Patent ID: 8118985

Claim:
A gas sensor comprising: a gas sensor element extending in a longitudinal direction thereof and having a leading end, the gas sensor comprising at the leading end of the gas sensor element: a first measurement chamber interposed between two solid-state electrolytic layers stacked with a space therebetween and into which a gas to be measured is introduced from outside the sensor; a first pumping cell that has a first interior pump electrode facing the first measurement chamber and a first counterpart electrode serving as a counterpart electrode of the first interior pump electrode, the first pumping cell being configured to control oxygen partial pressure in the first measurement chamber; a second measurement chamber partitioned from surroundings and in mutual communication with the first measurement chamber and into which a gas to be measured having a controlled oxygen partial pressure is introduced from the first measurement chamber; a second pumping cell having an interior second pumping electrode disposed within the second measurement chamber and a second counterpart electrode serving as a counterpart electrode of the second interior pump electrode, the second pumping cell being configured to detect a specific gas component in the gas to be measured within the second measurement chamber; and a heater which is disposed along the longitudinal direction of gas sensor element, the heater being configured to heat the first pumping cell and the second pumping cell, wherein the heater has first and second lead sections extending in the longitudinal direction, each of said first and second lead sections having a trailing end for electrical connection to a power source and a leading end, two parallel first resistance portions extending in the longitudinal direction, each having a leading end and a trailing end electrically connected to the leading end of the first and second lead sections, respectively, said first resistance portions having a higher resistance than the lead sections to which they are connected, and a main heating section which electrically connects the leading ends of the two parallel first resistance portions, and which main heating section includes two parallel second resistance portions that are disposed on a leading end side of the gas sensor element in the longitudinal direction relative to the leading ends of the two parallel first resistance portions, respectively; the second interior pump electrode does not overlap, in the longitudinal direction, the first interior pump electrode and its first counterpart electrode; and at least a portion of the second interior pump electrode overlaps the first resistance portion in the longitudinal direction.