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What
does a clutch do?
What parts make the clutch work?
What happens when the clutch pedal
is depressed?
The clutch allows engine
power to be applied gradually when a vehicle
is starting out, interrupts power to the transmission
to avoid gear clashing when shifting and prevents
engine stalling when bringing the vehicle
to a stop. Engaging the clutch (clutch pedal
fully raised) allows power to transfer from
the engine to the transmission and drive wheels.
Disengaging the clutch (clutch pedal fully
depressed) stops the power transfer and allows
the engine to continue turning without force
to the drive wheels.
Common
clutch-related components are:
Flywheel
– mounts to the engine crankshaft
Clutch Disk – the friction
material assembly that provides easy engagement
and firm torque transference
Pressure Plate – also
known as “Clutch Cover” –
this is the spring-loaded surface that locks
the clutch
Throw-out Bearing –
also known as “Release Bearing”
Pilot bearing –centers
and supports the transmission input shaft
(many cars do not have this bearing)
Clutch Cable – mechanical
release mechanism for some vehicles
Clutch Master Cylinder –
force-multiplying cylinder for vehicles with
hydraulic release mechanisms
Clutch Slave Cylinder –
used along with a Master Cylinder for hydraulic
release mechanisms
Misc. hoses, lines, brackets, linkages,
etc. – varies from vehicle
to vehicle
The
flywheel is a large steel or aluminum disc.
It acts as a balance weight for the engine,
dampening engine vibrations caused by the
firing of each cylinder and provides a surface
that the clutch can contact. The flywheel
also has teeth around its circumference for
the starter motor to engage and crank the
engine.
The
clutch disc is a steel plate, covered with
a frictional material that is sandwiched between
the flywheel and the pressure plate. The center
of the disc is the hub, which fits the spines
of the transmission input shaft. When the
clutch is engaged, the disc is "squeezed"
between the flywheel and pressure plate, and
power from the engine is transmitted by the
disc's hub to the input shaft of the transmission.
A
pressure plate is a metal spring-loaded friction
surface that is bolted to the flywheel. It
has a metal cover, heavy release springs,
a metal pressure surface, and a thrust ring
or fingers for the release bearing. The thrust
ring or fingers release the clamping force
of the springs when the clutch is disengaged.
When
the clutch pedal is depressed, the "Throw-out
bearing" pushes the pressure plate's
release fingers. The pressure plate pulls
away from the clutch disc, disengaging the
clutch, thus interrupting power flow. When
the clutch pedal is released and the clutch
is fully engaged, the release bearing is normally
stationary and does not rotate with the pressure
plate.
Clutch
operation is accomplished either mechanically
or with a hydraulic pressure system.
If
a vehicle has a mechanically operated linkage,
it will incorporate either a shaft-and-lever
linkage arrangement or a cable.
Systems
that are made up of linkages, levers and pivot
points are found primarily on older vehicles.
These systems require regular lubrication
and can only be designed to fit a limited
range of configurations.
A
cable operated clutch mechanism is relatively
simple. A cable connects the clutch pedal
directly to the clutch release fork. This
simple design is flexible and compact. There
is however, a tendency for cables to gradually
stretch and eventually break due to age and
wear.
On
a hydraulically operated clutch, a master
cylinder is usually directly operated by the
clutch pedal assembly. A slave cylinder at
the transmission is connected to the master
cylinder by high-pressure tubing. The slave
cylinder pushes either an operating lever
or directly on the release bearing. Hydraulic
systems require less pedal pressure and provide
a smooth “liquid” feel to clutch
engagement. Design configuration is very flexible
and can very easily be adapted to most any
required configuration.
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888-949-2738
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