Device for detecting air-fuel ratio of engine

Claim 1

A device for detecting an air-fuel ratio of an engine by measuring an oxygen concentration of an exhaust gas by means of an oxygen sensor including a pair of oxygen-ion conductive and solid electrolytic materials arranged in the gas to be measured, said solid electrolytic materials having electrodes formed on the surfaces thereof and being arranged in confronting relationship with each other with a predetermined restricted region therebetween, said restricted region being subject to the influence of pulsations existent in said exhaust gas, one of said solid electrolytic materials constituting an oxygen pump element and the other constituting a cell element that develops an electromotive force for use in measuring an oxygen concentration ratio, said device comprising means for applying a variable electromotive current to the oxygen pump element in response to variations in oxygen concentration for causing the cell element to generate a constant predetermined reference voltage, thereby detecting an air-fuel ratio of a mixed gas fed to the engine by means of a pump current value under such state that said oxygen concentration in said restricted region is held constant by feeding a variable current to the oxygen pump element so that a terminal voltage of the cell element becomes constant, means for producing an output signal of the oxygen pump, said output signal being subjected to variation as the result of variation of said oxygen concentration in said restricted region caused under the influence of said pulsation of said exhaust gas passing through said restricted region, and an air-fuel ratio detecting circuit which reads the output signal of the oxygen sensor and means for effecting the detection of the air-fuel ratio at a predetermined point in the engine operation following a TDC signal and a predetermined period previously set by a timer having passed after said TDC signal.

Claim 2

A device for detecting an air-fuel ratio of an engine by measuring an oxygen concentration of an exhaust gas by means of an oxygen sensor including a pair of oxygen-ion conductive and solid electrolytic materials arranged in the gas to be measured, said solid electrolytic materials having electrodes formed on the surfaces thereof and being arranged in confronting relationship with each other with a predetermined restricted region therebetween, said restricted region being subject to the influence of pulsations existent in said exhaust gas, one of said solid electrolytic materials constituting an oxygen pump element and the other constituting a cell element that develops an electromotive force for use in measuring an oxygen concentration ratio, said device comprising means for applying a variable electromotive current to the oxygen pump element in response to variations in oxygen concentration for causing the cell element to generate a constant predetermined reference voltage, thereby detecting an air-fuel ratio of a mixed gas fed to the engine by means of a pump current value under such state that said oxygen concentration in said restricted region is held constant by feeding a variable current to the oxygen pump element so that a terminal voltage of the cell element becomes constant, means for producing an output signal of the oxygen pump, said output signal being subjected to variation as the result of variation of said oxygen concentration in said restricted region caused under the influence of said pulsation of said exhaust gas passing through said restricted region, and an air-fuel ratio detecting circuit which reads the output signal of the oxygen sensor and means for effecting the detection of the air-fuel ratio at a predetermined point in the engine operation following a TDC signal and a predetermined period previously set by a timer having passed after said TDC signal.

Claim 5

A device for detecting an air-fuel ratio of an engine by measuring an oxygen concentration of an exhaust gas by means of an oxygen sensor including a pair of oxygen-ion conductive and solid electrolytic materials arranged in the gas to be measured, said solid electrolytic materials having electrodes formed on the surfaces thereof and being arranged in confronting relationship with each other, with a predetermined restricted region therebetween, said restricted region being subjected to the influence of pulsations existent in said exhaust gas, one of said solid electrolytic materials constituting an oxygen pump element and the other constituting a cell element that develops an electromotive force for use in measuring an oxygen concentration ratio, said device comprising means for applying a variable electromotive current to the oxygen pump element in response to variations in oxygen concentration for causing the cell element to generate a constant predetermined reference voltage, thereby detecting an air-fuel ratio of a mixed gas fed to the engine by means of a pump current value under such state that said oxygen concentration in said restricted region is held constant by feeding a variable current to the oxygen pump element so that a terminal voltage of the cell element becomes constant, means for producing an output signal of the oxygen sensor related to the electromotive current applied to the oxygen pump, said output signal being subjected to variation as the result of variation of said oxygen concentration in said restricted region caused under the influence of said pulsation of said exhaust gas passing through said restricted region, and an air fuel ratio detecting circuit which reads the output signal of the oxygen sensor and means for effecting the detection of air-fuel ratio at a predetermined point in the operation of the engine following a period of time after a TDC signal has been produced, said period of time depending upon the operation of the engine and being previously set to a value which is in inverse proportion to the number of revolutions per unit of time of the engine after said TDC signal.

Claim 6

A device for detecting an air-fuel ratio of an engine by measuring an oxygen concentration of an exhaust gas by means of an oxygen sensor including a pair of oxygen-ion conductive and solid electrolytic materials arranged in the gas to be measured, said solid electrolytic materials having electrodes formed on the surfaces thereof and being arranged in confronting relationship with each other, with a predetermined restricted region therebetween, said restricted region being subjected to the influence of pulsations existent in said exhaust gas, one of said solid electrolytic materials constituting an oxygen pump element and the other constituting a cell element that develops an electromotive force for use in measuring an oxygen concentration ratio, said device comprising means for applying a variable electromotive current to the oxygen pump element in response to variations in oxygen concentration for causing the cell element to generate a constant predetermined reference voltage, thereby detecting an air-fuel ratio of a mixed gas fed to the engine by means of a pump current value under such state that said oxygen concentration in said restricted region is held constant by feeding a variable current to the oxygen pump element so that a terminal voltage of the cell element becomes constant, means for producing an output signal of the oxygen sensor related to the electromotive current applied to the oxygen pump, said output signal being subjected to variation as the result of variation of said oxygen concentration in said restricted region caused under the influence of said pulsation of said exhaust gas passing through said restricted region, and an air fuel ratio detecting circuit which reads the output signal of the oxygen sensor and means for effecting the detection of air-fuel ratio at a predetermined point in the operation of the engine following a period of time after a TDC signal has been produced, said period of time depending upon the operation of the engine and being previously set to a value which is in inverse proportion to the number of revolutions per unit of time of the engine after said TDC signal.