| 摘要 |
PROBLEM TO BE SOLVED: To efficiently raise a temperature of an end of a heating tube with small power in a short time by forming a groove narrow in a radial direction on the tube red heated by a heating coil with insulating powder, and setting a width of the groove to a length of a specific range. SOLUTION: A heating tube 113 of a U-shaped cylindrical form is provided at an end of the glow plug. An integral heating coil 111 made of a high resistor for heating by energizing is arranged in the tube 113, and an insulating powder 112 of electrically insulating powder is filled in the tube 113. A groove 113a is formed on the tube 113 and has a groove width Q1 of 2 mm and a groove depth of 0.3 mm. Further, a distance R1 from the end to a center of the width Q1 is set to 7 mm and the tube 113a is formed in such a manner that a part from the end to the groove 113a is an end part 113b, and a part from the groove 113a to its rear end is a body part 113c.
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