US Patent 7237521 Engine starting method and engine starting device

An engine starting method includes maintaining a rotation speed of a crankshaft of an engine rotated by a motor at a first rotation speed, supplying fuel to the engine and igniting the fuel while the crankshaft is rotated by the motor at the first rotation speed, determining whether the fuel has been ignited in the engine, and maintaining the rotation speed of the crankshaft rotated at least by the motor at a second rotation speed that is greater than the first rotation speed upon determining that the fuel has been ignited.