Thermal-type air flow measuring instrument

摘要

The invention relates to a thermal-type air flow measuring instrument comprising: two temperature sensing resistors (1a, 1b) mounted respectively at an upstream side and a downstream side within a fluid passage (5) in close proximity to each other for measuring a flow rate of the fluid in said fluid passage (5); an auxiliary passage (3) provided in the fluid passage (5), the auxiliary passage (3) comprising a first passageway (302) in which the two temperature sensing resistors (1a, 1b) are disposed, a second passageway (304) through which most of the fluid which entered the first passageway (302) in a forward direction flows, and a third opening (309) which is arranged downstream of said two temperature sensing resistors (1a, 1b) inside the auxiliary passage (3), wherein the fluid passage (5) is an intake air passage of an internal combustion engine and wherein an overall length L of the flow passage through which the fluid flows in the auxiliary passage (3) is longer than the length l between an inlet port (301) and the outlet port (305). <IMAGE>