- crank pins
- Counterweights & Bearings
- Oil pump
The working forces of the pistons are transmitted to the crankshaft via the connecting rod. The crankshaft is a solid shaft that converts the translational movements of the connecting rod into rotary movements. A crankshaft is a long shaft with one or more protruding cranks on it. The connecting rods are mounted on these cranks, which in turn are connected to the pistons. As the piston moves from TDC to ODP, (from top to bottom) the connecting rod is pushed down which then spins the crankshaft.
At the front of the crankshaft are often the timing drive and the crankshaft pulley with any vibration damper. It's on the back flywheel and the link. Sitting at both ends crank seals which provide the seal between the rotating crankshaft and the engine block.
A crankshaft is an important part in anything that makes a motorized movement. The crankshaft must be designed accurately to the micrometer because a lot of forces are placed on it. In addition, a crankshaft makes very high rotational speeds, which means that a small construction or assembly error can lead to major imbalances and damage.
The engine speed, which is displayed for example by the rev counter in the instrument panel, is determined by the number of revolutions the crankshaft makes per minute. The crankshaft speed is measured by the crankshaft position sensor (sometimes called TDC sensor).
To distribute the combustion forces over the entire crankshaft, the power strokes are distributed. To this end, the crankshaft is equipped with crank pins. In a four-cylinder in-line engine, these crank pins are rotated every 180° relative to each other. In a V6 engine, the crank pins are often rotated 60° relative to each other.
Counterweights & Bearings:
The crankshaft is also loaded by mass forces that come from the up and down mass movement. To compensate for these mass forces, counterweights are used to compensate for the mass forces. With certain motor constructions it is not sufficient to limit the vibrations by means of the counterweights. Balance shafts are then used in the engine here. See the chapter here balance shaft.
The crankshaft is mounted in the engine block by means of main bearings. The crankshaft in the picture above has 5 main bearings, but there are also crankshafts that have 3 bearings. The connecting rods and pistons are lubricated through bores in the main bearings and crankshaft.
The crankshaft is also equipped with axial bearings in the case of a main bearing (flywheel side or middle). These bearings are intended to absorb the axial forces (in longitudinal direction) of the crankshaft as a result of depressing the clutch, accelerating and braking.
The oil pump is driven directly by the crankshaft. The drive can take place via sprockets, but also via a chain (see picture). Click here for more information about the oil pump.