Rocker arm having a reset slider disposed in a lash adjustment assembly

Abstract

The rocker arm includes an actuator piston slidably disposed within an actuator piston bore formed in the motion-imparting end of the rocker arm. The lash adjustment assembly is disposed at the motion-imparting end and includes an internal bore. A hydraulic passage is in fluid communication with the actuator piston bore and the internal bore. The reset assembly is disposed within the lash adjustment assembly and includes a reset slider and a check element in fluid communication with the internal bore. The reset slider is slidably disposed within the internal bore and has a first end configured to engage a valve train component or an engine valve and a second end including a reset pin disposed thereon, the second end configured to contact the check element in response to positioning of the rocker arm when the first end contacts the valve train component or the engine valve, thereby placing the check element in an unchecked state.

Description

[Technical Field]

[0001] The present disclosure relates generally to rocker arms for use in internal combustion engines, and more particularly to rocker arms including a reset slider disposed within a lash adjustment assembly. [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, push rods, valve bridges, etc. (each a valvetrain component, and collectively the valvetrain) that may be driven by rotation of the engine's crankshaft. When a camshaft is used to actuate the engine valves, i.e., acts as the source of valve actuation motion, the timing of the valve actuation motion may be fixed by the size and position of the lobes on the camshaft.

[0003] As known in the art, valve actuation may include so-called primary and / or auxiliary valve actuation. As used herein, the description "primary" refers to valve actuation used during positive power generation when fuel is combusted in the engine cylinder to provide net engine power, while the description "auxiliary" refers to other engine valve actuation intended to replace or in addition to the 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.).

[0004] Engine braking has traditionally been implemented using a dedicated brake rocker arm to transmit auxiliary valve actuation motion (e.g., compression-relief valve actuation) for any given cylinder that is separate from the exhaust rocker arm used to transmit the main exhaust valve actuation to the exhaust engine valve. More recent developments include so-called integrated rocker brakes (IRBs), in which dedicated brake and exhaust rocker arms are combined into one rocker arm to reduce costs and provide more compact valve train hardware.

[0005] As known in the art, and referring to FIG. 1 , an IRB 100 typically includes a rocker arm nose or motion-imparting end configured to transfer main event valve actuation motion to a pair of engine valves 104 via a valve bridge 102, and a selectable actuator 106 configured to transfer auxiliary (e.g., engine braking) valve actuation motion to only one of the engine valves 104 b via a bridge pin 108 in the valve bridge 102. A single valve actuation motion source 110, e.g., a cam, is provided that includes lobes for both main event valve actuation and engine braking valve actuation (or other auxiliary valve actuation). An example of such a cam is shown in FIG. 2, which shows a cam 240 with a main valve actuation cam lobe 242 and, in the illustrated example, two auxiliary valve actuation cam lobes 244 a, 244 b.

[0006] As is known in the art, and referring again to FIG. 1 , the IRB 100 is typically maintained in contact with the valve actuation motion source 110 such that all valve actuation motion (both primary and auxiliary) provided by the valve actuation motion source 110 is received by the rocker arm 100. As further shown in FIG. 1 , control of the actuator 106 in a typical IRB configuration is provided by a selectable hydraulic fluid supply 112 that operates to provide hydraulic fluid to a control valve 114 (or, in an alternative embodiment, via a check valve). In the absence of hydraulic fluid supplied to the control valve 114, the actuator piston of the actuator 106 is maintained in a retracted or trailing state such that no primary or auxiliary valve actuation is transmitted by the actuator 106 to the bridge pin 108 and engine brake valve 104b. At the same time, any auxiliary valve actuation motion applied to the rocker arm 100 is lost by a lost motion mechanism (not shown), and only the primary valve actuation motion is transmitted to the valve bridge 102 and, subsequently, to the engine valve 104.

[0007] On the other hand, when auxiliary actuation is desired, hydraulic fluid is supplied to control valve 114, which supplies hydraulic fluid to a high pressure chamber 116 in fluid communication with the actuator piston of actuator 106. Control valve 114 also functions to check hydraulic fluid in high pressure chamber 116, thus maintaining a hydraulic lock on the fluid in high pressure chamber 116, which keeps the actuator piston extended throughout the engine brake valve actuation movement, thus delivering auxiliary valve actuation movement to auxiliary valve 104b via bridge pin 108.

[0008] IRB valve trains have several concerns regarding valve-to-piston contact and seating velocity. Regarding the former, if the actuator piston remains in its extended state during main event valve actuation, the engine valve 104 experiences lift that exceeds the main event valve actuation, thereby extending the engine valve 104 further into the cylinder bore and potentially leading to destructive contact between the piston and the engine valve 104. One solution to this problem is to allow more space in the piston bore or less space in the piston stroke to avoid contact with the engine valve 104. However, this solution is undesirable because it reduces engine braking force due to reduced volume on both the compression and exhaust strokes. Regarding the latter, seating velocity is another concern because the rocker's braking component causes higher seating velocities for non-braked valves. High seating velocities can accelerate valve seat wear and potentially lead to valve or valve seat failure.

[0009] As is known in the art, one way to address these issues is to incorporate a reset assembly 118 into the IRB system, as further shown in FIG. 1. Often, the reset assembly 118 is provided by one or more components external to the IRB 100, as shown in FIG. 1. Alternatively, the reset assembly 118' may be incorporated into the IRB 100 itself. In any event, such reset assemblies 118, 118' generally operate by providing a hydraulic connection 120, 120' that can be controlled (typically by the angular position of the rocker arm 100 relative to another valve train component or fixed surface) to selectively and rapidly vent the high-pressure chamber 116, thereby retracting or retracting the actuator piston and transferring control of the engine braking valve 104 to the main event valve actuation movement, thus preventing its overextension and preventing high seating velocities of non-brake valves.

[0010] Despite the above advantages, current IRB systems that include reset still have problems, including the system exiting reset mode while in main event motion, which can reduce or completely eliminate the benefits of reset. Additionally, IRB systems, especially those external to the IRB, are typically bulky with many components, which adds undesirable weight and cost and makes packaging such systems more difficult. Summary of the Invention

[0011] The above-described shortcomings of prior art solutions are addressed by providing a rocker arm for actuating at least one engine valve in an internal combustion engine. In one embodiment, the rocker arm includes an actuator piston slidably disposed within an actuator piston bore formed in a motion-imparting end of the rocker arm. A lash adjustment assembly is disposed in the motion-transmitting end of the rocker arm and includes an internal bore. The rocker arm is provided with a hydraulic passage in fluid communication with the actuator piston bore and the internal bore of the lash adjustment assembly. A reset assembly is disposed within the lash adjustment assembly. The reset assembly includes a reset slider and a check element in fluid communication with the internal bore. The reset slider is slidably disposed within the internal bore and has a first end and a second end. A first end of the reset slider is configured to engage with at least one valve train component of the engine valve or the engine valve, and a second end of the reset slider has a reset pin disposed thereon, the reset pin being configured to contact the check element in response to positioning of the rocker arm when the first end contacts the valve train component or the engine valve, thereby placing the check element in an unchecked state.

[0012] In one embodiment, the actuator piston bore is configured to receive hydraulic fluid from a hydraulic fluid source, which may include a check valve, which may be further disposed within the control valve.

[0013] In one embodiment, the actuator piston is positioned to align with a first of the at least one engine valve. The actuator piston may be positioned closer to the motion-receiving end of the rocker arm than the lash adjustment assembly. In another embodiment, the actuator piston may be biased inward within the actuator bore.

[0014] In one embodiment, the lash adjustment assembly includes a lash adjustment screw threadably mounted within the rocker arm, the lash adjustment screw including a radial bore in fluid communication with the internal bore and configured to be aligned with the hydraulic passage. The internal bore may include a first bore and a second bore having an opening therebetween, the radial bore in fluid communication with the first bore, and the check element configured to hydraulically isolate the first bore from the second bore in a checking state. In this embodiment, the width of the reset pin may be smaller than the width of the opening such that fluid communication is established between the first bore and the second bore when the check element is in a non-checking state.

[0015] In one embodiment, the reset slider is configured to lose at least a portion of the valve actuation motion applied to the rocker arm before contacting the check element. For example, the reset slider may be configured to lose auxiliary valve actuation motion applied to the rocker arm. Further to this embodiment, the reset slider may include diametrically and longitudinally extending notches configured to define the portion of the valve actuation motion lost by the reset slider. Furthermore, the lash assembly may include a lateral pin configured to engage the notch and limit movement of at least a portion of the reset slider.

[0016] In one embodiment, the rocker arm further comprises a biasing element configured to bias the reset slider out of the internal bore. The biasing element can provide a biasing force sufficient to urge the rocker arm into contact with the source of valve actuation motion when the reset slider contacts a valve train component or an engine valve.

[0017] In one embodiment, the at least one engine valve includes two engine valves, and the valve train component is a valve bridge operably connected to the two engine valves.

[0018] In one embodiment, the lash adjustment assembly includes a vent passage in fluid communication with the internal bore, and the exhaust passage is configured to allow hydraulic fluid in the actuator piston bore to pass through the vent passage to the ambient environment when the reset pin unchecks the check element.

[0019] In one embodiment, the reset slider includes an e-foot movably attached to a second end of the reset slider and configured to contact a valve train component or an engine valve.

[0020] 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. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a schematic diagram of a prior art valve actuation system; [Figure 2] FIG. 1 is a schematic perspective side view of an IRB system according to the present disclosure. [Figure 3] FIG. 3 is a partial cross-sectional elevation view of the rocker arm shown in FIG. 2 showing further details of the actuator and reset assembly according to the present disclosure. [Figure 4] FIG. 3 is a partial cross-sectional elevation view of the rocker arm shown in FIG. 2 showing further details of the actuator and reset assembly according to the present disclosure. [Figure 5] FIG. 3 is an elevational cross-sectional view of a portion of the rocker arm reset assembly of FIG. 2 in accordance with the present disclosure. [Figure 6] FIG. 3 is an elevational cross-sectional view of a portion of the rocker arm reset assembly of FIG. 2 in accordance with the present disclosure. [Figure 7] FIG. 3 is an elevational cross-sectional view of a portion of the rocker arm reset assembly of FIG. 2 in accordance with the present disclosure. [Figure 8] FIG. 3 is an elevational cross-sectional view of a portion of the rocker arm reset assembly of FIG. 2 in accordance with the present disclosure. [Figure 9]FIG. 3 is an elevational cross-sectional view of a portion of the rocker arm reset assembly of FIG. 2 in accordance with the present disclosure. [Figure 10] FIG. 3 is an elevational cross-sectional view of a portion of the rocker arm reset assembly of FIG. 2 in accordance with the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0022] 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.

[0023] 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.

[0024] The present disclosure describes a cost-friendly rocker arm, specifically an integrated rocker brake, that includes a reset assembly integrated within the rocker arm, particularly a lash adjustment assembly. The technology described herein does not require an external reset assembly (e.g., a seat or contact pad) while still providing the ability to reset valve actuation throughout the main valve actuation motion. Additionally, the rocker arms described herein can include an integrated biasing element to maintain the rocker arm in contact with the source of motion, thereby avoiding the need for any external biasing component. The reset assembly preferably has a limited stroke to facilitate lash adjustment and minimize reduction in valve spring preload between the sub-base and base circle.

[0025] Referring to FIG. 2 , a valve actuation system 200 is shown that includes a rocker arm or IRB 202. The rocker arm 202 is mounted on a rocker shaft 204 and has a motion-receiving end 206 and a motion-imparting end 208. In accordance with known techniques, the rocker shaft 204 includes hydraulic passages (not shown) for supplying both constant and selectable hydraulic fluid to the rocker arm 202. While the rocker arm 200 is shown as a center-pivot rocker arm, the teachings of the present application may be equally applied to other types of rocker arms, such as end-pivot rocker arms. The motion-receiving end 206 of the rocker arm 202 includes a roller 210 configured to align with a single valve actuation motion source 240 to receive both main event and auxiliary valve actuation motion. As will be appreciated by those skilled in the art, the roller 210 may alternatively be implemented using other mechanisms, such as a tappet or contact surface.

[0026] In the illustrated embodiment, the motion-imparting end 208 of the rocker arm 202 includes a control valve 211, an actuator boss 212 having an actuator piston 214 disposed therein, and a lash / reset assembly boss 216 having a reset assembly 218 disposed therein. In one embodiment, the actuator boss 212, and therefore the actuator piston 214, is located closer to the motion-receiving end 206 of the rocker arm 202 than the lash / reset assembly boss 216 and therefore the reset assembly 218. However, it is understood that this location of the actuator piston 214 relative to the reset assembly 218 is not required.

[0027] The system further includes a valve bridge 220 that spans two engine valves 222, which may be either exhaust or intake valves. A lash / reset assembly boss 216 and a reset assembly 218 are configured to align with the center of the valve bridge 220, while an actuator boss 212 and an actuator piston 214 are configured to align with a bridge pin 224 disposed within the valve bridge 220, which in turn aligns with a first engine valve 222b. The reset assembly 218 includes a swivel or so-called e-foot 226 that is maintained in constant contact with the valve bridge 220 (or other valve train component or engine valve of the two engine valves 222) by a biasing force exerted by a biasing element 228, as described below; this biasing force also urges a motion-receiving end 206 of the rocker arm 202 (via a roller 210) into contact with a valve-actuation motion source 240.

[0028] Valve actuation motion source 240 is provided as a cam having cam lobes 242, 244 defined according to a so-called base circle 246 and a sub-base circle 248. In accordance with known techniques, base circle 246 and sub-base circle 248 are separated by a distance L, which defines the maximum height of an auxiliary valve actuation cam lobe 244 provided on cam 240. Such auxiliary lobe 244 provides auxiliary valve actuation motion to rocker arm 202, but is only selectively transmitted by actuator piston 214 and is lost in all cases by reset assembly 218, as described in more detail below. On the other hand, any portion of a cam lobe greater than the height of base circle 248, such as main valve actuation cam lobe 242, is transmitted in all cases by reset assembly 218 and causes reset of actuator piston 214 during auxiliary action, such as engine braking, as also described in more detail below.

[0029] 2, in the absence of hydraulic fluid supplied through control valve 211, and therefore operating rocker arm 202 in conventional or generate mode, actuator piston 214 is maintained in a retracted position such that it does not contact bridge pin 224 and is therefore prevented from transmitting valve actuation motion to first engine valve 222b. As will be explained in further detail below, reset assembly 218 is configured such that in the absence of hydraulic fluid applied to actuator piston 214, any auxiliary valve actuation motion applied thereto is lost, but any main event valve actuation motion applied thereto is transmitted to valve bridge 220 and engine valve 222.

[0030] On the other hand, when hydraulic fluid is supplied to the actuator piston 214 through the control valve 211, the actuator piston 214 is maintained in an extended position (due to the locked volume of hydraulic fluid) during any auxiliary motion applied to the rocker arm 202. Such auxiliary valve actuation motion induces contact between the actuator piston 214 and the bridge pin 224 such that the auxiliary valve actuation motion is transmitted to the first engine valve 222b. At the same time, the lost motion capability of the reset assembly 218 prevents the auxiliary valve actuation motion from being transmitted to the center of the valve bridge 220. However, when main event valve actuation motion is received by the rocker arm 202, the reset assembly 218 operates to cause the actuator piston 214 to retract (reset), so that both engine valves 222 are commanded solely by the transmission of main event valve actuation through the reset assembly 218 and the valve bridge 220.

[0031] 3, a partial cross-sectional view is shown illustrating further details of the actuator piston boss 212 and the actuator piston 214. In particular, the actuator piston boss 212 includes an actuator piston bore 302 formed therein with the actuator piston 214 slidably disposed in its open end. A threaded opening 304 is provided at the opposite end of the actuator piston bore 302, and an actuator lash adjustment screw 306 is threadably engaged with the opening 304. As is known in the art, an actuator lash adjustment nut 308 is threadably engaged with the actuator lash adjustment screw 306 to maintain the positioning of the actuator lash adjustment screw 306 within the actuator piston bore 302. The distal end of the actuator lash adjustment screw 306 (relative to the actuator lash adjustment nut 308) extends into an internal bore 310 formed in the actuator piston 214. A retainer 312 is attached to the actuator piston 214 at the open end of the inner bore 310 and is configured with a central opening 314 that allows the actuator lash adjustment screw 306 to be slidably received within the central opening 314. An actuator piston spring 316 is disposed between shoulders 318, 320 formed on the actuator lash adjustment screw 306 and the retainer 312, respectively, thereby tending to bias the retainer 312 and the actuator piston 214 into the actuator piston bore 302.

[0032] A source of hydraulic fluid is provided by a first hydraulic passage 322 formed in the rocker arm 202 that is in fluid communication between the output port of the control valve 211 and the actuator piston bore 302. Hydraulic fluid may be provided to the control valve 211 via passages formed in the rocker shaft and rocker arm 202 using techniques known in the art. As is further known in the art, the control valve provides a selectable means for providing hydraulic fluid to the first hydraulic passage 322 or venting hydraulic fluid from any hydraulic circuit in fluid communication with the first hydraulic passage 322 (e.g., by selectively applying hydraulic fluid thereto using an appropriate solenoid controlled by the engine controller). As described in more detail below, the reset assembly 218 provides another technique for venting hydraulic fluid, so the venting capability of the control valve 211 is not required. Thus, the control valve 211 may otherwise include a check valve disposed therein and may be replaced by a simple check valve that operates to allow hydraulic fluid to enter the first hydraulic passage 322 but not allow backflow of hydraulic fluid through the first hydraulic passage 322.

[0033] When pressurized hydraulic fluid is introduced into the first hydraulic passage 322 via the control valve 211 (or check valve) and thus the actuator piston bore 302, the bias of the actuator piston spring 316 may be overcome by the hydraulic pressure acting on the actuator piston 214, thereby causing the actuator piston 214 to extend out of the bore 302 until such time as the lower surface of the retainer 312 abuts the upper shoulder 324 of the actuator lash adjustment screw 306. In this manner, movement of the actuator piston 214 out of the actuator piston bore 302 is limited. Because the control valve 211 (or check valve) operates to check hydraulic fluid within the actuator piston bore 302, a hydraulic lock is established that maintains the extension of the actuator piston 214 from the bore 302 despite the application of any valving motion to the rocker arm 202. However, to prevent overextension of the engine valve 222, the reset assembly 218 is in fluid communication with the actuator piston bore 302 via a second hydraulic passage 326 that allows checked hydraulic fluid within the actuator piston bore 302 to be vented before the rocker arm 202 experiences the full lift of the main event valve actuation movement, as described in more detail below.

[0034] 4, a partial cross-sectional view is shown illustrating further details of lash / reset assembly boss 216 and reset assembly 218. In particular, lash / reset assembly boss 216 includes a lash / reset assembly bore 402 having a downwardly facing open end and a lash adjustment assembly disposed therein. In one embodiment, the lash adjustment assembly includes a lash adjustment screw 404 and a lash adjustment nut 408. A threaded opening 406 is provided at the end opposite the open end of lash / reset assembly bore 402, and lash adjustment screw 404 is threadably engaged with opening 406. As is known in the art, lash adjustment nut 408 is threadably engaged with lash adjustment screw 404 to maintain the positioning of lash adjustment screw 404 within lash / reset assembly bore 402. Lash adjustment screw 404 has an internal bore including a first or smaller diameter bore 410 and a second or larger diameter bore 412 both formed longitudinally therein, with each bore 410, 412 in fluid communication with one another but separated by an opening or check seat 414 configured to receive a check element. A feature of the present disclosure is that the lash adjustment assembly, and particularly lash adjustment screw 404 in the illustrated embodiment, includes a reset assembly 218, which includes a check element and reset slider 426 arranged as described further below.

[0035] In the illustrated example, the check element includes a check ball 416 disposed within first bore 410 and biased into contact with check seat 414 by a check spring 418 reacting against a check spring retainer 420. While a check ball configuration is shown in Figures 4-10 as implementing the check element, it will be appreciated that other configurations, such as a check disk configuration, may equally be used as a matter of design choice.

[0036] Lash adjustment screw 404 includes a radially extending bore 422 in fluid communication with first bore 410 and an annular channel 424 formed on an exterior surface of reset lash adjustment screw 404. Annular channel 424 has a sufficient longitudinal length such that it is at least partially aligned with second hydraulic passage 326 regardless of adjustments to lash adjustment screw 404.

[0037] The reset slider 426 is slidably disposed in the downwardly open end of the second bore 412 and includes a reset pin 428 disposed on an upper surface of the second end of the reset slider 426 and aligned with an opening forming the check seat 414. As shown, the reset pin 428 is integrally formed with the reset slider 426, but this is not required; for example, the reset pin 428 could comprise a separate member attached (e.g., threadedly) to the reset slider 426. The reset slider 426 is configured at its other end or first end to engage a valve train component (e.g., valve bridge 220 (not shown)) or an engine valve. For example, the first end of the reset slider 426 includes a spherical end 430 to which the e-foot 226 is movably secured. 6, 8, and 10, the reset slider 426 also includes a diametrically and longitudinally extending notch 432, and the reset lash adjustment screw 404 includes a lateral pin 434 that extends diametrically into the second bore 412 and is secured in an opening formed in a sidewall of the lash adjustment screw 404. The lateral pin 434 passes through the notch 432, thereby securing the reset slider 426 to the lash adjustment screw 404 while still allowing the reset slider 426 to slide within the second bore 412.

[0038] In the illustrated embodiment, the biasing element 228, preferably in the form of a compression spring, is disposed between shoulders 436, 438 formed on the lash adjustment screw 404 and the reset slider 426, respectively, thereby biasing the reset slider 426 away from the lash adjustment screw 404 and the rocker arm 202, i.e., out of the second bore 412. The biasing element 228 is designed to provide sufficient force so that when the e-foot 226 contacts a valve train component or an engine valve, the force provided by the biasing element 228 against the respective shoulders 436, 438 is sufficient to bias the rocker arm 202 into contact with the source of valve actuation motion.

[0039] 4 also shows a radially extending vent opening 440 located proximal to the check seat 414 that provides fluid communication between the first bore 412 and the ambient environment (as opposed to a hydraulic fluid source that provides hydraulic fluid to the rocker arm 202, as in some prior art systems, for example). As described in further detail below, when the check ball 416 is moved away from the check seat 414 by operation of the reset slider 426, hydraulic fluid from the actuator piston bore 302 can flow through the second hydraulic passage 326, the annular channel 424, the radial bore 422, the first bore 410, the check seat 414, and into the vent opening 440, thereby retracting the actuator piston 214.

[0040] Figures 5-10 show cross-sectional views of the lash adjustment screw 404, reset slider 426, and associated components through various stages of a valve actuation motion applied to the rocker arm 202 (not shown). In particular, Figures 5, 7, and 9 show cross-sectional views along a plane parallel to the extent of the lateral pin 434 and notch 432, while Figures 6, 8, and 10 show cross-sectional views along a plane perpendicular to the extent of the lateral pin 434 and notch 432 (i.e., along a plane orthogonal to the cross-sections of Figures 5, 7, and 9).

[0041] 4 and 5 show a state where no valve-actuating motion (auxiliary or main event) is being applied to the rocker arm 202, i.e., the cam roller 210 is at the sub-base circle 246 of the cam 240. In this state, the biasing element 228 biases the reset slider 426 away from the lash adjustment screw 404 until the e-foot 226 contacts the valve bridge 220 or until movement of the reset slider 426 away from the lash adjustment screw 404 is limited by the abutment of the upper surface of the notch 432 with the lateral pin 434. Note that in this state, the reset pin 428 is in its farthest position from the check ball 416, which is seated in the seat 414, due to the biasing force of the check ball spring 418, i.e., in the check state. As a result, the charge of hydraulic fluid retained in the actuator piston bore 302 (as well as the second hydraulic passage 326 and the first bore 410) remains hydraulically locked.

[0042] 7 and 8 illustrate a condition in which the maximum extent of any auxiliary valve actuation movement (as represented by auxiliary cam lobe 244), or the lower lift portion of the main event valve actuation movement (primary cam lobe 244), is applied to rocker arm 202. In this condition, maximum auxiliary lift / lower main event lift causes downward movement of lash adjustment screw 404 (as shown in FIGS. 7-10) via rotation of rocker arm 202. This, in turn, causes reset slider 426 to slide upward within second bore 412 (against the bias of biasing element 228). As reset slider 426 slides upward, reset pin 428 enters the opening formed by check seat 414 but does not lift check ball 416 from its seat. In this manner, maximum auxiliary lift / lower main event lift is absorbed by reset assembly 218, and again, any charge of hydraulic fluid held within actuator piston bore 302 (as well as second hydraulic passage 326 and first bore 410) remains hydraulically locked. However, when actuator piston bore 302 is filled with the locked amount of hydraulic fluid, this state of rocker arm 202 causes rigidly extending actuator piston 214 to transmit any auxiliary valve actuation motion to the corresponding engine valve, as described above.

[0043] 9 and 10 illustrate the condition where the main event lift (primary cam lobe 244) applied to the rocker arm 202 exceeds the maximum secondary lift (i.e., the limit established by the base circle 248), thus causing the reset slider 426 to slide further into the second bore 412 (but before the reset slider 426 bottoms out in the second bore 412), causing the reset pin 428 to contact the check ball 416 and overcome the bias of the check spring 418 (and any pressurized hydraulic fluid in the first bore 410). This causes the check ball 416 to lift from its seat 414. As the check ball 416 lifts from its seat 414, because the width of the reset pin 428 is smaller than the width of the opening 414 as shown, fluid communication is re-established between the first bore 410 and the second bore 412 as well as the vent opening 440, thereby rapidly venting the hydraulic fluid in the actuator piston bore 302. As mentioned above, this venting of hydraulic fluid retracts the actuator piston 214 into its bore 302, returning the command for both engine valves to main event lift.

[0044] While various embodiments according to the present 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. In various embodiments described herein, the rocker arm is shown as pivoting about a rocker shaft. However, it is understood that the present disclosure need not be limited in this respect, and pivoting configurations other than about a rocker shaft may equally be employed. For example, a portion of the disclosed rocker arm (e.g., an input portion including a motion-receiving end) may pivot about a different shaft. Furthermore, such a shaft may even be mounted on another portion of the rocker arm or on a separate shaft seat.

[0045] As noted above, the source of hydraulic fluid (via the first hydraulic passage 322) is disclosed as being in fluid communication with the actuator piston bore 302. However, it is understood that this is not a requirement. Indeed, the source of hydraulic fluid may be in fluid communication with any portion of the hydraulic circuit formed by the actuator piston bore 302, the hydraulic passage 326, and the internal bores 410, 412.

[0046] 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 actuating at least one engine valve of an internal combustion engine, the rocker arm having a motion-imparting end, the rocker arm comprising: an actuator piston slidably disposed within an actuator piston bore formed in the motion-imparting end of the rocker arm; a lash adjustment assembly disposed at the motion-imparting end of the rocker arm, the lash adjustment assembly comprising an internal bore; a hydraulic passage in fluid communication with the actuator piston bore and the internal bore; a reset assembly disposed within the lash adjustment assembly, the reset assembly comprising: a check element in fluid communication with the internal bore; a reset slider slidably disposed within the internal bore and having a first end and a second end, the first end configured to engage a valve train component or an engine valve of the at least one engine valve, the second end having a reset pin disposed thereon, the second end configured to contact the check element in response to positioning of the rocker arm when the first end contacts the valve train component or engine valve, thereby placing the check element in an unchecked state.

2. The rocker arm of claim 1 , wherein the actuator piston bore is configured to receive hydraulic fluid from a hydraulic fluid source.

3. The rocker arm of claim 2 , wherein the source of hydraulic fluid comprises a check valve.

4. The rocker arm of claim 3 , wherein the check valve is disposed within a control valve.

5. The rocker arm of claim 1 , wherein the actuator piston is positioned to align with a first of the at least one engine valve.

6. The rocker arm of claim 5 , wherein the actuator piston is located closer to the motion-receiving end of the rocker arm than the lash adjustment assembly.

7. The rocker arm of claim 1 , wherein the actuator piston is biased inwardly within the actuator bore.

8. 2. The rocker arm of claim 1, wherein the lash adjustment assembly comprises a lash adjustment screw threadably mounted within the rocker arm, the lash adjustment screw comprising a radial bore in fluid communication with the internal bore and configured to be aligned with the hydraulic passage.

9. 9. The rocker arm of claim 8, wherein the internal bore comprises a first bore and a second bore with an opening therebetween, the radial bore being in fluid communication with the first bore, and the check element being configured to hydraulically isolate the first bore from the second bore in a check condition.

10. 10. The rocker arm of claim 9, wherein a width of the reset pin is less than a width of the opening such that fluid communication is established between the first bore and the second bore when the checking element is in the unchecking condition.

11. 2. The rocker arm of claim 1, wherein the reset slider is configured to lose at least a portion of the valve actuation motion applied to the rocker arm before contacting the check element.

12. The rocker arm of claim 11 , wherein the reset slider is configured to lose auxiliary valve actuation motion applied to the rocker arm.

13. 12. The rocker arm of claim 11, wherein the reset slider includes a diametrically and longitudinally extending notch configured to define a portion of the valve actuation motion lost by the reset slider.

14. The rocker arm of claim 13 , wherein the lash assembly comprises a lateral pin configured to engage the notch and limit movement of at least a portion of the reset slider.

15. The rocker arm of claim 1 , further comprising a biasing element configured to bias the reset slider out of the internal bore.

16. 16. The rocker arm of claim 15, wherein the biasing element provides a biasing force sufficient to urge the rocker arm into contact with a source of valve actuation motion when the reset slider contacts the valve train component or the engine valve.

17. The rocker arm of claim 1 , wherein the at least one engine valve includes two engine valves, and the valve train component is a valve bridge operatively connected to the two engine valves.

18. 2. The rocker arm of claim 1, wherein the lash adjustment assembly includes a vent passage in fluid communication with the internal bore, the vent passage configured such that when the reset pin places the check element in the unchecked state, hydraulic fluid within the actuator piston bore passes through the vent passage to the ambient environment.

19. 2. The rocker arm of claim 1, wherein the reset slider comprises an e-foot movably mounted to the second end and configured to contact the valve train component or the engine valve.

Images