Patent Publication Number: US-2022235688-A1

Title: Exhaust gas sensor assembly

Description:
TECHNICAL FIELD 
     This disclosure relates to gas sensors and more particularly to gas sensors used in a vehicle exhaust system. 
     BACKGROUND 
     Internal combustion engines generate exhaust gases during the combustion process. An exhaust system transports these exhaust gases from the engine to the atmosphere. The exhaust gases include many different compounds including nitrous oxide (NOx), oxygen, unburnt fuel, carbon monoxide, and carbon dioxide. Modern computer-controlled engines monitor these compounds with sensors to facilitate operation of the engine. 
     SUMMARY 
     According to one embodiment, an exhaust gas sensor assembly for a vehicle includes a sampling tube having a proximal end connectable to a housing and a distal end configured to be suspended with a cavity of the housing. The tube defines a hollow center, an inlet, an outlet, and an exhaust gas flow path extending from the inlet, through the hollow center, and to the outlet. An exhaust gas sensor is disposed in the hollow center at the proximal end and includes a sensing element disposed in the exhaust gas flow path. a flow guide is disposed in the hollow center between the inlet and the sensing element and is configured to redirect the flow path through a passageway defined between the tube and the flow guide. 
     According to another embodiment, a sensor assembly for a vehicle includes a sensor and a sampling tube circumscribing the sensor. The tube defines an inlet, an outlet, and a hollow center configured to route a gas from the inlet, past the sensor, and to the outlet. The tube includes a flow guide partially blocking the hollow center and cooperating with the tube to define a gap. 
     According to yet another embodiment, a vehicle exhaust system includes an exhaust conduit having a sidewall and a sensor assembly attached to the sidewall. The sensor assembly includes a sampling tube projecting from the sidewall towards a center of the exhaust conduit. The sampling tube defines a hollow center, an inlet to the hollow center, and an outlet from the hollow center. The sensor assembly further includes a sensor extending through the sidewall to be received within the hollow center. A flow guide is disposed in the hollow center and cooperates with the tube to define a passageway. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a portion of an exhaust system having a gas sensor for sampling the exhaust gases. 
         FIG. 2  illustrates a diagrammatical side view of a gas sensor assembly. 
         FIG. 3  illustrates another diagrammatical side view of the gas sensor assembly. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations. 
     Referring to  FIG. 1 , a vehicle exhaust system  20  is configured to carry an exhaust gas stream  22  from the engine to the atmosphere. The exhaust system  20  may include one or more sections of exhaust pipe, catalytic converter(s), resonator(s), muffler(s), after-treatment components, and the like. In the illustrated embodiment, a gas sensor assembly  28  is attached to an expanded housing  30  of the system  20 . The housing  30  may be connected to upstream and downstream exhaust pipes  24  and  26 . The housing  30  may be part of the catalytic converter, an exhaust pipe or other structure. In the illustrated embodiment, the housing  30  is the shell of the catalytic converter. 
     The gas sensor assembly  28  may be attached to a sidewall  32  of the housing  30 . The gas sensor assembly  28  extends into an open cavity  34  of the housing  30  to be disposed within the exhaust gas stream  22 . The sensor assembly  28  includes an exhaust gas sensor  36  configured to read a concentration of one or more compounds of the exhaust gas stream  22 . For example, the sensor  36  may be configured to sense concentrations of nitrous oxide, oxygen, other gas, or combinations thereof. 
     As will be described in more detail below, the sensor assembly  28  includes a sampling tube  40  extending inwardly from the sidewall  32  towards a longitudinal centerline  42  of the housing  32 . The sampling tube  40  may be arranged radially as shown in the illustrated embodiment, or may be attached at an angle. The sampling tube  40  is configured to draw the gas stream  22  located near the center portion of the cavity  34  to the sensor  36  located near the sidewall  32 . The sampling tube  40  improves accuracy by routing more of the exhaust gas stream  22  to the sensor  36  than would otherwise occur without the sampling tube  40 . Since the sensor  36  is disposed on the sidewall  32 , it may receive less flow especially if the housing  30  is of a larger diameter. Additionally, it is possible for the exhaust stream  22  to be nonhomogeneous with differing concentrations of gases along its cross-section. If the sensor  36  is only sensing the exterior portions of the exhaust stream  22 , it is possible for inaccurate readings to be produced. The sampling tube  40  includes a plurality of inlets  44  located at different radial positions of the tube. The inlets  44  are disposed on an upstream side  48  of the tube  40 . The sampling tube  40  is hollow and routes the airstream entering the inlets  41  to the sensor  36 . An outlet  46  which is disposed adjacent to the sensor  36  allows the exhaust gasses to exit the sampling tube  40 . A sensing element of the sensor  36  senses the concentrations of the gases as it pass by. The outlet  46  is disposed on a downstream side  50  of the tube  40 . 
     While the hollow center  52  of the sampling tube is capable of routing exhaust gases  22  to the sensor  36 , testing has shown that this alone may be insufficient in certain situations. For example, it is possible for the gas stream within the sampling tube  40  to mostly bypass the sensor  36 , e.g., if a majority of the flow is along the downstream inner wall of the tube  40 . To solve this problem, a flow guide  54  is added to force the gas stream across the sensor  36 . The flow guide  54  may be a plate or wall that covers over a portion of the hollow center and forces the gas stream up along the upstream inner wall of the tube  40 . This may produce a perpendicular flow across the sensor  36  as the gas stream flows to the outlet hole  46 . 
     Referring to  FIG. 2 , the sensor  36  may be of any construction or design known in the art. At a high level, the sensor  36  may include a shell  60  and a sensing element  62  disposed within the shell. The shell  60  defines a plurality of inlet openings  64 , e.g., holes. The shell  60  may be cylindrical and the holes  64  may be provided circumferentially around the cylinder. The shell  60  may also define a plurality of outlet openings  66 , e.g., holes, which may also be circumferentially arranged. During operation, a portion of the gas stream  68  flows through the inlet openings  64 , across the sensing element  62 , and out the outlet openings  66 . The sensing element  62  is configured to sense concentrations of one or more gases as the stream  68  passes by. For example, the sensing element  62  may be configured to sense nitrous oxide, oxygen, or the like. The sensor may be attached utilizing a mounting boss configuration that may be integrated into the sampling tube. 
     Referring to  FIGS. 2 and 3 , the sampling tube  40  includes a proximal end  80 , a distal end  82 , a longitudinal centerline  84 , and a midline  86  that is perpendicular to the longitudinal centerline  84 . The sampling tube  40  includes a sidewall  88 , which may be a circular cylinder, that extends from the proximal end  80  to the distal end  82 . The distal end  82  may be generally closed with a drain hole. An end cap may be attached to the sidewall  88  to form the distal end  82 . The sidewall  88  includes an outer surface  90  and an inner surface  92 . The sidewall  88  also includes an upstream side  94  that faces the gas stream  22  and a downstream side  96 . The inlets  44  are located on the upstream side  96  to accept the incoming gas stream  22  into the hollow center  52 . The inlets  44  are one or more openings such as holes that extend through the sidewall  88  from the exterior surface  90  to the interior surface  92 . The holes may be circular, ovular, or any other shape. The inlets  44  may be arranged in a linear array along the axial direction (longitudinal direction)  100  of the sampling tube  40 . The inlets  44  are in higher concentration near the distal end  82  to capture the portion of the gas stream  22  near the centerline  42  of the exhaust system. The outlet  46  is located on the downstream side  96  and generally near the distal end  80 . Unlike the inlets  44 , the sampling tube  40  may only include a single outlet  46 . Although, in other embodiments, multiple outlets may be provided. The outlet  46  may be a hole that extends through the sidewall  88  from the outer surface  90  to the inner surface  92 . The hole  46  may be circular, ovular, or any other shape. 
     The sensor  36  is disposed within the hollow center  52  of the sampling tube  40 . For example, the sensor  36  may be received through the open distal end  80  of the sampling tube  40 . This suspends the sensing element  62  within the hollow center  52 . The outlet  46  is placed to be generally adjacent to the sensing element  62  of the sensor  36  to provide optimal readings. The sampling tube  40  and the sensor  36  may be attached to a head  104  of the sensor assembly  28 . The head  104  may be configured to attach to the housing  32  or other fixture, e.g. a pipe sidewall. The sensor assembly  28  may include threads or other means for securing to the exhaust system  20 . 
     To improve gas flow across the sensing element  62 , a flow guide  54  is provided within the sampling tube  40 . The flow guide  54  blocks a substantial portion of the hollow center  52  and forces the gas stream to flow through a passageway  106  located along the inner surface  92  of the upstream side  94 . The flow guide  54  may be a separate component attached to the sampling tube  40  or may be an integrally formed portion of the sampling tube  40 . In the illustrated embodiment, the flow guide  54  is a plate that is attached to the sampling tube  40  such as by welding or other means. The plate may be orthogonal to the axial direction  100 . The plate could also be angled within the sampling tube  40  in other embodiments. 
     The flow guide  54  includes a first planar surface  110  that extends over a substantial portion of the hollow center forcing the gas flow through the narrowed passageway  106 . The flow guide  54  may block at least 50% of the hollow center. In other embodiments, the flow guide  54  my block at least 60%, 70%, 80%, or 90% of the hollow center. The planar surface  110  may be oriented radially (direction  102 ) relative to the axial centerline  84  of the tube  40  (as shown) or may be slanted. The flow guide  54  may also include a second surface  112 , which may also be a planar surface parallel to the first planar surface  110 . Alternatively, second surface  112  may have a different shape or orientation than the planar surface  110 . The flow guide  54  may be generally shaped as a planar disk with a portion removed to create the passageway  106 . That is, the flow guide  54  may include a circumferential edge  114  that is disposed against the interior surface  92  of the sampling tube  40  at the downstream side and surrounding area, and a straight edge  116  that is spaced apart from the interior surface  92  at the upstream side and surrounding area to create a gap  105 , which forms the passageway  106 . The gap  105  may be located diametrically opposite to the outlet  46 . The size of the gap  105  can be tuned to provide the desired gas flow to the sensor  36 . 
     The flow guide  54  is axially positioned between the uppermost inlet  44  and the outlet  46 . This may place the flow guide  54  between the midpoint  86  and the distal end  80 . In the illustrated embodiment, flow guide  54  is closer to the distal end  80  than to the midpoint  86 . This, however, is not required and depends upon the flow characteristics of the assembly  28 . 
     It is to be understood that the above described flow guide  54  is merely an example and that the flow guide  54  may have any shape, size, or form that is capable of forming a restricted passageway to guide the flow near the upstream side of the sensor. 
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments can be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes can include, but are not limited to cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and can be desirable for particular applications.