Fuel injection control system for a two-cycle engine

Claim 1

In an air-fuel ratio control system for a two cycle engine having a cylinder with a scavenge port and an exhaust port, an intake passage communicating with said scavenge port, an exhaust passage connected to said exhaust port, a two-fluid type injector for directly separately injecting therein an amount of fuel and air for injection by the injector into said cylinder, a scavenge pump provided in said intake passage for supplying compressed air into said cylinder, and a throttle valve interposed in a bypass of said intake passage, the control system having a crank angle sensor provided at a crankshaft of the engine for detecting a crank angle of said crankshaft and for producing a corresponding crank angle signal, an engine speed sensor for detecting engine speed and for producing a corresponding engine speed signal, and an accelerator position sensor for detecting depressing degree of an accelerator pedal and for producing a corresponding degree signal, the accelerator pedal being operatively connected with said throttle valve, the improvement in the control system which comprises: detecting means responsive to said engine speed and degree signals for detecting a corresponding of engine operating conditions as a function of said engine speed and said depressing degree of said accelerator pedal and for producing a corresponding engine operating condition signal; a calculator responsive to said engine operating condition signal for calculating an air quantity and for producing a corresponding air quantity signal; air injection timing determining means responsive to said engine operating condition signal and said crank angle signal for deciding an air injection timing and for producing a corresponding air pulse signal; fuel injection timing determining means responsive to said air quantity, said engine operating condition, and said crank angle signals for deciding a fuel injection timing and for producing a corresponding fuel pulse signal; and said two-fluid type injector being responsive to said air and fuel pulse signals for injecting the fuel directly into a stream of air as the air is passing through the injector within a period of air injection from the injector into said cylinder after starting of the air injection during a light load range for injecting said fuel and air into said cylinder so as to form a stratified stream of said fuel and air and to effect complete combustion in said cylinder in all of the respective of said engine operating conditions.