Abstract
A coupling pin anti-rotation arrangement is provided for a switchable roller finger follower within a valve train of an internal combustion engine capable of switching between at least two valve lift modes. The switchable roller finger follower includes an inner lever, an outer lever, a coupling pin, and an anti-rotation clip. The coupling pin, located on one of the inner or outer levers, has a first locking surface, and a first, and preferably, second coupling pin-side anti-rotation flat. The coupling pin moves longitudinally within a coupling pin bore to a first, locked position and a second, unlocked position. The anti-rotation clip has a first and, preferably, second clip-side finger to slidably guide the first and second coupling pin-side anti-rotation flats to ensure alignment of the first locking surface with a second locking surface, located on the other of the inner lever or the outer lever, during all modes of operation.
Claims
1. A switchable roller finger follower comprising: an inner lever having first and second ends; an outer lever having: two outer arms that extend along longitudinal sides of the inner lever; and, a third end mounted for pivoting movement at the first end of the inner lever by a pivot axle; a coupling pin arranged to move longitudinally within a coupling pin bore located on one of the inner lever or the outer lever on an end opposite from the pivot axle, the coupling pin having: a coupling projection with a first locking surface; and, a first coupling pin-side anti-rotation flat; and, an anti-rotation clip arranged on a same one of the inner lever or the outer lever as the coupling pin bore, the anti-rotation clip having a first clip-side finger at a locking end; and, the coupling pin is moveable from a first, locked position with the first locking surface engaged with a second locking surface located on the other of the inner lever or the outer lever, to a second, unlocked position where the first locking surface is not engaged with the second locking surface, and the first coupling pin-side anti-rotation flat is slidably guided by the first clip-side finger.
2. The switchable roller finger follower of claim 1, wherein the first coupling pin-side anti-rotation flat is guided by a guide surface of the first clip-side finger.
3. The switchable roller finger follower of claim 1, further comprising a second clip-side finger on the anti-rotation clip and a second coupling pin-side anti-rotation flat on the coupling pin, the second coupling-pin side anti-rotation flat being slidably guided by the second clip-side finger as the coupling pin moves between the first and second positions.
4. The switchable roller finger follower of claim 3, wherein the first and second clip-side fingers are configured with guide surfaces that face one another and guide oppositely located first and second coupling pin-side anti-rotation flats.
5. The switchable roller finger follower of claim 1, wherein the first and second locking surfaces have a space defined therebetween that ranges from 0.001 to 0.300 mm.
6. The switchable roller finger follower of claim 1, wherein the first clip-side finger is engaged with a locking end of a coupling pin bore housing.
7. The switchable roller finger follower of claim 1, wherein the anti-rotation clip has at least one attachment hook at an end opposite the first clip-side finger.
8. The switchable roller finger follower of claim 7, wherein the at least one attachment hook is engaged with an end of a coupling pin bore housing opposite a locking end.
9. The switchable roller finger follower of claim 8, wherein the anti-rotation clip is elastically deflectable for engagement with the coupling pin bore housing.
10. The switchable roller finger follower of claim 1, wherein the first and second locking surfaces are formed as flats.
11. The switchable roller finger follower of claim 1, wherein the first coupling pin-side anti-rotation flat is slidably guided by the first clip-side finger in the first, locked and the second, unlocked positions.
12. The switchable roller finger follower of claim 1, wherein the first clip-side finger remains in constant contact with the first coupling pin-side anti-rotation flat.
13. The switchable roller finger follower of claim 1, wherein the first, locked position defines a first valve lift mode and the second, unlocked position defines a second valve lift mode.
14. The switchable roller finger follower of claim 13, wherein the first valve lift mode is a full valve lift mode and the second valve lift mode is a no valve lift mode.
15. The switchable roller finger follower of claim 14, wherein the second locking surface is located on the inner lever and the coupling pin bore and anti-rotation clip are located on the outer lever.
16. The switchable roller finger follower of claim 13, wherein the first valve lift mode is a high valve lift mode and the second valve lift mode is a low valve lift mode.
17. The switchable roller finger follower of claim 16, wherein the second locking surface is located on the outer lever and the coupling pin bore and anti-rotation clip are located on the inner lever.
18. The switchable roller finger follower of claim 1, further comprising a valve interface configured on the third end and a pivot interface configured on a fourth end of the outer lever.
19. The switchable roller finger follower of claim 1, further comprising a spring in contact with the coupling pin, the spring having a first compressed length in the first locked position and a second compressed length in the second unlocked position, wherein the first compressed length is greater than the second compressed length.
20. The switchable roller finger follower of claim 1, further comprising at least one lost motion spring arranged between the inner lever and the outer lever.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The foregoing Summary as well as the following Detailed Description will be best understood when read in conjunction with the appended drawings. In the drawings:
(2) FIG. 1 is a perspective view of a valve train system that includes a SRFF according to a first example embodiment of the disclosure with no valve lift and full valve modes of operation.
(3) FIGS. 2A and 2B are perspective views of the SRFF of FIG. 1.
(4) FIGS. 3A and 3B are perspective views of the outer lever of the SRFF of FIGS. 2A and 2B.
(5) FIGS. 4A and 4B are perspective views of the inner lever of the SRFF of FIGS. 2A and 2B.
(6) FIG. 5 is a perspective view of an anti-rotation clip utilized in FIGS. 2A through 3B.
(7) FIG. 6 is a perspective view of a coupling pin contained within the SRFF of FIGS. 2A, 2B, and 8.
(8) FIG. 7A is a cross-sectional view of the SRFF of FIGS. 2A and 2B in a first, locked position.
(9) FIG. 7B is a cross-sectional view of the SRFF of FIGS. 2A and 2B in a second, unlocked position.
(10) FIG. 8 is a perspective view of a SRFF according to a second example embodiment of the disclosure with high valve lift and low valve lift modes of operation.
(11) FIG. 9 is a perspective view of a tri-lobe camshaft for the SRFF shown in FIG. 8.
DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS
(12) Certain terminology is used in the following description for convenience only and is not limiting. The words inner, outer, inwardly, and outwardly refer to directions towards and away from the parts referenced in the drawings. A reference to a list of items that are cited as at least one of a, b, or c (where a, b, and c represent the items being listed) means any single one of the items a, b, c or combinations thereof. The terminology includes the words specifically noted above, derivatives thereof, and words of similar import.
(13) Referring to FIG. 1, a perspective view of a SRFF 12 is shown within a valve train system 10 of an IC engine that includes a camshaft 11, an engine valve 26 and a hydraulic pivot element 18. The camshaft 11 rotationally actuates the SRFF 12 through a roller 22 interface about the hydraulic pivot element 18, causing rotational lift provided by the camshaft 11 to be translated to linear valve lift. The SRFF 12 shown in FIG. 1 captures a first example embodiment of a coupling pin anti-rotation arrangement, which will be described in detail with reference to FIGS. 2A through 7B.
(14) FIGS. 2A and 2B show top-side and bottom-side perspective views of the SRFF 12, respectively. The SRFF 12 is comprised of an outer lever 16 attached to an inner lever 14 by a pivot axle 13. The outer lever 16 is configured with a valve interface 24 at a third end 21 and a hydraulic pivot element interface 20 at a fourth end 25.
(15) Referring now to FIGS. 3A to 7B, a detailed explanation of the design and function now follows for the SRFF 12 captured in FIGS. 1 through 2B. With specific reference to FIGS. 3A through 4B, the inner lever 14 is configured with a first pivot aperture 64 on a first end 34 and the outer lever 16 is configured with second and third pivot apertures 15A,15B on the third end 21. The pivot axle 13 shown in FIGS. 2A and 2B is disposed within the first, second, and third pivot apertures 64,15A,15B to pivotably connect the inner lever 14 to the outer lever 16. The outer lever 16 has two outer arms 50A,50B that extend along longitudinal sides 68A,68B of the inner lever 14. A cavity 61 within the inner lever 14 houses the roller 22 that interfaces with the camshaft 11 shown in FIG. 1. The roller 22 is connected to the inner lever 14 via a transverse axle pin 60 disposed within two axle apertures 70A,70B of the inner lever 14. Lost motion resilient elements or springs 54A,54B are arranged on respective lost motion spring posts 52A,52B of the outer lever 16. Lost motion spring retainers 56A,56B ensure containment of the lost motion springs 54A,54B on their respective lost motion spring posts 52A,52B during operation. The lost motion springs 54A,54B are arranged to apply an upward force against lost motion spring landings 58A,58B located on the inner lever 14 to bias the roller 22 of the inner lever 14 to an upper-most position.
(16) With reference to FIGS. 3A and 3B, a fourth end 25 of the outer lever 16 is configured with a coupling pin bore 66 that houses a coupling pin 40. Now referencing FIG. 6, the coupling pin 40 is shown that is configured with a coupling projection 42. The preferred material of the coupling pin 40 is steel, but other suitable materials are also possible. A first locking surface 44 is configured on the coupling projection 42 as a flat but can be of any suitable form for such a locking function. Adjacent to the first locking surface 44 is a first coupling pin-side anti-rotation flat 46A. A second coupling pin-side anti-rotation flat 46B can also be arranged opposite of the first coupling pin-side anti-rotation flat 46A. With reference to FIG. 4B, a second locking surface 62 is shown on the second end 35 of the inner lever 14, which receives the first locking surface 44 of the coupling projection 42 of the coupling pin 40. The second locking surface 62 is also formed as a flat but can be of any suitable form for such a locking function.
(17) With reference to FIG. 7A, the coupling pin 40 is shown in a first, locked position in which a coupling pin bias spring 38 is at a first compressed length L1. In this first, locked position, the inner lever 14 and the outer lever 16 pivot in unison about the hydraulic pivot element 18 (reference FIG. 1), resulting in a full valve lift mode.
(18) Now referencing FIG. 7B, the coupling pin 40 is longitudinally displaced within the coupling pin bore 66, defining a second, unlocked position in which the coupling bias spring 38 is at a second compressed length L2. The second compressed length L2 of the second, unlocked position is less than the first compressed length L1 of the first, locked position. In this second, unlocked position, the inner lever 14 is allowed to rotate about the pivot axle 13 during each camshaft rotation, resulting in an arcuate motion of the inner lever 14, often termed lost motion or lost motion stroke, while the outer lever 16 remains stationary.
(19) During the lost motion stroke it is necessary to prevent excessive rotation of the coupling pin 40 to ensure that the first locking surface 44 remains aligned with the second locking surface 62 of the inner lever 14. If this does not occur, the coupling pin 40 will not be displaceable to the first, locked position, as only a small space or gap is present between the first and second locking surfaces 44,62. While this space can be of any size, it is preferably in the range of 0.010 to 0.300 mm. Referring to FIGS. 3A, 3B, 5 and 6, in accordance with such an anti-rotation requirement of the coupling pin 40, an anti-rotation clip 26 is arranged on the outer lever 16. The anti-rotation clip 26 is configured with a first clip-side finger 28A at a locking end 31 of the anti-rotation clip 26. The first clip-side finger 28A has a first guide surface 30A that slidably guides a first coupling pin-side anti-rotation flat 46A arranged on a longitudinal coupling projection 42 of the coupling pin 40. A second clip-side finger 28B having a second guide surface 30B that faces the first guide surface 30A can also be arranged at the locking end 31 of the anti-rotation clip 26 to slidably guide the second coupling pin-side anti-rotation flat 46B. The first or second clip-side fingers 28A,28B can engage with a locking end 49 of a coupling pin bore housing 48 to secure or retain the anti-rotation clip 26 to the outer lever 16. To ensure that proper alignment of the first and second locking surfaces 44,62 is fulfilled, a small space or gap is present between the coupling pin-side anti-rotation flats 46A,46B and the first and second guide surfaces 30A,30B of the first and second clip-side fingers 28A,28B. While this space can be of any size, it is preferably in the range of 0.010 to 0.500 mm. This space ensures a free, non-binding movement between the coupling pin 40 and first and second clip-side fingers 28A,28B under all operating and size conditions, however, any rotation of the locking pin 40 will be limited by this space. For this reason, contact between either the first or second guide surface 30A,30B and the respective coupling pin-side anti-rotation flats 46A,46B may occur over a portion or the entirety of the coupling pin stroke, inclusive of the first, locked and second, unlocked coupling pin 40 positions. To further retain or secure the anti-rotation clip 26 to the outer lever 16, a first attachment hook 32A can be arranged on an end 33 of the anti-rotation clip 26 that is opposite to the first and second clip-side fingers 28A,28B. The first attachment hook 32A can engage with an end 51 of the coupling pin bore housing 48 that is opposite the locking end 49. A second attachment hook 32B (or more, if needed) can also provide further retention of the anti-rotation clip 26. Given the previously described retention features of the anti-rotation clip 26, easy installation and removal from the coupling pin bore housing 48 is possible and can be further enhanced by use of an elastically deflectable material for the anti-rotation clip 26.
(20) Referring now to FIG. 8, a SRFF 72 is shown that captures a second embodiment of a coupling pin anti-rotation arrangement. The SRFF 72 includes an outer lever 74 pivotably attached to an inner lever 76 via pivot shaft 78. The inner lever 76 is configured with a roller 80 to interface with a first low-lift camshaft lobe 92 of a tri-lobe camshaft configuration 90 shown in FIG. 9. The outer lever 74 is configured with two high lift slider pads 75A,75B that interface with second and third high-lift camshaft lobes 94A,94B of the tri-lobe camshaft configuration 90. The inner lever 76 is configured with a coupling pin bore (not shown) that houses the coupling pin 40 of the first example embodiment with the first locking surface 44 and adjacent coupling-side anti-rotation flats 46A,46B, as shown in FIG. 6. An anti-rotation clip 86 is arranged on the coupling pin bore housing 83. The coupling pin 40 moves longitudinally within the coupling pin bore of the inner lever 76 to engage and disengage a second locking surface 84 located on the outer lever 74. Engagement of the first locking surface 44 of the coupling pin 40 with the second locking surface 84 of the outer lever 74 defines a first, locked position that corresponds with a first valve lift mode. Disengagement of the first locking surface 44 of the coupling pin 40 from the second locking surface 84 of the outer lever 74 defines a second, unlocked position that corresponds with a second valve lift mode. Typically the first valve lift mode is greater than the second valve lift mode, therefore, the first valve lift mode is often termed full lift or high lift and the second valve lift mode is often termed low lift or partial lift. While in either of the first or second valve lift modes, anti-rotation of the coupling pin 40 is achieved by one or both of the coupling pin-side anti-rotation flats 46A,46B (reference FIG. 6) being slidably guided by one or both clip-side fingers 88A,88B arranged on a locking end 87 of the anti-rotation clip 86.
(21) The second example embodiment of this disclosure shown in FIG. 8, depicts a SRFF with two high lift slider interfaces 75A,75B on the outer lever 74 and a low lift interface on the inner lever 76 in the form of the roller 80. It would also be possible to have the high lift interface on the inner lever 76 in the form of a single interface and the low lift interface on the outer lever 74, in the form of two interfaces.
(22) Having thus described various embodiments of the present arrangement in detail, it is to be appreciated and will be apparent to those skilled in the art that many physical changes, only a few of which are exemplified in the detailed description above, could be made in the apparatus without altering the inventive concepts and principles embodied therein. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore to be embraced therein.
