Abstract:
An exhaust treatment system includes an exhaust treatment device. The exhaust treatment device includes a shell, and a sensor boss configured to support a sensor device is mounted to the shell. A Pitot tube that is configured to communicate exhaust to the sensor device is coupled to the sensor boss at a proximate end thereof, while a distal end is affixed to the shell of the exhaust treatment device to prevent detachment of the Pitot tube from the sensor boss, and ensure that exhaust gases are effectively communicated to the sensor device.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present disclosure claims priority to U.S. Provisional Application Ser. No. 61/568,222, filed Dec. 8, 2011, the disclosure of which is hereby incorporated by reference in its entirety. 
     
    
     FIELD 
       [0002]    The present disclosure relates to an exhaust system including an exhaust treatment device. 
       BACKGROUND 
       [0003]    This section provides background information related to the present disclosure which is not necessarily prior art. 
         [0004]    Exhaust gas sensors have been used in vehicles to sense the presence of constituents (e.g., oxygen, hydrocarbons, nitrous oxides, etc.) in an exhaust gas stream and to sense and/or signal, for example, when an internal combustion engine switches from rich to lean or from lean to rich operation, or when a catalyst of the exhaust treatment device is no longer operating within a desired range. 
         [0005]    Because exhaust gas sensors are required to be positioned within an exhaust gas flow, the exhaust gas sensor is usually mounted to a portion of the exhaust system. Due to application requirements, the exhaust system itself may have unique exterior configurations, which may not be optimal for mounting exhaust sensors to the system (e.g., due to irregular mounting surfaces). Accordingly, exhaust system designs limit the positioning and configuration of the gas sensor within the exhaust system. To account for these drawbacks, a prefabricated mounting boss can be secured to the exhaust system by an attachment method wherein the boss is inserted into or about a hole pierced in the shell of the exhaust system component, and the boss is welded to the shell. Such a configuration, however, does not ensure that a sufficient amount of exhaust gases reach the sensor device. 
         [0006]    In addition, the exhaust treatment device will typically have insulated catalyst bricks that are disposed within the shell. The catalyst bricks are wrapped in an insulating blanket (mat) disposed between the exterior of the catalyst brick and the interior surface of the exhaust treatment device. It is desirable to monitor the gases flowing through the catalyst bricks and to monitor the gas composition between the bricks. However, accurate sensing by known methods may require a sufficient amount of free space between the bricks for the sensing element of the gas sensor to be mounted within the flow path of and between the catalyst bricks (e.g., mid-stream mounting). Accordingly, it may be beneficial to provide an improved exhaust gas sensor system. 
       SUMMARY 
       [0007]    This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
         [0008]    The present disclosure provides an exhaust treatment system including an exhaust treatment device including a shell; a sensor boss configured to support a sensor device mounted to the shell; and a communication tube configured to communicate exhaust to the sensor device. The communication tube includes a first end coupled to the sensor boss and a second end fixed to the shell. 
         [0009]    Additional aspects of the exhaust treatment system include that the communication tube may be a Pitot tube, the first end may be press-fit to the sensor boss, and the second end may be welded to the shell. 
         [0010]    Additionally, at least one catalytic brick may be disposed in the shell, wherein the communication tube is located downstream from the brick. Alternatively, the communication tube may be located upstream from the brick. 
         [0011]    The communication tube may include at least one through hole for communicating exhaust to the sensor device. The communication tube may also include at least one exit aperture to allow gas to pass through the at least one through hole, communicate with the sensor device, and exit the communication tube. Preferably, the through hole faces an inlet of the exhaust treatment device. 
         [0012]    Lastly, the exhaust system of the present disclosure can include a sensor boss that may include an asymmetrical feature that aligns the through hole toward an inlet of the exhaust treatment device. 
         [0013]    The present disclosure also provides an exhaust treatment device including a shell; a catalyst brick disposed in the shell for treating an exhaust gas passing through the shell; a sensor in communication with the exhaust gas in the shell; a mounting structure for securing the sensor to the shell; and an exhaust gas communication tube disposed in the shell for directing at least a portion of the exhaust gas to the sensor, wherein a first end of the exhaust gas communication tube is non-fixedly coupled to the mounting structure, and a second opposite end of the exhaust gas communication tube is fixedly coupled to the shell. 
         [0014]    The exhaust gas communication tube may include at least one inlet aperture for receiving and directing the portion of the exhaust gas to the sensor. Further, the exhaust gas communication tube may include at least one exit aperture for allowing the portion of the exhaust gas received and directed to the sensor by the inlet aperture to exit the gas communication tube. 
         [0015]    The first end of the gas communication tube may be press-fit to the mounting structure, and the second end may be welded to the shell. 
         [0016]    The catalyst brick of the exhaust treatment device may be selected from the group consisting of diesel oxidation catalysts, selective catalytic reduction catalysts, and catalyst-coated particulate filters. 
         [0017]    The gas communication tube may be located downstream from the brick. Alternatively, the gas communication tube may be located upstream from the brick. Regardless, the at least one inlet aperture may face an inlet of the shell. To ensure that the at least one inlet aperture faces the inlet of the shell, the mounting structure may include an asymmetrical feature that aligns the at least one inlet aperture toward the inlet of the shell. 
         [0018]    Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0019]    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. 
           [0020]      FIG. 1  is a schematic representation of an exhaust system according to a principle of the present disclosure; 
           [0021]      FIG. 2  is a side-perspective view of an exhaust system treatment component according to a principle of the present disclosure; 
           [0022]      FIG. 3  is a top-perspective view of the exhaust system treatment component illustrated in  FIG. 2 ; 
           [0023]      FIG. 4  is a cross-sectional view of the exhaust system treatment component illustrated in  FIG. 2 ; 
           [0024]      FIG. 4A  is an enlarged view of a portion of  FIG. 4 ; and 
           [0025]      FIG. 5  is a cross-sectional view of the exhaust treatment component along line  5 - 5  illustrated in  FIG. 4 . 
       
    
    
       [0026]    Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
       DETAILED DESCRIPTION 
       [0027]    Example embodiments will now be described more fully with reference to the accompanying drawings. 
         [0028]      FIG. 1  schematically illustrates an exhaust system  10  according to the present disclosure. Exhaust system  10  includes at least an internal combustion engine  12  and a tailpipe assembly  14  including, for example, a muffler  16  and exhaust outlet pipe  18 . Engine  12  can be any type of internal combustion engine known to one skilled in the art such as, for example, a gasoline engine or a diesel engine. Exhaust system  10  may also include at least one exhaust treatment device  20  disposed downstream from engine  12  and upstream from tailpipe assembly  14 . In the exemplary illustrated embodiment, exhaust system  10  may include a pair of exhaust treatment devices  20  connected via exhaust lines  22  to tail pipe assembly  14 . Between exhaust treatment devices  20  and tailpipe assembly  14  may be disposed an extension pipe assembly  21 . 
         [0029]    Now referring to  FIGS. 2-6 , a configuration of exhaust treatment device  20  will be described. Exhaust treatment device  20  may include an outer shell  24  having an inlet end  26  and an outlet end  28 . Proximate to inlet end  26  is a first catalyst brick  30  and spaced therefrom proximate outlet end  28  is a second catalyst brick  32 . First and second catalyst bricks  30  and  32  may be spaced apart by gap  34 , and may be any type of catalyst brick known in the art. In some exemplary embodiments, first and second catalyst bricks  30  and  32  may be gas converter bricks. In other exemplary embodiments, first and second catalyst bricks  30  and  32  may be selective catalytic reduction (SCR) catalyst, diesel oxidation catalyst (DOC), catalyst-coated diesel particulate filter (DPF) bricks, or combinations thereof. Regardless, disposed between outer shell  24  and each catalyst brick  30  and  32  may be an insulating mat  36 . 
         [0030]    Although inlet end  26  and outlet end  28  are illustrated as being integral or unitary with outer shell  24 , it should be understood that inlet end  26  and outlet end  28  may be separately formed pieces that are subsequently welded to outer shell  24 . In this regard, in some exemplary embodiments, outer shell  24 , inlet end  26 , and outlet end  28  are pieces separately formed of materials such as stainless steel. Other materials, such as, for example, aluminum, are contemplated however. Inlet end  26  may also include an inner shell  38  coupled thereto. Between inner shell  38  and inlet end  26  can be formed another insulating mat  40 . Inlet end  26  may include inner shell  38  and insulating mat  40  due to higher exhaust temperatures generally being present at inlet end  26  in comparison to outlet end  28 . It should be understood, however, that outlet end  28  may also be formed to include an inner shell and insulating mat without departing from the scope of the present disclosure. 
         [0031]    During use of exhaust treatment device  20 , it is often desirable to use sensor devices to take various measurements as exhaust gases travel through exhaust treatment device. For example, in some embodiments, sensor devices such as a pressure sensor, a CMS sensor, a NO x  sensor, an oxygen (O 2 ) sensor, an ammonia (NH 3 ) sensor, a particulate matter sensor, a temperature sensor, or any other type of sensor known to one skilled in the art of exhaust treatment may be used to monitor the exhaust gas in order to better determine what operating parameters of the exhaust treatment system need to be adjusted. 
         [0032]    To connect the sensor device to exhaust treatment device  20 , a sensor boss  42  may be attached to exhaust treatment device  20 . As illustrated in  FIGS. 2 to 5 , sensor boss  42  is attached to outer shell  24  of exhaust treatment device  20  at a position located between catalyst bricks  30  and  32 . It should be understood, however, that sensor boss  42  is not limited to being attached to outer shell  24  at a position located between catalyst bricks  30  and  32 . Rather, the present disclosure contemplates that sensor boss  42  may be located upstream of catalyst brick  30  (i.e., adjacent inlet  26 ), or downstream of catalyst brick  32  (i.e., adjacent outlet  28 ). Regardless, sensor boss  42  may be formed of materials such as stainless steel, aluminum, or other metal materials that facilitate welding or brazing to outer shell  24  such that sensor boss  42  is rigidly attached to outer shell  24 . To facilitate communication with the exhaust gases to be monitored by the sensor device, sensor boss  42  has a centrally disposed aperture  44  that provides communication between the sensor device and the exhaust gases passing through exhaust treatment device  20 . To connect the sensor to the sensor boss  42 , a portion of aperture  44  may be threaded (not shown). Other connection methods between the sensor device and the sensor boss  42 , however, may be used. 
         [0033]    Aperture  44  may not be sufficiently sized or positioned to effectively communicate exhaust gases passing through exhaust treatment device  20  to the sensor device. To ensure that a sufficient portion of the exhaust gases are communicated through aperture  44  to the sensor device, an exhaust gas communication tube  46  (hereinafter “Pitot tube”) may be used. Pitot tube  46  may be a generally cylindrical tube formed of a material such as stainless steel, aluminum, titanium, or any other material satisfactory for withstanding exposure to the exhaust gases. To satisfactorily facilitate entry of the exhaust gases into Pitot tube  46  to the sensor device, Pitot tube  46  includes at least one through hole  48 . 
         [0034]    To ensure that through holes  48  are directed toward inlet end  26  to receive a flow of the exhaust gases, sensor boss  42  includes an asymmetrical feature (stepped portion)  50 . Pitot tube  46  may be press-fit or otherwise secured to sensor boss  42 . As Pitot tube  46  is secured to sensor boss  42 , through holes  48  may be aligned to face in the same direction as stepped portion  50 . Then, when sensor boss  42  including the press-fit Pitot tube  46  is placed through a first opening  52  in shell  24 , sensor boss  42  may be manipulated by the assembler such that stepped portion  50  faces toward inlet end  26 . As through holes  48  are aligned in the same direction as stepped portion  50 , when stepped portion  50  is aligned to face toward inlet end  26 , through holes  48  are also aligned to face inlet end  26 . Exhaust gases passing through exhaust treatment device  20  are then ensured to pass into through holes  48  and be in communication with the sensor device. After properly aligning sensor boss  42  and Pitot tube  46 , sensor boss  42  can be secured to shell  24  by welding or brazing. Exemplary welding techniques include metal inert gas (MIG) welding techniques, but other welding techniques may be used without departing from the scope of the present disclosure. 
         [0035]    To provide an exit for exhaust gases that communicate with the sensor device, Pitot tube  46  may also include secondary through holes  54 . Secondary through holes  54  may be arranged orthogonal to through holes  48  to ensure that the exhaust gases entering through holes  48  do not simply pass through Pitot tube  46  without at least a portion of the exhaust gases first being communicated to the sensor device. 
         [0036]    In the embodiment where Pitot tube  46  is press-fit to sensor boss  42 , central aperture  44  is radially expanded to provide a shoulder  56 . Shoulder  56  may be spaced apart from a terminal end  58  of Pitot tube  46  to provide for thermal expansion of Pitot tube  46  during use of exhaust treatment device  20 . In this regard, during use of the exhaust treatment device  20 , the exhaust gases will be high temperature, which will cause Pitot tube  46  to expand during use of engine  12 . When engine  12  is not operating, Pitot tube  46  will cool, which will cause Pitot tube  46  to contract to its original size. 
         [0037]    Press-fitting Pitot tube  46  to sensor boss  42  allows for Pitot tube  46  to expand and contract without detaching from sensor boss  42  during use of exhaust treatment device  20 . This is a beneficial aspect of the present disclosure because if Pitot tube  46  was rigidly fixed to sensor boss  42 , the expansion and contraction of Pitot tube  46  can weaken the connection between Pitot tube  46  and sensor boss  42 , which increases the risk of Pitot tube  46  eventually detaching from sensor boss  42 . In such a case, the efficacy of the sensor can be reduced because the amount of exhaust gases reaching the sensor will be reduced without the aid of Pitot tube  46 . 
         [0038]    To further ensure that Pitot tube  46  does not detach from sensor boss  42 , Pitot tube  46  has a length that allows Pitot tube  46  to extend entirely through shell  24 . That is, a first end  60  may be press-fit to sensor boss  42 , while a second end  62  extends through shell  24 . Second end  62 , in some exemplary embodiments, may be welded or brazed to shell  24 . To ensure that exhaust treatment device  20  remains gas tight, a cap  64  may be fixed to second end  58  of Pitot tube  48 . Cap  64  may be fixed to second end  62  by welding, brazing, or any other attachment method known to one skilled in the art so long as exhaust treatment device  20  remains sealed. 
         [0039]    According to one arrangement discussed above, Pitot tube  46  is press-fit to sensor boss  42  to account for thermal expansion, and rigidly attached to shell  24 . In this manner, Pitot tube  46  is prevented from detaching from sensor boss  42  during use of exhaust treatment device  20 , which ensures that a satisfactory amount of exhaust gases are communicated to the sensor device. 
         [0040]    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 disclosure. 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 disclosure, and all such modifications are intended to be included within the scope of the disclosure.