Originally,
spindle motor adopted ball bearing but considering the cost
issue, then change to sleeve
bearing and hydro bearing. The table below is the comparison
of the three different types of bearing.
For
ball bearing, because of processing precision and external pressure,
the unregular rolling is larger,
and the material is harder. It is easier to create resonance
while the motor spinning at high speed.
Sleeve
bearing is sintered with metal powder, the lubricant is stored
among the gap of metal parts.
The frication is face to face. To compare with ball bearing,
the material is softer. When rpm increased,
the gap between shaft and bearing will be enlarged. As well,
the lubrication of the sleeve bearing will be
reduced because of seal effect and shorten it's life expectancy.
For
hydro bearing, the shaft and bearing will be separate by hydro
oil membrane in order to maintain
lubrication. The effect of lubrication is not significant if
the rpm is too slow. It requires a certain operating
range. Since the hydro oil membrane has the anti-vibration effect
therefore the vibration can be reduced.
The material is harder than sleeve bearing
|
Type
|
advantage
|
weakness
|
| Ball
bearing |
1.
suitable for lower speed
2. high precision
3. seal type, no oil leadage problem |
1.
high cost
2. unregular rolling is larger while the motor spinning
at high speed and easier to create vibration
3. big vibration and big noise |
| Sleeve
bearing |
1.
low cost
2. easy to produce |
1. low life expectancy
2. face to face friction and easily to lead abrasion
3. material is softer |
| Hydro
bearing |
1.
suitable for high speed
2. longer life expectancy
3. lower vibration |
1.
the lubrication is not good while low speed spinning |
In order
to satisfy the requirement of low cost, long life expectancy,
high stability and high speed spinning, hydro bearing is the
best choice.
The
operation theory of hydro bearing
According
to the test result, obviously the hydro bearing can reach similar
stability of ball bearing. For example. That is, the hydro bearing
already obtains the requirement of long life expectancy for
computer system, telecommunication, measurement, and medical
equipments. Compare to ball bearing, hydro bearing is much competitive
because of lower noise, lower cost.
Sintered hydro bearing: The progress of hydro bearing processing
is owing to the development of sintering technology. Under high
pressure condition, to solid metal powder to a certain shape
and sintered at high temperature. Through the processing procedure,
it will generate many small holes among the metal powder. The
total cubic content of the hole is around 15~30% of the bearing
itself. Furthermore, to fill the lubricant into the holes by
vacuum©â¨ú process. Besides, there is
a recycle oil storage sink design on the bearing to ensure the
constant operation of the lubricant.
Even the fan is not rotating, the special design of hydro bearing
can ensure the lubrication. Even at the beginning of starting,
the shaft will not be dry. While the fan is at rest, the Capillarity
effect will generate a lubrication membrane between shaft and
bearing so that the lubricant will not leak out. When the fan
starts rotating, the slight pressure difference will generate
hydro wave between the gap of shaft and bearing. The rotation
of the shaft will conduct the lubricant recycled on the surrounding
of bearing. The hydro wave of hydro bearing will be generated
at the most narrow gap between shaft and bearing (where generate
the most friction). To ensure the shaft and bearing won't touch.
At the most narrow gap between shaft and bearing, where with
the most lubricant pressure, the pressure will fill the lubricant
into the holes among metal powder and recycle. At the same time,
the lubricant will flow from where with lower pressure to high
pressure (where need lubricant) to maintain the balance of lubricant.
This kind of recycling will keep on certain stability.
