Rocker systems, camshafts, and valve trains for use in internal combustion engines

Abstract

The internal combustion engine system includes an engine having a plurality of pistons housed in each of a plurality of cylinders. A valvetrain is provided for opening and closing intake and exhaust valves of the cylinders during nominal engine operation. The valvetrain is also configured to provide asynchronous switching between selected cam lobe lift profiles for opening and closing the intake and / or exhaust valves.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of the filing date of U.S. Provisional Patent Application No. 63 / 266,012, filed December 27, 2021, which is incorporated herein by reference.

[0002] This application relates to internal combustion engine systems, and more particularly, but not exclusively, to internal combustion engines and rocker systems, camshafts, and valve trains for use therewith. [Background technology]

[0003] Nominal valve opening / closing, compression-release braking, and other alternative valve lift operating modes can be produced using desired cam lobe profiles for the intake and / or exhaust valves of one or more engine cylinders during specific engine operating conditions. The cam lobe profiles produce selected lift profiles for the intake and / or exhaust valves during corresponding crank angles to, for example, operate more efficiently, provide engine braking, or produce other results.

[0004] Certain systems may employ an input rocker lever engaged with a cam lobe having a lobe profile to generate a desired valve lift and / or opening / closing timing. The input rocker lever is selectively engaged with another rocker lever that operates the intake or exhaust valve to couple the desired cam lobe profile with the output rocker lever to generate a selected valve lift. However, improper timing of the input rocker lever's transition into engagement with the output rocker lever can result in durability and operability issues for the switching device and / or the rocker lever associated with the transition. Therefore, there is a continuing need for further contributions in this field. Summary of the Invention

[0005] Certain embodiments of the present application include unique systems, devices, methods, and apparatus for operating one or more cylinders of an internal combustion engine. In one embodiment, one or more input rocker levers are selectively coupled to other rocker levers to generate desired valve lift for one or more cylinders, such as outputting nominal valve lift, compression release braking, swirl, high lift, low lift, or other alternative valve lift and / or timing at nominal opening and closing timing within the corresponding cylinders.

[0006] In one embodiment, a rocker system is provided for an internal combustion engine. The internal combustion engine includes a camshaft having at least one camshaft lobe. The camshaft lobe includes a cam lobe profile having a first portion, a second portion, and a third portion. The rocker system includes at least one input rocker lever rotatable about an engine component in response to motion received from the at least one camshaft lobe of the camshaft. The output rocker lever is rotatable about the engine component and configured to control opening and closing of at least one exhaust valve and an intake valve associated with a cylinder of the internal combustion engine. The at least one input rocker lever is rotated by a first portion of the cam lobe profile to generate a desired lift of at least one of the exhaust valve and the intake valve while the at least one input rocker lever is coupled to the output rocker lever. The at least one input rocker is rotated by a second portion of the cam lobe profile to offset the at least one input rocker lever and the output rocker lever to prevent coupling between the at least one input rocker lever and the output rocker lever. The at least one input rocker lever is rotated by a third portion of the cam lobe profile to align the at least one input rocker lever with the output rocker lever to couple the at least one input rocker lever to the output rocker lever.

[0007] In one embodiment, a camshaft for an internal combustion engine is provided, the camshaft having a cylinder and at least one intake valve and an exhaust valve associated with the cylinder. The camshaft includes at least one camshaft lobe configured to control the opening and closing of at least one of the intake and exhaust valves by guiding movement of a rocker lever. The at least one camshaft lobe includes a cam lobe profile having a first portion that generates lift to open at least one of the exhaust and intake valves via a rocker lever while the rocker lever is associated with at least one of the exhaust and intake valves. The cam lobe profile includes a second portion that offsets the rocker lever to prevent association of the rocker lever with at least one of the exhaust and intake valves. The cam lobe profile includes a third portion that aligns the rocker lever to associate the rocker lever with at least one of the exhaust and intake valves.

[0008] In one embodiment, one of the base circle profiles has a smaller radius than the other base circle profile. Also, each of the camshaft lobes includes a second profile portion that aligns the rocker lever during a second range of crank angles to enable engagement of the rocker lever via the switching device. In one embodiment, the valve lift profiles of the two camshaft lobes also generate different valve lifts and / or valve timings.

[0009] In one embodiment, a valve train is provided for an internal combustion engine. The valve train includes one of an intake valve or an exhaust valve. The valve train includes a camshaft including a camshaft lobe, a first rocker lever movable by the camshaft lobe, and a switching device for selectively coupling the first rocker lever to a second rocker lever. The camshaft lobe includes a lift profile having a first portion that lifts one of the intake valve or the exhaust valve associated with the camshaft lobe via the first rocker lever, a second portion that offsets the first rocker lever and the second rocker lever, and a third portion that aligns the first rocker lever and the second rocker lever.

[0010] In one embodiment, a method for operating a rocker system includes aligning an input rocker lever and an output rocker lever with a camshaft lobe, coupling the aligned input rocker lever to the output rocker lever, lifting at least one of an intake valve and an exhaust valve with the output rocker lever in response to movement of the input rocker lever induced by the camshaft lobe, decoupling the input rocker lever from the output rocker lever, and offsetting the input rocker lever and the output rocker lever with the camshaft lobe to prevent coupling of the input rocker lever and the output rocker lever until the input rocker lever and the output rocker lever are aligned by the camshaft lobe.

[0011] This Summary is provided to introduce a selection of concepts that are further described below in exemplary embodiments. This Summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended for use as an aid in limiting the scope of the claimed subject matter. Further embodiments, forms, objects, features, advantages, aspects, and benefits will become apparent from the following description and drawings. [Brief explanation of the drawings]

[0012] [Figure 1]1 is a schematic diagram of an embodiment of an internal combustion engine system having a valvetrain that provides asynchronous switching of alternative valve lift profiles for at least one cylinder. [Figure 2] 2 is a diagrammatic and schematic view of one embodiment of a cylinder and a schematic valve actuation mechanism for the internal combustion engine system of FIG. 1. FIG. [Figure 3] 10 is a graphical representation comparing intake and exhaust valve lift profiles for a cylinder of the internal combustion engine system of FIG. 1 using a camshaft lobe without a profile for displacing a rocker lever (FIG. 3) and a camshaft lobe with a profile for displacing a rocker lever (FIG. 4). [Figure 4] 10 is a graphical representation comparing intake and exhaust valve lift profiles for a cylinder of the internal combustion engine system of FIG. 1 using a camshaft lobe without a profile for displacing a rocker lever (FIG. 3) and a camshaft lobe with a profile for displacing a rocker lever (FIG. 4). [Figure 5] FIG. 10 is a schematic diagram of a cam lobe profile of a camshaft to provide asynchronous switching for connecting a rocker lever to another rocker lever. [Figure 6] FIG. 10 is a schematic diagram of a cam lobe profile of a camshaft to provide asynchronous switching for connecting a rocker lever to another rocker lever. [Figure 7] FIG. 10 is a schematic diagram of a portion of a valve train for providing asynchronous switching to connect rocker levers driven by alternative valve lift profiles. [Figure 8] 8 is a cross-sectional view taken along line 8-8 of FIG. 7 showing the rocker lever aligned for switching to connect a rocker lever driven by an alternative valve lift profile. [Figure 9] 9 is a cross-sectional view similar to FIG. 8, but with the rocker levers offset to prevent switching to engage rocker levers driven by alternative valve lift profiles. [Figure 10]2 is a perspective view showing the valve actuation system and intake and exhaust valves of the cylinder of the internal combustion engine system of FIG. 1. FIG. [Figure 11] FIG. 10 is an elevational view of the valve actuation system and intake and exhaust valves of FIG. [Figure 12] FIG. 10 is a perspective view of one embodiment of a rocker system of the valve actuation system of FIG. [Figure 13] FIG. 13 is a plan view of the rocker system of FIG. 12. [Figure 14] FIG. 13 is an elevational view of the rocker system of FIG. 12. [Figure 15] 14A-14C are cross-sectional views of the rocker system of FIG. 13 illustrating standard lift mode, cylinder deactivation mode, and supplemental lift mode of operation, respectively. [Figure 16] 14A-14C are cross-sectional views of the rocker system of FIG. 13 illustrating standard lift mode, cylinder deactivation mode, and supplemental lift mode of operation, respectively. [Figure 17] 14A-14C are cross-sectional views of the rocker system of FIG. 13 illustrating standard lift mode, cylinder deactivation mode, and supplemental lift mode of operation, respectively. [Figure 18] FIG. 2 is an elevation view of another embodiment of a rocker system for a cylinder of the internal combustion engine of FIG. 1. [Figure 19] FIG. 19 is a plan view of the rocker system of FIG. 18. [Figure 20] 19A-19C are cross-sectional views of the rocker system of FIG. 18 illustrating standard lift, cylinder deactivation, and braking modes of operation, respectively. [Figure 21] 19A-19C are cross-sectional views of the rocker system of FIG. 18 illustrating standard lift, cylinder deactivation, and braking modes of operation, respectively. [Figure 22] 19A-19C are cross-sectional views of the rocker system of FIG. 18 illustrating standard lift, cylinder deactivation, and braking modes of operation, respectively. [Figure 23] 10 is a flowchart showing an operation procedure of the locker system. DETAILED DESCRIPTION OF THE INVENTION

[0013] While the present invention may take many different forms to promote an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the embodiments. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any changes and further modifications of the described embodiments, and any further applications of the principles of the invention as described herein, are contemplated as would normally occur to one skilled in the art to which the invention pertains.

[0014] Referring to FIG. 1 , an internal combustion engine system 10 is shown, including, for example, an internal combustion engine 12. Any engine type is contemplated, including compression ignition, spark ignition, and combinations thereof. The engine 12 includes a plurality of cylinders 14. For illustrative purposes only, FIG. 1 illustrates a configuration of the plurality of cylinders 14, including six cylinders 14 arranged in series. Any number of cylinders and any configuration of cylinders suitable for use in the internal combustion engine 12 may be utilized. The number of cylinders 14 that may be used may range from, for example, two to eighteen cylinders, or more. Furthermore, the following description may refer to one of the cylinders 14. It should be recognized that corresponding features described in FIG. 2 and elsewhere herein with respect to a cylinder 14 may be present in all or a subset of the other cylinders 14 of the engine 12, unless otherwise specified.

[0015] The engine 12 further includes at least one intake valve 22 and at least one exhaust valve 24 associated with each of the cylinders 14. A valve actuation system 90 is provided to open and close the intake valve 22 and / or exhaust valve 24 based on the crank angle of the crankshaft 18. The valve actuation system 90 includes an engine component 570, such as a rocker shaft about which one or more rocker levers move to control the opening and closing of the intake valve 22 and / or exhaust valve 24.

[0016] 3-9 , and as further described below, the engine 12 includes a valvetrain 550, a rocker system 540, and / or a camshaft 520. In one embodiment, the valvetrain 550 includes one or more intake valves 22 and / or exhaust valves 24 that are opened and closed by one or more camshaft lobes 500, 510 of the camshaft 520 acting on one or more rocker levers 552, 560 of the rocker system 540, the one or more rocker levers 552, 560 being associated with the intake valves 22 or exhaust valves 24.

[0017] In one embodiment, the valve train 550 includes a camshaft 520, a first rocker lever 560, and one of the intake valve 22 or exhaust valve 24 associated with the cylinder 14. A switching device 580 selectively couples the first rocker lever 560 to a second rocker lever 5552. The camshaft 520 includes at least one camshaft lobe 510 having a lift profile with a first portion that lifts the intake valve 22 or the exhaust valve 24 via the first rocker lever 560, a second portion that offsets the first rocker lever 560 and the second rocker lever 552, and a third portion that aligns the first rocker lever 560 and the second rocker lever 552.

[0018] In one embodiment, the engine 12 includes a rocker system 540. The rocker system 540 includes an output rocker lever 552 that can be selectively coupled to one or more input rocker levers 560 to control the opening and closing of the intake valves 22 or exhaust valves 24 of the associated cylinders 14. The rocker levers 552, 560 are rotatable about an engine component 570. The input rocker lever 560 rotates in response to motion received from at least one camshaft lobe 510. The input rocker lever 560 is rotated by a first portion of the camshaft lobe 510 to generate a desired lift of the intake valves 22 or exhaust valves 24 while the input rocker lever 560 is coupled to the output rocker lever 552. The input rocker lever 560 is rotated by a second portion of the camshaft lobe 510 to offset the input rocker lever 560 and the output rocker lever 552 to prevent coupling between the input rocker lever 560 and the output rocker lever 552. The input rocker lever 560 is rotated by the third portion of the camshaft lobe 510 to align the input rocker lever 560 and the output rocker lever 552 to couple the input rocker lever 560 and the output rocker lever 552.

[0019] In one embodiment, camshaft 520 includes camshaft lobes 500, 510 configured to offset rocker levers 552, 560 to prevent coupling of rocker levers 552, 560 outside a desired allowable range of crank angles of crankshaft 18. Inhibiting coupling of rocker levers 552, 560 outside a desired range of crank angles may prevent a switching device from coupling rocker levers 552, 560 together during a valve lift event by one of rocker levers 552, 560, and may prevent the switching device from achieving full or proper engagement with rocker levers 552, 560 associated with a switching operation.

[0020] In one embodiment, a camshaft is provided that includes a camshaft lobe 510 that includes a first portion 512 that offsets the rocker lever 560 to prevent it from associating with the intake valve 22 or the exhaust valve 24. The camshaft lobe 510 includes a second portion 514 that generates lift to open the intake valve 22 or the exhaust valve 24 via the rocker lever 560 while the rocker lever 560 is associated with the intake valve 22 or the exhaust valve 24. The camshaft lobe 510 includes a third portion 516 that aligns the rocker lever 560 to associate with the intake valve 22 or the exhaust valve 24.

[0021] Functional operating modes that can be achieved by selectively coupling the rocker levers 552, 560 of the rocker system 540 of the present disclosure include, for example, nominal or standard intake and exhaust valve operation, Miller cycle intake valve operation, four-stroke engine compression braking exhaust valve operation, intake and / or exhaust valve cylinder deactivation, two-stroke intake and exhaust valve compression braking, variable swirl intake valve operation, dynamic skip fire, and / or nominal and alternate valve lift and / or opening / closing timing operation.

[0022] One exemplary embodiment of a cylinder 14 is shown in FIG. 2 , with it being understood that any suitable cylinder embodiment is contemplated herein. The cylinder 14 typically houses a piston 16 operably attached to a crankshaft 18 that rotates by reciprocating movement of the piston 16 within a combustion chamber 28 of the cylinder 14. Within a cylinder head 20 of the cylinder 14 are at least one intake valve 22, at least one exhaust valve 24, and, in certain embodiments, a fuel injector 26 that provides fuel to the combustion chamber 28 formed by the cylinder 14 between the piston 16 and the cylinder head 20. In other embodiments, fuel may be provided to the combustion chamber 28 by port injection or by injection within the intake system upstream of the combustion chamber 28. Additionally, in the following discussion, each cylinder 14 includes two intake valves 22 and two exhaust valves 24, although this is not required in all embodiments.

[0023] The term "four strokes" herein refers to the four strokes—intake, compression, power, and exhaust—completed by the piston 16 during two separate revolutions of the engine's crankshaft 18, which is a combustion cycle that occurs over 720 crank angle degrees (CAD) of rotation. A stroke begins at top dead center (TDC), when the piston 16 is at the top of the cylinder head 20 of the cylinder 14, or bottom dead center (BDC), when the piston 16 reaches its lowest point in the cylinder 14.

[0024] 3, exemplary nominal or standard intake and exhaust valve opening and closing profiles during a combustion cycle for intake valve (IV1) and exhaust valve (EV1) are shown. During the intake stroke of IV1, piston 16 leaves cylinder head 20 of cylinder 14 and descends to the bottom of the cylinder (not shown), thereby reducing pressure within combustion chamber 28 of cylinder 14. A combustion charge is created within combustion chamber 28 by drawing air through intake valve 22 when intake valve 22 opens.

[0025] Fuel from the fuel injectors 26 may be supplied, for example, by a high-pressure common rail system 30 ( FIG. 1 ) connected to a fuel tank 32. Fuel from the fuel tank 32 is drawn by a fuel pump (not shown) and delivered to the common rail fuel system 30. Fuel delivered from the fuel pump is stored in the common rail fuel system 30, and the stored fuel is supplied to the fuel injectors 26 of each cylinder 14 through fuel lines 34. The fuel stored in the common rail system may be pressurized to increase and control the fuel pressure of the fuel delivered to the combustion chambers 28 of each cylinder 14. However, as noted above, any type of fuel delivery system is contemplated.

[0026] During the compression stroke in a standard or nominal operating mode, both the intake valve 22 and the exhaust valve 24 may close at TDC, as indicated by the nominal valve lift profiles IV1 and EV1 in FIGS. 3 and 4. As the piston 16 moves back toward TDC, fuel is injected into the compression intake in a main injection event near TDC, and after a short delay, the compressed mixture ignites in the combustion chamber 28. If the engine 12 is a diesel engine, this results in ignition of the combustion charge. The ignition of the air and fuel rapidly increases the pressure in the combustion chamber 28, which is applied to the piston 16 during the combustion stroke toward BDC. Combustion phasing in the combustion chamber 28 is calibrated so that the increase in pressure in the combustion chamber 28 pushes the piston 16, causing it to provide a net positive force / work / power.

[0027] During the exhaust stroke, as indicated by EV1 (nominal) in Figures 3 and 4, the piston 16 moves back toward TDC while the exhaust valve 24 opens. This action expels combustion products from the combustion of fuel in the combustion chamber 28 and expels the spent mixture (exhaust gases) out through the exhaust valve 24. The next combustion cycle occurs using these same intake and exhaust valve opening and closing profiles, unless cylinder deactivation or alternating valve lift conditions are required, as discussed further below.

[0028] 1, intake air flows through an intake passage 36 and an intake manifold 38 before reaching the intake valve 22. The intake passage 36 may be connected to a compressor 41a and an intake throttle 42 of a turbocharger 40. The intake air may be cleaned by an air cleaner (not shown), compressed by the compressor 41, and then drawn into the combustion chamber 28 through the intake throttle 42. The intake throttle 42 may be controlled to affect the flow of air into the cylinders.

[0029] The intake passage 36 may further include an optional cooler 44 provided downstream of the compressor 41. In one example, the cooler 44 may be a charge air cooler (CAC). In this example, the compressor 41 may increase the temperature and pressure of the intake air, while the CAC 44 may increase the charge density to provide more air to the cylinders. In another example, the cooler 44 may be a low temperature aftercooler (LTA). The CAC 44 uses air as a cooling medium, while the LTA uses a refrigerant as a cooling medium.

[0030] Exhaust gases exit the combustion chamber 28 into an exhaust passage 46 through an exhaust manifold 48 that connects the cylinder 14 to the exhaust passage 46. The exhaust passage 46 is connected to a turbine 43 of the turbocharger 40 and a wastegate 50, which then connects to an aftertreatment system 52. The exhaust gases exiting the combustion chamber 28 drive the turbine 43 to rotate. The wastegate 50 is a device that allows a portion of the exhaust gases to bypass the turbine 43 through a passage 54. The wastegate 50 may include a control valve 56, which may be an open / closed (two-position) type valve, a full authority valve that allows control of the bypass flow rate, or anything in between. The exhaust passage 46 may also or alternatively include an exhaust throttle 58 to regulate the flow rate of exhaust gases through the exhaust passage 46. The exhaust gases, which may be a combination of the bypass flow rate and the turbine flow rate, then enter the aftertreatment system 52. Other embodiments contemplate variable inlet turbines, turbineless systems, and / or compressorless systems.

[0031] Optionally, a portion of the exhaust gases can be recirculated into the intake system via an EGR passage (not shown). The EGR passage can connect the exhaust passage upstream of the turbine 43b to the intake passage 36 downstream of the intake throttle 42. Alternatively or additionally, a low-pressure EGR system (not shown) can be provided downstream of the turbine 43b and upstream of the compressor 41. An EGR valve can be provided to regulate the flow of EGR through the EGR passage. The EGR passage can further include an EGR cooler and a bypass around the EGR cooler.

[0032] The aftertreatment system 52 may include one or more devices useful for treating and / or removing materials from the exhaust gas, which may be harmful components, including carbon monoxide, nitric oxide, nitrogen dioxide, hydrocarbons, and / or soot, in the exhaust gas. In some examples, the aftertreatment system 52 may include at least one of a catalytic device and a particulate filter. The catalytic device may be a diesel oxidation catalyst (DOC) device, an ammonia oxidation (AMOX) catalyst device, a selective catalytic reduction (SCR) device, a three-way catalyst (TWC), a lean NOx trap (LNT), or the like. The reduction catalyst may include any suitable reduction catalyst, for example, a urea selective reduction catalyst. The particulate filter may be a diesel particulate filter (DPF), a partial flow particulate filter (PFF), or the like. The PFF functions to trap particulate matter in a portion of the flow, as opposed to the entire amount of exhaust gas passing through the particulate filter.

[0033] A controller 80 is provided to receive data as input from various sensors and send command signals as output to various actuators. Some of the various sensors and actuators that may be employed are described in detail below. The controller 80 may include, for example, a processor, memory, a clock, and an input / output (I / O) interface.

[0034] The system 10 includes various sensors, such as an intake manifold pressure / temperature sensor 70, an exhaust manifold pressure / temperature sensor 72, one or more aftertreatment sensors 74 (differential pressure sensors, temperature sensors, pressure sensors, constituent sensors, etc.), engine sensors 76 (which may detect the air-fuel ratio of the mixture supplied to the combustion chamber, crank angle, crankshaft rotational speed, etc.), and a fuel sensor 78 for detecting fuel pressure and / or other characteristics of the fuel, common rail 38, and / or fuel injectors 26. Any other sensors known in the art of engine systems are contemplated.

[0035] System 10 may also include various actuators for opening and closing intake valve 22, opening and closing exhaust valve 24, injecting fuel from fuel injector 26, opening and closing wastegate valve 56, intake throttle 42, and / or exhaust throttle 58. Additionally, in one embodiment, the actuators for opening and closing intake valve 22 and exhaust valve 24 are provided as part of a valve actuation (VA) system 90, as shown schematically in FIG. 2 , and include rocker levers 552, 560 rotated by respective camshaft lobes 500, 510 to generate the opening and closing of intake valve 22 and exhaust valve 24 at times determined by the camshaft lobes 500, 510 coupled to intake valve 22 and exhaust valve 24 via VA system 90.

[0036] During particular operating conditions, one or more alternative valve lift profiles may be desired for one or more of the intake valve 22 and the exhaust valve 24. For example, Figures 3 and 4 show a braking profile of EV1, in which the exhaust valve is opened before top dead center and during at least a portion of the power stroke to provide compression-release braking. To provide compression-release braking, the VA system 90 may include a cam having a cam lobe profile that may be coupled to an actuator for opening the exhaust valve 24 to provide the opening and closing timing of the compression-release braking.

[0037] Figure 5 shows an example camshaft 500 having a first cam lobe 502 including a base circle portion 502 and a valve lift portion 504 to provide a nominal valve lift, such as that shown at EV1 and / or IV1 in Figures 3 and 4. Figure 6 shows a cam lobe 510 of a camshaft 520 that provides an alternative valve lift profile, such as for compression-release braking as shown in Figure 4. Cam lobe 510 is configured to stagger the rocker levers 552, 560 through a range of crank angles where mistimed actuation of the switches for coupling the rocker levers 552, 560 together may be problematic, preventing full or complete engagement of the switches.

[0038] The cam lobe 510 can be associated with an actuator for the intake valve 22 and / or the exhaust valve 24 by the VA system 90 to selectively couple a rocker lever 560 moved by the cam lobe 510 to a rocker lever that controls the opening and closing of the intake valve 22 and / or the exhaust valve 24 to provide alternative valve lift events. The cam lobe 510 includes a cam lobe profile having a first portion 512, which is a base circle portion, and a second portion 514, which is a valve lift portion. The cam lobe 510 also includes a third portion 516, which is an alignment portion between the base circle portion and the valve lift portion. The cam lobe 510 can further include a transition portion 518 between the second portion 514 and the third portion 516, which is smaller than the third portion 516 to offset the rocker lever and prevent coupling between the rocker levers 552 and 560 at crank angles along the second portion 514 while the valve is being lifted.

[0039] Referring back to FIG. 4 , the lift valves provided by cam lobes 500, 510 are shown. The valve lift portion 504 of cam lobe 500 controls a first rocker lever 552 to generate the nominal exhaust valve opening for EV1, while a second portion 514 of cam lobe 510 controls a second rocker lever 560 to generate the exhaust valve opening event timed for compression-release braking. The first portion 512 of cam lobe 510 is a smaller base circle than the base circle portion 502 of cam lobe 500 such that the rocker levers 552, 560 are offset along the first portion 512. When the positioning of the rocker lever controlled by cam lobe 510 is along a third portion 516 of cam lobe 510, the rocker levers 552, 560 can be aligned and coupled to provide the compression-release braking generated by the second portion 514 in combination with the valve lift generated by the valve lift portion 504. In contrast, FIG. 3 shows an arrangement in which the base circle portions of both the cam lobes controlling the nominal exhaust valve opening and the compression-release brake opening and closing are the same size so that there is no rocker lever misalignment except when the rocker lever is controlled by the respective valve lift portions.

[0040] 7 shows one embodiment of a valve actuation system 90 having a valvetrain 550. The valvetrain 550 includes a first rocker lever 552 and a second rocker lever 560 that are movable by a camshaft 520. The first rocker lever 552 is controlled by a cam lobe 500 for movement about a component 570, such as a rocker shaft, and the second rocker lever 560 is controlled by a cam lobe 510 for movement about the component 570. Alternatively, the first rocker lever 552 may be an output rocker lever and may be coupled to one or more other input rocker levers along the camshaft 520 that are directly coupled to associated cam lobes.

[0041] The switching device 580 includes a switch 582 housed in one of the rocker levers 552, 560, such as rocker lever 560, that is movable to selectively couple or connect rocker lever 560 to rocker lever 552. For example, in FIG. 8 , the rocker levers 552, 560 are shown aligned with one another such that switch 582 can be moved into the aligned passage 554 of rocker lever 552, as indicated by position 582a of switch 582. Switch 582 can include, for example, one or more pins that are moved into and / or out of passage 554 to couple and decouple rocker levers 552, 560.

[0042] Alignment between rocker levers 552, 560 occurs only while the position of rocker lever 560 is controlled by third portion 516 of cam lobe 510. When rocker lever 560 is controlled by the base circle along first portion 512, rocker lever 560 is misaligned with rocker lever 552, as shown in FIG. 9. This misalignment prevents switch 582 from being movable into passage 554 of rocker lever 552, as passage 554 is not aligned with switch 582.

[0043] 23 , a method 600 for operating the rocker system 540 is contemplated. The method 600 may include aligning 602 the input rocker lever 560 and the output rocker lever 552, for example, via the cam lobe 510. The alignment may include, for example, using the third portion 516 of the camshaft lobe 510 to position the input rocker lever 560 in a predetermined orientation relative to the output rocker lever 552 so that a switching device 580 can couple the rocker levers 552, 560 to one another. The aligned input rocker lever 560 is then coupled 604 to the output rocker lever 552, for example, using the switching device 580. The method 600 may further include lifting 606 at least one of the intake valve 22 and the exhaust valve 24 via the output rocker lever 552 in response to movement of the input rocker lever 560 induced by the camshaft lobe 510. For example, movement of the rocker lever 552 that lifts the intake valve 22 or the exhaust valve 24 via the rocker lever 560 may be rotation of the rocker lever 560 around an engine component 570, such as a rocker shaft, due to the third portion 516 of the camshaft lobe 510 acting on the rocker lever 560.

[0044] The input rocker lever 560 may then be decoupled from the output rocker lever 552 at 608. In one embodiment, decoupling may include disengaging or disconnecting a switch, such as the switching device 580 described above. The input rocker lever 560 is then offset from the output rocker lever 552 by the camshaft lobe 510 at 610 to prevent coupling between the input rocker lever 560 and the output rocker lever 552 until the camshaft lobe 510 aligns the input rocker lever 560 and the output rocker lever 552. In one embodiment, offsetting the rocker levers 552 and 560 includes rotating the rocker lever 560 to an offset position relative to the rocker lever 552 by the first portion 512 of the camshaft lobe 510 to prevent the switching device 580 from being able to engage the rocker lever 560 with the rocker lever 552.

[0045] 10-17, further details are shown regarding one embodiment of a VA system 90 applicable to cylinder deactivation of one or more of the cylinders 14 under cylinder deactivation conditions and / or to provide alternating lift profiles for the intake and / or exhaust valves of one or more of the cylinders 14 in addition to the standard lift profiles discussed above. FIGS. 10 and 11 illustrate a first intake-side VA system 90a and a second exhaust-side VA system 90b, which may be collectively and individually referred to herein as VA systems 90. The VA system 90 may be provided for operation of one or both of the intake valves 22, for operation of one or both of the exhaust valves 24, for operation of one of the intake valves 22 and one of the exhaust valves 24, or for operation of all of the intake and exhaust valves 22 and 24. Additionally, the first VA system 90a may provide one or more lift profiles for the intake valve 22 that are different from the lift profile of one or more of the exhaust valves 24.

[0046] Specifically, the first VA system 90a includes a first rocker system 100a configured to engage a lobe of the intake camshaft 92 along one or more of the cylinders 14. Alternatively or additionally, the second VA system 90b may include an identical, similar, or different second rocker system 100b configured to engage a lobe of the exhaust camshaft 94 along one or more of the cylinders 14. The first and second rocker systems 100a, 100b may be individually or collectively referred to herein as rocker systems 100.

[0047] In the illustrated embodiment, the intake camshaft 92 includes three camshaft lobes 93a, 93b, and 93c (collectively referred to as camshaft lobes 93) that provide at least two different valve lift profiles for the intake valves 22, and the exhaust camshaft 94 includes three camshaft lobes 95a, 95b, and 95c (collectively referred to as camshaft lobes 95) that provide at least two different valve lift profiles for the exhaust valves 24. Other embodiments contemplate only two lobes 93, 95, or more than two lobes 93, 95 on one or both of the camshafts 92, 94. The three camshaft lobes 93, 95 on each camshaft in the illustrated embodiment can provide one or more supplemental lift profiles for the associated valves 22, 24, e.g., an associated nominal or standard lift profile for the associated valves 22, 22, and one or more supplemental lift profiles for the valves 22, 24 that differ from the standard lift profile in height and / or timing of valve lift from their respective valve seats. Additionally, at least one of the camshaft lobes 93, 95 may include a cam lobe profile, such as cam lobe 510 described above, to offset the associated rocker lever during a first range of crank angles to prevent the rocker lever from coupling to another rocker lever, and to align the associated rocker lever for coupling to another rocker lever during a second range of crank angles prior to valve lift.

[0048] 12-14, rocker system 100 includes an output rocker lever 102 and at least one input rocker lever. In the illustrated embodiment, rocker system 100 includes a first input rocker lever 104, a second input rocker lever 106, and a third input rocker lever 108, each of which is rotatably mounted to an engine component, such as a rocker shaft 120, in a side-by-side relationship. First input rocker lever 104 includes a first roller 110 that contacts a corresponding camshaft lobe 93a, 95a. Second input rocker lever 106 includes a second roller 112 that contacts a corresponding camshaft lobe 93b, 95b. Third input rocker lever 108 includes a third roller 114 that contacts a corresponding camshaft lobe 93c, 95c. As explained further below, one or more of the input rocker levers 104, 106, 108 are selectively connectable to the output rocker lever 102 to transfer motion to the connected ones of the intake valves 22 or exhaust valves 24 from the respective camshaft lobes 93, 95. Additionally, the input rocker levers 104, 106, 108 can be disconnected from the output rocker lever 102 so that no valve lift is provided during cylinder deactivation.

[0049] The biasing mechanism 122 includes springs 124, 126, 128 that each contact the output rocker lever 102 and the input rocker levers 104, 106, 108, respectively, and bias the corresponding rollers 110, 112, 114 into contact with the respective camshaft lobes 93, 95. Also illustrated are hydraulic lash adjusters 130, 132 connected to each arm 102a, 102b of the output rocker lever 102 and, in turn, to the corresponding one of the intake valve 22 or exhaust valve 24. While the biasing mechanism 122 is located on the opposite side of the rocker system 100 from the hydraulic lash adjusters 130, 132 in the illustrated embodiment, this is not required. In alternative embodiments, adjustment screws or elephant feet may be provided instead of or in addition to the hydraulic lash adjusters 130, 132. A rocker seat 134 may be provided for mounting to the cylinder head, although embodiments are contemplated without the rocker seat 134. Additionally, embodiments are contemplated without the rocker shaft 120, in which the rocker lever can be mounted around any suitable engine component, such as an end pivot incorporated into the cylinder head on which the rocker lever mounts.

[0050] The rocker system 100 may include a first valve lift switch 150 for selectively connecting or coupling and disconnecting or decoupling the first input rocker lever 104 to the output rocker lever 102 to transmit or prevent the transmission of movement from the associated camshaft lobes 93 a, 95 a to the connected ones of the intake valves 22 and / or exhaust valves 24. The rocker system 100 may also include a second valve lift switch 200 for selectively connecting and coupling one or both of the second and third input rocker levers 106, 108 to the output rocker lever 102 to transmit or prevent the transmission of movement from the associated camshaft lobes 93 b, 95 b, 93 c, 95 c to the connected ones of the intake valves 22 and / or exhaust valves 24. As discussed above, one or more of the camshaft lobes 93, 95 may include a lobe profile with a third portion 516 that aligns the associated rocker lever 104, 106, 108 for actuation of the switch 150 and / or switch 200, and a different sized base circle along the first portion 512 that offsets the associated rocker lever 104, 106, 108 to prevent actuation of the switch 150 and / or switch 200.

[0051] 15-17, a first valve lift switch 150 is housed within a bore 152 extending within the output rocker lever 102 and from there to the first input rocker lever 104. The first switch 150 includes a first valve lift pin assembly 154 including a spring-biased first valve lift pin 156 with a plurality of shear pin portions 170, 172, 174 in abutting end-to-end engagement. As shown in FIG. 15, the first valve lift pin 156 is normally biased to an engaged position via springs 158a, 158b such that the first input rocker lever 104 is connected to the output rocker lever 102. In the engaged position, the valve lift pin 156 spans joints 160, 162 between the rocker levers 102, 104, forming shear interfaces 160a, 162a at the joints 160, 162. The engaged position of the first valve lift switch 150 is used during operating conditions when standard or nominal lift of the intake valve 22 or exhaust valve 24 is desired from the camshaft lobes 92a, 94a.

[0052] To disconnect or decouple the rocker levers 102, 104 from one another, hydraulic fluid pressure is supplied from the rocker shaft 120 of the engine 12 via the engine's hydraulic system, through the opening 166 into the bore 152, and into the space 164 at one end of the bore 152. As shown in FIGS. 16 and 17 , the hydraulic pressure displaces the valve lift pin 156 into contact with the base 168, compressing the springs 158a, 158b. In this state, the junction between the shear pin portions 170 and 172 is aligned with the joint 160, and the junction between the shear pin portions 172 and 174 is aligned with the joint 162. This disengaged position eliminates the shear interfaces 160a, 162a because no portion of the first valve lift pin 156 spans the joints 160, 162. As a result, rotation of the first input rocker lever 104 is not transmitted to the output rocker lever 102, and movement imparted by the camshaft lobes 93a, 95a is not transmitted to the intake valves 22 or exhaust valves 24 but is absorbed by the biasing spring 124. The disengaged position of the first valve lift switch 150 is used during operating conditions where cylinder deactivation is desired and / or while alternating lift profiles from the second and third input rockers 106, 108 are desired from the camshaft lobes 93b, 95b, 93c, 95c.

[0053] The second valve lift switch 200 is housed in a bore 202 that extends within the output rocker lever 102 and from there to the second input rocker lever 106 and the third input rocker lever 108. The second valve lift switch 200 includes a second valve lift pin assembly 204 that includes a second valve lift pin 206 with a plurality of shear pin portions 220, 222 in abutting end-to-end engagement. As shown in Figures 15 and 16, the second valve lift pin 206 is normally biased to a disengaged position via a spring 208.

[0054] 17, the second input rocker lever 106 and the third input rocker lever 108 are connected to the output rocker lever 102. In the engaged position, the valve lift pin 206 spans joints 210, 212 between the rocker levers 102, 106, 108, forming shear interfaces 210a, 212a at the joints 210, 212. The engaged position of the second valve lift switch 200 is used during operating conditions when alternative lift of the intake valve 22 or exhaust valve 24 is desired from the camshaft lobes 93b, 95b, 93c, 95c via the input rocker levers 106, 108. To connect or couple the rocker levers 102, 106, 108 together, hydraulic fluid pressure is supplied via the hydraulic system of the engine 12 from the rocker shaft 120 of the engine 12 through the opening 216 into the bore 202 and into the control pressure space 214 at one end of the bore 202. As shown in FIG. 17 , the hydraulic fluid pressure displaces the valve lift pin 206 into contact with the base 218, compressing the spring 208.

[0055] 15 and 16, the junction between shear pin portions 220 and 222 is aligned with joint 210, and the end of shear pin portion 222 is positioned within output rocker lever 102 such that shear pin portion 222 does not span joint 212. This disengaged position eliminates shear interfaces 210a and 212a because no portion of second valve lift pin 206 spans joints 210 and 212. As a result, rotation of second and third input rocker levers 106 and 108 is not transmitted to output rocker lever 102, and motion imparted by camshaft lobes 93b, 95b, 93c, and 95c is not transmitted to intake valve 22 or exhaust valve 24 but is absorbed by biasing springs 126 and 128. The disengaged position of the second valve lift switch 200 is used during operating conditions where cylinder deactivation is desired or when only a nominal or standard lift profile from the first input rocker 104 is desired for the camshaft lobes 93a, 95a.

[0056] 18-22 illustrate another embodiment of a locker system 300. The locker system 300 may be similar to the locker system 100 described above, and the following description will be directed to features of the locker system 300 that differ from the locker system 100. One or more aspects or features of the locker system 100 discussed above may be provided in the locker system 300, and vice versa.

[0057] 18 and 19, rocker system 300 includes an output rocker lever 302, a first input rocker lever 304, a second input rocker lever 306, and a third input rocker lever 308, each rotatably mountable to an engine component such as rocker shaft 120. First input rocker lever 304 includes a first roller 310 that contacts a corresponding camshaft lobe 93a, 95a. Second input rocker lever 306 includes a second roller 312 that contacts a corresponding camshaft lobe 93b, 95b. Third input rocker lever 308 includes a third roller 314 that contacts a corresponding camshaft lobe 93c, 95c. One or more of the input rocker levers 304, 306, 308 are selectively connectable to the output rocker lever 302 to transfer motion from the respective camshaft lobes 93, 95 to the connected ones of the intake valves 22 or exhaust valves 24. Additionally, the input rocker levers 304, 306, 308 can be disconnected from the output rocker lever 302 so that no valve lift is provided during cylinder deactivation.

[0058] The biasing mechanism 322 includes springs 324, 326, 328 that each contact a respective one of the output rocker lever 302 and input rocker levers 304, 306, 308 to bias the corresponding rollers 310, 312, 314 into contact with the respective camshaft lobe. The biasing mechanism 322 differs from the biasing mechanism 122 in that the spring 324 of the first input rocker lever 304 is located on the same side of the rocker assembly as hydraulic lash adjusters 330, 332. The hydraulic lash adjusters 330, 332 are connected to respective arms 302a, 302b of the output rocker lever 302 and corresponding ones of the intake valve 22 or exhaust valve 24.

[0059] The rocker system 300 includes a first valve lift switch 350 for selectively connecting and disconnecting the first input rocker lever 304 to the output rocker lever 302 to transmit or prevent the transmission of movement from the associated camshaft lobes 93a, 95a to the connected ones of the intake valves 22 and / or exhaust valves 24. The rocker system 300 also includes a second valve lift switch 400 for selectively connecting and coupling one or both of the second and third input rocker levers 306, 308 to the output rocker lever 302 to transmit or prevent the transmission of movement from the associated camshaft lobes 93b, 95b, 93c, 95c to the connected ones of the intake valves 22 and / or exhaust valves 24. As discussed above, one or more of the camshaft lobes 93, 95 may include a lobe profile with a third portion 516 that aligns the associated rocker lever 304, 306, 308 for actuation of the switch 350 and / or switch 400, and a different sized base circle along the first portion 512 that offsets the associated rocker lever 304, 306, 308 to prevent actuation of the switch 350 and / or switch 400.

[0060] 20-22, the first valve lift switch 350 is housed within a bore 352 that extends within the output rocker lever 302 and from there to the first input rocker lever 304. As shown in FIG. 20, the first valve lift switch 350 includes a first valve lift pin assembly 354 that includes a first valve lift pin 356 with multiple shear pin portions 370, 372 that are normally biased away from each other to an engaged position via a spring 358 such that the first input rocker lever 304 is connected to the output rocker lever 302. In the engaged position, the valve lift pin 356 spans joints 360, 362 between the rocker levers 302, 304, forming shear interfaces 360a, 362a at the joints 360, 362. The engaged position of the first switch 150 is used during operating conditions where a reference or nominal lift of the intake valve 22 or exhaust valve 24 is desired from the camshaft lobes 93a, 95a.

[0061] To disconnect or decouple the rocker levers 302, 304 from one another, hydraulic fluid pressure is supplied from the rocker shaft 120 of the engine 12 via the hydraulic system of the engine 12 through the openings 366a, 366b into the bore 352 and into the spaces 364a, 364b at opposite ends of the bore 352. As shown in FIGS. 21 and 22 , the hydraulic fluid pressure compresses the spring 358, thereby displacing the shear pin portions 370, 372 toward one another. In this state, the entire shear pin portions 370, 372 are moved into the first input rocker lever 304. This disengaged position eliminates the shear interfaces 160a, 162a because no portion of the first valve lift pin 356 spans the joints 360, 362. As a result, rotation of the first input rocker lever 304 is not transmitted to the output rocker lever 302, and movement imparted by the camshaft lobes 93a, 95a is not transmitted to the intake valves 22 or the exhaust valves 24. The disengaged position of the first valve lift switch 350 is used during operating conditions where cylinder deactivation is desired and / or while alternating lift profiles from the second and third input rockers 306, 308 are desired from the camshaft lobes 93b, 95b, 93c, 95c.

[0062] The second valve lift switch 400 is housed within bores 402 of the output rocker lever 302, the second input rocker lever 306, and the third input rocker lever 308. The second valve lift switch 400 includes a second valve lift pin assembly 404 that includes a second valve lift pin 406 in the bore 402 with a plurality of shear pin portions 420, 422. As shown in Figures 20 and 21, the shear pin portions 420 and 422 are normally biased within the bore 402 toward each other and against the central base 418 via springs 408, 409.

[0063] 22, the second input rocker lever 306 and the third input rocker lever 308 are connected to the output rocker lever 302. In the engaged position, shear pin portions 420, 422 of the shear pin 406 span joints 410, 412 between the rocker levers 302, 306, 308, forming shear interfaces 410a, 412a at the joints 410, 412. The engaged position of the second valve lift switch 400 is used during operating conditions when alternative lift of the intake valves 22 or exhaust valves 24 is desired from the camshaft lobes 93b, 95b, 93c, 95c via the input rocker levers 306, 308. To connect or couple the rocker levers 302, 306, 308 together, hydraulic fluid pressure is supplied from the rocker shaft 120 of the engine 12 via the hydraulic system of the engine 12, through the opening 416 into the bore 402 and into the control pressure space 414 of the bore 402 between the shear pin portions 420 and 422. As shown in FIG. 22 , the hydraulic fluid pressure displaces the shear pin portions 420, 422 from the base 418 and compresses the springs 408, 409 so that the shear pin portions span the joints 410, 412.

[0064] In the disengaged state, the shear pin portions 420, 422 are positioned within the output rocker lever 302 such that the shear pin portions 420, 422 do not span the joints 410, 412. This disengaged position eliminates the shear interfaces 410a, 412a because no portion of the second valve lift pin 406 spans the joints 410, 412. As a result, rotation of the second input rocker lever 306 and the third input rocker lever 308 is not transmitted to the output rocker lever 302, and motion imparted by the camshaft lobes 93b, 95b, 93c, 95c is not transmitted to the intake valves 22 or the exhaust valves 24. The disengaged position of the second valve lift switch 400 is used during operating conditions when cylinder deactivation is required or while a nominal or standard lift profile from the first input rocker lever 304 is desired from the camshaft lobes 93a, 95a.

[0065] The rocker systems 100, 300 disclosed herein may enable the use of a single hydraulic actuator to provide multiple operating modes for the intake and / or exhaust valves of one or more cylinders 14 of the engine 12. The operating modes may include, for example, a standard lift profile, no lift with cylinder deactivation, and an alternating lift profile. The alternating lift profile may be for providing engine braking, such as, for example, four-stroke compression braking or two-stroke compression braking. Two-stroke compression braking valve lift profiles for the intake and exhaust valves are shown in FIG. 3 as IV2 and EV2. Alternative lift profiles other than the compression braking lift profile are also contemplated.

[0066] The rocker system of the present disclosure can be used to upgrade the valve actuation assembly. For example, the valve actuation system can be upgraded from a standard lift function for the intake and exhaust valves to include cylinder deactivation or four-stroke compression braking. The valve actuation system can also be upgraded from a standard lift function for the intake and exhaust valves to include cylinder deactivation and four-stroke compression braking. The valve actuation system can also be upgraded from a standard lift function for the intake and exhaust valves to include cylinder deactivation and two-stroke compression braking.

[0067] During operation of the internal combustion engine system 10, the controller 80 may receive information from the various sensors listed above through the I / O interface, process the received information using a processor based on algorithms stored in the memory of the controller 80, and then send command signals to various actuators through the I / O interface. For example, the controller 80 may receive information regarding cylinder deactivation status, engine braking requests, vehicle or engine speed requests, combustion conditions, post-process temperature conditions, and / or engine load conditions. The controller 80 is configured to process the conditions and / or requests and then send one or more command signals to one or more actuators to provide cylinder deactivation and / or alternating valve lift profiles using associated camshaft lobes and input rocker levers based on a control strategy.

[0068] The controller 80 can be configured to implement the disclosed cylinder deactivation and alternating valve lift strategies using the VA system 90. In one embodiment, the disclosed method and / or controller configuration includes the controller 80 providing cylinder deactivation commands or alternating valve lift commands in response to cylinder deactivation conditions or engine operating conditions based on one or more signals from one or more of the above-described sensors of the internal combustion engine system 10. The cylinder deactivation and alternating valve lift commands control the VA mechanism 90 to switch input camshaft lobes to provide the desired intake and exhaust valve closing or opening / closing lift profile and / or timing.

[0069] The control procedures performed by the controller 80 may be performed by a processor of the controller 80 executing program instructions (algorithms) stored in the memory of the controller 80. The description herein may be implemented by the internal combustion engine system 10. In certain embodiments, the internal combustion engine system 10 further includes a controller 80 structured or configured to perform specific operations to control the internal combustion engine system 10 in achieving one or more target states. In certain embodiments, the controller forms part of a process subsystem that includes one or more computing devices having memory, processing, and communication hardware. The controller may be a single device or a distributed device, and the functions of the controller 80 may be performed by hardware and / or by instructions encoded on a computer-readable medium.

[0070] In particular embodiments, the controller 80 includes one or more modules structured to functionally perform the operations of the controller. The description herein of a module emphasizes structural independence from the aspects of the controller and illustrates one group of controller operations and responsibilities. Other groups performing similar overall operations are understood to be within the scope of this application. The modules may be implemented in hardware and / or software on a non-transitory computer-readable storage medium, and the modules may be distributed across various hardware or other computer components.

[0071] Certain operations described herein include operations for interpreting or determining one or more parameters. As used herein, interpreting or determining includes receiving a value by any method known in the art, including at least receiving a value from a data link or network communication, receiving an electronic signal (e.g., a voltage, frequency, current, or PWM signal) indicative of the value, receiving a software parameter indicative of the value, reading a value from a memory location on a non-transitory computer-readable storage medium, receiving a value as a run-time parameter by means known in the art, and / or by receiving a value from which the interpreted or determined parameter can be calculated, and / or by referencing a default value that is interpreted or determined to be the parameter value.

[0072] Various aspects of the present disclosure are contemplated as described herein. According to one aspect, a rocker system for an internal combustion engine having a camshaft including at least one camshaft lobe is disclosed, the at least one camshaft lobe including a cam lobe profile having a first portion, a second portion, and a third portion. The rocker system includes at least one input rocker lever rotatable about an engine component in response to motion received from the at least one camshaft lobe, and an output rocker lever rotatable about the engine component. The output rocker lever can be selectively coupled to the at least one input rocker lever associated with a cylinder of the internal combustion engine to selectively control opening and closing of at least one of an intake valve and an exhaust valve. The at least one input rocker is rotated by the first portion of the cam lobe profile to generate a desired lift of at least one of an exhaust valve and an intake valve while the at least one input rocker lever is coupled to the output rocker lever. The at least one input rocker is rotated by a second portion of the cam lobe profile to offset the at least one input rocker lever and the output rocker lever to prevent coupling between the at least one input rocker lever and the output rocker lever, and the at least one input rocker lever is rotated by a third portion of the cam lobe profile to align the at least one input rocker lever and the output rocker lever to couple the at least one input rocker lever to the output rocker lever.

[0073] In one embodiment, at least one input rocker lever is aligned with the output rocker lever for switching engagement with the output rocker lever over a first range of crank angles of a crankshaft of the internal combustion engine.

[0074] In a further embodiment, the at least one input rocker is offset from the output rocker to prevent switching engagement with the output rocker lever over a second range of crank angles of a crankshaft of the internal combustion engine. In another further embodiment, the output rocker lever controls opening and closing of at least one of the exhaust valve and the intake valve while switching engagement with the input rocker lever.

[0075] In one embodiment, the rocker system includes at least one valve lift switch for coupling the at least one input rocker lever to the output rocker lever when the at least one input rocker is aligned with the output rocker to transfer motion from the first portion of the at least one camshaft lobe to at least one of the exhaust valve and the intake valve.

[0076] In a further embodiment, the at least one input rocker lever includes a first input rocker lever and the rocker system includes a second input rocker lever, the first and second input rocker levers each rotatable about the engine component in response to motion received from a respective one of the first and second camshaft lobes of the camshaft.

[0077] In yet another embodiment, the at least one valve lift switch includes at least one pin movable to selectively couple each of the first and second input rocker levers to the output rocker lever. In yet another embodiment, the at least one valve lift switch includes a first pin movable to selectively couple the first input rocker lever to the output rocker lever and a second pin movable to selectively couple the second input rocker lever to the output rocker lever.

[0078] According to another aspect of the present disclosure, a camshaft for an internal combustion engine is provided. The engine has a cylinder and at least one of an intake valve and an exhaust valve associated with the cylinder. The camshaft includes at least one camshaft lobe configured to control the opening and closing timing of at least one of the exhaust valve and the intake valve by directing movement of a rocker lever. The at least one camshaft lobe includes a cam lobe profile including a first portion, a second portion, and a third portion. The first portion generates lift for opening at least one of the exhaust valve and the intake valve via the rocker lever while the rocker lever is associated with the at least one of the exhaust valve and the intake valve. The second portion offsets the rocker lever to prevent association of the rocker lever with the at least one of the exhaust valve and the intake valve. The third portion aligns the rocker lever for association with the at least one of the exhaust valve and the intake valve.

[0079] In one embodiment, the third portion of the cam lobe profile is a constant lift profile that lifts the rocker lever over a first range of crank angles of a crankshaft of the internal combustion engine.

[0080] In a further embodiment, the second portion of the cam lobe profile is a base circle profile that extends from the first portion of the cam lobe profile to the third portion of the cam lobe profile. In another further embodiment, the third portion of the cam lobe profile is connected to the first portion of the cam lobe profile by a transition portion that is smaller in size than the constant lift profile.

[0081] According to another aspect, a valve train for an internal combustion engine is provided. The valve train includes one of an intake valve or an exhaust valve, a camshaft including a camshaft lob, a first rocker lever movable by the camshaft lobe, and a switching device for selectively coupling the first rocker lever to a second rocker lever. The camshaft lobe includes a lift profile having a first portion that lifts one of the intake valve or the exhaust valve associated with the camshaft lobe via the first rocker lever, a second portion that offsets the first rocker lever and the second rocker lever, and a third portion that aligns the first rocker lever with the second rocker lever.

[0082] In one embodiment, the second at least one other rocker lever is an output rocker lever connected to one of the intake valve or the exhaust valve.

[0083] In one embodiment, the second rocker lever is moved by a second camshaft lobe, the second camshaft lobe including a second lift profile that lifts one of the intake valve or the exhaust valve when associated with the second camshaft lobe via the second rocker lever, the second camshaft lobe including a base circle portion that is the same size as a third portion of the camshaft lobe.

[0084] In one embodiment, the second portion of the camshaft lobe lift profile offsets the switching device to prevent binding between the first rocker lever and the second rocker lever.

[0085] In one embodiment, a second portion of the camshaft lobe lift profile aligns the switching device to couple the first rocker lever with the second rocker lever.

[0086] In one embodiment, the switching device includes at least one pin that is received in one of the first and second rocker levers when the first and second rocker levers are not coupled to one another. In a further embodiment, the at least one pin spans between the first and second rocker levers when the first and second rocker levers are coupled to one another.

[0087] Another aspect of the present disclosure includes a method of operating a rocker system, the method including aligning an input rocker lever and an output rocker lever with a camshaft lobe, coupling the aligned input rocker lever to the output rocker lever, lifting at least one of an intake valve and an exhaust valve with the output rocker lever in response to movement of the input rocker lever induced by the camshaft lobe, decoupling the input rocker lever from the output rocker lever, and offsetting the input rocker lever and the output rocker lever with the camshaft lobe to prevent coupling of the input rocker lever and the output rocker lever until the input rocker lever and the output rocker lever are aligned by the camshaft lobe.

[0088] While the present invention has been illustrated and described in detail in the drawings and foregoing description, it is to be understood that such illustration and description is to be considered exemplary and not limiting in character, and that only certain exemplary embodiments have been shown and described. Those skilled in the art will appreciate that many modifications are possible to the exemplary embodiments without materially departing from the invention. Accordingly, all such modifications are intended to be included within the scope of the present disclosure as defined in the following claims.

[0089] When reading a claim, the use of words such as "a," "an," "at least one," or "at least a portion" is intended to limit the claim to only one item unless the claim specifically states to the contrary. When the words "at least a portion" and / or "a portion" are used, the item can include a portion and / or the whole of the item unless the claim specifically states to the contrary.

Claims

1. 1. A rocker system for an internal combustion engine having a camshaft including at least one camshaft lobe, the at least one camshaft lobe including a cam lobe profile having a first portion, a second portion, and a third portion, the rocker system comprising: at least one input rocker lever rotatable about an engine component in response to motion received from said at least one camshaft lobe; an output rocker lever rotatable about the engine component, the output rocker lever being selectively coupled to the at least one input rocker lever to control opening and closing of at least one of an exhaust valve and an intake valve associated with a cylinder of the internal combustion engine, the at least one input rocker lever being rotated by the second portion of the cam lobe profile to generate a desired lift of the at least one of the exhaust valve and the intake valve while the at least one input rocker lever is coupled to the output rocker lever. wherein the at least one input rocker lever is rotated by the first portion of the cam lobe profile to offset the at least one input rocker lever and the output rocker lever to prevent coupling between the at least one input rocker lever and the output rocker lever, and the at least one input rocker lever is rotated by the third portion of the cam lobe profile to align the at least one input rocker lever and the output rocker lever to couple the at least one input rocker lever to the output rocker lever.

2. 2. The rocker system of claim 1, wherein the at least one input rocker lever is aligned with the output rocker lever for switching engagement with the output rocker lever over a first range of crank angles of a crankshaft of the internal combustion engine.

3. 3. The rocker system of claim 2, wherein the at least one input rocker lever is offset with respect to the output rocker lever to prevent the at least one input rocker lever from switching engagement with the output rocker lever over a second range of crank angles of the crankshaft of the internal combustion engine.

4. The rocker system of claim 2 , wherein the output rocker lever controls the opening and closing of the at least one of the exhaust valve and the intake valve through switching engagement with the input rocker lever.

5. 2. The rocker system of claim 1, further comprising at least one valve lift switch for coupling the at least one input rocker lever to the output rocker lever when the at least one input rocker lever is aligned with the output rocker lever to transfer motion from the first portion of the at least one camshaft lobe to the at least one of the exhaust valve and the intake valve.

6. 6. The rocker system of claim 5, wherein the at least one input rocker lever includes a first input rocker lever, the rocker system further comprising a second input rocker lever, the first input rocker lever and the second input rocker lever each rotatable about the engine component in response to motion received from a respective one of a first camshaft lobe and a second camshaft lobe of the camshaft.

7. 7. The rocker system of claim 6, wherein the at least one valve lift switch includes at least one pin movable to selectively couple each of the first input rocker lever and the second input rocker lever to the output rocker lever.

8. 7. The rocker system of claim 6, wherein the at least one valve lift switch includes a first pin movable to selectively couple the first input rocker lever to the output rocker lever, and a second pin selectively movable from the second input rocker lever to the output rocker lever.

9. 1. A camshaft for an internal combustion engine having a cylinder and at least one of an intake valve and an exhaust valve associated with the cylinder, the camshaft comprising: the at least one camshaft lobe is configured to control timing of opening and closing of the at least one of the exhaust valve and the intake valve by the at least one camshaft lobe inducing movement of a rocker lever, the at least one camshaft lobe having a cam lobe profile, a second portion that generates lift to open the at least one of the exhaust valve and the intake valve via the rocker lever while the rocker lever is associated with the at least one of the exhaust valve and the intake valve; a first portion that offsets the rocker lever from other rocker levers to prevent association of the rocker lever with the at least one of the exhaust valve and the intake valve; and a third portion aligning the rocker lever with the other rocker lever to associate the rocker lever with the at least one of the exhaust valve and the intake valve.

10. 10. The camshaft of claim 9, wherein the third portion of the cam lobe profile is a constant lift profile that lifts the rocker lever over a first range of crank angles of a crankshaft of the internal combustion engine.

11. 11. The camshaft of claim 10, wherein the first portion of the cam lobe profile is a base circle profile that extends from the second portion of the cam lobe profile to the third portion of the cam lobe profile.

12. 11. The camshaft of claim 10, wherein the third portion of the cam lobe profile is connected to the second portion of the cam lobe profile at a transition portion that is smaller in size than the constant lift profile.

13. 1. A valve train for an internal combustion engine, said valve train comprising: one of an intake valve or an exhaust valve; a camshaft including a camshaft lobe; a first rocker lever movable by the camshaft lobe; a switching device for selectively coupling the first rocker lever to a second rocker lever, wherein the camshaft lobe includes a lift profile having a second portion that lifts the one of the intake valve or the exhaust valve associated with the camshaft lobe via the first rocker lever, a first portion that offsets the first rocker lever and the second rocker lever, and a third portion that aligns the first rocker lever and the second rocker lever.

14. 14. The valve train of claim 13, wherein a second at least one other rocker lever is an output rocker lever connected to said one of said intake valve or exhaust valve.

15. 14. The valve train of claim 13, wherein the second rocker lever is moved by a second camshaft lobe, the second camshaft lobe including a second lift profile that lifts the one of the intake valve or the exhaust valve when associated with the second camshaft lobe via the second rocker lever, and the second camshaft lobe includes a base circle portion that is the same size as the third portion of the camshaft lobe.

16. 14. The valve train of claim 13, wherein the first portion of the lift profile of the camshaft lobe offsets the switching device to prevent binding between the first rocker lever and the second rocker lever.

17. 14. The valve train of claim 13, wherein the third portion of the lift profile of the camshaft lobe aligns the switching device to couple the first rocker lever and the second rocker lever.

18. 14. The valve train of claim 13, wherein the switching device includes at least one pin, the at least one pin being received in one of the first rocker lever and the second rocker lever when the first rocker lever and the second rocker lever are not coupled to one another.

19. 19. The valve train of claim 18, wherein the at least one pin spans between the first rocker lever and the second rocker lever when the first rocker lever and the second rocker lever are coupled to one another.

20. 1. A method for operating a rocker system, said method comprising: aligning the input rocker lever and the output rocker lever with a camshaft lobe; coupling the aligned input rocker lever to the output rocker lever; lifting at least one of an intake valve and an exhaust valve with the output rocker lever in response to movement of the input rocker lever induced by the camshaft lobe; decoupling the input rocker lever from the output rocker lever; offsetting the input rocker lever and the output rocker lever with the camshaft lobe to prevent coupling between the input rocker lever and the output rocker lever until the camshaft lobe aligns the input rocker lever and the output rocker lever.

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