Sunbeam ALPINE I SERIES: APLINE II SERIES, Руководство по ремонту, Страница: 338 / 413

I
st re-issue
Page 20
WSM. 124
Section N (Elec. Equip.)
DISTRIBUTOR
GENERAL
The coil ignition equipment comprises a high
tension induction coil and a combined distributor,
contact breaker and automatic timing control
assembly driven at half engine speed
via
the cam­
shaft. Current flowing through the primary or
low tension winding of the coil sets up a strong
magnetic field about it. This current is periodically
interrupted by a cam-operated contact breaker,
driven from the engine, and the subsequent
collapse of the magnetic field across the secondary
winding of the coil induces a high voltage in it.
At the same time, a rotor arm in the distributor
connects the secondary winding of the coil with
one of four metral electrodes, from which cables
lead to the sparking plugs in the engine cylinders.
Thus, a spark is produced in the cylinder under
compression at the optimum moment for com­
bustion of the mixture.
Mounted on the distributor driving shaft,
immediately beneath the contact breaker, Is an
automatic timing control mechanism. It consists
of a pair of spring-loaded governor weights, linked
by lever action to the contact breaker cam. At
slow engine speeds, the spring force retains the
cam in a position In which the spark is slightly
retarded. Under the centrifugal force imparted
by high engine speeds, the governor weights swing
out against the spring pressure, to move the contact
breaker cam and thereby advance the spark, to suit
engine conditions at the greater speed.
A vacuum-operated timing control is also fitted,
designed to give additional advance under part­
throttle conditions. The inlet manifold of the
engine is in direct communication with one side of
a spring-loaded diaphragm. This diaphragm acts
through a lever mechanism to rotate the heel of
the contact breaker about the cam, thus advancing
the spark for part-throttle operating conditions.
The combined effects of the centrifugal and vacuum­
operated timing controls give added efficiency over
the full operating range of the engine, with a
corresponding economy in fuel consumption.
Special ignition for cold climate countries.
The ignition coil is a 7-volt unit, and during normal
running the excess voltage Is dropped across a
ballast resistor In series with the coil primary
winding. For starting, an additional contact on the
solenoid starter switch shorts out the ballast
resistor, thus ensuring that the terminal voltage,
and hence the performance, of the coll at this time
remains practically unaffected by the drop in
battery voltage. As soon as the engine starts, and
the solenoid switch Is opened, the ballast resistor
is automatically reconnected Into the primary
circuit.
ROUTINE MAINTENANCE (See Fig. 20)
In general, lubrication and deaning constitute
normal maintenance procedure.
Lubrication
Take great care to prevent oil or
grease
from getting on
or
near the
contacts.
Lightly smear the cam and the pivot on which the
contact breaker works with lubricant as specified.
Lift off the rotor arm by pulling vertically and apply
to the spindle a few drops of engine oil to lubricate
the cam bearing. It is not necessary to remove the
exposed screw, since It affords a clearance to permit
passage of oil.
Replace the rotor arm carefully, locating its
moulded projection in the keyway In the spindle
and pushing it on as far as It will go, in order to
avoid the risk of the moulded cap being burned or
tracked.
Carefully add a few drops of engine oil through the
aperture at the edge of the contact breaker plate
to lubricate the automatic timing control.
Cleaning
Thoroughly clean the moulded distributor cap,
Inside and out, with a soft dry cloth, paying par­
ticular attention to the spaces between the metal
electrodes. Ensure that the small carbon brush
moves freely In Its holder.