To improve the response of temperature detection of a thermistor to the temperature change of a temperature sensing part by increasing the contact area of a thermistor and the temperature sensing part of a temperature sensing pipe.

The trunk part 21 of a temperature sensing pipe 2 is constituted as a pyramid having a polygonal section. A thermistor 1 having an external appearance of a round shaft is inserted in the temperature sensing pipe 2. By using this constitution, the trunk part 21 turning to the temperature sensing part of the temperature sensing pipe 2 comes into rectilinear contact with the thermistor 1, at two or more points in the peripheral direction of the thermistor 1. As compared with, e.g. the conventional case that the temperature sensing pipe 2 has an external appearance of a cylinder, the contact area of the temperature sensing part of the temperature sensing pipe 2 and the thermistor 1, i.e., the thermal conduction area, is doubled. Thereby the response of temperature detection of the thermistor 1 to the temperature change of the temperature sensing part is improved twice.