Abstract: A glow plug for preheating the combustion chamber of a diesel engine. The glow plug has a ceramic heater rod with an embedded resistor. A metal holder holds the front of the heater rod. A terminal assembly at the rear of the holder provides for two electrically isolated terminals which are connected to the heater rod by flexible, insulated wires. The insulating bush which isolates the terminals is formed by inserting insulating material between a metal pipe and the terminals. This pipe is then subject to external force to create an air-tight seal.

Abstract: In a glow plug for use in a diesel engine of the type comprising a first helical heating member, a second helical heating member connected to the first heating member and made of material having larger positive resistance temperature coefficient than that of the first heating member, and a sheath enclosing the first and second heating members, the ratio between the length of the first heating member and the sheath diameter is selected to be less than 1.5, and the resistance ratio at normal temperature of the first and second heating members is selected to lie in a range of from 2.5 to 7.0.

Abstract: A glow plug for use in a diesel engine comprises first and second helical heaters covered with a sheath. The second heater is made of material having larger resistance temperature coefficient than that of the first heater. A gap larger than winding pitches of the two heaters is provided there between and the two heaters are electrically interconnected in the gap.

Abstract: In a glow plug for use in a diesel engine of the type wherein a heater rod is connected to one end of a hollow holder, and an external connecting terminal is inserted into the other end of the hollow holder through an electric insulator and electrically connected to the heater rod, an integrally combined terminal unit including a metal pipe, an electric insulator and the external connecting terminal embedded in the insulator is prepared. After inserting the terminal unit into the other end of the hollow holder, an external pressure is applied to the other end to deform the metal pipe for firmly bonding the metal pipe to the insulator. Thereafter an end surface of the other end of the hollow holder is caulked to form an annular ring that holds the inserted terminal unit. With this construction, the completed glow plug is maintained in a perfect air tight state regardless of the variation in the ambient temperature.

Abstract: In a glow plug for use in a diesel engine of the type wherein a heater rod is connected to one end of a hollow holder, and an external connecting terminal is inserted into the other end of the hollow holder through an electric insulator and electrically connected to the heater rod, an integrally combined terminal unit including a metal pipe, an electric insulator and the external connecting terminal embedded in the insulator is prepared. After inserting the terminal unit into the other end of the hollow holder, an external pressure is applied to the other end to deform the metal pipe for firmly bonding the metal pipe to the insulator. Thereafter an end surface of the other end of the hollow holder is caulked to form an annular ring that holds the inserted terminal unit. With this construction, the completed glow plug is maintained in a perfect air tight state regardless of the variation in the ambient temperature.

Abstract: In a glow plug, a pair of ceramic rods having longitudinal bonding surfaces are used as a heating rod. A resistor including a heater, and a pair of lead portions connected to both ends of the heater and extending to rear ends of the ceramic rods is continuously disposed on one bonding surface of the ceramic rods. One of the lead portions extends through a hollow metal holder, while the other lead portion is connected to an external connecting terminal mounted through an insulating member.