Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2003-11-04
2004-12-07
Lam, Thanh (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S090000
Reexamination Certificate
active
06828705
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vibration motor having an improved support structure between a rotor for generating eccentric rotation and a stator for supporting rotation of the rotor.
2. Description of the Related Art
A communication device generally uses a bell and vibrator to notify a user of call incoming. In a vibration mode, generally a small-sized vibration motor is actuated transferring driving force to a housing of the communication device to vibrate the communication device.
The vibration motor currently applied to a mobile telephone is discriminated into a flat type vibration motor and a cylinder type vibration motor. The flat type vibration motor has a relatively simple vibration structure, e.g., for rotating a weight which is placed inside the motor. The flat type vibration can be fabricated thin so that components of a mobile phone can be miniaturized. Owing to these advantages, application of the flat type vibration motor is gradually spreading.
FIG. 1
is a sectional view of a conventional flat type vibration motor. The conventional flat type vibration motor comprises a stator (i.e., stator assembly) as a stationary member and a rotor (i.e., rotor assembly) as a rotary member. That is, a lower board
101
is bonded to an upper face of a circular flat bracket
100
, and an annular magnet
102
is attached concentrically to an upper face of the lower board
101
in an equal fashion.
The bracket
100
is covered from above with a housing
110
, and the bracket
100
and the housing
110
are connected by a central shaft
105
. The shaft
105
has a rotor
120
, as shown in
FIG. 2
, which includes a bearing
121
, an upper board
122
, a commutator
123
, winding coils
124
, a weight
125
and an insulator
126
.
The upper board
122
is a circular printed circuit board, and when powered from the commutator
123
which is attached to the underside of the upper board
122
, supplies different electric power to each of the winding coils
124
through a pattern formed in the top and the underside thereof. The commutator
123
has a number of segments which are buried in the underside of the upper board
122
around the center of rotation at a predetermined interval, exposing contact faces thereof. The winding coils
124
are arranged flush with each other on a common radius and opposed to the magnet
102
placed under the winding coils
124
. One of the winding coils
124
is supplied with electric power having a polarity different from that of the other one of the winding coils
124
.
The weight
125
is generally made of high specific gravity material such as tungsten (W), and attached to the upper board
122
in a position opposite to the winding coils
124
on the upper board
122
to determine the eccentricity of the motor. The insulator
126
is a component for ensuring secure mutual attachment among the bearing
121
, the winding coils
124
and the weight
125
on the upper board
122
as well as and imparting insulation to the same. At this time, the stator and the rotor
120
are electrically connected to each other by a pair of brushes
127
, which have their lower ends fixed to the lower board
101
and their upper ends in slidable contact with the commutator
123
.
The above vibration motor is referred to as a brush type vibration motor which has drawbacks that the brush
127
causes mechanical abrasion or generates electric sparks while passing through the interval of the segments during rotation of the rotor. This situation causes byproducts functioning as a major factor of damaging the stability of electric contacts, which in turn may generate noises or degrade the performance of the vibration motor. Then, the lifetime of the vibration motor may be also shortened.
In order to overcome drawbacks of the brush type vibration motor as above, there is currently being studied a brushless vibration motor which does not have the brush or the commutator. The brushless vibration motor is so designed that an Integrated Circuit (IC) chip is employed for actuation of the motor and a magnet is placed in a rotor unlike the existing brush type motor.
FIG. 3
is a sectional view of a conventional brushless vibration motor. In
FIG. 3
, a rotor includes a yoke
202
, a magnet
203
mounted on the underside of the yoke
202
and a weight
205
mounted on one end of the yoke
202
. A central portion of the yoke
202
is fixedly coupled with a rotary shaft
204
so that the rotary shaft
204
projects downward.
In
FIG. 3
, the stator includes a bearing
208
which supports rotation of the rotary shaft
204
while contacting the rotary shaft
204
of the rotor. The bearing
208
is inserted into a projected portion which is formed in a central portion of an underlying bracket
209
, and a board
206
is placed on the bracket
209
. A coil
210
is attached on the board
206
, and an IC chip
211
placed on the board
206
supplies AC power to the coil
210
.
The conventional brushless vibration motor is so designed that the rotary shaft
204
is fixed to the rotor. Then, during operation of the vibration motor, the rotor vertically moves to collide against a housing
201
and the bracket
209
, making loud noises as well as having bad effect to the lifetime of the housing and the bracket.
Furthermore, the rotor of the brushless vibration motor has a mass larger than that of the rotor of the conventional brush type vibration motor. When the rotary shaft is coupled with the rotor like the brush type vibration motor, load is concentrated to the bracket thereby degrading the reliability of the bracket.
SUMMARY OF THE INVENTION
The present invention has been made to solve the foregoing problems and it is therefore an object of the present invention to provide a vibration motor which comprises a bearing coupled with a rotor and a stationary shaft supported by a stator in order to ensure rotation of the rotor more stable, reduce noises and guarantee reliability.
It is another object of the invention to provide a vibration motor which has an improved structure of a bearing of a rotor and a washer for supporting the bearing in order to sufficiently endure the axial load of the rotor and thus elevate rotation rate while reducing power consumption.
According to an aspect of the invention for realizing the above objects, there is provided a vibration motor comprising: a rotor having an eccentric mass; a stator for supporting rotation of the rotor; a stationary shaft inserted into a rotation center of the rotor and having upper and lower ends supported by the stator; a bearing having upper and lower ends smaller in cross sectional area than a central portion of the bearing, and coupled with the rotor at the rotation center thereof to contact an outer periphery of the stationary shaft; a first washer mounted on an inner and upper central portion of the stator for elastically supporting the stationary shaft, and being in contact with an upper face of the stationary shaft; and a second washer being in contact with a lower end of the bearing and mounted on the stator around the stationary shaft to support the rotor.
Preferably, the rotor includes a coil and a commutator having a plurality of segments for alternating electric power to the coil, and wherein the stator includes a magnet mounted in a position corresponding to the position of the coil of the rotor and a brush contacting the commutator for applying electric power. Also preferably, the stator includes a coil and an Integrated Circuit (IC) chip for alternating electric power to the coil, and wherein the rotor includes a magnet.
Preferably, the stator has a recess formed in an inner and upper central portion thereof, and the first washer is positioned to cover the recess. Also preferably, the stator has a projected column in an inner and lower central portion thereof for receiving the stationary shaft, and wherein the second washer is placed on a top of the projected column.
Preferably also, the projected column is coupled with a bush for applying clamping force, and the
Choi Joon
Kim Ki Hyung
Lam Thanh
Lowe Hauptman & Gilman & Berner LLP
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