Patent Description:
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, to provide, for example, variable valve actuation (WA) for intake valves in a pushrod engine or in a space-constrained engine, and, for example, to provide two-position intake valve lift in which the first position may be normal valve closing and the second position may be late valve closing.

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.

Internal combustion engines may utilize a thermodynamic cycle known as a Miller cycle, which typically involves late closing of the intake valve (LIVC) to achieve desirable performance and emissions objectives. LIVC may result in a reduced engine compression ratio for improved emissions and fuel consumption under certain operating conditions. However, LIVC may not be desirable under all engine operating conditions. For example, during transient conditions, such as startup conditions, when there may be inadequate intake charge or pressure from a turbocharger, the system may need to run at full compression ratio. On the other hand, during steady state or normal operation, when adequate turbocharger boost pressure is available, LIVC can provide reduced NOx emissions and improved fuel consumption. As such, past efforts in the art have attempted to provide valve actuation systems that are capable of quickly and reliably transitioning from normal to late closing cycles on demand and as needed in order to fully realize the benefits offered by LIVC across a wide range of speeds, loads and other operating parameters that characterize typical operating environments for diesel and other engines.

Prior art systems that have attempted to address the above needs have included lost motion resetting rocker brake systems, or bridge brakes. For example, prior art systems developed by Jacobs Vehicle Systems, Inc. , include resetting bridge brakes, such as those described in <CIT>. These systems can add motion or lose motion (reset) based on control of the flow and/or pressure of oil supplied to the braking rocker arm. Known prior art systems are characterized by larger implementation costs and packaging that is not readily adaptable to many engine environments. For example, on a pushrod engine, it may not be possible to have added cam lobes and rocker arms to provide desired modified main event valve closing motion. The motion must come from the single cam lobe and pushrod. On some overhead cam engines there may not be enough space on the valvetrain for additional rockers and a lost motion intake may still be the best option for providing <NUM>-position WA/lost motion. Another relevant prior art document is <CIT>.

In some applications, it may be desirable to have selective reset that may facilitate two alternative valve closing profiles, such as normal valve closing and late valve closing, where reset is based, for example, on an engine parameter, such as engine load, engine speed or engine temperature. Since the system always has oil during opening to provide normal opening, it may not be desired to modify the opening of the intake valve in either operating mode. It would be desirable to provide a system that may utilize the availability of oil at beginning of the main event, and has selective resetting to either be filled with oil at closing, or to be drained of oil at closing. In the event that the engine is starting up and no oil pressure is available, such a lost motion system may default to mechanical lift providing a late opening and a normal closing main event. The late opening will have a minor impact on air flow, and the normal closing will provide a normal compression ratio to start the engine. Other systems that have early closing as the default lift will have potentially low compression ratio at startup, and therefore have difficulty with cold engine startup. Thus, it would be desirable to have a system that provides for leaving the intake motion profile of main event intake opening profile intact while making available the switching between two different main event intake closing profiles.

It would therefore be advantageous to provide systems and methods that address the aforementioned shortcoming and others in the prior art.

Responsive to the foregoing challenges in the prior art, the instant disclosure provides various embodiments of resetting lost motion systems, which meet the above challenges and provide improved operating characteristics and performance.

The above-mentioned difficulties may be overcome based on aspects reflected in the various embodiments disclosed herein. The disclosed advances are particular advantageous in providing rocker arm components that facilitate main event motion having unmodified opening and modified closing, while offering a compact package that integrates resetting components and reset blocking components.

As used herein, the term "component" denotes structure that includes either a single element or part, or a combination of elements or parts, to achieve an operational result associated with the component.

Implementations according to the disclosure provide resetting lost motion features in a rocker arm, or other valve train component, which eliminate the need for complex reset control components that would otherwise be situated external to the valve train component. A hydraulic control circuit may be integrated into the rocker arm. Advantageously, the reset components that perform reset of the lost motion component, as well as the control components that may perform blocking or unblocking of the reset component, and all hydraulic passages connecting these components, may be integrated, and packaged compactly and internally within the rocker arm.

Implementations according to the disclosure also provide valve train components, such as rocker arms, with resetting lost motion components and associated resetting systems that may be selectively turned "on" and "off' to provide either normal valve closing or late valve closing, respectively. Such systems may utilize a constant supply of hydraulic working fluid, such as oil, provided through existing engine working fluid distribution systems (rocker shaft and journal passages). Moreover, all of the dynamic (moving) parts associated with the reset system may be integrated into a rocker arm to provide compact packaging suitable for space constrained engine overhead environments. The integrated reset components may facilitate the resetting by fixed objects/surfaces in the engine overhead environment, such as simple contact surfaces or points arranged to engage the reset piston, which may extend from the valve train component (rocker arm) into which it is integrated. Embodiments described herein eliminate need for complex external reset triggering components.

According to an aspect of the disclosure, there is provided a valve actuation system for conveying motion from a motion source to at least one engine valve in a valve train in an internal combustion engine comprising: a housing adapted to support components of the system; a lost motion component disposed in the housing for selectively conveying motion from the motion source to the housing, the lost motion component adapted to absorb motion provided from the motion source in a lost motion state; a reset component for resetting the lost motion component to the lost motion state; and a reset blocking component for selectively preventing reset of the lost motion component.

According to a further aspect, the reset component may comprise a reset piston and the blocking component may comprise a blocking piston. In a non-resetting mode of operation, the blocking piston blocks flow in a reset passage regardless of the position of the reset piston. In a resetting mode of operation, the blocking piston allows resetting of the lost motion component by the reset piston. The reset piston may extend from the rocker arm housing such that the reset piston engages a fixed reaction or contact surface when the rocker arm moves to a predetermined rotational position in order to facilitate reset or motion loss in the actuator piston.

According to a further aspect, the reset component may comprise a reset piston, and the reset blocking component may comprise a blocking sleeve disposed concentrically relative to the reset piston. In a non-resetting mode of operation, the blocking sleeve blocks flow in a reset passage regardless of the position of the reset piston. In a resetting mode of operation, the blocking sleeve allows resetting of the lost motion component by the reset piston.

According to further aspects, the system may comprise a working fluid circuit, which may further comprise a supply and backflow prevention component, such as a check valve, the working fluid circuit being at least partially defined in the housing for controlling the flow of fluid to the lost motion component.

According to a further aspect, there is provided a method of controlling valve motion in a valve actuation system in an internal combustion engine, the valve actuation system comprising: a motion source; a housing; a lost motion component disposed in the housing for selectively conveying motion from the motion source to the housing, the lost motion component adapted to absorb motion provided from the motion source in a lost motion state; a reset component for resetting the lost motion component to the lost motion state; and a reset blocking component for selectively preventing reset of the lost motion component, the method comprising: operating the reset component to cause the lost motion component to at least partially absorb motion from the motion source; and operating the reset blocking component to block resetting of the lost motion component.

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> illustrate a first example valve train component in the form of a rocker arm <NUM>, in accordance with aspects of the disclosure. Referring particularly to <FIG> and <FIG>, rocker arm <NUM> may typically include a housing or rocker arm body <NUM> having a central journal portion <NUM>. A motion receiving portion <NUM>, which may receive motion from a motion source (i.e., cam) and motion conveying end <NUM> may extend in opposite directions from the central journal portion <NUM>. Motion conveying end may include an adjustable e-foot or swivel foot assembly <NUM> for engaging a valve bridge. Motion receiving end <NUM> may include an actuator piston assembly <NUM> housed therein to receive motion from the motion source through other valve train components, such as a pushrod. In accordance with aspects of the disclosure, the rocker arm body <NUM> may house and integrate an actuator piston assembly <NUM>, a reset piston assembly <NUM> and a blocking piston assembly <NUM>. An actuator piston bore or cavity <NUM> may house the actuator piston assembly <NUM>. A reset piston bore or cavity <NUM> may house the reset piston assembly <NUM> and a blocking piston bore or cavity <NUM> may house the blocking piston assembly <NUM>. A check valve <NUM> may be disposed in a check valve bore or cavity <NUM>, which may extend to the rocker shaft journal and may be plugged by a threaded check valve bore plug <NUM>. A rocker journal bushing and oil guide <NUM> may be disposed in the rocker journal to reduce wear and friction and to guide engine oil from an oil passage in the rocker shaft, via channels <NUM> to one or more ports <NUM> and further to corresponding ports in the rocker arm body <NUM> to provide working fluid to the various components integrated therein, as will further be described.

Referring more particularly to <FIG>, <FIG> and <FIG>, actuator piston assembly <NUM> may include an actuator piston <NUM>, sized to slide within and provide substantial sealing engagement with actuator piston bore or cavity <NUM>. Actuator piston may be formed as a hollow element with a cavity <NUM>, which may house a biasing element, such as a coil spring <NUM>, which may bias the actuator piston <NUM> in an extended direction (out of its bore) to manage inertia of the push rod or other valve train components, such as a cam follower cooperating with a cam motion source. For example, when the system is filling with oil the spring may maintain contact between the actuator piston, pushrod, cam follower, and camshaft. A spring clip retainer <NUM> may secure the actuator piston and spring <NUM> within the actuator piston cavity <NUM>. As best seen in <FIG>, actuator piston <NUM> may define an expandable actuator piston chamber with the piston actuator bore <NUM>. A supply passage <NUM> in the rocker arm body <NUM> may provide a constant flow of working fluid (engine oil) from the rocker shaft supply, through check valve <NUM> to the actuator piston chamber. Actuator piston <NUM> may function to vary the lash in the valve train between the rocker arm <NUM> and the motion source (cam). As will be further described, the motion of actuator piston assembly <NUM> may be controlled via the integrated reset component <NUM> and blocking component <NUM> to selectively provide for variations in valve motion (lost motion), to facilitate desirable operations, such as late intake valve closing.

Referring particularly to <FIG>, actuator piston reset may be controlled through selective venting of oil through an actuator piston reset (or venting) passage <NUM> defined in the rocker arm body <NUM>. Reset passage <NUM> may comprise a first portion <NUM>, extending from the actuator piston bore <NUM> to the blocking piston bore <NUM>, a second portion <NUM>, extending from the blocking piston bore <NUM> to the reset piston bore <NUM>, and a third portion <NUM> extending from the blocking piston bore <NUM> to a vent orifice <NUM>, which may control the flow of working fluid from the reset passage <NUM> to the external engine overhead environment (external to the rocker arm). Control of flow of oil within the reset passage <NUM> may be controlled by the interaction of the blocking component <NUM> and the reset component <NUM> with the reset passage. Referring additionally to <FIG>, the reset component may control flow in the reset passage <NUM> and may comprise a reset piston assembly <NUM>, which may include a reset piston <NUM>, reset piston spring <NUM>, reset piston spring retainer <NUM> and reset piston retainer <NUM>. Reset piston may be dimensioned slide within and form a seal with the surface of reset piston bore <NUM>. An annular groove or channel <NUM> provides for flow around the reset piston <NUM> when the annular groove <NUM> is aligned with the reset passage <NUM>. A piston retaining ring <NUM> retains the piston <NUM> in the rocker arm body <NUM>. A spring retaining shoulder <NUM> may be formed on an end of the reset piston <NUM> for engaging and supporting the reset piston spring <NUM> thereon. An opposite end of reset piston spring <NUM> engages a spring retainer <NUM> which is retained in place with a C-clip type reset piston retainer <NUM> which engages and expands into a groove in the rocker arm body <NUM>. An external end <NUM> of the reset piston <NUM> may extend from the rocker arm body <NUM> and be biased in the extended direction by reset piston spring <NUM>. External end <NUM> may engage a reaction surface that is external to the rocker arm and fixed with respect to the engine head in order to move the reset piston <NUM> relative to the rocker body to a reset state or position, as will be described further herein.

Referring again to <FIG>, a reset blocking component may comprise a blocking piston assembly <NUM>, which may include a blocking piston <NUM>, blocking piston spring <NUM>, spring retainer <NUM> and blocking piston retainer <NUM>. Blocking piston <NUM> may dimensioned to slide within and form sealing engagement with blocking piston bore or cavity <NUM>. Blocking piston <NUM> may have an annular groove or channel <NUM> defined therein for permitting flow past the blocking piston when the annular groove <NUM> is aligned with flow passages in the rocker arm, as will be described. Blocking piston spring <NUM> may extend within a spring receptacle <NUM> on the interior of blocking piston and may engage a spring receptacle shoulder <NUM> therein. Blocking piston spring <NUM> may thus bias the blocking piston in a direction towards the rocker arm journal <NUM>. An oil port <NUM> on the rocker arm bushing/oil guide <NUM> may selectively provide a supply of oil to the bottom of the blocking piston bore <NUM> as commanded by a control solenoid to cause the blocking piston <NUM> to move to a reset blocking position.

In <FIG>, the blocking piston is shown in a "resetting position" where resetting is allowed to occur. The blocking piston annular passage <NUM> is aligned with the reset passage <NUM>, allowing the high-pressure oil from the actuator piston bore <NUM> to pass through the reset passage portion <NUM> and into the reset piston bore <NUM>. The reset piston can then dump oil from the hydraulic circuit when the rocker moves to the reset position.

In <FIG>, the blocking piston <NUM> is shown in a "non-resetting" position. Oil is supplied to the bore for the piston through the passage <NUM> in the rocker arm bushing from the rocker shaft (not shown). Oil pressure exceeds the preload of blocking piston spring <NUM>, and the blocking piston moves to a position in which it isolates the high pressure reset passage portion <NUM> from the actuator piston bore <NUM>. High pressure oil is thus not permitted to escape from the circuit and reset or motion loss does not occur. This blocking of reset may thus provide for late closing intake motion on an intake valve. Advantageously, high pressure volume and the number of leakage paths is minimized with this arrangement. The operation of blocking piston <NUM> may be controlled based on one or more engine parameters, including engine speed, load, exhaust or oil temperature. Such control may implemented using a control solenoid, that may communicate with and is driven by an engine controller, to selectively supply oil to passage <NUM> to switch between the operating modes, which modes may be a Miller cycle and normal valve closing, as desired, based on engine operating parameters.

<FIG> illustrates the reset piston <NUM> in a position or state corresponding to cam base circle. In this position or state, reset piston <NUM> blocks reset passage <NUM> by preventing oil flow from reset passage portion <NUM> to reset passage portion <NUM>, thus preventing oil from escaping from the rocker arm body <NUM> regardless of the position of blocking piston <NUM>. In this position, the reset piston external end <NUM> may be held by reset piston spring <NUM> in contact with a fixed component on the cylinder head (see <FIG>, for example).

<FIG> illustrates the reset piston <NUM> in a position corresponding to the beginning of a valve reset height. As shown, the reset piston <NUM> has moved in to open the reset passage <NUM> by beginning to align the annular passage <NUM> with the reset passage <NUM>. If the blocking piston <NUM> is in the "resetting position" the oil from the actuator piston chamber may flow around the blocking piston <NUM> and through the reset piston annulus <NUM> to vent from the rocker arm to atmosphere. The reset passage vent orifice may regulate the rate of reset to smooth the transition between the two operating states.

<FIG> illustrates the reset piston in a position corresponding to peak valve lift. As the rocker moves through its full main event lift the reset piston annulus <NUM> is further aligned with the reset passage to provide adequate flow area to dump all the actuator piston oil within the main event valve lift. The vent orifice may provide a reset rate that is fast enough to vent the oil during the main event, but slow enough to prevent shock loads through the valve train that may be caused by impact between the actuator piston and the bottom of the actuator piston bore.

As will be recognized from the instant disclosure, the configuration of the blocking piston <NUM> may be modified to achieve different operational characteristics. For example, while blocking piston, in the above example, is configured for "normally resetting" mode, in which the annular passage aligns with the reset passage <NUM> and permits oil flow through the reset passage when the working fluid supply is interrupted, the blocking piston could be alternatively configured, with appropriate repositioning of the annular groove or channel, for example, for a "normally not resetting" mode, in which the blocking piston blocks oil through the reset passage when the working fluid supply is interrupted. For example, the modes of operation such as "normally resetting" or "normally not resetting" can be selected based on an appropriate duty cycle for the two operating modes to minimize oil consumption.

Thus, as described above, there are two pistons connecting across the reset passage: the reset piston <NUM> that may reciprocate in the reset piston bore <NUM> to open and close the reset passage as the rocker arm moves through its main event lift; and the blocking piston <NUM> that may have two positions controlled by a blocking piston supply passage that can move the piston when oil is selectively supplied to its bore. In one position the reset piston is free to communicate with and vent working fluid via the reset passage. In another position the reset passage is blocked by the blocking piston and the reset piston is thus precluded from communicating with and venting the working fluid via the reset passage.

<FIG> is a schematic illustration of a working fluid (i.e., hydraulic) circuit in accordance with the embodiment illustrated in <FIG>. As will be recognized from the instant disclosure, the constituent passages and components are integrated into a compact package within the rocker arm. The supply passage <NUM> may supply oil from an engine oil supply source (rocker shaft passages, for example) through check valve <NUM> and check valve bore <NUM> to the actuator piston assembly <NUM>. Reset passage portion <NUM> conveys working fluid to the blocking piston assembly <NUM> and reset passage portion <NUM> conveys working fluid to the reset piston assembly <NUM>. Passage portion <NUM> conveys working fluid from the reset piston assembly to the ambient engine environment, possibly through a vent orifice (not shown in <FIG>).

This arrangement may be preferred due to advantageous packaging, reduced potential for leakage, and hydraulic volume benefits. However, will be understood from the instant disclosure that other arrangements of the components may be provided without departing from the inventive scope of the disclosure. For example, an alternate arrangement where the positions of the reset piston assembly and blocking piston assembly may be switched, as schematically illustrated in <FIG>. As will be recognized from the instant disclosure, arrangement of the components may be optimized with due regard to the oil flow paths and minimization system losses due to oil flow and pressure demands of a particular configuration. For example, when the blocking piston is positioned as shown in the schematic in <FIG>, there is only a single leak path - the clearance between the blocking piston and the blocking piston bore - where high-pressure oil may leak from the system. Thus, in this configuration, oil leakage only occurs in the blocking piston. On the other hand, the configuration of <FIG>, while offering other advantages, may be susceptible to leakage of high-pressure oil past both the reset piston bore clearance and the blocking piston bore clearance. The annular passages and part of the drillings may be eliminated by positioning the blocking piston in close proximity to the actuator piston.

<FIG> is a graphical illustration of the operation of the rocker arm of <FIG>, in the "resetting mode. " As will be recognized from the instant disclosure, the "resetting mode" of operation corresponds to a normal valve closing profile. The depicted ideal valve lift is kinematic valve lift without any deflection of the valve train. The actual valve lift is shown for <NUM>, <NUM>, <NUM> RPM. The actual valve lift includes deflection due to mechanical and hydraulic deflection of the system. In this particular configuration, at a valve lift height of <NUM>, the rocker arm may be in a rotational position in which the reset piston may engage an external contact surface and the annular channel of the reset piston may thus register with the reset passage and begin to vent out ("dump") the oil from the actuator piston. As a result, the valve motion "resets" from the high lift down to follow the "ideal lift resetting" curve that is characterized by a normal closing angle for positive power. This plot thus shows the system's ability, when in a resetting mode of operation, to provide a normal opening angle and closing angle as would normally be provided for positive power operation without modification of compression ratio "miller cycle. " This is the lift curve desired for full compression ratio.

<FIG> shows a non-resetting mode of operation that corresponds to a ‴′late closing" cycle for the associated valve. The ideal valve lift shown is kinematic without hydraulic or mechanical compliance. The actual valve motion is simulated for <NUM>,<NUM>,<NUM> rpm. This actual motion includes mechanical and hydraulic compliance which reduce the lift compared to ideal. The open portion shows a small reduction in lift, and a retarding of timing due to this compliance. The "reset" in this figure is disabled by the blocking piston, and the oil is not permitted to vent from the actuator piston. The peak lift is increased and the late closing lift and later timing has been added to the lift curve. The late closing provides a lower compression ratio for improved fuel consumption and increased exhaust temperature desired for certain engine operating conditions.

Transition between the resetting and non-resetting operating modes may be controlled by an oil flow control solenoid or other component to move the blocking piston from the resetting state to the blocking state. For example, the control solenoid may be operated by an engine control unit (ECU) to selectively supply oil to move the blocking piston as desired to switch between Miller cycle and normal cycle operation. The ECU may implement various control strategies, which may vary depending on engine operational parameters, such as speed and load.

<FIG> show the rocker arm <NUM> of <FIG> above, installed in an engine overhead environment having a reset piston contact assembly <NUM> that may include an adjustment feature <NUM> for setting the reset position and controlling the height of the reset. As will be recognized, some features of the engine environment, such as the rocker shaft, are omitted from <FIG> for clarity. Moreover, while one adjustment feature <NUM> is illustrated, it will be recognized that contact assembly <NUM> may include multiple adjustment features, each for a respective associated rocker in a multiple cylinder environment. The feature <NUM> may include a set screw or other threaded fastener <NUM> extending through a threaded bore in an L-shaped bracket <NUM> that may be formed from a suitable gauge (thickness) metal stamping and fastened with threaded bolts (not shown) through holes <NUM> to the cylinder head or to any object in the overhead environment that is fixed relative to the rocker arm. An end of the setscrew <NUM> provides a reaction surface for engaging the external end <NUM> of reset piston <NUM>. A locking nut <NUM> maintains the set screw <NUM> in a precise locked position. As the rocker moves (rotates on the rocker shaft) the reset piston contacts this reaction surface and moves inward relative to the rocker arm to cause resetting of the actuator piston, and thus loss of motion otherwise conveyed by the actuator piston, at a precise rotational position of the rocker arm.

It will be recognized by the instant disclosure that the orientation of the contact assembly and adjustment feature may be modified. For example, the bracket <NUM> may include a surface that extends horizontally, vertically or any orientation. Moreover, the reaction surface position may be modified such that the reset piston may be maintained in a retracted position (i.e., moved into the reset piston bore) and allowed to extend from the bore when the rocker arm moves away from the reaction surface.

<FIG> illustrate another example rocker arm configuration as an alternative to the example of <FIG> above. This variant may comprise concentrically arranged elements to provide the blocking and resetting components in a single bore or cavity in the rocker arm, which reduces machining cost and complexity with regard to the rocker arm. This configuration may be viewed essentially as a spool valve within a spool valve.

Referring particularly to <FIG>, which is an exploded perspective view, a rocker arm <NUM> may have similar features to the embodiment of <FIG>, and may include a rocker arm body <NUM>, having a rocker arm journal <NUM>, and swivel foot assembly <NUM> at one end. An actuator piston assembly <NUM> may include an actuator piston <NUM>, actuator piston spring <NUM> and retainer <NUM> disposed in an actuator piston bore <NUM> in the rocker arm body <NUM>. A check valve <NUM> may be disposed in a check valve bore <NUM>, which may be plugged by a check valve bore plug <NUM>. A reset component may include a reset piston assembly <NUM>, and a blocking component may include a blocking sleeve assembly <NUM>, the details of which will be described. In accordance with the advantages of this example, the reset piston assembly <NUM> and blocking sleeve assembly <NUM> may be disposed in a single bore <NUM> in the rocker arm body <NUM>.

Reset piston assembly <NUM> may include a reset piston <NUM> having one or more longitudinally extending channels or grooves <NUM> and a reset piston biasing assembly including a reset piston spring <NUM> and a pair of reset piston spring retainers <NUM> and <NUM>. A pair of piston retainer clips <NUM> and <NUM> may engage retaining slots on ends of the reset piston <NUM> to retain the reset piston <NUM> and other elements of the reset assembly <NUM> and blocking assembly <NUM> in place, as will be described.

Blocking sleeve assembly <NUM> may include a blocking sleeve <NUM> having one or more radially extending blocking sleeve ports <NUM>, a blocking sleeve spring <NUM>, blocking spring retainer <NUM> and a blocking sleeve travel limiter <NUM>. Referring particularly to <FIG>, which illustrates an assembled version of the elements of <FIG>, blocking sleeve <NUM> is disposed in bore <NUM> concentrically with the reset piston <NUM>. Blocking sleeve spring <NUM> abuts one end of the blocking sleeve <NUM> and is retained in position on another end by blocking sleeve spring retainer <NUM>, secured within a channel in the rocker arm body <NUM>. Blocking sleeve <NUM> is thus biased upward in <FIG> by the blocking sleeve spring <NUM>. Blocking sleeve travel limiter <NUM> defines an upper travel limit for blocking sleeve <NUM>. Reset piston <NUM> extends through the blocking sleeve <NUM> and blocking sleeve spring <NUM> and is retained at one (lower) end by reset piston retainer <NUM>. An upper reset piston retainer <NUM> likewise retains the position of reset piston <NUM> relative to other elements. Reset piston spring <NUM> is supported between the reset spring retainers <NUM> and <NUM> and disposed concentrically relative to the reset piston <NUM>. Reset piston spring provides an upward biasing force on the reset piston <NUM>. An external end <NUM> of the reset piston <NUM> extends from the rocker arm body and may engage an external reaction surface during operation.

<FIG> shows the mechanism in the reset blocked position. A reset passage may include an annular channel <NUM> formed in the rocker arm body <NUM> and concentric with the reset piston <NUM> and blocking sleeve <NUM>. Annular channel <NUM> may be in fluid communication with the actuator piston chamber to permit flow of oil and reset. In <FIG>, the blocking sleeve <NUM> is disposed in a lower position to block the annular channel <NUM>. The blocking sleeve <NUM> may be moved downward, against the biasing force of the blocking sleeve spring <NUM>, by pressurizing an upper chamber <NUM>, defined by the annular blocking sleeve <NUM>, the rocker arm chamber bore <NUM>, reset piston <NUM> and sleeve travel limiter <NUM>, with selective supply oil. Chamber <NUM> may be selectively pressurized by an oil control solenoid in fluid communication with an oil passage connected to the rocker shaft passage. The oil control solenoid may be controlled by an engine ECU.

<FIG> shows the mechanism in a reset active position. The blocking sleeve <NUM> is moved upward to index the sleeve ports <NUM> with the reset passage annulus <NUM> to provide fluid communication between the actuator piston bore <NUM> and the reset piston longitudinal channels <NUM> (see <FIG> and <FIG>). In <FIG> and <FIG>, however, the reset piston is shown on base circle position. Therefore, in this position, the reset piston <NUM> prevents oil from being vented from the actuator piston chamber.

<FIG> shows the reset piston <NUM> at peak valve lift and the blocking piston <NUM> in the reset active position. In this position, the longitudinal channels <NUM> on the reset piston <NUM> are positioned to connect the blocking sleeve ports <NUM> to the lower portion of bore <NUM>, which permits the actuator piston chamber oil to evacuate to ambient and the reset of the actuator piston to occur.

In the embodiments described above, having the actuator piston spring biasing force applied to the valve train components, such as the pushrod and follower, may lead to excessive wear on the rocker arm bushing and other components that may not be properly lubricated when constantly loaded. <FIG> illustrates an adjustment system for addressing such problems by using an alternative arrangement for an actuator piston <NUM> that may provide stroke limits and precise stroke control. In this version the outward travel of the actuator piston <NUM> may be limited by a retaining ring <NUM>. A bias spring <NUM> located inside an actuator piston <NUM> applies a bias force towards the outward (extended) direction. Upward travel of the actuator piston <NUM> may be controlled by an adjusting screw <NUM> and jam nut <NUM> is added to set the stroke of the actuator piston accurately to account for manufacturing variation. Alternatively, as will be recognized from the instant disclosure, it may be possible, by match fitting and very high levels of precision, or by addition of various thickness shims, to control the actuator piston stroke without the lash setting screw. When the cam is on base circle, travel of the piston <NUM> is stopped by the retaining ring <NUM>. On base circle, the rocker arm <NUM> may have a lash space <NUM> in the valvetrain that is not taken up by the actuator piston stroke. In this configuration, only during the cam lift portion greater than the lash -<NUM> will the actuator piston spring load the pushrod. Preferably, the distance from the actuator piston to the bottom of the bore is greater than the stroke needed for lost motion.

The system of <FIG> provides a simple configuration in that the stroke of the actuator piston is set by the singular adjusting screw located on the motion receiving end of the rocker arm. Setting the stroke may be done easily by using a suitable thickness feeler gage beneath the e-foot, and, for example, adjusting until the actuator piston bottoms out in the bore. Setting the stroke may be done with the screw <NUM> on the motion receiving end and may be factory set using a fixture that measures travel, and locked indefinitely. Setting the lash can be done with the screw on the motion imparting side to accommodate engine tolerances and wear over time. A tamper proof method may be used so that the stroke is not changed by the end user.

<FIG> illustrates an alternative packaging arrangement of reset piston and separate blocking piston in a rocker arm. The internal components are similar to those described in <FIG> above. However, in this configuration, the orientation of the reset piston <NUM> is reversed, such that the reset piston end <NUM> is facing downward. With this configuration, motion of the rocker arm may extend of the reset piston relative to the rocker arm bore. This may be more suitable in some engines that to not have adequate overhead space for mounting a stamping, or in systems that already have a contact surface adjacent to the rocker arm. A reset surface (not shown in <FIG>), beneath the reset piston may act on the lower surface <NUM> of piston <NUM>. On the base circle the piston <NUM> will be displaced upwards relative to the rocker arm <NUM>. During main event lift the rocker arm <NUM> will rotate and move upwards relative to reaction surface and piston <NUM> will remain down against the reaction surface, and move outward relative to the bore in rocker arm <NUM>. The reset piston may essentially remain in contact with the stationary reaction surface, however, and move relative to the rocker arm as the rocker reciprocates.

Claim 1:
A valve actuation system for conveying motion from a motion source to at least one engine valve in a valve train in an internal combustion engine comprising:
a housing (<NUM>) adapted to support components of the system:
a lost motion component (<NUM>) disposed in the housing and adapted to selectively convey motion from the motion source to the housing, the lost motion component adapted to absorb motion provided from the motion source in a lost motion state;
a reset component (<NUM>) adapted to reset the lost motion component to the lost motion state; and
a reset blocking component (<NUM>) configurable to a non-resetting mode of operation in which reset of the lost motion component by the reset component is prevented, regardless of the position of the reset component.