Abstract
A switchable rocker arm for valve deactivation is provided for a valve train of an internal combustion engine. The switchable rocker arm includes a valve side lever assembly, a cam side lever assembly, and a hydraulically actuated coupling assembly. The valve side lever assembly includes a first housing with a first rocker shaft bore. The cam side lever assembly includes a second housing with a first arm with a second rocker shaft bore and a second arm with a third rocker shaft bore. The first and second arms extend along opposed longitudinal sides of the cam side lever assembly such that the first, second and third rocker shaft bores are axially aligned. The coupling assembly is arranged at an end furthest away from a pivot axis for minimal loading and provides locking and unlocking of the switchable rocker arm to achieve full valve lift and no valve lift modes, respectively.
Claims
1. A switchable rocker arm comprising: a valve side lever assembly including a first housing having a first end with a first rocker shaft bore and a second rocker shaft bore, and a second end with a shuttle pin bore; a cam side lever assembly including a second housing having a third end with a camshaft interface, a fourth end with a locking pin bore, and a third rocker shaft bore at a medial position; wherein, the third rocker shaft bore is axially aligned with the first and second rocker shaft bores; and, a coupling assembly, including a locking pin arranged at least partially within the locking pin bore, and a shuttle pin arranged at least partially within the shuttle pin bore with a first end engaging the locking pin.
2. The switchable rocker arm of claim 1, including: a first locked position with the locking pin bore axially aligned with the shuttle pin bore, the locking pin arranged partially within the shuttle pin bore and partially within the locking pin bore with a third end of the locking pin at a first distance from a fourth closed end of the locking pin bore of the first housing, and the first end of the shuttle pin at a second distance from a second closed end of the shuttle pin bore of the second housing; and, a second unlocked position with the third end of the locking pin at a third distance from the fourth closed end of the locking pin bore of the first housing, and the first end of the shuttle pin at a fourth distance from the second closed end of the shuttle pin bore of the second housing, wherein the third distance is less than the first distance and the fourth distance is greater than the second distance.
3. The switchable rocker arm of claim 2, further comprising a resilient element in contact with the locking pin, the resilient element 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.
4. The switchable rocker arm of claim 2, wherein the third distance defines a position where the locking pin is disengaged from the shuttle pin bore.
5. The switchable rocker arm of claim 2, wherein the first locked position defines a first valve lift mode and the second unlocked position defines a second valve lift mode.
6. The switchable rocker arm of claim 5, wherein the first valve lift mode is a full valve lift mode and the second valve lift mode is a no valve lift mode.
7. The switchable rocker arm of claim 1, further comprising a first arm having the first rocker shaft bore, a second arm having the second rocker shaft bore, the two arms defining a space therebetween, and extending along opposed longitudinal sides of the cam side lever assembly.
8. The switchable rocker arm of claim 3, further comprising a sleeve arranged within the locking pin bore at the fourth end of the second housing.
9. The switchable rocker arm of claim 3, further comprising a lost motion resilient element arranged between the first housing and the second housing.
10. The switchable rocker arm of claim 3, further comprising a cam roller follower arranged on the third end of the second housing.
11. The switchable rocker arm of claim 3, further comprising at least one second housing rotational stop configured on the first housing.
12. The switchable rocker arm of claim 3, further comprising at least one first fluid passage within the first housing from the first or second rocker shaft bore to the second closed end of the shuttle pin bore.
13. The switchable rocker arm of claim 3, further comprising an adjusting screw assembly arranged at the second end of the first housing.
14. The switchable rocker arm of claim 3, further comprising a hydraulic lash adjuster arranged at the second end of the first housing.
15. The switchable rocker arm of claim 14, further comprising at least one second fluid passage within the first housing from the first or second rocker shaft bore to the hydraulic lash adjuster, and at least one third fluid passage from the hydraulic lash adjuster to the second closed end of the shuttle pin bore.
16. The switchable rocker arm of claim 14, further comprising at least one first fluid passage within the first housing from the first or second rocker shaft bore to the hydraulic lash adjuster and at least one second fluid passage from the first or second rocker shaft bore to the second closed end of the shuttle pin bore.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] 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:
[0023] FIG. 1 is a perspective view of a first embodiment of a switchable rocker arm.
[0024] FIG. 2 is perspective view of a valve side lever assembly of the switchable rocker arm of FIG. 1.
[0025] FIG. 3 is a perspective view of a cam side lever assembly of the switchable rocker arm of FIG. 1.
[0026] FIG. 4 is a cross-sectional view of the switchable rocker arm of FIG. 1 in a first locked position.
[0027] FIG. 5 is a cross-sectional view of the switchable rocker arm of FIG. 1 in a second unlocked position.
[0028] FIG. 6 is a top view of a schematic of a fluid passage network for the switchable rocker arm of FIG. 1.
[0029] FIG. 7 is a top view of a variation of a schematic of a fluid passage network for the switchable rocker arm of FIG. 1.
[0030] FIG. 8 is a top view of a schematic of a fluid passage network for a second embodiment of a switchable rocker arm.
[0031] FIG. 9 is a perspective view of the second embodiment of a switchable rocker arm.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] 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.
[0033] Referring to FIGS. 1 through 5, a first embodiment of a switchable rocker arm 10 that provides for reduced coupling assembly loads is shown. The switchable rocker arm 10 is capable of switching between two discrete valve lift modes. The components of the switchable rocker arm 10 include a valve side lever assembly 12, a cam side lever assembly 14, a first lost motion spring 16A, and a second lost motion spring 16B. Those familiar with switchable valve train components are aware that various forms of lost motion springs are possible. The switchable rocker arm 10 rotates about a pivot axis 11 of a rocker shaft (not shown), which is typical for shaft-mounted switchable rocker arms.
[0034] Referring to FIG. 2, the valve side lever assembly 12 for the first embodiment of a switchable rocker arm 10 is shown. The valve side lever assembly 12 includes a first housing 22 having a first end with a first arm 24A and a second arm 24B, such that the first arm 24A is axially offset from the second arm 24B, creating a space or passage 25 in between the two arms 24A,24B. The first arm 24A includes a first rocker shaft bore 26A and the second arm 24B includes a second rocker shaft bore 26B. A first stop 28A protrudes inwardly from a first inner wall 27A on the first arm 24A and a second stop 28B protrudes inwardly from a second inner wall 27B on the second arm 24B; the first and second stops 28A,28B limit the rotation of the cam side lever assembly 14 with respect to the valve side lever assembly 12. A first retainer post 30A for the first lost motion spring 16A is present on a first outer wall 29A of the first arm 24A. A second retainer post 30B for the second lost motion spring 16B is present on a second outer wall 29B of the second arm 24B. A second end of the first housing 22 has a valve interface in the form of a hydraulic lash adjuster 20 and a shuttle pin bore 37. A second fluid passage 44 extends from the second rocker shaft bore 26B to the hydraulic lash adjuster 20; a third fluid passage 46, visible in FIGS. 4 and 5, extends from the hydraulic lash adjuster 20 to a second closed end of the shuttle pin bore 37.
[0035] Referring specifically to FIG. 3, the cam side lever assembly 14 for the first embodiment of a switchable rocker arm 10 is shown. The cam side lever assembly 14 includes a second housing 32 having a third end with a cam interface in the form of a roller follower 18, and a fourth end with a locking pin bore 35 that houses an optional sleeve 38 for guiding and interfacing with a locking pin 34. Without the presence of the optional sleeve 38, the locking pin 34 would interface directly with the locking pin bore 35. Other forms of cam interfaces at the third end of the second housing 32 are possible such as a slider pad. A third retainer post 31A for the first lost motion spring 16A is present on a third outer side 33A of the third end of the second housing 32. A fourth retainer post 31B for the second lost motion spring 16B is present on a fourth outer side 33B of the third end of the second housing 32. A third rocker shaft bore 26C is present at a medial position on the second housing 32. The cam side lever assembly 14 fits within the space or passage 25 created by the two arms 24A,24B of the first housing 22 of the valve side lever assembly 12, such that the first arm 24A extends along a first longitudinal side 48A of the second housing 32, and the second arm 24B extends along a second longitudinal side 48B of the second housing 32. In addition, the third rocker shaft bore 26C is in axial alignment with the first and second rocker shaft bores 26A,26B of the first and second arms 24A,24B, respectively, of the first housing 22.
[0036] The switchable rocker arm 10 captured in FIGS. 1 through 5 is capable of switching between two discrete valve lift modes, achieved by different longitudinal positions of the locking pin 34. Referring now to FIG. 4, a first locked position is shown at which the locking pin bore 35 of the second housing 32 is axially aligned with the shuttle pin bore 37 of the first housing 22, enabling engagement of the locking pin 34 with both the first housing 22 and the second housing 32. More specifically, the locking pin 34 is engaged with both the shuttle pin bore 37 of the first housing 22 and the optional sleeve 38 arranged within the locking pin bore 35 of the second housing 32. If the optional sleeve 38 is not present, the locking pin 34 would engage directly with the locking pin bore 35. The first locked position facilitates a full valve lift mode such that when the cam side lever assembly 14 is rotationally actuated by the cam, the valve side lever assembly 12 rotates in unison with the cam side lever assembly 14 about the pivot axis 11. In the first locked position, a locking pin bias spring or resilient element 40 with a first compressed length C1, urges the locking pin 34 with a pre-load force to its shown position in FIG. 4. The shown position of the locking pin 34 can be defined or limited by either of two design features: 1). (as shown) the adjacent shuttle pin 36 with a first end engaging the locking pin 34, reaches a second closed or blind end of the shuttle pin bore 37, or 2). any other suitable means of limiting the longitudinal travel of the locking pin 34 within the shuttle pin bore 37. At the first locked position, a third outer end of the locking pin 34 is at a first distance L1 from a fourth closed or blind end of the locking pin bore 35, while the first end of the shuttle pin 36 is at a second distance L2 from a second closed or blind end of the shuttle pin bore 37.
[0037] Referring now to FIG. 5, a second unlocked position is shown in which the locking pin 34 is completely retracted from the shuttle pin bore 37. This occurs when hydraulic fluid, typically at an engine fluid pump pressure, is delivered to the second closed end of the shuttle pin bore 37 and acts upon the second end of the shuttle pin 36. The force created by the hydraulic pressure acting on the shuttle pin 36 overcomes the pre-load urging force of the compressed bias spring 40 acting on the adjacent and engaged locking pin 34, causing the locking pin 34 to move longitudinally until it disengages the shuttle pin bore 37. Therefore, the third or outer end of the locking pin 34 is closer to the fourth or closed end of the locking pin bore 35, defining a third distance L3, and the first end of the shuttle pin 36 is further away from the second or closed end of the shuttle pin bore 37, defining a fourth distance L4. In the second unlocked position, the bias spring 40 compresses to a second compressed length C2 that is shorter than the first compressed length C1 in the first locked position. The second unlocked position facilitates a no valve lift mode in which the cam side lever assembly 14 is rotationally displaced about the pivot axis 11 by the camshaft independently from the valve side lever assembly 12, which remains stationary. While in the no valve lift or deactivation mode, the first and second lost motion springs 16A,16B provide a force that can: 1). act upon the cam side lever assembly via the third and fourth retainer posts 31A,31B, controlling the motion of the cam side lever assembly 14 such that separation with the camshaft does not occur at a maximum deactivation speed, and 2). act upon the valve side lever assembly 12 via the first and second retainer posts 30A,30B to prevent a pump-up or extended length condition of the hydraulic lash adjuster 20 which could hinder the switching function of the switchable rocker arm 10.
[0038] Referring again to FIG. 4, an alternative locking pin 34A and an alternative sleeve 38A are shown with broken lines. Compared to the previously described locking pin 34 and sleeve 38, the location of the alternative locking pin and sleeve 34A,38A are instinctive due to their proximity to the pivot axis 11, requiring low effort to integrate a short and simple hydraulic gallery for actuation of the locking pin 34A. However, analyzing the moment about the pivot axis 11 created by the reactive forces that correspond to each of the two locking pin positions provides further insight into the ideal location for a locking pin. A force F.sub.V applied to the hydraulic lash adjuster 20 (or other suitable valve interface) of the switchable rocker arm 10 by an engine valve (not shown) creates a moment about the pivot axis 11 equal to the magnitude of the force F.sub.V multiplied by a magnitude of a vector d.sub.V, as shown in FIG. 4 and by the equation below:
M.sub.11=F.sub.v×d.sub.v [0039] where: d.sub.V=perpendicular distance from the pivot axis 11 to a line of action of the force F.sub.V.
[0040] To counteract this moment created on the switchable rocker arm 10 by the engine valve, a counter-moment is present about the central axis 11 created by a reactive force F.sub.34 of the locking pin 34, hereafter termed “reactive shear force”, multiplied by a magnitude of vector d.sub.34. Assuming that a sum of moments about the pivot axis 11 is zero, the reactive shear force F.sub.34 can be expressed as shown below:
[00001] [0041] where: d.sub.34=perpendicular distance from the pivot axis 11 to a line of action of the reactive shear force F.sub.34.
[0042] One can observe that the magnitude of the reactive shear force F.sub.34 of the locking pin 34 is inversely proportional to the magnitude of vector d.sub.34. Therefore, as the magnitude of vector d.sub.34 increases, the reactive shear force F.sub.34 applied to the locking pin 34 decreases. Furthermore, with reference to FIG. 4 and the distance vectors d.sub.34 and d.sub.34A for the respective locations of the locking pin 34 located at the fourth end of the second housing 32 and the alternative locking pin 34A, the following equation provides an amount of reactive shear force reduction due to a more distant locking pin:
[00002] [0043] where: d.sub.34=perpendicular distance from the pivot axis 11 to a line of action of the reactive shear force F.sub.34. [0044] d.sub.34A=perpendicular distance from the pivot axis 11 to a line of action of the reactive shear force F.sub.34A.
[0045] Quantifying the difference in reactive shear force between the two locking pin locations, a distance of 14 millimeters is assumed for d.sub.34A that corresponds with the alternative locking pin 34A shown in broken lines, and a distance of 28 millimeters is assumed for d.sub.34 that corresponds with the locking pin 34 shown in solid lines. Using the equation for reactive shear force reduction, a reduction of 50% is achieved by locating the locking pin 34 at the fourth end of the second housing 32 versus the less distant location of the alternative locking pin 34A, providing significantly reduced locking pin stress and resulting wear.
[0046] Referring to FIG. 9, a second embodiment of a switchable rocker arm 80 is shown that utilizes an adjusting screw assembly 70 as a valve interface which potentially reduces the complexity and cost of the switchable rocker arm 80.
[0047] FIGS. 6 through 8 show various oil gallery or fluid passage networks in schematic form to accommodate the first and second embodiments of switchable rocker arms 10,80. FIG. 6 shows a schematic of a fluid passage network for the first embodiment of a switchable rocker arm 10 that utilizes a hydraulic lash adjuster 20 at the second end of the first housing 22 of the valve side lever assembly 12. Referencing FIG. 6 together with the perspective view of the valve lever side assembly 12 of FIG. 2, a second fluid passage 44 is shown that extends from the second rocker shaft bore 26B to the hydraulic lash adjuster 20. Optionally, an additional second fluid passage 45 can be utilized that extends from the first rocker shaft bore 26A to the hydraulic lash adjuster 20. A third fluid passage 46 extends from the hydraulic lash adjuster 20 to the second closed end of the shuttle pin bore 37. Thus, for the fluid passage network shown in FIG. 6, hydraulic fluid is provided first to the hydraulic lash adjuster 20, and then second to the second end of the shuttle pin 37, in series.
[0048] FIG. 7 shows a variation of a fluid passage network for the first embodiment of a switchable rocker arm 10 that utilizes a hydraulic lash adjuster 20 at the second end of the first housing 22 of the valve side lever assembly 12. Referring to FIG. 7 together with the perspective view of the valve lever side assembly 12 in FIG. 2, separate fluid passages exist for the hydraulic lash adjuster 20 and the shuttle pin bore 37. The second fluid passage 44 and optional additional second fluid passage 45 from FIG. 6 remain in FIG. 7's network; however, in this variation, the shuttle pin bore 37 receives hydraulic fluid via a first fluid passage 42 that extends from the second rocker shaft bore 26B to the second end of the shuttle pin bore 37. Optionally, an additional first fluid passage 43 can be utilized that extends from the first rocker shaft bore 26A to the second closed end of the shuttle pin bore 37.
[0049] FIG. 8 shows a fluid passage network for the second embodiment of a switchable rocker arm 80 that utilizes an adjusting screw assembly 70 as a valve interface. Since the adjusting screw assembly 70 does not typically require a hydraulic fluid feed, FIG. 8's fluid passage network is the simplest of the three fluid passage networks shown, requiring only the first fluid passage 42 and the optional additional first fluid passage 43 that extend from the second and first rocker shaft bores 26B,26A to the second end of the shuttle pin bore 37. In the event that the design of the adjusting screw assembly 70 incorporates a means of lubricating the interface with the valve and, thus, requires an oil feed, the fluid passage networks of either FIG. 6 or FIG. 7 could be applied.
[0050] Having thus described various embodiments of the present switchable rocker arm 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.
