Toyota R&D develops free piston engine,does not require a crankshaft!

R&D is the heart and soul of the automobile  industry. All companies invest huge amounts of money into deciding what their future will look like and indirectly decide the future course of mankind. Yes, the automobile industry has such a big effect in the world. Keeping yourself ahead of the competition and and developing new techniques for better ride, efficiency, handling, luxury etc are the top priorities.



Toyota R&D has developed an engine called the Free Piston Engine Linear Generator (FPEG). The “free” represents the fact that the piston is not connected to a crankshaft. Instead the piston produces a 3-phase AC current as it moves down during its Power stroke. This is made possible by encasing windings in the cylinder. The engine operates like a two-stroke engine but with Fuel injection and electrically operated valves. To use it with diesel, compression can be used instead of using a spark plug to ignite the fuel.



The piston in the FPEG is hollow and circularly shaped, Toyota calls it ‘W – shaped’.  This shape offers many advantages over the conventional shape. Toyota points out a few of them:

  • The piston has a hollow structure and moves along a column stay, which in turn enables the construction of a cooling oil passage within the stay. The key technologies to deliver stable continuous operation of an FPEG are lubricating, cooling, and control logic. (The Toyota team’s second paper deals exclusively with the control system.)
  • The magnet is set far from the piston top, preventing magnet degaussing by heating.
  • The inner periphery of the hollow piston also serves as a sliding surface on the column stay, enabling a steady small clearance between the magnets and coil for improved generating efficiency.
  • The larger cross-sectional area of the gas spring chamber leads to lower compression temperature of the gas spring chamber and consequently decreased heat loss.

FPEG`s , simply put, have good thermal efficiency, low vibrations and low friction.

See all the technical details at Green Car Congress.

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