Fuel tank cap for motor vehicle

Claim 1

A fuel tank cap for use in a motor vehicle including a cap body having a path communicating the interior of a fuel tank with the atmosphere and having incorporated therein a sensor valve unit, said sensor valve unit comprising: a valve housing having an upper wall with a first through-opening therein open to said path for communication with the atmosphere, a peripheral wall having a second through-opening at a predetermined portion thereof and open to said path for communication with the interior of the fuel tank, and a bottom wall having a funnel shape, a weight ball movably placed on said bottom wall for rolling motion thereover, a plunger type valve body resting on the weight ball, and an arm member fitted around diametrically opposite side portions of the peripheral surface of said weight ball, and pivotally connected to said valve body, said valve body being raised by said weight ball following upward movement of said weight ball during its rolling motion on said bottom wall so as to close said first through-opening in said upper wall, and being forcibly lowered by said arm member following downward movement of said weight ball during its rolling motion on said bottom wall so as to open said first through-opening.