Flow rate control system for fluid being supplied to an internal combustion engine, having initial position setting function for flow rate control valve actuator

An air/fuel ratio control system for controlling the air/fuel ratio of a mixture being supplied to an internal combustion engine, which comprises:

• a carburetor for producing said mixture;
• valve means for controlling the air/fuel ratio of said mixture;
• a pulse motor for driving said valve means;
• position detecting means for detecting the valve position of said valve means with respect to a reference position to produce two different levels of output depending upon a detected valve position;
• and an electrical circuit connected to said pulse motor, said position detecting means and a power switch, said electrical circuit being arranged for operation such that:
• (a) when said position detecting means produces one level of output upon turning on said power switch, said electrical circuit drives said pulse motor in the direction of said reference position until said position detecting means produces the other level of output:
• (b) when said position detecting means produces said other level of output upon turning on said power switch or when said position detecting means has come to produce said other level of output as a result of said driving of said pulse motor in said paragraph (a), said electrical circuit drives said pulse motor in the direction of said reference position until said position detecting means produces said one level of output:
• and (c) said electrical circuit is responsive to occurrence of said one level of output during said driving of said pulse motor in said paragraph (b), to stop said pulse motor.

An air/fuel ratio control system for controlling by means of feedback the air/fuel ratio of a mixture being supplied to an internal combustion engine, which comprises:

• means for detecting the concentration of an ingredient in exhaust gases emitted from said engine;
• a carburetor for producing said mixture;
• means connecting said concentration detecting means to said carburetor in a manner such as to control the air/fuel ratio of said mixture to predetermined values by means of feedback, in response to an output signal produced by said concentration detecting means, said connecting means comprising a valve for controlling the air/fuel ratio of said mixture, a pulse motor for driving said valve, and an electrical circuit for controlling said pulse motor;
• and means for detecting the position of said valve with respect to a reference position to produce two different levels of output depending upon a detected valve position;
• wherein said electrical circuit is connected to said power switch and said position detecting means for operation such that:
• (a) when said position detecting means produces one level of output upon turning on said power switch, said electrical circuit drives said pulse motor in the direction of said reference position until said position detecting means produces the other level of output:
• (b) when said position detecting means produces said other level of output upon turning on said power switch or when said position detecting means has come to produce said other level of output as a result of said driving of said pulse motor in said paragraph (a), said electrical circuit drives said pulse motor in the direction of said reference position until said position detecting means produces said one level of output:
• and (c) said electrical circuit is responsive to occurrence of said one level of output during said driving of said pulse motor in said paragraph (b), to stop said pulse motor.