Abstract:
A lock-pin cartridge for a valve deactivation rocker arm assembly. The cartridge comprises a body having an axial bore having first and second ends, the second end having a closure and a passage therethrough. A piston assembly comprising a locking pin and a piston is disposed in the bore. The locking pin extends through the second end passage to provide latching and unlatching of rocker arm elements. The piston is spaced apart from the ends to define a hydraulic chamber and a spring chamber within the bore on opposite sides of the piston. A spring is disposed in the spring chamber for urging the piston assembly toward one of the first and second ends. The hydraulic chamber includes means for communicating with a supply of hydraulic fluid for actuating the piston assembly.

Description:
This application is a Continuation-In-Part of a pending U.S. patent application Ser. No. 10/134,263, filed Apr. 29, 2002 now U.S. Pat. No. 6,668,775. 

   TECHNICAL FIELD 
   The present invention relates to mechanisms for altering the actuation of valves in internal combustion engines; more particularly, to a valve actuating mechanism such as a finger follower type rocker arm having means for changing between high and low or no valve lifts; and most particularly, to a pre-assembled lock-pin cartridge for a two-step finger follower type rocker arm. 
   BACKGROUND OF THE INVENTION 
   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. 
   Another known approach is to provide a deactivation mechanism in the hydraulic lash adjuster (HLA) upon which a cam follower rocker arm pivots. Such an arrangement is advantageous in that it can provide variable lift from a single cam lobe by making the HLA either competent or incompetent to transfer the motion of the cam eccentric to the valve stem. A shortcoming of providing deactivation at the HLA end of a rocker arm is that, because the cam lobe actuates the rocker near its longitudinal center point, the variation in lift produced at the valve-actuating end can be only about one-half of the extent of travel of the HLA deactivation mechanism. 
   Still another known approach is to provide a deactivation mechanism in the valve-actuating end of a rocker arm cam follower (opposite from the HLA pivot end) which locks and unlocks the valve actuator portion from the follower body. Unlike the HLA deactivation approach, this approach typically requires both high-lift and low-lift cam lobes to provide variable lift. 
   It is a principal object of the present invention to provide a simplified variable valve lift apparatus wherein manufacturing assembly is simplified and cost is reduced by incorporation of a pre-assembled lock-pin cartridge. 
   It is a further object of the invention to provide an increased range of motion between a high lift and a low lift position of an engine valve. 
   SUMMARY OF THE INVENTION 
   Briefly described, a two-step finger follower rocker arm assembly in accordance with the invention includes an elongate, rigid follower body having a socket at a first end for engaging a conventional hydraulic lash adjuster as a pivot means, and having an arcuate pad at a second and opposite end for engaging a valve stem or lifter means. A passage through the follower body in the direction of actuation by an engine cam lobe is slidingly receivable of a slider member for variably engaging a central cam lobe, preferably a high-lift lobe. A transverse bore in the follower body intersects the passage. A slotted passage is provided in the slider member, and an elongate pin extends through the bore in the slider member and through the slotted passage in the slider member such that the length of travel of the slider member in the passage is at least the length of the slotted passage therein. Outboard of the follower body, the pin is provided on either side of the body with first and second identical lateral roller followers, preferably rotatably mounted in bearings on the pin, for variably engaging first and second lateral cam lobes, preferably low-lift lobes, flanking the central cam lobe. A lost-motion spring urges the slider member into contact with the central lobe, and the hydraulic lash adjuster urges the lateral rollers into contact with the lateral lobes when the slider member is unlatched. A transverse locking pin can selectively engage and lock the slider member to the follower body such that the follower follows the motion of the central cam lobe. When the locking pin is disengaged from the slider member, the member slides within the follower body, allowing the lateral rollers to engage and follow the lateral lobes. Preferably, the central lobe is a high-lift lobe and the lateral lobes are low-lift lobes. Preferably, the locking pin is provided as a pre-assembled cartridge unit. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features and advantages of the invention will be more fully understood and appreciated from the following description of certain exemplary embodiments of the invention taken together with the accompanying drawings, in which: 
       FIG. 1  is an isometric view from the front of a finger follower type rocker arm assembly having means for changing between high and low or no lifts; 
       FIG. 2  is an exploded isometric view of the rocker arm assembly shown in  FIG. 1 ; 
       FIG. 3  is an isometric view from above of the rocker arm assembly shown in  FIG. 1 , the slider member being omitted for illustration; 
       FIG. 4  is an elevational cross-sectional view of the rocker arm assembly shown in  FIG. 1 , installed schematically in an internal combustion engine and having the associated valve closed, the locking pin unlocked, and the slider member on the base circle portion of the central cam lobe; 
       FIG. 5  is an elevational cross-sectional view like that shown in  FIG. 4 , showing the locking pin still unlocked, the lateral roller followers on the nose of the lateral cam lobes, and the valve opened to a low-lift position; 
       FIG. 6  is an elevational cross-sectional view like that shown in  FIG. 4 , showing the locking pin in locked position in the slider member, the nose of the central cam lobe on the slider member, and the valve opened to a high-lift position; 
       FIG. 7  is an elevational cross-sectional view of the locking pin assembly shown in  FIGS. 1–6 ; 
       FIG. 8  is an elevational cross-sectional view of a first embodiment of a locking pin assembly, showing a cartridge pin subassembly having a piston extension for mechanical actuation of the locking pin; 
       FIG. 9  is a view like that shown in  FIG. 8 , showing a cartridge pin subassembly without the piston extension, as would be configured for hydraulic actuation of the locking pin; 
       FIG. 10  is an elevational cross-sectional view of an example of a two-step finger follower, including the cartridge pin sub-assembly shown in  FIG. 8 , the pin and slider member being in the unlocked position; 
       FIG. 11  is an elevational cross-sectional view like that shown in  FIG. 10 , showing the pin and slider member in the locked position; 
       FIG. 12  is an elevational cross-sectional view of an alternate, open-ended version of the cartridge sub-assembly shown in  FIG. 8 , the pin and slider member being in the unlocked position; 
       FIG. 13  is an elevational cross-sectional view of a second embodiment of a locking pin sub-assembly; 
       FIG. 14  is an elevational cross-sectional view of a two-step finger follower in accordance with the invention, including the cartridge pin sub-assembly shown in  FIG. 13 , the pin and slider member being in the unlocked position; and 
       FIG. 15  is an elevational cross-sectional view of an alternate, open ended version of the cartridge pin sub-assembly shown in  FIG. 14 , the pin and slider member being in the unlocked position. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIGS. 1 through 6 , a typical two-step finger follower rocker arm assembly  10 , as described in pending application Ser. No. 10/134,263 and incorporated herein by reference, 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 . Body  12  is provided with a passage  28  therethrough between socket  20  and pad  24 , passage  28  being generally cylindrical 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  42   a,b  are mounted on opposite ends, respectively, of shaft  40 . 
   Slider member  32  further includes an actuating portion  44  having an arcuate upper surface  46  for engaging a central cam lobe  48  of an engine camshaft (not shown). 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  FIG. 10  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  57  comprises a stepped second bore  58  in body  12  and having an axis  60  intersecting passage  28 , preferably orthogonally, bore  58  being preferably cylindrical. 
   Referring to  FIGS. 4 through 7 , latching mechanism  57  disposed in body  12  of the typical two step finger follower mechanism described above is shown. Latching mechanism  57  includes piston assembly  61 , defining a locking pin  62  and piston  63 , biased outwards in bore  58  by a return spring  64  and extending toward slider member  32  to support a latch member  66  which may slide along a slide surface  68  in body  12 . Bore  58  is closed by a plug  70 , forming a hydraulic chamber  72  in communication via passage  74  with socket  20 . Pressurized oil may be supplied to chamber  72  in known fashion from HLA  16 , upon command from an engine control module (not shown), to cause piston assembly  61  to become hydraulically biased toward slider member  32 . When such biasing occurs, to overcome the counter-bias of return spring  64 , arcuate surface  46  being engaged on the base circle portion  76  of central cam lobe  48 , latch member  66  is urged axially into latching and locking engagement with latching surface  49 . As shown in  FIG. 6 , when cam lobe  48  rotates to engage nose portion  78  with surface  46 , valve stem  26  is actuated from a zero lift position  80  to a high lift position  82 . 
   Still referring to  FIGS. 4 through 6 , central cam lobe  48  is flanked by first and second identical lateral cam lobes  84  (only one visible in  FIGS. 4–6 ) for selectively engaging first and second lateral follower rollers  42   a,b , respectively. When the engine control module determines, in known fashion from various engine operating parameters, that a low-lift condition is desired, oil pressure is no longer supplied to chamber  72 , allowing return spring  64  to again bias piston  62  and associated latch member  66  away from slider member  32 . When cam lobe  48  rotates to place surface  46  on base circle portion  76  again, piston assembly  61  unlatches latch member  66  and slider member  32  is again free to slide in passage  28 . When the camshaft again rotates to place nose  78  on surface  46 , member  32  is depressed into body  12 , allowing noses  86  on lateral cam lobes  84  to be engaged by rollers  42   a,b , as shown in  FIG. 5 , thus displacing valve stem  26  from zero lift position  80  to a low-lift position  88 . As long as oil pressure is withheld from chamber  72 , latching mechanism  56  remains disengaged from slider member  32 , and assembly  10  functions as a low-lift rocker. 
   Of course, it will be seen by those of skill in the art that the dimensions of the lateral cam lobes and lateral follower rollers may be configured to provide any desired degree of lift to valve stem  26  in a range between positions  80  and  88 . 
   It will further be seen that, within the scope of the invention, the dimensions of all the lobes, follower rollers, and the slider member may be configured, and the engine control module so programmed, if desired such that low-lift is achieved via the central cam lobe and high lift via the lateral cam lobes. 
   Referring to  FIGS. 9 through 11 , a first embodiment in accordance with the invention is shown, comprising a latching cartridge  92  which may be inserted into bore  58  ( FIG. 7 ) and which is preferably and conveniently pre-assembled as a subassembly, thereby greatly simplifying the overall assembly of follower  10 . Cartridge  92  includes a body  94 , preferably tubular and including a bore  95  closed at outer end  96 . Body  94  is sized to be close-fitted into bore  58 , thereby eliminating the need for plug  70 . Catridge  92  includes piston assembly  61 ′ comprising piston  63  and locking pin  62 ′. Preferably, body  94  is constricted  98  to separate piston  63  from end  96 , thereby providing a hydraulic chamber  72 ′ within the cartridge. Constriction  98  is perforated  100  to allow hydraulic communication with passage  74  and socket  20  ( FIG. 7 ). Body  94  is partially closed at inner end  102  to retain return spring  64 ′ in spring chamber  65  and provide guidance for locking pin  62 ′ in driving latch member  66 ′ into engagement ( FIG. 11 ) and out of engagement ( FIG. 10 ) with latching surface  49 . 
   Referring to  FIG. 8 , a variation  92 ′ of cartridge  92  is provided with a piston extension  104  slidably extending through outer end  96  for engagement by mechanical or electromechanical actuation means (not shown), for example, a conventional solenoid actuator, in place of the previously-discussed hydraulic actuation. 
   Referring to  FIG. 12 , another variation  92 ″ is provided, which may be inserted into bore  58  ( FIG. 7 ) and which, like embodiment  92  and  92 ′, is preferably and conveniently pre-assembled as a subassembly, thereby greatly simplifying the overall assembly of follower  10 . Cartridge  92 ″ includes a body  94 , preferably tubular and including a bore  95  opened at outer end  96 . Body  94  is sized to be fitted into bore  58 , Bore  58  is sealed proximate body outer end  96  with plug  70 . Catridge  92 ″ includes piston assembly  61 ′ comprising piston  63  and locking pin  62 ′. Preferably, body  94  is provide with at least one slot or perforation  100  thereby providing hydraulic communication between chamber  72 ′ and oil passage  74 . Body  94  is partially closed at inner end  102  to retain return spring  64 ′ in spring chamber  65  and provide guidance for locking pin  62 ′ in driving latch member  66 ′ into engagement ( FIG. 11 ) and out of engagement ( FIG. 10 ) with latching surface  49 . 
   Referring to  FIGS. 13 and 14 , a second embodiment of a latching cartridge  112  is shown for a latching mechanism  57  in accordance with the invention. In embodiment  112 , the hydraulic chamber  72 ′ and return spring  64 ′ are reversed, such that assembly  10  is latched by spring  64 ′ when oil pressure is removed, and is unlatched when oil pressure is applied to chamber  72 ′. Latching cartridge  112  may be inserted into bore  58  and is preferably and conveniently pre-assembled as a subassembly, thereby greatly simplifying the overall assembly of follower  10 . Cartridge  112  includes a body  94 , preferably tubular and including a bore  95  closed at outer end  96 . Body  94  is sized to be close-fitted into bore  58 , thereby eliminating the need for plug  70 . Body  94  is perforated  100  to allow hydraulic communication of hydraulic chamber  72 ′ with passage  74  and socket  20 . Body  94  is partially closed at inner end  102  to provide guidance for locking pin  62 ′ in driving latch member  66 ′ into and out of engagement with latching surface  49 . Return spring  64  is captured in spring chamber  65  between piston  63  and end  96 . 
   Referring to  FIG. 15 , another version  112 ′ of the second embodiment is shown in accordance with the invention. Like embodiments  92 ,  92 ′, and  112 , cartridge  112 ′ is preferable and conveniently pre-assembled as a subassembly, thereby greatly simplifying the overall assembly of follower  10 . In embodiment  112 ′, as in embodiment  112 , the hydraulic chamber  72 ′ and return spring  64 ′ are reversed, such that assembly  10  is latched by spring  64 ′ when oil pressure is removed, and is unlatched when oil pressure is applied to chamber  72 ′. Cartridge  112 ′ includes a body  94 , preferably tubular and including a bore  95  opened at outer end  96 . Body  94  is sized to be fitted into bore  58 ; bore  58  is sealed proximate body outer end  96  with plug  70 . Body  94  is perforated  100  to allow hydraulic communication of hydraulic chamber  72 ′ with passage  74  and socket  20 . Body  94  is partially closed at inner end  102  to provide guidance for locking pin  62 ′ in driving latch member  66 ′ into and out of engagement with latching surface  49 . Return spring  64  is captured in spring chamber  65  between piston  63  and end  96 . 
   Cartridges  92 , 92 ′, 112  and  112 ′ are useful in all types of variable valve actuation rocker arm assemblies, not just those discussed above, wherein lock pin mechanisms are used to latch and unlatch components of a rocker arm mechanism to vary the lift of associated valves. Cartridges in accordance with the invention contain the entire locking mechanism in a single assembly, which reduces the precision required in a receiving bore in a rocker arm mechanism. The entire cartridge may be pre-assembled and tested inexpensively before insertion into the arm assembly, thereby simplifying rocker arm assembly, reducing the manufacturing cost, and increasing the reliability. 
   While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.