Temperature sensor

A temperature sensor comprises:

• a sheath tube;
• a pair of thermocouple wires inserted into the sheath tube;
• a temperature measuring junction formed by joining tip ends of a tip projecting portion of the pair of thermocouple wires with each other, the tip projecting portion being projected from the sheath tube;
• an insulating support disposed in the sheath tube;
• and
• a tip protective tube that covers an outer periphery of a tip-end of the sheath tube to surround the temperature measuring junction, wherein,
• the tip protective tube includes
• a base-end side tube portion that covers the outer periphery of the tip end of the sheath tube, and
• a tip end-side tube portion formed at a position adjacent to a tip-end side of the base-end side tube portion, the tip-end side tube portion having a diameter smaller than a diameter of the base-end side tube portion, a tip end of the tip-end side tube portion being closed;
• the tip-end side tube portion has a tip-end side portion filled with a first insulating filler, the first insulating filler burying the temperature measuring junction therein;
• and
• the tip-end side tube portion has a portion adjacent to a base-end side of the first filler, the portion being formed with an air layer.