48V demo vehicle highlights potential of mild hybrid

October 11, 2016 // By Christoph Hammerschmidt
The introduction of the 48V supply as complementing element to the 12V supply in passenger cars holds out the promise of better fuel economy without negatively impacting the driving experience. At the 25th Aachen Colloquium on engine and vehicle technology, mechatronics supplier Schaeffler AG showcased a vehicle that made extensive use of 48V components.

Though the increasing number of electric and electronic components in vehicles contribute to raise the energy consumption and thus the fuel consumption, a well-balanced design can actually reduce fuel consumption – this is the overarching claim of the masterminds of the 48V technology. Indeed, numerous vehicle functions that once were implemented with mechanic components are today electrified. Examples are roll stabilizers, electric turbo chargers, auxiliary air conditioning without engine support, stop-start systems and mild hybrid architectures. All these concepts and components are the drivers for the 48V concept, and hybridization is a proven concept to increase the fuel efficiency.

Schaeffler’s technology carrier shown at the Colloquium features a powertrain architecture with an electric motor as an “electric axle” on the rear axle, a configuration known as P4. The integrated electric drive adds 20 kW of purely electric power to the vehicle’s overall performance – and this not only for seconds or fractions of a minute but continuously. In this concept, the electric axle complements the internal combustion engine that drives the front axle. In the demo vehicle, the combustion engine was connected over a belt to a 48V starter generator.

The electric axle generates a maximum starting torque of 200 Nm, enabling electric driving at speeds up to 35 kmph as well as actively soaring at 70 kmph or more. Another unique feature of this two-speed axle is torque vectoring, the controlled distribution of the torque to the wheels. This feature increases agility and safety of driving, claims Schaeffler. In combination to the IEC-based front wheel drive, the electric axle turns the car to an all-wheel drive vehicle. In most cases, the kinetic energy of the vehicle is recuperated during braking and fed back into the energy circuit, enabling significant reductions of fuel consumption. In addition, in the Schaeffler implementation the power electronics unit is integrated into the electric motor, which reduces the space requirements in a critical area of