LOW FRICTION SWITCHING ROLLER FINGER FOLLOWER FOR HIGH VALVE LIFT

Abstract

A switching roller finger follower for valve actuation comprises a pair of outer arms comprising an axle mounting. A bridge portion joins the pair of outer arms. A latch assembly comprises a ferrule. The ferrule is configured to reciprocate in a latch recess. An inner arm is pivotably mounted to a main axle and comprises a bearing rotatably mounted to a bearing axle. The bearing is configured to transfer forces from a cam lobe to the inner arm. A catch on the inner arm is configured to latch against the lip when the ferrule is in a first position. The catch can pivot past the ferrule when the ferrule is in a second position.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No. PCT/US2016/068140 filed Dec. 21, 2016, which claims the benefit of priority of U.S. Provisional Patent Application No. 62/271,391 filed on Dec. 28, 2015, U.S. Provisional Patent Application No. 62/279,976 filed on Jan. 18, 2016, U.S. Provisional Application No. 62/349,983 filed on Jun. 14, 2016, U.S. Provisional Patent Application No. 62/350,621 filed on Jun. 15, 2016, and Indian Patent Application No. 201611029817 filed on Aug. 31, 2016, the contents of which are incorporated herein by reference in their entireties.

GOVERNMENT RIGHTS STATEMENT

This invention was made with Government support under Agreement No. DE-EE0005981, awarded by the US Department of Energy. The US Government has certain rights in the invention.

FIELD

This application provides a variable valve actuation switching roller finger follower for late intake valve closing.

BACKGROUND

Variable valve actuation refers to manipulating the timing of valve action with respect to engine cylinders. A cylinder of an engine has a reciprocating piston. An intake valve controls when the cylinder is open to intake a charge, and an exhaust valve controls when the cylinder is open to exhaust a spent charge. Techniques include early intake valve closing (EIVC) and late intake valve closing (LIVC). “Early” and “Late” are with respect to a normal Otto cycle valve closing timing, which is near bottom dead center of piston travel.

Another technique deactivates the valve motion altogether, resulting in a “lost motion.” Examples of mechanisms for cylinder deactivation can be seen in WO 2014/071373, and related applications, assigned to the present applicant. The mechanisms of WO 2014/071373 are used for implementing either a valve lift event or a cylinder deactivation event. The rocker arm can either actuate a valve, or accommodate “lost motion” during a cylinder deactivation event.

Trying to use such a rocker arm for alternative variable valve lift actuations is problematic, because there are two valve lift heights to accommodate when trying to provide both normal lift and one of EIVC or LIVC. Early intake valve closing (EIVC) can achieve some success using the prior art mechanisms. EIVC is a “low lift” event.

Late intake valve closing (LIVC) is a “high lift” event. Trying to use the cylinder deactivation rocker arm of WO 2014/071373 for LIVC results in a high friction, energy-losing event, as the LIVC event takes place on the sliding interface, and the normal lift event takes place on the rolling interface. The fuel savings benefits of LIVC are negated by the friction losses. Merely reversing the rolling and sliding events on the mechanism of FIGS. 53 & 77 of WO 2014/071373 does not sufficiently solve the dual goals of a high lift event with low loss parameters. The prior art arrangement is for deactivation, and not for low and high lift events. And, the design of FIG. 99 of WO 2014/071373 accommodates only a single cam lobe. The single cam lobe design works for the embodiment of FIG. 99 of WO 2014/071373 because the valve lift event is designed for a single height and the other event is a “no lift” event during cylinder deactivation. Thus, the prior art does not adequately provide a mechanism for providing two valve lift events of differing heights with simultaneous low friction losses on the cam rail.

What is needed is a variable valve lift assembly that provides two different valve lift heights with low actuation losses.

SUMMARY

The methods, devices, and assemblies disclosed herein overcome the above disadvantages and improves the art by way of a switching roller finger follower for valve actuation.

In a first aspect, the switching roller finger follower can comprise a pair of outer arms are configured to transfer forces from a pair of outer cam lobes. The pair of outer arms comprise respective axle mountings. A bridge portion joins the pair of outer arms. The bridge portion comprises a first spring seat opposite a second spring seat, and a latch recess between the first spring seat and the second spring seat. A latch assembly comprises a ferrule, and the ferrule is configured to reciprocate in the latch recess. A main axle is mounted in the respective axle mountings. An inner arm is pivotably mounted to the main axle. The inner arm comprises an inner bearing axle comprising portions extending through the inner arm. An inner bearing is rotatably mounted to the inner bearing axle. The inner bearing is configured to transfer forces from a cam lobe to the inner arm. A catch can be on the inner arm. The catch can be configured to latch against the ferrule when the ferrule is in a first position. The catch can be configured to pivot past the ferrule when the ferrule is in a second position. A first spring can be mounted to the first spring seat and a second spring can be mounted mounted to the second spring seat, wherein the first spring and the second spring are biased between the bridge portion and the portions of the inner bearing axle extending through the inner arm. The inner bearing axle is between the bridge portion and the axle mounting.

A switching roller finger follower according to another aspect can comprise a pair of outer arms comprising a wall portion comprising a projection, an axle mounting, and a bearing axle opening. A slider pad extends perpendicular to the wall portion, the slider pad configured to transfer forces from a cam lobe to the respective outer arm. A bridge portion joins the pair of outer arms, the bridge portion comprises a respective spring seat adjacent each wall portion. A latch recess is in fluid communication with a fluid port. The bearing axle opening is between the bridge portion and the axle mounting. A latch assembly comprises a ferrule, the ferrule comprises a lip. The ferrule is configured to reciprocate in the latch recess. A main axle is mounted in the axle mounting. An inner arm is pivotably mounted to the main axle and comprises a bearing rotatably mounted to a bearing axle. The bearing axle extends through the bearing axle openings in the outer arms, and the bearing is configured to transfer forces from a cam lobe to the inner arm. A catch on the inner arm is configured to latch against the lip when the ferrule is in a first position. The catch is configured to pivot past the ferrule when the ferrule is in a second position. A respective spring is mounted to a respective spring seat and is biased between a respective projection and the bearing axle so as to bias the bearing axle towards the slider pad.

The switching roller finger followers disclosed herein can be used in a variable valve lift assembly and can be used in methods of actuating valves.

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

FIG. 1 is a view of a switching roller finger follower.

FIG. 2 is a view of a switching roller finger follower coupled to cam lobes.

FIG. 3 is a view of a switching roller finger follower having a normal lift event.

FIG. 4 is a view of a switching roller finger follower in a high lift event.

FIG. 5 is a cross-section view of a switching roller finger follower in a variable valve lift assembly.

FIGS. 6 & 7 are views of an alternative switching roller finger follower.

FIG. 8 comprises explanatory lift profiles.

FIG. 9 is a flow diagram for a method of switching between normal lift and high lift valve actuation utilizing a switching roller finger follower.

DETAILED DESCRIPTION

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. Directional references such as “left” and “right” are for ease of reference to the figures.

The disclosure provides a variable valve lift assembly with two different valve lift heights and low actuation losses. A section of a cam rail 240, part of a cam assembly 200, is shown having three lobes 210, 220, 230. Normal lift event lobes 210, 220 are eccentric and designed to press on slider pads 610, 620 of switching roller finger follower 100. High lift event lobe 230 is also eccentric and designed to press on bearing 300. When an internal latch assembly 951 is unlatched, the normal lift event occurs, shown in FIG. 3. When the internal latch assembly 951 is latched, as by catching lip 975 of ferrule 970 against catch 350 of inner arm 310, a high lift event occurs, also shown in FIG. 4. The high lift event can correspond to a late intake valve closing (LIVC) event.

FIG. 1 shows a switching roller finger follower 100. An inner arm 310 is pivotably coupled to a pair of outer arms 600 via a main axle 500 mounted to axle mountings 650 in the outer arms. The main axle 500 also couples to a valve coupling 400. The outer arms 600 are joined by a bridge portion 690. The outer arms 600 each comprise a wall portion 670 comprising an axle mounting 650 and a bearing axle opening 640. A slider pad 610 extends perpendicular to the wall portion 670. The slider pad 610 can be arcuate. The slider pad 610 can be in the shape of a tab, and extend like a shelf from an upper edge of the outer arm 600. The slider pad 610 can be proximal and above the bearing axle opening 640. The bearing axle opening can be located between the bridge portion 690 and the axle mounting 650. The slider pad 610 can also be located between the bridge portion 690 and the axle mounting 650. The inner arm 310 pivots between the outer arms 600, and the inner arm 310 can latch to the outer arm assembly inside of the variable valve lift assembly. This protects the latching function from events that can interfere with the inner arm motion.

Inner arm 310 is coupled to a bearing 300 mounted via an inner surface 340 on rollers 330 on a bearing axle 320. The bearing axle 320 can protrude through opening 640 of outer arm 600 wall portion 670. Bearing axle 320 can include a “dog bone” shape to catch against a spring arm 715 of a spring 710. Spring 710 biases spring arm 717 against a projection 615 on the bridge portion 690 or wall portion 670 of outer arm 600. Projection 615 can be, for example, a ledge. a portion of a protruding surface of a groove, or other surface feature. Spring 710 coils around a spring seat 617 on bridge portion 690. Spring seat 617 is adjacent wall portion 670. A cap 800 secures spring 710 on spring seat 617. Spring arm 715 is biased to push bearing axle 320 towards slider pad 610, and thus towards cam rail 240, and in to contact with high lift cam lobe 230. Slider pad 610 can have a shelf-like configuration to extend from wall portion 670 while providing space for bearing axle 320 to reciprocate underneath. Spring arm 715 can move in a plane parallel to the wall portion 670, and beneath the slider pad 610, so that the spring 710 does not protrude past the slider pad 610. This optimizes packaging space. A mirror image arrangement for spring 720 is on the opposite side of switching roller finger follower 100.

Because bearing 300 can rotate (roll) around bearing axle 320, should the high lift cam lobe 230 frictionally drag against bearing 300, it can rotate, and dissipate drag losses. This prevents harm to the engine and the cam rail 240 and ensures the high valve lift event occurs in a low-force fuel economy cycle, such as LIVC.

In order to accommodate the normal and high lift cam lobes 210, 220, 230, the slider pads 610, 620 and bearing 300 must be designed to respect that if too much friction occurs with respect to the cam rail 240, the friction can negate the fuel economy benefits of the LIVC event by placing too much lossy resistance against the cam rail 240. So, the slider pads 610, 620 and associated normal lift cam lobes 210, 220 cannot be too wide. But, if the slider pads 610, 620 and bearing 300 are too narrow, there is high axial stack up of tolerances, issues with thermal growth, and the chance of mis-alignment between the cam lobes and switching roller finger follower surfaces, which can lead to engine failure. Also, poor design results in not enough force transfer from the cam rail to the switching roller finger follower to actuate the valve. So, the widths of the slider pads 610, 620 and bearing 300 must be wide enough to transfer forces from the normal and high lift cam lobes 210, 220, 230, yet not so wide as to deleteriously resist motion of the cam lobes, yet not so narrow as to elude manufacturability. Other design considerations include the bearing 300 and slider pads 610, 620 withstanding the contact stresses conveyed by the cam lobes 210, 220, 230, and designing the slider pads in light of deflection that can occur due to the shelf-like or tab shape portion extending out from the wall portion 670.

Contrasting against the drag and friction issues is spacing: the slider pads 610, 620 and bearing 300 cannot be so wide, nor the lobes so wide, that packaging constraints are not met. If the switching roller finger follower 100 cannot fit in its packaging space over the engine valves, the part goes unused, and so the widths of the slider pads 610, 620 and bearing 300 must be kept narrow.

The inner arm 310 and outer arm 600 also must be sufficiently sturdy, yet conform to packaging requirements.

To incorporate all of these variables, a narrow bearing 300 seats in narrow inner arm 310 to accommodate the high lift event lobe 230, which is always spinning pressed against the bearing 300. Outer arm 600 includes slider pads 610, 620. The slider pads 610, 620 can comprise a coating to reduce friction losses, and the normal lift event lobes 210, 220 slide against the slider pads 610, 620 to push the outer arm 600, and the valve, in a normal valve lift operation (power event). As shown by comparing FIGS. 3 & 4, the high lift event lobe 230 is always in contact with bearing 300, while the normal lift event lobes 210, 220 can pass over the slider pads 610, 620 during a high lift event.

When a normal lift event is selected, the lip 975 is withdrawn towards the latch recess 977 and the catch 350 can pivot past the lip 975. This “lost motion” set-up can be accomplished by applying hydraulic pressure to internal port 695 to a level that the pressure on the ferrule 970 overcomes the spring force of spring 960. The high lift event lobe 230 pushes the bearing 300 down between the outer arm 600. The inner arm 310 provides a “lost motion” function, preventing the high lift event lobe 230 from transferring its valve lift height LH to the valve attached to valve coupling 400. The high lift event is “lost” when the inner arm 310 moves in the unlatched condition. The normal lift lobes 210, 220 press on the slider pads 610, 620 to lift the valve.

When the high lift event is selected, the ferrule 970 is in a normally latched position, and the inner arm 310 catch 350 is latched to lip 975 of ferrule 970. Low hydraulic pressure to internal port 695 permits the spring force of spring 960 to push the ferrule 970 outward. The lip 975 extends out away from the latch recess 977. The inner arm 310 is latched to the outer arm 600. The inner arm 310 cannot move down between the outer arm 600. So, when the high lift event lobe 230, which is longer by a lift height LH than the normal lift event lobe, presses on the bearing 300, the inner arm 310 and outer arm 600 move together, giving the highest, longest valve lift event. The catch on the inner arm is thus configured to latch against the lip when the ferrule is in a first position, and configured to pivot past the ferrule when the ferrule is in a second position.

The outer arms 600 are joined by a bridge portion 690 flanked by projections 615, 625. Projections are designed to bias respective springs 710, 720, yet avoid contact with normal lift cam lobes 210, 220. Bridge portion 690 includes a latch recess 977 which receives internal latch assembly 951 for hydraulic control of latching action. The latch assembly 951 can be electrically actuated, but hydraulic actuation is illustrated. Frit 950 can interface with a hydraulic line and an actuatable valve via port 955. A spring 960 biases ferrule 970 towards the latched position.

An alternative, normally unlatched, arrangement could be implemented. A spring could alternatively bias the ferrule 970 to the unlatched position. An internal port 695 in the bridge portion 690 connects a fluid recess 973 in the ferrule 970 to hydraulic fluid, so as to supply actuation and deactivation forces on the latching action. For example, selecting appropriate fluid force to port 955, and selecting an appropriate spring force, can withdraw the ferrule 970 to the unlatched position. Supplying fluid pressure to the fluid recess 973 can extend the ferrule 970 to latch the lip 975 against catch 350. The same fluid pressure can be shared with a hydraulic lash adjuster (HLA) 900 mounted in a cup 979 of bridge portion 690. Internal ports 911 share fluid pressure from supply 913 with the HLA and internal port 695. Another supply 914 can interface with an alternate area 912 of the HLA.

The valve coupling 400 receives a valve stem 410 to actuate an engine valve. A spring seat 420 can be mounted on the valve stem 410. A portion 430 of the valve stem can be surrounded by a spring 440 for biasing the valve against the engine head. The engine valve is biased in a lifted position, which closes the cylinder. The switching roller finger follower 100 is acted on by the cam lobes 110, 120, 130 to open the valve one of two distances, as below. An overhead cam rail system pushes the valve downward with respect to the cam lobe, and the valve-opening action is referred to as a “lift event” in the art, despite that the valve lowers towards the cylinder in the engine head, and then lifts back via the spring force of spring 440.

A variable valve lift assembly, shown in FIGS. 2 & 5, can comprise the switching roller finger 100. The valve coupling 400 is mounted to the main axle 500. The valve stem 410 is mounted to the valve coupling 400. A pair of normal lift cam lobes 210, 220 can be aligned to transfer forces to respective slider pads 610, 620 of respective outer arms 600. A high lift cam lobe 230 comprises a larger diameter portion, delineated lift height LH in FIG. 2, than the normal lift cam lobes. The high lift cam lobe 230 is positioned between the pair of normal lift cam lobes 210, 220 and is further configured to transfer forces to the bearing 300. The normal lift cam lobes 210, 220 and the high lift cam lobe 230 are eccentric lobes mounted to a cam rail 240 for rotation against the switching roller finger follower 100.

When the latch assembly 951 is in a latched condition, the catch 350 on the inner arm 310 is latched against the lip 975, the ferrule 970 is in the first position, and the high lift cam lobe 230 pushes the switching roller finger follower 100 a first distance. The cam lobe is circular about a first portion, but extends eccentrically at a second portion. The eccentric second portion has a height. The first distance can be equal to the distance of the lift height LH plus the height of the segment of the eccentric portion of the lobe.

When the latch assembly 951 in in an unlatched condition, the lip 975 is unlatched from the catch 350, the ferrule 970 is in the second position, the high lift cam lobe 230 pushes the bearing 300 to pivot the catch 350 past the lip 975, and the normal lift cam lobes 210, 220 push on respective slider pads 610, 620 to move the switching roller finger follower 100 a second distance. The cam lobe is circular about a first portion, but extends eccentrically at a second portion. The eccentric second portion has a height. The second distance can be equal to the height of the segment of the eccentric portion of the lobe. The second distance is less than the first distance. This means that the valve is open for less time in a normal lift event than in a high lift event.

The variable lift valve assembly can be further configured so that the latch assembly further comprises a hydraulic fluid port, which can be internal port 695 in communication with port 955 or internal port 695 alone. The ferrule 970 is in fluid communication with the hydraulic fluid port. A hydraulic lash adjuster 900 can be mounted in fluid communication with the hydraulic fluid port.

An alternative switching roller finger follower 1601 is shown in FIGS. 6 & 7. Instead of slider pads, the outer arms 1670 comprise rotatable bearings 1630 for interfacing with outer cam lobes 210, 220. As above, a normal valve lift event can occur on the outer arms 1670 while a high lift valve event can occur, or be lost motion on, inner arm 310.

The pair of outer arms 1670 are mirror images of each other. Each of the pair of outer arms 1670 comprise an axle mounting 1650. One of the pair of outer arms comprises a first wall portion 1672 comprising a first bearing axle opening 1671. A second wall portion 1674 comprises a second bearing axle opening. The second wall portion can comprise a cut-out or other recess for permitting guiding and pivoting of the bearing axle 320. By including an inner recess on the second wall portion, the spring arms 1715, 1725 are less able to walk off the bearing axle 320, because the bearing axle 320 extends into a plane of the second wall portion 1674. Spring arms 1715, 1725 are biased against the bearing axle 320, and spring arms 1717, 1727 are biased against a projection 1615 on bridge portion 1690.

The second arm of the pair of outer arms 1670 comprises wall portions 1676 & 1678. The second arm and first arm of the pair of outer arms 1670 mirror the corresponding outer arms on the other side of the inner arm 310. An outer bearing axle 1635 is mounted across the first bearing axle opening 1671 and the second bearing axle opening. An outer bearing 1630 is mounted on the outer bearing axle 1635 and is configured to transfer forces from a cam lobe 210 to the outer arm 1670. The outer bearing 1630 can comprise, for example, a roller bearing or a rotating wheel.

Bridge portion 1690 is similar to bridge portion 690 above. Bridge portion 1690 joins the pair of outer arms 1670. Bridge portion 1690 comprises a first spring seat 617 opposite a mirror-image second spring seat. Bridge portion 1690 and outer arms 1670 cooperate to form projections 1615 for biasing spring arms 1717 & 1727 of springs 1710 & 1720. Alternative caps 8110 can secure springs 1710 & 1720 to mirror-image spring seats 617. Latch recess 977 for latch assembly 951 is between the first spring seat 617 and the second spring seat. Ferrule 970 is configured to reciprocate in the latch recess 977, as detailed above.

A main axle 500 is mounted in the pair of axle mountings 1650. Inner arm 310 is pivotably mounted to the main axle 500 and functions similarly as above. Optional snap rings. C-clips, or the like 510 can be included to prevent lateral or non-pivoting motion of the inner arm 310 on the main axle 500. Inner arm 310 is “U” shaped and comprises extensions 312 & 314 joined by a catch portion 355. An inner bearing axle 320 extends across the extensions 312 & 314 and comprises portions extending through the inner arm 310 and towards the outer arms 1670. A bearing 300 is rotatably mounted to the inner bearing axle 320 between the extensions 312 & 314. Bearing 300 can be a roller bearing configured to transfer forces from a cam lobe 230 to the inner arm 310.

A catch 350 on catch portion 355 of the inner arm 310 is configured to latch against the ferrule 970 when the ferrule 970 is in a first position. The catch 350 can interface with a lip 975, as described above. Catch 350 is configured to pivot past the ferrule 970 when the ferrule is in a second position.

A first spring 1710 mounted to the first spring seat 617 and a second spring 1720 mounted to the second spring seat are biased between the bridge portion 1690 and the portions of the inner bearing axle 320 extending through the inner arm 310 so as to bias the inner bearing axle 320 with respect to the ferrule 970. Biasing the inner bearing axle 320 in this manner can lift the catch 350 away from the ferrule 970 to make it easier to retract the ferrule 970. Springs 710 & 720 can similarly bias the bearing axle 320 in FIGS. 1-4. The catch 350 has less drag against the lip 975. And, the inner arm is biased to return to a starting position. Contact between inner cam lobe 230 and inner bearing 300 can also be maintained via the spring forces.

As can be seen, the bearing axle openings for the inner bearing axle 320 are between the bridge portion 1690 and the axle mountings 1650. The inner arm 310 pivots inwardly with respect to the outer arm.

A method of actuating the switching roller finger follower 100 can be seen in FIG. 9. The method can comprise steps of aligning a cam assembly 200 with the switching roller finger follower 100. A pair of normal lift cam lobes 210, 220 selectively transfer forces to respective slider pads 610, 620 or bearings 1630 of respective outer arms 600, 1670 when a normal lift event is selected. This is accomplished by rotating the outer normal lift lobes on outer arms of the roller finger follower, as in step S920. When a high lift event, which can be a late intake valve closing event, the method can comprise aligning and rotating a high lift cam lobe 230 to transfer forces to the bearing 300, as in step S950. The high lift cam lobe 230 can comprise a larger diameter portion delineated LH in FIG. 2 than the normal lift cam lobes 210, 220. The high lift cam lobe 230 can be positioned between the pair of normal lift cam lobes 210, 220. The method can rotate the normal lift cam lobes 210, 220 and the high lift cam lobe 230 on a cam rail 240. The high lift cam lobe 230 is configured to push the bearing 300 a larger distance than the normal lift cam lobes 210, 220 push the respective outer arms 600.

The method can further comprise reciprocating the ferrule 970 in the latch recess 690. When the latch assembly 951 is in a latched condition of step S940, the catch 350 on the inner arm 310 is latched against the lip 975, the ferrule 970 is in the first position, the normal lift cam lobes 210, 220 do not contact respective slider pads 610, 620, or bearings 1630 and the high lift cam lobe 230 pushes the switching roller finger follower 100 the larger distance. When the latch assembly 951 in in an unlatched condition of step S910, the lip 975 is unlatched from the catch 350, the ferrule 970 is in the second position, the high lift cam lobe 230 pushes the bearing 300 the larger distance to pivot the catch 350 past the lip 975, and the normal lift cam lobes 210, 220 push on respective slider pads 610, 620 or bearings 1630 to move the switching roller finger follower 100 a second distance that is less than the larger distance. The method can comprise performing a late intake valve closing event when the latch assembly is in a latched condition.

FIG. 9 outlines that a method of actuating a switching roller finger follower for valve actuation can comprise step S910 for unlatching an inner arm of the roller finger follower for a normal valve lift event. In step S920, Rotating outer cam lobes on outer arms of the roller finger follower 100, 1601 permit a normal valve lift event. With the inner arm 310 unlatched, in step S930, the inner high lift cam lobe rotates on the inner bearing 300 of the inner arm 310. The high lift event is lost in the pivoting motion of the inner arm within the outer arms so that contact between the normal lift outer lobes 210, 220 and the outer arms 670 & 1670 is maintained. The normal, or low, lift event can be seen in FIG. 8. The outer diameters of outer cam lobes 220, 210 are selected so that, as the cam rotates on cam rail 240, the valve affiliated with valve coupling 400 moves with respect a combustion cylinder.

FIG. 8 shows a sample lift profile for a high lift and a low lift valve event, along with a delta lift profile for illustrating the difference between the two valve lift events. The profiles are shown with the cam degrees centered about a zero point. The zero point corresponds to the peak opening for the high lift event. By arranging the cam lobes with respect to the engine valves, one can vary the rocker ratio and extent to which changes in the cam lobe profile impact valve lift. For example, one can tailor when the valve opens and closes with respect to a piston in an engine cylinder reaching top dead center (TDC). For example, the outer cam lobes 210, 220 can open the valve most fully prior to top dead center.

To convert from the normal, low, lift valve actuation to a high lift valve actuation, the inner arm 310 is latched with respect to the outer arms 670, 1670 in step S940. The inner high lift cam lobe 230 having the larger lift height LH rotates on the inner bearing 300 in step S950. The inner arm 310 and outer arms are designed with respect to the cam lobes 210, 220, 230 to maintain a minimum height between the outer arms and the outer cam lobes when the inner cam lobe 230 is rotating on the inner bearing 300 so that energy is not spent dragging or rolling the outer cam lobes 210, 220 against the outer arms 1670.

The valve follows the high lift profile shown in FIG. 8. The valve opens most fully closer to top dead center, and the valve opening is said to be “late” with respect to the normal valve lift event. The duration of time that the valve is open is also longer in this high lift example, because the inner lobe 230 is designed to push on the inner bearing 300 earlier in the rotation of the cam rail 240 than is designed for the normal lift outer lobes 210, 220. The inner lobe is also designed to push on the inner bearing 300 for a longer period of time than the normal lift outer lobes 210, 220 after the valve opens. The longer duration lift time and higher valve opening can be achieved by tailoring the eccentricity of the lift height of the center lobe 230 with respect to the outer lobes 210, 220. The lift height LH can vary around the center lobe 230 to have a longer duration high lift event and the lift height LH can vary around the center lobe 230 to have a higher valve opening high lift event. By varying the eccentricity, it is possible to vary how long the lobes 210, 220, 230 press on the roller finger follower before the lobes return to base circle BC. The time the cam spends on base circle BC can also be chosen so that the switching roller finger follower can switch between a high lift mode and a normal lift mode within one revolution of the cam rail. That is, the ferrule is configured to reciprocate within the latch recess within one revolution of the cam rail to switch the switching roller finger follower between a normal lift valve profile and a high lift valve profile. This permits an engine to operate in high lift mode on one cylinder intake, then to operate in normal lift mode on the next intake in the engine stroke cycle. Since the outer lobes 210, 220 have a smaller outer area than the inner high lift lobe 230, the latching and unlatching of the inner arm 310 is accomplished within one cam revolution of the outer lobes 210, 220, and preferably, the latching and unlatching of the inner arm 310 is completed while the cam lobes 210, 220, 230 are on base circle BC. The lift height LH formed on the inner cam lobe 230 results in the peak for the high lift event being greater than the peak for the low lift event. In the illustrated example of FIG. 8, the high lift event lifts the valve 1 millimeter (1 mm) higher than the normal lift event. By way of example, the lift height LH on the cam lobe can be 2-3 mm, yet this can yield only a 1 mm change in the height of the valve opening between low lift and high lift. Alternatively, the lift height ratio can result in the cam lift height LH being less than the minimum height difference between normal and high lift events.

As can be seen from the delta lift line, there is a height difference between the low lift and high lift events. The high lift event has more lift than the low lift event. The height difference can vary throughout the event and can be tailored by the cam lobe profiles. This technique can be used, for example, to implement “LIVC,” or late intake valve closing. LIVC can be one or both of a longer duration valve event with respect to a normal lift valve event, or a higher valve opening event with respect to a normal lift valve event. FIG. 8 is exemplary, only, and other lift profiles, lift heights, minimum heights, rocker ratios, degrees of cam rotation, etc. can be implemented without departing from the scope of the claims.

Other implementations will be apparent to those skilled in the art from consideration of the specification and practice of the examples disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope of the invention being indicated by the following claims.

Claims

1. A switching roller finger follower for valve actuation, comprising:

a pair of outer arms configured to transfer forces from a pair of outer cam lobes, the pair of outer arms comprising respective axle mountings;

a bridge portion joining the pair of outer arms, the bridge portion comprising a first spring seat opposite a second spring seat, and a latch recess between the first spring seat and the second spring seat;

a latch assembly comprising a ferrule, the ferrule configured to reciprocate in the latch recess;

a main axle mounted in the respective axle mountings;

an inner arm pivotably mounted to the main axle, the inner arm comprising: an inner bearing axle comprising portions extending through the inner arm; an inner bearing rotatably mounted to the inner bearing axle, the inner bearing configured to transfer forces from a cam lobe to the inner arm; and a catch on the inner arm, the catch configured to latch against the ferrule when the ferrule is in a first position, the catch configured to pivot past the ferrule when the ferrule is in a second position; and

a first spring mounted to the first spring seat and a second spring mounted to the second spring seat, wherein the first spring and the second spring are biased between the bridge portion and the portions of the inner bearing axle extending through the inner arm,

wherein the inner bearing axle is between the bridge portion and the axle mounting.

2. The switching roller finger follower of claim 1, wherein each arm of the pair of outer arms further comprises:

a wall portion comprising a projection, an axle mounting, and a bearing axle opening; and

a slider pad extending perpendicular to the wall portion, the slider pad configured to transfer forces from a cam lobe to the respective outer arm.

3. The switching roller finger follower of claim 1, wherein each arm of the pair of outer arms comprises an outer rotatable bearing.

4. The switching roller finger follower of claim 1, wherein the latch assembly further comprises a hydraulic fluid port, the ferrule in fluid communication with the hydraulic fluid port.

5. The switching roller finger follower of claim 4, wherein the ferrule further comprises a fluid recess.

6. The switching roller finger follower of claim 1, wherein the ferrule is configured to reciprocate in the latch recess in response to hydraulic fluid pressure.

7. (canceled)

8. (canceled)

9. The switching roller finger follower of claim 1, wherein each respective slider pad is in the shape of an arcuate tab, and each respective slider pad extends like a shelf from an upper edge of the outer arm.

10. The switching roller finger follower of claim 1, wherein each arm of the pair of outer arms comprise a bearing axle opening, and wherein the bearing axle reciprocates in the bearing axle openings when the inner arm pivots on the main axle.

11. (canceled)

12. A variable valve lift assembly, comprising the switching roller finger follower of claim 1, and further comprising:

a valve coupling mounted to the main axle;

a valve stem mounted to the valve coupling;

a pair of normal lift cam lobes aligned to transfer forces to respective outer arms; and

a high lift cam lobe comprising a larger diameter portion than the normal lift cam lobes, the high lift cam lobe positioned between the pair of normal lift cam lobes and further configured to transfer forces to the bearing,

wherein the normal lift cam lobes and the high lift cam lobe are eccentric lobes mounted to a cam rail for rotation against the switching roller finger follower.

13. The variable lift valve assembly of claim 12, wherein:

when the latch assembly is in a latched condition, the catch on the inner arm is latched against the ferrule, the ferrule is in the first position, and the high lift cam lobe pushes the switching roller finger follower a first distance; and

when the latch assembly in in an unlatched condition, the ferrule is unlatched from the catch, the ferrule is in the second position, the high lift cam lobe pushes the bearing to pivot the catch past the lip, and the normal lift cam lobes push on respective outer arms to move the switching roller finger follower a second distance; and

the second distance is less than the first distance.

14. The variable lift valve assembly of claim 12, wherein:

when the latch assembly is in a latched condition, the catch on the inner arm is latched against the ferrule, the ferrule is in the first position, and the high lift cam lobe pushes the switching roller finger follower a first duration; and

when the latch assembly in in an unlatched condition, the ferrule is unlatched from the catch, the ferrule is in the second position, the high lift cam lobe pushes the bearing to pivot the catch past the lip, and the normal lift cam lobes push on respective outer arms to move the switching roller finger follower a second duration; and

the second duration is less than the first duration.

15. The variable lift valve assembly of claim 12, wherein the latch assembly further comprises a hydraulic fluid port, and the ferrule is in fluid communication with the hydraulic fluid port, and wherein the assembly further comprises a hydraulic lash adjuster mounted in fluid communication with the hydraulic fluid port.

16. The variable valve lift assembly of claim 12, wherein the ferrule is configured to reciprocate within the latch recess within one revolution of the cam rail to switch the switching roller finger follower between a normal lift valve profile and a high lift valve profile.

17. A method of actuating the switching roller finger follower of claim 1, comprising:

aligning a pair of normal lift cam lobes to selectively transfer forces to respective outer arms; and

aligning a high lift cam lobe to transfer forces to the bearing, the high lift cam lobe comprising a larger diameter portion than the normal lift cam lobes, the high lift cam lobe positioned between the pair of normal lift cam lobes;

rotating the normal lift cam lobes and the high lift cam lobe on a cam rail, wherein the high lift cam lobe is configured to push the bearing more than the normal lift cam lobes push the respective outer arms.

18. The method of claim 17, further comprising:

reciprocating the ferrule in the latch recess, wherein: when the latch assembly is in a latched condition, the catch on the inner arm is latched against the ferrule, the ferrule is in the first position, the normal lift cam lobes do not contact the outer arms, and the high lift cam lobe pushes the bearing of the switching roller finger follower; and when the latch assembly is in an unlatched condition, the ferrule is unlatched from the catch, the ferrule is in the second position, the high lift cam lobe pushes the bearing to pivot the catch past the lip, and the normal lift cam lobes push on respective outer arms to move the switching roller finger follower less than the high lift cam lobe; and

performing a late intake valve closing event when the latch assembly is in a latched condition.

19. (canceled)

20. (canceled)

21. (canceled)

22. (canceled)

23. (canceled)

24. (canceled)

25. (canceled)

26. The switching roller finger follower of claim 1, wherein each arm of the pair of outer arms comprises:

a first wall portion comprising a first bearing axle opening;

a second wall portion comprising a second bearing axle opening;

an outer bearing axle mounted across the first bearing axle opening and the second bearing axle opening; and

an outer bearing mounted on the outer bearing axle configured to transfer forces from a cam lobe to the respective outer arm.

27. The switching roller finger follower of claim 26, wherein the inner bearing axle protrudes into the second wall portion of each arm of the pair of outer arms.

28. The switching roller finger follower of claim 26, wherein each second wall portion includes a guide recess to receive and guide the inner bearing axle.

29. The switching roller finger follower of claim 26, wherein the inner bearing axle extends into a plane of each second wall portion.