Fluid flow meter having an improved sampling channel

#The present invention relates to devices and methods for measuring fluid flow in a duct.

#Internal combustion engines today include electronic controls to provide optimal engine operation. Typically, the electronic control systems include a primary control unit for processing control algorithms and a variety of sensors for providing control signals to the primary control unit. One critically important sensor for achieving optimal engine control is a mass fluid flow sensor for measuring air intake into the internal combustion engine.

#It is critical that the mass fluid flow measurement is accurate in order to provide optimal engine operation. One significant problem affecting the mass fluid flow measurement, is reverse flow or back flow in the direction opposite of fluid intake. Typically, mass fluid flow sensors detect the flow of air in both the forward and reverse directions relative to air intake, therefore reverse flow causes an inaccurate mass fluid flow reading.

#FIG. 1 is an exploded view of a mass fluid flow sensor in accordance with the present invention;

#FIG. 2 is a perspective view of a mass fluid flow housing in accordance with the present invention;

#FIG. 3 is a perspective view of a mass fluid flow housing cover, in accordance with the present invention;

#Referring now to FIGS. 1 and 2, exploded and perspective views of a mass fluid flow sensor 10 for calculating the amount of fluid flowing in a duct is illustrated, in accordance with the present invention. One application or use for sensor 10 is for measuring the amount of air inducted into an internal combustion engine (not shown). However, the present invention contemplates other uses and application for sensor 10. For example, sensor 10 may be used to calculate the amount of fluid (other than air) flowing through a duct (other than an air intake duct of an internal combustion engine). Mass fluid flow sensor 10 includes a housing 12, housing cover 14, a secondary housing cover 16, an electronics cover 18, and a gasket 20.

#Housing 12 includes an integral connector 30 having connector terminals (not shown) that are in electrical communication with engine operation control electronics external to mass fluid flow sensor 10 and in electrical communication with a circuit module 32 disposed within a central housing portion 34. Adjacent to central housing portion 34, housing 12 further provides an integrally attached fluid sampling portion 36. Fluid sampling portion 36 includes an inlet 38 that opens into a nozzle 39. Nozzle 39 communicates with a substantially U-shaped flow passage 40. U-shaped flow passage 40 terminates at an outlet 42.

#Nozzle 39 has, generally, a jet nozzle configuration or shape. As will be further illustrated and described, nozzle 39 is defined by a generally circular opening or inlet 38 that meets longitudinally converging elliptical side surfaces (as shown in FIG. 7b). The longitudinally converging elliptical side surfaces of the nozzle create a relatively high pressure at an exit 41 of nozzle 39. Further, the jet nozzle configuration of nozzle 39 creates a critical area 43 located at exit 41 having a uniform fluid flow velocity across the critical area. This critical area created by the nozzle provides enhanced fluid flow detection and measurement as will be described hereinafter. To further enhance the flow of fluid through passage 40 a wedge deflector 45 is positioned on an end of housing 12 upstream of outlet 42. Wedge deflector 45 has a surface that is tilted to create an advantageously low pressure area adjacent outlet 42. If the angle of the surface of deflector 45 (indicated by the letter a in FIG. 7b) is too small with respect to the direction of fluid flow an insufficient pressure drop is created at outlet 42. Conversely, if the angle of the surface of deflector 45 is too large with respect to the direction of fluid flow an insufficient pressure drop is created at outlet 42. Preferably, the angle α of the surface of deflector 45 is between 47° and 600 with respect to a horizontal line.