FLOW MEASURING APPARATUS

PROBLEM TO BE SOLVED: To provide a flow measuring apparatus for highly accurately measuring the quantity of flow of a fluid while preventing breakage of a flow measuring part by a simple constitution. SOLUTION: An inflow part 130 of a bypass passage 120 of the flow measuring apparatus 10 is inclined toward the upstream side of the flow of a main stream which flows through a main passage 100 from an entrance 132. At the opening of the entrance 132 of the inflow part 130, the downstream side of the flow of the main stream is more separated than its upstream side is from the flow of suction air of a venturi passage 110 which passes through the entrance 132. The flow measuring part 20 having a heating-resistor-type flow measuring sensor 30 is arranged on the downstream side of the flow of a main stream of an inner circumferential wall 14 of a bypass member 12 which forms the bypass passage 120 immediately below and downstream from bypass flow of a bent part 134. Foreign matter 200 which has flown in the bypass passage 120 with suction air reduces energy by colliding with the downstream side of the flow of the main stream of the inner circumferential wall 14 of the bypass member 12 by inertia in the vicinity of the entrance 132 of the inflow part 130 and is bounded back to the upstream side of the flow of the main stream. COPYRIGHT: (C)2004,JPO