Air flow rate measurement device having a segmented board portion at an upstream side to suppress flow disturbances
An air flow rate measurement device capable of suppressing disturbance of a flow of measured gas and reducing a characteristic influence due to water droplets flowing with intake air is realized. An edge 800 of the upstream side where air flows in a circuit board 400 on which a flow rate detection portion 602 is mounted is provided with a segmentation portion 801 to be a semicircular notch structure to segment the edge 800 . Water droplets flowing with measured gas 30 can be captured by the segmentation portion 801 to inhibit the water droplets from arriving at the flow rate detection portion 602.
1. An air flow rate measurement device, comprising:
a board which has a flow rate detection portion to detect a flow rate of measured gas; and
a housing which is provided with a passage taking a part of the measured gas and fixes the board so that the flow rate detection portion is disposed in the passage;
wherein the board has a segmentation portion which is provided in an edge of the upstream side of a flow of the measured gas with respect to the flow rate detection portion and segments a part of the edge;
wherein the segmentation portion includes a notch formed at a boundary portion between a wall surface of the housing forming the passage and the edge of the board; and
wherein the notch is configured to capture water droplets flowing through the passage.
2. The air flow rate measurement device according to claim 1 , wherein the segmentation portion is formed at a position where water is concentrated, at the upstream side of the flow of the measured gas.
3. The air flow rate measurement device according to claim 2 , wherein the segmentation portion has a shape in which water droplets flowing through the passage are distant from the flow rate detection portion.
4. The air flow rate measurement device according to claim 1 , wherein the notch is also formed at an edge of a downstream side of the flow of the measured gas with respect to the flow rate detection portion.
5. The air flow rate measurement device according to claim 1 , wherein the notch has a semicircular shape.
6. The air flow rate measurement device according to claim 5 , wherein a radius of the notch is based on a lateral width of the board.
7. The air flow rate measurement device according to claim 5 , wherein a radius of the notch is based on a longitudinal limit point of a leading end portion of the board.
8. The air flow rate measurement device according to claim 1 , wherein the notch has a triangular shape.
9. The air flow rate measurement device according to claim 1 , wherein the notch has a rectangular shape.
10. The air flow rate measurement device according to claim 1 , wherein the notch has a polygonal shape of at least a pentagon.
11. The air flow rate measurement device according to claim 1 , wherein the board is fixed to the housing by integral molding.