Patent ID: 8148664

Claim:
A glow plug having a sheath heater, the sheath heater comprising: a sheath tube extending in an axial direction and having a tubular shape, a closed front end portion, and an open rear end portion; a heat-generating resistor disposed within the sheath tube; an insulating powder charged into a gap between the sheath tube and the heat-generating resistor; and a seal member received in said sheath tube and having a substantially cylindrical shape, the seal member including an expanded portion extending radially outwardly from an outer circumference of the seal member at least prior to receipt of said seal member in said sheath tube, and a non-expanded portion of a smaller outside diameter than the expanded portion at least prior to receipt of said seal member in said sheath tube, and formed on the outer circumference of the seal member at least at a leading end of the seal member; the seal member being fitted into the open rear end portion of the sheath tube such that the leading end enters the sheath tube first, and the sheath tube being deformed radially inwardly around the seal member for sealing the heat-generating resistor and the insulating powder contained in the sheath tube; and the sheath heater generating heat through conduction of electricity to the heat-generating resistor.