Abstract:
A switchable valve train member, such as a deactivating valve lash adjuster or a deactivating hydraulic valve lifter, including a pin housing slidably disposed within an axial bore in a body. A transverse bore in the pin housing contains a retractable locking pin that engages a feature in the body including a locking surface whereby the body and the pin housing are locked together for mutual actuation by rotation of a cam lobe. A lash ring at the outer end of the body includes a portion extending into the axial bore that limits the travel of the pin housing within the body and thereby sets the internal mechanical lash in the switchable member. The axial thickness of the lash ring may be varied between assemblies to compensate for manufacturing variation in the components and is secured to the body in any of various configurations.

Description:
TECHNICAL FIELD 
   The present invention relates to switchable valve train members such as deactivating hydraulic lash adjusters (DHLAs) and deactivating hydraulic valve lifters (DHVLs) in internal combustion engines; and more particularly, to an apparatus for setting internal mechanical lash in switchable valve train members. 
   BACKGROUND OF THE INVENTION 
   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 cam-in-block engines, a known approach to providing selective deactivation is to equip the hydraulic valve lifters for those valve trains with means whereby the lifters may be rendered incapable of transferring the cyclic motion of the engine cam into reciprocal motion of the associated valves. For an overhead-cam engine, a known approach is to equip the hydraulic lash adjusters for those valve trains with means whereby the rocker arm may be rendered incapable of transferring the motion of engine the cams into reciprocal motion of the associated valves. 
   Typically, a DHLA includes, in addition to the conventional hydraulic lash elimination means, a concentric inner pin housing and outer HLA body which are mechanically responsive to the force of the rocker arm as exerted by the cam lobe, and which may be selectively latched and unlatched hydromechanically to each other, typically by the selective engagement of pressurized engine oil on locking pins. 
   An important consideration in a DHLA is the amount of internal mechanical lash deliberately incorporated into the DHLA. In prior art DHLAs, a transverse bore in the pin housing contains the two opposed locking pins which are urged outwards of the pin housing by a pin-locking spring disposed in compression therebetween to engage a circumferential groove including a locking surface in the inner wall of the HLA body whereby the HLA body and the pin housing are locked together to produce reciprocal motion of a rocker arm disposed on the DHLA. When valve deactivation is desired, the pins are withdrawn from the DHLA body by application of hydraulic fluid such as engine oil to the outer ends of the pins at pressure sufficient to overcome the force of the pin-locking spring. 
   Prior art DHVLs, such as shown in U.S. Pat. No. 6,578,535, typically are assembled from a top end of the DHVL body (which is closed at its bottom end) by insertion of components through the open top end and securing the components with one or more retaining rings and the like, fitting into an annular groove formed in the inner wall of the DHVL body below the open end thereof. The rings also serve to set internal mechanical lash in the DHVL by the selection of rings of appropriate thickness during assembly of the DHVL. The rings act as a mechanical stop to limit the outward motion of the pin housing prior to engagement and disengagement of the locking pins. Preferably, the lash rings permit the pin housing to travel to a position wherein the locking pins can clear the bottom surface, or ledge, of the locking feature in the DHVL body by a small amount, typically about 0.005 inches or less. Excess internal mechanical lash results in clatter and wear of the DHVL during engine operation, and can have an adverse effect on the lift characteristics of the associated valve. Thus, controlling the axial position of the underside of the retaining rings with respect to the ledge of the locking feature is of critical importance. 
   Typically, because of variation in manufacturing tolerances of the body, pin housing, and pins, the correct lash is obtained only by iterative trial and measurement using rings of differing thickness. However, setting the lash in this fashion is difficult, requiring repeated assembly and disassembly of the pin housing from the DHVL body because accessing the lash-setting retaining snap rings to remove the pin housing once installed is difficult and complicated. 
   Further, in cases where the wall of the DHVL body is thin because of packaging constraints, the presence of an inner-wall annular groove for the retaining rings near the open end of the DHVL body structurally weakens the wall of the body. 
   Referring to U.S. Pat. No. 6,513,470, a spring seat is shown for an external lost motion (LM) spring in a DHVL, wherein the spring seat also functions as a variable-thickness shim for setting the internal mechanical lash in each valve deactivation assembly. The spring seat is held in place by the LM spring that is captured by a spring tower. The spring seat rests on the outer end of the lifter body and also includes a cylindrical portion that extends into the lifter bore to engage the pin housing therein, the cylindrical portion being selectively varied to control mechanical lash. Thus, the seat serves to control mechanical lash without a requirement for a retaining groove in the inner wall of the lifter bore. 
   This latter approach for setting lash is not adaptable to current DHLAs since, in prior art DHLAs, the LM spring is internal to the assembly, and thus there is no spring seat requirement at the outer end of the body. 
   What is needed in the art is an improved DHLA wherein components are easily assembled, wherein mechanical lash is easily set, and wherein an annular groove for locking a retaining ring is obviated. 
   It is a principal object of the present invention to reduce the cost and complexity of an improved DHLA, to improve the ease and reliability of assembly thereof, and to increase the operating reliability thereof. 
   SUMMARY OF THE INVENTION 
   Briefly described, a DHLA in accordance with the present invention includes a conventional hydraulic lash adjustment mechanism disposed within a plunger slidably disposed within a pin housing that is slidably disposed within an axial bore in a lifter body. A transverse bore in the pin housing contains two opposed, selectively-retractable locking pins that engage a circumferential groove including a locking surface in the lifter body whereby the lash adjuster 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 RFF pivotably disposed on a domed head of the plunger. 
   A lash ring disposed at the outer end of the DHLA body and surrounding the pin housing includes a portion extending into the bore in the DHLA body to engage the pin housing. The lash ring thus functions to limit the travel of the pin housing within the DHLA body and thereby sets the internal mechanical lash in the deactivation mechanism. The lash ring may be provided as an inexpensive 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 lifter. Preferably, the lash ring is provided as a single ring of desired thickness, which thickness varies from assembly to assembly to compensate for manufacturing variation in the components. The lash ring may be secured to the body in any of various configurations. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
       FIG. 1  is an elevational view of a DHVL for use in cam-in-block internal combustion engine, substantially as disclosed in U.S. Pat. No. 6,578,535 B2, showing the pin housing retained by a lash clip disposed in an annular groove in the inner wall of the DHVL body; 
       FIG. 2  is an elevational cross-sectional view of a prior art valve-deactivating hydraulic valve lifter for use in a cam-in-block engine, substantially as disclosed in U.S. Pat. No. 6,513,470 B1, showing the internal mechanical lash being set by a lost-motion spring seat without resort to an annular groove in the inner wall of the DHVL body; 
       FIG. 3  is an elevational view of a central portion of a first embodiment of a DHLA in accordance with the present invention, providing a first means for securing a lash ring to the DHLA body; 
       FIG. 4  is an elevational view of a central portion of a DHLA in accordance with the present invention, providing a second means for securing a lash ring to the DHLA body; 
       FIG. 5  is an elevational view of a central portion of a DHLA in accordance with the present invention, showing a third means for securing a lash ring to the DHLA body; 
       FIG. 6  is an elevational view of a central portion of a DHLA in accordance with the present invention, showing a fourth means for securing a lash ring to the DHLA body; 
       FIG. 7  is an elevational view of a central portion of a DHLA in accordance with the present invention, showing a fifth means for securing a lash ring to the DHLA body; 
       FIG. 8  is an elevational view of a central portion of a first embodiment of a DHLA in accordance with the present invention, showing a lash ring integral with a first means for securing the lash ring to the DHLA body; and 
       FIG. 9  is an elevational view of a central portion of a first embodiment of a DHLA in accordance with the present invention, showing a lash ring integral with a second means for securing the lash ring to the DHLA body. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 1 , a prior art DHVL  10  is shown, substantially as disclosed in U.S. Pat. No. 6,578,535, the relevant disclosure of which is incorporated herein by reference. DHVL  10  has a generally cylindrical body  12 . A pin housing  14  is slidably disposed within a first axial bore  16  in body  12 . Pin housing  14  itself has a second axial bore  18  for slidably receiving a plunger  20  having a pushrod seat  22  for receiving an end  28  of a valve actuator such as pushrod  30  in cam-in-block engine valve train (not shown). 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 body  12  is provide with an engagement feature such as circumferential groove  31  for receiving the outer ends of locking pins  26 , thrust outwards by spring  28  when pins  26  are axially aligned with groove  31 . In such configuration, DHVL  10  is in valve-activation mode. ( FIG. 1  is a split view of DHVL  10 . The left side shows DHVL  10  in a valve activation mode; the right side shows DHVL  10  in a valve deactivation mode). An LM spring  34  is disposed within a chamber  35  below pin housing for absorbing lost motion of pin housing  14  within bore  16  when DHVL  10  is in deactivation mode. 
   Groove  31  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 DHLA. In use, groove  31  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. 
   Plunger  20  includes a hydraulic lash adjuster (HLA) mechanism  42  lodged at an inner end thereof. The arrangement of components and operation of HLA mechanism  42  has been well known in the prior art for many years. HLA mechanism  42  comprises 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  formed between HLA mechanism  42  and pin housing  14 . Oil may be supplied to low pressure reservoir  48  annular chamber  51  from an engine oil gallery (not shown) via hollow passage  29  in pushrod  29 . 
   In operation, prior art DHVL  10  is disposed in a bore in engine  40  such that housing  12  is free to move up and down in the bore. When the associated cam  17  exert force on roller  19 , in lost motion (valve-deactivation) mode, plunger  20  and pin housing  14  are forced into body  12  in a lost-motion stroke, compressing LM spring  34 . 
   Of particular interest to the present invention is the means by which the outward stroke of pin housing  14  is limited in prior art body  12 . An annular groove  64  formed in bore  16  near the outer end thereof receives a retaining clip  66  that extends into bore  16  to engage the upper end  68  of pin housing  14 . The axial thickness  70  of clip  66  is selected from a family of such clips having differing thicknesses to set the amount of axial mechanical lash  72  in DHVL  10 . As described above, the amount of lash  72  is an important manufacturing parameter which must be calibrated for each DHVL assembly because of manufacturing variability in the length  74 , from lower end  69  of groove  64  to the lower edge  76  of pins  26 , and length  78 , from the upper edge  80  of groove  64  to the lower edge  82  of groove  31 . The trial-and-error method of assembly, measurement, disassembly, reassembly, and remeasurement is time-consuming, costly, and difficult when using prior art groove  64  and clip  66 . Further, the presence of groove  64  in the inner wall of bore  16  at this location is undesirable as the groove weakens the wall and, if the wall is already thin, can result in failure by rupture of the small flange remaining between the upper end of the groove and the end of body  12 . 
   Referring now to  FIG. 2 , a prior art DHVL  84  is shown substantially as disclosed in U.S. Pat. No. 7,296,548 B1, the relevant disclosure of which is incorporated herein by reference. DHVL  84  comprises all of the elements shown in DHVL  10  in  FIG. 1 , except that the lost motion spring  34 ′ is disposed externally of body  12 ′ on a spring seat  86  retained by spring  34 ′ and spring tower  88 . 
   Spring seat  86  comprises a flange portion  90  that rests on the upper end  92  of body  12 ′ and a cylindrical portion  94  that extends axially into bore  16 ′ in body  12 ′ to engage pin housing  14 ′. Thus, the axial length  96  of cylindrical portion  94  defines a gauge that sets the internal mechanical lash (not visible in  FIG. 2 ) for DHVL  84 . 
   It is an object of the present invention to adapt to a switchable valve train member DHLA the principles for setting internal mechanical lash as disclosed by DHVLs  10  and  84 , with important improvements thereto, thereby simplifying the setting of lash, and strengthening the wall of the switchable valve train member as seen as a shortfall in the groove design disclosed in DHVL  10 . 
   For simplicity of presentation, the improved mechanical lash setting mechanism is shown adapted to a DHLA. However, it is understood that the improvements can be applied to other switchable valve train members, such as DHVLs, with equal resulting benefits. 
   Referring now to  FIGS. 3 through 9 , a first embodiment  110  of an improved DHLA in accordance with the invention comprises many components identical or analogous to those described hereinabove for prior art DHVL  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. For clarity of presentation, only a central portion of a complete DHLA in accordance with the invention is shown; however, a complete DHLA having other portions generally comporting with the locking feature disclosed above in DHVLs  10  and  84 . 
   DHLA  110  has a generally cylindrical lash adjuster body  112 . The lash adjuster body is case hardened. A pin housing  114  is slidably disposed within a first axial bore  116  in lash adjuster body  112 . Pin housing  114  itself has a second axial bore  118  which in turn slidably receives a plunger  120 . In the case of a DHLA, the top of the plunger is domed to provide a pivot point to a socket end of the valve actuator such as a valve train rocker arm, as known in the art. Body  112  is provided with a stepped counterbore  121  defining an axial surface  123  for receiving a flange portion  190  of a lash-setting retaining ring  186  (also referred to herein as a “lash ring”). A hard turning process may be used to remove the hardened case to expose the softer inner core for subsequent processing. A cylindrical portion  194  extends axially into bore  116  in body  112  to engage pin housing  114 . Thus, the axial length  196  of cylindrical portion  194  defines a gauge that sets the internal mechanical lash (not visible in  FIG. 3 ) for DHLA  110 . As in the prior art, axial length  196  is selected to provide a specified amount of lash by compensating for manufacturing variation in various components as described above. 
   The remainder of the present disclosure deals with various means for securing a lash ring to the lash adjuster body after the appropriate-thickness lash ring has been selected and installed. 
   Lash ring  186  may be secured to lash adjuster body  112 , for example, by a weld  171 , after first removing the body&#39;s hardened case in the area of the weld by the hard turning process mentioned above. ( FIG. 3 ); by staking or crimping over a thinned extension  173  of lash adjuster body  112 , after the hardened case in the area of the thinned extension is first removed by the hard turning process ( FIG. 4 ); by providing a snap ring  175  engaged into an annular groove  177  formed in the outer surface of lash adjuster body  112  ( FIG. 5 ); by providing a radially crushable ring  179  similar to a beverage crown cap engaged into annular groove  177  ( FIG. 6 ); or by providing a threaded ring  181  engaged into a threaded portion  183  of lash adjuster body  112  ( FIG. 7 ). In  FIGS. 5 ,  6  and  7 , note that the feature (annular groove  177  or threaded portion  183 ) formed on the outer surface of the body need not be precisely positioned or formed since the position of the lash-setting retaining ring  186  will be controlled by its mating with the axial surface of the body ( 123  in  FIG. 4 ), which is readily accessible for precision machining. Further, in these embodiments, snap ring  175 , crushable ring  179  and threaded ring  181  can be manufactured inexpensively as well. 
   A lash ring may also be provided integrally with a retaining means. For example, an integral lash retaining ring  286  may also comprise a snap ring  279  for engaging into annular groove  177  ( FIG. 8 ), wherein offset  299  sets the internal mechanical lash; or an integral lash retaining ring  386  may also comprise a radially crushable ring  379  for engaging into annular groove  177  ( FIG. 9 ). 
   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.