Patent Description:
Internal combustion engines are utilized ubiquitously in many applications and industries, including transportation and trucking. Valve actuation systems for use in internal combustion engines are well known in the art. Such systems typically include one or more intervening components that convey valve actuation motions from a valve actuation motion source (e.g., a cam) to one or more engine valves, the intervening components constituting a valve train. These valve actuation systems may primarily facilitate a positive power mode of operation in which the engine cylinders generate power from combustion processes. The intake and exhaust valve actuation motions associated with the standard combustion cycle are typically referred to as "main event" motions. Known engine valve actuation systems may provide for modified main event valve motion, such as early or late intake valve closing. In addition to main event motions, known engine valve actuation systems may facilitate auxiliary valve actuation motions or events that allow an internal combustion engine to operate in other modes, or in variations of positive power generation mode (e.g., exhaust gas recirculation (EGR), early exhaust valve opening (EEVO), etc.) or engine braking in which the internal combustion engine is operated in an unfueled state, essentially as an air compressor, to develop retarding power to assist in slowing down the vehicle.

In many engine systems, the valve train may comprise a finger follower, which is essentially a lever pivoting at one end with the other end of the lever contacting the load, i.e., the engine valves. The finger follower typically comprises a motion receiving component, disposed between the ends of the lever, to receive the valve actuation motions from a motion source (such as a cam), which motions are then conveyed to the engine valves via the load end of the lever.

Known variations of the finger follower components described above include so-called "switching" finger followers, an example of which is described in <CIT>. As shown in <FIG>, the finger follower comprises a body <NUM> pivoting about, in this example, a hydraulic lash adjuster (HLA) <NUM>. The body <NUM> also supports, in this example, lateral followers <NUM> that may rotate about a shaft <NUM> and that may engage a locking mechanism <NUM>. As best illustrated in <FIG>, the body <NUM> further supports a central roller follower <NUM> positioned between the lateral followers <NUM>. As further shown in <FIG>, the locking mechanism <NUM> may be controlled such that a locking bar <NUM> is either maintained in an extended position and thereby in contact with tabs <NUM> of the lateral followers <NUM> (<FIG>), or maintained in a retracted position and thereby avoiding contact with the tabs <NUM> (<FIG>). When the locking bar <NUM> contacts the tabs <NUM> (i.e., in a locked or on condition), the lateral followers <NUM> are prevented from rotating about the shaft <NUM> and are therefore maintained in a rigid relationship with the body <NUM>. Thus, motions applied to the lateral followers <NUM> by lateral cam lobes <NUM> are conveyed to body and ultimately to the engine valve <NUM>. In this case, valve actuation motions provided by central cam lobe <NUM> are not conveyed to the central roller follower <NUM> with which it is aligned. On the other hand, when the locking bar <NUM> is retracted (i.e., in an unlocked or off condition), the lateral followers <NUM> are free to rotate about the shaft <NUM> such that any motions applied by the lateral cam lobes <NUM> are absorbed by the lateral followers <NUM> and not conveyed to the engine valve <NUM> by the body <NUM>. In this case, valve actuation motions provided by the central cam lobe <NUM> are conveyed to the central roller follower <NUM> and, thereby, on to the engine valve <NUM>.

Switching finger followers are most often found in light duty automotive applications. However, they have not been applied in heavy and medium duty diesel or natural gas engines partially because of the highly loaded events and failures due to partially engaged switching mechanisms. Failures are known to occur even in light duty applications due to the same partial engagement problem at much lower loads. With reference to the example in <FIG>, such a partial engagement occurs when the locking bar <NUM> only partially overlaps with the tab <NUM>, i.e., at a location between the engagements illustrated in <FIG>. When such partial engagements occur, contract stresses between the moving parts of the locking mechanism can increase significantly, leading to damage and/or failure of the locking mechanism.

Another disadvantage of prior art switching finger followers is that their use typically necessitates controls for precise timing in order to prevent partial engagement of their actuating or locking components. This may necessitate added cost and complexity, especially in multiple cylinder engine environments. For example, in such environments, it may be necessary to provide designated control solenoids for each switching finger follower in order to eliminate the potential for control circuit transients (i.e., lag in a hydraulic circuit) and to ensure precise timing of actuating components relative to the finger follower motion.

Switching finger followers may have application to lost motion valve actuation systems. In such systems, the switching finger follower may switch between a first position, in which the full valve motion from a motion source, such as a cam, is conveyed to the engine valves, and a second position, in which only part of the full valve motion is conveyed to the engine valves. An example of a single-source, lost motion lift profile as described herein may be found in <FIG>, curve <NUM> of <CIT>. Owing to the aforementioned disadvantages, however, prior art switching finger followers may have only limited applicability to lost motion valve actuation systems.

It would therefore be advantageous to provide systems and methods that address the aforementioned shortcoming and others in the prior art. <CIT> relates to a two-step roller finger cam follower having a spool-shaped low-lift roller. <CIT> relates to a hydraulic lash adjuster with electromechanical rocker arm latch linkage. <CIT> relates to a variable valve mechanism of an internal combustion engine. <CIT> relates to a locking mechanism for variable actuation using a shuttle pin and return spring.

Responsive to the foregoing challenges in the prior art, the instant disclosure provides various embodiments of a switching finger follower system with improved operating characteristics and improved performance and durability.

The above-mentioned difficulties with prior switching finger followers may be overcome based on various embodiments disclosed herein. The advances in the art described herein are particularly advantageous in that they eliminate the potential for partial engagement of finger follower switching mechanism actuating components. A related advantage is the elimination of variations in the locked or supported positions of the motion receiving component on the switching finger follower. The switching finger follower configurations have consistent contact geometries between cooperating parts and positively defined switching mechanism positions and thus positively defined positions of the finger follower lever and thus the motion receiving component relative to the body. This leads to more accurate and dependable operation and control of valve motion.

Additionally, because the switching finger follower configurations disclosed herein are not sensitive to partial engagement, activation of the switching mechanism, they may be utilized at lower cost and complexity in multiple cylinder engine environments. The improved switching mechanism and actuator therefore eliminate the need for precise timing by control components. For example, in the case of hydraulically actuated switching mechanisms under the control of solenoids, the disclosed embodiments may eliminate the need for a designated, controlled solenoid for each switching mechanism. Rather, the disclosed advances make it feasible for a single solenoid to activate switching mechanisms for multiple cylinders, thereby simplifying the overall system and reducing costs.

Further still, the embodiments described herein are applicable to and may be used to improve single-source lost motion systems where a single valve actuation motion source (such as a cam) provides one or more lower lift events where some (or all) lift is lost, and one or more higher lift events where more (or all) lift from the cam lobe is conveyed to the engine valves. Further still, the embodiments described herein are applicable to and may be used to improve lost-motion valve actuation systems in which valve motion is entirely lost, as may be required in systems that utilize cylinder deactivation.

The embodiments described herein may be particularly advantageous in achieving alternative valve motions, such as braking late intake valve closing (LIVC), early exhaust valve opening (EEVO), internal exhaust gas recirculation (IEGR) etc..

According to an aspect of the disclosure, there is provided a finger follower system for use in an internal combustion engine valvetrain as defined in claim <NUM> comprising: a follower body having a pivot end and a motion transmitting end; a lever adapted to pivot relative to the follower body; a motion receiving component having a motion receiving surface disposed between the follower body pivot end and the follower body motion transmitting end; and an adjustable support assembly including a movable latch for providing selective support to the lever, the adjustable support assembly adapted to maintain the latch in a first latch position and a second latch position relative to the follower body. According to a further aspect, the adjustable support assembly is further adapted to allow the latch to move to the first position when the latch is not in the second position. In some applications, the adjustable support assembly may be further adapted to support the lever in two defined positions, providing engagement between the lever and the latch when the latch is in the first latch position and when the latch is in the second latch position. In other applications where the finger follower may facilitate complete loss of motion source motion, such as in cylinder deactivation applications, the adjustable support assembly may be adapted to provide for engagement between the latch and lever when the latch is in a first latch position, and to permit the lever to pivot free of the latch (i.e., no engagement between the latch and lever) when the latch is in a second latch position.

A finger follower with an adjustable support assembly includes an adjustable latch or lever engaging member adapted to move within the follower body to support the finger follower lever in at least one position. The lever engaging member or latch cooperates with an actuating piston, which may extend through a transverse bore in the lever engaging member. The piston has first and second support surfaces which may provide for two respective positively defined positions for the lever engaging member. In some applications, these two positions may correspond to positively defined support positions for the finger follower lever. In other applications, only one of the latch positions may support the lever, and the other position of the latch may correspond to the lever being free to pivot to a (lower) position in which it is not engaged with the latch. The adjustable support assembly structure is adapted to avoid application of load forces to the actuating components when the lever engages the latch in a position other than the precisely defined positions defined by the adjustable support assembly, thus avoiding damage to the actuating components and/or lever due to partial engagement.

The finger follower includes a lever engaging member or latch supported for movement relative to the finger follower body and having a substantially planar lever engaging member surface or latch surface extending at an angle to a latch movement direction for engaging an arcuate surface on the lever. The finger follower lever may be provided with an arcuate surface adapted to be engaged by the planar lever engaging surface on the lever engaging member. The lever engaging member surface and lever surface are thus adapted to maintain a substantially similar contact geometry when the lever and lever engaging member surface are engaged. In addition to eliminating potential for partial engagement, these aspects provide for improved durability and operation.

According to another implementation, the finger follower assembly may be applied in single motion source lost motion engine valvetrain environments. In some applications, the adjustable support assembly may support the finger follower lever in at least two positions, at least one of which may be a lost motion position. In other applications, the adjustable support assembly may support the finger follower lever in at least one position, and in another position, permit the finger follower lever to pivot freely such that no motion source motion is conveyed to the engine valves (as maybe the case in cylinder deactivation applications). A biasing assembly may comprise at least one resilient element disposed between at least one spring support on the follower body and at least one spring support on the lever. A travel limiter on the body may limit upward movement of the lever. One or more precisely defined lever support positions may be implemented by the interaction of the lever engaging member and actuating piston to provide for full or partial conveyance (or full or partial loss) of valve motion through the lost motion finger follower.

According to another implementation, a finger follower may be provided with an eccentric pivot mount that may provide for adjustment of the position of the finger follower lever relative to the follower body.

Other aspects and advantages of the disclosure will be apparent to those of ordinary skill from the detailed description that follows and the above aspects should not be viewed as exhaustive or limiting. The foregoing general description and the following detailed description are intended to provide examples of the inventive aspects of this disclosure and should in no way be construed as limiting or restrictive of the scope defined in the appended claims.

The above and other attendant advantages and features of the invention will be apparent from the following detailed description together with the accompanying drawings, in which like reference numerals represent like elements throughout. It will be understood that the description and embodiments are intended as illustrative examples according to aspects of the disclosure and are not intended to be limiting to the scope of invention, which is set forth in the claims appended hereto. In the following descriptions of the figures, all illustrations pertain to features that are examples according to aspects of the instant disclosure, unless otherwise noted.

<FIG> is a perspective view of an example assembled switching finger follower system <NUM> in accordance with the instant disclosure. <FIG> is an exploded perspective view of the same system. In particular, the switching finger follower may comprise a body or housing <NUM>, arranged to support or house various other system components. Body <NUM> may extend in a longitudinal direction from a motion transmitting end or valve engaging end <NUM>, adapted to interface with or engage one or more engine valves, to a pivot end <NUM>, adapted to interface with or engage a pivot, which may include an HLA. Body <NUM> may further comprise a pair of lateral, longitudinally extending arms <NUM> and <NUM>, defining a lever recess or pocket <NUM> therebetween. Arms <NUM> and <NUM> may include respective pivot pin receiving bores <NUM> and <NUM> at the valve engaging end <NUM> for securing a lever pivot pin <NUM> therein. A pair of lateral roller followers <NUM> and <NUM> may be secured to arms <NUM> and <NUM> via shafts <NUM> and <NUM>, respectively. The lateral roller followers <NUM>, <NUM> are configured to receive valve actuation motions from complementarily configured valve actuation motion sources, for example, motion sources similar to the lateral cam lobes <NUM> illustrated in <FIG>. Although the lateral followers are illustrated in roller form, it is appreciated that the instant disclosure need not be limited in this regard as the lateral followers could be implemented, for example, as flat follower contact areas extending from the body <NUM>.

Body <NUM> may further support a lever <NUM> having a fastened end <NUM>, that may be mounted to pivotably cooperate with the follower body <NUM>, and extending in the longitudinal direction to a free end <NUM>. The fastened end of lever <NUM> may be fastened to the lever pivot pin <NUM> secured to arms <NUM>, <NUM> of the body <NUM>.

Lever <NUM> may have a shape that is complementary to the recess or pocket <NUM> in the body <NUM>, thereby providing for a nested positioning within the body <NUM> and an overall compact finger follower configuration. Lever <NUM> may be formed as a precision, unitary stamped metal (i.e., steel) component having a generally concave shape with a bottom wall <NUM> and an integral outer wall <NUM> extending from the bottom wall <NUM>. A central portion of lever <NUM> may support and house a motion receiving component, cooperatively associated with the lever. The motion receiving component may be a central roller follower <NUM> supported on a shaft <NUM> affixed to the lever <NUM>. Alternatively, the motion receiving component cooperatively associated with the lever may be a contact surface directly on or attached to the lever and adapted to directly engage the motion source or a valve train component cooperating with the motion source. A recess or cutout <NUM> may be formed in bottom wall <NUM> to accommodate the central roller follower <NUM>. Free end <NUM> of the lever may have an arcuate or otherwise curved lever end wall <NUM> having an arcuate or otherwise curved end surface <NUM>, for selectively engaging an adjustable support assembly <NUM> integrated into the body <NUM>, as will be described. End wall <NUM> may extend to and be contoured to have a smooth transition with the bottom wall <NUM>. Lever end wall <NUM> may extend between a reduced lateral dimension between the opposing portions of outer wall <NUM>, which may provide added stability and strength as well as reduce the potential for deformation of the end wall <NUM> during operation.

As will be recognized, central roller follower <NUM> may be configured to selectively receive valve actuation motions from a complementarily configured valve actuation motion source. Referring, for example, to the engine environment described above with respect to <FIG>, the central roller follower <NUM> may receive valve actuation motions from a central cam lobe, similar to cam lobe <NUM> in <FIG>. As will be recognized, according to aspects of the disclosure, the finger follower configurations described herein have the advantage of permitting wider lateral and central follower dimensions compared to prior art systems such as the system described above with respect to <FIG>. This, in turn, permits wider cam surfaces and may thus provide reduced contact stresses and wear between cams and followers, for example.

Referring additionally to <FIG>, the pivot end <NUM> of the finger follower body <NUM> may include a longitudinal bore <NUM> and a transverse bore <NUM> formed therein for housing components of an adjustable support assembly <NUM>. Pivot end <NUM> may also include a concave recess or pocket <NUM> for interfacing with a suitable pivot assembly, such as a hydraulic lash adjuster having a post adapted to fit within the recess or pocket <NUM>, and including a hydraulic passage <NUM> (<FIG>) for delivering a pressurized hydraulic working fluid (oil) to the finger follower, as will be further described.

Adjustable support assembly <NUM> includes lever engaging member or latch <NUM> and an actuating piston <NUM> cooperatively associated therewith. Lever engaging member or latch <NUM> may be disposed in longitudinal bore <NUM>, which includes a cylindrical guiding surface <NUM> for supporting and facilitating sliding movement of the lever engaging member or latch <NUM>. Lever engaging member or latch <NUM> may have a generally cylindrical shape including an outer cylindrical surface <NUM> and a substantially planar lever engaging surface <NUM>, which may extend at an angle to the axis of lever engaging member or latch <NUM>. A transverse actuating piston receiving bore <NUM> extends through the lever engaging member or latch <NUM> for receiving and cooperating with the actuating piston <NUM>. Moreover, lever engaging member or latch <NUM> may be provided with chamfered surfaces <NUM> (<FIG>) on each side, which transition from the outer surface of lever engaging member or latch <NUM> to the piston receiving bore <NUM> to provide for smooth interaction with the surfaces of piston <NUM>. It will also be recognized that chamfered surfaces <NUM> provide for a reduction in the width of transverse piston receiving bore <NUM> and thereby eliminate the need for precise alignment of the transverse bore <NUM> with the piston <NUM> in order for the transverse bore <NUM> to engage the reduced diameter piston surface <NUM>.

Actuating piston <NUM> includes a first support surface <NUM> adapted to engage and support the lever engaging member or latch <NUM> in a first position within longitudinal bore <NUM>, which first position may correspond to an unlocked, or lower or retracted position of the lever <NUM> and central follower <NUM> relative to body <NUM>. First support surface <NUM> is a cylindrical surface having a first diameter. Actuating piston <NUM> also includes a second support surface <NUM> adapted to engage and support the lever engaging member or latch <NUM> in a second position within longitudinal bore <NUM>, which second position may correspond to a locked, or raised, or deployed position of the lever <NUM> and central follower <NUM> relative to body <NUM>. Second support surface may be a cylindrical surface having a second diameter, greater than the first diameter of first support surface and substantially corresponding to the diameter of the transverse bore <NUM> of body <NUM> and substantially corresponding to the diameter of transverse actuating piston receiving bore <NUM>. Disposed between the first support surface <NUM> and second support surface <NUM> may be a transition surface <NUM> on the actuating piston <NUM>, which transition surface <NUM> may have a generally tapered or conical shape adapted to provide for smooth transition of the lever engaging member from the first support position to the second position during a locking movement of the actuating piston. Transition surface <NUM> may also facilitate the reversion of the actuating piston to an unlocked position if actuating piston may be in an intermediate position between a fully retracted or fully deployed position within transverse bore <NUM>, as will be explained in more detail below.

Operation of the adjustable support assembly <NUM> will now be described. <FIG> and <FIG> illustrate the example switching finger follower in an "unlocked" or off state, in which the lever <NUM> is in a lower position relative to the body <NUM>. Piston <NUM> is retracted fully within transverse bore <NUM>, bottoming against an end wall <NUM> of transverse bore <NUM>. A biasing device, such as a coil spring <NUM>, may be disposed in the transverse bore <NUM> to engage a spring seat <NUM> and bias the piston towards the retracted position. This position aligns the first support surface <NUM> of the actuating piston <NUM> with the transverse piston receiving bore <NUM> of lever engaging member or latch <NUM>. Lever engaging member or latch <NUM> is retracted within the longitudinal bore such that contact surface <NUM> is positioned to contact the lever end surface <NUM> along a first line of contact, which may be at a lower position on the surface <NUM> of (i.e., below the axis of) lever engaging member or latch <NUM>. A spring retaining cap <NUM> may be affixed to body <NUM> (i.e., by press fit or threads) to retain the spring <NUM> and piston <NUM> within the transverse bore <NUM>.

As shown in <FIG>, the pivot receiving pocket <NUM> of body <NUM> may be hydraulically connected, via a hydraulic passage <NUM>, to the transverse bore <NUM>. When pressurized hydraulic fluid is not supplied to the first transverse bore via the passage <NUM>, the biasing element (not shown) may bias the piston <NUM> leftward as illustrated in <FIG>. In this state, the reduced diameter surface <NUM> of the piston <NUM> is aligned with the lever engaging member or latch <NUM>. Because the lever <NUM> is thus maintained in a lower position relatively to the body <NUM>, the central roller follower <NUM> is likewise maintained in a lower position, thereby establishing lash between the central roller follower <NUM> and its corresponding valve actuation motion source. This lash space causes any valve actuation motions that would otherwise be applied to the central roller follower <NUM> to be lost.

With additional reference to <FIG> and <FIG>, according to aspects of the disclosure, adjustable support assembly <NUM> may be actuated to cause the lever <NUM> to be supported at a second position relative to body <NUM>. When pressurized hydraulic fluid is provided, for example, from a passage in the supporting HLA (not shown) via the passage <NUM> to the transverse bore <NUM>, the leftward bias applied to the piston <NUM> may be overcome such that the piston <NUM> displaces to a point where the second support surface <NUM> is aligned with and supports the lever engaging member or latch <NUM>. It will be recognized from the instant disclosure that other actuation techniques may be utilized instead of or in addition to the hydraulic fluid actuation system described by example herein. For example, pneumatic, electromagnetic or purely mechanically interacting components may be utilized to provide the motive force for actuation of elements, such as the actuating piston or pin <NUM> described. Transition surface <NUM> may cause the lever engaging member <NUM> to move (to the right in <FIG>), from a first latch position to a second latch position, as the piston <NUM> moves. Consequently, as best shown in <FIG>, the lever end surface <NUM> may contact the sliding member surface <NUM>, in this case, at a comparatively high point of the sliding member contact surface <NUM>. Lever <NUM> and central roller follower <NUM> are thus supported in a second position, in this case, higher than the position corresponding to the first (retracted) position of the lever support member <NUM> and central roller follower <NUM> may take up any lash between the central roller follower <NUM> and its corresponding valve actuation motion source. In this manner, valve actuation motions are applied to the central roller follower <NUM> and thereafter conveyed to the body <NUM> by virtue of the contact between the lever <NUM> and sliding member <NUM>, and the further contact between the sliding member <NUM> and the body <NUM>. As will be recognized from the instant disclosure, and as will be described in more detail in the context of a lost-motion, cylinder deactivation application below, the first and second positions of the latch may define alternative states of the lever. More particularly, in a lost-motion cylinder deactivation context, the first position of the latch may be a "normal" operating state facilitating a higher elevation of the lever relative to the follower body and the second position of the latch may be a (retracted) "lost-motion activated" operating state, wherein the lever does not engage the latch at all but instead may lower to a resting position relative to the follower body (i.e., facilitated by a stop defining a lower limit of travel of the lever). In this state, the lever is in a lower position such that all valve motion that would otherwise be conveyed by the motion source may be "lost" or absorbed by the finger follower system.

According to an aspect of the disclosure, the adjustable support assembly <NUM> provides advantages in distributing the load applied by the lever <NUM> (illustrated by the heavy black arrow in <FIG>). More particularly, a vertical component of the load is distributed to the body <NUM> (illustrated by the vertical dashed arrow) via the engagement of outer surface <NUM> of lever engaging member, also referred to herein as a latch, <NUM> with interior surface of longitudinal bore <NUM>. A horizontal component (illustrated by the horizontal dashed arrow) of the load is distributed through the lever engaging member or latch <NUM> to the piston <NUM>. As will be recognized, the angle of lever engaging member surface <NUM> may be selected to provide for a majority of the load to distributed across a larger area of the guide surface of longitudinal bore <NUM>, with a smaller component of the load being born by the actuating piston <NUM>. It will be further recognized that, this load distribution will result regardless of the position of the lever engaging member or latch <NUM> within the longitudinal bore <NUM>. Moreover, owing to the unique interaction of the lever end surface <NUM> with the surface <NUM> of the lever engaging member or latch <NUM>, the potential for partial engagement between these elements is effectively eliminated. Additionally, by providing the lever end surface <NUM> with a substantially arcuate shape as shown, the contact stress between the lever engaging member <NUM> and lever end surface <NUM> may be controlled, that is, the size and geometry of the contact area between elements can be kept substantially consistent, in all operating states and positions of the lever relative to the body, i.e., regardless of the position at which the lever engaging member <NUM> engages the lever end surface <NUM>. The lever engaging member surface <NUM> and lever end surface <NUM> may be adapted to maintain a substantially similar contact geometry in all positions of the lever in which it contacts the lever engaging member surface <NUM>. This leads to improved durability and performance.

Still further, the unique interaction between the support surfaces of piston <NUM> and the lever engaging member or latch <NUM> provide for two positively defined switched support positions for the lever <NUM>, which positions, and thus the corresponding motions of the actuated valves, may be very precisely controlled. Moreover, because the forces involved in the interaction of the piston <NUM> with the lever engaging member <NUM> are reduced, durability and consistency in performance are enhanced. A further related advantage of the example adjustable support assemblies according to aspects of the disclosure eliminate the potential for excessive contact stresses during intermediate engagement positions between the lever engaging member <NUM> and lever <NUM>. Such intermediate positions would be positions that are not either the first or second engagement positions as described above. As will be recognized, when the piston <NUM> is in the retracted position, there is only one position in which the lever engaging member <NUM> can possibly be supported. If the lever engaging member is not in the first retracted position, no reactive force from the piston surface <NUM> is provided. Thus, in the event the lever engaging member <NUM> might remain in the second position or fail retract fully into the longitudinal bore <NUM> after piston <NUM> retracts, no reactive force will be provided when the load of the motion source is transmitted to the lever <NUM> until the lever engaging member <NUM> is in the first position. In this manner, the system avoids the application of load forces when the actuating components are not in either the first or second positions. Stated another way, the lever support assembly <NUM> is adapted to provide supporting force to the lever only in a first position or a second position. That is, if the piston <NUM> is in the first position and the lever engaging member <NUM> is in a position where it is not engaging the piston, the system permits the lever engaging member <NUM> to "float" within the longitudinal bore <NUM> and no reactive force is provided by the piston on the lever engaging member until it properly seats against the piston <NUM>. The adjustable support assembly is thus adapted to allow the lever to move to the first position when the lever is not in the first position or the second position. This arrangement eliminates damage to the supporting components and provides for dependable and durable operation of the switching finger follower.

<FIG> illustrates a second implementation, which embodies additional aspects according to the instant disclosure. This implementation may be useful as a lost-motion device in engine environments that employ a single motion source, such as a cam, for providing one or more lower lift events, such as auxiliary events, where some lift may be lost, and one or more higher lift events, such as combustion main events, where more (or all) lift from the cam lobe is conveyed to the engine valves. An example lost-motion engine environment is described in <CIT>, for example, and the subject matter thereof is incorporated herein by reference in its entirety. As will be recognized, in such applications, a single cam profile having multiple lobes thereon would be used in place of the combination of the central <NUM> and lateral cam lobes <NUM> in the environment described above with regard to <FIG>.

<FIG> is a perspective view of an example assembled lost-motion finger follower system <NUM> according to an aspect of the disclosure. <FIG> is an exploded, perspective view of the same example system. The switching finger follower may have a general construction similar to the embodiment described above with respect to <FIG>. The structure and operation of the adjustable support assembly <NUM>, including piston <NUM>, lever engaging member <NUM> and the interaction thereof with end surface <NUM> are similar to the implementation described above, which will be understood to apply to this embodiment and need not be repeated. However, as will be recognized, the structure of the body <NUM> and lever <NUM> may be modified, as described below, to facilitate functioning of the system in lost-motion applications.

One modification may include the addition of a biasing assembly cooperating with the body <NUM> and lever <NUM> and adapted to bias the lever <NUM> towards a raised or deployed position away from the body <NUM>. The body <NUM> may include a pair of laterally extending spring retaining flanges <NUM> and <NUM>. Respective resilient elements (e.g., coil springs) <NUM> and <NUM> are retained between the flanges and thus bias the lever <NUM> and central roller follower <NUM> in a direction towards the motion source (i.e., upward in <FIG> and <FIG>).

Another modification is that a travel limiter <NUM> may be disposed on a pivot end <NUM> of the body <NUM> and be formed integrally therewith to limit rotation of the lever <NUM> away from the body <NUM> by engaging an upper surface <NUM> of the lever end wall <NUM>. While the travel stop <NUM> is illustrated as an integral component of the body <NUM>, it will be appreciated that the travel stop <NUM> could be implemented as a separate component attached to the body <NUM> or coupled thereto via another component. Moreover, travel stop <NUM> may be provided with adjustable features, such as an adjustment screw threaded through the illustrated limiter and secured with a retaining nut to allow adjustment of the upper limit of travel of the lever <NUM>.

As known in the art, when a hydraulic lash adjuster (HLA) is incorporated into a single-source lost motion valve train, it is necessary to prevent expansion of the HLA during those operating states in which valve actuation motion is being lost, i.e., to prevent the HLA from taking up lash space purposely provided to selective lose valve actuation motions. In the illustrated embodiments, this is achieved by operation of the resilient elements <NUM> and <NUM> that are chosen such that the force exerted by these elements on the lever <NUM> will be greater than force exhibited by an associated HLA when it attempts to expand to take up any available lash. In this manner, the resilient elements <NUM>, <NUM> cause a sufficient load to be applied to the HLA to prevent undesired expansion thereof. On the other hand, uncontrolled application of the force provided by the resilient elements <NUM> and <NUM> to the HLA could cause undue compression or bleed-down of the HLA. Thus, the travel limiter stop <NUM> may limit travel of the lever <NUM> and, consequently, the force applied by the resilient elements <NUM>, <NUM> to any accompanying HLA. The distance of travel of the lever <NUM> permitted by the travel stop <NUM> is preferably controlled so that when the HLA is operating to take up lash space in the valvetrain when the lever <NUM> is against the travel stop <NUM>, the travel of the lost motion is equal to the valve lift events that are lost. For example, if the travel stop <NUM> allows excessive stroke of the lever <NUM>, the lost motion operating state will lose excessive motion and the comparatively high-lift valve events (e.g., main events) will have excessive lash, resulting in undesirable lower valve lift and higher valve seating velocities. Conversely, if the travel stop <NUM> allows inadequate stroke of the lever <NUM>, an insufficient amount of lash space will be established during lost motion operation and some of the valve actuation motion intended to be lost will nevertheless be conveyed by the finger follower to the engine valve. This can lead to undesirable consequences such as changed valve lifts and durations, or possibly add unwanted lift events when they are not desired. In embodiments in which the travel stop <NUM> is attached to the body <NUM> (rather than formed integrally therewith), the travel stop <NUM> may be adjustable such the stroke of the lever <NUM> can be precisely controlled.

Yet another modification, compared to the embodiment described above relative to <FIG>, may include the elimination of the lateral roller followers, as such elements may not be necessary in a single motion source environment where the finger follower system <NUM> functions as a lost motion device.

In lost motion applications, the adjustable support assembly <NUM>, in similar fashion to the operations described above with regard to <FIG>, may provide at least two very precisely controlled positions of the lever <NUM> relative to the finger follower body <NUM>. These two controlled positions may provide for two levels of conveyed motion from the motion source to the actuated valves. The first position may correspond to a partial motion conveyance, and the second position may correspond to full motion conveyance, for example. As will be recognized from the instant disclosure, the described embodiments may be adapted for lost-motion applications where all valve motion that would otherwise be conveyed from the motion source (cam) can be "lost" or absorbed by the finger follower system. In such a case, the lever may have only one precisely defined engagement position with the latch <NUM> and the lever may assume a second position in which the latch has no engagement with the lever, or where the latch engages the lever and supports it at a low enough position that no valve lift is conveyed from the motion source. The non-engagement configuration of the lever may eliminate the need for precision in manufacturing at least to define the second, disengaged position of the lever.

Referring to <FIG>, in a state where the lever engaging member <NUM> is in a retracted position and supported on the smaller diameter of piston <NUM>, the lever surface <NUM> contacts the lever engaging member surface <NUM> at a comparatively low point thereof. Lever <NUM> and roller follower <NUM> are maintained in a lower position relative to the body <NUM>, thereby establishing lash between the roller follower <NUM> and its corresponding valve actuation motion source. This lash space causes any comparatively low-lift valve actuation motions that would otherwise be applied to the central roller follower <NUM> to be lost, whereas any comparatively high-lift valve actuation motions are still received by the roller follower <NUM> and conveyed to the finger follower body <NUM> and ultimate to the engaged valves.

Referring additionally to <FIG>, in a state where the piston <NUM> may be hydraulically actuated to overcome the spring biasing force, piston may move to a point where the full diameter portion thereof fully occupies the transverse bore in the lever engaging member <NUM>. Lever engaging member <NUM> is thus in a fully deployed position and the lever <NUM> and follower <NUM> are maintained in a comparatively high position to take up any lash between the follower <NUM> and the valve actuation motion source. In this state, any comparatively low-lift valve actuation motions, as well as comparatively high lift valve actuation motions are applied to the roller follower <NUM> and conveyed to the finger follower body <NUM> and ultimately to the valve engaged thereby.

In addition to the precisely controlled positions of the lever <NUM> relative to the finger follower body <NUM> described above, and the resultant precise control of lost motion capabilities provided by the finger follower system, the configuration describe above also provides the advantage of eliminating intermediate positioning of the lever <NUM> and thus intermediate conveyance of valve motion. As described above in detail with regard to the operation of the adjustable support assembly <NUM> in the embodiment of <FIG>, the adjustable support assembly <NUM> may be adapted to provide support in two defined positions, owing to the interaction of piston <NUM> and lever engaging member <NUM>.

<FIG> illustrates another embodiment according to aspects of the disclosure, which may be useful in applications, such as cylinder deactivation applications, where complete loss of valve motion may be facilitated. In this embodiment, lower lever positioning is facilitated by an adjustable support assembly <NUM> that permits the lever to pivot free of the latch <NUM> and thus to a (second) lever position that is a lower position relative to the follower body than provided with the previously described embodiments. <FIG> illustrates the latch <NUM> in a first position in which the larger diameter surface <NUM> engages the transverse bore of latch <NUM>, supporting it in the extended position shown, where latch surface <NUM> engages lever surface <NUM>, thereby retaining lever <NUM> in the (first) position shown. This position may correspond to a "de-energized" state of the actuator piston <NUM> (i.e., a "normally latched" lever position) where the lever <NUM> is positioned to convey normal valve motion. According to aspects of this embodiment, when the piston <NUM> is energized, the smaller diameter surface <NUM> aligns with the latch transverse bore, permitting the latch <NUM> to retract (i.e., move up and to the left in <FIG>). This position of latch <NUM> permits the lever <NUM> to pivot to a lower position in which it is entirely free and not engaging the latch <NUM>. This configuration may thus be useful in applications, such as cylinder deactivation applications, where such a low lever position is required for full loss of valve motion.

<FIG> illustrate details of a pivot pin <NUM> that may be used in either of the aforementioned implementations. As shown, the pivot member <NUM> comprises an eccentric shaft <NUM> formed therein. In particular, an axis of the shaft <NUM> is not aligned with an axis of the pivot member <NUM>. Additionally, a threaded mounting hole <NUM> is provided in the eccentric shaft <NUM>. As best shown in <FIG>, the pivot member <NUM> may be supported by the body <NUM> with the lever <NUM> mounted for rotation on the eccentric shaft <NUM>. A suitable fastener <NUM> may be used to secure the assembly of the pivot member <NUM>, lever <NUM> and body <NUM>. By selectively rotating the pivot member <NUM>, the position of the eccentric shaft <NUM> may be moved relative to the body <NUM> such that the pivoting end of the lever <NUM> is likewise shifted upward or downward relative to the body <NUM>. In this manner, the pivot member <NUM> can be used to adjust or control the position of the lever <NUM> to work with different cam profiles, establish varying lash settings or allow for less precise and costly manufacturing processes.

As will be recognized, various geometrical variations in the shapes of interacting surfaces of the lever engaging member or latch <NUM>, actuating piston <NUM>, lever end surface <NUM> and other surfaces described herein may be provided without departing from the herein claimed invention. For example, lever engaging member or latch <NUM> may be provided with a curved or arcuate surface and lever <NUM> provided with a flat surface. Moreover, while described and claimed as cylindrical shaped elements, piston and lever engaging member may be provided with square or rectangular or other cross-sectional shapes.

For further example, while the lever engaging member <NUM> has been illustrated ad described as operating under the control of mechanical interaction with the piston <NUM>, which is in turn hydraulically controlled, it is appreciated that other configurations for controlling the lever engaging member may be employed. For example, the lever engaging member <NUM> may be biased into its unlocked or off state by a resilient element, and a hydraulic passage may be connected to the bore in which the lever engaging member <NUM> resides such that application of hydraulic fluid to the passage causes extension of the lever engaging member <NUM> into its locked or on state while a locked volume of hydraulic fluid within the sliding member's bore maintains the lever engaging member <NUM> in its extended position. As another example, while the lever contact surface <NUM> has been illustrated as having an arcuate shape, this is not a requirement and other surface configurations, e.g., angled, semicircular, etc., may be equally employed. Further still, it will be appreciated that the configuration of the body <NUM> and lever <NUM> could be reversed, i.e., that a central body is provided with an outer, movable arm, which movable arm can be placed in an unlocked/off or locked/on state using one or more similarly configured sliding members as described above.

Claim 1:
A finger follower system for use in an internal combustion engine valvetrain, the finger follower system comprising:
a follower body (<NUM>) having a pivot end (<NUM>) and a motion transmitting end (<NUM>);
a lever (<NUM>) adapted to pivot relative to the follower body;
a motion receiving component (<NUM>) having a motion receiving surface disposed between the pivot end and the motion transmitting end; and
an adjustable support assembly (<NUM>) including a movable latch (<NUM>) configured to provide selective support to the lever, the adjustable support assembly adapted to maintain the latch in a first latch position and a second latch position corresponding to a locked position of the lever (<NUM>) and motion receiving component (<NUM>) relative to follower body (<NUM>),
wherein the adjustable support assembly includes an actuating piston (<NUM>) extending within a transverse actuating piston receiving bore (<NUM>) in the latch and cooperating with the latch to define the first latch position and the second latch position,
the actuating piston having a first cylindrical support surface (<NUM>) having a first diameter for supporting the latch in the first latch position and a second cylindrical support surface (<NUM>) having a second diameter, greater than the first diameter of the first support surface (<NUM>) and substantially corresponding to the diameter of the transverse actuating piston receiving bore (<NUM>) for supporting the latch in the second latch position.