Fresh Mazda rotary hybrid sports car patent revealed

Just when we thought the age-old Mazda rotary sports car saga couldn’t possibly have any more twists or turns, the Japanese brand has filed yet another patent application for a rotary-based hybrid powertrain housed within a coupe silhouette not unlike that of the 2015 RX-VISION concept.

Originally filed with the US Patent and Trademark Office  in 2021 but only just published this week, the design patent details an innovative new hybrid sports car powertrain comprising a rotary petrol engine, three electric motors and a unique variable-voltage battery system.

The rotary is understood to be the primary driving force of the package as opposed to a range-extender and is supported by a pair of 17kW induction motors up front – one at each wheel – and a 25kW permanent magnet synchronous motor that sits behind the petrol engine and helps drive the rear wheels.

Hybrid systems with more than one kind of motor aren’t especially common and the two used in this application are thought to have been chosen for their differing torque deliveries, which should yield a flat and wide torque band to offset the traditionally peaky nature of rotary engines.

The variable-voltage battery system is equally if not more complex in that it’s comprised of four 48-volt modules mounted behind the front seats, operating as traditional 48V batteries during low throttle applications but reconfiguring into two pairs of 96V modules when more power is called for, when they act in series to produce more current.

Mazda reckons this configuration saves weight and production complexity compared to having a larger capacity traditional battery with more high-voltage connections and pathways.

It isn’t clear if the powertrain is a self-charging or plug-in system, but the patent abstract reveals drive from the motors is prioritised while pottering around or cruising, leaving the rotary to engage when maximum power is required or the driver fancies some spirited driving.

“Assume here that the driver operates the switch to change the mode to the engine cruise mode and depresses the accelerator pedal,” it reads.

“In the engine cruise mode, the control unit starts supply of fuel to the engine, whereby the engine produces torque.

“Meanwhile, the control unit stops control on the inverter to stop the drive by the main drive motor.

“The driver then can enjoy the feeling of driving the vehicle driven by the engine.”

As we understand it, the front motors are still engaged in this mode, which means the hypothetical sports car operates as a heavily rear-biased all-wheel drive vehicle in its most aggressive drive modes.

But while all this is intriguing, the patent was submitted about 18 months before Mazda’s assistant manager of powertrain development, Yoshiaki Noguchi, poured cold water on the idea of a reborn rotary sports car, declaring in January it “is not the time for that”.

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