Device for regulating the fuel-air ratio in internal combustion engines

A system for regulating the fuel-air mixture ratio being combusted in an internal combustion engine, the system having

• a lambda sensor having an internal resistance;
• a regulating device connected to the internal combustion engine to regulate the fuel-air ratio;
• a regulating circuit for controlling said regulating device;
• a monitoring circuit connected to said lambda sensor for generating a signal indicating lambda sensor readiness as a function of said internal resistance;
• said monitoring circuit including:
• a resistor connected at a first end to said lambda sensor and connected at a second end to said monitoring circuit for generating a resultant voltage at the first end of said resistor;
• two comparator devices having different threshold values which are connected to said lambda sensor to receive said resultant voltage and to compare said resultant voltage to said respective threshold values and to thereby generate respective output signals indicative of said comparison;
• a logic processing circuit connected to receive said outputs of said two comparator devices for producing an output;
• an evaluation circuit connected to receive said logic processing circuit output and connected to said regulating circuit for generating a lambda sensor readiness signal to operate said regulating device and a lambda sensor non-readiness signal to shut off said regulating device whereby said system is switched to open-loop control according to said logic processing circuit output, said system further including:
• a voltage source connected to said monitoring circuit;
• a first voltage divider connected across said voltage source;
• a second voltage divider, connected parallel to said first voltage divider and having a pickup-point;
• and
• wherein said resistor has a high resistance value and connects said pickup-point with said lambda sensor.