3.4.1. Contactless system of ignition
Carburetor models and models with system of injection of Bosch L3 fuel. l-Jetronic and Bosch LU2-Jetronic are equipped with transistor contactless system of ignition.
The transistor system of ignition consists of the distributor with the magnetic sensor, the electronic module and the coil of ignition.
As well as the classical distributor, the contactless distributor has centrifugal and vacuum regulators (depression causes movement of the "magnet disk with ledges" hub).
The electronic module is attached to a body by means of the aluminum plate providing heat removal. Function of the module is transformation of a signal from the generator of impulses in the operating signal. The module has the scheme of formation of a signal of the distributor, the calculator of constant energy, the output amplifier with the transistor of Darlington and a time element.
The ignition coil which is specially picked up to system is fixed on a final collector.
Work
The magnetic part of the distributor called by the generator of impulses consists of the ring magnet fixed by four rivets on a disk with four ledges (on one on the cylinder), and of the inductance coil.
Other disk with four ledges is fixed on a distributor shaft.
The magnetic flux around the coil changes as movement of ledges of the rotating disk concerning ledges of a motionless disk. Change of a magnetic flux excites the electromotive force in the inductance coil. This force has the maximum value while the magnetic flux decreases with the largest speed and when suddenly changes the direction i.e. when ledges are against each other.
The calculator of the module recalculates the speed of rotation of the distributor, tension of the accumulator and an impedance of the coil so that in each timepoint energy size at the exit was a constant.
When the distributor generator does not emit additional impulses any more, the transistor of the amplifier is blocked and blocks current in primary winding of the coil.