System and Method for Injector Fault Remediation

Abstract

A machine includes an engine having an exhaust system. A diesel exhaust fluid (DEF) injector provides metered amounts of DEF and includes a valve adapted to selectively open in response to a command. A controller associated with the engine and the DEF injector monitors operation of the DEF injector to detect a fault and activates a failure remediation cycle when the fault has been detected. The remediation cycle includes heating the exhaust gas to heat the DEF injector and melt any urea crystals that may be causing the fault, and activating the valve of the DEF injector to evacuate molten urea from within the DEF injector.

We claim: 
     
         1 . A machine, comprising:
 an engine having an exhaust system associated therewith;   a diesel exhaust fluid (DEF) injector disposed to provide metered amounts of DEF into the exhaust system, the DEF injector including a valve adapted to selectively open in response to a command for injecting DEF into the exhaust system; and   a controller associated with the engine and the DEF injector;   wherein the controller is disposed to:
 monitor operation of the DEF injector to detect a fault; 
 activate a failure remediation cycle when a fault is detected, said remediation cycle including causing an increase in a temperature of an exhaust gas in the exhaust gas system to heat the DEF injector and melt any urea crystals that may be causing the fault, and activating the valve of the DEF injector to evacuate molten urea from within the DEF injector; 
 determine whether the fault has been cleared; and 
 when the fault is present for a predetermined period, set a failure flag signal. 
   
     
     
         2 . The machine of  claim 1 , further comprising a temperature sensor disposed to measure the temperature of the exhaust gas in the exhaust gas system and provide a temperature signal to the controller, wherein the controller is further disposed to estimate a temperature of the DEF injector based on the temperature signal. 
     
     
         3 . The machine of  claim 1 , wherein causing the increase in the temperature of the exhaust gas is accomplished by at least one of activating an exhaust gas heater device, increasing a back pressure of the engine, and providing unburned hydrocarbons in the exhaust gas system. 
     
     
         4 . The machine of  claim 1 , wherein the controller is further disposed to:
 determine an actual DEF injector valve position;   compare a commanded DEF injector valve position with the actual DEF injector valve position, and   determine that the fault is present when a difference between the commanded and actual DEF injector valve positions exceeds a predetermined threshold difference for a predetermined period.   
     
     
         5 . The machine of  claim 1 , further comprising a device disposed along the exhaust system and operable to increase the temperature of the exhaust gas in response to a command signal from the controller. 
     
     
         6 . The machine of  claim 5 , wherein the device includes a fuel fired heater configured to produce a flame within the exhaust system to thus increase the temperature of the exhaust gas. 
     
     
         7 . The machine of  claim 5 , wherein the device is a back-pressure device, which includes a valve disposed to selectively block the exhaust system against flow of exhaust gas therein, which operates to increase engine exhaust back-pressure and thus increase engine load and the temperature of the exhaust gas. 
     
     
         8 . The machine of  claim 1 , wherein the controller is configured to cause the increase in temperature of the exhaust gas by providing commands arranged to increase at least one of a speed and load outputs of the engine. 
     
     
         9 . A method for failure remediation of a diesel exhaust fluid (DEF) injector in a machine having an engine, the engine having an exhaust system, the method comprising:
 generating exhaust gas and routing the same through an exhaust gas system;   selectively injecting predetermined quantities of a diesel exhaust fluid (DEF) containing an aqueous solution of urea into the exhaust gas using a DEF injector that is responsive to command signals provided by a controller;   monitor operation of the DEF injector with the controller to detect a fault;   activate a failure signal in the controller when a fault in the DEF injector has been present for a predetermined period;   activate a failure remediation cycle in the controller while the failure signal is active and before the predetermined period has expired, said remediation cycle including causing an increase in a temperature of the exhaust gas in the exhaust gas system;   heating the DEF injector above a normal operating temperature but below a high temperature threshold;   melting any urea crystals that may be causing the fault; and   activating the DEF injector to evacuate molten urea from within the DEF injector.   
     
     
         10 . The method of  claim 9 , further comprising:
 determining whether the fault has been cleared; and   resetting the failure signal when the fault has been cleared.   
     
     
         11 . The method of  claim 9 , further comprising measuring the temperature of the exhaust gas, and providing a temperature signal to the controller, wherein heating the DEF injector above a normal operating temperature includes estimating a temperature of the DEF injector in the controller based on the temperature signal. 
     
     
         12 . The method of  claim 9 , further comprising determining an opening state of a valve of the DEF injector, and providing a position signal to the controller, wherein detecting a fault is accomplished at least in part on the basis of the position signal. 
     
     
         13 . The method of  claim 12 , wherein detecting the fault is accomplished by:
 comparing a commanded DEF injector valve position with an actual DEF injector valve position, which is established based on the position signal, and   determining that the fault is present when a difference between the commanded and actual DEF injector valve positions exceeds a predetermined threshold difference for a predetermined period.   
     
     
         14 . The method of  claim 9 , wherein heating the DEF injector above a normal operating temperature is accomplished by causing the temperature of the exhaust gas to increase by activating a device disposed along the exhaust system and operable to increase the temperature of the exhaust gas in response to a command signal from the controller. 
     
     
         15 . The method of  claim 14 , wherein the device includes a fuel fired heater configured to produce a flame within the exhaust system to thus increase the temperature of the exhaust gas. 
     
     
         16 . The method of  claim 14 , wherein the device is a back-pressure device, which includes a structural arrangement disposed to selectively block the exhaust system against flow of exhaust gas therethrough, and which operates to increase engine exhaust back-pressure and thus increase engine load and the temperature of the exhaust gas. 
     
     
         17 . The method of  claim 9 , heating the DEF injector above a normal operating temperature is accomplished by providing commands by the controller, said commands being arranged to increase at least one of a speed and a load output of the engine. 
     
     
         18 . A method for remediating a fault in a diesel exhaust fluid (DEF) injector, comprising:
 determining that a fault is present in the DEF injector, said fault being attributable to the condensation of crystalline urea within the injector after boiling and evaporation of water from an aqueous urea solution has occurred within the DEF injector;   activating a failure signal when the fault in the DEF injector is present;   heating the DEF injector to a temperature that is above a normal operating temperature to melt any crystalline urea within the DEF injector;   continuing to heat the DEF injector while the temperature of the DEF injector is below a maximum threshold temperature and while a timer has not elapsed;   periodically activating the DEF injector to evacuate any molten urea from within the DEF injector while the timer has not elapsed; and   determining whether the fault has been remediated.   
     
     
         19 . The method of  claim 18 , wherein the DEF injector is adapted to operate in association with an exhaust system of an internal combustion engine disposed in a machine, and wherein heating the DEF injector above a normal operating temperature is accomplished by causing a temperature of exhaust gas of the engine to increase. 
     
     
         20 . The method of  claim 19 , wherein, when the failure has been remediated as evidenced by normal operation of the DEF injector while the timer has not lapsed, the method further includes causing the temperature of the exhaust to lower to a normal operating temperature.