Patent Publication Number: US-2018051618-A1

Title: Geometrically optimized gas sensor heat shield

Description:
INTRODUCTION 
     Internal combustion engines (ICE) operate at very high temperatures, and appurtenant components such as exhaust gas manifolds and conduits are exposed to significant levels of heat. The heat can be harmful to some neighboring components if left unprotected, such as gas sensors. For example, oxygen sensors deployed on turbocharger exhaust gas circulation conduits can be subjected to temperatures over 600° C. Heat shields can be employed to protect sensitive components from heat, but dense packaging of components within a system, particularly automobile and motorcycle systems, can pose a challenge to designing space-efficient heat shields. 
     SUMMARY 
     One or more exemplary embodiments address the above issues by providing space-efficient gas sensor heat shields with optimized heat-protecting geometries. 
     According to an aspect of an exemplary embodiment, a gas sensor heat shield is provided. The heat shield can include at least one wall having a top edge and a bottom edge, wherein the wall forms a body, a base connected proximate the wall bottom edge defining a bottom diameter and a normal height relative to the wall top edge, wherein the base includes an aperture capable of receiving a gas sensor, and a circumferential lip proximate the wall top edge extending radially outward and defining an outer lip diameter. The at least one wall can be tapered radially outward at an angle of about 3 degrees to about 17 degrees, and the ratio of the outer lip diameter to bottom diameter can be at least about 5:3.5. The heat shields can be utilized for exhaust gas systems servicing ICEs and turbochargers. 
     According to an aspect of an exemplary embodiment, exhaust gas monitoring systems are included. An exhaust gas monitoring system can include an exhaust gas conduit including a wall defining a passage through which exhaust gas can collect or travel, a gas sensor having a first end disposed within the exhaust gas conduit and a second end disposed outside the exhaust gas conduit, an engine and/or turbocharger shield including an aperture, and a gas sensor heat shield disposed within the engine and/or turbocharger shield aperture, the gas sensor heat shield including at least one wall having a top edge and a bottom edge, wherein the wall forms a body; a base connected proximate the wall bottom edge defining a bottom diameter and a normal height relative to the wall top edge, wherein the base includes an aperture through which the gas sensor is positioned, and a circumferential lip proximate the wall top edge extending radially outward and defining an outer lip diameter. The at least one wall can be tapered radially outward at an angle of about 3 degrees to about 17 degrees, and the lip can be positioned above the engine and/or turbocharger shield relative to the exhaust gas conduit and overlaps the engine and/or turbocharger shield at least 8 mm. A vertical gap between the heat shield lip and the engine and/or turbocharger shield can be at most 9 mm. 
     Although many of the embodiments herein are describe in relation to oxygen sensors used for exhaust gas systems servicing ICEs and turbochargers, the embodiments herein are generally suitable for all gas sensors operating in high temperature environments. 
     Other objects, advantages and novel features of the exemplary embodiments will become more apparent from the following detailed description of exemplary embodiments and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a cross-sectional side-view of a heat shield, according to one or more embodiments; 
         FIG. 2  illustrates a cross-sectional side-view of an exhaust gas monitoring system, according to one or more embodiments. 
     
    
    
     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. 
     Provided herein are gas sensor heat shields which are space-efficient and geometrically optimized to shield gas sensors from heat in high temperature environments. The geometry of heat shields provided herein obviate the need to fully cover a gas sensor, and therefore reduce material and manufacturing costs in addition to saving space in densely packed component areas, such as in exhaust gas systems servicing ICEs and turbochargers. 
     Referring now to the drawings, wherein like reference numbers refer to like features throughout the several views, there is shown in  FIG. 1  a heat shield  100  comprising at least one wall  110  having a top edge  111  and a bottom edge  112 . In some embodiments, top edge  111  and/or bottom edge  112  can be rounded. Wall  110  defines a generally tubular body which connects to a base  120  proximate bottom edge  112 . Wall  110  can form a generally circular or ovular shell extending normal to base  120 . Wall  110  can be optionally tapered at an angle β, as shown. Angle β can be at least about 3 degrees, at least about 4 degrees, or at least about 5 degrees. Angle β can be about 3 degrees to about 17 degrees, about 4 degrees to about 16 degrees, or about 5 degrees to about 15 degrees. Alternatively, wall  110  can comprise a plurality of walls which form a generally hollow shell. Such a hollow shell can comprise various cross-sectional shapes, dependent upon the number of walls, including hemispherical, triangular, square, etc. 
     Wall  110  and base  120  converge to define a bottom diameter  125 . Bottom diameter  125  can be an average diameter in embodiments where bottom diameter  125  is not uniform. Base  120  can comprise an aperture  130 . As illustrated, aperture  130  is centered relative to a central axis  135 , however other aperture  130  positions can be suitable. Aperture  130  can be capable of receiving an object, such as a gas sensor. In particular, the aperture is capable of receiving an O2 sensor. Aperture  130  can comprise a shape (e.g., a circular shape) suitable for accepting an object, such as a gas sensor. 
     Wall  110  can adjoin a circumferential lip  140  proximate wall top edge  111 , and extend radially outward relative to axis  135 . In some embodiments, the lip can optionally also extend inward relative to axis  135 . Lip  140  can extend radially outward at a perpendicular angle relative to an axis of the body, as shown. The lip can alternatively extend radially outward at an angle α from the perpendicular relative to the axis  135  of the body. Angle α can be less than about +/−10 degrees, less than about +/−5 degrees, less than about +/−4 degrees, less than about +/−3 degrees, less than about +/−2 degrees, or less than about +/−1 degree. Angle α can be less than about 10 degrees, less than about 5 degrees, less than about degrees, less than about degrees, less than about degrees, or less than about degree. Lip  140  can extend radially outward from the wall  110  and define an outer lip diameter  145 . Outer lip diameter  145  can be an average diameter in embodiments where outer lip diameter  145  is not uniform. The ratio of the outer lip diameter  145  to body bottom diameter  125  can be at least about 5:3.5, at least about 5:3.4, at least about 5:3.3, at least about 5:3.2, at least about 5:3.1, or at least about 5:3.0. 
     Heat shield  100  can have a height  136  defined as the normal distance between base  120  and top edge  111 . In some embodiments, heat shield can optionally have a height  136  to bottom diameter  125  ratio of less than about 1:2.5, less than about 1:2.25, less than about 1:2, or less than about 1:1.75. 
     Heat shield  100  can comprise a metal, such as steel, which is capable of maintaining the described physical shape and structural stability under various operating conditions. Operating conditions can be those proximate an ICEs and/or exhaust gas manifold or conduit, and include temperatures in excess of 500° C., 550° C., or 600° C. Steel can include stainless steel, or SUS-304L, for example. For heat shields  100  comprising metal constructions, lip  140  can include a countered or folded lip edge to prevent damage to nearby components by sharp edges. 
     In a particular embodiment, heat shield  100  comprises at least one wall extending normal to base  120 , a lip  140  extending radially outward at a perpendicular angle relative to axis  135  of the body, and an outer lip diameter  145  to body bottom diameter  125  ratio of at least about 5:3.5. Optionally this heat shield  100  can comprise a height  136  to bottom diameter  125  ratio of less than about 1:2.5. 
     In a particular embodiment, heat shield  100  comprises at least one wall extending normal to base  120 , a lip  140  extending radially outward at a perpendicular angle relative to axis  135  of the body, and an outer lip diameter  145  to body bottom diameter  125  ratio of at least about 5:3.25. Optionally this heat shield  100  can comprise a height  136  to bottom diameter  125  ratio of less than about 1:2.5. 
     In a particular embodiment, heat shield  100  comprises at least one wall extending normal to base  120 , a lip  140  extending radially outward at a perpendicular angle relative to axis  135  of the body, and an outer lip diameter  145  to body bottom diameter  125  ratio of at least about 5:3. Optionally this heat shield  100  can comprise a height  136  to bottom diameter  125  ratio of less than about 1:2.5. 
     In a particular embodiment, heat shield  100  comprises at least one wall extending from base  120  at an angle β of at least 3 degrees, a lip  140  extending radially outward at a perpendicular angle relative to axis  135  of the body, and an outer lip diameter  145  to body bottom diameter  125  ratio of at least about 5:3.5. Optionally this heat shield  100  can comprise a height  136  to bottom diameter  125  ratio of less than about 1:2.5. 
     In a particular embodiment, heat shield  100  comprises at least one wall extending from base  120  at an angle β of at least 3 degrees, a lip  140  extending radially outward at a perpendicular angle relative to axis  135  of the body, and an outer lip diameter  145  to body bottom diameter  125  ratio of at least about 5:3.25. Optionally this heat shield  100  can comprise a height  136  to bottom diameter  125  ratio of less than about 1:2.5. 
     In a particular embodiment, heat shield  100  comprises at least one wall extending from base  120  at an angle β of at least 3 degrees, a lip  140  extending radially outward at a perpendicular angle relative to axis  135  of the body, and an outer lip diameter  145  to body bottom diameter  125  ratio of at least about 5:3. Optionally this heat shield  100  can comprise a height  136  to bottom diameter  125  ratio of less than about 1:2.5. 
       FIG. 2  illustrates an exhaust gas monitoring system  200  including an exhaust gas conduit  210 , a gas sensor  220  disposed within the exhaust gas conduit  210 , and heat shield  100  situated proximate gas sensor  220 . Exhaust gas conduit  210  includes a wall  202  defining a passage through which exhaust gas  205  can collect or travel. Exhaust gas  205  can be supplied by an ICE (not pictured), for example. Exhaust gas can include one or more of carbon dioxide (CO 2 ), water (H 2 O), oxygen (O 2 ), diatomic nitrogen (N 2 ), carbon monoxide (CO), unburned hydrocarbons, oxides of nitrogen (NO x ), oxides of sulfur (SO x ), and condensed phase materials (liquids and solids) that constitute particulate matter. Exhaust gas  205  can be supplied via exhaust gas conduit  210  to a turbocharger, for example. Gas sensor  220  can comprise an O 2  sensor, for example, and generally comprises a first end  230  disposed within exhaust gas conduit  210  and a second end  221  disposed outside exhaust gas conduit  210 . First end  230  can be configured to receive a gas sample from exhaust gas conduit  210 . For example, first end  230  can be configured to receive an exhaust gas  205  sample. Gas sensor  220  can comprise a body  222 , for example a metal body, which can be oriented contiguous with an exhaust gas conduit  210  aperture through which gas sensor  220  is disposed. Body  222  can form a fluid-tight seal with wall  202 , for example. 
     Gas sensor  220  can comprise an outer shell  223 , for example for maintaining a fluid-tight environment about the various internal components. Gas sensor  220  can comprise one or more lead wires  225  which extend beyond the outer shell  223  through an aperture, said aperture occupied by a grommet  224  to maintain the fluid-tight characteristics of shell  223 . Grommet  224  can comprise a rubber, polytetrafluoroethylene (PTFE), resin, polyimide, or other elastomeric material. Gas sensor  220  can be heat-sensitive. The performance of gas sensor  220  can be detrimentally impacted by excessive heat, particularly heat contacting second end  221 . It should be noted that the description and figure of gas sensor  220  is not meant to limit the application of the present disclosure to a particular type of gas sensor. It should further be noted that heat shield  100  and gas sensor  210  are not necessarily drawn to scale relative to each other, and/or to the diameter of the exhaust gas conduit  210  or thickness of the exhaust gas conduit wall  202 . 
     Gas sensor  220  is shown disposed within heat shield aperture  130 . Heat shield  100  can be contiguous with one or more of body  222 , outer shell  223 , and wall  202 . For example, an outer contour of body  222  can substantially conform to aperture  130 . Heat shield  100  base  120  can comprise attachment features, such as one or more of threads, bolt holes, and tabs for securing heat shield to one or more of gas sensor  220  and wall  202 . Heat shield  100  can advantageously, reduce, minimize, or prevent excess heat from contacting second end  221 , and/or grommet  224 . The characteristics of heat shield  100  can lend heat-shielding capabilities to gas sensor  220  even when gas sensor  220  extends vertically beyond the height  163  of heat shield  100 . Accordingly, heat shield  100  need not entirely cover gas sensor  220 , thereby reducing manufacturing costs, weight, and saving space within system  200 . 
     System  200  can further comprise an engine and/or turbocharger shield  250 . Gas sensor  220  and heat shield  100  can be disposed within an aperture  251  of shield  250 . Heat shield  100  lip  140  can be oriented above shield  250  relative to exhaust gas conduit  210 , as shown. In such embodiments, the length of lip  140  can be determined based upon an overlap distance  252  between lip  140  and shield  250 , rather than as an outer lip diameter  145  to body bottom diameter  125  ratio. In some embodiments, overlap  252  is at least 8 mm, at least 9 mm, or at least 10 mm. In some embodiments, lip  140  is substantially parallel to shield  250 . In other embodiments, lip  140  is not substantially parallel to shield  250 . In such embodiments, overlap  252  comprises an average overlap. Optionally, heat shield  100  height  136  can be determined based on a vertical gap  253  between lip  140  and shield  250 . In some embodiments, vertical gap  253  is at most 9 mm, at most 8 mm, or at most 7 mm. In some embodiments, lip  140  is substantially parallel to shield  250 . In other embodiments, lip  140  is not substantially parallel to shield  250 . In such embodiments, vertical gap  253  comprises an average vertical gap. 
     In system  200 , heat shield  100  is capable of protecting gas sensor  220  from damaging heat in temperature conditions which exceed at least about 500° C., at least about 550° C., or at least about 600° C. Damaging heat can be defined as a temperature threshold above which gas sensor  220  cannot suitably operate, or as a temperature threshold above which one or more components (e.g., grommet  224 ) of gas sensor  220  are irreparably damaged. 
     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.