Abstract:
A valve actuation sub-assembly for an internal combustion engine, the sub-assembly being adapted for attachment to an engine block ( 11 B) and including a conventional roller follower ( 21 ) and a deactivating roller follower ( 47 ). The sub-assembly comprises a follower guide member ( 71 ) defining a first guide receptacle ( 81 ) for receiving an upper portion ( 87 ) of the conventional roller follower ( 21 ), and a second guide receptacle ( 83 ) for receiving an upper portion ( 93 ) of the deactivating roller follower ( 47 ). In accordance with the invention, neither upper portion ( 87,93 ) will be received within the guide receptacle ( 81,83 ) intended for the other upper portion, thus preventing assembly errors, wherein one roller follower type is installed in a location on the engine intended for the other roller follower type.

Description:
BACKGROUND OF THE DISCLOSURE 
     The present invention relates to an improved valve gear train for an internal combustion engine, and more particularly, to a valve deactivator sub-assembly for use therein. 
     Although the valve deactivator sub-assembly of the present invention may be utilized to introduce some additional lash into the valve train, such that the valves open and close by an amount less than the normal opening and closing, the invention is especially suited for introducing into the valve train sufficient lash (also referred to hereinafter as “lost motion”), such that the valves no longer open and close at all, and the invention will be described in connection therewith. 
     Valve deactivators of the general type to which the invention relates are known, especially in connection with internal combustion engines having push rod type valve gear trains in which there is a rocker arm, with one end of the rocker arm engaging the push rod, and the other end engaging the engine poppet valve. Typically, a central portion of the rocker arm is fixed relative to the cylinder head (or other suitable structure) by a fulcrum arrangement as is well know to those skilled in the art, in which the fulcrum normally prevents movement of the central portion of the rocker arm in an “up and down” direction. At the same time, the fulcrum permits the rocker arm to engage in cyclical, pivotal movement, in response to the cyclical motion of the push rod, which results from the engagement of the push rod with the lobes of the rotating cam shaft. 
     There are a number of known valve deactivator sub-assemblies which are operably associated with the fulcrum portion of the rocker arm and which, in the latched condition, restrain the fulcrum portion of the rocker arm to move in its normal cyclical, pivotal movement. However, In an unlatched condition, the valve deactivator sub-assembly permits the fulcrum portion of the rocker arm to engage in “lost motion” such that the cyclical, pivotal movement of the push rod causes the rocker arm to undergo cyclical, pivotal movement about the end which is in engagement with the engine poppet valve. In other words, the rocker arm merely pivots, but the engine poppet valve does not move and therefore, is in its deactivated condition. 
     Although the known valve deactivator sub-assemblies of the type referred to above have performed in a generally satisfactory manner, such sub-assemblies do add substantially to the overall cost of the valve gear train, and in many cases also add undesirably to the space taken up by the overall rocker arm installation. In some engine designs, there is simply no room to add a valve deactivator sub-assembly of the type which is associated with the rocker arm fulcrum member. 
     Typically, in a push rod type of valve gear train, there is some sort of cam follower device having one portion thereof in engagement with the cam lobe on the engine cam shaft, and another portion thereof in engagement with the lower end of the push rod. It is also known for such a cam follower mechanism to include a hydraulic lash compensation element. It is now also known to incorporate a valve deactivator mechanism into the cam follower, thus eliminating the need for adding to the rocker arm assembly the type of expensive, space consuming structure described above. 
     On a normal internal combustion engine having valve gear train of the push rod type described above, and including some form of valve deactivation capability, it would be typical for less than all of the engine poppet valves to be equipped with the valve deactivation capability. In other words, on an eight cylinder engine, by way of example only, it would be typical to provide valve deactivation capability on both the intake and exhaust valves of four of the eight cylinders, while equipping the intake and exhaust valves of the other four cylinders with conventional roller followers. In such an engine configuration, installation of the proper roller follower at each location within the engine can be a problem because, typically, the valve deactivating roller follower and the conventional roller follower to be used in a particular engine would be the same overall size, shape, and configuration, such that during the engine assembly process, it would be very easy to put a valve deactivating roller follower in a location intended to have a conventional roller follower, or vice-versa. 
     It is known in valve gear train of the type to which this invention relates to provide some sort of guide member for the roller followers to prevent rotation of the roller followers about their longitudinal axes, in order to maintain the roller followers in their proper rotational orientation relative to the associated cam lobe. In other words, the axis of the roller of the roller follower must remain parallel to the axis of the cam shaft. 
     BRIEF SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide an improved valve deactivator sub-assembly, including a guide member, which overcomes the above-described disadvantages of the prior art. 
     It is a more specific object of the present invention to provide an improved valve deactivator sub-assembly and guide member which will insure that deactivating roller followers are installed only at deactivation follower locations, and that conventional roller followers are installed only at conventional follower locations. 
     It is another object of the present invention to provide an improved valve deactivator sub-assembly, including a guide member, which accomplishes the above-stated objects, and which also insures that each roller follower is oriented correctly, rotationally, so that, for example, each fluid port in the roller follower is aligned with the correct fluid passage in the engine block. 
     The above and other objects of the invention are accomplished by the provision of a valve actuation sub-assembly for an internal combustion engine of a type having a valve means for controlling the flow to and from a combustion chamber, and valve gear means operative in response to a cyclical input motion to effect cyclical opening and closing of the valve means. The valve actuation sub-assembly is adapted for attachment relative to an engine block including a cam shaft defining first and second cam profiles operable to provide the cyclical input motion in response to rotation of the cam shaft. The engine block defines first and second follower bores disposed adjacent the first and second cam profiles, respectively. The valve actuation sub-assembly comprises first and second roller followers, to be disposed in the first and second follower bores, respectively, each of the roller followers including a roller for operative engagement with its respective cam profile, an outer body fixed to move axially with its roller, and the outer body including an upper portion projecting out of its respective follower bore. Each roller follower includes an inner body disposed within the outer body, and including a push rod socket, and a push rod in engagement with the socket and operable to transmit the cyclical input motion to the valve gear means. The valve actuation sub-assembly further comprises a follower guide member adapted for attachment to the engine block and defining first and second guide receptacles operable to receive and guide the upper portions of the outer body of the first and second roller followers, respectively. 
     The improved valve actuation sub-assembly is characterized by the first guide receptacle defining a first internal profile configured to be closely spaced relative to the upper portion of the outer body of the first roller follower. The first internal profile is not capable of receiving the upper portion of the outer body of the second roller follower. The second guide receptacle defines a second internal profile configured to be closely spaced relative to the upper portion of the outer body of the second roller follower. The second internal profile is not capable of receiving the upper portion of the outer body of the first roller follower. 
     In accordance with a further aspect of the invention, the valve actuation sub-assembly is characterized by the first roller follower comprising a conventional roller follower and the second roller follower comprising a deactivating roller follower. The second roller follower includes a latching arrangement operable between a latched condition, latching the inner body for movement with the outer body, and an unlatched condition, permitting relative axial movement between the outer body and the inner body. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary, axial cross section taken through a vehicle internal combustion engine, illustrating a typical “PRIOR ART” valve gear train of the type with which the present invention may be utilized. 
     FIG. 2 is a fragmentary, transverse cross section, taken in a direction along the axis of the cam shaft shown in FIG. 1, illustrating one aspect of the present invention. 
     FIG. 3 is a top plan view of the follower guide member of the present invention, shown in axial cross section in FIG. 2, and on approximately the same scale. 
     FIG. 4 is a somewhat enlarged bottom plan view of the follower guide member of the present invention, but with none of the roller followers in place. 
     FIG. 5 is a substantially enlarged, axial cross section illustrating the valve deactivating roller follower which comprises part of the overall valve actuation sub-assembly of the present invention. 
     FIG. 6 is a broken, bottom plan view similar to FIG. 4, but on a larger scale, to illustrate the differences between the two types of guide receptacles in the present invention. 
     FIGS. 7 and 8 are simplified views of the external profiles of the upper portions of the outer bodies of the first and second roller followers, respectively, corresponding to the guide receptacles with which they are associated in FIG.  6 . 
     FIG. 9 is a bottom, perspective view of the follower guide member of the present invention, but viewed from the opposite direction as in FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings, which are not intended to limit the invention, FIG. 1 illustrates a valve actuating valve gear train of the push rod type, although it should be understood that the use of the present invention is not strictly limited to such. FIG. 1 illustrates a cylinder head  11 A and an engine block  11 B. On the engine block  11 B is mounted a drive assembly  13 , and on the cylinder head  11 A is mounted a rocker arm assembly  15  and an engine poppet valve assembly, generally designated  17 . Those skilled in the art will understand that the spatial relationship of the cylinder head  11 A and engine block  11 B, as shown in FIG. 1 are for ease of illustration only. 
     The drive assembly  13  includes a cam shaft  18  having a cam  19 , a hydraulic roller follower  21 , and a push rod  23 . An example of a conventional hydraulic roller follower, not having valve deactivation capability, is illustrated and described in U.S. Pat. No. 4,607,599, assigned to the assignee of the present invention and incorporated herein by reference. The cam  19  includes a lift portion  25  and a dwell (base circle) portion  27 . The poppet valve assembly  17  includes a poppet valve  29 , operable to control flow to and from a combustion chamber  30 , and further includes a spring  31  which biases the poppet valve toward the closed position shown in FIG. 1, as is well known to those skilled in the art. 
     The rocker arm assembly  15  includes a rocker arm  33  of the center-pivot type, the rocker arm  33  including one end  35  which is adapted to receive cyclical input motion from the push rod  23 , and another end  37  which is adapted to transmit to the valve  29  the cyclical motion of the push rod  23 . As a result, the engine poppet valve  29  has a cyclical opening and closing motion, corresponding to that of the push rod  23 , all of which is well known to those skilled in the art. In the subject embodiment, the only motion of the rocker arm  33  is its pivotal movement, with the ends  35  and  37  engaging in alternating up and down movement. 
     The rocker arm  33  includes a pivot portion  39 , disposed intermediate the ends  35  and  37 , and a fulcrum  41  is disposed within the pivot portion  39  in a manner which permits the rocker arm  33  to pivot as described previously. The fulcrum  41  has a threaded mounting bolt  43  extending therethrough and being in threaded engagement with an internally threaded bore  45  defined by the cylinder head  11 A. It should be understood that the present invention is not limited to any particular type or configuration of rocker arm or fulcrum arrangement. 
     Typically, the present invention would be utilized with an eight cylinder engine for which the valve gear train would include eight pairs of intake and exhaust valves, and eight pair of intake and exhaust valve rocker arms. Four of the eight pairs would be equipped with a valve deactivator assembly, comprising a valve deactivating roller follower  47  (see FIGS.  2  and  5 ). In other words, four of the eight cylinders can be selectively deactivated by introducing sufficient “lost motion” into the valve drive train for that particular valve, so that the cyclical motion of the push rod  23  does not result in any corresponding cyclical opening and closing movement of the poppet valve  29  (i.e., of either the intake valve or the exhaust valve for that particular cylinder). 
     The other four of the eight cylinders would not be equipped with a valve deactivating device, but instead, would be equipped with one of the conventional hydraulic roller followers  21  (as shown in both FIGS.  1  and  2 ). The four pairs of intake and exhaust engine poppet valves  29  which are provided with the conventional roller followers  21 , operate continually in their normal operating mode (i.e., there is never any “lost motion” introduced into the valve drive train for those particular valves), and as a result, rotation of the cam shaft  18  always results in cyclical motion of the push rod  23 , and corresponding cyclical opening and closing movement of the poppet valves  29 . 
     Referring now primarily to FIG. 2, as was indicated in the background of the disclosure, one of the problems associated with valve deactivating systems is making sure that the proper roller follower (whether a conventional roller follower  21  or a deactivating roller follower  47 ) is installed at each location. In addition, each deactivating roller follower  47  must be rotationally oriented correctly, as will be described subsequently in greater detail. Finally, it is important that each of the roller followers (both the conventional and the deactivating) is prevented from rotating about its axis, as will be discussed in greater detail subsequently. 
     Referring now to FIG. 2, in conjunction with FIG. 1, certain aspects of the present invention will be described. Each roller follower  21  or  47  includes an outer body member  53  which is disposed to reciprocate within a bore  55  in the engine block  11 B. The outer body member  53  is in contact with, and follows its respective cam  19 , through a conventional roller  57 , shown herein in FIG. 5 as being of the needle roller bearing type. Those skilled in the art will understand that the invention is not limited to any particular roller follower design, or, by way of example, whether the axle of the roller is provided with needle bearings or merely a bushing, etc. Reciprocally disposed within the outer body member  53  is an inner body member  59  which includes a socket portion  61  to engage the lower end of the push rod  23 . The inner body member  59  is biased upwardly in FIG. 5 toward its normal operating position by means of a lost motion spring  63 . 
     Operably associated with the inner body member  59  is a hydraulic lash compensation element, generally designated  65 , the details of which are well known to those skilled in the art, are not essential to the present invention, and therefore, will not be described further herein. Also operably associated with the inner body member  59  is a latching mechanism, generally designated  67 . The mechanism  67  is of the spring applied, pressure released type. Therefore, the outer body member  53  defines an annular pressure passage  69  which is in fluid communication through port  70  with a source (not shown herein) of control pressure by means of an appropriate pressure passage (also not shown herein) in the engine block  11 B. To the extent that the details of the construction and the operation of the valve deactivating roller follower  47  are not already well known to those skilled in the art, further understanding may be gained by reference to U.S. Pat. No. 6,196,175, assigned to the assignee of the present invention and incorporated herein by reference. 
     Referring again primarily to FIGS. 2-4, in accordance with an important aspect of the invention, a follower guide member, generally designated  71  is provided. To facilitate understanding of the invention, a prior art guide member, generally designated G, is shown in dashed lines in FIG. 1, with the guide member G being disposed in its assembled position. It should be understood that what is being shown in FIG. 2 is the follower guide member  71  as it is being lowered toward its installed position relative to the engine block  11 B. However, in FIG. 2, for ease of illustration, there is only one of the roller followers  21  and only one of the deactivating roller followers  47  assembled to the guide member  71  whereas, in the actual practice of the subject embodiment, there would be two of the roller followers  21  and two of the deactivating roller followers  47  assembled to the guide member  71 , as will become more readily apparent from the subsequent description. 
     Preferably, the follower guide member  71  comprises a molded plastic member, and in the subject embodiment, and by way of example only, the guide member  71  includes a conventional portion  73  and a deactivating portion  75 , the portions  73  and  75  being joined by an intermediate portion  77 , such that the guide member  71  comprises a single integral (unitary) molded member. It is also preferable that the guide member  71  be molded from any one of a number of known, heat resistant plastic materials, suitable for the particular engine application intended. It should be understood that the guide member  71  shown in FIGS. 2-4 is by way of example only, and is the preferred arrangement for a V-8 engine on which there are two adjacent cylinders associated with the guide member  71 , with one cylinder being conventional, and the other being of the deactivating type. However, on a V-6 engine, for example, one whole bank of cylinders may be conventional, while the other entire bank of cylinders is of the deactivating type, and such an arrangement is within the scope of the present invention. In that case, there would be at least two separate guide members which together would comprise the “guide member” recited in the appended claims, and that guide member would define at least one receptacle for a conventional roller follower, and at least one receptacle for a deactivating roller follower. 
     The term “conventional” is used in regard to the portion  73 , because the portion  73  defines a pair of substantially identical, generally cylindrical receptacles  81 , each of which receives one of the conventional roller followers  21 . Similarly, portion  75  is referred to as a deactivating portion because the portion  75  defines a pair of substantially identical, generally cylindrical receptacles  83 , each of which receives one of the deactivating roller followers  47 . 
     In accordance with one important aspect of the invention, even though the roller followers  21  and  47  appear, externally, to be almost identical, the roller followers  21  and  47  are made slightly different from each other, and the receptacles  81  and  83  are made different from each other. Aside from the differences between the receptacles  81  and  83 , as will be described in greater detail subsequently, the conventional portion  73  and the deactivating portion  75  may otherwise appear substantially identical except, that in the subject embodiment, the deactivating portion  75  defines an arcuate recess  85  (shown in both FIGS.  3  and  4 ), which is merely an example of a physical feature of the guide member  71  which may be used to orient the guide member  71  relative to the engine block  11 B. Thus, it will be understood that the arcuate recess  85  could, in some engine applications, be formed in the conventional portion  73  instead of in the deactivating portion  75 , and could have any number of other sizes, shapes and configurations. It is an important aspect of the invention however for the guide member  71  to include some sort of feature which, upon assembly, ensures that the guide member  71  is properly oriented relative to the engine block  11 B. 
     As will be understood by those skilled in the art, each of the portions  73  and  75  includes two receptacles (either  81  or  83 ) for roller followers only because, in the subject embodiment of the invention, the engine is of the two-valves-per-cylinder type. Furthermore, in the subject embodiment of the invention, each cylinder which is of the conventional type is disposed immediately adjacent a cylinder which is to be of the deactivating type, and therefore, each follower guide member  71  is formed to have the conventional portion  73  and the deactivating portion  75  combined in a single guide member  71 . 
     Referring now primarily to FIGS. 7 and 8, one important aspect of the invention will be described. FIG. 7 shows the preferred embodiment of an upper portion  87  of the outer body member  53  of the conventional roller follower  21 . The upper portion  87  is generally cylindrical, and has a slightly smaller diameter than that of the receptacle  81 , and includes a pair of flats  89 . The receptacle  81  defines a pair of flats  91  which are configured such that when the upper portion  87  is inserted into the receptacle  81 , the engagement of the flats  89  within the flats  91  will be sufficient to hold the roller follower  21  in the position shown in FIG. 2 during the assembly process. The engagement should also be sufficient so that the “torque-to-turn”, i.e., the amount of torque it would take to turn the roller follower  21  in the receptacle  81  would be greater that what is exerted on it during normal operation. 
     FIG. 8 shows the preferred embodiment of an upper portion  93  of the outer body member  53  of the deactivating roller follower  47 . The upper portion  93  is also generally cylindrical, and has a slightly smaller diameter than that of the receptacle  83  (which may be the same as the receptacle  81  diameter), and the upper portion  93  includes a pair of flats  95 , which appear very similar to the flats  89 , but in accordance with an important aspect of the invention, the flats  95  are somewhat narrower than the flats  89  or, stated another way, the flats  95  are further apart than are the flats  89 , for reasons which will become apparent subsequently. The one flat  95  includes an elongated rib  97  which extends along the axial length of the flats  95 . The receptacle  83  defines a pair of flats  99  which are configured such that when the upper portion  93  is inserted into the receptacle  83 , the engagement of the flats  95  within the flats  99  will be sufficient to hold the roller follower  47  in the position shown in FIG. 2 during the assembly process. 
     One of the flats  99  includes an elongated notch  101  (see also FIG. 9) which receives the rib  97 , so that the roller follower  47  can be inserted within the receptacle in only one rotational orientation, thus insuring that the pressure port  69  is in proper alignment (and communication) with the pressure passage in the engine block  11 B. 
     During the assembly process, if an attempt is made to locate one of the deactivating roller followers  47  in a conventional receptacle  81 , the flats  95  being further apart, plus the presence of the rib  97 , will prevent the insertion of the upper portion  93  into the receptacle  81 . If, on the other hand, an attempt is made to locate one of the conventional roller followers  21  in a deactivating receptacle  83 , the fact that the flats  89  are closer together than the flats  99  will permit insertion of the upper portion  87  into the receptacle  83 . However, when the guide member  71  is picked up and held in the position shown in FIG. 2, in preparation for assembly to the engine block  11 B, the conventional roller follower  21 , which has been erroneously placed in a deactivating location (receptacle  83 ) will simply fall out of the receptacle  83 , thus alerting the assembler of the error. 
     Therefore, as used hereinafter in the appended claims, the term “not being capable of receiving” in regard to the upper portions  87  and  93  being incorrectly inserted into the receptacles  83  and  81 , respectively, will be understood to mean either that the upper portion literally won&#39;t fit into the receptacle, or that the upper portion will fit into the receptacle, but won&#39;t be retained in the receptacle when the guide member is held in the position shown in FIG.  2 . It should also be apparent to those skilled in the art that what is important in the present invention is not the particular configuration of flats, ribs and notches shown herein, but the ability to make each type of roller follower not be capable of being “received” (as defined above) within the wrong receptacle. Therefore, those skilled in the art will understand that shapes other than flats, ribs and notches may, within the scope of the invention, be utilized to accomplish the intended purpose of preventing erroneous assembly, while at the same time correctly orienting at least the deactivating roller follower rotationally. 
     The invention has been described in great detail in the foregoing specification, and it is believed that various alterations and modifications of the invention will become apparent to those skilled in the art from a reading and understanding of the specification. It is intended that all such alterations and modifications are included in the invention, insofar as they come within the scope of the appended claims.