Valve actuation system with rocker assemblies sharing an output rocker

Abstract

A system for actuating at least one engine valve includes an output rocker operably connected to the at least one engine valve. The first rocker assembly includes a first input rocker arranged in series with a first lost motion component, the first input receiving a first valve actuation motion from the first valve actuation motion source, the first lost motion component operably connected to the output rocker. The second rocker assembly includes a second input rocker arranged in series with a second lost motion component, the second input rocker receiving a second valve actuation motion from the second valve actuation motion source, the second lost motion component operably connected to the output rocker.

Description

[Technical Field]

[0001] The present disclosure relates generally to internal combustion engines, and more particularly to valve actuation systems including rocker assemblies that share an output rocker. [Background technology]

[0002] Valve actuation in an internal combustion engine is required for the engine to operate. Typically, valve actuation forces to open engine valves (i.e., intake, exhaust, or auxiliary engine valves) are transmitted by a valve train, and such valve actuation forces may be provided by a primary motion source and / or an auxiliary motion source. As used herein, the description "primary" refers to so-called primary event engine valve movements, i.e., valve movements used during the production of positive power when fuel is combusted in the engine cylinder to provide net engine output, while the description "auxiliary" refers to other engine valve movements intended to replace or in addition to the production of positive power (e.g., compression release braking, bleeder braking, cylinder decompression, cylinder deactivation, brake gas recirculation (BGR), etc.) or in addition to the production of positive power (e.g., internal exhaust gas recirculation (IEGR), variable valve actuations (VVA), early exhaust valve opening (EEVO), late intake valve closing (LIVC), swirl control, etc.).

[0003] In many internal combustion engines, the primary and / or secondary sources of motion may be provided by fixed-profile cams, and more specifically, by one or more fixed lobes or bumps that may be an integral part of each of the cams. The ability to vary the timing and lift of the intake and / or exhaust valves can provide benefits such as improved performance, improved fuel economy, reduced emissions, and improved vehicle drivability. However, the use of fixed-profile cams can make it difficult to adjust the timing and / or amount of engine valve lift to optimize them for various engine operating conditions.

[0004] Given a fixed cam profile, one method of adjusting valve timing and lift has been to provide a “lost motion” or variable-length device in the valvetrain linkage between a given engine valve and its corresponding cam. Lost motion is a term applied to the field of engineering solutions for modifying valve motion prescribed by a cam profile with a variable-length mechanical, hydraulic, or other linkage assembly. In a lost motion system, the cam lobe can provide the “maximum” motion (longest dwell and maximum lift) required over the entire range of engine operating conditions, including positive power-producing and / or auxiliary motion, as needed. A variable-length system can then be included in the valvetrain linkage intermediate the valve to be opened and the cam providing the maximum motion to reduce or eliminate some or all of the motion imparted to the valve by the cam. Typically, such lost motion devices are controllable between a “locked” or motion-transmitting state and an “unlocked” or motion-absorbing state. During the locked state, the lost motion device is maintained in a substantially rigid configuration (with allowance for lash adjustment) so that valve actuation motion applied to it is transmitted to the corresponding engine valve. On the other hand, while in the unlocked state, the lost motion device is able to absorb or avoid, i.e., "lose," at least a portion (including up to all) of the valve actuation motion applied to it, thereby preventing such valve actuation motion from being transmitted to the corresponding engine valve.

[0005] Valve actuation systems incorporating lost motion features continue to be developed to provide greater valve actuation functionality and flexibility. However, increased cost, packaging, and size are factors that can often determine the desirability of such engine valve actuation systems. A valve actuation system with lost motion components that overcomes these limitations while still providing various valve actuation functionality and flexibility would represent a welcome advancement in the art. Summary of the Invention

[0006] This disclosure describes various embodiments of a valve actuation system for actuating at least one engine valve in an internal combustion engine. In one embodiment, a system for actuating at least one engine valve associated with a cylinder of an internal combustion engine includes an output rocker operably connected to the at least one engine valve. The first rocker assembly includes a first input rocker arranged in series with a first lost motion component, the first input rocker configured to receive a first valve actuation motion from the first valve actuation motion source, the first lost motion component operably connected to the output rocker. The first lost motion component is operable to prevent transmission of the first valve actuation motion from the first input rocker to the output rocker in a motion absorbing state and to transmit the first valve actuation motion from the first input rocker to the output rocker in a motion transmitting state. The second rocker assembly is operably connected to a second valve actuation motion source. The second rocker assembly includes a second input rocker disposed in series with a second lost motion component configured to receive the second valve actuation motion from a second valve actuation motion source, the second lost motion component operatively connected to the output rocker, the second lost motion component operable to prevent transmission of the second valve actuation motion from the second input rocker to the output rocker in a motion absorbing state and to transmit the second valve actuation motion from the second input rocker to the output rocker in a motion transmitting state.

[0007] In one embodiment, the output rocker includes at least one hydraulic lash adjuster.

[0008] In one embodiment, at least two engine valves are associated with the cylinder and the output rocker is operably connected to the at least two engine valves. Further to this embodiment, a valve bridge may be disposed between and operably connected to the output rocker and the at least two engine valves.

[0009] In one embodiment, the first rocker assembly and the output rocker are configured to operate as Type II rockers. Further to this embodiment, the output rocker and the first input rocker may each comprise a Type III rocker mounted on a shaft. Furthermore, the second rocker assembly and the output rocker may be configured to operate as Type II rockers, and the output rocker and the second input rocker may each comprise a Type III rocker mounted on a shaft.

[0010] In one embodiment, the output rocker comprises at least two arms, a first arm and a second arm of the output rocker defining a first central opening configured to receive the first input rocker between the first arm and the second arm. Further to this embodiment, the output rocker can comprise a third arm, the second arm and the third arm defining a second central opening configured to receive the second input rocker between the second arm and the third arm.

[0011] In one embodiment, the first lost motion component and the second lost motion component each include a hydraulically controlled locking mechanism.

[0012] In one embodiment, the first lost motion component includes a first spring that biases the first input rocker toward the first source of valve actuation motion and biases the output rocker toward the at least one engine valve, and in one embodiment, the second lost motion component includes a second spring that biases the second input rocker toward the second source of valve actuation motion and biases the output rocker toward the at least one engine valve.

[0013] In one embodiment, the first lost motion component is configured to provide a fail-safe lift. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1A is a schematic diagram of an embodiment of a valve actuation system including a single output rocker in accordance with the present disclosure. [Figure 2] FIG. 1 is a cross-sectional view of an example of a lost motion component that may be used to implement various embodiments described herein. [Figure 2A] 10A-10C are cross-sectional views of alternative examples of lost motion components that may be used to implement various embodiments described herein. [Figure 3] FIG. 2 illustrates a first implementation of the valve actuation system according to the embodiment of FIG. 1. [Figure 4] FIG. 2 illustrates a first implementation of the valve actuation system according to the embodiment of FIG. 1. [Figure 5] FIG. 2 illustrates a second implementation of the valve actuation system according to the embodiment of FIG. 1. [Figure 6] FIG. 2 illustrates a second implementation of the valve actuation system according to the embodiment of FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0015] As used herein, phrases substantially similar to "at least one of A, B, or C" are intended to be construed disjunctively, i.e., requiring A or B or C, or any combination thereof, unless otherwise stated or implied by context. Further, phrases substantially similar to "at least one of A, B, and C" are intended to be conjunctively, i.e., requiring at least one of A, at least one of B, and at least one of C, unless otherwise stated or implied by context. Further, the term "substantially" or similar words requiring subjective comparison are intended to mean "within manufacturing tolerances," unless otherwise stated or implied by context.

[0016] As used herein, the term "operably connected" is understood to refer to a functional relationship between at least two components, i.e., that the claimed components must be connected (potentially including the presence of intervening elements or components) such that the components perform the indicated function.

[0017] 1 schematically illustrates a valve actuation system 100 including a first rocker assembly 110a and a second rocker assembly 110b. As shown, the first rocker assembly 110a is operably connected to a first valve actuation motion source 120, and the second rocker assembly 110b is operably connected to a second valve actuation motion source 130. One or more engine valves 162 (which may be intake or exhaust valves, for example) are associated with cylinders 160 of the internal combustion engine, and the valves 162 are operably connected to the first rocker assembly 110a and the second rocker assembly 110b via a shared or common output rocker 116 as components of both the first rocker assembly 110a and the second rocker assembly 110b. In this manner, first rocker assembly 110a and second rocker assembly 110b, subject to the action of any incorporated lost motion components, as described in further detail below, operate to actuate (i.e., open and close) engine valves 162 as commanded by first valve actuation motion source 120 and second valve actuation motion source 130. Although only a single cylinder 160 is illustrated in Figure 1, it is understood that an internal combustion engine may include two or more cylinders, and the valve actuation systems described herein are applicable to any number of cylinders for a given internal combustion engine.

[0018] Valve actuation motion sources 120, 130 may comprise any combination of known elements capable of providing valve actuation motion, such as cams. Each of valve actuation motion sources 120, 130 may be dedicated to providing a main exhaust motion, a main intake motion, an auxiliary motion, or a combination of main exhaust or main intake motion along with auxiliary motion. For example, in one embodiment, first motion source 120 is configured to provide the auxiliary valve actuation motion, and second motion source 130 is configured to provide the main valve actuation motion (either exhaust or intake).

[0019] The first rocker assembly 110a includes a first input rocker 112, a first lost motion component 114, and an output rocker 116 arranged in series. As used herein, the term "series" refers to the transmission of valve-actuating motion; i.e., the components are in series to the extent that they transmit valve-actuating motion from one to another along a path from a source of valve-actuating motion to one or more engine valves, at least for exhaust. In particular, the first input rocker 112 is operably connected to a first source of valve-actuating motion 120, the output rocker 116 is operably connected to an engine valve 162, and the first lost motion component 114 is operably connected and disposed between the first input rocker 112 and the output rocker 116. The first input rocker 112 and the output rocker 116 may comprise center-pivot rocker arms or Type III rocker arms; various implementations based on center-pivot rocker arms are described in further detail below. However, it will be understood that first input rocker 112 and first output rocker 116 may also be implemented using end-pivot rocker arms or Type II rocker arms. Optionally (as shown in dashed lines), one or more hydraulic lash adjusters (HLA) 118 may be included in output rocker 116, which may include suitable hydraulic passages (known in the art and not shown) for providing hydraulic fluid to HLA 118. It will be understood that HLA 118 may instead be located as part of the other components 112, 114, 142, 144 that make up first rocker assembly 110a and / or second rocker assembly 110b.

[0020] The second rocker assembly 110b comprises a second input rocker 142, a second lost motion component 144, and an output rocker 116 arranged in series. In particular, the second input rocker 142 is operably connected to the second valve actuation motion source 130, and as before, the output rocker 116 is operably connected to the engine valve 162, with the second lost motion component 144 operably connected and disposed between the second input rocker 142 and the output rocker 116. Again, the first input rocker 142 and the output rocker 116 may comprise center pivot rocker arms or Type III rocker arms, with various implementations based on center pivot rocker arms being described in further detail below.

[0021] A feature of the present disclosure is that the output rocker 116 shared by the first rocker assembly 110a and the second rocker assembly 110b may be used to actuate a single engine valve or multiple engine valves, as commanded by either or both of the first motion source 120 and the second motion source 130. In the case of a single engine valve 162, the output rocker 116 may be operably connected to the single engine valve 162, possibly via an HLA 118 or other connection assembly (such as a lash adjustment screw and swivel as known in the art). In the case of multiple engine valves 162, the output rocker 116 may be operably connected to the engine valves 162, again possibly via multiple HLAs 118 (one for each engine valve 162) or connection assemblies, as in the case of a single engine valve. Optionally, in the case of multiple engine valves 162, a valve bridge 150, as known in the art, may be disposed between the single output point of the output rocker 116 and the multiple engine valves 162, as shown in FIG. 1 .

[0022] As further depicted in FIG. 1 , an engine controller 180 may be provided and operatively connected to the first lost motion component 114 and the second lost motion component 144. The engine controller 120 may comprise any electronic, mechanical, hydraulic, electro-hydraulic, or other type of control device for controlling the operation of the first lost motion component 114 and the second lost motion component 144, i.e., for switching them between their respective locked and unlocked states as described above. For example, the engine controller 180 may be implemented by a microprocessor and corresponding memory storing executable instructions used to implement the necessary control functions, including those described below, as known in the art. It will be understood that other functionally equivalent implementations of the engine controller 180, such as a suitably programmed application specific integrated circuit (ASIC), may equally be used. Additionally, engine controller 180 may include peripheral devices intermediate engine controller 180 and first lost motion component 114 and second lost motion component 144 that enable engine controller 180 to achieve independent control over the operating states of first lost motion component 114 and second lost motion component 144. For example, if first lost motion component 114 and second lost motion component 144 are both hydraulically controlled mechanisms (i.e., responsive to the absence or application of hydraulic fluid to an input), such peripheral devices may include suitable solenoids.

[0023] 1 , control of the first lost motion component 114 and the second lost motion component 144 by the engine controller 180 is provided directly thereto. However, in practice, such control may be provided via a path through at least one of the adjacent input rockers 112, 142 or output rocker 116. For example, in various embodiments described herein, such control is provided through the use of hydraulic fluid supplied under control of the engine controller 180 via one or more fluid passages formed in the first input rocker 112 and the second input rocker 142, respectively. However, as will be understood by those skilled in the art, other types of control schemes may equally be employed for this purpose.

[0024] 1 , the valve actuation system 100 provides various options for actuating the engine valves 162. For example, if the second valve actuation motion source 130 provides the primary valve actuation motion and the first valve actuation motion source 120 provides the auxiliary valve actuation motion, the first lost motion component 114 can be controlled to be in its unlocked or motion absorbing state so that the auxiliary valve actuation motion applied to the first input rocker 112 is not transmitted by the first lost motion component 114 to the output rocker 116, or thereby to the engine valve 162. In addition, the second lost motion component 144 can be controlled to be in its unlocked or motion absorbing state as well, so that the primary valve actuation motion applied to the second input rocker 142 is not transmitted by the second lost motion component 144 to the output rocker 116, or thereby to the engine valve 162. Such control of the engine valves 162, 164 may be used, for example, to implement cylinder deactivation (CDA) operation of the engine.

[0025] Alternatively, based on this same example, if first lost motion component 114 is again operated in its unlocked / motion-absorbing state and second lost motion component 144 is operated in its locked / motion-transmitting state, auxiliary valve actuation motion is not transferred to engine valve 162, but main valve actuation motion is transferred to engine valve 162. Such control of engine valve 162 may be used, for example, to implement positive power-producing operation of the engine.

[0026] In another alternative, based on this same example, if the first lost motion component 114 is operated in its locked / motion transmitting state and the second lost motion component 144 is operated in its locked / motion transmitting state, both the main valve actuation motion and the auxiliary valve actuation motion are transmitted to the engine valve 162. Such control of the engine valves 162, 164 may be used, for example, to implement conventional four-stroke compression-release engine braking operation of the engine, or to provide other additional auxiliary valve actuation motion of the type described above.

[0027] In yet another alternative, based on this same example, if first lost motion component 114 is operated in its locked / motion-transmitting state and second lost motion component 144 is operated in its unlocked / motion-absorbing state, auxiliary valve actuation motion is transmitted to engine valve 162, but main valve actuation motion is not transmitted to engine valve 162. Such control of engine valve 162 can be used to implement operating modes in which auxiliary valve actuation, rather than main valve actuation, is desired. For example, such operating modes may include so-called two-stroke or one-and-a-half-stroke compression-release engine braking operation of the engine.

[0028] FIG. 2 illustrates an example of a lost motion component 200 that may be used with the valve actuation system 100 shown in FIG. 1 as well as various specific implementations described below in connection with FIGS. 3-6. The lost motion component 200 is shown in cross section to better illustrate the hydraulically controlled locking mechanism 210, which constitutes a subassembly of the lost motion component 200 and is disposed between the housing 220 and the plunger 222. While the housing 220 may be formed as a single element, in the example shown in FIG. 2, the closed end of the housing 220 is provided by an end cap 221 attached to the housing 220. A plunger spring 224 is disposed outside the housing 220 and the plunger 222. In the illustrated embodiment, the plunger spring 224 is disposed between a flange 226 formed on or attached to the outer surface of the plunger 222 and a shoulder 228 formed within the housing 220. In this manner, the plunger spring 224 biases the housing 220 and the plunger 222 away from each other. In one embodiment, the biasing force exerted by plunger spring 224 is high enough to prevent extension of any hydraulic lash adjuster located in the same valve train as lost motion component 200. Additionally, although plunger spring 224 is located outside of housing 220 in the illustrated example, it should be understood that plunger spring 224 may also be located within housing 220 to provide a similar bias as described above.

[0029] As mentioned above, plunger spring 224 is strong enough to prevent extension of any hydraulic lash adjuster located in the same valve train as lost motion component 200. However, this can lead to collapse of the hydraulic lash adjuster if the biasing force of plunger spring 224 is too strong. To prevent this, a stroke limit may be provided within lost motion component 200 to prevent overextension of housing 220 and plunger 222 away from each other, which could otherwise exert sufficient compressive force on the hydraulic lash adjuster to collapse it. For example, although not shown in FIG. 2 , the end of plunger 222 adjacent plunger cap 243 may include a radially extending lip or flange configured to engage shoulder 231 formed on a surface defining housing bore 330. Thus, when plunger 222 is urged outward from housing 220 by plunger spring 224, engagement of the radially extending lip or flange with shoulder 231 prevents plunger 222 from moving further outward from housing 220. By limiting the movement of plunger 222 in this manner, lost motion component 200 is prevented from applying excessive compressive force to any hydraulic lash adjuster components in the valve train, thereby preventing collapse of the hydraulic lash adjuster.

[0030] As shown in FIG. 2 , the locking mechanism 210 includes a plunger 222 disposed within a housing bore 230 formed and extending along the longitudinal axis of the lost motion component 200 from a first end of the housing 220. An inner plunger 232 is slidably disposed within a longitudinal bore 234 formed in the plunger 222. A locking element in the form of a wedge 236 is provided, the wedge being configured to engage an annular outer recess 238 formed in a surface defining the housing bore 230. The illustrated embodiment is of the locking mechanism 210 normally locked, i.e., in the absence of hydraulic control applied to the inner plunger 232 via the lost motion hydraulic passage 240, an inner piston spring 242 biases the inner plunger 222 into position such that the wedge 236 extends radially from an opening formed in the plunger 232, thereby engaging the outer recess 238 and effectively locking the plunger 220 in position relative to the housing 220.

[0031] In this locked state, any valve-actuating motion (whether primary or secondary) applied to either end of lost motion component 200 is transmitted by lost motion component 200. Note that even in the locked state as shown in FIG. 2 , the longitudinal extent of outer recess 238 is greater than the thickness of wedge 236 so that a small amount of movement is permitted between plunger 222 and housing 220. Such additional space provided by outer recess 238 facilitates locking / unlocking of locking mechanism 310 when lost motion component 300 is removed. As shown in FIG. 2 , this additional space is occupied, for example, when valve-actuating motion is applied to lost motion component 200, thereby overcoming any outward bias applied to plunger 222 by plunger spring 224.

[0032] The bias applied by plunger spring 224 may be selected to further ensure that adjacent valve train components 252, 254 (or such additional upstream or downstream valve train components in the system, not shown) are biased into continuous contact with the respective endpoints of the valve train, i.e., the source of valve actuation motion and the engine valve.

[0033] 2, supplying hydraulic fluid sufficiently pressurized to the input receiving end (lowermost surface as shown in FIG. 2 ) of the inner plunger 232 via the lost motion hydraulic passage 240 to overcome the bias of the inner piston spring 242 causes the inner plunger 232 to translate within the bore 234 and causes the wedge 236 to retract and disengage from the outer recess 238, thereby effectively unlocking the plunger 222 from the housing 220 and allowing the plunger 222 to slide freely within its bore 230 under the bias, in this case provided by the plunger spring 224. In this unlocked state, any valve actuation movement applied to the lost motion component 200 causes the plunger 222 to reciprocate within its bore 230. In this manner, assuming the movement of plunger 222 within bore 230 is greater than the maximum range of any applied valve actuation motion (i.e., plunger 222 cannot bottom out within that bore 230), such valve actuation motion is not transferred by lost motion component 200 and is effectively lost. Alternatively, the movement of plunger 222 within bore 230 can be configured so that plunger 222 "bottoms out," i.e., contacts the closed end of bore 230, to always provide a "fail-safe" valve lift in the event of locking mechanism 210 failure.

[0034] 2 illustrates a particular embodiment and configuration of lost motion component 200, it should be understood that other configurations may likewise be utilized, and the disclosure is not limited in this respect. For example, as previously discussed, the illustrated lost motion component 200 is a normally locked lost motion component. However, as will be appreciated by those skilled in the art, a normally unlocked type of lost motion component may be used as well.

[0035] FIG. 2A shows an example of a normally unlocked lost motion component 200′. Elements having the same reference numbers in FIGS. 2 and 2A are substantially similar in structure and function, while reference numbers including a prime symbol (′) in FIG. 2A refer to elements characterized by different structure and / or function relative to their counterparts shown in FIG. 2, as explained below. In the embodiment shown in FIG. 2A, lost motion component 200′ again includes a housing 220 having a longitudinal bore 230 formed therein and a plunger 222′ slidably disposed within bore 230. Similarly, inner plunger 232′ is disposed within a bore 234′ formed in plunger 222′ and is biased out of bore 234′ by an inner plunger spring 242 disposed between inner plunger 232′ and plunger cap 243.

[0036] 2 , the inner plunger 232′ is configured essentially the opposite way around, such that in the absence of hydraulic control applied to the inner plunger 232′, the inner plunger spring 242 biases the inner plunger 232′ into position such that the wedge 236 does not extend radially from the opening formed in the plunger 220 and therefore does not engage the outer annular recess 238′, thereby effectively unlocking the plunger 222′ from the housing 220 and allowing the plunger 222′ to slide freely within its bore 230 under the bias provided by the plunger spring 224. In this unlocked state, any valve actuation motion applied to the lost motion component 200′ causes the plunger 222′ to reciprocate within its bore 230. In the illustrated embodiment, the plunger 222′ is configured such that movement of the plunger 222′ within its bore 230 allows the plunger 222′ to “bottom out,” i.e., in this case, contact between the plunger cap 243 and the closed end of the bore 230. In this manner, the lost motion component 200′ can prevent overextension of any hydraulic lash adjuster located in the same valve train as the lost motion component 200′. Additionally, such travel limiting of the plunger 222′ allows for the application of “fail-safe” auxiliary valve actuation motion, such as high-lift braking gas recirculation (BGR) motion, in the event of failure of the locking mechanism 210. Again, a stroke limit may be provided within the lost motion component 200′ to prevent overextension of the housing 220 and plunger 222′ away from each other, which could otherwise result in collapse of the hydraulic lash adjuster. For example, as shown in FIG. 2A, plunger cap 243 may be configured to include a radially extending lip or flange 233 configured to engage a shoulder 231 formed in bore 230, thereby preventing overextension of plunger 222′ from bore 230.

[0037] Meanwhile, supply of hydraulic fluid to the input receiving end (bottom-most surface shown in FIG. 2A ) of inner plunger 232′ that is sufficiently pressurized to overcome the bias of inner piston spring 242 causes inner plunger 232′ to translate within bore 234, forcing wedge 236 to extend and engage outer recess 238′, thereby effectively locking plunger 222′ relative to housing 220. In this locked state, valving motion applied to lost motion component 200′ causes plunger 222′ to engage housing 220, thereby transmitting such valving motion.

[0038] A further feature of the housing 220 is that the annular outer recess 238' has a longitudinal extent that allows the plunger 222' to slide within its bore 230 even when the lost motion component 200' is in its locked / motion transmitting state. This configuration of the outer recess 238' accommodates the separation between the first input rocker 112, 142 and the output rocker 116.

[0039] 3 and 4, a first implementation of the valve actuation system according to FIG. 1 is shown. In particular, the illustrated implementation includes a first rocker assembly 302a and a second rocker assembly 302b. The first rocker assembly 302a includes a first input rocker 306, an output rocker 308, and a first lost motion component 310. The first input rocker 306 includes a roller bearing 307 at a motion-receiving end thereof that is configured to receive valve actuation motion from a first valve actuation motion source, such as a cam disposed on an overhead camshaft (not shown). The first input rocker 306 is operably connected at its motion-imparting end to the input end of the first lost motion component 310. The first lost motion component 310, in turn, is operably connected at its output end to the motion-receiving end of the output rocker 308. In one embodiment, the first input rocker 306 may include one or more hydraulic passages (known in the art and not shown) configured to receive hydraulic fluid, for example from a rocker shaft (not shown), and route such hydraulic fluid to the first lost motion component 310 (thereby controlling its operation as described above with respect to FIG. 2 ).

[0040] The output rocker 308, in this embodiment, includes a first lateral arm 312 and a second lateral arm 314 defining a central opening 316 therebetween that is configured to receive the first input rocker 306, thereby surrounding or enclosing the first input rocker 306 between the first lateral arm 312 and the second lateral arm 314. The output rocker 308, in this embodiment, also includes an adjustable lash screw and swivel assembly 320 at its motion-imparting end that is configured to engage an engine valve or valve bridge (neither shown), if provided. Alternatively, an HLA may be provided in place of the illustrated lash screw and swivel assembly. If an HLA is provided, the output rocker 308 may also include one or more internal hydraulic passages (known in the art and not shown) configured to receive hydraulic fluid, for example, from a rocker shaft (not shown) and route such hydraulic fluid to the HLA.

[0041] 3 and 4, the output rocker 308 and the first input rocker 306 each include a rocker shaft bore. In the case of the output rocker 308, the rocker shaft bore is formed in both the first lateral arm 312 and the second lateral arm 314 configured to receive a rocker shaft. So configured, both the first input rocker 306 and the output rocker 308 can reciprocate about their rocker shafts in response to valve-actuated motion applied to the first input rocker 306 (and to the output rocker 308 via the first lost motion component 310), or, as described in more detail below, the output rocker 308 can reciprocate about its rocker shaft in response to valve-actuated motion applied to the output rocker 308 via the second rocker assembly 302b.

[0042] In this implementation, the second rocker assembly 302b includes a second input rocker 330 and a second lost motion component 332. The second input rocker 330 is a shaft-mounted center pivot rocker with a rocker shaft bore 334 configured to receive a rocker shaft. As shown, the second rocker assembly 302b resides adjacent to the first rocker assembly 302a; more specifically, the second input rocker 330 is disposed on the rocker shaft adjacent to the output rocker 308. The second rocker 330 also includes a roller bearing 331 at its motion-receiving end configured to receive valve-actuating motion from a second valve-actuating motion source (e.g., a cam disposed on an overhead camshaft). The second input rocker 330 is operably connected at its motion-imparting end to the input end of the second lost motion component 332. The second lost motion component 332 is, in turn, operably connected at its output end to the motion-receiving extension 334 of the output rocker 308. As shown, the motion-receiving extension 334 extends axially (relative to the rocker shaft) toward the adjacent second rocker assembly 302 so as to overlap the output end of the second lost motion component 332. In one embodiment, the second input rocker 330 can include one or more hydraulic passages (known in the art and not shown) configured to receive hydraulic fluid, for example, from a rocker shaft (not shown) and route such hydraulic fluid to the second lost motion component 332 (thereby controlling its operation as described above with respect to FIG. 2 ). So configured, the second input rocker 330 can reciprocate about the rocker shaft in response to valving motion applied by a second valving motion source and transmit such valving motion to the output rocker 308.

[0043] It should be noted that from the perspective of the first and second sources of valve actuation motion (applying valve actuation motion to the first input rocker 306 and the second input rocker 330) and the engine valves (receiving valve actuation motion from the output rocker 308), the first rocker assembly 302a and the second rocker assembly 302b operate like Type II or end-pivot rocker arms, similar to so-called finger followers known in the art. However, to achieve such operation, the first rocker assembly 302a relies on the combination of two Type III or center-pivot rocker arms (the first input rocker 306 and the output rocker 308) along with the first lost motion assembly 310. Similarly, the second rocker assembly 302b also relies on the combination of two Type III or center-pivot rocker arms (the second input rocker 330 and the output rocker 308) along with the second lost motion assembly 332. That is, both the first rocker assembly 302a and the second rocker assembly 302b can be considered quasi-Type II rockers or composite Type II rockers based on a combination of constituent Type III rockers.

[0044] 5 and 6, a second implementation of the valve actuation system according to FIG. 1 is shown. Based on FIG. 1, the implementation shown in FIGS. 5 and 6 includes a first rocker assembly 502a and a second rocker assembly 502b. The first rocker assembly 502a is essentially identical in function and structure to the first rocker assembly 302a shown in FIGS. 3-4. That is, the first rocker assembly 502a includes a first input rocker 506 (having a roller bearing 507 at its motion-receiving end) operably connected to a first lost motion assembly 510, which in turn is operably connected to an output rocker 508. In addition, the second rocker assembly 502b includes a second input rocker 530 (having a roller bearing 531 at its motion-receiving end) operably connected to a second lost motion assembly 540, which in turn is operably connected to the output rocker 508. In one embodiment, first input rocker 506 and second input rocker 530 may each include one or more hydraulic passages (not shown) configured to receive hydraulic fluid, for example from a rocker shaft (not shown), and route such hydraulic fluid to first lost motion component 510 and second lost motion component 540 (thereby controlling their operation as described above with respect to FIG. 2 ).

[0045] 5 and 6 differ from the implementation of FIGS. 3 and 4 in that the output rocker 508 is a unitary structure having a first arm 512, a second arm 514, and a third arm 516 that define a first central opening 518 (between the first arm 512 and the second arm 514) and a second central opening 520 (between the second arm 516 and the third arm 514). The first central opening 518 is configured to receive the first input rocker 506, and the second central opening 520 is configured to receive the second input rocker 530, such that the first central opening 518 and the second central opening 520 surround or enclose the respective first input rocker 506 and second input rocker 530. Each of the plurality of arms 512, 514, 516 has a rocker shaft bore 517 formed therein and configured to receive a rocker shaft. 5 and 6, the first input rocker 506 and the second input rocker 530 also include rocker shaft bores configured to receive rocker shafts. Configured in this manner, the implementations of Figures 5 and 6 can be used to provide single input source switching (i.e., switching between the first motion source 120 and the second motion source 130) for a single output, or application of both sources to a single output.

[0046] Unlike the embodiment of Figures 3 and 4, in which the output rocker 508 includes a single lash screw and swivel assembly that interfaces with the engine valves, the output rocker of Figures 5 and 6 includes hydraulic lash adjusters 542, 544 located at the motion-imparting end of the output rocker 508 and configured to engage a corresponding pair of engine valves. In this case, the output rocker 508 is configured to include the hydraulic passages (known in the art and not shown) required to operate the hydraulic lash adjusters 542, 544. Nevertheless, it will be understood that the HLAs 542, 544 may be replaced with suitable lash screw and swivel assemblies, as desired.

[0047] While various embodiments according to the present disclosure have been described in conjunction with specific implementations thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. In various embodiments described herein, the input rocker and output rocker are shown as pivoting about rocker shafts. However, it is understood that the present disclosure need not be limited in this respect, and pivoting configurations other than about rocker shafts may equally be employed. For example, the input rocker and output rocker may each pivot about a different shaft. Furthermore, such shafts may be attached to other rocker arms or separate shaft mounts.

[0048] Accordingly, the preferred embodiments of the invention described herein are intended to be illustrative only, and not limiting, provided that variations thereof come within the scope of the appended claims and their equivalents.

Claims

1. 1. A system for actuating at least one engine valve associated with a cylinder of an internal combustion engine, comprising: an output rocker operably connected to the at least one engine valve; a first rocker assembly operatively connected to a first source of valve actuation motion, the first rocker assembly comprising a first input rocker arranged in series with a first lost motion component, the first input rocker configured to receive a first valve actuation motion from the first source of valve actuation motion, the first lost motion component operatively connected to the output rocker, the first lost motion component operable to prevent transmission of the first valve actuation motion from the first input rocker to the output rocker in a motion absorbing state and to transmit the first valve actuation motion from the first input rocker to the output rocker in a motion transmitting state; a second rocker assembly operatively connected to a second source of valve actuation motion, the second rocker assembly including a second input rocker disposed in series with a second lost motion component, the second input rocker configured to receive second valve actuation motion from the second source of valve actuation motion, the second lost motion component operatively connected to the output rocker, the second lost motion component operable to prevent transmission of the second valve actuation motion from the second input rocker to the output rocker in the motion absorbing state and to transmit the second valve actuation motion from the second input rocker to the output rocker in the motion transmitting state.

2. The system of claim 1 , wherein the output rocker comprises at least one hydraulic lash adjuster.

3. The system of claim 1 , wherein at least two engine valves are associated with the cylinder, and the output rocker is operatively connected to the at least two engine valves.

4. 4. The system of claim 3, further comprising a valve bridge disposed between the output rocker and the at least two engine valves and operably connected to the output rocker and the at least two engine valves.

5. The system of claim 1 , wherein the first rocker assembly and the output rocker are configured to operate as Type II rockers.

6. The system of claim 5 , wherein the output rocker and the first input rocker each comprise a shaft-mounted Type III rocker.

7. The system of claim 1 , wherein the second rocker assembly and the output rocker are configured to operate as Type II rockers.

8. The system of claim 7 , wherein the output rocker and the second input rocker each comprise a shaft-mounted Type III rocker.

9. 2. The system of claim 1, wherein the output rocker comprises at least two arms, a first arm and a second arm of the output rocker defining a first central opening configured to receive the first input rocker between the first arm and the second arm.

10. 10. The system of claim 9, wherein the output rocker comprises a third arm, the second arm and the third arm defining a second central opening configured to receive the second input rocker between the second arm and the third arm.

11. The system of claim 1 , wherein the first lost motion component and the second lost motion component each include a hydraulically controlled locking mechanism.

12. 2. The system of claim 1, wherein the first lost motion component includes a first spring that biases the first input rocker toward the first source of valve actuation motion and biases the output rocker toward the at least one engine valve.

13. 2. The system of claim 1, wherein the second lost motion component includes a second spring that biases the second input rocker toward the second source of valve actuation motion and biases the output rocker toward the at least one engine valve.

14. The system of claim 1 , wherein the first lost motion component is configured to provide a fail-safe lift.

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