Abstract: An electronic control unit (12) calculates the heat receiving quantity of a thermo wax to estimate the temperature of the thermo wax on the basis of the calculated heat receiving quantity and the heat capacity of the thermo wax, and controls a heater so that the temperature of the thermo wax reaches a predetermined target value. Further, the electronic control unit (12) changes the value of the heat capacity used to estimate the temperature of the thermo wax depending on the variation of the estimated temperature of the thermo wax across the phase transition point of the thermo wax so as to preferably control a switching valve which is operated by heating the thermo wax.

Abstract: An electronic control unit (12) calculates the heat receiving quantity of a thermo wax to estimate the temperature of the thermo wax on the basis of the calculated heat receiving quantity and the heat capacity of the thermo wax, and controls a heater so that the temperature of the thermo wax reaches a predetermined target value. Further, the electronic control unit (12) changes the value of the heat capacity used to estimate the temperature of the thermo wax depending on the variation of the estimated temperature of the thermo wax across the phase transition point of the thermo wax so as to preferably control a switching valve which is operated by heating the thermo wax.

Abstract: In a thermostat device, a high-temperature cooling water inlet that introduces high-temperature cooling water from a bypass path that has been heated by an engine and has bypassed a radiator is provided at a side position of the valve housing that is substantially orthogonal to a direction in which the temperature sensitive movable portion moves, and a heater path inlet that introduces cooling water from a heater path that has been supplied to a heater core is provided at a lower end portion of the valve housing. The high-temperature cooling water inlet is provided with a plurality of guide portions protruding from the right and left sides of the inlet along the lower face of a cut-off portion toward the temperature sensitive movable portion, and the high-temperature cooling water introduced from the high-temperature cooling water inlet by the guide portions is guided toward the temperature sensitive movable portion.