Internal-combustion engines – Charge forming device – Crankcase vapor used with combustible mixture
Reexamination Certificate
2001-01-04
2002-04-23
McMahon, Marguerite (Department: 3747)
Internal-combustion engines
Charge forming device
Crankcase vapor used with combustible mixture
C123S19800E
Reexamination Certificate
active
06374815
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to relates to motorcycle engines and, more particularly, to air cleaner base assemblies that couple an air cleaner to a carburetor or fuel injection system and provide conduits for venting blow-by gases from the crankcase into a venturi air intake thereof.
As internal combustion engines wear, the annular spaces between the pistons and the cylinder tend to increase. In the combustion chamber of each cylinder, an air-fuel mixture is ignited. The expanding gas mixture forces the piston upwards generating power from the engine. In the expansion process, part of the gas mixture is forced between the annular spaces between the piston and the cylinder into the crankcase. These “blow-by” gases, which also include oil mist and unburned fuel, accumulate in the crankcase and must be vented from the crankcase to the atmosphere to prevent a potentially dangerous pressure build-up in the crankcase.
Pollution control laws and regulations restrict the emissions from internal combustion engines. As exhaust gases from internal combustion engines have become cleaner, the blow-by gases have become a more significant fraction of the total pollution generated from internal combustion engines. In many localities, the pollution control laws and regulations are such that vapors from the crankcase of internal combustion engines must be cleaned prior to discharge into the atmosphere. One method of reducing the pollution associated with the blow by gases is to recycle the gases through the engine. In some four cycle, two cylinder engines manufactured by Harley-Davidson, crank case venting and cleaning is accomplished by a crankcase breather system that conducts blow-by gases from the crankcase to an air cleaner, from which the gases are recirculated back into the engine through the carburetor for burning in the engine cylinders. A crankcase breather system is also used for engines employing a fuel injection system.
By way of example, in the Harley-Davidson four cycle, two cylinder engines each cylinder includes a pair of push rods that extend from the crankcase into the cylinder head for operating the intake and exhaust valves. Each of the push rods is disposed within a hollow push rod tube that communicates with the crankcase (e.g. provide a passageway for blow-by gases in the crankcase). Upper ends of the push rod tubes communicate with a chamber in the middle rocker box of each cylinder head. On each downstroke of the piston in each cylinder, an umbrella valve attached to a center rocker spacer opens, permitting blow-by gases to pass into the middle chamber. From the middle chamber, the blow-by gases are conducted to a second, upper chamber in the rocker box, and thence, via passageways, through a pair of spaced-apart, threaded holes in a right side of the cylinder heads. The threaded holes in combination with hollow bolts enable a stock plastic backing plate to be secured to the cylinder heads. The hollow bolts provide a passageway for the blow-by gases to vent from the holes in the cylinder heads. In a stock version of the Harley Davidson engine with a carburetor, a stock plastic carburetor or backing plate is provided, together with a pair of rubber tubes to conduct the blow-by gases from the hollow bolts to an air cleaner element.
To improve and customize engine performance, many purchasers of Harley Davidson motorcycles owners remove and discard the stock carburetor backing plate, hollow bolts and rubber tubes and replace the system with a substitute crankcase breather system. These substitute crankcase breather systems, for instance, by improving air flow to the engine, can significantly improve the horse power of the engine within certain operational ranges. Examples of substitute crank case breather systems are described in U.S. Pat. No. 5,233,967 by Peller et al. and U.S. Pat. No. 5,937,816 by Wincewicz et al.
In the background Wincewicz et al., the disadvantages of the Peller system are described in detail, such as a large part count and vibration/seal problems. The large part count of the Peller system increases the installation, the manufacturing and the maintenance costs associated with utilizing the system. The vibration/seal problems, however, may cause oil leakage at the joint between the breather system and the cylinder head or air leakage where the system attaches to the carburetor. Such leakage problems are also characteristic of other types of breather systems, as well.
While the breather system of Wincewicz is suitable in most applications, one problem associated with this design is that the blow-by gases, which contain oil and fuel mist, are vented directly into the air cleaner. These blowby gases tend to foul the air cleaner which substantially increases the replacement frequency of the air cleaner. Both the Peller system and the stock Harley-Davidson breather system, incidentally, also suffer from this fouling problem. Another disadvantage of the Wincewicz system is that the blow-by gases are vented from the cylinder heads in a manner where they may interfere with one another. Since the blow-by gases are vented into a common communication channel, the portions vented during the piston downstroke in one cylinder, can interfere with outflow of blow-by gases from the other cylinder during its piston upstroke.
Accordingly, it would be desirable to provide a crank case breather system that is easy to install, utilizes a minimum number of components, eliminates airflow interference effects, preserves air cleaner performance and minimizes seal leakage problems.
SUMMARY OF THE INVENTION
This invention addresses the needs indicated above by providing a combination backing plate and crankcase breather for a motorcycle engine having at least a pair of cylinders, a cylinder head mounted on each cylinder and a valve for connecting each cylinder head to the crankcase for venting the crankcase through an exit port in the cylinder head. The combination includes two hollow bolt alignment members integrally connected by brackets to a support member. The support member includes a venturi air intake, an air cleaner support surface and a backing plate. The backing plate is adapted to allow the support member to be mounted to the air intake of the motorcycle engine. The air intake of the motor cycle engine may be connected to a carburetor or a fuel injection system. The air cleaner support surface is adapted to allow an air cleaner and air cleaner cover to be mounted to the combination. Each bracket includes a conduit that allows blow-by gases vented from the engine through exit ports in the cylinder heads to be conducted.to an exit port in the venturi air intake where the blow-by gases are mixed with outside air and recirculated into the engine.
One aspect of the present invention provides an air cleaner base assembly for a motorcycle engine including at least one cylinder head having a communication port for venting a crankcase, an air cleaner and an air intake port of a fuel system. The base assembly can be generally characterized as including: 1) an air cleaner support member having a first side positioned adjacent the air intake port and an opposite second side adapted to seat the air cleaner thereto, the support member further including a venturi portion defining an intake aperture extending from the second side to the first side, and having a transverse cross-sectional dimension substantially similar to that of the air intake port of the fuel system for air flow from the air filter, through the intake aperture and into the air intake port; and 2) a flange member mounted to the support member, and adapted to mount said support member to the cylinder head, the flange member defining a communication conduit extending therethrough, and having an entrance port in flow communication with the communication port of the cylinder head and an opposite exit port terminating at the venturi portion.
In particular embodiments, the flange member may further define a bolt alignment passage formed for coaxial alignment with the communication port of the cylin
Border Jeffrey D.
Ness Cory A.
Arlen Ness Enterprises, Inc.
Beyer Weaver & Thomas LLP
McMahon Marguerite
LandOfFree
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