Patent ID: 7559237

Claim:
An air flow measuring device for measuring air flow flowing through an air intake passage of an internal combustion engine by detecting air flow flowing through a sub-passage disposed in the air intake passage, the air flow flowing through the sub-passage being a part of the air flow flowing through the air intake passage, said air flow measuring device comprising: a flow measuring element to measure air flow; an electrical circuit electrically connected to the flow measuring element; a housing containing the electrical circuit, wherein the sub-passage is formed therein and the flow measuring element is disposed in the sub-passage, and a flange connected to the housing at one end portion of the housing and disposed on an outside of a wall forming the air intake passage, wherein the housing is installed on the wall through the flange so that another end portion of the housing is projected into the air intake passage, and the sub-passage, the electrical circuit and the flange are arranged in the housing by order of the sub-passage, the electrical circuit and the flange in a direction from the another end portion of the housing to the one end portion of the housing, wherein the sub-passage includes: an inlet portion; an outlet portion; a first path whose one end communicates with the inlet portion and another end communicates with a vent; and a second path which branches off from the first path and communicates with the outlet portion, wherein the second path branches off from the first path toward the one end portion of the housing so that an intermediate area of the second path goes away from the inlet portion and gets close to the electrical circuit in the housing, and wherein the flow measuring element is disposed at the intermediate area in the second path.