Air flow rate measuring device

An air flow rate measuring device comprising

• main air passage means for introducing therethrough air into an internal combustion engine;
• venturi means provided in said main air passage means for contracting an air stream to make the pressure at a portion of said main air passage means relatively lower;
• by-pass passage means for by-passing a portion of said main air passage means;
• outlet means of said by-pass passage means formed at the relatively lower pressure portion of said main air passage means;
• inlet means of said by-pass passage means disposed upstream of said outlet means and formed angularly along the inner circumference of said main air passage means, said inlet means projecting slightly into said main air passage means and being open in radial and axial directions to said main air passage means so that the air at said inlet means is subjected to the dynamic pressure due to the air stream flowing in said main air passage means;
• and
• sensor means disposed in said by-pass passage means for measuring the flow rate of air flowing in said by-pass passage means, wherein said outlet means of said by-pass passage means is formed annular and opened normally to the main air stream.

An air flow rate measuring device comprising

• a suction tube for introducing air into an internal combustion engine, said suction tube having a throat portion which forms an inner shoulder inside said suction tube;
• a venturi tube disposed in said suction tube so that the lower end of said venturi tube rests on said inner shoulder;
• a cylinder disposed inside said suction tube so as to rest on the upper end of said venturi tube;
• a by-pass passage by passing said venturi tube, an inlet of said by-pass passage being defined by the lower end of said cylinder and the upper end of said venturi tube so as to project inside the inner face of said cylinder;
• an outlet of said by-pass passage being defined by the lower end of said venturi tube and said inner shoulder of said suction pipe;
• and
• means including a hot wire disposed in said by-pass passage for measuring the flow rate of air flowing in said by-pass passage.

An air flow rate measuring device for an internal combustion engine, comprising:

• main air passage means for introducing therethrough air into an internal combustion engine and having a relatively lower pressure portion at which the air stream is at a lower pressure than other portions thereof;
• by-pass passage means for by-passing a portion of said air stream of said main air passage means, including outlet means communicating with the air stream at said relatively-lower pressure portion of said main air passage means so that the air at said outlet means is subjected to the static pressure of the air stream flowing in the main air passage means at this point, and inlet means disposed upstream of said outlet means and formed as an annular slit along the inner circumference of said main air passage means, a downstream of a slit defining surface projects slightly into said main air passage means such that the inlet means is open in radial and axial directions so that the air at said inlet means is subjected to the dynamic pressure due to the air stream flowing in said main air passage means;
• and
• sensor means disposed in said by-pass passage means for measuring the flow rate of air flowing in said by-pass passage means.