Abstract:
A fast light-off time enhancement device and method may be used for an exhaust catalyst or particulate filter. The light-off time enhancement device may include a fuel injector, a carbon nano-tube injector, and a light source when active may generate heat. Heat generated thereby provides improving light-off time of the catalyst. Additionally, the same system may be used to generate heat to regenerate a particulate filter. An associated control system may be utilized to monitor vehicle parameters and determine the appropriate use of the light-off enhancement device.

Description:
FIELD 
       [0001]    This present disclosure relates to the field of automotive exhaust catalysts and particulate filters, more specifically this disclosure relates to a utilizing a ignition of fuels by light source to reduce light-off time and maintain catalyzation and filterization. 
       BACKGROUND 
       [0002]    This section provides background information related to the present disclosure which is not necessarily prior art. 
         [0003]    In typical gasoline engine, the majority of the emissions that come out of the engine may be converted to clean output (H 2 O and CO 2 ) by the catalyst in the catalytic converter. However, to maintain proper operation, the catalyst must be heated to a temperature equal to or above a light-off temperature and maintain that temperature. A typical light-off temperature threshold is approximately equal to 400° C., with the standard maintenance temperature ranging from 400° C. to 600° C. It is known in the art that a majority of the exhaust gas emissions that are captured exiting the exhaust gas treatment system during an emissions test occur during the first 60 seconds of engine operation while the catalyst temperature is below the light-off temperature, and cannot effectively convert the engine out emissions to H 2 O and CO 2 . 
         [0004]    Conventional vehicle powertrains typically will execute a light-off strategy immediately upon starting the engine when the drivetrain is in park or neutral and hope to finish before the driver shifts into a drive gear and presses the accelerator pedal to drive away. Generally this strategy has the engine operate at a higher RPM to produce enough heat to decrease the catalyst light-off time. However, some hybrid powertrain combinations can achieve the maximum acceleration that the driver requests with the electric motors with no assistance needed from the conventional gas motor. Therefore, not allowing any hot exhaust gas to flow through the catalyst thus allowing the catalyst to cool below an effective temperature. Additionally, hybrid vehicles typically employ smaller engines, which produce less heat and are usually not allowed to idle, also engine warm-up time may be longer compared to conventional vehicles. A supplemental heating system or a light-off time enhancement device may be used to accelerate engine warm-up thus contributing to improved efficiency and emissions. It is also known that exhaust particulate filters use a similar light-off strategy to regenerate, essentially burn off the particulates captured in the filter. 
       SUMMARY 
       [0005]    This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
         [0006]    An engine exhaust system that may comprise an engine and a housing that may be connected to the engine through an exhaust pipe. The housing may include at least one catalyst. Disposed upstream of the catalyst may be a light-off enhancement device. The light-off enhancement device may further comprise a fuel injector, a carbon nano-tube injector and a light source. 
         [0007]    A vehicle exhaust system that may comprise a catalytic converter. Upstream of the catalytic converter may be a light-off enhancement device. A control module may be configured to receive temperature data that may represent temperature of the catalyst of the catalytic converter. The control module may also activate the light-off enhancement device if the temperature of the catalyst is below an effective temperature. The control module may activate the light-off enhancement device by communicating with and activate a fuel injector, a carbon nano-tube injector and a light source. 
         [0008]    A catalyst light-off management method that may have the steps of monitoring the operation of an engine. If it is determined the engine is running then monitoring a catalyst temperature of a catalytic converter. Comparing the catalyst temperature to a preset light-off temperature. If it is determined that the catalyst temperature is below the preset light-off temperature, the control will power a light-off enhancement device to heat the catalytic converter. If the catalyst temperature is greater than or equal to the preset light-off temperature, the light-off enhancement device is disabled. Powering the light-off enhancement device may be activating a fuel injector to inject fuel upstream of the catalyst, initiating a carbon nano-tube injector to inject carbon nano-tubes upstream of the catalyst and powering a light source. 
         [0009]    Another embodiment may be an exhaust system with a catalytic converter. A muffler disposed downstream of the catalytic converter. 
         [0010]    The catalytic converter may contain a catalyst disposed inside. Upstream of the catalyst may be a combination injector that injects a mix of fuel and carbon nano-tubes. A light source may be disposed upstream of the catalyst. 
         [0011]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     
       DRAWINGS 
         [0012]    The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
           [0013]      FIG. 1  is a schematic representation of a vehicle having a exhaust system; 
           [0014]      FIG. 2  is a representation of an exhaust system; 
           [0015]      FIG. 3  is block diagram of a control strategy; 
           [0016]      FIG. 4  is a representation of an additional embodiment of an exhaust system; 
           [0017]      FIG. 5  is block diagram of another control strategy; and 
           [0018]      FIG. 6  is a representation of an additional embodiment of an exhaust system. 
       
    
    
       [0019]    Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
       DETAILED DESCRIPTION 
       [0020]    Example embodiments will now be described more fully with reference to the accompanying drawings. The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
         [0021]      FIG. 1  depicts a vehicle  10  with an internal combustion engine  12 , whether the sole source or joint source of vehicle power, produces exhaust gas which is expelled through exhaust system  14 . The exhaust system  14  may contain a catalytic converter  16 , a particulate filter  18 , and a muffler  20 .  FIG. 2  depicts an exploded block view of the exhaust system  14 . The exhaust system  14  includes a catalytic converter  16  which may include a catalyst  22 , also may be known in the art as a reforming catalyst, an exhaust treatment catalyst by way of non-limiting example. The catalyst  22  is disposed within the housing  24 . The catalyst  22  may comprise any catalyst material suitable for treatment of vehicle exhaust, including, but not limited to, for example, rhodium, platinum, their alloys, and combinations thereof. It is also known in the art that the catalytic converter  16  may contain multiple catalysts  22  within the housing  24  that may be in series to increase the effectiveness of reforming the exhaust. The exhaust system  14  may also include an upstream temperature sensor  26  that may be coupled to the housing  24  upstream of the catalyst  22 . A downstream temperature sensor  28  may be coupled to the housing  24  downstream of the catalyst  22 . The upstream temperature sensor  26  and downstream temperature sensor  28  may communicate with a control module  30 ; the engine may also communicate with the control module  30 . The upstream temperature sensor  26  and downstream temperature sensor  28  may also be embedded into the catalyst  22  by way of non-limiting example. The catalytic converter  16  may be connected to engine  12  by an exhaust pipe  32 . Untreated exhaust  34  leaves the engine  12  and flows through exhaust pipe  32  to the catalytic converter  16  to be treated. The treated exhaust gas  36  leaves the catalytic converter  16  into the tail pipe  38  to muffler  20 . 
         [0022]    The current embodiment may also contain a fuel injector  40  that may inject fuel upstream of the catalyst  22  in the exhaust system  14 . The fuel injector  40  receives fuel from fuel storage  42  through conduit  44 . The fuel storage  42  may be an independent reservoir or part of the vehicle main fuel supply tank for the engine  12  to reduce complexity of parts. The fuel that may be injected into the flow of exhaust gas from the engine  12  may include but not limited to gasoline, diesel fuel, or any combustible fuel that may be available. The fuel injector  40  and fuel storage  42  communicate with a control module  30 . The exhaust system  14  may also include a carbon nano-tube (CNT) injector  46  that may inject CNT&#39;s upstream of catalyst  22 . The CNT injector  46  may receive CNT&#39;s from CNT storage  48  through conduit  50 . The CNT injector  46  and CNT storage  48  communicate with a control module  30 . The exhaust system  14  may also include a light source  52  upstream of catalyst  22 . The light source  52  may communicate with control module  30  and may be downstream of fuel injector  40  and CNT injector  46 . This may allow fuel and CNT&#39;s to properly mix before light source  52  activates to ignite the mix. The fuel injector  40 , CNT injector  46 , and light source  52  may be collectively referred to as supplemental heating system or a light-off time enhancement device indicated by dotted box  54 . 
         [0023]    The general operation of the exhaust system  14  and light-off time enhancement device  54  will be described using structure in  FIG. 2  and flow chart represented by  FIG. 3 . The control module  30  may be programed to conduct the logic into whether the light-off time enhancement device  54  needs to be active or not, it is understood in the art that this control module  30  can be any suitable module or computer to receive and send information within the vehicle  10 . In decision block  60  control module  30  determines whether the engine  12  is running therefore may be generating untreated exhaust  34 . If the engine  12  is not running than the logic stops. If the engine  12  is running the control module communicates with temperature sensors  26  and  28  to determine the temperature of the catalyst  22 , represented by block  62 . Block  64  represents the control module  30  determining if the catalyst  22  is above the preset light off temperature. If yes then no action, if no then the light-off time enhancement device  54  may be activated, represented by block  66 . Activating the light-off enhancement device, represented by block  68 , may comprise injecting fuel from fuel injector  40 , represented by block  70  and injecting CNT&#39;s from CNT injector  46 , represented by block  72 . The control module  30  may active a light source  52 , block  74 , to ignite the CNT&#39;s which ignites the fuel injected by injector  40 . The heat created by the ignition may heat up the catalyst  22 . The control module  30  will continue to monitor the temperature of the catalyst  22 , block  62 , once the light-off temperature is reached, the light-off time enhancement device  54  may be inactive. This strategy can be utilized upon cold start of a vehicle  10 , or in the case of a hybrid vehicle to maintain catalyst  22  light-off temp in series of engine  12  stops and starts. 
         [0024]    An additional embodiment is represented by  FIG. 4 . In this embodiment the general exhaust layout is similar to  FIG. 2  however a particulate filter  76  may be included in the housing  78  of the catalytic converter with particulate filter assembly  80 . A catalyst  82  may also be in the same housing  78 . An upstream temperature sensor  84  is coupled to the housing  78  upstream of the catalyst  82 ; a middle temperature sensor  86  may be coupled to the housing  78  upstream of the particulate filter  76  but downstream of the catalyst  82 . A downstream temperature sensor  88  may be coupled to the housing  78 , wherein all temperature sensors may communicate with control module  30 . Temperature sensors  84 ,  86 ,  88  may be embedded into the catalyst and/or the filter by way of non-limiting example. In this embodiment the light-off time enhancement device  54  may be used to generate a great amount of heat to regenerate or burn off any trapped particles in the particulate filter  76 . It can be understood in the art the that particulate filter  76  and catalyst  82  may be in separate housings and may require two light-off enhancement devices  54 . The catalyst  82  and particulate filter  76  are shown together as a non-limiting example. 
         [0025]      FIG. 5  represents the flow chart of control for regenerating the particulate filter  76 . The control module  30  selectively enables particulate filter regeneration, which is initiated when the control module  30  estimates the particulate filter  76  is full of particulates; this is represented by block  90 . The control module  30  may continuously estimate the amount of emitted particulates since the last regeneration based on engine operating parameters. If the particulate filter  76  is determined not to be full then no action is taken. It is known in the art that regeneration is preferably initiated during conditions where exhaust temperatures exceed the required light-off threshold without special actions. For example, particulate filter  76  regeneration may be initiated during traveling at highway speeds. However, regeneration can be initiated at less than optimum conditions if required. The duration of particulate filter  76  regeneration varies based on the amount of estimated particulates within the particulate filter  76 . If the control module  30  determines the particulate filter is full it may initiate the light-off enhancement device  54  for a preset time at a preset temperature, represented by box  92 . The control module  30  will monitor the temperatures in the catalyst particulate filter assembly  80  using temperature sensors  84 ,  86 , and  88 . The light-off enhancement device  54  operation is consistent with what was previously described. Once the preset time at the preset temperature is met the operation may stop and the estimating process of step  90  starts over again. 
         [0026]      FIG. 6  represents an additional embodiment where the fuel from fuel supply storage  94  and CNT&#39;s from CNT storage  96  are delivered into the exhaust stream  98  through a combination injector  100 . A light source  102  may remain separate and downstream from the combination injector  100 . This configuration may allow for a thorough mix of fuel and CNT&#39;s, when the light source  102  is activated. A complete burn of fuel may be obtained for increased heat for catalyst  22  and efficiency as to not waste any fuel that is being injected. The control would operate in the same manner previously described and may be controlled by control module  30 . It can also be appreciated for this embodiment and the all previous embodiments that the location of the light-off enhancement device  54 , or combination injector  100  and light source  102  may be coupled to the exhaust pipe  32  leading to the catalytic converter  16  or the actual catalytic converter housing  24 . 
         [0027]    A unique property of CNT&#39;s is their ability to heat up and burn upon exposure to light. The present embodiments utilize this property as an ignition method that is simplistic in nature and versatile. The light source  52 ,  102  may be a flash device similar to those used with ordinary camera equipment or a flashlight by way of non-limiting example. Light sources  52 ,  102  could also be, without limitation, a light-emitting diode, laser diode, a laser, an arc lamp, LED, fiber optic or other light emitting device. By utilizing basic light sources this may reduce cost and complexity to implement an conventional igniting device in the exhaust system  14 . By utilizing CNT&#39;s mixed with fuel a more efficient ignition may be obtained as to not waste any of the fuel being supplied. Further details about CNT&#39;s and light source ignition can be found in U.S. Pat. Nos. 7,517,215 and 7,217,404 which are both incorporated herein by reference. Additionally information about igniting nanoparticles by using optical ignition can be found in US Application 2012/1511931 which is incorporated herein by reference. Additionally the creation of CNT&#39;s in US Application 2007/0025905 which is incorporated herein by reference. 
         [0028]    Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not 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. 
         [0029]    The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the invention, and all such modifications are intended to be included within the scope of the invention.