A pump exerts pressure on fluid that has higher saturation pressure than atmospheric
pressure at room temperature in a fluid reserving chamber in a fluid tank. The
pump is located near the fluid tank. The pump has a housing and a heat generating
mechanism. The housing defines a pump chamber, a motor chamber and a communication
passage between the pump chamber and the motor chamber and includes at least one
introducing port for introducing the fluid from the fluid reserving chamber into
the housing and a bleeding port located above the introducing port for returning
the fluid from the housing to the fluid reserving chamber. The heat generating
mechanism is located in the housing. The fluid circulates into the housing through
the introducing port and out of the housing through the bleeding port for substantially
reducing the temperature in the housing.
