Controlling engine operation during diesel particulate filter regeneration to avoid runaway

Abstract

A motor vehicle diesel engine ( 10 ) has an exhaust system ( 16 ) having a diesel particulate filter ( 18 ) that traps particulate matter in engine exhaust gases passing through the exhaust system. A control system ( 22 ) processes certain data to control engine and diesel particulate filter operation. In response to driver release of the accelerator, the engine decelerates toward idling at a lower low idle speed that has been predetermined appropriate for low idling when the diesel particulate filter is not being regenerated but inappropriate when the diesel particulate filter is being regenerated because of the potential for causing on-going regeneration to become uncontrolled. When the diesel particulate filter is being regenerated, a higher low idle speed sufficiently higher than the lower low idle speed is substituted as the low idle speed set-point essentially eliminating the potential for continuation of on-going diesel particulate filter regeneration becoming uncontrolled as the engine idles.

1 . A method for controlling operation of a diesel engine during controlled regeneration of a diesel particulate filter in an engine exhaust system, the method comprising: 
 processing certain data related to engine and diesel particulate filter operation, and when the processing discloses the engine being commanded to idle at a low idle speed that has been predetermined appropriate for low idling in the absence of diesel particulate filter regeneration but inappropriate for low idling in the presence of controlled diesel particulate filter regeneration because of the potential for causing on-going regeneration of the diesel particulate filter to become uncontrolled, commanding the engine to idle at a higher low idle speed that is high enough to essentially eliminate the potential for diesel particulate filter regeneration becoming uncontrolled as the engine idles.    
   
   
       2 . A method as set forth in  claim 1  comprising processing data indicative of soot load in the diesel particulate filter and conditioning the step of commanding the engine to idle at a higher low idle speed upon the processing disclosing that the indicated soot load in the diesel particulate filter exceeds a defined soot load.  
   
   
       3 . A method as set forth in  claim 2  comprising processing data indicating temperature of exhaust gas entering the diesel particulate filter and conditioning the step of commanding the engine to idle at a higher low idle speed upon the processing disclosing that indicated exhaust gas temperature entering the diesel particulate filter exceeds a defined temperature.  
   
   
       4 . A method as set forth in  claim 1  comprising processing data indicating temperature of exhaust gas entering the diesel particulate filter and conditioning the step of commanding the engine to idle at a higher low idle speed upon the processing disclosing that indicated exhaust gas temperature entering the diesel particulate filter exceeds a defined temperature.  
   
   
       5 . A method as set forth in  claim 1  comprising starting a timer upon occurrence of the step of commanding the engine to idle at a higher low idle speed, and thereafter commanding the engine to idle at a low idle speed that has been predetermined appropriate for low idling in the absence of diesel particulate filter regeneration but inappropriate for low idling in the presence of controlled diesel particulate filter regeneration upon occurrence of one or more of a) the timer timing out after a defined maximum amount of time, b) the processing of data indicating temperature of exhaust gas entering the diesel particulate filter disclosing a temperature less than a defined temperature after the timer has timed for a defined minimum amount of time, and c) the engine being commanded to accelerate from low idle.  
   
   
       6 . A method as set forth in  claim 1  comprising conditioning the step of commanding the engine to idle at a higher low idle speed upon a flag, that is selectively set and reset by the processing step, being set.  
   
   
       7 . A method as set forth in  claim 6  wherein the conditioning step comprises processing data indicative of soot load in the diesel particulate filter, setting the flag upon the processing disclosing indicated soot load in the diesel particulate filter exceeding a defined soot load, and resetting the flag upon the processing ceasing to disclose indicated soot load in the diesel particulate filter exceeding the defined soot load.  
   
   
       8 . A diesel engine comprising: 
 an exhaust system having a diesel particulate filter that traps particulate matter in engine exhaust gases passing through the exhaust system and that at times is regenerated; and    a control system comprising a processor for processing certain data to control engine and diesel particulate filter operation, and that in response to a command for the engine to run at low idle speed causes the engine to idle at a lower low idle speed that has been predetermined appropriate for low idling when the diesel particulate filter is not being regenerated but inappropriate when the diesel particulate filter is being regenerated because of the potential for causing on-going regeneration to become uncontrolled, and when the diesel particulate filter is being regenerated, to idle at a higher low idle speed sufficiently higher than the lower low idle speed to essentially eliminate the potential for continued diesel particulate filter regeneration becoming uncontrolled as the engine idles.    
   
   
       9 . An engine as set forth in  claim 8  wherein the processor is arranged to process data indicative of soot load in the diesel particulate filter and to condition the step of commanding the engine to idle at a higher low idle speed upon processing data disclosing that the indicated soot load in the diesel particulate filter exceeds a defined soot load.  
   
   
       10 . An engine as set forth in  claim 9  wherein the processor is arranged to process data indicating temperature of exhaust gas entering the diesel particulate filter and to condition commanding the engine to idle at a higher low idle speed upon indicated exhaust gas temperature entering the diesel particulate filter exceeding a defined temperature.  
   
   
       11 . An engine as set forth in  claim 8  wherein the processor is arranged to process data indicating temperature of exhaust gas entering the diesel particulate filter and to condition commanding the engine to idle at a higher low idle speed upon indicated exhaust gas temperature entering the diesel particulate filter exceeding a defined temperature.  
   
   
       12 . An engine as set forth in  claim 8  wherein the processor is arranged to start a timer upon commanding the engine to idle at a higher low idle speed, and thereafter to command the engine to idle at a lower low idle speed upon occurrence of one or more of a) the timer timing out after a defined maximum amount of time, b) the processing of data indicating temperature of exhaust gas entering the diesel particulate filter disclosing a temperature less than a defined temperature after the timer has timed for a defined minimum amount of time, and c) the engine is commanded to accelerate from low idle speed.  
   
   
       13 . An engine as set forth in  claim 8  wherein the processor is arranged to condition the step of commanding the engine to idle at a higher low idle speed upon a flag, that is selectively set and reset, being set.  
   
   
       14 . An engine as set forth in  claim 13  wherein the processor is arranged to process data indicative of soot load in the diesel particulate filter, to condition setting the flag upon the indicated soot load in the diesel particulate filter exceeding a defined soot load, and to condition resetting the flag upon the indicated soot load in the diesel particulate filter ceasing to exceed the defined soot load.  
   
   
       15 . An engine as set forth in  claim 8  wherein the diesel particulate filter comprises a catalyzed ceramic substrate.  
   
   
       16 . A motor vehicle comprising: 
 a diesel engine for accelerating the vehicle when a driver operates an accelerator;    an exhaust system having a diesel particulate filter that traps particulate matter in engine exhaust gases passing through the exhaust system and that at times is regenerated; and    a control system comprising a processor for processing certain data to control engine and diesel particulate filter operation, and that in response to release of the accelerator causes the engine to idle at a lower low idle speed that has been predetermined appropriate for low idling when the diesel particulate filter is not being regenerated but inappropriate when the diesel particulate filter is being regenerated because of the potential for causing on-going regeneration to become uncontrolled, and when the diesel particulate filter is being regenerated, to idle at a higher low idle speed sufficiently higher than the lower low idle speed to essentially eliminate the potential for continued diesel particulate filter regeneration becoming uncontrolled as the engine idles.    
   
   
       17 . A motor vehicle as set forth in  claim 16  wherein the processor is arranged to process data indicative of soot load in the diesel particulate filter and to condition the step of commanding the engine to idle at a higher low idle speed upon processing data disclosing that the indicated soot load in the diesel particulate filter exceeds a defined soot load.  
   
   
       18 . A motor vehicle as set forth in  claim 17  wherein the processor is arranged to process data indicating temperature of exhaust gas entering the diesel particulate filter and to condition commanding the engine to idle at a higher low idle speed upon indicated exhaust gas temperature entering the diesel particulate filter exceeding a defined temperature.  
   
   
       19 . A motor vehicle as set forth in  claim 16  wherein the processor is arranged to process data indicating temperature of exhaust gas entering the diesel particulate filter and to condition commanding the engine to idle at a higher low idle speed upon indicated exhaust gas temperature entering the diesel particulate filter exceeding a defined temperature.  
   
   
       20 . A motor vehicle as set forth in  claim 16  wherein the processor is arranged to start a timer upon commanding the engine to idle at a higher low idle speed, and thereafter to command the engine to idle at a lower low idle speed upon occurrence of one or more of a) the timer timing out after a defined maximum amount of time, b) the processing of data indicating temperature of exhaust gas entering the diesel particulate filter disclosing a temperature less than a defined temperature after the timer has timed for a defined minimum amount of time, and c) the accelerator is again operated to accelerate the vehicle.  
   
   
       21 . A motor vehicle as set forth in  claim 16  wherein the processor is arranged to condition the step of commanding the engine to idle at a higher low idle speed upon a flag, that is selectively set and reset, being set.  
   
   
       22 . A motor vehicle as set forth in  claim 21  wherein the processor is arranged to process data indicative of soot load in the diesel particulate filter, to condition setting the flag upon the indicated soot load in the diesel particulate filter exceeding a defined soot load, and to condition resetting the flag upon the indicated soot load in the diesel particulate filter ceasing to exceed the defined soot load.  
   
   
       23 . A motor vehicle as set forth in  claim 16  wherein the diesel particulate filter comprises a catalyzed ceramic substrate.