Rocker arm assembly for cylinder decompression

Abstract

A rocker arm assembly is operable in a drive mode and a cylinder decompression mode. The rocker arm assembly includes a rocker arm (110) pivotally mounted to a rocker shaft (120), and a decompression assembly pivotally mounted to a lever shaft (320) of the rocker arm. The rocker arm includes a valve end (150) configured to operatively engage one or more gas exchange valves (300) of a cylinder, and a cam end (200) configured to receive motion from a main cam (230). The decompression assembly includes a decompression lever (310) configured to provide an optimized decompression lift profile associated with the transitional states of engine operation.

Description

ATTORNEY DOCKET PATENT APPLICATION 006976.23521 of 24ROCKER ARM ASSEMBLY FOR CYLINDER DECOMPRESSIONTECHNICAL FIELD

[0001] This disclosure generally relates to engine valvetrain systems, and more particularly to valvetrains with rocker arms operable for cylinder decompression.BACKGROUND

[0002] Transitional states in engines, such as engine start / shutdown events and / or transitions between engine and other power source(s), can place significant loads on starter systems, lubrication systems, and / or other subsystems as well as components associated with the powertrain.

[0003] In particular applications, such transitions can be particularly frequent and / or significant (e.g., in start-stop applications, in medium and heavy-duty applications, and / or in hybrid powertrains). In some hybrid powertrains, an active source of power / propulsion may switch relatively frequently between an internal combustion engine and an electric motor.

[0004] The application of decompression systems on heavy duty and / or medium duty applications may be particularly beneficial based on trade-offs between design criteria such as operational load, complexity, packaging considerations, and / or cost.

[0005] Conventional decompression systems employ a constant lift and / or “keep-valve- open” (KVO) approach which is conceptually simple and can be easily integrated into existing valvetrains. For example, such decompression systems may use an extendable latch piston that, when extended, limits the pivotal motion of the rocker arm, thereby maintaining associated gas exchange valves in an open condition. Such decompression systems, however, take up considerable packaging space while providing a “one-size-fits-all” decompression lift profile that is limited to relatively small valve lifts so as to avoid impact with the piston during engine start-up and shutdown events.

[0006] Thus, there is a need for cylinder decompression during transitional states of engine operation in addition to engine start / shutdown events (e.g., when switching propulsion sources between an internal combustion engine and an electric motor in vehicles with hybrid powertrains). Further, there is a need for a cylinder decompression system that is more compact while providing an optimized decompression lift profile associated with the transitional states of engine operation.ATTORNEY DOCKET PATENT APPLICATION 006976.23522 of 24SUMMARY OF THE INVENTION

[0007] In particular embodiments, cylinder decompression systems and associated methods to manage transitional states in engines may be employed to provide benefits such as reduced friction, reduced transitional loads, reduced noise, vibration, and harshness (NVH), increased operating refinement, robust and timely supply of lubrication to bearings and / or other engine parts, reduced wear and tear, and / or longer operating life of engine components and systems.

[0008] In particular embodiments, features and systems disclosed herein may be configured to reduce engine negative torque during transitional states such as engine start-up and / or shut-off phases. By way of example and not limitation, cylinder decompression may involve selectively holding one or more gas exchange valves open. In particular embodiments, an additional decompression valve lift may be applied during a compression phase of engine operation so as to vent a gas (e.g., air) out of the cylinder.

[0009] In particular embodiments, a decompression assembly may comprise a lever system including a decompression lever. In particular embodiments, the decompression lever may be applied to a rocker arm such as a Type III rocker arm by way of non-limiting example. In particular embodiments, the decompression lever may pivot about a lever shaft extending from the rocker arm. In particular embodiments, the lever shaft may be an extension of a main lift cam roller axle. In particular embodiments, a first end of the decompression lever may include a sliding pad or at least one roller configured to contact an additional decompression lift cam. In particular embodiments, a second end of the decompression lever may selectively engage the rocker arm, such as via a latch pin integrated in the rocker arm that can selectively extend or retract. In particular embodiments, a torsional lost motion spring may be used to bias the decompression lever towards the decompression lift cam and into contact with a stop of the rocker arm. In particular embodiments, the lost motion spring may be a compression spring instead.

[0010] In particular embodiments, when in a drive mode, the decompression lever may be deactivated by retracting the latch pin so as to enable the decompression lever to freely pivot relative to the rocker arm such that a decompression lift is prevented from being transmitted to one or more gas exchange valves. In particular embodiments, when in a cylinder decompression mode, the latch pin is extended out of the rocker arm via an external actuator (e.g., a pneumatic, electromagnetic, or hydraulic actuator) such that the decompression leverATTORNEY DOCKET PATENT APPLICATION 006976.23523 of 24 may engage the latch pin so as to transmit the decompression lift to the one or more gas exchange valves via the rocker arm.

[0011] The clauses below summarize various embodiments described herein.

[0012] Clause 1. A rocker arm assembly for cylinder decompression in an engine, the rocker arm assembly comprising: a rocker arm pivotally mounted to a rocker shaft, the rocker arm comprising: a cam end configured to receive main lift motion from a main lift cam of a camshaft, a valve end configured to transmit the main lift motion to at least one gas exchange valve of the engine, and a lever shaft extending from the rocker arm at a position between a rocker shaft bore of the rocker arm and the camshaft; and a decompression assembly comprising: a decompression lever pivotally mounted to the lever shaft, the decompression lever including: a first end configured to receive decompression lift motion from a decompression lift cam, and a second end configured to selectively transmit the decompression lift motion to the rocker arm, a lost motion spring configured to bias the decompression lever towards the decompression lift cam, and a latch assembly associated with the second end of the decompression lever, the latch assembly configured to switch between (a) a drive mode in which the decompression lift motion received by the decompression lever is absorbed via the lost motion spring, and (b) a cylinder decompression mode in which the decompression lift motion received by the decompression lever is transmitted to the at least one gas exchange valve via the rocker arm.

[0013] Clause 2. The rocker arm assembly of clause 1, wherein the cam end of the rocker arm includes a main lift cam roller axle rotatably supporting a main lift cam roller configured to engage the main lift cam.

[0014] Clause 3. The rocker arm assembly of clause 2, wherein the lever shaft is an extension of the main lift cam roller axle.

[0015] Clause 4. The rocker arm assembly of any one of the preceding clauses, wherein the first end of the decompression lever includes a decompression lift cam roller configured to rotatably engage the decompression lift cam.

[0016] Clause 5. The rocker arm assembly any one of the preceding clauses, wherein the first end of the decompression lever includes a slider configured to engage the decompression lift cam.

[0017] Clause 6. The rocker arm assembly of any one of the preceding clauses, wherein the rocker arm further comprises a stop configured to limit a rotation of the decompression lever towards the decompression lift cam.ATTORNEY DOCKET PATENT APPLICATION 006976.23524 of 24

[0018] Clause 7. The rocker arm assembly of clause 6, wherein the lost motion spring is a compression spring pressed between a portion of the stop and a portion of the decompression lever.

[0019] Clause 8. The rocker arm assembly of any one of the preceding clauses, wherein the lost motion spring is a torsional spring mounted to the lever shaft.

[0020] Clause 9. The rocker arm assembly of any one of the preceding clauses, wherein the latch assembly includes: a latch pin slidably disposed in the rocker arm, the latch pin configured to switch between a retracted position and an extended position; and a latch return spring configured to bias the latch pin into the retracted position.

[0021] Clause 10. The rocker arm assembly of any one of the preceding clauses, wherein: in the drive mode, the latch pin is in the retracted position, and in the cylinder decompression mode, the latch pin is in the extended position so as to engage the second end of the decompression lever.

[0022] Clause 11. The rocker arm assembly of any one of the preceding clauses, wherein the latch assembly further includes: an external actuator assembly mounted to a valvetrain component, the external actuator assembly including an actuator piston configured to selectively actuate the latch pin into the extended position.

[0023] Clause 12. The rocker arm assembly of clause 11, wherein the external actuator assembly is positioned such that a movement direction of the actuator piston is coaxially aligned with, or parallel to, a movement direction of the latch pin.

[0024] Clause 13. The rocker arm assembly of clause 12, wherein the external actuator assembly is configured to selectively actuate the latch pin by extending the actuator piston so as to push against a latch pin tab that is mechanically coupled to the latch pin.

[0025] Clause 14. The rocker arm assembly of clause 13, wherein the latch pin tab is structurally coupled to a slidable housing positioned behind the latch pin in the latch assembly.

[0026] Clause 15. The rocker arm assembly of any one of clauses 11-14, wherein the external actuator assembly is actuated pneumatically or electromagnetically.

[0027] Clause 16. A method for operating a cylinder decompression system of an engine, the cylinder decompression system including a rocker arm pivotally mounted to a rocker shaft so as to transmit main lift motion from a main lift cam to at least one gas exchange valve of the engine; a decompression lever pivotally mounted to a lever shaft of the rocker arm so as to transmit decompression lift motion from a decompression lift cam to the at least one gas exchange valve via the rocker arm; and a latch assembly configured to selectively enable andATTORNEY DOCKET PATENT APPLICATION 006976.23525 of 24 disable the transmitting of the decompression lift motion, the method comprising: retracting a latch pin of the latch assembly in response to an activation of a drive mode; during the drive mode: transmitting the main lift motion from the main lift cam to the at least one gas exchange valve via the rocker arm; and absorbing, via a lost motion spring, the decompression lift motion received by the decompression lever from the decompression lift cam; extending the latch pin of the latch assembly in response to an activation of a cylinder decompression mode; during the cylinder decompression mode, transmitting the decompression lift motion received by the decompression lever from the decompression lift cam to the at least one gas exchange valve via the extended latch pin and the rocker arm.

[0028] Clause 17. The method of clause 16, wherein the retracting of the latch pin includes urging the latch pin into a retracted position via a latch return spring of the latch assembly.

[0029] Clause 18. The method of any one of clauses 16-17, wherein the latch pin of the latch assembly is extended pneumatically, electromagnetically, or hydraulically.

[0030] Clause 19. The method of any one of clauses 16-18, wherein the extending of the latch pin of the latch assembly includes extending an actuator piston of an external actuator assembly so as to mechanically extend the latch pin, wherein the external actuator assembly is mounted to a valvetrain component separate from the rocker arm.

[0031] Clause 20. The method of clause 19, wherein the actuator piston of the external actuator assembly is extended pneumatically or electromagnetically.BRIEF DESCRIPTION OF THE DRAWINGS

[0032] To assist in understanding the present disclosure, reference is now made to the following description taken in conjunction with the accompanying drawings, in which:

[0033] FIG. 1 is a schematic perspective view of a rocker arm assembly for cylinder decompression, according to a first embodiment.

[0034] FIG. 2 is a schematic side view of the rocker arm assembly of Fig. 1 in a cylinder decompression mode.

[0035] FIG. 3 is a schematic side view of the rocker arm assembly of Fig. 1 in a drive mode.

[0036] FIG. 4 is a schematic cross-section rear view of the rocker arm assembly of Fig. 1 illustrating a lever shaft and a main lift cam roller.

[0037] FIG. 5 is a schematic cross-sectional perspective view of the rocker arm assembly of Fig. 1 illustrating the latch pin in the drive mode.ATTORNEY DOCKET PATENT APPLICATION 006976.23526 of 24

[0038] FIG. 6 is a schematic cross-sectional perspective view of the rocker arm assembly of Fig. 1 illustrating the latch pin in the cylinder decompression mode.

[0039] FIG. 7 is a schematic perspective view of an external actuator assembly for actuating the latch pin in the rocker arm.

[0040] FIG. 8 is a schematic cross-sectional rear view of the external actuator assembly and latch pin of the rocker arm.

[0041] FIG. 9 is a schematic perspective view of a rocker arm assembly for cylinder decompression, according to a second embodiment.

[0042] FIG. 10 is a schematic perspective view of a rocker arm assembly for cylinder decompression, according to a third embodiment.

[0043] FIGs. 11 - 12 are schematic timing diagrams depicting features and / or operational aspects of rocker arm assemblies for cylinder decompression according to particular embodiments.

[0044] FIG. 13 shows comparative peak torque requirement curves based on engine speed in decompression systems with a constant lift and / or KVO approach relative to decompression systems with a dedicated cylinder decompression lift profile according to particular embodiments.DESCRIPTION OF EXAMPLE EMBODIMENTS

[0045] To facilitate a better understanding of the present disclosure, the following examples describing particular embodiments are provided as non-limiting examples. Accordingly, the following examples are not to be read to define or otherwise limit the scope of the disclosure. Other suitable implementations and / or combinations of components, devices, methods, and systems are possible, and fully contemplated herein.

[0046] FIGs. 1 - 10 show schematic views of a rocker arm assembly for cylinder decompression according to particular embodiments. In particular embodiments, the rocker arm assembly may comprise a rocker arm 110 pivotally mounted to a rocker shaft 120. In particular embodiments, the rocker arm 110 may include a valve end 150 configured to directly or indirectly engage one or more gas exchange valves 300. In particular embodiments, the rocker arm 110 may further include a cam end 200 configured to directly or indirectly receive motion from one or more valve lift components, such as one or more main lift cams 230 provided on one or more camshafts 220, the motion associated with opening the one or more gas exchange valves 300. In particular embodiments, the rocker arm 110 may be configured toATTORNEY DOCKET PATENT APPLICATION 006976.23527 of 24 selectively absorb or transmit some or all of the motion received by the cam end 200, such as from the one or more main lift cams 230.

[0047] In particular embodiments, the cam end 200 may comprise one or more motion receiving members, such as one or more rollers, sliders, and / or pushrods configured to receive the motion from the one or more main lift cams 230. By way of example and not limitation, in particular embodiments, the cam end 200 may comprise a main lift cam roller axle rotatably supporting at least one main lift cam roller 240 configured to receive the motion from at least one main lift cam 230 of the one or more main lift cams 230 configured to open the one or more gas exchange valves 300.

[0048] In particular embodiments, the rocker arm assembly may further comprise a decompression assembly including a decompression lever 310 configured to receive decompression lift motion specifically arranged to open the at least one valve 300 of the one or more gas exchange valves 300 for a cylinder decompression event. The decompression lift motion may be provided from a dedicated decompression lift cam 250. By way of example and not limitation, such decompression lift motion may be associated with a dedicated cylinder decompression lift profile provided by the dedicated decompression lift cam 250, as illustrated in FIG. 1.

[0049] In particular embodiments, the decompression lever 310 may be configured to pivot about the rocker shaft 120. In particular embodiments, the decompression lever 310 may be pivotally mounted to a lever shaft 320 extending parallel to the rocker shaft 120. For example, as shown, the rotational axes of the lever shaft 320 and rocker shaft 120 may be parallel but different. As seen from Fig. 4, by way of example and not limitation, the lever shaft 320 may be formed as an extension of, or otherwise shared with, the main lift cam roller axle rotatably supporting the at least one main lift cam roller 240. Alternatively, the lever shaft 320 may be provided separately from the main lift cam roller axle so as to extend from the rocker arm 110 at a position between a rocker shaft bore 130 of the rocker arm 110 and the one or more camshafts 220. In particular embodiments, the rocker arm 110 further includes a stop 160, 560 configured to limit a rotation of the decompression lever 310 towards the decompression lift cam 250 (e.g., in the orientation shown in FIG. 2, the stop 160 prevents a second end 370 of the decompression lever 310 from rotating clockwise past the stop 160).

[0050] In particular embodiments, the decompression lever 310 may be configured with one or more motion receiving members, such as a roller, slider, and / or pushrod, to receive motion from the dedicated decompression lift cam 250. By way of example and not limitation,ATTORNEY DOCKET PATENT APPLICATION 006976.23528 of 24FIGs. 1 - 3 depict the decompression lever 310 comprising a slider 340 formed at a first end 360 of the decompression lever 310, the slider 340 being configured to engage the decompression lift cam 250. Alternatively, although not shown, the first end 360 of the decompression lever 310 in FIGs. 1 - 3 may comprise at least one decompression lift cam roller (such as the decompression lift cam roller 550 shown in the embodiment of FIG. 10) configured to engage the decompression lift cam 250.

[0051] While particular cam contact members are depicted herein in particular combinations with other components, it will be appreciated that other known cam contact members are possible, and / or in combination with other components in various embodiments. All such cam contact members, components, and combinations thereof are fully contemplated herein for operation of cylinder decompression systems and methods.

[0052] In particular embodiments, the decompression lever 310 may be selectively enabled (as seen from FIG. 2) to transmit decompression lift motion from the decompression lift cam 250 to the at least one valve 300 via the rocker arm 110. In particular embodiments, the decompression assembly may further include a lost motion assembly configured to at least partially absorb said decompression lift motion when the decompression lever 310 is disabled (as seen from FIG. 3) so as to prevent transmission of the decompression lift motion to the at least one valve 300. In particular embodiments, the lost motion assembly is further configured to bias the first end 360 of the decompression lever 310 toward the decompression lift cam 250 and simultaneously bias the second end 370 of the decompression lever 310 towards the stop 160, 560. By way of example and not limitation, the lost motion assembly may comprise one or more lost motion springs.

[0053] In the embodiment depicted in FIG. 1, by way of example and not limitation, the stop 160 may be integrally formed with the rocker arm 110, and the one or more lost motion springs associated with the decompression lever 310 may include a torsional lost motion spring 330 disposed on or about a hub, boss, or other retaining feature associated with the lever shaft 320. A first end of the torsional lost motion spring 330 may press against a spring seat on the rocker arm 110, and a second end of the torsional lost motion spring 330 may press against a spring seat on the decompression lever 310. When cam motion causes the decompression lever 310 to rotate relative to the rocker arm 110, the torsional lost motion spring 330 stores energy in response to rotational displacement of its ends. This energy biases the first end 360 of the decompression lever 310 towards the decompression lift cam 250 (e.g., the decompression lever 310 is biased to rotate clockwise in the orientation shown in FIGs. 2 and 3). This featureATTORNEY DOCKET PATENT APPLICATION 006976.23529 of 24 enables the decompression lever 310 to follow a decompression lift profile of the decompression lift cam 250 as the decompression lift cam 250 rotates.

[0054] In the embodiments depicted in FIGs. 9 and 10, by way of example and not limitation, the stop 560 may be fastened to the rocker arm 110 via at least one fastener 570, and the one or more lost motion springs associated with the decompression lever 310 may include a compression lost motion spring 530 pressed between the stop 560 and the decompression lever 310. In the implementation shown, the stop 560 has a top portion which is fastened to the rocker arm 110 so as to limit a movement of the second end 370 of the decompression lever 310, and a bottom portion that defines a first spring seat. The decompression lever 310 may include a protruding portion that defines a second spring seat. The compression lost motion spring 530 may be secured between the first and second spring seats. When the decompression lift cam 250 transfers motion to the decompression lever 310 which causes the decompression lever 310 to rotate, the rotational movement causes the compression lost motion spring 530 to compress between the first and second spring seats. As the decompression lift cam 250 rotates to its base circle position, the compression lost motion spring 530 urges the second end 370 of the decompression lever 310 towards the stop 560, thereby urging the first end 360 of the decompression lever 310 towards the decompression lift cam 250.

[0055] The embodiments shown in FIGs. 9 and 10 both use a compression spring 530. The main difference between them is that the embodiment in FIG. 9 includes a slider 340 configured to engage the decompression lift cam 250, while the embodiment shown in FIG. 10 includes a decompression lift cam roller 550 configured to engage the decompression lift cam 250.

[0056] In particular embodiments, cylinder decompression may be selectively enabled by a controller, such as an engine control unit (ECU). In particular embodiments, cylinder decompression may be selectively enabled based on one or more predetermined and / or dynamic criteria. In particular embodiments, cylinder decompression may be selectively enabled in accordance with the transitional states of engine operation. By way of example and not limitation, cylinder decompression may be selectively enabled at engine startup and / or when switching propulsion sources from an electric motor to an internal combustion engine of a vehicle with a hybrid powertrain. In particular embodiments, cylinder decompression may be selectively disabled in response to a speed or mass flowrate of the engine reaching a predetermined value (e.g., corresponding to an idle speed or the like) following engine startup.ATTORNEY DOCKET PATENT APPLICATION 006976.235210 of 24Conversely, cylinder decompression may be selectively enabled in response to the speed or mass flowrate of the engine dropping below a predetermined value (e.g., corresponding to an engine shutdown event and / or when switching propulsion sources from the engine to the electric motor).

[0057] In particular embodiments, the decompression assembly may further include a latch assembly 400 configured to selectively enable or disable the decompression lever 310. This latch assembly 400 may be controlled by the aforementioned controller. In particular embodiments, the latch assembly 400 may be internally actuated, or the latch assembly may be externally actuated. In an internally actuated embodiment, such as depicted in FIGs. 5 and 6, the latch assembly 400 may comprise a latch pin 410 slidably disposed in the rocker arm 110. In a cylinder decompression mode of the latch assembly 400, the latch pin 410 may be selectively switched to an extended position so as to engage the second end 370 of the decompression lever 310, thereby enabling the decompression lever 310 to transmit the decompression lift motion from the decompression lift cam 250 to the at least one valve 300 via the rocker arm 110. For example, in the orientation shown in FIG. 2, when the latch pin 410 is in the extended position and the decompression lever 310 receives the decompression lift motion from the decompression lift cam 250, the second end 370 of the decompression lever 310 will press against the latch pin 410 and transfer the decompression lift motion to the rocker arm 110. Conversely, in a drive mode of the latch assembly 400, the latch pin 410 may be switched to a retracted position which disables the decompression lever 310 such that the decompression lift motion received by the decompression lever 310 may be absorbed via the lost motion assembly, thereby preventing the decompression lift motion from being transmitted to the at least one valve 300. For example, in the orientation shown in FIG. 3, when the latch pin 410 is in the retracted position and the decompression lift motion causes the decompression lever 310 to rotate counterclockwise, the second end 370 of the decompression lever 310 will not engage the latch pin 410. Thus, the decompression lever 310 will rotate relative to the rocker arm 110 and the torsional lost motion spring 330 will absorb the decompression lift motion from the decompression lift cam 250 without transferring it to the rocker arm 110.

[0058] In particular embodiments, the latch assembly 400 may be selectively actuated via an actuation means. By way of example and not limitation, the latch assembly 400 may be actuated pneumatically, electromagnetically, and / or hydraulically based on control signals provided by the controller. In particular embodiments, the latch assembly 400 may further comprise one or more biasing members, such as a latch return spring, configured to bias theATTORNEY DOCKET PATENT APPLICATION 006976.235211 of 24 latch pin 410 into the retracted position (as seen from FIG. 5) or the extended position (as seen from FIG. 6).

[0059] For example, the latch assembly 400 shown in FIG. 5 and 6 comprises a housing defined by a bore in the rocker arm, and a latch pin 410 slidably disposed therein. The bore may include a front bore section adjacent to an opening through which the latch pin 410 extends from the rocker arm, as well as a back bore section which houses the latch return spring. In some implementations, the back bore section may have a relatively larger diameter, and the front bore section may have a relatively smaller diameter. A wall or shoulder may be defined at a transition from the larger back bore section to the smaller front bore section. The latch pin 410 may include a forward, enlarged-diameter latch portion that is configured to slide within the forward bore section, and a rearward, reduced-diameter tail portion that is received within the back bore section. The latch return spring may be positioned concentrically about the reduced-diameter tail portion. A forward end of the latch return spring is seated against the wall or shoulder at the transition between the back and front bore sections, and a back end of the latch return spring bears against a spring-engagement surface provided on the latch pin 410.

[0060] In this embodiment, the latch return spring may be configured to bias the latch pin toward a default retracted position (FIG. 5) in which the forward latch portion remains at least partially within the bore so as to not interfere with a rotation of the decompression lever 310. The latch pin 410 may transition to an extended position (FIG. 6) upon application of an actuation force (e.g., pneumatic pressure, electromagnetic actuation, hydraulic pressure, etc.), during which movement the latch pin 410 is displaced longitudinally against a biasing force of the latch return spring, thereby compressing the latch return spring within the bore against the wall or shoulder. The extended latch pin 410 blocks the rotational movement of the decompression lever 310, thereby enabling the decompression lift motion received from the decompression lift cam 250 to be transferred to the rocker arm 110. Upon removal of the actuation force, the stored energy within the compressed latch return spring urges the latch pin 410 rearwardly, automatically returning the latch pin to the default retracted position. In an alternative embodiment, the latch return spring may be configured to bias the latch pin 410 toward a default extended position, and the latch pin 410 may transition to a retracted position upon application of the actuation force.

[0061] In an embodiment where the latch assembly is externally actuated, as seen from FIGs. 7 and 8, the latch assembly 400 may further comprise an external actuator assembly 500ATTORNEY DOCKET PATENT APPLICATION 006976.235212 of 24 mounted to a valvetrain component separate from the rocker arm 110, such as a bracket 520. By way of example and not limitation, the external actuator assembly 500 may be actuated pneumatically, electromagnetically, and / or hydraulically. In addition, the external actuator assembly 500 may include an actuator piston 510 configured to selectively engage a latch pin tab 450 of the latch pin 410 so as to switch the latch pin 410 into the extended position.

[0062] In one implementation, the external actuator assembly 500 may be mounted to the rocker arm 110 such that a movement direction of the actuator piston 510 is coaxially aligned with a movement direction of the latch pin 410. Thus, when the actuator piston 510 extends, it would push against the latch pin 410 and extend it. The external actuator assembly 500 may be energized pneumatically, electromagnetically, and / or hydraulically so as to extend the actuator piston 510.

[0063] In the implementation shown in FIG. 8, the external actuator assembly 500 may include a housing for the actuator piston 510. The actuator piston 510 may include a front end configured to engage the latch pin 410 or an associated component (e.g., latch pin tab 450). The actuator piston 510 may also include a back end, which may be concentrically surrounded by a piston return spring. The piston return spring may include a front end that abuts a wall or shoulder defined within the housing. The back end of the piston return spring may be mechanically coupled to the back end of the actuator piston 510. When an actuation force is applied to urge the actuator piston 510 to an extended position (e.g., via pneumatic pressure, electromagnetic actuation, or hydraulic pressure), the actuation force overcomes a biasing force of the piston return spring, causing the piston return spring to compress against the wall / shoulder. When the external actuator assembly 500 is no longer energized, the biasing force of the piston return spring will push against the wall / shoulder and return the actuator piston 510 to the default, retracted position. In an alternative embodiment, the piston return spring may be configured to bias the actuator piston 510 toward a default extended position, and the actuator piston 510 may be urged to a retracted position upon application of the actuation force.

[0064] The actuator piston 510 may transfer its motion to the latch pin 410 via any suitable mechanism. For example, in the embodiment shown in FIG. 8, the motion is transferred via a latch pin tab 450. The latch pin tab 450 may be structurally coupled to a slidable housing positioned behind the latch pin 410. Similar to the embodiment described with reference to FIGs. 5 and 6, the latch pin 410 may be disposed within a bore with an internal wall or shoulder. The front of the latch pin 410 is generally disposed within a front bore section, andATTORNEY DOCKET PATENT APPLICATION 006976.235213 of 24 the back of the latch pin 410 is generally disposed within the back bore section. The distal end of the back of the latch pin 410 may be configured to mechanically engage the slidable housing coupled to the latch pin tab 450. In one implementation, a latch return spring 430 may be positioned concentrically around the back end of the latch pin 410, with a front end of the latch return spring 430 pushing against the wall or shoulder within the bore, and a back end of the latch return spring 430 pushing against the slidable housing. In this design, the latch return spring 430 is not physically affixed to any other component, as the role of the latch return spring 430 is to bias the slidable housing away from the wall / shoulder and the opening of the bore. Thus, when the actuator piston 510 extends, the longitudinal motion of the actuator piston 510 is transferred to the latch pin tab 450. In turn, the latch pin tab 450 and the slidable housing move towards the decompression lever 310 so as to push the latch pin 410 through the opening of the bore. This motion also compresses the latch return spring 430 between the slidable housing and the internal wall / shoulder. Thus, when the actuator piston 510 is no longer exerting sufficient force to overcome the biasing force of the latch return spring 430, the compressed latch return spring 430 will push against the internal wall / shoulder, urging the slidable housing away from the decompression lever 310. The slidable housing, which may be coupled to the latch pin 410, would thereby retract the latch pin 410 to the default, retracted position.

[0065] In particular embodiments, a pneumatically and / or hydraulically actuated latch assembly may be fluidly connected to a pressurized fluid channel. It is particularly significant to maintain a pressure of the fluid within the pressurized fluid channel at a level sufficient to perform cylinder decompression event(s) as may be required by the transitional state applications associated with such embodiments, even at low engine speeds and / or engine off conditions. Moreover, since oil temperatures as well as supply pressures in conventional hydraulic systems may be low during engine startup, a latch assembly which is actuated pneumatically and / or electromagnetically is generally preferred over a hydraulically actuated latch assembly.

[0066] It will be appreciated that, while particular components, configurations, and / or combinations of the external actuator assembly 500 are depicted and described herein as nonlimiting examples, other components, configurations, and / or combinations may be used and are fully contemplated herein for controlling the extension and retraction of the latch pin 410.

[0067] FIGs. 11 and 12 illustrate schematic timing diagrams depicting features and operational aspects of rocker arm assemblies for cylinder decompression, according to particular embodiments.ATTORNEY DOCKET PATENT APPLICATION 006976.235214 of 24

[0068] In particular embodiments, in addition to providing an intake lift 610 and an exhaust lift 620, the systems and methods disclosed herein may provide a cylinder decompression lift 630, 640 to speed up a transitional state of engine operation and / or to reduce a peak torque requirement during the transitional state of engine operation. By way of example and not limitation, the decompression lift cam 250 may be configured to provide a constant lift and / or KVO decompression lift 640 during the transitional state of engine operation. Additionally or alternatively, the decompression lift cam 250 may be configured to provide an optimized and / or dedicated decompression lift 630 during the transitional state of engine operation at a timing corresponding to a compression phase of an engine cycle. In particular embodiments, the dedicated decompression lift 630 may be associated with fully closing each valve of the cylinder at least once during each engine cycle (i.e., during a 0°-720° crank angle engine cycle progression) when cylinder decompression is enabled.

[0069] In particular embodiments, the cylinder decompression lift 630, 640 may be provided by the systems and methods disclosed herein at low and / or moderate engine speeds, such as may be associated with engine startup and / or shutdown operations, as well as for propulsion source transitions between an internal combustion engine and an electric motor in a vehicle with a hybrid powertrain. By way of example and not limitation, low and / or moderate engine speeds associated with cylinder decompression may include engine speeds less than or equal to 750 rpm. By way of example and not limitation, moderate engine speeds associated with cylinder decompression may rise to a few thousand rpm. In particular embodiments, low and / or moderate engine speeds associated with cylinder decompression may correspond to relatively low gas flow velocities into and out of cylinders relative to high gas flow velocities associated with higher engine speeds.

[0070] In particular embodiments, the engine may require a peak torque input (e.g., as a torque received from a rotor, flywheel, starter, and / or equivalent corresponding to a transitional state, wherein a torque so received may be referred to as a negative torque) during the compression phase of an engine cycle. By way of example and not limitation, positively opening one or more valves during the compression phase to effectuate cylinder decompression can provide a significant reduction in peak torque required (e.g., from the rotor, flywheel, starter, and / or equivalent), such as may be associated with a transitional state of engine operation.

[0071] In particular embodiments, a decompression lift profile provided by a dedicated decompression lift cam 250 and associated with cylinder decompression may be optimized forATTORNEY DOCKET PATENT APPLICATION 006976.235215 of 24 transitional states of engine operation. In particular embodiments, the optimized decompression lift profile may comprise a variable radius about the dedicated decompression lift cam 250 (i.e., a non-constant radius).

[0072] In particular embodiments, a dedicated cam-based approach for cylinder decompression such as disclosed herein can be significantly larger than may be permissible in constant lift and / or KVO decompression approaches. By way of example and not limitation, such as depicted in FIGs. 11 and 13, maximum valve lift for constant lift and / or KVO decompression lift 640 can be limited by potential valve impact with the piston (e.g., at particular phases such as at or near top dead center (TDC)). Accordingly, such as depicted in FIG. 11, constant lift and / or KVO decompression approaches can be limited to relatively small valve lifts to avoid impact with the piston.

[0073] In contrast, an optimized decompression lift 630 using a dedicated cam-based approach, as depicted in FIG. 12, may incorporate one or more ramps providing more controlled initial and / or final valve lift rates to manage kinematic and / or dynamic transitions for valve motion. By way of example and not limitation, one or more ramps can reduce or eliminate impact risk between the rocker arm 110 and the at least one valve 300 during valve lift-off and / or seating events. By way of example and not limitation, the one or more ramps can provide smoother transitions for valve operation in particular embodiments, and can thereby reduce noise, vibration, and harshness (NVH) and / or increase component and system refinement and / or life. In particular embodiments, such as depicted in FIG. 11, constant lift and / or KVO decompression lift 640 may not be conducive to incorporating one or more ramps.

[0074] In particular embodiments, the challenges associated with constant lift and / or KVO decompression approaches as well as the benefits associated with a dedicated cam-based approach for cylinder decompression may be magnified with increased engine speeds. In particular embodiments, transitional states with increased engine speeds (e.g., much higher than startup / shutdown engine speeds) may be particularly relevant for hybrid powertrain applications with frequent transitions between engine and electric motor power / propulsion sources.

[0075] FIG. 13 illustrates comparative peak torque requirements for dedicated cam-based cylinder decompression systems relative to systems configured with a constant lift and / or KVO approach for cylinder decompression. By way of example and not limitation, dedicated cambased cylinder decompression systems, such as disclosed herein, may be able to provide larger values of valve lift, with correspondingly low fractions of peak torque requirements that remainATTORNEY DOCKET PATENT APPLICATION 006976.235216 of 24 consistently low with increasing engine speeds, than constant lift and / or KVO cylinder decompression systems. Accordingly, dedicated cam-based cylinder decompression systems may be uniquely capable of limiting engines to constant or decreasing fractions of peak torque requirements with increasing engine speed, such as illustrated in FIG. 13, relative to constant lift and / or KVO cylinder decompression systems.

[0076] It will be appreciated that, while particular numerical values, such as those included in FIGs. 11 - 13, may be provided herein as examples to help illustrate the benefits and challenges of the dueling decompression approaches disclosed herein, such numbers and / or other features disclosed herein are not limiting, and other scales, embodiments, and / or combinations are fully contemplated herein.

[0077] In particular embodiments, cylinder decompression systems associated with engine transition states can be distinct from other systems that may otherwise involve decompression. In particular embodiments, engine braking systems and implementations can be distinct from cylinder decompression systems and methods disclosed herein, such as to support engine transitional states. By way of example and not limitation, valve opening for engine braking may be associated with slowing down a vehicle. By way of example and not limitation, valve opening for engine braking may be associated with building compression in the cylinder and / or releasing compressed gas (e.g., air) in the cylinder, such that a return of compression energy to a crankshaft is impeded. In contrast, systems and methods of decompression disclosed herein are associated with pressure release during compression. By way of example and not limitation, valve opening for engine braking may be associated with opening an exhaust valve near an engine top dead center (TDC) phase. By way of example and not limitation, valve opening for engine braking may be associated with opening an exhaust valve to permit compression and subsequent release during one or more portions of the remaining engine cycle (e.g., compression release between about 07720° and about 360°). In particular embodiments, engine speeds and / or mass flowrates in applications considered herein may be significantly lower than those typically associated with engine braking applications, as previously discussed herein.

[0078] It will be appreciated that while the description and / or illustrations provided herein may depict particular types and / or architectures of rocker arm assemblies, any suitable types and / or architectures are fully contemplated herein to operate a cylinder decompression approach. By way of example and not limitation, systems and methods for cylinder decompression disclosed herein may be adapted to other types of rocker arm architectures (e.g., center pivot, end pivot, pushrod-based, any of type I-V rocker arms), and all such architecturesATTORNEY DOCKET PATENT APPLICATION 006976.235217 of 24 are fully contemplated herein. By way of example and not limitation, systems and methods for cylinder decompression disclosed herein may be adapted to modifications of rocker arm architectures (e.g., comprising lost motion and / or added motion modules, capsules or other switchable modules, variants enabling additional and / or different operating modes), and all such types and / or architectures are fully contemplated herein.Miscellaneous

[0079] The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that embodiment, but, where applicable, are interchangeable and can be used in various embodiments, even if not specifically shown or described. For example, it is possible that each of the characteristics described in one of the examples of an embodiment can be combined with one or a plurality of other desired characteristics from other embodiments, resulting in other embodiments that may not be described in words or by reference to the drawings, but which are fully contemplated. It will also be understood that changes and modifications may be made by those of ordinary skill within the scope of the disclosure, illustrations, and / or the following claims. Such variations are fully contemplated herein and not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

[0080] The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article “a” or “the” in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of “or” should be interpreted as being inclusive, such that the recitation of “A or B” is not exclusive of “A and B,” unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of “at least one of A, B and C” should be interpreted as one or more of a group of elements consisting of A, B and C, and should not be interpreted as requiring at least one of each of the listed elements A, B and C, regardless of whether A, B and C are related as categories or otherwise. Moreover, the recitation of “A, B and / or C” or “at least one of A, B or C” should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B and C.

[0081] It should be noted that figures provided herein may be illustrated schematically rather than literally or precisely; components and aspects of the figures may not necessarily beATTORNEY DOCKET PATENT APPLICATION 006976.235218 of 24 to scale. Moreover, while like reference labels or numerals may designate corresponding parts throughout the different views in many cases, like parts may not always be provided with like reference numerals or labels in each view. Further, like parts may not be labeled in every view or figure.

[0082] Numerical ranges recited in this application should be construed to be inclusive of the end points of the stated ranges. Particular axes, such as one or more rotational, lateral and / or longitudinal axes, which may be omitted herein in particular illustrations, should be construed to exist in every illustration or situation where it is referred to, or to which it reasonably corresponds.GLOSSARY / TABLE OF THE DRAWINGS

[0083] To assist in understanding the present disclosure, reference is now made to the following reference numbers associated with aspects of the accompanying drawings.

[0084] 110 Rocker Arm

[0085] 120 Rocker Shaft

[0086] 130 Rocker Shaft Bore

[0087] 150 Valve End

[0088] 160 Stop

[0089] 200 Cam End

[0090] 220 Camshaft

[0091] 230 Main Lift Cam

[0092] 240 Main Lift Cam Roller

[0093] 250 Decompression Lift Cam

[0094] 300 Gas Exchange Valves

[0095] 310 Decompression Lever

[0096] 320 Lever Shaft

[0097] 330 Torsional Lost Motion Spring

[0098] 340 Slider

[0099] 360 First End

[0100] 370 Second End

[0101] 400 Latch Assembly

[0102] 410 Latch Pin

[0103] 430 Latch Return SpringATTORNEY DOCKET PATENT APPLICATION 006976.235219 of 24

[0104] 450 Latch Pin Tab

[0105] 500 External Actuator Assembly

[0106] 510 Actuator Piston

[0107] 520 Bracket

[0108] 530 Compression Lost Motion Spring

[0109] 550 Decompression Lift Cam Roller

[0110] 560 Stop

[0111] 570 Fastener

[0112] 610 Intake Lift

[0113] 620 Exhaust Lift

[0114] 630 Decompression Lift (Dedicated)

[0115] 640 Decompression Lift (Constant Lift)

Claims

ATTORNEY DOCKET PATENT APPLICATION 006976.235220 of 24CLAIMS1. A rocker arm assembly for cylinder decompression in an engine, the rocker arm assembly comprising: a rocker arm pivotally mounted to a rocker shaft, the rocker arm comprising: a cam end configured to receive main lift motion from a main lift cam of a camshaft, a valve end configured to transmit the main lift motion to at least one gas exchange valve of the engine, and a lever shaft extending from the rocker arm at a position between a rocker shaft bore of the rocker arm and the camshaft; and a decompression assembly comprising: a decompression lever pivotally mounted to the lever shaft, the decompression lever including: a first end configured to receive decompression lift motion from a decompression lift cam, and a second end configured to selectively transmit the decompression lift motion to the rocker arm, a lost motion spring configured to bias the decompression lever towards the decompression lift cam, and a latch assembly associated with the second end of the decompression lever, the latch assembly configured to switch between (a) a drive mode in which the decompression lift motion received by the decompression lever is absorbed via the lost motion spring, and (b) a cylinder decompression mode in which the decompression lift motion received by the decompression lever is transmitted to the at least one gas exchange valve via the rocker arm.

2. The rocker arm assembly of claim 1, wherein the cam end of the rocker arm includes a main lift cam roller axle rotatably supporting a main lift cam roller configured to engage the main lift cam.

3. The rocker arm assembly of claim 2, wherein the lever shaft is an extension of the main lift cam roller axle.ATTORNEY DOCKET PATENT APPLICATION 006976.235221 of 244. The rocker arm assembly of claim 1 , wherein the first end of the decompression lever includes a decompression lift cam roller configured to rotatably engage the decompression lift cam.

5. The rocker arm assembly of claim 1, wherein the first end of the decompression lever includes a slider configured to engage the decompression lift cam.

6. The rocker arm assembly of claim 1, wherein the rocker arm further comprises a stop configured to limit a rotation of the decompression lever towards the decompression lift cam.

7. The rocker arm assembly of claim 6, wherein the lost motion spring is a compression spring pressed between a portion of the stop and a portion of the decompression lever.

8. The rocker arm assembly of claim 1 , wherein the lost motion spring is a torsional spring mounted to the lever shaft.

9. The rocker arm assembly of claim 1, wherein the latch assembly includes: a latch pin slidably disposed in the rocker arm, the latch pin configured to switch between a retracted position and an extended position; and a latch return spring configured to bias the latch pin into the retracted position.

10. The rocker arm assembly of claim 9, wherein: in the drive mode, the latch pin is in the retracted position, and in the cylinder decompression mode, the latch pin is in the extended position so as to engage the second end of the decompression lever.

11. The rocker arm assembly of claim 9, wherein the latch assembly further includes: an external actuator assembly mounted to a valvetrain component, the external actuator assembly including an actuator piston configured to selectively actuate the latch pin into the extended position.ATTORNEY DOCKET PATENT APPLICATION 006976.235222 of 2412. The rocker arm assembly of claim 11, wherein the external actuator assembly is positioned such that a movement direction of the actuator piston is coaxially aligned with, or parallel to, a movement direction of the latch pin.

13. The rocker arm assembly of claim 12, wherein the external actuator assembly is configured to selectively actuate the latch pin by extending the actuator piston so as to push against a latch pin tab that is mechanically coupled to the latch pin.

14. The rocker arm assembly of claim 13, wherein the latch pin tab is structurally coupled to a slidable housing positioned behind the latch pin in the latch assembly.

15. The rocker arm assembly of claim 11, wherein the external actuator assembly is actuated pneumatically or electromagnetically.

16. A method for operating a cylinder decompression system of an engine, the cylinder decompression system including a rocker arm pivotally mounted to a rocker shaft so as to transmit main lift motion from a main lift cam to at least one gas exchange valve of the engine; a decompression lever pivotally mounted to a lever shaft of the rocker arm so as to transmit decompression lift motion from a decompression lift cam to the at least one gas exchange valve via the rocker arm; and a latch assembly configured to selectively enable and disable the transmitting of the decompression lift motion, the method comprising: retracting a latch pin of the latch assembly in response to an activation of a drive mode; during the drive mode: transmitting the main lift motion from the main lift cam to the at least one gas exchange valve via the rocker arm; and absorbing, via a lost motion spring, the decompression lift motion received by the decompression lever from the decompression lift cam; extending the latch pin of the latch assembly in response to an activation of a cylinder decompression mode; andATTORNEY DOCKET PATENT APPLICATION 006976.235223 of 24 during the cylinder decompression mode, transmitting the decompression lift motion received by the decompression lever from the decompression lift cam to the at least one gas exchange valve via the extended latch pin and the rocker arm.

17. The method of claim 16, wherein the retracting of the latch pin includes urging the latch pin into a retracted position via a latch return spring of the latch assembly.

18. The method of claim 16, wherein the latch pin of the latch assembly is extended pneumatically, electromagnetically, or hydraulically.

19. The method of claim 16, wherein the extending of the latch pin of the latch assembly includes extending an actuator piston of an external actuator assembly so as to mechanically extend the latch pin, and wherein the external actuator assembly is mounted to a valvetrain component separate from the rocker arm.

20. The method of claim 19, wherein the actuator piston of the external actuator assembly is extended pneumatically or electromagnetically.

Images