ELEMENT STRUCTURE OF OXYGEN SENSOR FOR INTERNAL COMBUSTION ENGINE

摘要

PURPOSE:To perform air-fuel ratio control with characteristics of only a platinum catalyst layer by forming platinum electrodes to a size which enables them to contact a platinum catalyst layer so that an electromotive force can be led out and also is hardly contact with exhaust gas effectively. CONSTITUTION:The internal surface of a ceramic tube 1 is coated with platinum paste 4 and the platinum catalyst layer 5 at the tip position of the external surface on the side of an exhaust passage is formed to an size which enables the layer to be in contact with the exhaust gas sufficiently and effectively. Further, the platinum electrodes 2 and 3 are formed to the size which enables them to be in contact with the catalyst layer 5 to the extent where the electromotive force can be led out and is hardly in contact with the exhaust gas effectively. Then the electrode 3 on the external surface side does not affect the air fuel ratio control and the air fuel ratio characteristic of the catalyst alone matches the air fuel ratio characteristic of the whole element as it is. Consequently, a control air fuel ratio is held almost at an ideal air fuel ratio without variance and the control air fuel ratio is prevented from leading in case of the deterioration of the catalyst layer 4 at low temperature.