Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-03-31
2002-06-04
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C384S100000, C384S115000, C384S120000
Reexamination Certificate
active
06400052
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a motor, to a method of fabricating a motor and to a rotary apparatus utilizing the motor capable of providing excellent rotational accuracy and high durability.
Conventionally, in a rotary apparatus such as a rotary polygonal face mirror of a laser beam printer or HDD (hard disk drive), there is used a motor using dynamic pressure bearings.
In the conventional rotary body apparatus, a rotor member needs to rotate at a high speed and at a rate of several thousands through several ten thousands rotations/minute, and by using the dynamic pressure bearings, members on the side of a rotor are supported in noncontact relation during high speed rotation to thereby restrain wear of the members.
A motor shown by
FIG. 7
is an example of a motor using such dynamic pressure bearings. The motor shown by
FIG. 7
is provided with a base
110
fixed to a frame of a main body apparatus such as printer or HDD, a hub shaft
130
extended with a shaft
131
in a shape of a circular cylinder from the center of a hub
132
in a circular plate shape and a bearing ring
152
fixedly attached to an end portion of the shaft
131
.
The base
110
is provided with a fitting portion
110
a
projected in a circular ring shape and a stator coil
140
is fixed to an outer peripheral face of the fitting portion
110
a.
A retaining ring
151
is fixed to a front end portion of the fitting portion
110
a
coaxially with the fitting portion.
The stator coil
140
comprises a sheet-like yoke
141
laminated with a single or a plurality of sheets having the same shape and coils
142
formed by winding lead wires at the yoke
141
. The yoke
141
comprises a mounting portion in a circular ring shape and a plurality of winding portions extended from the mounting portion outwardly in the diameter direction and is fixed to the fitting portion
110
a
by inserting the fitting portion
110
a
into a hollow portion of the mounting portion. Coils
142
are formed by winding lead wires around the winding portions and a rotary magnetic field is formed by conducting electricity to the coils
142
.
A circular ring portion
133
is extended from a peripheral edge portion of the hub
132
of the hub shaft
130
toward a lower direction and rotor magnets
160
are fixed to an inner peripheral wall of the circular ring portion
133
.
A bearing ring
152
is coaxially fixed to the end portion of the shaft
131
of the hub shaft
130
, the shaft
131
penetrates the retaining ring
151
, the bearing ring
152
is rotatably arranged in the fitting portion
110
a
of the base
110
and the hub shaft
130
is rotatably supported by the base
110
. Oil for lubrication is filled between the fitting portion
110
a
of the base
110
and the bearing ring
152
.
Grooves for generating dynamic pressure are formed at an outer peripheral face and an upper and a lower end face of the bearing ring
152
.
According to the motor of the conventional technology, the rotor magnets
160
fixed to the circular ring portion
133
of the hub shaft
130
are urged by the rotary magnetic field formed by the stator coil
140
and the hub shaft
130
is rotated. Further, in accordance with rotation of the hub shaft
130
, the bearing ring
152
is rotated and the oil is drawn between the bearings ring
152
and the fitting portion
110
a
of the base
110
and between the bearing ring
152
and the retaining ring
151
. Further, when the rotational number of the hub shaft
130
becomes equal to or larger than a predetermined rotational number, the bearing ring
152
is supported to float by the dynamic pressure.
The motor using such dynamic pressure bearings is provided with advantages in which wear among members is inconsiderable even in high speed rotation and excellent durability is achieved.
Now, according to the above-described motor, in the bearing ring
152
, there is used a copper-series metal material and there is used a metal material of SUS for the base since the grooves for generating the dynamic pressure are easy to form and durability against wear to a degree of withstanding the use is provided. As other reason of using these materials, in a state in which temperature is elevated in rotating the motor, the linear expansion coefficient of the copper-series metal is larger than that of SUS, when a hollow portion of the inserting portion
110
a
of the base
110
is expanded, the bearing ring
152
is expanded more than the expansion of the hollow portion and a volume of a clearance between the fitting portion
110
a
and the bearing ring
152
is not varied considerably and accordingly, the generated dynamic pressure can be maintained constant regardless of temperature. Further, in the dynamic pressure bearing, it is necessary for generating predetermined dynamic pressure to maintain the clearance between the bearing ring
152
and the fitting portion
110
a
of the base
110
with accuracy of about ±1 micrometer.
Further, the bearing ring
152
is fixed to the shaft
131
of the hub shaft
130
by press fitting.
Further, the shaft
131
of the hub shaft
130
is formed in a circular cylinder shape since the shaft
131
is a rotary member and an inner vacant portion of the bearing ring
152
fixed to the shaft
131
is also formed in a circular cylinder shape. By influence of checking of a lathe, a section of either of an outer peripheral face of the shaft portion
131
a
and an inner peripheral face forming the inner vacant portion of the bearing ring
152
, cannot be machined to a completely round shape (complete roundness) and actually, the section is machined to an irregular circle including the complete roundness.
When the shaft
131
having an outer peripheral face of the section in an irregular circular shape, is mounted to the inner vacant portion of the bering ring
152
similarly having an irregular circular section, the state in which all the faces are brought into contact with each other is not produced and in either of the circumferential direction and the axial direction, there is brought about a state in which contact portions and separated portions are irregularly arranged and there is produced portions where stress is concentrated in press fitting.
Further, a material which is easy to form the dynamic pressure generating grooves and having the large expansion coefficient, as mentioned above, is generally provided with low hardness and when the bearing ring
152
is formed by such a material and the bearing ring
152
is press-fitted to the shaft
132
of the hub shaft
130
, the portions where stress is concentrated as mentioned above are liable to deform. When the bearing ring
152
is deformed in this way, it is difficult to generate and maintain the dynamic pressure having a predetermined magnitude, and therefore there poses a problem in which the rotational accuracy is deteriorated or there is a concern of wearing the bearing ring
152
.
SUMMARY OF THE INVENTION
The present invention has been carried out in order to resolve the above-described problem and it is an object thereof to provide a motor capable of achieving excellent rotational accuracy and high durability, a method of fabricating the motor and a rotary apparatus utilizing the motor.
The present invention achieves the above-described object by providing a motor comprising a rotor member having a shaft portion, a bearing ring having an inner vacant portion, the inner portion being inserted with the shaft portion and fixed to the shaft portion, a supporting member having a hollow portion containing the bearing ring relatively rotatably, a plurality of electromagnets arranged to the supporting member coaxially and in a fixed state for generating a rotary magnetic field, rotor magnets fixed to the rotor member and urged by the rotary magnetic field generated by the electromagnets for rotating the rotor member and the bearing ring, and dynamic pressure generating means arranged at either of the bearing ring and the supporting member for generating dynamic pressure between either one of the bearin
Goto Hiromitsu
Suzuki Takafumi
Adams & Wilks
Dinh Le Dang
Ramirez Nestor
Seiko Instruments Inc.
LandOfFree
Motor and rotary apparatus having motor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Motor and rotary apparatus having motor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Motor and rotary apparatus having motor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2940802