Fuel injection control system for internal combustion engine

摘要

A Karman vortex generator is disposed in the air intake passage of an internal combustion engine. The frequency of the Karman vortex generated by the generator is detected by a Karman vortex frequency detector to measure the flow rate of intake air. The frequency of the Karman vortex is in proportion to the flow rate of intake air with a Strouhal number being the constant of proportionality thereof. However, when the flow rate or the flow velocity of intake air is within a certain range, the Strouhal number fluctuates and the proportionality between the Strouhal number and the flow rate of intake air is broken. This range is shifted when the kinematic viscosity of intake air changes. The kinematic viscosity of intake air depends upon the temperature thereof. Thus, the temperature of intake air is detected, and the output of the Karman vortex frequency detector is corrected when the air flow velocity represented by the output of the Karman vortex frequency detector is in such a range as to vary the Strouhal number taking into account the shift of such range due to the change of the kinematic viscosity of intake air.