The Electric Transaxle Technology

The patented Electric Transaxle™ is a unique efficient device that can replace traditional geared differential units with a complete electric propulsion unit for land based applications. Due to its simplicity and efficiency, the Electric Transaxle provides a novel solution compared to that of other electric propulsion systems. Furthermore, it provides an added advantage of operating as a Continuously Variable Transmission (CVT), being able to vary the torque over a wide range of RPM.

The Electric Transaxle develops its range of torque through the combination of permanent magnet (PM) brushless DC Motors and two planetary gears sets, one for each drive wheel of the Electric Transaxle. The PM motors have a flat torque curve which provides significant torque at lower useable RPMs. This in conjunction with the planetary gear set provides torque multiplication from two motive inputs and combines them into one output. In the Electric Transaxle configuration we have decided to deploy, this is achieved by sharing a common ring gear structure between the two planetary gear sets. The two Sun gears are each powered by their own individual motive force, allowing the complete Electric Transaxle to operate each of the two wheels independently. Allowing independent control of each wheel in the Electric Transaxle gives a wide variety of drive modes including limited slip differential, locked differential, and variable torque differential all with regeneration.

Digital control of the Electric Transaxle implements the efficient use of torque on demand. As torque demand is required, the Electric Transaxle responds, supplying enough torque to move the dead load off the line and accelerate quickly. This is achieved by accurately applying different RPMs to each of the Electric Transaxle Components (Sun, Ring, and Sun). As the load decreases, the torque needed decreases, eventually ending up with the three main components (Sun, Ring, Sun), rotating precisely at the same RPM. When all the components of the Electric Transaxle are rotating at the same RPM, the two planetary gear sets are locked together and the motors have a one-to-one relationship to the wheel and load. This point of operation is the most efficient due to removing the loss from the planetary gear sets, and also reducing the wear and tear on the planetary gear sets as well.

Efficiency of any electric drive unit should be of the utmost importance. Where most competitors systems with fixed gear ratios have a maximum system efficiency of 88%, the Electric Transaxle efficiency utilizing the planetary gear sets starts at 88% and has a maximum efficiency of 93%.