Patent ID: 6395159
Filing Date: 2002-05-28
Classification: G01N

Abstract:
An oxygen sensor comprising:an oxygen sensing element with a shaft shape; a cylindrical casing for housing said oxygen sensing element; a gas introduction structure having a filter holding part marking a cylindrical form coaxial with said casing on a rear of said casing, having an inside communicating with said casing, and one or more gas introduction holes being formed in a wall and a filter being placed so as to block the gas introduction hole or holes of said filter holding part for rejecting permeation of liquid and allowing gas to pass through, said gas introduction structure for introducing outside air into said casing through the filter and the gas introduction hole or holes; and a protective cover being formed in the shape of a cylinder for covering said gas introduction structure from an outside thereof for blocking or suppressing a direct jet of liquid drops to said filter or deposition of oil or dirt on said filter, wherein said protective cover is joined to an outer face of the filter holding part by a cover joint part with a gas retention space produced between said protective cover and the filter at a position corresponding to the gas introduction hole; and wherein an external communication part for allowing the gas retention space to communicate with the outside and introducing outside air into the gas retention space is provided, wherein the cover joint part is formed annularly along a circumferential direction of said protective cover; wherein the external communication part is a passage crossing the annular cover joint part between said protective cover and the filter holding part, wherein a plurality of predetermined-length grooves as the external communication part extending in the axial direction of the filter holding part are formed with a predetermined spacing along the circumferential direction on the outer peripheral surface of the filter holding part ahead the gas introduction hole; the cover joint part is an annular crimp part formed so as to cross the grooves and leave a gap between said protective cover and the filter holding part at the bottom of each groove by crimping said protective cover toward the filter holding part; and outside air is introduced into the gas retention space through the grooves from a front opening of the gap formed between said protective cover and the filter holding part.