Mazda was granted a new U.S. patent this week for the design of an offset wheel-mounted motor for electric and hybrid vehicles. In previous wheel/hub motor configurations, the motor has typically been mounted concentric with the wheel. The essence of the patent is that the motor is offset from the wheel axis, with a gearset installed to provide drive torque to the hub.
Usually, a hub motor consumes most of the space inside the wheel, limiting the possible mounting locations for the suspension links and compromising ride and handling. In theory, Mazda's new arrangement provides more room in the wheel and flexibility for the suspension geometry. However, the gearset hardware at the wheel will increase unsprung mass and degrade the ride and handling accordingly.
There is another possible benefit of this type of installation, however. It provides Mazda with the flexibility to do either a through-the-road hybrid, by having motors on one axle and mechanical drive at the other end, or a power-split hybrid. By offsetting the motor, drive from an engine could still come in through the hub and the gearset could be used for torque blending. Whether this is actually better than the traditional power-split hybrid used by Toyota and Ford is debatable. Finally, there could be a simpler explanation: The real motivator for this patent might be to create a hybrid system that doesn't conflict with patents held by numerous other automakers. Thanks for the tip, Charlie!
