THERMAL FLOW METER

摘要

To improve measurement accuracy of a thermal flow meter. The present invention provides a thermal flow meter, in which a protrusion 356 having an orifice surface 503 and a recovery surface 505 is provided on a wall surface 501 of a bypass passage, an intersection line 506 between the orifice surface 503 and the wall surface 501 is arranged in an upstream side from an upstream side end 401 of a circuit package 400, an intersection line 507 between the recovery surface 505 and the wall surface 501 is arranged in a downstream side from a downstream side end 402 of the circuit package 400, and an apex 504 of the protrusion 356 is arranged in a downstream side from a heat transfer surface of an air flow sensing portion 602 and in an upstream side from the downstream side end 402 of the circuit package 400.

主权项

1. A thermal flow meter comprising a bypass passage for flowing 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 an air flow sensing portion inside the bypass passage to expose at least the heat transfer surface,
wherein a wall surface facing the measurement surface out of wall surfaces of the bypass passage, 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, an intersection line between the orifice surface and the wall surface is arranged in an upstream side from an upstream side end of the support body in a flow direction of the measurement target gas, an intersection line between the recovery surface and the wall surface is arranged in a downstream side from a downstream side end of the support body in a flow direction of the measurement target gas, and a portion of the protrusion farthest from the wall surface is arranged in a downstream side from the heat transfer surface of the air flow sensing portion in a flow direction of the measurement target gas and in an upstream side from a downstream side end of the support body.