Abstract:
An internal combustion engine is equipped to supply the camshaft bearings with pressurized oil via a first dedicated oil gallery independently of the hydraulic lash adjusters (HLAs) and any valve deactivation devices which are supplied from a second dedicated oil gallery. The galleries may be connected at their downstream ends and a flow restriction is placed in a connecting passage or within each HLA. An improved HLA is similar to a prior art HLA except that the prior art annular oil distribution groove in the outer surface of the HLA body is eliminated to prevent communication of the primary engine oil gallery with the HLA. The secondary gallery is formed remotely from the first oil gallery in the HLA residence bore in the engine, and the HLA is prevented from rotating within the residence bore.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to variable valve activation mechanisms for combustion valves of internal combustion engines; more particularly, to methods and apparatus for controllably supplying activating engine oil to such variable valve activation mechanisms including switchable cam followers; and most particularly, to an improved hydraulic lash adjuster and control scheme for such controllable valve actuation. 
       BACKGROUND OF THE INVENTION 
       [0002]    Mechanisms for varying the valve timing and/or lift of combustion valves in internal combustion engines are well known. A typical prior art selective valve deactivation mechanism includes a switchable cam follower such as an articulated two-step deactivation roller finger follower (DRFF) disposed between an engine camshaft lobe and a valve stem. The DRFF includes a hydraulically-actuated lock pin to engage or disengage the articulated members. In one example of a DRFF, the lock pin is engaged between the articulated members by a return spring, such that the valve train is in high-lift mode by default at shutdown or other times as desired. The lock pins are disengaged by application of high pressure hydraulic fluid, typically engine oil provided by the engine&#39;s oil distribution system to overcome the return spring. The DRFF is pivoted on a hydraulic lash adjuster (HLA) at an end opposite to the valve-engaging end. The HLA is mounted rotatably about its axis in a residence bore in the engine, typically in the engine head. The HLA is supplied with engine oil from a molded or bored engine gallery to feed the lash adjuster mechanism therein, and oil also flows from the HLA to the DRFF through a central opening in the ball head of the HLA and a mating passage in the DRFF. When oil is supplied through the engine gallery at low pressure, the lock pin spring overcomes the oil pressure and the DRFF is in high-lift mode. To overcome the lock pin spring, the oil pressure is increased via a regulating oil control valve (ROCV) to a higher pressure sufficient to cause the lock pin to be retracted, placing the DRFF in low-lift or no-lift mode. The engine oil gallery thus doubles as a switching gallery and an oil supply gallery for top engine functions such as camshaft bearings. 
         [0003]    A problem arises in using a single oil gallery in such a dual mode in that the pressure logic of a deactivation application mandates that oil pressure in the gallery be low (lock pin engaged, valves actuated) at the highest engine speeds and load conditions. Under these conditions, the camshaft bearings, which are oiled from the same gallery, are subjected to highest load and lowest oil flow which can result in premature bearing wear or outright failure. 
         [0004]    One known approach to preventing this problem is to provide a second gallery adjacent the first gallery specifically for supplying the DRFF and to relegate the primary gallery to satisfying the lash adjustment and camshaft bearing lubrication requirements. This approach avoids the necessity for an ROCV, which is both bulky and expensive, but it requires significant changes in the prior art HLA design to provide independent oil feeds for the lash adjustment and switching functions. See, for example, U.S. Pat. No. 7,047,925, depicting a dual feed HLA. Such designs significantly reduce the volume of the HLA low-pressure chamber, raising concerns for potential noise upon cold start of the engine. Further, it can be difficult and expensive to provide two adjacent galleries so close together within the engine block; and further, significant leakage can occur between the two galleries along the wall of the HLA residence bore. 
         [0005]    Instead of using a ROCV, the function may be provided by a combination of a three-way on/off valve in the switching gallery coupled to a pressure relief valve and an in-line flow restrictor to maintain low switching pressure at between about 0.3 bar and about 0.8 bar. However, this approach can be difficult to package on existing engine block or head arrangements because of the common oil gallery shared by the HLAs and the cam bearings. 
         [0006]    What is needed in the art is an HLA arrangement that may be packaged in an existing head wherein the camshaft bearings are lubricated via an existing first oil gallery and the HLA switching and lash adjusting functions are satisfied, at least in part, from a second, independently controlled oil gallery remote from the first oil gallery, and wherein the first and second galleries are readily purged of air. 
         [0007]    It is a principal object of the present invention to separate the camshaft oil supply requirements from the HLA oil supply requirements while using a common engine oil pressurizing pump. 
         [0008]    It is a further object of the present invention to readily and automatically purge all oil galleries of air. 
         [0009]    It is a still further object of the present invention to require the minimum changes in prior art engine casting molds by utilizing the existing HLA oil supply gallery and providing a second oil supply gallery. 
       SUMMARY OF THE INVENTION 
       [0010]    Briefly described, an internal combustion engine is equipped to supply the camshaft bearings with pressurized oil via a first dedicated oil gallery independently of the hydraulic lash adjusters and any valve deactivation devices which are supplied from a second dedicated oil gallery. To improve air purging of both galleries, the galleries are connected and a small-orifice flow restriction is placed either in a connecting passage between the first and second galleries or within the HLAs themselves. In an aspect of the present invention, the primary engine oil gallery is as in the prior art, to minimize required retooling of engine molds. An improved hydraulic lash adjuster, formed in accordance with the invention, is identical with a prior art HLA except that the prior art annular oil distribution groove in the outer surface of the body is eliminated to prevent communication of the primary engine oil gallery with the HLA. The secondary gallery is formed remotely from the first oil gallery in the HLA residence bore in the engine, and the HLA is prevented from rotating within the residence bore. Thus, the HLA can communicate for actuation with only the new, second oil gallery. Forming the improved HLA requires only the omission of the prior art annular oil groove in the HLA body and provision for non-rotation of the improved HLA. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
           [0012]      FIG. 1   a  is a schematic drawing of a first prior art oil supply system, showing a single-feed HLA supplied by a single oil gallery via a regulating oil control valve; 
           [0013]      FIG. 1   b  is an elevational cross-sectional drawing of a prior art single-feed HLA useful in the system shown in  FIG. 1   a;    
           [0014]      FIG. 2   a  is a schematic drawing of a second prior art oil supply system, showing a dual-feed HLA supplied by a conventional oil gallery and a switching oil gallery via a three-way on/off valve; 
           [0015]      FIG. 2   b  is an elevational cross-sectional view of a portion of a prior art valve train as shown schematically in  FIG. 2   a;    
           [0016]      FIG. 3  is a schematic drawing of a third prior art oil supply system, showing a single-feed HLA fed by a switching oil gallery, in low-pressure (high valve lift) mode, and the cam bearings fed by a conventional oil gallery; 
           [0017]      FIG. 4  is a schematic drawing of the third prior art oil supply system shown in  FIG. 3 , in high-pressure (low valve lift) mode; 
           [0018]      FIG. 5  is an elevational cross-sectional view of a first embodiment of an improved HLA in accordance with the invention, which improved HLA is suitable for use in the first improved oil supply system shown in  FIGS. 6 and 7 ; 
           [0019]      FIG. 6  is a schematic drawing of a first improved oil supply system in accordance with the invention, showing an improved single-feed HLA fed by a switching oil gallery, in low-pressure (high valve lift) mode, and the cam bearings fed by a conventional oil gallery, the two galleries being hydraulically connected but functionally isolated via a flow restriction; 
           [0020]      FIG. 7  is a schematic drawing of the first improved oil supply system in accordance with the invention shown in  FIG. 6 , in high-pressure (low valve lift) mode; 
           [0021]      FIG. 8  is an elevational cross-sectional view of a second embodiment of an HLA in accordance with the invention; 
           [0022]      FIG. 9  is a schematic drawing of a second improved oil supply system in accordance with the invention, showing an improved dual-feed HLA fed by a switching oil gallery, in low-pressure (high valve lift) mode, and the cam bearings fed by a conventional oil gallery, the two galleries being hydraulically connected but functionally isolated via a flow restriction in each HLA in the engine; and 
           [0023]      FIG. 10  is a schematic drawing of the second improved oil supply system in accordance with the invention shown in  FIG. 9 , in high-pressure (low valve lift) mode. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0024]    The advantages and benefits of an oil supply system in accordance with the invention may be better appreciated by first considering three prior art systems. 
         [0025]    Referring to  FIGS. 1   a  and  1   b , a first prior art oil supply system  100  includes a pressurizing pump  102  which draws intake hydraulic fluid  104  from a sump  106 . Fluid  104  is typically engine oil and sump  106  is typically an engine crankcase. Pressurized output oil  108  from pump  102  is directed through a regulating oil control valve (ROCV)  110  which regulates pressure in a conventional oil gallery  112  to about 0.5 bar. Pressurized oil is supplied from gallery  112  to cam bearings  114  and to a conventional hydraulic lash adjuster  116  disposed rotatably about its axis in a residence bore  115  in an engine head  117 . Oil enters HLA  116  through a first port  118  in HLA body  120 , thence into an inner annular groove  122  formed in plunger  124 , thence through a second port  126  in plunger  124  which opens into a low-pressure reservoir  128 . From reservoir  128 , oil flows both into lash adjusting mechanism  130  and also out of HLA  116  through a third port  132  which mates with a rocker arm or finger follower mechanism (not shown, but see  FIG. 2   b ). An outer annular groove  119  in HLA body  120  coincides with first port  118 , and HLA  116  thus is free to rotate about its longitudinal axis while oil is supplied to port  118  from groove  119  at any angular orientation of the HLA. ROCV  110  is controlled by an engine control module (not shown). The “normal” (“low”) operating pressure  134  as noted above is about 0.5 bar. When deactivation of an associated switchable cam follower such a DRFF is desired, ROCV  110  opens to permit higher oil pressure  136  (which may be the same as pressure  108  or not) to flow to HLA  116  and thence into the DRFF. Of course, the higher oil pressure is also felt by cam bearings  114 . As noted above, at high engine speed or high engine load a low oil pressure  134  required for full valve activation can rob the cam bearings  114  of adequate oil flow. 
         [0026]    Referring now to  FIGS. 2   a  and  2   b , a second prior art oil supply system  200  includes pressurizing oil pump  102  which draws intake oil  104  from sump  106 , as in prior art system  100  ( FIG. 1   a ). Pressurized output oil  108  from pump  102  is fed through a first flow restriction  240  into a conventional oil gallery  112  at an unregulated intermediate pressure  242  sufficient to lubricate cam bearings  114  and fill the low-pressure reservoir  228  and lash adjusting mechanism  230  of a second prior art HLA  216  disposed in a residence bore  215  in an engine head  217 . A second (switching) gallery  244  is provided in engine head  217  in parallel with conventional gallery  112  and communicates with a switchable cam follower such as DRFF  246  via a passage  248  independent of low-pressure reservoir  228 . In some engine systems, first flow restriction  240  is simply a small-diameter port where the oil feed passes through the engine head gasket. 
         [0027]    There is no ROCV in this second prior art system. Rather, a three-way on/off valve  250  controlled by an engine control module (not shown) governs flow of oil into switching gallery  244 . Oil flow into switching gallery  244  is either at high pressure  108  or a very low pressure  254 . Although the three-way valve  250  is only either open or closed, a bypass “bleed”  252  preferably is provided to maintain a slight charge pressure  254  in switching gallery  244 , as is desirable for some valve deactivation systems. 
         [0028]    Prior art system  200  desirably divorces the lash adjusting and cam bearing lubrication functions from the valve deactivation functions. However, the presence of conventional oil gallery  112  where formed in existing engine heads leaves little room for the addition of a switching gallery  244  adjacent thereto. Further, a longer HLA is required, having in some designs a two-piece plunger, and the volume of the low-pressure reservoir is quite small, making an engine equipped with this system vulnerable to cold-starting clatter. 
         [0029]    Referring to  FIGS. 3 and 4 , a third prior art oil supply system  300  includes pressurizing oil pump  102  which draws intake oil  104  from sump  106 , as in prior art systems  100  and  200  ( FIGS. 1   a  and  2   a ). As in system  200 , pressurized output oil  108  from pump  102  is fed through a first flow restriction  240  into a conventional oil gallery  112  at an unregulated intermediate pressure  242  sufficient to lubricate cam bearings  114 . However, the HLA is entirely divorced from gallery  112 . A second gallery  244  is provided in engine head  217  adjacent conventional gallery  112  and supplies an HLA  316  similar to HLA  116 , filling the low-pressure reservoir and lash adjusting mechanism via a single feed. 
         [0030]    Again, there is no ROCV in this third prior art system. Rather, a three-way on/off valve  350  governs flow of oil into switching gallery  244 . Oil flow into switching gallery  244  is either at low pressure  334  ( FIG. 3 , DRFF engaged for high valve lift)) or high pressure  108  ( FIG. 4 , DRFF disengaged for no or low valve lift). Although three-way valve  350  is only either open or closed, a second flow restriction  352  around valve  350  and a pressure relief valve  356  maintains low pressure  334  in switching gallery  244 , preferably about 0.5 bar similar to pressure  134  as in first system  100  for lash adjusting functions of HLA  316 . When high pressure to HLA  316  is desired, valve  350  opens to oil pressure  108  and closes to relief valve  356 . 
         [0031]    Third prior art system  300  achieves the objective of divorcing cam bearing lubrication from HLA activities while utilizing a substantially unmodified production HLA such as HLA  116  ( FIGS. 1   a  and  1   b ). However, the presence of the conventional oil gallery  112  where formed in existing engine heads leaves little room for the addition of a switching gallery  244  adjacent thereto. Further, the first and second galleries and the HLA are not readily purged of air and may have dead legs at various points therein. 
         [0032]    Referring now to  FIGS. 5 ,  6 , and  7 , a first improved oil supply system  400  in accordance with the invention is similar to but improves upon prior art system  300 . Improved system  400  includes pressurizing oil pump  102  which draws intake oil  104  from sump  106  as in prior art system  300  ( FIGS. 3 and 4 ). As in system  300 , pressurized output oil  108  from pump  102  is fed through a first flow restriction  240  into a conventional oil gallery  112  at an unregulated intermediate pressure  242  sufficient to lubricate cam bearings  114 . HLA  416  is entirely divorced from gallery  112 . A second gallery  244  is provided in engine head  217  in addition to the conventional gallery  112  and supplies an improved HLA  416  similar to conventional HLA  116 , filling the low-pressure reservoir and lash adjusting mechanism via a single feed. As shown in  FIG. 5 , however, HLA  416  differs from HLA  116  in having no annular oil supply groove  119  formed in the unfeatured cylindrical exterior of HLA body  420 ; and further, HLA  416  is prevented from free rotation in the HLA residence bore  215  ( FIG. 2   b ) in engine head  217  by inclusion of an anti-rotation flat or other obvious mechanical preventer as known in the art. Thus, the HLA fill port  418  in body  420  is inaccessible to the conventional oil gallery  112  disposed in an existing head in which HLA  416  might be retrofitted and is positioned to communicate with only second gallery  244  for all HLA oil supply functions. 
         [0033]    As in prior art embodiment  300 , there is no ROCV in first improved oil supply system  400 . Rather, a three-way on/off valve  350  governs flow of oil into switching gallery  244 . Oil flow into switching gallery  244  is either at low pressure  434  ( FIG. 6 , DRFF engaged for high valve lift)) or high pressure  108  ( FIG. 7 , DRFF disengaged for no or low valve lift). Although the three-way valve  350  is only either open or closed, a second flow restriction  452  in a connecting passage  453  between the distal ends  455 , 457  respectively of conventional oil gallery  112  and switching oil gallery  244 , which distal ends are not connected in the prior art embodiments, combined with a pressure relief valve  356  in gallery  244  maintains low pressure  434  in switching gallery  244 , preferably about 0.5 bar similar to pressure  134  as in first system  100  for lash adjusting functions of HLA  316 , when three-way valve  350  is closed to high pressure oil flow  108  in a first position. Switching gallery  244  is open to pressure relief valve  356 . Referring to  FIG. 7 , when high pressure oil to HLA  416  is desired, valve  350  opens switching gallery  244  to a second position to oil pressure  108  and closes switching gallery  244  to relief valve  356 . 
         [0034]    First improved oil supply system  400  achieves the objective of divorcing cam bearing lubrication from HLA activities while utilizing a minimally modified production HLA such as HLA  116  ( FIGS. 1   a  and  1   b ), and while accommodating a conventional oil gallery passage in a current head. 
         [0035]    System  400  also provides several other important advantages not available in the prior art. First, any air bubbles in either of the oil galleries are automatically purged through pressure relief valve  356  when the system is in low pressure mode as shown in  FIG. 6 . Second, because galleries  112  and  244  are connected at their distal ends by connector  453 , there are no dead legs in the flow path and thus all air is purged, unlike the prior art systems wherein each of the oil galleries has a dead terminal leg. Third, the conventional oil gallery  112  and the switching oil gallery  244  are formed in engine head  217  on opposite sides of HLA  416 . This arrangement makes it relatively easy to form the two galleries in an existing engine head mold with minimal required retooling of the mold. The arrangement also provides maximal flow separation of the two galleries within the residence bore of the HLA and thus minimizes hydraulic cross-talk between the two galleries, whereas in the prior art ( FIG. 2   b ) the two galleries, being adjacent and on the same side of the residence bore, are separated by only a few millimeters of bore wall. 
         [0036]    Referring now to  FIGS. 8 ,  9 , and  10 , a second improved oil supply system  500  in accordance with the invention is similar to first improved system  400 , differing only in the implementation of a pressure reducing flow restriction between the two galleries. 
         [0037]    As just described, in system  400  the ends of the conventional and switching galleries  112 , 244  are joined via a connector  453  containing flow restrictor  452 . In the low pressure mode ( FIG. 6 ), oil flows from the conventional gallery through restrictor  452  and into the switching gallery. Pressure relief valve  356  and flow restrictor  452  are sized to regulate the pressure in the switching gallery to the desired 0.5 bar pressure. In addition, air from gallery  112  is swept by pressurized oil through connector  453  where it joins with air in gallery  244  and both are purged through relief valve  356 . 
         [0038]    In system  500 , the ends of galleries  112 , 244  are not joined except through the final HLA in an engine bank; thus there are still no dead flow legs. However, in this embodiment, the pressure reducing flow restrictions are located in the body of the HLA rather than in connector  453  as in system  400 . 
         [0039]    Each HLA  516  ( FIG. 8 ) is identical to HLA  416  except that an orifice or flow restriction  552  is provided through HLA body  520  in communication with conventional oil gallery  112 . Thus, referring to  FIG. 9 , oil flows from the conventional gallery through the flow restriction into the HLA low pressure chamber and switching gallery and eventually out the pressure relief valve. The pressure relief valve and flow restrictors are sized to regulate the pressure in the switching gallery to the desired 0.5 bar pressure. This eliminates having to manufacture connector  453  containing restriction  452  of system  400 . Air in gallery  112  is purged into low-pressure reservoir  528  and thence out of the HLA via tip opening  532 . Continued purging from gallery  112  through HLA  516  drives air in port  518  and switching gallery  244  out through three-way valve  350  and relief valve  356  ( FIGS. 8 and 9 ). 
         [0040]    An added advantage of systems  400  and  500  is that in high-pressure mode ( FIGS. 7 and 10 ) the flow restrictions ( 452 ,  552 ) are slightly back flushed, which can help to keep the orifice from becoming plugged with engine debris in long-term use. As in system  400 , HLA  516  must be prevented from rotation to keep the supply ports in the HLA registered with the proper oil gallery. 
         [0041]    The benefits of improved oil distribution systems in accordance with the invention may be summarized as follows: 
         [0042]    a) they utilize a smaller, faster, and less expensive on/off OCV than the ROCV of the prior art; 
         [0043]    b) they utilize two separate oil galleries to avoid cam bearing lubrication concerns, especially in valve-deactivation applications; 
         [0044]    c) the conventional and switching oil galleries are in communication for excellent purging of air and have no dead legs; 
         [0045]    d)) the conventional and switching oil galleries are on opposite sides of the residence bore for the HLA; 
         [0046]    e) the low pressure limit for default operation of an associated DRFF can be set lower than for a prior art ROCV system, which aids switching performance; 
         [0047]    f) The conventional oil gallery remains positioned as in prior art engines, requiring minimal retooling of engine molds; and 
         [0048]    g) although a modified HLA is required, the necessary changes involve less risk than for the prior art dual feed system  200 ; further, only the HLA body requires modification, so the advantages of the prior art single-piece plunger can be retained. 
         [0049]    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.