Rocker arm with outwardly bounced hydraulic actuator piston

Abstract

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

Technical Field

[0001] The present disclosure relates to rocker arms used in internal combustion engines, and in particular to rocker arms with outwardly sprung hydraulic actuator pistons. Background Art

[0002] Internal combustion engines typically use 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 referred to as valve trains), which may be driven by 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 the cam lobes on the camshaft. In order to reduce impact damage to the cam and any valve train components and minimize any unnecessary noise or vibration, it is generally desirable to maintain contact between the cam and any valve train components that are configured to contact the cam.

[0003] One common design for maintaining continuous contact between a cam and a rocker arm consists of a spring rod or other fixed structure and a spring that reacts against the spring rod or fixed structure to bias 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 disposed between the cam-side surface of the rocker arm and the spring rod (which acts as a fixed surface relative to the reciprocating motion 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 can be applied to other valve train types (i.e., Type IV or Type V) in which a center-pivot rocker arm transmits valve actuation motion to the engine valve. Furthermore, although the teachings of the '232 Publication relate to a dedicated rocker arm for engine braking, the biasing solution described therein can be applied to various types of rocker arms.

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

[0005] The present disclosure addresses the aforementioned shortcomings and describes a rocker arm for delivering valve actuation motion, the rocker arm comprising a motion receiving portion configured to receive valve actuation motion from a valve actuation motion source, and a motion applying portion configured to deliver the valve actuation motion to a valvetrain component or at least one engine valve. The rocker arm also includes a hydraulic actuator piston slidably disposed within an actuator bore. An actuator spring is configured to bias the hydraulic actuator piston out of the actuator bore and into contact with the valvetrain component or at least one engine valve, wherein a reaction of the hydraulic actuator piston to the valvetrain component or 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 within the actuator bore.

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

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

[0008] In one embodiment, the actuator aperture is formed in the motion applying portion of the rocker arm.

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

[0010] In another embodiment, the rocker arm further comprises a control valve comprising a control valve piston slidably disposed in a control valve bore. A first hydraulic fluid channel is in fluid communication with the control valve bore and the actuator bore, and a second hydraulic channel is in fluid communication with the control valve bore and is configured to receive hydraulic fluid from a constant hydraulic fluid supply source. In addition, a drain port is provided in fluid communication with the first hydraulic channel and the control valve bore. In an unactuated state, the control valve piston is located within the control valve bore to allow hydraulic fluid to flow from the second hydraulic channel to the first hydraulic channel and the actuator bore, and to allow hydraulic fluid to flow from the first hydraulic channel through the drain port to the control valve bore. In an actuated state, the control valve piston is located within the control valve bore to block the first hydraulic channel and the drain port, thereby locking the hydraulic fluid in the first hydraulic channel and the actuator bore.

[0011] In one embodiment, the control valve hole is formed in the motion applying portion of the rocker arm.

[0012] In one embodiment, the rocker arm further comprises an optional hydraulic fluid passageway in fluid communication with the control valve bore and configured to receive hydraulic fluid from an optional hydraulic fluid supply source. Further to this embodiment, the control valve piston comprises 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, wherein the piston bore is configured to receive hydraulic fluid from the optional hydraulic fluid passageway via the control valve bore. Furthermore, the annular channel is configured to provide fluid communication between the first hydraulic channel and the second hydraulic channel during an unactuated state. A check element may be disposed in the control valve piston between the piston bore and the radial opening and configured to allow 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

[0013] The foregoing and other features and advantages will be discussed in detail in the following non-limiting description of specific embodiments in conjunction with the accompanying drawings, in which:

[0014] Figure 1 is a perspective view showing an example of a rocker arm according to the present disclosure;

[0015] Figures 2 to 4 It shows Figure 1 A cross-sectional view of the additional technical features of the rocker arm; and

[0016] Figure 5 is a perspective view of an alternative example of a rocker arm according to the present disclosure. DETAILED DESCRIPTION

[0017] As used herein, phrases substantially similar to "at least one of A, B, or C" are intended to be interpreted disjunctively, i.e., requiring A or B or C, or any combination thereof, unless the context indicates or implies otherwise. Additionally, phrases substantially similar to "at least one of A, B, and C" are intended to be interpreted conjunctionally, i.e., requiring at least one of A, at least one of B, and at least one of C, unless the context indicates or implies otherwise. Furthermore, the term "substantially" or similar words requiring a subjective comparison are intended to mean "within manufacturing tolerances," unless the context indicates or implies otherwise.

[0018] As used herein, the phrase "operably connected" refers to at least a functional relationship between two elements and may encompass configurations where two elements are directly connected to each other (ie, without any intervening elements) or indirectly connected to each other (ie, with intervening elements).

[0019] Now see Figure 1, a rocker arm 100 according to the present disclosure is shown. In the illustrated example, the rocker arm 100 is a so-called dedicated rocker arm actuator, but the present disclosure is not limited to such rocker arms. A dedicated rocker arm refers to a rocker arm that is arranged to actuate only a single engine valve in a system that includes more than one type of engine valve to be actuated. For example, a given valve actuation system may include a primary valve actuation motion source coupled to a valve train that is configured to provide main event engine valve motion received from the primary valve actuation motion source to two or more engine valves. In such a system, in addition to the valve train that delivers the main event engine valve motion, a dedicated rocker arm may be provided that is operatively connected to an auxiliary valve actuation motion source and is connected to only one engine valve of the two or more engine valves. As used herein, the descriptor "primary" refers to engine valve movement used during positive power generation, during which fuel is burned in the engine cylinders to provide a net output of engine power; and the descriptor "auxiliary" refers to other engine valve movement for the purpose of achieving an alternative to positive power generation (e.g., compression-release braking, blowdown 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 actuation (VVA), early exhaust valve opening (EEVO), late intake valve closing (LIVC), swirl control, etc.).

[0020] More generally, the teachings of the present disclosure are applicable to valvetrain types that utilize center-pivoting rocker arms, namely, the so-called Type III, Type IV, and Type V valvetrain 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 valves and / or intake engine valves.

[0021] The rocker arm 100 includes a motion receiving portion 102, a motion applying portion 104, and a rocker arm shaft hole 106 formed in a central body portion 107 of the rocker arm 100. Figure 1 Although not shown, rocker arm 100 may be embodied as a center-pivot rocker arm including an input rod and / or an output rod forming the rocker arm, which can be selectively coupled / decoupled (or locked / unlocked) to one another. In this configuration, one of the input rod or the output rod can reciprocate about the rocker arm shaft, but still reciprocate about an axis different from the axis defined by the rocker arm shaft. Furthermore, 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.

[0022] In any event, in the illustrated embodiment, the motion receiving portion 102 includes a roller follower 108 mounted on a suitable roller shaft 110 and configured to contact a valve actuating motion source 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 by a suitably constructed contact surface or other component (e.g., a tappet) configured to contact the valve actuating motion source. Further to the illustrated embodiment, the motion applying portion 104 has an actuator protrusion 112 formed therein and has a hole (actuator hole 202) in which a hydraulic actuator piston 114 is disposed. Additionally, in this exemplary embodiment, a control valve 116 is disposed in the motion applying portion 104 and is configured to selectively supply hydraulic fluid to the actuator protrusion 112 and the actuator piston 114, as described in further detail below. Although the hydraulic actuator piston 114 and the control valve 116 are Figure 1 104 of the rocker arm 100 , but this is not a requirement, ie, the hydraulic actuator piston 114 and / or the control valve 116 may likewise be deployed on the motion receiving portion 102 of the rocker arm 110 .

[0023] Now see Figure 2 , shows a front cross-sectional view of the rocker arm 100. In particular, Figure 2 Additional details of the motion-applying portion 104 of the rocker arm 100 are shown. 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 to allow passage of a lash adjustment screw 204, which can be adjusted to provide a desired lash for the hydraulic actuator piston 114 relative to another valve train component, such as a bridge pin in a valve bridge (not shown). A lash adjustment nut 206 is also provided, in accordance with known techniques, to hold the lash screw 204 in place once the desired lash is set. Within the actuator bore 202, the lash screw 204 has an actuator piston cap 210 slidably disposed thereon. In this embodiment, a cap 210 is configured to reside within a bore 208 formed in the hydraulic actuator piston 114 and is also attached to the end of the hydraulic actuator piston 114 by a suitable fastening mechanism, such as a snap ring 214. The travel of the actuator piston cap 210, and therefore 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 lash adjustment nut 206) of the lash adjustment screw 204. Additionally, a biasing spring 212 is disposed within the actuator piston bore 208, contacting the closed end of the actuator piston bore 208 and the shoulder 216 of the lash adjustment screw 204.

[0024] 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 an engine valve (not shown) or downstream valvetrain components (such as a bridge pin or valve bridge). This provides a reaction surface for the hydraulic actuator piston and rocker arm 100 to bias the rocker arm 100 toward the motion receiving portion 102, i.e., toward the camshaft (not shown). This eliminates the need for an external spring and spring rod as taught in the '232 publication, while still biasing the rocker arm 100 into contact with the cam. Preferably, the spring constant of the bias spring 212 is selected to be sufficiently high to ensure that the inertia of the rocker arm 100 can be reliably controlled by the force applied by the bias spring 212, but not so high as to affect the ability of the corresponding engine valve to close under the force of its valve spring.

[0025] In addition to springing outward to bias the rocker arm 100 into contact with the cam, the hydraulic actuator piston 114 is hydraulically controlled to assume either an unactuated (i.e., compliant and motion absorbing) or an actuated (i.e., stiff and motion conveying) state. To this end, and as Figure 2 As further shown, a first hydraulic fluid passage 218 is provided above the actuator piston cap 210 terminating at the actuator bore 202 for supplying hydraulic fluid to the actuator bore 202 and the actuator piston cap 210. Figure 3 and Figure 4 Described in more detail, hydraulic fluid can be supplied to the first hydraulic fluid channel and selectively checked or not checked by operation of the control valve 116. When the hydraulic fluid within the first hydraulic fluid channel 218 and the actuator bore 202 is not checked by the control valve 116, that is, 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, so that the valve actuating motion applied to the rocker arm is absorbed or lost by the bias spring 212, and when the hydraulic fluid within the first hydraulic fluid channel 218 and the actuator bore 202 is checked by the control valve 116, that is, when the hydraulic actuator piston 114 is in its actuated state, a lock volume of hydraulic fluid is formed in the actuator bore 202, and the lock volume of hydraulic fluid prevents the hydraulic actuator piston 114 from reciprocating within the actuator bore 202. Figure 3 and Figure 4 A further description of the operation of the control valve 116 is further described.

[0026] Figure 3 and Figure 4A top cross-sectional view of the rocker arm 100 is shown, showing the control valve 116 and associated hydraulic passages in greater detail. The control valve 116 includes a control valve piston 302 slidably disposed within a control valve bore 304 formed in the motion-applying portion 104 of the rocker arm 100. Although the control valve bore 304 is shown as being substantially transverse to the direction of reciprocating motion of the rocker arm 100, this is not a requirement. A piston spring 306 is disposed within a bore 309 formed in a control valve restrictor spacer 308, which in turn is disposed within the control valve bore 304. A snap ring or C-clip 310 is mounted at the open end of the control piston bore 304 to retain the control valve restrictor spacer 308, piston spring 306, and control valve piston 302 within the control piston bore 304. The piston spring 306 contacts the control valve piston 302 and reacts against the control valve limit spacer 308 and the snap ring 310 to bias the control valve piston 302 into the control valve bore 304 .

[0027] 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 that 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 an optional hydraulic fluid supply passage 322 so that hydraulic fluid, when provided by the optional hydraulic fluid supply passage 322, can impinge on the control valve piston 302 and the check seat 316 and also flow into the piston bore 314 and past the check element 312 (when displaced). In one embodiment, and in accordance with known techniques, an optional hydraulic fluid supply passage 322 terminates at the junction of the rocker arm 100 and the rocker shaft bore 106 and is in fluid communication with a hydraulic fluid supply passage disposed in the rocker shaft (not shown). Such a hydraulic fluid supply passage, in turn, is in fluid communication with a suitable solenoid (not shown), which can be controlled using known techniques to selectively supply hydraulic fluid to the optional hydraulic fluid supply passage 322 via the hydraulic fluid supply passage disposed in the rocker shaft.

[0028] like Figure 3 and Figure 4 As further shown, the first hydraulic fluid passage 218 intersects the actuator bore 202, as described above. The first hydraulic fluid passage 218 is also in fluid communication with the control valve bore 304, such that when the actuator bore 202 is in fluid communication with the control valve bore 304, the first hydraulic fluid passage 218 is in fluid communication with the control valve bore 304. Figure 3When the control valve piston 302 is shown fully biased into the control valve bore 304 by the piston spring 306, the first hydraulic fluid passage 218 is aligned with the annular passage 320 of the control valve piston 302. A drain port 324 is also provided at its corresponding end in fluid communication with the first hydraulic fluid passage 218 and the control valve bore 304. The drain port 324 intersects the control valve bore 304 so that when the drain port 324 is not blocked by the control valve piston 302, that is, when the control valve piston 302 is biased into the control valve bore 304 by the piston spring 306, any fluid in the first hydraulic fluid passage 218 and the actuator bore 202 can be drained from the rocker arm 100, as shown. Figure 3 To this end, the longitudinal length of the control valve piston 302 is selected so that when the control valve piston 302 is in its unactuated state, the exhaust port 324 is not blocked, as shown in FIG. Figure 3 shown.

[0029] In the illustrated embodiment, the rocker arm 100 also includes a second hydraulic fluid passage 326 that receives a constant supply of fluid via the rocker arm shaft. Again, techniques for providing a constant supply of hydraulic fluid via the rocker arm 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 so that when Figure 3 The second hydraulic fluid passage 326 is also aligned with the annular passage 320 of the control valve piston 302 when the control valve piston 302 is shown fully biased into the control valve bore 304 by the piston spring 306 .

[0030] like Figure 3 As shown, both the first hydraulic fluid passage 218 and the second hydraulic fluid passage 326 are aligned with the annular passage 320. This positioning of the control valve piston 302 occurs when the optional hydraulic fluid supply passage 322 is substantially deprived of hydraulic fluid. For example, in the illustrated example where the rocker arm 100 is provided in the form of a dedicated engine braking rocker arm, the control valve piston 302 will remain in this position so that the hydraulic actuator piston 114 is not allowed to rigidly extend out of the actuator bore 202, thereby losing valve actuation motion (e.g., engine braking valve actuation) applied to the rocker arm 100.

[0031] In any case, due to Figure 3 With the control valve piston 302 shown retained, the constant supply of hydraulic fluid received by the second hydraulic fluid passage 326 is permitted to flow through the annular passage 320 and into the first hydraulic fluid passage 218. In turn, at least some of the constant supply of hydraulic fluid is also able to flow into the actuator bore 202. Assuming the control valve piston 320 is not blocking the drain port 324, any constant supply of hydraulic fluid in excess of that required to fill the actuator bore 202 will be exhausted from the first hydraulic fluid passage 218 via the drain port 324.

[0032] Without 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 constant state of fill. However, any valve actuation motion applied to the rocker arm 100 that causes the hydraulic actuator piston 114 to react against a valvetrain component or 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 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 the bias spring 212—i.e., it is "lost." Because the drain port 324 remains unobstructed, any hydraulic fluid in the actuator bore 202 will be forced into the first hydraulic fluid passage 324 and thereafter exhausted from the rocker arm 100 via the drain port 324. As the rocker arm 100 rotates away from the engine valve, the biasing spring 212 will again extend the hydraulic actuator piston 114 out of the actuator bore 202, thereby again allowing a constant supply of hydraulic fluid to flow back into the actuator bore 202. This process of continuously filling and draining the actuator bore 202 with hydraulic fluid reduces the amount of time required to activate the hydraulic actuator piston 114 in order to interrupt the lost motion operation of the hydraulic actuator piston 114, an example of which is shown in FIG. Figure 4 Shown.

[0033] Figure 4 3 shows a state where hydraulic fluid has been supplied via the optional hydraulic fluid supply passage 322. In this case, the pressure applied by the hydraulic fluid to the control valve piston 302 and the check seat 316 overcomes the bias applied by the piston spring 306, thereby translating the control valve piston 302 downward (as shown in FIG. Figure 4324 ). However, in this case, the hydraulic fluid supplied by the optional hydraulic fluid supply passage 322 will overcome the bias applied to the check ball 312, thereby allowing hydraulic fluid to flow through the radial opening 318 and into the annular passage 320 and the first hydraulic fluid passage 216. This flow of hydraulic fluid will continue until the actuator bore 202 is completely filled, causing the pressure on either side of the check ball 312 to equalize, 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 the actuator bore 202. In this way, the hydraulic actuator piston 114 will be hydraulically locked in its extended position away from the actuator bore 202 so that the valve actuation motion applied to the rocker arm 100 will be delivered to the engine valve, that is, they are no longer lost. The hydraulic actuator piston 114 will remain in this state until the hydraulic fluid from the optional hydraulic fluid supply passage 322 is interrupted, 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 present as Figure 3 position as shown and allowing the trapped volume of hydraulic fluid to be discharged through the discharge port 324.

[0034] As mentioned above, the teachings of this application are applicable to various types of valve trains. For example, although Figures 1 to 4 The embodiment of FIG. 1 shows a rocker arm configured to function as a dedicated rocker arm brake, but the teachings of the present application can also be applied to a rocker arm brake as shown in FIG. Figure 5 The so-called integrated rocker brake 500 is shown. Figures 1 to 4 In the embodiment of FIG. 5 , the integrated rocker arm brake 500 includes a hydraulic actuator piston 502 and a control valve 504 , as well as various hydraulic passages and exhaust ports, substantially similar to those described above.

[0035] Although various embodiments according to the present disclosure have been described in conjunction with specific implementations of the present disclosure, it is apparent that many alternatives, modifications and variations will be apparent to those skilled in the art. Figures 1 to 4To the extent that the dedicated rocker arm actuator 100 is used in conjunction with a primary rocker arm operation that provides the main event valve actuation motion to the valve bridge, as is known in the art, it will be appreciated that there may be circumstances where such main event valve actuation motion will cause the valve bridge to move away from the dedicated rocker arm actuator 110. This, in turn, may cause the dedicated rocker arm actuator 100 to "fall" toward the valve bridge under the action of gravity. Therefore, it would be advantageous to configure the dedicated rocker arm actuator 100 to be balanced, such that the center of gravity of the rocker arm 100 is positioned relative to the rocker arm shaft so that the rocker arm 100 is less susceptible to uncontrolled rotation when the valve bridge moves away from the moving rocker arm 100.

[0036] Furthermore, to the extent that the first hydraulic fluid passage 218, the actuator bore 220, and the exhaust port 304 are in hydraulic communication with one another in all instances in the illustrated embodiment, it should be understood that variations are possible in the configuration of the exhaust port 324. For example, rather than terminating the exhaust port 324 at the first hydraulic fluid passage 218, it could be functionally equivalent to terminating the exhaust port 324 at the actuator bore 220.

[0037] It should also be understood that the control valve 116 need not be implemented in the rocker arm 100, but rather can be implemented further upstream in an alternative hydraulic circuit supplying the rocker arm 100, such as within a rocker shaft or rocker shaft base as is known in the art. Furthermore, rather than utilizing a control valve as described herein (whether in the rocker arm or upstream thereof), which combines the hydraulic filling, checking, and venting functions of the actuator bore, it is contemplated 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, whenever an actuated state of the actuator piston is desired, fluid is supplied through the check valve while the venting mechanism remains in a closed / non-venting state. When it is desired to restore the actuator piston to its unactuated state, the venting mechanism can be opened / placed in the venting state, thereby once again allowing the actuator piston bore to vent.

[0038] As described above, providing a second hydraulic channel and a constant supply of hydraulic fluid to the control valve bore and the first hydraulic channel provides the benefit of being able to keep the actuator piston bore filled at all times, so that switching to the actuated state can occur quickly. However, it will be understood that this is not a requirement, and that it may be sufficient if the second hydraulic channel and the constant supply of hydraulic fluid are not provided in communication with the control valve bore. In this case, and in accordance with known techniques, only the selectable fluid supply source may be used to fill the actuator bore via the piston bore / radial opening / annular channel / first hydraulic fluid channel before the lock volume of fluid is formed. In this case, the control valve piston may be configured such that when the actuator piston is in its unactuated state, it causes the first hydraulic fluid channel and the actuator piston bore to drain (i.e., the first hydraulic channel is not blocked by the control valve piston).

[0039] Therefore, the preferred embodiments of the present invention described herein are intended to be illustrative only and not restrictive, provided that variations come within the scope of the appended claims and their equivalents.

Claims

1. A rocker arm for delivering valve actuation motion, the rocker arm comprising a motion receiving portion and a motion applying portion, the motion receiving portion being configured to receive the valve actuation motion from a valve actuation motion source, the motion applying portion being configured to deliver the valve actuation motion to a valve train component or at least one engine valve, the rocker arm further comprising: a hydraulic actuator piston slidably disposed in the actuator bore; and an actuator spring configured to bias the hydraulic actuator piston out of an 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 allowed 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 motion received from the valve actuation motion 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 hole is formed in the motion applying 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 primary valve actuation motion source.

6. The rocker arm according to claim 1 , further comprising: a control valve, the control valve comprising a control valve piston slidably disposed in a control valve hole; 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 drain port in fluid communication with the first hydraulic passage and the control valve hole, wherein in the unactuated state, the control valve piston is located 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 to allow hydraulic fluid to flow from the first hydraulic passage through the exhaust port to the control valve bore, And wherein in the actuated state, the control valve piston is located in the control valve bore to block the first hydraulic passage and the exhaust port, thereby locking the hydraulic fluid in the first hydraulic passage and the actuator bore. 7 . The rocker arm of claim 6 , wherein the control valve hole is formed in the motion applying portion of the rocker arm.

8. The rocker arm according to claim 6, further comprising: A selectable hydraulic fluid passage is in fluid communication with the control valve bore and is configured to receive hydraulic fluid from a selectable hydraulic fluid supply source.

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 passage is configured to provide fluid communication between the first hydraulic passage and the second hydraulic passage during the unactuated state.

11. The rocker arm according to claim 9, further comprising: A non-return element is provided in the control valve piston between the piston bore and the radial opening and is configured to allow flow of hydraulic fluid from the piston bore to the annular channel via the radial opening, but not vice versa.

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