Patent Publication Number: US-5632237-A

Title: Hydraulic lash compensating element assembly

Description:
This invention relates to valve systems for automotive vehicles and particularly to hydraulic lash element assemblies. 
     BACKGROUND OF THE INVENTION 
     In valve systems for automotive vehicles, it is common to provide a hydraulic lash compensating element which is installed in a rocker arm, for example, as shown in U.S. Pat. No. 2,036,936. In such a construction, a foot section with a spherical cavity contacts a spherical protrusion of the lash element housing. This translates the relative axial movement of the push rod into the rotational movement of the rocker arm. In this patent, the foot section is secured by pressing a cylindrical section of the foot into a cavity in the push rod. (FIG. 1) 
     In some designs no separate foot section is used and the spherical end of the lash element housing is in direct contact with the engine valve. This is shown in U.S. Pat. No. 4,502,428. Such a design may have excessive contact stress between the lash element and the valve. (FIG. 2) 
     In other designs, the foot section has no external retaining device. It is simply held in place by valve spring preload pressure. Assembly of the rocker arm and lash element into the engine is very difficult with this type of design. In addition, this also forces the engine manufacture to inventory additional components. See U.S. Pat. No. 4,708,103 (FIG. 2). 
     In other designs the foot is attached to the valve stem. A flange on the foot engages a groove on the valve stem as shown in U.S. Pat. No. 4,570,582. This approach requires additional machining of the valve stem. (FIG. 4) 
     In another method described in U.S. Pat. No. 4,708,103, a retainer is attached to the lash element housing. It is roughly cylindrical in shape and has an inward flange on one end for retaining of the foot section but allowing relative rotation of the foot to the spherical protrusion of the housing. 
     Among the objectives of the present invention are to provide a hydraulic lash compensating element assembly which overcomes the deficiencies in the art; which minimizes stress between the lash element and the valve; which is easier to assemble; which reduces the inventory of component parts; which requires less machining; and which results in greater efficiency of the engine valve train. 
     SUMMARY OF THE INVENTION 
     A hydraulic lash compensation element assembly is installed into a cylindrical cavity in a rocker arm. The assembled rocker arm is used in the valve train of an internal combustion engine to translate the rotational movement of the camshaft into axial movement of the engine valve. The hydraulic element is designed to automatically eliminate any clearance in the valve train. The outer housing of the hydraulic lash adjuster has a spherical protrusion. This protrusion contacts a swivel foot. The swivel foot has a substantially spherical cavity on one end which contacts the spherical protrusion of the hydraulic element housing, and a flat surface on the other end which contacts the engine valve. This swivel foot allows for the relative angular motion between the center lines of the valve and the hydraulic lash element during valve opening and closing. The swivel foot is held in place using a new and unique retainer. This retainer is roughly cylindrical in shape and is permanently attached to the swivel foot by pressing a reduced diameter of the retainer over a flange on the swivel foot. This reduced diameter may extend over all or a portion of the circumference. This retainer also has a reduced diameter annular base flange on the other end which engages a groove on the lash adjuster housing beyond the spherical protrusion. In another embodiment of the invention, the reduced diameter engaging the element housing may be offset from the center line of the retainer. In another option the reduced diameter which is pressed over the flange on the pivot foot, may be replaced by a plurality of indentations. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view of a construction shown in prior art U.S. Pat. No. 2,036,936. 
     FIG. 2 is a sectional view of a construction shown in prior art U.S. Pat. No. 4,502,428. 
     FIG. 3 is a sectional view of a construction shown in prior art U.S. Pat. No. 4,708,103. 
     FIG. 4 is a sectional view of a construction shown in prior art U.S. Pat. No. 4,570,582. 
     FIG. 5 is a sectional view of another form shown in prior art U.S. Pat. No. 4,708,103. 
     FIG. 6 is a fragmentary sectional view of a hydraulic lash element embodying the invention. 
     FIG. 7 is an elevational view of a valve form embodying the invention, showing the valve closed. 
     FIG. 8 is a part sectional view of the valve form shown in FIG. 7, showing the valve open. 
     FIG. 9 is a fragmentary enlarged part sectional view of the valve form shown in FIG. 8. 
     FIG. 10 is an exploded view of the lash compensating element assembly. 
     FIG. 11 is a sectional exploded view similar to FIG. 10. 
     FIG. 12 is a bottom plan view of the retainer. 
     FIG. 13 is a sectional view taken along the line 13--13 in FIG. 12. 
     FIG. 14 is a bottom plan view of a modified form of retainer. 
     FIG. 15 is a sectional view taken along the line 15--15 in FIG. 14. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 6-13, a hydraulic lash compensating element assembly 20 is provided in an end 22 of a rocker arm 24 which is pivoted on a shaft 26 and has a roller 28 on a short arm 30 which engages a cam 32 on a cam shaft 34. The hydraulic lash compensating assembly 20 engages the free end 36 of a valve 38 in a manner well known in the art to move the valve and also eliminate clearance in the valve train. 
     Referring to FIG. 6, 10, and 11, the hydraulic lash compensating element assembly 20 comprises a hydraulic base element which includes an outer housing 40 which has an open upper end and a closed lower end having an integral spherical protrusion 42 at the lower end. The assembly 20 includes an inner housing 44 slideably mounted in the outer housing 40 and engaging a wear piece 46 mounted in the rocker arm 24 (FIG. 9). The lower end of the inner housing 44 is provided with a wall 48 having an opening 50 and a ball 52 in a ball retainer 56 is yieldingly urged toward the opening by a spring 54 interposed between a ball retainer and a lower end of the outer housing 40. A light spring 57 is interposed between the ball 52 and retainer 50. 
     In accordance with the invention, the spherical protrusion 42 engages a spherical surface 56 on a foot 58. The foot 58 is retained on the spherical protrusion 42 by a retainer 60 which includes a base wall 62 having an opening 64 and a peripheral flange 66 projecting from the base wall 62. Flange 66 includes an annular bead 68 on the internal surface thereof. The annular bead 68 may be continuous or interrupted. The retainer 60 is telescoped over the protrusion 42 and pressed onto the foot 58 over a flange 70 permanently attaching the swivel foot 58 to the retainer 60. The foot 58 includes a flat surface 72 which engages the free end 36 of the valve stem 38. 
     The diameter of the opening 64 is smaller than the diameter of the spherical protrusion 42 to prevent disassembly. The diameter of the opening 64 is sufficiently larger than the diameter of the neck portion 74 to allow angular movement. As a result, there is permissible relative angular movement between the swivel foot 58 and the hydraulic lash element outer housing 40. In addition, there is permissible relative rotational motion between the swivel foot 58 and the housing 40. 
     In the modified form of retainer shown in FIGS. 14 and 15, circumferentially spaced projections 80 are provided on the retainer 60a and the opening 64a is eccentric to the central axis of the retainer. The eccentric alternative design is used with a steel or other nonflexible retainer material. In this case, the hole 64a is slightly larger than the diameter of the protrusion 42. The retainer is first inserted over the protrusion 42 on the housing 40, then centered. Then it is pressed onto the swivel foot 58 preventing side to side motion. In this case, only a portion of the diameter is used to hold the foot in place. 
     It can thus be seen that there has been provided a hydraulic lash compensating element assembly which provides for rotational and angular movement during the valve opening and valve closing which is effective during the cam cycle (FIGS. 7-9). As a result the system minimizes wear, compensates for thermal expansion, minimizes contact stress between the lash element and the valve; minimizes the number of parts that must be maintained in inventory; minimizes machining; and contributes to longer life of the valve train.