Starting system (Engine)

Starting system is one of the engine`s system, which provides an engine start.  To make it, the crankshaft must be turned at some speed, so the engine sucks air-fuel mixture and compresses it.

The flywheel with a large gear ring is into the engine. The flywheel rim has the teeth on the surface. The drive gear of the starter engages with it and does the rotating the crankshaft, initiating the duty cycle of the engine. A starter is a special device used to rotate crankshaft an internal-combustion engine.

So as internal combustion engine rely on inertia from each working cycle to initiate the next working cycle and to start the first cycle of an engine the first working stroke powered with starter. In order to quickly turned on and off switch is use solenoid. Let’s see how it works: When you turn the ignition key current feeds to the solenoid and starter is switch on. The return spring serves to switch off starter, when you release the key.

How the starting system works

By the current feeding to the solenoid, the electromagnet attracts an iron rod. Two heavy contacts close the rod movement and the circuit from the battery to the starter is completed. The starter motor must turn no more time than needed, to start the motor. A long Engine and starter work at one time can do the starter badly damaged. These fault signs in starting system can help you to recognize the reasons why your car does not start. And at last, if you encountered the repair of the starting system, it is not a cheap procedure so it would be good to know how to repair a starter DIY. There is a table about how much does starter repair cost, if you’re interested.

Consider the electric motor of the starting system that creates torque. The body of the electric motor is made of steel and has the appearance of a cylinder. Inside the housing there are field windings wound around cores attached to the housing. These windings are made of thick conductive wire capable of withstanding strong electric current. The windings generate an electromagnetic field that can rotate the starter armature. One of the elements of the anchor is the core, with grooves along which are located the turns of the windings of the anchor. Both ends of each winding are connected to the collector. The torques created by each of the windings add up so that you can rotate the armature, more precisely the armature shaft. If you look at the starter from the side of the collector, you can see the brush holder at the anchor.

Starter construction

Starter anchor.  The starter anchor consists of a shaft, a core with grooves on which the starter winding is installed. For a detailed study, I suggest using the starter anchor circuit.

The solenoid relay is used to supply current to the starter motor and engages the bendix in engagement with the flywheel to start the engine.

Engine starting system curcuit:

Starter anatomy

1. The collector; 2 – a back cover; 3 – stator housing; 4 – traction relay; 5 – relay anchor; 6 – cover on the drive side; 7 – lever; 8 – lever bracket; 9 – a sealing lining; 10 – planetary gear; 11 – drive gear; 12 – lid insert; 13 – a restrictive ring; 14 – drive shaft; 15 – freewheel; 16 – a leash ring; 17 – support shaft drive with a liner; 18 – gear with internal gearing; 19 – drove; 20 – the central gear; 21 – support shaft anchors; 22 – a permanent magnet; 23 – anchor; 24 – brush holder; 25 – brush.

1. Engine starting system drive system

This mechanism transmits torque from the electric motor to the flywheel. A drive gear is installed on the armature shaft. The action of the electromagnetic switch forces the drive lever to translate the drive gear into engagement with the gear rim of the flywheel (in this position, the rotation is transmitted to the motor shaft). When the engine is started, the window clutch disengages, and now the drive gear rotates to idle. Later, with the ignition on, the drive gear disengages from the toothed rim.

Now consider the real mechanism: the window clutch transmits rotation in only one direction and is connected to the drive gear. There are screw slots on the starter motor clutch. Screw slots are also available on the armature shaft. The drive gear is able to slide along them while rotating. Screw slots provide smooth engagement of the drive gear with the gear rim. After the gear rim engages with the drive gear, the engine spins. The drive gear rotates the gear rim (while the window clutch works). When the engine is started, the engine rotates the drive gear, while the window clutch is disconnected. The drive gear rotates idle so as not to damage the electric motor.

2. The electromagnetic switch

Electromagnetic switch – forces the drive lever to move the drive gear and directs the current to the electric motor.

In the center of the switch is a plunger. The plunger performs two functions: it moves the drive lever connected to one end of the plunger, and also includes the main contacts through the contact plate connected to its other end. A plunger surrounds the plunger, which pulls the plunger to the main contacts. A retention winding is located over the retracting winding, which holds the plunger at the contacts. When you turn the ignition key, an electric current passes through the retracting and holding windings, creating a magnetic field. This field moves the plunger to the right. As a result, the contact plate closes the main contacts. Now terminal 30 closes with terminal C connected to the motor. A powerful current is supplied to the starting electric motor, at the same time, the drive lever engages the drive gear and it starts to spin the engine.

How is the electromagnetic switch?

The retracting and holding windings are fixed on the switch housing. The contact plate is located at the end of the plunger opposite the main contact. Retracting and holding windings are placed around the plunger, which is drawn by the return spring. After starting the engine, a return spring moves the drive gear to its original position.

Engine starting system diagram

  • Electric motor;
  • Transmission system;
  • Electromagnetic switch;

The electrical circuit of the engine starting system

electrical circuit of the engine starting system

The positive pole of the battery is connected to terminal 30 and the ignition switch. Terminal C is connected to the field windings and the armature winding, grounded to the housing and then connected to the negative pole of the battery. All connections are made by a powerful cable that can withstand high currents. Terminal 50 is connected to the positive terminal of the battery through the ignition switch.

When turning the ignition key, the current first passes through the retracting and holding windings, then along the field windings and the armature winding, and finally to the ground. Since the resistance of the armature and field windings is very low, almost all battery voltage falls on the retracting and holding windings. The field arising in them moves the plunger to the right. The drive lever associated with the plunger moves the clutch to the left, while turning it on the screw slots of the anchor. Together with the engagement of the drive with the flywheel ring gear, the main contacts are temporarily closed. When the main contacts are closed by the contact plate of the field winding and the armature is powered directly from the battery. After closing the contacts, the potentials of terminals C and 50 are equalized. The retracting winding no longer acts on the plunger. And it is held in its former position only by the magnetic field of the holding winding. When, after starting the engine, the ignition key is turned off, the main contacts remain closed. But now the current from the main contacts in the retracting winding comes in such a way that its magnetic field is opposite to the field holding the windings. Both magnetic fields cancel each other out. Now the return spring moves the plunger to its original position and opens the main contacts. At the same time, the drive gear disengages and returns to its original position.