Patent ID: 9709428
Date: 2017-07-18
CPC Classifications: G01F

Claim:
1. A thermal flow meter comprising: a bypass passage configured to flow a measurement target gas received from a main passage, an air flow sensing portion that measures a heat amount by performing heat transfer with the measurement target gas flowing through the bypass passage using a heat transfer surface, and a support body that supports the air flow sensing portion inside the bypass passage to expose at least the heat transfer surface, wherein a wall surface of the bypass passage facing the heat transfer surface, where the heat transfer surface of the air flow sensing portion of the support body is exposed, is provided with a protrusion including an orifice surface, approaching the support body from the wall surface along a flow direction of the measurement target gas, and a recovery surface, returning from a downstream side end of the orifice surface to the wall surface, a first intersection line between the orifice surface and the wall surface is arranged upstream from an upstream side end of the support body in the flow direction of the measurement target gas, a second intersection line between the recovery surface and the wall surface is arranged downstream from a downstream side end of the support body in the flow direction of the measurement target gas, and a portion of the protrusion farthest from the wall surface is arranged downstream from the heat transfer surface of the air flow sensing portion in the flow direction of the measurement target gas and upstream from the downstream side end of the support body, wherein the orifice surface and the recovery surface are asymmetrical to a plane perpendicular to the flow direction of the measurement target gas and passing through the portion of the protrusion farthest from the wall surface.