Abstract:
An engine ( 12 ) has an exhaust system ( 16 ) containing a diesel particulate filter (DPF  20 ) and timer-based warning structure ( 30 ) for detecting and indicating particulate overloading of the DPF as the engine runs.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to monitoring after-treatment devices in engine exhaust systems in motor vehicles, and in particular to a time-based structure for detecting and indicating an overloaded diesel particulate filter (DPF). 
       BACKGROUND OF THE INVENTION 
       [0002]    A DPF treats engine exhaust passing through the engine exhaust system by trapping particulate matter to prevent its escape to atmosphere. From time to time, a DPF requires regeneration in order to keep the trapped matter from imposing excessive back-pressure on the engine. Regeneration involves creating conditions that will burn off trapped particulates whose unchecked accumulation would otherwise eventually create excessive back-pressure. Such conditions may be created naturally as the engine operates, with the resulting regeneration being sometimes referred to as natural regeneration. Such conditions may also be created by a deliberate request for regeneration. The resulting regeneration is sometimes referred to active regeneration. 
         [0003]    A vehicle that is powered by an internal combustion engine whose exhaust system contains a DPF may operate over an extended period of time during which no regeneration of the DPF occurs. As trapped particulates accumulate, they impose increasing back-pressure on the engine. 
         [0004]    It is known to use an engine control system to automatically initiate a regeneration request when the amount of trapped particulates reaches a level appropriate for regeneration. It is also known to provide a warning to a driver of the vehicle when the amount of trapped particulates reaches a level at which active regeneration is appropriate so that the driver can manually initiate an active regeneration, for example by operating a switch that issues a regeneration request to the engine control system. 
       SUMMARY OF THE INVENTION 
       [0005]    One aspect of the invention relates to an engine comprising an exhaust system containing a diesel particulate filter (DPF) and timer-based warning structure for detecting and indicating particulate overloading of the DPF as the engine runs. 
         [0006]    The warning structure comprises a) a source for providing data representing current particulate loading of the DPF, b) processing apparatus for i) repeatedly processing the current particulate loading data and data defining a threshold level of particulate loading at which a request for regeneration of the DPF should be issued, and ii) when a result of that processing discloses that the current particulate loading is at least as great as the threshold level, enabling an indicator, and iii) when processing of the current particulate loading data and data defining a hierarchy of zones of successively greater particulate overloading of the DPF greater than the threshold level discloses that the current particulate loading has remained in one of those zones for a length of time set by a timer, causing the enabled indicator to give an indication that the DPF has become overloaded. 
         [0007]    Another aspect relates to an engine comprising an exhaust system containing a diesel particulate filter (DPF), and timer-based warning structure for detecting and indicating particulate overloading of the DPF as the engine runs. 
         [0008]    The warning structure comprises a) a source for providing data representing current particulate loading of the DPF, b) processing apparatus for repeatedly processing the current particulate loading data and data defining a hierarchy of zones of successively greater particulate overloading of the DPF, wherein each zone comprises a range bounded by a respective lower level of particulate loading and a respective upper level of particulate loading, and c) the processing apparatus comprises, for each zone, an input stage for determining if the current particulate loading is greater than some level of loading, a timer that runs concurrently with the input stage disclosing that current particulate loading is greater than that level, and an output stage that issues a signal to indicate when the respective timer has disclosed that particulate loading has remained greater than that level for some set length of time. 
         [0009]    The foregoing, along with further features and advantages of the invention, will be seen in the following disclosure of a presently preferred embodiment of the invention depicting the best mode contemplated at this time for carrying out the invention. This specification includes drawings, now briefly described as follows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  shows portions of an engine and exhaust system relevant to the present invention in a motor vehicle. 
           [0011]      FIG. 2  is chart showing various conditions related to the state of a DPF in the exhaust system. 
           [0012]      FIGS. 3A and 3B  collectively comprise a schematic illustration of a presently preferred embodiment of timer-based warning structure in accordance with principles of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0013]      FIG. 1  shows a truck  10  that is propelled by a diesel engine  12 . Engine  12  has one or more processors  14  that processes data from various sources to develop various data that is used for informational and/or control purposes. The data processed by control system  14  may originate at external sources, such as sensors, and/or be generated internally. 
         [0014]    Engine  12  also has an exhaust system  16  through which exhaust created by combustion of a combustible mixture in combustion chambers of the engine is conveyed to a tail pipe  18  that opens to the surrounding atmosphere. Exhaust system  16  comprises one or more after-treatment devices, one of which is a diesel particulate filter (DPF)  20  that traps exhaust particulates (soot) so that they do not pass through to tail pipe  18 . 
         [0015]    As explained earlier, DPF  20  must be regenerated from time to time in order to burn off trapped particulates. When a need for regeneration is determined by a frequently executed algorithm in a processor  14  disclosing that the particulate load in DPF  20  has reached a point where regeneration is required, a regeneration request is issued. If conditions are suitable for initiating regeneration, the engine control system may then automatically initiate regeneration, such as by changing fueling and/or air management, to suitably condition the exhaust. If conditions for regeneration are not suitable, regeneration is delayed, and particulates continue to accumulate in DPF  20  as engine  12  continues running. Some initial overloading of the DPF is tolerable, but beyond that, the operator of truck  10  needs to be alerted. 
         [0016]    The chart of  FIG. 2  defines seven possible states for DPF  20 : DPF missing; DPF leaking; DPF clean; DPF partly-loaded with soot; DPF loaded with soot to normal regeneration trigger point; DPF overloaded with soot greater than normal regeneration trigger point; and DPF severely overloaded. 
         [0017]    As shown by  FIG. 2 , each state has been defined in a processor  14  by a respective data value for a parameter STATE_EGBP_PF, using the numbers “7” through “1” inclusive in descending order. 
         [0018]    Certain recommendations by the industry suggest that four levels of soot overloading (Service, Warning, Stop, Critical) be identified and made known in some way to the operator of a motor vehicle that has a DPF in its exhaust system. While the existing data values shown in  FIG. 2  define important reference points for the amount of soot loading in DPF  20 , they do not provide direct correspondence with the industry recommendations. 
         [0019]    The present invention adapts the data values of  FIG. 2  for use in conforming to industry recommendations. 
         [0020]    A processor  14  processes data according to a time-based warning structure  30  shown in  FIGS. 3A and 3B . The processed data comprises the current data value for parameter STATE_EGBP_PF and a selectable data value for each of eight parameters C_STATE_EGBP_PF 1 , C_STATE_EGBP_PF 2 , C_STATE_EGBP_PF 3 , C_STATE_EGBP_PF 4 , C_STATE_EGBP_PF 5 , C_STATE_EGBP_PF 6 , C_STATE_EGBP_PF 7 , C_STATE_EGBP_PF 8 . 
         [0021]    While the data values for the each of the latter eight parameters can be selected from any of the values “7” through “1” in  FIG. 2 , the use of only “2” and “1” is needed to conform warning structure  30  to industry recommendations. 
         [0022]    Warning structure  30  comprises four sections  32 ,  34 ,  36 , and  38  that function to detect and indicate a respective one of these four portions of the range of DPF soot loading greater than normal regeneration trigger point. 
         [0023]    Section  32  is designated “Request Service” to correspond to “Service” of the industry recommendations; section  34 , “Warn Level” to correspond to “Warning” of the industry recommendations; section  36 , “Stop Level” to correspond to “Stop” of the industry recommendations; and section  38 , “Severe Level” to correspond to “Critical” of the industry recommendations. 
         [0024]    Each section  32 ,  34 ,  36 , and  38  comprises a similar processing strategy that uses three comparison functions, an AND logic function, and a timer function. Two of the comparison functions and the AND logic function form an input stage, and the third comparison function forms an output stage to which the timer function is one input. The other input to the third comparison function is a parameter that sets the length of time that the timer must run in order for the output stage to issue a signal that the time has elapsed. 
         [0025]    Section  32  comprises a comparison function  40  that compares the current value for STATE_EGBP_PF and the value of a parameter C_STATE_EGBP_PF_ 1 _ 1  and a comparison function  42  that compares the current value for STATE_EGBP_PF and the value of a parameter C_STATE_EGBP_PF_ 2 . When the amount of particulates in DPF  20  are within a range defined by C_STATE_EGBP_PF_ 1  and C_STATE_EGBP_PF_ 2 , an AND logic function  44  enables a timer function  46  to run. 
         [0026]    The running time on function  46  (parameter DPF REQ_TMR) is compared with a reference time (parameter DPF REQ_TM) by a comparison function  48 . When the running time exceeds the reference time, a signal represented by parameter REQ_DPF is given. 
         [0027]    Section  34  comprises a comparison function  50  that compares the current value for STATE_EGBP_PF and the value of a parameter C_STATE_EGBP_PF_ 3  and a comparison function  52  that compares the current value for STATE_EGBP_PF and the value of a parameter C_STATE_EGBP_PF_ 4 . When the amount of particulates in DPF  20  are within a range defined by C_STATE_EGBP_PF_ 3  and C_STATE_EGBP_PF_ 4 , an AND logic function  54  enables a timer function  56  to run. 
         [0028]    The running time on function  56  (parameter DPF_WARNLVL_TMR) is compared with a reference time (parameter DPF_WARNLVL_TM) by a comparison function  58 . When the running time exceeds the reference time, a signal represented by parameter WARN_DPF is given. 
         [0029]    Section  36  comprises a comparison function  60  that compares the current value for STATE_EGBP_PF and the value of a parameter C_STATE_EGBP_PF_ 5  and a comparison function  62  that compares the current value for STATE_EGBP_PF and the value of a parameter C_STATE_EGBP_PF_ 6 . When the amount of particulates in DPF  20  are within a range defined by C_STATE_EGBP_PF_ 5  and C_STATE_EGBP_PF_ 6 , an AND logic function  64  enables a timer function  66  to run. 
         [0030]    The running time on function  66  (parameter DPF_STOPLVL_TMR) is compared with a reference time (parameter DPF_STOPLVL_TM) by a comparison function  68 . When the running time exceeds the reference time, a signal represented by parameter STOP_DPF_DERATE_LVL_ 1  is given. 
         [0031]    Section  38  comprises a comparison function  70  that compares the current value for STATE_EGBP_PF and the value of a parameter C_STATE_EGBP_PF_ 7  and a comparison function  72  that compares the current value for STATE_EGBP_PF and the value of a parameter C_STATE_EGBP_PF_ 8 . When the amount of particulates in DPF  20  are within a range defined by C_STATE_EGBP_PF_ 7  and C_STATE_EGBP_PF_ 8 , an AND logic function  74  enables a timer function  76  to run. 
         [0032]    The running time on function  76  (parameter DPF_SEVLVL_TMR) is compared with a reference time (parameter DPF_SEVLVL_TM) by a comparison function  78 . When the running time exceeds the reference time, a signal represented by parameter SEVERE_DPF_DERATE_LVL_ 2  is given. 
         [0033]    Parameter REQ_DPF is an input to a switch function  80  that is used to operate an indicator shown as a lamp  82 . The state of switch function  80 , either ON or OFF, is controlled by a parameter DPF_LAMP_FLSH that is provided by the output of an OR logic function  84  to which parameters WARN_DPF, STOP_DPF_DERATE_LVL_ 1 , and SEVERE_DPF_DERATE_LVL_ 2  are inputs. The latter two parameters are also inputs to an OR logic function  86 . 
         [0034]    The four sections  32 ,  34 ,  36 , and  38  enable the conditions that start the respective timers and the length of time that each timer will run before giving a signal at a respective output to be set as deemed appropriate for a particular vehicle and/or engine. 
         [0035]    By selecting from “DPF overloaded with soot greater than normal regeneration trigger point” (“2”) and “DPF severely overloaded” (1), in conjunction with SELECTING values for DPF_REQ_TM, DPF_WARNLVL_TM, DPF_STOPLVL_TM, and DPF_SEVLVL_TM, it is possible to conform to the industry recommendations for alerting the operator. 
         [0036]    In one example, a selection of STATE_EGBP_PF=2 for both C_STATE_EGBP_PF_ 1  and C_STATE_EGBP_PF_ 2 , and a value of ten minutes for DPF_REQ_TM will cause REQ_DPF to enable switch function  80  ten minutes after a regeneration request has been issued and the engine continues running without any active regeneration having commenced. 
         [0037]    A selection of STATE_EGBP_PF=2 for both C_STATE_EGBP_PF_ 3  and C_STATE_EGBP_PF_ 4 , and a value of sixty minutes for DPF_WARNLVL_TM will cause WARN_DPF to operate switch function  80  to ON state after sixty minutes of continued running of the engine without any active regeneration having commenced after the regeneration request. With switch function  80  both enabled and operated, lamp  82  lights to give a warning to the vehicle operator. 
         [0038]    A selection of STATE_EGBP_PF=1 for both C_STATE_EGBP_PF_ 5  and C_STATE_EGBP_PF_ 6 , and a value of five minutes for DPF_STOPLVL_TM will cause the state of STOP_DPF_DERATE_LVL_ 1  to change. If timer function  46  is kept from being reset, STOP_DPF_DERATE_LVL_ 1  will continue to keep switch function  80  in the ON state via OR logic function  84  five minutes after the change in STATE_EGBP_PF from “2” to “1”. It also causes the engine control system to de-rate engine  12 . To indicate the continued lack of regeneration, STOP_DPF_DERATE_LVL_ 1  will also illuminate a second lamp  88  via OR logic function  86 . 
         [0039]    A selection of STATE_EGBP_PF=1 for both C_STATE_EGBP_PF_ 7  and C_STATE_EGBP_PF_ 8 , and a value of thirty minutes for DPF_SEVLVL_TM will cause SEVERE_DPF_DERATE_LVL_ 2  to continue to keep switch function  80  ON via OR logic function  84  thirty minutes after the change in STATE_EGBP_PF from “2” to “1”. It will also de-rate the engine even more severely than did STOP_DPF_DERATE_LVL_ 1  and will continue to illuminate lamp  88 . 
         [0040]    While a presently preferred embodiment of the invention has been illustrated and described, it should be appreciated that principles of the invention apply to all embodiments falling within the scope of the invention that is defined as follows.