Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2002-06-10
2003-08-19
Le, Dang Dinh (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C384S107000
Reexamination Certificate
active
06608415
ABSTRACT:
TECHNICAL FIELD
The present invention relates to, in a rotating device in which a spindle motor provided with a hydrodynamic gas bearing that has a radial hydrodynamic gas bearing and a thrust hydrodynamic gas bearing acts as a driving source for a rotator, such as a magnetic disk, an optical disk, or a polygon mirror, a structure for preventing the wear of a thrust hydrodynamic gas bearing surface caused by contacting/sliding especially when it starts.
BACKGROUND ART
In a rotating device for a rotator, such as a magnetic disk, an optical disk, or a polygon mirror, it is widely known that a spindle motor provided with a hydrodynamic gas bearing is employed as a driving source for the rotator. The reason is that the motor is characterized in, for example, that the hydrodynamic gas bearing is simple in structure and can be made more compact, that its noncontact rotation during steady-state rotation does not generate vibrations or rotational irregularity that is caused by the bearing, that it is superior in high-speed durability, and that there is no contamination caused by the dispersion of a lubricant because oil, grease, or the like, is not used.
However, the disadvantage of the spindle motor provided with the hydrodynamic gas bearing is that the hydrodynamic surface of the thrust bearing is in contact when stopped, which causes wear of the surface thereof due to contacting/sliding at the onset of operation. In order to overcome this disadvantage, there is a means in which the hydrodynamic surface of the thrust bearing is floated when stopped, a thrust load is then received by an axial center part of a cylinder of the radial hydrodynamic gas bearing that is a fixed member, and the axial center part of the cylinder is spaced by the thrust of radial hydrodynamic grooves generated with the increase of the revolution speed of the spindle motor so as to maintain the gap of the thrust bearing to have a set value.
Its embodiment is proposed in Japanese Unexamined Patent Publication No. 69715 of 1999.
FIG. 10
shows the structure of a shaft fixing type spindle motor
100
therein.
101
is a base plate of a stator
110
,
102
is a cylindrical member used also as a shaft erected on the base plate
101
, and
103
is a hollow cylindrical member that has a closed end. The hollow cylindrical member
103
, the closed end of which is placed upward, is rotatably fitted onto the cylindrical member
102
. A donut-shaped thrust member
104
is integrally formed on the outer periphery of the hollow cylindrical member
103
, and, at a position opposite to this, a thrust pressure member
106
is disposed through a cover
105
that engages with the base plate
101
. A rotor
108
acting as a rotator is fixed to a hub
107
formed integrally with the hollow cylindrical member
103
. A rotor magnet
109
is disposed on the outer circumferential surface of the lower part of the hollow cylindrical member
103
, and, at a position opposite to this, a motor coil
111
wound around the stator
110
that extends from the base plate
101
is disposed.
When the spindle motor
100
is stopped, the closed end of the hollow cylindrical member
103
and the top of the cylindrical member
102
come into contact with each other by the weight of the rotor
108
including the hub
107
, and a gap between the thrust member
104
and the thrust pressure member
106
is sufficiently secured. When an electric current is passed through the motor coil
111
, the hollow cylindrical member
103
rotates clockwise, viewed from the side of the rotor
108
. And, as its revolution speed increases, a thrust occurs at a herringbone groove
112
formed largely in the upper part of the outer circumferential surface of the cylindrical member
102
, whereby the closed end of the hollow cylindrical member
103
and the top of the cylindrical member
102
draw away from each other. Simultaneously, by thrust hydrodynamic that is generated by a spiral groove (not shown) formed in the upper face of the thrust member
104
, a gap to the thrust pressure member
106
is reduced and the rotor
108
floats to a position where the thrust and the thrust hydrodynamic preserve a balance.
The publication states that, by the construction as described above, the thrust member
104
and the thrust pressure member
106
are prevented from contact and sliding during the steady-state rotation, and rises no wear whatsoever occurs in this part. Additionally, it says that the rotor
108
up by the thrust generated in the herringbone groove
112
of the radial hydrodynamic gas bearing, and therefore it is possible to obtain a compact spindle motor in which extra additional means other than the hydrodynamic gas bearing are omitted.
However, in the structure of the spindle motor of
FIG. 10
, since the thrust member
104
disposed on the outer periphery of the hollow cylindrical member
103
must undergo processing to form a spiral groove, the shape becomes complex, and an integral construction is uneconomical. Additionally, since the thrust pressure member
106
is situated above the thrust member
104
which floats upward, the base plate
101
and the cover
105
are required to undergo processing for centering, thus making the shape complex and the assembly difficult. Furthermore, because of the accumulative errors of these interrelated members, it is extremely difficult to maintain the gap of the thrust hydrodynamic gas bearing to be several-microns in order. Therefore, in order to solve the aforementioned problem, the present invention provides a spindle motor capable of preventing contact between a fixed member and a rotating member also when stopped.
DISCLOSURE OF THE INVENTION
In a first embodiment, a cylinder of a radial hydrodynamic gas bearing that has radial hydrodynamic grooves in an outer circumferential surface thereof and a disk of a thrust hydrodynamic gas bearing that has thrust hydrodynamic grooves in an upper face thereof are disposed on an upper end on an axial center of a stator core having a stator around which a motor coil is wound; a hollow cylinder whose inner surface facing the cylinder of the radial hydrodynamic gas bearing is smooth and a rotor magnet facing the motor coil are disposed on a hub acting as a rotational member; a load in a radial direction is supported by the radial hydrodynamic gas bearing; and a load in a thrust direction is supported by using the thrust hydrodynamic gas bearing together with a magnetic bearing consisting of the stator and the rotor magnet.
In a second embodiment, a hub acting as a rotational member is disposed on an upper end of a motor shaft provided with a rotor magnet on an outer periphery thereof; below the motor shaft, there are disposed a disk of a thrust hydrodynamic gas bearing that has thrust hydrodynamic grooves in a lower face thereof and a cylinder of a radial hydrodynamic gas bearing that has radial hydrodynamic grooves in an outer circumferential surface thereof; as a fixed member, there are disposed a hollow cylinder whose inner surface facing the cylinder of the radial hydrodynamic gas bearing is smooth and a stator around which a motor coil is wound, the stator facing the rotor magnet; a load in a radial direction is supported by the radial hydrodynamic gas bearing; and a load in a thrust direction is supported by using the thrust hydrodynamic gas bearing together with a magnetic bearing consisting of the stator and the rotor magnet.
In a third embodiment, a cylinder of a radial hydrodynamic gas bearing that has radial hydrodynamic grooves in an outer circumferential surface thereof and a disk of a thrust hydrodynamic gas bearing that has thrust hydrodynamic grooves in an upper face thereof are disposed on an upper end on an axial center of a stator core having a stator around which a motor coil is wound; a hollow cylinder whose inner surface facing the cylinder of the radial hydrodynamic gas bearing is smooth and a rotor magnet facing the motor coil are disposed on a hub acting as a rotational member; a secondary magnetic bearing is disposed that comprises a first permanent mag
Komura Osamu
Murabe Kaoru
Otsuki Makoto
Takeuchi Hisao
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