Patent ID: 8636532

Claim:
A gas sensor comprising: a sensor element capable of detecting a concentration of a predetermined gas component in a gas under measurement, and having a plurality of front-surface electrodes arranged side by side on a front surface thereof and a plurality of back-surface electrodes arranged side by side on a back surface thereof; a plurality of long narrow first contact fittings having conducting portions in contact with the plurality of front-surface electrodes of the sensor element; a plurality of long narrow second contact fittings having conducting portions in contact with the plurality of back-surface electrodes of the sensor element; a first housing made of ceramic and configured to hold the plurality of first contact fittings such that the first contact fittings are arranged in a direction substantially orthogonal to the length of the first contact fittings and face the plurality of front-surface electrodes; a second housing made of ceramic and configured to hold the plurality of second contact fittings such that the second contact fittings are arranged in a direction substantially orthogonal to the length of the second contact fittings and face the plurality of back-surface electrodes; a cylindrical metal tube having a central axis along the length of the sensor element and disposed around the first housing and the second housing; a first elastic member substantially U-shaped in cross section, in contact with an inner periphery of the metal tube at both ends of the U-shape, and configured to press the first housing with an elastic force generated by pressure from the metal tube to bring the first housing closer to the second housing, with the sensor element interposed between the first housing and the second housing; and a second elastic member substantially U-shaped in cross section, in contact with the inner periphery of the metal tube at both ends of the U-shape, and configured to press the second housing with an elastic force generated by pressure from the metal tube to bring the second housing closer to the first housing, with the sensor element interposed between the first housing and the second housing, wherein an arithmetical mean roughness Ra of the inner periphery of the metal tube is 1 μm or less; at least one of both the ends of the first elastic member is formed as a curved contact portion having a curved surface that is in contact with the inner periphery of the metal tube and has a curvature radius smaller than or equal to a curvature radius of the contact portion of the inner periphery of the metal tube; and at least one of both the ends of the second elastic member is formed as a curved contact portion having a curved surface that is in contact with the inner periphery of the metal tube and has a curvature radius smaller than or equal to a curvature radius of the contact portion of the inner periphery of the metal tube.