TECHNICAL FIELD

[0001] The present disclosure relates generally to a rocker arm assembly for use in a valvetrain assembly, and more particularly to a rocker arm assembly that provides a compression engine brake function.

BACKGROUND

[0002] Compression engine brakes may be used as auxiliary brakes, in addition to wheel brakes, on relatively large vehicles powered by heavy or medium duty diesel engines. A compression engine braking system may be arranged, when activated, to provide early and/or additional opening of an engine cylinder's exhaust valve when the piston in that cylinder may be near a top-dead-center position of its compression stroke so that compressed air may be released through the exhaust valve. This may cause an engine to function as a power consuming air compressor, which may assist in slowing the vehicle.

[0003] In a typical valvetrain assembly used with a compression engine brake, one or more exhaust valves may be actuated by an exhaust rocker arm, which may engage one or more exhaust valves by means of a valve bridge. The exhaust rocker arm may rock in response to lift profiles of received from one or more rotating camshafts, and may accordingly press down on the valve bridge, which may itself press down on one or more of the exhaust valves to open them.

[0004] The description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this section, as well as aspects of the description that cannot otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

SUMMARY OF PARTICULAR EMBODIMENTS

[0005] In particular embodiments, an exhaust valve rocker arm assembly is disclosed that is capable of selectively operating in at least an engine braking enabled and an engine braking disabled mode, comprising a rocker arm configured to rotate about a rocker shaft; a valve end of the rocker arm being configured to selectively act on a valve bridge, the valve bridge being configured to selectively engage a first exhaust valve and a second exhaust valve, the valve end of the rocker arm comprising a brake capsule disposed on the rocker arm, the brake capsule being optionally removable, the brake capsule being optionally positionally adjustable relative to the rocker arm, the brake capsule comprising a plunger body that is selectively movable between a first position and a second position, the plunger body extending in the first position to act on the first exhaust valve through the valve bridge; the valve end further comprising a lost motion mechanism disposed on the rocker arm, the lost motion mechanism comprising a lost motion shaft, the lost motion shaft configured to translate along a lost motion receiving passage for selectively transmitting motion of the rocker arm to the valve bridge.

[0006] In particular embodiments, which may combine the features of some or all above embodiments, in an engine braking enabled mode, the plunger body of the brake capsule is extended in the first position, the plunger body acting on the valve bridge during rotation of the rocker arm to a first angle and opening (directly through acting on the valve bridge or indirectly through a pin) the first exhaust valve a predetermined distance, the second exhaust valve remaining closed.

[0007] In particular embodiments, which may combine the features of some or all above embodiments, in an engine braking enabled mode, subsequent to the opening of the first exhaust valve the predetermined distance, further rotation of the rocker arm causes the lost motion shaft to act on the valve bridge and open the second exhaust valve while further opening the first exhaust valve.

[0008] In particular embodiments, which may combine the features of some or all above embodiments, the brake capsule is a hydraulic brake capsule.

[0009] In particular embodiments, which may combine the features of some or all above embodiments, the brake capsule is threaded into the rocker arm.

[0010] In particular embodiments, which may combine the features of some or all above embodiments, the lost motion mechanism is a mechanical lost motion mechanism, and the mechanical lost motion mechanism further comprises a mechanical lash adjustment mechanism. [0011] In particular embodiments, which may combine the features of some or all above embodiments, the hydraulic brake capsule comprises an actuator configured to selectively release oil pressure in the hydraulic brake capsule.

[0012] In particular embodiments, which may combine the features of some or all above embodiments, the plunger body occupying the first position is associated with providing pressurized oil through a controllable hydraulic line, the pressurized oil acting on the actuator.

[0013] In particular embodiments, which may combine the features of some or all above embodiments, the actuator comprises a needle and a check ball, the needle comprising a longitudinal pin portion and a disk portion, the needle configured to selectively open the check ball based on pressurized oil acting on the disk portion.

[0014] In particular embodiments, which may combine the features of some or all above embodiments, the exhaust valve rocker arm assembly further comprises an oil discharge circuit configured to selectively depressurize oil under the disk portion of the needle.

[0015] In particular embodiments, which may combine the features of some or all above embodiments, the lost motion mechanism is longitudinally aligned with the center of the valve bridge.

[0016] In particular embodiments, which may combine the features of some or all above embodiments, the brake capsule is longitudinally aligned with the first exhaust valve.

[0017] In particular embodiments, which may combine the features of some or all above embodiments, the plunger body is held extended in the first position in the engine braking enabled mode for all rotational positions of the rocker arm.

[0018] In particular embodiments, which may combine the features of some or all above embodiments, in an engine braking disabled mode, the plunger body is retracted to a second position and configured into a collapsible state, thereby preventing the plunger body from exerting a valve opening force on the valve bridge, and the first exhaust valve and the second exhaust valve follow an exhaust lift profile motion transmitted to the valve bridge by the lost motion mechanism. [0019] In particular embodiments, which may combine the features of some or all above embodiments, a method of operating a valvetrain system is disclosed, the valvetrain system comprising an exhaust valve rocker arm assembly, the method comprising, in an engine braking enabled mode, extending a plunger body of a brake capsule to a first position, the exhaust valve rocker arm assembly comprising the brake capsule and a lost motion mechanism, the plunger body in the first position acting on a valve bridge during rotation of a rocker arm to a first angle to open a first exhaust valve a predetermined distance, a second exhaust valve remaining closed, and causing a lost motion shaft of the lost motion mechanism to act on the valve bridge, subsequent to the opening of the first exhaust valve the predetermined distance and based on further rotation of the rocker arm, to open the second exhaust valve while further opening the first exhaust valve, while holding the plunger body of the brake capsule extended in the first position for all rotational positions of the rocker arm.

[0020] In particular embodiments, which may combine the features of some or all above embodiments, a method of operating a valvetrain system is disclosed wherein, in an engine braking disabled mode, the plunger body is retracted to a second position and a collapsible state, thereby preventing the plunger body from exerting a valve opening force on the valve bridge, and the first exhaust valve and the second exhaust valve are constrained to follow an exhaust lift profile motion transmitted to the valve bridge by the lost motion mechanism.

[0021] In particular embodiments, which may combine the features of some or all above embodiments, a valvetrain system of an engine is disclosed, the valvetrain system capable of selectively engaging an engine braking enabled mode or an engine braking disabled mode, the valvetrain system comprising an exhaust camshaft provided with an engine braking profile; an exhaust valve rocker arm assembly operatively coupled with the exhaust camshaft and selectively operable in at least an engine braking enabled mode and an engine braking disabled mode; a valve bridge; and a plurality of exhaust valves comprising at least one first exhaust valve and at least one second exhaust valve, the plurality of exhaust valves configured to be selectively acted upon by the valve bridge, wherein the exhaust valve rocker arm assembly further comprises a rocker arm configured to rotate about a rocker shaft; a brake capsule disposed on the rocker arm and comprising a plunger body selectively movable between a first position and a second position, the plunger body extending in the first position to act on the first exhaust valve through the valve bridge; and a lost motion mechanism disposed on the rocker arm comprising a lost motion shaft configured to translate along a lost motion receiving passage for selectively transmitting motion of the rocker arm to the valve bridge, the plunger body of the brake capsule held extended in the first position for all rotational positions of the rocker arm. [0022] In particular embodiments, which may combine the features of some or all above embodiments, a valvetrain system of an engine is disclosed, wherein as the plunger body of the brake capsule is held extended in the first position in an engine braking enabled mode, the plunger body acts on the valve bridge during rotation of the rocker arm to a first angle and opening (directly through acting on the valve bridge or indirectly through a pin) the first exhaust valve a predetermined distance, the second exhaust valve remaining closed, and subsequent to the opening of the first exhaust valve the predetermined distance, further rotation of the rocker arm causes the lost motion shaft to act on the valve bridge and open the second exhaust valve while further opening the first exhaust valve.

[0023] In particular embodiments, which may combine the features of some or all above embodiments, a valvetrain system of an engine is disclosed, wherein in an engine braking disabled mode, the plunger body is retracted to a second position and configured into a collapsible state, thereby preventing the plunger body from exerting a valve opening force on the valve bridge, and the first exhaust valve and the second exhaust valve follow an exhaust lift profile motion transmitted to the valve bridge by the lost motion mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be described in greater detail below based on the exemplary figures. The invention is not limited to the exemplary embodiments. Other features and advantages of various embodiments of the present invention will become apparent by reading the following detailed description with reference to the attached drawings which illustrate the following:

[0025] FIG. 1 illustrates a schematic perspective partial view of an exhaust rocker arm assembly for use with compression engine braking, according to particular embodiments.

[0026] FIG. 2 illustrates a schematic perspective partial sectional view of an exhaust rocker arm assembly, according to particular embodiments.

[0027] FIG. 3 illustrates a schematic perspective partial sectional view of an exhaust rocker arm assembly, according to particular embodiments.

[0028] It should be noted that figures provided may be illustrated schematically rather than literally or precisely; components and aspects of the figures may also not necessarily be to scale. Moreover, while like reference numerals may designate corresponding parts throughout the different views in many cases, like parts may not always be provided with like reference numerals in each view.

DESCRIPTION OF EXAMPLE EMBODIMENTS

[0029] In accordance with various embodiments of the present disclosure, rocker arm assemblies and related mechanisms, devices, and methodologies are provided herein. For clarity, not all features of each actual implementation or embodiment may be described in this specification. Additionally, some aspects and features may be described at a level Further, features and aspects that are disclosed, illustrated, and/or apparently otherwise contemplated in certain specific configurations are fully contemplated to be mixed or combined to produce any and all resulting configurations using features and aspects from any embodiments and/or configurations considered herein. Thus, modifications and/or combinations of features and aspects may be made that result in embodiments that are fully contemplated to fall within the scope of this disclosure.

[0030] FIG. 1 illustrates a schematic perspective partial view of an exhaust rocker arm assembly of a valvetrain assembly for use with compression engine braking, according to particular embodiments. In this regard, the present disclosure may be used in any valvetrain assembly that may utilize engine braking.

[0031] In particular embodiments, a valvetrain assembly may include an exhaust rocker arm assembly 30, and a rocker shaft 18 that may cooperate with exhaust rocker arm assembly 30. In particular embodiments, rocker arm 11 may be configured to rotate about rocker shaft 18. In particular embodiments, rocker shaft 18 may separately or additionally communicate a hydraulic and/or control fluid, such as oil, to the exhaust rocker arm assembly 30. As a non-limiting example, pressurized oil may be supplied through rocker shaft 18 from a main engine oil pump or other pressure source.

[0032] In particular embodiments, exhaust rocker arm assembly 30 may be provided with a valve end 12. In particular embodiments, a valve bridge 42 of the valvetrain assembly may be located toward the valve end 12 of exhaust rocker arm assembly 30; valve bridge 30 may selectively engage a first exhaust valve and a second exhaust valve associated with a cylinder of an engine (valves and cylinder not shown). In particular embodiments, a first end 50-A of valve bridge 42 may engage with the first exhaust valve, which may also be called the brake valve. In particular embodiments, a pin or socket 51 may be optionally provided in and/or through first end 50-A of valve bridge 42 for engaging with the first exhaust valve. In particular embodiments, a second end 52-A of valve bridge 42 may engage with the second exhaust valve.

[0033] In particular embodiments, exhaust rocker arm assembly 30 may be configured to receive and/or respond to a lift profile from a cam of a camshaft (not shown). As a non-limiting example, exhaust rocker arm assembly 30 may be provided with a roller 23 at an end opposite the valve end 12. Roller 23 may be supported at and/or by axle bore 29 of exhaust rocker arm assembly 30. In particular embodiments, roller 23 may be operatively coupled to, engage with, and/or be otherwise directly acted upon by the cam.

[0034] In particular embodiments, instead of roller 23, exhaust rocker arm assembly 30 may be provided with a different mechanism for receiving a lift profile from the cam of a camshaft. As another non-limiting example, a pushrod (not shown) may be configured to reciprocate or otherwise translate, such as move upward or downward, based on a lift profile received from the cam. The motion of the pushrod resulting from the received lift profile from a cam of a camshaft may then be directly or indirectly transferred to the rocker arm 11.

[0035] As seen in the frame of reference of at least FIGs. 1-3, starting from a lowest (i.e., base circle) position of a cam of a camshaft, a lift profile received from the cam may cause rocker arm 11 to initially rotate counter-clockwise around the rocker shaft 18 until a maximum lift is received; subsequently, rocker arm 11 may rotate clockwise around the rocker shaft 18 as the lift profile received from the cam reduces back to its minimum lift, corresponding to the cam’s base circle.

[0036] In particular embodiments, exhaust rocker arm assembly 30 may generally include a lost motion mechanism 44, and/or a brake capsule 46. In particular embodiments, brake capsule 46 may be longitudinally aligned (as seen in at least FIG. 1) with the first end 50-A of valve bridge 42, and/or the first exhaust valve, also designated as the brake valve. In particular embodiments, lost motion mechanism 44 may be longitudinally aligned (as seen in at least FIG. 1) with or near the center of valve bridge 42, so as to be capable of influencing and/or exerting opening force on both first and second exhaust valves, when intended.

[0037] In particular embodiments, an exertion of influence and/or opening force on the first exhaust valve may occur by a first socket or elephant foot or e-foot 173 of brake capsule 46 acting on first end 50-A of valve bridge 42. In particular embodiments, first socket or e-foot 173 of brake capsule 46 may separately or additionally act on the first exhaust valve via pin or socket 51. As a non-limiting example, valve bridge 42 may comprise a pin or socket 51 traversing through a hole or passage, the pin or socket receiving valve lift from brake capsule 46 and directly or indirectly transmitting and/or making contact with a first exhaust valve, also called brake valve. In particular embodiments, such as shown in FIG. 3, first socket or e-foot 173 may be replaced by a sliding pad 174.

[0038] In particular embodiments, valve bridge 42 may separately or additionally receive valve lift from lost motion mechanism 44, such as by second socket 132, and valve bridge 42 may be in contact with the second exhaust valve via second end 52- A. As previously noted, in particular embodiments, lost motion mechanism 44 may be longitudinally aligned with or near the center of valve bridge 42, so as to be capable of influencing and/or exerting opening force on both first and second exhaust valves, when intended.

[0039] In particular embodiments, brake capsule 46 may be purely mechanically controlled and/or actuated. In other embodiments, brake capsule 46 may be controlled and/or operated by electromagnetic actuation, such as by one or more solenoids. In particular embodiments, brake capsule 46 may be a removable, replaceable, and/or adjustable module. In particular embodiments, brake capsule 46 may be positionally adjustable relative to rocker arm 11.

[0040] In particular embodiments, brake capsule 46 may be hydraulically controlled and/or actuated. In particular embodiments, a hydraulic brake capsule 46 may be a removable component or module. In particular embodiments, the longitudinal position of brake capsule 46 may be adjustable within rocker arm 11. As a non-limiting example schematically illustrated in at least FIGs. 2 and 3, a removable brake capsule 46 may be provided within a first bore 66 of valve end 12 of exhaust rocker arm assembly 30 by means of appropriate coupling mechanism(s), such as threaded coupling(s) 67. In particular embodiments, threaded coupling(s) 67 and/or other mechanisms and mechanical features may separately or additionally enable longitudinal positional adjustment of brake capsule 46 relative to rocker arm 11 , so as to vary and/or adjust the mechanical gap between engaging parts of brake capsule 46 and valve bridge 42, such as for initial and/or periodic maintenance adjustment based on changes due to operating conditions, usage, and/or wear. As non-limiting examples, engaging parts of interest may comprise e-foot 173 and/or sliding pad 174 relative to valve bridge 42 and/or pin 51. [0041] In particular embodiments, a removable hydraulic brake capsule 46 may be separately or additionally provided with indexing and/or alignment features to engage with one or more hydraulic supply line(s), such as hydraulic supply passage 160 providing fluid communication for oil from a controllable, pressurized oil line or circuit 150 via rocker shaft 18. While one or more particular embodiments of oil circuit 150 may be disclosed particularly herein as non- limiting examples, it will be appreciated that a variety of configurations and/or feature combinations for oil circuit 150 may be used to accomplish the operational goals of the disclosed embodiments. Additionally, all disclosed aspects of one or more oil circuits may not be visible in each or all view(s), based on physical reality in a visualized plane, and/or omission for clarity of disclosing particular features.

[0042] In particular embodiments, brake capsule 46 may comprise a plunger assembly 60, which may include plunger body 62 and/or an upper plunger assembly 64. In particular embodiments, such as illustrated in FIG. 2, plunger body 62 may have a first spigot 169, which may be received in a first socket 173 that may act against the valve bridge 42. In particular embodiments, such as illustrated in FIG. 3, plunger body 62 may have a sliding pad 174, which may directly or indirectly act against the valve bridge 42.

[0043] In particular embodiments, upper plunger assembly 64 may have an opening that may define a valve seat 76. A check ball assembly 80 may be positioned between upper plunger assembly 64 and plunger bodies 62. In particular embodiments, check ball assembly 80 may include check ball 90, and/or one or more biasing member(s), such as first biasing member 82. As a non-limiting example, first biasing member 82 may comprise a spring.

[0044] In particular embodiments, brake capsule 46 may include an actuator or needle 100. As a non-limiting example, needle 100 may act as an actuator that selectively releases pressure in the brake capsule 46. In particular embodiments, needle 100 may include a longitudinal pin portion 110 and an upper disk portion 112. A first cap 116 may be provided to contain and/or close the brake capsule 46, and may capture a second biasing member 120 therein. Second biasing member 120 may act between the first cap 116 and the upper disk portion 112 of the needle 100. In the non-limiting examples illustrated in at least FIGs. 2 and 3, second biasing member 120 may bias the needle 100 downward. As a non-limiting example, second biasing member 120 may comprise a spring. [0045] In particular embodiments, pressurized hydraulic fluid, such as oil, may be selectively supplied to upper disk portion 112, such as via a hydraulic supply passage 160. As a non-limiting example, based on receiving one or more control signals, and/or responsive to input from a driver or operator and/or Engine Control Unit, an oil control valve (OCV) may be used to permit or prevent flow of pressurized hydraulic fluid in hydraulic supply passage 160. In particular embodiments, when hydraulic supply passage 160 has a low pressure level and/or may not supplied with pressurized oil, upper disk portion 112 of actuator or needle 100 may be biased downward by second biasing member 120, holding check ball 90 open and permitting oil flow around and past valve seat 76. Consequently, this may cause brake capsule 46 to become "soft," i.e., enter a collapsible state and become incapable of influencing or exerting an opening force upon the valve bridge 42.

[0046] In particular embodiments, when hydraulic supply passage 160 has a high pressure level and/or is supplied with suitably pressurized oil, upper disk portion 112 of actuator or needle 100 may be lifted up against the bias of biasing member 120. As a result, longitudinal pin portion 110 may moved away from check ball 90, closing the check ball 90 against valve seat 76. Consequently, brake capsule 46 may act as a no-retum valve, with the first plunger body 62 extending (and held extended) toward valve bridge 42, with a rigid structure relative to a valve opening force that may be exerted upon brake capsule 46 via valve bridge 42.

[0047] As a result, in particular embodiments, brake capsule 46 may provide a switchable system for selectively enabling or disabling the ability of plunger body 62 to influence or exert an opening force on valve bridge 42 and/or the first exhaust valve (also called brake valve). Although this disclosure describes providing particular means of actuation and/or control of a brake capsule, this disclosure contemplates providing any suitable means of actuation and/or control of one or more capsules, such as brake capsules, in any suitable manner. As a non-limiting example, In particular embodiments, brake capsule 46 may be electrically actuated and/or controlled. By way of illustration and not limitation, an electric actuator may comprise an electric motor controllable by an external signal based on requirement. As another non-limiting example, an electric actuator may be electromagnetically operated, such as using one or more solenoids.

[0048] According to some embodiments, brake capsule 46 may be of a non-resetting design, whereby when engine braking mode is enabled, plunger body 62 of brake capsule 46 may be rigidly extended, and/or otherwise configured to provide engine braking lift to first exhaust valve, for the full cycle or duration of rotation of the cam of a camshaft operation. Stated differently, a non-resetting design may be “always on” when engine braking mode is enabled. As a non-limiting example, a non-resetting design of brake capsule 46 may provide benefits of lower complexity, fewer moving parts and/or opportunities for failure, a more compact and/or lighter assembly, and/or lower cost.

[0049] While several embodiments of this disclosure may pertain to a non-resetting design of brake capsule 46, this disclosure is not limited to a non-resetting design. By way of illustration and not limitation, according to particular embodiments, brake capsule 46 may be provided with a resetting capability, whereby when engine braking mode is enabled, plunger body 62 of brake capsule 46 may be rigidly extended for only the fraction of each rotation cycle of the cam of a camshaft wherein engine braking lift is designed to be applied to first exhaust valve, and whereby plunger body 62 of brake capsule 46 may be deactivated, softened, collapsed, and/or otherwise made ineffective for providing engine braking lift for the remaining fraction(s) of each rotation cycle of the cam. Such a reset function may be enabled in multiple ways. As a non-limiting example, for a hydraulic brake capsule 46, a controller for an oil control valve may be used to selectively actuate and/or activate pressurizing a oil line during the designed fraction of a cam cycle, based upon the desired brake lift profile and/or timing. As another non-limiting example, an electromagnetic actuator, such as a solenoid, may be selectively energized during the designed fraction of a cam cycle, based on the desired brake lift profile and/or timing.

[0050] In particular embodiments, a lost motion mechanism 44 may be incorporated into a rocker arm assembly 3. In particular embodiments, lost motion mechanism 44 may include a lost motion shaft 130 having a distal end that is received by a second socket 132, and a proximal end that may extend into a second bore or lost motion receiving passage 136 defined in the rocker arm 11. A collar 138 may extend from a portion of the lost motion shaft 130. In particular embodiments, a second cap 140 may be coupled to the rocker arm 11 and/or may close second bore 136. One or more biasing members, such as biasing member 144, may be provided to act on lost motion shaft 130. In particular embodiments, biasing member 144 may comprise a spring. In particular embodiments, such as illustrated in FIG. 2, biasing member 144 may be provided so as to directly act on collar 138 of lost motion mechanism 44. In particular embodiments, such as illustrated in FIG. 3, biasing member 144 may act between second cap 140 and one or more features, such as groove(s), provided within lost motion shaft 130. Lost motion shaft 130 may be permitted to translate along its axis within the lost motion receiving passage 136. In particular embodiments, lost motion mechanism 44 may be therefore absorb a portion of motion corresponding to the collar 138 translating against the force of biasing member 144 until collar 138 engages, interferes with, and/or otherwise “bottoms out” against a portion of rocker arm 11, or another rigid member. Thereafter, in particular embodiments, no further absorption of motion may be possible due to lost motion mechanism 44; further motion may then be transmitted rather absorbed.

[0051] In particular embodiments, lost motion mechanism 44 may be a hydraulic lost motion mechanism. In still other embodiments, lost motion mechanism 44 may be be electrically controlled and/or operated. In particular embodiments, lost motion mechanism 44 may use a combination of operational methodologies. In particular embodiments, such as illustrated in at least FIGs. 2 and 3, lost motion mechanism 44 may be a mechanical lost motion mechanism. As a non-limiting example, particular mechanical lost motion mechanisms may be configured so that the while oil may be used for lubrication, any primary functions may be governed by mechanical structures, fasteners, and couplings, such as due to biasing based on springs, relative adjustments determined and configured using threaded fasteners, and relative interferences and/or stops created by mechanical features.

[0052] In particular embodiments, lost motion mechanism 44 may be provided with lash adjustment provisions and/or mechanisms. As a non-limiting example, lost motion mechanism 44 may include a hydraulic lash adjustment mechanism. In particular embodiments, such as illustrated in at least FIGs. 2 and 3, lost motion mechanism 44 may be provided with a mechanical lash adjustment mechanism. By way of illustration and not limitation, the relative distance, gap, and/or lash between engaging surfaces of second socket 132 and valve bridge 42 may be adjusted based on determining and setting a longitudinal offset position of lost motion shaft 130 within lost motion receiving passage 136. As a non-limiting example, longitudinally withdrawing or further lowering upper shaft or lash adjustment screw 131 by threaded insertion and/or locking may permit adjustment of the relative longitudinal offset between second socket 132 and collar 138.

[0053] As will become appreciated herein, in particular embodiments, the exhaust rocker arm assembly 30 may operate in a default combustion engine mode and/or with engine braking off or disabled, and an engine braking mode enabled mode. When the exhaust rocker arm assembly 30 is operating with engine braking mode disabled, an oil control valve (not shown) may be closed, i.e., not energized. As a result, in particular embodiments, the oil supply passage 160 defined in the rocker arm 11 may have a low pressure level. Other oil pressures may be used. With low pressure, the biasing member 120 may force the needle 100 in a downward direction, causing the longitudinal pin portion 110 to urge the ball 90 away from the valve seat 76. The check ball assembly 80 may therefore open, permitting oil to flow out or discharge rather than be trapped in the chamber below the check ball 90, causing the brake capsule 46 to become "soft" or enter a collapsible state throughout operation with engine braking mode disabled, and thereby rendering brake capsule 46 unable to influence a downward force upon the valve bridge 42.

[0054] Therefore, in particular embodiments with engine braking mode disabled, starting from minimum (base circle) lift received by rocker arm 11 from a cam of a camshaft, lost motion shaft 130 of lost motion mechanism may absorb an initial portion of the lift as rocker arm 11 rotates counter-clockwise direction (as seen in the frame of reference of at least FIGs. 1-3). As a nonlimiting example, this initial portion of the lift may correspond to an engine braking lift, which may not be desired to be applied to valve bridge 42 with engine braking mode disabled, and may be therefore absorbed by design. Continued rotation of the rocker arm 11 in the counter-clockwise based on positive lift received beyond the minimum (base circle) profile may eventually cause the collar 138 on the lost motion shaft 130 to reach its maximum longitudinal travel extent. At such a maximum-travel position, the full designed lost motion extent of the mechanism has been absorbed, wherein collar 138 may engage and/or be otherwise stopped by contacting the rocker arm 11 , limiting its traverse thereafter. Further continued counter-clockwise rotation of the rocker arm 11 corresponding to continuing positive lift received from the cam may then cause both the first and the second exhaust valves to open together, and/or in parallel. Finally, as the lift received from the cam reaches its maximum lift and subsequently begins to recede, decreasing now back to the minimum (base circle) profile, rocker arm 11 may now rotate clockwise (again, as seen in the frame of reference of at least FIGs. 1-3), which may cause both the first and second exhaust valves to close together, and/or in parallel, still following the valve lift profile received by rocker arm 11 , directly or indirectly, from the cam of a camshaft. [0055] When an engine braking mode is enabled, according to particular embodiments, oil pressure may be increased in oil supply passage 160, causing the needle 100 to move upward against the bias of the biasing member 120. As a result, the longitudinal pin portion 110 may be moved away from the check ball 90, which is then seated against valve seat 76, sealing off the intermediate oil passage. The brake capsule 46 may therefore act as a no-retum valve, with the first plunger body 62 extending, and held rigidly extended, toward the valve bridge 42.

[0056] In particular embodiments with engine braking mode enabled, starting from minimum (base circle) lift received by rocker arm 11 from a cam of a camshaft, rocker arm 11 may rotate counter-clockwise (as seen in the frame of reference of at least FIGs. 1-3) by an initial angle around the rocker shaft 18 as positive lift is initially received from the cam. As a non- limiting example, the rocker arm 11 may have initially rotated 2.72 degrees counter-clockwise from its position corresponding to the cam’s base circle. In particular embodiments, based on the brake capsule 46 being extended and rigid in this scenario, first socket 173 or sliding pad 174 may be forced against the valve bridge 42 and/or pin 51, causing the first valve to move off its valve seat. As a nonlimiting example, the first valve may move off the first valve seat by a distance of 2.85 mm. It will be appreciated that other distances and angles of rotation of the rocker arm 11 are fully contemplated herein. Notably, the second valve may remain closed against a second valve seat at this angle of rotation of rocker arm 11. The collar 138 on the lost motion shaft 130, while traveling toward the rocker arm 11 , may not have yet reached the maximum-travel position at the rocker arm 11. Stated differently, in particular embodiments, lost motion mechanism 44 may be absorbing the initial brake lift component from influencing or exerting force on valve bridge 42 or the second exhaust valve, thereby keeping the second valve closed during an initial portion of the lift.

[0057] Continuing with the above non-limiting example for illustrating operation with engine braking mode enabled, in particular embodiments, the rocker arm 11 may continue to rotate further counter-clockwise (in the frame of reference of FIGs. 1-3) around the rocker shaft 18 with further positive lift received from the cam. As a non-limiting example for illustration, the rocker arm 11 may now have rotated 4.41 degrees. At this position, the brake capsule 46 may remain rigidly extended, with the first socket 173 or sliding pad 174 continuing to act against the valve bridge 42 and/or pin 51, thereby causing the first valve to move further off the first valve seat. In this nonlimiting example, the first valve may have moved off the first valve seat by a distance of 4.09 mm. It will be appreciated that other distances (and angles of rotation of the rocker arm 11) are contemplated. At this point the collar 138 may have made contact with the rocker arm 11 (i.e., lost motion has “bottomed”), and both the first and second valves may be opened concurrently.

[0058] Continuing with the above non-limiting example for illustrating operation with engine braking mode enabled, in particular embodiments, the rocker arm 11 may have rotated further counter-clockwise (in the frame of reference of FIGs. 1 -3) around the rocker shaft 18. In the nonlimiting example shown, the rocker arm 11 may have rotated 8.82 degrees. In particular embodiments, the bridge 42 may be in a horizontal position. Again, the brake capsule 46 may remain rigidly extended. The lost motion shaft 130 may now urge the bridge 42 downward to open the first and second valves off their respective valve seats. In this non-limiting example, the first and second valves may have the same lift, and may have moved off their respective valve seats by a distance of 9.1 mm. It will be appreciated that other distances (and angles of rotation of the rocker arm 11) are contemplated. In particular embodiments, the first and second valves may be kinematically constrained to open in parallel from this angular position.

[0059] In particular embodiments having a non-resetting design for brake capsule 46, while both valves may close in parallel through most of the valve closing sequence of the cycle, the first exhaust valve (also known as the brake valve) may fully close later in the cycle than the second exhaust valve when engine braking mode is enabled, based on at least the “always on” and rigidly extended nature of brake capsule 46. In other specific embodiments having a resetting capability for brake capsule 46, the first and second exhaust valves may close together and/or in parallel when engine braking mode is enabled.

[0060] Thus, in particular embodiments, a single exhaust rocker arm may provide simultaneous opening and closing of both exhaust valves with engine braking disabled, inventively employing at least a lost motion mechanism, while providing the ability in an engine braking enabled mode to operate the brake valve first in a cycle, and then operate both exhaust valves during the rest of the cycle, by using the brake capsule in conjunction with the lost motion mechanism. In doing so, among other benefits, disclosed embodiments provide a compact, integrated means of performing selectable engine braking functions while occupying little space within the often cramped confines of valvetrain spaces. As a non-limiting aspect, such features may be especially beneficial in small engines. [0061] 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 particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are 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.

[0062] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. It will be understood that changes and modifications may be made by those of ordinary skill within the scope of the following claims. In particular, the present invention covers further embodiments with any combination of features from different embodiments described above and below. Additionally, statements made herein characterizing the invention refer to an embodiment of the invention and not necessarily all embodiments.

[0063] 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.

[0064] Numerical ranges recited in this application should be construed to be inclusive of the end points of the stated ranges. The longitudinal axis of the valve body, which may have been omitted in some illustrations for convenience of scale, should be construed to exist in every illustration where it is referred to.