Mazda files patent for hybrid rotary engine IS MAZDA REINVENTING THE WHEEL? atent applications in Japan show Mazda has come up with a new rotary engine for a new era of low-weight, hybrid vehicles. The new hybrid design has a front-mounted combustion engine paired with an electric motor that controls the rear wheels. In addition, the front wheels would each carry their own electric motors running at a higher voltage than the rest of the vehicle. The rear-wheel system utilizes a relatively lowpower 3.5 kWh lithium-ion battery suitable for city driving. When more power is required, two inverters and an under-the-hood double-layer capacitor kick in, that are charged by the engine and also by regenerative braking. The high power output at high revs and low weight of rotary engines are better suited to this high-demand demand environment than the trundling around town they also had to cope with in their previous petrol-only heyday. Mazda did not release any details of a scheduled release. It is expected the new system would be used in a possible flagship sports car or other higher-priced model.
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On paper the Wankel rotary engine, named after its inventor, Felix Wankel, replaced on the piston and rods and cylinders in a conventional engine with a single a rotating shaft offering smother running, improved cooling and lower weight. But there were downsides: As described by Jason Fenske of the automotive online community DriveTribe, the old rotary engine suffered four key disadvantages: "Rotary engines have a low thermal efficiency as a result of a long combustion chamber and unburnt fuel making it to the exhaust," he stated in an online post in 2018. "They also have problems with rotor sealing as a result of uneven temperatures in the combustion chamber since combustion only occurs in one portion of the engine. Oil consumption is also a problem, as oil is injected to add lubrication and
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Auto Channel Issue #24 May 2020
help keep the rotor sealed. Finally, emissions are poor and fuel economy is terrible, and ultimately this was the cause of its death." Still, rotary engines have found useful lives beyond automobiles. They can be found in planes, go-karts, jet skis, snowmobiles, chainsaws and auxiliary power units. It would be great to see this bold new iteration overcoming those drawbacks and making use of its inherent qualities.
