Apparatus for measuring gas flow rate in a bypass passage and having a passage restriction portion downstream of the detecting element

An apparatus for measuring gas flow rate, comprising:

• a pipe body whose inside space performs as a passage for flowing gas to be measured;
• a housing disposed at an inside space of said pipe body so as to diametrically project from a pipe wall toward a center axis of said pipe body;
• a bypass passage through which part of the gas to be measured flows, said bypass passage being formed in said housing into a generally U-shape and having an inlet port located in the vicinity of a center axis of said pipe body and at least one outlet port located in the vicinity of the pipe wall of said pipe body;
• a passage restricting portion disposed in said bypass passage so as to decrease a passage cross-sectional area of said bypass passage;
• and
• a flow rate detecting element disposed in said bypass passage and upstream of said passage restricting portion,
• wherein an inlet portion of said bypass passage is formed into a tapered shape such that a passage cross-sectional area thereof is gradually decreased.