Reducing agent supply apparatus abnormality diagnosis unit and reducing agent supply apparatus

Abstract

[Problem] To provide a reducing agent supply apparatus abnormality diagnosis unit that can reduce the limitation on when to perform abnormality diagnosis and on the applicability of abnormality diagnosis to facilitate the implementation of abnormality diagnosis of a reducing agent supply apparatus and to provide the reducing agent supply apparatus. [Means for Resolution] The reducing agent supply apparatus abnormality diagnosis unit includes: a reducing agent injection valve controller for determining an energization on/off duty ratio according to an instructed injection amount of the reducing agent to issue an instruction for driving the reducing agent injection valve; a pump controller for determining an energization on/off duty ratio to issue an instruction for driving the pump so that the pressure in the reducing agent passage is maintained at a predetermined system pressure, based on the difference between the detected pressure in the reducing agent passage and the system pressure; and an abnormality determiner for performing abnormality determination of the reducing agent supply apparatus based on the duty ratio of the reducing agent injection valve and the duty ratio of the pump in a predetermined period.

1 . A reducing agent supply apparatus abnormality diagnosis unit for performing abnormality diagnosis of a reducing agent supply apparatus, the reducing agent supply apparatus comprising: a storage tank for storing liquid reducing agent; a pump for pumping the reducing agent; a reducing agent injection valve for injecting the reducing agent pumped by the pump in an exhaust pipe of an internal-combustion engine; a reducing agent passage connecting the pump to the reducing agent injection valve; and a pressure sensor for detecting pressure in the reducing agent passage, wherein the reducing agent supply apparatus abnormality diagnosis unit comprises:
 a reducing agent injection valve controller for determining an energization on/off duty ratio according to an instructed injection amount of the reducing agent to issue an instruction for driving the reducing agent injection valve;   a pump controller for determining an energization on/off duty ratio to issue an instruction for driving the pump so that the pressure in the reducing agent passage is maintained at a predetermined system pressure, based on the difference between the detected pressure in the reducing agent passage and the system pressure; and   an abnormality determiner for performing abnormality determination of the reducing agent supply apparatus based on the duty ratio of the reducing agent injection valve and the duty ratio of the pump in a predetermined period.   
     
     
         2 . The reducing agent supply apparatus abnormality diagnosis unit according to  claim 1 , wherein the abnormality determiner performs the abnormality determination by determining whether or not the instruction for driving the pump with an output power assumed from the integration of the reducing agent injection valve duty ratio during the predetermined period has been issued. 
     
     
         3 . The reducing agent supply apparatus abnormality diagnosis unit according to  claim 1 , wherein the abnormality determiner performs the abnormality determination based on the reducing agent injection valve duty ratio and the pump duty ratio when the reducing agent injection valve duty ratio is within a range in which the change in the pump duty ratio is in proportion to the change in the reducing agent injection valve duty ratio. 
     
     
         4 . The reducing agent supply apparatus abnormality diagnosis unit according to  claim 1 , wherein the abnormality determiner performs the abnormality determination such that the predetermined period is a period from when the integration of the reducing agent injection valve duty ratio is started to when the calculated integration reaches a predetermined determination start value. 
     
     
         5 . The reducing agent supply apparatus abnormality diagnosis unit according to  claim 1 , wherein the abnormality determiner performs the abnormality determination by setting as a reference duty ratio the pump duty ratio when the reducing agent injection valve duty ratio is zero, then comparing the ratio of the integration of the reducing agent injection valve duty ratio during the predetermined period to the integration of the difference between the pump duty ratio and the reference duty ratio during the predetermined period, with a determination threshold. 
     
     
         6 . The reducing agent supply apparatus abnormality diagnosis unit according to  claim 1 , wherein the abnormality determiner performs the abnormality determination by setting as a reference duty ratio the pump duty ratio when the reducing agent injection valve duty ratio is zero, then comparing the integration of the product of the reducing agent injection valve duty ratio and the difference between the pump duty ratio and the reference duty ratio during the predetermined period, with a determination threshold assumed from the integration of the reducing agent injection valve duty ratio during the predetermined period. 
     
     
         7 . The reducing agent supply apparatus abnormality diagnosis unit according to  claim 1 , wherein the abnormality determiner performs the abnormality determination by setting as a reference duty ratio the pump duty ratio when the reducing agent injection valve duty ratio is zero, then comparing the integration of the difference between the pump duty ratio and the reference duty ratio during the predetermined period, with a determination threshold assumed from the integration of the reducing agent injection valve duty ratio during the predetermined period. 
     
     
         8 . The reducing agent supply apparatus abnormality diagnosis unit according to  claim 1 , wherein an upper threshold and a lower threshold are set as a determination threshold, and the abnormality determiner uses the upper threshold and the lower threshold to separately determine an abnormality of excessive injection amount condition and an abnormality of insufficient injection amount condition. 
     
     
         9 . A reducing agent supply apparatus comprising the reducing agent supply apparatus abnormality diagnosis unit according to  claim 1 . 
     
     
         10 . The reducing agent supply apparatus abnormality diagnosis unit according to  claim 2 , wherein the abnormality determiner performs the abnormality determination based on the reducing agent injection valve duty ratio and the pump duty ratio when the reducing agent injection valve duty ratio is within a range in which the change in the pump duty ratio is in proportion to the change in the reducing agent injection valve duty ratio. 
     
     
         11 . The reducing agent supply apparatus abnormality diagnosis unit according to  claim 10 , wherein the abnormality determiner performs the abnormality determination such that the predetermined period is a period from when the integration of the reducing agent injection valve duty ratio is started to when the calculated integration reaches a predetermined determination start value. 
     
     
         12 . The reducing agent supply apparatus abnormality diagnosis unit according to  claim 11 , wherein the abnormality determiner performs the abnormality determination by setting as a reference duty ratio the pump duty ratio when the reducing agent injection valve duty ratio is zero, then comparing the ratio of the integration of the reducing agent injection valve duty ratio during the predetermined period to the integration of the difference between the pump duty ratio and the reference duty ratio during the predetermined period, with a determination threshold. 
     
     
         13 . The reducing agent supply apparatus abnormality diagnosis unit according to  claim 12 , wherein the abnormality determiner performs the abnormality determination by setting as a reference duty ratio the pump duty ratio when the reducing agent injection valve duty ratio is zero, then comparing the integration of the product of the reducing agent injection valve duty ratio and the difference between the pump duty ratio and the reference duty ratio during the predetermined period, with a determination threshold assumed from the integration of the reducing agent injection valve duty ratio during the predetermined period. 
     
     
         14 . The reducing agent supply apparatus abnormality diagnosis unit according to  claim 11 , wherein the abnormality determiner performs the abnormality determination by setting as a reference duty ratio the pump duty ratio when the reducing agent injection valve duty ratio is zero, then comparing the integration of the difference between the pump duty ratio and the reference duty ratio during the predetermined period, with a determination threshold assumed from the integration of the reducing agent injection valve duty ratio during the predetermined period. 
     
     
         15 . The reducing agent supply apparatus abnormality diagnosis unit according to  claim 14 , wherein an upper threshold and a lower threshold are set as a determination threshold, and the abnormality determiner uses the upper threshold and the lower threshold to separately determine an abnormality of excessive injection amount condition and an abnormality of insufficient injection amount condition.