Patent ID: 10018492

Abstract:
Provided is a thermal flow meter through which a measurement with high accuracy and has a discharge function. In a thermal flow meter 300 of the invention, a part of a measurement target gas 30 flowing through the main passage 124 flows into a bypass passage. A drainage passage 3528 is provided in the bypass passage to communicate a bypass passage 4232 on the inlet port (between the inlet port 350 and the measurement surface 430 serving as the air flow sensing portion) and a bypass passage 4234 on the outlet port (between the measurement surface 430 serving as the air flow sensing portion and the outlet port 352). The drainage passage 3528 includes a through hole 3512. The through hole 3512 includes an inlet port 3542 which penetrates a wall surface 4212 forming the bypass passage 4232 on the inlet port and is opened in the bypass passage 4232 on the inlet port, and an outlet port 3544 which is opened in a rear surface 4213 of the wall surface. Water 3552 flowing into the bypass passage is guided to the through hole 3512, and guided to the bypass passage 4234 on the outlet port through the drainage passage 3528, and discharged to the main passage 124. Therefore, an influence of the water flowing into a measuring portion can be reduced, and the measurement accuracy can be improved.