Patent ID: 7942053

Claim:
An air flow measuring instrument, comprising: an auxiliary passage arranged inside a main passage through which a fluid flows, a tabular member on which a pattern of a heating resistor for measuring an air flow is provided on one face, the tabular member being disposed inside the auxiliary passage so that the one face on which the heating resistor pattern of the tabular member is provided is disposed along a flow of fluid inside the auxiliary passage, a heating resistor pattern-side fluid passage portion formed so that the fluid flows between the one face of the tabular member and a passage-forming surface of the auxiliary passage, and a back-surface side fluid passage portion formed so that fluid flows between a face on a side opposite to the one face of the tabular member, and the passage-forming surface of the auxiliary passage; wherein, on an upstream end of the tabular member, a protrusion member is provided; the protrusion member comprises a face that is parallel to the one face of the tabular member, and an inclined face that is at an angle relative to the flow, such that it guides the flow to the back-surface side fluid passage portion side; and one of the protrusion member and the inclined face is formed by a member that is softer and has a smaller restitution coefficient than the tabular member.