阅读说明：本技术 发动机阀门致动系统中的间隙调节器控制 (Lash adjuster control in engine valve actuation systems ) 是由 J·D·巴尔特鲁基 G·S·罗伯茨 M·亚历山德鲁 J·曼德尔 于 2020-05-07 设计创作，主要内容包括：用于内燃机中的阀门致动的系统为液压间隙调节器和阀门致动阀门机构组件提供配置,所述配置尤其适于防止包含II型阀门机构架构的专用凸轮环境中的HLA顶升。在一个实施方案中,可包括与主事件阀门机构相关联的行程受限的弹簧偏置活塞的间隙调节器加载组件将所述间隙调节器保持在恒定压缩力下以防止顶升。(A system for valve actuation in an internal combustion engine provides a configuration for a hydraulic lash adjuster and a valve actuated valvetrain assembly that is particularly adapted to prevent HLA lift-up in a dedicated cam environment that includes a type II valvetrain architecture. In one embodiment, a lash adjuster loading assembly, which may include a limited travel spring biased piston associated with a primary event valve mechanism, maintains the lash adjuster under a constant compressive force to prevent jacking.)

1. An apparatus for actuating at least one of two or more engine valves in an internal combustion engine, comprising:

a primary event motion source;

a main event valve mechanism for transmitting motion from the main event motion source to the valve through a first load path;

a secondary event motion source separate from the primary event motion source;

an auxiliary event valve mechanism for transmitting motion from the auxiliary motion source to one or more engine valves through a second loading path;

a lash adjuster cooperatively associated with the first load path;

a lash adjuster loading assembly cooperatively associated with the first loading path for preventing over-extension of the lash adjuster.

2. The apparatus of claim 1, wherein the lash adjuster loading assembly includes a biasing assembly, and wherein the source of primary event motion includes a primary event cam having a primary event cam surface defining a primary event motion in the primary event valve mechanism and a preload cam surface defining a preload motion in the primary event valve mechanism, wherein the lash adjuster loading assembly applies a biasing force to the lash adjuster.

3. The apparatus of claim 2, wherein the auxiliary event motion source comprises an auxiliary event cam having an auxiliary event cam surface defining at least one auxiliary valve event, and wherein the preload motion in the main event valve mechanism occurs during at least one auxiliary valve event.

4. The apparatus of claim 3, wherein the primary event motion source is configured to cause the preload motion in the lash adjuster loading assembly for the duration of at least one secondary event.

5. The apparatus of claim 1, wherein a main event loading path includes a valve bridge, and wherein the lash adjuster loading assembly includes a piston cooperatively associated with the valve bridge.

6. The apparatus of claim 1, wherein the lash adjuster loading assembly includes a travel limit assembly for limiting travel of the lash adjuster loading assembly in a lash adjuster compression direction.

7. The apparatus of claim 1, wherein the lash adjuster loading assembly includes a travel limit assembly for limiting the travel of the lash adjuster loading assembly in a lash adjuster extension direction.

8. The apparatus of claim 5, wherein the lash adjuster loading assembly has a travel limit assembly including an annular shoulder on the piston.

9. The apparatus of claim 8, wherein the stroke of the lash adjuster loading assembly is substantially equal to a translational distance between a lash adjuster refill period on the primary event motion source and primary event open and closed positions.

10. The apparatus of claim 1, wherein the master event motion source includes a master event cam surface defining a master event motion in the master event valve mechanism, and a lash adjuster refill cam surface defining a lash adjuster refill motion in the master event valve mechanism that permits refilling of the lash adjuster.

11. The apparatus of claim 10, wherein the master event cam includes a preload cam surface that defines a preload movement in the master event valve mechanism, wherein the lash adjuster loading assembly applies a biasing force to the lash adjuster.

12. The apparatus of claim 11, wherein an auxiliary motion source includes an auxiliary cam having an auxiliary cam surface defining at least one auxiliary event, wherein the primary and auxiliary motion sources cooperate such that the lash adjuster refill motion begins prior to the at least one auxiliary event during at least one operating cycle of the internal combustion engine.

13. The apparatus of claim 11, wherein the auxiliary motion source includes an auxiliary cam having an auxiliary cam surface defining at least one auxiliary event, wherein the primary and auxiliary motion sources cooperate such that a lash adjuster preload motion is applied during the at least one auxiliary event during at least one operating cycle of the internal combustion engine.

14. The apparatus of claim 1, wherein the lash adjuster loading assembly comprises:

a piston cooperatively associated with the valve bridge and a piston biasing assembly for biasing the piston in a lash adjuster compression direction along which the piston tends to compress the lash adjuster;

a first limiting assembly for limiting the travel of the piston in the lash adjuster compression direction; and

a second limiting assembly for limiting the travel of the piston in a lash adjuster extension direction along which the piston tends to permit the lash adjuster to extend;

wherein the primary event motion source includes a primary event cam having a primary event cam surface defining a secondary sub-circular lash adjuster refill period that permits refilling of the lash adjusters;

wherein the second limiting assembly limits the travel of the piston in the lash adjuster extension direction to a distance substantially equal to the translational distance between the lash adjuster refill period on the cam and a primary event open and closed position.

15. The apparatus of claim 1, wherein the primary event loading path includes an end pivot rocker for acting on at least one engine valve, wherein the lash adjuster loading assembly includes a piston cooperatively associated with the end pivot rocker and a piston biasing assembly for biasing the piston in a lash adjuster compression direction in which the piston tends to compress the lash adjuster.

16. The apparatus of claim 15, wherein the lash adjuster loading assembly includes a first limiting assembly for limiting travel of the piston in a compression direction of the lash adjuster.

17. The apparatus of claim 15, wherein the lash adjuster loading assembly has a travel limit loading assembly including a first surface on an annular shoulder on the piston, and wherein the second limiting assembly includes a second surface on the annular shoulder on the piston.

18. The apparatus of claim 17, wherein the stroke of the lash adjuster loading assembly is substantially equal to the translational distance between the lash adjuster refill period and a primary event open and closed position on the primary event motion source.

19. The apparatus of claim 1, wherein the primary event loading path includes an end pivot rocker for acting on at least one engine valve, and wherein the lash adjuster loading assembly is located in the end pivot rocker.

20. The apparatus of claim 19, wherein the lash adjuster loading assembly comprises a first limiting assembly for limiting travel of the lash adjuster loading assembly in the lash adjuster compression direction, and wherein the travel of the lash adjuster loading assembly is substantially equal to the translational distance between a lash adjuster refill period and a primary event open and closed position on the primary event motion source.

21. The apparatus of claim 1, wherein the lash adjuster loading assembly includes an adjustable travel limit assembly.

22. The apparatus of claim 21, wherein the adjustable travel limit assembly is a threaded element adapted to permit a user to adjust the travel of the lash adjuster loading assembly.

Technical Field

The present disclosure relates generally to systems for actuating valves in internal combustion engines. More specifically, the present disclosure relates to engine valve actuation systems that include features for controlling and preventing over-extension of lash adjusters.

Background

Internal combustion engines require valve actuation systems to control the flow of combustible components (typically fuel and air) to one or more combustion chambers during operation. Such systems control the movement and timing of intake and exhaust valves during engine operation. In the positive power mode, an intake valve is opened to allow fuel and air to enter the cylinder for combustion, and an exhaust valve is subsequently opened to allow products of combustion to escape the cylinder. This operation is commonly referred to as "positive power" operation of the engine, and the motion imparted to the valve during positive power operation is commonly referred to as "primary event" valve actuation motion. Auxiliary valve actuation motions, such as those that produce engine braking (power absorption), may be achieved using "auxiliary" events that are transmitted to one or more of the engine valves.

During the primary event positive power mode of operation, valve movement is typically controlled by one or more rotating cams as a source of motion. Cam followers, pushrods, rocker arms and other elements disposed in the valve train effect a direct transfer of motion from the cam surfaces to the valves. The use of a valve bridge may transfer motion from a single upstream valve mechanism to multiple valves. For auxiliary events, "lost motion" devices may be used in the valve train to facilitate auxiliary event valve movement. Lost motion devices refer to a class of technical solutions in which the valve movement is modified compared to the movement that would otherwise occur due to the individual actuation of the respective cam surfaces. The lost motion device may comprise a device whose length, stiffness or compressibility is varied and controlled so as to facilitate the selective occurrence of a secondary event in addition to or instead of the primary event operation of the valve. The assist event may also be facilitated by a dedicated cam system, wherein separate assist or brake cams and valve mechanisms may be used to transfer assist motion to one or more valves to facilitate selective occurrence of the assist event.

Lash adjustment features are typically provided on the valve actuation system to facilitate elimination of lash, which is an excess clearance between valve train components that may generate excessive noise, vibration, impact forces, and wear. For example, during a braking event, substantial clearance may be introduced into the engine valve mechanism. Lash adjusters, typically hydraulic lash adjusters ("HLA"), may include mechanical components that cooperate in a lash take-up mode to expand under hydraulic pressure during one portion of the valve cycle, typically when the valve mechanism is at zero lift or unload, and then employ a hydraulic "lock-in" or incompressible mode during the valve open portion of the valve cycle, typically when the valve mechanism is at high load, such as during a major event actuation. One challenge associated with using an HLA is preventing over-extension or "lift-up" of the HLA, which can occur when the HLA is permitted to extend far in a tensioned mode and becomes hydraulically locked in an over-extended position. This may produce excessive valve train forces and other undesirable results. Therefore, measures have been taken in the prior art to prevent jacking by maintaining a suitable load on the HLA, or to limit HLA extension.

Lost motion cam systems typically use at least one cam having differently contoured lift segments on the same cam lobe to impart motion for respective primary and one or more secondary events. Separate lost motion mechanisms, such as pistons or actuators, located in the valve mechanism are used to activate or deactivate these differently contoured lift segments. Example auxiliary events include engine braking, Early Exhaust Valve Opening (EEVO), or Late Intake Valve Closing (LIVC) lift events, and may be delivered to one or more valves in a valve set (i.e., two exhaust valves for respective cylinders). Lost motion assisted valve lift systems, such as lost motion braking systems, may use a single rocker associated with a lost motion cam and a valve bridge associated with the rocker for actuating two engine valves in a primary event motion. The auxiliary valve lift or braking motion on one of the valves is facilitated by an auxiliary valve lift or braking actuator, which is a lost motion device, receivable in the rocker and selectively transferrable to the valve by means of a bridge pin disposed in the bridge and enabling independent motion relative to the bridge. An auxiliary valve lift or braking actuator is selectively activated and deactivated such that an auxiliary or braking event lift profile segment or lobe on the lost motion cam produces an auxiliary or braking motion on the valve only when an auxiliary event, such as engine braking, is required.

In another aspect, a dedicated cam valve actuation system may utilize a dedicated auxiliary motion source and a dedicated auxiliary valve train assembly, at least some of which are separate from the primary event motion source and the valve train to facilitate auxiliary events. For example, the subject matter of U.S. patent No. 8,851,048 to meisterick, which describes a dedicated cam system in which the main event motion is transferred to a valve bridge and ultimately to two engine valves cooperating therewith, is incorporated herein by reference in its entirety. The auxiliary motion of one of the engine valves may be facilitated by a dedicated auxiliary motion source (cam) that cooperates with an auxiliary rocker to transmit auxiliary motion by a bridge pin in the valve bridge and ultimately to transmit auxiliary motion to one of the engine valves to cause an auxiliary event, such as a braking event.

The dedicated cam valve actuation system may comprise what is commonly referred to as a "type II" valve train architecture, as described in the society of automotive Engineers Technical Paper (SAE Technical Paper)2007-01-1285 entitled "Design and Development of a 2-Step Rocker Arm" for 2-Step Rocker Arm. These architectures may include a rocker arm that pivots at one end about a fulcrum, with an opposite end engaging a valve or valve train component with which the valve cooperates. The primary event motion may be transmitted at a central or intermediate position on the rocker arm by a primary event motion source, such as a primary event cam. These systems may utilize lash adjusters. In a type II architecture, the lash adjuster may not be disposed directly in the main event load path, but may instead act as a reaction force to the main event load, and may be disposed in a position that adjusts the lash, such as by relative movement of the rocker pivot.

In engine environments where assist motion is facilitated by a dedicated assist motion source, such as a dedicated cam and rocker or bolt-on master/slave brake, which may be separate from the primary event motion source, challenges to prevent lash adjusters from over-extending may be presented in the type II architectures described above and in other environments.

It would therefore be advantageous to provide a system that addresses the foregoing and other shortcomings in the prior art.

Disclosure of Invention

In response to the above challenges, the present disclosure provides various embodiments of valve actuation systems having features for controlling and preventing over-extension of lash adjusters that may be applied in lost motion and dedicated cam-assisted motion systems. More specifically, the present disclosure describes systems in which a lash adjuster loading assembly may cooperate, directly or indirectly, with a lash adjuster through other valve train components to prevent over-extension of the lash adjuster. The lash adjuster loading assembly may be disposed in or cooperate with various elements in the valve mechanism, and may exert or facilitate the application of a biasing force on the lash adjuster during engine cycles when the lash adjuster may otherwise be susceptible to over-extension. Thus, in an integrated lost motion and dedicated auxiliary cam/valve train engine environment, the described system facilitates lash adjuster operation and reduces the risk of lash adjuster over-extension or "lift-up".

According to one aspect, a system for actuating at least one of two or more engine valves in an internal combustion engine may comprise: a primary event motion source; a master event valve mechanism for transmitting motion from a master event motion source to the at least one valve through a master event load path; a secondary event motion source; an auxiliary event valve mechanism for transmitting auxiliary motion to the at least one valve; a lash adjuster cooperating with the primary event loading path; and a lash adjuster loading assembly cooperating with the lash adjuster.

According to another aspect of the present disclosure, an apparatus or system for actuating at least one of two or more engine valves that may be particularly suited to a dedicated cam system in an internal combustion engine may include: a primary event motion source; a master event valve mechanism for transmitting motion from a master event motion source to the valve bridge through a first loading path; an auxiliary event motion source separate from the primary event motion source; an auxiliary event valve mechanism for transmitting motion from an auxiliary motion source to one of the two or more engine valves through a second loading path; a lash adjuster disposed in the first loading path; and a lash adjuster loading assembly disposed in the first loading path for preventing over-extension of the lash adjuster. The lash adjuster loading assembly may include a limited travel spring loaded piston disposed in a valve bridge or other main event valve mechanism assembly, such as a rocker arm, and may have a fixed travel defined by upper and lower limits and a biasing assembly, such as a compression spring, for biasing the piston against the lash adjuster to control lash adjuster extension during an assist event. The lash adjuster loading assembly may present: a lash adjuster refill state that permits refilling of the lash adjuster; a preload state in which the lash adjuster loading assembly applies a biasing force to the lash adjuster; and a main event state, wherein the lash adjuster loading assembly transmits a high load from the main event motion source to the valve bridge. In addition to the primary event lift surface, the primary event motion source may also include a preload cam surface and a lash adjuster refill cam surface such that the lash adjuster loading assembly assumes lash adjuster refill and preload states during operation. In an operating environment that may include separate primary and secondary sources of motion, the lash adjuster loading assembly may thus provide control over lash adjuster refill and prevent lash adjuster overextension.

According to another aspect of the present disclosure, an apparatus or system for actuating at least one of two or more engine valves that may be particularly suited for a dedicated cam system in a type II valvetrain architecture in an internal combustion engine. The system may include: a primary event motion source; a master event valve mechanism for transmitting motion from a master event motion source to the valve bridge through a first loading path; an auxiliary event motion source separate from the primary event motion source; an auxiliary event valve mechanism for transmitting motion from an auxiliary motion source to the engine valve through a second loading path; a lash adjuster; and a lash adjuster loading assembly cooperating with the first loading path for preventing over-extension of the lash adjuster. The lash adjuster loading assembly may include a limited travel spring-loaded piston or spring-loaded lever arm disposed in or cooperatively associated with an end pivoting rocker arm, pivot shaft, or another valve train assembly. The spring biased piston may have a fixed stroke defined by upper and lower limits and a biasing assembly, such as a compression spring, for biasing the piston against the lash adjuster to control lash adjuster extension during an assist event. The lash adjuster loading assembly may present: a lash adjuster refill state that permits refilling of the lash adjuster; a preload state in which the lash adjuster loading assembly applies a biasing force to the lash adjuster; and a main event state, wherein the lash adjuster loading assembly transmits a high load from the main event motion source to the valve bridge. In addition to the primary event lift surface, the primary event motion source may also include a preload cam surface and a lash adjuster refill cam surface such that the lash adjuster loading assembly assumes lash adjuster refill and preload states during operation. In a type II operating environment, which may include separate primary event and auxiliary motion sources, the lash adjuster loading assembly may thus provide control over lash adjuster refill and prevent lash adjuster over-extension.

Other aspects and advantages of the disclosure will be apparent to those of ordinary skill in the art from the following detailed description, and the above aspects should not be taken as being exhaustive or limiting. The foregoing general description and the following detailed description are intended to provide examples of inventive aspects of the present disclosure, and should not be construed to limit or restrict the scope as defined in the appended claims in any way.

Drawings

The above and other attendant advantages and features of the present invention will become apparent from the following detailed description and the accompanying drawings, wherein like reference numerals refer to like elements throughout. It will be understood that the description and examples are intended as illustrative examples according to aspects of the present disclosure, and are not intended to limit the scope of the invention, which is set forth in the following claims.

Fig. 1 is a schematic block diagram of a valve actuation system according to aspects of the present disclosure.

Fig. 2 is a schematic example embodiment of a valve actuation system according to the present disclosure and the system of fig. 1.

Figure 3 is a graphical representation of a lost motion cam profile.

Fig. 4A is a cross-section showing details of another embodiment of a lash adjuster and lash adjuster loading assembly in an improved configuration compared to the configuration of fig. 1 and 2. Fig. 4B is a cross-section showing details of yet another implementation of a lash adjuster and lash adjuster loading assembly in an improved configuration compared to fig. 4A.

Fig. 5 is a schematic block diagram of a valve actuation system according to other aspects of the present disclosure.

Fig. 6 is a schematic example embodiment of a valve actuation system according to the present disclosure and the system of fig. 5.

Fig. 7 is a schematic block diagram of a valve actuation system including a dedicated auxiliary motion source according to another aspect of the present disclosure.

Fig. 8 is a perspective view of an example valve actuation assembly including a lash adjuster loading assembly that may be used in a dedicated auxiliary motion source system according to aspects of the present disclosure.

Fig. 9.1 is a cross-section showing the valve actuation system of fig. 8 including a lash adjuster loading component shown at the highest position permitting refilling of the lash adjuster.

Fig. 9.2 is a cross-section showing the valve actuation system of fig. 8 including a lash adjuster loading assembly shown in a preloaded position in which the lash adjuster is subjected to a biasing force transmitted from the lash adjuster loading assembly.

Fig. 9.3 is a cross-section showing the valve actuation system of fig. 8 including the lash adjuster loading assembly shown in the lowermost position with the primary event motion transmitted to the valve bridge.

FIG. 10 is a graphical representation of example operation of the valve actuation system of FIG. 8 showing respective main and auxiliary event (braking) valve lifts as a function of crankshaft angle.

FIG. 11 is a detail of an example cam surface.

Fig. 12 is a schematic representation of a valve actuation system 1200 according to aspects of the present disclosure with respect to a type II valve architecture.

FIG. 13 is a schematic representation of a first example lash adjuster loading assembly arrangement in a type II valve architecture.

FIG. 14 is a schematic representation of a second example lash adjuster loading assembly arrangement in a type II valve architecture.

FIG. 15 is a schematic representation of a third example lash adjuster loading assembly arrangement in a type II valve architecture.

FIG. 16 is a schematic representation of a fourth example lash adjuster loading assembly arrangement in a type II valve architecture.

FIG. 17 is a schematic representation of a fifth example lash adjuster loading assembly arrangement in a type II valve architecture.

Detailed Description

The functionality of the components in an example valve actuation system according to aspects of the present disclosure will first be generally explained, and then more detailed example implementations will be described. These general and example descriptions are intended to be illustrative, and not exhaustive or limiting with respect to the invention reflected in this disclosure.

Fig. 1 is a schematic block diagram of a valve actuation system 100 according to aspects of the present disclosure. The valve actuation motion source 104 may include a primary event motion source assembly 104.1 and a secondary event motion source assembly 104.2. For example, the valve actuation motion source 104 may include a cam and camshaft drive assembly. The primary event motion source assembly 104.1 may include a primary event cam lobe on a cam and the secondary event motion source 104.2 may include one or more secondary or lost motion cam lobes on the cam.

Motion from the motion sources 104.1 and 104.2 is transmitted to the valve mechanism 102, which may include a main event moving valve mechanism assembly 102.1 and an auxiliary event moving valve mechanism assembly 102.2. It will be appreciated that the valve train moving assemblies 102.1 and 102.2 may comprise common elements. For example, the main event moving valve mechanism assembly 102.1 and the auxiliary event moving valve mechanism assembly 102.2 may utilize a common cam follower and a common rocker arm. The main event valve mechanism assembly 102.1 may include a lash adjuster 102.11, which may be a hydraulic lash adjuster.

The lash adjuster 102.11 may be disposed in one of the primary event motion valvetrain components 102.1, in which case the component may act as a housing for the lash adjuster. The lost motion assembly 102.21 may be included in the auxiliary event motion valve mechanism component 102.2, in which case the component may act as a housing for the lost motion assembly.

The valve mechanism 102 and its components cooperate with a valve bridge 106, which can transfer motion to the engine valves 108.1 and 108.2. In accordance with an aspect of the present disclosure, a lash adjuster loading assembly 106.1 may be housed in the valve bridge 106 and may cooperate with the lash adjuster 102.11 to maintain the lash adjuster in a loaded state (i.e., applying a force opposite the direction of extension of the lash adjuster). The valve bridge 106 may also house an auxiliary motion bridge component 106.2, which may be a component that permits motion to be transmitted from the lost motion assembly 102.21 to the brake engine valve 108.2 without transferring motion to the valve bridge 106.

Fig. 2 is a schematic illustration of a valve actuation system 200 in an embodiment according to the functional block diagram of fig. 1. The source of valve actuation motion may be a lost motion cam 210 that includes a main event lobe 212 and auxiliary event lobes 214 and 216. The auxiliary event may include, but is not limited to, a braking event, such as Compression Release (CR) braking, EEVO, LIVC, or Exhaust Gas Recirculation (EGR). Referring additionally to fig. 3, additional details of the lost motion cam are illustrated. Example profiles for the lost motion cam may include a main event lobe profile 312, and auxiliary event lobe profiles 314 and 316. During each full rotation of the lost motion cam 210, a corresponding motion is transmitted to the rocker arm 220. As will be further explained, such motion may be selectively further transmitted to other valve train components to achieve a desired motion on the engine valve during primary and secondary events.

The rocker arm 220 contains a cam follower 222 and is mounted for pivotal or rotational movement about a rocker shaft (not shown) that extends through a rocker journal 224. The rocker arm 220 may include a first bore 226 for receiving the inboard valve actuator 240 and a second bore 228 for receiving the HLA 250. As will be recognized by those skilled in the art, the rocker arm 220 will typically include a fluid passage 229 (represented schematically) therein for constantly supplying pressurized hydraulic fluid from the rocker arm journal 224 internal surface to the second bore 228 and HLA. The drain port 230 may allow hydraulic fluid to flow out of the piston bore 228. Hydraulic fluid is typically supplied through a rocker shaft (not shown). As known in the art, HLA can be employed passively: a lash adjustment mode in which the HLA is filled with pressurized hydraulic fluid through ported passages in the rocker arm such that the HLA expands to take up lash in the valve mechanism; and a hydraulic "lock-out" mode in which the HLA is hydraulically isolated, hydraulic fluid within the HLA being checked to prevent egress and thus being incompressible, thereby acting substantially as a solid component. The HLA may support a pivot 252, and a cooperating base or foot 254 that may pivot or rotate relative to the pivot 252 to effect, to some extent, pivotal movement of the valve bridge 260. The passage 227 may contain a control valve for preventing oil from flowing back from the actuator piston circuit when a load is applied.

In this embodiment, according to an inventive aspect of the present disclosure, the HLA is subjected to a stroke limited compression force provided by a lash adjuster loading assembly in the form of a stroke limited piston 270 disposed in a bore 262 in a valve bridge 260. The lash adjuster loading assembly is biased in such a way as to compress the HLA, but is also limited by a travel limiter 276 to prevent over-compression of the HLA. A compression spring 272 is disposed in an internal bore 274 of the piston 270 in engagement with an end wall 275 thereof. The opposite end of the compression spring 272 engages the bottom wall 263 of the valve bridge bore 262 and thus provides an upward force on the piston 270. The travel limiter 276 may be a snap ring or retaining ring secured to the valve bridge 260 that may engage and prevent upward travel of a shoulder 277 of the piston 270 and thus limit upward movement of the piston 270 relative to the valve bridge 260.

The main event valve motion may be communicated from the motion source (lost motion cam) 210 to both engine valves 280, 282 along a first load path. More specifically, the first loading path may be defined by cam follower 222, rocker arm 220, HLA 250, and valve bridge 260. The first load path from the motion source to the engine valve may thus include the cam follower 222, the rocker arm 220, and the valve train components of the HLA, including the pivot 252 and the base 254.

Auxiliary motion, such as braking motion, may be transmitted to one of the engine valves 282 through a second loading path that includes the inboard valve actuator 240. An auxiliary motion bridge assembly, in this case in the form of a bridge pin 266, may transmit motion separate from the motion of the valve bridge 260 from the inboard valve actuator 240 to the brake valve 282. The inboard valve actuator 240 is a lost motion assembly or device that can be selectively hydraulically activated and deactivated at appropriate times during an engine cycle through the switched hydraulic passage 227 to effect an auxiliary event, such as engine braking. The switched hydraulic passage 227 provides hydraulic fluid to the piston bore 226, typically from an axially extending passage (not shown) in the rocker shaft that provides hydraulic fluid to a plurality of valve rockers mounted on the shaft. In the activated state, the pistons 242 forming the inboard valve actuators 240 may extend out of the corresponding piston bores 226 and remain in an incompressible or solid extended state, and thus transmit motion. In the deactivated state, the actuator piston 242 of the inboard valve actuator may be permitted to retract into its bore 226, losing any motion transmitted from the rocker arm and thus being in a compressible or motion absorbing state. As will be appreciated, in this embodiment, the second loading path from the motion source to the brake valve 282 is defined by the auxiliary event motion valve mechanism assembly (cam follower 222, rocker arm 220, inboard valve actuator 240) and the bridge pin 266.

As will be appreciated, the above-described embodiments provide separate loading paths for the main event valve actuation and the auxiliary event (brake) valve actuation that adjust the clearance, according to inventive aspects of the present disclosure. In operation, when engine braking is applied, the inboard valve actuator 240 will extend to transfer motion only to the inboard valve 282, recognizing that the rocker arm 220 will have motion transferred by one of the auxiliary lobes on the lost motion cam at substantially the same time. As the rocker moves from the inner base circle of the cam to the base circle defined by the auxiliary lobe, the rocker 220 will make more travel at the HLA that is disposed farther from the rocker arm pivot (the center of the rocker shaft) than the inboard valve actuator. The lash adjuster loading assembly (limited travel bridge piston 270) will therefore create a compressive load on the HLA and prevent any over-extension or jacking as the inner side of the bridge 260 (right side in fig. 2) pivots downward in conjunction with the downward movement of the bridge pin 266, which moves under force from the inner valve actuator 240.

As shown in fig. 2, there is a gap between the bottom surface of the piston 270 and the bottom wall 263 of the valve bridge bore. This clearance defines a lost motion travel distance 279 for the piston lash adjuster loading assembly. The lost motion travel distance may be selected to ensure that the secondary event motion of the rocker arm 220 is "lost" and does not cause undesirable motion of the valve bridge 260 and the engine valves 280 and 282. That is, in a braking event, the valve 282 will be actuated under the motion from the braking lobe in the cam 210 transmitted by the inboard valve actuator, while the rocker arm 220 and HLA motion will be "lost" by the stroke limited piston 270 and not transmitted to the valve bridge or engine valve 280 until the piston 270 bottoms out against the bottom wall 263 of the valve bridge bore and the resulting movement of the valve bridge and opening of the two valves for the main event movement. The lost motion gap is designed to "lose" the motion that would otherwise be generated by the auxiliary event cam lift profile, but not the main event motion.

Fig. 4A illustrates an alternative arrangement for a lash adjuster loading assembly and HLA, according to aspects of the present disclosure. In this embodiment, the features of the stroke limited piston are integrated into the rocker arm rather than the valve bridge (as in fig. 2). This arrangement permits valve braking motion to be achieved through the same loading path in which the lash adjuster is disposed, and thus can be used to eliminate the need for a separate valve actuator (inboard valve actuator) for facilitating valve braking motion. In this regard, the loading path in which the lash adjuster is disposed (first loading path) and the loading path in which the auxiliary valve movement actuator is disposed (second loading path) are the same. The rocker arm 420 may include a bore 428 for receiving a stroke limited piston 470, which in turn includes a bore 471 for receiving an HLA for supporting the HLA therein. The travel limiter 476 limits travel (in a downward direction) of the piston 470. A compression spring 472 is disposed in the rocker arm bore 428 and engages a shoulder 477 on the piston 470 at one end and a bottom bore wall 429 at the other end, providing a compressive force on the HLA against a bridge (not shown) that engages the pivot 452 and the base 454. As in the configuration illustrated in fig. 2, the piston 470 is configured to define a chamber 430 having a bore 428 and a bottom wall 429 and to provide a lost motion travel distance 479 to prevent the transmission of an auxiliary valve event through the first loading path. The piston 470 may include an annular region 472 that permits hydraulic fluid to flow from the constant (continuous) supply passage 421 in the rocker arm 420 to the HLA-receiving aperture 471 and the HLA. The switched fluid supply passage 424 may provide fluid to the aperture 428 under the control of the control valve 425. Fluid from the HLA is prevented from flowing out of the bore 429 by the tight clearance between the piston 470 and the bore 428. A drain port 473 may be provided in the piston 470 and a check valve 474 may be provided in the piston to facilitate one-way flow to the HLA. In operation, when it is desired to activate the auxiliary motion valve, the hydraulic fluid control valve 425 may be switched to provide hydraulic pressure (oil) to the chamber 430 and extend the lash adjuster loading assembly (piston 470) and lock it in the extended position, thereby initiating the valve braking motion. When the control valve 425 is closed, the lash adjuster check valve becomes the "closed" position and the chamber 430 may be vented by delivering fluid through the vent port 472 and check valve 474 to permit the brake to be deactivated. As will be appreciated, this configuration permits braking motion through the same loading path in which the lash adjuster is disposed. This can be used to eliminate the need for a separate valve actuator, such as the inboard valve actuator described above, to achieve auxiliary valve movement.

Fig. 4B illustrates an alternative arrangement for a lash adjuster loading assembly and HLA, according to aspects of the present disclosure. In this embodiment, the features of the stroke limited piston are integrated into the rocker arm rather than the valve bridge (as in fig. 2). This arrangement permits the second loading path in which the lash adjuster is disposed to effect the valve braking motion, and thus may be used in implementations that utilize a separate valve actuator for facilitating the valve braking motion, such as the inboard valve actuator described above. The rocker arm 420 may include a bore 428 for receiving a stroke limited piston 470, which in turn includes a bore 471 for receiving an HLA for supporting the HLA therein. The travel limiter 476 limits travel (in a downward direction) of the piston 470. A compression spring 472 is disposed in the rocker arm bore 428 and engages a shoulder 477 on the piston 470 at one end and a bottom bore wall 429 at the other end, providing a compressive force on the HLA against a bridge (not shown) that engages the pivot 452 and the base 454. As in the configuration illustrated in fig. 2, the piston 470 is configured to define a chamber 430 having a bore 428 and a bottom wall 429 and to provide a lost motion travel distance 479 to prevent the transmission of an auxiliary valve event through the first loading path. The piston 470 may include an annular region 472 that permits hydraulic fluid to flow from the constant (continuous) supply passage 421 in the rocker arm 420 to the HLA-receiving aperture 471 and the HLA. Fluid from the HLA is prevented from flowing out of the bore 429 by the tight clearance between the piston 470 and the bore 428. In operation, hydraulic fluid is supplied to the lash adjusters through the continuous supply passage 421 and the annular region 472. The chamber 430 may not have any hydraulic fluid, i.e. be occupied by air. The discharge 427 may discharge air to the outside environment. Air from the lash adjuster may be discharged to the chamber 430 through the discharge port 473. As will be appreciated, this configuration may be used in an engine environment, eliminating the need to utilize a separate valve actuator, such as the inboard valve actuator described above, to effect auxiliary valve movement.

As will be recognized by those skilled in the art, the embodiments described above with respect to fig. 2 and 4B may be used in an environment where auxiliary motion is applied to at least one valve, where the auxiliary motion source is separate from the primary event motion source. For example, in an auxiliary motion system, where auxiliary motion is facilitated by a dedicated rocker arm or bolt-fixed master-slave brake, or any auxiliary motion source that is not necessarily a lost motion master event motion source. The movement of the primary event rocker arm may be synchronized with the secondary motion event such that the compression spring (e.g., 274 in fig. 2 or 472 in fig. 4B) remains at least partially compressed during these events, rather than fully compressing to a point that provides lift at positive power or during the secondary lift event. This prevents the lash adjuster from stretching during any secondary motion event by preloading the lash adjuster with primary event motion.

Fig. 5 is a schematic block diagram of a valve actuation system 500 according to other aspects of the present disclosure. This system is similar to the system described above with respect to fig. 1. However, some differences relate to the position of the lash adjuster. More specifically, a lash adjuster 506.3 may be disposed in the valve bridge 506 along with a lash adjuster loading assembly 506.1. The valve actuation motion source 504 may include a primary event motion source assembly 504.1 and a secondary event motion source assembly 504.2. Motion from the motion sources 504.1 and 504.2 is transmitted to the valve train 502, which may include a main event moving valve train assembly 502.1 and an auxiliary event moving valve train assembly 502.2. These sets of components may include common elements, such as a single rocker arm. The lost motion assembly 502.21 may be included in the auxiliary event motion valve mechanism component 502.2, in which case the component may act as a housing for the lost motion assembly.

The valve train assembly transmits motion to the valve bridge 506 and/or components thereof. A lash adjuster 506.3 and a lash adjuster loading assembly 506.1 may be disposed in the valve bridge 506. The auxiliary motion bridge component 506.2 may be provided as a component of the valve bridge 506, and may include, for example, a bridge pin that permits motion to be communicated from the lost motion assembly 502.21 to the brake engine valve 508.2 without transferring motion to the valve bridge 506. According to an aspect of the present disclosure, a lash adjuster loading assembly 506.1 is used to maintain the lash adjuster 506.3 in a loaded state (i.e., applying a force opposite the direction of extension of the lash adjuster).

Fig. 6 is a schematic illustration of a valve actuation system 600 in an embodiment according to the functional block diagram of fig. 5. The rocker arm 620 is driven by the lost motion cam 610 and includes an inboard valve actuator 640 that cooperates with a bridge pin 666 to transfer motion to a brake valve 682. The rocker arm 620 also includes a stationary (solid) extension pivot 652 extending from the end of the rocker arm and having a swivel or ball. Pivot 652 cooperates with an e-leg base 654 that engages HLA base 655 to transfer motion to the HLA/bridge assembly as further described. Hydraulic fluid passage 622 may extend from the journal through pivot 652, base 654, and rocker arm to hydraulically actuated components, such as inboard valve actuator 640 and HLA 650.

A stroke limited piston 670 is mounted within a bore 662 in the valve bridge 660. A shoulder 677 may be provided on the upper surface of the piston for engaging a travel limiter 676 secured to the bridge 660. The plunger 670 also includes an inner annular wall 678 that is configured to receive components of the HLA. The annular wall 678 further defines an annular recess 680 that partially houses a compression spring 672 to bias the piston in an upward direction. The compression spring 672 engages a bottom wall 663 of the bridge bore 662 and an upper wall defined within the annular recess 680 of the piston 670. A lost motion gap with void 679 is defined between the bottom end of piston 670 and bridge bottom wall 663.

In operation, during a main event (positive power) motion of the engine, the rocker arm 620 transfers the main event motion from the lost motion cam 610 to the valve bridge through the pivot 652, the base 654 and the HLA 650. The constant pressure provided on the bridge lash adjuster loading assembly, which includes spring piston 670 and associated components, is used to ensure that over-extension or "jacking" of HLA 650 does not occur. During assist movement, when a braking operation is performed or active, movement from the rocker arm 620 is transmitted through the activated inboard valve actuator 640 to the bridge pin 666 and the brake valve 682. Because of the rocker ratio and the corresponding position of the inboard actuator and fulcrum 652 on the rocker arm 620, movement of the rocker arm will cause a displacement or stroke of HLA that is greater than the stroke of the inboard valve actuator. This greater stroke will cause a compressive force from the stroke limited piston 670 to act on the HLA, preventing over-extension. Due to the clearance 679 between the piston 670 and the bridge bore bottom wall 663, the lost motion function of the HLA mounted arrangement will serve to "hide" the auxiliary motion of the rocker arm from the valve bridge 660 and thus from the engine valves 680 and 682, it being understood that the valve 682 will still move in accordance with the braking action.

Fig. 7 is a schematic block diagram of a valve actuation system 700 according to aspects of the present disclosure. In this example system, the motion sources 702 may include a primary event motion source 702.1 and an auxiliary motion source 702.2. These motion sources may include cams or other devices for imparting motion through respective loading paths represented by arrows and schematically represented components (blocks) in fig. 7, and ultimately to one or more engine valves 720.1 and 720.2. The main event motion source 702.1 and the auxiliary event motion source 702.2 may be separate sources, such as separate cams, including a main event cam and an auxiliary event (dedicated or braking) cam. The primary event valve mechanism assembly 704 transmits primary event motion (and load) to the engine valves 720.1 and 720.1. The lash adjuster 706 may be a Hydraulic Lash Adjuster (HLA) that may be disposed in the main event load path so as to take up clearance between components in the main event valve mechanism. As will be appreciated, the lash adjuster 706 may include internal components that cause the lash adjuster to assume an expanded semi-rigid state when the valve mechanism component is at a relatively low load, and a rigid state when the valve mechanism component is at a high load, such as during a primary event valve motion.

The auxiliary motion source 702.2 may transmit motion (and load) through an auxiliary event loading path, which may include an auxiliary event initiating system 708 that may selectively transmit or absorb motion in the auxiliary event loading path to facilitate auxiliary event valve motion, such as engine braking, in the engine valve 720.2. One or more auxiliary motion valve mechanism components 710 may be provided as a subset of the main event valve mechanism component 704. For example, the main event valve mechanism component 704 may include a valve bridge, and the auxiliary motion valve mechanism component may include a bridge pin slidably disposed in the valve bridge such that the bridge pin transmits the main event motion from the bridge during the main event valve operation. When the auxiliary event initiating system is active to facilitate, for example, engine braking movement in the valve 720.2, the bridge pin may be moved relative to the bridge to transmit auxiliary movement independent of the bridge primary event movement.

According to an aspect of the present disclosure, the main event valve mechanism component 704 may include a lash adjuster loading component 730 disposed in the main event valve mechanism. The lash adjuster loading assembly 730 interacts with the lash adjuster 706 to prevent over-extension or "jacking" of the lash adjuster 706 during engine operation. More specifically, and as will be described in further detail below, the lash adjuster loading assembly 730 may maintain a biasing force on the lash adjuster during periods of relatively low load, such as during an assist event or during transitions to or from the assist event. The biasing force will have a magnitude sufficient to counteract the lash adjuster hydraulic pressure and thus prevent over-extension of the lash adjuster. Further, the lash adjuster loading component 730 may permit refilling of the lash adjuster 706 and will permit high loads, such as loads present in the master event valve mechanism during master event valve operation, to be transmitted to the master event valve mechanism.

Fig. 8 is a perspective view showing example components of a valve actuation system 800 including a valve bridge 804 with an integrated lash adjuster loading assembly 830, according to aspects of the present disclosure. Fig. 8 shows the spring biased piston 840 extending from the valve bridge 804, although other internal details will be described. An adjustment set screw 860 and lock nut 870 may be provided to adjust operating parameters of the spring biased piston, as will be explained. The valve bridge 804 may directly contact a valve stem of the first engine valve 820.1 that extends through the valve guide 822.1. The bridge pin 810 may be received for sliding movement in a bore in the opposite end of the valve bridge 804 and may interact with the valve stem of the second engine valve 820.2 to effect primary and secondary movements thereof. The valve 820.2 may extend through a valve guide 822.2.

Fig. 9.1, 9.2, and 9.3 are cross-sections of the example valve actuation system 800 of fig. 8 that includes a lash adjuster loading assembly 830 and a lash adjuster 906. These figures show the lash adjuster loading assembly 830 in three different configurations or "states". The valve bridge 804 may include a piston guide bore 805 formed in a central portion thereof for receiving a piston 840 and permitting sliding movement in a vertical direction relative to fig. 9.1. The piston 840 may have a generally cylindrical shape and cooperate with a biasing component, in this example in the form of a biasing compression spring 848. The spring 848 may be partially received in the bore 842 of the piston 840 with the upper end of the spring 848 seated against the bore end wall 844. The piston 840 may include an annular piston skirt or shoulder 846 having a diameter greater than the diameter of the piston guide bore 805. A valve bridge counterbore 807, which is generally axially aligned with piston guide bore 805 and has a larger diameter and internal threads 808, may be formed on the bottom side of bridge 804. The countersink 807 can define a countersink end wall 809 in the bridge 804. The counterbore 807 thus accommodates and permits limited travel of the piston annular shoulder 846 therein, it being understood that the counterbore end wall 809 provides an upper limit to the travel of the annular shoulder 846 and thus the piston 840 within the valve bridge 804. The set screw 860 may include external threads 862 that cooperate with the counter-bore internal threads 808 and may include a set screw spring seat 864. The lower end of the spring 848 may be received in a spring seat 864 with the lower end of the spring seated against a seat end wall 866. The set screw end wall 868 may define a lower limit of travel for the piston ring shoulder 846. The set screw 860 may adjust the position of the lower limit of the piston, as well as the biasing force provided by the compression spring 848 on the piston 840.

Fig. 9.1, 9.2, and 9.3 depict a hydraulic lash adjuster 906 in cooperative relationship with the spring piston arrangement described above, which serves as a lash adjuster loading assembly 830 in the valve bridge 804. Fig. 11 is a detailed view of the example cam illustrated in fig. 9.1, 9.2 and 9.3. The lash adjuster 906 may have: an expansion direction, which is a downward direction in the orientation of fig. 9.1, 9.2 and 9.3; and a contraction or compression direction, which is an upward direction. As will be appreciated, the piston 840 is biased in an upward direction within the valve bridge 804 by the compression spring 848, thus tending to apply a spring force to the lash adjuster 906. However, the stroke of the piston is limited in both upward directions, and this biasing force is only applied when the piston position is between the stroke limits.

Fig. 9.1 shows the piston 840 in a lash adjuster refill state, where the piston is at its highest travel limit. Specifically, the piston annular shoulder 846 engages the counterbore end wall 809 to limit upward travel of the piston 840. With the piston 840 in this position, the biasing force of the compression spring 848 is isolated relative to the lash adjuster, and the lash adjuster is expandable to take up any lash created in the valve mechanism. Such an extension would cause the lash adjuster to be refilled with hydraulic control fluid that is typically circulated within the control system at a predetermined operating pressure. Also depicted in fig. 9.1 is an example master event cam 902.1, as well as valve train components, such as cam rollers, rocker arms, and push rods that may be present between the master event cam 902.1 and the HLA 906, represented by dashed line 912. Referring additionally to fig. 11, the base circle 922 of the main event cam 902.1 is indicated by a dashed line. The primary event cam 902.1 may include a primary event lift surface 928. The master event cam 902.1 also includes an operating surface for facilitating HLA refill and spring bridge preload states of the lash adjuster loading assembly. Example HLA refill cam surface 924 may be a sub-circular surface that may facilitate lash adjuster loading assembly 830 to assume an HLA refill state, as will be further explained. The master event cam 902.1 may also include a lash adjuster loading assembly preload surface 926, which may also be a sub-circular surface, to facilitate the lash adjuster loading assembly 830 assuming a lash adjuster loading assembly preload state, as will also be explained further. As illustrated in fig. 9.1, the master event cam 902.1 is rotationally positioned such that the master event valve mechanism assembly 912 interacts with the HLA refill cam surface 924. As further detailed in fig. 11, the primary event cam 902.1 may include a primary event surface 928, a first transition surface 921, a second transition surface 923, and a third transition surface 925 between the HLA refill cam surface 924 and the lash adjuster loading assembly preload surface 926. As will be appreciated, the cam 902.1 may be rotated in a clockwise direction to facilitate master event movement, HLA refill, and lash adjuster loading assembly movement in a master event valve mechanism, as will be further described herein.

Fig. 9.2 shows the piston 840 in a preloaded state, wherein the preloaded cam surface 926 of the main event cam 902.1 interacts with the main event valve mechanism assembly 912. In this preloaded state, the piston annular shoulder 846, and thus the piston 840, is positioned between an upper limit (the counterbore end wall 809) and a lower limit (the set screw end wall 868) within the piston guide bore 805. Thus, the biasing force of the spring 848 is exerted on the lash adjuster 906, thereby maintaining the lash adjuster in a preloaded state and preventing the lash adjuster 906 from over-extending. This state of the piston 840 will typically be assumed during an auxiliary event, such as braking, in which the auxiliary motion source 902.2 applies a force to the bridge pin 810 through an auxiliary valve mechanism (not fully shown in fig. 9.2, except for the bridge pin). As the bridge pin 810 is displaced downward, the valve bridge 804 may tilt or pivot about the stem of the valve 820.1, it being understood that the valve 820.1 may remain in the same position (i.e., closed) during an assist event. The pivoting of the valve bridge 804 tends to move the center of the valve bridge downward. The lash adjuster loading assembly, the piston 840, may thus apply the biasing force of the spring 848 and prevent the lash adjuster from over-extending.

Fig. 9.3 shows the piston 840 in a master event motion state, wherein the master event lift surface 928 of the master event cam 902.1 interacts with the master event valve mechanism assembly 912. In this state, piston annular shoulder 846, and therefore piston 840, "bottoms out" at the lower range of travel within valve bridge 804. Specifically, piston annular shoulder 846 engages set screw end wall 868. This state permits the transfer of the high loads (through the piston 840 to the valve bridge 804) normally associated with the main event actuations of the engine valves 820.1 and 820.1. During this state, because the lash adjuster 906 is under high load due to the primary event provided by the primary event lift surface 928, the lash adjuster 906 remains in a rigid state that otherwise cannot expand.

FIG. 10 is a graphical representation depicting example operating characteristics and sequencing of the valve actuation system of FIG. 8. This figure shows the main event and the auxiliary event (braking) valve movement (lift) as a function of crankshaft angle. The main event valve mechanism movement is shown by the dashed lines. The auxiliary event valvetrain motion 1110 is shown by solid lines and it should be noted that it coincides with the zero valve lift axis (x-axis) at crankshaft angles of about 30 degrees to about 530 degrees. In one embodiment, the main event lift and the auxiliary event lift are provided by two separate motion sources, such as a main event cam and a separate and dedicated auxiliary cam as illustrated in fig. 9.1-9.3, through separate load paths and valve train assemblies.

Fig. 10 shows two auxiliary valve events occurring in the auxiliary valve mechanism that cause the lifting of one or more valves (e.g., valve 820.2 through bridge pin 810 in fig. 9.1). The Brake Gas Recirculation (BGR) event 1112 may occur at a crankshaft angle of about 530 degrees to about 620 degrees. The Compression Release (CR) braking event 1114 may occur at about 665 degrees to about 30 degrees of crankshaft angle (i.e., to begin the next engine cycle). Those skilled in the art will appreciate that any of a number of other auxiliary events may be used instead of or in addition to the auxiliary event illustrated in fig. 10.

According to aspects of the present disclosure, a lash adjuster loading assembly may provide controlled loading of a lash adjuster in a main event valve mechanism. The lash adjuster loading assembly may enable lash adjuster refilling after the primary event lifts and before the secondary events 1112 and 1114 occur. More specifically, still referring to fig. 10, after the main lift event, starting from about 360 degrees to about 420 degrees, the lash adjuster loading assembly transitions to a lash adjuster refill period or phase 1120 that extends from about 420 degrees to about 520 degrees. It will be appreciated that the main-event valve mechanism movement 1010 during this stage may be implemented by a sub-circular surface on the main-event cam, as depicted by the dashed line in the negative valve lift region in fig. 10. It will further be appreciated that the duration of the refill period may be controlled by an appropriate configuration of the primary event motion source, e.g., a primary event cam surface, which may be provided with a refill cam surface (924 in fig. 9.1) thereon to cause the lash adjuster loading assembly to assume the refill state as described above. The sub-base circle movement will typically cause a gap to occur in the main event valve mechanism. During this stage, the lash adjuster loading assembly will assume the lash adjuster refill state depicted in fig. 9.1, wherein the travel of the piston 840 is limited by an upper limit (bore end wall 809). In this state, the lash adjuster loading assembly will allow the lash adjuster to be refilled after the primary event moves and before the secondary event.

In accordance with other aspects of the present disclosure, the lash adjuster loading assembly may ensure that over-extension or "jacking" of the lash adjuster during a secondary event does not occur. With continued reference to fig. 10, before the start of the aiding events 1112 and 1114, at a crankshaft angle of approximately 520 degrees, the lash adjuster loading assembly may transition from the refill phase 1120 to a preload period or phase 1130. It will be appreciated that the main-event valve mechanism movement during this stage may be implemented by a sub-circular surface on the main-event cam, as depicted by the dashed line in the negative valve lift region in fig. 10. However, the pre-load phase sub-circular cam surface may typically have a higher height (radial distance) from the cam axis of rotation than the refill cam surface, which places the lash adjuster loading assembly in a state in which the piston 840 (fig. 9.1) is between the upper and lower limits of travel and thus permits the biasing force of the compression spring 848 to be applied to the lash adjuster. The timing of and transition to the preload phase may be accomplished by an appropriate control surface on the source of the primary event motion, such as a primary event cam, which may include a preload cam surface (926 in fig. 9.1). During this stage, the lash adjuster loading assembly will be in the preloaded state depicted in fig. 9.2, with the piston 840 maintaining a biasing force against the lash adjuster, preventing the lash adjuster from over-extending. The preload state may continue beyond 720 crank angle degrees and into the next engine power cycle as shown in fig. 10, where the preload state continues at 1032, beyond the end of the CR event and into a new engine cycle for about 120 crank angle degrees. As will be appreciated from the present disclosure, the duration of the preload state may be extended at least as long as the duration of any auxiliary event. Although in the above example two auxiliary events occur in sequence and the duration of a single preload event extends the duration of both auxiliary events, the present disclosure also contemplates that the preload occurs at intermittent times in a given engine cycle to coincide with separate respective durations of the plurality of auxiliary events. As will be appreciated from the present disclosure, the biasing force provided by the biasing assembly, e.g., the compression spring 848, in the lash adjuster loading assembly should be of a suitable degree to counteract any force in the lash adjuster, e.g., a force generated by hydraulic pressure in the lash adjuster.

As will be appreciated from the present disclosure, the timing and duration of the primary event state, HLA refill state and preload state of the lash adjuster loading assembly may be controlled by appropriately configuring the aforementioned operating parameters, including the refill and preload cam surfaces on the primary event cam, as well as configuring the travel limits for the lash adjuster loading assembly. It will be further recognized that the piston stroke should substantially match the translational distance between the HLA refill surface on the master event cam and the desired master event open and closed positions on the master event cam in order to ensure optimal refill of the HLA and achieve other benefits.

Fig. 12 is a schematic representation of a valve actuation system 1200 according to aspects of the present disclosure with respect to a type II valve architecture. In this example system, the motion sources 1202 may include a primary event motion source 1202.1 and an auxiliary motion source 1202.2. These motion sources may include cams or other devices for imparting motion through respective loading paths represented by arrows and schematically represented components (blocks) in fig. 12, and ultimately to the engine valve 1220. The main event motion source 1202.1 and the auxiliary event motion source 1202.2 may be separate sources, such as separate cams, including a main event cam and an auxiliary event (dedicated or braking) cam. The primary event valve mechanism assembly 1204 transmits the primary event motion (and load) to the engine valve 1220. Lash adjuster 1206, which may be a Hydraulic Lash Adjuster (HLA), may be disposed in the end pivot of the rocker and thus not directly disposed in the main event load path. In other words, the HLA may be parallel to the main event load path and may provide a reactive force to the main event load so as to take up the clearances between the components in the main event valve mechanism.

The auxiliary motion source 1202.2 may transmit motion (and load) through an auxiliary event loading path 1205 that may include an auxiliary event actuation system 1208 that may selectively transmit or absorb motion in the auxiliary event loading path to facilitate auxiliary event valve motion, such as engine braking, in the engine valve 1220. One or more auxiliary motion valve mechanism assemblies 1210 may be provided as a subset of the main event valve mechanism assembly 1204. For example, the primary event valve mechanism component 1204 may include an end pivot rocker and the secondary motion valve mechanism component 1210 may include the same end pivot rocker.

According to an aspect of the present disclosure, the main event valve mechanism component 1204 may include a lash adjuster loading component 1230 disposed in the main event valve mechanism. In various specific examples as will be further described, the lash adjuster loading assembly 1230 interacts with components in the main event valve mechanism in which the lash adjuster 1206 may be disposed to prevent overextension or "lift-up". More specifically, and as will be described in further detail below, the lash adjuster loading assembly 1230 may act on components in the valve mechanism to induce a biasing force on the lash adjuster during periods of relatively low load, such as during an auxiliary event or during transitions to or from the auxiliary event. Further, the lash adjuster loading component 1230 may permit refilling of the lash adjuster 1206 and will permit high loads, such as loads present in the master event valve mechanism during master event valve operation, to be transmitted to the master event valve mechanism.

Fig. 13 is a schematic representation of a first example lash adjuster loading assembly arrangement 1300 in a type II valve architecture. The primary source of event motion may be a cam 1302.1 that operates on an intermediate region of a rocker 1304, which may be of a type known as a finger follower, mounted on a pivot 1350. The secondary motion source 1302.2, which may be a secondary (dedicated) cam separate from the primary event cam 1302.1, may act on the rocker 1304 through a secondary valve train assembly shown in phantom in fig. 13 for ease of illustration. Although shown as separate from the primary event cam, the auxiliary cam may be on the same camshaft as the primary event cam and may operate on the same region (i.e., middle or middle zone) of the rocker 1304. The rocker 1304 operates on a valve 1320. The lash adjuster 1306 may cooperate or be integrated with the pivot 1350 so as to take up the lash that exists between the rocker and the primary event motion source 1302.1. Lash adjuster loading assembly 1330 may be disposed in or cooperate with rocker 1304 to react against primary event motion source 1302.1 and rocker 1304 to maintain a load on lash adjuster 1306 and thereby prevent it from over-extending. As will be appreciated, the internal components of the lash adjuster loading assembly 1330 may provide spring-loaded, travel-limited functionality as described above such that the lash adjuster 1306 is maintained in a controlled position during primary and secondary events. Furthermore, the master event cam 1302.1 may be provided with sub-circular regions to implement HLA refill and preload functions as described above with reference to fig. 9.1-9.3, 10 and 11.

FIG. 14 is a schematic representation of a second example lash adjuster loading assembly arrangement 1400 in a type II valve train architecture. The primary source of event motion may be a cam 1402.1 operating on a mid-region of a rocker 1404, which may be of a type known as a finger follower, mounted on a pivot 1450. The secondary motion source 1402.2, which may be a secondary (dedicated) cam separate from the primary event cam 1402.1, may act on the rocker 1404 through a secondary valve train assembly shown in phantom in fig. 14 for ease of illustration. Although shown as separate from the primary event cam, the auxiliary cam may be on the same camshaft as the primary event cam, and may operate on the same region (i.e., middle or middle zone) of the rocker 1404. The rocker 1404 operates on the valve 1420. The lash adjuster 1406 may cooperate or be integrated with the pivot 1450 so as to take up the lash that exists between the rocker and the primary event motion source 1402.1. Lash adjuster loading assembly 1430 may be disposed adjacent to and/or may cooperate with lash adjuster 1406 to react against the fixed portion of the engine and lash adjuster 1406 to maintain a load on lash adjuster 1406 and thereby prevent it from over-extending. As will be appreciated, the internal components of the lash adjuster loading assembly 1430 may provide spring-loaded, travel-limited functionality as described above such that the lash adjuster 1406 is maintained in a controlled position during primary and secondary events. As will be appreciated, the master event cam 1402.1 may be provided with a sub-circular region to implement HLA refill and preload functions as described above with reference to fig. 9.1-9.3 and 10.

FIG. 15 is a schematic representation of a third example lash adjuster loading assembly arrangement 1500 in a type II valve architecture. The primary source of event motion may be a cam 1502.1 that operates on a middle region of a rocker 1504, which may be of a type known as a finger follower, mounted on a pivot 1550. The auxiliary motion source 1502.2, which may be an auxiliary (dedicated) cam separate from the primary event cam 1502.1, may act on the rocker 1504 through an auxiliary valve train assembly shown in phantom in fig. 15 for ease of illustration. Although shown as separate from the primary event cam, the auxiliary cam may be on the same camshaft as the primary event cam, and may operate on the same region (i.e., middle or middle zone) of the rocker 1404. The rocker 1504 operates on the valve 1520. The lash adjuster 1506 may cooperate with the pivot 1550 to take up the lash that exists between the rocker and the primary event motion source 1502.1. A lash adjuster loading assembly 1530 may be inserted between the lash adjuster 1506 and the pivot 1550 to maintain a load on the lash adjuster 1506 and thereby prevent it from over-extending. As will be appreciated, the internal components of the lash adjuster loading assembly 1530 may provide spring-loaded, travel-limited functionality as described above such that the lash adjuster 1506 is maintained in a controlled position during the primary and secondary events. As will be appreciated, the master event cam 1502.1 may be provided with a sub-circular region to implement HLA refill and preload functions as described above with reference to fig. 9.1-9.3 and 10.

Fig. 16 is a schematic representation of a fourth example lash adjuster loading assembly arrangement 1600 in a type II valve architecture. The primary source of event motion may be a cam 1602.1 operating on a mid-region of a rocker 1604, which may be of a type known as a finger follower, mounted on a pivot 1650. The secondary motion source 1602.2, which may be a secondary (dedicated) cam separate from the primary event cam 1602.1, may act on the rocker 1604 through a secondary valve mechanism assembly shown in phantom in fig. 16 for ease of illustration. Although shown as separate from the primary event cam, the auxiliary cam may be on the same camshaft as the primary event cam and may operate on the same region (i.e., middle or middle zone) of the rocker 1604. The rocker 1604 operates on a valve 1620. The lash adjuster 1606 may cooperate or be integrated with the pivot 1650 to take up the lash that exists between the rocker and the primary event motion source 1602.1. A sliding pin 1607 may be disposed in the rocker 1604. The lash adjuster loading assembly 1630 may be located at a rocker-to-slide pin position in the rocker 1604 to maintain the load on the lash adjuster 1606 and thereby prevent it from over-extending. As will be appreciated, the internal components of the lash adjuster loading assembly 1630 may provide spring-loaded, travel-limited functionality as described above such that the lash adjuster 1606 is maintained in a controlled position during primary and secondary events. As will be appreciated, the master event cam 1602.1 may be provided with a sub-circular region to implement HLA refill and preload functions as described above with reference to fig. 9.1-9.3 and 10. The fixed stroke lash adjuster loading assembly 1630 may bias the sliding pin 1607 away from the rocker to the pin contact surface and may provide a fixed stroke. This may allow the lash adjuster 1606 to set the lash with the rocker on the base circle, and without the need to compress the lash adjuster loading element from its stop. During the secondary motion, the rocker arm is pressed against the lash adjuster loading element by a lift event on the main event cam profile. When the auxiliary motion source 1602.2 opens the valve by acting on the sliding pin 1606, the lash adjuster loading element is maintained in a compressed state relative to the rocker arm and prevents HLA overextension. The pin 1607 can be provided with a biasing structure and travel limiting structure such as described above with respect to the spring piston in fig. 9.1, 9.2, and 9.3, and can be biased away from the valve end of the rocker 1604 a fixed travel with a spring force sufficient to prevent extension of the HLA 1606. This spring may be partially compressed during a preload period on the main event cam, such that when the 1602.2 motion source moves pin 1607 downward, spring 1602 remains in a compressed state and prevents HLA 1606 from expanding.

Fig. 17 is a schematic representation of a fifth example lash adjuster loading assembly arrangement 1700 in a type II valve architecture. The primary event motion source may be a cam 1702.1 operating on an intermediate region of a rocker 1704, which may be of a type known as a finger follower, mounted on a pivot 1750. The secondary motion source 1702.2, which may be a secondary (dedicated) cam separate from the primary event cam 1702.1, may act on the rocker 1704 through a secondary valve train assembly shown in phantom in FIG. 17 for ease of illustration. Although shown as separate from the primary event cam, the auxiliary cam may be on the same camshaft as the primary event cam and may operate on the same region (i.e., middle or middle zone) of the rocker 1704. The rocker 1704 operates on the valve 1720. Lash adjuster 1706 may cooperate with pivot 1750 to take up the lash that exists between the rocker and the primary event motion source 1702.1. The rocker 1704 may include a pivot arm 1707 mounted to it at a pivot point 1705. Lash adjuster loading assembly 1730 may be located at the rocker-to-pivot arm position and may include internal structures similar to those described above with respect to the limited travel spring piston in the embodiment of fig. 9.1, 9.2, and 9.3. Further, a set screw similar to those shown in the figures may be used to adjust the stroke. The fixed stroke lash adjuster loading assembly 1730 may bias a pivot arm 1707 that includes a contact surface with the primary event cam 1702.1. The pivot point 1705 may operatively engage the rocker 1704 and may also include a rolling element (not shown) that may have a fixed stroke allowing HLA refill when the pivot arm is in a fully extended state, and the primary event cam 1702.1 is oriented such that the lash adjuster refill stage of the primary event cam operates on the pivot arm 1707. When lash adjuster loading assembly 1730 is in its fully compressed state, it allows primary event cam 1702.1 to transmit primary event lift. When the lash adjuster loading assembly 1730 is partially compressed during the "preload period" of the primary event cam, it allows motion from the primary event cam 1702.2 to move the rocker body 1704 downward without losing preload on the HLA. Lash adjuster loading assembly 1730 may thus bias pivot arm 1707 a fixed stroke away from the rocker and toward the cam. This may allow the lash adjuster 1706 to set the lash with the rocker on the base circle and without the need to compress the lash adjuster loading assembly 1730 from its stop. During the assist motion, the rocker arm 1704 is pressed against the lash adjuster loading assembly 1730 by a lift event on the primary event cam 1702.1 acting on the pivot arm 1707. When the auxiliary motion source 1702.2 opens the valve 1720 by acting on the rocker 1704 (with or without a sliding pin), the lash adjuster loading assembly 1730 is maintained in a partially compressed state relative to the rocker arm and prevents the lash adjuster 1706 from over-extending. Pivot arm 1707 may contain rolling elements, flat surfaces, or curved contact surfaces. As will be appreciated, the primary event cam 1702.1 may be provided with a base dome to implement lash adjuster refill and preload functions as described above with reference to fig. 9.1-9.3, 10 and 11.

Although the present embodiments have been described with reference to specific example embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the invention as set forth in the claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.