Intake air flow rate measurement apparatus

An intake air flow rate measurement apparatus for measuring a flow rate of intake air taken in an internal combustion engine, using an electrothermal resistor type air flowmeter, said intake air flow rate measurement apparatus comprising:

• an input/output port;
• a memory to which a waveform of an output signal sent from said electrothermal resistor type air flowmeter is input via said input/output port, and to store a relationship between designated angular frequencies at which frequency component strength is to be obtained and a crank angular frequency in said engine;
• and
• a calculation apparatus to execute correcting an output signal of said electrothermal resistor type air flowmeter for a response delay and a non-linearity of said electrothermal resistor type air flowmeter;
• obtaining said crank angular frequency in said engine;
• calculating frequency component strength of said waveform of said output signal, which has been sent from said electrothermal resistor type air flowmeter and has been corrected for said response delay and non-linearity, at each designated angular frequency which is obtained using said stored relationship between said designated angular frequencies and said crank angular frequency;
• obtaining a back flow ratio based on said calculated frequency component strength;
• obtaining a correct flow rate of the intake air by correcting said waveform of said output signal, which has been sent from said electrothermal resistor type air flowmeter and has been corrected for said response delay and non-linearity, with said back flow ratio, and outputting said correct flow rate of the intake air from said input/output port.