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Future hybrid Vehicles with advanced 48V electrified drive train technology to reduce Co2 emission
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on November 21, 2019 by SAE International in United States
Event: NuGen Summit
Future hybrid vehicles with advanced 48V electrified drive train technology to reduce CO2 emission. Chandrakant Palve* Pushkaraj Tilak * * Mercedes-Benz Research & Development India Pvt. Ltd. Bangalore. India. Key Words: 48V, CO2, P3 Hybrid, Electrified powertrain, AMT, emission, shift comfort, motor Research and/or Engineering Questions/Objective Global automotive industry is putting effort in moving from conventional powertrain technology to hybrid & electric powertrains. This efforts plays a vital role to achieve cleaner environment, improved performance, reduced fossil-fuel dependency, low noise for meeting regulatory & customer requirements. Automotive industry is facing a challenge of meeting stringent CO2 emission targets of 95g & 175g per kilometer for passenger cars & light commercial vehicles respectively. 48V is an important stepping stone in this direction. By taking motivation from this strategic challenge, advanced 48V P3 electrified powertrain technology has been proposed. The objective of this research is a novel electrified powertrain which offers Dual Clutch Transmission (DCT) level of shift comfort in combine with CO2 benefit without additional cost and weight penalty. Methodology The present study describes a unique architecture of combining Automated Manual Transmission (AMT) along with high performance 48V electric motor. Technical concept selection from multiple hybrid layouts to arrive at P3 configuration for optimum results are described. Incorporation of primary shaft speed sensor, position sensor for Clutch Slave Cylinder & AMT module interface with shifter shaft are proposed with detail design. Power flow from electric motor to transmission shaft posed a particular challenge due to restrictions on complexity of changes to transmission. Further, reverse drive functionality is achieved by electric drive thus enabling elimination of reverse gear & mechanism. It will give dual benefit of decontenting & light weighting. Novel axial coupling using claw washer for torque transfer to existing secondary shaft was developed. Extensive virtual analysis including belt drive performance, permissible axial & angular misalignment analysis, stress & NVH analysis for electric drive integration components & 1D cooling system analysis has been carried out before manufacturing of all the Components for P3 hybrid configuration. Manufacturing processes included block machining, Electro Discharge Machining, hardening & 3D printing were used to achieve the timeline & reliability during typical operating conditions. Special assembly procedure was developed to ensure seamless integration of electric drive to existing transmission. Two stage testing was carried out. AMT test was carried out on aggregate test bench followed by complete eAMT powertrain (along with engine) test on bench. Results Test bench results indicate that with the new eAMT, a 95% reduction in torque variation during gear shifts was achieved compared to base manual transmission. Powertrain performance enhancement of 24% & 60% in power & torque respectively is possible. Recuperation functionality of electric drive helped to achieve considerable CO2 reductions with respect to baseline powertrain. Above all benefits were achieved without any weight penalty compared to Dual Clutch Transmission. Conclusion 1. This study demonstrates a promising option to meet stringent CO2 emission norms for passenger car application by integration of high performance 48 V hybrid technology. 2. Proposed technology can be easily implemented with minimal modifications & short timelines on existing conventional powertrains for automotive application. 3. Smart synergy of technologies can achieve combined benefits of enhanced drivability along with CO2 reduction.