CN117321291A

CN117321291A - Valve actuation system including tandem lost motion components disposed in rocker front valve train components and valve bridge

Info

Publication number: CN117321291A
Application number: CN202280035092.XA
Authority: CN
Inventors: J·D·巴尔特鲁基
Original assignee: Jacobs Vehicle Systems Inc
Current assignee: Jacobs Vehicle Systems Inc
Priority date: 2021-06-03
Filing date: 2022-06-03
Publication date: 2023-12-29
Also published as: WO2022254408A1; BR112023023770A2; EP4348013A1; KR20230169369A

Abstract

A valve actuation system includes a valve actuation motion source configured to provide a primary valve actuation motion and an auxiliary valve actuation motion for actuating at least one engine valve via a valve actuation load path. A lost motion relief mechanism is disposed in the rocker arm front valvetrain component and is configured to transfer at least the main valve actuation motion in a first default operating state and is configured to consume the main valve actuation motion and the auxiliary valve actuation motion in a first activated state. In addition, a lost motion addition mechanism is disposed in the valve bridge and configured to lose the auxiliary valve actuation motion in a second default operating state and configured to transfer the auxiliary valve actuation motion in a second activated state, wherein the lost motion addition mechanism is in series with the lost motion subtraction mechanism in the valve actuation load path.

Description

Valve actuation system including tandem lost motion components disposed in rocker front valve train components and valve bridge

Technical Field

The present disclosure relates generally to valve actuation systems, and in particular to valve actuation systems including lost motion components in series along a valve actuation load path, which may be used to achieve both cylinder deactivation and auxiliary valve actuation.

Background

Valve actuation systems for internal combustion engines are known in the art. During positive power operation of an internal combustion engine, such valve actuation systems are used to provide so-called main valve actuation motions to the engine valves in connection with combustion of fuel, so that the engine output may be used, for example, to operate the power of the vehicle. Alternatively, the valve actuation system may be operated to provide so-called auxiliary valve actuation motions in addition to the main valve actuation motion. The valve actuation system may also be operated in a manner that completely ceases operation of a given engine cylinder, i.e., by eliminating any engine valve actuation without operating in either the primary or auxiliary modes of operation, commonly referred to as cylinder deactivation. As is further known in the art, these various modes of operation may be combined to provide desired benefits. For example, future emission standards for heavy duty diesel trucks require technologies that improve fuel economy and reduce emission output. The leading technique that provides both of these functions is cylinder deactivation. There are data indicating that cylinder deactivation reduces fuel consumption and increases temperature, thereby providing improved aftertreatment emission control.

A known system for cylinder deactivation is described in U.S. patent No. 9,790,824, which describes a hydraulically controlled lost motion mechanism disposed in a valve bridge, an example of which is shown in fig. 11 of the' 824 patent and reproduced herein as fig. 1. As shown in fig. 1, the lost motion mechanism includes an outer plunger 120 provided with a bore 112 formed in the body 110 of the valve bridge 100. A locking element in the form of a wedge 180 is provided which is configured to engage with an annular outer recess 172 formed in the surface defining the aperture 112. Without hydraulic control applied to the inner plunger 160 (in this case, via a rocker arm, not shown), the inner piston spring 144 biases the inner plunger 160 into position such that the wedge 180 protrudes out of the opening formed in the outer plunger 120, thereby engaging the outer recess 172 and effectively locking the outer plunger 120 in place relative to the valve bridge body 110. In this state, any valve actuation motion (whether primary or secondary) applied to the valve bridge via the outer plunger 120 is transferred to the valve bridge body 110 and ultimately to the engine valve (not shown). However, providing sufficiently pressurized hydraulic fluid to the top of the inner plunger 160 causes the inner plunger 160 to slide downward, allowing the wedge 180 to retract and disengage from the outer recess 172, thereby effectively unlocking the outer plunger 120 relative to the valve bridge body 110, and allowing the outer plunger 120 to freely slide within its bore 112, experiencing the bias provided by the outer plunger spring 146 toward the rocker arm. In this state, any valve actuation motion applied to the outer plunger 120 will cause the outer plunger 120 to reciprocate in its bore 112. In this manner, and assuming that the travel of the outer plunger 120 within its bore 112 is greater than the maximum extent of any applied valve actuation motion, such valve actuation motion is not transferred to the engine valve and is effectively lost such that the corresponding cylinder is deactivated.

However, one disadvantage of deactivating cylinders is that the flow of air mass through the engine is reduced, thus also reducing the energy in the exhaust system. During the vehicle warm-up from cold start, it is important to have an elevated exhaust gas temperature to rapidly increase the catalyst temperature to the effective operating temperature. Although cylinder deactivation provides elevated temperatures, significant reduction in air mass flow is ineffective for rapid warm-up.

To overcome this disadvantage of cylinder deactivation and provide rapid warm-up, one proven technique is to open the exhaust valve early to release increased thermal energy to the exhaust system, known as Early Exhaust Valve Opening (EEVO), which is a specific type of auxiliary valve actuation motion in addition to the main valve event. In practice, such a system is based on the principle of adding valve actuation motion that would otherwise be lost during main valve actuation to provide the early opening event. Systems combining both the early exhaust gas opening and cylinder deactivation capabilities may meet warm-up requirements and provide reduced emissions and improved fuel consumption.

The valve actuation system for providing EEVO may be provided using a rocker arm having a hydraulically controlled lost motion component in the form of an actuator, such as the lost motion component shown in U.S. patent No. 6,450,144, an example of which is shown in fig. 19 of the' 824 patent and reproduced herein as fig. 2. In this system, the rocker arm 200 is provided with an actuator piston 210 disposed in the motion transmitting end of the rocker arm 200. The actuator piston 210 is biased out of its bore by a spring 217 such that the actuator piston 210 continuously contacts the corresponding engine valve (or valve bridge). Hydraulic passages 231, 236 are provided such that hydraulic fluid may be provided by the control passage 211 to fill the actuator piston bore. In these cases, hydraulic fluid remains in the bore by means of the check valve 241 and as long as the hydraulic passage 236 is not aligned with the control passage 211, in which case the actuator piston 210 is rigidly held in the extended position and cannot reciprocate in its bore. On the other hand, when the bore is not filled with hydraulic fluid (or such fluid is evacuated when the passages 236, 211 are aligned), the actuator piston 210 is free to reciprocate within its bore to the extent permitted by the lash adjustment screw 204. In such systems, the cam includes cam lobes for providing primary and auxiliary valve actuation motions. In the main valve actuation operation, hydraulic fluid is not provided to the actuator piston 210, allowing the actuator piston 210 to reciprocate within its bore. In this case, as long as the allowed travel of the actuator piston 210 into its bore is at least as great as the maximum motion provided by the EEVO lobe, but less than the maximum motion provided by the main event lobe, any valve actuation motion provided by the EEVO lobe will be lost through the reciprocating motion of the actuator piston 210, but the main event valve actuation will bottom out the actuator piston 210 in its bore (or through solid contact with some other surface) thereby transmitting the main event motion. On the other hand, when the actuator piston is hydraulically locked in its extended position, EEVO motion is not lost and is transferred to the engine valve, although position-based draining of the actuator bore (i.e., resetting by alignment of the passages 236, 211) prevents over-extension of the engine valve during main valve event motion.

It should be possible, at least in theory, to combine cylinder deactivation based on lost motion with an auxiliary valve actuation motion system of the type described above to provide the desired cylinder deactivation and EEVO operation. However, it is not straightforward to incorporate such systems to provide the desired results.

For example, as described above, EEVO lost motion combines normal main event lift with early lift on the same camshaft. An example of this is shown in fig. 3. In fig. 3, a first curve 310 shows an idealized version of the main event valve lift, which in this example has a maximum lift of about 14 millimeters. The second curve 311 shows a typical actual main event experienced by the engine valve that would occur when any EEVO motion provided by the cam is lost, such as when the rocker arm actuator described above in fig. 2 is allowed to reciprocate. The upper dashed curve 312 shows an idealized valve lift if all of the valve actuation motion provided by the EEVO-capable cam is provided, such as when the rocker arm actuator is fully extended. As shown, the idealized lift 312 includes an EEVO event 313 of approximately 3mm valve lift during valve opening, which translates to approximately 2 mm valve lift 314 during implementation. The example shown in FIG. 3 also illustrates the occurrence of a reset, wherein the actuator piston is allowed to collapse at a lift of about 10mm in this example (i.e., the locking hydraulic fluid in the actuator bore is expelled in this cycle of the engine valve), causing a normal lift main event 311 to occur. The combination of these two lift events (as shown by idealized lift profile curve 312) results in a total travel of approximately 17mm and when lost by the lost motion mechanism shown in fig. 1, will exert a relatively high stress on outer plunger spring 146 as it attempts to bias outer plunger 120 throughout the 17mm travel of outer plunger 120.

As a further example, it is known that during cylinder deactivation as described above, the normal force applied by the engine valve spring to bias the rocker arm into continuous contact with the valve actuation motion source (e.g., cam) is no longer provided. While the outer piston plunger spring 146 provides some force back toward the rocker arm via the outer plunger 120, the force is relatively small and insufficient to control the rocker arm as desired. Thus, a separate rocker arm biasing element is typically provided to bias the rocker arm into contact with the cam, for example by applying a biasing force towards the cam on the motion receiving end of the rocker arm via a spring located above the rocker arm. Failure to adequately control the inertia created by the rocker arm (due to the valve actuation motion imparted to the rocker arm despite deactivation) may result in separation between the rocker arm and the cam, which in turn may result in destructive impact therebetween. Similarly, EEVO valve actuation motion that would otherwise be lost if EEVO operation were not required would still transfer inertia to the rocker arm that must be similarly controlled. One complicating factor in this operation of the rocker arm biasing element is that each of these operations (cylinder deactivation and EEVO) typically occur at a significantly different speed range.

Typically, cylinder deactivation typically occurs at engine speeds no greater than about 1800rpm, and the rocker arm biasing element is configured to provide sufficient force at these speeds to ensure proper contact between the rocker arm and the cam. On the other hand, the otherwise lost EEVO valve actuation motion will exist even at high engine speeds (e.g., about 2600 rpm) are reached. Thus, to obtain the benefits of combined cylinder deactivation and EEVO operation, the rocker arm biasing element will need to accommodate the relatively high speeds at which EEVO valve actuation motion may still be applied to the rocker arm. Rocker arm control for lost EEVO valve actuation motions requires high forces to be applied by the rocker arm biasing element due to the relatively high speeds at which they can still occur. However, this occurs at the small valve lift where the rocker arm biasing spring has its lowest preload. Cylinder deactivation, on the other hand, typically occurs at a lower rate and is at a higher lift portion of increased preload (main valve actuation motion) throughout the rocker arm biasing element. However, providing a rocker arm biasing element that is capable of providing both high forces (as required by EEVO) at minimum preload and withstanding the stresses required during full travel (as required by cylinder deactivation) is a difficult challenge to overcome.

Disclosure of Invention

The above-described drawbacks of the prior art solutions are addressed by providing a valve actuation system for actuating at least one engine valve according to the present disclosure. Specifically, the valve actuation system includes a valve actuation motion source configured to provide a primary valve actuation motion and an auxiliary valve actuation motion for actuating at least one engine valve via a valve actuation load path. A lost motion relief mechanism is disposed in a rocker front valve train (valve train) component and is configured to transfer at least the main valve actuation motion in a first default operating state and is configured to lose the main valve actuation motion and the auxiliary valve actuation motion in a first activated state. In addition, a lost motion addition mechanism is disposed in the valve bridge and configured to lose the auxiliary valve actuation motion in a second default operating state and configured to transfer the auxiliary valve actuation motion in a second activated state, wherein the lost motion addition mechanism is in series with the lost motion subtraction mechanism in the valve actuation load path.

Examples of auxiliary valve actuation motions include at least one of an exhaust valve early-opening valve actuation motion, an intake valve late-closing valve actuation motion, or an engine braking valve actuation motion.

In one embodiment, the valve actuation system further includes an engine controller configured to operate the internal combustion engine using the lost motion mitigation mechanism and the lost motion addition mechanism. In the positive power mode, the engine controller controls the lost motion imparting means to operate in a first default operating state and controls the lost motion imparting means to operate in a second default operating state. In the deactivated mode, the engine controller controls the lost motion imparting means to operate in a first activated operational state and controls the lost motion imparting means to operate in a second default operational state. In the assist mode, the engine controller controls the lost motion imparting means to operate in a first default operating state and controls the lost motion imparting means to operate in a second activated operating state.

Corresponding methods are also disclosed.

Drawings

The features described in the present disclosure are set forth with particularity in the appended claims. These features and attendant advantages will become apparent from a consideration of the following detailed description, when taken in conjunction with the accompanying drawings. One or more embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which like reference numerals refer to like elements, and in which:

FIG. 1 illustrates a lost motion mechanism suitable for providing cylinder deactivation according to the prior art;

FIG. 2 illustrates a lost motion mechanism suitable for providing auxiliary valve actuation according to the prior art;

FIG. 3 is a graph illustrating an example of EEVO valve actuation motion according to the present disclosure;

fig. 4 and 5 are schematic diagrams of embodiments of valve actuation systems according to the present disclosure;

FIG. 6 illustrates a partial cross-sectional view of an embodiment of a valve actuation system according to the embodiment of FIG. 4;

FIG. 7 is an exploded view of a reset rocker arm according to the embodiment of FIG. 6;

fig. 8-11 are partial top and side cross-sectional views, respectively, of a reset rocker arm according to the embodiment of fig. 6-8;

FIG. 12 is a partial cross-sectional view of a first embodiment of a valve actuation system according to the embodiment of FIG. 5;

FIG. 13 is a partial cross-sectional view of a second embodiment of a valve actuation system according to the embodiment of FIG. 5;

FIG. 14 is a flow chart illustrating a method of operating an internal combustion engine according to the present disclosure;

FIG. 15 is a schematic diagram of an embodiment of a valve actuation system according to the variation of the valve actuation system depicted in FIG. 4 and according to the present disclosure;

FIG. 16 is a side view of an embodiment of a valve actuation system according to the embodiment of FIG. 15;

FIG. 17 is a side cross-sectional view of the embodiment according to FIG. 16; and is also provided with

Fig. 18 is a side cross-sectional view of the lm+ mechanism of fig. 17 shown in more detail.

Detailed Description

Fig. 4 schematically illustrates a valve actuation system 400 according to the present disclosure. Specifically, the valve actuation system 400 includes a valve actuation motion source 402 that serves as the sole source of valve actuation motion (i.e., valve opening and closing motion) to one or more engine valves 404 via a valve actuation load path 406. One or more engine valves 404 are associated with a cylinder 405 of the internal combustion engine. As is known in the art, each cylinder 405 typically has at least one valve actuation motion source 402 uniquely corresponding thereto for actuating a corresponding engine valve 404. Additionally, while only a single cylinder 405 is shown in FIG. 4, it should be appreciated that an internal combustion engine may, and often does, include more than one cylinder, and that the valve actuation system described herein is applicable to any number of cylinders of a given internal combustion engine.

The valve actuation motion source 402 may include any combination of known elements capable of providing valve actuation motion, such as a cam. The valve actuation motion source 110 may be dedicated to providing exhaust motion, intake motion, auxiliary motion, or a combination of exhaust or intake motion and auxiliary motion. For example, in a presently preferred embodiment, the valve actuation motion source 402 may include a single cam configured to provide both the primary valve actuation motion (exhaust or intake) and at least one auxiliary valve actuation motion. For another example, where the main valve actuation motion includes a main exhaust valve actuation motion, the at least one auxiliary valve actuation motion may include EEVO valve events and/or compression-release engine brake valve events. For another example, where the main valve actuation motion comprises a main intake valve actuation motion, the at least one auxiliary valve actuation motion may comprise an intake valve late closing (LIVC) valve event. Other types of auxiliary valve actuation motions that may be combined with the main valve actuation motion on a single cam may be known to those skilled in the art, and the present disclosure is not limited in this respect.

The valve actuation load path 406 includes any one or more components, such as lifters, pushrods, rocker arms, valve bridge, automatic lash adjusters, etc., disposed between the valve actuation motion source 402 and the at least one engine valve 404 and operable to transfer motion provided by the valve actuation motion source 402 to the at least one engine valve 404. Additionally, as shown, the valve actuation load path 406 also includes a lost motion addition (lm+) mechanism 408 and a lost motion subtraction (LM-) mechanism 410. As used herein, an lm+ mechanism is a mechanism that defaults to or "normally" in a state (i.e., when the control input is not asserted) in which it does not transmit any auxiliary valve actuation motion applied thereto, and may or may not transmit any main valve actuation motion applied thereto. On the other hand, when the lm+ mechanism is in an activated state (i.e., when the control input is asserted), the mechanism does transfer any auxiliary valve actuation motion applied thereto, and also transfers any main valve actuation motion applied thereto. Further, as used herein, an LM-mechanism is a mechanism that defaults to or "normally" in a state (i.e., when the control input is not asserted) in which it does transmit any primary valve actuation motion applied thereto, and may or may not transmit any secondary valve actuation motion applied thereto. On the other hand, when the LM-mechanism is in an activated state (i.e., when the control input is asserted), the mechanism does not transmit any valve actuation motion applied thereto, whether primary or auxiliary valve actuation motion. In short, the lm+ mechanism when actuated is capable of adding or including valve actuation motions relative to its default or normal operating state, while the LM-mechanism when actuated is capable of subtracting or losing valve actuation motions relative to its default or normal operating state.

Various types of lost motion mechanisms that can be used as lm+ or LM-mechanisms are well known in the art, including hydraulically or mechanically based lost motion mechanisms that can be hydraulically, pneumatically, or electromagnetically actuated. For example, the lost motion mechanism shown in FIG. 1 and set forth in U.S. Pat. No. 9,790,824 (the teachings of which are incorporated herein by reference) is an example of a hydraulically controlled mechanically locked LM-mechanism. As described above, in the absence of hydraulic fluid input to the inner plunger 160 (i.e., in a default state), the locking element 180 is received in the outer recess 772, thereby "locking" the outer plunger 120 to the body 120 such that actuation motions applied thereto are transferred. On the other hand, when hydraulic fluid input is provided to the inner plunger 160 (i.e., in an activated state), the locking element 180 is allowed to retract, thereby "unlocking" the outer plunger 120 from the body 120 such that actuation motions applied thereto are not transferred or lost. As another example, the lost motion mechanism shown in fig. 2 and set forth in U.S. patent No. 6,450,144 (the teachings of which are incorporated herein by reference) is an example of a hydraulically controlled, hydraulic-based lm+ mechanism. As described above, without hydraulic fluid input to the channels 231, 236 (i.e., in the default state), the actuator piston 210 is free to reciprocate in its bore such that any actuation motion imparted thereto that is less in magnitude than the maximum distance the actuator piston 210 can retract into its bore (actuator piston stroke length) is not transferred or lost, but rather any actuation motion imparted thereto that is greater than the actuator piston stroke length is transferred.

As further depicted in fig. 4, an engine controller 420 may be provided and operatively connected to lm+ and LM-mechanisms 408, 410. Engine controller 420 may include any electronic, mechanical, hydraulic, electro-hydraulic, or other type of control device for controlling the operation of lm+ and LM-mechanisms 408, 410, i.e., switching between their respective default and activated operating states as described above. For example, engine controller 420 may be implemented by a microprocessor and corresponding memory storing executable instructions for implementing desired control functions, including those described below, as known in the art. It should be appreciated that other functionally equivalent implementations of engine controller 130 (e.g., an appropriately programmed Application Specific Integrated Circuit (ASIC), etc.) may be equivalently employed. Additionally, engine controller 420 may include peripheral devices located intermediate engine controller 420 and lm+ and LM-mechanisms 408, 410 that allow engine controller 420 to effect control of the operating states of lm+ and LM-mechanisms 408, 410. For example, where both lm+ and LM-mechanisms 408, 410 are hydraulic control mechanisms (i.e., in response to no hydraulic fluid or application of hydraulic fluid to an input), such peripheral devices may include suitable solenoids as known in the art.

In system 400 shown in fig. 4, lm+ mechanism 408 is disposed closer to the valve actuation motion source along valve actuation load path 406 than LM-mechanism 410. Examples of such systems are described in more detail below with reference to fig. 6-12. However, this is not necessary. For example, fig. 5 and 15 illustrate valve actuation systems 400', 1500, wherein like reference numerals indicate like elements as compared to fig. 4, wherein LM-mechanisms 410, 410' are disposed closer to valve actuation motion source 402 than lm+ mechanisms 408, 408 '. Examples of the system of fig. 5 are described in more detail below with reference to fig. 12 and 13, and examples of the system of fig. 15 are described in more detail below with reference to fig. 16-18.

Referring again to fig. 4, in all operating states of lm+ mechanism 408, lm+ mechanism 408 is in series with LM-mechanism 410 along valve actuation load path 406. That is, any primary valve actuation motion provided by valve actuation motion source 402 is transferred by lm+ mechanism 408 to LM-mechanism 410, whether lm+ mechanism 408 is in its default state or its activated state as described above. However, again, this is not required, as shown in FIG. 5, where LM+ mechanism 408 is shown in series or not with LM-mechanism 410 depending on the operational state of LM+ mechanism 408. In this case, when lm+ mechanism 408 is in its default operating state, i.e., when it is controlled to lose any auxiliary valve actuation motion applied thereto, lm+ mechanism 408 is not active in transmitting the main valve actuation motion transmitted by LM-mechanism 410; this is illustrated by the solid arrows between LM-mechanism 410 and engine valve 404. In fact, in this state, lm+ mechanism 408 is removed from valve actuation load path 406, as shown in fig. 5. On the other hand, when lm+ mechanism 408 is in its active operating state, i.e., when it is controlled to transmit any auxiliary valve actuation motions applied thereto, lm+ mechanism 408 participates in the transmission of both the main valve actuation motions and auxiliary valve actuation motions received from LM-mechanism 410, effectively concatenating lm+ mechanism 408 therewith; this is illustrated by the dashed arrows between LM-mechanism 410 and LM + mechanism 408 and between LM + mechanism 408 and engine valve 404.

The valve actuation systems 400, 400' of fig. 4 and 5 facilitate operation of the cylinder 405, and thus the internal combustion engine, in a positive power mode, a deactivated mode, or an auxiliary mode in a system having a single valve actuation motion source 402 that provides all valve actuation motion to the engine valve 404. This will be further described with reference to the method shown in fig. 14. At block 1402, lm+ and LM-mechanisms are arranged in a valve actuation load path as described above. Specifically, the LM-mechanism is configured to transmit at least the main valve actuation motions applied thereto in a first default operating state, and is configured to lose any main and auxiliary valve actuation motions applied thereto in a first activated state. In addition, the lm+ mechanism is configured to lose any auxiliary valve actuation motion applied thereto in a second default operating state, and is configured to transfer auxiliary valve actuation motion in a second activated state, wherein the lm+ mechanism is concatenated with the LM-mechanism in the valve actuation load path at least during the second activated state.

After the valve actuation system is provided at step 1402, processing continues at any one of blocks 1406-1410, wherein the engine is operated in a positive power mode, a deactivated mode, or an auxiliary mode, respectively, based on control of the operational states of the lm+ and LM-mechanisms. Thus, at block 1406, to operate the engine in the positive power mode, the LM-mechanism is placed in its first default operating state and the lm+ mechanism is placed in its second default operating state. Then, in this mode, the lm+ mechanism will not transmit any auxiliary valve actuation motion, but may transmit any main valve actuation motion transmitted by the LM-mechanism (depending on whether the lm+ mechanism is arranged as in fig. 4 or 5). The net effect of this configuration is to transfer only the main valve actuation motion to the engine valve, as required for positive power operation.

At block 1408, to operate the engine in the deactivated mode, the LM-mechanism is placed in its first activated operating state and the lost motion adding mechanism is in its second default operating state. Then, in this mode, the LM-mechanism will not transmit any valve actuation motion applied thereto. Thus, the corresponding cylinder will be deactivated to the extent that no valve actuation motion will be transferred to the engine valve. In view of this operation of the LM-mechanism, the operating state of the lm+ mechanism will not have an effect on the engine valve. However, in a presently preferred embodiment, during deactivated mode operation, the lm+ mechanism is placed in its second default operating state.

At block 1410, to operate the engine in the assist mode, the LM-mechanism is placed in its first default operating state and the lm+ mechanism is placed in its second activated operating state. Then, in this mode, the lm+ mechanism will transmit any auxiliary valve actuation motions and any main valve actuation motions transmitted by the LM-mechanism. The net effect of this configuration is that both the primary and auxiliary valve actuation motions are transferred to the engine valve, thereby providing any auxiliary operations provided by the particular auxiliary valve actuation motion, such as EEVO, LIVC, compression-release engine braking, etc.

As long as the engine is running, engine operation between any of the various modes provided at steps 1406-1410 may continue as shown in block 1412.

Fig. 6 illustrates a partial cross-sectional view of a valve actuation system 600 according to the embodiment of fig. 4. Specifically, the system 600 includes a valve actuation motion source 602 in the form of a cam operatively connected to a rocker arm 604 at a motion receiving end 606 of the rocker arm 604. A rocker arm biasing element 620 (e.g., a spring) may be provided that acts on a fixed surface 622 to help bias the rocker arm 604 into contact with the valve actuation motion source 602. As is known in the art, the rocker arm 604 rotationally reciprocates about a rocker shaft (not shown) to transfer valve actuation motion provided by a valve actuation motion source to a valve bridge 610 via a motion transfer end 608 of the rocker arm 604. In turn, the valve bridge 610 is operatively connected to a pair of engine valves 612, 614. As further shown, the valve bridge 610 includes an LM-mechanism 616 (locking piston) of the type shown and described above in fig. 1, while the rocker arm 604 includes an lm+ mechanism 618 (actuator) substantially similar to the type shown and described above in connection with fig. 2.

Details of lm+ mechanism 618 are further shown in fig. 7 along with other components disposed within rocker arm 604. Lm+ mechanism 618 includes an actuator piston 702 attached to retainer 703 such that actuator piston 702 is slidably disposed on gap adjustment screw 704. Further details of lm+ mechanism 618 are described below with reference to fig. 9. As best shown in fig. 9, lash adjustment screw 704 is threadably secured in actuator piston bore 710 such that lm+ mechanism 618 is disposed in a lower portion of actuator piston bore 710. A lock nut 704 is provided to secure the gap adjustment screw 704 at its desired gap setting in use.

Fig. 7 also shows a reset assembly 712 disposed within a reset assembly bore 724 that includes openings on the top and bottom (not shown) of the rocker arm 604. The reset assembly 712 includes a reset piston 714 slidably disposed within a reset assembly bore 724. A return piston spring 715 is disposed above the return piston 714 and a lower end of the return piston spring 716 is secured to the return piston 714 using a c-clip 718 or other suitable means. A washer 720 is disposed at the upper end of the return piston spring 716. The reset assembly 712 is retained in a reset assembly aperture 724 by a spring clip 722, as is known in the art. As described in further detail below in connection with fig. 10 and 11, the return piston spring 716 biases the return piston 714 out of the lower opening of the return assembly bore 724 such that the return piston 714 can contact a stationary surface (not shown in fig. 7). As the rocker arm 604 reciprocates, the reset piston 714 slides within the reset assembly bore 724 in a controlled manner as dictated by the rotation of the rocker arm 604. Specifically, at a desired position of rocker arm 604, reset piston 714 may be configured such that an annular groove 715 formed therein is aligned with reset passage 802 (fig. 8) to effect reset of lm+ mechanism 618, as described in further detail below.

Fig. 7 also shows an upper hydraulic passage 730 formed in the rocker arm 604 that receives a check valve 732. As described in more detail below, the upper hydraulic passage 730 provides hydraulic fluid (provided by a suitable supply passage formed in the rocker shaft, not shown) to the actuator piston bore 710 to control operation of the lm+ mechanism 618. To ensure a fluid tight seal on the upper hydraulic passage 730 after installation of the check valve 732, a threaded plug 734 or similar device may be employed. In addition, for completeness, fig. 7 also shows a rocker arm bushing 740 that may be inserted into the rocker arm shaft opening 742 and over the rocker arm shaft, as is known in the art. In addition, cam follower 744 may be mounted on a cam follower shaft 746 disposed within a suitable opening 748.

However, unlike actuator piston 210 in fig. 2, and as best shown in fig. 9, actuator piston 702 of lm+ mechanism 618 includes hydraulic passages 904, 906 that allow hydraulic fluid to be supplied to LM-mechanism 616 via actuator piston 702. As shown in fig. 9, a lower hydraulic passage 908 formed in the rocker arm 604 receives hydraulic fluid from a supply slot in a rocker shaft (not shown) and delivers the hydraulic fluid to a lower portion of the actuator piston bore 710. The actuator piston 702 includes an annular groove 910 formed in a sidewall surface thereof that is aligned with the hydraulic supply passage 908 throughout the stroke of the actuator piston 702. In turn, annular groove 910 communicates with horizontal channel 904 and vertical channel 906 formed in actuator piston 702. Vertical channel 906 directs hydraulic fluid to adapter 706, which has an opening formed therein, for delivering hydraulic fluid to LM-mechanism 616. In this manner, hydraulic fluid may be selectively supplied to LM-mechanism 616 as a control input.

As described above, and further shown in fig. 9, lm+ mechanism 618 includes a lash adjustment screw 704 that extends into actuator piston bore 710. An actuator piston spring 918 is disposed between the lash adjustment screw 704 and the actuator piston 702 and abuts a lower surface of a shoulder 920 formed in the lash adjustment screw 704, thereby biasing the actuator piston 702 out of the actuator piston bore 710. In this embodiment, actuator piston 702 is secured via suitable threads to retainer 703 that engages the upper surface of gap adjustment screw shoulder 920, thereby limiting the outward travel of actuator piston 702, as described in further detail below.

Fig. 8 and 9 further illustrate (dashed lines in fig. 9) an upper hydraulic passage 730 formed in the rocker arm 604 for selectively supplying hydraulic fluid (e.g., via a high-speed solenoid, not shown) to the actuator piston bore 710 above the actuator piston 702. (note that in fig. 8, various components forming lm+ mechanism 618 and reset assembly 712 are not shown for ease of illustration.) a check valve 732 is disposed in widened portion 730' of upper hydraulic passage 730 to prevent hydraulic fluid from actuator piston bore 710 from flowing back to the supply passage that feeds upper hydraulic passage 730. In this manner, and without resetting of lm+ mechanism 618 as described below, a high pressure chamber in actuator piston bore 710 may be formed between check valve 732 and actuator piston 702 such that a locking volume of hydraulic fluid maintains actuator piston 702 in the extended (activated) state.

As described above in connection with fig. 3, a valve actuation system in which a single valve actuation motion source provides both main and auxiliary valve actuation motions may require the ability to reset to avoid excessive engine valve stick out during the combined auxiliary and main valve actuation motions. In the context of the embodiment shown in fig. 6-11, the venting of the locked volume of hydraulic fluid and the resetting of the actuator piston 702 is provided by operation of the reset assembly 712. As best shown in fig. 8, a reset passage 802 is provided in fluid communication with a portion of the actuator piston bore 710 that forms the high pressure chamber with the actuator piston 702 and the reset piston bore 804. The return piston 714 is effectively a spool valve having an end that extends out of the bottom of the rocker arm 604 under the bias of a return piston spring 716. In the embodiment shown in fig. 10 and 11, the return piston 714 is of sufficient length and the return piston spring 716 has sufficient travel to ensure that the return piston 714 continuously contacts the fixed contact surface 1002 at all positions of the rocker arm 604.

As shown in fig. 10, the rocker arm 604 is at base circle relative to the cam 602 (i.e., rotated toward the cam 602 to a maximum extent). In this state, and with a relatively low lift (e.g., below the reset height shown in fig. 3), the annular groove 715 is not aligned with the reset passage 802 (hidden behind the upper hydraulic passage 730, as shown in fig. 10 and 11), such that the outer diameter of the reset piston 714 cuts off communication with the reset passage 802, thereby maintaining a trapped volume of fluid in the actuator piston bore 710 (when provided). When the rocker arm 604 rotates at a higher valve lift (e.g., at or above the reset height shown in fig. 3), as shown in fig. 11, the reset piston 714 pivots about its contact point with the fixed surface 1002 and slides relative to the reset piston bore 804 such that the annular groove 715 aligns with the reset passage 802, allowing trapped hydraulic fluid to flow through the annular groove 715, into a radial bore 1004 formed in the reset piston 714 and out through the top of an axial passage 1006 (shown in phantom) formed in the reset piston 714. When the rocker arm 604 rotates back again after a high-lift event, as shown in FIG. 10, the reset piston 714 translates in its bore 804 and re-closes the reset passage 802, allowing refilling of the actuator piston bore 710.

As described above, the reset assembly 712 shown in fig. 6-11 is configured to maintain constant contact with the fixed contact surface 1002. However, it should be understood that this is not required. For example, the reset assembly may alternatively include a poppet valve that contacts the stationary surface only when the desired reset height is reached.

As previously described, the rocker arm biasing element 620 may be provided to help bias the rocker arm 604 into contact with the cam 602. A feature of the disclosed system 600 is that neither the rocker arm biasing element 620 nor the actuator piston spring 918, individually, are configured to individually provide sufficient force to bias the rocker arm 604 into contact with the cam 602 under substantially all operating conditions. However, in this embodiment, the rocker arm biasing element 620 and the actuator piston spring 918 are selected to work in combination for this purpose under substantially all operating conditions of the rocker arm 604. For example, to assist in biasing the rocker arm 604 toward the cam 602, the actuator piston spring 918 provides high force only during relatively low lift valve actuation motions (e.g., EEVO, LIVC, etc.), which is most desirable due to the high speed operation possible. If uncontrolled, the biasing force exerted by actuator piston spring 918 may cause actuator piston 702 to push against LM-mechanism 616 with a significant force. Where LM-mechanism 616 is a mechanical locking mechanism such as described with reference to fig. 1, such force may be strong enough to interfere with the ability of locking element 180 to extend and retract and thereby prevent locking and unlocking of LM-mechanism 616. The travel limit imposed on actuator piston 702 by lash adjustment screw shoulder 920 prevents such excessive loading on LM-mechanism 616, thereby maintaining the normally provided lash space within LM-mechanism 616 that allows locking element 180 to freely extend/retract as desired.

In addition, the extension of actuator piston 702 caused by actuator piston spring 918, while relatively small, reduces the range of stresses that outer plunger spring 146 will have to withstand. In turn, the actuator piston spring 918 may be a high force, low travel spring that provides a particularly desirable high force for the potentially high speed valve actuation motions of low lift. This burden shared by the actuator piston spring 918 and the outer plunger spring 146 may also reduce the need to provide a high preload to the rocker arm biasing element 620 and allow the design of the rocker arm biasing element 620 to focus on the lower speed, higher lift portions for the main valve actuation motion that occurs during deactivated operation, which is a less stringent design constraint.

Fig. 12 shows a partial cross-sectional view of a valve actuation system 1200 according to the embodiment of fig. 5. In this system 600, the valve actuation motion source includes a cam (not shown) operatively connected at the motion-receiving end 1206 of the rocker arm 1204 via a push tube 1202 and an intermediate LM-mechanism 1216 of the type shown and described above in fig. 1. As with the embodiment shown in fig. 6-11, rocker arm 1204 rotationally reciprocates about a rocker shaft (not shown) to transfer valve actuation motion provided by a valve actuation motion source to valve bridge 1210 via a motion transfer end 1208 of rocker arm 1204. In turn, the valve bridge 1210 is operatively connected to a pair of engine valves 1212, 1214. As further shown, rocker arm 1204 includes an lm+ mechanism 1218 of a type substantially similar to that shown and described above in connection with fig. 2. In this case, hydraulic fluid is provided to LM-mechanism 1216 via appropriate passages formed in rocker shaft and rocker arm 1204 and ball joint 1220. Similarly, hydraulic fluid is provided to lm+ mechanism 1218 via appropriate passages formed in rocker shaft and rocker arm 1204. However, in this implementation, the check valve 732 of the previous embodiment is replaced with a control valve 1222 to establish the hydraulic lock required to maintain the actuator piston in the extended state. The embodiment of fig. 12 is also characterized in that the arrangement of lm+ mechanism 1218 interacts with a single engine valve 1214 via only a suitable cross pin 1224.

In this embodiment, LM-mechanism 1216 includes a relatively strong spring to bias the outer plunger of the locking mechanism outwardly against push rod 1202 such that push rod 1202 is biased into contact with the cam and such that the rocker arm is biased in the direction of the engine valves 1212, 1214. In this implementation, the outer plunger of LM-mechanism 1216 is not travel limited during engine operation (as opposed to an engine assembly, where application of a travel limit to LM-mechanism 1216 facilitates the assembly).

In view of the configuration of lm+ mechanism 1218, and in particular the inward sprung actuator piston, a clearance is provided between the actuator piston and the cross arm pin when lm+ mechanism 1218 is in its default state. Thus, during this default state, lm+ mechanism 1218 is not concatenated with LM-mechanism 1216 along the moving load path, as described above in connection with fig. 5. In addition, the actuator piston will not be fully extended given the strength of the outer plunger piston spring, as described above, despite the clearance that exists during the default state. Then, in this case, the actuator piston cannot fully extend until the main motion valve event has occurred, thereby creating sufficient clearance between the actuator piston and the bridge pin 1224 to allow full extension. However, when in the extended (activated) state, the actuator piston will not only transfer the auxiliary valve actuation motion imparted thereto, but will also transfer the main valve actuation motion imparted thereto to its corresponding engine valve 1214. In this case, lm+ mechanism 1218 is placed in series with LM-mechanism 1216 during the activated state of the actuator piston, as described above in connection with fig. 5.

Fig. 13 shows a partial cross-sectional view of a valve actuation system 1300 according to the embodiment of fig. 5. Specifically, the embodiment shown in fig. 13 is substantially the same as the embodiment of fig. 12, except that the ball joint 1220 is replaced by an outwardly biased, limited travel sliding pin 1320. In this case, the outer plunger spring of LM-mechanism 1216 is preferably designed to have a low preload during zero or low valve lift (e.g., on the base circle) and to have the spring rate required to obtain peak force during deactivated mode operation to control full range of motion of rocker arm 1204 over main valve actuation motion.

On the other hand, the sliding pin spring 1322 for biasing the sliding pin 1320 outward is configured with a relatively high preload and short travel (substantially similar to the actuator piston spring 918 discussed above). Because the sliding piston 1320 is capable of sliding within its bore, the sliding piston 1320 includes an annular groove 1334 and a radial opening 1336 aligned therewith such that the alignment of the annular groove 1334 with the fluid supply channel throughout the travel of the sliding piston 1320 ensures continuous fluid communication between the rocker arm 1204 and the LM-mechanism 1216. In addition, travel adjustment screw 1338 is used to limit the travel of sliding pin 1320 out of its bore toward LM-mechanism 1216. As described above with respect to the travel limiting capability applied to actuator piston 702, travel adjustment screw 1338 prevents the maximum force of sliding pin spring 1322 from being applied to LM-mechanism 1216, which would otherwise be overloaded, possibly interfering with its operation. By properly selecting the travel provided by travel adjustment screw 1338, i.e., the movement that is equal to the lm+ mechanism must be lost during its default operating state, the clearance provided to the locking element within LM-mechanism 1216 can be selected to ensure its normal operation, as previously described. In practice, then, the assembly of sliding pin 1320, sliding pin spring 1322 and travel adjustment screw 1338 forms part of the lm+ mechanism in this embodiment.

As set forth above, various specific combinations of outward (extended) and inward sprung (retracted) elements within the lm+ and LM-mechanisms may be provided, with travel limits as desired. More generally, in one implementation, the LM-mechanism (more specifically, an element or component thereof) may be biased to an extended position, and the lm+ mechanism (also, more specifically, an element or component thereof) may be biased to a retracted position. In this case, the extended position of the LM-mechanism may be travel limited. In another implementation of any given embodiment, the LM-mechanism may be biased to the extended position by a first force, and the lm+ mechanism may also be biased to the extended position by a second force. In this case, the first biasing force is preferably greater than the second biasing force. In addition, as such, the extended position of the LM-mechanism may be travel limited. In yet another implementation, the LM-mechanism may be biased to the extended position, and the lm+ mechanism may also be biased to the extended position. However, in this case, the extended position of the lm+ mechanism is travel limited. In this implementation, a possible benefit of limiting the travel of the lm+ mechanism is to allow zero load on the valve train while on the cam base circle to reduce bushing wear.

As described above with respect to fig. 4, and as shown with respect to fig. 15, like reference numerals refer to like elements in fig. 15 as compared to fig. 4, a system 1500 may be provided in which LM-mechanism 410 'is disposed closer to valve actuation motion source 402 along valve actuation motion path 406 than LM-mechanism 408'. However, unlike system 400 'of FIG. 5, LM+ mechanism 408' shown in FIG. 15 is always concatenated with LM-mechanism 410 'regardless of the operational state (default or active) of LM+ mechanism 408', such that LM+ mechanism 408 'is always functional in transmitting the primary valve actuation motion transmitted by LM-mechanism 410' and is never removed from valve actuation load path 406.

In particular, when lm+ mechanism 408' is in its default operating state, lm+ mechanism 408' is configured to lose any auxiliary valve actuation motion, but transfer the main valve actuation motion applied thereto by valve actuation motion source 402 and LM-mechanism 408 '. On the other hand, when lm+ mechanism 408 'is in its active operating state, i.e., when it is controlled to transmit any auxiliary valve actuation motions applied thereto, lm+ mechanism 408 participates in the transmission of both the main and auxiliary valve actuation motions received from valve actuation source 402 and LM-mechanism 410'. So configured, the valve actuation system 1500 facilitates operation of the cylinder 405, and thus also the internal combustion engine, in a positive power mode, a deactivated mode, or an auxiliary mode (e.g., engine braking) in a system having a single valve actuation motion source 102 that provides all valve actuation motion to the engine valve 404. That is, the system 1500 is capable of implementing the method shown in and described above with reference to FIG. 14. However, in this case, the configuration of the LM-mechanism and LM+ mechanism at block 1402 occurs in the rocker front valve train component and the valve bridge, respectively, as described in further detail below.

Fig. 16-18 illustrate a valve actuation system 1600 according to the embodiment of fig. 15. In this embodiment, the valve actuation system 1600 includes an LM-mechanism 1602 disposed in or on a rocker arm front valve train component and an LM+ mechanism 1604 disposed in a valve bridge. As used herein, a rocker arm front valve train component may include any valve train component disposed within a valve train between a valve actuation motion source (e.g., a cam; not shown) and a rocker arm 1620. For example, this may include devices known in the art, such as pushrods, lifters, roller followers, and the like. In the example shown in fig. 16 and 17, the rocker front valvetrain component includes a pushrod 1610, which in turn is operatively connected to a roller follower 1612, establishing contact between the pushrod 1610 and a cam (not shown). In this embodiment, LM-mechanism 1602 is mounted on the upper end of push rod 1610 such that LM-mechanism 1602 is operatively connected to both push rod 1610 and rocker arm 1620. Also in this example, the rocker arm 1620 is mounted on a rocker shaft (not shown) for reciprocating movement thereon. The rocker arm 1620 is in turn operatively connected to a valve bridge 1630 in which the lm+ mechanism 1604 is deployed. In accordance with conventional internal combustion engines, the valve bridge 1630 is operatively connected to two or more engine valves 1642, 1644 (intake or exhaust valves) that are biased into a closed position by corresponding valve springs 1646, 1648. FIG. 16 also shows a stationary reaction surface 1650 in contact with the upper end of LM-mechanism 1602, as described in further detail below.

Referring now to fig. 17 and 18, further details of the embodiment of fig. 16 are shown and described. As described above, push rod 1610 has LM-mechanism 1602 mounted thereon. In this embodiment, LM-mechanism 1602 includes a housing 1702 mounted to pushrod 1610 by an interference fit or threaded engagement between a peg 1704 extending away from a bottom wall 1703 of housing 1702 and an inner diameter 1705 of pushrod 1610. Alternatively, the housing 1702 may be integrally formed as part of the push rod 1610, or the push rod 1610 may be inserted into a receptacle formed on the exterior of the bottom wall 1703 of the housing 1702. A closed housing aperture 1706 is formed in the housing 1702 and is configured to receive an outer plunger 1708, an inner plunger 1712, an inner plunger spring retainer 1714, an inner plunger spring 1716, an outer plunger spring 1709, and one or more locking elements 1718, illustrated in this embodiment as wedges. An outer plunger spring 1709 disposed within the housing bore 1706 and between the bottom wall 1703 and the outer plunger 1708 biases the outer plunger 1708 upwardly within the housing bore 1706 (as shown in FIG. 17). The inner plunger 1712 is disposed within the inner bore 1710 formed in the outer plunger 1708. An inner plunger spring 1716 disposed between an inner plunger spring retainer 1714 (which is attached to and closes the lower end of the inner bore 1710) and the inner plunger 1712 biases the inner plunger 1712 upwardly in the inner bore 1710. The upward travel of the inner plunger 1712 is limited by a stop surface 1726 formed at the upper end of the inner bore 1710. The outer plunger 1708 includes an opening extending through a sidewall of the outer plunger 1708 in which a wedge 1718 is disposed, the wedge 1718 configured to engage with an annular outer recess 1720 formed in a surface defining the housing aperture 1706.

Without applying hydraulic control to inner plunger 1712 via the opening at the upper end of inner bore 1710, i.e., the default state of LM-mechanism 1602 shown in fig. 17, inner piston spring 1716 biases inner plunger 1712 into position such that wedge 1718 protrudes from the opening formed in outer plunger 1708, engaging outer recess 1720 and effectively locking outer plunger 1708 in position relative to housing 1702. In this default state, any valve actuation motion (whether primary or secondary) applied to push tube 1610 is transferred by LM-mechanism 1602 by outer plunger 1708 being effectively locked in place relative to housing 1702. However, providing sufficiently pressurized hydraulic fluid to the top of the inner plunger 1712 causes the inner plunger 1712 to slide downward, allowing the wedge 1718 to retract and disengage from the outer recess 1720, thereby effectively unlocking the outer plunger 1708 relative to the housing 1702 and allowing the outer plunger 1708 to slide freely within the housing bore 1706, thereby experiencing the bias provided by the outer plunger spring 1709. In this activated state, any valve actuation motion imparted to the housing 1702 by the push rod 1610 will cause the push rod 1610 and the housing 1702 to reciprocate in accordance with the imparted actuation motion while the outer plunger 1708 remains stationary. In this manner, and assuming that the travel of the outer plunger 1708 within the housing bore 1706 is greater than the maximum extent of any applied valve actuation motion, such valve actuation motion is not transferred to the engine valve and is effectively lost such that the corresponding cylinder is deactivated.

In the illustrated embodiment, a biasing spring 1722 is disposed between and in contact with a flange 1724 formed on and extending radially away from the outer surface of the housing 1702 and a stationary contact surface 1650. As shown, the fixed contact surface 1650 is configured to allow the outer plunger 1708 to pass through into contact with a lash adjustment screw 1730 provided on the rocker arm 1620 while still engaging the upper end of the biasing spring 1722. The biasing spring 1722 is provided to manage the inertia of the push rod 1610 and the LM-mechanism 1602 as the push rod 1610 and the LM-mechanism 1602 reciprocate according to the valve actuation motion applied to the push rod 1610 and to ensure that the push rod 1610 remains in contact with the valve actuation motion source (via the roller follower 1612 in this example). The use of fixed contact surface 1650 for this purpose prevents the relatively large bias applied by biasing spring 1722 from being applied to lm+ mechanism 1604 (via rocker 1620) as well and interfering with its operation. In contrast, outer plunger spring 1709 is a relatively light spring that is sufficient to bias outer plunger 1708 into contact with rocker arm 1620/lash adjustment screw 1730, but not so strong as to interfere with the operation of lm+ mechanism 1604.

As is known in the art, a rocker shaft (not shown) may be provided with slots for supplying pressurized hydraulic fluid to hydraulic passages 1736, 1738 formed in the rocker arm 1620. As is also known in the art, the supply of such hydraulic fluid may be controlled under the supervision of the controller 420 through the use of a suitable solenoid (not shown). Hydraulic channels 1736, 1738 direct hydraulic fluid to respective ones of LM-mechanism 1602 and lm+ mechanism 1604. By selectively controlling the flow of hydraulic fluid through the respective channels 1736, 1738, the respective default/activated states of the LM-mechanism 1602 and LM-mechanism 1604 may be similarly controlled.

To this end, the rocker arm 1620 is equipped with a lash adjustment screw 1730 having a first fluid passage 1734 formed therein and terminating in a ball joint 1732, as is known in the art. Ball joint 1732 is formed to engage a complementarily configured upper surface of outer plunger 1708 such that fluid communication between first fluid channel 1734 and inner bore 1710 is provided throughout operation of valve actuation system 1600. First hydraulic channel 1736 is in fluid communication with first fluid channel 1734 such that hydraulic fluid may be selectively provided to LM-mechanism 1602 as a control input, as described above.

Similarly, in this example, the rocker arm 1620 is equipped with a ball joint 1742 having a second fluid passageway 1740 formed therein and communicating with a second hydraulic passageway 1738. Ball joint 1742 is coupled to an adapter or e-pin 1744 having an opening 1746 formed therein such that fluid communication is continuously provided between first fluid passageway 1740 and lm+ mechanism 1604. Again, this continuous fluid communication allows hydraulic fluid to be selectively provided to lm+ mechanism 1604 as a control input, as described above.

Further details of lm+ mechanism 1604 are illustrated with reference to fig. 18. In particular, the lm+ mechanism 1604 includes a lost motion piston 1802 disposed in a closed, centrally formed bore 1804 in a valve bridge 1630. The lost motion piston 1802 includes a piston opening 1803 that provides fluid communication between a first fluid passageway 1740/opening 1746 and a bore 1813 formed in the lost motion piston 1802. The lost motion piston 1802 also includes a check valve assembly including a check disc (or ball) 1802 disposed in the bore 1813, a check spring 1808, a check spring retainer 1810, and a retainer clip 1812. Retainer clip 1812 retains check spring retainer 1810 in a fixed position within bore 1813 such that check spring 1808 continuously biases check disk 1806 into contact with the upper wall of lost motion piston 1802, thereby sealing first fluid passageway 1740 from bore 1813 without the sufficiently pressurized hydraulic fluid provided from first fluid passageway 1740. The lost motion piston 1802 is biased out of the bore 1804 and into contact with the adapter 1744 by a piston spring 1814 disposed in the bore 1804, thereby ensuring continuous contact between the lost motion piston 1802 and the adapter 1744 and, thus, continuous fluid communication between the lost motion piston 1802 and the adapter 1744.

As is known in the art, the lost motion piston 1802 is configured to travel a distance (lost motion lash) that is at least as great as any auxiliary valve actuation motion imparted thereto by the rocker arm 1620. Thus, when hydraulic fluid is not provided to the lost motion piston 1802 and its check valve assembly, the lost motion piston 1802 will retract into the bore 1804 and bottom out in the bore 1804 under the influence of the bias applied to the rocker arm 1620 by the outer plunger 1709 via the outer plunger 1708, and remain bottomed out in the bore 1804 when valve actuation motion is applied to the lost motion piston 1802. Because the amount of lost motion piston 1802 travel is at least as great as any auxiliary valve actuation motion applied thereto, such auxiliary valve actuation motion will be lost in this case, while greater valve actuation motion (such as main event valve actuation) will be transferred through the lost motion piston 1802 to the valve bridge 1630.

However, when sufficiently pressurized hydraulic fluid is provided to the lost motion piston 1802 via the check valve assembly, the hydraulic fluid will flow through the check disk 1806 and into the bore 1804 below the lost motion piston 1802. As is known in the art, this will establish a locking volume of relatively incompressible hydraulic fluid behind the lost motion piston 1802, causing the lost motion piston 1802 to extend out of its bore 1804 and remain in the extended state while valve actuation motion is imparted thereto. Thus, all valve actuation motions (both primary and secondary valve actuation motions) applied to the lost motion piston 1802 will be transferred to the valve bridge 1630.

As described above, the embodiment shown in fig. 16-18 is based on using a pushrod as a rocker front valve train component configured to include an LM-mechanism. However, as also noted above, the rocker front valve train component may be implemented with other valve train components. For example, in one embodiment, an LM-mechanism such as the locking mechanism described above may be implemented in a cam follower, lifter or the like. In this case, the hydraulic fluid required to control the locking mechanism may be provided by means of a suitable channel formed in the push rod or by means of other hydraulic fluid supply techniques known to those skilled in the art.

Claims

1. A valve actuation system for use in an internal combustion engine including a cylinder, at least one engine valve associated with the cylinder, and a valve actuation load path including a valve bridge operatively connected to a rocker arm and a rocker arm front valve train member operatively connected to the rocker arm, the valve actuation system comprising:

a single cam configured to provide both primary and auxiliary valve actuation motions to actuate the at least one engine valve via the valve actuation load path;

A lost motion relief mechanism disposed in the rocker arm front valve train member and configured to transmit at least the main valve actuation motion in a first default operating state and configured to lose the main valve actuation motion and the auxiliary valve actuation motion in a first activated state; and

a lost motion imparting mechanism disposed in the valve bridge and configured to lose the auxiliary valve actuation motion in a second default operating state and configured to transfer the auxiliary valve actuation motion in a second activated state, wherein the lost motion imparting mechanism is disposed in series with the lost motion imparting mechanism in the valve actuation load path.

2. The valve actuation system of claim 1, further comprising:

an engine controller configured to operate the internal combustion engine using the lost motion imparting mechanism and the lost motion imparting mechanism in:

a positive power mode wherein the lost motion imparting means is in the first default operating state and the lost motion imparting means is in the second default operating state, or

A deactivated mode wherein the lost motion imparting means is in the first activated operational state and the lost motion imparting means is in the second default operational state, or

An assist mode wherein the lost motion imparting means is in the first default operating state and the lost motion imparting means is in the second activated operating state.

3. The valve actuation system of claim 1, wherein the auxiliary valve actuation motion is at least one of an exhaust valve early opening valve actuation motion, an intake valve late closing valve actuation motion, or an engine braking valve actuation motion.

4. A valve actuation system according to claim 1, wherein the lost motion relief mechanism is a hydraulically controlled mechanical locking mechanism.

5. A valve actuation system according to claim 1, wherein the lost motion addition mechanism is a hydraulically controlled actuator.

6. The valve actuation system of claim 5, wherein the lost motion addition mechanism further comprises a hydraulically controlled check valve that provides hydraulic fluid to the hydraulically controlled actuator.

7. The valve actuation system of claim 1, further comprising:

a first spring configured to bias the rocker arm front member toward the single cam.

8. The valvetrain actuation system of claim 7, wherein the rocker front component comprises a pushrod, and wherein the first spring is operatively connected to the pushrod.

9. The valve actuation system of claim 1, further comprising:

a second spring configured to bias the rocker arm toward the single cam.

10. The valve actuation system of claim 7, wherein the second spring is disposed in the lost motion addition mechanism.

11. A method of operating an internal combustion engine including a cylinder and at least one engine valve associated with the cylinder, and further including a single cam configured to provide a primary valve actuation motion and an auxiliary valve actuation motion to actuate the at least one engine valve via a valve actuation load path including a valve bridge operatively connected to a rocker arm and a rocker arm front valve train member operatively connected to the rocker arm, the method comprising:

providing a lost motion relief mechanism disposed in the rocker arm front valve train component and configured to transmit at least the main valve actuation motion in a first default operating state and configured to lose the main valve actuation motion and the auxiliary valve actuation motion in a first activated state;

Providing a lost motion imparting mechanism disposed in the valve bridge and configured to lose the auxiliary valve actuation motion in a second default operating state and configured to transfer the auxiliary valve actuation motion in a second activated state, wherein the lost motion imparting mechanism is disposed in series with the lost motion imparting mechanism in the valve actuation load path; and

operating the internal combustion engine in: