FIELD
The instant disclosure relates generally to systems and methods for actuating one or more engine valves in an internal combustion engine. More particularly, the instant disclosure relates to systems and methods for varying the operational relationship between a motion source, such as a cam, and one or more engine valves. Such systems and methods may include a rocker arm in the form of a finger follower, which provides for selectively switching between lobes on a cam and/or for operating as lost motion devices in an engine valve train. The instant disclosure further relates to valvetrain components, such as finger followers, that are capable of switching between two or three operating states and to methods of operating internal combustion engines in different operating modes, such as cylinder deactivation, main event positive power, or auxiliary events, such as lost-motion braking, early exhaust valve opening (EEVO) or late intake valve closing (LIVC) using such valvetrain components.
BACKGROUND
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 U.S. Pat. No. 7,546,822, the subject matter of which is incorporated herein by reference. As shown in FIG. 1, the finger follower comprises a body 11 pivoting about, in this example, a hydraulic lash adjuster (HLA) 2. The body 11 also supports, in this example, lateral followers 30 that may rotate about a shaft 17 and that may engage a locking mechanism 40. As best illustrated in FIGS. 2 and 3, the body 11 further supports a central roller follower 20 positioned between the lateral followers 30. As further shown in FIGS. 2 and 3, the locking mechanism 40 may be controlled such that a locking bar 48 is either maintained in an extended position and thereby in contact with tabs 38 of the lateral followers 30 (FIG. 2), or maintained in a retracted position and thereby avoiding contact with the tabs 38 (FIG. 3). When the locking bar 48 contacts the tabs 38 (i.e., in a locked or on condition), the lateral followers 30 are prevented from rotating about the shaft 17 and are therefore maintained in a rigid relationship with the body 11. Thus, motions applied to the lateral followers 30 by lateral cam lobes 9 are conveyed to body and ultimately to the engine valve 3. In this case, valve actuation motions provided by central cam lobe 8 are not conveyed to the central roller follower 20 with which it is aligned. On the other hand, when the locking bar 48 is retracted (i.e., in an unlocked or off condition), the lateral followers 30 are free to rotate about the shaft 17 such that any motions applied by the lateral cam lobes 9 are absorbed by the lateral followers 30 and not conveyed to the engine valve 3 by the body 11. In this case, valve actuation motions provided by the central cam lobe 8 are conveyed to the central roller follower 20 and, thereby, on to the engine valve 3.
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 FIGS. 2 and 3, such a partial engagement occurs when the locking bar 48 only partially overlaps with the tab 38, i.e., at a location between the engagements illustrated in FIGS. 2 and 3. 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. 5, curve 502 of U.S. Pat. No. 9,347,383, the teachings of which are incorporated herein by this reference. 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.
SUMMARY
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 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.
In one implementation, a finger follower with an adjustable support assembly may include 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 may cooperate with an actuating piston, which may extend through a transverse bore in the lever engaging member. The piston may have 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.
In one implementation, the finger follower may include 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.
According to yet another aspect of the disclosure, there is provided a method of controlling motion of at least one valve in an internal combustion engine using a valvetrain component disposed between a motion source and a motion receiving component, the valvetrain component including a main body, a lever adapted to pivot relative to the main body, and an adjustable support assembly for providing selective support to the lever, the valvetrain component being configurable to least two states of operation by actuation of the adjustable support assembly, the method comprising: configuring the valvetrain component to a first state, in which the valvetrain component conveys a first range of motion from the motion source to the motion receiving component; operating the engine in a first operating mode when the valvetrain component is in the first state; configuring the valvetrain component to a second state, in which the valvetrain component conveys a second range of motion from the motion source to the motion receiving component; and operating the valvetrain component in a second operating mode when the valvetrain component is in the second state.
According to one example implementation, the adjustable support assembly may comprise a three-position latch, which provides for three corresponding states or positions of the finger follower, each state or position absorbing a corresponding range of motion. A motion source, such as a cam, may be provided with multiple lobes and interact with the finger follower to achieve different valve motions and thus different engine operating modes.
According to one example, the three-position finger follower may be configured in a first state supporting engine operation in a cylinder deactivation mode. The finger follower may further be configured in a second state supporting engine operation in a main event positive power mode. The figure follower may be further configured in third state supporting engine operation in an auxiliary valve motion mode, which may include lost motion braking, late intake valve closing (LIVC) or early exhaust valve opening (EEVO).
According to another example, the three-position finger follower may be configured in a first state supporting engine operation in a lost motion braking mode. The finger follower may further be configured in a second state supporting engine operation in an EEVO mode. The figure follower may be further configured in third state supporting engine operation in a main event positive power mode.
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.
DESCRIPTION OF THE DRAWINGS
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. 1 is a perspective of an example prior art switching finger follower and an engine valve train environment, which environment may be suitable for implementing aspects of the instant disclosure.
FIG. 2 is a cross-section of the finger follower system of FIG. 1 in an “on” state.
FIG. 3 is a cross-section of the finger follower system of FIG. 1 in an “off” state.
FIG. 4 is a perspective, assembled view of an example finger follower assembly.
FIG. 5 is a perspective, exploded view of the example finger follower assembly of FIG. 4.
FIG. 6 is a detailed perspective exploded view of a finger follower adjustable support assembly.
FIG. 7 is cross-section in a lateral plane of the finger follower assembly of FIG. 4 in a first state, which may be an “off” or “unlocked” state.
FIG. 8 is a cross section in a transverse plane of the finger follower assembly of FIG. 4, in a first state.
FIG. 9 is cross-section in a lateral plane of the finger follower assembly of FIG. 4 in a second state, which may be “on” or “locked” state.
FIG. 10 is a cross section in a transverse plane of the finger follower assembly of FIG. 4 in a second state.
FIG. 11 is a perspective, assembled view of a finger follower assembly according to a second embodiment, with application as a lost motion device.
FIG. 12 is an exploded perspective view of the lost motion finger follower assembly of FIG. 11.
FIG. 13 is a cross-section in a lateral plane of the finger follower assembly of FIG. 11 in a first state, which may be a state where some or all of the valve train motion is lost.
FIG. 14 is a cross-section in a lateral plane of the finger follower assembly of FIG. 11 in a second state, which may be a state where some or all of the valve train motion is conveyed. FIG. 15 is a cross-section in a lateral plane of another embodiment of a finger follower assembly which permits the lever to pivot free of a support assembly to facilitate full motion loss.
FIG. 16 is a perspective view showing an eccentric pivot mount.
FIG. 17 is a cross section of the pivot mount of FIG. 16.
FIG. 18 is an end cross-sectional view of a three-position switching finger follower.
FIGS. 19-21 illustrate an example first implementation of the three-position embodiment in accordance with FIG. 18.
FIG. 22 illustrates an example second implementation of the three-position embodiment in accordance with FIG. 18.
FIG. 23 illustrates a cross-sectional view of an alternative embodiment of a three-position valve train component, adaptable to a type III rocker configuration.
FIG. 24 illustrates a profile of a three-position valve train component to achieve different engine operating modes.
FIG. 25 illustrates an example cam profile, lost motion, and valve lift motion that may be achieved in three different operating states using a three-position finger follower according to aspects of the disclosure.
FIG. 26 illustrates steps in an example method of performing cylinder deactivation, main event positive power and auxiliary events, such as lost-motion braking, LIVC or EEVO in an internal combustion engine using a three-position finger follower.
FIG. 27 illustrates steps an example method of performing main event positive power, EEVO and lost-motion braking using a three-position finger follower in an internal combustion engine using a three-position finger follower.
DETAILED DESCRIPTION
FIG. 4 is a perspective view of an example assembled switching finger follower system 100 in accordance with the instant disclosure. FIG. 5 is an exploded perspective view of the same system. In particular, the switching finger follower may comprise a body or housing 400, arranged to support or house various other system components. Body 400 may extend in a longitudinal direction from a motion transmitting end or valve engaging end 410, adapted to interface with or engage one or more engine valves, to a pivot end 420, adapted to interface with or engage a pivot, which may include an HLA. Body 400 may further comprise a pair of lateral, longitudinally extending arms 402 and 404, defining a lever recess or pocket 406 therebetween. Arms 402 and 404 may include respective pivot pin receiving bores 403 and 405 at the valve engaging end 410 for securing a lever pivot pin 412 therein. A pair of lateral roller followers 430 and 434 may be secured to arms 402 and 404 via shafts 432 and 436, respectively. The lateral roller followers 430, 434 are configured to receive valve actuation motions from complementarily configured valve actuation motion sources, for example, motion sources similar to the lateral cam lobes 9 illustrated in FIG. 1. 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 400.
Body 400 may further support a lever 450 having a fastened end 452, that may be mounted to pivotably cooperate with the follower body 400, and extending in the longitudinal direction to a free end 460. The fastened end of lever 450 may be fastened to the lever pivot pin 412 secured to arms 402, 404 of the body 400.
Lever 450 may have a shape that is complementary to the recess or pocket 406 in the body 400, thereby providing for a nested positioning within the body 400 and an overall compact finger follower configuration. Lever 450 may be formed as a precision, unitary stamped metal (i.e., steel) component having a generally concave shape with a bottom wall 454 and an integral outer wall 456 extending from the bottom wall 454. A central portion of lever 450 may support and house a motion receiving component, cooperatively associated with the lever. The motion receiving component may be a central roller follower 440 supported on a shaft 442 affixed to the lever 450. 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 458 may be formed in bottom wall 454 to accommodate the central roller follower 440. Free end 460 of the lever may have an arcuate or otherwise curved lever end wall 461 having an arcuate or otherwise curved end surface 462, for selectively engaging an adjustable support assembly 500 integrated into the body 400, as will be described. End wall 461 may extend to and be contoured to have a smooth transition with the bottom wall 454. Lever end wall 461 may extend between a reduced lateral dimension between the opposing portions of outer wall 456, which may provide added stability and strength as well as reduce the potential for deformation of the end wall 461 during operation.
As will be recognized, central roller follower 440 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. 1, the central roller follower 440 may receive valve actuation motions from a central cam lobe, similar to cam lobe 8 in FIG. 1. 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 FIGS. 1-3. 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 FIGS. 6-10, the pivot end 420 of the finger follower body 400 may include a longitudinal bore 422 and a transverse bore 424 formed therein for housing components of an adjustable support assembly 500. Pivot end 420 may also include a concave recess or pocket 426 for interfacing with a suitable pivot assembly, such as a hydraulic lash adjuster having a post adapted to fit within the recess or pocket 426, and including a hydraulic passage 428 (FIG. 8) for delivering a pressurized hydraulic working fluid (oil) to the finger follower, as will be further described.
Adjustable support assembly 500 may include lever engaging member or latch 510 and an actuating piston 530 cooperatively associated therewith. Lever engaging member or latch 510 may be disposed in longitudinal bore 422, which includes a cylindrical guiding surface 423 for supporting and facilitating sliding movement of the lever engaging member or latch 510. Lever engaging member or latch 510 may have a generally cylindrical shape including an outer cylindrical surface 512 and a substantially planar lever engaging surface 514, which may extend at an angle to the axis of lever engaging member or latch 510. A transverse actuating piston receiving bore 516 may extend through the lever engaging member or latch 510 for receiving and cooperating with the actuating piston 530. Moreover, lever engaging member or latch 510 may be provided with chamfered surfaces 518 (FIG. 5) on each side, which transition from the outer surface of lever engaging member or latch 510 to the piston receiving bore 516 to provide for smooth interaction with the surfaces of piston 530. It will also be recognized that chamfered surfaces 518 provide for a reduction in the width of transverse piston receiving bore 516 and thereby eliminate the need for precise alignment of the transverse bore 516 with the piston 530 in order for the transverse bore 516 to engage the reduced diameter piston surface 532.
Actuating piston 530 may include a first support surface 532 adapted to engage and support the lever engaging member or latch 510 in a first position within longitudinal bore 422, which first position may correspond to an unlocked, or lower or retracted position of the lever 450 and central follower 440 relative to body 400. First support surface 532 may be a cylindrical surface having a first diameter. Actuating piston 530 may also include a second support surface 534 adapted to engage and support the lever engaging member or latch 510 in a second position within longitudinal bore 422, which second position may correspond to a locked, or raised, or deployed position of the lever 450 and central follower 440 relative to body 400. 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 424 of body 400 and substantially corresponding to the diameter of transverse actuating piston receiving bore 516. Disposed between the first support surface 532 and second support surface 534 may be a transition surface 536 on the actuating piston 530, which transition surface 536 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 536 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 424, as will be explained in more detail below.
Operation of the adjustable support assembly 500 will now be described. FIGS. 7 and 8 illustrate the example switching finger follower in an “unlocked” or off state, in which the lever 450 is in a lower position relative to the body 400. Piston 530 is retracted fully within transverse bore 424, bottoming against an end wall 425 of transverse bore 424. A biasing device, such as a coil spring 533, may be disposed in the transverse bore 424 to engage a spring seat 539 and bias the piston towards the retracted position. This position aligns the first support surface 532 of the actuating piston 530 with the transverse piston receiving bore 516 of lever engaging member or latch 510. Lever engaging member or latch 510 is retracted within the longitudinal bore such that contact surface 514 is positioned to contact the lever end surface 462 along a first line of contact, which may be at a lower position on the surface 514 of (i.e., below the axis of) lever engaging member or latch 510. A spring retaining cap 535 may be affixed to body 400 (i.e., by press fit or threads) to retain the spring 533 and piston 530 within the transverse bore 424.
As shown in FIG. 8, the pivot receiving pocket 426 of body 400 may be hydraulically connected, via a hydraulic passage 428, to the transverse bore 424. When pressurized hydraulic fluid is not supplied to the first transverse bore via the passage 428, the biasing element (not shown) may bias the piston 530 leftward as illustrated in FIG. 8. In this state, the reduced diameter surface 532 of the piston 530 is aligned with the lever engaging member or latch 510. Because the lever 450 is thus maintained in a lower position relatively to the body 400, the central roller follower 440 is likewise maintained in a lower position, thereby establishing lash between the central roller follower 440 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 440 to be lost.
With additional reference to FIGS. 9 and 10, according to aspects of the disclosure, adjustable support assembly 500 may be actuated to cause the lever 450 to be supported at a second position relative to body 400. When pressurized hydraulic fluid is provided, for example, from a passage in the supporting HLA (not shown) via the passage 428 to the transverse bore 424, the leftward bias applied to the piston 530 may be overcome such that the piston 530 displaces to a point where the second support surface 536 is aligned with and supports the lever engaging member or latch 510. 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 530 described. Transition surface 536 may cause the lever engaging member 510 to move (to the right in FIG. 9), from a first latch position to a second latch position, as the piston 530 moves. Consequently, as best shown in FIG. 9, the lever end surface 462 may contact the sliding member surface 514, in this case, at a comparatively high point of the sliding member contact surface 506. Lever 450 and central roller follower 440 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 510 and central roller follower 440 may take up any lash between the central roller follower 440 and its corresponding valve actuation motion source. In this manner, valve actuation motions are applied to the central roller follower 440 and thereafter conveyed to the body 400 by virtue of the contact between the lever 450 and sliding member 510, and the further contact between the sliding member 510 and the body 400. 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 500 provides advantages in distributing the load applied by the lever 450 (illustrated by the heavy black arrow in FIG. 9). More particularly, a vertical component of the load is distributed to the body 400 (illustrated by the vertical dashed arrow) via the engagement of outer surface 512 of lever engaging member, also referred to herein as a latch, 510 with interior surface of longitudinal bore 422. A horizontal component (illustrated by the horizontal dashed arrow) of the load is distributed through the lever engaging member or latch 510 to the piston 530. As will be recognized, the angle of lever engaging member surface 514 may be selected to provide for a majority of the load to distributed across a larger area of the guide surface of longitudinal bore 422, with a smaller component of the load being born by the actuating piston 530. It will be further recognized that, this load distribution will result regardless of the position of the lever engaging member or latch 510 within the longitudinal bore 422. Moreover, owing to the unique interaction of the lever end surface 462 with the surface 514 of the lever engaging member or latch 510, the potential for partial engagement between these elements is effectively eliminated. Additionally, by providing the lever end surface 462 with a substantially arcuate shape as shown, the contact stress between the lever engaging member 530 and lever end surface 462 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 530 engages the lever end surface 462. The lever engaging member surface 514 and lever end surface 462 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 514. This leads to improved durability and performance.
Still further, the unique interaction between the support surfaces of piston 530 and the lever engaging member or latch 510 provide for two positively defined switched support positions for the lever 450, 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 530 with the lever engaging member 530 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 530 and lever 450. 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 530 is in the retracted position, there is only one position in which the lever engaging member 530 can possibly be supported. If the lever engaging member is not in the first retracted position, no reactive force from the piston surface 532 is provided. Thus, in the event the lever engaging member 530 might remain in the second position or fail retract fully into the longitudinal bore 422 after piston 530 retracts, no reactive force will be provided when the load of the motion source is transmitted to the lever 450 until the lever engaging member 530 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 500 is adapted to provide supporting force to the lever only in a first position or a second position. That is, if the piston 1530 is in the first position and the lever engaging member 1510 is in a position where it is not engaging the piston, the system permits the lever engaging member 1510 to “float” within the longitudinal bore 422 and no reactive force is provided by the piston on the lever engaging member until it properly seats against the piston 1530. 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.
FIGS. 11-13 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 U.S. Pat. No. 9,347,383, 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 8 and lateral cam lobes 9 in the environment described above with regard to FIGS. 1-3.
FIG. 11 is a perspective view of an example assembled lost-motion finger follower system 1000 according to an aspect of the disclosure. FIG. 12 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 FIGS. 4-10. The structure and operation of the adjustable support assembly 1500, including piston 1530, lever engaging member 1510 and the interaction thereof with end surface 1462 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 1400 and lever 1450 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 1400 and lever 1450 and adapted to bias the lever 1450 towards a raised or deployed position away from the body 1400. The body 1400 may include a pair of laterally extending spring retaining flanges 1402 and 1404. Respective resilient elements (e.g., coil springs) 1422 and 1424 are retained between the flanges and thus bias the lever 1450 and central roller follower 1440 in a direction towards the motion source (i.e., upward in FIGS. 11 and 12).
Another modification is that a travel limiter 1425 may be disposed on a pivot end 1430 of the body 1400 and be formed integrally therewith to limit rotation of the lever 1450 away from the body 1400 by engaging an upper surface 1463 of the lever end wall 1461. While the travel stop 1425 is illustrated as an integral component of the body 1400, it will be appreciated that the travel stop 1425 could be implemented as a separate component attached to the body 1400 or coupled thereto via another component. Moreover, travel stop 1425 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 1450.
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 1422 and 1424 that are chosen such that the force exerted by these elements on the lever 1450 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 1422, 1424 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 1422 and 1424 to the HLA could cause undue compression or bleed-down of the HLA. Thus, the travel limiter stop 1425 may limit travel of the lever 1450 and, consequently, the force applied by the resilient elements 1422, 1424 to any accompanying HLA. The distance of travel of the lever 1450 permitted by the travel stop 1425 is preferably controlled so that when the HLA is operating to take up lash space in the valvetrain when the lever 1450 is against the travel stop 1425, the travel of the lost motion is equal to the valve lift events that are lost. For example, if the travel stop 1425 allows excessive stroke of the lever 1450, 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 1425 allows inadequate stroke of the lever 1450, 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 1425 is attached to the body 1400 (rather than formed integrally therewith), the travel stop 1425 may be adjustable such the stroke of the lever 1450 can be precisely controlled.
Yet another modification, compared to the embodiment described above relative to FIGS. 4-10, 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 1000 functions as a lost motion device.
In lost motion applications, the adjustable support assembly 1500, in similar fashion to the operations described above with regard to FIGS. 4-10, may provide at least two very precisely controlled positions of the lever 1450 relative to the finger follower body 1400. 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 510 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. 13, in a state where the lever engaging member 1510 is in a retracted position and supported on the smaller diameter of piston 1530, the lever surface 1462 contacts the lever engaging member surface 1514 at a comparatively low point thereof. Lever 1450 and roller follower 1440 are maintained in a lower position relative to the body 1400, thereby establishing lash between the roller follower 1440 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 1440 to be lost, whereas any comparatively high-lift valve actuation motions are still received by the roller follower 1440 and conveyed to the finger follower body 1400 and ultimate to the engaged valves.
Referring additionally to FIG. 14, in a state where the piston 1530 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 1510. Lever engaging member 1510 is thus in a fully deployed position and the lever 1450 and follower 1440 are maintained in a comparatively high position to take up any lash between the follower 1440 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 1440 and conveyed to the finger follower body 1400 and ultimately to the valve engaged thereby.
In addition to the precisely controlled positions of the lever 1450 relative to the finger follower body 1400 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 1450 and thus intermediate conveyance of valve motion. As described above in detail with regard to the operation of the adjustable support assembly 500 in the embodiment of FIGS. 4-10, the adjustable support assembly 1500 may be adapted to provide support in two defined positions, owing to the interaction of piston 1530 and lever engaging member 1510.
FIG. 15 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 2500 that permits the lever to pivot free of the latch 2510 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. 15 illustrates the latch 2510 in a first position in which the larger diameter surface 2534 engages the transverse bore of latch 2510, supporting it in the extended position shown, where latch surface 2514 engages lever surface 2462, thereby retaining lever 2450 in the (first) position shown. This position may correspond to a “de-energized” state of the actuator piston 2530 (i.e., a “normally latched” lever position) where the lever 2450 is positioned to convey normal valve motion. According to aspects of this embodiment, when the piston 2530 is energized, the smaller diameter surface 2532 aligns with the latch transverse bore, permitting the latch 2510 to retract (i.e., move up and to the left in FIG. 15). This position of latch 2510 permits the lever 2450 to pivot to a lower position in which it is entirely free and not engaging the latch 2510. 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.
FIGS. 16 and 17 illustrate details of a pivot pin 1412 that may be used in either of the aforementioned implementations. As shown, the pivot member 1412 comprises an eccentric shaft 920 formed therein. In particular, an axis of the shaft 920 is not aligned with an axis of the pivot member 912. Additionally, a threaded mounting hole 922 is provided in the eccentric shaft 920. As best shown in FIG. 17, the pivot member 912 may be supported by the body 400 with the lever 408 mounted for rotation on the eccentric shaft 920. A suitable fastener 1002 may be used to secure the assembly of the pivot member 912, lever 408 and body 400. By selectively rotating the pivot member 912, the position of the eccentric shaft 922 may be moved relative to the body 1400 such that the pivoting end of the lever 408 is likewise shifted upward or downward relative to the body 1400. In this manner, the pivot member 912 can be used to adjust or control the position of the lever 1450 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 510, actuating piston 530, lever end surface 462 and other surfaces described herein may be provided without departing from the spirit and scope of the invention. For example, lever engaging member or latch 510 may be provided with a curved or arcuate surface and lever 450 provided with a flat surface. Moreover, while described 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 530 has been illustrated ad described as operating under the control of mechanical interaction with the piston 530, 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 530 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 530 resides such that application of hydraulic fluid to the passage causes extension of the lever engaging member 530 into its locked or on state while a locked volume of hydraulic fluid within the sliding member's bore maintains the lever engaging member 530 in its extended position. As another example, while the lever contact surface 462 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 400 and lever 450 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.
Referring now to FIG. 18, an actuating piston 1804 in accordance with various three-position embodiments is illustrated. As shown, the piston 1804 comprises, from right to left as shown in FIG. 18, a minimum diameter portion 1806, an intermediate diameter portion 1808 and a maximum diameter portion 1810. Referring additionally to FIG. 8, the embodiment of FIG. 18 may include one or more hydraulic passages, such as the hydraulic passage 428 of FIG. 8, and one or more biasing elements, such as one or more springs or biasing elements 533 of FIG. 8, which may be used to control alignment of any of the piston portions 1806, 1808, 1810 with a sliding member 1802, in a manner substantially similar to that described above relative to FIG. 8. For example, with no hydraulic pressure applied to the leftmost side (as shown in FIG. 18) of the actuating piston 1804, the resilient element on the rightmost side of the piston 1804 will cause the piston 1804 to index leftward to the fullest extent possible, thereby aligning the minimum diameter portion 1806 with the sliding member 1802. Through application of a first pressure to the leftmost side of the piston 1804, the leftward biasing force applied by the resilient element may be overcome to a sufficient degree to permit the piston 1804 to index rightward such that the intermediate diameter portion 1808 of the piston 1804 is aligned with the sliding member 1802. Application of a second pressure, higher than the first pressure, to the leftmost side of the piston 1804 further overcomes the biasing force of the resilient element such that the piston 1804 indexes rightward further still such that the maximum diameter portion 1810 of the piston 1804 aligns with the sliding member 1802.
Thus, when the minimum diameter portion 1806 is aligned with the sliding member 1802, the sliding member 1802 is able to retract within its longitudinal bore to a maximum extent permitted by the piston 1804 (maximum retracted state). On the other hand, when the maximum diameter portion 1810 is aligned with the sliding member 1802, the sliding member 1802 is unable to retract (or only able to minimally retract) within its longitudinal bore and is instead maintained in an extended position out of the longitudinal bore to a maximum extent permitted by the piston 1804 (maximum extended state). Finally, when the intermediate diameter portion 1808 is aligned with the sliding member 1802, the sliding member 1802 is able to partially retract into its longitudinal bore, i.e., to a position between the maximum retracted state and the maximum extended state. Various examples of such operation are further illustrated in FIGS. 19-22.
FIGS. 19-21 illustrate a first implementation of a three-position switching finger follower in which the sliding member 1802 is provided with stepped contact surfaces 1902, 1904. Further, the lever arm 408 comprises a contact surface 1906 configured to complementarily engage with either of the stepped contact surfaces 1902, 1904. One or more resilient elements such as springs or other biasing mechanism (e.g., hydraulic passage) may be provided to normally bias the sliding member 1802 away from the lever arm and into its maximum retracted state. In FIG. 19, the minimum diameter portion 1806 of the piston 1804 is aligned with the sliding member 1802 such that the sliding member 1802 is permitted to assume its maximum retracted state. (Note that, in FIGS. 19-21, the transverse bore in the sliding member 1802 and the piston 1804 are omitted for clarity.) In this state, the sliding member 1802 is retracted to such an extent that the contact surface 1906 of the lever arm 408 is prevented from contacting the sliding member 1802 at all. In this case, downward deflection of the lever arm 408 is limited when the contact surface 1906 contacts a lower stop 1908 of the body 402. Configured in this manner, the illustrated switching finger follower loses the maximum amount of motion applied thereto and may correspond, for example, to an operating mode in which a corresponding cylinder has been deactivated.
FIG. 19 also illustrates a sample motion source 1920, which is shown displaced from a normal operating position relative to the finger follower, for clarity. Motion source 1920 may be a rotating cam having a main even lobe 1922, and two auxiliary lobes 1922 and 1924. It will be recognized that auxiliary lobes 1922 and 1924 may be positioned on the cam body at various rotational positions to achieve various lift profiles. Cam 1920 may interact with the follower roller the finger follower to impart motion. The motion of finger follower is conveyed or transmitted to a valve 1930.
The cam, or motion source 1920 shown in FIG. 19 may be utilized, in combination with a three-state finger follower, to selectively achieve, for example, the performance of main event valve lift, lost motion braking valve lift, and cylinder deactivation (no valve lift). It will be recognized that alternative valve lift motions may be achieved with suitable modification of the motion source profile(s) (cam lobes) and suitable modification of the motion-conveying attributes of each state of the three-state finger follower. For example, if CDA were not utilized in a third state, and a different lift event, such as EEVO, were desired, the motion source may have a different profile, such as that shown and described below with respect to FIG. 24.
FIG. 20 illustrates the case where the intermediate diameter portion 1808 of the piston 1804 is aligned with the sliding member 1802 such that the sliding member 1802 extends from the longitudinal bore more than its maximum retracted state but less than its maximum extended state. In this state, the sliding member 1802 extends to sufficient degree to permit contact between a first stepped contact surface 1902 of the sliding member 1802 and the contact surface 1906 of the lever arm 408. Configured in this manner, the illustrated switching finger follower loses any applied motions below a first level (i.e., motions less than that required to bring the contact surface 1906 into contact with the first stepped contact surface 1902) but conveys any applied motions above the first level. For example, in this operating mode, the switching finger follower may convey comparatively high valve lifts such as main event lifts, but lose comparatively low lifts such as braking or other auxiliary valve events.
FIG. 21 illustrates the case where the maximum portion 1110 of the piston 1804 is aligned with the sliding member 1802 such that the sliding member 1802 is permitted to assume its maximum extended state. In this state, the sliding member 1802 extends to sufficient degree to permit contact between a second stepped contact surface 1904 of the sliding member 1802 and the contact surface 1906 of the lever arm 408. Configured in this manner, the illustrated switching finger follower loses any applied motions below a second level (i.e., motions less than that required to bring the contact surface 1906 into contact with the second stepped contact surface 1904) but conveys any applied motions above the second level, where the second level in FIG. 21 is lower than the first level from the embodiment of FIG. 20. For example, in this operating mode, the switching finger follower may convey comparatively low valve lifts such as braking or other auxiliary valve events as well as comparatively high valve lifts such as main event lifts.
FIG. 22 illustrates a second implementation of a three-position switching finger follower in which the sliding member 2202 is provided with an angled contact surface 2206 and, further, the lever arm 408 comprises an arcuate contact surface 2208 in a manner substantially similar to the embodiment illustrated in, for example, FIGS. 4-10. In FIG. 22, the transverse bore in the sliding member 2202 and the piston 1804 are shown. Further, unlike the embodiment of FIGS. 19-21 and for the reasons described below, no biasing mechanism is required to bias the sliding member 2202 away from the lever arm and into its maximum retracted state.
FIG. 22 particularly illustrates the case where the intermediate diameter portion 1808 of the piston 1804 is aligned with the sliding member 2202 such that the sliding member 2202 extends from the longitudinal bore more than its maximum retracted state but less than its maximum extended state. Consequently, the lever arm contact surface 2208 engages the sliding member contact surface 2206 at a comparatively low point on the sliding member contact surface 2206. Configured in this manner, similar to the embodiment illustrated in FIG. 20, the illustrated switching finger follower loses any applied motions below a first level (i.e., motions less than that required to bring the lever arm contact surface 2208 into contact with the sliding member contact surface 2206) but conveys any applied motions above the first level. For example, in this operating mode, the switching finger follower may convey comparatively high valve lifts such as main event lifts, but lose comparatively low lifts such as braking or other auxiliary valve events.
On the other hand, when the minimum diameter portion 1806 of the piston 1804 is aligned with the sliding member 2202, the sliding member will assume its maximum retracted state such that the lever arm contact surface 2208 does not engage with the sliding member contact surface 2206 at all, thereby permitting the lever arm 408 to lose the maximum amount of applied valve actuation motions, similar to the embodiment of FIG. 19. Further still, when the maximum diameter portion 1110 of the piston 1804 is aligned with the sliding member 2202, the sliding member will assume its maximum extended state such that the lever arm contact surface 2208 engages with a comparatively high point on the sliding member contact surface 2206, thereby permitting the lever arm 408 to convey comparatively low-level valve actuation motions, similar to the embodiment of FIG. 21. Given the angled nature of the sliding member contact surface 2206 and the arcuate nature of the lever arm contact surface 2208, any contact between the sliding member contact surface 2206 and the lever arm contact surface 2208 inherently biases the sliding member 2202 to retract into its longitudinal bore. Consequently, unlike the embodiment of FIGS. 19-21, no separate biasing mechanism is needed to bias the sliding member into its longitudinal bore. Further, unlike the embodiment of FIGS. 19-21, but similar to the embodiment of FIGS. 4-14, the configuration of the sliding member contact surface 2206 and the lever arm contact surface 2208 in FIG. 22 substantially avoids the potential for partial or incomplete engagement between contact surfaces.
FIG. 23 illustrates an embodiment in which a three-position sliding member 2308 is incorporated into a valve train component other than a finger follower. For example, the valve train component 2302 may comprise a center-pivot type rocker arm or a valve bridge. As shown, an actuator piston 2304 is disposed within a vertical bore 2303 formed in the valve train component. A hydraulic channel 2306 is provided in fluid communication with the vertical bore 2303. In an embodiment, the hydraulic channel 2306 provides unchecked, low pressure hydraulic fluid to the vertical bore 2303 such that the actuator piston 2304 is constantly biased out of the vertical bore 2304. As further shown, the valve train component 2302 includes a horizontal bore 2307 that intersects with the vertical bore 2303. As shown, a sliding member 2308 (similar to the sliding member 1802 illustrated in FIGS. 19-21) is disposed in the horizontal bore 2307 such that the stepped contact surfaces of the sliding member 2308 may engage with an end 2305 of the actuator piston 2304. A piston 2310 (similar to the piston 1804 illustrated in FIG. 18) is provided to control extension/retraction of the sliding member 2308 in substantially the same manner as described above relative to FIGS. 18-22.
When the actuator piston 2304 is placed under load (as in the case, for example, of a valve opening actuation motion applied to the valve train component 2302), the hydraulic fluid in the vertical bore 2303 will flow back into the hydraulic channel 2306, thereby permitting the actuator piston 2304 to retract into the vertical bore 2303 until the end 2305 of the actuator piston 2304 contacts one of the stepped surfaces of the sliding member 2308 or bottoms out in the vertical bore 2303. In this latter case, i.e., where the sliding member 2308 is positioned to avoid contact with the actuator piston 2304 (or to only contact the actuator piston 2304 at its lowest contact surface step), if the stroke length of the actuator piston 2304 thus provided is larger than the largest available valve actuation motion, all such valve actuation motions will be lost. Conversely, where the sliding member is positioned such that one of the higher contact surface steps engages the end 2305 of the actuator piston, the stroke length of the actuator piston 2304 is correspondingly limited such that varying degrees of lost motion may be provided.
While particular preferred embodiments have been shown and described, those skilled in the art will appreciate that changes and modifications may be made without departing from the instant teachings. It is therefore contemplated that any and all modifications, variations or equivalents of the above-described teachings fall within the scope of the basic underlying principles disclosed above and claimed herein. For example, while the sliding member 502 has been illustrated as operating under the control of mechanical interaction with the piston 504, which is in turn hydraulically controlled, it is appreciated that other configurations for controlling the sliding member 502 may be employed. For example, the sliding member 502 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 sliding member 502 resides such that application of hydraulic fluid to the passage causes extension of the sliding member 502 into its locked or on state while a locked volume of hydraulic fluid within the sliding member's bore maintains the sliding member 502 in its extended position. As another example, while the lever arm contact surface 508 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 is appreciated that the configuration of the body 402 and lever arm 408 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. In this same vein, rather than being deployed in the body 402, the sliding member 502 could instead be deployed in the lever arm 408 such that the sliding member contact surface 506 interacts with another contact surface on the body 402. It is also appreciated that multiple operating modes resulting from the embodiments of FIGS. 18-22 could be expanded to more than three states through the use of additional intermediate diameter portions of the piston 1804. For those embodiments in which the sliding member comprises multiple stepped contact surfaces, it appreciated that the unitary sliding member could be replaced by separate sliding members that engage the lever arm at different positions.
FIG. 24 illustrates lost motion profiles in an example finger follower and example engine operating modes that may correspond to the three positions or states of three-position finger follower, as described above. The portions of the curve represent relative stroke lengths of an example three-state finger follower, the stroke length being the range of cam (motion source) motion that may be absorbed by the finger follower before the finger follower conveys cam motion to the valve. In this figure, the stroke length (y-axis) is related to the position (x-axis) of the sliding member 1802 (FIG. 19) or 2308 (FIG. 23). A first state, represented by curve portion 2402 and a corresponding first stroke length when the sliding member 1802 is in the position shown in FIG. 21 may absorb a first (smallest) range of motion and provide for conveyance of lost motion braking (LMB) motion to the valve. A second state, represented by curve portion 2406 and a corresponding second stroke length, greater than the first stroke length, may absorb a second range of motion, greater than the first absorbed range of motion, and provide for conveyance of EEVO motion to the valve. A third state, represented by curve portion 2408 and a third stroke length, greater than the first and second stroke lengths, may absorb a third range of motion, greater than the first and second ranges of motion, and provide for conveyance of main event (ME) motion to the valve.
Referring additionally to FIG. 25, this figure further illustrates how cam motion may be lost (or conveyed) to a valve by an example finger follower. Cam profile 2502 may correspond to a cam that is similar to cam 1920, shown in FIG. 19. The profile 2502 may include a main event lift profile 2522, a first auxiliary lift profile 2524, and second auxiliary lift profile 2526. Example ranges of motion conveyed (lost) by the finger follower in three different states are represented by R1, R2 and R3. In this illustration, a first state of the finger follower is represented by a line that coincides with the x-axis and a range of motion or stroke length (R1, in this case zero) absorbed by the finger follower. In other words, all motion is conveyed by the finger follower in this state. The (long/short) dashed line represents a second state of the finger follower and a corresponding absorbed second range of motion or stroke length (R2). As can be seen, in this state, the motion of the auxiliary lobes 2524 and 526 may be hidden (lost) and only motion of the main event lobe 2522 is conveyed. The upper dashed line represents a third state of the finger follower and a third range of absorbed motion or stroke length (R3). In this state, a central peak portion of the main event profile 2522 may be conveyed. As will be recognized, the cam profiles described above with reference to FIGS. 24 and 25 are merely examples, and may be implemented in other configurations and using other mechanisms without departing from the scope of the instant disclosure.
It will be recognized, particularly from FIG. 25, that the incremental increase in step height between stepped contact surfaces 1902 and 1904 in FIG. 19, for example, although shown as uniform (i.e. steps of the same height), may be of differing step heights, as represented in FIG. 25 by the difference between R3 and R2, and the difference between R2 and R1. That is, the height of the first and second steps may be different and not necessarily the same.
It will further be recognized that the various engine operating modes achieved by the example implementations according to the instant disclosure can be configured with appropriate variation in the height and number of the available cam lobes. For example, cylinder deactivation (CDA) may be implemented as one of the operating modes, in which case, even the main event motion could be lost. Referring back to FIG. 24, in such an implementation, CDA/Main Event/Auxiliary Event motion may be used to replace the LMB/EEVO/ME modes illustrated in FIG. 24. More particularly, auxiliary valve motion may occur when operating with the third portion 2408, main event exhaust operation would occur with the second portion 2406, and an auxiliary operation may be added (lost motion braking/LIVC/EEVO/etc.) with the first plateau 2402.
FIG. 26 illustrates example method steps that may be achieved according to aspects of the disclosure. At 2602, the finger follower is configured to a first state/position in which the sliding member 1802 (FIGS. 18 and 19, for example) is moved to its leftmost position and the finger follower conveys no lift from the cam 1920. At 2604, the engine is operated in a cylinder deactivation mode, since all motion from the cam lobe is absorbed by the follower. At 2606, the finger follower may be configured to a second state/position, in which the sliding member 1802 is shifted rightward (FIG. 19) to a second position (FIG. 20) such that the finger follower conveys a second range of motion from the cam. At 2608, the engine is operated in a main event, positive power mode of operation. At 2610, the finger follower may be configured to a third state/position, in which the sliding member 1802 is shifted even further rightward (FIG. 19) to a third position (FIG. 21). At step 2612, the engine is operated in an auxiliary mode such as lost-motion braking, late intake valve closing or early exhaust valve opening.
FIG. 27 illustrates another example method that may be achieved according to aspects of the disclosure. At 2702, the finger follower is configured to a first state/position in which the sliding member 1802 (FIGS. 18 and 19, for example) is moved to its leftmost position and the finger follower conveys main event lift from the cam 1920. Thus, the first position in this case corresponds to the valvetrain component (finger follower) conveying only the highest lift (i.e., main event) profile on the motion source. At 2706, the finger follower may be configured to a second state/position, in which the sliding member 1802 is shifted rightward (FIG. 19) to a second position (FIG. 20) such that the finger follower conveys a second range of motion from the cam. At 2608, the engine is operated in an EEVO operation. At 2710, the finger follower may be configured to a third state/position, in which the sliding member 1802 is shifted even further rightward (FIG. 19) to a third position (FIG. 21). At step 2712, the engine is operated in lost motion braking mode.
Although the present implementations have been described with reference to specific example embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the invention as set forth in the claims. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.
Patent Application
20200291826
