Abstract:
A system and method for including the effect of regeneration of a diesel particulate filter ( 22 ) on quality of engine motor oil.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates generally to motor vehicles, such as trucks, that are powered by internal combustion engines, particularly diesel engines that have certain exhaust gas treatment devices for treating exhaust gases passing through their exhaust systems. The invention especially relates to a system and method for including the effect of regenerating an aftertreatment device on quality of motor oil in the engine. 
       BACKGROUND OF THE INVENTION 
       [0002]    Known systems and methods for indicating when the motor oil that lubricates moving internal parts of an engine needs to be changed are commonly based on elapse of time and/or miles traveled after the immediately previous oil change. The lengths of time and/or of mileage may be based on data developed through prior studies of the effect of vehicle operation on motor oil lubricating quality. 
         [0003]    Commonly owned U.S. Pat. No. 6,513,367 mentions other known systems and methods. One involves using a dielectric sensor to monitor the quality of motor oil. Another involves estimating oil quality by tracking vehicle operation after the most recent addition of fresh motor oil. That patent also identifies various factors that contribute to contamination of engine motor oil. 
         [0004]    One of those factors is soot created by combustion of fuel in the engine. The patent describes a sophisticated algorithm for estimating the amount of soot added to the motor oil by each combustion event in each cylinder. Specifically, soot addition is estimated as a function of fuel flow, load, coolant temperature, and an injection timing factor. When the quality of the oil has deteriorated to some defined extent suggesting that the oil be changed, a signal to that effect is given. 
         [0005]    Certain engines, diesel engines especially, may have one or more aftertreatment devices in their exhaust systems for removing undesired materials from engine exhaust so that those materials don&#39;t enter the atmosphere. Such devices may at times require regeneration. As used here, “regeneration” of an aftertreatment device applies here to any aftertreatment device that on occasion requires a specific cylinder combustion event that creates additional soot, HC, and the like in order to maintain effectiveness of the aftertreatment device. 
         [0006]    One such device is a diesel particulate filter (DPF) that traps certain particulates in the exhaust. A DPF requires regeneration from time to time in order to maintain particulate trapping efficiency. Regeneration as applied to a DPF involves the presence of conditions that will burn off trapped particulates whose unchecked accumulation would otherwise impair DPF effectiveness. While “regeneration” of a DPF often refers to the general process of burning off DPM from a DPF, two particular types of DPF regeneration are recognized by those familiar with DPF regeneration technology as presently being applied to motor vehicle engines. 
         [0007]    “Passive regeneration” is generally understood to mean regeneration that can occur anytime that the engine is operating under conditions that burn off DPM without having been initiated by a specific regeneration strategy embodied by algorithms in an engine control system. “Active regeneration” is generally understood to mean regeneration that is initiated intentionally, either by the engine control system on its own initiative, or by the driver causing the engine control system to initiate a regeneration, with the goal of elevating temperature of exhaust gases entering the DPF to a range suitable for initiating and maintaining burning of trapped particulates. 
         [0008]    Active regeneration may be initiated before a DPF becomes loaded with DPM to an extent where regeneration would be mandated by the engine control system on its own due to the amount of DPM loading. 
         [0009]    The creation of conditions for initiating and continuing active regeneration, whether forced by the control system on its on or by driver action, generally involves elevating the temperature of exhaust gas entering the DPF to a suitably high temperature to initiate and continue buring of trapped particulates. Because a diesel engine typically runs relatively cool and lean, the post-injection of diesel fuel is one technique used as part of a regeneration strategy to elevate exhaust gas temperatures entering the DPF while still leaving excess oxygen for burning the trapped particulate matter. Post-injection may be used in conjunction with other procedures and/or devices, a diesel oxidation catalyst ahead of the DPF for example, for elevating exhaust gas temperature to the relatively high temperatures needed for active DPF regeneration. 
         [0010]    The post-injection of fuel for DPF regeneration however inherently creates certain additional exhaust constituants, including an excess of unburned fuel, to be exhausted from each combustion chamber. Hence, active regeneration of a DPF, even if only occasional, creates an additional contamination component. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention is directed toward a strategy that specifically takes active regeneration of a DPF into account when calculating quality of engine motor oil. 
         [0012]    One general aspect of the invention relates to a method for estimating lubricating quality of motor oil in an internal combustion engine that propels a vehicle and has an exhaust system containing an aftertreatment device that is occasionally regenerated. 
         [0013]    In a data processing system associated with the engine, various data are processed to develop a data estimate of the lubricating quality of motor oil currently in the engine. The data includes data to identify occurrence of an active regeneration event and data that is indicative of an amount of degradation in lubricating quality of motor oil in the engine due to the identified occurrence of the forced regeneration event. A data estimate of the amount of degradation in lubricating quality of motor oil in the engine due to the forced regeneration event is developed, and then processed to in calculating the data estimate of the quality of motor oil currently in the engine. 
         [0014]    Another generic aspect relates to a method for estimating degradation in lubricating quality of motor oil in an internal combustion engine that propels a motor vehicle due to occasional forced regeneration of an aftertreatment device in an exhaust system of the engine. 
         [0015]    In a data processing system associated with the engine, the following data is processed: data that identifies each occurrence of an active regeneration event that has occurred over a span of time during which the vehicle has been in use without any fresh motor oil being introduced into the engine; and data that is indicative of degradation in lubricating quality of motor oil in the engine due to each identified occurrence of an active regeneration event. The processing yields a data estimate of the amount of degradation due to each event. The individual data estimates are accumulated and used in calculating a data estimate of the amount of degradation that has occurred over the span of time during which the vehicle has been in use without any fresh motor oil being introduced into the engine. 
         [0016]    A further generic aspect relates to a motor vehicle comprising an internal combustion engine for propelling the vehicle, a lubrication system for circulating motor oil to lubricate moving internal parts of the engine, an exhaust system through which exhaust passes from combustion chambers of the engine into surrounding atmosphere, an aftertreatment device for treating exhaust passing through the exhaust system before the exhaust enters the atmosphere, and an engine control system for processing various data to control various aspects of engine operation. 
         [0017]    The control system a) occasionally forces regeneration of the aftertreatment device to remove at least some material whose unchecked accumulation in the device would otherwise impair effectiveness of the device, and b) develops a data estimate of the lubricating quality of motor oil currently in the engine, including processing data to identify occurrence of an active regeneration event, processing data that is indicative of an amount of degradation in lubricating quality of motor oil in the engine due to the identified occurrence of the forced regeneration event to develop a data estimate of the amount of degradation in lubricating quality of motor oil in the engine due to the identified occurrence, and processing the data estimate of the amount of degradation in lubricating quality of motor oil in the engine due to the identified occurrence to develop the data estimate of the quality of motor oil currently in the engine. 
         [0018]    According to a still further aspect, the control system a) occasionally causes forced regeneration of the aftertreatment device to remove at least some material whose unchecked accumulation in the device would impair effectiveness of the device, and b) processes data that identifies each occurrence of an active regeneration event that has occurred over a span of time during which the vehicle has been in use without any fresh motor oil being introduced into the engine, processes data that is indicative of degradation in lubricating quality of motor oil in the engine due to each identified occurrence of an active regeneration event to develop a data estimate of the amount of degradation due to each identified occurrence of an active regeneration event, and accumulates the individual data estimates to develop a data estimate of the amount of degradation that has occurred over the span of time during which the vehicle has been in use without any fresh motor oil being introduced into the engine. 
         [0019]    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 
         [0020]      FIG. 1  is an illustration of a representative motor vehicle having a diesel engine with an exhaust after-treatment device that requires occasional regeneration. 
           [0021]      FIG. 2  is a diagram showing steps of a representative embodiment of the present invention as implemented in a control system of the vehicle of  FIG. 1 . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0022]      FIG. 1  shows a truck  10  having a diesel engine  12  and a drivetrain  14  that couples the engine to driven wheels  16  for propelling the truck. Engine  12  has a processor-based engine control system (ECS)  18  that processes data from various sources to develop various control data for controlling various aspects of engine operation. 
         [0023]    Engine  12  also has an exhaust system  20  for conveying exhaust gases generated by combustion of fuel in cylinders of engine  12  from the engine to the surrounding atmosphere. Exhaust system  20  contains one or more after-treatment devices, one of which is a diesel particulate filter (DPF)  22 , for treating exhaust gases before they pass into the atmosphere via a tailpipe  24 . 
         [0024]    Internally, engine  12  has a lubrication system for lubricating moving parts. The diagram of  FIG. 2  illustrates steps that are embodied in an algorithm in ECS  18  that frequently calculates the quality of motor oil used in the engine lubricating system. Various data are processed to calculate a data estimate of the quality of motor oil currently in engine  12 . 
         [0025]    In accordance with principles of the invention, certain additional data are processed when an active regeneration occurs. First the occurrence of an active regeneration event is identified in any suitably appropriate way. (Step  30  in  FIG. 2 ). Data values representing contamination that being contributed to the oil as the regeneration proceeds are accumulated. The data values are related to certain parameters such as engine fueling and exhaust temperature. A map may be populated with data values for contaminant contribution based on engine fueling and exhaust temperature. Engine fueling and exhaust temperature are used to select a corresponding contaminant contribution from the map, or the contaminant contribution may be calculated using a suitable formula. 
         [0026]    Because the regeneration time may vary from regeneration to regeneration, data values for contamination contribution may be selected, or calculated, at selected times during a regeneration and accumulated. The accumulation is added to a total calculation for all other contamination contributions. (Step  32  in  FIG. 2 .) The aggregate amount of contaminant serves to indicate oil quality. When quality drops below a certain threshold, ECS  20  issues a signal to suggest changing the oil. (Step  34  in  FIG. 2 .) 
         [0027]    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 defined by the following claims.