Engine cylinder head

Details Engine cylinder head Engine cylinder head

2000-04-24

2001-04-10

Kwon, John (Department: 3747)

Internal-combustion engines

Means to whirl fluid before, upon, or after entry into...

Having multiple oxidant inlet means

C123S315000

Reexamination Certificate

active

06213090

ABSTRACT:

TECHNICAL FIELD
The invention relates to a cylinder head for a four valve per cylinder internal combustion engine.
BACKGROUND OF THE INVENTION
Generally to start a cold engine, a richer fuel mixture is required, which results in a majority of the exhaust emissions generated. Therefore it is desirable to design a cylinder head that can tolerate relatively lean fuel mixtures in a cold engine. It is also desirable to design an engine to accommodate relatively high levels of exhaust gas recirculant (EGR) for reducing emissions, without sacrificing a loss in combustion stability or power output. Such an increased tolerance for air dilution may be accomplished by generating charge turbulence. Research has shown that an approximately even combination of swirl, circular flow about the cylinder axis, and tumble, circular flow about an axis transverse to the cylinder axis, leads to an optimal flow condition by maximizing the dilution tolerance per total angular motion imparted to the charge. A four valve per cylinder engine tends to provide primarily tumble because the two intake valves are located symmetrically about the cylinder center, whereas a two valve per cylinder engine inherently provides swirl since the single intake valve is offset from the center of the cylinder. Therefore the two engine configurations have different hurdles to overcome to generate the desired angular motion.
Mechanisms such as variable valve and variable port actuation may generate the charge motion desired, but at increased expense. Fixed geometry structure may also generate motion, but may lead to a loss in engine power by restricting air flow. The need remains for a fixed geometry configuration that provides the proper angular motion while not impeding air flow, and therefore power output.
SUMMARY OF THE INVENTION
The present invention is directed to a cylinder head having fixed geometrical features for use in a four valve per cylinder internal combustion engine. The fixed features generate swirl motion to be added to the inherent tumble motion of a four valve per cylinder engine, without sacrificing engine power. A proper combination of swirl and tumble optimizes flow conditions, which in turn increases the tolerance for more air and EGR in the intake charge.
The cylinder head includes an intake passage which divides into a first intake port and a second intake port, with each intake port having an associated intake valve. A port protrusion projects from the intake passage and has a swirl-inducing ramp on an upstream side of the protrusion to redirect a portion of the intake charge entering the first intake port and to induce swirl about the first intake valve. The protrusion has a back angled ramp on the downstream side so as to not hinder swirl induced by the swirl-inducing ramp. Therefore the first intake port delivers intake charge to the cylinder having a swirl component about the cylinder axis, also referred to as the swirl axis.
The cylinder head may also comprise a valve shroud partially about the first intake opening into the combustion chamber to further enhance the swirl component developed by the port protrusion. The valve shroud includes a shroud wall extending into the combustion chamber and shielding a circumferential portion of the first intake opening, thereby forcing the intake charge towards the second intake valve and promoting swirl in the same direction as the swirl generated by the port protrusion. The valve shroud further includes a smooth ramp portion to blend the shroud wall into the bowl-shaped combustion chamber recess to ensure the swirl component is not hindered.
The swirl component of the intake charge generated by the fixed features of the cylinder head combines with the tumble component inherently generated by the four valve per cylinder engine to result in an angularly charged intake motion. Such angularly charged motion may lead to an optimal flow condition for tolerating increased dilution.


REFERENCES:
patent: 4606303 (1986-08-01), Mezger et al.
patent: 4706623 (1987-11-01), Gadefelt et al.
patent: 5558061 (1996-09-01), Suminski
patent: 5836284 (1998-11-01), Oda et al.
patent: 5913554 (1999-06-01), Oda et al.
patent: 5983856 (1999-11-01), Oda et al.

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