Abstract: A first sub passage portion and a second sub passage portion are configured so as to form layers on both sides of a separation wall, respectively. A linear passage portion of a third sub passage portion is formed so that a cross section thereof extends within a range across both sides of the separation wall in a direction perpendicular to a wall surface of the separation wall. The cross section is taken along a direction perpendicular to a flow direction of a fluid flowing through the linear passage portion. The separation wall separates the layer of the first sub passage portion and the layer of the second sub passage portion from each other. A first communication passage portion which allows the first sub passage portion to communicate with the third sub passage portion curves to make a directional change and connects a passage wall surface of the first sub passage portion to a side wall of the third sub passage portion by an inclined surface. The passage wall surface is defined by the separation wall.

Abstract: A first sub passage portion and a second sub passage portion are configured so as to form layers on both sides of a separation wall, respectively. A linear passage portion of a third sub passage portion is formed so that a cross section thereof extends within a range across both sides of the separation wall in a direction perpendicular to a wall surface of the separation wall. The cross section is taken along a direction perpendicular to a flow direction of a fluid flowing through the linear passage portion. The separation wall separates the layer of the first sub passage portion and the layer of the second sub passage portion from each other. A first communication passage portion which allows the first sub passage portion to communicate with the third sub passage portion curves to make a directional change and connects a passage wall surface of the first sub passage portion to a side wall of the third sub passage portion by an inclined surface. The passage wall surface is defined by the separation wall.

Abstract: It is an object of the present invention to expand an air flow measuring range of a thermal type air flow measuring instrument. A squeeze 157 is provided upstream of a thermal type air flow measuring instrument 100 of a main air passage 155 to expand an air flow measuring range on the low flow rate side. Furthermore, a slit 158 is provided to introduce air from the outside of the main air passage 155 to a position downstream of the squeeze 157 where flow exfoliation occurs without passing thorough a main air passage inlet 156 to prevent a pressure drop from increasing at a high flow rate and expand the air flow measuring range on the high flow rate side.