Patent Application
20080196698
N/A
N/A
The present invention relates to internal combustion engines and, more particularly, to apparatuses and methods for controlling or restricting evaporative emissions from such engines.
Internal combustion engines are used in a wide variety of applications. As a result of the internal combustion process, and the need for fuels to perform that process, such engines necessarily generate emissions having a variety of carbon-based and other substances. Increasingly, it is desired that internal combustion engines operate in a manner such that at least one or more components of these emissions be reduced or eliminated.
Further, small engine manufacturers are subject to both exhaust and evaporative emissions regulations by the Environmental Protection Agency (EPA) and California Air Resource Board (CARB) commencing with engines produced for the 2006 model year. The emissions limitations set by these agencies will become more stringent with each successive year and are expected to plateau in the year 2009. Hydrocarbon molecule concentration is the primary component measured by the EPA and CARB.
A major source of hydrocarbon emissions from internal combustion engines is evaporated fuel emanating from plastic fuel tanks, which are typically made from high density polyethylene (HDPE), polypropylene, polyamide (PA) or other low cost materials, as well as fuel tank caps. An additional source of evaporative emissions is evaporated fuel emanating from carburetors.
One approach being adopted by the small engine industry to reduce such evaporative emissions is to employ the use of a carbon canister (CC) as a temporary repository of fuel vapors produced by the fuel tank, the carburetor fuel bowl or a combination of the two when the engine is not functioning. At some time upon start-up of the engine, the CC is purged of the stored vapor. This type of control system is commonly referred to as an “open system design.”
There are typically two types of control valves associated with a CC. The first type of valve is known as a roll-over valve (ROV). Most commonly, a ROV couples the CC to the fuel tank, and functions to allow vapor to vent only from the fuel tank. The ROV must prevent liquid from entering the CC or it will be rendered useless. In some systems, there is an additional ROV by which the CC is attached to the carburetor fuel bowl vent. The second type of valve is known as a purge valve (PV), and functions to control vapor flow from the CC into the main induction line of the carburetor to the engine. The PV is controlled by engine manifold operation, venturi vacuum operation, or a combination of the two processes.
Although the open system design does provide some control over evaporative emissions, such a system has several disadvantages. First, the CC can be damaged from excessive engine vibration. Second, the CC can be rendered useless if liquid fuel enters the carbon chamber. Third, it can be difficult to locate the components of an open system design such that the components are not damaged from interaction or friction with other engine components. Fourth, when the system contains only one ROV, hydrocarbon emission from the carburetor is not accounted for and can potentially be released, thereby resulting in undesirably high emissions (such as could result in an emission level test failure). The addition of a second ROV to the carburetor can potentially help to reduce this problem but can be costly.
Therefore, it would be advantageous if an improved system (or systems) could be developed for reducing hydrocarbon leakage or evaporation of fuel (or potentially other emissions) into the surrounding environment from internal combustion engines including, for example, small engines. In at least some embodiments, it would be advantageous if such an improved system was capable of reducing the amount of fuel vapor escaping from several engine components including, for example, the carburetor, the carburetor fuel supply hose, vacuum hoses, the fuel tank and/or the fuel tank filler cap.
In at least some embodiments, the present invention relates to an emission control apparatus for an engine that includes a first valve assembly that regulates a first flow of fuel from a fuel bowl into a carburetor, a second valve assembly that regulates a second flow of fuel vapors from a fuel bowl and a fuel tank into a region upstream of an engine cylinder, and an actuator that controls opening and closing of said first valve assembly and said second valve assembly.
Further, in at least some embodiments, the present invention relates to an engine that includes (a) a carburetor; (b) a fuel bowl supported in relation to the carburetor; (c) a fuel tank coupled to the fuel bowl; and (d) a first valve assembly, where the first valve assembly comprises an input port coupled to the fuel tank and the fuel bowl to receive vapors therefrom. Also, the engine includes; (e) a second valve assembly, where the second valve assembly regulates a flow of fuel from the fuel bowl into the carburetor, and (f) an actuator coupled at least indirectly to each of the first and second valve assemblies, whereby opening and closing of the first valve assembly and second valve assembly is regulated.
Additionally, in at least some embodiments, the present invention relates to a method for reducing emissions from an engine. The method includes providing an assembly including a fuel tank, a carburetor, a fuel bowl coupled to the fuel tank and the carburetor, a first valve assembly coupling the fuel bowl with the carburetor and governing a first flow of fuel from the fuel bowl to the carburetor, and a second valve assembly coupling at least one of the fuel tank and the fuel bowl to a region upstream of a cylinder. The method further includes opening the second valve assembly to allow a first flow of fuel vapors from the at least one fuel bowl and fuel tank into the region, and subsequently opening the first valve assembly to allow a second flow of fuel from the fuel bowl into the carburetor.
Further, in at least some embodiments, the present invention provides a method by which, when first and second valve assemblies are both closed, evaporative emissions from the carburetor, the fuel bowl and the fuel tank are substantially prevented. Also, in at least some embodiments, the present invention relates to a method by which, when first and second valve assemblies are both closed, a rapidity with which the fuel within the fuel tank becomes stale is reduced.
The present invention relates to a variety of embodiments of systems and related methods of operation of mechanical components for reducing evaporation of fuel or hydrocarbon leakage into the environment from a variety of different internal combustion engines including, for example, gasoline or diesel engines. Although several specific embodiments are described below with reference to the FIGS., it should be understood that the present invention is intended to encompass a variety of other embodiments of mechanical components and related parts other than (or in combination with) the particular systems and components that are shown and described with reference to the FIGS.
Also, while the systems of mechanical components to reduce evaporation or hydrocarbon leakage of fuel to the surrounding atmosphere encompassed within the present invention are intended to be applicable to a wide variety of engines, in particular, the described invention is intended to be applicable to Class 1 and Class 2 small off-road engines such as those implemented in various machinery and vehicles, including, for example, lawn mowers, snow mobiles and the like. In at least some such embodiments, the present invention is intended to be applicable to “non-road engines” as defined in 40 C.F.R. §90.3, which states in pertinent part as follows: “Non-road engine means . . . any internal combustion engine: (i) in or on a piece of equipment that is self-propelled or serves a dual purpose by both propelling itself and performing another function (such as garden tractors, off-highway mobile cranes, and bulldozers); or (ii) in or on a piece of equipment that is intended to be propelled while performing its function (such as lawnmowers and string trimmers); or (iii) that, by itself or in or on a piece of equipment, is portable or transportable, meaning designed to be and capable of being carried or moved from one location to another. Indicia of transportability include, but are not limited to, wheels, skids, carrying handles, dolly, trailer, or platform.”
Further, at least some additional embodiments, the present invention applies to engines that have less than one liter in displacement, or engines that both have less than one liter in displacement and fit within the guidelines specified by the above-mentioned regulations. In still further embodiments, the present invention is intended to encompass other small engines, large spark ignition (LSI) engines, and/or other larger (mid-size or even large) engines. In at least some embodiments, the present invention applies to a v-twin engine.
Referring to
The second valve assembly 8 has an input port 35 (which is partially hidden in
As shown in
As shown, the fuel tank 12 includes a fuel cap 13 at a top (or upper) surface 15. The fuel tank vapor hose 10 also is coupled to the fuel tank 12 proximate to the top surface 15, since that is where vapors tend to collect, while the supply line 14 is coupled proximate a bottom surface 17 of the fuel tank. In an alternative embodiment, a first fuel tank vapor hose can be used to couple the input port 35 with the fuel tank 12 and a second fuel tank vapor hose can be used to couple the fuel tank to the exit port 81 of the fuel bowl 4.
The fuel tank 12, fuel cap 13, fuel tank vapor hose 10, and engine fuel supply line 14 all are preferably manufactured from materials that are non-permeable with respect to hydrocarbon/fuel vapors. Low permeation materials that can be utilized for these structures (and particularly for the fuel tank) depending upon the embodiment can include, for example, injection molded (single-layer) materials such as polyphthalamide (PPA), compounded blends of polycarbonate and polybutylene terephthalate (PC+PBT), or polyphenylene sulfide (PPS). Multi-layer (e.g., blow, roto or hot plate twin sheet molded) materials such as EVOH (ethylene vinyl alcohol copolymer) sandwiched between HDPE (high density polyethylene) or PP (polypropylene) can also be employed. Additionally for example, an overmold process involving 2-injection molded materials can be employed (for example, where an inexpensive material such as polyamide (PA) is molded over a thin PPS shell).
Referring to
As for the second valve assembly 8, that valve assembly serves to control the provision of hydrocarbon or fuel vapors at the input port 35, which are from the fuel tank 12 and the fuel bowl 4, to the output port 37. When the handle 16 is in the “off” position, the second valve assembly 8 is closed, such that hydrocarbon/fuel vapors are prevented from escaping from the fuel tank 12 or fuel bowl 4 to the atmosphere via the airbox/air filter housing 9 (or otherwise).
In contrast, as the handle 16 is moved along a direction indicated by an arrow 73 toward an “on” position, which in the present embodiment also results in the engine being turned on, the second valve assembly 8 is opened partly. While the input port 35 of the second valve assembly 8 is connected to the fuel tank 12 and the fuel bowl 4, the output port 37 of that assembly is coupled to the air filter housing 9 (as mentioned above, particularly downstream of the air filter) of the engine, which can be located along the intake of the engine such as between the air filter and the carburetor 6. Thus, when the second valve assembly 8 is opened, fuel vapors and excess pressure buildup within the fuel tank 12, fuel bowl 4 and fuel tank vapor hose 10 is discharged to the airbox and the engine intake.
As the handle 16 continues to be opened further along the direction of the arrow 73, the second valve assembly 8 allows for a continued connection between the fuel tank 12, fuel bowl 4 and the airbox, and additionally the first valve assembly 2 is opened so as to allow fuel from the fuel bowl 4 to enter the carburetor 6. Fuel is provided to the carburetor 6 due to the pressure differential between atmospheric pressure and the reduced pressure existing within the carburetor due to its venturi action. Additionally at this time, fumes arising from the fuel tank 12 and fuel bowl 4, including fumes that arose from the fuel tank 12 and fuel bowl 4 while the engine was off, are drawn into the engine by way of the intake rather than discharged into the atmosphere.
Given the above-described design, the present embodiment of the evaporative emissions control system 1 can be referred to as a “closed system design” insofar as it largely, if not entirely, eliminates the discharge of fuel and/or other hydrocarbon fumes to the atmosphere. More particularly, the emission of fuel fumes from the carburetor 6 when the engine is turned “off” is reduced since fuel is precluded from flowing from the fuel bowl 4 to the carburetor 6 at this time. Also, fuel fumes arising from the fuel tank 12 and the fuel bowl 4 are trapped by the second valve assembly 8 when the engine is off. By manufacturing the fuel tank 12 (including fuel cap 13), fuel bowl 4 and fuel tank vapor hose 10 out of materials that themselves are not permeable to hydrocarbon/fuel vapors, these vapors thus cannot escape to the atmosphere at this time. Additionally, because the system 1 prevents the release of fumes while the engine is off, the system also provides the added benefit of preventing the fuel remaining within the fuel tank 12 and fuel bowl 4 from becoming stale during long periods of engine inactivity.
The triggering of the second valve assembly 8 to open just when the engine is being turned on is advantageous insofar as the commencement of engine operation tends to create a vacuum pressure causing the hydrocarbon/fuel vapors within the fuel tank 12, fuel bowl 4 and fuel tank vapor hose 10 to be sucked into the engine via the second valve assembly. Additionally, the staggered opening of the second valve assembly 8 subsequent to the opening of the first valve assembly 2 in the above-described manner is desirable in that it reduces pressure buildup within the fuel tank 12 and the fuel bowl 4 prior to allowing fuel to flow into the carburetor 6. As a result, the likelihood that a premature and excessive injection of fuel into the carburetor 6 will occur upon opening of the first valve assembly 2 is reduced. In at least some alternate embodiments, the opening of the first and second valve assemblies 2, 8 is performed in an intermittent manner, a non-staggered manner, or in other manners.
Turning to
In addition to the body portions 28, 30, the first valve assembly 2 further includes a piston 33 that extends axially through both of the body portions. A first end 75 of the piston 33 that protrudes from the neck portion 18 of the first body portion includes a fuel-impervious overmolded fluorosilicone rubber plunger tip 22. Two valve body piston sealing O rings 24, which also are made from fuel impervious fluorosilicone rubber, seal between the internal surface of the neck portion 18 and piston 33 to prevent external leakage of the valve assembly. Further, the first valve assembly 2 includes a stainless steel (or brass) piston return spring 26.
When the engine is not running (e.g., the handle 16 is in the “off” position), the piston return spring 26 forces the piston 33 toward the neck portion 18 as shown, so as to force the piston tip 22 into the carburetor fuel supply passage 79 (see
Turning to
In at least some embodiments, the body portions 32, 39 and piston 34 are injection molded with a thermoplastic material, for example, various forms of PA including PA-6 and PA-66 (e.g., Zytel® nylon available from E. I. du Pont de Nemours and Company of Wilmington, Del., or Gelon® A100 nylon available from the General Electric Company of Fairfield, Conn.), PPA (e.g., Amodel® polyphthalamide available from Solvay Advanced Polymers, L.L.C. of Alpharetta, Ga.), PC+PBT (e.g., Xenoy® resins also available from GE), or PPS thermoplastic material. The caplike body portion 88 can in some embodiments be a Metalok Bantam plastic industrial circular connector (e.g., as available from Souriau USA of York, Pa.). Depending upon the material that is used, various degrees of fuel vapor permeation rates can be achieved.
Additionally as shown, the piston 34 has an upper portion 96 having a greater diameter substantially equaling the inner diameter of the first cylindrical body portion 32, a lower portion 99 having a relatively lesser diameter equaling the inner diameter of the second cylindrical body portion 39, and an intermediate portion 69 having largely an hour-glass shape that at its maximum points (e.g., at the opposite ends) has only the lesser diameter of the lower portion 99. Also, in the present embodiment, the piston 34 is molded around a vapor control valve piston actuation rod 36, which can be made from steel or other suitable material, and which extends through the body portions 32, 39 along the central axis 97. The rod 36, which can be used to govern movement of the piston 34, can be influenced both along a top end 61 extending outward past the caplike body portion 88 and also along a bottom end 63 extending outward from the valve assembly from its lower end opposite the caplike body portion.
Further, two grooves are also formed around the exterior of the piston 34, which serve to support two (upper and lower) sealing O-rings 38, which can be made from fluorosilicone rubber material (e.g., made from Viton® flouroelastomer also available from du Pont). In the present embodiment, the upper one of the O-rings 38 (the O-ring closer to the caplike body portion 88) is positioned proximate the upper end of the piston 34 (again, the end that is closer to the body portion 88) and has at least a 5 psi minimum design rating, while the lower one of the two O-rings is positioned proximate the lower end of the piston 34 and has at least a 10 psi minimum design rating. Further, the second valve assembly 8 includes a piston return spring 40, which can be made from any suitable material including but not limited to stainless steel (or possibly other metallic materials).
In addition to the O-rings 38, the piston 34 along an annular lower rim 64 of the upper portion 96 also includes a washer seal 68 (e.g., again made from Viton® flouroelastomer and having at least a 10 psi minimum design rating). Movement of the piston 34 within the body portions 32, 39 is restricted insofar as the upper portion 96 is precluded from traveling downward within the first cylindrical body portion 32 beyond an annular ridge 74 that extends inwardly at approximately the same level as the upper edge of the input port 35 and the lower edge of the output port 37. When the piston 34 moves sufficiently downward within the valve assembly 8, the washer seal 68 on the upper portion 96 encounters the ridge 74 and forms a seal therewith.
Operation of the valve assembly 8 proceeds as follows. When the handle 16 (see
Although normally the handle 16 is in the “off” position and the valve assembly 8 (due to the operation of the spring 40) is in a closed position such as that shown in
As alluded to above, force applied to the top end 61 of the rod 36, for example by way of a system control cable 66 (see
Referring to
Further as shown, fuel tank portion 44 is composed of two body portions 48 and 49 that are welded together at a weld line 89. The upper body portion 48 of the tank portion 44 contains mounting features 78 for the complete assembly of the unified fuel tank and blower housing 42 to the engine. The lower body portion 49 of the tank 44 contains additional devices. For instance, the lower body portion 49 of the fuel tank 44 supports a shaft 50 along which a fuel float 52 can travel up or down depending on fuel volume. In at least some embodiments, the float mechanism can be constructed from two hemispheres and provide three functions: (1) to indicate a full fuel level condition, achieved with visual feed back from the upper float hemisphere; (2) to serve as a fuel restricting device and prevent fuel from entering the tank quickly, by partially sealing itself at the filler neck (e.g., as is necessary when an over full condition results from filling the tank quickly); and (3) to allow for the slow release of a fuel stabilizing chemical agent. The chemical agent can be added to the interior of the lower hemisphere of the float, slowly dissolving when in contact with fuel over a predetermined time. The chemical agent can be added in any suitable form including but not limited to liquid, a gel, or a solid. In at least some embodiments, the chemical agent is added as a gel or a solid. The chemical agent can be any agent that stabilizes fuel including but not limited to STA-BIL, Store Safe Fuel Stabilizer or Neutra Fuel Stabilizer.
The fuel tank portion 44 also includes a neck 98 to which can be coupled a fuel tank filler cap such as the cap 13 of
In at least some embodiments, the present invention additionally relates to a method to prime the engine with fuel for cold engine starting. More particularly, as discussed above, when the handle 16 is moved toward the “on” position, the second valve assembly 8 is opened allowing fuel vapors and excess pressure buildup within the fuel tank 12, fuel bowl 4 and fuel tank vapor hose 10 to be discharged to the airbox and the engine intake. The release of this pressure can serve to “prime” the engine.
The present invention is intended to be applicable to a wide variety of different types of engines, and in particular is not limited to single-cylinder engines. For example, embodiments of the present invention can be used in two-cylinder, four-cylinder or other multi-cylinder engines. Further, while the above-described embodiments primarily relate to a system of mechanical components to prevent evaporation or hydrocarbon leakage of fuel to the environment, in other embodiments, other types of evaporative emissions could also be prevented or reduced. Additionally, it is intended that the present invention also encompass embodiments in which there is variation of the individual components of the first and second valve assemblies but the first and second valve assemblies continue to function in the manner recited herein or in a similar manner. It should further be understood that the terms used herein to suggest relative positioning of different components (e.g., the use of the terms “upper” and “lower” in relation to the components of the valve assembly 8 of
It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein, but include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims.
