AIR/FUEL RATIO MEASURING APPARATUS

摘要

PURPOSE:To miniaturize the equipment with the stabilization of an output of a sensor, by a method wherein the oxygen concentration sensor is surrounded by a double wall through which a mixed gas flows and a fresh air path is provided on the circumference of a waste heat recovery device so arranged on the circumference of the wall to let mixed gas pass. CONSTITUTION:Air taken in from an upstream tube 93 of an air intake pipe 9 is preheated at an intermediate position 91 by heat of an exhaust gas flowing through a tape pipe 17. A sampled exhaust gas and fresh air flowing through a double-spiralled exhaust gas path 101 and an air path 102 are subjected to a mutual heat exchange through a partition while a heat exchange takes place between the gas and air and an exhaust recovery device 104. With the suction of a mixing chamber 106 by a vacuum pump 12, the exhaust gas and air flow into the mixing chamber 106 being measured with orifices 4 and 5 via the pipes 8 and 9 and the paths 101 and 102 respectively. An output of a thermocouple 7 within a path 107 is inputted into a heater controller 15 to control the temperature of a mixed gas to the activation concentration range of an oxygen concentration sensor 2. A double wall tube 103 stabilizes the temperature thereof by the mixed gas flowing therethrough thereby achieving a higher output accuracy of the sensor 2.