Variable timing device for reciprocating engines, engines comprising same and distribution and turbocharging method

Method according to claim 9, characterised in that, in order to facilitate cold starting of a 4-stroke diesel engine, the phase shifters are programmed as in claim 15, but the exhaust cut-off is advanced even further in order to reverse the flow of air through the engine so as to accumulate, upstream of the engine, an air load which reaches auto-ignition temperature stepwise, over several cycles, the exhaust cut-off being retarded immediately after ignition in order to start a flow of gas through the engine.

Turbocharging method for a 4-stroke engine capable of developing its maximum torque starting from a speed of rotation of full torque that is markedly lower than the maximum speed of rotation (Nmax), equipped with two turbochargers, namely a low-pressure (BP) turbocharger and a high-pressure (HP) turbocharger, which are mounted in series in the gas circuit, characterised in that there is used a low-pressure (BP) compressor of a size to deliver, at its maximum speed, substantially the flow of air necessary for maximum power with an elevated output at the altitude at which decalibration of the engine is accepted, in that there is used a high-pressure (HP) compressor of a size as if the maximum speed of rotation Nmax of the engine was equal to the speed of rotation at which the maximum torque is achieved, in that a ratio is established between the cross-section of the low-pressure (BP) turbine and of the high-pressure (HP) turbine in order to limit the pressure ratio of the high-pressure (HP) compressor to a value at which the output is substantially optimum, and in that the admission device is configured to create a drop in the static pressure of the air introduced into the cylinder such that, at the admission bottom dead centre, the pressure in the cylinder is substantially the same at the maximum speed (Nmax) and at the speed of maximum torque.

Method according to claim 18, characterised in that turbochargers of fixed geometry are used.

Turbocharging method for a 4-stroke engine which delivers its maximum torque from the speed 0.4 Nmax, Nmax being its maximum speed of rotation, characterised in that the low-pressure compressor is of a size to deliver the flow of air of the engine at its maximum power for a pressure ratio at sea level of the order of 2.5, and in that the volumetric capacity of the high-pressure compressor is of the order of 40% of that of the low-pressure compressor, the ratio between the distributor cross-sections of the low-pressure turbine and of the high-pressure turbine being of the order of 2.

Variable timing method for engines, in which, for one and the same cylinder, at least under certain operating conditions, the start of the admission and/or exhaust phases is controlled by a cam that belongs to one of the camshafts and the end of said phases is controlled by a cam that belongs to another camshaft, by modifying, during operation, the phase shift between said camshafts, and hence the angular duration of the phase in question, by phase shift means which are sensitive to one or more operating parameters of the engine, characterised in that, in order to optimise the respiration of a 4-stroke engine, the phase shifters are programmed to increase the admission opening advance, the exhaust cut-off retardation, the exhaust opening advance and the admission cutoff retardation when the speed increases.

Variable timing method for engines, in which, for one and the same cylinder, at least under certain operating conditions, the start of the admission and/or exhaust phases is controlled by a cam that belongs to one of the camshafts and the end of said phases is controlled by a cam that belongs to another camshaft, by modifying, during operation, the phase shift between said camshafts, and hence the angular duration of the phase in question, by phase shift means which are sensitive to one or more operating parameters of the engine, characterised in that, in order to create a retention of hot gases in a 4-stroke engine, especially a diesel engine, the phase shifters are programmed to advance the exhaust cut-off and, correlatively, to retard the admission opening without substantially modifying the exhaust opening and the admission cut-off.

Variable timing method for engines, in which, for one and the same cylinder, at least under certain operating conditions, the start of the admission and/or exhaust phases is controlled by a cam that belongs to one of the camshafts and the end of said phases is controlled by a cam that belongs to another camshaft, by modifying, during operation, the phase shift between said camshafts, and hence the angular duration of the phase in question, by phase shift means which are sensitive to one or more operating parameters of the engine, characterised in that, in order to accelerate a turbocharger of an engine, the phase shifters are programmed to increase the exhaust opening advance without substantially modifying the exhaust cut-off, and the admission cut-off/opening.

Variable timing method for engines, in which, for one and the same cylinder, at least under certain operating conditions, the start of the admission and/or exhaust phases is controlled by a cam that belongs to one of the camshafts and the end of said phases is controlled by a cam that belongs to another camshaft, by modifying, during operation, the phase shift between said camshafts, and hence the angular duration of the phase in question, by phase shift means which are sensitive to one or more operating parameters of the engine, characterised in that, in order to increase the rotary movement of the air admitted into the cylinder through a tangential or helicoidal pipe, the phase shifters are programmed to retard the admission opening in order to increase the drop in pressure and accordingly the speed of flow at the seat of the valve.