Air flow measuring device

Abstract

An air flow measuring device is adapted to be attached to a duct. The device includes a first housing, a second housing, and a flow sensor. The first housing defines a bypass flow passage which takes in a part of air flowing in the duct, and includes a hollow part and a recess. The bypass flow passage is formed in the hollow part. The recess is formed on an upper side of the hollow part in a vertical direction of the device, and at the recess, an outer surface of the first housing is recessed inward of the first housing. The second housing is formed through secondary formation with the first housing as a primary formed part. The first housing is held on a lower side of the second housing in the vertical direction. The flow sensor is disposed in the bypass flow passage.

What is claimed is: 
     
         1 . An air flow measuring device comprising:
 a first housing including a flow sensor that detects a flow rate in a bypass flow passage which takes in a part of air flowing in a duct;   a second housing that is formed through secondary formation with the first housing as a primary formed part, wherein:   the first housing includes a hollow part; and   the second housing includes a connector part for electrically connecting the flow sensor to an external device; and   a recess at which an outer surface of the first housing is recessed inward of the first housing on the connector part-side of the hollow part in a direction perpendicular to a mainstream direction when installing the air flow measuring device to the duct, which defines an intake passage.   
     
     
         2 . The air flow measuring device according to  claim 1 , wherein the recess is configured as a circumferential groove that is formed continuously along an entire periphery of the outer surface of the first housing. 
     
     
         3 . The air flow measuring device according to  claim 1 , wherein:
 the recess includes side surfaces on both sides in the direction perpendicular to the mainstream direction;   one of the side surfaces of the recess is located on the connector part-side; and   a part of a die is inserted into the recess at time of formation of the second housing, so that the one of the side surfaces serves as a die cramp surface.   
     
     
         4 . The air flow measuring device according to  claim 2 , wherein:
 the recess includes side surfaces on both sides in the direction perpendicular to the mainstream direction;   one of the side surfaces of the recess is located on the connector part-side; and   
       a part of a die is inserted into the recess at time of formation of the second housing, so that the one of the side surfaces serves as a die cramp surface.