Patent ID: 6064039
Filing Date: 2000-05-16
Classification: F23Q,H05B

Abstract:
A glow plug comprising:a sheath tube having a closed leading end;a cylindrical main metal shell disposed on an exterior surface of said sheath tube, said sheath tube having a projecting portion at a leading end of said sheath tube projecting beyond an end of said main metal shell; anda plurality of resistance-wire coils disposed in an axial direction in said sheath tube, said plurality of resistance-wire coils including a heating coil and a control coil in said projecting portion, said heating coil being disposed adjacent to the leading end of the projecting portion, said control coil being connected to a rear end of said heating coil in series and arranged to be heated by said heating coil to raise electrical resistance of said control coil so as to control a supply of electric power to said heating coil;wherein said projecting portion of said sheath tube has a substantially uniform outer diameter along the axial direction of said projecting portion and the outer diameter of said projecting portion is in a range of 3.0 mm to 4.4 mm so that a temperature rising characteristic at an exterior surface of the leading end of said sheath tube has a peak temperature TP in an initial stage of energization and saturates at a temperature not higher than the peak temperature TP.