How a Mechanical Ignition Distributor Works

Mechanical ignition distributor

Mechanical ignition distributor

Every candle, at the right time

Mallory Coil (Performance Throne) and Beru (BorgWarner)

Mallory Coil (Performance Throne) and Beru (BorgWarner)

Coil

We will start the story of the ignition distributor with another part of the Otto engine electrical system. Of course, although its construction is relatively simple, this part of our story is also necessary for "the whole thing" to work at all. Namely, on the way in between of the battery and the ignition distributor housed the part known as the bobbin. Behind the wise expert name of the bobbin (German Zündspule) is actually a kind of voltage transformer.

It is known that (most) car batteries deliver 12V DC voltage. But this is far from enough for the spark to jump the gap between the spark plug electrodes. Therefore, it is necessary to increase the voltage. This is taken care of by a coil that looks like a metal cylindrical box and has two coils of wire wrapped around a metal core.

Basic parts of the bobbin

Basic parts of the bobbin

If we recall elementary school physics now, it is clear that the low voltage current coming to the primary winding can create a magnetic field around the metal core. This, in turn, magnetic field induces a high voltage in the secondary winding consisting of 15-30 thousand turns of wire (the primary winding consists of several hundred turns of wire of large cross section). Thus, the initial 12V is transformed into several tens of thousands of V needed for the spark plug to work. In doing so, between 30 and 70 mJ (millijoules) of energy are released in each spark plug.

And so on. We have now learned how to obtain the required voltage using the accelerated course method. But there are still problems. It is clear that engines, in principle, have one spark plug per cylinder (with some exceptions). Therefore, there should be some kind of device that will distribute our high voltage to all the spark plugs exactly when they need it, that is, at the moment when it is necessary to light the mixture. To make this possible, an ignition distributor is used.

Ignition Distributor for 4-cylinder Otto engine

Ignition Distributor for 4-cylinder Otto engine

Mechanical ignition distributor

A distributor is a device that consists of a drive part that is indirectly driven by the engine crankshaft, a rotor with a rotating electrode, a switch (platinum), a system for adjusting the ignition timing and a distributor cap. Thus, the high voltage current from the induction coil comes to the central terminal (contact) of the ignition distributor and passes to the rotating electrode of the rotor.

Inside the hood (cover, if you like) of the manifold, and around the central terminal, there are stationary electrodes (there are as many spark plugs, therefore with our theoretical engine as many cylinders) through which current flows when they are connected to a rotating electrode. .

Main parts of the distributor

Mechanical ignition distributor - Basic parts

This actually means that the rotor and its electrode "walk" in a circle touching the static electrodes and thus transmitting current to the spark plugs. In this way, it was decided that each spark plug receives a high voltage current at a time determined by the speed of rotation of the engine (which in turn determines the speed of rotation of the rotor in the ignition distributor).

The rotor is driven by the ignition distributor drive shaft which rotates at "half speed" crankshaft rotation. More understandably, for every two turns of the engine crankshaft (let's say four operating strokes = two turns of the crankshaft), the ignition distributor drive shaft rotates once.

Platinum - a nightmare of self-taught servicemen

The switch, popularly called "platinum", is actually a moving contact that breaks the connection between of the battery and the primary circuit in the coil. When this circuit is interrupted, a high voltage current is induced in the secondary winding, which at that moment passes to the ignition distributor and from there via a rotating electrode, to the spark plug. The switch is set so that it is opened by a distributor shaft that has as many cams on it as there are cylinders in the engine. So, every time the bank turns towards the switch, the primary circuit breaks and the spark plug gets its high voltage current.

Switch: large opening angle and small contact distance - properly tuned platinum

Switch: large opening angle and small contact spacing - properly adjusted platinum

The ignition switch, or the popular "platinum", is one of the nightmares of anyone who has ever tried to adjust the operation of their car's engine at home. Primary wear of the contacts causes irregularities in the operation of the switch, which therefore needs to be adjusted from time to time. And, although they are completely extinct in today's cars, mechanical contacts still lead a "parallel life" in the air.

Namely, like any mechanical assembly, "platinum" will not (like electronics) fail at once, but their condition slowly degrades in case of wear. That is why today they are still used in aircraft engines because their way of spending offers a higher level of safety than electronic (I work - I do not work) systems for the same purpose.

Let's say that the high voltage coil (coil) with the ignition distributor and the ignition distributor with spark plugs are connected by high voltage lines. Code e.g. The 12-cylinder engine is the "funny noise" of 13 cables that, a bit messy, crawl inside the engine compartment.

Schematic representation of the ignition system

Schematic representation of the ignition system

The last, but by no means least, part of the manifold we will mention is the ignition timing system. Specifically, there are two basic systems: centrifugal and vacuum. Their role is to move the ignition timing forward when the engine speed is increased. Of course, the goal is to ensure that the mixture has sufficient time for complete combustion and at high operating speeds.

Here is so much about the "former" ways of high voltage distribution. Of course, fans of old or classic cars will not agree with the name "former", and fortunately, several car equipment manufacturers still have in their program the mechanical systems necessary to maintain beautiful, older tin pets.

Mechanical Ignition Distributor (Aldon Automotive Ltd.)

Mechanical Ignition Distributor (Aldon Automotive Ltd.)

by AUTONET.HR
Retrieved from: www.autonet.hr


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