Abstract: An air flow meter comprises a main passage for an axial main air flow; an axial subpassage for air flow, disposed in the main passage and formed so that part of the air in the main passage is taken in at an upstream side thereof and flows in the same direction as the axial main air flow; a radial subpassage for air flow, intersecting the axial subpassage at a downstream side of the axial subpassage so that air from the axial subpassage flows into the radial subpassage and is divided into two radial air flows running in different radial directions; the air having passed through the radial subpassage joining the axial main air flow. An air flow sensing means is disposed in the radial subpassage for sensing a flow rate of air therein, and a projection is disposed in the radial subpassage around the intersection of the axial and radial subpassages, for suppressing turbulence of air flow around the intersection.

Abstract: A thermal air flow meter for measuring the flow rate of intake air supplied to an internal combustion engine comprises a thermal sensor disposed in an intake air passage, a drive circuit including a circuit pattern formed on a circuit board for driving the thermal sensor, a shielding case having at least a bottom wall on which the circuit board is mounted and side walls, a through capacitor disposed on one of the side walls of the shielding case, a conductor extending through the capacitor so that the conductor is electrically connected in an AC mode through the capacitor to the shielding case and having one end connected to a corresponding terminal of the drive circuit and the other end connected to an external terminal, a metal case in which the shielding case is mounted and a connecting member electrically connecting the shielding case to the metal case at an area on the bottom wall selected between an edge of the bottom wall connected to the one side wall and an edge of the pattern formed on the circuit b