Internal-combustion engines – Charge forming device – With fuel pump
Reexamination Certificate
1998-05-20
2001-06-19
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
With fuel pump
C123S467000
Reexamination Certificate
active
06247454
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention generally relates to internal combustion engine fuel injection systems and, more particularly, to an improved rocker lever for an internal combustion engine fuel injection system.
BACKGROUND OF THE INVENTION
In order to achieve good quality emissions from an internal combustion engine (i.e., fairly complete combustion of fuel with a low percentage emission of noxious substances in the engine exhaust), it is necessary to maintain the fuel injection pressure as high as possible. In most internal combustion engines which do not employ a common rail fuel injection system, the fuel injector comprises a translating plunger within the fuel injector body which is actuated by a camshaft that rotates in relation to the engine speed (usually at one-half engine speed). The camshaft operates upon a push rod which in turn moves a rocker lever that pushes on the plunger within the fuel injector, as is known in the art. At full-rated power, the internal combustion engine runs at a relatively high speed, which translates to a relatively high speed of the plunger within the fuel injector. This high-speed motion of the plunger in the fluid fuel creates extra injection pressure which helps to maintain emission quality.
FIG. 1
illustrates a graph of fuel injection pressure versus engine RPM for a typical prior art internal combustion engine. It can be seen that at full-rated power (labeled RPM 2), the fuel injection pressure is relatively high at P
SAC2
.
As the speed of the engine decreases to the torque peak condition (labeled RPM 1), this speed-induced injection pressure decreases, lowering the total fuel injection pressure to P
SAC1
. Because of this lower fuel injection pressure, the quality of emissions produced by the engine also decreases at torque peak.
In order to improve the emission quality of the engine, it is therefore desirable to increase the fuel injection pressure created at torque peak conditions. The present invention is directed toward meeting this need.
SUMMARY OF THE INVENTION
The present invention relates to an improved fuel injector rocker lever designed to maintain relatively high fuel injection pressures when the engine speed decreases from full-rated power to torque peak conditions. The fuel injector rocker lever is designed with a size and shape so as to make the rocker lever flexible, thereby allowing the rocker lever to store and release strain energy when actuating the fuel injector. Thus, as engine speed decreases, the fuel injection pressure decreases at a lower rate when compared to a stiff actuating train because the fuel injector train is storing more strain energy due to its flexible nature. Generally, the improved rocker lever is designed with a vertically thin and horizontally wide arm which increases its width from the fuel injector actuator to the pivot point of the rocker lever. By reducing the thickness of the rocker lever, the stiffness decreases significantly, thereby permitting more strain energy to be stored and released by the rocker lever. Moreover, the stress experienced over the length of the lever arm is constant since the lever width increases away from the fuel injector contact point. Ultimately, the present design permits higher average fuel injection pressures during decreasing engine speed transients and therefore improves engine emissions.
In one form of the invention, a rocker lever is disclosed, comprising a pivot, a lever arm extending from said pivot, said lever arm having a substantially constant first thickness, a flange coupled to said lever arm opposite said pivot, said flange operable to actuate a fuel injector when said rocker lever is rotated about said pivot in a first direction, wherein said first thickness is such tat said lever arm flexes during actuation of said fuel injector.
In another form of the invention, a rocker lever is disclosed comprising a pivot, a flange, a lever arm extending between said pivot and said flange, said lever arm having a substantially constant first thickness and a width that increases with increasing distance from said flange, wherein said flange is operable to actuate a fuel injector when said rocker lever is rotated about said pivot in a first direction.
In another form of the invention, a fuel injection system for an internal combustion engine is disclosed, comprising at least one fuel injector, at least one rocker lever coupled to said at least one fuel injector, a camshaft operable to cause said at least one rocker lever to periodically actuate said at least one fuel injector, wherein each said at least one rocker lever comprises, a pivot a lever arm extending from said pivot, said lever arm having a substantially constant first thickness, a flange coupled to said lever arm opposite said pivot, said flange operable to actuate one of said at least one fuel injector when said rocker lever is rotated about said pivot in a first direction, wherein said first thickness is such that said lever arm flexes during activation of said one of said at least one fuel injector.
In another form of the invention, a fuel injection system for an internal combustion engine is disclosed, comprising at least one fuel injector, at least one rocker lever coupled to said at least one fuel injector, a camshaft operable to cause said at least one rocker lever to periodically actuate said at least one fuel injector, wherein each said at least one rocker lever comprises, a pivot, a flange, a lever arm extending between said pivot and said flange, said lever arm having a substantially constant first thickness and a width that increases with increasing distance from said flange, wherein said flange is operable to actuate one of said at least one fuel injector when said rocker lever is rotated about said pivot in a first direction.
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Cummins Engine Company, Inc.
Miller Carl S.
Woodard Emhardt Naughton Moriarty & McNett
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