Patent ID: 7793491

Claim:
An exhaust emission purifying apparatus comprising: a reduction catalytic converter that is disposed in an engine exhaust pipe for reductively purifying nitrogen oxides in an exhaust emission using a reducing agent supplied from a reducing agent container; a concentration sensor that detects a concentration of the reducing agent stored in the reducing agent container; a residual amount sensor that detects that a residual amount of the reducing agent stored in the reducing agent container becomes equal to or smaller than a predetermined amount; and a control unit incorporating therein a computer, wherein the control unit executes: a reducing agent judging process of judging that a liquid in the reducing agent container is any different kind of aqueous solution or that the reducing agent is deficient, when the concentration of the reducing agent detected by the concentration sensor deviates from a predetermined range or when it is detected by the residual amount sensor that a residual amount becomes equal to or smaller than a predetermined amount; and an engine control process of inhibiting restarting of an engine operation even when the restarting of an engine operation is performed, when such an initial judgment is made by the reducing agent judging process that the liquid in the reducing agent container is the different kind of aqueous solution or the reducing agent is deficient and also when such a subsequent judgment is made that a traveling distance of a vehicle driven by the engine after the initial judgment is equal to or longer than a predetermined distance, while permitting the restarting of the engine operation for rest conditions except for a condition of combination of the initial and subsequent judgments.