Rocker arm with outwardly springing hydraulic actuator piston

Abstract

The rocker arm includes a hydraulic actuator piston slidably disposed within the actuator bore. An actuator spring is configured to bias the hydraulic actuator piston out of the actuator bore and into contact with a valve train component or at least one engine valve, such that rebound of the hydraulic actuator piston against the valve train component or at least one engine valve biases the motion-receiving portion of the rocker arm into contact with a valve-actuation motion source. A non-actuated state of the hydraulic actuator piston allows hydraulic fluid to flow out of the actuator bore, and a non-actuated state of the hydraulic actuator piston confines hydraulic fluid within the actuator bore.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE This disclosure relates to rocker arms for internal combustion engines, and more particularly to rocker arms having outwardly springing hydraulic actuator pistons. [Background technology]

[0002] Internal combustion engines typically use mechanical, electrical, or hydromechanical valve actuation systems to operate the engine valves. These systems may include a combination of camshafts, rocker arms, pushrods, and other components (collectively, the valve train), which may be driven by the rotation of the engine's crankshaft. When a camshaft is used to actuate the engine valves, the timing of valve actuation may be fixed by the size and position of lobes on the camshaft. To reduce impact damage to the cam and any valvetrain components and minimize any unwanted noise or vibration, it is often desirable to maintain contact between the cam and any valvetrain components configured to contact the cam.

[0003] One common design for maintaining continuous contact between the cam and rocker arm consists of a spring bar or other fixed structure and a spring that rebounds against the spring bar or fixed structure and 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, the valve actuation system includes a spring deployed between the cam-side surface of the rocker arm and a spring bar (which acts as a fixed surface associated with the reciprocating motion of the rocker arm) to bias the rocker arm into contact with the cam. Although the '232 Publication describes a Type III (center pivot) valve train, the system described therein may also be applied to other valve train types (i.e., Type IV or Type V) in which a center-pivot rocker transmits valve actuation motion to the engine valves. Furthermore, while the teachings of the '232 Publication are directed to dedicated rocker arms used for engine braking, the biasing solution described therein may also be applied to various types of rocker arms.

[0004] Although the system taught by the '232 publication functions satisfactorily, the presence of the spring bars reduces the amount of clearance within the engine valve cover, increases the cost of the engine, and increases the number of components and engine assembly steps required. A valve actuation system that provides the same benefits as the '232 publication, but does not require spring bars, would be a welcome addition to the art. Summary of the Invention

[0005] The present disclosure addresses the above-mentioned shortcomings and describes a rocker arm for transmitting valve actuation motion, the rocker arm including a motion-receiving portion configured to receive valve actuation motion from a valve actuation motion source and a motion-imparting portion configured to transmit the valve actuation motion to a valve train component or at least one engine valve. The rocker arm further includes a hydraulic actuator piston slidably disposed within the actuator bore. An actuator spring is configured to bias the hydraulic actuator piston out of the actuator bore and into contact with the valve train component or at least one engine valve, such that rebound of the hydraulic actuator piston against the valve train component or at least one engine valve biases the motion-receiving portion of the rocker arm into contact with the valve actuation motion source. A non-actuated state of the hydraulic actuator piston allows hydraulic fluid to flow out of the actuator bore, and a non-actuated state of the hydraulic actuator piston confines hydraulic fluid within the actuator bore.

[0006] In one embodiment, the actuator spring is configured to absorb valve actuation motion received from the valve actuation motion source during the unactuated state.

[0007] In one embodiment, the rocker arm is a center pivot rocker arm.

[0008] In one embodiment, the actuator bore is formed in the motion-imparting portion of the rocker arm.

[0009] In one embodiment, the at least one engine valve comprises at least one exhaust valve, and the source of valve actuation motion is an auxiliary source of valve actuation motion separate from the main source of valve actuation motion.

[0010] In another embodiment, the rocker arm further includes a control valve including a control valve piston slidably disposed within the 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 continuously receive hydraulic fluid from a hydraulic fluid source. Additionally, an exhaust port is provided in fluid communication with the first hydraulic passage and the control valve bore. In an inactivated state, the control valve piston is positioned within the control valve bore to allow hydraulic fluid to flow from the second hydraulic passage to the first hydraulic passage and the actuator bore, and from the first hydraulic passage through the exhaust port to the control valve bore. In an activated state, the control valve piston is positioned within the control valve bore to block the first hydraulic passage and the exhaust port, thereby confining hydraulic fluid within the first hydraulic passage and the actuator bore.

[0011] In one embodiment, the control valve bore is formed in the motion-imparting portion of the rocker arm.

[0012] In one embodiment, the rocker arm further includes a selectable hydraulic fluid passageway in fluid communication with the control valve bore and configured to receive hydraulic fluid from a selectable hydraulic fluid source. Also in this embodiment, the control valve piston has a piston bore formed therein, an annular channel formed in an outer diameter of the control valve piston, and a radial opening in fluid communication with the piston bore and the annular channel, the piston bore configured to receive hydraulic fluid from the selectable hydraulic fluid passageway through the control valve bore. Furthermore, the annular channel is configured to provide fluid communication between the first hydraulic passageway and the second hydraulic passageway during an unactuated state. A check element may be disposed within the control valve piston between the piston bore and the radial opening and configured to allow hydraulic fluid to flow from the piston bore to the annular channel via the radial opening, but not vice versa. [Brief explanation of the drawings]

[0013] The foregoing and other features and advantages are discussed in detail in the following non-limiting description of specific embodiments, taken in conjunction with the accompanying drawings. [Figure 1] FIG. 1 is a perspective view illustrating an example rocker arm according to the present disclosure. [Figure 2] 2 is a cross-sectional view illustrating additional features of the rocker arm of FIG. 1. [Figure 3] 2 is a cross-sectional view illustrating additional features of the rocker arm of FIG. 1. [Figure 4] 2 is a cross-sectional view illustrating additional features of the rocker arm of FIG. 1. [Figure 5] FIG. 10 is a perspective view of an alternative rocker arm according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0014] As used herein, phrases substantially similar to "at least one of A, B, or C" are intended to be construed disjunctively, i.e., requiring A or B or C, or any combination thereof, unless otherwise stated or implied by context. Further, phrases substantially similar to "at least one of A, B, and C" are intended to be conjunctively, i.e., requiring at least one of A, at least one of B, and at least one of C, unless otherwise stated or implied by context. Further, the term "substantially" or similar words requiring subjective comparison are intended to mean "within manufacturing tolerances," unless otherwise stated or implied by context.

[0015] As used herein, the phrase "operably connected" refers to at least a functional relationship between two elements and can encompass configurations in which two elements are directly connected to each other, i.e., without intervening elements, or indirectly connected to each other, i.e., connected with intervening elements.

[0016] Referring now to FIG. 1 , a rocker arm 100 according to the present disclosure is illustrated. In the illustrated example, the rocker arm 100 is a so-called dedicated rocker brake, although the present disclosure is not limited to such rocker arms. A dedicated rocker arm refers to a rocker arm provided to actuate only a single engine valve in a system having two or more actuated engine valves. For example, a given valve actuation system may include a main valve actuation motion source coupled to a valve train configured to provide main event engine valve motion received from the main valve actuation motion source to two or more engine valves. In such a system, a dedicated rocker arm may be provided that is separate from the valve train transmitting the main event engine valve motion and operably connected to an auxiliary valve actuation motion source and to only one of the two or more engine valves. As used herein, the term "primary" refers to engine valve movements used during positive power generation, which involves burning fuel within the engine cylinders to provide a net output of engine power, while the term "auxiliary" refers to other engine valve movements intended to replace or add to positive power generation (e.g., compression release braking, bleeder braking, cylinder decompression, cylinder deactivation, brake gas recirculation (BGR), etc.) (e.g., internal exhaust gas recirculation (IEGR), variable valve actuations (VVA), early exhaust valve opening (EEVO), late intake valve closing (LIVC), swirl control, etc.).

[0017] More generally, the teachings of the present disclosure are applicable to center pivot rocker arms, i.e., so-called Type III, Type IV, and Type V valve train types, as well as valve train types employing Type II (end pivot). Additionally, the rocker arm 100 described herein may be applicable to any type of engine valve, including exhaust and / or intake engine valves.

[0018] Rocker arm 100 includes a motion-receiving portion 102, a motion-imparting portion 104, and a rocker shaft bore 106 formed within a central body portion 107 of rocker arm 100. Additionally, although not illustrated in FIG. 1 , rocker arm 100 may be embodied as a center-pivot rocker arm with input and / or output levers forming a rocker arm that can be selectively coupled / uncoupled (locked / unlocked) relative to one another. In this configuration, one of the input or output levers may reciprocate about the rocker shaft and / or about an axis other than that defined by the rocker shaft. Additionally, the teachings of the present disclosure may also be applied to rocker arms other than center-pivot rocker arms, i.e., end-pivot rocker arms.

[0019] In any event, the motion-receiving portion 102, in the illustrated embodiment, includes a roller follower 108 mounted on a suitable roller shaft 110 and configured to contact a source of valve-actuating motion in the form of a cam on a camshaft (not shown). However, as is known in the art, the roller follower 108 may be replaced with a suitably configured contact surface or other component (e.g., a tappet) configured to contact the source of valve-actuating motion. In addition to the illustrated embodiment, the motion-imparting portion 104 includes 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 within the motion-imparting portion 104 and configured to selectively supply hydraulic fluid to the actuator boss 112 and the actuator piston 114, as described in further detail below. Although FIG. 1 illustrates the hydraulic actuator piston 114 and control valve 116 as being deployed within the motion-imparting portion 104 of the rocker arm 110, this is not required; i.e., the hydraulic actuator piston 114 and / or control valve 116 may equally be deployed within the motion-receiving portion 102 of the rocker arm 100.

[0020] Referring now to FIG. 2, a cross-sectional elevation view of the rocker arm 100 is illustrated. In particular, FIG. 2 illustrates additional details of the motion-imparting portion 104 of the rocker arm 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. The closed end of the actuator bore 202 is formed with a threaded opening 203, which allows a play adjustment screw 204 to pass therethrough, and the screw 204 can be adjusted to provide a desired play of the hydraulic actuator piston 114 relative to another valve train component, for example, a bridge pin (not shown) in a valve bridge. In accordance with known techniques, a play adjustment nut 206 is also provided to hold the play screw 204 in position once the desired play is set. Within the actuator bore 202, the play screw 204 has an actuator piston cap 210 slidably disposed thereon. In this embodiment, the cap 210 is configured to reside within a bore 208 formed in the hydraulic actuator piston 114 and is also secured to the end of the hydraulic actuator piston 114 by a suitable fastening mechanism, such as a snap ring 214. Movement of the actuator piston cap 210, and consequently movement of the hydraulic actuator piston 114 out of the actuator bore 202, is limited by a shoulder 216 formed on the distal end (relative to the play adjustment nut 206) of the play adjustment screw 204. Additionally, a biasing spring 212 is disposed within the actuator piston bore 208 in contact with the closed end of the actuator piston bore 208 and the shoulder 216 of the play adjustment screw 204.

[0021] The biasing spring 212 configured in this manner reacts against the shoulder 216 of the free play adjustment screw 204 and against the hydraulic actuator piston 114, thereby urging the hydraulic actuator piston 114 out of the actuator bore 202 and toward a downstream valve train component such as an engine valve (not shown) or bridge pin or valve bridge, thereby providing a reaction surface for the hydraulic actuator piston and rocker arm 100 to urge the rocker arm 100 in a direction toward the motion-receiving portion 102, i.e., urging 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 urging the rocker arm 100 into contact with a cam. Preferably, the spring constant of the biasing spring 212 is selected to be high enough to ensure that the inertia of the rocker arm 100 can be reliably controlled by the force applied by the biasing spring 212, but not so high that the force of the valve spring affects the ability to close the corresponding engine valve.

[0022] In addition to springing outward to urge rocker arm 100 into contact with the cam, hydraulic actuator piston 114 is hydraulically controlled to be in an actuated state (i.e., flexible and absorbing motion) or an actuated state (i.e., rigid and transmitting motion). To this end, as further shown in FIG. 2, a first hydraulic fluid passage 218 is provided that terminates in actuator bore 202 above actuator piston cap 210 to supply hydraulic fluid to actuator bore 202 and actuator piston cap 210. As will be described in more detail below with respect to FIGS. 3 and 4, hydraulic fluid is supplied to the first hydraulic fluid passage and may be selectively checked or unchecked through operation of control valve 116. When hydraulic fluid in 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 motion applied to the rocker arm is absorbed or lost by the biasing spring 212, whereas when hydraulic fluid in 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 trapped volume of hydraulic fluid is established within the actuator bore 202, preventing reciprocating motion of the hydraulic actuator piston 114 within the actuator bore 202. A further explanation of the operation of the control valve 116 is provided further below with reference to Figures 3 and 4.

[0023] 3 and 4 illustrate a top cross-sectional view of the rocker arm 100, illustrating the control valve 116 and associated hydraulic passages in more detail. The control valve 116 includes 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. While the control valve bore 304 is illustrated as being substantially transverse to the direction of reciprocating motion of the rocker arm 100, this is not required. A piston spring 306 is deployed within a bore 309 formed in a control valve limit spacer 308, which is in turn disposed within the control valve bore 304. A snap ring or C-clip 310 is attached to the open end of the control piston bore 304 to retain the control valve limit spacer 308, piston spring 306, and control valve piston 302 within the control piston bore 304. A piston spring 306 contacts the control valve piston 302 and biases the control valve piston 302 into the control valve bore 304 against a control valve restrictor spacer 308 and a snap ring 310 .

[0024] A check element (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 check seat 316 by a check spring 313. The piston bore 314 has a radial opening 318 formed in a sidewall of the control valve piston 302, which provides fluid communication between the piston bore 314 and an annular channel 320 formed in the 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, which allows hydraulic fluid, when provided by the selectable hydraulic fluid supply passage 322, to impinge on the control valve piston 302 and check seat 316 and further flow into the piston bore 314 (when displaced) past the check element 312. In one embodiment, 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 developed in the rocker shaft (not shown). Such hydraulic fluid supply passage is in turn in fluid communication with a suitable solenoid (not shown), which 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 developed in the rocker shaft.

[0025] 3 and 4, as described above, the first hydraulic fluid passage 218 intersects with the actuator bore 202. 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 is aligned with the annular channel 320 of the control valve piston 302 when the control valve piston 302 is fully biased into the control valve bore 304 by the piston spring 306, as shown in FIG. 3. Exhaust ports 324 are also provided at each end thereof in fluid communication with the first hydraulic fluid passage 218 and the control valve bore 304. The exhaust port 324 intersects with the control valve bore 304 so that when the exhaust 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 FIGURE 3, any fluid in the first hydraulic fluid passage 218 and the actuator bore 202 may be exhausted from the rocker arm 100. To this end, as shown in FIGURE 3, the longitudinal length of the control valve piston 302 is selected so that the exhaust port 324 is unblocked when the control valve piston 302 is in its unactuated state.

[0026] In the illustrated embodiment, the rocker arm 100 further includes a second hydraulic fluid passage 326 that receives a constant fluid supply via the rocker shaft. 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 when the control valve piston 302 is fully biased into the control valve bore 304 by the piston spring 306, as shown in FIG. 3 , the second hydraulic fluid passage 326 is also aligned with the annular channel 320 of the control valve piston 302.

[0027] 3, both the first hydraulic fluid passage 218 and the second hydraulic fluid passage 326 are aligned with the annular channel 320. This positioning of the control valve piston 302 occurs 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 is maintained in this position to prevent the hydraulic actuator piston 114 from rigidly extending out of the actuator bore 202, thereby losing any valving motion (e.g., engine brake valve actuation) applied to the rocker arm 100.

[0028] 3, the constant supply 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. At least a portion of the constant supply hydraulic fluid is then permitted to flow into the actuator bore 202. Provided that the control valve piston 320 does not block the exhaust port 324, any constant supply hydraulic fluid in excess of the amount required to fill the actuator bore 202 is exhausted from the first hydraulic fluid passage 218 via the exhaust port 324.

[0029] Without any movement of the hydraulic actuator piston 114 into the actuator bore 202, hydraulic fluid supplied by the constant supply remains within the actuator bore 202, thereby keeping the actuator bore 202 constantly filled. However, any valve actuation motion applied to the rocker arm 100 that causes the hydraulic actuator piston 114 to recoil against a valve train component or engine valve will cause the hydraulic actuator piston 114 to overcome the bias applied by the biasing 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 is known in the art, this essentially results in such valve actuation motion being absorbed by the hydraulic actuator piston 114 and biasing spring 212, i.e., the valve actuation motion being "lost." Because the exhaust port 324 remains unblocked, all hydraulic fluid within the actuator bore 202 is forced into the first hydraulic fluid passage 324 and then exhausted out of the rocker arm 100 through the exhaust port 324. When the rocker arm 100 rotates away from the engine valve, the biasing spring 212 again extends the hydraulic actuator piston 114 out of the actuator bore 202, thereby allowing the constant supply of hydraulic fluid to once again return into the actuator bore 202. This process of continuously charging and discharging hydraulic fluid to the actuator bore 202 reduces the time required to actuate the hydraulic actuator piston 114 to interrupt its lost motion, an example of which is illustrated with reference to FIG.

[0030] 4 illustrates a condition in which hydraulic fluid is supplied through the selectable hydraulic fluid supply passage 322. In this case, the pressure applied by the hydraulic fluid to the control valve piston 302 and check seat 316 overcomes the bias applied by the piston spring 306, thereby translating the control valve piston 302 downward into the control valve bore 304 (as illustrated in FIG. 4 ) until a lower shoulder 402 formed in the control valve piston 302 abuts an upper shoulder 404 established by the control valve restrictor 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, thereby preventing the flow of a constant supply of 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 through the exhaust port 324. However, in this case, hydraulic fluid provided by the selectable hydraulic fluid supply passage 322 overcomes the bias applied to the check ball 312, thereby allowing hydraulic fluid to flow through the radial openings 318, into the annular channel 320 and into the first hydraulic fluid passage 216. This hydraulic fluid flow continues until the actuator bore 202 is completely filled, thereby causing pressure to equalize on both sides of the check ball 312 and further re-seating the check ball 312, trapping a trapped volume of hydraulic fluid within the first hydraulic fluid passage 216 and the actuator bore 202. In this way, the hydraulic actuator piston 114 is hydraulically trapped in its extended position outside the actuator bore 202 so that valve actuation motion applied to the rocker arm 100 is transmitted to the engine valve, i.e., the motion is no longer lost. The hydraulic actuator piston 114 remains in this state until such time as hydraulic fluid from the selectable hydraulic fluid supply passage 322 is interrupted, thereby allowing the piston spring 306 to urge the control valve piston 302 back into the control valve bore 304 to once again assume the position shown in FIG. 3 and allowing the trapped volume of hydraulic fluid to be exhausted through the exhaust port 324.

[0031] As noted above, the teachings of the present application are applicable to various types of valve trains. For example, while the embodiment of Figures 1-4 illustrates a rocker arm configured as a dedicated rocker brake, the teachings of the present application are equally applicable to a so-called integrated rocker brake 500, as shown in Figure 5. Like the embodiment of Figures 1-4, the integrated rocker brake 500 includes a hydraulic actuator piston 502 and control valve 504, as well as various hydraulic passages and exhaust ports, substantially similar to those described above.

[0032] While various embodiments according to the present disclosure have been described in conjunction with specific implementations thereof, it is apparent 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 with a primary rocker arm that provides a main event valve actuation motion to a valve bridge, as is known in the art, it is recognized that there may be instances where such main event valve actuation motion causes the valve bridge to move away from the dedicated rocker brake 110. This, in turn, may cause the dedicated rocker brake 100 to "drop" toward the valve bridge under the force of gravity. Therefore, it is advantageous to configure the center of gravity of the rocker arm 100 relative to the rocker shaft, thereby balancing the dedicated rocker brake 100, so that the rocker arm 100 is not prone to uncontrollable rotation when the valve bridge moves away from the rocker arm 100.

[0033] Furthermore, it is recognized that variations in the configuration of the exhaust port 324 are possible, so long as the first hydraulic fluid passageway 218, actuator bore 220, and exhaust port 304 of the illustrated embodiment are in hydraulic communication with one another under all circumstances. For example, rather than terminating the exhaust port 324 at the first hydraulic fluid passageway 218, it may be functionally equivalent to instead terminate the exhaust port 324 at the actuator bore 220.

[0034] It is additionally recognized that the control valve 116 need not be implemented in the rocker arm 100, but instead could be implemented further upstream in the selectable hydraulic circuit supplying the rocker arm 100, for example, in the rocker shaft or rocker shaft pedestal, as known in the art. Furthermore, rather than using the control valve described herein (whether in the rocker arm or upstream thereof), which combines the functions of hydraulic filling, checking, and draining the actuator bore, it is contemplated to employ a check valve and a separate vent or reset mechanism in fluid communication with the hydraulic passageway supplying the actuator bore. In this case, whenever actuator piston activation is desired, fluid is provided past the check valve while the drain mechanism is maintained in a closed / non-draining state. When resumption of actuator piston deactivation is desired, the vent mechanism can be opened / positioned in a vented state to allow the actuator piston bore to drain again.

[0035] As described above, providing a second hydraulic passageway and a constant hydraulic fluid supply to the control valve bore and the first hydraulic passageway provides the benefit of keeping the actuator piston bore filled at all times, thereby allowing switchover to an actuated state to occur quickly. However, it is recognized that this is not required, and that it may be sufficient if the second hydraulic passageway and constant hydraulic fluid supply are not provided in communication with the control valve bore. In this case, according to known techniques, only a selectable fluid source may be used to fill the actuator bore via the piston bore / radial opening / annular channel / first hydraulic fluid passageway prior to establishing a fluid containment volume. In this case, the control valve piston may be configured to bleed from the first hydraulic fluid passageway and the actuator piston bore (i.e., the first hydraulic passageway is not blocked by the control valve piston) when the actuator piston is in its unactuated state.

[0036] Accordingly, the preferred embodiments of the invention described herein are intended to be illustrative only, and not limiting, provided that variations thereof come within the scope of the appended claims and their equivalents.

Claims

1. 1. A rocker arm for transmitting valve actuation motion, the rocker arm comprising: a motion-receiving portion configured to receive the valve actuation motion from a valve actuation motion source; and a motion-imparting portion configured to transmit the valve actuation motion to a valve train component or at least one engine valve, the rocker arm comprising: a hydraulic actuator piston slidably disposed within the actuator bore; an actuator spring configured to bias the hydraulic actuator piston out of the actuator bore and into contact with the valve train component or the at least one engine valve, wherein rebound 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; a hydraulic actuator piston in an unactuated state allows hydraulic fluid to flow out of the actuator bore, and a hydraulic actuator piston in an actuated state confines hydraulic fluid within the actuator bore.

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

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 said actuator bore is formed in said motion-imparting portion of said rocker arm.

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

6. a control valve including a control valve piston slidably disposed within the 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 continuously receive hydraulic fluid from a hydraulic fluid supply; a drain port in fluid communication with the first hydraulic passage and the control valve bore; in the unactuated condition, the control valve piston is positioned within the control valve bore to allow hydraulic fluid to flow from the second hydraulic passage to the first hydraulic passage and to the actuator bore, and from the first hydraulic passage through the exhaust port to the control valve bore; 2. The rocker arm of claim 1, wherein in the actuated condition, the control valve piston is positioned within the control valve bore to block the first hydraulic passage and the exhaust port, thereby trapping hydraulic fluid within the first hydraulic passage and the actuator bore.

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

8. 7. 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 source.

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

11. 10. The rocker arm of claim 9, further comprising a check element disposed within the control valve piston between the piston bore and the radial opening, the check element configured to allow hydraulic fluid to flow from the piston bore to the annular channel through the radial opening, but not vice versa.

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