Patent Application
20240287920
The present disclosure relates generally to rocker arms for use in internal combustion engines and, in particular, to a rocker arm comprising a reset slider disposed in a lash adjustment assembly.
Internal combustion engines typically use either a mechanical, electrical, or hydro-mechanical valve actuation systems to actuate the engine valves. These systems may include a combination of camshafts, rocker arms, push rods, valve bridges, etc. (each, a valve train component and, collectively, a valve train) that may be driven by the engine's crankshaft rotation. When a camshaft is used to actuate the engine valves, i.e., acting as a valve actuation motion source, the timing of the valve actuation motions may be fixed by the size and location of the lobes on the camshaft.
As known in the art, valve actuations may comprise so-called main valve actuation motions and/or auxiliary valve actuation motions. As used herein, the descriptor “main” refers to engine valve motions used during positive power generation in which fuel is combusted in an engine cylinder to provide a net output of engine power, whereas the descriptor “auxiliary” refers to other engine valve motions for purposes that are alternative to positive power generation (e.g., compression-release braking, bleeder braking, cylinder decompression, cylinder deactivation, brake gas recirculation (BGR), etc.) or in addition to positive power generation (e.g., internal exhaust gas recirculation (IEGR), variable valve actuations (VVA), early exhaust valve opening (EEVO), late intake valve closing (LIVC), swirl control, etc.).
Engine braking has conventionally been implemented using, for any given cylinder, a dedicated braking rocker arm for conveying auxiliary valve actuation motions (e.g., compression-release valve actuations) that is separate from the exhaust rocker arm used to convey main exhaust valve actuations to exhaust engine valves. More recent developments include the so-called integrated rocker brake (IRB) in which the dedicated braking 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
As known in the art, and referring once again to
On the other hand, when auxiliary operation is desired, hydraulic fluid is supplied to the control valve 114 and 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 auxiliary valve actuation motions to the auxiliary 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 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. High seating velocities can result in accelerated seat wear as well as potential failure of valves or 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
Notwithstanding the above-noted benefits, current IRB systems that include resets have issues including the system coming out of the reset mode while still in the main event motion, which can reduce, or even completely obviate, the benefits of the reset. Additionally, IRB systems, particularly those that are external to the IRB, are typically bulky with a lot of components, thereby adding undesirable weight and expense and further making packaging of such systems more difficult.
The above-noted shortcomings of prior art solutions are addressed through the provision of a rocker arm for actuating at least one engine valve in an internal combustion engine. In an embodiment, the rocker arm comprises an actuator piston slidably disposed in an actuator piston bore formed in a motion imparting end of the rocker arm. A lash adjustment assembly is disposed in the motion imparting end of the rocker arm and comprises an internal bore. A hydraulic passage is provided in the rocker arm in fluid communication with the actuator piston bore and the internal bore of the lash adjustment assembly. A resetting assembly is disposed in the lash adjustment assembly. The resetting assembly comprises a reset slider and a checking element in fluid communication with the internal bore. The reset slider is slidably disposed in the internal bore and has a first end and a second end. The first end of the reset slider is configured to engage a valve train component or engine valve of the at least one engine valve and the second end of the reset slider has a resetting pin disposed thereon configured to contact and place the checking element in an unchecked state in response to positioning of the rocker arm when the first end contacts the valve train component or engine valve.
In an embodiment, the actuator piston bore is configured to receive hydraulic fluid from a hydraulic fluid source. The hydraulic fluid source may comprise a check valve, which check valve may be further disposed within a control valve.
In an embodiment, the actuator piston in disposed to align with a first valve of the at least one engine valve. The actuator piston may be disposed at a position closer to a motion receiving end of the rocker arm than the lash adjustment assembly. In another embodiment, the actuator piston may be inwardly biased in the actuator bore.
In an embodiment, the lash adjustment assembly comprises a lash adjustment screw threadedly mounted in the rocker arm, the lash adjustment screw comprising a radial bore in fluid communication with the internal bore and configured to register with the hydraulic passage. The internal bore may comprise a first bore and a second bore with an opening therebetween, wherein the radial bore is in fluid communication with the first bore and wherein the checking element is configured, in a checked state, to hydraulically isolate the first bore from the second bore. In this embodiment, a width of the resetting pin may be less than a width of the opening such that fluid communication between the first and second bores is established when the checking element is in the unchecked state.
In an embodiment, the reset slider is configured to lose at least a portion of valve actuation motions applied to the rocker arm before contacting the checking element. For example, the reset slider may be configured to lose auxiliary valve actuation motions applied to the rocker arm. Further to this embodiment, the reset slider may comprise a diametrically and longitudinally extending notch configured to define the portion of valve actuation motions lost by the reset slider. Further still, the lash assembly may comprise a transverse pin configured to engage the notch and limit at least some movement of the reset slider.
In an embodiment, the rocker arm further comprises a biasing element configured to bias the reset slider out of the internal bore. The biasing element may provide a bias sufficient to urge the rocker arm into contact with a valve actuation motion source when the reset slider contacts the valve train component or engine valve.
In an embodiment, the at least one engine valve comprises two engine valves, and the valve train component is a valve bridge operative connected to the two engine valves.
In an embodiment, the lash adjustment assembly comprises a venting passage in fluid communication with the internal bore and configured such that, when the resetting pin places the checking element in the unchecked state, hydraulic fluid in the actuator piston bore passes through the venting passage to an ambient environment.
In an embodiment, the reset slider comprises an e-foot movably attached to the second end of the reset slider and configured to contact the valve train component or engine valve.
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:
As used herein, phrases substantially similar to “at least one of A, B or C” are intended to be interpreted in the disjunctive, i.e., to require A or B or C or any combination thereof unless stated or implied by context otherwise. Further, phrases substantially similar to “at least one of A, B and C” are intended to be interpreted in the conjunctive, i.e., to require at least one of A, at least one of B and at least one of C unless stated or implied by context otherwise. Further still, the term “substantially” or similar words requiring subjective comparison are intended to mean “within manufacturing tolerances” unless stated or implied by context otherwise.
As used herein, the phrase “operatively connected” refers to at least a functional relationship between two elements and may encompass configurations in which the two elements are directly connected to each other, i.e., without any intervening elements, or indirectly connected to each other, i.e., with intervening elements.
The instant disclosure describes a cost friendly, rocker arm, specifically, an integrated rocker brake, that includes a resetting assembly incorporated into the rocker arm, particularly within lash adjustment assembly. The techniques described herein do not require any external reset assemblies (e.g., pedestals or contact pads) and yet provides the ability to reset valve actuations throughout the entirety of main valve actuation motions. Additionally, the rocker arm described herein may include an integrated biasing element to maintain the rocker arm in contact with the motion source, thereby avoiding the need for any external biasing component. The resetting assembly is preferably stroke limited to allow for ease of lash adjustment and minimize valve spring preload reduction between sub-base and base circle.
Referring to
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 resetting assembly 218 disposed therein. In an embodiment, the actuator boss 212, and therefore the actuator piston 214, is positioned closer to the motion receiving end 206 of the rocker arm 202 than the lash/reset assembly boss 216, and therefore the resetting assembly 218. However, it is appreciated that this position of the actuator piston 214 relative to the resetting assembly 218 is not a requirement.
The system further comprises a valve bridge 220 that spans two engine valves 222, which valves could be either exhaust or intake valves. The lash/reset assembly boss 216 and resetting assembly 218 are configured to align with a center of the valve bridge 220, whereas the actuator boss 212 and actuator piston 214 are configured to align with a bridge pin 224 disposed within the valve bridge 220 that, in turn, aligns with a first engine valve 222b. The resetting assembly 218 comprises a swivel or so-called e-foot 226 that, as described below, is maintained in constant contact with the valve bridge 220 (or other valve train component or engine valve of the two engine valves 222) due to a bias force applied by a biasing element 228, which force also biases the motion receiving end 206 of the rocker arm 202 (via the roller 210) into contact with the valve actuation motion source 240.
The 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 sub-base circle 248. In accordance with known techniques, the base circle 246 and sub-based circle 248 are separated by a distance, L, defining a maximum height for auxiliary valve actuation cam lobes 244 provided on the cam 240. Such auxiliary lobes 244, though resulting in auxiliary valve actuation motions in the rocker arm 202 are only selectively conveyed by the actuator piston 214 and are lost, in all instances, by the resetting assembly 218 as described in further detail below. On the other hand, any portions of cam lobes greater than the height of the base circle 248, e.g., the main valve actuation cam lobe 242, are conveyed by the resetting assembly 218 in all instances, and also cause reset of the actuator piston 214 during periods of auxiliary operation, e.g., engine braking, again as described in greater detail below.
That is, as shown in
On the other hand, when hydraulic fluid is supplied to the actuator piston 214 via the control valve 211, the actuator piston 214 will be maintained in an extended position (due to a locked volume of hydraulic fluid) during any auxiliary motion applied to the rocker arm 202. Such auxiliary valve actuation motions will induce contact between the actuator piston 214 and bridge pin 224 such that the auxiliary valve actuation motions are conveyed to the first engine valve 222b. At the same time, the lost motion capability of the resetting assembly 218 will prevent the auxiliary valve actuation motions from being conveyed to the center of the valve bridge 220. However, when a main event valve actuation motion is received by the rocker arm 202, the resetting assembly 218 will operate to cause the retraction (reset) of the actuator piston 214 such that both engine valves 222 are commanded solely through conveyance of the main event valve actuation through the resetting assembly 218 and valve bridge 220.
Referring now to
A hydraulic fluid source is provided by a first hydraulic passage 322 formed in the rocker arm 202 in fluid communication between an 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 a rocker shaft and the rocker arm 202 using techniques known in the art. As further known in the art, the control valve provides a selectable means (via selectable application of hydraulic fluid thereto using, for example, a suitable solenoid controlled by an engine controller) for providing hydraulic fluids to the first hydraulic passage 322 or venting hydraulic fluid from any hydraulic circuits in fluid communication with the first hydraulic passage 322. Because, as described in greater detail below, the resetting assembly 218 provides another technique for evacuating hydraulic fluid, the venting capability of the control valve 211 is not a requirement. As such, the control valve 211, which otherwise includes a check valve disposed therein, may be replaced by a simple check valve operative permit hydraulic fluid to enter the first hydraulic passage 322, but not otherwise permit reverse flow of hydraulic fluid through the first hydraulic passage 322.
When pressurized hydraulic fluid is introduced into the first hydraulic passage 322 via the control valve 211 (or check valve) and, therefore, the actuator piston bore 302, the bias of the actuator piston spring 316 may be overcome by the hydraulic pressure acting upon the actuator piston 214, thereby causing the actuator piston 214 to extend out of the bore 302 until such time that a lower surface of the retainer 312 abuts an upper shoulder 324 of the actuator lash adjustment screw 306. In this manner, travel 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 the hydraulic fluid in the actuator piston bore 302, a hydraulic lock is established that maintains extension of the actuator piston 214 out of the bore 302 notwithstanding application of any valve actuation motions to the rocker arm 202. However, in order to prevent overextension of the engine valves 222, the resetting assembly 218 is in fluid communication with the actuator piston bore 302 via a second hydraulic passage 326 that, as described in further detail below, allows the checked hydraulic fluid in the actuator piston bore 302 to be vented prior to the rocker arm 202 experiencing full lift of a main event valve actuation motion.
Referring now to
In the illustrated example, the checking elements comprises a check ball 416 disposed in the first bore 410 and biased into contact with the check seat 414 by a check spring 418 that reacts against a check spring retainer 420. Although a check ball arrangement is illustrated in
The lash adjustment screw 404 comprises a radially extending bore 422 in fluid communication with the first bore 410 and an annular channel 424 formed on an external surface of the reset lash adjustment screw 404. The annular channel 424 is of sufficient longitudinal length so as to at least partially register with the second hydraulic passage 326 regardless of adjustments to the lash adjustment screw 404.
The reset slider 426 is slidably disposed in a downward facing open end of the second bore 412 and comprises a resetting pin 428 disposed on an upper surface of a second end of the reset slider 426 and aligned with the opening forming the check seat 414. As shown, the resetting pin 428 is integrally formed in the reset slider 426, though this is not a requirement, as it could also, for example, comprises a separate member that is attached to the reset slider 426 (e.g., in threaded fashion). At its other or first end, the reset slider 426 is configured to engage with a valve train component (e.g., the valve bridge 220; not shown) or an engine valve. For example, the first end of the reset slider 426 comprises a spherical end 430 with the e-foot 226 movably secured thereto. As best shown in
In the illustrated embodiment, the biasing element 228, preferably in the form of a compression spring, is disposed between shoulders 436, 438 respectively formed in the lash adjustment screw 404 and the reset slider 426, thereby biasing the reset slider 426 away from the lash adjustment screw 404 and rocker arm 202, i.e., out of the second bore 412. The biasing element 228 is designed to provide a sufficient force such that, when the e-foot 226 contacts the valve train component or engine valve, the force provided by the biasing element 228 against the respective shoulders 436, 438 is sufficient to cause the rocker arm 202 to be biased into contact with the valve actuation motion source.
More particularly,
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. In the various embodiments described herein, the rocker arm is depicted as pivoting about a rocker shaft. However, the instant disclosure need not be limited in this regard, and it is understood that pivoting arrangements other than about a rocker shaft may be equally employed. For example, a portion of the disclosed rocker arm (e.g., an input portion comprising the motion receiving end) may pivot about different shafts. Further, such shafts could even be mounted on other portions of the rocker arms or on separate shaft pedestals.
As described above, the hydraulic fluid source (via the first hydraulic passage 322) is disclosed as being fluid connection with the actuator piston bore 302. However, it is appreciated that this is not a requirement. In fact, the hydraulic fluid source may be in fluid communication with any part of the hydraulic circuit formed by the actuator piston bore 302, hydraulic passage 326 and internal bore 410, 412.
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.
| Number | Date | Country | |
|---|---|---|---|
| 63487341 | Feb 2023 | US |
