PURPOSE: To open the outlet of an auxiliary passage in a position shifted from a throttle shaft and specify the projected air passing area formed by a throttle valve to reduce the measurement error of an air flowmeter in a throttle body having a main passage forming an intake air passage and the auxiliary passage having a flow rate detecting element arranged therein.
CONSTITUTION: The intake air passage of an engine is formed of a main passage 2 and an auxiliary passage 3 having a heating resistor 4 for air flow rate detection and a thermosensitive resistor 5 for intake air temperature detection, and the heating resistor 4 and the thermosensitive resistor 5 are electrically connected to a module 7. The outlet of the auxiliary passage 3 is opened in a position shifted from a throttle shaft 9, and a throttle valve 8 is formed such that the projected air passing area formed by the valve 8 is larger on the side having the outlet part 3b of the auxiliary passage with the throttle shaft 9 as the axis in all angles from full open to full close of the throttle valve. Thus, a constant flow is regularly carried to the auxiliary passage 3 to reduce the measurement error.
IGARASHI SHINYA
TAWARA SHIGENORI
HOUKIDA ATSUSHI
HITACHI AUTOMOTIVE ENG