Patent ID: 7927475

Claim:
A gas sensor comprising: a gas sensor element extending in an axial direction and having gas sensing characteristics at least at its own leading end portion; a cylindrical metal shell enclosing said gas sensor element such that said leading end portion of said gas sensor element protrudes from its own leading end, and including a support face formed on its inner circumference for supporting an axial direction of said gas sensor element; and a protector fixed on said metal shell and covering said leading end portion of said gas sensor element, wherein said protector has a double structure including a cylindrical inner cover portion covering said leading end portion of said gas sensor element through a clearance and a cylindrical outer cover portion arranged around said inner cover portion, said outer cover portion includes an outer cylindrical portion having outer gas introducing apertures capable of introducing an object gas to be measured from an outside into an inside of said outer cover portion, said inner cover portion includes: an inner cylindrical portion enclosing said leading end portion of said gas sensor element; and an inner leading end air vent hole positioned on a leading end side of said inner cylindrical portion, and a leading end portion positioned on a leading end side of said support face of said metal shell, said outer cylindrical portion and said inner cylindrical portion are arranged to construct an inner gas introducing passage for guiding said object gas introduced from said outer gas introducing apertures, between said outer cylindrical portion and said inner cylindrical portion, across an edge of said inner cylindrical portion disposed at a trailing end of said inner cylindrical portion farthest from a leading end of the inner cylindrical portion in an axial direction into a clearance formed between said inner cover portion and said leading end portion of said gas sensor element, wherein when a shortest distance between said leading end portion of said metal shell and a trailing end of said inner cylindrical portion is designated by d and when a shortest distance in an axial direction between a trailing end of said inner cylindrical portion and a trailing side end of said outer gas introducing apertures is designated by D, a ratio d/D is within a range from 0.075 to 0.200, wherein an outer circumferential surface of the inner cylindrical portion is not provided with an air vent hole.