Sensor

A sensor comprising:

• a sensor element;
• a metallic shell that accommodates the sensor element:
• a terminal fitting that is disposed on a rear end side of the sensor element and electrically connected to the sensor element;
• a cylindrical case that extends in an axial direction and is disposed and connected on a rear end side of the metallic shell:
• one or more lead wires that are electrically connected to a rear end side of the terminal fitting and extend from inside to outside of the case;
• a connector portion that is connected to a rear end side of the lead wires and that protrudes radially outward of the lead wires;
• and
• a cylindrical heat shield tube that covers an outer surface of a rear end side of the case, extends rearward of the case and surrounds the lead wires, wherein
• the heat shield tube includes a first tube, a second tube that has an inner diameter larger than an outer diameter of the first tube and is capable of accommodating the first tube, and a third tube that has an inner diameter larger than an outer diameter of the second tube and is capable of accommodating the second tube,
• the third tube is disposed on a distal end side of the second tube and covers an outer surface of the rear end side of the case, while providing a first overlapping portion that overlaps the second tube,
• the second tube is disposed on a distal end side of the first tube while providing a second overlapping portion that overlaps the first tube,
• a rear end side of the first tube is adjacent to the connector portion,
• a total length T of the heat shield tube, a length S1 of the first overlapping portion and a length S2 of the second overlapping portion satisfy T/10≤S1≤T/5 and T/10≤S2≤T/5, and a length L1 of the first tube, a length L2 of the second tube and a length L3 of the third tube satisfy T/3≤L3<L2<L1.