Valve Actuation System Comprising a Discrete Lost Motion Device

The instant application is related to co-pending U.S. patent application Ser. No. 18/484,045, filed Oct. 10, 2023.

Valve actuation in an internal combustion engine is required for the engine to operate. Typically, valve actuation forces to open the engine valves (i.e., intake, exhaust or auxiliary engine valves) are conveyed by valve trains where such valve actuation forces may be provided by main and/or auxiliary motion sources. As used herein, the descriptor “main” refers to so-called main event engine valve motions, i.e., valve motions used during positive power generation in which fuel is combusted in an engine cylinder to provide a net output of engine power, whereas the descriptor “auxiliary” refers to other engine valve motions for purposes that are alternative to positive power generation (e.g., compression release braking, bleeder braking, cylinder decompression, cylinder deactivation, brake gas recirculation (BGR), etc.) or in addition to positive power generation (e.g., internal exhaust gas recirculation (IEGR), variable valve actuations (VVA), early exhaust valve opening (EEVO), late intake valve closing (LIVC), swirl control, etc.).

In many internal combustion engines, the main and/or auxiliary motion sources may be provided by fixed profile cams, and more specifically by one or more fixed lobes or bumps which may be an integral part of each of the cams. Benefits such as increased performance, improved fuel economy, lower emissions, and better vehicle drivability may be obtained if the intake and/or exhaust valve timing and lift can be varied. The use of fixed profile cams, however, can make it difficult to adjust the timings and/or amounts of engine valve lift to optimize them for various engine operating conditions.

One method of adjusting valve timing and lift, given a fixed cam profile, has been to provide a “lost motion” or variable length device in the valve train linkage between a given engine valve and its corresponding cam. Lost motion is the term applied to a class of technical solutions for modifying the valve actuation motion defined by a cam profile with a variable length mechanical, hydraulic, or other linkage assembly. In a lost motion system, a cam lobe may provide the “maximum” motion (longest dwell and greatest lift) needed over a full range of engine operating conditions including, as required in some cases, for positive power generation operation and/or auxiliary operation. A variable length system may then be included in the valve train linkage, intermediate of the valve to be opened and the cam providing the maximum motion, to subtract or lose part or all of the motion imparted by the cam to the valve. Typically, such lost motion devices are controllable between a “locked” or motion conveying state and an “unlocked” or motion absorbing state. During the locked state, the lost motion device is maintained in a substantially rigid configuration (with allowances for lash adjustments) such that valve actuation motions applied thereto are conveyed to the corresponding engine valve(s). On the other hand, during the unlocked state, the lost motion device is permitted to absorb or avoid, i.e., “lose,” any valve actuation motions applied thereto, thereby preventing such valve actuation motions from being conveyed to the corresponding engine valve(s).

schematically illustrates an embodiment of a conventional valve actuation systemincorporating a lost motion component. As shown, the valve actuation systemcomprises a valve actuation motion sourcethat serves as the sole source of valve actuation motions (i.e., valve opening and closing motions) to one or more engine valvesvia a valve actuation load path. The one or more engine valvesare associated with a cylinderof an internal combustion engine. As known in the art, each cylindertypically has at least one valve actuation motion sourceuniquely corresponding thereto for actuation of the corresponding engine valve(s). Further, although only a single cylinderis illustrated in, it is appreciated that an internal combustion engine may comprise, and often does, more than one cylinder and the valve actuation systems described herein are applicable to any number of cylinders for a given internal combustion engine.

The valve actuation motion sourcemay comprise any combination of known elements capable of providing valve actuation motions, such as a cam. The valve actuation motion sourcemay be dedicated to providing exhaust motions, intake motions, auxiliary motions or a combination of exhaust or intake motions together with auxiliary motions.

As shown, the valve actuation load pathmay comprise one or more valve train components (in the illustrated example, first and second valve train components,) deployed between the valve actuation motion sourceand the at least one engine valveand used to convey motions provided by the valve actuation motion sourceto the at least one engine valve, e.g., tappets, pushrods, rocker arms, valve bridges, automatic lash adjusters, etc. Although two valve train components,are illustrated in, it is understood that a greater or lesser number of valve train components may be deployed. Further, in this example, the valve actuation load pathincludes a lost motion componenthoused within the second valve train component. That is, while the lost motion componentmay contact other components in the valve train, it is fully supported by and maintained within the valve trainby virtue of being housed within the second valve train component. For example, the second valve train componentmay be embodied by a rocker arm or valve bridge having a bore formed therein in which constituent components forming the lost motion componentare deployed.

As further depicted in, an engine controllermay be provided and operatively connected to the lost motion component. The engine controllermay comprise any electronic, mechanical, hydraulic, electrohydraulic, or other type of control device for controlling operation of the lost motion mechanism, i.e., switching between its respective locked and unlocked states as described above. For example, the engine controllermay be implemented by a microprocessor and corresponding memory storing executable instructions used to implement the required control functions, including those described below, as known in the art. It is appreciated that other functionally equivalent implementations of the engine controller, e.g., a suitable programmed application specific integrated circuit (ASIC) or the like, may be equally employed. Further, the engine controllermay include peripheral devices, intermediate to engine controllerand the lost motion device, that allow the engine controllerto effectuate control over the operating state of the lost motion device. For example, where the lost motion deviceis a hydraulically controlled mechanism (i.e., responsive to the absence or application of hydraulic fluid to an input), such peripheral devices may include suitable solenoids, as known in the art.

schematically illustrates another embodiment of a conventional valve actuation system′ incorporating a lost motion component, in which like reference numerals refer to like elements as compared to. In this second embodiment, the lost motion component, rather than being housed within one of the valve train components,, is instead housed within a fixed member, such as a cylinder head or engine block, while still contacting the second valve train component. For example, in the case where the second valve train componentis an end pivot type rocker arm or finger follower, the lost motion componentmay be embodied by a collapsible pivot as known in the art.

Cost, packaging, and size are factors that may often determine the desirability of an engine valve actuation system. Often, where it is desirable to incorporate one or more lost motion components into valve trains, the ability to include valve train components that house such lost motion components may be constrained by a variety of factors, e.g., lack of space requirements due to their bulky size and/or greater expense. Thus, the provision of valve actuation systems comprising lost motions components that overcome these limitations would represent a welcome advancement of the art.

The instant disclosure describes various embodiments for a valve actuation system for actuating at least one engine valve in an internal combustion engine. In various embodiments, the valve actuation system comprises a first arm operatively connected to a valve actuation motion source to receive valve actuation motions therefrom, the first arm further having a first arm contact surface. A second arm is operatively connected to the at least one engine valve to impart valve actuation motions thereto, the second arm further having a second arm contact surface. A discrete lost motion device comprises a housing having a housing contact surface and a plunger controllable between a first state in which the plunger is rigidly maintained relative to the housing and a second state in which the plunger is permitted to reciprocate relative to the housing, the plunger further comprising an end having a plunger contact surface. The housing contact surface is configured to engage one of the first arm contact surface or the second arm contact surface, and the plunger contact surface is configured to engage another of the first arm contact surface and the second arm contact surface. Further, the first arm contact surface, the second arm contact surface, the housing contact surface and the first plunger contact surface are configured to support the discrete lost motion device between the first arm and the second arm.

In an embodiment, the housing comprises a housing bore extending longitudinally into the housing from a first end of the housing and the plunger is disposed in the housing bore through the first end of the housing. In this embodiment, either a second end of the housing or the end of the plunger comprises a lost motion hydraulic passage is configured to receive hydraulic fluid for controlling the plunger between its first and second states. Further still, either the first arm or the second arm comprises a hydraulic supply passage configured to register with the lost motion hydraulic passage.

In an embodiment, the first and second arm contact surfaces are configured to permit rotation of the lost motion device relative to the first and second arms. For example, the first arm contact surface may be concave and at least one of the housing contact surface or the plunger contact surface is convex, or the first arm contact surface may be convex and at least one of the housing contact surface or the plunger contact surface is concave. As another example, the second arm contact surface may be concave and at least one of the housing contact surface or the plunger contact surface is convex, or the second arm contact surface may be convex and at least one of the housing contact surface or the plunger contact surface is concave.

In an embodiment, either the first arm or the second arm is configured for center pivoting. When the first arm is configured for center pivoting, the first arm may comprise a first arm pivot and the second arm may be configured for mounting on, and pivoting about, the first arm pivot. Alternatively, when the second arm is configured for center pivoting, the second arm may comprise a second arm pivot and the first arm may be configured for mounting on, and pivoting about, the second arm pivot. In yet another alternative, both the first arm and the second arm are configured for center pivoting.

In another embodiment, each of the first and second arms comprises an input end and an output end. In this embodiment, the discrete lost motion component is disposed between the output end of the first arm and the input end of the second arm. In this case, the output end of the first arm comprises the first arm contact surface and the input end of the second arm comprises the second arm contact surface.

In another embodiment, the first arm comprises a first arm stop surface and the second arm comprises a second arm stop surface. The first arm stop surface and the second arm stop surface are configured to prevent over-rotation of the first arm and the second arm away from each other.

In yet another embodiment, the first arm contact surface and the second arm contact surface are configured to be rotatably affixed to corresponding ones of the plunger contact surface and the housing contact surface.

As used herein, the term “operatively connected” is understood to refer to at least a functional relationship between two components, i.e., that the claimed components must be connected (potentially including the presence of intervening elements or components) in a way to perform an indicated function.

schematically illustrates an embodiment of a valve actuation systemin accordance with the instant disclosure incorporating a discrete lost motion component, and in which like reference numerals refer to like elements as compared to. As used herein, “discrete” refers to its conventional meaning of constituting a separate entity or part. Thus, in this second embodiment, the discrete lost motion component, rather than being housed or supported within one of the valve train components,, as in the case of, or housed or supported within a fixed member, as in the case of, is instead formed as a discrete component that is supported within the valve trainby one or more of its adjoining valve train components,, as described in further detail below. Generally, support of the discrete lost motion componentis provided by one or more supporting joints. As used herein, a supporting joint is a meeting of two elements that are (i) joined in the sense of being in close association or relationship with each other, from being in separatable contact with each other up to and including being inseparably connected to each other, and (ii) configured to bear or hold the discrete lost motion component within a valve train. Additionally, a supporting joint may provide freedom for the discrete lost motion componentto rotate relative to one or more adjoining valve train components.

In the example shown in, such support joints,are schematically illustrated as comprising contact surface,deployed on the lost motion componentand corresponding contact surfaces,deployed on the adjoining valve train components,. As described in greater detail below, the contact surfaces,of the lost motion componentand the corresponding contact surfaces,of the valve train components,are complementarily configured to facilitate support of the lost motion componentby the valve train components,, as well as to facilitate operation of the lost motion componentdespite movement of the valve train components,. Thus, it is understood that the various complementary contact surfaces described herein are examples of supporting joints, or portions thereof, that may be employed to implement the lost motion component(and various specific embodiments thereof described below).

Thus, the valve actuation systemis seen to comprise the discrete lost motion componentand the adjacent valve train components,that support the discrete lost motion component.

As further shown in, control of the discrete lost motion componentby the engine controlleris provided via a path through at least one of the adjoining valve train components,. For example, in the various embodiments described hereinbelow, such control is provided through the use of hydraulic fluid supplied under the control of the engine controller. However, as will be appreciated by those having skill in the art, other types of control schemes may be equally employed for this purpose. In the case of fluid supplied under the control of the engine controller, a feature of the instant disclosure is that such fluid supply passage passes through at least one of the contact surfaces,,,, various examples of which are further illustrated and described below.

Although specific implementations of the discrete lost motion componentbased on specific configurations of sub-components and locking mechanisms are described in greater detail below, a discrete lost motion componentin accordance with the instant disclosure is generally characterized in that it is capable of being controlled between a rigid/unlocked state and a compliant/unlocked state, regardless of the mechanism(s) employed for this purpose, and in that it is configured to be a discrete component that is supported by adjacent valve train components.

illustrate an embodiment of a valve actuation systemthat can be used to implement the valve actuation systemof. As illustrated, the valve actuation systemcomprises a discrete lost motion componentin addition to a shaft-mounted first armand a pivot-mounted, valve-side second arm. As best shown in, the valve actuation systemis operatively connected to a valve actuation motion source(in this embodiment, in the form of a cam, though other configurations are possible as known to those skilled in the art) and to a valve bridgeand corresponding engine valves,. In accordance with known techniques, the camincludes one or more cam lobesconfigured to provide main and/or auxiliary valve actuation motions to the engine valves,.

In this embodiment, the first armis configured to be mounted on a rocker shaft (not shown) via a rocker shaft boreformed in the first arm. Additionally, the first armincludes a motion receiving componentin the form, in this case, of a cam roller configured to contact the cam. Additionally, the first armincludes a bossextending opposite the motion receiving component, i.e., on the opposite side of the rocker shaft boreand toward the engine valves,. The bossincludes a pivotthat permits mounting of the second armthereon and further permits reciprocating movement of the second armabout the pivot. A distal end of the second arm(relative to the first arm) includes a swivel or e-footconfigured to establish contact with the valve bridge.

It is noted that, while the various embodiments illustrated and described herein comprise two engine valves and a corresponding valve bridge, it is appreciated that the valve actuation systems described herein may be equally applied to single-valve systems, i.e., system in which no valve bridge is required.

In a particular embodiment, the first armand the second armare “half rockers” in that, while they are operatively connected to respective ones of the valve actuation motion sourceand valve bridge/valves,, they do not fully span the distance between the valve actuation motion sourceand valve bridge/valves,, as in the case of “full rockers” known in the art. As described in further detail below, in combination with the discrete lost motion componentwhen operated in a locked or motion-conveying state, the first and second arms,may be operated as an essentially rigid unit such that valve actuation motions provided by the valve actuation motion sourceare conveyed to the valve bridge/valves,or, when the discrete lost motion componentis controlled to be in an unlocked state, as a compliant unit in which all valve actuation motions applied thereto (or almost all, as in the case of a “failsafe” lift provided even in the unlocked state) result in reciprocation of the first armrelative to the second arm, thus absorbing such motions relative to the valve bridge/valves,.

Referring again to, the discrete lost motion componentis deployed between, and supported by, the first armand the second arm. The discrete lost motion componentincludes a housingand a plungerdisposed therein through a first end of the housing. The housingand plungermay be both centered on a longitudinal axis of the lost motion component. As used herein, the modifier “discrete” refers to the configuration of the lost motion componentsuch that its exists as a separate structure relative to, and not encompassed by or contained in, other valve train components, yet still in communication with other valve train components via supporting joints for support within the overall valve train. As best shown in, the plungeris slidably disposed in a housing boreformed in the housing.

As further shown in, the housinghas a housing contact surfaceformed at a second end of the housing, and the plungerhas a plunger contact surfaceformed at a first end of the plungerextending out the housing. In a particular embodiment, each of the housing and plunger contact surfaces,, such as contact surfaces,shown in, is configured to mate with a complementary contact surface formed in adjoining valve train components, i.e., the first and second arms,. That is, the plunger contact surfaceand a corresponding contact surfaceof the first arm(such as contact surfaceshown in) collectively form one supporting joint and the housing contact surfaceand a corresponding contact surfaceof the second arm(such as contact surfaceshown in) collectively form another supporting joint.

In the illustrated example, both the housing and plunger contact surfaces,are formed as convex surfaces configured to engage corresponding and complementary concave surfaces,respectively formed in the first and second arms,as described below. However, it is appreciated that convex/concave surfaces illustrated inmay be switched, i.e., the housing and plunger contact surfaces,formed as concave surfaces and the first and second arm contact surfaces,formed as convex surfaces. Further still, the housing and plunger contact surfaces,may comprise a combination of concave and convex surfaces, with the corresponding contact surfaces,of the first and second arms also being a combination of complementary convex and concave surfaces. By combining convex and concave contact surfaces in this manner, a degree of manufacturing “fool proofing” is provided in that becomes difficult, if not impossible, to incorrectly orient the lost motion componentrelative to the first and second arms,. The illustrated embodiment further comprises a lost motion hydraulic passageformed in the first end the plungerand, more particularly, with an opening of the lost motion hydraulic passageformed within the plunger contact surface. Although the lost motion hydraulic passageis illustrated as being formed within the plunger, it is appreciated that such a passage may alternatively be formed in the second end of the housingand, more particularly with an opening of the lost motion hydraulic passageformed within the housing contact surface.

also illustrates additional features of the second arm. As noted above, the second armis mounted on the pivotprovided by the first arm. The pivotmay include a hydraulic passageoperatively connected to a constant supply of hydraulic fluid (not shown) provided by the rocker shaft. The hydraulic passagemay be in fluid communication with an annular channel (not shown) formed in an exterior surface of the pivot. The annular channel may align, and be in fluid communication, with a first lubricant supply passageformed in the second armthat, in turn, is in fluid communication with a second lubricant supply passageformed in the second arm. The first lubricant supply passageis fluid communication with a lash screw hydraulic passageformed in a lash screwextending from an end of the second arm distal relative to the pivot. In this manner, lubricating hydraulic fluid is supplied to the swivelcontacting the valve bridge. Similarly, the second lubricant supply passageprovides lubricating hydraulic fluid to the supporting joint established by the housing contact surfaceand the corresponding contact surfaceprovided by the first arm.

As noted above, the convex housing and plunger contact surfaces,are shown engaging with corresponding, concave contact surfaces,respectively formed in the first and second arms,. When biasing forces are applied to (or by) the lost motion component, resulting in contact between the lost motion componentand the adjoining first and second arms,, the mating engagement of the housing and plunger contact surfaces,with the corresponding contact surfaces,tends to prevent dislodgment of the lost motion componentfrom between the first and second arms,due to other forces applied to either the housingor plungerand not substantially parallel to the longitudinal axis of the lost motion component(e.g., vibrations or torques). While other configurations of the complementary contact surfaces,,,may be employed for this purpose, as described below, the illustrated convex and concave surfaces permit rotational movement of the first or second arms,relative to either the housingor plungerto the extent that the contact surfaces,,,are permitted to slide relative to one another without losing the mating engagement, i.e., operating as flexible supporting joints. In an embodiment, any of the respective concave and convex contact surfaces illustrated and described herein may be formed as spherical contact surfaces.

As will be appreciated by those skilled in the art, the mating engagement of the contact surfaces,,,helps facilitate the retention of the lost motion componentbetween the first and second arms,so long as the contact surfaces,,,are permitted to stay in close relationship with each other. In order to ensure such close relationship throughout all operating states of the valve actuation system(as well as assembly thereof during manufacturing), it is desirable to ensure that the first and second arms,are not permitted to rotate away from each other such that the close relationship between the corresponding contact surfaces,,,is lost, which could allow inadvertent displacement of the lost motion component. To this end, the first armmay comprise a first arm stop surfaceand the second armmay comprise a second arm stop surfaceconfigured to engage with the first arm stop surfaceso as to prevent over-rotation of the first and second arms,relative to each other. In the example illustrated in, the first arm stop surfaceand the second arm stop surfaceare configured to be in relative to proximity to each other such that rotation of the second armabout the pivotand away from the first arm(clockwise, as illustrated in) will cause the first arm stop surfaceand the second arm stop surfaceto engage each other, thereby preventing further rotation. By selecting the distance between the first arm stop surfaceand the second arm stop surfaceto be completely taken up (i.e., for the surfaces,to contact each other) when a maximum permitted rotation of the first armaway from the second armis reached, such over rotation of the first armaway from the second armmay be prevented.

As further shown in, the first armis configured with first, second and third hydraulic passages,,, where first hydraulic passageis configured to register with a selectable (switched) hydraulic fluid supply provided by the rocker arm (not shown) as known in the art, the third hydraulic passageis configured to register with the lost motion hydraulic passageformed in the plungerand the second hydraulic passageprovides a connection between the first and third hydraulic passages,. In an embodiment, the respective diameters of the third hydraulic passageand the plunger's lost motion hydraulic passageare sufficiently large to ensure fluid communication between these hydraulic passages,despite rotational movement of the first armrelative to the plunger. As described below, the supply or removal of pressurized hydraulic fluid through the hydraulic passages,may provide control of locked and unlocked states of operation of the lost motion component.

Once again referring to, the lost motion componentis depicted in cross section, thereby better illustrating a hydraulically controlled locking mechanism, constituting a subassembly of the lost motion component, deployed between the housingand plunger. As further shown, a plunger springis provided to bias the plungerout of the housing. The locking mechanismshown inis generally of the type described in U.S. Pat. No. 9,790,824, the teachings of which patent are incorporated herein by this reference and replicated in relevant part below.

As shown in, the locking mechanismincludes the plungerdisposed within a housing boreformed in and extending along a longitudinal axis of the lost motion componentfrom a first end of the housing. An inner plungeris slidably disposed in a longitudinal boreformed in the plunger. Locking elements in the form of wedgesare provided, which wedges are configured to engage with an annular outer recessformed in a surface defining the housing bore. The illustrated embodiment is of a normally locked locking mechanism, i.e., in the absence of hydraulic control applied to the inner plungervia, in this case, the lost motion hydraulic passage, an inner plunger springbiases the inner plungerinto position such that the wedgescontact a larger-diameter portion of the inner plungerand thereby radially extend out of openings formed in the plunger, thereby engaging the outer recessand effectively locking the plungerin place relative to the housing.

In this locked state, any valve actuation motions (whether main or auxiliary motions) applied to the lost motion componentare conveyed by the lost motion component. It is noted that, despite being in the locked state as shown in, a longitudinal extent of the outer recessis greater than a thickness of the wedgessuch that a small amount of movement is nevertheless permitted between the plungerand housingas described in further detail below. As shown in, this additional space has been taken up as in the case, for example, where a valve actuation motion has been applied to the lost motion componentthereby overcoming any outward bias applied by the plunger springto the plunger.

Alternately, when the lost motion componentis unloaded (e.g., during cam base circle) while still in the locked state, the bias applied by the plunger springcauses the plungerto translate in its boreto the extent permitted by the longitudinal extent of the outer recess, i.e., to the left as shown inuntil the wedgesabut the leftmost surface of the outer recess. In this manner, the plunger springensures that the housing and plunger contact surfaces,continue to be biased into contact with the corresponding contact surfaces,of the adjacent arms,.

Such bias applied by the plunger springcan be selected to additionally ensure that the arms,(or additional up- or downstream valve train components in the system, not shown) are biased into continuous contact with respective endpoints of the valve train, i.e., valve actuation motions sources and engine valves. Further still, because outward travel of the plungerfrom within its boreis limited by the longitudinal extent of the outer recess(when in the locked state), the bias applied by the plunger springto the adjacent arms,(and, once again, any additional up- or downstream valve train components in the system) will not apply excess biasing forces against the normal operation of any automatically adjustable, compliant components within the valve train, e.g., hydraulic lash adjusters (HLAs) or the like. It is appreciated that other techniques for such travel limiting of the plungerrelative to the housing, even during an unlocked state of the lost motion component, may also be employed for this purpose. Additionally, the plunger springis preferably selected such that, regardless of the locked/unlocked state of the locking mechanism, the force applied by the plunger springon any of the valve train components will not apply excess biasing forces on compliant valve train components {such as HLAs) or engine valve springs.

Referring again to, provision of hydraulic fluid to the top (leftmost surface as shown in) of the inner plungervia the lost motion hydraulic passage, sufficiently pressurized to overcome the bias of the inner piston spring, causes the inner plungerto translate within the boresuch that the wedgescontact a smaller-diameter portion of the inner plungerand are permitted to retract and disengage from the outer recess, thereby effectively unlocking the plungerrelative to the housingand permitting the plungerto slide freely within its bore, subject, in this case, to the bias provided by the plunger spring. In this unlocked state, any valve actuation motions applied to the lost motion componentwill cause the plungerto reciprocate in its bore. In this manner, and presuming travel of the plungerwithin its boreis greater than the maximum extent of any applied valve actuation motions (i.e., that the plungeris unable to bottom out in its bore), such valve actuation motions are not conveyed by the lost motion componentand are effectively lost. Alternatively, as noted previously, travel of the plungerwithin its borecould be configured such that the plunger“bottoms out,” i.e., makes contact with the closed end of the bore, so as to always provide a “failsafe” valve lift in the event of a failure of the locking mechanism.

As noted above, the contact surfaces,,,provided by the lost motion componentand the first and second arms,are configured to accommodate rotation of the lost motion componentrelative to either or both of the first and second arms,. Such rotations, being dependent upon the operating state of the lost motion component, are further illustrated and described, in highly schematic fashion, with reference to.illustrate a valve actuation systemin accordance with the instant disclosure including, in particular, a first arm, second armand lost motion component, as described in accordance with the various embodiments set forth herein, rotating (in this case) about a rocker shaft. As further shown the lost motion componentcomprises a housingand a plungeras described herein.

illustrate the condition in which the locking mechanism of the lost motion componentis maintained in its locked state such that the lost motion componentand first and second arms,essentially function as a single, rigid unit and valve actuations motions applied by the valve actuation motion sourceare conveyed from the first arm, to the lost motion componentand then to the second arm. For ease of illustration, the first armand second armare depicted as having perpendicular portions,, respectively, extending therefrom and providing fixed contact surfaces for the corresponding contact surfaces of the housingand the plunger. In this locked state, as shown in, the plungerextends from the housingby a length Land contacts the perpendicular portionof the first armat an angle θ. Similarly, the housing, including that portionof the housingcontacting the second arm, has a substantially unchanging length Land, in this locked state, contacts the perpendicular portionof the second armat an angle θ. As further shown in, when no valve actuation motions (e.g., cam base circle) are applied to the first arm, no deflection or valve lift is realized by the second arm.

Because the lost motion componentand first and second arms,operate as a single unit during this locked state, application of a maximum valve actuation motion by the valve actuation motion sourceto the first arm(as shown in) results in application of such valve actuation motion to the second armand a deflection or valve lift, D, of the second arm. Despite application of such valve actuation motion, the locked state of the lost motion componentensures that the values of L, L, θand θremain essentially the same, resulting in little to no rotation of the plungeror housing,relative to the first or second arms,, respectively.

In contrast,illustrates the condition in which the locking mechanism of the lost motion componentis maintained in its unlocked state such that the lost motion component, via the plungerand first arm, absorbs any valve actuation motions applied to the first armwith the result that no valve actuation motions are conveyed to the second arm. This is depicted inby the lack of any deflection or valve lift experienced by the second arm. However, the angles θ′, θ′ at which the plungerand the housing,respectively contact the first and second arms,and the length L′ of the plungerextending out of the housingduring this unlocked state are changed relative to the unlocked state during application of the maximum valve actuation motion as shown in. More specifically, application of the maximum valve actuation motion results in L1′<L1 and rotation of the lost motion componentas evidenced by θ′<θand θ′<θ. Once again, however, such rotation of the lost motion componentis facilitated by the configuration of the respective contact surfaces as described herein.

, wherein like reference numerals represent like elements, illustrate an alternative embodiment of a valve actuation systemthat can be used as the valve actuation systemshown in. The valve actuation systemcomprises a lost motion componentin addition to a pivot-mounted, cam-side first armand a shaft-mounted second arm. As with the systemillustrated in, the valve actuation systemis operatively connected to a valve actuation motion source(e.g., a cam) and to a valve bridgeand corresponding engine valves,.

In this embodiment, the second armis configured to be mounted on a rocker shaft (not shown) via a rocker shaft boreformed in the second arm. A distal end of the second arm(away from the rocker shaft bore) includes a swivel or e-footconfigured to establish contact with the valve bridge. Additionally, the second armincludes a bossextending opposite the swivel or e-foot, i.e., on the opposite side of the rocker shaft boreand toward the valve actuation motion source. The bossincludes a pivotthat permits mounting of the first armthereon and reciprocating movement of the first armabout the pivot. Additionally, the first armincludes a motion receiving componentin the form, in this case, of a cam roller configured to contact the cam.

In an embodiment, and once again as with the systemillustrated in, the first armand the second armare “half rockers.” Thus, once again, in combination with the lost motion component, the first and second arms,may be operated as an essentially rigid unit such that valve actuation motions provided by the valve actuation motion sourceare conveyed to the valve bridge/valves,or, when the lost motion componentis controlled to be in an unlocked state, as a compliant unit in which all valve actuation motions applied thereto result in reciprocation of the first armrelative to the second arm, thus absorbing such motions relative to the valve bridge/valves,.

As before, and as best illustrated in, each of the housing and plunger contact surfaces,is configured to mate with a complementary contact surface formed in adjoining valve train components, i.e., the first and second arms,. In the illustrated example, both the housing and plunger contact surfaces,are formed as convex surfaces configured to engage corresponding and complementary concave surfaces,respectively formed in the first and second arms,. However, it is appreciated that convex/concave surfaces illustrated inmay be switched, i.e., the housing and plunger contact surfaces,formed as concave surfaces and the first and second arm contact surfaces,formed as convex surfaces. Further still, the housing and plunger contact surfaces,may comprise a combination of concave and convex surfaces, with the corresponding contact surfaces,of the first and second arms also being a combination of complementary convex and concave surfaces. By combining convex and concave contact surfaces in this manner, a degree of manufacturing “fool proofing” is provided in that becomes difficult, if not impossible, to incorrectly orient the lost motion componentrelative to the first and second arms,.

As shown in, the first armis mounted on the pivotprovided by the second arm. The pivotmay include a hydraulic passageoperatively connected to a selectable (switched) supply of hydraulic fluid (not shown) provided by the rocker shaft. As shown in, the hydraulic passageis in fluid communication with a lubrication passagethat provides lubricating hydraulic fluid to the motion receiving component. The hydraulic passagemay additionally be in fluid communication with an annular channel (not shown) formed in an exterior surface of the pivot. The first armis further configured with a first hydraulic passagein fluid communication with a second hydraulic passageas shown in. The annular channel formed in the pivotmay align, and be in fluid communication, with the first hydraulic passage. In turn, the second hydraulic passageis configured to register with the lost motion hydraulic passageformed in the plunger. In this case, the respective diameters of the second hydraulic passageand the plunger's lost motion hydraulic passageare sufficiently large to ensure fluid communication between these hydraulic passages,despite rotational movement of the first armrelative to the plunger. As before, the supply or removal of pressurized hydraulic fluid through the hydraulic passages,,may provide control of locked and unlocked states of operation of the lost motion component.

As further shown in, a first lubricant supply passageis formed in the second armthat, in turn, is in fluid communication with a second lubricant supply passageformed in the second arm. The first lubricant supply passageis in fluid communication with a constant supply of hydraulic fluid (not shown) provided by the rocker shaft and is also in fluid communication with a lash screw hydraulic passageformed in a lash screwextending from an end of the second arm distal relative to the pivot. In this manner, lubricating hydraulic fluid is supplied to the swivelcontacting the valve bridge. Similarly, the second lubricant supply passageprovides lubricating hydraulic fluid to the joint established by the housing contact surfaceand the corresponding contact surfaceprovided by the second arm.