Abstract:
A method comprises determining a temperature of a particulate matter (PM) filter in communication with an exhaust gas from an engine; and reducing a power output of the engine when the PM filter is not being regenerated and the temperature exceeds a first predetermined temperature. A control module comprises a PM filter temperature determination module that determines the temperature of a PM filter in communication with an exhaust gas from an engine; and a reduced engine power module in communication with the PM filter temperature determination module that reduces the power output of the engine when the PM filter is not being regenerated and the temperature exceeds a first predetermined temperature.

Description:
FIELD 
     The present disclosure relates to particulate matter (PM) filters, and more specifically, to systems and methods for limiting a temperature of a PM filter. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     Engines such as diesel engines produce particulate matter (PM) that is filtered from exhaust gas by a PM filter. The PM filter is disposed in an exhaust system of the engine. The PM filter reduces emission of PM that is generated during combustion. 
     Over time, the PM filter becomes full. During regeneration, the PM may be burned within the PM filter. Regeneration may involve heating the PM filter to a combustion temperature of the PM. There are various ways to perform regeneration including modifying engine management, using a fuel burner, using a catalytic oxidizer to increase the exhaust temperature with after injection of fuel, using resistive heating coils, and/or using microwave energy. 
     The increased temperature of the PM filter during regeneration may exceed the temperature at which the collected PM combusts without exceeding the temperature at which the PM may be damaged. For example, PM from a diesel engine may combust at temperatures of 550 degrees Celsius (° C.) or above while a PM filter such as one employed in a full-size pickup truck may be damaged at temperatures as low as 800° C. 
     High PM filter temperatures may also occur in situations other than regeneration. Fault conditions may exist such that the PM filter temperature unintentionally rises during vehicle operation to a level that may damage the PM filter if continued for a period of time. Examples of other fault conditions that may occur in a diesel vehicle include an exhaust gas recirculation (EGR) valve leaking or sticking open, or leaks in the EGR gasket, turbocharger, intake manifold gasket, fuel injectors, charge air cooler (CAC), CAC pipes, or CAC hoses. In general, the PM filter temperature may rise to a potentially damaging level during any underboost or overfueling condition that results in abnormally high exhaust gas temperatures. 
     SUMMARY 
     A method comprises determining a temperature of a particulate matter (PM) filter in communication with an exhaust gas from an engine; and reducing a power output of the engine when the PM filter is not being regenerated and the temperature exceeds a first predetermined temperature. 
     A control module comprises a PM filter temperature determination module that determines the temperature of a PM filter in communication with an exhaust gas from an engine; and a reduced engine power module in communication with the PM filter temperature determination module that reduces the power output of the engine when the PM filter is not being regenerated and the temperature exceeds a first predetermined temperature. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. The present teachings will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a schematic illustration of an exemplary vehicle; 
         FIG. 2  is a block diagram of a control module of a vehicle; and 
         FIG. 3  is a flow diagram describing steps in control system for a PM filter. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is in no way intended to limit the present teachings, applications, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the term module refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, or other suitable components that proved the described functionality. 
     Referring now to  FIG. 1 , an exemplary vehicle  10  is schematically illustrated. Vehicle  10  may include engine  12  in communication with intake system  14 , exhaust system  16 , fuel system  18 , and control module  36 . Intake system  14  may include intake manifold  22  and throttle  24 . Exhaust system  16  may include exhaust manifold  26  in communication with PM filter  30 , as well as one or more PM filter temperature sensors such as PM filter inlet sensor  38  and PM filter outlet sensor  40 . Control module  36  may be in communication with engine  12 , fuel system  18 , throttle  24 , PM filter inlet sensor  38  and PM filter outlet sensor  40 . 
     For purposes of illustration, vehicle  10  will be described as having a diesel engine  12 . Although vehicle  10  is disclosed with a diesel engine  12 , it should be understood that the present disclosure applies to other types of engines in vehicles  10  that include a PM filter  30 . 
     Throttle  24  may control air flow into diesel engine  12  and fuel system  18  may control a fuel flow into diesel engine  12 . Exhaust gas created by combustion of the air/fuel mixture may exit diesel engine  12  through exhaust system  16 . PM filter inlet sensor  38  and PM filter outlet sensor  40  may provide signals to control module  36  indicative of the temperature of the exhaust gas at the inlet and outlet of the PM filter  30 . 
     Referring to  FIG. 2 , a block diagram of control module  36  is depicted. Control module  36  may include PM filter temperature determination module  42  and reduced engine power module  44 . PM filter temperature determination module  42  may be in communication with reduced engine power module  44  and may receive information from the PM filter inlet sensor  38  and/or PM filter outlet sensor  40 , as discussed below. Reduced engine power module  44  may be in communication with throttle  24  and fuel system  18  to control the power of diesel engine  12 . 
     Referring to  FIG. 3 , a flow diagram of steps in a control system for a PM filter is depicted in control logic  100 . At block  102 , PM filter temperature determination module  42  may monitor PM filter inlet sensor  38  and/or PM filter outlet sensor  40  to determine a PM filter  30  temperature. Control logic  100  may then continue to block  104 . 
     At block  104 , reduced engine power module  44  may use the PM filter  30  temperature determined from PM filter temperature determination module  42  at block  102  to analyze whether the PM filter  30  temperature is at a level that requires corrective action. More specifically, block  104  may compare the determined PM filter temperature to a temperature value that operates as a shut down limit. The value of the shut down limit may be a temperature at which continued diesel engine  12  operation at any power level may produce an exhaust gas that results in damage to PM filter  30 , such as a temperature approaching 800° C. for an exemplary full-size pickup. 
     If the determined PM filter  30  temperature exceeds the shut down limit, control logic  100  may continue to block  106 . At block  106 , reduced engine power module  44  may gradually shut down diesel engine  12  by gradually ceasing to supply fuel and air from fuel system  18  or intake system  14  to diesel engine  12 . Before shut down occurs, a chime, message or other indication may be provided to the driver to indicate that a gradual shut down will be occurring. If the determined PM filter  30  temperature does not exceed the shut down limit, control logic  100  may continue to block  108 . 
     At block  108 , reduced engine power module  44  may use the PM filter  30  temperature determined from PM filter temperature determination module  42  at block  102  to analyze whether the PM filter temperature is at a level such that vehicle  10  may continue to operate but only at an idle speed. More specifically, block  108  may compare the determined PM filter  30  temperature to a temperature value that operates as an idle limit. The value of the idle limit may be a temperature at which continued operation of diesel engine  12  at an engine speed greater than an idle may continue to increase an exhaust temperature to a level that may contribute to damage to PM filter  30 . In an exemplary full-size pickup, the idle limit may be approximately 750° C. 
     If the determined PM filter  30  temperature exceeds the idle limit, control logic  100  may continue to block  110 . At block  110 , reduced engine power module  44  may force diesel engine  12  to operate at an idle speed by controlling intake system  14  and fuel system  18  to provide air and fuel sufficient to operate diesel engine  12  at an idle speed. If the determined PM filter  30  temperature does not exceed the idle limit, control logic  100  may continue to block  112 . 
     At block  112 , reduced engine power module  44  may use the PM filter  30  temperature determined from PM filter temperature determination module  42  at block  102  to analyze whether the PM filter  30  temperature is at a level such that the vehicle may continue to operate up to a reduced power limit. More specifically, block  112  may compare the determined PM filter  30  temperature to a temperature value that operates as a power limiting threshold. The value of the power limiting threshold may be a temperature at which diesel engine  12  may continue to operate at a power requested by the operator up to a reduced power limit below which normal vehicle operation should not create exhaust that damages PM filter  30 . In an exemplary full-size pickup the power limiting threshold may be 700° C. 
     If the determined PM filter  30  temperature exceeds the power limiting threshold, control logic  100  may continue to block  114 . At block  114 , reduced engine power module  44  may limit the power of diesel engine  12  by controlling intake system  14  and fuel system  18  to provide air and fuel as needed to operate diesel engine  12  up to a reduced power limit at which further air and fuel will not be supplied to diesel engine  12 . If the determined PM filter  30  temperature does not exceed the power limiting threshold, control logic  100  may then be ended. 
     Those skilled in the art may now appreciate from the foregoing that the broad teachings of the present disclosure may be implemented in a variety of forms. Therefore, while this disclosure has been described in connection with particular examples thereof, the true scope of the disclosure should no be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.