JPH0418116Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a magnetic disk device in which magnetic flux from an index magnet does not adversely affect the magnetic properties of a magnetic head.

(Prior Art) A magnetic disk device directly rotates a magnetic disk by a spindle hub drive motor, and writes information signals by sliding a magnetic head on the recording surface of the magnetic disk, and also reads the information signals. The writing and reading of this information signal is started at the detection timing of an index magnet provided on the rotor wheel of the motor.

FIG. 6 shows an example of such a conventional magnetic disk device. In FIG. 6, a shaft 24 is rotatably supported by a bearing 19 on a substrate 18 made of an iron plate, and a rotor wheel 13 is fixedly fixed to the shaft 24.
A spindle hub 11 is integrally fixed above 3. On the inner circumference of the rotor wheel 13,
Although not shown, a rotor magnet is fixed, and the substrate 18 is placed opposite to the rotor magnet.
The rotor wheel 13 is driven to rotate by controlling the supply of electricity to the drive coil 20 disposed above. The rotor magnet, rotor wheel 13, and drive coil 20 constitute a spindle hub drive motor 12. As the rotor wheel 13 is driven to rotate, the spindle hub 11 is driven to rotate, and a magnetic disk (not shown) mounted on the spindle hub 11 is driven to rotate. This magnetic disk has upper carriage 2.
The upper and lower magnetic heads 15 and 16 supported by the lower carriage 23 and the upper and lower magnetic heads 15 and 16 are in sliding contact with the magnetic disk from above and below, so that information signals can be written to and read from the recording tracks of the magnetic disk. It's getting old. A ring-shaped index magnet 14 is fixed to the outer periphery of the rotor wheel 13.
A Hall element 21 is attached to the substrate 18 in close proximity to and opposite to. The index magnet 14 is
As shown in FIG. 7, only a portion of the index portion 2 is magnetized to a different magnetic pole than most of the other portion.
5 is formed, and writing or reading of signals to or from the magnetic disk is started at the timing when the Hall element 21 detects this index portion 25. The magnetic heads 15 and 16 move left and right in FIG. 6 while tracing the recording track of the magnetic disk.

Although it has been conventionally practiced to fix an index magnet piece to a part of the outer periphery of the rotor wheel 13, it is troublesome to adjust the position of the index magnet piece with respect to the rotor wheel.

On this point, in the conventional example shown in FIG. 6, in which a ring-shaped index magnet 14 is attached to the outer periphery of the rotor wheel 13, a part of the index magnet 14 can be removed while observing the index timing. The index portion 25 can be formed by magnetization, and the index portion 25 can be formed without requiring difficult adjustment.

(Problems to be Solved by the Invention) According to the above-mentioned conventional magnetic disk device, the magnetization pattern of the index magnet 14 is mostly uniform, as shown in FIG. Furthermore, if the rotary drive unit of the magnetic disk is made thinner in order to miniaturize the magnetic disk device, it is not possible to provide a sufficient distance between the index magnet 14 and the magnetic heads 15 and 16. Therefore, as shown by the loop-shaped line in FIG.
The magnetic field emitted from the magnetic head reaches the position of the magnetic head 15, 16 and affects the magnetic head 15, 16, deteriorating the magnetic properties of the magnetic head 15, 16. On the other hand, if the magnetization of the index magnet 14 is weakened in an attempt to reduce the influence of the magnetic field from the index magnet 14 on the magnetic heads 15 and 16, the sensitivity of the Hall element for index detection has a limit, and the index It is not preferable to weaken the magnetization of the index magnet 14 because detection becomes difficult.

The present invention was devised to solve the problems of the conventional magnetic disk device described above, and it does not weaken the magnetization of the index magnet.
It is an object of the present invention to provide a magnetic disk device capable of reducing the negative influence of an index magnet on a magnetic head.

(Means for Solving the Problems) The present invention provides a device for attracting magnetic flux generated from the index magnet between the magnetic head and the index magnet and in the vicinity of the index magnet. The present invention is characterized in that the magnet is arranged with its polarity opposite to that of the index magnet.

(Function) The magnetic flux leaving the index magnet and heading towards the magnetic head is drawn into a magnet of opposite polarity to the index magnet before reaching the position of the magnetic head, reducing the magnetic flux density near the magnetic head.

(Embodiment) FIGS. 1 to 5 show an embodiment of the magnetic disk device according to the present invention, and the common components with the conventional example shown in FIGS. 6 to 8 are the same. In the embodiments shown in FIGS. 1 and 2, which are indicated by reference numerals, a ring-shaped magnet 17 is placed on top of the ring-shaped index magnet 14, and is magnetized in the opposite direction to the index magnet 14. The magnet 17 is placed between the index magnet 14 and the magnetic heads 15 and 16 and in the vicinity of the index magnet 14 by overlapping them. Since the magnet 17 is magnetized in the opposite direction to the index magnet 14, the magnetic flux emitted from the index magnet 14 is directed toward the magnetic head, as shown by the looped line in FIG. 15,
On the way to the magnetic head 16, the magnetic flux is drawn into the magnet 17, and the magnetic flux density near the magnetic heads 15 and 16 decreases. Therefore, it is possible to prevent the magnetic flux emitted from the index magnet 14 from having an adverse effect on the magnetic head.

In the embodiment shown in FIG. 3, a non-magnetized zone 28 is formed between a ring-shaped index magnet 14 and a ring-shaped magnet 17 which is magnetized in the opposite direction. With this configuration, the magnetic flux emitted from the index magnet 14 is not drawn into the magnet 17 immediately, but after passing through the non-magnetic band 28, it is drawn into the magnet 17, as shown in FIG. The amount of magnetic flux emitted from the index magnet 14 is large compared to that of the above structure, and it is possible to reduce the decrease in the detection ability of the index magnet by the Hall element.
The magnetic flux emitted from the index magnet 14 toward the magnetic head is drawn into the magnet 17, and the magnetic flux density near the magnetic head decreases.

The present invention is applicable not only to a ring-shaped index magnet but also to a magnet piece fixed to a rotor wheel. FIG. 4 shows an embodiment thereof, in which an index magnet piece 30 is fixed to the outer peripheral surface of the rotor wheel 13.
A reversely magnetized magnet piece 31, which has substantially the same shape as the magnet piece 30 and is magnetized in the opposite direction to that of the magnet piece 30, is fixed to the outer peripheral surface of the upper rotor wheel 13. In this embodiment as well, the reversely magnetized magnet piece 31 is disposed between the index magnet piece 30 and a magnetic head (not shown), and the magnetic flux emitted from the index magnet piece 30 reaches the position of the magnetic head. This prevents it from being drawn into the magnet piece 31 and having an adverse effect on the magnetic head.

(Effects of the invention) According to the invention, a magnet for attracting magnetic flux generated from the index magnet is placed between the magnetic head and the index magnet and in the vicinity of the index magnet. Since the index magnet is arranged with the polarity opposite to that of the index magnet, the magnetic flux density near the magnetic head based on the magnetic flux from the index magnet is reduced, and deterioration of the magnetic properties of the magnetic head can be prevented. Furthermore, since the magnetic flux density near the magnetic head can be reduced without reducing the amount of magnetization of the index magnet, it is possible to prevent a decrease in the detection ability of the magnetic detection element. Further, by arranging the magnet for attracting magnetic flux, the magnetic flux is concentrated on the magnetic detection element, so the magnetic flux density in the magnetic detection element portion is increased, and the signal detection ability of the magnetic detection element is improved.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of an index magnet and a magnet used in a magnetic disk device according to the present invention, and FIG. 2 is a front view showing an example of a magnetic disk device using the same index magnet and magnet. , FIG. 3 is a perspective view showing another example of the index magnet and magnet used in the magnetic disk device according to the present invention, FIG. 4 is a perspective view showing still another example of the index magnet and the magnet, Fifth
The figure is a partially sectional front view showing an example of a conventional magnetic disk device, FIG. 6 is a perspective view showing an example of an index magnet used in the conventional magnetic disk device, and FIG. FIG. 3 is a front view showing the action of the magnet. 11...Spindle hub, 12...Spindle hub drive motor, 13...Rotor wheel, 1
4... Index magnet, 15, 16...
Magnetic head, 17... magnet, 30... index magnet, 31... magnet.

Claims (1)

[Scope of utility model registration request] In a magnetic disk device in which an index magnet is provided on the outer periphery of a rotor wheel of a spindle hub drive motor, the index magnet is located between a magnetic head provided in the magnetic disk device and the index magnet. A magnetic disk device characterized in that a magnet for attracting magnetic flux generated from the index magnet is arranged near the index magnet with a polarity opposite to that of the index magnet.