Abnormality detection device for reductant addition valve

Abstract

An addition valve is instructed to add a reductant (step 122 ). A cumulative specified addition amount is then determined (step 124 ). An air-fuel ratio A/Fcal is estimated in accordance with the operating status of an internal combustion engine (step 126 ). An estimated air-fuel ratio A/Fcal and air-fuel ratio sensor output A/Fs are used to determine a measured addition amount (Δt) at the current moment (step 128 ). A cumulative measured addition amount is then determined (step 130 ). The error between the measured addition amount and specified addition amount are compared against a reference value (step 134 ) to detect an abnormality in the addition valve.

1 . A reductant addition valve abnormality detection device for detecting an abnormality in a reductant addition valve that adds a reductant to upstream of a catalyst to recover the purification capability of the catalyst, the reductant addition valve abnormality detection device comprising:
 addition amount designation means for designating the amount of reductant to be added by said reductant addition valve;   first air-fuel ratio detection means for detecting a first air-fuel ratio, which is an exhaust air-fuel ratio prevailing downstream of said reductant addition valve;   second air-fuel ratio acquisition means for acquiring a second air-fuel ratio, which is an exhaust air-fuel ratio of an internal combustion engine, during reductant addition by said reductant addition valve;   addition amount measurement means for measuring the amount of reductant added by said reductant addition valve in accordance with the second air-fuel ratio, which is acquired by said second air-fuel ratio acquisition means, and the first air-fuel ratio, which is detected by said first air-fuel ratio detection means; and   abnormality detection means for detecting an abnormality in said reductant addition valve by comparing an addition amount measured by said addition amount measurement means against an addition amount designated by said addition amount designation means.   
   
   
       2 . The reductant addition valve abnormality detection device according to  claim 1 , further comprising:
 difference calculation means for calculating the difference between the first air-fuel ratio detected by said first air-fuel ratio detection means, and the second air-fuel ratio acquired by said second air-fuel ratio acquisition means, before said reductant addition valve adds the reductant; and   correction means for correcting said first air-fuel ratio or said second air-fuel ratio in accordance with the difference calculated by said difference calculation means.   
   
   
       3 . The reductant addition valve abnormality detection device according to  claim 1 , wherein said second air-fuel ratio acquisition means includes at least either second air-fuel ratio estimation means, which estimates said second air-fuel ratio in accordance with an operating state of said internal combustion engine, or second air-fuel ratio detection means, which detects said second air-fuel ratio prevailing upstream of said reductant addition valve. 
   
   
       4 . A reductant addition valve abnormality detection device for detecting an abnormality in a reductant addition valve that adds a reductant to upstream of a catalyst to recover the purification capability of the catalyst, the reductant addition valve abnormality detection device comprising:
 addition amount designation device for designating the amount of reductant to be added by said reductant addition valve;   first air-fuel ratio detection device for detecting a first air-fuel ratio, which is an exhaust air-fuel ratio prevailing downstream of said reductant addition valve;   second air-fuel ratio acquisition device for acquiring a second air-fuel ratio, which is an exhaust air-fuel ratio of an internal combustion engine, during reductant addition by said reductant addition valve;   addition amount measurement device for measuring the amount of reductant added by said reductant addition valve in accordance with the second air-fuel ratio, which is acquired by said second air-fuel ratio acquisition device, and the first air-fuel ratio, which is detected by said first air-fuel ratio detection device; and   abnormality detection device for detecting an abnormality in said reductant addition valve by comparing an addition amount measured by said addition amount measurement device against an addition amount designated by said addition amount designation device.