Abstract:
A gas sensor includes a gas sensing element positioned at least partially within a body and exposed at a first end to measure a gas in contact with the first end. The gas sensing element defines an axial direction. A flange extends from the body in a direction transverse to the axial direction. The flange has a first side facing toward the first end and a second side facing toward a remote end of the gas sensor. An O-ring is configured to sealingly position the gas sensor within a bore. An insertion portion of the gas sensor is defined by a wall and configured to hold the O-ring. The wall of the insertion portion is spaced a distance from the body at an axial position of the O-ring to provide a gap therebetween.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 61/813,922, filed Apr. 19, 2013, the entire contents of which are hereby incorporated by reference herein. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    This invention was made with Government support under DE-EE0005975 awarded by the Department of Energy. The Government has certain rights in this invention. 
     
    
     BACKGROUND 
       [0003]    The present invention relates to various gas (e.g., oxygen) sensor designs. Currently oxygen sensors are designed for high temperature applications. The sensors are mounted in exhaust manifolds or exhaust systems which are inherently designed to handle high temperature due to normal exposure to hot exhaust gas of 1030 C or more. For adaptation to low temperature environments, which may include various plastic or resin components, the sensor itself (e.g., the heated sensing element therein) becomes the primary heat source. At operating temperature, a conventional gas sensor may distort, melt, or otherwise damage adjacent structures not originally intended for such heat. 
       SUMMARY 
       [0004]    In one aspect, the invention provides a gas sensor having a gas sensing element positioned at least partially within a body and exposed at a first end to measure a gas in contact with the first end. The gas sensing element defines an axial direction. A flange extends from the body in a direction transverse to the axial direction. The flange has a first side facing toward the first end and a second side facing toward a remote end of the gas sensor. An O-ring is configured to sealingly position the gas sensor within a bore. An insertion portion of the gas sensor is defined by a wall and configured to hold the O-ring. The wall of the insertion portion is spaced a distance from the body at an axial position of the O-ring to provide a gap therebetween. 
         [0005]    In another aspect, the invention provides a gas sensor having a gas sensing element positioned at least partially within a body and exposed at a first end to measure a gas in contact with the first end. The gas sensing element defines an axial direction. A flange extends from the body in a direction transverse to the axial direction. The flange has a first side facing toward the first end and a second side facing toward a remote end of the gas sensor. An O-ring is configured to sealingly position the gas sensor within a bore. An insertion portion of the gas sensor is defined by a wall and configured to hold the O-ring. There is no heat conduction path radially between the wall of the insertion portion and the body at an axial position of the O-ring. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a front view of a gas sensor according to one aspect of the invention. 
           [0007]      FIG. 2  is a cross-section of the gas sensor of  FIG. 1 . 
           [0008]      FIG. 3  is a front view of a gas sensor according to one aspect of the invention. 
           [0009]      FIG. 4  is a cross-section of the gas sensor of  FIG. 3 . 
           [0010]      FIG. 5  is a front view of a gas sensor according to one aspect of the invention. 
           [0011]      FIG. 6  is a cross-section of the gas sensor of  FIG. 5 . 
           [0012]      FIG. 7  is a front view of a gas sensor according to one aspect of the invention. 
           [0013]      FIG. 8  is a cross-section of the gas sensor of  FIG. 7 . 
           [0014]      FIG. 9  is a schematic thermal model of a gas sensor having no heat shielding. 
           [0015]      FIG. 10  is a schematic thermal model of a gas sensor having heat shielding. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Direct conduction from the metal oxygen sensor housing to the intake manifold or other mounting location is decreased by introducing a gap (e.g., an air gap) and a smaller mass of material in contact with the intake manifold. The heat flow from the housing to the mounting area is by convection and by conduction through a smaller cross section. This reduces the amount of heat transferred to the intake manifold and to the O-ring as shown in the thermal model of  FIG. 10  compared to the thermal model of  FIG. 9  representing a conventional arrangement. In the various constructions disclosed herein, the mounting surface of the O-ring is displaced from the sensor housing. The temperature rise of the mounting surface is reduced due the gap between the sensor housing and the mounting surface. If the sensor uses an elastomeric O-ring for mounting and sealing, the O-ring is protected from melting or taking a permanent set from the heat. 
         [0017]    The O-ring heat shield can have several constructions, some of which are described and illustrated herein.  FIGS. 1 and 2  illustrate an O-ring heat shield member attached to the sensor at the flange and at the protection tube.  FIGS. 3 and 4  illustrate an integrated flange and O-ring heat shield in which an O-ring heat shield member similar to  FIGS. 1 and 2  further includes an integrated flange.  FIGS. 5 and 6  illustrate an integrated O-ring heat shield and protection tube in which an O-ring heat shield member similar to  FIGS. 1 and 2  further includes an integrated outer protection tube.  FIGS. 7 and 8  illustrate an integrated flange and O-ring heat shield and protection tube in which an O-ring heat shield member similar to  FIGS. 1 and 2  further includes an integrated flange similar to  FIGS. 3 and 4 , and an integrated outer protection tube similar to  FIGS. 5 and 6 . 
         [0018]    In all cases the device may be made in one piece or as an assembly of pieces from similar or dissimilar materials. 
         [0019]      FIGS. 1 and 2  illustrate a gas sensor  100  according to a first construction. The gas sensor  100  is particularly adapted for use in a low temperature (non-exhaust) environment such as an intake manifold  20 , for example, of an internal combustion engine. The intake manifold  20  may be non-metallic, and constructed of plastic or resin, for example. In addition, the gas sensor  100  can be used in another portion of an intake system of an internal combustion engine. For example, the gas sensor  100  can be used in a charge air cooler pipe, upstream of a throttle valve and intake manifold and downstream of an intercooler which receives compressed intake gas from a turbocharger. The charge air cooler pipe may also be non-metallic (e.g., plastic or resin). 
         [0020]    The gas sensor  100  includes a sensor subassembly (or “short sensor assembly”)  102  that includes a gas sensing element  104  positioned within a sensor sub-housing or body  106  and defining an axis X. The body  106  can be metallic. Ceramic bushings  108  and a soft ceramic seal packing  110  can be used to position the gas sensing element  104  within the body  106 . Outside the body  106 , an insertion portion  112  and a transverse flange portion  114  are provided. The insertion portion  112  receives an O-ring  116 , and is configured to be received within a bore  117  in the intake manifold  20  in sealing relationship. The insertion portion  112  and the O-ring  116  allow the sensor  100  to simply “plug into” the bore  117  in the intake manifold  20  (e.g., simple axial insertion into a non-threaded bore). The flange portion  114  can include one or more apertures  118  to receive fasteners (not shown) for securing the sensor  100  to the intake manifold  20  or other structure. A gasket may also be provided between the flange portion  114  and the intake manifold  20 . One or more protection tubes  120  at a first end or sensing end A of the gas sensor  100  cover a sensing end of the sensing element  104 , while allowing fluid communication with passing gases. The first end of the sensing element  104  extends from the body  106  and, except for the protection tube(s)  120 , is otherwise exposed to ambient gas. When energized, the sensor subassembly  102  enables a gas sensing function of the gas sensor  100  (e.g., an oxygen sensor, such as a pumped-reference wide-band oxygen sensor). 
         [0021]    At a second end B of the gas sensor  100  opposite the sensing end A, a connector housing (not shown) may be provided to cover the remote or interior end of the sensing element  104  and provide a plug housing or plug connector portion and electrical terminals or connectors for connection with an external plug member at the remote end B of the gas sensor  100 . Alternately, a conventional wire harness can be coupled to the sensing element  104  at the second end B. 
         [0022]    It will be noted that the insertion portion  112  is provided by a wall  113  of considerably less thickness than that of the body  106 , and furthermore, the wall  113  forming the insertion portion  112  is spaced radially away from the outside of the body  106  to introduce a gap (e.g., an air gap) therebetween. In some constructions, the gap defines a space that is in fluid communication with neither one of a process gas (i.e., gas to be sampled by the sensor  100 ) nor a reference gas chamber. The wall  113  can be an O-ring heat shield, which is provided to limit the amount of heat transferred from the sensing element  104  to the O-ring  116  during operation of the gas sensor  100 . By constructing the gas sensor  100  to limit the heat transfer to the O-ring  116  (and to the insertion portion  112 ), the materials of the O-ring  116  and the surrounding structure (e.g., intake manifold  20 ) do not have to be specially modified to accommodate high temperature. For example, the O-ring  116  can be constructed of a common synthetic rubber (e.g., fluoropolymer elastomer such as Viton®), rather than a vastly more expensive perfluoroelastomer O-ring. In some constructions, the wall  113  has a material thickness between about 0.010 inch and about 0.030 inch. In some constructions, the gap between the body  106  and the insertion portion is between about 0.040 inch and about 0.250 inch, measured radially at the axial position of the O-ring  116 . The insertion portion  112  can be stamped metal (e.g., steel) in some constructions. The insertion portion  112  may be secured and/or sealed with one or both of the body  106  and the flange portion  114  (e.g., by crimping, laser welding, adhesive bonding, etc.) at its respective ends, but is not in heat conductive relationship with the body  106  at any point between the ends of the insertion portion  112 . In other words, the insertion portion  112  has an axial length L 1 , between the ends of which, space is maintained between the inside of the wall  113  and any portion of the body  106 , the ceramic bushings  108 , the seal packing  110 , and the sensing element  104 . The length L 1  is defined as a portion corresponding to and overlapping with the bore  117  of the manifold  20  in cross-section. The length L 1  of the insertion portion can be at least twice an axial height or length L 2  of the O-ring  116 , which is positioned somewhere within the length L 1 .  FIGS. 9 and 10  are thermal models comparing an O-ring  116  mounted on the body  106  to the O-ring  116  mounted on the insertion portion  112 , spaced from the body  106  by the gap. 
         [0023]    Although the space between the outside of the body  106  and the inside of the wall  113  may be a closed or sealed space as described above, it may also be a vented space in some constructions. In some constructions, the wall  113  is sealed at a first axial end (e.g., by a circumferentially securing to the transverse flange  114  by laser welding or another means) and unsealed at the opposite second end. Although it may or may not be touching the body  106  at the second end, the second end may be completely free from connection to the body  106 . In some constructions, one or more venting apertures are provided in the wall  113 . 
         [0024]      FIGS. 3 and 4  illustrate a gas sensor  200  according to a second construction. The gas sensor  200  is particularly adapted for use in a low temperature (non-exhaust) environment. Features of the gas sensor  200  that are similar to the gas sensor  100  are not described in detail again, and similar reference numbers are used, incremented by  100 . 
         [0025]    The gas sensor  200  is identical to the gas sensor  100  of  FIGS. 1 and 2 , except that the wall  213  of the insertion portion  212  is integrally formed as a single piece with the transverse flange portion  214 . For example, the wall  213  of the insertion portion  212  and the transverse flange portion  214  can be stamped as a single contiguous piece. The flange portion  214  can have a wall thickness substantially equal to that of the wall  213 . This may be significantly thinner than the thickness of the flange portion  114  of  FIGS. 1 and 2 , although the flange portion  114  may be provided with a thinner wall thickness in other constructions. 
         [0026]      FIGS. 5 and 6  illustrate a gas sensor  300  according to a third construction. The gas sensor  300  is particularly adapted for use in a low temperature (non-exhaust) environment. Features of the gas sensor  300  that are similar to the gas sensors  100 ,  200  are not described in detail again, and similar reference numbers are used, incremented by  100 . 
         [0027]    The gas sensor  300  is identical to the gas sensor  100  of  FIGS. 1 and 2 , except that the wall  313  of the insertion portion  312  is integrally formed as a single piece with a protection tube  320 . For example, the wall  313  of the insertion portion  312  and an outer protection tube  320  of a pair of protection tubes  320  can be formed (e.g., stamped) as a single contiguous piece. The protection tube  320  can have a wall thickness substantially equal to that of the wall  313 . 
         [0028]      FIGS. 7 and 8  illustrate a gas sensor  400  according to a fourth construction. The gas sensor  400  is particularly adapted for use in a low temperature (non-exhaust) environment. Features of the gas sensor  400  that are similar to the gas sensor  100 ,  200 ,  300  are not described in detail again, and similar reference numbers are used, incremented by  100 . 
         [0029]    The gas sensor  400  is identical to the gas sensor  100  of  FIGS. 1 and 2 , except that the wall  413  of the insertion portion  412  is integrally formed as a single piece with the transverse flange portion  414  as in the gas sensor  200  of  FIGS. 3 and 4 , and is integrally formed as a single piece with a protection tube  420  as in the gas sensor  300  of  FIGS. 5 and 6 . For example, the wall  413  of the insertion portion  412 , the transverse flange portion  414 , and the protection tube  420  (e.g., an outer protection tube) can be stamped as a single contiguous piece. The flange portion  414  and the protection tube  420  can each have a wall thickness substantially equal to that of the wall  413 . 
         [0030]    Various features and advantages of the invention are set forth in the claims.