Motion System Design

Pancake motors go for an e-drive

Engineers at The Timken Co., Canton, Ohio, are developing one of the key components for tomorrow's electric cars. For the past few years, they've been working on electric automotive wheel drives, or e-drives, designed to convert electrical current to mechanical drive torque, right at the wheels.

Timken's latest design incorporates an axial-gap motor, hub sensor, gear reducer, and roller bearing in a high torque-density package. It has been tested under simulated road conditions and the results so far have been promising, closely matching analytically predicted performance. According to the developers, the unit is able to accept heavy loads and is well suited for a wide range of vehicle platforms.

Most of the components in the wheel drive are of Timken's own making. The company best known for its tapered roller bearings also manufactures automotive wheel-hub (speed) sensors and designed and built the axial-gap motors that it's using in prototypes. The choice of the axial-gap technology was dictated by the application more than anything else.

Axial-gap motors, as their name suggests, produce flux in an axial, rather than radial, airgap. Both their rotor and stator are flat, not cylindrical as in ordinary motors. The resulting disc-shaped envelope makes axial-gap motors ideal for integration into spaces such as the recess of an automotive wheel hub.

For automotive designers, the mere thought of putting torque generators inside of each wheel should stoke the imagination. For one thing, it would give engineers unprecedented design freedoms in the use of under-vehicle space. Not only does it eliminate drive shafts, universal joints, and differentials, but also exhaust systems, yokes, mufflers, hangers, and catalytic converters. What's more, self-driving wheels allow for independent wheel control, translating to better vehicle handling and traction.

For more information, contact The Timken Co. at (330) 471-4392.

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