Internal-combustion engines – Charge forming device – Supercharger
Reexamination Certificate
2003-06-10
2004-09-07
Trieu, Thai-Ba (Department: 3748)
Internal-combustion engines
Charge forming device
Supercharger
C123S439000, C123S437000, C261S069100, C261SDIG001, C261SDIG003, C261SDIG006, C137S494000
Reexamination Certificate
active
06786208
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to boost fuel enrichers used in internal combustion engines equipped with a turbocharger or supercharger. More specifically, the enricher is a device which is usable in carbureted or fuel injected engines with a boost pressure from a turbocharger or supercharger in a blow-through configuration, and which mechanically bypasses more fuel into the air-fuel mixture in order to avoid lean operation.
2. Description of the Related Art
A naturally aspirated internal combustion engine has a volumetric efficiency which is less than 100%. In order to compensate for this problem, many vehicles are equipped with a compressor in the form of a supercharger, in which the compressor is driven either directly by the crankshaft or indirectly by a belt and pulley, or in the form of a turbocharger, in which the compressor is mounted on the same shaft as a turbine driven by the engine's exhaust gases. The compressor enables a greater density of air to enter the engines cylinders through the intake manifold. The greater density of air in the cylinders permits more complete combustion of the fuel, and a greater mass of gas pushing against the piston, thereby generating more horsepower.
However, one problem associated with supercharged and turbocharged engines is proper adjustment of the air/fuel ratio. In a naturally aspirated engine, a vacuum develops in the intake manifold. When the throttle is opened, air at atmospheric pressure enters the intake manifold to fill the vacuum. The stoichiometric air/fuel ratio is about 14.5:1. The fuel system in a naturally aspirated engine is designed to deliver fuel at a slightly richer ratio under load, about 12:1 to 13:1.
In a supercharged or turbocharged engine, however, the air in the intake manifold is more dense, with pressures often greater than atmospheric. The boost pressure is often defined as the difference between barometric pressure and the pressure in the intake manifold in a supercharged or turbocharged engine. The boost pressure in an automobile designed for ordinary highway use often reaches a pressure of 8-10 psi of boost. Unless a greater quantity of fuel is added to the air/fuel mixture than would be provided in a naturally aspirated engine, the engine may run lean, leading to detonation. In a street machine, detonation can result in damage to the piston, rings, head gasket and other components. In a racing vehicle, which may use aluminum rods and pistons, detonation may result in more sever damage, such as a broken rod and resultant damage to the crankshaft and cylinder walls.
In modern fuel injection engines, this problem is usually addressed by the mass air flow sensor and the electronic engine control, which controls the frequency and duration of the injection pulses according to the quantity of air sensed by the mass air flow sensor. Many engines also have a knock sensor, which may also signal the electronic engine control to increase fuel injection when knock indicative of detonation is sensed. Some fuel injection engines run with little or no modification with a supercharger or turbocharger. Other fuel injection systems require pressure or temperature sensors, or are not programmed or mapped to handle boost pressures above atmospheric pressure, and therefore require chip replacement.
In any event, fuel injection systems frequently respond on the basis of historical data, i.e., the sensors do not respond dynamically to correct the condition sensed, but merely transmit the information to the electronic engine control where the information reported from multiple sensors is analyzed. Further, a response to sensor input may not be formulated immediately. The electronic engine control may have a delay built in to require that the sensor input be repeated over a predetermined time interval to eliminate spurious data before responding. Only then does the controller send an appropriate signal to an actuator or transducer to initiate corrective action, so that in electronic fuel injection systems, there may be a time lag in responding to high boost pressures in the intake manifold.
In carbureted engines, when a supercharger or turbocharger is added, usually a higher octane gasoline is selected to prevent detonation. Other measures include retarding spark ignition, enriching the air/fuel mixture, and cooling the intake charge by water injection or an intercooler. Enriching the fuel mixture usually involves increasing the size of the jets, changing the spring on the main power piston or metering rod, adjusting the idle screw, and other such measures. However, these measures can prove to be quite expensive. It is not unheard of for adjustments to the carburetor and fuel system of a racing car to cost into the five figure range, depending upon the fuel being used. Further, these adjustments cause the engine to run rich whether operated under a light or heavy load. P. Ganahl in
Street Supercharging
(CarTech, Inc., North Branch, Minn., 1999) describes several such adjustments at pp. 107-118.
Superchargers and turbochargers may be mounted in different configurations. In a “blow-through” configuration, the compressor is upstream from the carburetor, and blows dry air into the carburetor air horn. In a “draw-through” configuration, the compressor is mounted between the carburetor and the intake manifold, and draws an air-fuel mixture into the manifold. The draw-through configuration presents another problem when used with a carburetor designed for naturally aspirated engines.
As explained by H. MacInnes in Turbochargers, (The Berkley Publishing Group, New York, 1984) at pp. 54-55, a conventional carburetor has a passage extending from below the throttle plate to a power piston or diaphragm controlling a metering rod. When there is vacuum below the throttle plate, the power valve remains closed, but when the throttle plate is opened, the piston or metering rod opens to allow more fuel to enter the air horn. However, when the throttle is then partially released, as under cruise conditions, the power valve closes. In a draw-through configuration, this may result in the power valve closing while the engine is still under boost, resulting in detonation. MacInnes describes modifications to the power valve to avoid this problem, including plugging the passage and providing a separate passage from the power valve to the intake manifold, thereby bypassing the compressor. However, MacInnes points out that this only solves the problem of proper actuation of the power valve, and not adjusting the air/fuel ratio to the increased boost pressure provided by the compressor.
U.S. Pat. No. 4,241,711, issued Dec. 30, 1980 to C. A. Detwiller, describes a fuel control system which adjusts the response of the main metering rod according to the load in a draw-through turbocharger configuration. The system includes a device having a diaphragm which separates a control chamber connected to the intake manifold downstream from the compressor from a regulating chamber connected to the carburetor plenum between the throttle and the compressor. An output tube is connected between the regulating chamber and a vacuum regulator connected to the metering rod. A bias spring is normally set for a low vacuum output. Differential pressure between the control chamber and the regulating chamber controls the metering rod according to the load. However, this only addresses the power valve actuation problem, and does not address the problem of adjusting the air/fuel ratio to the boost pressure.
MacInnes also describes devices which are directed towards adjusting the air/fuel ratio according to the boost pressure in Turbochargers, supra, at pp. 55-58. One such device is a pressure switch connected to the intake manifold which operates a solenoid valve that opens when boost pressure exceeds a specified limit in order to inject additional fuel into the air horn. Another device described is a pressure activate fuel valve with a diaphragm that opens to admit more fuel to the air horn, the fuel valve sensing press
Litman Richard C.
Trieu Thai-Ba
LandOfFree
Boost fuel enricher does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Boost fuel enricher, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Boost fuel enricher will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3262928