Oxygen sensor for monitoring oxygen content in exhaust gases - protected with refractory oxide coating on side exposed to exhaust gases

摘要

Oxygen sensor contains a layer of a metal oxide permeable to oxygen ions; it is provided on both sides with electrodes; one of the sides is in contact with the gas whose oxygen content is to be measured; the other side is in contact with a reference gas, pref. air. A catalyst promoting oxidation of some components of the gas mixt. to be analysed is provided on the side of this mixt. The sensor is improved in that the electrode on the side of the gas mixt. is covered with a porous layer of a refractory metal oxide, a layer of a metallic catalyst particles and another porous layer of a refractory metal oxide. When there is a difference between the oxygen contents of the gas mixts. and the reference gas (air), e.m.f. is created in the sensor; its value permits the determ. of the oxygen content in the gas mixt. being analysed. This senser is esp. suitable for monitoring the oxygen content in exhaust gases of an internal combustion engine with the aim of maintaining the air:fuel ratio at the optium. The disposition of the catalyst particles between two refractory metal oxide layers prevents coalescence of the catalyst particles and their poisoning by lead, sulphur or phosphorus impurities. The electrode surface is also protected. Thus variations in the tensor's readings with time (thermal ageing) are diminished.