Field

[001] This application provides a shift roller assembly that can be used according to alternative systems & methods to enable variable valve actuation in a valvetrain.

Background

[002] Prior art switchable valvetrains can be heavy, as when side-by-side rocker arms are used. And while the teachings herein can be used with, for example, an engine braking rocker arm to actuate a valve in a valve bridge, it is desired to eliminate the use of a second or third rocker arm next to a primary rocker arm when enabling variable valve lift.

SUMMARY

[003] The methods disclosed herein overcome the above disadvantages and improves the art by way of A roller shifter for a valvetrain can comprise a shift bar assembly, a shift roller assembly, and a roller axle. The shift bar assembly can comprise a first limiter and a first spring biased against the first limiter and a second limiter and a second spring biased against the second limiter. The shift roller assembly can be mounted to slide on the shift bar in between the first spring and the second spring. The shift roller assembly can comprise a shift roller mount comprising a bushing connected to a roller coupling and a roller assembly comprising a shift roller. Roller axle can join the shift roller and the roller coupling.

[004] A valvetrain can comprise the roller shifter and can further comprise a cam assembly configured to rotate around an axis. The cam assembly can comprise a rocker arm cam and a shift cam. The shift roller can be configured with the shift bar to selectively engage against or disengage from the shift cam. The shift roller can be configured to selectively engage and disengage against the shift cam when a shift bar actuator actuates the shift bar assembly. The valvetrain can further comprise a rocker arm configured to actuate against the rocker arm cam, the rocker arm mounted to a portion of the roller axle. [005] Additional objects and advantages will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the disclosure. The objects and advantages will also be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[006] FIGs. 1 A & 1 B are perspective views of a valvetrain, rocker arm, cam assembly, roller shifter, shift roller assembly, shift roller mount, and roller assembly with the shift bar assembly in a disengaged position.

[007] FIGs. 2A & 2B show first variable valve actuation teachings for cylinder decompression.

[008] FIGs. 2C & 2D show additional variable valve actuation teachings for late intake valve closing (LIVC).

[009] FIGs. 3A-3C show the drive mode.

[010] FIG. 4 shows the shift bar assembly actuated to preload first spring against shift roller mount thereby readying shift roller 321 to move in the latching window.

[011] FIGs. 5A & 5B show the shift roller moved into the latching window from the disengaged position.

[012] FIGs. 5C & 5D show the shift roller engaged on the shift cam to implement cylinder decompression.

[013] FIGs. 6A & 6B show the shift bar assembly preloaded to disengage the shift roller from the shift cam. Second spring is compressed by second limiter against shift roller mount.

[014] FIG. 7 shows a first view of the shift roller relative to the shift cam for the late intake valve closing.

[015] FIG. 8 shows the rocker arm roller engaged on the rocker arm cam for drive mode.

DETAILED DESCRIPTION

[016] Reference will now be made in detail to the examples which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. [017] A first step towards possible electrification of commercial vehicles will lead through hybridization of the powertrain. An integrated de-compressor system helps to spin an engine easier during starts or during coasting on electric power.

[018] During engine starts, a starter has to overpower forces from compression inside a combustion chamber. Therefore, an initiation of turning the crankshaft has a significant electric consumption from a battery. With the premise that an engine is going to be equipped with an ability to switch between conventional powertrain and electric powertrain or start/stop system, there will be an effort to decrease electric consumption from batteries. One intention is to keep the vehicle operation range on electric energy as high as possible. Cylinder decompressor helps to the starter smoothly turn the engine with lower required torque.

[019] In a first aspect, a shift roller assembly 30 is formed with a shift roller mount 300 and a roller assembly 320. Such can be incorporated in a roller shifter 10 comprising a shift bar actuator 11 acting on a shift bar assembly 20. The shift bar assembly 20 can be configured to push the shift roller mount 300 towards and away from adjacent cam assembly 60, 70. The cam assembly 60, 70 can be configured to act on a rocker arm 40. Figures 1 A-2B, 3A-6B illustrate a first aspect of variable valve actuation while Figures 2C, 2D, 7A, & 7B illustrate a second aspect of variable valve actuation.

[020] The shift roller assembly 30 can be pulled or pushed by the roller shifter 10 to engage or disengage the cam assembly 60, 70. When disengaged, the shift roller assembly 30 does not drag on the cam assembly 60, 70, thereby avoiding an energy drain as when compared to side-by-side rocker arm of the prior art where roller bearings engage the cam assembly at all times. Further, the shift roller assembly 30 can be light-weighted over prior art multiple rocker arm valvetrains. In lieu of an additional rocker arm and its weight and drag, the shift roller assembly can be driven by a shift fork in the form of shift roller mount 300. Linear movement of the shift bar assembly 20 biases or moves the shift roller mount 300. For example, a shift bar actuator 11 , such as a linear motor, worm gear, solenoid, electromagnetic plates, among others, can be configured with controls such as an electronic control unit (ECU) with wiring, programming, feedback, among others. Shift bar actuator 11 can drive the shift bar 21 back and forth. [021] Latching window portions S1 , S12 between window boundaries W1 , W2, W12, W22 can be devised to smoothly engage and disengage the shift roller assembly 30 with the cam assembly 60, 70. In case the shift bar actuator 11 moves the roller assembly 320 at a time when the shift roller 321 cannot move onto or off of the corresponding cam assembly 60, 70, a preload arrangement on the shift bar assembly 20 provides an ability to act in the latching window. When the latching window is open, switching areas S1 , S12 (latching window portions) are aligned with the shift roller 321 , and the shift roller mount 300 can be moved via the preload arrangement.

[022] As one implementation, the shift roller valve lift curve S1 of cam assembly 60 can be configured to switch between cylinder decompression and a drive mode D1 . As another variable valve actuation technique, the shift roller valve lift curve S12 of cam assembly 70 can be configured to switch between a nominal lift (drive mode D12) and Late Intake Valve Closing (LIVC). Alternatives of late or early intake or exhaust valve opening and closing (e.g. EEVO, EIVO, EEVC, EIVC, LIVO, LEVO, LEVC, etc.) exist in the art and can even be combined for techniques such as negative valve overlap (NVO) & internal exhaust gas recirculation (iEGR).

[023] The at-rest position of the roller shifter 10 can be chosen to facilitate start-up and shut down operations. For example, during shut-down, it can be possible to engage the shift roller 321 with the cam assembly 60, 70. Then, when power is off, the shift roller 321 remains engaged. At start-up, no power is needed to begin a cylinder decompression operation. When the speed of the engine moves beyond one benefitting from cylinder decompression, ECU can send a control signal to shift bar actuator 11 , such as a linear actuator, which will move the shift bar assembly 20 to disengage the shift roller 321 and convert the cylinder of the valvetrain to the drive mode. Being aligned along a shift bar 21 , the system is conducive to actuating banks and rows of valves.

[024] A roller shifter 10 for a valvetrain 1 can comprise a shift bar assembly 20, a shift roller assembly 30, and a roller axle 310. The shift bar assembly 20 can comprise a first limiter 23 and a first spring 25 biased against the first limiter 23, and a second limiter 24 and a second spring 26 biased against the second limiter 26. Example braces 22 are shown and are omitted in Figure 3A, 7, & 8 to provide unobstructed side views. The shift roller assembly 30 can be mounted to slide on the shift bar 21 in between the first spring 25 and the second spring 26. The shift roller assembly 30 can comprise a shift roller mount 300 comprising a bushing 302 connected to a roller coupling 307 and a roller assembly 320 comprising a shift roller 321 . Roller axle 310 can join the shift roller 321 and the roller coupling 307.

[025] Roller shifter 10 can comprise the shift bar assembly 20 as a unit that can be joined to a shift bar actuator 11 , or these can be an integrated unit. Shift bar actuator 11 and controls therefor can be installed with valvetrain 1 . Shift bar 21 can be connected to the shift bar actuator 11 for linear motion. The first and second limiters 23, 24 can be pressed to or pushed from the respective first and second springs 25, 26. These springs 25, 26 can be at least one coil spring, a leaf spring, a wave spring or another biasing mechanism known in the art, such as a plunger assembly.

[026] With the shift roller mount 300 of the shift roller assembly 30 mounted between the first and second springs 25, 26, it is pushed by the spring forces spanning the first and second limiters 23, 24 and the shift roller mount 300. A roller mount body 301 forming the shift roller mount 300 can comprise several aspects. A bushing 302 can encircle a portion or all of the shift bar 21 and can abut one of the first or second spring 25, 26 (illustrated against second spring 26).

[027] The bushing 302 can be connected to guide body 303 with the guide body 303 comprising at least one guide feature 304 configured to engage against a guiding surface. An optional guide body 303 can act as a bracket and can form a surface against the other of the first or second spring 25, 26 can press upon. Guide body 303 can project away from the bushing 302 to abut a manifold or a portion of the tower surrounding the valvetrain 1 . A guiding surface 304 can be a flat, for example, to slide against a seating surface of a manifold or tower. Guide body 303 can also form a counterbalance for the roller assembly 320.

[028] The shift roller mount 300 comprises extension arms 305, 306 to connect the bushing 302 and the roller coupling 307. Roller coupling 307 can comprise prongs to surround the roller axle 310 or a bore 308 through a body of material at the end of the extension arms 305, 306. Roller assembly 320 can be suspended from the roller coupling 307.

[029] The roller assembly 320 can comprise a shift plate 323 fixed to the shift roller 321 . The shift roller mount 300 is seated in between the shift plate 323 and the shift roller 321 . Shift plate 323 can be sized to stabilize the shift roller 321 against wobble. Shift plate 323 can be pressed against extension arms 305, 306. A connector 322 can be gripped by the roller coupling 307. Shift roller 321 can be connected to the connector 322 for rotation. A slider pad is an alternative for the shift roller 321 . A lightweight plate can form the shift roller 321 , or arrangements comprising roller bearings, needle bearings, and axles can be included.

[030] Valvetrain 1 can additionally comprise a cam assembly 60, 70 configured to rotate around an axis centered through the cam rail bore 63. The cam assembly 60, 70 can comprise a rocker arm cam 61 , 71 and a shift cam 62, 72. The shift roller 321 is configured with the shift bar 21 to selectively engage against or disengage from the shift cam 62, 72. Shift bar actuator 11 can be controlled to act on the shift bar 21 for the selective engagement or disengagement. So, the shift roller 321 is configured to selectively engage and disengage against the shift cam 62, 72 when a shift bar actuator 11 actuates the shift bar assembly 20.

[031] The valvetrain 1 can further comprise a rocker arm 40 configured to actuate against the rocker arm cam 61 , 71 . The rocker arm 40 can be mounted to a portion of the roller axle 310. Rocker arm 40 can comprise a rocker arm body 401 . A rocker shaft bore 402 can be formed through the rocker arm body 401 for rotation around rocker shaft 420. On a valve end 403, a capsule bore 405 can seat an insert 406 such as a spigot, lash assembly, switchable capsule, or the like. For example, a hydraulic lash adjuster or mechanical lash adjuster can be the insert 406, or a castellation device or piston or plunger arrangement can form the insert 406. Switching like cylinder deactivation, engine braking, or the like can thereby be accomplished. An e-foot (elephant foot) 407 can be affixed to the insert 406 to act on an optional valve bridge 408 for valves 409. Valve bridge 408 can be switchable, as by including a pass-through. On a cam end 404, rocker arm 40 can comprise rocker arm roller arms 410, 411 . Rocker arm axle bores 413 can pass through the rocker arm roller arms 410, 411 for seating the roller axle 320, a portion of which is shared with the shift roller assembly 320. A rocker arm roller 414 can be seated for rotation on the roller axle 320 with or without internal needle bearings. It is also possible for one or both of the rocker arm roller arms 410, 411 to comprise guide walls or guide grooves for guiding or stabilizing the roller assembly 320. [032] With the rocker arm 40 configured to open and close the valves 409 on the combustion cylinders of cylinder head 80, alternative variable valve actuation examples will be shared, with other VVA techniques being compatible herewith by adjusting the profile of the shift cams 62, 72 and shift rollers 321 .

[033] The first example of using a valvetrain 1 for cylinder decompression is shown in Figures 2A & 2B. Piston reciprocations and cam angles CA are graphed in Figure 2A with valve motions illustrated for comparisons. The piston can go among bottom dead center BDC and top dead center TDC with the one or more exhaust valve EX and intake valve IN opening and closing in the drive mode. VVA mode can comprise the cylinder decompression CDC with several alternative curves shown in dashed lines alongside the exemplary solid line curve. Cylinder decompression CDC holds one or more valve open for a selected duration, typically the exhaust valve. To switch between the drive mode and cylinder decompression CDC modes, it is possible to configure the rocker arm cam 63 to comprise a first base circle portion BC1 and a first drive mode portion D1 . The shift cam 62 can be configured to comprise a second drive mode portion D2 different than the first drive mode portion D1 , and a latching window portion (also called a switching window) S1 between window boundaries W1 , W2. The second drive mode portion D2 can align along the axis with the first base circle portion BC1 . A center point for the axis is represented by the dot in Figure 2B. A reference line RL1 is shown in Figure 2B to represent that the latching window portion S1 of the shift cam 62 is of a reduced diameter compared to first base circle position BC1 . Window boundary W2 can comprise a step portion, while window boundary W1 can comprise a smooth portion. If the cam assembly 60 of Figure 2B is rotating counterclockwise, the shift roller 321 can slide over from the disengaged position of Figures 1 A & 1 B into the latching window shown in Figures 5A & 5B. Such motion can be direct, meaning that the shift bar assembly 20 is actuated in the latching window to move the shift roller 321 to or from the disengaged position and the position over the latching window portion S1 . Or, a preload technique can be used. A preload can be applied as shown in Figures 4, 6A, & 6B. The preload activates before the shift roller 321 slides on roller axle 310 to put shift roller 321 over the latching window portion S1 . Then, the timing of the control signal can have more tolerance, and the signal can be sent to the shift bar actuator 11 without causing any critical shifts. [034] For implementing cylinder decompression, the latching window portion S1 comprises a reduced lift profile relative to the first base circle portion BC1 . This is seen by extending the reference line RL1 out from base circle and comparing to the latching window portion S1. And, the latching window portion S1 aligns along the axis with the first drive mode portion D1 . In other words, the latching window portion S1 has overlapping cam angle with the first drive mode portion. Instead of the rocker arm roller 414 seating on base circle BC1 , the shift roller 321 seats on the second drive mode portion D2 and lifts the rocker arm roller 414 above the base circle BC1 (see Fig. 5C).

[035] The preload can comprise the first spring 23 configured to exert a first spring force on the shift roller mount 300 when the shift bar assembly 20 is moved to an engaging position. The shift roller 321 can be configured to adjoin the shift cam 62 while it rotates until the latching window portion S1 aligns with the shift roller 321 . With the alignment, the shift roller 321 can move over the latching window portion S1 for engaging with the shift cam 62. Then, to disengage, the second spring 25 can be configured to exert a second spring force on the shift roller mount 300 when the shift bar assembly 20 is moved to a disengaging position. The shift roller 321 can be configured to roll on the shift cam 62 while it rotates until the latching window portion S1 aligns with the shift roller 321 . Then the shift roller 321 can move out from the latching window portion S1 and return to the disengaged position. Moving the shift roller 321 out of engagement in this way avoids placing weight on the cam assembly 60 and prevents the shift roller 321 from dragging on the shift cam 62 when the shift roller is not used for WL.

[036] In a second aspect, valvetrain 1 and components thereof enable a change of valve lift in a type III valve train. The cam assembly 70 comprises two cam lobes, a rocker arm cam 71 and a shift cam 72. As explained in Figures 2C & 2D, this is useful for variable valve lift (VVL) with a working example of late intake valve closing (LIVC) and with other WL techniques compatible herewith. In Figure 2C it can be seen that a valve lift height over time can change from the intake drive profile DRIVE IN to the late intake valve closing LIVC. The cam diagram in Figure 2D shows that both lift profiles share base circle so that the rocker arm cam 71 comprises a first base circle BC12 and a second base circle portion that is also the switching window (latching window portion S12). Reference line RL2 is useful to show the relative lift of the remaining lobes as compared to first base circle BC12. If the cam of Figure 2D were rotating clockwise, the drive mode D12 in solid line would yield the intake drive profile DRIVE IN. Figure 7 shows the shift roller 321 aligned with the latching window portion S1 , as the shift roller 321 can be smaller in size than the other embodiment. Shift roller 321 can have a diameter the same or smaller than the rocker arm roller 414. The shift roller 321 can have a moment on base circle where it gaps from the cam assembly 70, yielding easy switching between the engaged and disengaged positions.

[037] Ever tightening emission standards forces OEM to add variability to Internal Combustion Engines (ICs), to operate in as efficient regions as possible. One of the ways to achieve it is to add variability to the valvetrain and thus achieve other than standard valve timing (e.g.: LIVC, EEVO, LIVO). Mechanisms described in this disclosure enables this variability, also called variable valve actuation (“VVA”) and as a subset of WA, cylinder decompression or engine braking.

[038] A shift roller 321 enables engaging with a secondary cam lobe, also called a shift cam 72. During the drive mode, shown in Figure 8, shift roller 321 is held by shift fork (shift roller mount 300) in a position out of reach of the shift cam 72 and the rocker arm roller 414 follows the primary cam lobe (rocker arm cam 71 ). When a controller such as an electronic control unit (ECU) sends a control signal, a shift bar actuator 11 such as a linear actuator moves with shift bar assembly 20 and preloads first spring 23 on the shift bar 21 . When an actuation window (latching window) occurs, the spring force of the first spring engages the shift roller 321 with the shift cam 72 and the shift fork (shift roller mount 300) holds the shift roller 321 on position. To return to the drive mode, ECU sends another control signal to shift bar actuator 11. Shift bar assembly 20 moves with or without the preloading of second spring 26. If the shift roller 321 is unloaded (is on base circle), shift roller 321 moves out of reach of the shift cam 72. Moving the shift roller 321 out of engagement in this way avoids placing weight on the cam assembly 70 and prevents the shift roller 321 from dragging on the shift cam 722 when the shift roller 321 is not used forVVL.

[039] So, the rocker arm cam 71 can comprise a first base circle portion BC12 and a first drive mode portion D12. The shift cam 72 can comprise a second base circle portion BC22, a second drive mode portion D22 different than the first drive mode portion D12, and a latching window portion S12 overlapping with the second base circle portion BC22. The second base circle portion corresponding to latching window portion S12 aligns along the axis with the first base circle portion BC12. The latching window portion S1 can comprise a reduced or same lift profile relative to the first base circle portion BC12. The second drive mode portion D22 can comprise a second portion of lift profile that is greater than a first portion of lift profile of the first drive mode portion D12. The greater second portion of lift profile can provide a variable valve lift function such as late intake valve closing. The first portion of lift profile is aligned along the axis with the second portion of lift profile. That is, the first portion of lift profile has overlapping cam angle with the second portion of lift profile.

[040] The first spring 25 can be configured to exert a first spring force on the shift roller mount 300 when the shift bar assembly 20 is moved to an engaging position. And, the shift roller 321 can be configured to adjoin the shift cam 72 while it rotates until the latching window portion S12 aligns with the shift roller 321.

[041] The second spring 26 can be configured to exert a second spring force on the shift roller mount 300 when the shift bar assembly 20 is moved to a disengaging position. The shift roller 321 can be configured to roll on the shift cam 72 while the shift cam rotates until the latching window portion S12 aligns with the shift roller 321 .

[042] Other implementations will be apparent to those skilled in the art from consideration of the specification and practice of the examples disclosed herein.