Patent ID: 6868722

Claim:
An air flow rate measuring apparatus comprising: a detector flow tube projecting into an airflow channel so as to be perpendicular to a main direction of flow of air inside said airflow channel, a diversion passage through which a portion of said air is permitted to flow being formed in said detector flow tube; and a flow rate detecting element disposed inside said diversion passage, wherein: said 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 said detector flow tube communicate by means of a curved portion, an inflow port of said diversion passage is constructed by removing a portion of a wall of said upstream diversion passage on an upstream side in said main direction of flow of said air, and removing at least a portion of first and second side walls of said upstream diversion passage facing each other in a direction perpendicular to said main direction of flow of said air and said direction of projection of said detector flow tube, and a wall surface on a downstream side of said upstream diversion passage in said main direction of flow of said air at said inflow port is formed into a curved surface shape that is gradually displaced upstream relative to said direction of projection of said detector flow tube to constitute an air lead-in surface.