Cluch
A clutch is
a mechanical device which engages and disengages power transmission especially
from driving shaft to driven shaft.
In the simplest
application, clutches connect and disconnect two rotating shafts (drive shafts
or line shafts). In these devices, one shaft is typically attached to an engine
or other power unit (the driving member) while the other shaft (the driven
member) provides output power for work. While typically the motions involved
are rotary, linear clutches are also possible.
In a
torque-controlled drill, for instance, one shaft is driven by a motor and the
other drives a drill chuck. The clutch connects the two shafts so they may be
locked together and spin at the same speed (engaged), locked together but
spinning at different speeds (slipping), or unlocked and spinning at different
speeds (disengaged).
Friction clutches
A friction clutch
The vast majority of clutches ultimately rely on frictional
forces for their operation. The purpose of friction clutches is to connect a
moving member to another that is moving at a different speed or stationary,
often to synchronize the speeds, and/or to transmit power. Usually, as little
slippage (difference in speeds) as possible between the two members is desired.
Materials
Various materials have been used for the disc-friction
facings, including asbestos in the past. Modern clutches typically use a
compound organic resin with copper wire facing or a ceramic material. Ceramic
materials are typically used in heavy applications such as racing or heavy-duty
hauling, though the harder ceramic materials increase flywheel and pressure
plate wear.
In the case of "wet" clutches, composite paper
materials are very common. Since these "wet" clutches typically use
an oil bath or flow-through cooling method for keeping the disc pack lubricated
and cooled, very little wear is seen when using composite paper materials.
Dampers
A clutch damper is a device that softens the response of the
clutch engagement/disengagement. In automotive applications, this is often
provided by a mechanism in the clutch disc centres. In addition to the damped
disc centres, which reduce driveline vibration, pre-dampers may be used to
reduce gear rattle at idle by changing the natural frequency of the disc. These
weaker springs are compressed solely by the radial vibrations of an idling
engine. They are fully compressed and no longer in use once the main damper
springs take up drive.
Load
Mercedes truck examples: A clamp load of 33 kN is normal for
a single plate 430. The 400 Twin application offers a clamp load of a mere 23
kN. Bursts speeds are typically around 5,000 rpm with the weakest point being
the facing rivet.
Manufacturing
Modern clutch development focuses its attention on the
simplification of the overall assembly and/or manufacturing method.
