\Ot"to cy`cle\ (Thermodynamics)
A four-stroke cycle for internal-combustion engines
consisting of the following operations: First stroke, suction
into cylinder of explosive charge, as of gas and air; second
stroke, compression, ignition, and explosion of this charge;
third stroke (the working stroke), expansion of the gases;
fourth stroke, expulsion of the products of combustion from
the cylinder. This is the cycle invented by Beau de Rochas in
1862 and applied by Dr. Otto in 1877 in the Otto-Crossley gas
engine, the first commercially successful internal-combustion
engine made.