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AssigneeHitachi, Ltd.
InventorsHiroshi Kuroiwa, Yoshishige Ohyama, Yutaka Nishimura, Nobuaki Miyakawa
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An air flow metering apparatus for measuring a suction air flow fed to an internal combustion engine comprises at least two Karman' vortex type air flow meters disposed separately in at least two air suction passages, respectively. The output signals from the flow meters are switched in such manner that in a predetermined range of high air flow rates, the output signal from one of the flow meter is utilized for measuring or sensing the air flow rate, while in a predetermined low flow rate range, the output signal from the other flow meter is utilized for the same purpose. Alternatively, in a predetermined low flow rate range, only one of the air suction passages is employed, while both of the air suction passages are employed in a predetermined range of high air flow rates. The air flow metering apparatus assures the detection or measurement of the suction air flow rate over a whole operation range of the engine with a high reliability and enhanced accuracy.
An air flow metering apparatus for an internal combustion engine in which suction air flow fed to said engine is measured by a Karman vortex type air flow meter disposed in an air suction passage, comprising at least two air suction passages each of which has a Karman vortex type flow meter disposed therein, and input switching circuit means for receiving output signals from said vortex flow meters and for generating an output signal utilizing only the input signal from a first of said vortex flow meters when said input signal is below a predetermined reference value and utilizing the output of another of said flow meters when said reference value is exceeded, said reference value being set so as to result in detection of only stable vortexes over the whole operational range of the internal combustion engine, wherein one of said flow meters is disposed in the narrowest portion of a small size venturi having a suction passage of a relatively small crosssectional area, while the other flow meter is disposed in an annular space between the narrowest portion of a small venturi and a large venturi having a suction passage of a relatively large crosssectional area, said small venturi being concentrically disposed within the large venturi.
An air flow metering apparatus for an internal combustion engine in which suction air flow fed to said engine is measured by a Karman vortex type of air flow meter disposed in an air suction passage, comprising at least two air suction passages each of which has a Karman vortex type flow meter disposed therein, and input switching circuit means for receiving output signals from said vortex flow meters and for generating an output signal utilizing only the input signal from a vortex flow meter in a first of said passages when the flow through the other of said passage is below a predetermined value and utilizing the sum of the outputs of said flow meters when said value is exceeded, said reference value being set so as to result in detection of only stable vortexes over the whole operational range of the internal combustion engine.
Dependencies are inferred from the claim text.