VS - Electrical Systems From Stop-Start to Hybridization

11

Belt Starter Generator drives To new Front End Accessory Drive Conventional belt drives do not comply with Stop- Start torque transmission needs, they are not able to maintain enough driveability between the belt and the pulley in cranking conditions requiring adaptations: in the belt layout, in the tensioner and in the belt type. The figure below illustrates the slippage phase that occurs if using a conventional tensioner in a cranking phase, a long slippage event occurs prior the drive is able to put in motion the engine crankshaft.

Starting by the StARS Micro-Hybrid and followed by Mild-Hybrid belt drive generations, all Belt Starter Generator drives (BSG) differ from conventional Front End Accessory Drive (FEAD) in several ways and are designed to: ●● Delivering torque to the crankshaft when starting ●● Delivering torque to the crankshaft in torque assist phases ●● Absorbing torque from the crankshaft when producing electricity ●● Absorbing torque from the crankshaft in the “engine stalling help” mode ●● Absorbing torque from the crankshaft in electrical recovery phases ●● Supporting peak dynamic forces Considering the maximum torque during these cycles: ●● Belt performances are made higher ●● Wrap angle is increased Considering belt tension fluctuations during start and charge modes (slack span & tight span), a new tensioner concept is required to guarantee power transmission to the engine crankshaft and from the engine crankshaft without slippage.

Conventional tensioning

Starter Alternator

500

Belt Starter Generator rotation

400

Crankshaft

Starter Alternator

500

300

400

Crankshaft

200

300

Slippage

200

100

Slippage

100

000

Rotary speed (reduced) in U/min. 000

Rotary speed (reduced) in U/min.

1

0

1

0

Time in sec.

Time in sec.

A unique conventional tensioner does not allow Sto Belt Starter Generator rotation A unique conventional tensioner does not allow Stop-Start features

Starter Alternator

500

400

Crankshaft

Belt Starter Generator rotation

300

200

Slippage

100

24

000

Rotary speed (reduced) in U/min.

1

0

Time in sec.

A unique conventional tensioner does not allow Stop-Start features