Abstract:
A low-resistance hydrocarbon adsorber comprising a spiral-wound laminated structure for mounting into an entrance port of an engine air intake system to prevent hydrocarbon evaporations from reaching atmosphere. Preferably, the adsorber is formed as a cartridge and comprises a flexible polymeric sheet support to which a thin flexible sheet of activated carbon sheeting is laminated on a first support side. The support is provided on a second side with features, for example, ribs or bumps, extending above the surface. When the laminate is spirally wound, the spiral convolutions are spaced apart by the features. Preferably, the convolutions are spaced apart by a distance such that there is a high probability that hydrocarbons migrating out of a shut down engine will encounter the adsorber and thus be adsorbed before reaching the atmosphere. The windings may fill all or a portion of the open area of the intake port.

Description:
RELATIONSHIP TO OTHER APPLICATIONS AND PATENTS  
       [0001]     The present application is a Continuation-In-Part of a pending U.S. patent application Ser. No. 11/044,504, filed Jan. 27, 2005. 
     
    
     TECHNICAL FIELD  
       [0002]     The present invention relates to internal combustion engines; more particularly, to devices for controlling hydrocarbon emissions from internal combustion engines; and most particularly, to a spiral-wound hydrocarbon adsorber, having low resistance to air flow, for preventing hydrocarbon leakage from the intake manifold of an internal combustion engine after engine shutdown.  
       BACKGROUND OF THE INVENTION  
       [0003]     Gasoline-fueled motor vehicles have many sites from which hydrocarbons (HC) may evaporate into the environment. HC in the atmosphere is a major contributor to smog formation. One such known site is the intake manifold of an engine. As HC emission regulations are tightened, a mechanism is needed to prevent HC vapor from escaping from the intake manifold after engine shutdown. Known approaches have included, among others, closing off the intake and idle air with the throttle valve when the engine is shut off; adding a rigid monolith structure formed of activated carbon into the intake air flow path of the air cleaner (see U.S. Pat. No. 6,692,551 B2); and lining the intake manifold, other air ducts, and/or the air cleaner with adsorptive carbon sheeting.  
         [0004]     Closing the intake and idle air with the throttle valve requires that the engine be equipped with electronic throttle control; many inexpensive engines are not so equipped. Further, so employing an engine&#39;s electronic throttle control may impair the desirable option of so-called “limp home” mode in which a vehicle may be driven in event of a partial failure of the engine electronics control system.  
         [0005]     Carbon sheeting applied to inner surfaces of the manifold and air ducts is only partially successful because some HC laden air could escape the manifold without being brought into proximity with an adsorptive surface. Relatively large areas of carbon sheeting are required to ensure that an adequate quantity of HC comes into contact with the adsorber.  
         [0006]     An adsorptive rigid monolith formed from activated carbon is unsatisfactory as it is expensive to fabricate, brittle and therefore vulnerable to breakage during assembly and use, and inherently restricts the flow of intake air. A known carbon monolith has an open area of only about 80%. The last shortcoming is especially undesirable as both engine performance and fuel efficiency can be adversely affected by undue air flow restriction.  
         [0007]     What is needed in the art is a means for providing hydrocarbon adsorption during engine shutdown near the main air entrance to an engine while minimizing intake air restriction during engine operation.  
         [0008]     It is a principal object of the present invention to reduce hydrocarbon emissions from a shut down internal combustion engine.  
         [0009]     It is a further object of the invention to minimize the restriction of combustion air inflow into the engine caused by a hydrocarbon-adsorptive device.  
       SUMMARY OF THE INVENTION  
       [0010]     Briefly described, a low-flow resistance hydrocarbon adsorber in accordance with the invention comprises a spiral-wound structure for mounting into an entrance port of an engine air intake system for adsorbing hydrocarbon evaporations and thereby preventing such evaporations from reaching atmosphere outside the engine. In a currently-preferred embodiment, the structure is formed as a cartridge to permit ready replacement as needed. The structure comprises a flexible inert polymeric sheet support, for example, polyethylene or polypropylene sheet, to which a thin flexible sheet of activated carbon sheeting is laminated on a first support side. The support is provided on a second and obverse side with a plurality of features, for example, ribs or bumps, extending above the surface such that when the laminate is spirally wound the spiral convolutions are spaced apart by the plurality of features. The spiral-wound structure is oriented and mounted into an air intake manifold inlet port with the spiral axis being parallel to the direction of air flow. Preferably, the convolutions are spaced apart by a distance (the height of the features) that is small relative to the extent of the structure in the direction of engine air flow such that a high probability is created that hydrocarbons migrating out of a shut down engine&#39;s intake manifold will encounter an adsorptive surface and thus be adsorbed before reaching the atmosphere. The spiral windings may fill all or only a portion of the open area of the intake duct. If spacing permits, the windings could be positioned so that the inner diameter of the hydrocarbon adsorber does not encroach into the air flow path. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:  
         [0012]      FIG. 1  is an exploded isometric view of a first prior art rigid hydrocarbon adsorber, comprising a rigid monolith, installed in an air intake for an internal combustion engine;  
         [0013]      FIG. 2  is an isometric view of a prior art cartridge comprising a spiral-wound carbon paper adsorption element;  
         [0014]      FIG. 3  is an isometric view of a laminated sheet for forming a spiral-wound adsorber in accordance with the invention;  
         [0015]      FIG. 4  is a front elevational view of a first embodiment of a spiral-wound adsorber formed from the laminated sheet shown in  FIG. 3 ; and  
         [0016]      FIG. 5  is a cross-sectional elevational view of a flexible intake manifold entrance element showing installation of the novel adsorber shown in  FIG. 4 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]     Referring now to  FIG. 1 , there is shown an exploded perspective view of a prior art engine intake air cleaner assembly  10  substantially as disclosed in U.S. Pat. No. 6,692,551 B2, the relevant disclosure of which is incorporated herein by reference. Air cleaner assembly  10  generally comprises a lower case  12  and an upper case  14  that houses one or more filter elements (not shown) for removing particulate matter from an air stream during operation of the internal combustion engine. Conduit  22  extends from upper case  14  to provide inlet-opening  24 . Preferably, conduit  22  is cylindrically shaped having an annular wall structure. During operation, inlet opening  24  permits entry of air into air cleaner assembly  10  and thence to the engine combustion chamber or chambers.  
         [0018]     A retainer  26 , preferably made from a resilient material, is disposed onto conduit  22  of upper case  14  and has a first open end  30  and a second open end  32 .  
         [0019]     An adsorber member  34 , also referred to as a flow straightener, is press fit into the opening defined by the first open end  30 . The conformity of shape of first open end  30  is preferably such as to produce an airtight seal between adsorber member  34  and wall  28  defining first open end  30 . As such, adsorber member  34  can generally be any shape that conforms to the shape of the opening defined by the first open end  30 . In this manner, all gases flowing into the air cleaner assembly  10  must flow through the adsorber member  34 . Likewise, any gases contained within the air cleaner assembly  10  such as, for example, those fuel gases that may accumulate in the air cleaner assembly  10  or migrate from the intake manifold after engine shutoff, must pass through the adsorber member  34  in order to escape the engine and enter the atmosphere.  
         [0020]     Prior art adsorber member  34  may comprise a substrate coated with pollutant treating material. The substrate can include any material designed for use in a spark ignition or diesel engine environment and which is capable of operating at elevated temperatures dependent upon the device&#39;s location and the type of system, which is capable of withstanding exposure to hydrocarbons, nitrogen oxides, carbon monoxide, particulate matter (e.g., soot and the like), carbon dioxide, and/or sulfur, and which has sufficient surface area and structural integrity to support a pollutant treating material, and, where desired, a catalyst. Some possible support materials include cordierite, silicon carbide, metal, metal oxides (e.g., alumina, and the like), glasses, and the like, and mixtures comprising at least one of the foregoing materials. Some ceramic materials include “Honey Ceram”, commercially available from NGK-Locke, Inc, Southfield, Mich., and “Celcor”, commercially available from Corning, Inc., Corning, N.Y. These materials are preferably in the form of monoliths (e.g., a honeycomb structure, and the like). Preferred monolith supports are carriers of the type having a plurality of fine, parallel gas flow passages extending therethrough from an inlet face to an outlet face of the carrier so that the passages are open to air flow entering and passing through the monolith.  
         [0021]     Although the substrate can have any size or geometry, the prior art size and geometry are preferably chosen to optimize surface area in the given design parameters. Preferably, the prior art substrate has a honeycomb geometry, with the combs&#39; through-channels having any multi-sided or rounded shape, with substantially square, triangular, pentagonal, hexagonal, heptagonal, or octagonal or similar geometries preferred due to ease of manufacturing and increased surface area. Also, although each comb forming the honeycomb may be of a different size, the prior art substrate preferably comprises a honeycomb structure wherein all combs are of about equal size. The substrate may comprise about 60 to about 600 or more fluid passageways (cells) per square inch of cross section. The thickness of the substrate may be about ⅛ inch to about 12 inches with about 0.5 to about 3 inches preferred. Preferably the passages are essentially straight from their inlet to their outlet and are defined by walls in which the pollutant treating material may be coated as a washcoat so that the gases flowing through the passages contact the pollutant treating material.  
         [0022]     The pollutant treating material can be capable of adsorbing pollutants contained in the air surrounding the substrate. Although the types of pollutants may vary widely depending on the environmental conditions to which the adsorber member  34  is exposed, contemplated pollutants include, but are not limited to, saturated and unsaturated hydrocarbons, certain carbon oxides (e.g., carbon monoxide), nitrates, sulfides, ozone, and the like, and combinations comprising at least one of the foregoing. Such pollutants may typically comprise 0 to 400 parts per billion (ppb) ozone, 1 to 20 parts per million carbon monoxide, 2 to 3000 ppb unsaturated hydrocarbons such as C.sub.2 to C.sub.20 olefins and partially oxygenated hydrocarbons such as alcohols, aldehydes, esters, ketones, and the like. In a preferred embodiment, the pollutant treating material selectively adsorbs unsaturated hydrocarbons such as those unsaturated hydrocarbons utilized in fuels and byproducts caused by combustion.  
         [0023]     The pollutant treating material may include adsorbers, such as silicate materials, activated carbon, activated carbons, sulfides, and the like, and combinations comprising at least one of the foregoing.  
         [0024]     As noted above, a honeycomb monolith structure preferred in accordance with the prior art, although an effective adsorber of hydrocarbons and other environmental pollutants, creates a large and undesirable pressure drop and flow restriction in the intake air flow path due to a large cross-sectional area of the structure and small-diameter air passages. What is needed is a cartridge for replacing a honeycomb monolith structure which has a large adsorptive surface area to maintain high adsorption but a low cross-sectional area to reduce intake air flow restriction and viscous drag flow losses.  
         [0025]     Referring to  FIG. 2 , a second prior art embodiment  134  of a cartridge is substantially as disclosed in parent US patent application Ser. No. 11/044,504. Embodiment  134  is suitable for use anywhere in an intake system  135  of an internal combustion engine  137  and preferably has the adsorption capabilities of prior art adsorber  34  as described above.  
         [0026]     Embodiment  134  comprises a structural housing  100  having an axis  101  and having a size and shape specifically selected to fit into a predetermined portion of the air intake ducting of an internal combustion engine, for example, cylindrical. A continuous strip  102  of a thin, flexible, activated charcoal sheet material is spirally disposed within opening  110  of housing  100  and may be bonded as by adhesive or insert molding to a plurality of radial retainers  104  to control and maintain spacing between the convolutions of the spiral. Retainers  104  may optionally include fingers  104   a  for holding adjacent strips of material in place. The width of strip  102  (which is the length of the adsorption path), the number of convolutions, and the spacing of the convolutions may be varied to meet specific application requirements. Of course, the convolutions alternatively may be formed by using a plurality of individual concentric cylindrical sheet elements.  
         [0027]     A suitable pollutant-treating material for strip  102  is an activated carbon paper available from MeadWestvaco Specialty Papers, Stamford, Conn., USA. This material contains up to 50% by weight of activated carbon and avoids the problem of carbon dusting because the carbon is added to the papermaking slurry prior to paper formation, resulting in a sheet with minimum shedding.  
         [0028]     While prior art cartridge  134  is highly effective in adsorbing hydrocarbon vapors, it has several practical problems.  
         [0029]     First, the activated carbon sheet material  102  can be difficult to roll precisely without creasing or cracking; hence, a durable support for the sheet material would be desirable.  
         [0030]     Second, the cabon sheet material is free-standing within housing  100  and can be subject to damage by unintended entry of foreign objects, thus partially blocking the inflow of air and potentially creating debris to be sucked into the engine.  
         [0031]     Third, the convolutions of carbon sheet material are not inherently spaced apart in the spiral and thus require retainers  104  and preferably fingers  104   a  extending from retainers  104  for positioning and retaining the convolutions in place, adding to the cost and complexity of manufacture of cartidge  134 .  
         [0032]     Referring to  FIG. 3 , a laminated sheet element  200  for forming a hydrocarbon adsorber apparatus comprises an activated carbon sheet material  202  substantially the same as pollutant-treating material  102  previously disclosed. A sheet backing element  203  is formed as by extrusion of a fuel-inert polymer such as polyethylene, polypropylene, nylon, or the like. Element  203  is of substantially uniform base thickness  205  and is provided with features  207  raised above a first planar surface  209 . Exemplary features shown in  FIG. 3  are transverse ribs  207   a  and bumps  207   b . Sheet material  202  is bonded in known fashion to a second planar surface  211  of backing element  203  to provide a durable support for the pollutant-treating material during fabrication and subsequent use of an adsorber in accordance with the invention.  
         [0033]     Referring to  FIG. 4 , a hydrocarbon adsorber  300  in accordance with the invention is formed by spiral-winding sheet element  200  such that features  207  define spacers against adjacent portions of carbon sheet material  202 , creating a spiral space  313  between the convolutions  314  of the spiral for flow of gas. Sheet element  200  may be wound with either the carbon sheet material  202  or the inert sheet backing element  203  on the outside, although in a currently preferred embodiment carbon sheet material  202  is on the inside to maximize exposure of the adsorptive material to migrating hydrocarbon vapors. Preferably, the convolutions are held together by conventional radial fasteners  315  such as staples, rivets, screws, pins, or the like.  
         [0034]     The number of convolutions in the spiral may be varied to meet the requirements of any specific engine application. In the extreme, the entire inner region  317  of adsorber  300  may be filled with convolutions, similar to prior art adsorber  134 . In less demanding applications, and especially where high airflow volumes are a requirement, fewer convolutions may be preferable, as shown exemplarily in  FIG. 4 .  
         [0035]     In a currently-preferred embodiment, adsorber  300  is fitted into a housing (not shown) similar to prior art housing  100  to form a cartridge.  
         [0036]     Referring to  FIG. 5 , an intake duct  400  for an engine  450  may be conveniently formed as a resilient corrugated boot having a pocket  452  molded therein for receiving adsorber  300 .  
         [0037]     While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.