Although single-speed transmissions are a staple of today’s electric vehicle (EV) designs, the gearbox design gurus at UK-based Antonov Plc recently announced some very encouraging test results on a super-efficient three-speed automatic designed specifically for use in the EVs of tomorrow. The data was presented last week in Stuttgart, Germany, at the IDTechEX Electric Vehicles Conference, where Antonov’s transmission received the Technology Award for being the most significant EV development during the past two years. In accepting the plaudit, Antonov’s business development manager, Dave Paul, noted that real-world testing in Jaguar’s Limo-Green XJ experimental research vehicle saw the firm’s new three-speed yield a 14.7-percent increase in efficiency compared to the single-speed transmission that was originally fitted.
Today’s conventional thinking on EV transmissions is that the virtually flat torque curve of an electric motor negates the need for the extra weight and complexity of additional gearing. However, Antonov claims that’s only one part of the overall power delivery equation. By upping the ratio count, the firm contends it’s possible not only to decrease the size of the motor itself, but to keep it operating at the most efficient rotational speed, which can vary between about 90 percent at best to a about a mere 60-percent level. That consideration, Paul says, ultimately has far greater impact on the system’s total energy use than does the torque curve. One additional benefit of the Antonov EV transmission is its innovative hydraulic cooling circuit. Capable of being directly linked to a parallel system on the electric traction motor, it can help reduce critical power-sapping heat levels when the vehicle is stationary to further boost efficiency.
Like many of today’s conventional automated manual gearboxes, Antonov’s transmission incorporates a dual-clutch “powershift” design that allows cog changes to be made with zero torque interruption. Although the current example is capable of handling a motor that produces up to 295 pound-feet of torque, it’s a fully scalable design and also employs programmable computerized control logic that permits customized actuation mapping for any specific application. Compact and lightweight, Antonov says it has the potential to delivers quicker acceleration, quieter and more relaxed cruising also can be linked to the vehicle’s on-board telematics system to better anticipate things like road gradients, a feature that adds even more to its inherent range-enhancing capabilities. Depending on a manufacturer’s per-charge range requirements, this multi-speed transmission also opens the door to fitting smaller and therefore lighter and less-costly battery packs. Although Antonov is currently working on a commercial application for an EV delivery van, there’s still no word as to when its new transmission will appear on a battery-powered passenger car.
