Patent ID: 8469010

Claim:
A measuring device that is a device for measuring a mass flow rate of NOx recirculated to an intake passage with a blowby gas in an internal combustion engine in which the blowby gas is recirculated to the intake passage, comprising: a NOx sensor attached to a downstream side from a position where the blowby gas is recirculated in said intake passage; an air flowmeter attached to an inlet port of said intake passage; and a signal processing device that processes each of signals from said NOx sensor and air flowmeter, wherein said signal processing device includes: a NOx concentration measuring unit that converts a signal from said NOx sensor into a NOx concentration; an oxygen concentration measuring unit that converts the signal from said NOx sensor into an oxygen concentration; a fresh air mass flow rate measuring unit that converts a signal from said air flowmeter into a mass flow rate of fresh air; a blowby gas mass flow rate calculating unit that calculates a mass flow rate of the blowby gas recirculated to said intake passage from the oxygen concentration and the mass flow rate of the fresh air; an all gas mass flow rate calculating unit that calculates a mass flow rate of all gases in said intake passage from the mass flow rate of the fresh air and the mass flow rate of the blowby gas; and a NOx mass flow rate calculating unit that calculates a mass flow rate of NOx in said intake passage from the mass flow rate of all the gases and the NOx concentration.