Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2001-05-15
2002-11-05
Waks, Joseph (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S156050
Reexamination Certificate
active
06476528
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a rotor for a spindle motor having a rotor magnet on its rotor yoke and an index signal output device.
2. Description of Related Art
For a spindle motor which rotates a rotary recording medium such as a floppy disk, one index signal is required per rotation of the disk in order to determine the starting point for writing data or a similar purpose. This index signal is used to detect the rotation of the floppy disk or the motor during the drive of the floppy disk to generate a ready signal for preparation for writing or reading or for the system to start writing upon formatting and stop it after completion of one rotation.
FIGS. 6 and 8
conceptually show the structure of a spindle motor index position detector which detects the index position for the spindle motor by such an index signal. The structure is composed of a reinforcing plate
101
as a metal mount, a circuit board
102
which is superimposed on the reinforcing plate
101
and a rotor yoke
103
constituting the main body of the rotor. The reinforcing plate
101
consists of a metal plate, and integrally provided at three places around the plate are tabs
101
a
which are bent uprightly like the letter L. These tabs
101
a
each have a hole
101
b
for fixing the reinforcing plate
101
on a floppy disk drive case, etc with screws or other fasteners. In addition, at other four places on the periphery of the reinforcing plate
101
are virtually L-shaped chucking claws
101
c
which are standing upright. These claws
101
c
hold the circumference of the circuit board
102
superimposed on the reinforcing plate
101
by pressure from above; application of this pressure is achieved by bending some portion of each of the claws
101
c
horizontally in a dog-legged manner using a tool, as shown in FIG.
7
.
The circuit board
102
consists of an insulating substrate which bears a wiring pattern, components for the spindle motor drive circuit and drive control circuit and so on (not shown in the figures); in the center of the circuit board
102
is a bearing hole
102
a
in which a bearing
104
with a shaft hole
104
a
, which is attached to the reinforcing plate
101
, is protruding upward. On the outer circumference of this protruding bearing
104
is a core
105
having twelve magnetic poles
105
a
spaced at regular intervals. A stator coil
106
is wound around each of the magnetic poles
105
a
. These stator coils
106
constitute three coil sets for three phases U, V and W. These three-phase coil terminals
106
a
and one common coil terminal
106
b are soldered to the right-hand land
102
b
on the circuit board
102
. The core
105
consists of a layered core made by laying a plurality of punched silicon steel plates one on top of another. Also a Hall element
107
for detecting the index position for s rotary recording medium is provided opposite to one of the magnetic poles
105
a
on the circuit board
102
.
As shown in
FIGS. 9 and 10
, the rotor yoke
103
as the main body of the rotor looks like a shallow bowl turned upside down on the circuit board
102
, and has an integral ring flange
103
a
. Attached to the inner circumference of this flange
103
a
is a rubber or plastic rotor magnet
108
which forms a ring. The entire circumference of this ring is divided into equal parts as, for example,
16
poles which are magnetized as S and N poles alternately. In some portion of the flange
103
a
is a window
103
b
with a specified width in which magnets
108
a
and
108
b
as integral parts of the rotor magnet
108
are fitted. These magnets
108
a
and
108
b
are protruding outwards from the outer circumference
103
a
of the flange. Alternatively, the magnets
108
a
and
108
b
may be separate from the rotor magnet
108
and the separate magnet
108
a
may be attached to the outer circumference of the rotor magnet
108
.
A shaft
109
is passed through the center hole of the rotor yoke
103
; the lower half of the shaft
109
can be inserted into the shaft hole
104
a
of the bearing
104
. This enables the rotor yoke
103
to be rotatably mounted on the circuit board
102
, covering the stator coils
106
, as shown in FIG.
3
. The Hall element
107
is located around and opposite to the outer circumference of the flange
103
a
. Although not shown in the figures, a thrust bearing is provided at the bottom of the shaft hole
104
a
and the lower end of the shaft
109
is supported by this thrust bearing. Therefore, the shaft
109
can rotate smoothly while being supported by the shaft hole
104
a
and the thrust bearing. A chuck or similar device is also fitted on the rotor yoke
103
so that the center hub (not shown) of the floppy disk can rest on it and be held in place by it.
In a spindle motor index position detector as mentioned above, when three-phase alternating current from a three-phase AC power supply is supplied to U-phase, V-phase and W-phase stator coils
106
with phase changes in a predetermined order, a magnetic repulsive force is continuously generated between the rotor magnet
108
on the rotor yoke
103
and the coils, which causes the rotor yoke
103
to rotate on the circuit board
102
as part of the stator. The above mentioned electric current changes are performed by making, for example, three Hall elements as position sensors located between the stator coils
106
detect the rotational position of the rotor yoke
103
and using resulting detection signals as current change control signals.
As the rotor yoke
103
of the spindle motor rotates as described above, the magnets
108
a
and
108
b
rotate as well, coming near to or going away from the Hall element
107
. When the Hall element
107
is away from the magnets
108
a
and
108
b
, it is hardly exposed to a magnetic flux generated by the magnets
108
a
and
108
b
and thus the detection output is almost zero. When it comes near to the magnets
108
a
and
108
b
, it is exposed to a magnetic flux from the magnets
108
a
and
108
b
and the detection output increases or decreases depending on the degree of its distance from them. As a result, the detection output Vf from the Hall element
107
is expressed by the equation Vf=k&PHgr;. Consequently, Vf varies in proportion to the amount of magnetic flux inputted to the Hall element
107
as shown in FIG.
11
. The detection output is compared with a predetermined reference voltage; a rectangular pulse signal which depends on the result of this comparison is generated and an index signal is generated, for example, at the time of pulse rise of this signal.
The rotor yoke
103
in combination with the rotor magnets
108
constitutes the rotor of the spindle motor; the rotor magnets
108
are attached to the inside of the rotor yoke
103
by gluing, as mentioned above. However, when a glue is applied to the rotor yoke
103
and the rotor magnets
108
, it may splash over the surrounding area or overflow the area to be glued. In addition, since it takes a considerable time for the glue to set, it is difficult to decide whether the adhesion is perfect or not, from its external appearance.
SUMMARY OF THE INVENTION
This invention solves the above problem. An object of the invention is to ensure that the rotor magnets are securely fixed to the rotor yoke. Another object of it is to provide a spindle motor rotor and an index signal output device that can accurately detect an index signal generated every rotation of the rotor yoke while distinguishing it from other signals and a floppy disk drive which has the rotor and device.
In order to achieve the above objects, according to one aspect of the invention, the spindle motor rotor has: windows at plural places in the flange of the rotor yoke of the spindle motor; projections, integrally provided in some areas of the ring rotor magnet fitted to the inner circumference of the flange, which protrude outwards through the windows, wherein the rotor magnet is joined to the rotor yoke by welding these projections and one of the projections stretches over
Brinks Hofer Gilson & Lione
Waks Joseph
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