Engine starting system

An engine starting system for automatically stopping an engine which comprises:

• fuel injectors for injecting fuel directly into a plurality of cylinders;
• spark plugs provided to the individual cylinders;
• a throttle valve for regulating the quantity of intake air of the engine;
• an electronic control unit for controlling the quantity of fuel to be injected by each of said fuel injectors and fuel injection timing thereof as well as ignition timing of said spark plugs and the opening of said throttle valve;
• an alternator driven by the engine;
• and an engine speed sensor for detecting engine speed;
• said engine starting system comprising:
• an automatic engine stop controller for automatically stopping the engine by interrupting fuel injection from the fuel injectors as necessary for keeping the engine running when predefined automatic engine stop conditions are satisfied, and
• an automatic engine restart controller for automatically restarting the engine by causing the fuel injector of at least one of the cylinders which is on expansion stroke at engine stop and causing the spark plug of that cylinder to ignite a mixture produced therein when predefined engine restart conditions are satisfied;
• wherein said automatic engine stop controller and said automatic engine restart controller are functionally included in said electronic control unit;
• and
• wherein said automatic engine stop controller sets the quantity of intake air regulated by said throttle valve at a level higher than a minimum quantity of intake air necessary for keeping the engine running by a specific amount and sets a scavenging mode period for expelling in-cylinder exhaust gas by decreasing the amount of electric power generated by said alternator prior to fulfillment of the automatic engine stop conditions in an early part of automatic engine stop control operation,
• said automatic engine stop controller causes said throttle valve to decrease the quantity of intake air and causes said alternator to once decrease the amount of electric power generated thereby at a point in time when the engine speed drops down to a predetermined reference engine speed, and
• said automatic engine stop controller causes said alternator to increases the amount of electric power generated thereby after a lapse of a specific period of time.