Patent ID: 7666286

Claim:
A gas sensor comprising a sensor element having a gas-introducing hole at an end of said sensor element, and having upper and lower surfaces; said sensor element including a reference gas-introducing space, a clogging preventative space, a buffering space, a first space for introducing a measurement gas thereinto from said gas-introducing hole via the clogging preventative space, the buffering space and a first diffusion rate-determining section, a main pumping means for controlling a partial pressure of oxygen contained in said measurement gas introduced into said first space to be substantially constant, a second space for introducing said measurement gas thereinto from said first space via a second diffusion rate-determining section, an electric signal-generating converting means for reducing or decomposing a NOx component contained in said measurement gas introduced from said second space via a third diffusion rate-determining section to generate an electric signal corresponding to an amount of oxygen produced thereby so that a concentration of NOx existing in said measurement gas is determined from said electric signal, a first detecting means including an inner electrode in said first space and a reference electrode in said reference gas-introducing space, and a heater for maintaining at least said first space and said second space at a predetermined temperature, said heater being disposed only at a lower potion of said sensor element, wherein 0.3≦( Wc/We )<0.7 wherein We represents a lateral width of said end of said sensor element, and Wc represents a lateral width of said gas-introducing hole, and 0.2<( La/We )<0.5 wherein La represents a distance from a projected position of an end of said heater on said upper surface of said sensor element to said end of said sensor element, wherein a starting end position is defined as a projected position of an end of said first space close to said gas-introducing hole on said upper surface of said sensor element, and said projected position of said end of said heater on said upper surface of said sensor element extends to said starting end position, and wherein an air-fuel ratio of said measurement gas is determined by said first detecting means from a voltage between said inner electrode and said reference electrode and a pumping current of said main pumping means.