The device and principle of operation of the engine starting system

The engine starting system provides the initial cranking of the engine's crankshaft, due to which the air-fuel mixture is ignited in the cylinders and the engine starts to work independently. This system includes several key elements and nodes, the work of which we will consider later in the article.

What is the

In modern cars, an electric engine start system is implemented. It is also often referred to as a starter starting system. Simultaneously with the rotation of the crankshaft, the timing, ignition and fuel supply system is activated. The air-fuel mixture burns in the combustion chambers and the pistons turn the crankshaft. After reaching certain revolutions of the crankshaft, the engine starts to work independently, by inertia.

To start the engine, you need to reach a certain speed of the crankshaft. This value is different for different types of engines. For a gasoline engine, a minimum of 40-70 rpm is required, for a diesel engine - 100-200 rpm.

At the initial stage of the automotive industry, a mechanical starting system with the help of a crank was actively used. It was unreliable and inconvenient. Now such decisions have been abandoned in favor of an electric launch system.

Engine starting system device

The engine starting system includes the following key elements:

• control mechanisms (ignition lock, remote start, start-stop system);
• accumulator battery;
• starter;
• wires of a certain section.

The key element of the system is the starter, which in turn is powered by the battery. This is a DC motor. It generates torque that is transmitted to the flywheel and crankshaft.

How engine starting works

After turning the key in the ignition lock to the "start" position, the electrical circuit is closed. The current through the positive circuit from the battery goes to the winding of the starter traction relay. Then, through the excitation winding, the current passes to the plus brush, then along the armature winding to the minus brush. This is how the traction relay works. The movable core retracts and closes the power dimes. When the core moves, the fork extends, which pushes the drive mechanism (bendix).

After closing the power dimes, the starting current is supplied from the battery through the positive wire to the stator, brushes and rotor (armature) of the starter. A magnetic field arises around the windings, which drives the armature. In this way, the electrical energy from the battery is converted into mechanical energy.

As already mentioned, the fork, during the movement of the solenoid relay, pushes the bendix to the flywheel crown. This is how engagement occurs. The armature rotates and drives the flywheel, which transmits this movement to the crankshaft. After starting the engine, the flywheel spins up to high revs. In order not to damage the starter, the overrunning clutch of the bendix is ​​activated. At a certain frequency, the bendix rotates independently of the armature.

After starting the engine and turning off the ignition from the "start" position, the bendix takes its original position, and the engine works independently.

Features of the battery

The condition and power of the battery will determine the successful start of the engine. Many people know that indicators such as capacity and cold cranking current are important for a battery. These parameters are indicated on the marking, for example, 60 / 450A. Capacity is measured in ampere hours. The battery has a low internal resistance, so it can deliver large currents for a short time, several times higher than its capacity. The specified cold cranking current is 450A, but subject to certain conditions: + 18C ° for no more than 10 seconds.

However, the current supplied to the starter will still be less than the indicated values, since the resistance of the starter itself and the power wires is not taken into account. This current is called the starting current.

Help. The internal resistance of the battery averages 2-9 mΩ. The resistance of the starter of a gasoline engine is on average 20-30 mOhm. As you can see, for proper operation, it is necessary that the resistance of the starter and wires be several times higher than the resistance of the battery, otherwise the internal voltage of the battery will drop below 7-9 volts when starting, and this cannot be allowed. At the moment the current is applied, the voltage of a working battery sags to an average of 10,8V for a few seconds, and then recovers back to 12V or slightly higher.

The battery delivers starting current to the starter for 5-10 seconds. Then you need to pause for 5-10 seconds for the battery to "gain strength."

If, after an attempt to start, the voltage in the on-board network drops sharply or the starter scrolls by half, then this indicates a deep discharge of the battery. If the starter gives out characteristic clicks, then the battery has finally sat down. Other causes may include starter failure.

Start current

Starters for gasoline and diesel engines will differ in power. For gasoline internal combustion engines, starters with a capacity of 0,8-1,4 kW are used, for diesel ones - 2 kW and above. What does it mean? This means that the diesel starter needs more power to crank the crankshaft in compression. A 1 kW starter consumes 80A, 2 kW consumes 160A. Most of the energy is spent on the initial cranking of the crankshaft.

The average starting current for a gasoline engine is 255A for successful cranking of the crankshaft, but this is taking into account a positive temperature of 18C ° or higher. At minus temperatures, the starter needs to turn the crankshaft in thickened oil, which increases resistance.

Features of starting the engine in winter conditions

In winter, it can be difficult to start the engine. The oil thickens, which means it is more difficult to crank it. Also, the battery often fails.

At minus temperatures, the internal resistance of the battery rises, the battery sits down faster, and also reluctantly gives the required starting current. For a successful start of the engine in winter, the battery must be fully charged and must not be frozen. Additionally, you need to monitor the contacts on the terminals.

Here are some tips to help you start your engine in winter:

1. Before turning on the starter to cold, turn on the high beam for a few seconds. This will start the chemical processes in the battery, so to speak, "wake up" the battery.
2. Do not turn the starter for more than 10 seconds. So the battery runs out quickly, especially in cold weather.
3. Depress the clutch pedal fully so that the starter does not need to turn additional gears in the viscous transmission oil.
4. Sometimes special aerosols or "starter fluids" that are injected into the air intake can help. If the engine is in good condition, it will start.

Thousands of drivers start their engines every day and drive on business. The start of movement is possible thanks to the well-coordinated work of the engine starting system. Knowing its structure, you can not only start the engine in a variety of conditions, but also select the necessary components in accordance with the requirements specifically for your car.