Abstract:
A system and method for driver-initiation of regeneration of a diesel particulate filter using a service brake pedal in a motor vehicle to reduce the risk that the vehicle will become unattended during on-going regeneration.

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 controlled regeneration of an after-treatment device, a diesel particulate filter (DPF) in particular, while a vehicle is parked with the engine running. 
       BACKGROUND OF THE INVENTION 
       [0002]    A known system for treating exhaust gas passing through an exhaust system of a diesel engine comprises a diesel oxidation catalyst (DOC) associated with a diesel particulate filter (DPF). The combination of these two exhaust gas treatment devices promotes chemical reactions in exhaust gas and traps diesel particulate matter (DPM) as exhaust flows through the exhaust system from the engine, thereby preventing significant amounts of pollutants such as hydrocarbons, carbon monoxide, soot, SOF, and ash, from entering the atmosphere. 
         [0003]    A DPF requires regeneration from time to time in order to maintain particulate trapping efficiency. Regeneration involves the presence of conditions that will burn off trapped particulates whose unchecked accumulation would otherwise impair DPF effectiveness. While “regeneration” refers to the general process of burning off DPM, two particular types of regeneration are recognized by those familiar with the regeneration technology as presently being applied to motor vehicle engines. 
         [0004]    “Passive regeneration” is generally understood to mean regeneration that can occur anytime that the engine is operating under conditions that burn off DPM without initiating 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 programmed regeneration strategy, with the goal of elevating temperature of exhaust gases entering the DPF to a range suitable for initiating and maintaining burning of trapped particulates. 
         [0005]    Active regeneration may be initiated even before a DPF becomes loaded with DPM to an extent where regeneration would be mandated by the engine control system on its own. When DPM loading beyond that extent is indicated to the engine control system, the control system forces active regeneration, and that is sometimes referred to simply as a forced regeneration. 
         [0006]    The creation of conditions for initiating and continuing active regeneration, whether forced or not, generally involves elevating the temperature of exhaust gas entering the DPF to a suitably high temperature. 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 for elevating exhaust gas temperature to the relatively high temperatures needed for active DPF regeneration. 
         [0007]    When a vehicle is being operated in a way conducive to active DPF regeneration, such as cruising on a highway, the regeneration process may be conducted with little or no significant effect on vehicle driveability and may be initiated either by the driver or else automatically by a regeneration initiation strategy, possibly even before the DPF becomes loaded with DPM to an extent where forced regeneration would be mandated by the engine control system. The elevated temperature of tailpipe exhaust is typically not a concern on the open road. 
         [0008]    However, when a vehicle is parked with the engine running, regeneration may be inappropriate for the surrounding environment due to the elevated temperature of exhaust coming out of the tailpipe. Yet the after-treatment device may at times need regeneration in just such a situation. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention is directed toward a strategy that allows regeneration to proceed in such a situation, provided that certain conditions indicative of the driver&#39;s continuing presence in the vehicle during regeneration are satisfied. In that way, the risk that a driver will initiate a regeneration and then leave the vehicle unattended while the regeneration proceeds is significantly reduced. 
         [0010]    Briefly, the invention involves a requirement that with a vehicle parked and the engine running, the driver keep the brake pedal depressed in order to initate and maintain a regeneration. Failure to do so before the process has been completed will terminate the process. The inventive strategy also conditions continuance of a driver-initiated regeneration on other factors indicating that the vehicle remains stationary and that conditions for regeneration remain favorable. 
         [0011]    One general aspect of the invention relates to a vehicle comprising wheels on which the vehicle travels, an engine comprising an exhaust system having an exhaust after-treatment device that requires occasional regeneration, service brakes for braking the wheels when a brake pedal is depressed; a drivetrain for coupling driven wheels to the engine including a device for selectively coupling and decoupling driven wheels to and from the engine, and a system for enabling regeneration of the exhaust after-treatment device. 
         [0012]    The system comprises a first signal for indicating to an occupant of the vehicle a need for regeneration and a second signal for enabling regeneration upon concurrence of the signal and depression of the brake pedal. 
         [0013]    A second generic aspect relates to the method performed by the system. 
         [0014]    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 
         [0015]      FIG. 1  is an illustration of a representative motor vehicle having a diesel engine with an exhaust after-treatment device that requires occasional regeneration. 
           [0016]      FIG. 2  is a general strategy diagram showing application of the present invention to the motor vehicle. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0017]      FIG. 1  shows a truck  10  having a diesel engine  12  and a drivetrain  14 , including a transmission  16 , that couples the engine to driven rear wheels  18 R for propelling the truck. Engine  12  has a processor-based engine control system (ECS)  20  that processes data from various sources to develop various control data for controlling various aspects of engine operation. 
         [0018]    Engine  12  also has an exhaust system  22  for conveying exhaust gases generated by combustion of fuel in cylinders of engine  12  from the engine to the surrounding atmosphere. Exhaust system  22  contains one or more after-treatment devices, one of which is a diesel particulate filter (DPF)  24 , for treating exhaust gases before they pass into the atmosphere via a tailpipe  26 . 
         [0019]    Truck  10  also has a steering system  28 , including a steering wheel  30 , for steering front wheels  18 F, and a service brake system  32 , including a brake pedal  34  that when depressed brakes all wheels  18 F,  18 R. 
         [0020]    ECS  20  comprises one or more processors that process various data for calculating control data for various devices in the truck. ECS  20  repeatedly processes data relevant to determining the extent to which DPF  24  is loaded with DPM. When the result of such processing discloses that DPF  24  requires regeneration, ECS  20  provides an appropriate signal. 
         [0021]    If a regeneration initiation algorithm in ECS  20  provides for automatically forced regeneration in consequence of such a signal, provided that favorable regeneration conditions, such as highway cruising, are present, then regeneration proceeds under control of ECS  20  without driver initiation. 
         [0022]    If truck  10  were parked with engine  12  running when ECS issued a signal disclosing a need for DPF regeneration, then the inventive strategy would be utilized. That strategy will now be explained with reference to  FIG. 2  where the general reference numeral  40  refers to the inventive strategy. 
         [0023]    Strategy  40  is performed by suitable algorithms implemented in ECS  20  to process data from various sources for accomplishing the steps shown in  FIG. 2 . The reader should therefore appreciate that  FIG. 2  does not include detail of actual processing programs in ECS  20 , while recognizing that such processing programs can be developed by conventional programming techniques based on the level of detail presented in  FIG. 2 , as further detailed by the written text presented here. 
         [0024]    With engine  12  running normally (reference numeral  42 ), a processing step  44  monitors data to ascertain if DPF  24  requires regeneration. As long as no need for regeneration is disclosed (reference numeral  46 ), step  44  will be repeated at the next iteration of the algorithm. 
         [0025]    Once a need for regeneration is disclosed (reference numeral  48 ), the strategy seeks information about certain other aspects of vehicle/engine operation. A need for regeneration can be determined by any of various known techniques that need not be described in detail here. One item of information of interest, determined by a step  50 , is whether engine  12  is or is not engaged with driven wheels  18 R. That item is provided by the status of transmission  16 . If transmission  16  is in gear, meaning that wheels  18 R can be or actually are being driven by engine  12  and that the transmission is not in a neutral position (reference numeral  52 ), the strategy proceeds to the next item of interest which is the possibility of potential damage if regeneration were to be initiated (reference numeral  54 ). 
         [0026]    If the potential is found not to be present (reference numeral  56 ), as determined by an appropriate algorithm whose specific details need not be described here, a step  58  seeks still further information about whether the truck is moving. The specific data processed by step  58  can be obtained from any suitable source, such as a vehicle speed sensor. 
         [0027]    If the truck is not in motion (reference numeral  60 ), the strategy iterates by repeatedly performing steps previously described until step  58  discloses that the truck is in motion (reference numeral  62 ). With the truck in motion, regeneration is initiated (reference numeral  64 ), with the process thereafter being controlled by a regeneration algorithm. This would not be a driver-initiated regeneration although it would be an active regeneration. 
         [0028]    Had step  54  disclosed that the potential for internal damage to the engine and/or its associated systems existed (reference numeral  66 ), then steps  68  and  70  would have been repeatedly performed until appropriate measures had been taken to allow step  58  to be performed. When the potential for damage is indicated, step  68  informs the operator, i.e. driver, via any suitable medium such as a lamp or message to perform a service procedure. Step  70  is a protective de-rate step that restricts engine power to limit soot production. This should alert the driver to the importance of the situation while allowing engine operation to be prolonged. 
         [0029]    Had step  50  disclosed that transmission  16  was not in gear (reference numeral  72 ), then a step  74  would have determined whether or not engine  12  was being controlled by ECS  20  in a manner that would be expected to allow the engine to continue running (reference numeral  74 ), meaning in other words that the engine either was operating a vehicle-controlled operating system, such as a power take-off (PTO), that was maintaining or increasing engine speed above idle or matching engine torque output independent of engine load, or that an idle shut-down timer that is commonly present in some trucks had been overridden by some appropriate action of the driver so that idle shut-down won&#39;t occur. 
         [0030]    Should step  74  determine that engine  12  is not being controlled appropriately for continued operated (reference numeral  76 ), then step  54  will follow, with further processing occurring by steps as already described. Should step  74  determine that engine  12  is being controlled appropriately for continued operated (reference numeral  78 ), then a step  80  occurs, followed by a step  82  that is like step  54  in that it determines whether the potential for damage to the engine and/or engine systems exists. 
         [0031]    If step  82  discloses that the potential for damage exists (reference numeral  84 ), then a step  86  that is like step  70  occurs with the consequence of the strategy determining that no regeneration is required (step  46 ), with the strategy ceasing to execute further until its next iteration. 
         [0032]    If step  82  discloses that no potential for damage exists (reference numeral  88 ), then a step  90  determines whether or not brake pedal  34  is being depressed. Depression of the brake pedal can be disclosed by the actuation of a brake pedal switch. 
         [0033]    If step  90  discloses that brake pedal  34  is not being depressed (reference numeral  92 ), the strategy ceases to execute further until its next iteration. 
         [0034]    If step  90  discloses that brake pedal  34  is being depressed (reference numeral  94 ), the strategy performs a step  96  that starts a timer as a countdown before regeneration is actually initiated. The length of the countdown defines a certain amount of time that can be a programmable preset in a processor of ECS  20 . 
         [0035]    For regeneration to be initiated at the end of the countdown time, the brake pedal must either have been kept continually depressed during the countdown time to keep the timer running, or if released after having started the timer with the timer being allowed to continue counting after release, must be depressed at the time that the countdown time ends. Steps  98  and  100  define those possibilities, and when either is satisfied, regeneration is initiated (step  102 ). This would be a driver-initiated active regeneration, sometimes referred to simply as a manual regeneration (manual regen). 
         [0036]    Once initiated by step  102 , regeneration is allowed to continue only so long as brake pedal  34  remains depressed. Therefore, should brake pedal  34  cease to be depressed, that fact will be disclosed by step  98  as steps  98 ,  100  repeat during iterations of the strategy. When cessation of pedal depression is disclosed (reference numeral  104 ), active regeneration is promptly discontinued (reference numeral  106 ), with passive regeneration possibly continuing for a short time, perhaps up to about three minutes depending on factors such as filter size, operating temperature, and flow rate through the engine. The use of a continually depressed brake pedal to continue regeneration, once regeneration has been initiated, is intended to assure that the driver remains in the vehicle and avoid a situation that allows the driver to depart the vehicle and leave it unattended while regeneration continues. The control system may allow for occasional time-limited release of the brake pedal to avoid driver fatigue while still accomplishing the objective of maintaining driver diligence to vehicle operation, for example by requiring the driver to regularly tap the brake pedal. 
         [0037]    When step  44  discloses that regeneration is needed, a signal is given to the driver. The signal may be given in any appropriate way that will be recognized by the driver for what it is, such as by a message on a message screen, illumination of a light on the instrument panel, etc. 
         [0038]    After step  44  has caused a signal to be given, the act of depressing the brake pedal merely enables a regeneration but does not actually cause the engine and/or associated devices to begin operating in ways that begin to raise exhaust gas temperature. Such enablement is represented by an enabling signal. A signal that actually causes the engine and/or associated devices to begin operating in ways that start raising exhaust gas temperature is given only after countdown mentioned above has been completed. 
         [0039]    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.