INTEGRATED ROCKER BRAKE WITH RESET PLUNGER FOR ACTUATING A SINGLE ENGINE VALVE

FIELD

The present disclosure relates generally to valve actuation systems for actuating engine valves in an internal combustion engine and, in particular, to an integrated rocker brake with a reset plunger for actuating a single engine valve.

BACKGROUND

In the domain of internal combustion engines, compression-release engine braking has conventionally been implemented using a dedicated compression-release brake rocker arm that is separate from the exhaust rocker arm used to convey main event valve actuation motions (i.e., those valve actuations typically used to support positive power generation). More recent developments include the so-called integrated rocker brake (IRB) in which the compression-release brake rocker arm and exhaust rocker arm are combined into one rocker arm for cost savings as well as provision of more compact valvetrain hardware.

As known in the art, and with reference to FIG. 1, an IRB 100 typically includes a nose (or motion imparting end) of the rocker arm configured to transfer main event valve actuation motions through a valve bridge 102 to a pair of engine valves 104 and a selectable actuator 106 configured to transfer engine braking valve actuation motions to only one of the engine valves (an engine braking valve) 104b 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 actuations and engine braking valve actuations (or other auxiliary valve actuations). 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 operated to provide hydraulic fluid to a control valve 114. In the absence of hydraulic fluid supplied to the control valve 114, an actuator piston of the actuator 106 is maintained in a retracted or compliant state such that no valve actuations are conveyed by the actuator 106 to the bridge pin 108 and engine braking valve 104b. On the other hand, when hydraulic fluid is supplied to the control valve 114, the hydraulic fluid is, in turn, supplied to a high pressure chamber 116 in fluid communication with the actuator piston of the actuator 106. The control valve 114 also serves to check the hydraulic fluid in the high pressure chamber 116, thereby maintaining a hydraulic lock on the fluid in the high pressure chamber 116, which causes the actuator piston to remain in an extended state throughout the engine braking valve actuation motions, thereby delivering such valve actuation motions to the engine braking valve 104b via the bridge pin 108.

An IRB valvetrain does have several concerns regarding valve-to-piston contact and seating velocity.

Regarding the former, if the actuator piston remains in its extended state during a main event valve actuation, the engine valves 104 (more particularly, the engine braking valve 104b) will experience lift beyond the main event valve actuation, thereby causing the engine valves 104 to extend further into the cylinder bore and potentially leading to catastrophic contact between the piston and engine valves 104. One solution to this problem is to budget more room in the piston bore or less of a piston stroke in order to avoid contact with the engine valves 104. However, this solution is undesirable because engine braking power would be reduced due to the reduced volume in both the compression and exhaust strokes.

Regarding the latter, seating velocity is another concern due to the braking component of the rocker causing a higher seating velocity of the non-braking valve 104a. High seating velocities can result in accelerated seat wear as well as potential failure of engine valves or their corresponding seats.

One way to combat these problems, as known in the art, is to incorporate a reset assembly 118 into the IRB system as further shown in FIG. 1. Often, a reset assembly 118 is provided by one or more components external to the IRB 100 as illustrated in FIG. 1. Alternatively, a reset assembly 118′ may be incorporated into the IRB 100 itself. Regardless, such reset assemblies 118, 118′ generally operate by providing a hydraulic connection 120, 120′ that can be controlled (typically by virtue of 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 causing the actuator piston to retract or collapse and to transfer control of the engine brake valves 104 to the main event valve actuation motion and thus prevent overextension thereof as well as preventing high seating velocities of non-braking valves.

Techniques that permit the benefits of IRB systems to be realized in a wider range of internal combustion engines would represent a welcome addition to the art.

SUMMARY

The above-noted shortcomings of prior art solutions are addressed through the provision of an IRB-type rocker arm configured to actuate at least one engine valve in an internal combustion engine. In an embodiment, the rocker arm, which comprises a motion imparting end, also comprises a biasing contact surface configured to receive a force to bias the motion imparting end toward the at least one first engine valve. An actuator piston is slidably disposed in a vertical bore formed in the motion imparting end of the rocker arm, where the actuator piston and vertical bore are configured to align with the at least one first engine valve. The rocker arm further comprises a hydraulic chamber in fluid communication with the vertical bore and a checking element in fluid communication with the hydraulic chamber and configured to permit one-way passage of selectively applied hydraulic fluid into the hydraulic chamber. A reset plunger is provided in the rocker arm, which reset plunger is in sealing engagement with a reset plunger bore that is, in turn, in fluid communication with the hydraulic chamber. The reset plunger has an end extending out of the rocker arm and configured to contact a reaction surface external to the rocker arm in response to positioning of the rocker arm, thereby interrupting the sealing engagement of the reset plunger with the reset plunger bore and permitting hydraulic fluid to vent out of the hydraulic chamber.

In an embodiment, the biasing contact surface is disposed on an upward facing surface of the rocker arm. In an embodiment, the rocker arm comprises a lateral projection and the biasing contact surface is formed on the lateral projection.

In an embodiment, the actuator piston includes a resilient element to bias the actuator piston into the vertical bore. In one example, the resilient element comprises an actuator piston spring disposed within the actuator piston and vertical bore and configured to bias the actuator piston into the vertical bore.

In an embodiment, the hydraulic chamber comprises a first bore parallel to an axis of rotation of the rocker arm, wherein the checking element is arranged in the first bore.

In an embodiment, the reset plunger is biased into sealing engagement with the reset plunger bore. For example, the rocker arm may further comprise a reset plunger spring configured to bias the reset plunger into sealing engagement with the reset plunger bore. In an embodiment, the reset plunger bore is perpendicular to an axis of rotation of the rocker arm. The rocker arm can include a reset plunger sleeve disposed within a second bore formed in the rocker arm, where the reset plunger sleeve defines the reset plunger bore.

In an embodiment, a valve actuation system for actuating the at least first engine valve comprises the presently disclosed rocker arm, where the rocker arm is rotatably mounted on a rocker shaft and where a resilient element is attached to the rocker shaft and configured to apply the force to the biasing contact surface.

In an embodiment, a valve actuation system for actuating the at least first engine valve comprises the presently disclosed rocker arm, and further comprises a fixed structure relative to movement of the rocker arm, where the reaction surface is formed on the fixed structure. In one implementation, the fixed structure is a camshaft bearing support.

In an embodiment, a valve actuation system is configured for actuating at least two engine valves and comprises the presently disclosed rocker arm, where the at least two engine valves include the at least first engine valve. In one implementation, this system comprises another rocker arm for actuating a second engine valve of the at least two engine valves. In another implementation, this system further comprises a first valve actuation motion source configured to provide a main event valve actuation motion and one or more first auxiliary valve actuation motions to the at least first engine valve. In yet another implementation, this system comprises a second valve actuation motion source configured to provide the main event valve actuation motion and one or more second auxiliary valve actuation motions to the second engine valve, where the first auxiliary valve actuation motions are not identical to the second auxiliary valve actuation motions. In another embodiment of this system, the other rocker arm is a rocker arm in accordance with the instant disclosure, where the actuator piston and vertical bore of the other rocker arm are configured to align with the second engine valve.

BRIEF DESCRIPTION OF THE DRAWINGS

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

FIG. 1 is schematic illustration of an IRB system in accordance with prior art techniques;

FIG. 2 is a schematic illustration of a single valve IRB system in accordance with the instant disclosure;

FIG. 3 is an isometric view of an IRB system in accordance with the instant disclosure;

FIG. 4 is an isometric view of an IRB rocker arm for use with a single engine valve in accordance with the instant disclosure;

FIGS. 5 and 6 are partial elevational cross-section views of the IRB rocker arm of FIG. 4 and illustrating further details of an actuator and reset assembly in accordance with the instant disclosure; and

FIG. 6 is a top down partial cross-sectional view of a portion of the IRB rocker arm of FIG. 4 and illustrating further details of an actuator and reset assembly in accordance with the instant disclosure.

DETAILED DESCRIPTION OF THE PRESENT EMBODIMENTS

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

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

As used herein, the phrase “fluid communication” refers to a configuration between two or more elements in which fluid is able to flow in at least one direction between such elements.

The instant disclosure describes embodiments of an IRB-type rocker arm for use in actuating a single engine valve, as opposed to an intervening valve bridge configured to actuate two or more engine valves. However, it is understood that IRB-type rocker arms as described herein may also be used to actuate two or more engine valve via an intervening valve bridge. Additionally, the disclosed IRB-type rocker arms described herein comprise a resetting assembly. An example of a valve actuation system 200 in accordance with the instant disclosure is further described with reference to FIG. 2.

FIG. 2 illustrates a valve actuation system 200 configured to actuate two engine valves 206, 212 associated with an internal combustion engine cylinder 201. In particular, the illustrated valve actuation system 200 comprises a first rocker arm 202 operatively connected to a first valve actuation motion source 204 and a first engine valve 206, and a second (or IRB) rocker arm 208 operatively connected to a second valve actuation motion source 210 and a second engine valve 212. That is, unlike conventional IRB systems of the type illustrated in FIG. 1, each engine valve 206, 212 is actuated according to separate valve actuation motion sources 204, 210 and rocker arms 202, 208, thereby obviating the need for a valve bridge. As those skilled in the art will appreciate, further valve train components not illustrated in FIG. 2 (e.g., pushrods, tappets, etc.) may be incorporated into the respective valve trains comprising the first and second rocker arms 202, 208. The first and second engine valves 206, 212 are preferably both of the same type, i.e., both intake valves or both exhaust valves. Furthermore, both the first and second valve actuation motions sources 204, 210 may be implemented as suitable cams as known in the art.

In particular, in one embodiment, the first valve actuation motion source 204 may comprise a lobe for providing main event valve actuation motion whereas the second motion source 210 may comprise lobes for both the main event valve actuation motion and one or more engine braking valve actuations using a so-called base circle and sub-base circle implementation as known in the art. Alternatively, the first valve actuation motion source 204 may comprise, in a addition to the lobe providing the main event valve actuation motion, additional lobes for providing additional auxiliary valve actuation motions. That is, stated more generally, in the various valve actuation systems described herein, the first motion source 204 may be configured to provide a main event valve actuation motion only, or the main event valve actuation motion along with one or more first auxiliary valve actuation motions, whereas the second motion source may be configured to provide the main event valve actuation motion along with one or more second auxiliary valve actuation motions. In this case, the first and second auxiliary valve actuation motions need not be identical to each other. For example, when provided, the first auxiliary valve actuation motion(s) may be configured to provide early exhaust valve opening (EEVO), whereas the second auxiliary valve actuation motion(s) may be configured to provide compression-release engine braking.

As depicted, the first rocker arm 202 actuates the first engine valve 206 in a conventional manner, i.e., according to valve actuation motions received by the first rocker arm 202 from the first motion source 204 and conveyed to the first engine valve 206. Similarly, the second rocker arm 208 receives valve actuation motions from the second motion source 210 and conveys them to the second engine valve 212. However, unlike the first rocker arm 202, the second rocker arm 208 implements various components in keeping with IRB operation.

Specifically, the second rocker arm 208 comprises a selectable actuator 214 configured to transfer engine braking valve actuation motions (received from the second motion source 210) to the second engine valve (also referred to as an engine braking valve) 212. As further shown in FIG. 2, control of the actuator 214 is provided by a selectable hydraulic fluid supply 216 operated to provide hydraulic fluid through a checking element 218 (which, as known in the art, may comprise a check valve that, in turn, may be incorporated into a control valve). For example, flow of hydraulic fluid from the fluid supply 216 may be controlled through use of a solenoid commanded by a suitable processing device, such as an engine control unit (ECU) as known in the art (not shown). In the absence of hydraulic fluid supplied to the checking element 218, an actuator piston of the actuator 214 is maintained in a retracted or compliant state such that no auxiliary valve actuations (i.e., valve actuations that are received by the second rocker arm 208 only when the second rocker arm 208 is controlled to contact the sub-base circle of the second motion source 210) are conveyed by the actuator 214 to the second engine valve 212.

On the other hand, when hydraulic fluid is supplied to the checking element 218, the hydraulic fluid is, in turn, supplied to the hydraulic or high pressure chamber 220 in fluid communication with the actuator piston of the actuator 214. The checking element 218 serves to check the hydraulic fluid in the high pressure chamber 220, thereby maintaining a hydraulic lock on the fluid in the high pressure chamber 220, which causes the actuator piston to remain in an extended state so long as the hydraulic lock is maintained, thereby delivering the sub-base circle auxiliary valve actuation motions to the second engine valve 212.

As further shown in FIG. 2, the second rocker arm 208 incorporates a reset assembly 222. The reset assembly 222 is configured to have a hydraulic connection 224 with the high pressure chamber 220 as shown. The reset assembly 222 can be controlled through interaction with a fixed reaction surface 226 (fixed relative to the typical reciprocating movement of the rocker arm 208) to vent the high pressure chamber 220 selectively and rapidly, thereby causing the actuator piston of the actuator 214 to retract or collapse. In turn, this causes the second rocker arm 208 to lose contact with the sub-base circle of the second motion source 210 thereby losing the auxiliary valve actuations provided by the second motion source 210.

FIG. 2 also schematically illustrates a biasing contact surface 215 formed on the second rocker arm 208 and configured to receive a force 217 that biases the second rocker arm 208 toward the second engine valve 212. Such biasing is desirable in order to control inertia of the rocker arm 208. As will be appreciated by those skilled in the art, the biasing contact surface 215 may be formed at different locations on the second rocker arm 208 depending on the location of the fulcrum point for the second rocker arm.

Additionally, it is noted that, while FIG. 2 illustrates a valve actuation system 200 in which two rocker arms 202, 208 are provided to separately actuate two engine valves 206, 212 of the same type (intake or exhaust), this is not a requirement. That is, in some internal combustion engines, only one engine valve of a given type may be provided for a cylinder 201, e.g., a single exhaust valve. In this case, the IRB rocker arm 208 as described herein may be used to actuate that single valve both with and without auxiliary event valve actuation motions (in addition to main event valve actuation motions). Alternatively, in systems in which two or more engine valves of the same type are provided for a cylinder 201, the IRB rocker arm 208 may still be used to actuate the two or more engine valves via, for example, an intervening valve bridge.

In yet another embodiment, the conventional first rocker arm 202 could be replaced by an IRB rocker arm substantially identical in structure and operation to the second rocker arm 208. In this manner, particularly in the case where the first motion source is configured to provide a main and one or more first auxiliary valve actuation motions and the second motion source is configured to provide the main and one or more second auxiliary valve actuation motions, as mentioned above, the use of two IRB rocker arms in accordance with the instant disclosure allows for combinations of main, first auxiliary and second auxiliary valve actuation motions to be selectively applied to the first and second engine valves 206, 212.

An implementation of the valve actuation system of FIG. 2 is illustrated with regard to FIGS. 3-7. In particular, FIG. 3 illustrates a valve actuation system 300 comprising a first rocker arm 302 and a second rocker arm 308 both rotatably mounted on a rocker shaft 330. The first rocker arm 302 is configured to actuate a first engine valve 306 and the second rocker arm 308 is configured to actuate a second engine valve 312, which engine valves are biased into their closed or seated positions by corresponding valve springs 338, 340. A camshaft 332 is supported by upper and lower camshaft bearing supports 334, 336, which camshaft 332 provides a first cam 304 and a second cam 310 respectively aligned with the first and second rocker arms 302, 308. In keeping with an embodiment of FIG. 2, the first cam 304 comprises a lobe providing a main event valve actuation whereas the second cam 310 comprises lobes for providing substantially the same main event valve actuation motion as the first cam 304 as well as one or more lobes providing one or more auxiliary valve event actuation motions such as engine braking.

As further shown in the embodiment of FIG. 3, a fixed (relative to rotational/reciprocal movement of the second rocker arm 308) reaction surface 342 is implemented by the upper camshaft bearing support 336, which reaction surface 342 is in alignment with a reset plunger 344 implemented by the second rocker arm 308. As described in further detail below, the reaction surface 342 and reset plunger 344 are configured such that contact between the two occurs at desired rotational positions of the second rocker arm 308, thereby effectuating resetting as described above. As will be appreciated by those skilled in the art, the reaction surface 342 may be provided by some other fixed structure depending on the configuration of the engine.

In an embodiment, the second rocker arm 308 comprises a biasing contact surface that is formed on an upper surface of the second rocker arm 308 and, more particularly, is configured such that application of a force to the biasing contact surface will tend to bias the second rocker arm 308 toward the second engine valve 312. A specific example of this is illustrated in FIG. 3, which shows a lateral projection 348 extending from the second rocker arm 308 in a direction substantially parallel to an axis of rotation of the second rocker arm 308 (i.e., a longitudinal axis of the rocker shaft 330). FIG. 3 additionally illustrates a resilient element in the form of a flat spring 346 secured to the rocker shaft 330 (i.e., a fixed structure external to the second rocker arm 308) adjacent to the second rocker arm 308 and in alignment with the lateral projection 348 of the second rocker arm 308. The spring 346 is configured such that the second rocker arm 308 is biased toward its corresponding second engine valve 312, particularly when the second rocker arm 308 contacts the second cam 310 only at its base circle (as opposed to its sub-base circle). Those skilled in the art will appreciate that other configurations of resilient elements for biasing the second rocker arm 308 in this manner may be readily devised.

Although the biasing contact surface described herein is preferably configured to bias the rocker arm toward the engine valve, it would also be possible to configure the biasing contact surface toward the valve actuation motion source instead.

Referring now to FIG. 4, a more detailed view of the second rocker arm 308 is shown. In particular, the second rocker arm comprises a rocker arm body 402 having a motion receiving end 404 and a motion imparting end 406. In accordance with known techniques, the motion receiving end 404 is equipped with a roller follower 408 configured to receive valve actuation motions from a valve actuation motion source, e.g., the second cam 310. The motion imparting end 406 comprises an actuator boss 410, a check valve boss 412 and a reset assembly boss 414, the respective configurations of each and their relationships to each other being described in further detail below.

The rocker arm body 402 further comprises a rocker shaft opening 416 formed between the motion receiving and motion imparting ends 404, 406 and configured to receive the rocker shaft 330 (not shown in FIG. 4). In accordance with known techniques, an inner surface of the rocker shaft opening 416 may have one or more hydraulic passages 418 formed therein. As known in the art, the hydraulic passage(s) 418 are configured to receive hydraulic fluid from corresponding hydraulic passages formed in the rocker shaft 330, which hydraulic fluid may be used to control operation of the second rocker arm 308 as further described below.

The rocker arm body 402 further comprises, at the motion imparting end 406 thereof, the lateral projection 348 extending substantially perpendicularly relative to a plane in which the second rocker arm 308 rotates (or substantially parallel to an axis of rotation of the second rocker arm 308). As shown, the lateral projection 348 may comprise a substantially flat surface configured to establish contact with the flat spring 346 shown in FIG. 3. Thus configured, contact by the lateral projection 348 with the spring 346 causes the motion imparting end 406 to be rotated counter-clockwise as depicted in FIG. 4 (i.e., towards a corresponding engine valve).

As further shown in FIG. 4, the reset assembly boss 414 comprises the reset plunger 344 extending downwardly (as depicted in FIG. 4) and the actuator boss 410 comprises a threaded lash adjustment screw 424 extending therein and secured by a lash adjustment nut 426. A swivel or so-called elephant foot 428 is secured to an actuator piston (not shown), which swivel is configured to contact the second engine valve 312.

Further details of the second rocker arm 308 are described below in connection with FIGS. 5-7, which illustrate various cross sectional views.

FIG. 5 illustrates an elevational, partial cross-sectional view of the second rocker arm 308 taken along section line V-V as shown in FIG. 4. FIG. 5 particularly illustrates the reset assembly boss 414, a reset assembly 502, and a check valve boss 412 housed therein. The check valve boss 412 comprises a horizontal bore 504 and the reset assembly boss 414 comprises a vertical bore 506 in fluid communication with each other at a first intersection. The horizontal bore 504 terminates at one end (second intersection) in fluid communication with a hydraulic fluid inlet 508, and is sealed closed at another end with a threaded plug 510, thereby creating a hydraulic chamber 512. A check valve 514 is disposed within the horizontal bore 504 between the first and second intersections. In the illustrated embodiment, the check valve 514 comprises a check valve body 516 and a check ball 518 biased by a check valve spring 520 into contact with a seat defined by the check valve body 516. In this manner, one-way fluid flow is established from the hydraulic fluid inlet 508 into the hydraulic chamber 512.

The reset assembly 502 further comprise a sleeve 522 disposed in the vertical bore 506, which sleeve 522 defines a sleeve bore 524. The sleeve 522 may be press fit into the vertical bore 506 or using other known techniques, e.g., threaded engagement. The reset plunger 344 is slidably disposed in the sleeve bore 524 and comprises a plunger contact surface 526 that terminates an end of the reset plunger extending out of the sleeve bore 524. In a presently preferred embodiment, the plunger contact surface 526 has a curvature that permits the reset plunger 344 to maintain smooth and even contact with the reaction surface 342 throughout rotation of the second rocker arm 308 relative to the reaction surface 342. The reset plunger 344 further comprises a head 528 configured to conform with a seat 530 formed in an upper end of the sleeve 522. A reset plunger spring 532 is disposed in the hydraulic chamber 512 in contact with the reset plunger 344 and configured to bias the reset plunger 344 out of the sleeve bore 524. However, the reset plunger 344 is prevented from sliding out of the sleeve 522 through conformal contact or sealing engagement of the plunger head 528 with the seat 530, thereby providing a seal against escape of hydraulic fluid disposed in the hydraulic chamber 512.

The reset plunger 344, which is generally cylindrical in the illustrated embodiment, further comprises a planar surface 534 as shown in FIGS. 5 and 6. When reset plunger 344 is pushed upward through contact with the reaction surface 342 and against the bias of the reset plunger spring 532, the seal provided by the conformal contact of the plunger head 528 and seat 530 is interrupted, thereby providing a fluid communication path between the hydraulic chamber 512 and a channel 536 established between a wall defining the sleeve bore 524 and the planar surface 534. When established, this fluid communication allows hydraulic fluid in the hydraulic chamber 512 to escape to ambient via the channel 536. As described in further detail below, the selective control of hydraulic fluid in the first hydraulic chamber, by virtue of operation of the reset plunger 344, permits an actuator piston to be extended and retracted as necessary to effectuate a resetting of the IRB rocker arm 308.

FIG. 6 illustrates an elevational, cross-sectional view of the second rocker arm 308 taken along section line VI-VI as shown in FIG. 4. In particular, FIG. 6 illustrates the actuator boss 410 and an actuator assembly 602 housed therein. The actuator boss 410 comprises a vertical bore 604 formed therein and having a downward-facing open end and a closed end. An actuator piston 606 is slidably disposed in the vertical bore 604 and comprises a ball 608 formed on an end of the actuator piston 606. A swivel 428 is rotatably connected to the ball 608 using known techniques. Further in accordance with known techniques, the lash adjustment screw 424 is threadedly mounted on the actuator boss 410 such that it extends through the closed end of, and into, the vertical bore 604 as well an actuator piston bore 610 formed in the actuator piston 606. In an embodiment, a flange 612 is slidably mounted on the lash adjustment screw 424 and affixed to the actuator piston 606 at an open end of the actuator piston bore 610. Further this embodiment, an actuator spring 614 is disposed between and reacts between a shoulder 616 formed on a distal end of the lash adjustment screw 424 (relative to the lash adjustment screw nut 426) and the flange 612. In this manner, the actuator piston 606 is biased into the vertical bore 604 such that, in the absence of hydraulic actuation of the actuation piston 606, solid contact is established between the lash adjustment screw 424 and the actuator piston 606, as shown in FIG. 6. Although the embodiment of FIG. 6 illustrates the actuator spring 614 disposed within the actuator piston 606 and the vertical bore 604, it is appreciated that this is not a requirement, i.e., the actuator spring 614 could be configured outside of the actuator piston 606 and even outside of the vertical bore 604.

In another embodiment, the actuator spring 614 is not provided. In this case, in the absence hydraulic actuation of the actuation piston 606, the actuation piston 606 is maintained in its retracted position according to the bias applied by the flat spring 346 to the second rocker arm 308.

FIG. 6 additionally illustrates an intermediate hydraulic passage 618 formed in the second rocker arm 308 and in fluid communication with the vertical bore 604. The intersection of the intermediate hydraulic passage 618 and the vertical bore 604 is configured such that sufficiently pressurized hydraulic fluid supplied through the intermediate hydraulic passage 618 flows into the vertical bore 604, past the flange 612 and into contact with the actuator piston 606. In an embodiment, the hydraulic force thus applied to the actuator piston 606 is sufficient to overcome the bias of the actuator piston spring 614 (if provided), thereby causing the actuator piston 606 to extend out of the vertical bore 604, i.e., such that solid contact between the lash adjustment screw 424 and actuator piston 606 is no longer present. As further shown in FIG. 7, which illustrates a partial cross-sectional view of the second rocker arm 308 taken along section line VII-VII as shown in FIG. 4, the intermediate hydraulic passage 618 establishes fluid communication between the hydraulic chamber 512 and the vertical bore 604.

Configured in this manner, and with reference to FIGS. 3 and 5-7, when hydraulic fluid is not supplied to the hydraulic chamber 512 via the hydraulic fluid inlet 508, hydraulic fluid is likewise not provided to the vertical bore 604 and the actuator piston 606 remains in its resting or non-actuated position, i.e., biased into the vertical bore 604 and in solid contact with the lash adjustment screw 424 (or at least in a compliant state in the absence of the actuator spring 614). Because the second rocker arm 308 is biased toward the second engine valve 312 by the flat spring 346, the second rocker arm 308 is positioned at the base circle level of the second cam 310 such that any cam lifts below the base circle, e.g., auxiliary valve actuation motions such as engine braking, are lost, whereas cam lifts above the base circle, e.g., main event valve actuation motions, are received by the second rocker 308 and conveyed to the second engine valve 312 by virtue of the solid contact between the lash adjustment screw 424 and the actuator piston 606.

However, when hydraulic fluid is supplied to the hydraulic chamber 512 via the hydraulic fluid inlet 508, hydraulic fluid flows through the hydraulic chamber 512 and intermediate hydraulic passage 618 and into the vertical bore 604, thereby causing the actuator piston 606 to extend out of the vertical bore 604, i.e., into its actuated position. Once the hydraulic chamber 512, intermediate hydraulic passage 618 and vertical bore 604 have been filled with hydraulic fluid, pressure on either side of the check valve 514 equalizes and permits the check ball 518 to reseat, thereby establishing a locked volume of hydraulic fluid behind the actuator piston 606 which is thereafter maintained in its extended state. Because the second rocker arm 308 continues to be biased into contact with the second engine valve 312, extension of the actuator piston 306 against the resistance of the engine valve 312 (caused by the valve spring 340) will cause the bias of the flat spring 346 (and actuator spring 614, if provided) to be overcome. In turn, the second rocker arm 308 will then rotate toward the second cam 310 such that the second rocker arm 308 is positioned at the sub-base circle level of the second cam 310. Thus, any cam lifts below the base circle level will be received by the second rocker arm and conveyed to the second engine valve 312 via the now-extended actuator piston 606.

As described above, however, if the actuator piston 606 were to remain extended during lift provided by a main event valve actuation motion, overextension of the second engine valve 312 would occur, potentially leading to contact with the cylinder piston and catastrophic damage. To prevent such overextension, the reset plunger 344 and reaction surface 342 are configured such that contact between the two is established when rotation of the second rocker arm 308 corresponds to lifts sufficient to ensure loss of main events without overextension, which may occur, for example, at lift heights corresponding to a substantial portion of the maximum main event lift, or at any other desired lift such at or just below the base circle level of the second cam 310. As described above, such contact of the reset plunger 344 with the reaction surface 342 causes the plunger head 528 to lift off the seat 530, thereby allowing hydraulic fluid otherwise trapped in the hydraulic chamber 512, intermediate hydraulic passage 618 and vertical bore 604 to escape (particularly rapidly when such hydraulic fluid is highly pressurized, as during a cam lift/valve actuation). The venting of this hydraulic fluid allows positioning of the actuator piston 606 to once again be commanded exclusively according to the bias of the actuator piston spring 614, i.e., back into the vertical bore 604, which in turn permits positioning of the second rocker arm 308 to once again be commanded exclusively by the flat spring 346, i.e., toward the second engine valve 312 and positioned at the base circle level relative to the second cam 310.

While the various embodiments in accordance with the instant disclosure have been described in conjunction with specific implementations thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the preferred embodiments of the invention as set forth herein are intended to be illustrative only and not limiting so long as the variations thereof come within the scope of the appended claims and their equivalents.

INTEGRATED ROCKER BRAKE WITH RESET PLUNGER FOR ACTUATING A SINGLE ENGINE VALVE

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