JPH01129745A - Motor for disk drive unit - Google Patents

Abstract

PURPOSE:To obtain a signal of multipulse per rotation, by providing a rotor frame having an uneven disk part and providing a flux variation detection type index sensor facing the rotor frame and fitted to a bracket. CONSTITUTION:A rotor frame A 4a made of a ferromagnetic material comprises a cylindrical part 32 and a disk part A33. Provided on the circumference of the disk part A33 are a large number of recessed and projected parts 31 for index pulses. An index sensor 30 for generating a signal of multipulse per rotation in accordance with the flux variations is fitted to a bracket 11, facing the parts 31 for the index pulses. The rotor frame 4Aa is made of a ferrous sintered alloy, and the parts 31 for the index pulses are accurately made by a metal mold.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a motor for a disk drive device using a brushless motor for rotationally driving a magnetic disk of a magnetic disk device.

BACKGROUND OF THE INVENTION In recent years, brushless motors for magnetic disks are required to have high precision, high quality, and miniaturization.

Hereinafter, the conventional brushless motor mentioned above will be explained with reference to the drawings.

FIG. 4 shows a cross-sectional view of a conventional brushless motor. In FIG. 4, 1 is a motor shaft, 2 is a hub fixed to the shaft 1, 3 is a ring-shaped rotor magnet, and 4 is a rotor frame that fixes the rotor magnet 3, and is fixed inside the hub 2. There is. 5 is a stator core provided at a position facing the rotor magnet 3, and 6 is a winding wound around the stator core 5. 1
Reference numeral 1 denotes a bracket, which has a cylindrical portion 12 extending in the axial direction at the center. The core 5 is fixed to this cylindrical portion 12. Further, a stator board 10 is attached to the bracket 11, and the stator board 10 has a position detection element 16 for controlling the excitation of the winding 6 and an index magnet 17 provided around the open end of the hub 2. 1 in the opposite position of
Hall IC for obtaining index signal of rotation pulse
l3 is located.

A lower bearing 8 and an upper bearing 7 are formed in the cylindrical portion 12 of the bracket 11 at positions separated from each other in the axial direction, and a preload spring 9 applies preload to the lower bearing 8 and the upper bearing 7. 22 is a magnetic fluid seal, which includes a seal yoke 13 made of two ferromagnetic materials, a seal magnet 14 placed between the seal yokes 13, and a magnetic fluid 15 injected into the gap between the shaft l and the seal yoke 13. This prevents dust from entering through the upper bearing 7,
This prevents grease from scattering from the bearings 7 and 8. 19 is a rotor boss fixed to the shaft 1 by press fitting, adhesive, etc. 20 is the earth pole, shaft 1
is press-fitted into the Reference numeral 21 denotes a disk tightening screw hole provided in the hub 2, which is provided for tightening a disk (not shown).

Problems to be Solved by the Invention Magnetic disk drives are moving toward higher density and faster access, and one of the problems with this is thermal off-track, in which the track position shifts when the temperature changes. In order to increase the density, the track density is determined by thermal off-track, so it is necessary to improve this thermal off-track. In the past, measures were taken to match the expansion coefficients of base plates, magnetic disks, gimbal arms, head drive steel belts, etc., but recently, in order to increase density, methods of electrically correcting track positions have been considered. It is being - For example, there is a method called index burst servo in which servo information is written on each track only once per revolution to position the head.

The index burst servo mentioned earlier is a simple method that does not require complicated electronic circuits, but on the other hand,
Since there is servo information only once per rotation, there are problems such as a long positioning time.Recently, a servo method called servo surface servo has been used as a way to achieve both high density and high-speed access. .

In order to perform servo surface servo, it has become necessary to detect a signal with multiple pulses per revolution from a rotor section that rotates in synchronization with the disk in order to write servo information on the servo-dedicated disk surface. However, in the conventional configuration, the index magnet 17 is attached to the end face of the hub 2 and the hole 1c1 is attached to the stator board 10 on the bracket.
8, an index pulse signal generated once per rotation was obtained and this signal was used as servo information.

In order to obtain a signal with multiple pulses per rotation, a large number of index magnets 17 are required, which makes the installation complicated, and also has problems such as poor installation accuracy and workability. The information magnetically recorded on the disk becomes demagnetized by the magnetic flux leaking from the motor, making it impossible to reproduce the recorded information.
Also, there were other problems such as a decrease in the reliability of playback.

Furthermore, with the trend toward smaller and thinner magnetic disks, Hub 2
As the thickness of the closed end side becomes thinner, the depth of the screw hole 21 for tightening the disk holding plate that fixes the disk with the screw becomes too deep (there is a problem that the tightening strength is insufficient. Since the screw holes are not penetrating, processed metal powder tends to accumulate in the screw holes during screw hole machining (there were problems such as cleanliness contamination and foreign matter entering the equipment).

Means for Solving the Problems In order to solve the above problems, the motor of the present invention is a disk drive motor equipped with at least one disk having an opening in the center, which includes a rotatably supported shaft; a hub that is fixed to the shaft and has a portion to which the disk is attached; a winding that is wound around the stator core and rotates the rotor when energized; and a bracket that has a cylindrical portion that supports a bearing and extends in the axial direction; a magnetic fluid seal provided on the upper part of the cylindrical portion of the bracket and configured to face the outer periphery of the shaft; a stator board on which electronic components are mounted and attached to the bracket; and the hub. a cylindrical part made of a ferromagnetic material that is attached to the cylindrical part and holds a rotor magnet therein; and a disc-shaped part extending radially from one end of the cylindrical part and having an uneven part for obtaining an index pulse. and a magnetic flux change detection type index sensor attached to the bracket to face the rotor frame.

Further, in the above configuration, the rotor frame includes a cylindrical part that is attached to the hub and is made of a ferromagnetic material and holds the rotor magnet inside, and a cylindrical part that extends in the center radial direction from one end of the cylindrical part and is provided on the hub. It has a structure of a disc-shaped part that is brought into close contact with one end of a screw hole that passes through the disc to fix it.

Function The present invention has a cylindrical portion that is attached to the hub as described above and serves as a magnetic path of the ferromagnetic material that holds the rotor magnet in the inner ring, and an index pulse that extends in the radial direction from one end of the cylindrical portion. By configuring a rotor frame consisting of a disk-shaped part having an uneven part to obtain a magnetic flux change, and a magnetic flux change detection type index sensor that faces the rotor frame and is attached to a bracket, a magnetic flux change detection type index sensor is installed. An index pulse can be obtained by changing the interlinking magnetic flux of the detection coil wound around the index sensor due to the unevenness of the disk-shaped portion of the rotor frame. By providing the concavo-convex portion in the disk-shaped portion of the rotor frame in this way, a signal with multiple pulses per revolution can be obtained.

Further, since the disk-shaped portion extends in the radial direction from one end of the cylindrical portion of the rotor frame, magnetic flux leaking from the motor can be shielded.

Furthermore, one side of the screw hole is sealed by extending from one end of the cylindrical portion of the rotor frame to the disk-shaped portion in the center radial direction and closely contacting one end surface of the through screw hole that fixes the disk provided on the hub. Can be done.

EXAMPLE Hereinafter, a brushless morph according to a first example of the present invention will be described with reference to the drawings.

FIG. 1 shows a sectional view of a brushless morph in an embodiment, and FIG. 2 shows an embodiment of a rotor frame of the present invention.

In the figure, 4a is a rotor frame A made of a ferromagnetic material, and is composed of a cylindrical portion 32 and a disk-shaped portion A33. Further, the outer periphery of the disc-shaped portion A33 is provided with a large number of concave and convex portions 31 for detecting index pulses, and the bracket 11 is provided with an index that generates an output according to changes in magnetic flux in order to obtain a signal of multiple pulses per rotation. A sensor 30 is attached opposite to a concavo-convex portion 31 for detecting an index. Further, the rotor frame A4a is made of an iron-based sintered alloy material, and the concave and convex portions 31 for index detection are obtained with high precision by a mold. The brushless morph of this embodiment shown in FIG. 1 basically has the same configuration as the conventional brushless morph shown in FIG. 4, so the same components are given the same numbers and will not be described in detail. omitted.

FIG. 3 shows a cross-sectional view of a brushless morph in a second embodiment of the invention. In the same figure, 21a
2b is a hub B having a screw hole 21a for tightening the disk.

4b is a rotor frame B consisting of a cylindrical portion 32 made of a ferromagnetic material attached to the hub B and a disk-shaped portion B34 extending inward in the center radial direction from one end of the cylindrical portion 32; The shaped portion 34 seals one end surface of the disk fastening screw 21a through which it passes. The other components have the same configuration as the brushless morph of this embodiment shown in FIG. 1, so the same components are given the same numbers and detailed explanations are omitted.

Effects of the Invention As described above, the present invention has a cylindrical portion that is attached to a hub and is made of a magnetic path made of a ferromagnetic material that holds a rotor magnet inside, and a cylindrical portion that extends in the radial direction from one end of the cylindrical portion.・Constructs a rotor frame having a disk-shaped portion having an uneven portion for obtaining pulses, and a magnetic flux change detection type index sensor attached to a bracket in opposition to the uneven portion of the disk-shaped portion of this rotor frame. By doing so, it is possible to easily obtain a signal with multiple pulses per revolution. Furthermore, since the shape of the uneven portion can be manufactured using a mold, the pitch, width, and depth of the uneven portion can be determined with high accuracy. Furthermore, since the disc-shaped portion of the rotor frame having the uneven portion extends in the radial direction, it also has the effect of shielding magnetic flux leaking from the motor. In this way, the servo information for the multiple pulses per revolution required for the servo surface servo method of magnetic disk drives can be obtained with a simple and accurate configuration, and leakage magnetic flux from the motor can be reduced, resulting in improved reliability. We can provide expensive equipment.

Furthermore, the cylindrical shape of the rotor frame, and the disk-shaped part extending inward in the center radial direction from one end of the part is in close contact with one end surface side of the through-hole disc tightening screw hole provided in the hub, and the disc-shaped part extends inward in the center radial direction from one end of the rotor frame. By sealing one side of the motor, it is safe to prevent metal debris generated when the disk is tightened from entering the motor, and it is also possible to prevent cleanliness and contamination around the disk and head. In addition, since the screw hole for tightening the disk goes through the hub when it is a single hub, the cleaning effect is sufficient and the problem of metal debris easily accumulating during screw hole machining can be solved.

Furthermore, it is economically advantageous to manufacture the rotor frame from a ferrous sintered alloy.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the present invention, FIG. 2 is a perspective view of a rotor frame of an embodiment of the invention, FIG. 3 is a sectional view of a second embodiment of the invention, and FIG. 4 is a sectional view of a conventional example. 1...Shaft, 2a...Hub A12
b...Hub B13...Rotor magnet, 4 a.Old...Rotor frame A14b...
・Rotor frame B15...Stator core, 6
...Winding, 7...Top bearing, 8
...Lower bearing, 10...Stator board, 11...Bracket, 21,218.
Old...screw hole for disc tightening, 22...magnetic fluid seal, 30...magnetic flux change detection index sensor, 31...irregularities, 32...・
・Cylindrical part, 33...Disc-shaped part A13
4...Disc-shaped part B0 Name of agent Patent attorney Toshio Nakao 1 person Figure 2 , 3

Claims (3)

[Claims] (1) A motor for a disk drive device equipped with at least one disk having an opening in the center, including a shaft rotatably supported by a bearing, a hub fixed to the shaft and having a portion for attaching the disk, and a stator core. a bracket having a cylindrical part extending in the axial direction that supports the bearing; a cylindrical part extending in the axial direction that supports the bearing; a ferrofluidic seal configured to face the
a stator board attached to the bracket on which electronic components are mounted; a cylindrical part made of a ferromagnetic material that holds a rotor magnet inside and attached to the hub; and an index extending radially from one end of the cylindrical part. - A motor for a disk drive device comprising a rotor frame consisting of a disk-shaped portion having an uneven portion for obtaining pulses, and a magnetic flux change detection type index sensor attached to the bracket facing the rotor frame. . (2) The motor for a disk drive device according to claim 1, wherein the rotor frame is made of a ferrous sintered alloy. (3) A disk drive motor equipped with at least one disk having an opening in the center, including a shaft rotatably supported by a bearing, and one or more penetrating motors fixed to the shaft and fixing the disk. A hub having a screw hole, a winding wound around a stator core and rotating the rotor when energized, a bracket having a cylindrical portion supporting the bearing, and a cylindrical portion extending in the axial direction of the bracket. a magnetic fluid seal provided on the upper part and configured to face the outer periphery of the shaft; a stator board on which electronic components are mounted and attached to the bracket; and a stator board attached to the hub and holding a rotor magnet inside. A cylindrical part made of a ferromagnetic material, and a disc-shaped part that extends from one end of the cylindrical part in the center radial direction and closes and closes one end surface of a through screw hole provided in the hub and that fixes the disk. A disk drive motor with a rotor frame.