VS - Electrical Systems From Stop-Start to Hybridization

Engine acyclisms The functioning of Integral Combustion Engines is characterized by the alternation between the phases of compression and combustion. The Cyclic Variations of the pressure inside the cylinder cause rotational speed variations, these variations are called acyclisms. Acyclisms cause a non-uniform rotation speed; they are also defined as torsional vibrations. This succession of acceleration and decelerations in the rotation-cycle is transmitted to the belt drive, as the auxiliaries inertia do not allow to follow this sudden deceleration a counter torque applies to the belt drive, leading to slippage.

Tailored belt drives are mandatory to perform Micro- Hybrid and further Mild-Hybrid function with Belt Starter Generator machines, their design depends on: ●● Hybridization level (recovery, torque assist, boost..levels) ●● Engine capacity (torque level to crank the engine) ●● Engine torsional vibrations ●● Engine driveline (Dual mass Flywheels architectures impact crankshaft front end rotational vibrations due to a lower primary wheel inertia) ●● Engine front-end layout ●● Dynamic loads

A dual tensioner secures the slack side of the drive and avoids belt slippage With dual t nsion r

Starter Alternator

500

400

300

With dual tensioner

200

Crankshaft

100

Crankshaft

Rotary speed (reduced) in U/min.

Auxiliary pulley

000

1

0

Time in sec.

400

-200 -100 0 100 200 300

Engine irregularities expressed in torque variation (Nm)

Engine irreg in torque var

Torque (Nm)

0

90

180

270

360

450

540

630

720

Crankshaft angle (°)

0.1

0.05

0

Engine irregularities expressed in angular displacement (deg)

Engine irreg in angular di

-0.05

-0.1 Displacement (°)

-1.15

0

90

180

270

360

450

540

630

720

25

Cranshaft angle (°)