Method of operating an internal combustion engine during a combustion process

A method of operating an internal combustion engine during a combustion process, the engine having at least one cylinder and an associated piston for forming a working chamber in which intake, compression, combustion, expansion and exhaust operational events occur as the result of piston movement, the piston comprising (1) an upper portion having a working face defining a movable wall of the working chamber, (2) a lower portion having means for connection with a motor mechanism and (3) an elastic means for resiliently connecting the upper portion with the lower portion, the lower portion being operatively connected to the motor mechanism for moving the piston during the operational events and thereby generally increasing the working chamber in volume during the combustion, the method comprising:

• (A) initiating the combustion of a combustible charge inside of the working chamber in the vicinity of piston top dead center position for generating a relatively abrupt initial increase in the gas pressure;
• (B) additionally increasing the working chamber in volume by deforming the corresponding elastic means because of the initial increase of the gas pressure and thereby producing a relative movement of the upper portion with reference to the lower portion;
• and
• (C) controlling the increase of the working chamber in volume by a predeterminate deformation of the corresponding elastic means to brake the initial increase of the gas pressure within the combustion chamber and at least partially to replace it by a substantially isobaric combustion.