This ignition device consists of an igniter and an ignition coil that is integrated into a single unit. In the past, high-voltage current was sent to the cylinders via high-tension cords. Now, an ignition coil can be connected directly to the spark plug of each cylinder through the use of the ignition coil united with igniter. The distance that the high voltage flows will be short by directly connecting the ignition coil and spark plug, causing the voltage-loss and electromagnetic interference to be decreased. Thus, the reliability of the ignition system is improved.

Operation

Here is an operation example based on the DIS of the 1NZ-FE engine, which uses the ignition coil united with igniter.

1. The engine ECU receives signals from various sensors and calculates the optimal ignition timing. (The engine ECU also effects timing advance control).

2. The engine ECU sends the IGT signals to the ignition coil united with igniters. The IGT signals are sent to each igniter according to the ignition order (1-3-4-2).

3. The ignition coil, to which the primary current has been shut off rapidly, generates a high-voltage current.

4. The IGF signal is sent to the engine ECU when the primary current exceeds a prescribed value. 5. High-voltage current, which is the generated in the secondary coil, flows to the spark plugs, causing ignition.

Operation Principle of the Transistorized Type

1. The signal generator generates an ignition signal.

2. The igniter receives the ignition signal and causes the primary current to flow intermittently.

3. The ignition coil, to which the primary current has been shut off abruptly, generates a high-voltage current.

4. The distributor distributes the highvoltage current generated by the secondary coil to the spark plugs.

5. The spark plugs receive the highvoltage current and ignite the air-fuel mixture. The timing advance is controlled through the use of the governor advancer or vacuum advancer.

The engine ECU, which receives signals from various sensors, calculates the ignition timing and transmits ignition signals to the igniter. The ignition timing is calculated continuously in accordance with the conditions of the engine, based on the optimal ignition timing values that are stored in the computer in the form of an ESA map. Compared to the mechanical ignition timing control of the conventional system, the control method with the ESA provides higher precision, and the freedom to set the ignition timing. As a result, this system offers improved fuel economy and power output.

REFERENCE:

The TDI is also known as DIS (Direct Ignition System) or DLI (Distributor- Less Ignition).

Components

The direct ignition system consists of the following components:

1. Crankshaft position sensor (NE)

Detects the crankshaft angle (Engine speed).

2. Camshaft position sensor (G)

Identifies the cylinder and the stroke and detects the camshaft timing.

3. Knock sensor (KNK)

Detects the knocking of the engine.

4. Throttle position sensor (VTA)

Detects the opening angle of the throttle valve.

5. Air flow meter (VG/PIM)

Detects the amount of the intake air. (On some models, this detection is performed by a manifold pressure sensor)

6. Water temperature sensor (THW)

Detects the engine coolant temperature.

7. Ignition coil with igniter

Turns the primary coil current on and off at the optimal timing. Sends the IGF signal to the engine ECU.

8. Engine ECU

Generates an IGT signal based on

the signals from various sensors and

sends the signal to the ignition coil

with igniter.

9. Spark plug

Generates electric sparks to ignite

the air-fuel mixture.

The high voltage generated in the secondary winding of the ignition coil produces a spark between the center and ground electrodes of the spark plug in order to ignite the air-fuel mixture that is compressed in the cylinder.

Ignition Mechanism

The explosion of the air-fuel mixture by a spark from the spark plug is generally called combustion. Combustion, however, does not occur in an instant, but proceeds as described below. The spark travels through the air-fuel mixture from the center electrode to the ground electrode. As a result, the air-fuel mixture is activated along the path of the spark, reacts chemically (through oxidation), and generates heat to form a so-called flame nucleus. The flame nucleus activates the surrounding air-fuel mixture, which further activates the surrounding air-fuel mixture. Thus, the heat of the flame nucleus expands outward in a process known as flame propagation, to burn the air-fuel mixture. If the temperature of the electrodes is too low or the spark plug gap is too small, the electrodes will absorb the heat that was generated by the spark. As a result, the flame nucleus is extinguished, causing a misfire. This phenomenon is called electrode quenching. If the quenching effect of the electrodes is great due to the heat generated by the flame nucleus, the flame nucleus will be extinguished. The smaller the electrode is, the lesser the quenching function will be. And the squarer the electrode is, the easier the discharge will be. Some spark plugs have a U-shaped groove in the ground electrode or a V-shaped groove in the center electrode in order to improve ignitability. Those spark plugs provide a smaller quenching effect than the spark plugs without grooved electrodes, which allows the flame to form a large nucleus. Also, there are some spark plugs that reduce the quenching effect by providing thinner electrodes.

On the platinum-tipped and iridiumtipped spark plugs, the center electrode and the opposing ground electrode are covered with a thin platinum or iridium tip. Therefore, these spark plugs provide a longer service life than conventional spark plugs. Because platinum and iridium resist wear, the center electrode of these spark plugs can remain small and offer excellent sparking performance.

1. Platinum-tipped spark plug

On the platinum-tipped spark plug, platinum is welded onto the tip of the center electrode and the ground electrode. The diameter of the center electrode is smaller than in the conventional spark plug.

2. Iridium-tipped spark plug

On the iridium-tipped spark plug, iridium (which provides a higher wear resistance than platinum) is welded onto the tip of the center electrode, and platinum is welded onto the ground electrode. The diameter of the center electrode is smaller than in the platinum-tipped spark plug.

HINT:

Some of these plugs do not have platinum welded onto their ground electrodes.

The platinum-tipped and iridium-tipped spark plugs must be replaced at the specified intervals. They do not require the plug gap adjustment or cleaning between replacements if the engine is running properly.

HINT:

Platinum- and iridium-tipped spark plug replacement intervalsEvery 100,00to 240,000km The replacement intervals may vary by vehicle model, engine specifications, and area of use.

NOTICE:

To prevent the electrodes from being damaged, do not clean platinum- or iridium-tipped spark plugs. Cleaning will damage the electrodes and will inhibit the full ability of the spark plugs. However, if the electrodes are sooty or excessively dirty, they may be cleaned for a short period of time (2seconds maximum) in a spark plug cleaner. The gap of these spark plugs does not require adjustment except when installing as new. The illustration on the left shows the type of caution label that is affixed in the engine compartment of a vehicle using platinum- or iridium-tipped spark plugs.