PURPOSE: To prevent a heat radiating effect from being reduced due to the miniaturization of a projection TV.

CONSTITUTION: Since a heat radiating member 9 is provided in the approximately intermediate part of a pressure regulator valve 6 excluding a curved part 6a participating in pressure regulating action, the heat of a coolant 4 can be efficiently exhausted to the outside without interrupting pressure regulator, and even when heat radiating fins which are conventionally fixed to a coupler 5 are reduced, the valve 6 can be provided with an effect more than the reduction, so that the heat radiating effect can be prevented from being reduced due to the miniaturization of the projection TV.