Patent Application
20210156319
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.
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 (and thus, the vehicle as well). 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 and gained widespread acceptance.
The typical compression-release engine brake system opens an exhaust valve(s) just prior to Top Dead Center (TDC) at the end of a compression stroke. 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 both high mechanical loading and engine speeds. Also, the sudden release of the highly compressed gas comes with a high level of noise. In some areas, typically urban, 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. It is the loud sound that 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, i.e., custom designed and engineered to a particular engine make and model. 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.
U.S. Pat. No. 8,272,363 describes a self-contained compression brake control module (CBCM) for controlling exhaust valve motion, primarily for, but not limited to, the purpose of engine retarding. The CBCM described in U.S. Pat. No. 8,272,363 is often required to operate with a significant axial offset between a longitudinal axis of the CBCM and a longitudinal valve axis of an exhaust valve it acts upon, as illustrated in FIGS. 2A-C of the U.S. Pat. No. 8,272,363.
The CBCM described in U.S. Pat. No. 8,272,363 comprises an actuation piston retaining ring and seal engaging the same bore within a single casing of the CBCM. This causes an increased diameter requirement in a portion of the bore due to assembly concerns with passing a seal past a retaining ring groove. The CBCM of U.S. Pat. No. 8,272,363 utilized a casing that contained the actuation piston while still requiring a support housing, adding diameter to the overall assembly. These contributors to a required offset generates a side force acting on the actuation piston of the CBCM, which causes a risk of wear and/or jamming of the actuation piston in its bore. Practical applications for the CBCM often dictate both a reduction in overall height and diameter in order to fit within existing engine packages without interference or undesired changes to other components. It is therefore advantageous to be able to reduce the size of the CBCM module, to both better center it over the loading generated by the exhaust valve, and to package it into tighter space constraints.
Thus, 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 is easier to assemble, is more robust and compact when assembled, enhances performance and significantly reduces the development time and cost of the compression-release engine brake system.
The present invention provides a compression-release brake system for an internal combustion including a more compact self-contained compression brake control module in the form of a hydraulically expandable linkage that is integrated with mounting hardware into the valve train of the I.C. engine. The compact design results in easier device assembly; and, a more robust and compact device when assembled.
The compression-release brake system comprises a self-contained compression brake control module (CBCM) operatively coupled to the exhaust valve for controlling a lift and a phase angle thereof. The CBCM includes a casing defining an actuator cavity, an actuation piston disposed outside the casing so as to define an actuation piston cavity between the casing, the actuation piston, and the bore into which the CBCM has been installed. The CBCM further includes a check valve provided between the actuation piston cavity and a compression brake actuator disposed in the actuator cavity. The actuation piston reciprocates relative to the casing and the bore. The compression brake actuator includes an actuator element and a biasing spring. The actuator element selectively engages the check valve when deactivated to unlock fluid contained within the actuation piston cavity and disengages from the check valve when activated so as to lock fluid within the actuation piston cavity.
The present invention provides advantages owing to its relatively smaller and more compact design. This design fits under valve train covers without major modification of existing fuel injection or valve train components and minimum increased valve cover height. In addition, the compact size enables design flexibility to install the CBCM even on engines configurations with a single valve cover per cylinder.
By virtue of the compact design and inclusion of an internal check valve, locking pressurized hydraulic fluid in a similarly compact actuation piston chamber, the present device provides a design using a minimum fluid volume thereby reducing the compliance of the trapped hydraulic fluid. The compactness thus yields a stiffer system to more readily maintain a constant exhaust valve(s) lift at higher engine loading in the CBCM engine braking mode. The compactness also creates the possibility of closer axial alignment between the CBCM and an underlying actuated exhaust valve.
The compact design can more easily be accommodated to more engine configurations and hardware with the same CBCM integrated hardware design and can be accomplished with much lower engineering design costs and time, prototype fabrication and validation testing.
Additional 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:
Reference will now be made in detail to exemplary embodiments and methods of the invention as illustrated in the accompanying drawings, in which like reference characters designate like or corresponding parts throughout the drawings. It should be noted, however, that the invention in its broader aspects is not limited to the specific details, representative devices and methods, and illustrative examples shown and described in connection with the exemplary embodiments and methods.
This description of exemplary embodiment(s) is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description, relative terms such as “horizontal,” “vertical,” “up,” “down,” “upper”, “lower”, “right”, “left”, “top” and “bottom”, “front” and “rear”, “inwardly” and “outwardly” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing figure under discussion. These relative terms are for convenience of description and normally are not intended to require a particular orientation. Terms concerning attachments, coupling and the like, such as “connected” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. The term “operatively connected” is such an attachment, coupling or connection that allows the pertinent structures to operate as intended by virtue of that relationship. The term “integral” (or “unitary”) relates to a part made as a single part, or a part made of separate components fixedly (i.e., non-moveably) connected together. The words “smaller” and “larger” refer to relative size of elements of the apparatus of the present invention and designated portions thereof. Additionally, the word “a” and “an” as used in the claims means “at least one” and the word “two” as used in the claims means “at least two”.
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 exemplary embodiment, illustrated in
The CBCM 40 further comprises an actuation piston 48 slidingly mounted to the casing 42 for slidingly reciprocating within a cylindrical bore 98 in the support member 51 (best shown in
The actuation piston 48 is coaxial with the longitudinal axis XM of the CBCM 40, as best shown in
The actuation piston 48 has an annular retaining ring 58 disposed in a complementary groove in an annular outer peripheral surface of the cylindrical inner portion 53 of the casing 42 of the CBCM 40. The groove is sufficiently shallow such that a portion of the retaining ring 58 projects radially outwardly from the cylindrical inner portion 53 of the casing 42. Moreover, a cylindrical inner surface 53 of the casing 42 is formed with an annular piston groove 54 having annular flat, axially opposite outer and inner stop surfaces 55 and 56, respectively.
As shown in
The hydraulic seal 52 mounted to an outer peripheral surface of the actuation piston 48 and the retaining ring 58 disposed within the actuation piston 48 provides a decrease in overall CBCM diameter, thereby allowing for a reduction in offset distance between the longitudinal axis of the CBCM 40 and the longitudinal valve axis of the brake exhaust valve 182.
The compression brake control module 40 further comprises a supply (or inlet) port 60 formed within the body of the casing 42. This provides a pressurized hydraulic fluid from a source 34 of the pressurized hydraulic fluid to the hydraulic actuation piston chamber 50 through the connecting passage 47. This pressure extends the actuation piston 48 to the extended position thereof when there is a gap 6A between the actuation piston 48 and the exhaust valve pin 25 of the brake exhaust valve 182. This gap can occur 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, i.e., timing and duration, for the compression brake actuation mode of the I.C. engine 10.
The compression-release brake system 12 according to the 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, and an actuator opening 47b. As illustrated in detail in
The CBCM 40 further comprises a check valve 62 provided in the valve cavity 44 of the cylindrical inner portion 53 of the casing 42 between the supply port 60 and the actuation piston chamber 50 to hydraulically lock the actuation piston chamber 50 when a pressure of the hydraulic fluid within the actuation 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 actuation piston chamber 50 (i.e., between the inner end face 49a of the actuation piston 48 and the separation wall 46 of the casing 42) to selectively isolate and seal the actuation 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 separation 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 high-pressure actuation piston chamber 50 and hold the actuation piston 48 in the retracted position without an additional return spring.
The CBCM 40 also comprises a hydraulic compression brake actuator 70 mounted within the actuator cavity 45 of the casing 42. Actuator 70 selectively engages the ball member 64 of the check valve 62 when the CBCM is deactivated so as to unlock the actuation piston chamber 50 and fluidly connect the actuation piston chamber 50 to the source 34 of the pressurized hydraulic fluid. When activated, actuator 70 disengages the ball member 64 of the check valve 62 so as to lock the actuation piston chamber 50 and fluidly disconnect the actuation piston chamber 50 from the source 34 of the pressurized hydraulic fluid. The compression brake actuator 70 includes a reciprocating actuator element (or control piston) 72 slidingly mounted within the casing 42 for reciprocating within the actuator cavity 45 between a retracted position (shown in
Thus, the compression brake control module 40 incorporates a system to trap engine hydraulic oil in a actuation piston chamber 50 above the actuation 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 actuation piston chamber 50. The CBCM 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 thus provides a miniaturized CBCM 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 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 84.
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 solenoid 36′ closes the compression brake control valve 36 and the hydraulic compression brake control module 40 is in the depressurized condition (or de-energized state) so that no hydraulic fluid is supplied to the compression brake control module 40, and the actuation piston chamber 50 and the actuation piston cavity 57 are filled with hydraulic fluid but not the pressurized hydraulic fluid. In such a condition, shown in
The actuation piston 48 is able to extend if the friction of the hydraulic seal 52 is overcome, but will then retract under load in this state. The de-energized state is utilized during the normal engine operation. The actuation piston 48 is set with an initial spacing (lash) to an exhaust valve or exhaust valve bridge (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.
Pressurized hydraulic fluid enters the CBCM 40 from the support member 51 through the inlet port 60 and passes through machined facets (or ribs) of the control piston 72 of the compression brake actuator 70 to the connecting passage 47. Consequently, the pressurized hydraulic fluid fills the actuation piston cavity 57, building pressure in the CBCM 40, which extends the actuation piston 48 and the control piston 72 until they contact the retaining ring 58 and the end cap 76, respectively. Moreover, when the pressurized engine oil is supplied to the inlet port 60 of the compression brake control module 40, the control piston 72 of the compression brake actuator 70 is forced outward by the supply oil pressure allowing the ball member 64 to be seated. The ball member 64 lands on the valve seat 47a of the casing 42, creating the one-way (i.e., check) valve 62 which traps hydraulic fluid in the actuation piston cavity 57. The energized state is utilized during the engine braking operation.
At the same time, the pressurized hydraulic fluid will flow into the actuation piston chamber 50 and the actuation piston cavity 57. As the pressurized supply oil fills the actuation piston chamber 50 and the actuation piston cavity 57, the pressure of the supply oil forces the actuation piston 48 outwardly until the actuation piston 48 contacts the mechanical stop (in the form of the retaining ring 58), as shown in
In a position illustrated in
Thus, when the exhaust cam member 30 moves the exhaust valve 18 away during the normal exhaust motion, the actuation piston 48 extends and ‘catches’ the exhaust valve 18 upon its return, in order to hold it open a fixed amount during the remainder of the engine cycle. There is a constant load on the actuation piston 48 from the exhaust valve return spring force, and a varying load due to pneumatic pressure in the engine cylinder acting on a face of the exhaust valve 18. Hydraulic pressure builds within the trapped oil in the actuation piston cavity 57 to support this load.
When the engine braking mode is deactivated, the solenoid valve 36 is turned off to cut the pressurized oil supply to the compression brake control module 40, thereby resulting in the control piston spring 78 forcing the control piston 72 toward the ball check valve 62, which unseats the ball member 64 from its seated position. The released oil flows out the actuation piston chamber 50 through the external three-way solenoid valve 36 and back to an oil sump 35, shown in
In other words, when hydraulic fluid pressure is removed from the CBCM 40, the control piston 72 moves back into contact with the ball member 64 until a subsequent normal exhaust valve event, at which point the hydraulic pressure in the actuation piston cavity 57 is reduced sufficiently for the force of the control piston spring 78 to unseat the ball member 64. The actuation piston 48 is provided with a hydraulic bypass feature (or passage) 59 to prevent the retaining ring 58 from trapping hydraulic fluid within the actuation piston cavity 57 when the CBCM 40 is de-energized.
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 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.
| Number | Date | Country | |
|---|---|---|---|
| 62938595 | Nov 2019 | US |
