Patent Application
20140311212
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.
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.
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.
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
The O-ring heat shield can have several constructions, some of which are described and illustrated herein.
In all cases the device may be made in one piece or as an assembly of pieces from similar or dissimilar materials.
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).
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.
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 L1, 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 L1 is defined as a portion corresponding to and overlapping with the bore 117 of the manifold 20 in cross-section. The length L1 of the insertion portion can be at least twice an axial height or length L2 of the O-ring 116, which is positioned somewhere within the length L1.
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.
The gas sensor 200 is identical to the gas sensor 100 of
The gas sensor 300 is identical to the gas sensor 100 of
The gas sensor 400 is identical to the gas sensor 100 of
Various features and advantages of the invention are set forth in the claims.
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.
This invention was made with Government support under DE-EE0005975 awarded by the Department of Energy. The Government has certain rights in this invention.
| Number | Date | Country | |
|---|---|---|---|
| 61813922 | Apr 2013 | US |
