| 摘要 |
PURPOSE:To perform feedback control for the different air/fuel ratios in correspondence with the operating conditions by providing a plurality of detecting elements having the different characteristics, and connecting electrodes in series. CONSTITUTION:The characteristic of electromotive voltage which is generated between a first inner electrode 15A and a first outer electrode 15B of a first detecting element 1 becomes the characteristic as follows: the oxygen component of NOx is excellently detected by the NOx reduction action of the reducing catalyst particles in the NOx in a first electrode protecting layer 17; and the characteristic is suddenly changed at a point close to a theoretical air/fuel ratio when NOx is increased. On the contrary, the characteristic of the electromotive voltage generated between an inner electrode 16A and an outer electrode 16B in a second detecting element 13 becomes the characteristic as follows: the oxygen component of NOx is not detected as the concentration of oxygen is exhaust gas; and a point where the electromotive voltage is suddenly changed in correspondence with the increase in concentration of NOx is shifted to the lean side. Therefore the output voltage characteristic between the electrodes 15A and 16B at both ends of the part wherein the electrodes of the elements 12 and 13 are connected in series becomes the characteristic obtained by adding the individual electromotive voltage characteristics. Thus, the feedback control can be performed for the different air/fuel ratios in correspondence with the operating conditions at a low cost. |
