Abstract:
An improved pin housing sub-assembly configured for reliable assembly and stability as an intermediate sub-assembly. The length of the plunger return spring is greater than the diameter of the spring well in the pin housing, such that the spring cannot be accidentally installed sideways in the well. During assembly, the non-compressed longer spring places the pushrod seat flush with the end of the pin housing. A shallow annular groove is provided in the inner wall of the pin housing near the outer end thereof, and an expansion ring may be installed therein when the plunger return spring is slightly compressed. The expansion ring holds the sub-assembly together as an intermediate but is displaced by the spring tower in a subsequent assembly step to become the locking ring between the pin housing and the spring tower, as in the prior art.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates to hydraulic valve lifters for use with internal combustion engines; more particularly, to valve deactivation hydraulic lifters for use in push-rod internal combustion engines; and most particularly, to a pin housing sub-assembly for use in such a lifter, including a plunger return spring having a greater length than diameter and a shallow annular groove in the pin housing for a retaining compression ring.  
       BACKGROUND OF THE INVENTION  
       [0002]     Hydraulic valve lifters for internal combustion engines are well known. Some prior art lifters are specially constructed to permit selective deactivation of an engine valve as desired, thereby selectively deactivating the corresponding engine cylinder; see, for example, U.S. Pat. No. 6,497,207 B2, issued Dec. 24, 2002 to Spath et al., the relevant disclosure of which is herein incorporated by reference.  
         [0003]     A typical prior art deactivation lifter includes an elongate lifter body having a lower end configured for engaging a cam of an engine. An elongate pin housing slidably disposed within the lifter body includes a radially directed pin bore. A plunger is concentrically disposed within the pin housing. A deactivation pin assembly is disposed within the pin bore and includes two pin members that are biased radially outward relative to each other by a spring therebetween to selectively couple the pin housing to the lifter body when valve activation is desired. The pin members are configured for moving toward each other when the pin chamber is pressurized, thereby retracting the pin members from within the lifter body and decoupling the lifter body from the pin housing when valve deactivation is desired. An elongate spring tower for retaining a lost motion spring has an outer wall concentrically disposed and retained within the outer end of the pin housing. The spring tower typically has slotted tabs or other engagement means and is flexible enough to be pushed downward into the pin housing during assembly until each of the tabs is received within and snaps into or otherwise engages an upper annular groove formed in the inside wall of the pin housing, or into an expansion ring disposable into the annular groove.  
         [0004]     The assembly procedure requires that many steps be performed correctly to produce a usable pin housing and spring tower sub-assembly. The procedure is subject to error, however, in that the length of the plunger return spring is less than the diameter of the receiving well in the pin housing, such that the spring may inadvertently and catastrophically turn sideways in the pin housing prior to installation of the plunger sub-assembly against the spring rendering the lifter inoperative or adding significantly to the assembly time of the lifter.  
         [0005]     Further, in lifter manufacture, it would be useful to have a pin housing sub-assembly that is self-contained and may be transported or tested or inventoried without falling apart.  
         [0006]     Therefore, what is needed in the art is a pin housing sub-assembly wherein the plunger return spring cannot be mis-installed by turning sideways, and wherein the sub-assembly including an expansion ring is held together by the expansion ring itself.  
       SUMMARY OF THE INVENTION  
       [0007]     Briefly described, an improved pin housing sub-assembly is configured for reliable assembly and stability as an intermediate sub-assembly of a valve deactivation hydraulic valve lifter. The length of the plunger return spring is greater than the diameter of the spring well, such that the spring cannot be accidentally installed sideways in the well. The longer spring requires a deeper spring well. However, unlike the prior art sub-assembly wherein a relatively short spring, without compression, allows a retaining ring to be inserted into the pin housing bore adjacent a pushrod seat, in an improved sub-assembly in accordance with the invention, wherein the spring is longer, the pushrod seat now becomes flush with the end of the pin housing because of the longer spring. Therefore, a shallow annular groove is provided in the inner wall of the pin housing near the outer end thereof, and an expansion ring may be installed therein when the plunger return spring is slightly compressed. The ring holds the sub-assembly together as an intermediate but is overcome and displaced by the spring tower in a subsequent assembly step to become the locking ring between the pin housing and the spring tower, as in the prior art.  
         [0008]     An advantage of the present invention is that it prevents the plunger return spring from being installed sideways or from tipping over during assembly of the pin housing sub-assembly.  
         [0009]     Another advantage of the present invention is that it permits the pin housing sub-assembly to be transported and inventoried as a stable unit, the expansion ring in the new groove holding the assembly together, while still fitting into the prior art assembly process for installing a lost motion spring mechanism wherein a spring tower overcomes and displaces the ring in a subsequent assembly step. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:  
         [0011]      FIG. 1  is an axially-sectioned view of a portion of a prior art deactivation roller hydraulic valve lifter;  
         [0012]      FIG. 2  is an axially-sectioned view of a prior art pin housing sub-assembly suitable for use in the prior art lifter shown in  FIG. 1 ; and  
         [0013]      FIG. 3  is an axially-sectioned view of an improved pin housing sub-assembly in accordance with the invention.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0014]     The particular benefits and advantages of the invention may be best appreciated by first considering a prior art deactivation lifter.  
         [0015]     Referring now to the drawings and particularly to  FIGS. 1 and 2 , there is shown a prior art embodiment of a deactivation roller hydraulic valve lifter  10 . Deactivation roller hydraulic valve lifter (DRHVL)  10  includes roller  12 , lifter body  14 , deactivation pin sub-assembly  16 , plunger sub-assembly  18 , pin housing  20 , pushrod seat assembly  22 , spring seat  23 , lost motion spring  24 , and spring tower  26 .  
         [0016]     A pin housing sub-assembly  28  includes pin sub-assembly  16 , plunger sub-assembly  18 , a plunger return spring  19 , seat assembly  22 , and expansion ring  30 , all disposed within pin housing  20 . Pushrod seat assembly  22  is disposed concentrically within pin housing  20  above plunger sub-assembly  18  to form hydraulic chamber  17 . Pin housing sub-assembly  28 , in turn, is disposed concentrically within lifter body  14 .  
         [0017]     Roller  12  is associated with lifter body  14 . Roller  12  may ride on the cam of an internal combustion engine and be displaced vertically thereby. Roller  12  translates the rotary motion of the cam to vertical motion of lifter body  14 . Deactivation pin sub-assembly  16  normally engages lifter body  14 , thereby transferring the vertical reciprocation of lifter body  14  to pin housing  20  and, in turn, to plunger sub-assembly  18  and pushrod seat assembly  22 . In this engaged position, the vertical reciprocation of DRHVL  10  opens and closes a valve of the internal combustion engine. Deactivation pin sub-assembly  16  disengages to decouple lifter body  14  from pin housing  20  and, in turn, decouples plunger sub-assembly  18  and pin housing  20  from the vertical reciprocation of lifter body  14 . Thus, when deactivation pin sub-assembly  16  is in the disengaged position, only lifter body  14  undergoes vertical reciprocation.  
         [0018]     Details of prior art lifter construction are fully disclosed in the incorporated reference and need not be repeated here.  
         [0019]     The prior art assembly operation for lifter  10  includes the steps of: 
        a) inserting a plunger return spring  19  into a well  21  in the pin housing bore  25 ;     b) installing a plunger sub-assembly  18  into the pin housing bore  25  to engage the plunger return spring  19 , forming a pin housing intermediate sub-assembly;     c) prefilling and leakdown testing the pin housing intermediate sub-assembly (by means not shown);     d) transferring the intermediate sub-assembly to a pin housing/body assembly machine (not shown);     e) assembling the intermediate sub-assembly into the lifter body  14 ;     f) installing a pushrod seat sub-assembly  22  into the pin housing bore  25 ;     g) positioning an expansion ring  30  slidably within bore  25  above pushrod seat sub-assembly  22  to form a lifter body intermediate sub-assembly;     h) transferring the lifter body intermediate sub-assembly to a tower assembly machine (not shown);     i) positioning a lost motion spring seat  23  on the end of pin housing  20 ;     j) assembling a lost motion spring  24  onto a spring tower  26  having pin housing engagement means  32 ; and     k) extending the spring tower engagement means  32  through the lost motion spring seat  23  and into the pin housing bore  25 , collecting the expansion ring  30  on the end of the engagement means  32 , compressing the plunger return spring  19  by displacement of the plunger sub-assembly  18  and pushrod seat sub-assembly  22 , displacing the expansion ring  30  axially of the pin housing into an annular groove  34  in the pin housing, and forcing the engagement means through the expansion ring  30  to lock the spring and spring tower into the pin housing.        
 
         [0031]     It will be seen that a true pin housing sub-assembly  28 , as is shown in  FIG. 2 , is never actually formed in this assembly sequence, as the pin housing is assembled into the lifter body before the pushrod seat assembly and the expansion ring are added. However, if desired, the sequence of steps could be changed to permit formation of a pin housing sub-assembly  10 .  
         [0032]     The detailed mechanism by which spring tower  26  is retained in pin housing  20  must be understood in order to fully understand the improvement afforded by the invention. Spring tower  26  is configured to include engagement means  32 , preferably comprising a ring groove  40  and beveled bottom edge  42 . Expansion ring  30  is shown as a square or rectangular ring member, although ring  30  can be alternately configured, such as, for example, a round retaining ring. As described above, in order to assemble DRHVL  10 , spring tower  26  is pushed downward into pin housing  20 . As spring tower  26  is inserted into pin housing  20  and pushed axially downward, beveled bottom edge  42  of spring tower  26  contacts ring  30  which is, in turn, displaced axially downward. This downward displacement of ring  30  continues until ring  30  contacts the bottom of annular groove  34 , which prevents further downward movement of ring  30 . As downward motion of spring tower  26  continues, beveled edge  42  then acts to expand the resiliently deformable ring  30 . Thus, ring  30  is resiliently expanded by beveled bottom edge  42  as spring tower  26  is pushed farther downward into pin housing  20 . The expanded ring  30  slides over beveled edge  42  of spring tower  26 . When ring groove  40  and ring  30  are in axial alignment, ring  30  snaps into ring groove  40 . As downward pressure upon spring tower  26  is removed, the action of lost motion spring  24  exerts an upward force on spring tower  26  until ring  30  contacts the top edge of annular groove  34 . Thus, expansion ring  30  retains a portion of spring tower  26  within pin housing  20 , and determines the axial position of spring tower  26  relative to pin housing  20 .  
         [0033]     Referring now to  FIG. 3 , an improved pin housing sub-assembly  28 ′, when assembled into a deactivation lifter such as prior art lifter  10 , is preferably identical in size and function to prior art pin housing sub-assembly  28 . The differences between prior art pin housing sub-assembly  28  and improved pin housing sub-assembly  28 ′ are entirely internal.  
         [0034]     The effective aspect ratio of prior art plunger return spring  19  ( FIG. 2 ) is less than 1.0; that is, spring length L is less than diameter D of well  21  (L&lt;D). Thus, during assembly of a prior art lifter, it is possible (and is known) for spring  19  to tip sideways, turning 90° from its intended orientation (not shown), which represents a an assembly failure requiring disassembly and correction.  
         [0035]     Contrarily, plunger return spring  19 ′, in accordance with the invention, is formed having length L′ greater than diameter D′ (L′&gt;D′), such that the spring cannot fit sideways into well  21 , thus preventing all such assembly failures. For example, in a prior art lifter, well  21  has a diameter D of 10.7 mm and spring  19  has a non-compressed length of 10.2 mm. Improved spring  19 ′ preferably may have a non-compressed length L′ of about 11.5 mm, and preferably diameter D is unchanged (D′ =D), such that the aspect ratio is greater than 1.0 (L′/D′ =1.07). Both springs meet the load requirements of 10 N at 6.993 mm and 32-36 N at 3.05 mm.  
         [0036]     A consequence of employing longer spring  19 ′ is that the space within bore  25  previously available for ring  30  is no longer available without first compressing spring  19 ′ slightly. However, means must then be provided for retaining ring  30  within bore  25  against the force of spring  19 ′. This is achieved by providing a second annular groove  50  between primary annular groove  34 ′, the eventual tower-locking groove, and the open end of bore  25 . Groove  50  is quite shallow, its purpose being to retain ring  30  during the pin housing sub-assembly stage and to release ring  30  when the ring is engaged by spring tower  26  during a subsequent assembly step as in the prior art. The ring is now performing two functions. First, the ring is assembled into groove  50  to resist the spring pressure of the slightly-compressed plunger return spring, preferably about 2 lbs., and to hold the sub-assembly together without interfering with subsequent tower installation into the pin housing. Second, the ring is pushed out of groove  50  by the spring tower and into tower retaining groove  34  to lock the tower and pin housing together for the life of the lifter. Preferably, groove  50  is about 0.004-0.005 inches deep and preferably is chamfered at, for example, about 15° on the inner edge to facilitate ring collection and removal by the spring tower.  
         [0037]     It will be seen that the combination of a plunger return spring having an effective aspect ratio greater than 1.0 and a intermediate ring-retaining groove in the pin housing bore provides an improved pin housing sub-assembly wherein the plunger return spring cannot be mis-installed and which can be transported as a stable sub-assembly unit.  
         [0038]     While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the present invention using the general principles disclosed herein. Further, this application is intended to cover such departures from the present disclosure as come within the known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.