US20210095584A1

US20210095584A1 - Switching roller finger follower for bleeder braking

Info

Publication number: US20210095584A1
Application number: US17/118,647
Authority: US
Inventors: Mark VanWingerden
Original assignee: Eaton Intelligent Power Ltd
Current assignee: Eaton Intelligent Power Ltd
Priority date: 2018-06-12
Filing date: 2020-12-11
Publication date: 2021-04-01
Also published as: EP3807502A1; WO2019238271A1; CN112204230A

Abstract

A switching rocker arm assembly includes an inner arm, an outer arm pivotably secured to the inner arm, and a camshaft having a first lobe to contact one of the outer arm and the inner arm to perform a normal valve motion, and a second lobe to contact the other of the outer arm and the inner arm to perform at least one of: a full cycle bleeder brake exhaust valve motion, a partial cycle bleeder brake exhaust valve motion, an additional engine brake intake valve motion, and a compression relief braking exhaust valve motion.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No. PCT/EP2019/025180 filed Jun. 12, 2019, which claims priority to U.S. Provisional Application No. 62/683,904 filed on Jun. 12, 2018. The disclosure of the above application is incorporated herein by reference.

FIELD

The present disclosure generally relates to switching rocker arm assemblies for internal combustion engines and, more particularly, to a switching rocker arm assembly for engine braking operations.

BACKGROUND

A switching roller finger follower or rocker arm allows for control of valve actuation by alternating between two or more states. In some examples, the rocker arm can include multiple arms, such as an inner arm and an outer arm. In some circumstances, these arms can engage different cam lobes, such as low-lift lobes, high-lift lobes, and no-lift lobes. Mechanisms are required for switching rocker arm modes in a manner suited for operation of internal combustion engines.
Engine braking can be used to retard forces within an engine to ultimately slow a vehicle down. In a typical valve train assembly used with an engine brake, an exhaust valve is actuated by a rocker arm which engages the exhaust valve by means of a valve bridge. The rocker arm rocks in response to a cam on a rotating cam shaft and presses down on the valve bridge which itself presses down on the exhaust valve to open it. One form of engine braking includes a bleeder brake. Bleeder brakes can be used as auxiliary brakes, in addition to wheel brakes, on relatively large vehicles, for example trucks, powered by heavy or medium duty diesel engines. A bleeder brake typically includes a piston that selectively extends to a full stroke. In the full stroke, the piston can maintain an exhaust valve open a fixed amount throughout an engine cycle.
The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

SUMMARY

According to various aspects of the present disclosure, a switching rocker arm assembly is provided. In one example, the assembly includes an inner arm, an outer arm pivotably secured to the inner arm, and a camshaft having a first lobe to contact one of the outer arm and the inner arm to perform a normal valve motion, and a second lobe to contact the other of the outer arm and the inner arm to perform at least one of: a full cycle bleeder brake exhaust valve motion, a partial cycle bleeder brake exhaust valve motion, an additional engine brake intake valve motion, and a compression relief braking exhaust valve motion.
In addition to the foregoing, the described assembly may include one or more of the following features: a latching mechanism configured to selectively latch the inner arm to the outer arm; wherein when the inner arm is latched to the outer arm, the second lobe is configured to impart motion to the other of the outer arm and the inner arm to perform at least one of the following: (i) hold open an exhaust valve to perform the full cycle bleeder brake exhaust valve motion, (ii) hold open an exhaust valve to perform the partial cycle bleeder brake exhaust motion, and/or (ii) open an intake valve after a normal intake valve opening to perform an additional intake valve opening; and wherein when the inner arm is not latched to the outer arm, the other of the inner arm and the outer arm undergoes lost motion when the second lobe imparts motion thereto such that the motion is not imparted to exhaust valve.
In addition to the foregoing, the described assembly may include one or more of the following features: a biasing mechanism mounted around a spring retainer and including a first end engaged with the outer arm and a second end engaged with the inner arm; a pair of outer rollers rotatably coupled to the outer arm, wherein the first lobe comprises a pair of first lobes configured to selectively engage the pair of outer rollers to impart motion to the outer arm, and an inner roller rotatably coupled to the inner arm, wherein the second lobe is configured to selectively engage the inner roller to impart motion to the inner arm; and a deactivating hydraulic lash adjuster, the outer arm configured to pivot about the deactivating hydraulic lash adjuster.
In addition to the foregoing, the described assembly may include one or more of the following features: wherein the full cycle bleeder brake exhaust valve motion holds an exhaust valve open throughout intake, compression, and expansion cycles of an engine, wherein the partial cycle bleeder brake exhaust valve motion holds the exhaust valve open throughout the compression and expansion cycles of the engine, wherein the additional engine brake intake valve motion adds a small intake lift opposite a normal intake event, and wherein the compression relief braking exhaust valve motion includes at least one compression relief event and at least one brake gas recirculation event; wherein the second lobe is an enlarged base circle having a first radius larger than a second radius of a base circle of the first lobe, wherein the enlarged base circle is configured to contact the other of the outer arm and the inner arm to perform the full cycle bleeder brake exhaust valve motion; and wherein the second lobe has a lengthened lobe with a first radius larger than a second radius of a base circle of the first lobe, wherein the lengthened lobe is configured to contact the other of the outer arm and the inner arm to perform the partial cycle bleeder brake exhaust valve motion.
According to various aspects of the present disclosure, a valvetrain assembly configured to perform an engine braking operation is provided. In one example, the valvetrain assembly includes a first switching rocker arm assembly having a first outer arm pivotably secured to a first inner arm, and a camshaft having a first lobe to contact one of the first outer arm and the first inner arm to perform a normal valve motion, and a second lobe to contact the other of the first outer arm and the first inner arm to perform at least one of (i) a full cycle bleeder brake exhaust valve motion, (ii) a partial cycle bleeder brake exhaust valve motion, (iii) an additional engine brake intake valve motion, and (iv) compression relief braking exhaust valve motion.
In addition to the foregoing, the described valvetrain assembly may include one or more of the following features: a second switching rocker arm assembly having a second outer arm pivotably secured to a second inner arm, and the camshaft having a third lobe to contact one of the second outer arm and the second inner arm to perform a normal valve motion, and a fourth lobe to contact the other of the second outer arm and the second inner arm to perform the additional engine brake intake valve motion, wherein the second lobe contacting the other of the first outer arm and the first inner arm performs at least one of (i) the full cycle bleeder brake exhaust valve motion, and (ii) the partial cycle bleeder brake exhaust valve motion.
In addition to the foregoing, the described valvetrain assembly may include one or more of the following features: wherein the second lobe is an enlarged base circle having a first radius larger than a second radius of a base circle of the first lobe, wherein the enlarged base circle is configured to contact the other of the first outer arm and the first inner arm to perform the full cycle bleeder brake exhaust valve motion; wherein the second lobe has a lengthened lobe with a first radius larger than a second radius of a base circle of the first lobe, wherein the lengthened lobe is configured to contact the other of the first outer arm and the first inner arm to perform the partial cycle bleeder brake exhaust valve motion; and wherein the fourth lobe has a smaller lobe with a first radius smaller than a second radius of the first lobe, wherein the smaller lobe is configured to contact the other of the second outer arm and the second inner arm to perform the additional engine brake intake valve motion.
In addition to the foregoing, the described valvetrain assembly may include one or more of the following features: wherein the first switching rocker arm assembly includes a first latching mechanism configured to selectively latch the first inner arm to the first outer arm, and wherein the second switching rocker arm assembly includes a second latching mechanism configured to selectively latch the second inner arm to the second outer arm; and wherein when the first inner arm is latched to the first outer arm, the second lobe is configured to impart motion to the other of the first outer arm and the first inner arm to perform at least one of the following: (i) hold open an exhaust valve to perform the full cycle bleeder brake exhaust valve motion, and (ii) hold open an exhaust valve to perform the partial cycle bleeder brake exhaust motion, and wherein when the second inner arm is latched to the second outer arm, the fourth lobe is configured to impart motion to the other of the second outer arm and the second inner arm to open an intake valve after a normal intake valve opening to perform the additional engine brake intake valve motion.
In addition to the foregoing, the described valvetrain assembly may include one or more of the following features:
In addition to the foregoing, the described valvetrain assembly may include one or more of the following features: wherein when the first inner arm is not latched to the first outer arm, the other of the first outer arm and the first inner arm undergoes lost motion when the second lobe imparts motion thereto such that the motion is not imparted to the exhaust valve, and wherein when the second inner arm is not latched to the second outer arm, the other of the second outer arm and the second inner arm undergoes lost motion when the fourth lobe imparts motion thereto such that the motion is not imparted to the intake valve.
According to various aspects of the present disclosure, a method of operating a valvetrain assembly comprising a first switching rocker arm assembly having a first outer arm pivotably secured to a first inner arm, and a camshaft having a first lobe to contact one of the first outer arm and the first inner arm, and a second lobe to contact the other of the first outer arm and the first inner arm is provided. The method includes operating in a normal mode where the first inner arm is unlatched from the first outer arm such that (i) when the first lobe contacts the one of the first outer arm and the first inner arm, motion is imparted to an exhaust valve to perform a normal exhaust valve opening, and (ii) when the second lobe contacts the other of the first outer arm and the first inner arm, the other of the first outer arm and the first inner arm undergoes lost motion such that motion is not imparted to the exhaust valve. The method further includes operating in an engine brake mode where the first inner arm is latched to the first outer arm such that (i) when the first lobe contacts the one of the first outer arm and the first inner arm, motion is imparted to the exhaust valve to perform the normal exhaust valve opening, and (ii) when the second lobe contacts the other of the first outer arm and the first inner arm, the other of the first outer arm and the first inner arm imparts motion to the exhaust valve to perform at least one of (a) a full cycle bleeder brake exhaust valve motion, and (b) a partial cycle bleeder brake exhaust valve motion.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:

FIG. 1 is a perspective view of a valvetrain assembly constructed in accordance to one example of the present disclosure;

FIG. 2 is an enlarged view of a switching rocker arm assembly of the valvetrain assembly shown in FIG. 1;

FIG. 3 is a perspective view of another switching rocker arm assembly that may be used with the valvetrain assembly shown in FIG. 1, constructed in accordance to one example of the present disclosure;

FIG. 4A is a side view of an example camshaft that may be used with the valvetrain assembly shown in FIG. 1;

FIG. 4B is a side view of another example camshaft that may be used with the valvetrain assembly shown in FIG. 1;

FIG. 4C is a side view of yet another example camshaft that may be used with the valvetrain assembly shown in FIG. 1;

FIG. 5A is a graph of an example full-cycle bleeder brake valve lift profile of the valvetrain assembly shown in FIGS. 1-4;

FIG. 5B is a graph of an example partial-cycle bleeder brake valve lift profile of the valvetrain assembly shown in FIGS. 1-4;

FIG. 6A is a graph of an example two-stroke full-cycle bleeder brake valve lift profile of the valvetrain assembly shown in FIGS. 1-4;

FIG. 6B is a graph of an example two-stroke partial-cycle bleeder brake valve lift profile of the valvetrain assembly shown in FIGS. 1-4; and

FIG. 7 is a graph of an example compression relief and brake gas recirculation valve lift profile of the valvetrain assembly shown in FIGS. 1-4.

DETAILED DESCRIPTION

Described herein are variable valve actuation (VVA) valvetrain systems for performing engine braking events such as bleeder braking operations. The systems include a switchable roller finger follower (SRFF) that may be utilized with either an intake valve or exhaust valve is configured to interface with a multi-lobe camshaft to selectively add or eliminate the engine braking events. A hydraulic lash adjuster (HLA) pivot may be included with a deactivating element to provide further functionality.
During bleeder engine braking, in addition to the main exhaust valve event, one or more exhaust valves are held open throughout the remaining engine cycles (i.e., the intake, compression, and expansion cycles) for a full-cycle bleeder brake or during a portion of the remaining engine cycles (i.e., the compression and expansion cycles) for a partial-cycle bleeder brake.
With initial reference to FIG. 1, a Type II valvetrain arrangement constructed in accordance to one example of the present disclosure is shown and generally identified at reference 10. In the example embodiment, the valvetrain arrangement 10 can generally include a switching rocker arm assembly 12, a three lobed camshaft 14, a lash adjuster 16, a valve 18, a spring 20, and a spring retainer 22. Additionally, lash adjuster 16 can include a hydraulic lash adjuster (HLA) pivot 24, which optionally includes a deactivating element with individual control over each engine valve 18.
In the example embodiment, the camshaft 14 can have first and second high- lift lobes 26, 28 and a low-lift lobe 30. In one configuration, high- lift lobes 26, 28 are configured to perform a normal valve lift, and low-low lift lobe 30 includes features configured to perform an engine braking event (e.g., bleeder brake operation). However, it will be appreciated that other arrangements are contemplated such as, for example, one high-lift lobe for normal lift and two low-lift lobes for engine braking events. In other arrangements, no lobes are provided to perform the engine braking events.
With additional reference to FIG. 2, in the example embodiment, the switching rocker arm assembly 12 has an outer arm 40 and an inner arm 42 that pivot about a pivot axle 44. A pair of biasing mechanisms 46 (e.g., torsion springs) are each mounted around a spring retainer 48 and include a first end 50 engaged with the outer arm 40, and a second end 52 engaged with the inner arm 42 to bias the inner arm 42 into an upward position. In the example embodiment, a pair of outer rollers 54 are rotatably coupled to the outer arm 40, and an inner roller 56 is rotatably coupled to the inner arm 42. During operation, the high- lift lobes 26 and 28 contact the outer arm 40 via outer rollers 54, while the low-lift lobe 30 contacts the inner arm 42 via inner roller 56. However, it will be appreciated that rocker arm assembly 12 may include sliding or contact pads instead of rollers. The lobes are configured to cause periodic downward movement of the outer arm 40 and the inner arm 42. This downward motion is transferred to the valve 18 by the outer arm 40, thereby opening the valve 18.
In the example embodiment, the rocker arm assembly 12 can include a latching mechanism 58 for latching the inner arm 42 to the outer arm 40. Although not shown, in some configurations, latching mechanism 58 can include a latch pin that moves between an extended position and a retracted position relative to a latch pin bore in a latch pin housing. It will be appreciated that latching mechanism 58 can be actuated in any suitable manner such as, for example, hydraulically or electrically. As such, rocker arm assembly 12 is switchable between a normal mode and a bleeder brake mode. In the normal mode, the outer arm 40 is not latched to the inner arm. In the bleeder brake mode, the outer arm 40 is latched to the inner arm 42.
When rocker arm assembly 12 is in the normal mode (unlatched), the high- lift lobes 26, 28 periodically push the outer arm 40 downward via outer rollers 54, which motion is transferred to the valve 18. Similarly, the low-lift lobe 30 pushes the inner arm 42 downward via inner roller 56. However, because the inner arm 42 is not latched to the outer arm 40, the downward motion causes inner arm 42 to pivot about a pivot axle 44 without transferring motion to the valve 18. As such, in the normal mode, the inner arm 42 operates in lost motion.
When rocker arm assembly 12 is in the bleeder brake mode (latched), the high- lift lobes 26, 28 periodically push the outer arm 40 downward, which motion is transferred to the valve 18. The low-lift 30 constantly or periodically pushes the inner arm 42 downward, and because the outer arm 40 is latched to the inner arm 42, the low-lift motion is transferred from the inner arm 42 to the outer arm 40 and further to valve 18.
It will be appreciated that the rocker arm assembly 12 is provided by way of example only. In this regard, the configuration of the rocker arm assembly 12 is not limited to the configuration of the rocker arm assembly 12 shown in FIG. 1, and it will be appreciated that the rocker arm assembly 12 can be configured to have the outer arm normally latched to the inner arm or unlatched to the inner arm depending on configuration and/or application. Moreover, the camshaft 14 can have one or two lobes (two shown in FIG. 1) for normal lift (e.g., normal exhaust motion or normal intake motion), and the remainder one or two lobes (one shown in FIG. 1) can have an increased base circle (e.g., FIG. 4A) or a smaller, lengthened lobe (e.g., FIG. 4B) to prevent valve 18 from closing to thereby perform engine braking motion or events.
For example, as shown in FIG. 4A, camshaft 14 can include low-lift lobe 30 with a no-lobed, increased base circle 60 having a radius ‘r1’ that is larger than a radius ‘r2’ of a base circle 62 of the high- lift lobes 26, 28. In the example embodiment, increased base circle 60 is configured to constantly push the inner arm 42. In this way, while in the latched mode, the valve 18 is maintained open to enable bleeding of cylinder air to thereby perform a full-cycle bleeder type engine braking, for example as shown in FIG. 5A.
In another example shown in FIG. 4B, camshaft 14 can include low-lift lobe 30 with a lengthened lobe 64 having a radius ‘r3’ that is larger than radius ‘r2’ of the base circle 60 of high- lift lobes 26, 28. As illustrated, lengthened lobe 64 extends only partially about a circumference of the low-lift lobe 30. Accordingly, the lengthened lobe 64 is configured to periodically push the inner arm 42 downward. In this way, while in the latched mode, the valve 18 is maintained open during a portion of the cycle to enable bleeding of cylinder air to thereby perform a partial-cycle bleeder type engine braking, for example as shown in FIG. 5B.
Turning now to additional configurations, it will be appreciated that the described rocker arm assembly is advantageously not limited to exhaust valves and may also be utilized with intake valves of the engine to interface with all three lobes and selectively add, eliminate, or enhance engine braking events.
FIG. 3 illustrates an alternative switching rocker arm assembly 120 that may be utilized within valvetrain assembly 10 to add a second bleeder event by adding a small intake lift at approximately 180° opposite a normal intake event. Such an operation can increase the power of a bleeder brake operation by allowing more air into the cylinder during the second intake event, which occurs during a normal power stroke. In the example embodiment, switching rocker arm assembly 120 is configured to operate with valvetrain components including camshaft 14, lash adjuster 16, engine valve 18, spring 20, spring retainer 22, and optional deactivating HLA pivot 24.
In the example embodiment, the switching rocker arm assembly 12 has an outer arm 140 and an inner arm 142 that pivot about a pivot axle 144. A biasing mechanism 146 (e.g., torsion spring) is mounted around pivot axle 144 and is configured to bias the inner arm 142 into an upward position. In the example embodiment, a pair of outer rollers 154 are rotatably coupled to the outer arm 140, and an inner roller 156 is rotatably coupled to the inner arm 142. During operation, the high- lift lobes 26 and 28 contact the outer arm 140 via outer rollers 154, while the low-lift lobe 30 contacts the inner arm 142 via inner roller 156. However, it will be appreciated that rocker arm assembly 120 may include sliding or contact pads instead of rollers. The lobes are configured to cause periodic downward movement of the outer arm 140 and the inner arm 142. This downward motion is transferred to the intake valve 18 by the outer arm 140, thereby opening the intake valve 18.
In the example embodiment, the rocker arm assembly 12 can include a latching mechanism 158 for latching the inner arm 142 to the outer arm 140. Although not shown, in some configurations, latching mechanism 158 can include a latch pin that moves between an extended position and a retracted position relative to a latch pin bore in a latch pin housing. It will be appreciated that latching mechanism 158 can be actuated in any suitable manner such as, for example, hydraulically or electrically. As such, rocker arm assembly 120 is switchable between a normal intake mode and an intake event engine brake mode. In the normal mode, the outer arm 140 is not latched to the inner arm. In the intake event engine brake mode, the outer arm 140 is latched to the inner arm 142.
When rocker arm assembly 120 is in the normal intake mode (unlatched), the high- lift lobes 26, 28 periodically push the outer arm 140 downward via outer rollers 154, which motion is transferred to the valve 18. Similarly, the low-lift lobe 30 pushes the inner arm 142 downward via inner roller 156. However, because the inner arm 142 is not latched to the outer arm 140, the downward motion causes inner arm 142 to pivot about a pivot axle 144 without transferring motion to the valve 18. As such, in the normal mode, the inner arm 142 operates in lost motion.
When rocker arm assembly 12 is in the intake event engine brake mode (latched), the high- lift lobes 26, 28 periodically push the outer arm 140 downward, which motion is transferred to the valve 18. The low-lift lobe 30 constantly or periodically pushes the inner arm 142 downward, and because the outer arm 140 is latched to the inner arm 142, the low-lift motion is transferred from the inner arm 142 to the outer arm 140 and further to valve 18.
It will be appreciated that the rocker arm assembly 120 is provided by way of example only. In this regard, the configuration of the rocker arm assembly 120 is not limited to the configuration of the rocker arm assembly 120 shown in FIG. 3, and it will be appreciated that the rocker arm assembly 120 can be configured to have the outer arm normally latched to the inner arm or unlatched to the inner arm depending on configuration and/or application. Moreover, the camshaft 14 can have one or two lobes for normal lift (e.g., normal exhaust motion or normal intake motion), and the remainder one or two lobes can have a smaller lobe (e.g., FIG. 4C) to perform a smaller, duplicate intake event approximately opposite the normal intake event.
For example, as shown in FIG. 4C, camshaft 14 can include low-lift lobe 30 with a smaller lobe 66 having a radius ‘r4’ that is smaller than a radius ‘r5’ of the high- lift lobes 26, 28. Moreover, the smaller lobe 156 is positioned 180° or approximately 180° relative to the high- lift lobes 26, 28. Accordingly, the smaller lobe 156 is configured to periodically push the inner arm 142 downward while in the latched mode. In this way, the intake valve is slightly opened to perform a small, supplemental intake lift event at 180° or approximately 180° opposite the normal intake event. As noted, this can provide additional power during the bleeder brake event.
FIG. 5A shows a graph 200 illustrating an example full-cycle bleeder brake operation where valvetrain assembly 10 utilizes the camshaft configuration shown in FIG. 4A with camshaft 14 including low-lift lobe 30 with the increased base circle 60. In the example embodiment, line 202 indicates the motion of a first exhaust valve 18 associated with a first rocker arm assembly 12 where camshaft 14 contacts the first rocker arm assembly 12 to operate with a normal exhaust valve opening profile.
Line 204 indicates motion of a second exhaust valve 18 associated with a second rocker arm assembly 12 where camshaft low-lift lobe 30, with the increased base circle 60, contacts the inner roller 56 in the latched, bleeder brake mode. In this way, the increased base circle 60 prevents the second exhaust valve 18 from closing by riding on the inner roller 56. The second exhaust valve 18 then goes through a normal lift during normal exhaust motion when high- lift lobes 26, 28 contact outer rollers 54, and subsequently returns to being held slightly open (bleeder brake operation).
Thus, the second rocker arm assembly 12 can be controlled (e.g., via a controller) to hold the second exhaust valve 18 open a predetermined amount to perform a bleeder brake operation during all or substantially all of the intake, compression, and expansion strokes of the piston, and then open second exhaust valve 18 normally during the exhaust stroke of the piston. Line 206 indicates motion of a first intake valve 18 operating under normal intake motion, and line 208 indicates motion of an associated engine piston.
FIG. 5B shows a graph 210 illustrating an example partial-cycle bleeder brake operation where valvetrain assembly 10 utilizes the camshaft configuration shown in FIG. 4B with camshaft 14 including low-lift lobe 30 with lengthened lobe 64. In the example embodiment, line 212 indicates motion of a first exhaust valve 18 associated with a first rocker arm assembly 12 where camshaft 14 contacts the first rocker arm assembly 12 to operate with a normal exhaust valve opening profile.
Line 214 indicates motion of a second exhaust valve 18 associated with a second rocker arm assembly 12 where camshaft low-lift lobe 30 (with the lengthened lobe 64) contacts the inner roller 56 in the latched, bleeder brake mode. In this way, lengthened lobe 64 periodically prevents the valve 18 from closing by riding on the inner roller 56. The second exhaust valve 18 then goes through a normal lift during normal exhaust (via high-lift lobes 26, 28), intake, and expansion motion and then returns to being held slightly open (bleeder brake operation).
Thus, the second rocker arm assembly 12 can be controlled (e.g., via controller) to hold the second exhaust valve 18 open a predetermined amount to perform a bleeder brake operation during all or substantially all of the compression stroke of the piston, and then move the second exhaust valve 18 normally during the remaining piston motion. Line 216 indicates motion of a first intake valve 18 operating under normal intake motion, and line 218 indicates motion of an associated engine piston (not shown).
FIG. 6A shows a graph 220 illustrating an example two-stroke full-cycle bleeder brake operation. In one example arrangement, valvetrain assembly 10 includes an intake and exhaust SRFF, and optional cylinder deactivation (CDA) on the other intake and exhaust. In the example embodiment, valvetrain assembly 10 utilizes the camshaft configurations shown in FIGS. 4A and 4C with camshaft 14 including one low-lift lobe 30 with the increased base circle 60, and another low-lift lobe 30 with smaller intake lobe 66.
In the example embodiment, line 222 indicates the motion of a first exhaust valve 18 associated with a first rocker arm assembly 12 where camshaft 14 contacts the first rocker arm assembly 12 to operate with a normal exhaust valve opening profile. Line 224 indicates motion of a second exhaust valve 18 associated with a second rocker arm assembly 12 where camshaft 14 includes low-lift lobe 30 with the increased base circle 60 to contact the inner roller 56 in the latched, bleeder brake mode. In this way, the increased base circle 60 prevents the valve 18 from closing by riding on the inner roller 56. The second exhaust valve 18 then goes through a normal lift during normal exhaust motion when high- lift lobes 26, 28 contact outer rollers 54, and subsequently returns to being held slightly open (bleeder brake operation).
Line 226 indicates motion of a first intake valve 18 associated with a third rocker arm assembly 120 where camshaft 14 includes a third low-lift lobe 30 (with smaller intake lobe 66) to contact the inner roller 156 in the latched, intake event engine brake mode. In this way, the third rocker arm assembly 120 performs an additional intake engine brake event and adds a supplemental intake lift 228 during the expansion stroke of the piston.
Thus, the second rocker arm assembly 12 is controlled (e.g., via a controller) to hold the second exhaust valve 18 open a predetermined amount to perform a bleeder brake operation during all or substantially all of the intake, compression, and expansion strokes of the piston, and then open second exhaust valve 18 normally during the exhaust stroke of the piston, while also adding an additional, smaller intake event to the enable increased power to the bleeder brake.
FIG. 6B shows a graph 230 illustrating an example two-stroke partial-cycle bleeder brake operation. In one example arrangement, valvetrain assembly 10 includes an intake and exhaust SRFF, and optional CDA on the other intake and exhaust. In the example embodiment, valvetrain assembly 10 utilizes the camshaft configurations shown in FIGS. 4B and 4C with camshaft 14 including one low-lift lobe 30 with the lengthened lobe 64, and another low-lift lobe 30 with smaller intake lobe 66.
In the example embodiment, line 232 indicates the motion of a first exhaust valve 18 associated with a first rocker arm assembly 12 where camshaft 14 contacts the first rocker arm assembly 12 to operate with a normal exhaust valve opening profile. Line 234 indicates motion of a second exhaust valve 18 associated with a second rocker arm assembly 12 where camshaft low-lift lobe 30 (with the lengthened lobe 64) contacts the inner roller 56 in the latched, bleeder brake mode. In this way, lengthened lobe 64 periodically prevents the valve 18 from closing by riding on the inner roller 56. The second exhaust valve 18 then goes through a normal lift during normal exhaust (via high-lift lobes 26, 28), intake, and expansion motion and then returns to being held slightly open (bleeder brake operation).
Line 236 indicates motion of a first intake valve 18 associated with a third rocker arm assembly 120 where camshaft 14 includes a third low-lift lobe 30 (with smaller intake lobe 66) to contact the inner roller 156 in the latched, intake event engine brake mode. In this way, the third rocker arm assembly 120 performs an additional intake engine brake event and adds a supplemental intake lift 228 during the expansion stroke of the piston.
Thus, the second rocker arm assembly 12 is controlled (e.g., via controller) to hold the second exhaust valve 18 open a predetermined amount to perform a bleeder brake operation during all or substantially all of the compression stroke of the piston, and then move the second exhaust valve 18 normally during the remaining piston motion, while also adding an additional, smaller intake event to the enable increased power to the bleeder brake.
FIG. 7 shows a graph 240 illustrating an example compression relief and brake gas recirculation operation. In the one example embodiment, valvetrain assembly 10 utilizes a camshaft configuration low-lift lobe 30 having dual lobes (not shown) or an additional lobe input to produce the illustrated valve lift.
In the example embodiment, line 242 indicates the motion of a first exhaust valve 18 associated with a first rocker arm assembly 12 where camshaft 14 contacts the first rocker arm assembly 12 to operate with a normal exhaust valve opening profile. Line 244 indicates motion of a second exhaust valve 18 associated with a second rocker arm assembly 12 where camshaft low-lift lobe 30 (with the dual lobes) contacts the inner roller 56 in a latched, brake mode. A first lift 246 provides a brake gas recirculation event that allows air into the cylinder from the exhaust manifold during the intake stroke to pre-charge the cylinder, and a second lift 248 provides a compression relief event at the end of the compression stroke, to thereby provide compression relief braking. In this way, low-lift lobe 30 periodically opens valve 18 to enable compression relief braking. The second exhaust valve 18 then goes through a normal lift during normal exhaust (via high-lift lobes 26, 28) motion.
Thus, the second rocker arm assembly 12 is controlled (e.g., via controller) to open the second exhaust valve 18 at predetermined times to perform a compression relief braking operation during all or part of the intake and compression stroke of the piston, and then move the second exhaust valve 18 normally during the remaining piston motion.
Described herein are systems and methods for providing bleeder brake event functionality and additional engine brake intake event functionality to a valvetrain assembly with switching rocker arms. The systems include one or more switching rocker arm assemblies movable between an unlatched, normal mode and a latched, engine brake mode. A camshaft includes first lobes to engage the rocker arm assembly and perform a normal lift, and second lobes to engage the rocker arm assembly and selectively perform a bleeder brake operation. An optional camshaft includes first lobes to engage an intake rocker arm assembly and perform a normal intake lift, and second lobes to engage the intake rocker arm and perform a smaller, supplemental intake lift to improve the bleeder brake operation.
As used herein, the term controller refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality.
The foregoing description of the examples has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular example are generally not limited to that particular example, but, where applicable, are interchangeable and can be used in a selected example, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Claims

What is claimed is:

1. A switching rocker arm assembly comprising:

an inner arm;

an outer arm pivotably secured to the inner arm; and

a camshaft having a first lobe to contact one of the outer arm and the inner arm to perform a normal valve motion, and a second lobe to contact the other of the outer arm and the inner arm to perform at least one of:

a full cycle bleeder brake exhaust valve motion;

a partial cycle bleeder brake exhaust valve motion;

an additional engine brake intake valve motion; and

compression relief braking exhaust valve motion.

2. The assembly of claim 1, further comprising a latching mechanism configured to selectively latch the inner arm to the outer arm.

3. The assembly of claim 1, wherein when the inner arm is latched to the outer arm, the second lobe is configured to impart motion to the other of the outer arm and the inner arm to perform at least one of the following: (i) hold open an exhaust valve to perform the full cycle bleeder brake exhaust valve motion, (ii) hold open an exhaust valve to perform the partial cycle bleeder brake exhaust motion, and/or (ii) open an intake valve after a normal intake valve opening to perform an additional intake valve opening.

4. The assembly of claim 3, wherein when the inner arm is not latched to the outer arm, the other of the inner arm and the outer arm undergoes lost motion when the second lobe imparts motion thereto such that the motion is not imparted to exhaust valve.

5. The assembly of claim 2, further comprising a biasing mechanism mounted around a spring retainer and including a first end engaged with the outer arm and a second end engaged with the inner arm.

6. The assembly of claim 5, further comprising:

a pair of outer rollers rotatably coupled to the outer arm, wherein the first lobe comprises a pair of first lobes configured to selectively engage the pair of outer rollers to impart motion to the outer arm; and

an inner roller rotatably coupled to the inner arm, wherein the second lobe is configured to selectively engage the inner roller to impart motion to the inner arm.

7. The assembly of claim 1, further comprising a deactivating hydraulic lash adjuster, the outer arm configured to pivot about the deactivating hydraulic lash adjuster.

8. The assembly of claim 1, wherein the full cycle bleeder brake exhaust valve motion holds an exhaust valve open throughout intake, compression, and expansion cycles of an engine,

wherein the partial cycle bleeder brake exhaust valve motion holds the exhaust valve open throughout the compression and expansion cycles of the engine,

wherein the additional engine brake intake valve motion adds a small intake lift opposite a normal intake event, and

wherein the compression relief braking exhaust valve motion includes at least one compression relief event and at least one brake gas recirculation event.

9. The assembly of claim 1, wherein the second lobe is an enlarged base circle having a first radius larger than a second radius of a base circle of the first lobe, wherein the enlarged base circle is configured to contact the other of the outer arm and the inner arm to perform the full cycle bleeder brake exhaust valve motion.

10. The assembly of claim 1, wherein the second lobe has a lengthened lobe with a first radius larger than a second radius of a base circle of the first lobe, wherein the lengthened lobe is configured to contact the other of the outer arm and the inner arm to perform the partial cycle bleeder brake exhaust valve motion.

11. A valvetrain assembly configured to perform an engine braking operation, the valvetrain assembly comprising:

a first switching rocker arm assembly having a first outer arm pivotably secured to a first inner arm; and

a camshaft having a first lobe to contact one of the first outer arm and the first inner arm to perform a normal valve motion, and a second lobe to contact the other of the first outer arm and the first inner arm to perform at least one of (i) a full cycle bleeder brake exhaust valve motion, (ii) a partial cycle bleeder brake exhaust valve motion, (iii) an additional engine brake intake valve motion, and (iv) compression relief braking exhaust valve motion.

12. The valvetrain assembly of claim 11, further comprising:

a second switching rocker arm assembly having a second outer arm pivotably secured to a second inner arm; and

the camshaft having a third lobe to contact one of the second outer arm and the second inner arm to perform a normal valve motion, and a fourth lobe to contact the other of the second outer arm and the second inner arm to perform the additional engine brake intake valve motion,

wherein the second lobe contacting the other of the first outer arm and the first inner arm performs at least one of (i) the full cycle bleeder brake exhaust valve motion, and (ii) the partial cycle bleeder brake exhaust valve motion.

13. The valvetrain assembly of claim 12, wherein the second lobe is an enlarged base circle having a first radius larger than a second radius of a base circle of the first lobe, wherein the enlarged base circle is configured to contact the other of the first outer arm and the first inner arm to perform the full cycle bleeder brake exhaust valve motion.

14. The valvetrain assembly of claim 12, wherein the second lobe has a lengthened lobe with a first radius larger than a second radius of a base circle of the first lobe, wherein the lengthened lobe is configured to contact the other of the first outer arm and the first inner arm to perform the partial cycle bleeder brake exhaust valve motion.

15. The valvetrain assembly of claim 12, wherein the fourth lobe has a smaller lobe with a first radius smaller than a second radius of the first lobe, wherein the smaller lobe is configured to contact the other of the second outer arm and the second inner arm to perform the additional engine brake intake valve motion.

16. The valvetrain assembly of claim 12, wherein the first switching rocker arm assembly includes a first latching mechanism configured to selectively latch the first inner arm to the first outer arm; and

wherein the second switching rocker arm assembly includes a second latching mechanism configured to selectively latch the second inner arm to the second outer arm.

17. The valvetrain assembly of claim 16, wherein when the first inner arm is latched to the first outer arm, the second lobe is configured to impart motion to the other of the first outer arm and the first inner arm to perform at least one of the following: (i) hold open an exhaust valve to perform the full cycle bleeder brake exhaust valve motion, and (ii) hold open an exhaust valve to perform the partial cycle bleeder brake exhaust motion, and

wherein when the second inner arm is latched to the second outer arm, the fourth lobe is configured to impart motion to the other of the second outer arm and the second inner arm to open an intake valve after a normal intake valve opening to perform the additional engine brake intake valve motion.

18. The valvetrain assembly of claim 17, wherein when the first inner arm is not latched to the first outer arm, the other of the first outer arm and the first inner arm undergoes lost motion when the second lobe imparts motion thereto such that the motion is not imparted to the exhaust valve, and

wherein when the second inner arm is not latched to the second outer arm, the other of the second outer arm and the second inner arm undergoes lost motion when the fourth lobe imparts motion thereto such that the motion is not imparted to the intake valve.

19. The valvetrain assembly of claim 18, further comprising:

a first pair of outer rollers rotatably coupled to the first outer arm, wherein the first lobe comprises a pair of first lobes configured to selectively engage the first pair of outer rollers to impart motion to the first outer arm;

a first inner roller rotatably coupled to the first inner arm, wherein the second lobe is configured to selectively engage the first inner roller to impart motion to the first inner arm;

a second pair of outer rollers rotatably coupled to the second outer arm, wherein the third lobe comprises a pair of third lobes configured to selectively engage the pair of second outer rollers to impart motion to the second outer arm; and

a second inner roller rotatably coupled to the second inner arm, wherein the fourth lobe is configured to selectively engage the second inner roller to impart motion to the second inner arm.

20. A method of operating a valvetrain assembly comprising a first switching rocker arm assembly having a first outer arm pivotably secured to a first inner arm, and a camshaft having a first lobe to contact one of the first outer arm and the first inner arm, and a second lobe to contact the other of the first outer arm and the first inner arm, the method comprising:

operating in a normal mode where the first inner arm is unlatched from the first outer arm such that (i) when the first lobe contacts the one of the first outer arm and the first inner arm, motion is imparted to an exhaust valve to perform a normal exhaust valve opening, and (ii) when the second lobe contacts the other of the first outer arm and the first inner arm, the other of the first outer arm and the first inner arm undergoes lost motion such that motion is not imparted to the exhaust valve; and

operating in an engine brake mode where the first inner arm is latched to the first outer arm such that (i) when the first lobe contacts the one of the first outer arm and the first inner arm, motion is imparted to the exhaust valve to perform the normal exhaust valve opening, and (ii) when the second lobe contacts the other of the first outer arm and the first inner arm, the other of the first outer arm and the first inner arm imparts motion to the exhaust valve to perform at least one of (a) a full cycle bleeder brake exhaust valve motion, and (b) a partial cycle bleeder brake exhaust valve motion.