Starter motor full mirror!!!! Part 1

   Starter motor is one of the MOST important parts of an engine. How important it is can be described as the margin between a sleeping engine and a running engine. What is does: crank the engine using its own power. Where does this "power" come from: battery. How does this happen: First it's the human who switches the ignition key that connects the control circuit to the starter. The control circuit consists of a hold-in solenoid widing and a pull-in solenoid winding. What most of my collegues don't understand was why hold-in and pull-in were activated @the same time. It is because same voltage applied for each winding, the one with smaller resistance will have a higher power output(i.e V=IR; P=IV) and hence the pull-in wins, which pulls the plunger to close the contacts for the main/ higher current/armature circuit. Also, the plunger is mechanically connected to the  moveable shaft of the armature, which connected to the pinion gear/running clutch bunch. So when the plunger is pulled in, this pushes the pinion gear in contact with the flywheel. That the whole reason why this stater type is called "pre-engaged".

When the contacts close, the pull-in winding is nolonger needed therefore the circuitry was designed to short circuit the pull-in winding.

   After pre-engagement, it is...engagement! The contacts close, the BIG current for the armature circuit kicks in, excites the solenoids that act like magnets to turn the armature rotating. The armature then spins so quickly because of huge magnetic force can effectively turn a circle of linear conductors cutting through it. And when the armature shaft turns, it creates torque, transfers it to the flywheel that moves the crankshaft. And thats how the engine is cranked and started.

 

   Aftermath, when the engine starts, the idle speed and the gear ratio of the flywheel make it obsolate for the starter to spin with them, this can cause so many damages like overheating parts and circuit(deadly), corrosion to the moving parts etc... Therefore, the starter needs to back down. How can it back down? Apparently, the human knows that the engine has already started, hence releases the ignition switch, in which the starter motor control circuit is switched open again. No excited solenoid winding to pull/hold the plunger, but the plunger arm needs to be pushed back. Fortunately, it already has a spring that coils itself back. In the end, the pinion gear is pull back from the flywheel. There is a notable part called the running clutch which is also essential that it protects the armature circuit from excessive torque by the engine. Its clutch-roller and spring housing system are designed to allow the housing to spin freely from the shaft when it is sensed that the flywheel is spinning faster than the armature's original speed. The springs will retract that will allow the rollers to contact-free with the shaft, making it possible for the pinion to spin with the flywheel without spinning the shaft. This operation is also connected with the ignition switch. So when the key is turned, the springs lock the pinion with the shaft, when it releases, the springs free the rollers.( To be continued...)