| 摘要 |
PROBLEM TO BE SOLVED: To provide a thermal flowmeter that can prevent contaminants guided toward the outer circumference of a sub-passage by centrifugal force and particulate or liquid contaminants not readily permitting centrifugal separation from reaching the heat transmitting face of a flow rate detecting unit and thereby achieve a high level of measuring precision.SOLUTION: A thermal flowmeter has an upstream side curved path 390 in which a sub-passage is formed in a curved shape along a plane intrinsic to the side farther upstream than a flow rate detecting unit at least in the flowing direction of gas to be measured and a branching wall 378 formed from the downstream side of the upstream side curved path 390 to the downstream side of the flow rate detecting unit. The sub-passage on the downstream side of the upstream side curved path 390 is branched by the branching wall 378 into a main flow path 377 fluidly continuous to the outer circumferential wall side of the upstream side curved path 390 and a branch path 388 fluidly continuous to the inner circumferential wall side of the upstream side curved path 390, and the flow rate detecting unit is so arranged within the main flow path 377 that its heat transmitting face exposing part 436 is in a posture parallel to the intrinsic plane of the upstream side curved path 390. |
