Patent ID: 7560666

Claim:
A glow plug comprising: a cylindrical housing; a cylindrical sleeve having a front end portion projecting from an end of the housing and a rear end portion secured by press-fitting to the housing; and a ceramic heater of rod-like configuration held in the sleeve with a front end portion thereof projecting from a front end of the sleeve and a rear end portion thereof inserted in the sleeve, wherein the ceramic heater is capable of generating heat when energized and includes an electrically conductive heat generating portion, an insulator of insulating ceramic in which the heat generating portion is buried, and a lead portion electrically connected to the heat generating portion and having an end portion exposed to an outer peripheral surface of the insulator inside the sleeve, wherein the exposed end portion of the lead portion and an inside surface of the cylindrical sleeve are electrically connected together to form a joint portion, and the sleeve has a press-fit portion where the sleeve is secured by press-fitting to the housing, wherein the press-fit portion and the joint portion are offset in position relative to each other along an axis of the cylindrical housings, wherein a portion of an outside surface of the sleeve and a corresponding portion of the inside surface of the housing, which are located in a radial outward direction of the joint portion, are so configured as to define a space therebetween; wherein the portion of the outside surface of the sleeve, which is located in the radial outward direction of the joint portion, is configured to recede in a radial inward direction relative to a portion of the outside surface of the sleeve located at the press-fit portion; and wherein the portion of the outside surface of the sleeve, which is located in the radial outward direction of the joint portion, is configured to form a small-diameter portion having an outside diameter smaller than an outside diameter of the portion of the outside surface of the sleeve located at the press-fit portion.