Internal-combustion engines – Engine speed regulator – Responsive to deceleration mode
Reexamination Certificate
1999-11-17
2001-09-04
Solis, Erick (Department: 3747)
Internal-combustion engines
Engine speed regulator
Responsive to deceleration mode
C123S446000, C123S090160
Reexamination Certificate
active
06283090
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to an internal combustion engine, and more particularly to a method and apparatus for operating a hydraulically-powered compression release brake assembly of an internal combustion engine.
BACKGROUND OF THE INVENTION
Engine retarding devices of the compression release type are commonly utilized in work machines such as on-highway trucks and the like. A compression release brake assembly utilizes compression within the truck's engine to assist the truck's main braking system in order to slow the truck. In effect, such compression release brake assemblies convert the truck's internal combustion engine into an air compressor in order to develop retarding horsepower which is utilized to assist in slowing the truck.
Compression release brake assemblies which have heretofore been designed typically include a hydraulic system having a master cylinder having a piston which is actuated by a cam lobe or push rod associated with an exhaust valve, intake valve, or fuel injector corresponding to a first engine cylinder. Actuation of the piston associated with the master cylinder controls actuation of a piston associated with a slave cylinder which selectively opens and closes an exhaust valve near the end of the compression stroke thereby causing the mechanical work performed during the compression stroke to be dissipated and hence not “recovered” during the subsequent power stroke. It should be appreciated that the exhaust valve opened by the slave cylinder may be associated with either the first engine cylinder, or may alternatively be the exhaust valve associated with a second, different engine cylinder.
However, such heretofore designed compression release brake assemblies have a number of drawbacks associated therewith. For example, such heretofore designed compression release brake assemblies are relatively mechanically complex and often require a relatively large number of repairs during the useful life of the engine. In addition, such mechanical complexity generally increases the costs associated with manufacture of the engine. Yet further, such heretofore designed compression release brake assemblies typically have limited design freedoms in regard to the opening of the respective exhaust valves during braking since actuation of the respective master cylinders must be selected from a cam lobe or push rod associated with an intake valve, exhaust valve, or fuel injector which is the “closest fit” to the timing requirements of the individual exhaust valves.
In an effort to overcome the above-mention drawbacks, a number of compression release brake assemblies have been designed for use in conjunction with a hydraulically-powered fuel injection system. In such devices, the hydraulic supply system which is utilized to operate the fuel injectors of the engine is also utilized to operate the compression release brake assembly. However, such systems typically require modification to the exhaust valves in order to allow an actuator such as a hydraulic piston to contact the stem of the exhaust valve. Such modification to the exhaust valve undesirably increases costs associated with manufacture of the engine.
What is needed therefore is a method and apparatus for operating a compression release brake assembly which overcomes one or more of the abovementioned drawbacks.
DISCLOSURE OF THE INVENTION
In accordance with a first embodiment of the present invention, there is provided a method of operating an internal combustion engine having a hydraulic supply circuit, a hydraulically-powered fuel injector assembly, and a hydraulically-powered compression release brake assembly. The method includes the step of advancing a pressurized hydraulic fluid to the fuel injector assembly from the hydraulic supply circuit so as to cause fuel to be injected into a cylinder associated with the engine when the engine is being operated in a drive mode of operation. The method also includes the step of advancing the pressurized hydraulic fluid to the compression release brake assembly so as to cause a piston to be moved from a retracted position to an extended position when the engine is being operated in a brake mode of operation. Yet further, the method includes the step of rotating a rocker arm about a rocker arm shaft so as to cause the rocker arm to contact an exhaust valve thereby urging the exhaust valve into an open exhaust valve position in response to movement of the piston from the retracted position to the extended position.
In accordance with a second embodiment of the present invention, there is provided an internal combustion engine. The engine includes an engine block having a cylinder defined therein and an exhaust valve movably secured to the engine block. The engine also includes a rocker arm shaft secured to the engine block and a rocker arm rotatably coupled to rocker arm shaft. The engine further includes a hydraulically-powered fuel injector assembly secured to the engine block so as to selectively inject fuel into the cylinder. Moreover, the engine includes a hydraulically-powered compression brake assembly having a piston associated therewith. In addition, the engine includes a hydraulic supply circuit fluidly coupled to both the fuel injector assembly and the compression brake assembly. The hydraulic supply circuit is configured to advance a pressurized hydraulic fluid to the fuel injector assembly so as to cause the fuel to be injected into the cylinder when the engine is being operated in a drive mode of operation. The hydraulic circuit is further configured to advance the pressurized hydraulic fluid to the compression release brake assembly so as to cause the piston to be moved from a retracted position to an extended position when the engine is being operated in a brake mode of operation. The rocker arm is rotated about the rocker arm shaft so as to cause the rocker arm to contact the exhaust valve thereby urging the exhaust valve into an open exhaust valve position when the piston is moved from the retracted position to the extended position.
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Caterpillar Inc.
Maginot Addison & Moore
Solis Erick
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