1. Field of the Invention
The present invention relates to a device for detecting a mass flow of air fed into an engine cylinder.
2. Description of the Related Art
It is necessary to detect the amount of air fed into the cylinders of an engine to control, for example, the ignition timing and the amount of fuel fed into the engine cylinders. Consequently, to detect the amount of air fed into the engine cylinders, in a known engine equipped with a charger such as a turbocharger or a mechanically driven supercharger, a movable vane type air flow meter or a Karman vortex type air flow meter is arranged in the intake passage upstream of the charger (see, for example, Japanese Unexamined Patent Publication No. 55-35253).
Nevertheless, where the engine is equipped with the charger, the range of change in the amount of air fed into the engine cylinders is wide compared with the case where the engine is not equipped with the charger. Conversely, the range of the amount of air which can be correctly detected by the movable vane type air flow meter or the Karman vortex type air flow meter is restricted. Consequently, if such an air flow meter is arranged in the intake passage upstream of the charger, a problem occurs in that the amount of air can not be correctly detected by the air flow meter over the entire operating state of the engine.