Toyota Free Piston Engine Design: When Old Becomes New Again

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toyota free piston

In 1807, Francois Isaac de Rivaz developed and patented a first combustion engine applying the concept of crankless, free-floating pistons, housed in a contiguous structure. At the time, Rivaz was way ahead of the curve when it came to engine design, and his effort went largely unnoticed until 1930, when pre-war engineering efforts were coming up to full-song.

Spanish engine designer and aviator Raul Pateras Pescara de Castelluccio, started working on Rivaz’ original thinking, and the effort ultimately lead to an air-compressed, 1933 design. This in turn, led to an 1100 HP, floating-piston generator while Pescara was working at the French SIGMA company during World War II.

Now, Toyota has taken another look at the same technology, with an eye toward integrating and leveraging these historic designs, in order to produce another solution for electrical production in future PHEV’s. The free-floating approach suggests that, since the engine-generator complex is simpler, smaller and lighter than current generation systems, the conversion process for combustion-to-electrical-generation can be considerably enhanced.

Essentially, the unit eliminates a direct connection between an ICE and a vehicle’s electrical generator, by utilizing a gas spring mechanism that cycles the dual-action of the piston stoke, in order to create electrical current. The pistons themselves will be integrated with coils, and the stoke-action causes the pistons to come in contact the unit’s magnetized housings, thereby completing a circuit.

Currently, the design approach is in the hands of Toyota’s R&D group, although should the technology show early promise, the Japanese giant could certainly go from an R&D mode to a production footing virtually on-demand. Spokespeople for the company also offered that, since the design uses a ‘gas spring’ mechanism, that hydrogen applications could be in the offing as well.

This is somewhat coincidental, particularly since Toyota recently announced that is was moving away from all-electric development, in favor of becoming more efficient with it PHEV’s products, in addition to new interest in further-evolving its H2 technology.