TECHNICAL FIELD

The present disclosure relates generally to a valve actuation system, and more particularly to an anti-rotation device for valve lifters.

BACKGROUND

Internal combustion engines typically employ numerous valves to control the fluid connections amongst different parts of the engine, such as intake valves and exhaust valves to open and close intake and exhaust connections to a combustion cylinder. It is common for engine valve actuation to be achieved by a mechanical linkage between a crankshaft of the engine and one or more rotating camshafts, in turn rotatable to actuate the valves. In a typical valve actuation system the camshaft is rotated by a cam gear in mesh with an engine flywheel, and includes a plurality of non-circular cams that engage valve lifters to open engine valves, and permit the engine valves to be closed with biasing springs. Rocker arms are provided to reciprocate back and forth to open and close the valves, with pushrods or other intervening hardware coupling the valve lifters to the rocker arms.

In operation, cam followers such as rollers directly contact the cams and enable the valve lifters to reciprocate within bores in the engine housing. Proper operation generally requires an angular orientation of the valve lifters to be maintained relative to their axes of reciprocation, or permitted to rotate within a relatively tightly controlled range. Internal combustion engine operation is a dynamic process, however. Valve lifters can become misaligned, potentially requiring service or even resulting in catastrophic engine failure. Many designs for limiting rotation of valve lifters have been proposed over the years, ranging from geometry of the valve lifters themselves, relative to one another and/or relative to the engine housing, to specialized spring clips coupled with valve lifters and structured to engage with parts of the engine housing. One known anti-rotation roller valve lifter is set forth in U.S. Pat. No. 8,826,874. The '874 patent proposes a roller lifter having a first end with a first diameter, and a second end with a greater diameter and having a flat surface configured to engage a corresponding flat surface on an adjacent lifter. The strategy set forth in the '874 patent may have various applications, but there is always room for improvement and development of alternative strategies.

SUMMARY OF THE INVENTION

In one aspect, an anti-rotation device for valve lifters in a valve actuation system includes a collar having a sleeve portion and a boss portion. The sleeve portion includes an inner peripheral guide surface forming a lifter bore defining a bore center axis. The inner peripheral guide surface has a shape that is varied, circumferentially around the bore center axis, to limit rotation of a first valve lifter slidably received in the lifter bore. The boss portion includes an outer peripheral surface facing a radially outward direction. The anti-rotation device further includes a bridge connector projecting from the outer peripheral surface for engagement with a second valve lifter.

In another aspect, a valve lifter assembly includes an anti-rotation device having a collar with a sleeve portion including, an inner peripheral guide surface forming a lifter bore and a boss portion having an outer peripheral surface. The anti-rotation device further includes a bridge connector projecting from the outer peripheral surface. The valve lifter assembly further includes a valve lifter coupled to the anti-rotation device and defining a longitudinal lifter axis extending between a first axial body end and a second axial body end. The valve lifter includes a lifting surface facing a direction of the first axial end, and a cam follower mounted to the second axial body end.

In another aspect, an engine valve actuation system includes a rotatable camshaft having a first cam with a first cam profile about a cam axis of rotation, and a second cam having a second cam profile, different from the first cam profile, about the cam axis of rotation. The engine valve actuation system further includes a first valve lifter having a lifting surface structured to actuate a first valve in the engine, and a cam follower in contact with the first cam to reciprocate the first valve lifter in response to rotation of the first cam. The engine valve actuation system further includes a second valve lifter having a lifting surface structured to actuate a second valve in the engine, and a cam follower in contact with the second cam to reciprocate the second valve lifter in response to rotation of the second cam. The engine valve actuation system still further includes an anti-rotation device including, a collar having a sleeve portion with an inner peripheral guide surface forming a lifter bore and a boss portion having an outer peripheral surface, and a bridge connector projecting from the outer peripheral surface. The first valve lifter is slidably received in the lifter bore and in contact with the inner peripheral guide surface to inhibit rotation of the first valve lifter. The second valve lifter is fixedly coupled to the bridge connector, such that the anti-rotation device is moved with the second valve lifter, and relative to the first valve lifter, between a lifted position and a dropped position in response to rotation of the second cam.

