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Mild Hybridization

PO Mild Hybrid

With System Competence to Maximum Efficiency

I. Introduction

II. PO Mild Hybrid as an efficient integration strategy

III. Effects on the belt drive system

Video 1 Functionality of the decoupling tensioner

Figure 1 Operating modes of a decoupling tensioner

Figure 2 Tensioning elements and decoupling tensioners for PO belt drives

Figure 3 Decoupling function of a PO system, based on two individual tensioners (above), compared to a PO system with a decoupling tensioner. Graphed here are speeds over time during generator operation; the BSG speed is converted to the crankshaft

Figure 4 Belt pulley decoupler

Figure 5 Decrease in engine irregularities by using a crankshaft decoupler. Graphed here are speeds over time during generator operation; the BSG speed is converted to the crankshaft

IV. Design criteria for maximum benefits

Figure 6 Simulation of a PO 48V system during boost operation: Average belt slippage at the belt pulley on the generator side for two pulleys 51.3 mm (light-green characteristic curve) and 56.0 mm (green characteristic curve) in diameter.

Figure 7 Torque limits of the e-machine due to the maximum admissible belt forces, depending on the belt width, BSG diameter, and wrap angle.

Figure 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

Figure 9 Electromechanical belt tensioner

Figure 10 Torque at the interface to the crankshaft Left: standard design; right: optimized characteristic curve of the “shifting error” load case

Figure 11 Switchable belt pulley decoupler for air conditioning when the combustion engine is stopped

V. System behavior in the drive

Figure 12 Reduction in the bearing forces on the crankshaft pulley by using a crankshaft decoupler

Figure 13 Friction power vs. effective medium pressure and speed in a three-cylinder engine with a displacement of 1.0 l and a PO belt drive. Using color gradients, the diagram shows the advantage in the overall drive torque in the case of a rolling bearing arrangement in the first position of the crankshaft.

Figure 14 Vibration system of the belt drive – decoupler – crankshaft – dual-mass flywheel: rotational irregularities when starting the engine, both before (middle) and after optimization (right); green: crankshaft; bright green: belt pulley

Figure 15 Sample parameter test of dual-mass flywheel and decoupler characteristic curves

VI. Vehicle system integration

Figure 16 Schaeffler components interacting in the GTC I technology car: PO belt drive with decoupling tensioner and crankshaft decoupling on the left; E-clutch actuator on the right

Figure 17 Time-weighted occurrence of various loads in the PO drive over the electric motor speed for two operating strategies: histogram analysis in sport mode on the left and in comfort mode on the right

Figure 18 Results of RDE test drives: influence of the clutch closure time on the recuperated energy in the same vehicle

VII. Maximum efficiency

VIII. Summary

The digital version of the Schaeffler Symposium 2018 “Mobility for Tomorrow” conference transcript

II. PO Mild Hybrid as an efficient integration strategy

VII. Maximum efficiency