Low-Height Differential Concepts for EVs 2018-01-1294
Compared to the internal-combustion-engine (ICE) vehicles on the road today, Electric Vehicles (EV) deliver more torque to vehicle wheels, and require smaller driveline packaging envelopes. Current differentials use asymmetrical ring gears with differential housings that are roughly a third of the tire outside diameter. New differential architecture concepts are shown here to deliver more torque to the wheels, while decreasing the height of the differential as much as fourfold. Most EV’s are driven by one or more torsion motors, delivering torque to the left side and the right side of the EV’s at different speeds during a vehicle turn, or a wheel “spinout.” At low speeds, the EV motors deliver more torque to the wheels than comparably sized ICE vehicles, so EV differentials must be built stronger and stiffer to manage the distribution of available drive torque. But, less space is available within EV’s as battery space is added while passenger and cabin space is expanded, leaving a smaller envelope for the driveline in competitive models. New concepts that reduce the vertical envelope by seventy-five percent are depicted here, with analysis of the methods of higher torque in a smaller package. Novel methods with smaller ring gears, internal cases, reduction of residual loading, and redistribution of components are depicted, explained, and justified for size, torque, shape, and mass. The open space necessary for additional componentry such as limited slip or lock-up are shown, so the EV driveline can be optimized for cabin space, road clearance, aerodynamics, and energy efficiency. Although these architectures focus on EV applications, they can be used for retrofit into ICE pass-car, light truck, and heavy truck vehicles.