Two-step finger follower rocker arm

#The present invention relates to mechanisms for altering the actuation of valves in internal combustion engines; more particularly, to finger follower type rocker arms having means for changing between high and low or no valve lifts; and most particularly, to a two-step finger follower type rocker arm having a slider member disposed in a finger follower body for sliding motion in the direction of lift between high and low positions and having a locking pin operative in an orthogonal bore in the finger follower body for latching and unlatching the slider member and the finger follower body to shift between high lift and low lift modes.

#Variable valve activation (VVA) mechanisms for internal combustion engines are well known. It is known to be desirable to lower the lift, or even to provide no lift at all, of one or more valves of a multiple-cylinder engine, especially intake valves, during periods of light engine load. Such deactivation can substantially improve fuel efficiency.

#Various approaches have been disclosed for changing the lift of valves in a running engine. One known approach is to provide an intermediary cam follower arrangement which is rotatable about the engine camshaft and is capable of changing both the valve lift and timing, the cam shaft typically having both high-lift and low-lift lobes for each such valve. Such an arrangement can be complicated and costly to manufacture and difficult to install onto a camshaft during engine assembly.

#The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

#FIG. 1 is an isometric view from the front of a first embodiment of a two-step finger follower rocker arm assembly in accordance with the invention;

#FIG. 2 is an exploded isometric view of the rocker arm assembly shown in FIG. 1;

#Referring to FIGS. 1 through 6 and 12, a first embodiment 10 of a two-step finger follower rocker arm assembly in accordance with the invention includes a follower body 12 having a first end 14 having means for receiving the head of a hydraulic lash adjuster 16 for pivotably mounting assembly 10 in an engine 18. The receiving means is preferably a spherical socket 20, as shown in FIGS. 4-6. A second and opposite end 22 of follower body 12 is provided with a pad 24, preferably arcuate, for interfacing with and actuating a valve stem 26 of gas valve 27. Body 12 is provided with a passage 28 therethrough between socket 20 and pad 24, passage 28 being generally cylindrical and having sliding surface 29 for slidably receiving a partially-cylindrical mating portion 30 of a slider member 32 having a longitudinal slot 33 therein. Body 12 is further provided with a first bore 34 transverse of passage 28, ending in bosses 36 for receiving roller bearings 38 for rotatably supporting a shaft 40 extending through bore 34 and slot 33 to slidably retain slider member 32 in passage 28. First and second lateral follower rollers 42a,b are mounted on opposite ends, respectively, of shaft 40.

#Slider member 32 further includes an actuating portion 44 having an arcuate outer surface 46 for engaging a central cam lobe 48 of an engine camshaft 47. Portion 44 extends toward first and second ends 14,22 of 12 to define, respectively, a latching surface 49 and a spring seat 50. Second end 22 is provided with a well 52 for receiving a lost-motion spring 54 disposed between end 22 and spring seat 50 (spring 54 shown in FIGS. 10 and 12-14 but omitted from the other drawings for clarity).

#First end 14 is further provided with a latching mechanism 56 for engaging and locking slider member 32 at its most outward extreme of motion in passage 28. Mechanism 56 comprises a stepped second bore 58 in body 12 and having an axis 60 intersecting passage 28, preferably orthogonally, bore 58 being preferably cylindrical.