JP2589705Y2 - Rotor of thin brushless motor with improved inertia - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotor of a thin brushless motor for driving an FD mounted on an FDD device, and more particularly to a rotor having improved inertia.

[0002]

2. Description of the Related Art In a spindle motor for driving an FD mounted on an FDD device, it is necessary to increase the inertia of a rotor in order to improve jitter. As a conventional structure for improving this inertia, there is a structure in which a flange 2 is formed on the outer periphery of a case 1 constituting a rotor as shown in FIG. In the figure, reference numeral 3 denotes a field magnet.

[0003]

However, when the collar 2 is arranged on the outer periphery, the outer periphery becomes large, and when a PG (index pulse) is picked up on the outer periphery, it is difficult to arrange the PG Hall element. That is, if the PG magnet 4 is disposed at the tip of the flange 2 as shown in FIG. 2, the PG cannot be picked up and the attitude of the Hall element 5 becomes a problem, and the PG magnet 6 is disposed on the outer periphery of the case as shown by the imaginary line. In this case, the collar 2 becomes an obstacle and the Hall element 5 cannot be placed. This invention solves the above problems with a simple configuration.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a thin brushless motor rotor comprising a field magnet and a case for holding the field magnet .
The outer periphery is folded back to make it thicker and this thicker part
A notch is provided in a part of the
The magnet is protruded to form a PG magnet .

[0005]

[Function] If the outer periphery of the case is folded back to make it thicker,
With a simple configuration, the inertia during rotation can be increased,
A notch is provided in a part of this thick part, and the notch
Magnet for PG by projecting a field magnet
It can also be used as a unit .

[0006]

FIG. 1 is a sectional view showing an essential part of an embodiment of a rotor of a thin brushless motor according to the present invention.
The rotor comprising the case 11 for holding the field magnet 3 is the same as the conventional one, but is characterized in that the outer peripheral portion 22 is thickened by folding up the flange portion and overlapping it.

When picking up a PG (index pulse), the thickened outer peripheral portion 22 is cut out 22a, and a part of the field magnet 3 is slightly projected to form a PG magnetized portion 23. In the figure, S is an armature.

As the means for increasing the wall thickness, the above-described structure in which the wall is folded and stacked is exemplified. However, it is also possible to make a discard hole for releasing the wall on the upper surface of the thick case material and reduce the upper surface with a press.

[0009]

[Effect of the invention] Since the invention is made as described above, the outer diameter only needs to be increased by the thickness of the plate, and the PG can be sufficiently picked up by a normal Hall element implantation structure. Without increasing the diameter, it is made thick except for the notch.
Magnetic flux can be prevented from leaking.
The field magnet arranged in the notch is for PG
PG is not affected by leakage magnetic flux and large output is obtained.
Therefore, the SN ratio can be improved . Also, as above
If the field magnet arranged in the notch is
Gnet can also be used as
The need for a simple PG magnet is eliminated .

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of an embodiment of a rotor of a thin brushless motor with improved inertia according to the present invention.

FIG. 2 is a sectional view of a main part of a rotor of the motor in which a conventional inertia countermeasure is taken.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Case 2 Flange 3 Field magnet 11 Case 22 Thick outer peripheral part

Claims (1)

(57) [Scope of request for utility model registration] 1. A rotor for a thin brushless motor comprising a field magnet and a case for holding the field magnet, wherein an outer peripheral portion of the case is folded back to increase a wall thickness.
And a notch in a part of this thick part.
The field magnet is projected into this notch.
A rotor for a thin brushless motor with improved inertia, wherein the rotor is a PG magnet .