Abstract:
A low-resistance hydrocarbon-adsorptive cartridge for an air intake of an internal combustion engine comprising a structure for being mounted into a portion of an engine air intake system. The structure is adapted to orient and retain one or more thin sheets of activated carbon sheeting in the intake system. Preferably, a plurality of sheets is oriented such that the leading edge of each sheet is presented to the engine intake air stream, thereby minimizing reduction in total cross-sectional area of the intake system. Preferably, the one or more sheets are spaced apart by a distance that is small relative to the extent of the elements 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 a surface of at least one of the adsorptive sheets and thus be adsorbed.

Description:
TECHNICAL FIELD  
       [0001]     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 hydrocarbon adsorber cartridge, 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  
       [0002]     Gasoline-fueled motor vehicles have many sites from which hydrocarbons (HC) may evaporate into the environment, thereby contributing to the formation of smog. 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 means 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.  
         [0003]     Employing an engine&#39;s electronic throttle control to close the intake at shut down may impair the desirable option of a so-called “limp-home” mode in which a vehicle may be driven in the event of a partial failure of the engine electronics control system. Systems with mechanical throttles not employing electronic throttle controls typically close the throttle at shut down leaving a separate “idle air” passage open. In these systems, achieving a completely sealed manifold is difficult and expensive.  
         [0004]     Carbon sheeting applied to inner surfaces of the manifold and air ducts is only partially successful because much HC laden air can 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.  
         [0005]     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 volume 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.  
         [0006]     What is needed in the art is a means for providing hydrocarbon adsorption during engine shutdown at the main air entrance to an engine while minimizing intake air restriction during engine operation.  
         [0007]     It is a principal object of the present invention to reduce hydrocarbon emissions from a shut down internal combustion engine.  
         [0008]     It is a further object of the invention to minimize the restriction of combustion air inflow into the engine caused by a hydrocarbon-adsorptive means.  
       SUMMARY OF THE INVENTION  
       [0009]     Briefly described, a low-resistance hydrocarbon-adsorptive cartridge in accordance with the invention comprises a structure for mounting into a portion of an engine air intake system. The structure is adapted to orient and retain one or more thin sheets of activated carbon sheeting in the intake system. Preferably, a plurality of such sheets is oriented such that the cross-sectional area of each sheet is presented to the engine intake air stream, thereby minimizing reduction in total open area of the intake system. Preferably, the one or more sheets are spaced apart by a distance that is small relative to the extent of the sheets 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 a surface of at least one of the adsorptive sheets and thus be adsorbed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:  
         [0011]      FIG. 1  is an exploded isometric view of a prior art rigid monolithic hydrocarbon adsorber installed in an air intake for an internal combustion engine;  
         [0012]      FIG. 2  is an isometric view of a first embodiment in accordance with the invention of a cartridge for use in adsorbing hydrocarbons in an engine air intake;  
         [0013]      FIG. 2   a  is a front elevational view of a variation of the first embodiment shown in  FIG. 2 ;  
         [0014]      FIG. 3  is an isometric view of a second embodiment of a cartridge;  
         [0015]      FIG. 4  is a front elevational view of a third embodiment of a cartridge;  
         [0016]      FIG. 5  is a side elevational view of the cartridge shown in  FIG. 4 ;  
         [0017]      FIG. 6  is a side elevational view of an alternate embodiment of the cartridge shown in  FIG. 5 ;  
         [0018]      FIGS. 7-9  are elevational views of various shaped slates in a view shown as circle A in  FIG. 5 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]     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.  
         [0020]     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 .  
         [0021]     An adsorber member  34 , also referred to as a flow regulator, 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 enter the atmosphere.  
         [0022]     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.  
         [0023]     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.  
         [0024]     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.  
         [0025]     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.  
         [0026]     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 large-diameter flow passages to reduce viscous drag flow losses.  
         [0027]     Referring to  FIG. 2 , a first embodiment  134  of a cartridge in accordance with the invention 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. Preferably, the embodiments shown herein can replace or substitute directly for prior art monolithic adsorber  34 .  
         [0028]     First 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  102   a  ( FIG. 2   a ), but the spiral configuration is currently preferred for manufacturing simplicity.  
         [0029]     A currently preferred 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.  
         [0030]     Cartridge  100  presents only the thin leading edge  106  of strip  102  to air  140  flowing through the cartridge and thus provides a very large open area and very low air restriction in comparison to the preferred honeycomb monolith of prior art adsorber  34  which has relatively large wall cross-sections with respect to the open area.  
         [0031]     Referring to  FIG. 3 , a second embodiment  234  of a cartridge in accordance with the invention is similar to first embodiment  134 . However, the adsorptive element is formed as a plurality of corrugated sheets  202  installed longitudinally into opening  210  of housing  200  and preferably separated by spacers  204 . Preferably, sheets  202  are formed of the same carbon paper material as strip  102 . As in first embodiment  134 , cartridge  200  presents only the thin leading edges  206  of strips  202  to air  240  flowing through the cartridge and thus provides a very large open area and very low air restriction. Further, as in first embodiment  134 , the adsorptive element is curved or folded in a direction transverse to air flow through the cartridge and thus has great rigidity and dimensional stability.  
         [0032]     Referring to  FIGS. 4 and 5 , a third embodiment  334  includes a rectangular housing  300  for use with a rectangular air duct. Individual strips  302  of carbon paper material extend across an opening  310  of housing  300 , presenting strip edges  306  to air  340  flowing through the cartridge. Because strips  302  are substantially planar and thus lack the rigidity imparted by bending in embodiments  134 , 234 , unsupported strips  302  can flutter from the air flow and therefore generally require support in the form of slats  312  extending from sides  314   a , 314   b  of housing  300 . Preferably, a strip  302  is disposed on each side of each slat  312 , as well as on the inner surfaces of sides  314   a , 314   b , and sides  316   a , 316   b . Strips  302  may be secured preferably by lamination with adhesive in known fashion. Of course, the number of slats  312  and the dimensions of housing  300  may be varied to meet specific application requirements.  
         [0033]     Further, the cross-sectional shape of slats  312  may be varied to create the intended effect and surface area of strips  302 . For example, slats  312  may be planar, as shown in  FIGS. 4 and 5 , or may be V-shaped ( 312 ′- FIG. 7 ), bull-nosed ( 312 ″- FIG. 8 ), or curved ( 312 ′″- FIG. 9 ) to provided a predetermined pressure drop, flow direction, and carbon surface area for an intended application. Slats  312  may also be varied in length  350  ( FIG. 6 ) to further provide a desired pressure drop, flow direction and absorptive area.  
         [0034]     Referring to  FIGS. 10-13 , a fourth embodiment  400  of a hydrocarbon-adsorptive cartridge in accordance with the invention is formed by die-cutting and folding from a suitable sheet  402  of material comprising an inert support  404  and a layer  406  containing activated carbon. Preferably, support  404  is formed of an inexpensive polymeric material, for example, polypropylene, that is capable of taking a heat set after final forming of the cartridge shape. Preferably, layer  406  is substantially equivalent or identical to carbon paper composition  102  and may be coated or bonded to support  404 . If desired, layer  406  may be coated to support  404  on both sides ( 406   a ,  406   b ) to increase further the adsorptive surface area of cartridge  400 .  
         [0035]     In an exemplary method of forming cartridge  400 , a suitably-sized portion  408  of material  402  is die-cut in a predetermined pattern  410  to form a plurality of flaps  412  which are then folded ( FIG. 13 ) to a predetermined angle  414  from portion  408  and then secured at angle  414  as by heat treating. Angle  414  may be an angle between 0 degrees and 90 degrees, as may be desired for optimal engine and adsorptive performance. Further, pattern  410  in the cutting die may be varied to provide any desired number and shape of flaps  412 . The border  416  surrounding flaps  412  defines a housing by which the cartridge may be attached or mounted.  
         [0036]     As shown in  FIG. 13 , the orientation of flaps  412  is selected to offer lesser resistance to the flow of engine induction air  450  when the engine is running. Optionally, the thickness and resilience of polymeric sheet  402  is selected to allow flaps  412  to flexibly open from a static position, to an extent, from the flow of induction air  450  and to flexibly close to the static position, after engine shut down.  
         [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.