Patent ID: 7437925

Claim:
A flow detecting device that is provided to a fluid passage through which a main flow of fluid passes, the flow detecting device comprising: a sensor body that has a bypass passage through which a bypass flow passes, the bypass flow being a part of the main flow, the bypass passage having a bent portion and an outflow passage, the bent portion being located midway through the bypass passage, the outflow passage being located downstream of the bent portion, the bypass passage defining a flow direction of the bypass flow, the flow direction of the bypass flow changing at the bent portion toward the outflow passage through the bypass passage; and a heating element that is arranged in the bypass passage, the heating element generating heat by being supplied with electricity for detecting a flow amount of fluid in accordance with an amount of heat released from the heating element, wherein the sensor body has a side surface parallel to the main flow and a lateral opening, such that when fluid causes a counterflow in the fluid passage in a direction opposite to a flow direction of the main flow, dynamic pressure caused by the counterflow is released to an outside of the outflow passage through the opening, and the outflow passage communicates with an outside of the sensor body through the opening of the side surface.