BRIEF DESCRIPTION OF DRAWINGS
Various of the above mentioned and further features and advantages may be better understood from this description of embodiments thereof, including the attached drawing figures wherein like reference characters refer to like elements.
FIG. 1 is a schematic side view in partial cross-section of a lost motion valve actuation system constructed in accordance with a first embodiment of the present invention.
FIG. 2 is an isometric view of the first embodiment of the present invention illustrated in FIG. 1.
FIG. 3 is a schematic side view of a lost motion valve actuation system constructed in accordance with a second embodiment of the present invention.
FIG. 4 is a schematic side view of a lost motion valve actuation system constructed in accordance with a third embodiment of the present invention.
FIG. 5 is a schematic side view of a lost motion valve actuation system constructed in accordance with a fourth embodiment of the present invention.
FIG. 6 is a schematic side view in partial cross-section of a lost motion valve actuation system constructed in accordance with a fifth embodiment of the invention.
FIGS. 7
a-b are schematic views in partial cross-section of a lost motion valve actuation system constructed in accordance with a sixth embodiment of the present invention.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
One approach to lost motion valve actuation may employ a mechanical linkage including a finger follower disposed between the cam and the valve being controlled. Such mechanical linkage may be designed to permit selective variation of the engine valve actuation on a dynamic basis. The valve actuation provided by a cam and finger follower combination may be a function of, without limitation: (1) the sizes and shapes of the cam lobe(s) that act directly or indirectly on the finger follower; (2) the position and control of a lost motion piston which supports either a free end of the finger follower or a member directly or indirectly connected to the finger follower; and (3) the position and control of a valve seating device which may be employed to manage valve seating.
FIG. 1 is a schematic illustration of a first embodiment of the present invention comprising a variable valve actuation system 10 operatively connected to an internal combustion engine valve assembly 400. The VVA system 10 may include a linkage assembly 100, a cam or other means for imparting motion 200, a valve seating device 300, and a lost motion piston 500. The VVA system 10 may be connected to, in contact with, and partially housed in an engine member 600, such as an engine head.
The linkage assembly 100 may include a finger follower support member 110, a link 120, and a finger follower 130. The support member 110 may be connected to the engine member 600 and pivotally connected to a first end of the link 120 by a hinge pin 111. A second end of the link 120 may include a convex hardened surface 124 adapted to contact the valve seating device 300 through the seating pin 310.
With reference to FIGS. 1 and 2, the link 120 may include two longitudinally extending arms which define an internal open space therebetween for receipt of the finger follower 130. A first end of the finger follower 130 may be pivotally connected to a second end of the link 120 by a pivot pin 122. The finger follower 130 may include a cam follower 134 connect to it by a roller pin 132. A free end of the finger follower 130 may include a hardened surface 136 that contacts an upper surface of the lost motion piston 500. The hardened surface 136 may be convex to allow it to pivot on the upper surface of the lost motion piston. The pivot pin end of the finger follower 130 may also include a convex hardened surface 138 that contacts the upper end of a valve stem 410 or alternatively a valve bridge. An engine valve spring 410 may bias the valve stem 410 towards the surface 138 of the finger follower.
With continued reference to FIG. 1, when the cam 200 rotates, the one or more lobes on the cam may act against the cam follower 134. If the lost motion piston 500 is hydraulically locked into position, the free end of the finger follower 130 at hardened surface 136 may be prevented from being pushed downward. As a result, the finger follower may pivot about its free end, and the end of the finger follower with the hardened surface 138 will be displaced downward to actuate the engine valve 410. Because the link 120 is connected to the finger follower 130 by the pivot pin 122, the link may rotate downward about the hinge pin 111. This may cause the hardened surfaces 136 and 138 to slide slightly along the surface of the lost motion piston 500 and the upper end of the valve 410, respectively. At the same time, the seating pin 310 may follow the free end of the link 120 downward a predetermined distance. If the lost motion piston is maintained in a static position for the duration of the time that the cam 200 lobe acts on the cam follower 134, the ramps that form the beginning and the end of the cam lobe may seat the engine valve in cooperation with the valve seating device 300.
The valve actuation provided by the one or more lobes of the cam 200 may be modified by selectively changing the position of the lost motion piston 500 while the cam lobe(s) are acting on the cam follower 134. Selective change of the position of the lost motion piston 500 may be accomplished by releasing hydraulic fluid from a chamber (not shown) below the lost motion piston. If the valve actuation provided by the one or more lobes of the cam 200 is truncated by releasing the hydraulic lock on the lost motion piston 500, the valve spring 400 and/or pressurized gas in the engine cylinder may cause the valve 410 to return (travel upwards) rapidly towards its seat. If this occurs, the valve seating device 300 may prevent the engine valve 410 from seating too quickly by opposing its upward motion through the seating pin 310.
If the lost motion piston 500 is not hydraulically locked in place when the cam lobe begins to act on the cam follower 134, the free end of the finger follower 130 at hardened surface 136 may be pushed downward. As a result, the finger follower 130 may pivot about the end connected to the link 120 by the pivot pin 122 and the link 120 may remain relatively stationary so that the engine valve 410 is not actuated. By selectively controlling the times that the lost motion piston 500 is hydraulically locked into position, and the position (height) of the lost motion piston relative to the engine member 600, lost motion and/or variable valve actuation may be provided using the system 10.
With reference to FIG. 3, in an alternative embodiment of the present invention, the finger follower 130 may include an end distal from the first contact surface 136 which extends past the end of the link 120. The finger follower 130 may include a fourth contact surface 139 at the end distal from the first contact surface. A spring 129 may contact the fourth contact surface and bias the finger follower 130 towards the engine valve assembly that contacts the second contact surface 138.
With reference to FIG. 4, in another alternative embodiment of the present invention, the finger follower 130 may include an end proximal to the first contact surface 136 located within the longitudinally extending arms of the link 120 with the fourth contact surface 139. A spring 129 may contact the fourth contact surface 139 and bias the finger follower towards the engine valve assembly that contacts the second contact surface 138. The fourth contact surface 139 and the first contact surface 136 may be adjacent to each other as shown in the figure. The fourth contact surface 139 may also include features to assist in retaining the spring 129 in position relative to the finger follower.
With reference to FIG. 5, in still another alternative embodiment of the present invention, the finger follower 130 may include a fourth contact surface 139 at the end distal from the first contact surface 136, and the link 120 may include a fifth contact surface 126 located above the fourth contact surface. A spring 129 may be disposed between and contact the fourth 139 and fifth 126 contact surfaces and thereby bias the finger follower 130 towards the engine valve assembly that contacts the second contact surface 138. The fourth contact surface 139 and the second contact surface 138 may be adjacent to each other as shown in the figure. The fourth and fifth contact surfaces may also include features to assist in retaining the spring 129 between them.
Another embodiment of the present invention is shown in FIG. 6 in which a substantial portion of the finger follower 130 may not be disposed between the arms of the link 120. In this embodiment, the link 120 and the finger follower 130 may be disposed laterally adjacent to each other.
In a further embodiment of the present invention, FIGS. 7a and 7b illustrate an embodiment for maintaining the link 120 and finger follower 130 aligned with valve stem included in the valve assembly 410. In this embodiment, the valve assembly 410 may include a cap 420 disposed between the top of valve stem and the second contact surface 138. The contact surface of finger follower 120 bears on top of cap 420. Link 120 may have projections on each side that guide the outer diameter of cap 420, keeping the finger follower centered over the cap.
STATEMENT REGARDING PREFERRED EMBODIMENTS
It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
Patent Application
20080072853
