Air flow rate measuring apparatus

摘要

A diversion passage is constructed into an inverted U shape in which an upstream diversion passage and a downstream diversion passage each having a passage direction in a direction of projection of a detector flow tube communicate by means of a curved portion. An inflow port is constructed by removing a portion of a wall of the upstream diversion passage on an upstream side in the main direction of flow, and removing a portion of first and second side walls of the upstream diversion passage facing each other in a direction perpendicular to the main direction of flow and the direction of projection of the detector flow tube. In addition, a wall surface on a downstream side of the upstream diversion passage in the main direction of flow at the inflow port is formed into a curved surface shape that is gradually displaced upstream relative to the direction of projection of the detector flow tube to constitute an air lead-in surface.