Finger follower for lobe switching and single source lost motion
A switching finger follower for an engine valve train utilizes an adjustable support assembly that eliminates potential for partial engagement during operation. A lever engagement member or latch is disposed for movement on the follower body and interacts with a lever to provide a constant contact geometry. The finger follower may be configured as a lost motion device and may include a biasing assembly and a travel limiter. The latch may support the lever in at least one precise position and may support the lever in a second position for partial lost motion, or permit the lever to pivot free of the latch for complete lost motion, as in cylinder deactivation applications.
1. A finger follower system for use in an internal combustion engine valvetrain, the finger follower system comprising:
a follower body having a pivot end and a motion transmitting end;
a lever adapted to pivot relative to the follower body;
a motion receiving component having a motion receiving surface disposed between the pivot end and the motion transmitting end; and
an adjustable support assembly including a movable latch configured to provide selective support to the lever, the adjustable support assembly adapted to alternately maintain the latch in a first latch position and a second latch position relative to the follower body wherein the adjustable support assembly further includes an actuating piston extending within a piston receiving bore in the latch and cooperating with the latch so as to define the first latch position and the second latch position.
2. The finger follower system of claim 1 , wherein the actuating piston includes a transition surface which enables the lever to move the latch to the first latch position when the transition surface is engaged by the latch.
3. The finger follower system of claim 1 , wherein the adjustable support assembly is further adapted to provide engagement between the lever and the latch when the latch is in the first latch position.
4. The finger follower system of claim 1 , wherein the adjustable support assembly is further adapted to permit the lever to pivot to a lever position in which the lever is not engaged with the latch.
5. The finger follower system of claim 1 , wherein the adjustable support assembly is further adapted to provide engagement between the lever and the latch when the latch is in the second position.
6. The finger follower system of claim 1 , wherein the actuating piston is adapted to provide a reactive supporting force on the latch when the latch is in the first latch position and when the latch is in the second latch position, and wherein the actuating piston includes a transition surface that is adapted to permit the latch and actuating piston to move when the latch is between the first latch position and the second latch position.
7. The finger follower system of claim 1 , wherein the follower body further includes a guide bore, and wherein the latch is arranged to move within the guide bore.
8. The finger follower system of claim 1 , wherein the follower body further includes a working fluid passage in fluid communication with the actuating piston.
9. The finger follower system of claim 1 , wherein the actuating piston includes a first actuating piston surface adapted to support the latch in the first latch position, and a second actuating piston surface adapted to support the latch in the second latch position.
10. The finger follower system of claim 9 , wherein the first actuating piston surface extends at a first distance from an axis of the actuating piston, and wherein the second actuating piston surface extends at a second distance from the axis of the actuating piston.
11. The finger follower system of claim 9 , wherein the second actuating piston surface corresponds to the piston receiving bore.
12. The finger follower system of claim 9 , wherein the actuating piston further includes a transition surface between the first actuating piston surface and the second actuating piston surface, the transition surface adapted to move the latch from the first latch position to the second latch position when the actuating piston is actuated.
13. The finger follower system of claim 1 , wherein the lever includes a lever surface adapted to engage a latch surface of the latch, wherein at least one of the latch surface and the lever surface includes an arcuate surface.
14. The finger follower system of claim 1 , wherein the lever includes a lever surface adapted to engage a latch surface of the latch, wherein the latch surface and the lever surface are adapted to maintain a substantially similar contact geometry when the latch surface and the lever surface are engaged in all positions of the lever.
15. The finger follower system of claim 1 , wherein the latch is adapted to move relative to the follower body in a latch motion direction and wherein the latch includes a substantially planar latch surface extending at a latch surface angle relative to the latch motion direction.
16. The finger follower system of claim 15 , wherein the latch is adapted to move relative to a guide surface on the follower body and wherein the latch surface angle is such that a majority of a loading force exerted by the lever on the latch is applied to the guide surface.
17. The finger follower system of claim 1 , wherein the motion receiving component is a cam follower roller cooperating with the lever.
18. The finger follower system of claim 1 , wherein the motion receiving surface is formed integrally on the lever.
19. The finger follower system of claim 1 , wherein the lever is coupled to the follower body via an eccentric mounting element, which permits a position of a pivoting end of the lever to be adjusted relative to the follower body.
20. The finger follower system of claim 1 , further comprising a lever biasing assembly for biasing the lever towards a motion source.
21. The finger follower system of claim 20 , further comprising a travel limiter for limiting travel of the lever relative to the follower body.
22. The finger follower system of claim 20 , further comprising a hydraulic lash adjuster in the valvetrain, the hydraulic lash adjuster having a lash adjustment force, wherein the lever biasing assembly provides a biasing force on the lever that is greater than the lash adjustment force.
23. The finger follower system of claim 20 , wherein the lever biasing assembly comprises at least one resilient element disposed between the lever and the follower body.
24. The finger follower system of claim 20 , further comprising at least one follower body spring support disposed on the follower body and at least one lever spring support disposed on the lever, the lever biasing assembly including at least one respective resilient element disposed between the follower body spring support and the lever spring support.
25. The finger follower system of claim 21 , wherein a position of the travel limiter relative to the follower body is adapted to provide for adjustment of an upper limit of the travel of the lever relative to the follower body.