Internal-combustion engines – Poppet valve operating mechanism – Plural valve trains – single actuator
Reexamination Certificate
2002-08-01
2003-12-09
Denion, Thomas (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
Plural valve trains, single actuator
C123S090270, C123S090400, C123S193500
Reexamination Certificate
active
06659056
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention generally relates to an internal combustion engine including a plurality of cylinders, at least one intake valve per cylinder and at least one exhaust valve per cylinder. The present invention specifically relates to an internal combustion engine further including a valve train with a single camshaft operatively opening and closing the intake and exhaust valves.
BACKGROUND OF THE INVENTION
An internal combustion engine includes an engine block and a cylinder head. The engine block includes one or more cylinders, each cylinder having a piston movably disposed therein. The cylinder head is mounted upon the engine block to form a combustion chamber for each cylinder. The perimeter of a combustion chamber is defined by a bottom surface of the cylinder head, an upper portion of a cylinder, and a crown of the piston disposed within the cylinder. The cylinder head includes one or more intake passageways leading into the combustion chamber, and one or more exhaust passageways leading out of the combustion chamber. Each intake and exhaust passageway is constructed with a valve seat adjacent the combustion chamber and the construction includes a valve for cooperation with a corresponding valve seat. To obtain optimal engine performance, each combustion chamber is designed to be as compact as possible in view of the overall performance requirements for the engine and dimensional specifications for the engine block and the cylinder head. As such, the intake valve seats and the exhaust valve seats are typically arranged in close proximity with a bore disposed between the valves seats for either a spark plug or a fuel injector.
For an internal combustion engine which includes a valve train having dual overhead camshafts and associated cam followers mounted upon the cylinder head, the lateral width of the cylinder head must be sufficiently dimensioned to accommodate the dual camshafts, the cam followers, and either a spark plug or a fuel injector. However, the required lateral width for the cylinder head configured in this manner may exceed the dimensional specifications for the overall width of an engine, particularly if the engine is configured in a conventional “V” arrangement. Moreover, a close proximity arrangement of the intake valve seats and the exhaust valve seats normally necessitates an angular orientation of the valve heads of the intake valves and the exhaust valves toward a center longitudinal axis of the associated combustion chamber. As a result, the distance between the stem tops of the intake valves and the exhaust valves is expanded causing the distance between the two camshafts as mounted on the cylinder head to be expanded. Consequently, the lateral width of the cylinder head must be increased to support the two camshafts. This increase may cause the lateral width of an otherwise acceptable cylinder head to exceed the desired dimensional specifications.
Additionally, there are further disadvantages associated with a valve train having dual overhead camshafts and associated cam followers. First, any friction loss by the two camshafts and associated cam followers as the two camshafts are rotating may increase fuel consumption. Second, duel overhead camshafts and associated cam followers may not be economically feasible. Third, the minimization of manufacturing imperfections can be costly. Specifically, a cam follower has a planar or convex surface for engaging a cam of a camshaft. The cam follower is machined upon a rocker arm that is pivotally mounted onto the cylinder head and operatively mounted upon a valve. To achieve optimal engine performance, it is necessary that manufacturing imperfections are minimized for both the cam follower and the rocker arm. However, the overall cost for the valve train must be increased to attain a minimization of manufacturing imperfections.
Moreover, cylinder heads as known in the art for valve trains having dual overhead camshafts are not suitable for diesel engines. For each intake valve, known cylinder heads include a fluid intake passage extending from an intake port to an intake valve seat. Generally, the fluid intake passage has an arcuate configuration. As a result, air flowing into the intake port through the fluid intake passage will uniformly circulate along an open intake valve as the air enters into the corresponding combustion chamber. Consequently, the air tumbles within the combustion chamber. A tumbling of the air within the combustion chamber facilitates optimal engine performance for a gas engine. However, such tumbling would hinder optimal engine performance for a diesel engine.
In view of the foregoing issues, there is a need for minimizing the lateral width of a cylinder head while designing combustion chambers that are suitably compact to render optimal engine performance. There is also a need for improving upon valve trains having dual overhead camshafts, particularly for diesel engines. The present invention satisfies these needs in a novel and unobvious manner.
SUMMARY OF THE INVENTION
According to one embodiment of the present invention, a valve train with a single camshaft is disclosed. The single camshaft operatively opens and closes one or more intake valves and one or more exhaust valves. In one form of the present invention, a valve train is disclosed, comprising a cylinder head, one or more valves (intake or exhaust) movably positioned within the cylinder head, a crosshead pivotally adjoined to the cylinder head and operatively adjoined to each valve (intake or exhaust), a rocker arm pivotally adjoined to the cylinder head and operatively adjoined to the crosshead, and a camshaft rotatably adjoined to the cylinder head and operatively adjoined to the rocker arm. When the camshaft is rotated, the rocker arm and the crosshead pivot about the cylinder head to thereby move the valve(s) (intake or exhaust) within the cylinder head.
In a related embodiment of the present invention, a valve train is disclosed, comprising a cylinder head, one or more intake valves movably positioned within the cylinder head, one or more exhaust valves movably positioned within the cylinder head, an intake crosshead pivotally adjoined to the cylinder head and operatively adjoined to each intake valve, an exhaust crosshead pivotally adjoined to the cylinder head and operatively adjoined to each exhaust valve, an intake rocker arm pivotally adjoined to the cylinder head and operatively adjoined to the intake crosshead, an exhaust rocker arm pivotally adjoined to the cylinder head and operatively adjoined to the exhaust crosshead, and a camshaft rotatably adjoined to the cylinder head and operatively adjoined to both the intake rocker arm and exhaust rocker arm. When the camshaft is rotated, the intake rocker arm and the intake crosshead pivot about the cylinder head to thereby move the intake valve(s) within the cylinder head, and the exhaust rocker arm and the exhaust crosshead pivot about the cylinder head to thereby move the exhaust valve(s) within the cylinder head.
In yet another related embodiment of the present invention, a valve train is disclosed, comprising a cylinder head a valve train is disclosed, comprising a cylinder head including one ore more valve seats. The valve train further comprises a valve (intake or exhaust) removably seated within a corresponding valve seat, a crosshead pivotally adjoined to the cylinder head and operatively adjoined to the valves (intake or exhaust), a rocker arm pivotally adjoined to the cylinder head and operatively adjoined to the crosshead, and a camshaft rotatably adjoined to the cylinder head and operatively adjoined to the rocker arm. As the camshaft cyclically rotates, the rocker arm and the crosshead undulatedly pivot about the cylinder head to thereby undulatedly seat and unseat the valves (intake or exhaust) within the valve seat(s).
In yet another related embodiment of the present invention, a valve train is disclosed, comprising a cylinder head including one or more intake valve seats and one or more exhaust valve seats. T
Chang Ching
Cummins Inc.
Denion Thomas
Woodward, Emhardt, Moriarty, McNett & Henry LLP
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