Lost motion rocker brake actuation and stroke limiting system

Abstract

A system for valve actuation in an internal combustion engine provides control of rocker arms and other valve train components by utilizing biasing and stroke limiting components. Such features may be implemented in any valve train component, including an e-foot assembly or a pushrod assembly. The biasing component may bias the cam side of the lost motion rocker toward the cam. Each component may be extendable to allow the biasing mechanism to keep the valve train component in a controlled position at all times. The stroke limiting feature may promote the formation of a small gap between the valve train components during the engine cycle for improved lubrication. The stroke limiting feature may also hold the valve train component in an assembled configuration even when not installed in an engine or valve actuation system.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS AND PRIORITY CLAIM) This application claims priority to U.S. Provisional Application No. 63 / 266,505, entitled "LOST MOTION ROCKER BRAKE BIASING AND STROKE LIMITING SYSTEMS," filed January 6, 2022. This application also claims priority to International Application No. PCT / IB2020 / 053904 (WO2022106907), entitled "ROCKER CONTROL IN LOST MOTION ENGINE VALVE ACTUATION SYSTEMS," filed May 7, 2021, which claims priority to U.S. Provisional Application No. 63 / 198,902, entitled "LOST MOTION ROCKER BRAKE BIASING SYSTEM," filed November 20, 2020. The subject matter and specifications of the above-listed applications are incorporated herein by reference in their entireties.

[0002] FIELD OF THEINVENTION This disclosure relates generally to systems for actuating valves and generally to lost motion rocker brakes for internal combustion engines. This disclosure also relates to systems and components for controlling rocker arm movement and stroke limiting and energizing valve train components of lost motion rocker brakes. [Background technology]

[0003] Internal combustion engines require valve actuation systems to control the flow of combustible components, usually fuel and air, into one or more combustion chambers during operation. Such systems control the movement and timing of the intake and exhaust valves during engine operation. In a positive power mode, the intake valve is opened to allow fuel and air into the cylinder for combustion, followed by the exhaust valve to allow the products of combustion to escape the cylinder. This operation is typically referred to as "positive power" operation of the engine, and the movements applied to the valves during positive power operation are typically referred to as "primary event" valve actuation movements. Auxiliary valve actuation movements, such as those that result in engine braking (power absorption), may be accomplished using "auxiliary" events applied to one or more of the engine valves.

[0004] Valve movement during the main event positive output mode of operation is usually controlled by one or more rotating cams as the source of motion. Cam followers, push rods, rocker arms, and other elements disposed within the valve train provide direct transfer of motion from the cam surface to the valve. Valve bridges may be used to impart motion to multiple valves from a single upstream valve train. For auxiliary events, "lost motion" devices may be utilized in the valve train to facilitate auxiliary event valve movement. Lost motion devices refer to a class of technology solutions in which valve motion is modified compared to the motion that would otherwise occur due to actuation by the respective cam surface alone. Lost motion devices may include devices whose length, stiffness, or compressibility are changed and controlled to facilitate the selective occurrence of auxiliary events in addition to, or as an alternative to, the main event operation of the valve. Auxiliary events may also be facilitated by dedicated cam systems that may impart auxiliary motion to one or more valves using separate auxiliary or brake cams and valve trains to facilitate the selective occurrence of auxiliary events.

[0005] In braking and other auxiliary lost motion applications, multiple valve events may be incorporated into the same cam lobe and different events may be activated or deactivated based on selective extension or retraction of a lost motion element, such as an actuator piston. A lost motion cam system typically uses at least one cam with different profile lift sections on the same cam lobe to impart motion to each primary event and one or more auxiliary events. These different profile lift sections are activated or deactivated using separate lost motion mechanisms, such as pistons or actuators located in the valve train. Examples of auxiliary events include engine braking, early exhaust valve opening (EEVO), late intake valve closing (LIVC) lift events, and internal exhaust gas recirculation events (IEGR), which may be imparted to one or more valves in a valve set (i.e., two exhaust valves for each cylinder). A lost motion auxiliary valve lift system, such as a lost motion braking system, may employ a single rocker associated with a lost motion cam and a valve bridge associated with the rocker for actuating two engine valves in a primary event motion. The auxiliary valve lift or brake motion on one of the valves is facilitated by an auxiliary valve lift or brake actuator, which may be housed within the rocker and is a lost motion device that may selectively impart auxiliary or brake motion to the valve via a bridge pin disposed within the bridge. The bridge pin provides independent motion of one of the two engine valves relative to the other of the two engine valves.The auxiliary valve lift or braking actuator can be selectively actuated such that an auxiliary or braking event lift profile section or lobe on the lost motion cam causes movement of the bridge pin and auxiliary or braking movement of one engine valve when desired.

[0006] Some lost motion valve actuation systems may utilize sub-base circle lost motion profiles on one or more cams. In such systems, a primary event valve lift profile may be provided to a cam above the cam base circle, while a lost motion profile is provided to the same cam below the cam base circle. During primary event motion, with the lost motion actuator deactivated, a lost motion gap is created in the valve train and the sub-base circle profile is consequently lost and not passed to the engine valves. When the lost motion actuator is activated, the lost motion gap in the valve train is picked up and a secondary motion profile may be transmitted to the engine valves.

[0007] Existing solutions for rocker control in such lost motion environments utilize biasing mechanisms that can bias the cam side of the rocker toward the cam, preventing uncontrolled movement of the rocker during events that would otherwise cause a gap in the valve train because the rocker cam follower is always in contact with the cam. Biasing mechanisms that achieve these results can include spring bars, actuator piston springs, or undermount rocker biasing springs.

[0008] Prior art cam-side rocker biasing solutions are not without drawbacks. For example, such solutions may require strong biasing forces, on the order of hundreds of Newtons, and properly designed biasing components to maintain contact between the cam roller (follower) and the cam lobe in the brake-off state when the secondary motion lift actuator is in a deactivated state, especially when sub-base circle auxiliary events are utilized. Such biasing forces are required because when the secondary motion lift actuator is deactivated, the full mass of the rocker arm is exposed to acceleration and deceleration forces that are typically generated by the cam, and as a result, the rocker arm and cam follower may tend to separate from the cam surface as they would otherwise.

[0009] Lost motion rocker brakes are commonly known in the art of valve train and valve actuation system design for internal combustion engines. The lost motion system allows for multiple valve events to be incorporated into the same exhaust cam lobe and different events to be activated or deactivated based on selective extension or retraction of a lost motion element, such as a lost motion actuator piston.

[0010] One concern with lost motion rocker brakes is that retraction of the lost motion element can create a large gap when the brake is in a non-actuated or "off" state. More specifically, a gap can form between the lost motion element and other valve train components, such as a source of motion or a cam. This gap can leave the rocker brake unloaded or unbound, thus allowing uncontrolled movement of the rocker brake. Past solutions intended to address this problem have utilized a biasing mechanism that biases the lost motion rocker brake toward the valve to keep the rocker brake in constant contact with the valve bridge and avoid uncontrolled movement in the valve train.

[0011] The present disclosure describes additional embodiment details for biasing and stroke limiting that are particularly adaptable to lost motion rocker brake systems. The disclosed embodiments are particularly adaptable to e-foot, push rod, and other valve train components and environments. Summary of the Invention

[0012] In response to the aforementioned problems, according to one aspect, the present disclosure provides various embodiments of a valve actuation system having features for controlling rocker motion that may be applied in a lost motion system. More specifically, the present disclosure describes a system in which a biasing component is configured and adapted to bias a cam side of a rocker in a direction toward the cam. Additional aspects may provide a biasing component on the e-foot that cooperates with the valve bridge to eliminate the gap and further enhance control of the rocker and the valve bridge. The e-foot may further comprise a defined stroke to facilitate the formation of a gap between the valve train components to allow a layer of oil to form during the valve cycle. The e-foot may further be provided with a retention feature to keep the e-foot assembled even when the e-foot is not in contact with another valve train component (i.e., the valve bridge). The described system facilitates rocker control even during deactivation of the lost motion component, improves lubrication, and facilitates assembly.

[0013] According to one aspect, the present disclosure provides a system for actuating at least one of two or more engine valves in an internal combustion engine, the system comprising: a motion source defining a primary event motion profile and an auxiliary motion profile; a valve train for transferring motion from the motion source to the at least one engine valve, the valve train having at least two valve train components; a biasing component configured to apply a biasing force to maintain at least one of the valve train components in a controlled state; and a stroke-limiting component adapted to cooperate with the biasing component and create a lash gap between the at least two valve train components. According to a further aspect, the system may further comprise a lost motion component cooperating with the valve train, the lost motion component configurable in a first mode in which the lost motion component absorbs the auxiliary motion and a second mode in which the lost motion component transfers the auxiliary motion.

[0014] According to a further aspect, the biasing component may be a spring configured as part of the e-foot assembly. In a further aspect, the e-foot assembly may include an extendable portion and the spring may be configured to bias the extendable portion toward the extended position. In a further aspect, the e-foot assembly may include a telescoping portion.

[0015] According to a further aspect, the stroke limiting component may be an e-foot assembly. The e-foot assembly may include an extendable portion. The extendable portion may include a stop for limiting extension of the extendable portion.

[0016] According to a further aspect, the biasing component may be a spring configured as part of the push rod assembly. In a further aspect, the push rod assembly may include an extendable portion. In a further aspect, the spring may be configured to bias the extendable portion toward the extended position. In a further aspect, the push rod assembly may include a telescoping portion.

[0017] According to a further aspect, the stroke limiting component may be a push rod assembly. In a further aspect, the push rod assembly may include an extendable portion, which may include a stop to limit extension of the extendable portion. According to a further aspect, the biasing component may be configured to bias the source of motion (cam) side of the rocker toward the source of motion (cam).

[0018] According to a further aspect, the system further comprises an e-foot biasing component for maintaining the e-foot in contact with other valve train components.

[0019] According to a further aspect, the e-foot is configured to be extendable in length to define the stroke. According to a further aspect, the biasing or stroke limiting component may comprise an e-foot assembly comprising a screw boss, a swivel boss, a pin, a cap, and a biasing spring. According to a further aspect, the biasing or stroke limiting component may comprise a push rod assembly comprising a screw boss, a swivel boss, a push rod boss, a pin, and a biasing spring. In another aspect, the stroke limiting component may comprise a push rod adjustment screw. In a further aspect, the stroke limiting component may comprise a pin, a lip, a C-clip, or a step to limit the extension of the extendable portion. According to a further aspect, the biasing component may be configured to control the inertia of the rocker arm to prevent a non-compliance condition between the sub-base circle and the base circle of the cam. According to a further aspect, the biasing component may be adapted to provide a zero bias load gap between the rocker and the valve bridge at the sub-base circle of the cam.

[0020] According to further aspects, the valve train may be a Type 3 overhead cam valve train or a Type 4 valve train or a Type 5 valve train.

[0021] Other aspects and advantages of the present disclosure will become apparent to those skilled in the art from the following detailed description, and the above aspects should not be considered as exhaustive or limiting. The above general description and the following detailed description are intended to provide examples of the inventive aspects of the present disclosure, and should not be construed in any way as limiting or restrictive of the scope defined in the appended claims. [Brief description of the drawings]

[0022] The above features and attendant advantages, as well as other features and advantages, will become apparent from a consideration of the following detailed description in conjunction with the accompanying drawings, in which like reference numerals represent like elements and in which one or more embodiments will now be described by way of illustrative example only and are not intended to limit the scope of the invention as set forth in the appended claims. [Figure 1] FIG. 1 is a perspective view of an assembled lost motion rocker brake system having an actuated stroke limited e-foot assembly according to the present disclosure. [Diagram 2] FIG. 2 is a perspective view of the lost motion rocker brake system of FIG. 1 showing the actuated stroke limited e-foot assembly in an exploded view. [Diagram 3] FIG. 2 is a cross-sectional view showing internal features of the example lost motion rocker and e-foot of FIG. 1 in cooperation with the valve bridge and cam, with the lost motion components in a deactivated state. [Figure 4] FIG. 2 is a cross-sectional view showing internal features of the example lost motion rocker and e-foot of FIG. 1 in cooperation with the valve bridge and cam and with the lost motion components in an activated state. [Diagram 5] FIG. 5 is a cross-sectional view of the biased stroke limited e-foot assembly of FIGS. 1-4 in an assembled, extended configuration. [Figure 6] 6 is a cross-sectional view of the biased stroke limited e-foot assembly of FIG. 5, taken in a plane perpendicular to the plane of FIG. [Figure 7]FIG. 6 is a cross-sectional view of the biased stroke limited e-foot assembly of FIG. 5 in an assembled, retracted configuration. [Figure 8] FIG. 7 is a cross-sectional view of the biased stroke limited e-foot assembly of FIG. [Figure 9] FIG. 1 is a perspective view of a lost motion rocker brake with an actuated stroke limiting push rod shown in an exploded view. [Figure 10] FIG. 10 is another perspective view of the lost motion rocker brake with biased stroke limiting push rod of FIG. [Figure 11] FIG. 1 is a cross-sectional view of a biased stroke-limited pushrod according to one aspect of the present disclosure. [Figure 12] 12 is a cross-sectional view of the biased stroke limiting pushrod of FIG. 7 taken in a plane perpendicular to the plane of FIG. 11. [Figure 13] FIG. 12 is a cross-sectional view of the push rod of FIG. 11 in an extended state. [Figure 14] FIG. 13 is a cross-sectional view of the push rod of FIG. 12 in an extended state. [Figure 15] FIG. 13 is a cross-sectional view of a second embodiment of a biased stroke limited pushrod according to an aspect of the present disclosure. [Figure 16] 16 is a cross-sectional view of the biased stroke limiting pushrod of FIG. 9 taken in a plane perpendicular to the plane of FIG. 15. [Figure 17] FIG. 16 is a cross-sectional view of the push rod of FIG. 15 in an extended state. [Figure 18] FIG. 17 is a cross-sectional view of the push rod of FIG. 16 in an extended state. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] 1-8 illustrate an exemplary lost motion rocker brake with an integrated biased stroke-limiting e-foot assembly according to aspects of the present disclosure. As will be appreciated, the present disclosure features components for providing a biasing force to the rocker arm in a direction such that the motion-receiving (follower) side of the rocker brake is biased toward the motion source / cam side of the engine and away from the valve. The present disclosure also features components for limiting the stroke of the e-foot assembly or other valve train components. Although stroke limiting and biasing features are described in combination with one another in each embodiment, it will be appreciated that these features and associated teachings may be utilized separately to improve control of the lost motion rocker brake according to aspects of the present disclosure.

[0024] 1-4, an example valve actuation system may include a rocker 100, a lost motion component 200, and an e-foot assembly 600 having an e-foot or seat 690 adapted to contact a valve bridge 310. The rocker 100 may include a valve side 110 and a cam side 120 on opposite sides of a rocker shaft journal 102. Further details of the rocker 100 and associated components are described below.

[0025] 1-4, an exemplary valve actuation system 10 may include a rocker 100, a lost motion component 200, a valve bridge and e-foot assembly 600, and a rocker biasing component 680. The rocker 100 may include a main rocker body 104. The rocker cam side 120 may include a cam roller or follower 122 that may receive motion from a motion source in the form of a cam 500 (see FIGS. 3 and 4). The cam follower 122 may be fixedly mounted to the main rocker body 104 by a follower shaft 124. As previously mentioned, the rocker body 104 may include an integral bore and cavity for housing the lost motion component 200, as well as control components and passages for controlling hydraulic fluid used to activate and deactivate the lost motion component 200, as is commonly known in the art.

[0026] The valve side 110 of the rocker 100 may include an e-foot assembly 600 and a valve bridge 310. The e-foot assembly may form part of a primary event load path for transferring primary event motion from the rocker 100 to the valve bridge 310 and ultimately to two engine valves (see FIG. 4) that are configured to receive motion from the valve bridge 310. A bridge pin 312 may extend into a bridge bore 314 to transfer motion from the lost motion component 200 (upon activation) to one of the engine valves, thereby providing an auxiliary event and auxiliary motion for that one engine valve.

[0027] As best seen in Figures 3 and 4, the lost motion component 200 may include an actuator piston 210 that engages an end of the bridge pin 312 and transmits motion thereto when extended in an activated mode. The actuator piston 210 may cooperate with a lost motion actuator post 220 and a lost motion actuator spring to bias the actuator piston 210 against the rocker 100. The actuator piston 210 may extend under hydraulic pressure when the lost motion component 200 is activated and retract under the force of the lost motion actuator spring when the lost motion component 200 is deactivated. The lost motion actuator post 220 may be secured to the rocker 100 with a threaded fastener 222 to allow adjustment of the axial position of the lost motion actuator post 220 relative to the rocker 100. As will be appreciated from this disclosure, the lost motion component 200 may constitute a portion of an auxiliary load path that, when activated, transfers auxiliary motion from the rocker 100 to the bridge pin 312 and to one of the engine valves to support the auxiliary motion of that one engine valve. FIG. 3 illustrates an exemplary state of the e-foot assembly 600 when the lost motion component 200 is in a deactivated state, with the piston 210 retracted into the rocker 100. FIG. 4 illustrates an exemplary state of the e-foot assembly 600 when the lost motion component 200 is in an activated state, with the piston 210 extending from the rocker 100 and able to engage the bridge pin 312, which may be displaced (downward) relative to the valve bridge 310. Although shown in a horizontal position in FIG. 4, the valve bridge 310 may be subject to a slight tilt (with the bridge pin / brake valve side lower than the opposing non-brake valve side) and the e-foot assembly may accommodate such tilt and may be in a nearly but not fully compressed state.

[0028] As will be appreciated from the present disclosure, when the lost motion component 200 is activated, a sub-base circle auxiliary motion profile of the motion source can be transferred to one of the engine valves. As shown in FIGS. 3 and 4, an exemplary motion source 500 can include a cam 510 having a primary event profile 520 that extends radially beyond the base circle 530 to define a primary event valve motion. Auxiliary event profiles 540 and 550 that can define auxiliary events can be provided within (below) the base circle 530. In FIGS. 3 and 4, the cam 500 is shown diagrammatically. It will be appreciated that the rotational position of the cam 500, as well as the orientation of the rocker 100 and the e-foot assembly 600, may be different than that shown at different times in the engine and / or brake cycle. For example, the auxiliary event profile 540 can engage the cam follower 122 during a braking mode of operation in which the piston actuator 210 is in an extended position. When the lost motion component 200 is deactivated, only the primary event motion is transferred from the cam 510. In a deactivated state of the lost motion component, when the sub-base circle surface of cam 500 encounters cam follower 122, a gap tends to form between cam roller 122 and motion source 500, such that the sub-base circle auxiliary motion defined by auxiliary motion profiles 540 and 550 is not transferred to rocker 100. On the other hand, when lost motion component 200 is activated, auxiliary motion profiles 540 and 550 will engage cam follower 122, such that the auxiliary motion defined by them will be transferred to one of the engine valves via bridge pin 312.

[0029] With further reference to FIGS. 5-8, biasing components may be integrated into an e-foot assembly 600. The e-foot assembly 600 may include an upper portion 620 and a lower portion 650 configured and adapted to move relative to one another in a telescopic manner. The upper portion 620 may include a cylindrical fastening post 624 that is received within a bore in the rocker 100 and thereby fastened to the rocker 100 with a threaded fastener (nut) 322 (FIGS. 3 and 4). The upper portion 620 may include an annular shoulder 626, which provides additional mounting support as well as an upper seating surface for a biasing component such as a spring 680. The upper portion 620 may also include a lower annular skirt 630 having an axially extending cavity or bore 628 (see FIGS. 5 and 6) for receiving a complementary shaped protrusion 652 of the lower portion 650. The lower portion 650 may include an annular shoulder 656 that provides a lower seat for the spring 680. Thus, lower portion 650 and upper portion 620 provide an extendable, telescoping e-foot post that can be biased by spring 680 to an extended position to exert a biasing force on the rocker that tends to move the motion source side of the rocker toward the motion source. Thus, a rocker biasing component can be integrated into the e-foot assembly by features of this embodiment.

[0030] According to aspects of the disclosure, a stroke limiting component may also be integrated into the e-foot assembly 600. The protrusion 652 of the lower portion 650 may be provided with an axially extending slot or channel 654. The upper portion 620 may be provided with a lateral bore 658 that receives a retaining pin 670. The retaining pin 670 extends through both the lateral bore 658 and the slot 654 of the lower portion 650, thus retaining the lower portion 650 within the upper portion 620 and limiting the movement of the lower portion 650 relative to the upper portion 620. The stroke length "S" may be defined by the range of movement of the lower portion 650 relative to the upper portion 620, which may be defined by the contact of different portions. For example, the upper limit of travel of the lower portion 650 within the upper portion 620 may be defined by the dimensions of the lower annular skirt 630 of the upper portion 620, which may impinge on the shoulder 656 to define the upper limit of travel of the lower portion 650 within the upper portion 620. FIGS. 7 and 8 show the lower portion 650 at its upper limit of travel. Alternatively, the projection 652 may bottom out within the bore 628 to define the upper limit of travel. The lower limit of travel of the lower portion 650 relative to the upper portion 620 may be defined by the impact of the retaining pin 670 with the upper surface of the slot 654, as shown in FIGS. 5 and 6. As will be appreciated, the stroke "S" may be configured to achieve the desired absorption and transmission of the respective portions of the motion defined on the source of motion (the cam) and thus the corresponding desired modification of the valve motion, particularly in combination with the sub-base circle portion of the cam 500. For example, the stroke may be limited such that when the cam follower is engaged by the sub-base circle portion of the motion source, a gap may be formed between the e-foot and bridge and / or the cam follower and cam to allow a lubricant film to develop during that portion of the valve motion cycle. The stroke length of the e-foot assembly may be selected and adjusted so that only small gaps or zero applied load gaps are formed, thereby avoiding gap sizes or play in the valve train that would result in loss of control of the rocker position.

[0031] Thus, in this and other embodiments, consistent with aspects of the present disclosure, the stroke-limited e-foot may be configured to provide a small gap between the e-foot and the valve bridge when the rocker encounters the sub-base circle portion of the cam. This configuration allows for removal of the e-foot and allows for the formation or reformation of a lubricant layer within the e-foot assembly, such as between the e-foot cap and bushing, and elsewhere in the valve train (valve train component interface). This configuration may also provide for the reduction or elimination of any valve spring preload. The e-foot assembly may also be configured such that the mechanism bottoms out after stroking between the sub-base and base circles of the cam.

[0032] As will be appreciated from this disclosure, the lost motion rocker brake system as described above biases the rocker brake towards the engine cam and away from the valve. This has several advantages including a reduction in the components required to assemble the rocker brake to the valve train. Additionally, the stroke limited e-foot reduces wear on the valve bridge and e-foot cap due to lost motion gaps where excess oil can get in. Furthermore, the stroke limited feature reduces bushing wear resulting from loading the bushing area during 100% of the rocker duty cycle.

[0033] The following operational description serves to further illustrate aspects of the disclosure and the interaction of the described components. In "brake off" mode, when the cam follower encounters the sub-base circle portion of the cam and the actuator piston is retracted, the e-foot assembly may be in an extended position and maintain engagement with the valve bridge. When the system is still in brake off mode, but the cam follower encounters the base circle portion of the cam (the actuator piston is still retracted), the e-foot assembly may undergo partial compression from its extended position, with the compression of the e-foot assembly spring and the e-foot still maintaining contact with the valve bridge, biasing the rocker cam side towards the cam.

[0034] In the "brake on" mode, with the actuator piston extended (but possibly not contacting the bridge pin) and the cam follower encountering the sub-base circle portion of the cam, the e-foot assembly may be in an extended position to maintain contact between the e-foot and the valve bridge. Still in the "brake on" mode, with the actuator piston extended, the valve bridge may undergo a slight tilt due to contact with the bridge pin. The e-foot assembly may be in a compressed state to maintain contact between the e-foot and the valve bridge.

[0035] According to aspects of the disclosure, biasing and stroke limiting features may be incorporated into valve train components other than the e-foot assembly, as described above. For example, biasing and stroke limiting features may be incorporated into components of a pushrod arrangement, as shown in two embodiments in FIGS. 9-18. With particular reference to FIGS. 9-14, a pushrod biasing and stroke limiting assembly 700 may include an upper portion 720 that receives a protrusion 752 of a lower portion 750 for sliding, telescoping movement. The upper portion 720 may include a fastening post 724 that fits into a bore on the rocker. The lower portion 750 may include a channel 754 formed on the protrusion 752. A circular (outwardly biased) spring clip 770 may be placed into an internal groove on an inner wall of the upper portion 720 such that the spring clip 770 is positioned within the channel 754, thereby limiting movement of the lower portion 750 relative to the upper portion 720. That is, channel 754 allows limited movement of lower portion 750, but it cannot otherwise move up or down beyond the limit defined by the position of spring clip 770. In this manner, spring clip 770 and channel 754 define a limited stroke "S" (FIG. 11).

[0036] A biasing component may also be implemented in the embodiment of Figures 9-14. A coil spring 780 may be housed within the bore 728 of the upper portion 720, with an upper inner wall 729 of the bore 728 of the upper portion 720 defining an upper spring seating surface. An upper surface 759 of the lower portion 750 may define a lower spring seating surface. Thus, the coil spring 780 may bias the lower component 750 to an extended position relative to the upper portion 720. Figures 11 and 12 show a retracted position or state of the push tube assembly, and Figures 13 and 14 show an extended position or state of the push tube assembly.

[0037] 15-18 show another embodiment of a biasing and stroke limiting component suitable for a push rod environment. In this configuration, a biasing and stroke limiting push rod assembly 800 can include an upper portion 820 and a lower portion 850 configured and adapted for telescopic relative motion. A laterally extending retaining pin 870 extends through a lateral bore on the upper portion 820 and through an axially extending slot 854 in the lower portion 850. As with the embodiment of FIGS. 1-8, the pin 870 limits the axial movement of the lower portion 850 relative to the upper portion 820, thereby providing a limited stroke "S" of the push rod component. In this embodiment, the biasing feature can include an external coil spring 880 seated between annular shoulders 826 and 856 of the upper and lower portions 820 and 850, respectively, to bias the push rod assembly to the extended position. 15 and 16 show the push rod assembly in a contracted or compressed position or condition, and FIGS. 17 and 18 show the push rod assembly in an extended position or condition.

[0038] It will be appreciated that the stroke limiting and biasing arrangements of the pushrod embodiment of Figures 5-10 may be adapted to other valve train components, including the e-foot environment described above. For example, the spring clip 770 and channel 754 in the embodiment of Figures 5-8 may be adapted to replace the pin and slot limiting arrangement in the embodiment of Figures 1-4. In this regard, these various mechanical devices for limiting stroke and biasing should be considered interchangeable and adaptable to different valve train components other than the e-foot and pushrod environment described herein.

[0039] As will be appreciated from this disclosure, the lost motion rocker brake system as described above biases the rocker brake towards the valve side of the engine and away from the cam. This has several advantages including a significant reduction in the biasing force required to control the rocker brake during brake-off conditions. The valve train is easier to design with less biasing force required on the pushrod side. Lighter biasing forces allow the overall system to be lighter, potentially at lower cost as well.

[0040] The stroke limiting feature described above also provides advantages. In combination with the biasing component, the stroke limiting function provides a predetermined stroke in the valve train that may facilitate adjustment of the e-foot or pushrod position for all operating conditions, including brake "off" (or lost motion deactivated) operating conditions. This, in turn, may allow for a desired gap formation between the e-foot and the valve bridge or other valve train components. Additionally, the stroke limiting feature may act as a retention feature that allows a pre-assembled e-foot or pushrod system to be assembled and shipped as a pre-assembled component that can be easily installed in a larger engine environment without a separate installation or assembly step on-site.

[0041] While specific embodiments have been shown and described, those skilled in the art will appreciate that changes and modifications can be made without departing from the teachings herein. Accordingly, any and all modifications, variations, or equivalents of the teachings described above are deemed to be within the scope of the basic underlying principles disclosed above.

[0042] For example, although the above examples are described in the context of a Type 3 valvetrain (center pivot) rocker or a Type 5 valvetrain (push rod), it will be appreciated that the described biasing and stroke limiting components may be implemented in other valvetrain types, such as a Type 2 (end pivot rocker) or Type 4 (center pivot rocker with follower).

[0043] Additionally, while the disclosed biasing and stroke-limiting components are described using the exemplary embodiment of an e-foot and pushrod, it will be appreciated that the described biasing and stroke-limiting components may be implemented as part of other valve train components, such as, for example, cam followers.

[0044] Additionally, while the disclosed embodiments may feature lost motion components as part of the valve train, it will be recognized that the biasing and stroke limiting features of the disclosed embodiments may be utilized in valve train systems that do not incorporate lost motion components.

Claims

1. 1. A system for actuating at least one of two or more engine valves in an internal combustion engine, comprising: a motion source defining a primary event motion profile and a secondary motion profile; a valve train for transmitting motion from the motion source to the at least one engine valve, the valve train having at least two valve train components; a biasing component configured to apply a biasing force to maintain at least one of the valve train components in a controlled state; and a stroke-limiting component adapted to cooperate with the biasing component to create a lash gap between the at least two valve train components.

2. The system of claim 1 , wherein the biasing component is a spring configured as part of an e-foot assembly.

3. The system of claim 2 , wherein the e-foot assembly includes an extendable portion, and the spring is configured to bias the extendable portion toward an extended position.

4. The system of claim 2 , wherein the e-foot assembly includes a telescoping portion.

5. The system of claim 1 , wherein the stroke-limiting component is an e-foot assembly.

6. The system of claim 5 , wherein the e-foot assembly includes an extendable portion, the extendable portion including a stop for limiting extension of the extendable portion.

7. The system of claim 1 , wherein the biasing component is a spring configured as part of a push rod assembly.

8. The system of claim 7 , wherein the push rod assembly includes an extendable portion, and the spring is configured to bias the extendable portion toward an extended position.

9. The system of claim 7 , wherein the push rod assembly includes a telescoping portion.

10. The system of claim 1 , wherein the stroke-limiting component is a push rod assembly.

11. The system of claim 10 , wherein the push rod assembly includes an extendable portion, the extendable portion including a stop for limiting extension of the extendable portion.

12. 2. The system of claim 1, wherein the valve train is a Type 3 overhead cam valve train.

13. The system of claim 1 , wherein the biasing component or the stroke-limiting component comprises an e-foot assembly, the e-foot assembly comprising a screw boss, a swivel boss, a pin, a cap, and a biasing spring.

14. The system of claim 1 , wherein the stroke limiting component is a push rod adjustment screw.

15. 2. The system of claim 1, wherein the valve train is a Type 4 overhead valve train.

16. The system of claim 1 , wherein the biasing component or the stroke limiting component comprises a push rod assembly, the push rod assembly comprising a threaded boss, a push rod boss, a pin, and a biasing spring.

17. The system of claim 1 , wherein the stroke limiting component comprises a pin, a lip, a C-clip, or a step for limiting the extension of the extendable portion.

18. 2. The system of claim 1, wherein the biasing component is configured to control the inertia of the rocker arm to prevent a non-compliance condition between a sub-base circle and a base circle of a cam.

19. 2. The system of claim 1, wherein the biasing component is adapted to provide a zero bias load gap between a rocker and a valve bridge at a sub-base circle of a cam.

20. 2. The system of claim 1, further comprising a lost motion component cooperating with the valve train, the lost motion component being configurable in a first mode in which the lost motion component absorbs the auxiliary motion and in a second mode in which the lost motion component transmits the auxiliary motion.

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