Charge air systems for four-cycle internal combustion engines

A two stage charge air system for an internal combustion engine, said internal combustion engine having an exhaust gas manifold and an intake air manifold, comprising:

• a first stage charge air compressor capable of supplying less than about one-third of the charge air requirements of the internal combustion engine operating at full rated speed and load, said first stage charge air compressor having an air inlet and a compressed air outlet;
• an electric motor for driving said first stage charge air compressor;
• a first charge air conduit connected with the compressed air outlet at one end and a junction at the other end;
• a second charge air conduit connected with the junction at one end and open to atmosphere at the other end;
• a pressure activated check valve for the second charge air conduit adjacent the junction;
• a turbocharger, having an exhaust gas driven turbine connected with the exhaust gas manifold of the internal combustion engine and a second stage charge air compressor driven by the exhaust gas turbine, said second stage charge air compressor of the turbocharger, having a charge air outlet connected with the air intake manifold of the internal combustion engine, and an air inlet connected with the junction of the first and second charge air conduits;
• and
• a control for the two stage charge air system, said control being connected with an internal combustion engine speed sensor and an engine acceleration demand sensor and having an output for energizing the first stage electric motor in the presence of an engine acceleration demand signal and de-energizing the first stage electric motor above a predetermined engine operating speed.