Patent ID: 8857241
Filing Date: 2014-10-14
Classification: G01N

Abstract:
1. A gas sensor comprising: a gas sensor element extending in a direction of an axis and having a detection portion at its front end portion for detecting a gas-to-be-measured; a tubular metallic shell holding the gas sensor element in such a manner as to allow the detection portion to project from its front end; and a protector fixed to a front end portion of the metallic shell and enclosing the detection portion; wherein the protector comprises: an inner protector which accommodates the detection portion of the gas sensor element in its interior space and has a tubular side wall having an inner gas introduction hole for introducing the gas-to-be-measured into the interior space, and a bottom wall provided at a front end of the side wall, and an outer protector which accommodates the inner protector therein with a gap formed between the outer protector and the side wall of the inner protector and has a tubular side wall having an outer gas introduction hole provided frontward of the inner gas introduction hole with respect to the direction of the axis and adapted to introduce the gas-to-be-measured into the gap; the outer protector has a frustum-like taper wall tapering frontward from a front end of the side wall with respect to the direction of the axis and an outer gas discharge hole formed inside a front end edge of the taper wall and establishing communication between the interior and the exterior of the outer protector; when SL represents an area defined by the front end edge of the taper wall, the outer gas discharge hole has an area S which satisfies a relational expression ½×SL≦S≦SL; and the bottom wall of the inner protector has a bottom wall opening, the inner protector has a cover portion covering the bottom wall opening from a rear side with respect to the direction of the axis and recessed rearward of the bottom wall with respect to the direction of the axis, and the cover portion and the bottom wall are partially away from each other along the direction of the axis, thereby forming a side opening.