Patent Grant
7900597
1. Field of the Invention
The present invention relates to compression-release brake systems for internal combustion engines in general, and, more particularly, to a self-contained compression-release brake control module for a compression-release engine brake system of an internal combustion engine.
2. Description of the Prior Art
For internal combustion engines (IC engine), especially diesel engines of large trucks, engine braking is an important feature for enhanced vehicle safety. Consequently, the diesel engines in vehicles, particularly large trucks, are commonly equipped with compression-release engine brake systems (or compression-release retarders) for retarding the engine (thus, vehicle). The compression release engine braking provides significant braking power in a braking mode of operation. For this reason, the compression-release engine brake systems have been in North America since the 1960's.
The typical compression-release engine brake systems open exhaust valve(s) just prior to Top Dead Center (TDC) at the end of a compression stroke, which is a standard technology for a compression-release engine braking. This creates a blow-down of the compressed cylinder gas and the energy used for compression is not reclaimed. The result is engine braking, or retarding, power. A conventional compression-release engine brake system has substantial cost associated with the hardware required to open the exhaust valve(s) against the extremely high load of a compressed cylinder charge. Valve train components must be designed and manufactured to operate reliably at high mechanical loading. Also, the sudden release of the highly compressed gas comes with a high level of noise. In some areas, engine brake use is not permitted because the existing compression-release engine brake systems open the valves quickly at high compression pressure near the TDC compression that produces high engine valve train loads and a loud sound, which has resulted in prohibition of engine compression release brake usage in certain urban areas.
Typically, the compression-release engine brake systems up to this time are unique and custom designed and engineered to a particular engine make. The design, prototype fabrication, bench testing, engine testing and field testing typically require twenty four (24) months to complete prior to sales release. Accordingly, both the development time and cost have been an area of concern.
Exhaust brake systems can be used on engines where compression release loading is too great for the valve train. The exhaust brake mechanism consists of a restrictor element mounted in the exhaust system. When this restrictor is closed, backpressure resists the exit of gases during the exhaust cycle and provides a braking function. This system provides less braking power than a compression release engine brake, but also at less cost. As with a compression release brake, the retarding power of an exhaust brake falls off sharply as engine speed decreases. This happens because the restriction is optimized to generate maximum allowable backpressure at rated engine speed. The restriction is simply insufficient to be effective at the lower engine speeds.
While known compression-release engine brake systems have proven to be acceptable for various vehicular driveline applications, such devices are nevertheless susceptible to improvements that may enhance their performance and cost. With this in mind, a need exists to develop improved compression-release engine brake systems that advance the art, such as a self-contained compression brake control module for a compression-release brake system of an internal combustion engine that significantly reduces the development time and cost of the compression-release engine brake system and enhances performance thereof.
The present invention provides a novel compression-release brake system for operating at least one exhaust valve of an internal combustion engine during a compression-release engine braking operation. The compression-release brake system of the present invention comprises an exhaust rocker assembly for operating the exhaust valve, a self-contained compression brake control module (CBCM) operatively coupled to the exhaust valve for controlling a lift and a phase angle thereof, and a source of a pressurized hydraulic fluid in fluid communication with the CBCM. The CBCM is provided to maintain the exhaust valve open during a compression stroke of the engine when the engine performs the compression-release engine braking operation.
The CBCM of the present invention comprises a casing including a single-piece body defining a piston cavity and an actuator cavity separated by a separation wall and being in fluid communication with each other through a connecting passage in the separation wall, and a slave piston slidingly mounted within the piston cavity for reciprocating within the piston cavity between an extended position and a collapsed position so as to engage the exhaust valve in the extended position thereof. The casing and the slave piston define a variable volume hydraulic slave piston chamber within the piston cavity between the separation wall and the slave piston. The CBCM further comprises a supply conduit formed within the casing so as to provide the pressurized hydraulic fluid from the source of pressurized hydraulic fluid to the hydraulic slave piston chamber to extend the slave piston to the extended position thereof when there is a gap between the slave piston and the exhaust valve, a check valve provided between the supply conduit and the hydraulic slave piston chamber to hydraulically lock the hydraulic slave piston chamber by closing the connecting passage in the separation wall when a pressure of the hydraulic fluid within the hydraulic slave piston chamber exceeds the pressure of the hydraulic fluid from the source, and a compression brake actuator disposed in the actuator cavity.
The compression brake actuator includes an actuator element slidingly mounted within the actuator cavity for reciprocating between an extended position when deactivated and a retracted position when activated, and a compression spring biasing the actuator element toward the extended position. The actuator element selectively engages and opening said check valve when deactivated solely by the biasing force of the compression spring so as to unlock the hydraulic slave piston chamber and fluidly connect the hydraulic slave piston chamber to the source of pressurized hydraulic fluid, and disengage from the check valve when activated so as to lock the hydraulic slave piston chamber and fluidly disconnect the hydraulic slave piston chamber from the source of pressurized hydraulic fluid. Moreover, the actuator element is exposed to atmospheric pressure.
According to a first exemplary embodiment of the present invention, the CBCM is hydraulically actuated and the compression-release brake system further comprises an external control valve to supply the pressurized hydraulic fluid to the CBCM during the compression-release engine braking operation. To deactivate the compression-release brake system, the external control valve dumps the pressurized hydraulic fluid to a hydraulic fluid sump. With the hydraulic controlled CBCM, the slave piston chamber is completely filled with the hydraulic fluid during the normal exhaust stroke when the exhaust valve is lifted off its valve seat by the normal exhaust cam profile. The hydraulic fluid in the slave piston chamber is hydraulically locked by the check valve located above the slave piston to hold the slave piston in the extended position. At the completion of the normal exhaust valve motion, the extended slave piston stops the exhaust valve from returning to the valve seat and thereby holds the exhaust valve open.
According to a second exemplary embodiment of the present invention, the CBCM is electrically actuated and the compression-release brake system does not require an additional external control valve to supply and turn on and off the supply of the pressurized hydraulic fluid. The compression brake actuator of the electrically actuated CBCM comprises a solenoid including a solenoid coil and the actuator element in the form of an armature slidingly mounted within the solenoid coil for reciprocating therewithin.
According to a third exemplary embodiment of the present invention, the CBCM is electrically actuated and the compression-release brake system further comprises an external control valve to supply the pressurized hydraulic fluid to the CBCM during the compression-release engine braking operation so as to define a timed electronically controlled compression-release brake system. The solenoid of the compression brake actuator of the electrically actuated CBCM is energized and de-energized during each engine cycle to control the engine brake exhaust valve opening and closing events. The external control valve supplies the CBCM with low pressure hydraulic fluid and the CBCM integrated solenoid allows opening and closing of the check valve to control the timed compression-release engine braking operation.
According to a fourth exemplary embodiment of the present invention, the CBCM is pneumatically actuated and the compression-release brake system further comprises a source of a compressed air so as to provide the compressed air from the source to the CBCM and an external compression brake control valve provided to selectively fluidly connect the source of the compressed air to the pneumatically actuated CBCM, but does not require an additional external control valve to supply the pressurized hydraulic fluid to the CBCM during the compression-release engine braking operation.
Moreover, according to the second to fourth exemplary embodiments of the present invention, the CBCM is spaced from the exhaust rocker assembly so that the exhaust rocker assembly is movable relative to the CBCM so that the single-piece body of the CBCM is non-movably fixed to a cylinder head or a cylinder block of the engine.
According to a fifth exemplary embodiment of the present invention, the compression-release brake system includes a dedicated brake rocker assembly added in addition to conventional intake and exhaust rocker assemblies. The dedicated brake rocker assembly comprises a dedicated compression-release cam member and a dedicated brake rocker arm. The CBCM is mounted to one end of the brake rocker arm so that the CBCM is disposed adjacent to the exhaust valve for operatively coupling the dedicated brake rocker assembly with the exhaust valve.
Therefore, a compression-release brake system in accordance with the present invention with a self-contained compression brake control module improves and optimizes operational characteristics of the internal combustion engine and provides small compact and universal design, allows for individual cylinder application and component flexibility, requires minimum fluid compliance, lowers engineering and component cost, and reduces development time.
Other objects and advantages of the invention will become apparent from a study of the following specification when viewed in light of the accompanying drawings, wherein:
The preferred embodiments of the present invention will now be described with the reference to accompanying drawings.
For purposes of the following description, certain terminology is used in the following description for convenience only and is not limiting. The words such as “front” and “rear”, “left” and “right”, “inwardly” and “outwardly” designate directions in the drawings to which reference is made. The words “smaller” and “larger” refer to relative size of elements of the apparatus of the present invention and designated portions thereof. The terminology includes the words specifically mentioned above, derivatives thereof and words of similar import.
The valve train of the present invention includes an intake rocker assembly 22 for operating the intake valves 17, and an exhaust rocker assembly 24 for operating the exhaust valves 18. The intake rocker assembly 22 includes an intake cam member 26, an intake rocker arm 28 mounted about an intake rocker shaft 29 and provided to open the intake valves 17 through an intake valve bridge 27. Similarly, the exhaust rocker assembly 24 includes an exhaust cam member 30, an exhaust rocker arm 32 mounted about an exhaust rocker shaft 33 and provided to open the exhaust valves 18 (i.e., the exhaust valves 181 and 182) through an exhaust valve bridge 31.
As further illustrated in
In the first exemplary embodiment, illustrated in
The slave piston 48 can reciprocate within the piston cavity 44 between two mechanical slave piston stops defining the extended position (shown in
The compression brake control module 40 further comprises a supply/dumping conduit 60 formed within the body 42 of the casing so as to provide the pressurized hydraulic fluid from a source 34 of a pressurized hydraulic fluid to the hydraulic slave piston chamber 50 through the connecting passage 47 to extend the slave piston 48 to the extended position thereof when there is a gap δA between the slave piston 48 and the exhaust valve pin of the brake exhaust valve 182, such as when the exhaust valves 18 are open by the exhaust rocker assembly 24 (as illustrated in
Thus, the hydraulically activated compression brake control module 40 of the compression-release brake system 12 holds the exhaust valve 18 off the exhaust valve seat at a predetermined setting for the compression brake actuation mode of the I.C. engine 10.
The compression-release brake system 12 according to the first exemplary embodiment of the present invention further includes an external compression brake control valve 36 (shown in
The connecting passage 47 formed longitudinally through the separation wall 46, includes a piston opening 47a, an actuator opening 47b and an intake opening 47c. As illustrated in detail in
The compression brake control module 40 further comprises a check valve 62 provided in the piston cavity 44 between the supply/dumping conduit 60 and the slave piston chamber 50 to hydraulically lock the slave piston chamber 50 when a pressure of the hydraulic fluid within the slave piston chamber 50 exceeds the pressure of the hydraulic fluid from the source 34 during the compression brake actuation mode. In other words, the check valve 62 is disposed in the slave piston chamber 50 (i.e., between the inner end face 49a of the piston 48 and the inner wall 46 of the casing 42 to selectively isolate and seal the slave piston chamber 50. Preferably, the check valve 62 includes a valve member, preferably in the form of a substantially spherical ball member 64 provided to seal against the piston port 47a of the connecting passage 47. It should be understood that an edge of the inner wall 46 forming the piston port 47a defines a valve seat of the ball member 64 of the check valve 62. Preferably, the ball member 64 is biased against the piston opening 47a of the connecting passage 47 by a biasing coil spring 66. The hydraulically activated CBCM 40 provides a seal to eliminate oil leakage from the slave piston high pressure chamber 50 and hold the slave piston 48 in the extended position without an additional return spring.
The compression brake control module 40 also comprises a hydraulic compression brake actuator 70 mounted within the actuator cavity 45 of the casing 42 and provided to selectively engage the ball member 64 of the check valve 62 when deactivated so as to unlock the slave piston chamber 50 and fluidly connect the slave piston chamber 50 to the source 34 of the pressurized hydraulic fluid, and to disengage from the ball member 64 of the check valve 62 when activated so as to lock the slave piston chamber 50 and fluidly disconnect the slave piston chamber 50 from the source 34 of the pressurized hydraulic fluid. The compression brake actuator 70 according to the first exemplary embodiment of the present invention is a hydraulic (i.e., hydraulically operated) actuator. Specifically, the compression brake actuator 70 includes a reciprocating actuator element (or master piston) 72 slidingly mounted within the casing 42 for reciprocating within the actuator cavity 45 between an extended position (shown in
Thus, the compression brake control module 40 incorporates a system to trap engine hydraulic oil in a slave piston chamber 50 above the slave piston 48 to prevent the exhaust valve 18 from returning to the valve seat at the end of the compression stroke. The system assures an absolute minimum trapped oil volume to minimize the bulk modulus compressibility of the trapped oil in the slave piston chamber 50. The compression brake control module 40 is attached to the engine 10 (preferably to a cylinder head) through an attaching hardware that incorporates a stiff mounting hold-down to minimize mechanical hardware flexibility during engine braking operation. Incorporation of minimum oil compliance and hardware deflections provides predictable and optimal engine brake retarding performance. The present invention also provides a miniature compression brake control module 40 housing package.
The compression-release brake system 12 of the I.C. engine 10 can be used in conjunction with a fixed orifice exhaust brake, a pressure regulated exhaust brake or a variable geometry turbocharger (VGT) to incorporate two cycle engine braking. The combination uses the compression and exhaust strokes to produce a quieter system with reduced engine valve train loading while yielding excellent brake retarding power. Thus, the diesel engine 10 further comprises a turbocharger 80 including a compressor 82 and a turbine 83, and a variable exhaust brake 84 fluidly connected to the turbocharger 80 through an exhaust passage 21. As illustrated in
As illustrated in
In accordance with the present invention illustrated in
The exhaust brake actuator 86 is controlled by a microprocessor (or exhaust brake electronic controller) 87. The microprocessor 87 controls the variable exhaust restrictor 85, thus the amount of exhaust braking, based on the information from a plurality of sensors 88 including, but not limited, an pressure sensor and a temperature sensor sensing pressure and temperature of the exhaust gas flowing through the exhaust restrictor 85 of the exhaust brake 84. It will be appreciated by those skilled in the art that any other appropriate sensors, may be employed. The pneumatic actuator 86 is operated by a solenoid valve 89 provided to selectively connect and disconnect the pneumatic actuator 86 with a pneumatic pressure source (not shown) through a pneumatic conduit 89′ in response from a control signal from the microprocessor 87.
The compression-release brake system 12 according to the first exemplary embodiment of the present invention is controlled by an electronic controller 90 (as illustrated in
The exhaust brake 84 reads exhaust system pressure and temperature from the sensors 92 at the microprocessor 90 and regulates a signal 89 to the exhaust brake actuator 86 that adjusts the variable exhaust restrictor 85. The electronic controller 90 also provides a signal 96 to the microprocessor 87 of the exhaust brake 84. When the engine 10 is operating in engine brake mode, the control signal 96 adjusts the variable exhaust restrictor 85 in order to maintain a desired exhaust backpressure.
The braking operation of the I.C. engine 10 of the present invention has two integral components: a compression release (weeper) braking provided by the compression-release brake system 12, and an exhaust braking provided by the exhaust brake 84. The compression release braking component is provided by action of the compression brake control module 40 of the compression-release brake system 12, while the exhaust braking is provided by the exhaust brake 44.
The operation of the compression-release brake system 12 is described in detail below.
When the engine 10 performs positive power operation (i.e., operates in the normal engine cycle), the compression brake control valve 36 is closed and the hydraulic compression brake control module 40 is in the depressurized condition so that no hydraulic fluid is supplied to the compression brake control module 40, and the slave piston chamber 50 is filled with the hydraulic fluid but not the pressurized hydraulic fluid. In such a condition, shown in
During the engine braking operation, when it is determined by the electronic controller 90 based on the information from the plurality of sensors 92 that the braking is demanded, such as when a throttle valve (not shown) of the engine 10 is closed, the exhaust brake 84 is actuated by at least partially closing the butterfly valve 85 in order to create a backpressure resisting the exit of the exhaust gas during the exhaust stroke. Moreover, during the engine braking operation, the electronic controller 90 opens the compression brake control valve 36 to turn on the supply of the pressurized hydraulic fluid to the compression brake control module 40, thus setting the compression brake control module 40 to the pressurized condition. When the pressurized engine oil is supplied to the supply/dumping conduit 60 of the compression brake control module 40, the master piston 72 of the compression brake actuator 70 is forced outward by the supply oil pressure allowing the check ball 64 to be seated. At the same time, the pressurized hydraulic fluid will flow into the slave piston chamber 50. As the pressurized supply oil fills the slave piston chamber 50, the pressure of the supply oil forces the slave piston 48 outwardly until the slave piston 48 contacts the mechanical stop (in the form of the snap ring 58), as shown in
In a position illustrated in
When the engine braking mode is deactivated, the solenoid valve 36 is turned off to cut out the pressurized oil supply to the compression brake control module 40, thereby resulting in the compression spring 78 forcing the actuation piston 72 toward the ball check valve 62, which unseats the ball member 64 from its seated position. The released oil flows out the slave piston chamber 50 through the external three way solenoid valve 36 and back to an oil sump 35, shown in
The compression-release brake system 12 with the hydraulically activated compression brake control module 40 holds the exhaust valve 18 off the exhaust valve seat at a predetermined setting for the complete engine brake cycle (weeper brake event). The compression-release brake system 12 can be used in conjunction with a fixed orifice exhaust brake, a pressure regulated exhaust brake or a VGT turbocharger to incorporate two cycle engine braking. The combination uses the compression and exhaust strokes to produce a quieter system with reduced engine valve train loading while yielding excellent brake retarding power.
The compression-release brake system 12 used in combination with the pressure regulated exhaust brake 84 provides advantages over using a compression-release brake system with a fixed orifice exhaust brake. When a compression-release brake and exhaust brake combination is designed for maximum exhaust backpressure and the compression-release brake component fails to function for any reason the typical extended exhaust/intake valve overlap condition will be eliminated. The elimination of the extended valve overlap results in much higher exhaust manifold pressures and the engine can experience unacceptable valve seating velocities which can result in major engine damage and excessive valve seat wear.
Major engine damage can result from valve seat damage or valve spring failure. Valve spring failure can cause engine valves to drop into the combustion chamber and can cause progressive engine damage. Valve seat damage can progress because the exhaust valve will not adequately seal compression pressures and/or not provide good heat transfer from the exhaust valve to the cylinder head during high positive power engine loading.
The pressure regulated exhaust brake that is used in combination with the compression-release brake system has the advantage that the exhaust brake can be used alone on a combination compression-release/exhaust brake engine with no possibility of over-pressurizing the exhaust manifold and thereby avoiding excessive valve floating and unacceptable valve seating velocities. Because the pressure regulated exhaust brake is self-regulating, over-pressurization of the exhaust manifold cannot occur because the restriction orifice in the exhaust brake increases in area automatically to maintain a highest constant exhaust manifold pressure in compliance with engine manufacture specifications.
The main difference of the compression-release brake system 112 of
The compression brake actuator 170 according to the second exemplary embodiment of the present invention is an electric (i.e., electrically operated) actuator. Specifically, the compression brake actuator 170 includes a solenoid coil 171 fixed to an inner peripheral surface of the cylindrical actuator cavity 45 of the casing 42 and an armature (or actuator element) 172 slidingly mounted within the solenoid coil 171 for reciprocating within the actuator cavity 45 between an extended position (shown in
The armature 172 is provided with an O-ring seal 172′ for sealing the vent port 177, and O-ring seals 172″ for sealing the actuator chamber 174. The compression brake actuator 170 also includes a compression spring 178 acting between the armature 172 and the end cap 176 to bias the armature 172 toward the extended position thereof. The armature 172 is adapted to reciprocate between the inner wall 46 of the casing 42 and the end cap 176. In other words, the solenoid compression brake actuator 170 is provided to switch the CBCM 140 between an activated (or “On”) condition (shown in
During brake-on operation the compression brake actuator 170 of the CBCM 140 is controlled by an electronic controller (ECU) 90 based on the information from a plurality of sensors 92 representing engine and vehicle operating parameters as control inputs, including, but not limited to, an engine speed, an engine load, an engine operating mode, etc., switching the internal solenoid coil 171 off and on. The solenoid brake actuator 170 will be power on after the normal exhaust valve closing and be powered off after the start of the expansion stroke.
When the engine 10 performs positive power operation (i.e., operates in the normal engine cycle), the solenoid compression brake actuator 170 is de-energized (i.e., the solenoid coil 171 of the solenoid actuator 170 is not supplied with the electric current) so that the armature 172 is in the extended position (shown in
In operation, the engine oil supply is continuously supplied to the compression brake control module 140. When the internal solenoid actuator 170 of the CBCM 140 is energized, the solenoid armature 170 is pulled to its retracted position (shown in
The main difference of the compression-release brake system 212 of
The timed electronically controlled compression-release brake system 212 utilizes the external three-way solenoid valve 36 (i.e., exterior to the CBCM 140) to supply and dump the pressurized engine oil applied in combination with the internal solenoid actuator 170 of the CBCM 140 to control the on/off engine brake function. To activate the engine brake, electrical power is supplied to both the internal solenoid actuator 170 of the CBCM 140 and the external three-way solenoid valve 36. The external solenoid valve 36 supplies the CBCM 140 with low pressure engine oil and the internal solenoid actuator 170 of the CBCM 140 allows closing and opening of the check valve 62 to control the timed compression-release brake cycle. The electronically controlled timed compression-release brake system 212 of the invention improves engine braking performance over non-timed hydraulically controlled compression-release engine brake system 12. The timed compression-release brake event requires the electric power supplied to the internal solenoid actuator 170 integrated into the CBCM 140. The solenoid actuator 170 is energized and de-energized during each engine cycle to control the engine brake valve opening and closing events.
The timed compression-release brake system 212 holds the exhaust valve off the valve seat during the compression stroke, and de-energizes the solenoid actuator 170 during the beginning of the expansion stroke, closing the exhaust (brake) valve opening. This valve closing results in a stopping of exhaust manifold air to flow into the cylinder 14, thereby reducing cylinder pressure at the end of the expansion stroke, and causing additional piston work.
Closing the exhaust (compression brake) valve opening prior to the exhaust/intake valve overlap event prevents the exhaust/intake event from being extended. With an extended exhaust/intake valve overlap the higher pressure in the exhaust manifold forces exhaust manifold air back into the combustion chamber during the intake stroke and out through the open intake valve 17, thereby reducing exhaust manifold air mass and backpressure. Eliminating the extended exhaust/intake valve overlap provides a higher average exhaust manifold pressure, creating additional work done by the piston during the exhaust stroke.
Just after the beginning of the intake stroke, the electronic controller 90 of the timed compression-release brake system 212 triggers power to the external solenoid valve 36 and the internal solenoid actuator 170, thereby providing pressurized engine oil to the slave piston chamber 50. The slave piston 48 extends to a position of contact with the exhaust valve pin 25 but cannot open the brake exhaust valve 182 because the exhaust valve 182 is biased closed by the engine exhaust valve spring 18′. Near the end of intake stroke the pressure in the cylinder 14 is low and the pressure in the exhaust manifold 20 is high, due to the exhaust brake 84, resulting in the greatest pressure differential across the exhaust valves 18. This pressure differential causes the exhaust valves 18 to float off their valve seats forming a gap δA between the slave piston 48 and the exhaust valve pin 25 of the brake exhaust valve 182, as illustrated in
During the exhaust valves 18 float near the end of the intake stroke, the slave piston 48 of the CBCM 140 will continue to the mechanical stop position and the engine oil will be locked in the slave piston chamber 50 by the ball check valve 62. The slave piston 48 stops the floating brake exhaust valve 182 from returning to its valve seat. The brake exhaust valve 182 is held off its valve seat by the extended slave piston 48 a preset lift amount during compression stroke. After completion of the compression stroke, the cycle is completed.
After the start of the expansion stroke, the electronic controller 90 of the timed compression-release brake system 212 triggers the power to the external solenoid valve 36 and the internal solenoid actuator 170 to be shut off. The slave piston 48 retracts and the brake exhaust valve 182 is fully closed until the cycle repeats itself just after the beginning of the intake stroke.
The electronic package required for the electronic timed compression-release/exhaust combination brake provides additional engine retarding power. The timed compression-release/exhaust combination brake system of the invention is able to satisfy heavy duty vehicle applications that require higher retarding power than a non-timed compression-release/exhaust combination brake system.
The oil supply requires the external three way solenoid valve 36 to be energized when engine brake is switched on to supply oil to the CBCM 140. During brake-on operation the timed compression-release brake system 212 can be controlled by the electronic controller 90 switching the internal solenoid actuator 170 of the CBCM 140 off and on. The internal solenoid actuator 170 will be powered on after the normal exhaust valve closing and be powered off after the start of the expansion stroke. The exhaust brake must be on and develop enough exhaust manifold pressure to float the exhaust valves 18 during the engine braking speed range. To start the exhaust valve weeper event the internal solenoid actuator 170 can be energized by the electronic controller 90 after the closing of the exhaust valves 18 allowing the ball check 64 to return to its seat. During the exhaust valve float near the ending of the inlet stroke the exhaust valve floating will permit the slave piston 48 to move downward allowing the slave piston chamber 50 to be filled and contact the mechanical stop 58, lock in oil and hold off the brake exhaust valve 182 from returning to the valve seat to for next weeper brake cycle.
The fail safe spring 66 will lift the ball member 64 off its seat when the internal solenoid 170 is powered off, releasing the oil in the slave piston chamber 50 back into the oil supply to allow the exhaust valve(s) 18 to return to their valve seat. Next the electronic controller 90 signals for powering the internal solenoid 170 and cycle starts again.
The operation of the timed compression-release brake system 212 is described in detail below.
The timed compression-release brake system 212 requires the electronic controller 90 to time the electrical actuation signal to energize and de-energize the internal solenoid actuator 170 of the CBCM 140. The supply oil pressure is supplied by the external three way solenoid valve 36 to supply to the inlet port 60 of the CBCM 140 when the engine brake is activated. The integrated solenoid of the CBCM 140 controls the opening and closing of the ball check valve 62 during weeper brake activation and deactivation. The ball check valve 62 locks the oil in the slave piston chamber 50, preventing the slave piston 48 from returning. The slave piston 48 is locked in place by the trapped oil in the slave piston chamber 50, which prevents the brake exhaust valve 182 from closing. The location of the slave piston stop 58, piston stroke limiting feature and the slave piston lash adjustment determine the amount of distance that the brake exhaust valve 182 is held off the valve seat for the weeper braking event.
In a timed weeper brake system 212, an electronic trigger mechanism energizes and de-energizes the internal solenoid 171, 172 of the CBCM 140 to shut the exhaust valve lift of the weeper brake just after the start of the expansion stroke of the engine 10 to eliminate any increase in the normal engine exhaust/intake valve overlap condition. The closed exhaust valve 18, prior to the intake stroke, eliminates the increased valve overlap condition which occurs on the non-timed weeper brake system 112 where the weeper brake holds the exhaust valve 18 open for the entire engine braking event. The condition of increased overlap on the non-timed weeper brake allows exhaust air mass to flow from the exhaust manifold 20 into the cylinder 14′ and then out the intake valve 17 into the inlet manifold 19. This considerable loss of air mass in the exhaust manifold prohibits obtaining the maximum desired exhaust manifold pressure. In the timed weeper engine brake system 212 of the present invention, engine retarding power is increased by the increased work done during the exhaust stroke. The higher retarding power results from the increased exhaust manifold pressure and the additional negative work done on the expansion stroke by closing the exhaust valve 18 at the beginning of the expansion stroke.
In the timed weeper brake system 212, just after the start of the engine intake stroke an electronic trigger mechanism causes power to be applied to the internal solenoid 171, 172 integrated into the CBCM 140. The external three-way solenoid valve 36 supplies pressurized engine oil to the oil supply port 60 of the CBCM 140 continuously during brake activation, and the internal solenoid coil 171 pulls in the armature 172 to allow the ball check valve 62 to seal the slave piston chamber 50. The supply oil pressure forces the slave piston 48 against the exhaust valve pin 25 and brake exhaust valve 182. The exhaust valve spring 18′ prevents the slave piston 48 from opening the brake exhaust valve 182. With the combination exhaust brake operating, the exhaust brake orifice is sized to float the exhaust valves 18 off the valve seats a predetermined amount. The exhaust valve float occurs near bottom dead center (BDC) of the intake stroke because the differential pressure across to exhaust valve 18 is greatest at that time. During the exhaust valve float the slave piston 48 can fully extend because of the elimination of the valve spring force from the slave piston 48. When the exhaust valve 18 floats back towards the valve seat, the extended slave piston 48 holds the brake exhaust valve 182 off the valve seat the predetermined weeper brake opening. The weeper brake opening is held open for the full duration on the compression stroke. Just after top dead center (TDC) compression stroke, an electronic trigger mechanism causes the brake exhaust valve 182 to close and the weeper braking cycle repeats.
When the engine braking mode is deactivated, the external solenoid valve 36 releases the pressurized supply oil back to the sump 35 and the internal solenoid actuator 170 of the CBCM 140 is also deactivated causing the spring loaded armature 172 to force the ball member 64 of the check valve 62 off the seat releasing the oil from the slave piston chamber 50. The released oil will flow out the supply port 60 and through the external solenoid valve 36 back to the oil sump 35. The slave piston 48 will now be forced back to the collapsed position in the casing 42 by the exhaust valve spring 18′. The brake exhaust valve 182 will now be allowed to return to the valve seat to allow for normal engine valve motion.
The main difference of the compression-release brake system 312 of
More specifically, as illustrated in details in
The slave piston 348 can reciprocate within the piston cavity 344 between two mechanical slave piston stops defining the extended position and the collapsed position. Preferably, the slave piston 348 is formed with an opening 354 having outer and inner stop surfaces 355 and 356, respectively, while the casing 342 is provided with a slave piston stop member 358 extending across the piston cavity 344 through the opening 354 between the outer and inner stop surfaces 355 and 356 thereof and to mechanically limit of inward and outward movements of the slave piston 348. As illustrated in
The pneumatically actuated CBCM 340 further comprises a supply (or inlet) conduit (port) 360 and a dumping conduit (port) 361 formed within the body 342 of the casing so as to provide the pressurized hydraulic fluid from a source 34 of a pressurized hydraulic fluid to the hydraulic slave piston chamber 350 through the connecting passage 347 to extend the slave piston 348 to the extended position thereof when there is a gap δA between the slave piston 348 and the exhaust valve pin 25 of the brake exhaust valve 182. Preferably, an engine lubricating oil is used as the working hydraulic fluid stored in a hydraulic fluid sump 35. It will be appreciated that any other appropriate source of the pressurized hydraulic fluid and any other appropriate type of fluid will be within the scope of the present invention. Thus, the pneumatically actuated CBCM 340 of the compression-release brake system 312 holds the brake exhaust valve 182 off the exhaust valve seat at a predetermined setting for the compression brake actuation mode of the I.C. engine 10.
The pneumatically actuated CBCM 340 further includes a pneumatic compression brake actuator 370 located within the actuator cavity 345 of the casing 342 and provided to selectively engage a ball member 364 of a check valve 362 when deactivated so as to unlock the hydraulic slave piston chamber 350 and fluidly connect the slave piston chamber 350 to the source 34 of the pressurized hydraulic fluid, and to disengage from the ball member 364 of the check valve 362 when activated so as to lock the slave piston chamber 350 and fluidly disconnect the slave piston chamber 350 from the source 34 of the pressurized hydraulic fluid. Moreover, as illustrated in
The CBCM actuator 370 includes a spool valve 372 slidingly mounted within the casing 342 for reciprocating within the actuator cavity 345 between an extended position and a retracted position. The spool valve 372 is provided with a conduit 372′ fluidly connecting an annular groove 375 of the spool valve 372 with the connecting passage 347 in the inner wall 346. An outer end face 372a of the spool valve 372 is provided to engage an end cap (or stop member) 376 in the retracted position thereof. As illustrated in
The pneumatic compression brake actuator 370 further includes an actuator piston 377 slidingly mounted within the casing 342 for reciprocating within the actuator cavity 345 between an extended position and a retracted position so as to form a pneumatic actuator chamber 380 between the end cap 376 and the actuator piston 377. The actuator piston 377 sealingly engages an inner wall of the actuator cavity 345. The pneumatically actuated CBCM 340 further comprises an air inlet port 371 formed within the body 342 so as to provide the compressed air from the source 334 to the pneumatic actuator chamber 380 through the compressed air passageway 337 to extend the actuator piston 377 to the extended position thereof. The top face of the actuator piston 377 is subject to atmospheric pressure. The actuator piston 377 is non-movably (i.e., integrally) connected to the spool valve 372 through a connecting shaft 379 so as to form an actuator element 390 of the pneumatic compression brake actuator 370 (shown in
The operation of the compression-release brake system 312 is described in detail below.
Compressed air is supplied to the air inlet port 371 forcing the actuator piston 377 to stroke up until the outer end face 372b of the spool valve 372 contacts the stop member 376. The spool valve movement opens the engines oil supply port 360 and closes the oil dumping port 361. In addition, the upward spool movement allows the ball check valve 364 to close, thereby sealing the slave piston chamber 350. The oil supply pressure flows through the ball check valve 362 and into the slave piston chamber 350. The force on the slave piston 348 from the oil pressure supply moves the slave piston 348 down until the slave piston 348 contacts the slave piston stop 358 when the exhaust valve 18 is off the valve seat during the normal exhaust valve lift. The spring loaded check ball 364 locks the oil above the slave piston 348, preventing the slave piston 348 from returning. The slave piston 348 is now locked in place by the trapped oil in the slave piston chamber 350, which prevents the exhaust valve 18 from returning to the valve seat. The location of the slave piston stop 358 determines the amount of distance that the exhaust valve 18 is held off the valve seat during the engine braking mode.
When the engine braking mode is deactivated, the compressed air is released from the pneumatic actuator chamber 380, allowing the spool valve 372 (or the actuator element 390) to be forced downward (or inwardly) solely by the biasing force of the compression spring 378 and open the check valve 362. This allows the slave piston 348 to move upward by a compression spring 351 until the outer stop surface 355 of the slave piston 348 contacts the slave piston stop 358. In other words, the compression spring 351 biases the slave piston 348 toward the collapsed position thereof. The movement of the spool valve 372 (or the actuator element 390) closes the supply oil port 360, opens the dumping port 361 and forces the ball check 364 off its seat, thereby releasing the oil from the slave piston chamber 350. The released oil flows out the slave piston chamber 350 and through the connecting passage 347 and the dumping port 361 back to the oil sump 35. The slave piston 348 is forced back to the seated position in the housing 342 by the exhaust valve spring 18′ and the compression spring 351. The exhaust valve 18 returns to the valve seat to allow for normal engine valve operation.
The compression-release brake system 412 according to the fifth exemplary embodiment of the present invention includes a dedicated brake rocker assembly 420 added to each engine cylinder in addition to conventional intake and exhaust rocker assemblies 422 and 424, respectively. The dedicated brake rocker assembly 420 comprises a dedicated compression-release cam member 425 (shown in
The self-contained compression brake control module (CBCM) according to the fifth exemplary embodiment of the present invention may be a hydraulically actuated CBCM 40 of
To activate the compression-release brake system 412, engine oil supply is provided through a rocker pedestal 433 to the engine brake solenoid valve 36. When engine braking is activated, the solenoid valve 36 allows the pressurized oil flow through an exit passageway in the rocker pedestal 433 through dedicated brake oil drilling 435 in the rocker shaft 431 and then into the oil conduit 437 formed in the brake rocker arm 429 and finally into the CBCM 40 over the brake exhaust valve 182, as shown in
The operation of the compression-release brake system 412 is described in detail below.
With the dedicated cam engine brake system 412, the brake camshaft member 425 is added to each cylinder to provide the lift profile to open the compression release brake exhaust valve 182. The difference between the constant lift weeper brake system and the dedicated cam engine brake system is the dedicated cam engine brake system has a variable exhaust valve lift profile that doesn't release any compressed air during the compression stroke until near TDC compression stroke. The weeper brake system, since the exhaust valve is continuously open during the compression stroke, allows cylinder compressed air to escape through the slightly opened valve opening. Because the dedicated cam engine brake system doesn't bleed any cylinder air mass until near TDC compression, more work is done on the air with the dedicated cam engine brake system during compression.
At the start of the expansion stroke, the weeper lift is small compared to the dedicated cam brake lift, so the cylinder blow-down during the expansion stroke for the dedicated cam brake system is greater. The net result is that less work is obtained during the weeper stroke than the dedicated cam compression stroke and therefore the dedicated cam retarding power is much larger. The oil supply to the dedicated cam brake system can be routed from the engine oil pump 34 to the rocker pedestal 433 to the exterior engine brake solenoid valve 36 installed in the rocker pedestal 433. Down-stream of the solenoid valve 36 the engine brake supply oil can be routed through the brake drilling 435 in the rocker shaft 431 to the brake rocker arm 429 to supply the oil inlet port of the CBCM 40. The CBCM 40 can be arranged in the brake rocker arm 429 located over the inner exhaust valve (or brake exhaust valve) 182. The exhaust valve bridge 31 that bridges the two exhaust valves 18 shown in
When the engine brake solenoid valve 36 is activated, the pressurized oil flows into the CBCM 40 and the slave piston 48 extends to the stop. The ball check valve 62 is allowed to check the oil in the slave piston chamber 50 to lock the extended slave piston 48 in the extended position. The extended slave piston 48 removes all or nearly all of the valve train lash to activate the dedicated brake cam 425. The dedicated cam 425 forces the extended slave piston 48 to contact the exhaust valve bridge pin 25 near TDC compression. It then continues to open the brake exhaust valve 182 at a fast rate of rise to maximum brake lift near TDC compression and to close the brake exhaust valve 182 soon after TDC compression during the beginning of the expansion stroke. The profile of the engine brake dedicated cam member 425 is designed to optimize engine brake retarding performance and to meet EOEM valve train and other engine design specifications.
Therefore, the present invention provides a novel compression-release brake system for an internal combustion including a self-contained compression brake control module in the form of a hydraulically expandable linkage that is integrated into the valve train of the I.C. engine. The present invention provides the following design advantages over the prior art:
Small Compact Design—Fits under valve cover without major modification of existing fuel injection or valve train components and minimum increased valve cover height;
Individual Cylinder Application—Unique design provides design flexibility to install the CBCM on engines configurations with a single valve cover per cylinder;
Minimum Fluid Compliance—A check valve locking pressurized hydraulic fluid in a slave piston chamber provides a design using a minimum fluid volume thereby reducing the compliance of the trapped hydraulic fluid yielding a stiffer system to maintain a fairly constant exhaust valve(s) lift at higher engine loading in the engine braking mode;
Universal Design—Can accommodate most engine configuration with the same CBCM integrated hardware design with the exception of mounting the CBCM to the rocker arm overhead or cylinder head.
Lower Engineering Cost—Because of universal CBCM design, different engine applications can be accomplished with much lower engineering design, prototype fabrication and validation testing;
Reduced Development Time—New engine applications will not require designing complete engine brake hardware but only require adapting to specific mounting locations on the engine cylinder head and/or valve train;
Reduced Component Cost—Standardization of the universal design CBCM components increases volume of similar parts, thus enabling lower manufacturing and purchasing costs;
Hydraulic CBCM—The slave piston has a seal which eliminates piston to bore leakage and holds the slave piston in the upper or off position when the CBCM is off; and
Component Flexibility—The engine manufacturer or the engine brake manufacturer can supply brackets to mount the CBCM to the engine overhead. This allows for the engine manufacture to choose the low cost option. Other components besides the CBCM have the same option.
The foregoing description of the preferred embodiments of the present invention has been presented for the purpose of illustration in accordance with the provisions of the Patent Statutes. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiments disclosed hereinabove were chosen in order to best illustrate the principles of the present invention and its practical application to thereby enable those of ordinary skill in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated, as long as the principles described herein are followed. Thus, changes can be made in the above-described invention without departing from the intent and scope thereof. It is also intended that the scope of the present invention be defined by the claims appended thereto.
This Application claims the benefit under 35 U.S.C. 119(e) of U.S. Provisional Application No. 61/085,110 filed Jul. 31, 2008 by Meneely, V. et al.
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