Internal-combustion engines – Engine speed regulator – Responsive to deceleration mode
Reexamination Certificate
2000-09-18
2002-05-28
Kwon, John (Department: 3754)
Internal-combustion engines
Engine speed regulator
Responsive to deceleration mode
C123S322000
Reexamination Certificate
active
06394067
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the field of compression release engine retarders for internal combustion engines. In particular, it relates to a method for increasing the retarding power of the retarder by generating two braking events, one per engine revolution, for each cylinder of the engine “two cycle braking.” More specifically, the invention involves modifying the cam and rocker arms on a overhead cam engine to provide a dedicated cam lobe for braking. In addition, the classic compression release retarder housing is eliminated and the compression release retarder is associated with the rocker arms.
The exhaust valves of a typical internal combustion engine open at least once during its two-stroke or four-stroke cycle. A second opening of the exhaust valves can be introduced on the compression stroke to achieve additional compression release retarding. The present invention eliminates the first exhaust valve opening on the normal exhaust stroke and substitutes a compression release event later in the exhaust stroke. In addition, the opening of the intake valve is delayed, to increase the effectiveness of the second compression release event, at the end of the exhaust stroke. The present invention can also be combined with exhaust gas recirculation on either the compression or exhaust strokes, or both, to further enhance retarding power.
This provides a number of benefits, including: increased retarding power, reduced cost, and further integration of the compression release retarder with the design of the engine overhead. Furthermore, under positive power the present invention provides greater control over the operation of the intake valves and the exhaust valves. This provides for improved fuel economy, emissions and optimized performance over the complete engine speed range.
BACKGROUND OF THE INVENTION
With many engines it is desirable to have both a positive power mode of operation (in which the engine produces power for such purposes as propelling an associated vehicle) and a braking mode operation (in which the engine absorbs power for such purposes as slowing down an associated vehicle). It is well known that a highly effective way of operating an engine in braking mode is to cut off the fuel supply to the engine and to then open the exhaust valves in the engine near top dead center of the compression strokes of the engine cylinders. This allows air that the engine has compressed in its cylinders to escape to the exhaust system of the engine before the engine can recover the work of compressing the air during the subsequent “power” strokes of the engine pistons. This type of engine braking is known as compression release engine braking.
It takes a great deal more force to open an exhaust valve to produce a compression release event during compression release engine braking than to open either an intake or exhaust valve during positive power mode operation of the engine. During positive power mode operation the intake valves typically open while the piston is moving away from the valves, thereby creating a low pressure condition in the engine cylinder. Thus the only real resistance to intake valve opening is the force of the intake valve return spring which normally holds the intake valve closed. Similarly, during positive power mode operation the exhaust valves typically open near the end of the power strokes of the associated piston after as much work as possible has been extracted from the combustion products in the cylinder. The piston is again moving away from the valves and the cylinder pressure against which the exhaust valves must be opened is again relatively low. (Once opened, the exhaust valves are typically held open throughout the subsequent exhaust stroke of the associated piston, but this only requires enough force to overcome the exhaust valve return spring force.)
Four cycle internal combustion engines, conventionally, are outfitted with either mechanical or hydro-mechanical intake and exhaust opening systems. These systems may include a combination of camshafts, rocker arms and push rods that operate synchronously with the engine's crankshaft rotation. The timing of the valve openings is fixed in relationship to the position of the crankshaft by direct mechanical connection of the valve actuating system with the crankshaft. In any cylinder, of a multi-cylinder internal combustion engine, intake and exhaust valve openings and closings in conjunction with the fuel mixture and either ignition or fuel injection, are predetermined to provide optimum positive power over a range of engine speeds. This relationships between the piston motion of a cylinder and its intake and exhaust valve openings and closings, for a conventional internal combustion engine is illustrated in FIG.
1
.
The crankshaft of a four-cycle internal combustion engine rotates through 720° during one series of its four strokes (i.e., compression, expansion, exhaust and intake).
FIG. 1
depicts the relationships between the piston and valves beginning with the piston at top dead center (“TDC”) of the compression stroke
5
. Both the intake and exhaust valves are closed, and remain closed during most of the expansion stroke wherein the piston is traveling away from the cylinder head (i.e., the volume between the cylinder head and the piston head is increasing). Fuel is burned during the expansion stroke and positive power is delivered by the engine. As the piston reverses direction at the end of the expansion stroke, the exhaust valve opens, illustrated as
7
in
FIG. 1
, and combustion gases are forced out of the cylinder as the piston travels again to exhaust TDC
6
. Just prior to the exhaust TDC, the intake valve opens, illustrated as
8
in FIG.
1
. Immediately after the exhaust TDC, the exhaust valve closes, and air or fuel mixture is drawn into the cylinder chamber through the intake valve as the piston travels away from the cylinder head. The intake valve closes when the piston is near the or in the proximity of the furthest distance from the cylinder head. Subsequently, both the intake and exhaust valves are closed, and the compression stroke begins bringing the piston to TDC and the four cycle repeats.
FIG. 2
illustrates the required intake and exhaust valve openings that occur when an internal combustion engine operates in a braking mode (i.e., as a compressor wherein the compressed air is evacuated at the vicinity of TDC compression).
FIG. 2
also illustrates engine piston motion. During the braking mode, no fuel is being supplied to the engine. As a result, only air is being compressed during the compression stroke.
FIG. 2
depicts the normal intake and exhaust valve openings (i.e., during positive power) during the exhaust and intake strokes of the piston. Additionally, an exhaust valve opening
9
is shown immediately before the completion of the compression stroke and subsequent to the closing prior to the beginning of the exhaust stroke. There are other options. This is just one example of an exhaust cam operated compression release brake. Engine braking is achieved during the compression stroke and the evacuation, by way of the added exhaust valve opening, of the compressed air immediately following.
The aforementioned process described compression release engine braking. The additional exhaust valve opening is achieved by adding components that actuate an exhaust valve independently from the normal actuating mechanisms. This is typically achieved by actuating the lifting mechanism of the exhaust valve by way of a secondary hydro-mechanical system that can be deactivated when the engine is operating in its positive power mode. In summary, the secondary system lifts the exhaust valve, at an appropriate time, and does not interfere with, nor interrupt, the normal valve lifting mechanism, and is inactive during positive power operation. Timing of the secondary systems valve lifting is usually derived from the activation of an adjacent cylinder's normal intake or exhaust valve's opening or the injection actuation mechan
Swanbon Bruce N.
Usko James N.
Collier Shannon Scott PLLC
Coulby John N.
Diesel Engine Retardersk, Inc.
Kwon John
Rygiel Mark W.
LandOfFree
Apparatus and method to supply oil, and activate rocker... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus and method to supply oil, and activate rocker..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus and method to supply oil, and activate rocker... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2908575