280 MILD H Y B R IDI Z AT I O N 17 28117 M ILD H Y B R IDI Z AT I O NSchaeffler Symposium 2018 hybrids and standard applications is already cove red The main focus of more recent developments is on an increased power density and a greater transfer capacity of the decoupler so that even challenging P0 applications can be handled effi ciently Particularly with P0 applications the inter action with the activation strategy of the starter generator is an important aspect the effect of which is accounted for by the holistic system ap proach when defining the characteristic curve Thanks to the optimizations it is possible for Schaeffler to offer belt pulley decouplers that pro vide the automobile manufacturer with additional degrees of freedom for its application strategy The characteristics ranging from overload pro tection during dynamic operation to the factoring in of misuse operating conditions are heavily dependent on the system environment such as powertrain rigidity levels and torque gradients when the clutch closes quickly Since there is an extensive and equalized simulation environment ley interface is not exceeded Figure 10 This is particularly important for central screw connec tions With the switchable decoupler Schaeffler is of fering a comfort extension in the portfolio of de coupled belt pulleys This delivers all of the ad vantages of a standard decoupler for P0 mild hybrid applications and is also additionally equipped with actuators used to separate the torque flow between the crankshaft and belt drive as needed This makes it possible to continue ope rating the air conditioner compressor located in the belt drive via the P0 starter generator when the combustion engine has stopped such as du ring sailing or after stopping at a traffic light The fact that temperature fluctuations in the vehicle interior are now prevented causes customer ac ceptance of start stop operation to go up consi derably It is also possible to attain consumption advantages by stopping the combustion engine during real driving when air conditioning is needed The combustion engine is comfortably restarted through the belt starter generator after the ac tuators close The current optimizations of the switchable de coupler enable the possible applications to be extended to typical installation space situations thereby reducing the need for space Moreover there is also the option of keeping the link to the crankshaft open even during combustion engine operation allowing the belt drive to come to a standstill Schaeffler already has a broad portfolio of tensioners and belt pulley decouplers for stand ard and P0 mild hybrid belt drives The further developments shown for the components and subsystems can be used to bring about additio nal advantages and thus more efficient utiliza tion of the P0 strategy at the customer s Never theless the optimizations must not be seen as relating only to the belt drive as a system regar ded in isolation 9 Electromechanical belt tensioner Basic variant Optimization PYD characteristic optimization in misuse case 0 0 5 1 1 5 2 Time in s 100 0 200 300 400 500 600 700 To rq ue in N m ca 645 Nm ca 480 Nm Decoupling tensioner Gen 1 6 PK up to 7 PK SOP 2017 Decoupling ring tensioner Gen 2 Pulley down Weight 20 max starter Db 70 mm 6 up to 8 PK Decoupling ring tensioner Gen 3 Pulley up Weight 30 max starter Db 70 mm 6 up to 8 PK 8 Decoupling tensioners in comparison left series standard middle tensioner pulleys facing in the direction of the e machine right tensioner pulleys facing away from the e machine 10 Torque at the interface to the crankshaft Left standard design right optimized characteristic curve of the shifting error load case 11 Switchable belt pulley decoupler for air conditioning when the combustion engine is stopped including the power train on the one hand and extensive exper tise for designing and applying arc springs derived from applica tions of the dual mass flywheel on the other it is already possible to make high quality predictions at an early stage with regard to how various combina tions will behave later on The upshot of these optimizations is that even in cases of misuse the admis sible torque at the crankshaft belt pul

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