ROCKER ARM WITH OUTWARDLY SPRUNG HYDRAULIC ACTUATOR PISTON

Abstract

A rocker arm comprises a hydraulic actuator piston slidably disposed in an actuator bore. An actuator spring is configured to bias the hydraulic actuator piston out of actuator bore and into contact with a valve train component or at least one engine valve, wherein reaction of the hydraulic actuator piston against the valve train component or the at least one engine valve biases a motion receiving portion of the rocker arm into contact with the valve actuation motion source. In an unactuated state of the hydraulic actuator piston, hydraulic fluid is permitted to flow out of the actuator bore and, in an actuated state of the hydraulic actuator piston, hydraulic fluid is locked in the actuator bore.

Description

FIELD

The present disclosure concerns rocker arms for use in internal combustion engines and, in particular, to a rocker arm with an outwardly sprung hydraulic actuator piston.

BACKGROUND

Internal combustion engines typically use either a mechanical, electrical, or hydro-mechanical valve actuation systems to actuate the engine valves. These systems may include a combination of camshafts, rocker arms, push rods and other components (collectively, a valve train) that may be driven by the engine's crankshaft rotation. When a camshaft is used to actuate the engine valves, the timing of the valve actuation may be fixed by the size and location of the lobes on the camshaft. To reduce impact damage to the cam and any valve train components and to minimize any unnecessary noise or vibration, it is often desirable to maintain contact between the cam and any valve train component configured to contact the cam.

One common design for keeping continuous contact between a cam and a rocker arm consists of a spring bar or other fixed structure and a spring, reacting against the spring bar or fixed structure, that biases the rocker arm into contact with the cam as described, for example, in U.S. Patent Application Publication No. 2012/0048232 (“the '232 publication”). As taught in the '232 publication, a valve actuation system comprises a spring that is deployed between a cam-side surface of a rocker arm and the spring bar (acting as a fixed surface relative to the reciprocation of the rocker arm) to bias the rocker arm into contact with the cam. Although a type III (center pivot) valve train is described in the '232 publication, the system described therein may be applied to other valve train types (i.e., type IV or type V) in which a center pivoting rocker transfers valve actuation motions to an engine valve. Furthermore, while the teachings of the '232 publication are directed to a dedicated rocker arm used for engine braking, the biasing solution described therein may be applied to various types of rocker arms.

While the system taught by the '232 publication works well, the presence of the spring bar reduces the amount of clearance within the engine valve cover, adds to the cost of the engine and increases the number of required components and engine assembly steps. A valve actuation system that provides the same benefits as the '232 publication but without the requirement of the spring bar would be a welcome addition to the art.

SUMMARY

The instant disclosure addresses the above-described shortcoming and describes a rocker arm for conveying valve actuation motions, the rocker arm comprising a motion receiving portion configured to receive the valve actuation motions from a valve actuation motion source and a motion imparting portion configured to convey the valve actuation motions to a valve train component or at least one engine valve. The rocker arm further comprises a hydraulic actuator piston slidably disposed in an actuator bore. An actuator spring is configured to bias the hydraulic actuator piston out of actuator bore and into contact with the valve train component or the at least one engine valve, wherein reaction of the hydraulic actuator piston against the valve train component or the at least one engine valve biases the motion receiving portion of the rocker arm into contact with the valve actuation motion source. In an unactuated state of the hydraulic actuator piston, hydraulic fluid is permitted to flow out of the actuator bore and, in an actuated state of the hydraulic actuator piston, hydraulic fluid is locked in the actuator bore.

In an embodiment, the actuator spring is configured to absorb the valve actuation motions received from the valve actuation motions source during the unactuated state.

In an embodiment, the rocker arm is a center pivot rocker arm.

In an embodiment, the actuator bore is formed in the motion imparting portion of the rocker arm.

In an embodiment, the at least one engine valve comprises at least one exhaust valve and the valve actuation motion source is an auxiliary valve actuation motion source separate from a main valve actuation motion source.

In another embodiment, the rocker arm further comprise a control valve comprising a control valve piston slidably disposed in a control valve bore. A first hydraulic fluid passage is in fluid communication with the control valve bore and the actuator bore, and a second hydraulic passage is in fluid communication with the control valve bore and configured to receive hydraulic fluid from a constant hydraulic fluid supply. Additionally, vent port is provided in fluid communication with the first hydraulic passage and the control valve bore. In the unactuated state, the control valve piston is positioned within the control valve bore to permit flow of hydraulic fluid from the second hydraulic passage to the first hydraulic passage and the actuator bore and to permit flow of hydraulic fluid from the first hydraulic passage to the control valve bore through the vent port. In the actuated state, the control valve piston is positioned within the control valve bore to occlude the first hydraulic passage and the vent port thereby locking hydraulic fluid in the first hydraulic passage and the actuator bore.

In an embodiment, the control valve bore is formed in the motion imparting portion of the rocker arm.

In an embodiment, the rocker arm further comprises a selectable hydraulic fluid passage in fluid communication with the control valve bore and configured to receive hydraulic fluid from a selectable hydraulic fluid supply. Further this embodiment, the control valve piston has a piston bore formed therein, an annular channel formed on an outer diameter of the control valve piston and a radial opening in fluid communication with the piston bore and the annular channel, and wherein the piston bore is configured to receive hydraulic fluid from the selectable hydraulic fluid passage via the control valve bore. Furthermore, the annular channel is configured to provide fluid communication between the first and second hydraulic passages during the unactuated state. A checking element may be disposed in the control valve piston between the piston bore and the radial opening and configured to permit flow of hydraulic fluid from the piston bore to the annular channel via the radial opening, but not vice versa.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages will be discussed in detail in the following non-limiting description of specific embodiments in connection with the accompanying drawings, in which:

FIG. 1 is a perspective view illustrating an example of a rocker arm in accordance with the instant disclosure;

FIGS. 2-4 are cross-sectional views illustrating additional features the rocker arm of FIG. 1; and

FIG. 5 is a perspective view of an alternative example of a rocker arm in accordance with the instant disclosure;

DETAILED DESCRIPTION OF THE PRESENT EMBODIMENTS

As used herein, phrases substantially similar to “at least one of A, B or C” are intended to be interpreted in the disjunctive, i.e., to require A or B or C or any combination thereof unless stated or implied by context otherwise. Further, phrases substantially similar to “at least one of A, B and C” are intended to be interpreted in the conjunctive, i.e., to require at least one of A, at least one of B and at least one of C unless stated or implied by context otherwise. Further still, the term “substantially” or similar words requiring subjective comparison are intended to mean “within manufacturing tolerances” unless stated or implied by context otherwise.

As used herein, the phrase “operatively connected” refers to at least a functional relationship between two elements and may encompass configurations in which the two elements are directly connected to each other, i.e., without any intervening elements, or indirectly connected to each other, i.e., with intervening elements.

Referring now to FIG. 1, a rocker arm 100 in accordance with the instant disclosure is illustrated. In the illustrated example, the rocker arm 100 is a so-called dedicated rocker brake, though the instant disclosure is not limited to such rocker arms. A dedicated rocker arm refers to a rocker arm that is provided to actuate only a single engine valve in a system comprising more than one engine valve of the type being actuated. For example, a given valve actuation system may comprise a main valve actuation motion source coupled to a valve train that is configured to provide main event engine valve motions, received from the main valve actuation motion source, to two or more engine valves. In such a system, a dedicated rocker arm, apart from the valve train conveying the main event engine valve motions, may be provided that is operatively connected to an auxiliary valve actuation motion source and to only one of the two or more engine valves. As used herein, the descriptor “main” refers to engine valve motions used during positive power generation in which fuel is combusted in an engine cylinder to provide a net output of engine power, whereas the descriptor “auxiliary” refers to other engine valve motions for purposes that are alternative to positive power generation (e.g., compression release braking, bleeder braking, cylinder decompression, cylinder deactivation, brake gas recirculation (BGR), etc.) or in addition to positive power generation (e.g., internal exhaust gas recirculation (IEGR), variable valve actuations (VVA), early exhaust valve opening (EEVO), late intake valve closing (LIVC), swirl control, etc.).

More generally, the teachings of the instant disclosure are applicable to valve train types employing a center pivot rocker arm, i.e., so-called type III, IV and V valve train types as well as type II (end pivoting). Additionally, the rocker arm 100 described herein may be applicable to any type of engine valve, including exhaust and/or intake engine valves.

The rocker arm 100 comprises a motion receiving portion 102, a motion imparting portion 104 and a rocker shaft bore 106 formed in a central body portion 107 of the rocker arm 100. Further, though not illustrated in FIG. 1, the rocker arm 100 may be embodied by a center pivot rocker arm comprising an input and/or output lever forming the rocker arm that may be selectively coupled/decoupled (or locked/unlocked) to/from each other. In this configuration, one of the input or output levers may reciprocate about a rocker shaft, yet still about an axis other than that defined by a rocker shaft. Furthermore, the teachings of the instant disclosure may also be applied to rocker arms other than center pivot rocker arms, i.e., end pivot rocker arms.

Regardless, the motion receiving portion 102 comprises, in the illustrated embodiment, a roller follower 108 mounted on a suitable roller shaft 110 and configured to contact a valve actuation motion source in the form of a cam on a camshaft (not shown). As known in the art, however, the roller follower 108 may be replaced by a suitably configured contact surface or other component (e.g., a tappet) configured to contact the valve actuation motion source. Further to the illustrated embodiment, the motion imparting portion 104 has an actuator boss 112 formed therein and having a bore (actuator bore 202) in which a hydraulic actuator piston 114 is disposed. Additionally, in this exemplary embodiment, a control valve 116 is disposed in the motion imparting portion 104 and configured to selectively supply hydraulic fluid to the actuator boss 112 and actuator piston 114, as described in further detail below. While the hydraulic actuator piston 114 and control valve 116 are illustrated in FIG. 1 as being deployed within the motion imparting portion 104 of the rocker arm 110, this is not a requirement, i.e., the hydraulic actuator piston 114 and/or control valve 116 may be equally deployed on the motion receiving portion 102 of the rocker arm 100.

Referring now to FIG. 2, an elevational, cross-sectional view of the rocker arm 100 is illustrated. In particular, FIG. 2 illustrates additional detail of the motion imparting portion 104 of the rocker 100. As shown, the actuator boss 112 has an actuator bore 202 formed therein and in which the hydraulic actuator piston 114 is slidably disposed. A threaded opening 203 is formed at the closed end of the actuator bore 202, thereby permitting passage of a lash adjustment screw 204, which screw 204 may be adjusted to provide a desired lash for the hydraulic actuator piston 114 relative to another valve train component, e.g., a bridge pin in a valve bridge (not shown). In accordance with known techniques, a lash adjustment nut 206 is also provided to retain the lash screw 204 in its position once set to the desired lash. Within the actuator bore 202, the lash screw 204 has an actuator piston cap 210 slidably disposed thereon. The cap 210 is configured, in this embodiment, to reside within a bore 208 formed in the hydraulic actuator piston 114, and is also affixed to an end of the hydraulic actuator piston 114 by a suitable fastening mechanism such as a snap ring 214 or the like. Travel of the actuator piston cap 210 and, consequently, of the hydraulic actuator piston 114 out of the actuator bore 202, is limited by a shoulder 216 formed on a distal end (relative to the lash adjustment nut 206) of the lash adjustment screw 204. Additionally, a bias spring 212 is disposed within the actuator piston bore 208 in contact with a closed end of the actuator piston bore 208 and the shoulder 216 of the lash adjustment screw 204.

Configured in this manner, the bias spring 212 reacts against the shoulder 216 of the lash adjustment screw 204 and against the hydraulic actuator piston 114, thereby biasing the hydraulic actuator piston 114 out of the actuator bore 202 toward the engine valves (not shown) or a downstream valve train component, such as a bridge pin or valve bridge, thereby providing a reaction surface for the hydraulic actuator piston and rocker arm 100 to bias the rocker arm 100 in a direction toward the motion receiving portion 102, i.e., biasing the rocker arm 100 toward the camshaft (not shown). In this manner, the need for an external spring and spring bar, as taught by the '232 publication, may be eliminated while still biasing the rocker arm 100 into contact with the cam. Preferably, the spring constant of the bias spring 212 is chosen to be sufficiently high to ensure that the inertia of the rocker arm 100 may be reliably controlled by the force applied by the bias spring 212, but not so high as to effect that ability of the corresponding engine valve to close under the force of its valve spring.

In addition to being outwardly sprung in order to bias the rocker arm 100 into contact with the cam, the hydraulic actuator piston 114 is hydraulically controlled to assume an unactuated (i.e., compliant and motion absorbing) or actuated (i.e., rigid and motion conveying) state. To this end, and as further shown in FIG. 2, a first hydraulic fluid passage 218, terminating at the actuator bore 202 above the actuator piston cap 210, is provided in order to supply hydraulic fluid to the actuator bore 202 and the actuator piston cap 210. As described in greater detail below relative to FIGS. 3 and 4, hydraulic fluid may be supplied to the first hydraulic fluid passage and selectively checked or unchecked through operation of the control valve 116. When hydraulic fluid within the first hydraulic fluid passage 218 and actuator bore 202 is unchecked by the control valve 116, i.e., when the hydraulic actuator piston 114 is in its unactuated state, the hydraulic actuator piston 114 is free to reciprocate within the actuator bore 202 such that valve actuation motions applied to the rocker arm are absorbed or lost by the bias spring 212, whereas when the hydraulic fluid within the first hydraulic fluid passage 218 and actuator bore 202 is checked by the control valve 116, i.e., when the hydraulic actuator piston 114 is in its actuated state, a locked volume of hydraulic fluid is established in the actuator bore 202 that prevents reciprocation of the hydraulic actuator piston 114 within the actuator bore 202. Further description of operation of the control valve 116 is further described with reference to FIGS. 3 and 4 below.

FIGS. 3 and 4 illustrate top, cross-sectional views of the rocker arm 100 in which the control valve 116 and related hydraulic passages are illustrated in greater detail. The control valve 116 comprises a control valve piston 302 slidably disposed within a control valve bore 304 formed in the motion imparting portion 104 of the rocker arm 100. Although the control valve bore 304 is illustrated as being substantially transverse relative to the direction of reciprocation of the rocker arm 100, this is not a requirement. A piston spring 306 is deployed within a bore 309 formed in a control valve limiting spacer 308 that, in turn, is disposed within the control valve bore 304. A snap ring or C-clip 310 is mounted at an open end of the control piston bore 304 to retain the control valve limiting spacer 308, piston spring 306 and control valve piston 302 in the control piston bore 304. The piston spring 306 contacts the control valve piston 302 and reacts against the control valve limiting spacer 308 and snap ring 310 to bias the control valve piston 302 into the control valve bore 304.

A checking elements (in this embodiment, a check ball) 312 is disposed within a piston bore 314 formed in the control valve piston 302 and is biased into contact with a checking seat 316 by a check spring 313. The piston bore 314 has a radial opening 318 formed in a side wall of the control valve piston 302, which opening 318 provides fluid communication between the piston bore 314 and an annular channel 320 formed on an outer diameter surface of the control valve piston 302. The control valve bore 304 is in fluid communication with a selectable hydraulic fluid supply passage 322 such that hydraulic fluid, when provided by the selectable hydraulic fluid supply passage 322, can impinge upon the control valve piston 302 and checking seat 316 and also flow into the piston bore 314 and past the checking element 312 (when displaced). In an embodiment, and in accordance with known techniques, the selectable hydraulic fluid supply passage 322 terminates at the interface of the rocker arm 100 and the rocker shaft bore 106 and is in fluid communication with a hydraulic fluid supply passage deployed in a rocker shaft (not shown). Such hydraulic fluid supply passage is, in turn, in fluid communication with a suitable solenoid (not shown) that may be controlled using known techniques to selectively supply hydraulic fluid to the selectable hydraulic fluid supply passage 322 via the hydraulic fluid supply passage deployed in the rocker shaft.

As further shown in FIGS. 3 and 4, the first hydraulic fluid passage 218 intersects with the actuator bore 202 as described above. The first hydraulic fluid passage 218 is additionally in fluid communication with the control valve bore 304 such that the first hydraulic fluid passage 218 registers with the annular channel 320 of the control valve piston 302 when, as shown in FIG. 3, the control valve piston 302 is biased fully into the control valve bore 304 by the piston spring 306. A vent port 324 is also provided in fluid communication, at respective ends thereof, with the first hydraulic fluid passage 218 and the control valve bore 304. The vent port 324 intersects with the control valve bore 304 such that any fluid in the first hydraulic fluid passage 218 and actuator bore 202 may be vented out of the rocker arm 100 when vent port 324 is unblocked by the control valve piston 302, i.e., when the control valve piston 302 is biased into the control valve bore 304 by the piston spring 306 as shown in FIG. 3. To this end, a longitudinal length of the control valve piston 302 is selected such that the vent port 324 is un-occluded when the control valve piston 302 is in its unactuated state, as shown in FIG. 3.

In the illustrated embodiment, the rocker arm 100 further comprises a second hydraulic fluid passage 326 that receives a constant fluid supply via the rocker shaft. Once again, techniques for providing a constant supply of hydraulic fluid via a rocker shaft are known to those skilled in the art. The second hydraulic fluid passage 326 is in fluid communication with the control valve bore 304 such that the second hydraulic fluid passage 326 also registers with the annular channel 320 of the control valve piston 302 when, as shown in FIG. 3, the control valve piston 302 is biased fully into the control valve bore 304 by the piston spring 306.

As shown in FIG. 3, both the first and second hydraulic fluid passages 218, 326 are registered with the annular channel 320. This positioning of the control valve piston 302 would result when substantially no hydraulic fluid is provided by the selectable hydraulic fluid supply passage 322. For example, in the illustrated example in which the rocker arm 100 is provided as a dedicated engine brake rocker, the control valve piston 302 would be maintained in this position such that the hydraulic actuator piston 114 is not permitted to rigidly extend out of the actuator bore 202, thereby losing the valve actuation motions (e.g., engine braking valve actuations) applied to the rocker arm 100.

Regardless, as a result of maintaining the control valve piston 302 as illustrated in FIG. 3, the constantly supplied hydraulic fluid received by the second hydraulic fluid passage 326 is permitted to flow through the annular channel 320 and into the first hydraulic fluid passage 218. In turn, at least some of the constantly supplied hydraulic fluid is also able to flow into the actuator bore 202. Any of the constantly supplied hydraulic fluid beyond that required to fill the actuator bore 202 will vent out of the first hydraulic fluid passage 218 via the vent port 324 given that the control valve piston 320 is not blocking the vent port 324.

Absent any movement of the hydraulic actuator piston 114 into the actuator bore 202, the hydraulic fluid thus supplied by the constant supply source will remain in the actuator bore 202, thereby maintaining the actuator bore 202 in a constantly charged state. However, any valve actuation motions applied to the rocker arm 100 that cause the hydraulic actuator piston 114 to react against a valve train component or an engine valve will cause the hydraulic actuator piston 114 to overcome the bias applied by the bias spring 212 and retract into the actuator bore 202 to an extent proportional to the valve lift being applied to the rocker arm 100. As known in the art, this essentially results in such valve actuation motions being absorbed by the hydraulic actuator piston 114 and bias spring 212, i.e., they are “lost.” Because the vent port 324 remains unblocked, any hydraulic fluid in the actuator bore 202 will be forced into the first hydraulic fluid passage 324 and thereafter vent out of the rocker arm 100 via the vent port 324. As the rocker arm 100 rotates away from the engine valve, the bias spring 212 will once again cause the hydraulic actuator piston 114 to extend out of the actuator bore 202, thereby once again permitting the constantly supplied hydraulic fluid to flow back into the actuator bore 202. This process of continuously charging and discharging the actuator bore 202 with hydraulic fluid decreases the amount of time required to activate the hydraulic actuator piston 114 in order to discontinue lost motion operation of the hydraulic actuator piston 114, an example of which is illustrated with reference to FIG. 4.

FIG. 4 illustrates a state in which hydraulic fluid has been supplied via the selectable hydraulic fluid supply passage 322. In this case, the pressure applied by the hydraulic fluid to the control valve piston 302 and the checking seat 316 overcomes the bias applied by the piston spring 306, thereby causing the control valve piston 302 to translate downward (as illustrated in FIG. 4) into the control valve bore 304 until such time that a lower shoulder 402 formed in control valve piston 302 abuts an upper shoulder 404 established by the control valve limiting spacer 308. In this position, the outer diameter or surface of the control valve piston 302 blocks and prevents fluid flow from the second hydraulic fluid passage 326 to the annular channel 320, i.e., prevents flow of the constantly supplied hydraulic fluid to the first hydraulic fluid passage 216 and the actuator bore 202. At the same time, the outer surface of the control valve piston 302 also blocks and prevents fluid flow from the first hydraulic fluid passage 216 via the vent port 324. However, in this case, the hydraulic fluid provided by the selectable hydraulic fluid supply passage 322 will overcome the bias applied to the check ball 312, thereby permitting the hydraulic fluid to flow through the radial opening 318, into the annular channel 320 and first hydraulic fluid passage 216. This flow of hydraulic fluid will continue until the actuator bore 202 is completely filled, thereby causing an equalization of pressure on either side of the check ball 312, and further causing the check ball 312 to reseat and trap a locked volume of hydraulic fluid in the first hydraulic fluid passage 216 and actuator bore 202. In this manner, the hydraulic actuator piston 114 will be hydraulically locked in its extended position out of the actuator bore 202 such that valve actuation motions applied to the rocker arm 100 will be conveyed to the engine valve, i.e., they are no longer lost. The hydraulic actuator piston 114 will remain in this state until such time that hydraulic fluid from the selectable hydraulic fluid supply passage 322 is discontinued, thereby allowing the piston spring 306 to once again bias the control valve piston 302 back into the control valve bore 304 and once again assuming the position as shown in FIG. 3 and allowing the trapped volume of hydraulic fluid to vent through the vent port 324.

As noted above, the teachings of the instant application are applicable to various type of valve trains. For example, while the embodiment of FIGS. 1-4 illustrate a rocker arm configured as a dedicated rocker brake, the teaching of the instant application could be equally applied to a so-called integrated rocker brake 500 as shown in FIG. 5. As in the embodiment of FIGS. 1-4, the integrated rocker brake 500 comprises a hydraulic actuator piston 502 and control valve 504, as well as the various hydraulic passages and vent port, substantially similar to those described above.

While the various embodiments in accordance with the instant disclosure have been described in conjunction with specific implementations thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. For example, to the extent that the dedicated rocker brake 100 of FIGS. 1-4 operates, as known in the art, in conjunction with a main rocker arm providing main event valve actuation motions to a valve bridge, it is appreciated that there may be instances in which such main event valve actuation motions will cause the valve bridge to move away from the dedicated rocker brake 110. This could, in turn, cause the dedicated rocker brake 100 to “fall” towards the valve bridge under the force of gravity. Thus, it would be advantageous to configure the dedicated rocker brake 100 to be balanced such that a center of gravity of the rocker arm 100 is located relative to the rocker shaft such that the rocker arm 100 is not prone to uncontrolled rotation when the valve bridge is moved away from the rocker arm 100.

Furthermore, to the extent that the first hydraulic fluid passage 218, actuator bore 220 and vent port 304 in the illustrated embodiment are in hydraulic communication with each other under all circumstance, it is appreciated that variations in the configuration of the vent port 324 are possible. For example, rather than terminating an end of the vent port 324 at the first hydraulic fluid passage 218, it may be functionally equivalent to instead terminate an end of the vent port 324 at the actuator bore 220.

It is additionally appreciated that the control valve 116 need not be implemented in the rocker arm 100, and instead could be implemented further upstream in the selectable hydraulic circuit supplying the rocker arm 100, e.g., within a rocker shaft or rocker shaft pedestal as known in the art. Further still, rather than using a control valve as described herein (whether in the rocker arm or upstream thereof), which combines the functions of hydraulic filling, checking and venting of the actuator bore, it is conceivable to employ a check valve and a separate venting or reset mechanism in fluid communication with the hydraulic passage supplying the actuator bore. In this case, fluid is supplied past the check valve while the venting mechanism is maintained in a closed/non-venting state whenever the actuated state of the actuator piston is desired. When resumption of the unactuated state of the actuator piston is required, the venting mechanism may be opened/placed in a venting state such that the actuator piston bore is once again permitted to vent.

As described above, the provision of the second hydraulic passage and the constant hydraulic fluid supply to the control valve bore and first hydraulic passages provides the benefit of being able to keep the actuator piston bore consistently charged such that switch over to the actuated state may be occur rapidly. However, it is appreciated that this is not a requirement and that it may be sufficient if the second hydraulic passage and the constant hydraulic fluid supply are not provided in communication with the control valve bore. In this case, and in accordance with known techniques, only the selectable fluid supply could be used to fill the actuator bore via the piston bore/radial opening/annular channel/first hydraulic fluid passage prior to establishing the locked volume of fluid. In this case, the control valve piston may be configured such that it vents the first hydraulic fluid passage and actuator piston bore (i.e., the first hydraulic passage is un-occluded by the control valve piston) when the actuator piston is in its unactuated state.

Accordingly, the preferred embodiments of the invention as set forth herein are intended to be illustrative only and not limiting so long as the variations thereof come within the scope of the appended claims and their equivalents.

Claims

1. A rocker arm for conveying valve actuation motions, the rocker arm comprising a motion receiving portion configured to receive the valve actuation motions from a valve actuation motion source and a motion imparting portion configured to convey the valve actuation motions to a valve train component or at least one engine valve, the rocker arm further comprising:

a hydraulic actuator piston slidably disposed in an actuator bore; and

an actuator spring configured to bias the hydraulic actuator piston out of actuator bore and into contact with the valve train component or the at least one engine valve, wherein reaction of the hydraulic actuator piston against the valve train component or the at least one engine valve biases the motion receiving portion of the rocker arm into contact with the valve actuation motion source,

wherein, in an unactuated state of the hydraulic actuator piston, hydraulic fluid is permitted to flow out of the actuator bore and, in an actuated state of the hydraulic actuator piston, hydraulic fluid is locked in the actuator bore.

2. The rocker arm of claim 1, wherein the actuator spring is configured to absorb the valve actuation motions received from the valve actuation motions source during the unactuated state.

3. The rocker arm of claim 1, wherein the rocker arm is a center pivot rocker arm.

4. The rocker arm of claim 1, wherein the actuator bore is formed in the motion imparting portion of the rocker arm.

5. The rocker arm of claim 1, wherein the at least one engine valve comprises at least one exhaust valve and the valve actuation motion source is an auxiliary valve actuation motion source separate from a main valve actuation motion source.

6. The rocker arm of claim 1, further comprising:

a control valve comprising a control valve piston slidably disposed in a control valve bore;

a first hydraulic fluid passage in fluid communication with the control valve bore and the actuator bore;

a second hydraulic passage in fluid communication with the control valve bore and configured to receive hydraulic fluid from a constant hydraulic fluid supply; and

a vent port in fluid communication with the first hydraulic passage and the control valve bore,

wherein, in the unactuated state, the control valve piston is positioned within the control valve bore to permit flow of hydraulic fluid from the second hydraulic passage to the first hydraulic passage and the actuator bore and to permit flow of hydraulic fluid from the first hydraulic passage to the control valve bore through the vent port,

and wherein, in the actuated state, the control valve piston is positioned within the control valve bore to occlude the first hydraulic passage and the vent port thereby locking hydraulic fluid in the first hydraulic passage and the actuator bore.

7. The rocker arm of claim 6, wherein the control valve bore is formed in the motion imparting portion of the rocker arm.

8. The rocker arm of claim 6, further comprising:

a selectable hydraulic fluid passage in fluid communication with the control valve bore and configured to receive hydraulic fluid from a selectable hydraulic fluid supply.

9. The rocker arm of claim 8, wherein the control valve piston has a piston bore formed therein, an annular channel formed on an outer diameter of the control valve piston and a radial opening in fluid communication with the piston bore and the annular channel, and wherein the piston bore is configured to receive hydraulic fluid from the selectable hydraulic fluid passage via the control valve bore.

10. The rocker arm of claim 9, wherein the annular channel is configured to provide fluid communication between the first and second hydraulic passages during the unactuated state.

11. The rocker arm of claim 9, further comprising:

a checking element disposed in the control valve piston between the piston bore and the radial opening and configured to permit flow of hydraulic fluid from the piston bore to the annular channel via the radial opening, but not vice versa.