AIR/FUEL RATIO SENSOR FOR AUTOMOBILE

摘要

PURPOSE:To detect air/fuel ratio from the lean to rich area, by inverting the polarity of a voltage to be applied to a platinum electrode composing an air/fuel detection cell according to a theoretical air/fuel ratio signal detected with a theoretical air/fuel detection cell. CONSTITUTION:A zirconia solid electrolyte 1 is formed with a E-shape cross-sec tion and layers 1A, 1B and 1C are formed. The layer 1A is provided with plati num electrodes 2 and 3 while the layer 1C with platinum electrodes 6 and 7. The layer 1A and the electrodes 2 and 3 compose an air/fuel detection cell while the layer 1C and the electrodes 6 and 7 a theoretical air/fuel ratio detec tion cell. Both the cells are integrated to be exposed to an exhaust gas. The electromotive force of the theoretical air/fuel ratio cell is composed with a threshold voltage Vth by a comparator C1 to control the turning On or OFF of a transistor TR. This produces an air/fuel ratio sensor which can obtain analog and continuous output V1P in the full air/fuel ratio range from the lean to rich area.