US2962011A - Mechanical valve lash adjuster - Google Patents

Description

Nov. 29, 1960 M. s. ROSENBERGER MECHANICAL VALVE usn ADJUSTER Filed Aug. 20, 1958 MECHANICAL VALVE LASH ADJUSTER Maurice S. Rosenberger, Birmingham, Mich.,' assiguor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed Aug. 20, 1958, Ser. No. 756,177

Claims. (Cl. 123-90) This invention relatestointernalcombustion engines and thelike, andparticularly' to selfadjusting mounts for rockers such as are used mover-head type valve operating mechanisms thereof. More specifically, the invention concernsan improved arrangement for automatically adjusting the rocker fulcrum-to take up lash in the system and compensate for thermal expansion and contraction of the parts.

It has heretoforebeen proposed to efliect such adjustment of the so-called studxmounted valve rocker of Leach US. Patent Re. 24,035 by inter-threading the rocker bearing ball and the supporting stud so that the ball is induced to screwupwardly during each valve lifting stroke, a spring on the stud opposingsuch-ball movement and acting to return the rocker to the nolash condition when the engine valve returns to its seat. It has been found, however, thata very critical friction condition between the bearing surfaces of the. ball and rocker exists in that arrangement which limitsthe durability life below that which is commerclally satisfactory The difiiculty arises from the fact that wear of these surfaces caused" by rockingrrnovements'ofthe rocker prevents their maintaining theinecessary coefiici'ent ofifriction'required for proper rotation of theball :to' insure its automatic adjustment axiallyfof the stud. This invention serves to overcome this diificultybyceliminating thereffect of bearing-to-rocker1friction on the.'.thrust: irlduced rotation required for proper functioning.

The means by which this and other'objects'of the invention arecarried out will be: more clearly understood .from the following description, having reference :to the drawing wherein:

Figure 1 is a fragmentary transverse sectional view through a combustion engine incorporating the improved lash adjuster, certain of the parts being shown in elevation.

Figure 2 is a further enlarged view, similar to Figure 1, showing additional parts of the adjuster in section for greater clarity.

Figure 3 is a plan view of the parts shown in Figure 2.

Figure 4 is a perspective view of the rocker adjusting nut per se.

Referring now in detail to the drawing, there is shown an engine of a conventional over-head valve type including a cylinder block 1 having a cylinder head 2. Slidably guided for axial reciprocation in the bore 3 of the cylinder head is the stem 4 of a poppet valve 5, the upper end 6 of which projects above the cylinder head. Also suitably guided in the cylinder head in a push rod 8 which is disposed laterally of the valve stem 4 and has its upper end 9 also projecting above the cylinder head. The usual valve return spring is shown at 10. The lower end of the push rod abuts a tappet 11 which is slidably guided for axial reciprocation in the tappet bore 12 provided in the cylinder block. A cam 13 is shown on which rests the lower end of the tappet and whose shaft 14 is rotatively driven in any desired States Patent 2 manner (not shown) to cyclically liftthe tappetand push rod.

Operatively connecting the push rod and valve stem is avalve rocker 15 whose ends 16. and 17 overlie and rest upon the upper ends9 and 6 of the push .rod and valve stem, respectively. Adjacent .its end16 the bottom reciprocating movementsbetween the push rod .and valve.

" Centrally of its. bearing surface 18. the rocker. is provided .with an-opening 29 through whichextends a bearing supportin the..form. of astudfZl, with ample clearance to accommodate full oscillatoryv movement of the rocker. The cylinder head serves as the support for this stud, as

. by. a press fit ofthelower endof the stud therein. .The

rocker bearing member 19 slidably embraces the stud .whichuservestas atguide therefor and extends therethrough. Axially adjacent: thebearing member is a.. nut

.22 having non-locking threads-engaging external. threads 23 on the stud. .The. under side of .the nutanditheupper end of the bearing.-member...19 have Jsubstantiallyflat .annular surfaces 25 and 2.4, respectively, which coact with each other .inthrust anclrotarybearing relation. Resilient .means, shown in the form-of..a..torsion spring 30 encircling the studabovethelnut, has: its lowcrend 26 connected. to..the,:nut and its;.upper end. 27. anchored to.the studby, a retainermeans 28. The retainer means .isillustratedinthe form ofasheet metal stampingwhose .central.portion.-31.is.- fixed -as .by. a, press :fit..to theupper .end .of .the .stud.

Thelflatannular. surface 25 .of the nut :is limited. in

v.width by counterboring .thenutas .at-32..in.ordentonnsure. a constant. area..of contacttwitlnthe.bearingpsurface '24, which,. in- .turn,..serves .to. maintain .rauconstant .-co-

iti'allyrwithwear..1of;these-s1ii:faces. Theocoefiicienta-of friction between these surfaces must accommodate rotation of the nut under the turning force induced by the non-locking threads in response to the rocker thrust loads imposed by the valve spring 10. This thrust is zero, of course, when the valve 5 is seated and increases proportionately (neglecting inertia effects) with the extent to which the valve is opened by the cam 13. The torsion spring 30 serves both to supplement the friction holding force opposing rotation of the nut by the bearing member during thrust application, and to maintain the nut in abutment with the bearing member as the thrust load is removed.

Accordingly, in operation, during each valve-open period of the cam cycle the thrust load imposed on the rocker is transmitted by its bearing 19 to the nut 22. By reason of the non-locking threads between the stud and nut, the nut is consequently forced to screw upwardly on the stud, against the friction restraining forces imposed by the bearing member at the surfaces 24 and 25 and against the biasing force of the torsion spring 3%. When the valve thereafter returns to closed position, thereby relieving the thrust load on the rocker, the torsion spring screws the nut back down on the stud to its initial position, taking up all lash (operating clearance) between the cam 13 and the valve stem 4. Of course, any minute wear of the various abutting surfaces of the valve 3 operating parts as well as thermal expansion and contraction thereof occurring during the cam cycle will be compensated for in establishing a new initial position of the nut in. thevalve-closed condition.

It will be evident that in accordance with the invention as described wear between the bearing member 19 and the rocker, and any consequent change in either the area of their mutually contacting surfaces or coefficient of friction therebetween, is ineffective to alter the controlled extent of threaded adjustment of the nut on the stud during the valve operating cycle, hence proper functioning of the lash adjusting parts is assured.

It is appreciated that various minor changes in the construction and arrangement of the parts will readily suggest themselves to those skilled in the art without departing from the spirit and scope of the invention as hereinafter claimed.

I claim:

1. In a self-adjusting rocker mounting for use in a poppet valve or like operating linkage, a rocker having an opening extending therethrough in the thrust direction, a bearing support extending through said opening, bearing means slidable on said support and journaling the thrust side of the rocker adjacent said openng, a nut on the support oppositely of the bearing means from the rocker, said nut and support being interthreaded with non-locking threads, and resilient means reacting operatively between the support and nut in opposing movement of the nut in the direction of rocker thrust, said nut and bearing means having coacting surfaces accommodating rotation of the nut under rocker thrust loads transmitted thereto by the bearing means.

2. In a support for a rocker having an opening extending therethrough normal to its fulcrum axis, a stud adapted to extend through the opening with clearance accommodating oscillatory movement of the rocker in operation, a nut on the stud, said nut and stud being interthreaded with nonlocking threads, a spring secured to the stud and nut and acting to screw the nut therealong in the direction opposite to the direction of rocker thrust, said spring being yieldable to accommodate unscrewing of the nut under thrust loads imposed by the rocker in operation, and a bearing adapted to journal oscillatory movement of the rocker in operation, said nut and bearing having coacting thrust surfaces accommodating nut rotation under the turning force induced by said threads in response to rocker thrust.

3. In combination with a rocker drivingly connected to oppositely reciprocating elements, rocker supporting means including a member journaling the rocker for oscillation about its fulcrum axis, a guide mounting said member for movement in response to rocker thrust, a part rotatably and thrustably bearing on said member and having a non-locking interthreaded connection to the guide whereby rocker operating thrust transmitted to said part by the member induces said part to threadedly rotate on the threads of the'guide, and a torsion spring interconnecting the guide and said part and resiliently opposing their relative rotation induced by rocker thrust.

4. In combination with a rocker having an opening extending therethrough in the thrust direction, supporting and journaling means for the rocker including a fixed support, a stud fixed to said support and extending through said opening with sufficient clearance to accommodate rocking movement of the rocker, first and second members embracing the stud oppositely of the rocker from the support and having coacting thrust bearing surfaces, one of said members being slidable longitudinally of the stud and journaling rocking movements of the rocker, the other of said members having a non-locking interthreaded engagement with the stud, and a torsion spring reacting between the stud and said other member to bias the latter in opposition to rotation thereof induced by rocker thrust transmitted by said first member.

5. In combination with a rocker for transmitting motion between oppositely reciprocating driving and driven elements, said rocker having an opening extending therethrough in the thrust direction and a concave bearing surface adjacent the opening on the thrust side of the rocker, a fixed stud extending through the opening with clearance to accommodate rocking movements of the rocker, an apertured bearing slidably embracing the stud having a convex surface journaling said bearing surface of the rocker and a substantially flat annular surface facing away from the rocker, a nut on the stud axially adjacent the bearing and having a substantially fiat annular bearing surface rotatably seating on said last named surface of the bearing, said nut and stud having non-locking interengaging threads, a torsion spring encircling the stud on the opposite side of the nut from the bearing, and means anchoring one end of said spring to the extended end of the stud and the opposite end of the spring to the nut, said spring being torsionally stressed to resiliently oppose rotary adjustment of the nut under rocker operating thrust transmitted to the nut by the bearing.

References Cited in the file of this patent UNITED STATES PATENTS

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