Vibration motor

Details Vibration motor Vibration motor

2001-09-25

2003-07-15

Nguyen, Tran (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S081000

Reexamination Certificate

active

06593675

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a vibration motor installed in a mobile terminal as call incoming means together with a bell, and more particularly, to a vibration motor which is fixed through the press fit by a shaft thereby enabling the axis with precise erectness while eliminating malfunctions due to a mechanical assembly error.
2. Description of the Prior Art
In general, one of essential functions in communication instruments is a call incoming function, which is mostly provided in a sound mode such as melody or bell and a vibration mode vibrating a communication instrument.
In other words, when a user previously selected a call incoming function, the selected function is operated at the time of call incoming so that the user can notice the call incoming.
In such call incoming modes, in particular, the vibration mode is generally used in a place where a number of people are gathered so as not to interrupt others.
In the sound mode such as melody or bell of the call incoming function, a number of melody or bell types are previously stored in the instrument to be outwardly transmitted through a small sized speaker allowing the user to notice the call incoming. In the vibration mode, generally a small sized vibration motor is operated to transfer a vibration force to a housing of the instrument so that the instrument can be vibrated.
Meanwhile, the vibration mode of the prior art is obtained by using a vibration motor installed in the instrument. As shown in FIG.
1
and
FIG. 2
, one of the most typical vibration motors, so-called “pan cake” or “coin type” motor, has the outer shape with the diameter relatively larger than the thickness.
Such a vibration motor has a plate-type cover plate
100
in the bottom. The cover plate
100
has a tubular burring part
100
a
in the center. The tubular burring part
100
a
has an axial hole in the center projected at a certain height so that the lower end of a shaft
140
can be fixedly press fit into the axial hole. Also, in the upper surface of the cover plate
100
is a lower board
110
with a printed circuit which enables external power application.
At the upper surface of the cover plate
100
having the lower board
110
like this are arranged magnets
130
in the annular shape having a vertical through-hole defined in the center of the magnets
130
and N and S poles arranged alternately with the equal gap at the round periphery thereof.
The lower board
110
in the bottom of a central space of the magnets
130
is spaced from a pair of brushes
120
with one ends respectively connected to input and output ends of the magnets
130
and the other ends positioned higher than the upper surfaces of the magnets
130
.
Meanwhile, a cylindrical housing
150
is coupled with the cover plate
100
the end of outer periphery thereof to cover the cover plate
100
. The housing
150
has a shaft hole
150
a
in the upper center for receiving the shaft
140
while supporting the same.
In this manner, the shaft
140
, the lower board
110
, the magnets
130
and the pair of brushes
120
supported by the cover plate
100
define a stator. In respect to the stator is rotationally arranged an eccentric rotor
200
comprising an upper board
210
, commutators
220
and winding coils
240
.
Here, the upper board
210
is a typical printed circuit board which is made of a plate-type member cut at an arbitrary angle, and supported by the shaft
140
and a bearing b so that the upper board
210
can be eccentrically rotated. Such an upper board
210
, in the bottom opposed to the cover plate
100
, is integrally provided with the commutators
220
comprising a number of segments. The segments of the commutators
220
contact with the upper ends of a pair of brushes
120
with the lower ends connected to the lower board
110
.
The winding coils
240
are attached to the upper surface of the upper board
210
without a printed circuit, and are composed of at least one coil according to an operation mode of the vibration motor. In particular, when the winding coils
240
are made of the plurality of coils, the coils are spaced at a predetermined angle from one another.
Also, the upper board
210
, in the surface without the winding coil
240
, is integrally provided with an insulator
250
for enhancing insulation and eccentric load between the winding coils
240
in the upper board
210
. The insulator
250
is integrally formed through insert extrusion together with the commutators
220
and the winding coils
240
attached to the upper board
210
when the upper board
210
is made. The adjacent pair of winding coils
240
have a weight
230
made of a heavy metal such as tungsten in order to maximize the eccentric amount.
Meanwhile, the shaft
140
is in the peripheries of the upper and lower ends coupled into discal upper and lower washers w
1
and w
2
with through holes in the center thereof. When the eccentric rotor
200
is elevated or dropped in the operation of the motor, the upper and lower washers w
1
and w
2
directly contact with the housing
150
and the cover plate
100
to prevent destruction.
In the conventional vibration motor having the foregoing configuration, when an electric power is externally applied through the lower board
110
, the electric power is induced to the commutators
220
through the brushes
120
with the lower ends connected to the lower board
110
and then supplied to the winding coils
240
through the printed circuit on the upper board
210
from the commutators
220
so that an electromagnetic force is generated from the interaction between magnetic fluxes from the winding coils
240
and the magnets
130
to rotate the eccentric rotor
200
.
Here, the eccentric rotor
200
is eccentrically supported by the shaft
140
to exert an eccentric driving force, which is transferred to the cover plate
100
and the housing
150
through the shaft
140
to drive silent call-incoming means of a mobile communication terminal.
However, in the vibration motor of the prior art, while the lower end thereof is fixedly press fit into the cover plate
100
, the upper end of the shaft
140
is simply inserted into the shaft hole
150
a
of the housing
150
so that the erectness of the shaft is unstable resultantly lowering the performance of the motor as a problem.
In other words, the shaft hole
150
a
has the inside diameter larger in respect to the outside diameter of the shaft to assemble the shaft
140
into the shaft hole
150
a
of the housing
150
so that a play, even if slight, is created between the shaft
140
and the shaft hole
150
a
when the shaft
140
is assembled into the shaft hole
150
a
. Therefore, the upper end of the shaft
140
is played within the shaft hole
150
a
due to side pressure to incur damage and noise according to inter-component contact in the operation of the motor. In particular, as the erectness of the shaft
140
becomes unstable, the operation features of the eccentric rotor
200
is also degraded causing problems such as reduced life time.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been proposed to solve the foregoing problems and it is an object of the present invention to provide a vibration motor which can ensure the erectness of a shaft more precise while stably fixing one end of the shaft into a housing through press fit so that operation features and endurance can be enhanced.
It is another object of the present invention to enable absorptive damping of the impact in the operation of the eccentric motor to stably maintain the operation features of the motor.
According to an embodiment of the invention to obtain the foregoing object, it is provided a vibration motor comprising: a cover plate for fixedly receiving the lower end of a shaft in a central part; a housing coupled with the cover plate to define a certain size of space and having a recess in an upper inner central part; a lower board attached to the upper surface of the cover plate and having brushes projected at one end; magnet

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