Abstract:
A deactivating hydraulic valve mechanism includes a hydraulic element assembly disposed within cup within a pin housing slidably disposed within a bore in a body. A transverse bore in the pin housing contains selectively-retractable locking pins that engage a locking feature in the body to selectively lock together the body and the pin housing. A lost motion spring is disposed in a vented annular chamber between the body and the pin housing. An oil passage from an engine gallery to the hydraulic element assembly includes an axial component formed in the cup and bypasses the lost motion chamber. A ring holds the lifter assembly together and also sets mechanical lash. The ring may combine a standard-thickness ring and a shim selected to provided a predetermined amount of mechanical lash in the assembled mechanism to ensure facile engagement and disengagement of the locking pins in the body.

Description:
[0001]     This application claims priority from Provisional U.S. Patent Application Ser. No. 60/670,360, filed Apr. 12, 2005 and from Provisional U.S. Patent Application Ser. No. 60/681,623, filed May 17, 2005. 
     
    
     TECHNICAL FIELD  
       [0002]     The present invention relates to hydraulic valve mechanisms for activating valves in response to rotation of a camshaft in an internal combustion engine; more particularly, to such mechanisms having a locking mechanism for selectively engaging and disengaging such activation; and most particularly, to such a deactivating hydraulic valve mechanism having a vented internal lost motion spring and oil supply to the hydraulic element assembly that bypasses the lost motion spring chamber to minimize oil pumping by the mechanism while in deactivation mode.  
       BACKGROUND OF THE INVENTION  
       [0003]     It is well known that overall fuel efficiency in a multiple-cylinder internal combustion engine can be increased by selective deactivation of one or more of the engine valves, especially the intake valves, under certain engine load conditions. For a cam-in-block pushrod engine, a known approach to providing selective deactivation is to equip the hydraulic lifters for those valves with a locking mechanism whereby the lifters may be rendered incapable of transferring the cyclic motion of engine cams into reciprocal motion of the associated pushrods. Typically, a deactivating hydraulic valve lifter (DHVL) includes, in addition to the conventional hydraulic lash compensation element, an outer body and a concentric locking pin housing disposed inside the outer body. The inner locking pin housing and outer body are mechanically connected to the pushrod and to the cam lobe, respectively, and may be selectively latched and unlatched hydromechanically to each other, typically by the selective engagement of one or more locking pins by pressurized engine oil.  
         [0004]     U.S. Pat. No. 6,497,207 discloses such a DHVL wherein a lost motion coil spring is disposed between the lifter body and a tower extension of the inner pin housing. The tower extension is hollow and open at the outer end to admit an engine pushrod. This arrangement is functionally satisfactory for many but not all engine designs. In particular, the tower results in a relatively long overall length of the DHVL and, in order for the pushrod to clear the outer edge of the tower extension, the pushrod must be aligned nearly coaxial with the DHVL. Thus, this arrangement may be incompatible with engines having limited axial space for the added length DHVL, or for engines having relatively large pushrod engagement angles.  
         [0005]     It is known in the art to shorten the operative length of a body and locking pin housing assembly by packaging the lost motion (LM) spring between the adjacent walls of the outer lifter body and the inner pin housing, thereby obviating the need for a tower and its concomitant length. U.S. Pat. No. 6,321,704 B1 (“the &#39;704 patent”) discloses a hydraulic lash adjuster for valve deactivation in a cam-in-head roller finger follower engine having an outer body and an inner locking pin housing wherein the LM spring is disposed in an annular spring chamber between the walls of the body and locking pin housing.  
         [0006]     A significant shortcoming of disposing the LM spring between the outer body and inner locking pin housing, as shown in the &#39;704 patent, is that oil being supplied to the hydraulic element assembly (HEA) must pass through the LM spring chamber. Thus the chamber is always filled with oil, which must be pumped out of the chamber with every stroke of the lifter body in deactivation mode. Pumping oil reduces engine efficiency, as during at least part of the pumping stroke the oil pressure generated in the LM chamber opposes the engine&#39;s own oil pressure, and may cause valve train stability issues, wear, and noise due to induced air bubbles or cavitations. Still further, juxtaposition of the oil passages in the outer body and inner locking pin housing under certain lash conditions can allow for a low oil drawdown (drainage) level in the lash adjuster reservoir during engine shutdown, resulting in significant engine noise at restart.  
         [0007]     In addition, the disclosure fails to account for mechanical lash in the deactivation mechanism resulting from inherent manufacturing variability in the deactivation components. The entire assembly is held together by a standard stop clip which is full-fitting in a groove in the outer body member. Thus, the amount of lash between the latching member and the latching surface after assembly, resulting from manufacturing variability in the components, cannot be compensated or adjusted in individual lifter or lash adjuster assemblies.  
         [0008]     What is needed in the art is a deactivation lifter or lash adjuster assembly wherein the LM spring chamber is not in communication with the engine oil being supplied to the HEA.  
         [0009]     What is further needed in the art is a deactivation lifter or deactivation lash adjuster assembly wherein mechanical lash within the lifter or lash adjuster may be readily set by appropriate shimming during assembly.  
         [0010]     It is a principal object of the present invention to provide improved valve deactivation without pumping of deactivation oil in an LM spring chamber in engines requiring short overall length and large pushrod angle capability in a deactivation lifter or deactivation lash adjuster.  
       SUMMARY OF THE INVENTION  
       [0011]     Briefly described, a deactivating hydraulic valve lifter or deactivating hydraulic lash adjuster, hereinafter referred to as a deactivation mechanism or DHVL, in accordance with the invention includes a conventional hydraulic lash adjustment element, also referred to herein as a hydraulic element assembly (HEA), disposed between a plunger and a cup member. The plunger and cup member are, in turn, disposed in a pin housing that is slidably disposed within an axial bore in a body. A transverse bore in the pin housing contains at least one locking pin that engages a locking feature such as a circumferential groove including a locking surface in the body whereby the body and the pin housing are locked together for mutual actuation by rotary motion of the cam lobe to produce reciprocal motion of an engine pushrod disposed against the hydraulic lash adjustment element.  
         [0012]     A lost motion coil spring is disposed in an annular chamber formed within the envelope of the deactivation mechanism between the body and the pin housing. A vent of the annular chamber permits ready discharge of any accumulated oil from the chamber on the first lost-motion stroke of the body and thereafter.  
         [0013]     An oil passage is provided from an engine gallery to the hydraulic element assembly, at the interface between the cup member and pin housing thereby bypassing the lost motion annular chamber.  
         [0014]     An expansion ring holds the assembly together and also functions to set the mechanical lash in the deactivation mechanism. The ring may be provided as a two-part ring, the first part being a standard-thickness ring and the second part being a shim having a thickness selected to provided a predetermined amount of mechanical lash in the assembled mechanism to ensure facile engagement and disengagement of the locking pins in the body. The ring may also be provided as a one piece ring, its thickness being selected to set mechanical lash. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     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:  
         [0016]      FIG. 1  is an elevational cross-sectional view of a deactivating hydraulic lash adjuster for use as a roller finger follower pivot in an overhead cam engine, substantially as disclosed in U.S. Pat. No. 6,321,704 B1;  
         [0017]      FIG. 2  is an elevational view of a first embodiment of a deactivating hydraulic valve lifter in accordance with the invention for use in a pushrod internal combustion engine;  
         [0018]      FIG. 3  is a plan view of the lifter shown in  FIG. 2 , shown rotated 90° counterclockwise;  
         [0019]      FIG. 4  is a first elevational cross-sectional view taken along line  4 - 4  in  FIG. 2 ;  
         [0020]      FIG. 5  is a second elevational cross-sectional view taken along line  5 - 5  in  FIG. 3 , this view being orthogonal to the view shown in  FIG. 4 ;  
         [0021]      FIG. 6  is a cross-sectional elevational view showing the lifter shown in  FIG. 4  disposed in an engine block adjacent a cam, the lifter being on the base circle portion of the cam lobe; and  
         [0022]      FIG. 7  is a view like that shown in  FIG. 6 , but with the lifter in deactivation (lost motion) mode and the lifter being on the eccentric portion of the cam lobe, showing that the lifter body stays outside of the desired cone of activity for an associated pushrod. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]     Referring to  FIG. 1 , a deactivating hydraulic lash adjuster  10  is substantially as disclosed in U.S. Pat. No. 6,321,704 B1. Lash adjuster  10  has a generally cylindrical adjuster body  12 . A pin housing  14  is slidably disposed within a first axial bore  16  in adjuster body  12 . Pin housing  14  itself has a second axial bore  18  for slidably receiving a plunger  20  having a domed end  22  for receiving a socket end (not shown) of a roller finger follower in an overhead-cam engine valve train.  
         [0024]     Pin housing  14  has a transverse bore  24  slidably receivable of two opposed locking pins  26  separated by a pin-locking spring  28  disposed in compression therebetween. First axial bore  16  in adjuster body  12  is provided with a circumferential groove  30  for receiving the outer ends of locking pins  26 , thrust outwards by spring  28  when pins  26  are axially aligned with groove  30 . In such configuration, lash adjuster  10  is in valve-activation mode. (As shown in  FIG. 1 , lash adjuster  10  is in valve-deactivation mode.)  
         [0025]     Upper end  32  of pin housing  14  defines a first seat for a loss-of-motion (LM) return spring  34  disposed within an annular spring chamber  35  formed between bore  16  and pin housing  14 . LM spring  34  finds a second seat at an annular stop  37  in bore  16 .  
         [0026]     Groove  30  further defines a reservoir for providing high pressure oil against the outer ends  36  of locking pins  26  to overcome spring  28  and retract the locking pins into bore  24 , thereby unlocking the pin housing from the adjuster body to deactivate the adjuster. Groove  30  is in communication via at least one port  38  with an oil gallery (not shown) in an engine  40 , which in turn is supplied with high pressure oil by an engine control module (not shown) under predetermined engine parameters in which deactivation of valves is desired.  
         [0027]     Plunger  20  includes check valve components  42  lodged at an inner end thereof. The arrangement of the components and operation of feature  42  has been well known in the prior art for many years. Check valve components  42  include a spring loaded check ball  44  lodged against a seat  46  formed in plunger  20  separating a low-pressure oil reservoir  48  from a high-pressure chamber  50 . Oil is supplied to annular chamber  35  from an engine oil gallery (not shown) via port  54  in adjuster body  12 . Chamber  35  is also in communication with reservoir  48  via port  56  and annular groove  58  in pin housing  14  and annular groove  60  and port  62  in plunger  20 . Oil may be supplied from reservoir  48  to an associated roller finger follower (not shown) via port  52  in the outer end  22  of plunger  20 .  
         [0028]     In operation, lash adjuster  10  is disposed in a bore in engine  40  such that housing  12  remains stationary. When the associated cam and rocker arm (not shown) exert force on plunger end  22 , in lost motion (valve-deactivation) mode, plunger  20  and pin housing  14  are forced into adjuster body  12  in a lost-motion stroke, compressing LM spring  34 . A serious operational problem exists with the arrangement shown for lash adjuster  10 . As spring  34  is compressed and the volume of chamber  35  is diminished, oil within chamber  35  must be pumped out, to the detriment of the mechanism and engine performance as described hereinabove.  
         [0029]     A DHVL (not shown) having an internal LM spring arrangement similar to lash adjuster  10  is known in the art. Such a lifter performs for a pushrod engine the same LM function as does lash adjuster  10  for an overhead-cam engine. In operation during valve-deactivation mode, of course, it is the plunger and pin housing that remain stationary against a valve pushrod while the lifter body reciprocates past the pin housing, compressing the LM spring and diminishing the volume of the annular spring chamber. Such a prior art DHVL suffers from the same shortcomings as lash adjuster  10 , the pumping of oil in the LM chamber during operation in deactivation mode.  
         [0030]     What is needed in the art, for deactivating hydraulic lash adjusters as well as for DHVLs, is a mechanism whereby oil is supplied to a central reservoir in the lifter or adjuster from an engine oil gallery without passing through an internal lost-motion chamber.  
         [0031]     Referring now to  FIGS. 2 through 5 , a first embodiment  110  of an improved DHVL in accordance with the invention comprises many components identical or analogous to those described hereinabove for lash adjuster  10 , which components bear the same identification numbers plus 100. Components which are different or significantly modified bear new numbers in the 100 and 200 series.  
         [0032]     DHVL  110  has a generally cylindrical body  112 . A pin housing  114  is slidably disposed within a stepped first axial bore  116  in body  112 . Pin housing  114  itself has a second axial bore  118  for receiving a cup member  119  which in turn slidably receives a plunger  120  supporting a pushrod seat  122  for receiving a ball end  123  of a pushrod in an engine valve train.  
         [0033]     Pin housing  114  has a transverse bore  124  slidably receivable of two opposed locking pins  126  separated by a pin-locking spring  128  disposed in compression therebetween. First axial bore  116  in body  112  is provided with a locking feature such as, for example, circumferential groove  130  for receiving the outer ends of locking pins  126 , thrust outwards by spring  128  when pins  126  are axially aligned with groove  130 . In such configuration, DHVL  110  is in valve-activation mode. (As shown in  FIGS. 4 and 5 , DHVL  110  is in valve-activation mode.)  
         [0034]     Upper end  132  of pin housing  114  defines a first seat for a loss-of-motion (LM) return spring  134  disposed within an annular spring chamber  135  formed between stepped bore  116  and pin housing  114 . LM spring  134  finds a second seat at annular step  137  in bore  116 .  
         [0035]     Groove  130  further defines a reservoir for providing high pressure oil against the outer ends  136  of locking pins  126  to overcome spring  128  and retract the locking pins into bore  124 , thereby unlocking the pin housing from the lifter body to deactivate the lifter. Groove  130  is in communication via at least one port  138  with a first oil gallery  131  ( FIGS. 6 and 7 ) in an engine  140 , which in turn is supplied with high pressure oil by an engine control module (not shown) under predetermined engine parameters in which deactivation of valves is desired.  
         [0036]     Plunger  120  includes check valve components  142  lodged at an inner end thereof which, like check valve components  42  of lash adjuster  10 , has been well known in the prior art for many years. Components  142  comprises a spring loaded check ball  144  lodged against a seat  146  formed in plunger  120  separating a low-pressure oil reservoir  148  from a high-pressure chamber  150 .  
         [0037]     DHVL  110  includes a conventional cam follower roller assembly  111  that is well known in the prior art and need not be further elaborated here. Roller assembly  111  is recited solely for completion of disclosure and forms no part of the novelty of the present invention.  
         [0038]     The oil passage  147  by which oil is supplied to reservoir  148  is an improved and distinguishing feature of DHVL  110  over lash adjuster  10 . Oil is supplied to reservoir  148  from a non-switched second engine oil gallery  170  ( FIGS. 6 and 7 ) via port  154  in lifter body  12  circumventing LM spring chamber  135 , as follows:  
         [0039]     Oil from second gallery  170  is fed through body port  154 , thence through an annular oil distribution groove  172  formed in bore  116 , thence through port  157  in pin housing  114 , thence through an axially-extending passage  174 , such as a groove, formed in the outer surface of cup member  119  and leading around LM spring chamber  135 , thence through an adjacent headspace  178  beyond the end of cup member  119 , and thence through a transverse groove  180  formed in the underside of pushrod seat  122  and into reservoir  148 . Note that this oil path provides a high drainback residual oil level in reservoir  148  compared to the level in prior art plunger  20  which is fixed by the level of port  62 . Note also that any oil from oil passage  147  that may undesirably be trapped in an area beneath the cup member  119  is vented away through pin housing  114  to the outside of the DHVL via vent passages  149  a and b formed in the bottom of pin housing  114 .  
         [0040]     Cup member  119  is a novel element over a prior art valve-deactivation lifter or lash adjuster, and is necessitated as follows. Note that reservoir  148  is contained fully within the axial extent of LM chamber  135  and is therefore not directly accessible in a radial direction for an oil supply passage except undesirably through chamber  135  as disclosed in the prior art shown in  FIG. 1 . Ergo, supply port  154  must be located beyond the axial limit of chamber  135 ; however, inspection shows that a port at that axial location, absent intervening cup member  119 , intersects high pressure chamber  150 , which is clearly infeasible. Thus, intervening cup member  119  is necessitated. An additional benefit of cup member  119  is that it provides a ready bed for axial passage  174  and thereby provides means for conveying oil desirably to the upper end of plunger  120  for entry into reservoir  148 , resulting in a maximally high drainback level in reservoir  148 .  
         [0041]     Passage  174  is shown in  FIG. 4  as being an axial groove formed in the outer surface of cup member  119 . Of course, passage  174  may be formed alternately as an axial groove on the inside surface of pin housing  114 .  
         [0042]     Further, transverse groove  180  is shown as being formed in pushrod seat  122 . Of course, alternatively oil may be supplied from headspace  178  to reservoir  148  via other means which will occur to those of ordinary skill in the art, for example, a notch in the end of plunger  120  mating with seat  122  or a bore through plunger  120  near seat  122 . All such alternative passage means are fully contemplated by the invention.  
         [0043]     Referring now to  FIGS. 6 and 7 , in operation, DHVL  110  is disposed in a bore  182  in engine  140  such that body  112  is slidably disposed therein. When the associated cam  184  exerts valve-opening force on roller follower assembly  111  in lost motion (valve-deactivation) mode ( FIG. 7 ), body  112  is forced past plunger  120 , cup member  119 , and pin housing  114  (which are prevented from moving by a pushrod and associated valve spring, not shown) in a lost-motion stroke, compressing LM spring  134 . As spring  134  is compressed and the volume of chamber  135  is diminished, there is no oil systematically provided within chamber  135  to be pumped out, as in the prior art. Further, a vent port  186  is provided in lifter body  112  which overlaps an axial passage  188  formed in engine  140  to permit venting and refilling of chamber  135  with air as the lifter body reciprocates past the stationary pin housing and engine, thereby minimizing the non-productive work required by HDVL  110 .  
         [0044]     An important feature of an DHVL in accordance with the invention is that a wide range of pushrod angles may be accommodated in a relatively short assembly. Cone  190  represents the cone of operation available for pushrods, which in the example shown is a full cone angle of 22°, accommodating pushrod angles from the lifter axis  192  of up to 11°. At the extreme of the lost motion stroke ( FIG. 7 ), the outer end  196  of body  112  does not extend into cone  190 . Another noteworthy feature is that the outer diameter of pushrod seat  122  is larger than the sealing diameter of plunger  120 , that is, to some extent, the pushrod seat overhangs the plunger. This feature is important because the pushrod seat is a sealing type relying on the close fit between its outer diameter and the inside diameter of the pin housing to direct oil from passage  147  into reservoir  148 . Thus, any wear or deformation of the bottom face of the pushrod seat caused by contacting the plunger will be contained on the bottom face and not be translated to the sealing diameter (outer diameter) of the pushrod seat.  
         [0045]     Referring again to  FIGS. 4 and 5 , it is yet another important feature of a DHVL in accordance with the invention that each DHVL unit as manufactured may be adjusted to provide a desired amount of internal mechanical axial lash to ensure ready locking and unlocking of the latching pins. Such lash is defined as the clearance between locking surface  197  and pin face  198  when the DHVL is assembled and the pins are therefore in locking position. Sufficient clearance is needed to permit the pins to lock and unlock easily and reliably, but additional clearance creates clatter and accelerated wear in operation of the DHVL. Because of inherent variability in components of a DHVL as manufactured, variations in lash must occur in the mechanism shown in  FIG. 1  wherein a single retaining ring is employed. See, for example, axial stop  37  in lash adjuster  10  which governs the stroke of pin housing  14  by engaging flange  15  when lock pin housing  14  is in its up-most position and thus positioning pins  26  for engagement into bores  30 . As can be seen in lash adjuster  10 , a change in the thickness of stop  37  has no affect on lash. In contrast, in an assembly in accordance with the invention, groove  130  is formed having a length in the axial direction greater than the axial length of locking pins  126 . After assembly of any one DHVL using a standard ring  202  having a thickness intended to yield excessive mechanical lash between the locking surface and locking pin, the resulting lash can be measured directly, and a shim ring  204  of a thickness selected to provide optimum lash may be subsequently installed adjacent to ring  202 . Alternately, the resulting accumulated lash of a particular DHVL may be measured and a one piece ring of a desired thickness may be installed to achieve the desired mechanical lash.  
         [0046]     Referring again to  FIG. 3 , body  112  preferably is provided with a single off-center flat  113  for antirotation and error-proofing of DHVL installation into engine  140  to ensure that the oil ports are correctly aligned with their respective feed galleries. Preferably, a guide plate (not shown) is employed during installation of a DHVL into an engine block. The guide plate includes asymmetric features such as bolt holes or a mating recess in the engine block such that the guide plate cannot be installed over the DHVL, or mated to the engine, unless the DHVL is properly oriented to the engine. In a V-6 application, typically all lifters in one engine bank are DHVLs.  
         [0047]     While the text of the specification relates this invention to a deactivating hydraulic valve lifter (DHVL), it is understood that the invention is equally applicable to other valve deactivating devices such as deactivating roller hydraulic valve lifters (DRHVL) as shown in  FIGS. 2-7  and to deactivating hydraulic lash adjusters (DHLA) as shown in  FIG. 1 .  
         [0048]     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.