Patent Publication Number: US-2010114463-A1

Title: System for cold starting machine

Description:
TECHNICAL FIELD  
     The present disclosure relates generally to a system and, more particularly, to a system for cold starting a machine. 
     BACKGROUND  
     Combustion engines, including diesel engines, and other engines known in the art, may exhaust a complex mixture of air pollutants, which may include nitrogen oxide (NO x ). Due to heightened environmental concerns, exhaust emission standards for machines including combustion engines have become increasingly stringent. To comply with these emission standards, machine manufacturers sometimes equip machines with selective catalytic reduction (hereafter “SCR”) systems having reductant tanks. An SCR system reduces an amount of nitrogen oxide in an exhaust flow of a machine by injecting from a reductant tank a gaseous or liquid reductant (e.g., a mixture of urea and water) into the exhaust flow upstream of an SCR catalyst. Unfortunately, the reductant can freeze in the reductant tank, preventing the SCR system from injecting it into the exhaust flow, and causing the machine to fail to comply with the emission standards. For example, a mixture of urea and water can freeze at temperatures below approximately −11° C., which are frequently experienced by some machines operating in cold weather. Reductants stored in reductant tanks of these machines can freeze when the machines are shut down overnight. Although reductant is sometimes heated during operation of a machine, the reductant can remain frozen for unacceptably long periods of time when the machine is cold started (i.e., started when experiencing a low temperature), causing the machine to fail to comply with the emission standards. 
     One way to speed a thawing of a reductant is disclosed in U.S. Pat. No. 6,901,748 B2 (the &#39;748 patent) issued to Gomulka on Jun. 7, 2005. The &#39;748 patent discloses a diesel engine having an SCR system with a urea tank. The &#39;748 patent also discloses a heater element, which is mounted to the urea tank for cold weather starts, and which is connected to a cord. An operator plugs the cord into an external power source to heat contents of the urea tank in anticipation of a cold weather start. 
     The disclosed method and systems are directed to overcoming one or more problems associated with the art. 
     SUMMARY  
     In one aspect, the present disclosure is related to a system for cold starting a machine. The system may include an engine and a reductant tank. The system may also include a temperature sensor, which may be configured to generate a signal indicative of a temperature within the reductant tank. Additionally, the system may include a controller, which may be in communication with the engine and the temperature sensor. The controller may be configured to increase an operating temperature of the engine, based on the signal. 
     In another aspect, the present disclosure is related to a method of operating a machine. The method may include sensing a parameter indicative of a temperature of a reductant. The method may also include increasing an operating temperature of an engine of the machine based on the sensed parameter. 
     In yet another aspect, the present disclosure is related to a reductant heating system for a machine. The system may include an engine, which may include a cylinder. The engine may also include at least one exhaust valve, which may be associated with the cylinder. The at least one exhaust valve may be actuatable between an open position and a closed position. Additionally, the engine may include an engine passageway. The system may also include a reductant tank, which may include a tank passageway. The tank passageway may be in fluid communication with the engine passageway. Additionally, the system may include a temperature sensor, which may be configured to generate a signal indicative of a temperature within the reductant tank. The system may also include a controller, which may be in communication with the at least one exhaust valve and the temperature sensor. The controller may be configured to open the at least one exhaust valve during a power stroke of the cylinder, based on the signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         FIG. 1  is a diagrammatic illustration of an exemplary disclosed reductant heating system including an exemplary disclosed combustion engine; and 
         FIG. 2  is a flow chart describing an exemplary method of operating the reductant heating system of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION  
       FIG. 1  illustrates a combustion engine  10  for a machine. For example, the machine may be a mobile machine that performs some type of operation associated with an industry such as mining, construction, farming, transportation, power generation, tree harvesting, forestry, recreation, or another industry known in the art. 
     Engine  10  may be an internal combustion engine, such as, for example, a diesel engine. Alternatively, engine  10  may be a gasoline engine, a gaseous fuel-powered engine, or another type of combustion engine known in the art. As illustrated in  FIG. 1 , engine  10  may have cylinders  12 . Each cylinder  12  (hereafter “cylinder  12 ”) may be associated with a piston  13 , at least one intake valve  14  (hereafter “intake valve  14 ”), and at least one exhaust valve  16  (hereafter “exhaust valve  16 ”). Intake valve  14  and exhaust valve  16  may be opened and closed (i.e., actuated) in accordance with a four stroke cycle of cylinder  12  of engine  10 . These four strokes may include an intake stroke, a compression stroke, an expansion or power stroke, and an exhaust stroke. During the intake stroke (intake valve  14  open and exhaust valve  16  closed), piston  13  may move downward, sucking air and fuel into cylinder  12  through intake valve  14 . Next, during the compression stroke (intake valve  14  closed and exhaust valve  16  closed), piston  13  may move upward, compressing the air and fuel within cylinder  12 . Next, during the expansion or power stroke (intake valve  14  closed and exhaust valve  16  closed), the air and fuel within cylinder  12  may be combusted. This combustion may produce thermal energy, which may cause the combusted air and fuel to expand, powering downward movement of piston  13 . Next, during the exhaust stroke (intake valve  14  closed and exhaust valve  16  open), piston  13  may move upward, exhausting the combusted air and fuel from cylinder  12  through exhaust valve  16 . 
     Alternatively or additionally, intake valve  14  and exhaust valve  16  may be opened and closed irrespective of the four stroke cycle of cylinder  12 . For example, exhaust valve  16  may be opened during the expansion or power stroke (hereafter the “power stroke”) of cylinder  12  of engine  10 . In such a scenario, the combusted air and fuel within cylinder  12  may be exhausted from cylinder  12  before fully expanding. Thus, some of the thermal energy produced by the combustion of the air and fuel, which might otherwise power movement of piston  13 , may cause an operating temperature of engine  10  to increase. Additionally, since movement of piston  13  may be insufficiently powered without this energy, more fuel may be used in subsequent intake strokes, increasing the thermal energy produced by subsequent combustions of air and fuel, and causing the operating temperature of engine  10  to increase further. 
     The combusted air and fuel exhausted from cylinder  12  (hereafter the “flow of exhaust”) may include several chemicals such as, for example, carbon monoxide, carbon dioxide, nitrogen oxide, ammonia, aldehyde(s), soot, oxygen, nitrogen, sulfur, water vapor, and/or hydrocarbons such as hydrogen and methane. Some of the chemicals may be subject to emission standards (i.e. subject to minimum and/or maximum allowable emission concentrations). Therefore, the flow of exhaust may be directed through an exhaust pipe  18  to an exhaust treatment device such as, for example, an SCR system  20 . 
     SCR system  20  may include a reductant tank  25 , which may or may not be located remotely from engine  10 . For example, although engine  10  may be located within an engine compartment of the machine, reductant tank  25  may not be located within the engine compartment of the machine. Additionally, SCR system  20  may include a reductant pipe  30 , an injector  35 , and an SCR catalyst  37 . A gaseous or liquid reductant may be stored within reductant tank  25 . For example, the reductant may be a mixture of urea and water, and may freeze at temperatures below approximately −11° C. The reductant may flow from reductant tank  25  to injector  35  via reductant pipe  30 . Injector  35  may inject the reductant into exhaust pipe  18  upstream of SCR catalyst  37  to reduce an amount of nitrogen oxide in the flow of exhaust. Unfortunately, the reductant can freeze in reductant tank  25 , preventing injector  35  from injecting it into exhaust pipe  18 . Therefore, the machine may include a reductant heating system  40  for thawing the reductant, and thereby allowing injector  35  to again inject the reductant into exhaust pipe  18 . Although reductant heating system  40  may or may not operate independently of other systems of the machine, it should be understood that reductant heating system  40  may be a component of another system of the machine. For example, reductant heating system  40  may be a component of, and may operate in conjunction with, a system for cold starting the machine. The system for cold starting the machine may also include, for example, an engine block heater, an electric reductant heating system, a window defroster, and/or another component or system, which may be used to cold start the machine. 
     Reductant heating system  40  may thaw the reductant by transferring heat from engine  10  to the reductant. For example, heat may be transferred from engine  10  to the reductant via an engine coolant (e.g., water, antifreeze, or another type of engine coolant known in the art). The engine coolant may be circulated between an engine passageway  55  of engine  10  and a tank passageway  60  of reductant tank  25 . In other words, there may be fluid communication between engine passageway  55  and tank passageway  60 . The engine coolant may absorb heat from engine  10  as it flows through engine passageway  55 , and may transfer heat to reductant tank  25  as it flows through tank passageway  60 . Some of the heat transferred to reductant tank  25  may be transferred to the reductant, thawing the reductant. 
     In addition to engine  10  and reductant tank  25 , reductant heating system  40  may include components for controlling the transfer of heat from engine  10  to the reductant. For example, reductant heating system  40  may include at least one coolant valve  75  (hereafter “coolant valve  75 ”), which may be situated to control the fluid communication between engine passageway  55  and tank passageway  60 , and which may be actuatable between an open position and a closed position. When coolant valve  75  is open, coolant valve  75  may permit circulation of the engine coolant between engine passageway  55  and tank passageway  60 . And, when coolant valve  75  is closed, coolant valve  75  may prevent circulation of the engine coolant between engine passageway  55  and tank passageway  60 . 
     Reductant heating system  40  may also include a controller  85 , which may include one or more processors (not shown) and one or more memory devices (not shown). Controller  85  may communicate with a temperature sensor  90  to determine a temperature of the reductant. In particular, temperature sensor  90  may sense a parameter indicative of a temperature within reductant tank  25 , and may generate a signal indicative of this parameter. For example, the temperature within reductant tank  25  may be a temperature of the reductant. Therefore, the parameter indicative of the temperature within reductant tank  25  may also be indicative of the temperature of the reductant. Controller  85  may receive the signal, and may determine the temperature of the reductant based on the signal. Controller  85  may then communicate with exhaust valve  16  and/or coolant valve  75  to control the transfer of heat from engine  10  to the reductant, based on the determined temperature of the reductant. Specifically, controller  85  may open exhaust valve  16  during a power stroke of cylinder  12  of engine  10  to increase the operating temperature of engine  10 , thereby allowing the engine coolant to absorb more heat from engine  10 . Additionally, controller  85  may open coolant valve  75  to permit circulation of the engine coolant between engine passageway  55  and tank passageway  60 . This may allow the engine coolant to transfer heat from engine  10  to reductant tank  25  and the reductant. 
       FIG. 2  illustrates an exemplary method of operating reductant heating system  40  of the machine.  FIG. 2  will be discussed in the following section to further illustrate reductant heating system  40  and its operation. 
     INDUSTRIAL APPLICABILITY  
     The disclosed reductant heating system may be applicable to mobile machines. The reductant heating system may be a component of a system for cold starting the mobile machines. In particular, the reductant heating system may thaw reductant stored within and used by a machine. Specifically, the reductant heating system may thaw the reductant by transferring heat from an engine of the machine to the reductant. Operation of the reductant heating system will now be described. 
     As illustrated in  FIG. 2 , reductant heating system  40 , and more specifically, controller  85  (referring to  FIG. 1 ), may communicate with temperature sensor  90  to determine the temperature of the reductant within reductant tank  25  (step  200 ). For example, controller  85  may receive from temperature sensor  90  a signal indicative of a parameter, which is indicative of the temperature within reductant tank  25 . Controller  85  may then determine the temperature of the reductant based on this signal. 
     Next, controller  85  may compare the temperature of the reductant (determined during step  200 ) to a threshold temperature (step  210 ). The threshold temperature may be equivalent to a melting temperature of the reductant. For example, the threshold temperature may be approximately −11° C. Alternatively, the threshold temperature may be above a melting temperature of the reductant. If the temperature of the reductant (determined during step  200 ) is not below the threshold temperature, controller  85  may proceed to step  200  and again determine the temperature of the reductant. 
     Otherwise, controller  85  may open coolant valve  75  (step  230 ), thereby permitting fluid communication between engine passageway  55  and tank passageway  60 , and permitting circulation of the engine coolant between engine passageway  55  and tank passageway  60 . The engine coolant, which may absorb heat from engine  10  as it flows through engine passageway  55 , may then transfer heat to reductant tank  25  as it flows through tank passageway  60 . Some of this heat may be transferred to the reductant, thawing the reductant. 
     In order to increase the amount of heat absorbed by the engine coolant and transferred to the reductant, controller  85  may increase the operating temperature of engine  10  (step  240 ). Specifically, controller  85  may increase the operating temperature of engine  10  by opening exhaust valve  16  during a power stroke of cylinder  12  of engine  10 . For example, controller  85  may open exhaust valve  16  between approximately 30 degrees and approximately 130 degrees after top dead center. Alternatively, controller  85  may increase the operating temperature of engine  10  using another method known in the art. For example, controller  85  may increase an amount of fuel supplied to engine  10 . 
     Controller  85  may then again, as in step  200 , communicate with temperature sensor  90  to determine the temperature of the reductant within reductant tank  25  (step  250 ). Next, controller  85  may, as in step  210 , compare the temperature of the reductant (determined during step  250 ) to the threshold temperature (step  260 ). If the temperature of the reductant (determined during step  250 ) is below the threshold temperature, controller  85  may proceed to step  240  and again increase the operating temperature of engine  10 . Otherwise, controller  85  may close coolant valve  75  (step  270 ), ceasing circulation of the engine coolant between engine passageway  55  and tank passageway  60 , and preventing the engine coolant from transferring heat to reductant tank  25  and the reductant. Controller  85  may then proceed to step  200  and again determine the temperature of the reductant. 
     It is contemplated that reductant heating system  40  may speed thawing of the reductant when the machine is cold started. This speeding of the thawing of the reductant may be automatic, and may not require action by an operator of the machine. Specifically, controller  85  may determine, during step  210 , that the temperature of the reductant is below the threshold temperature. Since the threshold temperature may be equivalent to the melting temperature of the reductant, this determination may mean that the reductant is frozen. Alternatively, if the threshold temperature is above the melting temperature of the reductant, the determination may mean that the reductant is colder than desired. In either case, controller  85  may open coolant valve  75  during step  230 , based on the determination. The engine coolant may then circulate between engine passageway  55  and tank passageway  60 . This circulation may allow the engine coolant to transfer heat from engine  10  to the reductant. 
     Although the transfer of heat from engine  10  to the reductant via the engine coolant may speed the thawing of the reductant, it is contemplated that controller  85  may further speed the thawing of the reductant by increasing the amount of heat transferred via the engine coolant. Controller  85  may accomplish this by increasing the operating temperature of engine  10  during step  240 . Specifically, controller  85  may increase the operating temperature of engine  10  by opening exhaust valve  16  during a power stroke of cylinder  12  of engine  10 . 
     While it may be desirable to transfer heat from engine  10  to the reductant during the thawing of the reductant, it is contemplated that transferring heat from engine  10  to the reductant once the reductant has thawed may be undesirable. Therefore, controller  85  may automatically stop transferring heat from engine  10  to the reductant. Specifically, controller  85  may determine, during step  260 , that the temperature of the reductant is not below the threshold temperature. Since the threshold temperature may be equivalent to the melting temperature of the reductant or above the melting temperature of the reductant, this determination may mean that the reductant has thawed. Based on the determination, controller  85  may refrain from increasing the operating temperature of engine  10 . Additionally, controller  85  may close coolant valve  75  during step  270 . 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the method and systems of the present disclosure. Other embodiments of the method and systems will be apparent to those skilled in the art from consideration of the specification and practice of the method and systems disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.