Patent Application
20070079604
This invention relates generally to emission control systems for internal combustion engines and, more specifically, to a secondary air supply system for an engine.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings.
a and 3b illustrate the connections and detail of the reed valve assembly;
The present invention is ideally suited for motor vehicles such as all-terrain vehicles (ATVs) as illustrated in
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.
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.
The air intake system of engine 14 as shown in
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.
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.
The details of reed valve assembly 44 are illustrated in
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.
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.
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.
Another preferred embodiment for supplying secondary air to the exhaust gases while creating the positive pressure in a somewhat different manner is illustrated in
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.
Air is supplied to clutch compartment 26 with clutch air inlet 72. A hose extends from a region behind radiator 30 (not shown in
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.
This embodiment, as illustrated in
If multiple cylinders are used, secondary air hose 42 or 42a 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.
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.
