Abstract:
An engine valve actuator assembly is provided that includes a movable roller finger follower operatively engaged with a displaceable engine valve. A rotatable camshaft with a plurality of different cam lobes having different profiles rotates about the roller finger follower. A plurality of intermediate finger followers contact different ones of the cam lobes and pivot about a common axis. One of the intermediate finger followers is in continuous contact with the roller finger follower. One or more additional intermediate finger followers are separately selectively engageable for common pivoting with the intermediate finger follower that remains in continuous contact with the roller finger follower, thereby varying displacement of the engine valve depending upon the various cam profiles.

Description:
TECHNICAL FIELD 
     The present invention relates to an engine valve actuator assembly for variable valve lift and cylinder deactivation for an engine. 
     BACKGROUND OF THE INVENTION 
     Engine valve actuator assemblies for an engine such as an internal combustion engine on a motor vehicle typically require a two-piece roller finger follower connected with the engine valve and pivotable in response to cam motion to lift the valve. A two-piece roller finger follower presents significant design, control and durability challenges. The two-pieces are not necessarily in continuous contact with one another; therefore, noise control measures may be required to prevent noise from occurring when the two pieces of the roller finger follower separate from one another. There are also significant side forces that act upon the two pieces of the roller finger follower, thus requiring significant component strength of each piece. 
     SUMMARY OF THE INVENTION 
     An engine valve actuator assembly is provided that achieves variable valve displacement (i.e., lift) and/or valve deactivation (i.e., keeping the valve closed) while maintaining components of the assembly in continuous contact with one another to prevent unwanted noise. The assembly utilizes a conventional engine valve and roller finger follower so that minimal change to the valve head is required. 
     Specifically an engine valve actuator assembly is provided that includes a movable engine valve and a movable roller finger follower that is continuously operatively engaged with the engine valve. A rotatable camshaft is provided with a plurality of cam lobes having different profiles, including at least a first and a second cam lobe axially displaced from one another. The first cam lobe is of a first profile and the second cam lobe is of a second profile larger than the first profile. A plurality of intermediate finger followers are each contactable with a different one of the cam lobes and are pivotable about a common axis. One of the intermediate finger followers is in continuous contact with the roller finger follower and is contactable with the first cam lobe having the first (smallest) profile. The second intermediate finger follower may be selectively engaged for common pivoting with the first intermediate finger follower to vary displacement of the engine valve. The larger profile of the second cam lobe will dominate when the first and second intermediate finger followers are engaged for common pivoting, thus causing a greater displacement of the engine valve. Optionally, a third intermediate finger follower may be positioned such that it is contactable with a third cam lobe having a third profile larger than the first profile but smaller than the second profile. The third intermediate finger follower may be selectively engaged for common pivoting with the first intermediate finger follower, thereby causing a third level of displacement because the larger third cam profile will dominate over any displacement otherwise caused by the first cam profile. Pins may be used for selectively engaging or locking the respective intermediate finger followers to the first intermediate finger follower. The pins may be hydraulically or electrically actuated. 
     Preferably, springs urge the intermediate finger followers into contact with the respective cam lobes to maintain smooth and continuous engagement of the components. 
     Optionally, a camshaft phaser may be operatively connected to the camshaft to selectively modify phasing or timing of engine valve opening and closing. 
     The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic perspective illustration of an engine having an engine valve actuator assembly within the scope of the invention; and 
         FIG. 2  is a schematic side illustration in partial cross-sectional view of the engine valve actuator assembly of  FIG. 1  positioned in an engine block of the engine of  FIG. 1 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings, wherein like reference numbers refer to like components, in  FIG. 1 , one embodiment of an engine  10  equipped with an engine valve actuator assembly  12  is depicted. The engine  10  includes an engine block  14 . As may be better viewed in  FIG. 2 , engine block  14  has at least one opening  16  that is in communication with an internal combustion chamber. The combustion chamber is not shown, but is understood by those skilled in the art. 
     The engine valve actuator assembly  12  includes a movable engine valve  18  for each opening  16 . The valve  18  has a valve stem  20  with a valve head  22  at one end of the valve stem  20 . The valve head  22  is sized to close the opening  16  when the valve  18  is closed. An engine valve spring  24  is disposed about the valve stem  20  in contact with the engine block  14  to bias to engine valve  18  toward a closed position as shown in  FIG. 2 . The valve opening  16  can also be referred to as a valve port. 
     The engine valve actuator assembly  12  includes a roller finger follower  30  that pivots to control the position of the engine valve  18 . Roller finger follower  30  has one end in contact with one end of the valve stem  20  opposite the valve head  22  at a contact point  32 . The engine valve actuator assembly  12  also includes a hydraulic lash adjuster  34  adjacent the other end of the roller finger follower  30 . The lash adjuster  34  is pivotally connected to the other end of the roller finger follower  30  at an attachment point  36 , preferably, with a ball and socket type connector, as is known in the art. It should be appreciated that the attachment point  36  is a pivot point for the roller finger follower  30 . 
     The engine valve actuator assembly  12  also includes first, second and third axially-spaced intermediate finger followers,  40 ,  42  and  44 , respectively. As may be better viewed in  FIG. 2 , the intermediate finger followers  40 ,  42  and  44  are each pivotable about a pivot axis running through point  46 . Unless pinned together as described below, the intermediate finger followers  40 ,  42  and  44  independently pivot about the pivot axis through point  46  in response to rotation of camshaft  50  spaced thereabove. Camshaft  50  is and rotatable about an axis through point  52 . 
     More specifically, the camshaft  50  is formed with three different cam lobes. The first cam lobe  54  is centrally located and may be in contact with the first intermediate finger follower  40  if neither of intermediate finger followers  42  and  44  are pinned to intermediate finger follower  40 . The first intermediate finger follower  40  is in continuous connect with the roller finger follower  30  as described below. The second and third intermediate finger followers  42 ,  44 , are axially spaced from the first intermediate finger follower  40  and are not in direct in physical contact with the roller finger follower  30 . A second cam lobe  56  is positioned above the second intermediate finger follower  42  to cause pivoting movement thereof when the camshaft  50  rotates. A third cam lobe  58  is positioned above the third intermediate finger follower  44  to cause pivoting movement thereof when the camshaft  50  rotates. The first cam lobe  54  has a first cam profile  60  which is partially visible in  FIG. 2  and is smaller than a second cam profile  62  of the second cam lobe  56 . The third cam lobe  58  has a third cam profile  64  that is larger than the first cam profile  60  but smaller than the second cam profile  62 . Accordingly, when the cam shaft  50  rotates, the first intermediate finger follower  40  will pivot the least amount, the second intermediate finger follower  42  will pivot the greatest amount and the third intermediate finger follower  44  will pivot an amount between that of the first intermediate finger follower  40  and the second intermediate finger follower  42 , assuming that none of the intermediate finger followers are pinned or otherwise engaged with one another for common pivoting. When neither of the second and third intermediate finger followers  42  and  44  are engaged with the first finger follower  40  for common pivoting, only the pivoting action of the first intermediate finger follower  40  affects the movement of the roller finger follower  30  and thus the valve stem  18  to cause a first displacement of the engine valve  20 . The amount of the first displacement may be zero, i.e., the engine valve  20  may remain in the closed position absent any engagement of the second or third intermediate finger followers  42 ,  44  with the first intermediate finger follower  40 . Alternatively, the amount of the first displacement may be positive. The first cam profile  60  governs the amount of first displacement. If the first displacement is zero, the engine valve remains closed, or deactivated. Optional deactivation of engine cylinders, or displacement on demand, may be desirable when the engine  10  is an internal combustion engine used with a conventional transmission and less torque is required, for example, during cruising. Cylinder deactivation may also be applied to an engine used in conjunction with an electrically variable transmission when engine power contribution is not desired under existing vehicle operating conditions. 
     A spring  66 , which is a torsion spring centered around the pivot axis that extends through point  46 , biases the intermediate finger follower  44  into contact with cam lobe  58 . Two additional springs (not shown) may be placed between the first and second intermediate finger followers  40 ,  42  and the first and third intermediate finger followers  40 ,  44 , respectively, for biasing intermediate finger followers  40  and  42  into contact with respective cam lobes  56  and  54 . 
     To vary displacement of the engine valve  20 , a pin  70  may be actuated to move from a first position in which it is supported within the first intermediate finger follower  40 , to a second position in which it extends within a recess  71  in the second intermediate finger follower  42  to lock the second intermediate finger follower  42  and first intermediate finger follower  40  together for common pivoting (i.e., to pivot a same amount of rotational displacement) about the pivot axis through point  46 . Thus, with the first and second intermediate finger followers  40 ,  42  locked together, the second cam  56 , with its larger second cam profile  62 , will cause both the first and second intermediate finger followers  40 ,  42  to pivot an amount determined by the second cam profile  62 . Thus, the roller finger follower  30  in continuous connect with the first intermediate finger follower  40  will cause the valve stem  18  and thus the engine valve  20  to displace a second amount of displacement greater than the first displacement, moving valve head  22  further away from opening  16  and thus allowing greater flow into the combustion chamber. The pin  70  may be hydraulically or electrically actuated in response to a control signal received from an electronic control unit as described below and as is understood by those skilled in the art. 
     Alternatively, if a third amount of displacement is desired, a second actuator pin  72  may be moved to extend from a first position in which it is supported within the first intermediate finger follower  40  to an extended position in which it extends into a recess  73  in the third intermediate finger follower  44  and locks the first and third intermediate finger followers  40 ,  44  together for common pivoting about the pivot axis through point  46 . Thus, third cam profile  64  of third cam  58  will dominate and cause greater pivoting of the first intermediate finger follower  40  via the engagement with the third intermediate finger follower  44  to cause a third amount of displacement of the engine valve  20 . Like the pin  70 , pin  72  may be hydraulically or electrically actuated. It should be appreciated that pins  70 ,  72  may alternatively be supported in the second and third intermediate finger followers  42 ,  44 , respectively and actuate into recesses formed in the first intermediate finger follower  40 . In either case, the pins and corresponding recesses may be located anywhere on the intermediate finger followers. Finally, it should also be appreciated that recesses may not be required if the pins are of a sufficient size and impart a sufficient tangential force upon the respective adjacent intermediate finger followers to affect common pivoting. 
     Optionally, a camshaft phaser  80  may be operatively connected to the camshaft  50  to vary phasing of the engine valve  20  (i.e., vary the opening and closing of the engine valve  20  as caused by rotation of the camshaft  50  in relation to a rotational position of an engine crankshaft (not shown) as is understood by those skilled in the art). 
     Those skilled in the art will understand that the pins  70  and  72  as well as the camshaft phaser  80  are controlled via an electronic control unit (not shown) which selects optimal valve lift and phasing dependent upon a variety of selected engine operating conditions according to an algorithm stored within the control unit. 
     Accordingly, the engine valve actuator assembly  12  provides varying amounts of valve displacement or actuation using a conventional roller finger follower  30  and a first intermediate finger follower  40  which is always in contact with the roller finger follower  30 , thereby avoiding potential noise associated with engagement and disengagement of these components. The engine valve  20  and the roller finger follower  30  are typical of those used in other designs; thus the engine valve actuator assembly  12  may be employed without expensive redesign of the engine head. 
     While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.