Karman vortex flowmeter

Claim 1

Apparatus including a Korman vortex generator for measuring the quantity of air inhaled by an internal combustion engine from the frequency of displacement of a vibrator member comprising a pipe line for supplying inhaled air to the engine; pillar means disposed in said line for generating Korman's vortex streets by being subjected to the inhaled air; means forming a chamber outside said pipe line; a plate member including a vibrator member positioned within said chamber for partitioning it into first and second portions, said first portion in communication with the pipe line for vibration of the plate member by the vortex pressure generated by the pillar means, said second portion in communication with outside air by way of a restrictor and a filter for limiting the degree of communication and supplying a prescribed amount of outside air to said second portion; and means for optically detecting the frequency of vibration of said vibrator member located within the second portion of the chamber; the chamber being adapted to be maintained at a negative pressure relative to the outside air by the inhaled air in the pipe whereby filtered outside air is drawn into the chamber for keeping clean the optical detecting means within the second portion of the chamber.