Service Manual

ELECTRICAL SYSTEM 8-11
Charging, Ignition System
Circuit Composition
Co: Ignition Coil Core
C: Condenser
D1: Diode
D2: Diode
D3: Diode
E: Exciter C oil
L1: Primary Coil
L2: Secondary Coil
SCR: Thyristor
SP: Spark Plug
Act ion Principle
(1) Fundamental action
1. Genarated positive direction voltage by rotor rotated in the exciter coil (E) flow the electrical current
through the diode (D1), and discharged to the condenser (C).
2. Generated opposite direction current flow to the thyristor (SCR) because of voltage had generated
in the exciter coil (E) also at the opposite direction.
3. If the voltage of opposite direction reaches to the trigger voltage of the thyristor (SCR), the thyris-
tor (SCR) will be ON state, and voltage is charged by the condenser (C) discharge rapidly t o the
primary coil (L1).
4. The primary voltage of several hundreds volt generate because of large electrical current flows
rapidly to the primary coil (L1), the primary voltage are pressure risen by the secondary coil (L2),
and turn into the secondary voltage of several thousands volt, and spark generate to the spark plug
(SP) of output side.
(2) Spark advance characteristic
1. If the revolutions number rises, t he opposite direction voltage of exciter coil (E) which the trigger po-
sition of the thyristor (SCR) changes and spark advance because of voltage wave form will change.
2. Spark advance is controlled by spark advance characteristic control circuit in the figure.
(3) Spark delay characteristic
1. The trigger position of the thyristor (SCR) changes and spark delay by decreasing the voltage wave
form applied to the thyristor (SCR) in the revolutions number set up in the spark delay characteristic
control circuit in the f igure.
2. The start revolutions number of spark delay is controlled by spark delay characteristic control circuit
in the figure.