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Title:
VALVE ACTUATION SYSTEM
Document Type and Number:
WIPO Patent Application WO/2014/152944
Kind Code:
A1
Abstract:
Described herein is a valve actuation system for an internal combustion engine having a fluid port includes a camshaft that is rotatably coupled to the internal combustion engine. The camshaft includes a first lobe that has a non-round profile and a second lobe. In some implementations of the system, the second lobe has a round profile. The system also includes a rocker lever that is pivotally coupled to the internal combustion engine. The rocker lever includes a first arm that is operably coupled to the fluid port to open and close the fluid port. The rocker lever also includes a second arm comprising a first follower in engagement with the first lobe and a second follower selectively engageable with the second lobe. Engagement between the first follower and the first lobe and engagement between the second follower and the second lobe controls operation of the first arm.

Inventors:
LYNCH BRADFORD L (US)
Application Number:
PCT/US2014/028350
Publication Date:
September 25, 2014
Filing Date:
March 14, 2014
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
LYNCH BRADFORD L (US)
International Classes:
F01L1/24
Foreign References:
US7392772B22008-07-01
US4796573A1989-01-10
US2764141A1956-09-25
US7861680B22011-01-04
US7047925B22006-05-23
US20130306016A12013-11-21
Attorney, Agent or Firm:
BROWN, Marshall, J. et al. (3000 K St. NW.Washington, DC, US)
Download PDF:
Claims:
What is claimed is:

1. A valve actuation system for an internal combustion engine having a fluid port, comprising:

a camshaft rotatably coupled to the internal combustion engine, the camshaft comprising a first lobe having a non-round profile and a second lobe;

a rocker lever pivotally coupled to the internal combustion engine, the rocker lever comprising:

a first arm operably coupled to the fluid port to open and close the fluid port, a second arm,

a first follower in engagement with the first lobe, and

a second follower selectively engageable with the second lobe,

wherein engagement between the first follower and the first lobe and engagement between the second follower and the second lobe controls operation of the first arm.

2. The valve actuation system of claim 1 , wherein the second lobe has a round profile.

3. The valve actuation system of claim 1 , wherein the first follower is translationally fixed relative to the second arm, and the second follower is translationally movable relative to the second arm.

4. The valve actuation system of claim 3, wherein the second arm comprises a channel within which the second follower is translationally movable.

5. The valve actuation system of claim 4, wherein the channel contains a pressurized fluid, and wherein the second follower is selectively engageable with the second lobe by increasing a pressure of the pressurized fluid within the channel.

6. The valve actuation system of claim 3, wherein movement of the second follower relative to the second arm is selectively fixed to selectively engage the second follower with the second lobe.

7. The valve actuation system of claim 1, wherein engagement between the first follower and the first lobe to open the fluid port is based on a rotational speed of the camshaft, and engagement between the second follower and the second lobe to open the fluid port is based independently of the rotational speed of the camshaft.

8. The valve actuation system of claim 1, wherein the fluid valve is a combustion chamber exhaust valve, and wherein the first follower engages the first lobe to open the fluid port for a scheduled combustion exhaust release event in a combustion cycle, and the second follower engages the second lobe to open the fluid valve for an engine breaking event.

9. The valve actuation system of claim 1, wherein at least one of the first and second followers comprises a roller.

10. The valve actuation system of claim 1 , wherein the second arm comprises a stop mechanism that prevents rotation of the second follower about an axis perpendicular to an axis about which the camshaft rotates.

1 1. The valve actuation system of claim 10, wherein the stop mechanism comprises an aperture formed in one of the second arm and second follower, and a pin extending from the other of the second arm and second follower through the aperture.

12. The valve actuation system of claim 1 1, wherein the stop mechanism comprises a biasing element that biases the second follower away from the second lobe.

13. The valve actuation system of claim 1 , wherein the second arm comprises a hydraulic cylinder, the second follower being coupled to the hydraulic cylinder, and wherein the second follower is selectively engageable with the second lobe via selective actuation of the hydraulic cylinder.

14. A lever for controlling the opening and closing of a fluid port of an internal combustion engine, comprising:

a first arm operably coupled to the fluid port to open and close the fluid port;

a second arm opposing the first arm, wherein the first and second arms are pivotable about an axis; a translationally fixed follower;

a translationally adjustable follower; and

a fluid valve comprising a channel and a carrier movable along the channel, the carrier separating the channel into first and second chambers, wherein the fluid valve further comprises a low pressure fluid line fluidly coupled with the first chamber, a high pressure fluid line fluidly coupled with the second chamber, and an adjustable follower fluid line fluidly coupling the channel and the adjustable follower, the carrier being movable between a first position and a second position within the channel, wherein in the first position the adjustable follower fluid line is fluidly coupled with the first chamber, and in the second position the adjustable follower fluid line is fluidly coupled with the second chamber.

15. The lever of claim 14, further comprising a shaft positioned between the first and second arms, the shaft being rotatable to rotate the first and second arms, wherein the shaft defines the axis and comprises at least a portion of one of the low pressure fluid line and high pressure fluid line.

16. The lever of claim 14, further comprising a biasing member configured to bias the carrier into the first position.

17. The lever of claim 16, wherein the carrier comprises a third chamber, the third chamber comprising a chamber inlet open to the second chamber and an outlet closed to the adjustable follower fluid line when the carrier is in the first position and open to the adjustable follower fluid line when the carrier is in the second position, wherein the carrier further comprises a check plug biased into sealed engagement with the inlet.

18. The lever of claim 17, wherein the check plug is biased into sealed engagement with the inlet via a second biasing member, the biasing force of the second biasing member being greater than the biasing force of the first biasing member.

19. The lever of claim 14, wherein when the carrier is in the first position, a pressure applied against the adjustable follower by fluid in the first chamber and channel is less than a threshold pressure to actuate the lever, and when the carrier is in the second position, a pressure applied against the adjustable follower by fluid in the second chamber and channel is more than the threshold pressure to actuate the lever.

20. A method for facilitating a scheduled exhaust release event in a combustion cycle and a non-scheduled compression relief event in a combustion cycle with a single rocker lever, the method comprising:

providing a rocker lever comprising a translationally fixed follower and a translationally adjustable follower at a first end portion of the rocker lever, the rocker lever being coupled to an exhaust port valve at a second end portion of the rocker lever;

positioning the fixed follower into contact with a non-round cam lobe, wherein contact between the fixed follower and the non-round cam lobe actuates the second end portion of the rocker lever and the exhaust port valve according to a predetermined schedule;

applying a pressure to the adjustable follower to urge the adjustable follower into contact with a cam lobe; and

adjusting a pressure applied to the adjustable follower to actuate the second end portion of the rocker lever and the exhaust port valve.

Description:
VALVE ACTUATION SYSTEM

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of United States Provisional Patent

Application Number 61/783,089, filed on March 14, 2013, the contents of which are incorporated herein by reference in their entirety.

FIELD

[0002] This disclosure relates to valve actuators, and more particularly to exhaust brake valve actuators for internal combustion engines.

BACKGROUND

[0003] Engine braking mechanisms for slowing a vehicle are known in the art. One typical engine braking mechanism is a compression release engine brake. When activated, compression release engine brakes open an exhaust valve in the combustion cylinders of the engine during the compression cycle to release compressed air in the cylinder. In other words, the compression stroke of the engine pushes at least a portion of the compressed air out of the cylinder through the open exhaust valve and into the exhaust line of the engine. Because the compressed air is released through the open exhaust valve, the compressed air is prevented from pushing back on (e.g., accelerating) the descending piston after the compression stroke. Without the accelerating effect on the piston, the work performed during the compression stroke is not negated and the vehicle slows down due to a net decrease in the rotational speed of the crankshaft.

[0004] Some conventional compression release engine brakes include a rocker lever attached to a dedicated engine brake exhaust valve that is separate from the regular exhaust stroke valve of the cylinder. The engine brake rocker lever is actuated to open the engine brake exhaust valve as a fixed follower of the lever engages a non-round lobe of a camshaft and a solenoid locks the engine brake exhaust valve to the rocker lever. The regular exhaust stroke valve also is attached to a separate rocker lever that is actuated to open the exhaust stroke valve according to a set schedule as a fixed follower of the rocker lever engages a separate non-round lobe of the camshaft. As described, each combustion cylinder of such typical engines has two separate rocker levers, each with fixed cam followers engaging non-round cam lobes and each actuating separate exhaust valves.

[0005] Further, conventional compression release engine brake levers have lash adjusters or actuators on the exhaust valve end of the rocker or the arm of the rocker attached to the exhaust valve stem. Such a configuration increases the inertia of the valve, which negatively affects the responsiveness of the lever.

SUMMARY

[0006] The subject matter of the present application has been developed in response to the present state of the art, and in particular, in response to the problems and needs in engine braking and other valve actuation art that have not yet been fully solved by currently available valve actuators. Accordingly, the valve actuation system of the present application has been developed to overcome many of the shortcomings of the prior art. For example, in some embodiments, as opposed to prior art systems with two levers each with a fixed follower and each controlling a separate exhaust valve of the same combustion cylinder, the system of the present disclosure includes a single rocker lever with dual followers, one translationally fixed and one selectively actuatable, that cooperatively control actuation of a single exhaust valve of a combustion cylinder to provide exhaust expelling and engine braking functionality.

[0007] According to one embodiment, a valve actuation system for an internal combustion engine having a fluid port includes a camshaft that is rotatably coupled to the internal combustion engine. The camshaft includes a first lobe that has a non-round profile and a second lobe. In some implementations of the system, the second lobe has a round profile. The system also includes a rocker lever that is pivotally coupled to the internal combustion engine. The rocker lever includes a first arm that is operably coupled to the fluid port where the arm's motion is able to open and close the fluid port. The rocker lever also includes a second arm comprising a first follower in engagement with the first lobe and a second follower selectively engageable with the second lobe. Engagement between the first follower and the first lobe and engagement between the second follower and the second lobe controls operation of the first arm.

[0008] In some implementations of the system, the first follower is translationally fixed relative to the second arm, and the second follower is translationally movable relative to the second arm. The second arm may include a channel within which the second follower is translationally movable. The channel can contain a pressurized fluid, and the second follower can be selectively engageable with the second lobe by increasing a pressure of the pressurized fluid within the channel. Movement of the second follower relative to the second arm can be selectively fixed to selectively engage the second follower with the second lobe. [0009] According to certain implementations of the system, engagement between the first follower and the first lobe to open the fluid port is based on a rotational speed of the camshaft, and engagement between the second follower and the second lobe to open the fluid port is based independently of the rotational speed of the camshaft. In one implementation, the fluid valve is a combustion chamber exhaust valve, the first follower engages the first lobe to open the fluid port for a scheduled combustion exhaust release event in a combustion cycle, and the second follower engages the second lobe to open the fluid valve for an engine braking event. According to some implementations, at least one of the first and second followers includes a roller.

[0010] In some implementations of the system, the second arm includes a stop mechanism that prevents rotation of the second follower about an axis perpendicular to an axis about which the camshaft rotates. This minimizes misalignment of the follower relative to the cam lobe, thus reducing wear. The stop mechanism can include an aperture formed in the second arm or second follower, and a pin extending from either the second arm or the second follower through the aperture. The stop mechanism can be a biasing element that biases the second follower away from the second lobe.

[0011] According to certain implementations, the second arm includes a hydraulic cylinder. The second follower can be coupled to the hydraulic cylinder. Moreover, the second follower can be selectively engageable with the second lobe via selective actuation of the hydraulic cylinder.

[0012] According to another embodiment, a lever for controlling the opening and closing of a fluid port of an internal combustion engine includes a first arm that is operably coupled to the fluid port to open and close the fluid port. The lever also includes a second arm oriented at an angle to the first arm. The second arm includes a translationally fixed follower and a translationally adjustable follower. The first and second arms are pivotable about an axis. The lever also includes a fluid valve that has a channel and a carrier movable along the channel. The fluid valve includes a one-way valve which only allows oil flow in one direction. The carrier separates the channel into first and second chambers. The fluid valve further includes a low pressure fluid line fiuidly coupled with the first chamber. The second chamber is fluidly coupled with the translationally adjustable follower. The fluid valve is able to seal the second chamber such that high pressures can develop in the chamber when a cam lobe acts on the follower. The carrier is movable between a first position and a second position within the channel. In the first position, the adjustable follower fluid line is fluidly coupled with the first chamber, and in the second position, the adjustable follower fluid line is fluidly coupled with the second chamber. When the adjustable follower is fluidly coupled with the first chamber, high-pressure cannot develop in the hydraulic cylinder that the adjustable follower is attached to. When the adjustable follower is fluidly coupled to the second chamber high-pressure can develop in the hydraulic cylinder that the adjustable follower is attached to.

[0013] In some implementations, the lever includes a shaft positioned between the first and second arms. The shaft can be rotatable to rotate the first and second arms. Moreover, the shaft can define the axis and include at least a portion of one of the low-pressure fluid line and high-pressure fluid line.

[0014] According to certain implementations, the lever includes a biasing member that is configured to bias the carrier into the first position. The carrier may include a third chamber that includes a chamber inlet open to the second chamber, and an outlet closed to the adjustable follower fluid line when the carrier is in the first position and open to the adjustable follower fluid line when the carrier is in the second position. The carrier may also include a check plug biased into sealed engagement with the inlet. The biasing member can be a first biasing member which acts on the plug and the carrier. The carrier can be biased into sealed engagement with the inlet via a second biasing member. The second biasing member can act on the carrier and the lever. The biasing force of the second biasing member can be greater than the biasing force of the first biasing member.

[0015] In some implementations of the lever, when the carrier is in the first position, a pressure applied against the carrier valve is less than a threshold pressure and the adjustable follower is fluidly coupled to the first chamber. This prevents fluid pressure from building in the hydraulic cylinder attached to the adjustable follower and any motion of the adjustable follower is not transferred to the lever. When the pressure applied against the carrier valve is above a threshold pressure the carrier valve is in the second position and the adjustable follower is fluidly coupled to the second chamber. Fluid cannot exit this second chamber, meaning that fluid pressure can build in the chamber. This allows for the motion of the adjustable follower to be transmitted to the lever through the fluid.

[0016] In yet another embodiment, a method for facilitating a scheduled exhaust release event in a combustion cycle and a non-scheduled compression relief event in a combustion cycle with a single rocker lever includes providing a rocker lever comprising a translationally fixed follower and a translationally adjustable follower at a first end portion of the rocker lever. The rocker lever is coupled to an exhaust port valve at a second end portion of the rocker lever. The method further includes positioning the fixed follower into contact with a non-round cam lobe. Contact between the fixed follower and the non-round cam lobe actuates the second end portion of the rocker lever and the exhaust port valve according to a predetermined schedule.

Additionally, the method includes applying a pressure to the adjustable follower to urge the adjustable follower into contact with a round cam lobe. The method also includes adjusting a pressure applied to the adjustable follower to actuate the second end portion of the rocker lever and the exhaust port valve.

[0017] The described features, structures, advantages, and/or characteristics of the subject matter of the present disclosure may be combined in any suitable manner in one or more embodiments and/or implementations. In the following description, numerous specific details are provided to impart a thorough understanding of embodiments of the subject matter of the present disclosure. One skilled in the relevant art will recognize that the subject matter of the present disclosure may be practiced without one or more of the specific features, details, components, materials, and/or methods of a particular embodiment or implementation. In other instances, additional features and advantages may be recognized in certain embodiments and/or

implementations that may not be present in all embodiments or implementations. Further, in some instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the subject matter of the present disclosure. The features and advantages of the subject matter of the present disclosure will become more fully apparent from the following description and appended claims, or may be learned by the practice of the subject matter as set forth hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order that the advantages of the subject matter may be more readily understood, a more particular description of the subject matter briefly described above will be rendered by reference to specific embodiments that are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the subject matter and are not therefore to be considered to be limiting of its scope, the subject matter will be described and explained with additional specificity and detail through the use of the drawings, in which:

[0019] Figure 1 is a cross-sectional side view of a valve actuation system according to one embodiment;

[0020] Figure 2 is a top view of a valve actuation system according to one embodiment;

[0021] Figure 3 is a cross-sectional front view of a valve actuation system showing an internal fluid valve in a first position according to one embodiment;

[0022] Figure 4 is a cross-sectional front view of the valve actuation system of Figure 3 showing the internal fluid valve in a second position;

[0023] Figure 5 is a cross-sectional schematic view of an internal fluid valve of a valve actuation system according to one embodiment with the internal fluid valve in a first position;

[0024] Figure 6 is a cross-sectional schematic view of the internal fluid valve of Figure 5 with the internal fluid valve in a second position;

[0025] Figure 7 is a perspective view of a valve actuation system according to another embodiment; and

[0026] Figure 8 is a perspective view of a valve actuation system according to yet another embodiment. DETAILED DESCRIPTION

[0027] Reference throughout this specification to "one embodiment," "an

embodiment," or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Appearances of the phrases "in one embodiment," "'in an embodiment," and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment. Similarly, the use of the term "implementation" means an implementation having a particular feature, structure, or characteristic described in connection with one or more embodiments of the present disclosure, however, absent an express correlation to indicate otherwise, an implementation may be associated with one or more embodiments.

[0028] Referring to Figure 1 , according to one embodiment, a valve actuation system 10 includes a rocker lever 20 that is pivotally coupled to an internal combustion engine or other device having one or more controllable valves. The rocker lever 20 is supported by a shaft 12, which extends through a central channel 16 formed in the rocker lever. In certain

implementations, the rocker lever 20 pivots about the shaft 12. In yet other implementations, the shaft 12 is pivotable relative to the internal combustion engine and the rocker lever 20 is fixedly attached to the shaft such that the shaft and rocker lever co-rotate relative to the internal combustion engine. In either implementation, the rocker lever 20 is pivotable about a pivot axis 14, which can be co-axial with the central axes of the shaft 12 and channel 16, as indicated by directional arrows 70. The rocker lever 20 also includes a top channel 18 that extends between the central channel 16 and an exterior of the rocker lever.

[0029] The rocker lever 20 includes first and second opposing arms 30, 32 that move in opposite linear directions as the rocker lever rotates about pivot axis 14. In other words, the rocker lever 20 converts rotational movement of the lever into linear movement of the component in contact with the end of the first arm 30. The channel 16 and pivot axis 14 effectively separate the rocker lever 20 into the first arm 30 and second arm 32. Generally, the length of the first arm 30 (i.e., distance away from the pivot axis 14) is longer than that of the second arm 32. [0030] The first arm 30 is operatively coupled to a fluid port of the internal combustion engine via a mechanism 50. The mechanism 50 is in contact with a valve stem 52. The rocker lever 20 is rotatable to translationally move the valve stem 52 as indicated by directional arrows 74. A distal end of the valve stem 52 seals the fluid port to close the engine valve and unseals the fluid port to open the engine valve. In one implementation, the fluid port is an exhaust port open to a combustion cylinder of the engine, and the engine valve is an exhaust valve.

[0031] The second arm 32 includes a valve actuation mechanism 40 that is selectively controllable to rotate the rocker lever 20 and move the valve stem 52 between sealed and unsealed engagement with the engine fluid port. Because the length of the second arm is conventionally shorter than that of the first arm, the addition of the valve actuation or lash adjustment mechanism 40 to the second arm does not increase the inertia of the lever as much as a lash adjustment mechanism attached to the longer first arm of the lever. The valve actuation mechanism 40 includes a translationally adjustable follower 42 and a fluid valve 100. The fluid valve 100 includes a fluid conduit 46 that directs a pressurized fluid from the fluid valve 100 into a follower channel or chamber 44. The fluid valve 100 is operable to control the flow in and out of the fluid chamber 44. In one position, the fluid valve 100 allows fluid to flow freely in and out of the fluid chamber 44. In a second position, the fluid valve 100 only allows for flow into the fluid chamber 44. The follower 42 is positioned within and translationally (e.g., linearly) movable within channel 44. Moreover, the follower 42 is in sealed engagement with the walls of the channel 44 such that the pressurized fluid in the channel 44 is contained within the channel and leakage around the follower is minimal or zero. Accordingly, in certain implementations, an upper or stem portion of the follower, the pressurized fluid, and the channel 44 collectively define a hydraulic cylinder.

[0032] The fluid valve 100 is in communication with a low pressure fluid source. Fluid from the low pressure fluid source can be supplied to the fluid valve 100 in any of various ways.

For example, in one embodiment, fluid from the low pressure fluid source is supplied to the fluid valve 100 via fluidly coupled internal conduits formed in the shaft 14 and rocker lever (see, e.g., internal conduits 104 and 1 18 of Figures 3 and 4). In the illustrated embodiment, fluid from the low pressure fluid source is supplied to the fluid valve 100 via a fluid port 83 formed in the rocker lever 20. For example, an external fluid conduit or supply line can be coupled between the low pressure fluid source and the fluid port 83. In some implementations, the fluid supplied by the low and high pressure fluid sources is motor oil. In other implementations, the fluid is a hydraulic fluid other than oil, such as transmission fluid, brake fluid, fuel, coolant, and the like.

[0033] The second arm 32 also includes a second follower. In one embodiment, the second follower is a fixed follower 82 as shown in Figure 2, but the second follower could also be a translationally adjustable follower. The fixed follower 82 is coupled to the second arm 32 at a location that is spaced-apart from and laterally adjacent the adjustable follower 42 (e.g., in a direction parallel to the pivot axis 14). Unlike the adjustable follower 42, the translational position of the fixed follower 82 is fixed relative to the second arm 32.

[0034] The translationally adjustable and fixed followers 42, 82 can be any of various types of followers. For example, in one implementation, at least one of the followers 42, 82 is a stationary (e.g., non-rolling) follower, such as a point, flat-faced, or curve-faced follower. As shown in Figure 1, the adjustable follower 42 is a curve-faced stationary follower. In the same or other implementations, at least one of the followers 42, 82 is a roller follower or a follower that rolls along the opposing surface of a cam lobe. As shown in Figures 7 and 8, the adjustable followers 342, 442 and fixed followers 382, 482 are roller followers.

[0035] The valve actuation system 10 also includes a rotating camshaft 66. In some embodiments, the camshaft 66 is a typical camshaft used to actuate multiple air and exhaust valves for an internal combustion engine. During operation of the engine, the camshaft 66 is rotated at varying speeds depending on design parameters and operating conditions of the engine. The camshaft 66 includes at least one non-round lobe 62 and in one embodiment one non-round lobe 64. The non-round lobe 62 is substantially round, but for a valve lift riser 68 or nubbin. The height of the riser 68 is proportional to the amount of linear movement of the valve stem 52 as will be explained in more detail below. The lobes 62, 64 are coupled to the camshaft 66 and co- rotate with the camshaft.

[0036] The rocker lever 20 is positioned such that the fixed follower 82 of the second arm 32 engages (e.g., is supported on, comes in contact with, etc.) the non-round lobe 62.

Similarly, the rocker lever 20 is positioned such that the adjustable follower 42 of the second arm 32 engages the non-round lobe 64. As shown, in one configuration, the followers 42, 82 contact the respective lobes 64, 62 at a top-center location of the lobes such that the force applied to the followers by the lobes is in a direction that is substantially parallel to the valve stem 52 (e.g., vertical). In other configurations, the followers 42, 82 may contact the respective lobes 64, 62 at locations other than top-center such that the force applied to the followers by the lobes is in a direction other than parallel relative to the valve stem 52. As the camshaft 66, and corresponding lobes 62, 64, rotate, the followers 42, 82 remain in contact and move (e.g., glide, slide, roll, etc.) along the circumferential surfaces of the respective lobes.

[0037] Similar to conventional configurations, engagement and disengagement between the fixed follower 82 and the valve lift riser 68 of the non-round lobe 62 controls the lash of the rocker during a normal exhaust stroke. For example, the engagement between the fixed follower 82 and valve lift riser 68 results in the second arm 32 of the rocker 20 raising and lowering, respectively, as indicated by directional arrows 72, the first ami 30 (and valve stem 52) of the rocker lowering and raising, respectively, and indicated by direction arrows 74, and the rocker pivoting about the pivot axis 14 in opposing directions as indicated by directional arrows 70. Because the fixed follower 82 is translationally fixed relative to the rocker 20, for each full rotation of the camshaft 66 and lob 62, the follower engages and disengages the riser 68 a corresponding one time (or a number of times equal to the number of risers for lobes with multiple risers).

[0038] The frequency of engagement and disengagement between the fixed follower 82 and riser 68 (i.e., the frequency of opening and closing of the fluid valve via the valve stem 52) is based on the size of the non-round lobe 62 and the rate of rotation of the camshaft 66, which is dependent upon the speed of the engine. More specifically, as the rotational speed of the camshaft 66 increases, the frequency of the opening and closing of the fluid valve (e.g., lowering and raising of the valve stem 52) increases. The opening of the fluid valve, which is an exhaust valve in some embodiments, via engagement between the fixed follower 82 and riser 68 corresponds to a fixed schedule or timing according to the speed of the engine. In certain implementations, the fixed schedule or timing corresponds with the exhaust stroke of a four- stroke internal combustion engine. Although the frequency of the opening of the exhaust valve may vary, the schedule or timing of the opening of the exhaust valve via engagement between the fixed follower 82 and riser 68 is fixed because every rotation of the camshaft 66 produces such exhaust valve opening event. Moreover, even though the frequency of exhaust valve opening events varies based on engine speed, the schedule or timing of the exhaust valve opening event produced by the fixed follower 82 can be considered fixed in that the number of exhaust valve opening events per cycle is not adjustable.

[0039] In contrast to the exhaust valve opening event produced by engagement between the fixed follower 82 and the riser 68 of the non-round cam lobe 62, the schedule or timing of the exhaust valve opening event produced by engagement between the adjustable follower 42 and the round cam lobe 64 is adjustable. For example, every rotation of the camshaft 66 and lobe 64 does not necessarily result in an exhaust valve opening event via engagement between the follower 42 and the lobe 64. Additionally, the number of exhaust valve opening events per cycle produced by the adjustable follower 42 can be adjustable.

[0040] The adjustability of the adjustable follower 42 (e.g., the lash of the rocker lever

20), and the adjustability of the associated schedule of exhaust valve opening events generated by the adjustable follower, is facilitated by varying the pressure of the fluid within a first chamber 1 18 in figures 3 and 4. When the pressure of the fluid within the first chamber 1 18 is below a threshold pressure, the fluid valve 100 is in the first position. The force of the round cam lobe 64 against the follower overcomes the pressure applied to the adjustable follower 42 by the fluid and the fluid in chamber 44 is pumped out of the chamber and back into the fluid circuit. Accordingly, when the pressure of the fluid is below the threshold pressure, the follower

42 effectively floats or recedes within the channel when engaged with cam lobe 64 such that the second arm 32 of the rocker does not move as the follower 42 moves along the circumferential surface of the cam lobe 64. The threshold pressure is proportional to the force required to cause the fluid valve 100 to move from the first position to the second position. In one

implementation, this threshold pressure is a function of the area of fluid valve 100 that the pressure is acting on and the biasing spring 122. When the pressure of the fluid within the first chamber 1 18 is above the threshold pressure (e.g., about 3 bar or more in some

implementations), the pressure applied to the fluid valve 100 compresses the biasing spring 122 and the fluid in chamber 44 is trapped. The cam lobe 64 then applies a force on the adjustable follower 42 which raises the pressure in the chamber 44 (e.g., about 200 bar or more in some implementations), this pressure then acts on the arm 32. This causes the second arm 32 of the rocker 20 to move upwardly, the rocker 20 to rotate counterclockwise, and the first arm 30 and valve stem 52 to move downwardly to open the exhaust valve as illustrated in Figure 1.

[0041] Accordingly, in certain implementations, actuation of the exhaust valve by increasing the pressure of the fluid in the first chamber 1 18 above the pressure threshold is accomplished independently of the rotational speed and position of the camshaft 66.

Nevertheless, when the exhaust valve is used as an engine brake, it may be desirable for certain applications to increase the pressure of the fluid for actuation the exhaust valve at regular intervals corresponding with the rotational speed and position of the camshaft. For example, conventionally, engine braking is accomplished by opening the exhaust valve during the compression stroke of a 4-cycle engine. Accordingly, in certain implementations, an engine control system (not shown) may be operable to increase the pressure of the fluid in the chamber 1 18 above the pressure threshold for the compression stroke at the same frequency as the opening of the exhaust valve by the fixed follower 82 for the exhaust stroke. However, because the compression stroke occurs before the exhaust stroke, the engine control system would be operable to increase the pressure of the fluid at a rotational position of the camshaft opposite that for the exhaust stroke. Moreover, the pressure of the fluid within the first chamber 1 18 can be increased for a duration necessary for accomplishing the compression relief event associated with engine braking. In some implementations, the duration of the pressure exceeding the threshold pressure and the exhaust valve being open during the compression stroke is substantially the same as the duration of the exhaust valve being open during the exhaust stroke.

[0042] As discussed above, the pressure of the fluid in the channel 44 of the valve actuation mechanism 40 can be regulated by the fluid valve 100 shown in detail in Figures 3 and

4 according to one embodiment. The fluid valve 100 is formed within the second arm 32 of the rocker lever 20. As shown, the fluid valve 100 includes an enclosed central channel 102. For manufacturability, the enclosed central channel 102 may be formed by cutting an open-ended bore within the second arm 32 and plugging the open-end 80 of the bore with a plug 84. In some implementations plug 84 may have a hole to vent the central channel 102. The fluid valve 100 also includes a carrier 1 10 that is movable within (e.g., slidable along) the central channel 102.

The carrier 1 10 separates the central channel into two chambers, the first chamber 1 18 adjacent one side of the carrier and a second chamber 120 adjacent an opposing side of the carrier. The carrier 1 10 sealingly engages the interior walls of the central channel 102 such that the chamber 1 18 is fluidly decoupled (e.g., sealed off) from the second chamber 120. In the illustrated embodiment, the first chamber 1 18 is fluidly coupled with a high pressure fluid source (not shown) via the fluid port 83 and the second chamber 120 is fluidly coupled with the same fluid source or a lower pressure fluid source (not shown) via an internal conduit, such as the conduit 104 extending from the shaft 14 through the second arm 32 and into the second low pressure fluid chamber. The second chamber 120 is created by the body of the fluid valve 100 and thus the pressure in the chamber exerts a force on the fluid valve 100. In some implementations the areas normal to the axis that fluid valve 100 translates along, which make up the second chamber 120, may be equal and the net force exerted on the fluid valve 100 will be zero. In yet other implementations the areas normal to the axis that fluid valve 100 translates along may not be equal and the net force exerted on the valve by the fluid pressure will be nonzero.

[0043] The shape and size (e.g., volume) of the fluid chamber 1 18 is not fixed but varies as the carrier 1 10 moves within the channel 102. For example, as the carrier 102 moves from a first non-engaged position (see, e.g., Figure 3) to a second engaged position (see, e.g., Figure 4), the volume of the fluid chamber 1 18 increases. Of course, as the carrier 102 moves from the second engaged position to the first non-engaged position, the volume of the high pressure fluid chamber 1 18 decreases. In contrast to the high pressure fluid chamber 1 18, the volume of the low pressure fluid chamber 120 is fixed and defined by a first portion 1 12 of the carrier. The portion 112 is substantially spindle-shaped such that the low pressure fluid chamber 120 has a substantially annular shape. The annular shape of the low pressure fluid chamber 120 facilitates the recirculating flow of low pressure fluid into and out of the fluid conduit 46 and follower channel 44, which also help facilitate a uniform or balanced pressure against the follower 42 in the channel when the carrier 1 10 is in the non-engaged position as will be explained in more detail below.

[0044] The carrier 1 10 is biased into the first non-engaged position by a biasing member, such as compression spring 122. The compression spring 122 is positioned between the carrier 112 and the plugged open end 80 of the channel 102. The compression spring 122 applies a first biasing force against the carrier 1 10. In the non-engaged position, the chamber 1 18 is fluidly decoupled from the fluid conduit 46 such that fluid in chamber 1 18 is prevented from flowing into the follower channel 44. In contrast, in the non-engaged position, the chamber 120 is fluidly coupled with the fluid conduit 46 such that fluid in the chamber flows into or out of the follower channel 44. In this first position of the fluid valve 100, when the cam lobe 64 applies a force or lift onto the adjustable follower 42, oil can flow freely out of the chamber 44 through the fluid conduit 46, into the annular passage 120, and out into the fluid network via the fluid conduit 104. Accordingly, the first position of the carrier 1 12 is defined as the non-engaged position. When the pressure of the fluid in the chamber 1 18 is above the pressure threshold the carrier 112 is moved into the second engaged position. As shown in figure 4. In some implementations, the pressure in chamber 1 18 is higher than the pressure in chamber 120. This difference in pressure allows there to be a biasing spring, 464 in figure 8, that keeps the adjustable follower 42 from contacting the cam lobe 64 unless the chamber 44 is connected to the higher pressure chamber 1 18. In this case, because the pressure of the fluid flowing into the follower channel 44 is above the pressure threshold defined by the biasing spring 464 and the design of the adjustable follower 42, the follower 42 engages the cam lobe 64. Accordingly, the second position is defined as the engaged position.

[0045] The carrier 1 10 includes a second portion 1 14 that defines a third check valve chamber 130 that is fluidly decoupled from the second low pressure fluid chamber 120 and fluidly decouplable from the first high pressure fluid chamber 1 18 via a check valve mechanism. The check valve mechanism includes a check ball 136 that is biased into sealed engagement with a first channel 132 (e.g. inlet) of the third check valve chamber 130 via a biasing element, such as a compression or return spring 138. The compression spring 138 applies a second biasing force against the check ball 136. Further, the compression spring 138 may be seated in a recess 1 17 formed in the carrier 1 10 (e.g., the spindle portion 1 12 of the carrier). In the engagement position shown in Figure 4, the biasing force of the compression spring 138 is overcome such that the check ball 136 breaks the seal with the inlet 132, which creates a fluid connection between the high pressure fluid chamber 1 18, check valve fluid chamber 130, and the conduit 46. The second portion 114 also includes a second channel 134 (e.g., outlet) that is closed to the conduit 46 when the carrier 1 10 is in the non-engagement position and open to the conduit 46 when the carrier is in the engagement position. In some embodiments, the first and second portions 1 12, 1 14 of the carrier 1 10 are separately formed and attached to each other to construct the carrier. However, in other embodiments, the first and second portions 1 12, 1 14 of the carrier 1 10 are formed together in a one-piece monolithic construction.

[0046] Operation of the fluid valve 100 is now described with reference to Figures 5 and 6, which schematically represent the fluid valve 100 as fluid valve 200. Accordingly, the fluid valve 200 includes features analogous to the features of fluid valve 100, with like numbers referring to like features. In engine braking applications, the fluid valve 200 is selectively operable to open an exhaust valve during a compression stroke to initiate an engine braking event and to close the exhaust valve to complete the engine braking event. Accordingly, the fluid valve 200 is selectively operable or switchable between a valve open mode and a valve closed mode. The fluid valve 200 is in the valve open mode when the carrier 210 is in the engaged position as shown in Figure 6, and the fluid valve is in the valve closed mode when the carrier 210 is in the non-engaged position as shown in Figure 5. Therefore, in the illustrated

embodiment, the spring 222 biases the fluid valve 200 into the valve closed mode. However, in other embodiments, the bias of the spring 222 can be reversed such that the fluid valve 220 is biased into the valve open mode.

[0047] As shown in Figure 5, in the valve closed mode, the low pressure fluid chamber 220 is open to the adjustable follower fluid conduit 246, which supplies fluid to the follower channel for application against the follower. Accordingly, in the valve closed mode, low pressure fluid 260 in the low pressure fluid chamber 220 is allowed to flow into the fluid conduit 246 and engage the adjustable follower. The low pressure fluid 260 is supplied to the low pressure fluid chamber 220 from a low pressure fluid source via the low pressure conduit 204. As discussed above, because the pressure of the fluid 260 is low (e.g., about 2.4 bar in certain

implementations), and the fluid is allowed to recirculate about the spindle portion 212 of the carrier 210. In implementations where there is a biasing spring to keep the adjustable follower 42 from contacting the cam lobe 64, such as in figure 8, the low pressure fluid 260 applied to the adjustable follower is insufficient to cause the follower 42 to contact the cam lobe 64. In implementations without a biasing spring, such as in figure 7, the oil can freely flow out of the chamber 44 through the fluid conduit 246. For this reason, when the fluid valve 200 is in the valve closed mode, engagement between an adjustable follower and a round cam lobe does not open the exhaust valve.

[0048] When an engine brake event or compression relief event is desired, the pressure of the high pressure fluid 270 supplied form a high pressure fluid source via the high pressure fluid port 283 is increased above a threshold pressure. The threshold pressure is a predetermined pressure determined to be sufficient enough to overcome the biasing force of both the spring 222 and spring 238. In operation, as the pressure of the high pressure fluid 270 is increased, the pressure applied to the carrier 210 also increases, until at some first pressure, the biasing force of the spring 222 is overcome and the carrier begins to slide within the channel in the direction indicated by directional arrow 250. With a sufficient increase in pressure, the carrier 210 is moved into the engaged position shown in Figure 6. Generally, the carrier 210 is in the engaged position when the outlet 234 of the second portion 214 of the carrier is at least partially open to the adjustable follower fluid conduit 246.

[0049] However, even with the carrier 210 in the engaged position within the channel 202, the high pressure fluid 270 is not allowed to flow into the fluid conduit 246 through the outlet 234 until the check valve 231 is opened to unseal the inlet 232 of the check valve chamber 230. The check valve 231 , which includes the check ball 236 and the spring 238, opens when the pressure of the high pressure fluid 270 is greater than the threshold pressure corresponding with the biasing force of the spring 238. Accordingly, as the pressure of the high pressure fluid 270 is increased above the threshold pressure, the compression spring 238 compresses causing the check ball 236 to move away and disengage from the inlet 232 as indicated by directional arrow 252 in Figure 6. With the check ball 236 disengaged from the inlet 232, and the carrier 210 moved into the engaged position, the high pressure fluid 270 is allowed to flow into the adjustable follower fluid conduit 246 as shown. In this position, high pressure oil in the chamber 44 cannot freely flow out of the chamber via the fluid valve 200 because the check valve mechanism prevents this from occurring. Any motion on the cam lobe 64 will be transmitted to the adjustable follower 42 which will then increase the pressure in chamber 44 and cause the rocker lever 20 to rotate. Any leakage of oil out of chamber 44 will be refilled when the pressure in the chamber 44 drops low enough for the check valve ball 236 to lift off of the carrier 214. [0050] To end the engine braking event, the pressure of the high pressure fluid 270 is reduced below the threshold pressure (e.g., biasing force of the spring) to allow the carrier 210 to slide back into the non-engaged position via the bias of the spring 250.

[0051] After the check ball 236 reengages the inlet 232, a portion of the high pressure fluid 270 remains within the check valve chamber 230 and outlet 234. Moreover, it can be recognized that as the carrier 210 moves between the non-engaged and engaged positions, fluid remains within the adjustable follower fluid conduit 246. The pressure of the fluid within the adjustable follower fluid conduit 246 fluctuates according to which of the high and low fluid pressure chambers 218, 220 are open to the adjustable follower fluid conduit. Nevertheless, at all times, the fluid conduit 236 is filled with fluid such that no interior fluid chambers or conduits of the valve are unfilled with fluid. In this manner, the responsiveness of the fluid valve 200 is preserved because the fluid valve avoids delays associated with filling unfilled portions of the valve.

[0052] In other embodiments, opening and closing the exhaust valve is accomplished by modulating the pressure of the high pressure fluid 270 between a pressure above the threshold and below the threshold via a selectively controlled fluid pressure modulation device. In one embodiment, the fluid pressure modulation device is an electronically or mechanically actuated fluid pump in communication with an electronic control module of the engine. Alternatively, the fluid pressure modulation device can be a solenoid-controlled valve coupled to a high pressure fluid source. The electronic control module may be configured to modulate the pressure of the high pressure fluid 270 to effectuate engine braking under predefined or preselected operating conditions. For example, the electronic control module may be configured to execute engine braking within certain vehicle or engine speed ranges, and when an acceleration pedal of the vehicle is released. Also, the electronic control module may control engine braking according to user-selected preferences, such as an engine braking ON/OFF switch.

[0053] As discussed above, the adjustable follower of the rocker lever described herein can be any of various types. For particular types, such as a roller type, maintaining the adjustable roller follower in alignment with a cam lobe (e.g., keeping the rolling face of the roller square with the cam lobe) improves the operation and durability of the follower and cam lobe. Figures 7 and 8 illustrate two rocker levers 320, 420, respectively, with respective alignment or stop mechanisms 390, 490 configured to maintain the respective roller followers 342, 442 in alignment with a cam lobe (not shown). The rocker levers 300, 400 include features analogous to the features of rocker lever 10, with like numbers referring to like features.

[0054] Referring to Figure 7, the adjustable rolling follower 342 of the rocker lever 320 is rotatably coupled to a fork 392 via a pivot pin 396. The rolling follower 342 is configured to rotate about the pivot pin 396 as the rolling follower rolls along a cam lobe during use. The upper portion or stem 394 of the fork 392 is movably positioned within a follower channel 344 (shown in cut-away) formed in the second arm 332 of the rocker lever 320. The follower channel 344 is fluidly coupled with an internal fluid valve (not shown) that may be similar to and controlled using a similar technique as the fluid valves 100, 200 described above.

[0055] Although sealingly engaged with each other, the stem 394 and channel 344 are substantially cylindrical. Accordingly, the stem 394 may be susceptible to rotation within the channel 344, which can lead to misalignment of the rolling follower 342 relative to the cam lobe.

To alleviate this susceptibility, in one implementation, the stem 394 and channel 344 may have a non-round cross-sectional shape, such as rectangular, triangular, polygonal, ovular, and the like, such that the stem is prevented from rotating relative to the channel, and the adjustable rolling follower 342 is maintained in proper alignment with the cam lobe. However, because

constructing the stem 394 and channel 344 to have matching non-round cross-sectional shapes may be difficult, alternative techniques for preventing relative rotation of cylindrical stems and channels, which are easier to manufacture, may be desirable. Accordingly, the lever 320 includes the stop mechanism 390. Generally, the stop mechanism 390 includes a thickened sidewall 395 of the lever 320 adjacent the fork 392. The thickened sidewall 395 may contain the pivot pin 397 for the fixed follower 382. Generally, the thickened sidewall 395 is made by increasing the thickness of the sidewall with additional material such that the surface of the sidewall 395 facing the fork 392 is just adjacent, and in some implementations, contacting, the fork. In this manner, the thickened sidewall 395 (e.g., flat surface of the sidewall) engages the fork 392 (e.g., inward facing flat surface of the fork) to resist (e.g., prevent) relative rotation of the fork and sidewall. In some implementations, the sidewall 395 may be slightly spaced apart from the fork 392 such that some nominal amount of relative rotation of the fork and sidewall is allowed. However, in other implementations, the sidewall 395 is flush against the fork 392 such that substantially no rotation between the sidewall and fork is allowed.

[0056] Referring to Figure 8, like the follower 342 of lever 320, the adjustable rolling follower 442 of the rocker lever 420 is rotatably coupled to a fork 492 via a pivot pin 496. The rolling follower 442 is configured to rotate about the pivot pin 496 as the rolling follower rolls along a cam lobe during use. The upper portion or stem 494 of the fork 492 is movably positioned within a follower channel (not shown) formed in the second arm 432 of the rocker lever 420. The follower channel of the lever 420 also is fluidly coupled with an internal fluid valve (not shown) that may be similar to and controlled using a similar technique as the fluid valves 100, 200 described above.

[0057] In the illustrated embodiment, the stem 494 and follower channel are substantially cylindrical. Accordingly, as discussed above, the stem 494 may be susceptible to rotation within the follower channel. Accordingly, the lever 420 includes the stop mechanism 490. Generally, the stop mechanism 490 includes a first lateral extension member 460 coupled to the second arm 432 of the lever 420 and a second lateral extension member 498 coupled to the fork 492. The first and second lateral extension members 460, 498 are configured to receive a pin 461. The pin 461 is fixedly received in an aperture formed in the first lateral extension member 460 and the pin is movably received in an aperture formed in the second lateral extension member 498. The aperture of the second lateral extension member 498 is just slightly larger than the outer dimension of the pin 461 such that the second lateral extension member is allowed to move along the pin in a direction parallel to the central axis of the pin, but substantially not laterally or perpendicularly relative to the central axis of the pin. Accordingly, with the pin 461 fixed to the first lateral extension member 460, and the second lateral extension member 460 prevented from more than nominal lateral movement via engagement with the pin, the fork 492 is prevented from rotating relative to the second arm 420. Accordingly, the stop mechanism 490 maintains the adjustable follower 442 in proper alignment with the cam lobe.

[0058] In certain implementations, the stop mechanism 490 includes a biasing member or spring 464 positioned between the second lateral extension member 460 of the fork 492 and a free end portion of the pin 461. The spring 464 is position about the pin 461 and retained on the pin via a lip 462 formed in the free end portion of the pin. The spring 464 biases the fork 492 and adjustable roller follower 442 toward the second arm 432. Accordingly, the spring 464 urges the follower 442 back into the follower channel following an engine exhaust or compression relief event. In this manner, the responsiveness of the rocker lever 420 during the transition between opening the exhaust valve and closing the exhaust valve is enhanced. Generally, the biasing force of the spring 464 is not greater than the force equivalent of the threshold pressure for opening the exhaust valve or overcoming the bias of the check valve spring of the rocker's internal fluid valve.

[0059] Further, although the use of the valve actuation system has be described with reference to an exhaust valve of an internal combustion engine, the same or analogous features, concepts, and principles of the valve actuation system can be used with other types of performance valves of an internal combustion engine or any of various valves in other types of systems. Moreover, although described in relation to a 4-stroke combustion cycle engine, the valve actuation system is equally applicable to 2-stroke combustion cycle engines or other differently configured engines if desired.

[0060] The present subject matter may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.