Toyota develops high-efficiency ‘free piston’ no-crankshaft combustion engine… to power an EV
A new free piston engine linear generator (FPEG) from Toyota Central in Maine appeared on YouTube.
The piston is called “free” because there is no crankshaft. On its power stroke, the piston dumps its kinetic energy into the fixed windings which surround it, generating a shot of three-phase AC electricity. It can be run sparkless through a diesel cycle or run on standard gasoline. What has folks excited is the claimed thermal efficiency for the device — at 42% it blows away the engines used in cars today. Toyota’s demo engine, just 8 inches around and 2 feet long, was able to generate 15 hp. A two-cylinder model would be self-balancing and have much reduced vibration.
Not surprisingly, the valves are electrically operated and can therefore be better used to fine-tune the power delivery through the full range of the stroke. Speaking of strokes, the video indicates a two-stroke design, which might present a few problems for a road-worthy design. For one thing, emissions would be suspect. Nonetheless Toyota imagines that a twin unit design pumping out 20 kW could power a light electric vehicle at a cruise speed of 120 kph (75 mph).
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