Patent ID: 7826225

Claim:
An expansion tank device, comprising: a tank installation base having a cooling liquid channel; and an expansion tank provided on an upper surface of the installation base, wherein the tank installation base has a communication hole for holding space above the upper surface thereof in communication with the cooling liquid channel, the expansion tank has a tank main body including an upwardly bulging portion having an opening at a lower end thereof, and a bottom plate joined to a lower end of the tank main body for closing the lower-end opening of the bulging portion and joined to the upper surface of the tank installation base, the bottom plate of the expansion tank is provided at a portion thereof corresponding to the communication hole with a through hole communicating with the communication hole of the tank installation base, and the bottom plate is provided with a baffle plate formed along the entire circumference of an inner peripheral edge thereof defining the through hole and slanting upwardly toward a central portion of the through hole.