Proterra has selected Eaton’s eMobility business to supply a 4-speed medium-duty electrified vehicle (EV) transmission for the company’s ProDrive drivetrain used in Proterra ZX5 electric transit buses.

The medium-duty 4-speed transmission, to be used in city buses in North America, addresses the primary issue related to single-speed drives that have contradictory requirements for high efficiency at top speeds and increased torque at launch and low speeds.

The transmission is a lightweight, countershaft gearbox with torque capacity up to 1,200 N·m (885 lb.-ft.) and electric gearshift actuation that enables manufacturers to use smaller, more efficient motors.

Eaton’s 4-speed medium-duty electrified vehicle (EV) transmission has fine-pitch helical gears that ensure smooth, low-noise operation and a shifting strategy designed to extend range and battery life.

Eaton’s 4-speed transmission has fine-pitch helical gears that ensure smooth, low-noise operation and a shifting strategy designed to extend range and battery life. Road tests have shown a 20% to 30% efficiency improvement in energy consumption under normal driving conditions compared with a direct-drive transmission and a 10% to 15% improvement compared with a current 2-speed solution.

Eaton has been in the hybrid transmission business for over 15 years, and we have more than two billion miles of reliable operation of hybrid transmission-equipped trucks and buses on the road. Our 4-speed transmission provides uncompromised launch-ability on grade and has shift points to keep the electric motor operating in its most efficient region while drivability and vehicle safety is taken into account.

—Julie Marshaus, manager, New Product Introductions, ePowertrain, Eaton’s Vehicle Group

Eaton’s eMobility business was formed by combining products, expertise and global manufacturing capabilities from Eaton’s Electrical and Vehicle Groups. The eMobility product portfolio includes intelligent power electronics, reliable power distribution and protection solutions, and efficient ePowertrain solutions for passenger car, commercial vehicle and off-highway customers.