US Patent 8037852 Free piston electromagnetic engine

Methods of operating an internal combustion engine are disclosed that may include a first piston slidably disposed in a first cylinder having a first and a second closed end, and a first converter operable with the first cylinder. The first converter may be configured to convert mechanical energy to electrical energy, and vice versa. As a non-limiting example, such disclosed embodiments may be used to convert mechanical energy of the first piston to electrical energy during a power stroke, and to drive the first piston during one or more of an exhaust stroke, an intake stroke, or a compression stroke.