Structure/Function - BMW F97 Technical Training Manual

F97/F98￿Complete￿Vehicle
4.￿Powertrain
F97/F98,￿M￿GHAS￿external￿view
Demand-controlled￿lock
The￿lock￿is￿a￿demand-controlled￿rear￿axle￿differential￿lock￿which￿is￿active￿in￿the￿following￿situations:
• Pullaway
• Differential￿speed￿at￿the￿rear￿axle￿for￿straight-ahead￿driving￿under￿tension￿due￿to￿various
coefficients￿of￿friction,￿left/right
• M￿dynamic￿cornering￿tensioned
• Power￿oversteer￿(slight￿steering￿drift￿in￿MDM￿mode)
• Stabilization￿in￿coasting/overrun￿mode.
Traction,￿handling￿and￿driving￿stability￿are￿optimized￿by￿adjusting￿a￿defined￿differential￿speed￿or
differential￿torque￿at￿the￿rear￿axle.
The￿regulated￿M￿rear￿axle￿differential￿lock￿works￿with￿a￿position-controlled￿electric￿motor￿and￿a￿ball
ramp.
4.3.6.￿Structure/Function
The￿lock-up￿torque￿is￿generated￿by￿a￿multidisc￿clutch.￿The￿necessary￿axial￿pressure￿is￿applied￿to￿the
multidisc￿clutch￿by￿the￿position-controlled￿direct￿current￿motor￿by￿means￿of￿gears￿and￿a￿ball￿ramp
mechanism.￿The￿clutch￿package￿operates￿between￿the￿expansion￿tank￿housing￿(steel￿outer￿discs)￿and
the￿right￿output￿(steel￿inner￿discs￿with￿carbon￿friction￿lining).
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