LOST MOTION ROCKER BRAKE BIASING AND STROKE LIMITING SYSTEMS

Abstract

Systems for valve actuation in internal combustion engines provide for control of rocker arms and other valvetrain components by utilizing biasing and stroke limited components. Such features may be implemented in any valvetrain component, including e-foot assemblies or pushrod assemblies. The biasing component may bias the cam side of a lost motion rocker toward the cam. The components may be extendable to permit a biasing mechanism to keep the valvetrain components in a controlled position at all times. Stroke limiting features may facilitate the formation of small gaps between valvetrain components during the engine cycle for improved lubrication. Stroke limiting features may also retain valvetrain components in an assembled configuration even when not installed in an engine or valve actuation system.

Claims

1. 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 main event motion profile and an auxiliary motion profile; a valvetrain for conveying motion from the motion source to the at least one engine valve, the valvetrain having at least two valvetrain components; a biasing component arranged to apply a biasing force to maintain at least one of the valvetrain components in a controlled state; and a stroke limited component cooperating with the biasing component and adapted to create a lash gap between the at least two valvetrain components.

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

3. The system of claim 2, wherein the e-foot assembly includes an extendable portion and wherein the spring is arranged to bias the extendable portion towards 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 limited component is an e-foot assembly.

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

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

8. The system of claim 7, wherein the push rod assembly includes an extendable portion and wherein the spring is arranged to bias the extendable portion towards 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 limited component is a pushrod assembly.

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

12. The system of claim 1, where in the valvetrain is a Type 3 overhead cam valvetrain.

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

14. The system of claim 1 wherein the stroke limited component is a pushrod adjustment screw.

15. The system of claim 1, where in the valvetrain is a Type 4 overhead valve valvetrain.

16. The system of claim 1, wherein the biasing component or stroke-limiting component comprise a pushrod assembly, wherein the pushrod assembly comprises a screw boss, a push rod boss, a pin, and a bias spring.

17. The system of claim 1, where in the stroke limited component comprises a pin, a lip, a c-clip or a step for limiting extension of an extendable portion.

18. The system of claim 1, where in the biasing component is arranged to control inertial forces of the rocker arm to prevent a no follow condition between sub-base and base circle of a cam.

19. 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 sub-base circle of a cam.

20. The system of claim 1, further comprising a lost motion component cooperating with the valvetrain, the lost motion component being configurable to a first mode, in which the lost motion component absorbs the auxiliary motion, and a second mode, in which the lost motion component conveys the auxiliary motion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above features and attendant advantages, and others thereof will become apparent from consideration of the following detailed description, taken in conjunction with the accompanying drawings. One or more embodiments are now described, by way of illustrative example only, and not intended to be limiting to the scope of invention set forth in the claims appended hereto, with reference to the accompanying drawings wherein like reference numerals represent like elements and in which:

[0023] FIG. 1 is a perspective view of an assembled lost motion rocker brake system with a biasing stroke-limited e-foot assembly in accordance with the instant disclosure;

[0024] FIG. 2 is a perspective view of the lost motion rocker brake system of FIG. 1, showing the biasing stroke-limited e-foot assembly in an exploded view;

[0025] FIG. 3 is a cross-sectional view showing internal features of the example lost motion rocker and e-foot of FIG. 1, cooperating with a valve bridge and cam, with a lost motion component in a deactivated state;

[0026] FIG. 4 is a cross-sectional view showing internal features of the example lost motion rocker and e-foot of FIG. 1, cooperating with a valve bridge and cam, and with a lost motion component in an activated state;

[0027] FIG. 5 is a cross-sectional view of the biasing stroke-limited e-foot assembly of FIGS. 1-4 in an assembled, extended configuration;

[0028] FIG. 6 is a cross-sectional view of the biasing stroke-limited e-foot assembly of FIG. 5. In a plane that is orthogonal to that of FIG. 5;

[0029] FIG. 7 is a cross-sectional view of the biasing stroke-limited e-foot assembly of FIG. 5, in an assembled, retracted configuration;

[0030] FIG. 8 is a cross-sectional view of the biasing stroke-limited e-foot assembly of FIG. 6;

[0031] FIG. 9 is a perspective view of a lost motion rocker brake with a biasing stroke limited push rod shown in exploded view;

[0032] FIG. 10 is another perspective view of the lost motion rocker brake with a biasing stroke limited push rod of FIG. 9;

[0033] FIG. 11 is a cross-sectional view of a biasing stroke limited push rod in accordance with an aspect of the instant disclosure;

[0034] FIG. 12 is a cross-sectional view of the biasing stroke limited push rod of FIG. 7, viewed in a plane that is orthogonal to that of FIG. 11;

[0035] FIG. 13 is a cross-sectional view of the push rod of FIG. 11 in an extended state;

[0036] FIG. 14 is a cross-sectional view of the push rod of FIG. 12 in an extended state;

[0037] FIG. 15 is a cross-sectional view of a second embodiment of a biasing stroke limited push rod in accordance with an aspect of the instant disclosure;

[0038] FIG. 16 is a cross-sectional view of the biasing stroke limited push rod of FIG. 9, viewed in a plane that is orthogonal to that of FIG. 15;

[0039] FIG. 17 is a cross-sectional view of the push rod of FIG. 15 in an extended state; and

[0040] FIG. 18 is a cross-sectional view of the push rod of FIG. 16 in an extended state.

DETAILED DESCRIPTION

[0041] FIGS. 1-8 illustrate an example lost motion rocker brake with an integrated biasing stroke limited e-foot assembly according to aspects of the instant disclosure. As will be recognized, the disclosure features components for providing a biasing force on the rocker arm, in a direction such that a motion receiving (follower) side of the rocker brake is biased towards the motion source/cam side of the engine and away from the valves. The disclosure also features components for limiting the stroke of the e-foot assembly or other valvetrain components. While the stroke-limiting and biasing features are described in combination with one another in the embodiments, it will be recognized that these features and related teachings may be utilized separately to improve control of lost motion rocker brakes according to aspects of the disclosure.

[0042] Referring particularly to FIGS. 1-4, an example valve actuation system may include a rocker 100, lost motion component 200 and an e-foot assembly 600 with an e-foot or pedestal 690 adapted to contact a valve bridge 310. 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 related components are described below.

[0043] Still referring to FIGS. 1-4, an example 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. Rocker 100 may include a main rocker body 104. Rocker cam side 120 may include a cam roller or follower 122 which may receive motion from a motion source in the form of a cam 500 (see FIGS. 3 and 4). Cam follower 122 may be secured to the main rocker body 104 by a follower shaft 124. As previously mentioned, rocker main body 104 may include integral bores and cavities 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 generally known in the art.

[0044] Valve side 110 of the rocker 100 may include an e-foot assembly 600 and a valve bridge 310. The e-foot assembly may constitute a portion of a main event load path for conveying main event motion from the rocker 100 to a valve bridge 310, and ultimately to two engine valves (see FIG. 4) that are arranged to receive motion from the valve bridge 310. A bridge pin 312 may extend within a bridge bore 314 to transmit motion from the lost motion component 200 (when activated) to one of the engine valves, thereby providing for auxiliary events and auxiliary motion of the one engine valve.

[0045] As best seen in FIGS. 3 and 4, lost motion component 200 may include an actuator piston 210, which, when extended in an activated mode, engages and transmits motion to an end of the bridge pin 312. Actuator piston 210 may cooperate with a lost motion actuator post 220, and a lost motion actuator spring to bias the actuator piston 210 relative to the rocker 100. Actuator piston 210 may extend under hydraulic pressure when the lost motion component 200 is activated and retract under 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, in a manner that permits adjustment of the axial position of the lost motion actuator post 220 relative to the rocker 100. As will be recognized from this disclosure, lost motion component 200 may constitute a portion of an auxiliary load path, which, when the lost motion component 200 is activated, will convey auxiliary motion from the rocker 100 to the bridge pin 312 and to one of the engine valves to support auxiliary motion of the one engine valve. FIG. 3 shows an example state of the e-foot assembly 600 when the lost motion component 200 is in a deactivated state, with piston 210 retracted into the rocker 100. FIG. 4 shows an example state of the e-foot assembly 600 when the lost motion component 200 is in an activated state, in which piston 210 may extend from the rocker 100 and may engage the bridge pin 312, which may, in turn, be displaced (downward) relative to the valve bridge 310. Although shown in a horizontal position in FIG. 4, the valve bridge 310 may undergo a slight tilt (bridge pin/braking valve side lower than the opposite, non-braking valve side) and the e-foot assembly may accommodate such tilt and be in a near-fully but not fully compressed state.

[0046] As will be recognized from the disclosure, when the lost motion component 200 is activated, sub-base circle auxiliary motion profiles of a motion source may be conveyed to one of the engine valves. As shown in FIGS. 3 and 4, an example motion source 500 may include a cam 510 having a main event profile 520 extending radially beyond a base circle 530 to define main event valve motion. Auxiliary event profiles 540 and 550, which may define auxiliary events, may be provided within (beneath) base circle 530. In FIGS. 3 and 4, cam 500 is shown schematically. It will be recognized that the rotational position of cam 500, and the orientation of rocker 100 and e-foot assembly 600 may be different from that illustrated at different times in the engine and/or braking cycle. For example, the auxiliary event profile 540 may engage cam follower 122 during a braking mode of operation in which piston actuator 210 is in an extended position. When the lost motion component 200 is deactivated, only main event motion is conveyed from the cam 510. In the deactivated state of the lost motion component, when the sub-base circle surface of the cam 500 encounters cam follower 122, a gap will tend to be formed between the cam roller 122 and the motion source 500 such that the sub-base circle auxiliary motion defined by auxiliary motion profiles 540 and 550 will not be conveyed to the rocker 100. On the other hand, when the lost motion component 200 is activated, the auxiliary motion profiles 540 and 550 will engage the cam follower 122 such that the auxiliary motion defined thereby will be conveyed via the bridge pin 312 to one of the engine valves.

[0047] Referring additionally to FIGS. 5-8, a biasing component may be integrated into an e-foot assembly 600. E-foot assembly 600 may include an upper part 620 and a lower part 650 arranged and adapted to move relative to one another in telescoping fashion. Upper part 620 may include a cylindrical fastening post 624 to be received within a bore in the rocker 100 and thereby fastened to the rocker 100 in conjunction with a threaded fastener (nut) 322 (FIGS. 3 and 4). Upper part 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 spring 680. Upper part 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 projection 652 of lower part 650. Lower part 650 may include an annular shoulder 656, which provides a lower seat for spring 680. Lower part 650 and upper part 620 thus provide an extendable, telescoping e-foot post, which may be biased to the extended position by spring 680 to exert a biasing force on the rocker, the biasing force tending to move the motion source side of the rocker toward the motion source. Thus, a rocker biasing component may be integrated into the e-foot assembly by virtue of the features of this embodiment.

[0048] According to aspects of the disclosure, a stroke limited component may also be integrated into the e-foot assembly 600. The projection 652 of lower part 650 may be provided with an axially extending slot or channel 654. The upper part 620 may be provided with a transverse bore 658, which receives a retaining pin 670. Retaining pin 670 extends through both the transverse bore 658 and the slot 654 in lower part 650, thus retaining the lower part 650 within the upper part 620 and limiting the movement of lower part 650 relative to upper part 620. A stroke length “S” may be defined by the range of movement of lower part 650 relative to upper part 620, which may in turn be defined by the contact of different parts. For example, an upper extent of travel of lower part 650 within upper part 620 may be defined by the dimensions of the lower annular skirt 630 of upper part 620, which may impact the shoulder 656 to define an upper travel limit of lower part 650 within upper part 620. FIGS. 7 and 8 show the lower part 650 at an upper limit of travel. Alternatively, projection 652 may bottom out in the bore 628 to define an upper travel limit. A lower travel limit for lower part 650 relative to upper part 620 may be defined by the impact of retaining pin 670 with an upper surface of slot 654, as shown in FIGS. 5 and 6. As will be recognized, the stroke “S” may be configured to achieve desirable absorption and conveyance of respective portions of motion defined on the motion source (cam) and thus to achieve corresponding desired modification of valve motion, particularly in combination with the sub-base circle portions of 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 form between the e-foot and bridge and/or the cam follower and cam to permit a lubrication film to develop during that portion of the valve motion cycle. The stroke length of the e-foot assembly may be selected and adjusted such that only a small gap or zero bias load gap is formed, thereby avoiding a gap size or play in the valvetrain that would result in loss of control of the rocker position.

[0049] Thus, in this and other embodiments, and consistent with aspects of the disclosure, the stroke limited e-foot may be configured to provide for a small gap between the e-foot and valve bridge when the rocker encounters a sub-base circle portion of the cam. This configuration permits unloading of the e-foot and allows for the formation or reformation of a lubrication layer within the e-foot assembly, such as between the e-foot cap and bushing, and at other locations (valvetrain component interfaces) in the valvetrain. This configuration may also provide for reduction or negation of any valve spring pre-load. The e-foot assembly may also be configured such that the mechanism bottoms out after stroking between sub-base and base circle of the cam.

[0050] As will be recognized from the instant disclosure, lost motion rocker brake systems, such as those described above, bias the rocker brake towards the cam of the engine and away from the valves. This has several benefits, including a reduction in the components needed to assemble the rocker brake into the valvetrain. Additionally, the stroke limited e-foot reduces valve bridge and e-foot cap wear due to the lost motion gap where extra oil can penetrate. Furthermore, the stroke limited feature reduces bushing wear which occurs from loading the bushing area during 100% of the rocker's duty cycle.

[0051] The following operational description will serve to further illustrate aspects of the disclosure and interaction of the described components. In a “brake off” mode, when the cam follower encounters a sub-base circle portion of the cam and the actuator piston is retracted, the e-foot assembly may be in an extended position to maintain engagement with the valve bridge. When the system is still in a brake off mode, but when the cam follower encounters a base circle portion of the cam (with the actuator piston still retracted), the e-foot assembly may undergo partial compression from its extended position, with compression of the e-foot assembly spring and the e-foot still maintaining contact with the valve bridge and biasing of the rocker cam side toward the cam.

[0052] In a “brake on” mode, with the actuator piston extended (but possibly not touching the bridge pin), and the cam follower encountering a 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 a “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 of the e-foot with the valve bridge.

[0053] According to aspects of the disclosure, biasing and stroke limiting features may be integrated into valvetrain components other than an e-foot assembly, as described above. For example, biasing and stroke limiting features may be integrated into components of a push rod configuration as shown in the two embodiments in FIGS. 9-18. Referring particularly to FIGS. 9-14, a push rod biasing and stroke limiting assembly 700 may include an upper part 720 which receives a projection 752 of a lower part 750 for sliding, telescoping movement. Upper part 720 may include a fastening post 724, which fits within a bore on the rocker. Lower part 750 may include a channel 754 formed on projection 752. A circular (outwardly biased) spring clip 770 may be installed in an internal groove on the inner wall of upper part 720 such that the spring clip 770 is positioned within channel 754 and thereby limits movement of the lower part 750 relative to the upper part 720. That is, channel 754 permits limited movement of the lower part 750 but otherwise cannot move up or down beyond the limits defined by the position of spring clip 770. In this manner, spring clip 770 and channel 754 define a limited stroke “S” (FIG. 11)

[0054] A biasing component may be implemented in the embodiment of FIGS. 9-14 as well. A coil spring 780 may be housed within a bore 728 of the upper part 720, with an upper interior wall 729 of the bore 728 of upper part 720 defining an upper spring seating surface. An upper surface 759 of the lower part 750 may define a lower spring seating surface. Coil spring 780 may thus bias the lower component 750 into an extended position relative to upper part 720. FIGS. 11 and 12 show a contracted position or state of the push tube assembly while FIGS. 13 and 14 show an extended position or state of the push tube assembly.

[0055] FIGS. 15-18 illustrate another embodiment of biasing and stroke limited components suitable for push rod environments. In this configuration, a biasing and stroke limiting push rod assembly 800 may include an upper part 820 and lower part 850 arranged and adapted for telescoping relative movement. A transversely extending retaining pin 870 extends through a transverse bore on the upper part 820 and through an axially extending slot 854 in the lower part 850. In a manner like the embodiment of FIGS. 1- 8, pin 870 limits axial movement of the lower part 850 relative to the upper part 820 and thereby provides a limited stroke “S” of the push rod component. In this embodiment, a biasing feature may include an external coil spring 880 seated between respective annular shoulders 826 and 856 of upper part 820 and lower part 850 to bias the push rod assembly into an extended position. FIGS. 15 and 16 show the push rod assembly in a contracted or compressed position or state while FIGS. 17 and 18 show the push rod assembly in an extended position or state.

[0056] It will be recognized that the stroke-limiting and biasing configurations of the push rod embodiments of FIGS. 5-10 may be adapted to other valvetrain components, including the previously described e-foot environment. For example, the spring clip 770 and channel 754 in the embodiment of FIGS. 5-8 could be adapted to replace the pin and slot limiting configuration in the embodiment of FIGS. 1-4. In this regard, the various mechanical implements for limiting stroke and for biasing should be viewed as interchangeable and adaptable to different valvetrain components beyond the e-foot and push rod environments described herein.

[0057] As will be recognized from the instant disclosure, lost motion rocker brake systems, such as those described above, bias the rocker brake towards the valve-side of the engine and away from the cam. This has several benefits, including a significant reduction in the biasing force needed to control the rocker brake in a brake off condition. The valvetrain becomes easier to design with less biasing force required on the push rod side. With a lighter biasing force, the overall system can be lighter with potential lower costs as well.

[0058] The stroke limiting features described above also provide advantages. The stroke limiting functionality provides for a predefined stroke in the valvetrain which, in combination with the biasing component, may facilitate the adjustment of e-foot or push rod position for all operating conditions, including brake “off” (or lost motion deactivated) states of operation. This in turn may allow for a desirable gap formation between the e-foot and valve bridge or between other valvetrain components. In addition, the stroke limiting features may function as retaining features that allow a preassembled e-foot or push rod system to be assembled and shipped as an assembled component that may be easily installed in a larger engine environment without separate installation or assembly steps in the field.

[0059] While particular embodiments have been shown and described, those skilled in the art will appreciate that changes and modifications may be made without departing from the instant teachings. It is therefore contemplated that all modifications, variations, or equivalents of the above-described teachings fall within the scope of the basic underlying principles disclosed above.

[0060] For example, while the above examples have been described in the context of a Type 3 valvetrain (center pivot) rocker or a Type 5 valvetrain (pushrod), it will be recognized that the described biasing components and stroke limited components may be implemented in other valvetrain types, such as Type 2 (end pivot rocker) or Type 4 (center pivot rocker with follower).

[0061] Further, while the disclosed biasing components and stroke limited components are explained using the illustrative embodiments of an e-foot and pushrod, it will be recognized that the described biasing components and stroke limited components may be implemented as part of other valvetrain components, such as cam followers, for example.

[0062] Still further, while the disclosed embodiments may feature a lost motion component as part of the valvetrain, it will be recognized that the biasing and stroke limiting features of the disclosed embodiments may be utilized in valvetrain systems that do not incorporate lost motion components.