Internal combustion engine at alternating cycle with controlled variable compression ratio (CVRC) that includes: - a crankshaft, - a first connecting rod, - a transmission lever-composed of two parts: - an elastic part which: • is connected to two coaxial pistons by connecting rods; • is flexible; • consists of two coupled leaf springs; - a rigid rhomboidal shaped part which: • has an opening in a centre that allows the crankshaft to pass to its centre in a symmetrical position with respect to the system of the two Pistons; • the fulcrum of the rhomboidal lever is fixed to a base of the engine; • is connected to the crankshaft through a the first connecting rod to which it transmits its movement; • is positioned with the fulcrum placed in the base of the engine and is held in the engine block with a pin passing through the fulcrum of the lever, the pin is fixed by tightening bolts in the base of the engine; wherein the flexibility on the flexible part of the lever is controlled by two lateral standstills which are part of the rigid part of the lever, placed on both side of the flexible part, the degree of flexibility is controlled by hydraulic pistons that are inside the lateral standstills or near the fulcrum of the lever and limit the amplitude of the flexion of the flexible part of the lever. - a crankshaft, - a first connecting rod, - a transmission lever-composed of two parts: - an elastic part which: • is connected to two coaxial pistons by connecting rods; • is flexible; • consists of two coupled leaf springs; - a rigid rhomboidal shaped part which: • has an opening in a centre that allows the crankshaft to pass to its centre in a symmetrical position with respect to the system of the two Pistons; • the fulcrum of the rhomboidal lever is fixed to a base of the engine; • is connected to the crankshaft through a the first connecting rod to which it transmits its movement; • is positioned with the fulcrum placed in the base of the engine and is held in the engine block with a pin passing through the fulcrum of the lever, the pin is fixed by tightening bolts in the base of the engine; - an elastic part which: • is connected to two coaxial pistons by connecting rods; • is flexible; • consists of two coupled leaf springs; • is connected to two coaxial pistons by connecting rods; • is flexible; • consists of two coupled leaf springs; - a rigid rhomboidal shaped part which: • has an opening in a centre that allows the crankshaft to pass to its centre in a symmetrical position with respect to the system of the two Pistons; • the fulcrum of the rhomboidal lever is fixed to a base of the engine; • is connected to the crankshaft through a the first connecting rod to which it transmits its movement; • is positioned with the fulcrum placed in the base of the engine and is held in the engine block with a pin passing through the fulcrum of the lever, the pin is fixed by tightening bolts in the base of the engine; • has an opening in a centre that allows the crankshaft to pass to its centre in a symmetrical position with respect to the system of the two Pistons; • the fulcrum of the rhomboidal lever is fixed to a base of the engine; • is connected to the crankshaft through a the first connecting rod to which it transmits its movement; • is positioned with the fulcrum placed in the base of the engine and is held in the engine block with a pin passing through the fulcrum of the lever, the pin is fixed by tightening bolts in the base of the engine;