Internal-combustion engines – Engine speed regulator – Responsive to deceleration mode
Reexamination Certificate
2000-01-14
2001-07-03
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Engine speed regulator
Responsive to deceleration mode
Reexamination Certificate
active
06253730
ABSTRACT:
TECHNICAL FIELD
This invention relates to compression braking systems for internal combustion engines for selectively operating an engine in either a power mode or a braking mode, i.e. compression braking. More specifically, this invention relates to a simple, effective compression braking system capable of minimizing the size and weight of the associated engine while providing optimal predictable compression braking.
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, three-way solenoids are energized which cause 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 in the control valves (see U.S. Pat. Nos. 5,386,809 to Reedy et al. and U.S. Pat. No. 4,996,957 to Meistrick) and the piston actuation assembly (see U.S. Pat. No. 4,475,500 to Bostelman). A typical modern compression braking system found in the prior art is shown in U.S. Pat. No. 4,423,712 to Mayne et al. where 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. A three-way solenoid valve, positioned upstream of the control valve, controls the flow of low pressure fluid to the control valve, and thus, controls the beginning and end of the braking mode.
The system disclosed in Mayne el al. also includes a reset valve which operates to cause the slave piston to retract after an initial opening of the exhaust valve during braking. As a result, the exhaust valve is closed prior to the end of the expansion stroke and before the hydraulic pressure drops due to a return motion of the master piston. This design advantageously avoids shock or asymmetric loading of the crosshead by the exhaust rocker arm at the start of the main opening event of the exhaust valve following the initial opening event. However, the reset valve is formed in the slave cylinder for contact, and thus tripping, by the slave piston. Thus, the reset valve relies on the movement of the slave piston relative to the piston housing. Also, the reset valve is closed when the engine is operating in a power mode thereby undesirably creating a small volume in the slave piston which is not connected to the low pressure drain. As a result, air pockets may form in this volume disrupting slave piston or reset valve motion thereby possibly adversely affecting the predictability of the braking event.
U.S. Pat. No. 5,680,841 to Hu discloses an electro-hydraulic engine valve control system for permitting engine braking operation which includes a slave piston mounted in a bore formed in a rocker lever, a control oil circuit formed in the rocker lever and rocker shaft and a check valve positioned in the oil control circuit between the slave piston and a central oil passage formed in the rocker shaft. The system also includes an electronically controlled valve and an accumulator positioned along the oil control circuit. However, this system uses a cam profile which causes the exhaust valve to completely close between the initial opening of the exhaust valve and the primary opening of the exhaust valve during braking. This invention also requires the electronic control solenoid valve to open and close every engine cycle in both power and braking modes. Also, this design appears to undesirably require a solenoid for each cylinder.
Therefore, there is a need for an improved engine compression braking system having an integral rocker lever and reset valve capable of effectively avoiding asymmetric loading of a valve crosshead while providing accurate and predictable compression braking.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to overcome the deficiencies of the prior art and to provide an engine compression braking system capable of utilizing an integral rocker lever and reset valve to achieve optimum compression braking.
Another object of the present invention is to provide an engine compression braking system which incorporates a slave piston into the rocker lever along with a reset valve while eliminating other components of conventional systems, such as a control valve, master piston, adjusting screw and brake housing.
A further object of the present invention is to provide an engine braking system at a reduced cost while also minimizing weight and size.
Yet another object of the present invention is to provide an engine braking system including an integrated rocker lever and slave piston and a cam having a profile which avoids reverse pivoting of the rocker lever between an initial opening of the exhaust valve during braking and a main opening event.
It is yet another object of the present invention to provide an engine compression braking system including a rocker lever and a reset valve integrated into the rocker lever which is capable of effectively causing the return of an exhaust valve to a closed position without the reverse pivot of the rocker arm.
A still further object of the present invention is to provide an integrated rocker lever and reset valve wherein the reset valve is positioned to be operated by contact with an adjacent engine component.
Yet another object of the present invention is to provide an engine braking system including an integrated rocker lever and slave piston wherein the slave piston is positioned in a bore continuously connected to a braking fluid supply when the engine brake is off and the engine is operating in a normal power mode.
These and other objects are achieved by providing a braking system for an internal combustion engine having at least one engine piston reciprocally mounted within a cylinder for cyclical successive compression and expansion strokes and at least one exhaust valve operable to open near the end of an expansion stroke of the engine piston when the engine is operated in a power mode and operable to open in a timed relationship to the engine piston compression stroke when the engine is operated in a braking mode. The braking system includes a rocker lever pivotally mounted adjacent the exhaust valve for opening the exhaust valve and a braking fluid circuit formed in the rocker lever and including a low pressure circuit and a high pressure circuit. The braking system further includes a control valve positioned along the braking fluid circuit and operable in a first position to cause engine operation in the power mode and a second position to cause engine operation in the braking mode. The braking system further includes an actuator piston bore formed in the rocker lever in communication with the high pressure circuit and an actuator piston slidably mounted in the actuator piston bore. In addition, the braking system includes a reset valve mounted on the rocker lever a spaced distance from the actuator piston so
Argenbright Tony M.
Brackett Tim L.
Cummins Engine Company, Inc.
Leedom Jr. Charles M.
Nixon & Peabody LLP
LandOfFree
Engine compression braking system with integral rocker lever... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Engine compression braking system with integral rocker lever..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Engine compression braking system with integral rocker lever... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2559208