| 摘要 |
<p>The present invention aims to provide a thermal flow meter capable of avoiding pollutants guided to an outer circumference side of the bypass passage by virtue of a centrifugal force or particle or liquid pollutants that are not centrifugally separated from reaching a heat transfer surface of an air flow sensing portion and obtaining high measurement accuracy. In the thermal flow meter of the present invention, the bypass passage has an upstream side curved path 390 formed in a curved shape along an unique plane at least in an upstream side from an air flow sensing portion 602 in a flow direction of the measurement target gas 30, and a branching wall 378 formed from a downstream side of the upstream side curved path 390 to a downstream side of the air flow sensing portion 602. The bypass passage of the downstream side of the upstream side curved path 390 is branched by the branching wall 378 into a main flow path 377 that fluidly communicates with an outer wall side of the upstream side curved path 390 and a branching path 388 that fluidly communicates with an inside wall side of the upstream side curved path 390. The air flow sensing portion 602 is arranged inside the main flow path 377 such that the heat transfer surface exposing portion 436 is in parallel with the unique plane of the upstream side curved path 390.</p> |
