Internal-combustion engines – Engine speed regulator – Responsive to deceleration mode
Reexamination Certificate
2000-09-18
2002-01-01
Kwon, John (Department: 3747)
Internal-combustion engines
Engine speed regulator
Responsive to deceleration mode
C123S321000
Reexamination Certificate
active
06334429
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the control of exhaust and intake valves during positive power and engine braking. In particular, the present invention is directed to a control valve that combines a check valve and a shuttle valve for use in a lost motion engine brake system. The present invention is also directed to a system and method to allow the clipping or resetting of a lost motion engine brake system.
BACKGROUND OF THE INVENTION
For many internal combustion engine applications, such as for powering heavy trucks, it is desirable to operate the engine in a braking mode. This approach involves converting the engine into a compressor by cutting off the fuel flow and opening the exhaust valve for each cylinder near the end of the compression stroke.
An early technique for accomplishing the braking effect is disclosed in U.S. Pat. No. 3,220,392 to Cummins, wherein a slave hydraulic piston located over an exhaust valve opens the exhaust valve near the end of the compression stroke of an engine piston with which the exhaust valve is associated. To place the engine into braking mode, the three-way solenoids are energized, which causes pressurized lubricating oil to flow through a control valve, creating a hydraulic link between a master piston and a slave piston. The master piston is displaced inward by an engine element (such as a fuel injector actuating mechanism) periodically in timed relationship with the compression stroke of the engine which in turn actuates a slave piston through hydraulic force to open the exhaust valves. The compression brake system as originally disclosed in the '392 patent has evolved in many aspects, including improvements on the control valves (see, for example, U.S. Pat. No. 5,386,809 to Reedy et al.; see also U.S. Pat. No. 4,996,957 to Meistrick, which is assigned to the assignee of the present application and incorporated herein by reference.) Improvements have also been made in the piston actuation assembly (see U.S. Pat. No. 4,475,500 to Bostelman). In a typical modem compression braking system, the exhaust valves are normally operated during the engine's power mode by an exhaust rocker lever. To operate the engine in a braking mode, a control valve separates the braking system into a high pressure circuit and a low pressure circuit using a check valve which prevents flow of high pressure fluid back into the low pressure supply circuit, thereby allowing the formation of a hydraulic link in the high pressure circuit.
Various problems are known in conventional compression braking system. First, a time delay may occur between the actuation of the three-way solenoid valve and the onset of the braking mode. This time delay is due in part to the positioning of the solenoid valve a spaced distance from the control valve, which creates longer than ideal fluid passages and thus delayed response time. The high pressure circuit may also comprise long fluid passages between the master and slave pistons, which disadvantageously increase the compressed fluid volume and thus the response time.
In addition, in conventional compression braking systems, the braking system is a bolt-on accessory that fits above the overhead. In such systems, in order to provide space for mounting the braking system, a spacer is positioned between the cylinder head and the valve cover. The valve cover is bolted to the spacer, which adds unnecessary height, weight, and costs to the engine. Many of the above-noted problems result from viewing the braking system as an accessory to the engine rather than as part of the engine itself.
One possible solution is to integrate components of the braking system with the rest of the engine components. One attempt at integrating parts of the compression braking system is found in U.S. Pat. No. 3,367,312 to Jonsson, which discloses an engine braking system including a rocker arm having a plunger, or slave piston, positioned in a cylinder integrally formed in one end of the rocker arm. The plunger may be locked in an outer position by hydraulic pressure in order to permit braking system operation. Jonsson also discloses a spring for biasing the plunger outward from the cylinder into continuous contact with the exhaust valve to permit the cam-actuated rocker lever to operate the exhaust valve in both the power and braking modes.
In addition, a control valve is used to control the flow of pressurized fluid to the rocker arm cylinder so as to permit selective switching between braking operation and normal power operation. The control valve unit is positioned separately from the rocker arm assembly, however, which results in unnecessarily long fluid delivery passages and therefore a longer response time. This may also lead to an unnecessarily large amount of oil that must be compressed before activation of the braking system can occur, resulting in less control over the timing of the compression braking.
Jonsson also discloses using the control valve to control the flow of fluid to a predetermined set of cylinders in the engine, thereby undesirably preventing individual engine cylinders or different groups of engine cylinders from being selectively operated in the braking mode.
Furthermore, the control valve as disclosed by Jonsson is a manually-operated, rotary type valve requiring actuation by the driver. Manual operation often results in unreliable and inefficient braking operation. Also, rotary valves are subject to undesirable fluid leakage between the rotary valve member and its associated cylindrical bore.
Other designs known in the art include U.S. Pat. No. 3,332,405 to Haviland, assigned to the assignee of the present application and incorporated herein by reference. Haviland discloses a compression braking system with a control valve unit for enabling the formation of a hydraulic link. The control valve unit is mounted in a cavity formed in a rocker arm that operates the exhaust valves during the braking mode. Separate cam lobes are used for normal power operation and braking operation. However, a single rocker arm is used to actuate the exhaust valves during both normal and braking modes. A drawback in this design is that the braking cam lobe profile design, and therefore the braking system operation, may be at least partially dependent on, or influenced by, the design of the cam lobe used for operating the exhaust valve during normal engine operation.
Another known design is disclosed in U.S. Pat. No. 4,251,051 to Quenneville, assigned to the assignee of the present application and incorporated herein by reference. Quenneville discloses a solenoid valve assembly with an inlet communicating with a supply of fluid, and one or more outlet passages communicating with respective loads requiring intermittent fluid supply and a drain passage. A respective ball valve is positioned between the inlet and each outlet and is spring-biased to block flow between the supply and outlet passage while opening the drain passage. An armature and pin are actuated to move the ball valve so as to connect the supply to the outlet and close the drain passage. However, while the valve assembly in the actuated position permits supply flow to the outlet passage, it does not prevent the return flow of fluid from the outlet passage into the supply passage and therefore does not permit the formation of a hydraulic link between different pressurized circuits as required by a control valve during compression braking system operation.
Designs in the known art have required independent check and shuttle valves in order to control a lost motion integrated rocker brake. Accordingly, there is a need for a simplified rocker brake control valve assembly. The design of the present invention integrates the check and shuttle valves into a single unit. This single unit serves to control the flow of oil within the integrated lost motion rocker brake. In addition, there have been many attempts to design systems to clip or reset lost motion circuits. The present invention also provides a system and method to allow the clipping or resetting
Collier Shannon Scott PLLC
Diesel Engine Retarders
Kwon John
LandOfFree
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