Supercharging system for automotive engines

A supercharging system for an automotive engine comprising:

• a turbocharger driven by exhaust-gas of the engine;
• a supercharger;
• an intake passage connecting the turbocharger and the supercharger in series, for supplying air to the engine;
• driving means for driving the supercharger by the engine;
• clutch means provided in the driving means;
• a first bypass provided around the supercharger;
• a control valve provided in the first bypass;
• a second bypass provided around the turbine of the turbocharger;
• a waste gate valve provided in the second bypass;
• a first actuator for operating the control valve;
• a second actuator for operating the waste gate valve;
• first means for operating the second actuator to open the waste gate valve when supercharging pressure exceeds a predetermined value;
• an engine speed sensor for detecting speed of the engine;
• an engine load sensor for detecting load on the engine;
• a control unit responsive to output signals of the engine speed sensor and engine load sensor for operating the clutch means and first actuator;
• the control unit including second means for disengaging the clutch means at light load on the engine in a predetermined low engine speed range, third means for engaging the clutch means at heavy load in the low engine speed range, fourth means for disengaging the clutch means in a predetermined high engine speed range;
• fifth means for controlling the opening of the control valve in accordance with variation of engine speed and load when the engine operation is in a transient state.