The Schaeffler Group, a multinational conglomerate that makes a range of electric drivetrain components, fielded an EV at July’s E-Car Rally in Montafon, Austria, held on the dream roads of the Alps.
The STEP2, Schaeffler’s third entry in this yearly event, is an EV with a drive from the Schaeffler subsidiary IDAM and a two-speed powershift transmission.
“With a two-speed gearshift system, a low ratio for high tractive force and a high ratio for good overall efficiency also at high driving speeds, we offer higher dynamics and at the same time we achieve a longer range of electric operation,” said Schaeffler VP Uwe Wagner.
An electric motor has “islands of efficiency” with regard to torque generation and the speed of the rotor. When the rpm of the motor is fixed to the vehicle’s speed, the case with a single-speed transmission, you slip in and out of the most efficient zone (90 to 95 percent) pretty quickly. A two-speed transmission helps the efficiency of the system, both in the delivery of energy to the road and regeneration of energy. “We have predicted by simulation, and hopefully will be measuring pretty soon, that having a two-speed transmission can add about 6 percent more range, because you can keep the electric motor closer to its peak efficiency while driving and during regenerative braking,” Jeff Hemphill, Schaeffler North America’s VP and CTO, told Charged in a interview last year.
The STEP2’s electric motor can be coupled with two ratios via a transmission made up of a planetary gear set, wet multi-disk clutch, band brake and lightweight differential. The first and second gear ratios are produced by alternately closing the brake and clutch. System output is up to 70 kW (peak) and 50 kW in continuous operation.
In simulations and test drives, the STEP2 concept vehicle has achieved a reduction in energy consumption of around six percent compared to a comparable vehicle with only one gear, according to the company.