Abstract:
The present specification discloses a system for providing a secondary air supply to an internal combustion engine so as to reduce undesirable exhaust gases. The system includes a hose running from a region of higher pressure to the exhaust port of the engine so as to supply air to such port. The area of higher pressure preferably comes from either a forward portion of the vehicle or from a high pressure region within the clutch compartment of the engine. A one-way valve is provided adjacent the exhaust port to eliminate any back flow. The method of providing secondary air supply is also disclosed.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates generally to emission control systems for internal combustion engines and, more specifically, to a secondary air supply system for an engine.  
       BACKGROUND OF THE INVENTION  
       [0002]     Systems have been developed to supply additional air to the hot exhaust gases of an internal combustion engine in order to reduce carbon monoxide and hydrocarbon emissions. Systems, such as that described in U.S. Pat. No. 6,382,197 to Matsumoto, employ a secondary air valve apparatus that pulls air from the air cleaner. The air is fed to the exhaust port—drawn by negative pressure created at the port when the combustion-chamber exhaust valves are closed. The additional air combined with the high temperatures present at the exhaust port helps complete combustion of unburned hydrocarbons and reacts with the carbon monoxide present to produce carbon dioxide.  
         [0003]     The exhaust gases are emitted in pulses, controlled by the exhaust valves as spent fuel from a combustion cycle is allowed to exit the combustion chamber. The resultant pressure waves are formed as the valves open and close. During the high-pressure portion of the wave, one-way valves, such as reed valves have been used to stop reverse flow of gases in the secondary air supply system. Further, air cut-off valves are employed to prevent excessive air from entering into the exhaust gas passage.  
         [0004]     An air supply system is also described in U.S. Pat. No. 5,590,522. An exhaust gas silencer includes suction plates to pull additional air into the exhaust gases running through the silencer. The plates are arranged against the exhaust gas flow so additional air is pulled through ports into the exhaust gas flow.  
         [0005]     The systems employed rely on complex arrangements of valves, springs, chambers, and pipes to properly send air to the exhaust port at the right time without backfire problems. Such systems are bulky and costly and may not adequately provide a pressure differential to supply adequate air for most efficient emissions cleaning without a separate air pump or loss of power.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention provides a secondary air supply to the hot exhaust of an internal combustion engine without expensive, complex control devices and bulky components. Installation on vehicles, such as all-terrain vehicles (ATVs), is simplified, effective, and inexpensive.  
         [0007]     The present invention provides a secondary air supply system for an internal combustion engine of a vehicle. The system includes a one-way valve in fluid communication with an exhaust port of the engine. A fluid channel extends from a region of relatively high air pressure to the exhaust port of the engine. The one-way valve is coupled to the fluid channel. In one preferred embodiment of the invention, the fluid channel extends from an area of air intake at the front of the vehicle. In another preferred embodiment, the fluid channel extends from a clutch compartment of the engine.  
         [0008]     In the first embodiment, the fluid channel comprises a hose extending from a front part of the ATV chassis, for example, forward of the engine radiator. The hose extends back to a reed valve coupled to the exhaust port of the engine. The rearward end of the hose is coupled to the reed valve. A short passage is disposed in the exhaust port running from the reed valve into a region of the exhaust gas exit from the combustion chamber. Preferably, the region of the short passage is cooled with a cooling means, such as air fins or an engine coolant fluid.  
         [0009]     In the second preferred embodiment, the air inlet is disposed in a region of relatively high air pressure created by the clutch fan. In this embodiment, preferably, the fluid channel is created with a hose extending from the clutch compartment to the exhaust port.  
         [0010]     A method of supplying a secondary air supply to the hot exhaust of an internal combustion engine of a vehicle is also provided. The method includes channeling air in the high-pressure region through a one-way valve to the hot exhaust gases exiting the combustion chamber of the engine. In a first preferred embodiment, the air is channeled from a forward end of the vehicle, preferably in front of an engine coolant system.  
         [0011]     In a second preferred embodiment, the air is channeled from a clutch compartment with a clutch fan. Air is fed to the channel from the region of the clutch compartment where the clutch fan blows air creating a region of higher air pressure.  
         [0012]     The present invention provides the advantages of simplicity and cost effectiveness. An auxiliary pump is not necessary to increase the pressure of the air that is fed to the exhaust port. The system is also small and easy to arrange in position since it is mainly comprised of a hose; the reed valve preferably being the only moving part. The secondary air supply assists the engine by creating lower emissions of noxious gases including hydrocarbons and carbon monoxide without adding significant weight or complication.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     Preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings.  
         [0014]      FIG. 1  is a side-elevational view of an all-terrain vehicle (ATV) with the system of the present invention;  
         [0015]      FIG. 2  is a view of the air intake system in a semi-schematic side-elevational view;  
         [0016]      FIGS. 3   a  and  3   b  illustrate the connections and detail of the reed valve assembly;  
         [0017]      FIG. 4  is a perspective view of an engine with the clutch compartment air source; and  
         [0018]      FIG. 5  is a semi-schematic view of a secondary air supply channeled into an exhaust pipe. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0019]     The present invention is ideally suited for motor vehicles such as all-terrain vehicles (ATVs) as illustrated in  FIG. 1  with ATV  10 . The invention, however, may be used with any internal combustion engine where cleaner emissions are desired.  
         [0020]     All-terrain vehicle  10  includes a frame  12  holding an engine  14 , wheels  16 , seat  18 , and handlebars  20 . A conventional ATV arrangement is thus provided and used as an example herein of how the present invention may be situated for use in a vehicle application.  
         [0021]     Engine  14  includes at least one cylinder  22 , a crankcase  24 , and a clutch compartment  26 . Cylinder  22  is generally positioned atop crankcase  24 . However, in alternate embodiments, multiple cylinders may be employed in various arrangements with crankcase  24 .  
         [0022]     The air intake system of engine  14  as shown in  FIGS. 1 and 2  includes an air intake plenum  28  at the forward end of the vehicle. Plenum  28  includes an air inlet in front of a radiator  30 . The air inlet of plenum  28  is at a forward portion of the vehicle for a maximum free flow of air into plenum  28 . The flow of air may increase as ATV  10  is driven in a forward direction. Air from plenum  28  is directed rearwardly through a hose into air box  32 . Air box  32  contains an air filter. The air is then channeled from air box  32  through another hose to carburetor  34 . Alternatively, other fuel mixture devices may be used such as throttle bodies and fuel injector systems. Fuel is mixed with air and sent through a hose or a pipe to cylinder  22  for combustion therein. In the preferred embodiment of the present invention, a four-stroke engine is employed, which uses valves to allow the entrance of a fuel air mixture and to allow the exit of exhaust gases once combustion is complete. However, the present invention may alternatively be employed with a two-stroke engine.  
         [0023]     The hot exhaust gases are allowed to exit exhaust port  36  through the side of cylinder  22 . Exhaust pipe  38  is secured to the side of cylinder  22  to allow the exit of the exhaust gases from ATV  10  through muffler  40 . Muffler  40  is typically mounted at a rear portion of ATV  10  such that the exhaust gases are not in the immediate vicinity of the area of the user of ATV  10 .  
         [0024]      FIG. 2  also illustrates, somewhat schematically, the connection of a secondary air hose  42  to the air inlet region of plenum  28  for channeling the secondary air supply to mix with the hot exhaust gases escaping cylinder  22 . Mixture of additional air with the hot exhaust gases can more thoroughly complete the combustion of unburned hydrocarbons and also react with the carbon monoxide present to produce carbon dioxide. Thus, the gases that escape exhaust pipe  38  and muffler  40  (not shown in  FIG. 2 ) are somewhat cleaner. An air hose inlet  46  is provided near the air inlet to plenum  28 . Secondary air hose  42  extends toward exhaust port  36  to feed air into exhaust port  36 . Alternatively, secondary air may be fed into exhaust pipe  38 . The primary concern for effective use of the secondary air supply is to feed the air at a point where the exhaust gas temperatures are high such that more completion of combustion and combination with carbon monoxide can be driven by the high temperatures.  
         [0025]     A one-way valve assembly  44  is connected between exhaust port  36  and secondary air hose  42 . In the preferred embodiment, a reed valve assembly  44  provides a one-way valve such that hot exhaust gases do not escape into secondary air hose  42 . A basic reed valve assembly may be employed comprising a stainless steel plate over an aperture. The plate is only able to open with pressure behind it such that any back pressure will close reed valve assembly  44  by pushing the stainless steel plate against the aperture that leads to secondary air hose  42 .  
         [0026]     The details of reed valve assembly  44  are illustrated in  FIGS. 3   a  and  3   b . Reed valve assembly  44  is secured to cylinder  22  adjacent exhaust port  36  at one end of a port passage  48  that extends from the main channel of exhaust port  36  through a wall of cylinder  22  to reed valve assembly  44 . Port passage  48  is kept short to avoid condensation and provide air quickly from secondary air hose  42  and reed valve assembly  44  to enter into the stream of exhaust gases exiting exhaust port  36  into exhaust pipe  38  (not shown in  FIG. 3 ). In a liquid-cooled engine, coolant is channeled nearby in a water jacket  49  in fluid communication with the main water jacket of cylinder  22 .  
         [0027]     Reed valve assembly  44  includes a valve body  50  having a hose connector  52  extending outwardly therefrom. Hose connector  52  is dimensioned to receive secondary air hose  42  thereon. A clamp or other fastening device is preferably employed to secure secondary air hose  42  to hose connector  52 . Valve body  50  includes holes for securement fasteners  54  to extend into cylinder  22  for a secure connection between reed valve assembly  44  and exhaust port  36 . A gasket or other sealing member (not shown) may be used between reed valve assembly  44  and exhaust port  36 .  
         [0028]     Hose connector  52  includes a channel that opens into a valve chamber  56 . Valve chamber  56  provides space for the movement of a reed valve  58  secured to an upstream face of valve chamber  56  and positioned to cover the aperture that leads from hose connector  52  into valve chamber  56 . Thus, when a positive pressure differential exists between secondary air hose  42  and valve chamber  56 , reed valve  58  is allowed to open to allow air to enter valve chamber  56 . However, when a negative pressure occurs, reed valve  58  is forced against the aperture to close off any backflow into secondary air hose  42 . A positive pressure situation will generally occur when the engine exhaust valves are closed such that the exit of gases from the cylinder is stopped. The exhaust valves (not illustrated) thus create waves or pulses of pressure with the exhaust gases. A high-pressure situation occurs when the gases are allowed to exit exhaust port  36 . In this situation, reed valve  58  experiences positive pressure such that it closes to ensure that the exhaust gases do not enter secondary air hose  42 . Immediately thereafter, however, reed valve  58  opens to admit fresh air into exhaust port  36  that will mix with the next pulse of exhaust gases to exit cylinder  22 .  
         [0029]     Not only is the trough of the pressure wave of exhaust gases used to create the negative pressure differential for transfer of fresh air to exhaust port  36 , the air intake of secondary air hose  42  being secured at the front of the vehicle where air is forced therein through movement of the vehicle also helps to create positive pressure.  
         [0030]     Another preferred embodiment for supplying secondary air to the exhaust gases while creating the positive pressure in a somewhat different manner is illustrated in  FIG. 4 . In this preferred embodiment, secondary air hose  42   a  does not extend from the front of the vehicle, but rather from a high-pressure region of clutch compartment  26 . Clutch compartment  26  has fresh air therein with certain regions of higher pressure as will be explained below. In this embodiment, secondary air hose  42   a  extends from a hose fitting  60  on clutch compartment  26 . Hose fitting  60  is screwed or otherwise fastened to clutch compartment  26  and includes a fitting onto which secondary air hose  42   a  may be secured. Secondary air hose  42   a  then extends to reed valve assembly  44  for supply of fresh air thereto. Secondary air hose  42   a  is preferably constructed of a Teflon ™ material with a flexible abraided stainless sheath thereabout for heat shielding protection.  
         [0031]     Clutch compartment  26  houses a drive clutch assembly  62  and a driven clutch assembly  64  with a belt  66  between the two. Such a combination of clutch assemblies provides an automatic variable transmission for ATV  10 . In this instance, it also provides a region of higher pressure within clutch compartment  26 . This is due to the arrangement of drive clutch assembly  62  having an inner sheave  68  with a clutch fan  70  thereon. Clutch fan  70  includes fins on the back side of inner sheave  68  that force air outwardly from the center of inner sheave  68  to the outer perimeter thereof along an area of clutch compartment  26  for circulating air thereabout to cool belt  66  and the other components within clutch compartment  26 .  
         [0032]     Air is supplied to clutch compartment  26  with clutch air inlet  72 . A hose extends from a region behind radiator  30  (not shown in  FIG. 4 ), to supply fresh air to clutch air inlet  72  at the forward end of clutch compartment  26 . A clutch air outlet  74  is provided at the other end of clutch compartment  26 . Thus, as air enters clutch air inlet  72 , it is circulated throughout clutch compartment  26  by clutch fan  70 , which is spinning with inner sheave  68  as it is connected to the crank shaft of engine  14 . The air from clutch fan  70  is driven against the region of clutch compartment  26  to which hose fitting  60  is secured. Thus, a positive pressure air supply is provided for feeding into secondary air hose  42   a .  
         [0033]     Various alternate embodiments may be employed that do not include an automatic variable transmission. For example, a fan may be employed to create a positive pressure differential within a standard clutch compartment that does not include a belt drive setup as illustrated herein. Other alternate embodiments of positive pressure regions that include an air supply are also contemplated and fall within the scope of the present invention.  
         [0034]     This embodiment, as illustrated in  FIG. 4 , provides a simplified system with very little components and only a single moving part (for a single cylinder engine). Thus, minimal maintenance is required to maintain a secondary air supply system. The system is easy to install and does not take up excess room or have excess weight to add to engine  14 . No external electric pumps are required, nor are complicated valve and diaphragm systems needed. Furthermore, the air supply system does not reduce engine power.  
         [0035]     If multiple cylinders are used, secondary air hose  42  or  42   a  may simply be channeled or split to the various cylinders with a reed valve for each cylinder. The system will work with catalytic converters if necessary as the gases can all be channeled to catalytic converters after mixing with the fresh air. The system can also be used with two-stroke engines, as mentioned above. Exhaust gas pulses still exist with two-stroke engines such that the feed of fresh air into the hot gases can likewise be accomplished.  
         [0036]      FIG. 5  illustrates another preferred embodiment of the invention with the secondary air supply entering an exhaust pipe  138 . A secondary air hose  142  is in fluid communication with an air supply. The air supply may be as described above from the front of the vehicle or from another source such as the clutch compartment. However, in this embodiment a positive pressure source of air is not necessary, as the arrangement creates negative pressure at the secondary air outlet. Preferably, air hose  142  channels air through a valve assembly  144  and an air channel  143 . Air channel  143  feeds air into exhaust pipe  138  with the end of the channel open to the interior of exhaust pipe  138 . Thus, hot, escaping gases rushing past the end of channel  143  create a low pressure region (venture effect) to pull additional air into the exhaust stream.  
         [0037]     While the preferred embodiments of the invention have been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the the preferred embodiment. Instead, the invention should be determined entirely to the claims that follow.