Ejector and negative-pressure supply apparatus using the same

摘要

An ejector can obtain a sufficiently large suction air quantity without reducing the ultimate vacuum. A diffuser is disposed downstream of a nozzle to form a single Laval nozzle. A suction port is provided between the nozzle and the diffuser. The inlet of the diffuser is enlarged in width so that the side walls thereof extend approximately parallel to each other along the axis of the diffuser over a predetermined length. When air is caused to flow from an inlet closer to the nozzle toward an outlet by the engine intake negative pressure, the flow velocity at a throat portion reaches the sound velocity owing to the effect of the Laval nozzle. Consequently, a high negative pressure is generated at the suction port. The parallel portion formed by enlarging the inlet of the diffuser allows the suction air quantity to be increased without reducing the effect of the Laval nozzle.