Eaton to supply medium-duty transmissions to Proterra for electric transit vehicles

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

“Our EV transmissions have unmatched performance, providing class-leading acceleration, horsepower, range and durability,” said Julie Marshaus, manager, New Product Introductions, ePowertrain, Eaton’s Vehicle Group. “The transmissions also have the ability to enable longer range due to efficiency gains.” 

The medium-duty four-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 Nm (885 lb.-ft.) and electric gearshift actuation that enables manufacturers to use smaller, more efficient motors. 

Eaton’s four-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 percent­ to 30 percent efficiency improvement in energy consumption under normal driving conditions compared with a direct-drive transmission and a 10 percent to 15 percent improvement compared with a current two-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,” Marshaus said. “Our four-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.”