Diesel exhaust fluid filter permeability detection strategy and machine using same

Abstract

A reductant dosing system for an exhaust aftertreatment system of a diesel engine includes a reductant tank with an inlet volume separated from an outlet volume by a sock filter. A filter permeability condition is detected by the electronic controller using a filter status algorithm that compares fluid level sensor data to expected data. A filter permeability condition might be indicated when the reductant dosing rate exceeds the rate at which fluid can move through the sock filter from the inlet volume to the outlet volume. A filter permeability condition may eventually lead to a system fault.

What is claimed is: 
     
         1 . A machine comprising:
 an engine mounted on a chassis and including an exhaust after treatment system;   the exhaust after treatment system including a reductant dosing system that includes a reductant tank with a fluid level sensor in communication with an electronic controller;   the reductant tank including a filter separating an inlet volume from an outlet volume, and the fluid level sensor being positioned in the outlet volume, and the reductant tank including an inlet that opens to the inlet volume and an outlet that opens to the outlet volume; and   the electronic controller including a filter status algorithm configured to detect a filter permeability condition based at least in part on data from the fluid level sensor.   
     
     
         2 . The machine of  claim 1  wherein the fluid level sensor is a float sensor; and
 the filter is a sock filter; and 
 a header of the reductant tank and the sock filter define the outlet volume. 
 
     
     
         3 . The machine of  claim 2  wherein the electronic controller includes a reductant system fault algorithm configured to log a reductant system fault responsive to a pressure in a fluid circuit of the reductant system that is less than a dosing pressure threshold. 
     
     
         4 . The machine of  claim 3  wherein the system fault algorithm is configured to disable the reductant system responsive to a reductant system fault; and
 the electronic controller is configured to maintain the reductant system operational responsive to the filter permeability condition. 
 
     
     
         5 . The machine of  claim 4  wherein the fluid circuit includes the outlet, a pump and a return line that opens into the outlet volume; and
 a second filter positioned in the fluid circuit. 
 
     
     
         6 . The machine of  claim 5  wherein the filter status algorithm is configured to determine a time rate of change in the tank level data; and
 the filter status algorithm is configured to log a filter permeability condition responsive to the time rate of change in the tank level data being greater than an expected time rate of change while reductant is being dosed from the reductant system into an exhaust pipe of the engine. 
 
     
     
         7 . The machine of  claim 6  wherein the filter status algorithm is configured to log a filter permeability condition responsive to an increase in the tank level data that is greater than an expected increase threshold after reductant dosing has ceased and the inlet is closed. 
     
     
         8 . The machine of  claim 1  wherein the electronic controller includes a reductant system fault algorithm configured to log a reductant system fault responsive to a pressure in a fluid circuit of the reductant system that is less than a dosing pressure threshold;
 the system fault algorithm is configured to disable the reductant system responsive to a reductant system fault; 
 the electronic controller is configured to maintain the reductant system operational responsive to the filter permeability condition; 
 the fluid circuit includes the outlet, a pump and a return line that opens into the outlet volume; and 
 a second filter positioned in the fluid circuit. 
 
     
     
         9 . The machine of  claim 1  wherein the filter status algorithm is configured to determine a time rate of change in the tank level data;
 the filter status algorithm is configured to log a filter permeability condition responsive to the time rate of change in the tank level data being greater than an expected time rate of change while reductant is being dosed from the reductant system into an exhaust pipe of the engine; and 
 the filter status algorithm is configured to log a filter permeability condition responsive to an increase in the tank level data that is greater than an expected increase threshold after reductant dosing has ceased and the inlet is closed. 
 
     
     
         10 . A method of operating a machine, comprising the steps of:
 running an engine supported on a chassis of the machine;   moving exhaust through an exhaust pipe from the engine;   circulating reductant around a fluid circuit from an outlet volume of a reductant tank, through a pump and into a return line that opens back into the outlet volume;   dosing reductant into an exhaust pipe of the engine;   moving reductant from the inlet volume to the outlet volume through a filter;   communicating tank level data from a fluid level sensor, which is positioned in the outlet volume, to an electronic controller;   comparing the tank level data to expected data; and   logging a filter permeability condition responsive to the tank level data differing from the expected data by greater than a predetermined threshold.   
     
     
         11 . The method of  claim 10  wherein the circulating step includes pumping the reductant through a second filter fluidly positioned in the fluid circuit. 
     
     
         13 . The method of claim  12  including a step of measuring a system pressure of the reductant in the fluid circuit;
 logging a reductant system fault responsive to the system pressure being below a dosing pressure threshold. 
 
     
     
         14 . The method of  claim 13  including a step of maintaining the reductant dosing system operational responsive to the filter permeability condition; and
 disabling the reductant dosing system responsive to the reductant system fault. 
 
     
     
         15 . The method of  claim 10  wherein the comparing step includes comparing a time rate of change in the tank level data to an expected time rate of change. 
     
     
         16 . The method of  claim 15  including determining a dosing rate; and
 determining the expected time rate of change based at least in part on the dosing rate. 
 
     
     
         17 . The method of  claim 16  including ceasing dosing of reductant into the exhaust pipe;
 the comparing step includes detecting an increase in the tank level data that is greater than an expected increase threshold after the dosing has ceased. 
 
     
     
         18 . The method of  claim 15  including ceasing dosing of reductant into the exhaust pipe;
 the logging step includes detecting an increase in the tank level data that is greater than an expected increase threshold after the dosing has ceased. 
 
     
     
         19 . The method of  claim 10  including replacing the sock filter responsive to the filter permeability condition. 
     
     
         20 . The method of  claim 19  including adding sock filter replacement to a previous maintenance schedule for the machine responsive to the filter permeability condition.