Operation - Toro TC 1000 Service Manual

SECTION 3 IGNITION
Ignition Operation
The firing of the spark plug at the proper time is
the culmination of a number of components
working together. In the TC1000, the compo-
nents used are:
Flywheel
Ignition Coil
Trigger Module
Spark plug
See Fig. 48.
a
TRIGGER MODULE
Figure 48
The following describes the function of each of
the above components.
Ignition Operation Flywheel
The flywheel is connected directly to the crank-
shaft and turns at the same speed as the engine.
Imbedded in the flywheel are three magnets.
These magnets rotate past the coil to generate
electricity.
Imbedded in theoppositesideof theflywheel is a
steel counterweight which offsets the weight of
the three magnets. It is not magnetic.
Ignition Operation Ignition Coil
The ignition coil is actually a transformer. It is
positioned close to the flywheel to allow the
magnetic field of the flywheel magnets to cut
through the coils to generate electricity. See
Fig. 49.
23
FLYWHEEL MAGNETS
Figure 49
Low voltage is produced in the primary coil
which is sent to the trigger module. The primary
voltage is much too low to produce a spark at the
spark plug.
The secondary coil serves to amplify the voltage
produced in the primary. To accomplish this, the
secondary coil must have many more windings
than the primary. The higher the ratio between
the primary coil windings to secondary coil
windings, the greater the voltage amplification
will be.
However, even though the secondary coil in the
TCIOOO has many more windings than the
primary, the voltage produced is still not high
enough to produce spark across the spark plug
electrodes. To further amplify the voltage, the
trigger module is used
Ignition Operation Trigger Module
The trigger module amplifies the voltage in the
secondary coil by breaking the primary circuit
just as the primary voltage reaches its peak. This
breaking of the primary circuit results in a rapid
collapse of the magnetic field surrounding the
primary coil. The collapse of the primary mag-
netic field induces a large voltage surge in the
secondary which is sufficient to produce a spark
across the spark plug electrodes.
Before getting into the actual electronics used
inside the trigger module, it is important to have
an understanding of the voltage waveform pro-
duced by the flywheel magnets moving by the
ignition coil. See Fig. 50.