Patent Application
20220307392
The present invention relates to compression-release engine brake systems for internal combustion engines in general and, more particularly, to a “low profile” or compact compression-release brake reset mechanism for a compression-release engine brake system including an adjacent actuation piston and a proximate accumulator.
For internal combustion engines (IC engine), especially four-stroke diesel engines of large trucks, engine braking is an important feature for enhanced vehicle safety. Consequently, the four-stroke 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). Compression release engine braking provides significant braking power when in braking mode of operation and the fuel supply deactivated. For this reason, 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 the 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.
Exhaust brake systems can also be used on engines where compression release loading is too great for the valve train. In such instances, the exhaust brake mechanism typically 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.
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, reduced overall size, robustness, and cost. To gain broader applicability of engine brake technology, overall size dimensions are a major consideration for the engine brake designer and engine manufacturer, ensuring safe clearances between the engine brake device and the surrounding valve train components. Overall engine brake height is a particularly important consideration. Increasing the height of the engine's valve cover is historically common for engine brake equipped engines. However, optimization and packaging restrictions are now common in the industry. Increases to valve cover height to allow for added engine brake clearance have down-stream effects to vehicle manufacturers. The vehicle manufacturer must allow for this increased clearance in truck design. Restrictions are therefore imposed on engine brake designers to adapt to existing architecture with minimal to zero changes allowable to the overall engine geometry.
According to a first aspect of the present invention, there is provided a compression-release engine brake system for effectuating a compression-release engine braking operation in connection with an internal combustion engine comprising at least one exhaust valve and at least one exhaust valve spring exerting a closing force on the at least one exhaust valve to urge the at least one exhaust valve into a closed position. The engine is a four-stroke piston cycle comprising an intake stroke, a compression stroke, an expansion stroke and an exhaust stroke. The compression-release system comprises a lost motion exhaust rocker assembly that comprises an exhaust rocker arm, an actuation device including an actuation piston slidably disposed in an actuation bore formed in the exhaust rocker arm and movable between retracted and extended positions, and a reset device including a reset check valve disposed in a reset bore in the exhaust rocker arm, a slider-piston slidably disposed in the reset bore of the exhaust rocker arm and operatively connected to the reset check valve, a reset pressure control spring disposed within the slider-piston, and an external slider bias spring biasing the slider-piston away from the reset bore to engage the at least one exhaust valve. The actuation device is operatively associated with the at least one exhaust valve to unseat the at least one exhaust valve from the closed position. The external slider bias spring is disposed outside the reset bore in the exhaust rocker arm and around the piston-slider. The actuation bore defines an actuation cavity delimited by the actuation piston within the actuation bore above the actuation piston. The reset bore is in fluid communication with the actuation cavity in the actuation device through a reset conduit within the exhaust rocker arm. The reset check valve is operable between an open position and a closed position. Hydraulic fluid is locked in the actuation cavity when the reset check valve is in the closed position, and flows bi-directionally through the reset check valve when the reset check valve is in the open position. The reset check valve is biased toward the open position by the reset pressure control spring. The slider-piston is moveable relative to the exhaust rocker arm between an extended position and a retracted position. The slider-piston is biased toward the extended position by the external slider bias spring. The slider assembly is operatively associated with the reset check valve so that in the extended position of the slider-piston the reset check valve is moveable toward the closed position, and in the retracted position of the slider-piston the reset check valve is moveable to the open position thereof by the slider-piston. The slider-piston is operatively associated with a stop member such that when the exhaust rocker arm is farthest away from the stop member, the slider-piston is in the extended position, and as the exhaust rocker arm rotates toward the stop member the slider-piston is moved toward the retracted position.
According to a second aspect of the present invention, there is provided a method of operation of a compression-release engine brake system in a brake-on mode for operating at least one exhaust valve of an internal combustion engine during a compression-release engine braking operation. The compression-release brake system maintains the at least one exhaust valve open during a portion of a compression stroke of the engine when performing the compression-release engine braking operation. The compression-release brake system comprises a lost motion exhaust rocker assembly that comprises an exhaust rocker arm, an actuation device including an actuation piston slidably disposed in an actuation bore formed in the exhaust rocker arm and movable between retracted and extended positions, and a reset device. The actuation device is operatively associated with the at least one exhaust valve to unseat the at least one exhaust valve from the closed position. The reset device includes a reset check valve disposed in a reset bore in the exhaust rocker arm, a slider-piston slidably disposed in the reset bore of the exhaust rocker arm and operatively connected to the reset check valve, a reset pressure control spring disposed within the slider-piston, and an external slider bias spring biasing the slider-piston away from the reset bore to engage the at least one exhaust valve. The external slider bias spring is disposed outside the reset bore in the exhaust rocker arm and around the piston-slider. The actuation bore defines an actuation cavity delimited by the actuation piston within the actuation bore above the actuation piston. The reset bore is in fluid communication with the actuation cavity in the actuation device through a reset conduit within the exhaust rocker arm. The reset check valve is operable between an open position and a closed position. Hydraulic fluid is locked in the actuation cavity when the reset check valve is in the closed position and flows bi-directionally through the reset check valve when the reset check valve is in the open position. The reset check valve is biased toward the open position by the reset pressure control spring. The slider-piston is movable relative to the exhaust rocker arm between an extended position and a retracted position, the slider-piston being biased toward the extended position by the external slider bias spring. The slider assembly is operatively associated with the reset check valve so that in the extended position of the slider-piston the reset check valve is moveable toward the closed position, and in the retracted position of the slider-piston the reset check valve is moveable to the open position thereof by the slider-piston. The method comprises the steps of mechanically and hydraulically biasing the reset check valve closed during a lost-motion rotation of the exhaust rocker arm, executing a brake valve lift of the at least one exhaust valve of the internal combustion engine, and resetting the at least one exhaust valve of the engine by opening the reset check valve and releasing hydraulic fluid from the actuation cavity to close the at least one exhaust valve.
The present invention is an engine brake design that reduces the overall size and height of the current engine brake technology shown, for example, in U.S. Pat. No. 10,767,522, which is incorporated herein by reference. The disclosed invention re-configures the components of a modern resetting engine brake in order to reduce the overall height of the brake system. Further improvements are made to the existing technology to improve robustness of critical interfaces and allow greater control over these connections.
The accompanying drawings are incorporated in and constitute a part of the specification. The drawings, together with the general description given above and the detailed description of the exemplary embodiments and methods given below, serve to explain the principles of the invention. In these drawings:
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 “integrally”) or “unitary” (or “unitarily”) 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”. For the purpose of clarity, some technical material that is known in the related art has not been described in detail in order to avoid unnecessarily obscuring the disclosure.
The present invention is an engine brake design that reduces the overall size and height of the current engine brake technology shown, for example as shown in U.S. Pat. No. 10,767,522, which is incorporated herein by reference in its entirety.
The compression-release engine brake system 10 includes a lost motion exhaust rocker assembly 12 for operating at least one of the first exhaust valve 21 and the second exhaust valve 22. The lost motion exhaust rocker assembly 12, shown in
The rocker arm compression-release engine brake system 12 is operated by an exhaust valve cam 6, as best shown in
The compression-release brake system 10 operates in the compression brake-on mode during engine brake operation and in a compression brake deactivation (or brake-off) mode during positive power operation.
The exhaust rocker arm 14, as best shown in
The lost motion exhaust rocker assembly 12 further comprises a low-profile brake reset device 20, an actuation piston assembly 50, and an accumulator device 64, all mounted to the exhaust rocker arm 14. The low-profile brake reset device 20 is disposed above the exhaust valve bridge 4 in the driving end 151 of the exhaust rocker arm 14. The brake reset device 20 is configured to drive the exhaust valve bridge 4 during positive power operation, i.e., normal exhaust valve operation, and is used to open the exhaust valve 21 during an end portion of the compression stroke of the internal combustion engine when the engine brake system 10 is in the ON (braking mode) state. Moreover, the exhaust rocker arm 14 has a supply conduit 21, a connecting conduit 22C and a reset conduit 22R, all formed within the exhaust rocker arm 14, best shown in
The low-profile brake reset device 20, as best shown in
The external arrangement of the external slider bias spring 30 allows for a more compact design of the low-profile brake reset device 20 than previous technology, and allows for a much greater (larger) spring force to be used. The increased spring force helps to control high-speed dynamic motion of the valvetrain system, where vibrations can even cause the valve bridge to potentially fall off the exhaust valves 2. The upper reset bore 191 and the lower reset bore 192 of the exhaust rocker arm 14 are fluidly connected by a central opening 41 formed in the separation wall 193 therebetween. Also, the upper reset bore 191 and the lower reset bore 192 together define a reset bore for the exhaust rocker arm 14.
The slider-piston 24 defines a piston cavity 25 therewithin. The low-profile brake reset device 20 further comprises a spring washer 32 and a retaining ring 34, both disposed within the piston cavity 25. The spring washer 32 has one or more (i.e., at least one) openings 33 therethrough. The retaining ring 34 allows a set preload to be maintained on the reset pressure control spring 27, and also retains the reset pressure control spring 27 within the slider-piston 24.
The low-profile brake reset device 20, as best shown in
The valve closing member 38 is integrally formed with a curved sealing portion 44 disposed in the upper reset bore 191 and complementary to the check-valve seat 40. An upset pin 45 is formed integrally with the valve closing member 38 and extends from the sealing portion 44 into the lower reset bore 192 through the central opening 41 in the and is partially disposed in the slider-piston 24. The upset pin 45 is integrally formed with a reset pin flange 46 to allow engagement with the spring washer 32. The sealing portion 44 of the valve closing member 38 has a cylindrical spring pocket 49 receiving the valve spring 42 therein. As best shown in
The valve closing member 38 is movable between a disengaged (or retracted) state, where the sealing portion 44 is spaced from the check-valve seat 40, as shown in
The spring washer 32 is slidably mounted about the upset pin 45 for supporting the reset pressure control spring 27 inside the slider-piston 24. Moreover, the spring washer 32 is rectilinearly moveable relative to the upset pin 45. The upset pin 45 has a retention section 47 at a lower (or second) distal end 392 of the valve closing member 38 (or of the upset pin 45 opposite the sealing portion 44). The retention section 47 of the upset pin 45 retains the spring washer 32 (thus, the slider-piston 24) on the upset pin 45 and prevents the spring washer 32 from becoming separated from the upset pin 45. This retention function is important for handling and installation of the brake reset device 20 into an engine, inasmuch as it maintains the engine brake as a single assembly within the driving end 151 of the exhaust rocker arm 14.
The slider-piston 24 has a distal end 241 adjacent to the exhaust valve bridge 4, and a proximal end 242 facing the check-valve seat 40. The slider-piston 24 has one or more (i.e., at least one) piston ports 26 therethrough. The piston ports 26 are disposed below the check-valve seat 40 and the sealing portion 44 of the valve closing member 38 of the reset check valve 36 and maintain fluid connection between the piston cavity 25 of the slider-piston 24 with the lower reset bore 192 and the connecting conduit 22C, and with the upper reset bore 191 and the reset conduit 22R (when the reset check valve 36 is open) for all positions of the slider-piston 24.
The check-valve seat 40 has the central opening 41 therethrough, as best shown in
The low-profile brake reset device 120 comprises a support body 122 having a cylindrical outer peripheral surface at least partially threaded into the upper reset bore 191 so as to be threadedly received in the partially internally threaded upper reset bore 191 in the driving end 151 of the exhaust rocker arm 14. The hollow slider-piston 24 is configured to rectilinearly reciprocate within the lower reset bore 192 formed in the exhaust rocker arm 14, and a reset check valve 136, as shown in
The support body 122 defines a check-valve seat 140 for sealing against the sealing portion 44 of the valve closing member 38. A central opening 141 is formed in the check-valve seat 140, and a bearing surface 122B for supporting loads transmitted by the slider-piston 24. The central opening 141 fluidly connects the upper reset bore 1191 and the lower reset bore 1192 of the exhaust rocker arm 14. The upper reset bore 1191 and the lower reset bore 1192 of the exhaust rocker arm 14 are separated from one another by a separation wall 1193. The support body 122 is threaded into the upper reset bore 1191 to engage the separation wall 1193. The support body 122 allows design control over the specific material performance properties of these two connection points (i.e., the bearing surface 122B and the check-valve seat 140), allowing greater flexibility than having these features integrated into the exhaust rocker arm 14, as shown in
The support body 122 is provided with one or more (i.e., at least one) communication ports 123 therethrough. The communication ports 123 are disposed above the check-valve seat 140 of the support body 122, so as to maintain fluid connection of the upper reset bore 191 with the reset conduit 22R.
The actuation piston 54 is moveable between retracted and extended positions relative to the actuation bore 52 and is adapted to contact a top end surface of the single-valve actuation thru-pin 5 (best shown in
The accumulator device 64, best shown in
The cylindrical accumulator bore 68 defines an accumulator cavity disposed above the accumulator piston 66 within the exhaust rocker arm 14. The accumulator piston 66 rectilinearly reciprocates within the accumulator bore 68. The accumulator bore 68, disposed above the accumulator piston 66, is fluidly connected with an accumulator conduit 22A (best shown in
In operation of the compression-release engine brake system 10, the pressurized hydraulic fluid is continuously supplied through the supply conduit 21 and the connecting conduit 22C to the lower reset bore 192 of the brake reset device 20 of the exhaust rocker arm 14 at a pressure lower than that which would extend the actuation piston 54. Engine brake activation is effected by increasing the pressure of the hydraulic fluid in the exhaust rocker assembly 12 above the hydraulic pressure necessary to extend the actuation piston 54 against the bias force of the actuation piston return spring 55 of the actuation piston assembly 50.
The overall engine brake-on/brake-off operation is described hereafter.
The positive power operation, i.e., normal brake-off operation, of the engine is as follows. The supply conduit 21 provides continuous flow of low inlet pressure hydraulic fluid, such as motor oil, to the lower reset bore 192 through the connecting conduit 22C. The low inlet pressure hydraulic fluid in the lower reset bore 192 and the external slider bias spring 30 bias the slider-piston 24 with the piston foot 28 downward toward the exhaust valve bridge 4 to maintain consistent contact between the piston foot 28 and the exhaust valve bridge 4. The pressurized engine oil completely fills the actuation cavity 53 of the actuation piston assembly 50 through the open reset check valve 36 and the reset conduit 22R.
In this configuration, as the cam lobe of exhaust valve cam 6 decreases in radius, the slider-piston 24 of the brake reset device 20 will extend outwardly from the exhaust rocker arm 14 to drive the exhaust rocker arm 14 away from the exhaust valve bridge 4, while maintaining constant contact between the piston foot 28 and the exhaust valve bridge 4. The low inlet pressure of the hydraulic fluid is set to a pressure incapable of generating sufficient force to extend the actuation piston 54 against the actuation piston return spring 55 of the actuation piston assembly 50. The combined force applied to extend the slider-piston 24 by the slider bias spring 30 and the regulated hydraulic fluid pressure will never exceed the retaining force of the exhaust valve springs 31 and 32 such that, as the exhaust rocker arm 14 is pivoted toward the exhaust valve bridge 4 by increasing radius of the cam lobe of the exhaust valve cam 6, the slider-piston 24 is retracted with respect to the exhaust rocker arm 14. During normal exhaust cam lift by the engine exhaust cam profile 71 of the exhaust valve cam 6, the slider-piston 24 is driven further into the exhaust rocker arm 14, taking up all lash, until the proximal end 242 of the slider-piston 24 contacts the separation wall 193 of the exhaust rocker arm 14, thus placing the slider-piston 24 in the fully retracted position and allowing the lost motion exhaust rocker assembly 12 to open the exhaust valves 21 and 22.
In the fully retracted position of the slider-piston 24, best shown in
To start the engine brake-on mode, continuous flow of a full (or high) inlet pressure hydraulic fluid is provided through the supply conduit 21 and the connecting conduit 22C to the lower reset bore 192 of the brake reset device 20. The highly pressurized engine oil is supplied to the actuation cavity 53 of the actuation piston assembly 50 through the open reset check valve 36 and the reset conduit 22R. The full inlet pressure within the actuation cavity 53 of the exhaust rocker arm 14 generates sufficient force to extend the actuation piston 54 against the biasing force of the actuation piston return spring 55, but still insufficient, by itself, to overcome the retaining forces of the exhaust valve 21 such as the exhaust valve spring 31 and engine gas pressures acting on the exhaust valve 21.
The slider-piston 24 will continue to behave as in normal brake-off mode, whereas the actuation piston 54, on the other hand, will now extend from the actuation bore 52 of the exhaust rocker arm 14 until the actuation piston 54 comes into contact with the single-valve actuation thru-pin 5. The cam lobe of the exhaust valve cam 6 will fall to lower base circle 81 prior to the pre-charge lift profile 73 or the engine brake lift profile 72, allowing the exhaust rocker arm 14 to rotate away from the exhaust valve bridge 4. The lower base circle 81 is a point of a lowest cam radius. At this point the exhaust rocker arm 14 will be rotated furthest from the exhaust valve bridge 4, allowing the actuation piston 54 to be at maximum extension from the exhaust rocker arm 14. In this state, the proximal end 242 of the slider-piston 24 is farthest from the separation wall 193 of the exhaust rocker arm 14 and the check-valve seat 40 (i.e., the slider-piston 24 is in the fully extended position thereof), as shown in
Then, the hydraulic fluid will be trapped within both the actuation cavity 53 and the reset conduit 22R. Consequently, hydraulic pressure will be built sufficiently within the actuation cavity 53 to maintain extension of the actuation piston 54 from the exhaust rocker arm 14, moving the single-valve thru-pin 5 and opening the exhaust valve 21 for pre-charge or compression release. Accordingly, when the actuation piston 54 presses the single-valve thru-pin 5 towards the first exhaust valve 21 just prior to TDC of the compression stroke during the compression-release engine braking event, the fluid pressure in the actuating cavity 53 and the reset conduit 22R become higher than the fluid pressure in the upper and lower reset bores 191 and 192, thus forcing the sealing portion 44 of the valve closing member 38 of the reset check valve 36 to be seated on the check-valve seat 40, and thus hydraulically locking the engine oil (hydraulic fluid) in the actuating cavity 53, as shown in
The cam lobe of the exhaust valve cam 6 will rise as it enters the pre-charge lift profile 73 or the engine brake lift profile 72, which will rotate the exhaust rocker arm 14 back toward the exhaust valve bridge 4 and the force of the engine cylinder pressure acting on the face of the first exhaust valve 21 and the first exhaust valve spring 31 will attempt to retract the actuation piston 54 into the actuation bore 52 of the exhaust rocker arm 14 to maintain the closed position of the first exhaust valve 21. The actuation piston 54 will not be retracted, however. Instead, the trapped hydraulic oil within the actuation cavity 53 and reset conduit 22R will increase in pressure to support the force, and the single exhaust valve 21 will be opened according to the cam lift profile.
During the opening of the single exhaust valve 21 with the single-valve thru-pin 5, the cylinder pressure is increasing and rapidly reaches peak cylinder pressure just prior to TDC compression, and then cylinder pressure drops rapidly just after TDC compression. Because of the compression release near TDC and the engine piston in the cylinder moving downwardly in the engine cylinder, the cylinder pressure decreases rapidly and so does the pressure in the actuation cavity 53.
Resetting of the first exhaust valve 21 is effected as the exhaust valve cam 6 rises to the upper base upper base circle 82. The forward motion (or clockwise pivoting) of the exhaust rocker arm 14 causes the slider-piston 24 to retract into the lower reset bore 192 of the exhaust rocker arm 14, consequently moves the valve closing member 38 with the upset pin 45 of the reset check valve 36 out of engagement with the check-valve seat 40. During a compression release event, the engine cylinder pressure continues to increase as the first exhaust valve 21 opens, which in turn acts on a face of the first exhaust valve 21 to create a force on the actuation piston 54 through the single-valve thru-pin 5, thus increasing the hydraulic pressure in the actuation cavity 53 of the exhaust rocker arm 14.
During the actual engine compression release event, when the engine brake lift profile 72 of the exhaust valve cam 6 acts on the exhaust rocker arm 14, the engine cylinder pressure is high. Although the slider-piston 24 is retracted far enough for the upset pin 45 to move the sealing portion 44 of the valve closing member 38 of the reset check valve 36 away from the check-valve seat 40, the sealing portion 44 of the valve closing member 38 is not lifted from the check-valve seat 40, i.e., the reset check valve 36 is not open. Instead, the spring washer 32 is displaced within the slider-piston 24 to compress the reset pressure control spring 27, as shown in
During the resetting of the first exhaust valve 21, a portion of the hydraulic fluid in the actuation cavity 53 is discharged in order to facilitate retraction of the actuation piston 54 into the actuation bore 52 of the exhaust rocker arm 14. The optional accumulator device 64 manages the discharged hydraulic fluid from the exhaust rocker arm 14 to aid the hydraulic performance of the rocker arm compression-release engine brake system 10. In the presence of sufficient hydraulic pressure, the accumulator piston 66 moves towards the accumulator cap 72 to increase the volume of the accumulator cavity in the accumulator bore 68, which is fluidly connected with the accumulator conduit 22A, and compresses the accumulator pressure control spring 70, allowing the hydraulic fluid to be stored within the accumulator cavity at a predetermined pressure. When the exhaust valve cam 6 rotates to the lower base circle 81, the accumulator pressure control spring 70 extends to force the displacement of the accumulator piston 66 towards the retracted position, driving the stored hydraulic fluid into the accumulator conduit 22A and the actuation cavity 53, helping to re-extend the actuation piston 54 (i.e., displacing the actuation piston 54 toward the extended position, or toward the first exhaust valve 21).
The engine cylinder pressure, at which reset of the first exhaust valve 21 occurs, is tunable by adjusting the active forces of the reset pressure control spring 27. The tuning capability of the exhaust valve reset creates a reset that initiates early in the expansion stroke to ensure that the exhaust valve is closed prior to a start of a normal exhaust valve motion defined by the normal exhaust cam profile 71 of the exhaust valve cam 6.
Various modifications, changes, and alterations may be practiced with the above-described embodiment, including but not limited to the additional embodiments shown in
The compression-release engine brake system 210 according to the second exemplary embodiment, illustrated in
The lost motion exhaust rocker assembly 212 further includes a low-profile brake reset device 220, an actuation piston assembly 50, and an accumulator device 64, all mounted to the exhaust rocker arm 214. The low-profile brake reset device 220 is disposed above the exhaust valve bridge 4 in the driving end 2151 of the exhaust rocker arm 214. Moreover, the exhaust rocker arm 214 has a supply conduit 21, a connecting conduit 22C and a reset conduit 22R, all formed within the exhaust rocker arm 214, as best shown in
Components of the brake reset device 220, which are unchanged from the first exemplary embodiment of the present invention, are labeled with the same reference characters. Components, which function in the same way as in the first exemplary embodiment of the present invention depicted in
The low-profile brake reset device 220, as best shown in
The hollow slider-piston 24 rectilinearly reciprocates within the lower reset bore 2192 formed in the exhaust rocker arm 214, as shown in
The support body 222 has one or more (i.e., at least one) communication ports 223 therethrough. The communication ports 223 are disposed above the check-valve seat 240 of the support body 222 to maintain fluid connection of the upper reset bore 2191 with the reset conduit 22R for all positions of the slider-piston 24.
The low-profile brake reset device 320 of
Unlike the brake reset device 220 of the second exemplary embodiment, the brake reset device 320 is configured without a threaded plug. Instead, an engagement feature 348k is integrated into the threaded support body 322 of the brake reset device 320. The brake reset device 320 includes a check-valve seat member 335 as a separate component, that is fixedly (i.e., non-moveably) connected to the threaded support body 322, allowing, as above, for optional material selection for the check-valve seat member 335. The check-valve seat member 335 is force-fit (interference fit) into the support body 322, or otherwise secured with an additional retaining means. The check-valve seat member 335 is formed with a check-valve seat 340, as best shown in
The compression-release engine brake system 410 according to the third exemplary embodiment illustrated in
The compression-release engine brake system 510 according to the fourth exemplary embodiment illustrated in
The actuation piston assembly 550 includes a cylindrical actuation piston 54 that rectilinearly reciprocates within actuation bore 552 of the exhaust rocker arm 514. Actuation piston return spring 55 is mounted within the actuation piston 54 for biasing the actuation piston 54 in a direction away from the brake valve 21. The cylindrical actuation bore 552 defines an actuation cavity 553 delimited by the actuation piston 54 within the exhaust rocker arm 514 above the actuation piston 54. Hydraulic pressure in the actuation cavity 553 above the actuation piston 54 pushes (or displaces) the actuation piston 54 toward the brake valve 21. The actuation piston 54 has an annular groove 54G fluidly connecting the supply conduit 21 with the connecting conduit 22C.
As shown in
The supplemental check valve 80 includes a moveable sealing member 84, such as a ball-valve member 84, disposed in the valve cavity 82 and lands on a check-valve seat 86 formed in the valve cavity 82, a biasing spring 88, and a spring cap 89, as shown in
The compression-release engine brake system 610 according to the fifth exemplary embodiment illustrated in
The actuation piston assembly 650 further comprises a support washer 656 that provides an extension limiter for the actuation piston 654 and supports the actuation piston return spring 655 around the actuation piston 654. The support washer 656 is retained within the actuation bore 652 by a piston retaining ring 657, such as a C-ring. The actuation piston 654 has one or more (i.e., at least one) actuator ports 660 therethrough for fluidly connecting the supply conduit 21 with the connecting conduit 22C. Hydraulic pressure in the actuation cavity 653 above the actuation piston 654 pushes (or displaces) the actuation piston 654 toward the brake valve 21. The actuation piston 654 has an annular groove 654G fluidly connecting the supply conduit 21 with the connecting conduit 22C through the actuator ports 660.
As shown in
Moreover, the actuation piston 654 utilizes the actuation piston return spring 655 to maintain a retracted position during the brake-OFF mode, and allows the actuation piston 654 to extend from the actuation bore 652 during the brake-ON mode. The fluid pressure in the reset conduit 22R is increased during the brake-ON mode. The fluid pressure applies a force onto an upper surface of the actuation piston 654 and urges the actuation piston 654 against the actuation piston return spring 655, causing the actuation piston return spring 655 to compress and the actuation piston 654 to extend.
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 of U.S. Provisional Patent Application Ser. No. 63/165,873 filed Mar. 25, 2021 by Taylor et al., which is hereby incorporated herein by reference in its entirety and to which priority is claimed.
| Number | Date | Country | |
|---|---|---|---|
| 63165873 | Mar 2021 | US |
