Internal-combustion engines – Engine speed regulator – Responsive to deceleration mode
Reexamination Certificate
1999-07-20
2001-01-30
Solis, Erick (Department: 3747)
Internal-combustion engines
Engine speed regulator
Responsive to deceleration mode
Reexamination Certificate
active
06178946
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a compression release engine braking system for a compression ignition or diesel engine.
BACKGROUND OF THE INVENTION
Diesel engines have no inherent braking effect like that experienced with spark ignition engines. The reason is that diesel engines do not have a throttle, which, when closed, causes an increase in intake manifold vacuum to retard the rpm of the engine.
It was first proposed in C. L. Cummins U.S. Pat. No. 3,220,392 to operate a diesel engine in such a manner that the engine produces a retarding effect when the engine is in a motoring condition (fuel to the engine is cut off).
The principle on which the compression relief engine braking system relies is that the energy required by the engine to compress air during the compression stroke is discharged and wasted by opening an exhaust valve at the end of the compression stroke. Since the engine is motoring, the compression stroke is no longer followed by a power stroke so that no energy is generated at any time in the engine cycle. The engine therefore acts as an air pump which discharges the air that it compresses into the exhaust system and thereby uses up the kinetic energy of the vehicle in heating intake air.
The Cummins patent describes a hydraulic mechanism which utilizes the cam motion of a unit injector fuel system to selectively actuate the exhaust valve at top dead center TDC. For engines not utilizing a unit injector fuel system, a lost motion camshaft may be proposed, like the one in Pellizoni U.S. Pat. No. 3,786,792. When this type of lost motion mechanism is applied to an engine with multiple exhaust valves and a floating crosshead, the increased clearances may permit the crosshead to float and become disconnected from the valves.
SUMMARY OF THE INVENTION
The above problems are solved by a compression relief engine braking system for an engine having two exhaust valves per cylinder, a crosshead for actuating both exhaust valves and a rocker arranged in the drive train between an exhaust cam and the crosshead, one end of the rocker acting on a point on the crosshead lying between the exhaust valves and the other end of the rocker being arranged to follow the surface of the exhaust cam. The braking system comprises a hydraulic primary piston arranged in a hydraulic circuit with a secondary cylinder acting on one of the exhaust valves, the primary cylinder being biased by a spring away from said other end of the rocker when the compression brake is inactive and being biased by the pressure in the hydraulic circuit to move with said other end of the rocker when the compression brake is active.
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Baginski Jerzi
Matthews Jeff A.
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