Patent ID: 7560012

Claim:
A gas sensor comprising: a gas sensing element extending in an axial direction, and having a gas contact part, which is brought into contact with a gas to be measured, at its front end; a case that surrounds the gas sensing element in a radial direction in such a manner that the gas contact part protrudes from a front end of the case; and a protector, formed into a bottomed cylinder, fixed to the case in such a manner that the protector covers the gas contact part of the gas sensing element, wherein the protector is composed of an inner hollow-cylindrical portion, and an outer hollow-cylindrical portion which is provided coaxially with a side wall of the inner hollow-cylindrical portion with an air space in between, the inner hollow-cylindrical portion is formed into a bottomed cylinder, the outer hollow-cylindrical portion is formed into a bottomed cylinder, the inner hollow-cylindrical portion is passed through an insertion hole provided in a bottom wall of the outer hollow-cylindrical portion, so that the bottom wall of the inner hollow-cylindrical portion protrudes nearer to the front end than the bottom wall of the outer hollow-cylindrical portion, the bottom wall of this inner hollow-cylindrical portion being made a bottom wall positioned at an utmost front end of the protector, plural number of outer-wall gas inlet openings are formed in a side wall of the outer hollow-cylindrical portion, with guiding bodies extending inward so that the gas to be measured is introduced to the air space, plural number of inner-wall gas inlet openings are formed in the side wall of the inner hollow-cylindrical portion, the inner-wall gas inlet openings being arranged nearer to the case than the outer-wall gas inlet openings so that the gas to be measured is introduced around the gas contact part, and, an outer circumferential face of the side wall of the inner hollow-cylindrical portion positioned opposite to the outer-wall gas inlet openings is formed so as to be parallel to an outer circumferential face of the side wall of the outer hollow-cylindrical portion or so as to have a slope-like shape with a diameter enlarging in an axial direction toward the bottom wall of the protector, and a discharge opening for discharging the gas to be measured, which is introduced to inside of the inner hollow-cylindrical portion directly to outside of the protector, is formed in the bottom wall positioned at the utmost front end of the protector, wherein the side wall of the inner hollow-cylindrical portion, which protrudes nearer to the front end than the bottom wall of the outer hollow-cylindrical portion, has a taper part so that an outer diameter of the side wall becomes smaller toward the front end, and the bottom wall of the outer hollow-cylindrical portion has a taper part so that that an outer diameter of the bottom wall becomes smaller toward the front end, and wherein a tip end of the taper part of the bottom wall of the outer hollow-cylindrical portion faces the taper part of the side wall of the inner hollow-cylindrical portion.