Patent ID: 8257577

Claim:
A method of manufacturing a gas sensor, comprising: providing a sensor element, a cylindrical metal shell and a cylindrical protection cover, the sensor element having a gas sensing portion at a front end thereof and an electrode portion at a rear end thereof, the metal shell having a flange portion and a rear end portion located on a rear side of the flange portion and including a first cylindrical section and a second cylindrical section located on a rear side of the first cylindrical section and being smaller in diameter than the first cylindrical section; assembling the sensor element and the metal shell together to retain the sensor element in the metal shell with the gas sensing portion and the electrode portion protruding from front and rear ends of the metal shell, respectively; placing a front end of the protection cover around the second cylindrical section of the rear end portion of the metal shell and allowing an end face of the front end of the protection cover to abut a rear end face of the first cylindrical section of the rear end portion of the metal shell, wherein the front end of the protection cover is placed around the second cylindrical section of the rear end portion of the metal shell; swaging the front end of the protection cover and the rear end portion of the metal shell radially inwardly to form a swaged part circumferentially astride from the end face of the front end of the protection cover to the first cylindrical section of the rear end portion of the metal shell; and laser welding the entire circumference of the front end of the protection cover to the first cylindrical section of the rear end portion of the metal shell to form a weld joint therebetween, in the swaged part, extending from the end face of the front end of the protection cover to the first cylindrical section of the rear end portion of the metal shell.