housing 6 The spacing between the outer rings 5a, 5a' is regulated to a predetermined value. In addition, the inner rings 5b, 5b'
A wave washer-like preload spring 19 is sandwiched between them. The spindle shaft 4 is fitted inside the inner rings 5b and 5b' and is rotatably supported.

The spindle shaft 4 is inserted into and removed from the inner rings 5b and 5b'.

Next, the upper part of the spindle shaft 4 has an outer peripheral part 7 on the upper surface.
A flange 7, which is a disk-shaped rotating member, is fixed by a method such as press fitting, and a is a mounting surface (mounting surface) for the hub 15 of the disk, and a ferromagnetic material such as iron is attached to the outer periphery of the flange 7. A disc-shaped rotor yoke 8 consisting of a rotor yoke 8 is fitted into the flange 7 and fixed by caulking or the like, and is integrated with the flange 7.

On the lower surface of the outer periphery of the rotor yoke 8, there are a drive magnet 9 for generating the driving force of the motor, an FG magnet 10 constituting an FG (frequency generator) that generates a signal with a frequency corresponding to the rotational speed of the motor, and An index magnet 11 is fixed thereto for performing the aforementioned index detection by acting on a Hall element 23, which is a magnetic sensor, to generate an index detection signal.

The rotor yoke 8 is biased downward in FIG. The flange 7 is pulled downward, thereby coming into contact with the inner ring 5b of the bearing 5 and pressing it down. In this way, the urging force applied to the flange 7 applies a downward thrust load to the inner ring 5b, and the thrust load is applied to the lower bearing 5 via the preload spring 19.
It is transmitted to the inner ring 5b' of the angle and is also applied to the inner ring 5b'. Relatively speaking, an upward thrust load is applied to the outer rings 5a, 5a. The bearing 5.5'' is preloaded by this thrust load, and play is removed, and the flange 7 comes into contact with the inner ring 5b, so that the spindle shaft 4 is positioned and held in the thrust direction.

The spring force of the preload spring 19 is about half of the force that urges the flange 7 downward, and
Set to a value that ensures rigidity. In this way, the thrust load can be balanced by 5.5 degrees between the two bearings, resulting in a bearing mechanism that does not cause unnecessary loss. however,
The spring force of the preload spring 19 may be made sufficiently larger than the biasing force, so that the flange 7 is always positioned at a fixed position in the thrust direction (vertical direction in FIG. 3) regardless of the magnitude of the biasing force. , has the advantage that its position does not change and the rigidity of the bearing increases.

Further, the preload spring 19 may be a coil spring or other elastic member.

Next, the outer peripheral part of the disc-shaped rotor yoke 8 is bent into an L-shape, and a ring plate-shaped auxiliary yoke 8' is stacked and fixed on the inside of the vertical part of the bent part 8a, and a drive magnet 9 is attached to the inside of the ring plate-shaped auxiliary yoke 8'. is fixed. The auxiliary yoke 8' prevents the rotor yoke 8 from being magnetically saturated, and also prevents the magnetic flux caused by the drive magnet 9 from leaking outward from the outer circumference of the rotor yoke 8, that is, the arms 3c and 3d of the head carriage.
This is provided to prevent leakage to the magnetic helads 3a and 3b supported by the magnets, and is made of a ferromagnetic material such as iron.

Conventionally, in order to prevent the above-mentioned magnetic saturation and magnetic flux leakage, the first
The entire rotor yoke was made thicker as shown by reference numeral 84 in FIG. In contrast, in this embodiment, the outside of the drive magnet 9 is covered and the magnetic head 3a is
By providing the auxiliary yoke 8' overlapping the bent portion 8a on the outer circumference of the rotor yoke 8 close to 3b, the cross-sectional area of the magnetic path in the particularly problematic part is increased (and the above-mentioned The problems of magnetic flux leakage and magnetic saturation can be prevented. Furthermore, by making the rotor yoke 8 thinner, the entire motor can be made thinner, which can contribute to making the FDD thinner.

The auxiliary yoke 8' may be fixed to the outside of the vertical portion of the bent portion 8a of the outer circumferential portion of the mouth-to-mouth yoke 8, as shown in FIG. Further, as shown in FIG. 5, the bent portion 8a is formed as an auxiliary yoke, separate from the main body of the rotor yoke 8, and thicker than the main body, and is fixed to the main body of the rotor yoke 8 by caulking or other methods. A similar effect can be obtained.

On the other hand, the drive magnet 9 is formed in a ring shape, and is magnetized in the circumferential direction with about 8 to 16 poles of S, N, and S-. A salient pole type iron core yoke 12 is provided parallel to the rotor yoke 8, facing the inner periphery of the drive magnet 9. The iron core yoke 12 is usually formed with about 6 to 18 salient poles, and a well-known current switching circuit in which a coil 13 is wound around each of the salient poles is used to energize and excite the coil 13. By switching, the magnet 9 rotates due to the attraction and repulsion of the electromagnetic force acting between the coil 13 and the magnet 9, and the rotor 8, flange 7, and shaft 4 rotate together with it.

Next, the FG magnet 10 is formed of a rubber-based ferrite magnet or the like, and is multi-polarized with several tens of poles over the entire circumference. Wiring of an FG pattern (not shown) is provided on the upper surface of the metal substrate 2 at a portion facing the FG magnet 10, and as the motor rotates, a signal with a frequency corresponding to the rotational speed is generated in the FG pattern6. Next, the index magnet 11 is attached to the rotor yoke 8
It is fixed to a predetermined portion of the outer peripheral edge of the lower surface of the bent portion 8a, and acts on the Hall element 23, which is a magnetic sensor provided on the substrate 2, and thereby corresponds to the starting point of the track on the disk as described above. Index detection is performed to detect a predetermined rotational position. A yoke 24 is provided on the Hall element 23 to collect the magnetic flux of the magnet 11 and guide it to the Hall element 23. The yoke 24 is not necessarily necessary, as long as the leakage magnetic flux that can be detected by the Hall element 23 can be obtained from the magnet 11 even in yaw.

Here, the Hall element 23 is arranged so as to face the index magnet 11 in the vicinity of the magnetic head 3a, 3b, that is, in the vicinity of the position where the index magnet 11 approaches the magnetic head 3a, 3b closest due to the rotation angle of the rotor yoke 8. has been done. Due to this arrangement of the Hall element 23.

It is possible to prevent read/write errors from occurring due to leakage magnetic flux from the index magnet 11. The reason for this will be explained below.

If the index magnet 11 is magnetized along the radial direction of the rotor yoke 8 as shown in FIG.
1 tends to jump in when it approaches the magnetic heads 3a, 3b.

However, in the track of a magnetic disk, a predetermined area before and after the position of the rotation angle that matches the index magnet 11, the so-called index position, is not used for data recording.For example, in a normal 3.5-inch FDD, the disk rotation speed is 1. In the case of a rotation of 200 m5, there is no data recording area until a rotation angle of about 2.5 ms after the index position, and there is no data recording area before the index position until a rotation angle of about 12 ms. That is, Hall element 2
No data is read or written during a period of 14.5 ms before and after the index detection time when the index magnet 11 is detected by the index magnet 11.

Therefore, if the Hall element 23 is arranged as described above, index detection is performed at the timing when the index magnet 11 rotates closest to the magnetic heads 3a and 3b, and at that time, the leakage magnetic flux from the index magnet 11 is transferred to the magnetic head 3a. , 3b, since it is within the 14.5 ms period before and after index detection during which no data is read or written, no read/write error occurs due to the influence of the leakage magnetic flux.

In addition, reading and writing are performed outside the 14.5 ms period, but at that time the index magnet 11 is separated from the magnetic heads 3a and 3b, and the influence of leakage magnetic flux of the index magnet 11 can be almost ignored, and errors caused by it can be ignored. There have been no outbreaks.

In short, the index magnet 11 is inserted into the magnetic head 3 during the 14.5ms period when no data is read or written.
a, 3b, and is separated from the magnetic head during the reading/writing period, thereby reliably preventing the occurrence of the above-mentioned error.

Note that the Hall element 23 is placed at a position shifted from the position shown in FIG. 3, and the yoke 24 is placed at the position shown in FIG.
Alternatively, the index magnet 11 may be formed in a shape that draws magnetic flux from the illustrated position to the Hall element 23. Alternatively, the index magnet 11 may be formed in the vicinity of the magnetic heads 3a, 3b within a period of 14-5 ms before and after index detection in the same manner as above. This will also prevent errors from occurring.

Further, FIG. 6 shows a case where the index magnet 11 is magnetized in the vertical direction. In this case, the tip of the yoke 24 is located near directly below the magnet 11, and the magnetic flux is transmitted from directly below the magnet 11 to the Hall element 23. It is bent into a crank shape so that it can be pulled upward. In this way, leakage magnetic flux toward the magnetic heads 3a, 3b is reduced, and errors can be more reliably prevented from occurring. Note that in this case, the Hall element 23 does not necessarily need to be placed directly below and near the magnetic head.

Next, the iron core yoke 12 is fixed on the flange 6a formed in the housing 6 in the configuration shown in FIG.

For this fixing, a female threaded screw hole 12a is formed in the inner circumference of the disk-shaped iron core yoke 12, and a corresponding screw hole 2C16b is formed in the flange of the board 2 and the housing 6. The iron core yoke 12 is fixed on the substrate 2 together with the housing 6 by inserting the screw 17 into the screw hole 2C16b and tightening it into the screw hole 12a.

According to this fixing structure of the iron core yoke 12, since the screw hole 12a is female threaded, the iron core yoke 12 can be fixed without using a nut, and the nut protrudes onto the iron core yoke 12. Never.

This allows the drive bin 14 to be avoided, which is advantageous for making the FDD thinner.

In other words, in a 3.5-inch FDD, the drive pin 14 that transmits rotational force to the disk is located at a location offset from the rotation center of the motor, and as shown in FIGS. If the drive pin engaging hole 15a of the hub 15 is not directly above the drive pin 14 during kinging, the drive pin 14 is pushed downward by the hub 15 and falls as shown by the two-dot chain line in FIG. Therefore, a space is required on the iron core yoke 12 to avoid the drive bin 14. If the nut does not protrude above the iron core yoke 12 as described above, the height of the space can be reduced accordingly, which is advantageous for making the FDD thinner.

Next, the chucking mechanism of the FDD will be explained with reference to FIGS. 7 to 9. Figure 7 is a bottom view of the main parts of the chucking mechanism.
FIG. 8 is a sectional view taken along line aa' in FIG. 7, and FIG. 9 is a top view.

The drive bin 14 shown in its entirety in FIG.
0 and an arm part 141 continuous to the lower end thereof, and the whole is integrally molded. The left end of the arm portion 141 in the figure is rotatably supported by a shaft 18 caulked to the rotor yoke 8, so that the drive bin 14 as a whole rotates in the directions of arrows A and B in FIG. 7 about the shaft 18 as a fulcrum. possible.

Further, in the arm portion 141, a portion near the base end (near the axis 18 of the rotational fulcrum) indicated by reference numeral 14a is a thin hinge portion that can be elastically deformed only in the vertical direction toward and away from the rotor yoke 8. The portion other than the portion 14a is a rigid body.

From the hinge part 14a of the arm part 141 to the bottle main body 140
The side parts were originally formed with an upward slope of several positions,
The hinge portion 14a is lightly biased upward by the spring force of the hinge portion 14a, and is pressed against the rotor yoke 8. Due to the upward biasing force, the bottle main body 140 protrudes from the hole 8b formed in the rotor yoke 8 to the upper surface of the rotor yoke 8.

When chucking a floppy disk, the hub 15 of the disk is first placed on the rotor yoke 8 (on the flange 7), and the spindle shaft 4 is fitted into the center hole 15b of the hub 15 as shown in FIG. At this time hub 15
If the position of the drive bin engagement hole 15a is misaligned with the drive bin 14, the hub 15 will push down the bin body 140, bend the hinge part 14a, and the entire drive bin 14 will be
It goes down to the position indicated by the two-dot chain line in the figure.

Thereafter, as the motor rotates, the drive bin 14 comes directly under the hole 15a, and the spring force of the hinge part 14a causes the drive bin 14 to return upward, and the bin body 140 enters the hole 15a, and the outer periphery of the bin body 140 14e comes into contact with the edge of the hole 15a,
The rotational force of the motor is transmitted to the hub 15 to rotate the disk.

Here, the drive bin 14 is made of a rigid body except for the hinge part 14a, and the hinge part 14a only elastically deforms in the vertical direction. The arm portion 141 is not twisted or elastically deformed backward in the rotational direction, and the outer peripheral portion 14 is not twisted by the rotational torque of the motor (rotational torque of the rotor yoke 8).
e presses the edge of the hole 15a with force Fl. Then, the drive pin 14 is pressed toward the outer circumferential side of the rotor yoke 8 by the component force of the reaction force in the outer circumferential direction of the rotor yoke 8, and the force is pushed toward the outer circumferential side of the rotor yoke 8.
The outer peripheral portion 14f contacts and presses the edge of the hole 15a. This pressing force F2 is expressed by the following formula: F2=F1tanθ-α. Note that the angle θ is an angle formed by the center of the bottle body 140 and the center of the spindle shaft 4 with respect to the center 0 of the shaft 18. Further, a is the frictional force between the rotor yoke 8 and the drive bin 14, and the upward pressing force of the drive bin 14 against the rotor yoke 8 is reduced, and the drive bin 14 is made of a material with good sliding properties, such as polyacetal resin. If formed, the value will be almost negligible.

As the drive pin 14 pushes the hub 15 outward with this force F2, the two sides of the center hole 15b of the hub 15 abut and engage with the two points 4a and 4b of the spindle shaft 4, and centering of the disk is performed. , the disk is retained. That is, chucking is completed. Drive bin 14 as above
Since the arm portion 141 does not twist or elastically deform backward in the direction of rotation, the centering operation described above is performed reliably and chucking is performed reliably.

In this way, the drive bin 14 of this embodiment is capable of reliably centering and reliably chucking with an extremely simple configuration of the chucking mechanism that uses only the drive bin 14 and does not use any other spring members. This corresponds to a combination of the five members 104 to 108 of the conventional example shown in FIGS. 11 and 12, and the number of parts can be significantly reduced and the cost of the FDD can be reduced.

Since the drive bottle 14 is molded with a molding material, it can be shaped freely, and as shown in FIG. 8, obliquely tapered portions 14b and 14c are formed on the bottom and top surfaces of the bottle body 140. By doing this, the drive bin 14 can be
By forming the tapered portion 14b when the drive pin 14 is pressed down by the hub 15, the amount of downward protrusion from the rotor yoke 8 can be reduced in proportion to the amount of descent of the drive pin 14, and moreover, the tapered portion 14W is formed. Accordingly, the bottle body 140
When pushed downward, the top surface becomes horizontal, making it possible to reduce the amount of descent required.

In this way, the amount of descent of the drive bin 14 can be reduced, and the amount of downward protrusion from the rotor yoke 8 during descent can be reduced.
The vertical distance between the rotor yoke 8 and the iron core yoke 12 can be reduced, making the entire motor thinner and allowing FDD
This can contribute to making the product thinner.

Furthermore, by cutting the portion 14d on the outer periphery of the pin body 140, the inner width of the rotor yoke 8 can be increased and the workability of the rotor yoke 8 can be improved.

Further, the outer circumferential portions 14e and 14f of the bottle main body 140 that come into contact with the edge of the hole 15a may be formed flat since the rounded portions are likely to wear out.

According to the above embodiment, the Hall element 2
3 or yoke 24 directly below the magnetic heads 3a, 3b (the index magnet 11 is located near the magnetic heads 3a, 3b).
By arranging the index magnet 11 (near the position closest to the index magnet 11), it is possible to prevent read/write errors from occurring due to leakage magnetic flux from the index magnet 11. Furthermore, even if the rotor yoke 8 is provided close to the magnetic heads 3a, 3b, the above-mentioned read/write errors can be prevented from occurring, which can contribute to making the FDD thinner.

[Effects of the Invention] As is clear from the above description, the present invention provides a magnetic disk drive device that rotates a magnetic disk and records or reproduces information using a magnetic head, which rotates together with the magnetic disk. In a magnetic disk drive device, a magnet is fixed to a rotating member, and a predetermined rotational position corresponding to the start point of a track on a magnetic disk is detected by detecting the magnet with a magnetic sensor. A configuration is adopted in which a yoke that guides the magnetic flux of the magnetic sensor or the magnet to the magnetic sensor is arranged near the position closest to the magnetic head, so that reading/writing errors due to leakage magnetic flux from the magnet are reliably prevented. This provides an excellent effect in that it can be prevented and contribute to making the magnetic disk drive device thinner.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a spindle motor for FDD according to an embodiment of the present invention, Fig. 2 is a side sectional view of the same motor, Fig. 3 is an enlarged view of main parts of Fig. 2, and Figs. 4 and 5 are 6 is a side sectional view showing different structural examples of the outer circumference of the rotor yoke, FIG. 6 is a side sectional view showing different structural examples of the index detection section, FIG. 7 is a bottom view of the main part of the chucking mechanism, and FIG. a-a of
9 is a top view illustrating the action of the chucking mechanism, and FIG. 10 is a sectional side view of a main part of a rotor yoke of a conventional FDD motor. 1--Base 2--Metal substrate 3a, 3b
--Magnetic head 4 --Spindle shaft 5.5' --Bearing 6 --Housing 7 --Flange 8 ---
Rotor yoke 8'... Auxiliary yoke 9 - Drive magnet 10... FG magnet 11 - Index magnet 12 - Salient pole type iron core yoke 13... Coil 14 - - Drive bin 15 -
... Disc center hub 19 ... Preload spring 23 ... Hall element 24
-・- Yoku patent applicant Canon Electronics Co., Ltd. 31. Y) Is the lower button of the 1st part of Fuiso old figure 7 a-a' dark side? Figure 8 Figure 9

Claims (1)

[Scope of Claims] 1) A magnetic disk drive device that records or reproduces information using a magnetic head by rotating a magnetic disk, in which a magnet is fixed to a rotating member that rotates together with the magnetic disk, and the magnet is In a magnetic disk drive device that detects a predetermined rotational position corresponding to a starting point of a track on a magnetic disk by detecting it with a sensor, the magnetic disk is positioned near a position where the magnet approaches the magnetic head closest to the magnetic head due to the rotation angle of the rotating member. A magnetic disk drive device characterized by disposing a sensor. 2) A magnetic disk drive device that rotationally drives a magnetic disk to record or reproduce information using a magnetic head, in which a magnet is fixed to a rotating member that rotates with the magnetic disk, and the magnet is detected by a magnetic sensor. In a magnetic disk drive device that detects a predetermined rotational position corresponding to a starting point of a track on a magnetic disk, the magnetic flux of the magnet is directed to a position near a position where the magnet approaches the magnetic head according to a rotation angle of the rotating member. A magnetic disk drive device characterized in that a yoke is arranged to guide the sensor.