Patent ID: 8511285

Claim:
An evaporated fuel treatment apparatus provided in an internal combustion engine including a throttle valve in an intake passage, the evaporated fuel treatment apparatus being arranged to treat evaporated fuel generated in a fuel tank by collecting the evaporated fuel in a canister and purging the collected evaporated fuel to the intake passage through a purge passage, wherein the evaporated fuel treatment apparatus comprises: a bypass passage provided for the intake passage, the bypass passage being placed to communicate an upstream portion and a downstream portion of the intake passage with respect to the throttle valve in the intake passage; an ejector placed in the bypass passage and arranged to generate a negative pressure by air flowing from the intake passage to the bypass passage, the purge passage being connected to the ejector so that the negative pressure generated in the ejector draws the collected evaporated fuel from the canister to the ejector through the purge passage, the evaporated fuel being to be purged to the intake passage through the bypass passage; and an air-flow adjusting device for allowing or blocking flow of air from the intake passage into the bypass passage according to a pressure difference between pressure in an upstream portion and pressure in a downstream portion of the bypass passage during operation of the internal combustion engine, the air-flow adjusting device includes a pressure-sensitive open/close valve placed upstream of the ejector and arranged to open and close the bypass passage, the ejector has a double-pipe structure including an outer pipe and an inner pipe placed inside the outer pipe, the outer pipe includes a front end portion having a funnel-like shape, an intermediate portion, and a rear end portion, the front end portion including an outlet pipe joint connected to the downstream portion of the bypass passage, the rear end portion including an inlet pipe joint connected to the upstream portion of the bypass passage and the intermediate portion including a purge pipe joint connected to the purge passage, the inner pipe includes a front end portion and a rear end portion, the front end portion including a funnel-like nozzle and being directed toward the front end portion of the outer pipe, and the rear end portion being communicated with the bypass passage through the inlet pipe joint of the outer pipe, the ejector is configured to introduce the air flowing in the bypass passage into the inner pipe as drive gas, eject the air in the form of a low-pressure supersonic flow from the nozzle of the inner pipe to generate a negative pressure between the nozzle and the front end portion of the outer pipe, and the open/close valve includes a spring and a valve element, the valve element being placed to open and close an opening of the rear end portion of the inner pipe between the rear end portion of the inner pipe and an inner wall of the rear end portion of the outer pipe.