Idle speed control system for an automotive engine

Claim 1

A system for controlling idle speed of an automotive engine having a fuel injection system comprising: a throttle position sensor for producing an idle signal when a throttle valve of the engine is closed; a neutral state detector responsive to the idle signal for producing a neutral signal when a transmission of a motor vehicle is in a neutral state; an engine temperature detector responsive to the neutral signal for producing a temperature signal dependent on temperature of the engine; cold-engine operation detector means for producing a cold-engine signal when the engine temperature is lower than a predetermined temperature; an engine speed detector for producing an engine speed signal dependent on speed of the engine; a first memory storing desired engine speeds in accordance with the engine temperature signal; a second memory storing dead zone for input of engine speed with respect to th desired engine speed in accordance with engine temperature, width of the dead zone being provided to increase with decrease of the engine temperature; first deriving means responsive to the cold-engine signal for deriving a desired engine speed from the first memory in accordance with the temperature signal; second deriving means for deriving a range of the dead zone in accordance with the temperature signal; comparator means for comparing actual engine speed dependent on the engine speed signal with a derived desired engine speed and for producing a comparator signal when the actual engine speed does not coincide with the desired engine speed; determining means responsive to the comparator signal for producing an actuating signal when the actual engine speed is out of a derived range of the dead zone; driving means responsive to the actuating means for actuating an actuator provided in the idle speed control system for controlling the actual engine speed to the derived desired engine speed.

Claim 2

A system for controlling idle speed of an automotive engine having a fuel injection system comprising: a throttle position sensor for producing an idle signal when a throttle valve of the engine is closed; a neutral state detector responsive to the idle signal for producing a neutral signal when a transmission of a motor vehicle is in a neutral state; an engine temperature detector responsive to the neutral signal for producing a temperature signal dependent on temperature of the engine; cold-engine operation detector means for producing a cold-engine signal when the engine temperature is lower than a predetermined temperature; an engine speed detector for producing an engine speed signal dependent on speed of the engine; a first memory storing desired engine speeds in accordance with the engine temperature signal; a second memory storing dead zone for input of engine speed with respect to th desired engine speed in accordance with engine temperature, width of the dead zone being provided to increase with decrease of the engine temperature; first deriving means responsive to the cold-engine signal for deriving a desired engine speed from the first memory in accordance with the temperature signal; second deriving means for deriving a range of the dead zone in accordance with the temperature signal; comparator means for comparing actual engine speed dependent on the engine speed signal with a derived desired engine speed and for producing a comparator signal when the actual engine speed does not coincide with the desired engine speed; determining means responsive to the comparator signal for producing an actuating signal when the actual engine speed is out of a derived range of the dead zone; driving means responsive to the actuating means for actuating an actuator provided in the idle speed control system for controlling the actual engine speed to the derived desired engine speed.