Internal-combustion engines – Intake manifold – For in-line engine
Patent
1996-07-15
1997-08-05
Okonsky, David A.
Internal-combustion engines
Intake manifold
For in-line engine
12318449, 12318459, F02M 3510
Patent
active
056532024
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to an intake manifold system for a multi-cylinder four stroke spark-ignition internal combustion engine.
The invention seeks to provide an intake system that improves control over the distribution of fuel and air within the charge in the engine combustion chamber.
According to the present invention, there is provided an intake manifold system for a multi-cylinder four stroke spark-ignition internal combustion engine wherein each cylinder has at least one intake port, each intake port being connected at one end to the combustion chamber by at least one intake valve and at the other end to a first intake duct that is connected to a first plenum common to the first intake ducts of other engine cylinders, wherein each intake port is further supplied with gases containing no fuel by a second intake duct having a fixed outlet cross-sectional area equal to between 25% and 45% of the maximum effective through flow cross-sectional area of the open intake valve, the second intake duct being directed towards the closed end of the intake port whereby, during the periods that the intake valve is closed, gas is drawn in through the second intake duct by manifold vacuum and stored in the first intake duct, and wherein the solid boundary walls of the intake port and of the discharge end of the second intake duct define a U-shaped flow path for guiding the gas entering the intake port from the second intake duct, the geometry of the solid boundaries being such that during operation gas enters from one side of the intake port, performs a single U-turn by flowing around the intake valve stem while adhering to the walls of the intake port and enters the first intake duct from the other side of the intake port, the gas being thereby constrained to scavenge the closed end of the intake port and to displace substantially all the gases previously present therein into the first intake duct.
The invention is not the first proposal to blow air into the intake port to improve charge preparation. It is known for example to provide an intake manifold system in which an air assisted fuel injector is positioned near the intake valve to introduce air and fuel into the intake port. Small amounts of air, bypassing the butterfly throttle, have also been introduced into the intake port to assist charge preparation by stirring the air near the intake valve when it is closed. In all such systems, the size of the air jet has to be small in order to give the maximum jet velocity for fine atomising of the fuel or deep penetration for good turbulent mixing. Furthermore, the size of such an air jet cannot be made larger because the flow from it must be limited to less than the engine air intake flow during idling; otherwise it would interfere with the idle speed control of the engine. This limits the size of each air jet to less than 1% of the open intake valve area delivering no more than 80% of the throttled idle air flow to the engine.
In the present invention, the effective flow cross-section of the second intake duct is much larger to give significantly larger flows to satisfy at least 60% of the maximum engine air flow requirement and is not limited by the engine idle operating condition. The flow velocity emitted from the duct is kept low to give an organised flow around the end of the intake port with substantially no turbulent mixing.
It is also known to provide an exhaust gas recirculation (EGR) system in a spark ignition engine. In such an engine, the EGR pipe is conventionally connected to the intake plenum where the exhaust gases can mix thoroughly with the intake air before entering the intake ports. This is because it is not an acceptable practice to introduce the exhaust gases directly into each intake port where there is wet fuel since any fuel entrained within the neat exhaust gases will not find oxygen for combustion and will result in excessive hydrocarbons emissions in the exhaust gases and unstable combustion.
The present invention proposes taking in a major proportion
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patent: 5421296 (1995-06-01), Hitomi et al.
patent: 5427078 (1995-06-01), Hitomi et al.
Drouillard Jerome R.
Ford Motor Company
Okonsky David A.
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