Patent ID: 7690335

Claim:
A water pump which is driven by a driving force generated by an internal combustion engine, and which generates a larger driving force as a pressure introduced into a pressure chamber becomes higher, comprising: a first passage connected to the pressure chamber; a second passage connected to a portion of an intake passage for the internal combustion engine, which is located downstream of a throttle valve; a third passage connected to an atmospheric pressure space; and a switching valve connected to the first passage, the second passage, and the third passage, wherein the switching valve changes a connection between the first passage and the second passage, and a connection between the first passage and the third passage, using a material whose volume is changed based on a temperature of a coolant for the internal combustion engine, to increase a ratio of a cross sectional area of an opening portion of the third passage, which is connected to the first passage, to a cross sectional area of an opening portion of the second passage, which is connected to the first passage, as the temperature of the coolant increases.