US3179094A - Internal combustion engine valve gear - Google Patents

Description

April 20, 1965 J. RxBEToN INTERNAL COMBUSTION ENGINE VALVE GEAR Filed May 28, 1963 United States Patent O 3,179,094 INTERNAL coMBiTgN ENGINE VALVE This invention relates to the valve actuating mechanisms of internal combustion engines.

It has already been proposed to provide automatic clearance take-up or compensating devices for the valve actuating mechanisms of internal combustion engines, in order to ensure at all times minimum clearance during engine operation notwithstanding dilerential thermal expansion, wear and other similar causes. These compensating devices have usually taken the form of miniature hydraulic cylinder-and-piston actuators interposed in the tappets transmitting the actuating forces from the cams to the rocker arms actuating the valves, and fed with oil under pressure by way of a check-valve so as at all times to urge the rocker arm in a direction to take up the clearance. One disadvantage of this arrangement has been the comparative inaccessibility or the location at which the hydraulic compensators were disposed, requiring the dismantling of a considerable portion of the valve gear whenever it was necessary to inspect or replace the hydraulic compensators.

In another respect, it is well-known that since the valve stems of an internal combustion engine perform a linear reciprocatory motion while the rocker arms actuating the valve stems describe arcuate paths, a certain amount of friction and wear necessarily arises at the cooperating end surfaces of the valve stem and rocker arm. To eliminate this objectionable effect, it has been suggested to interpose a short link provided with spherical swivel means at its ends, between the active end of the rocker arm and the free end of the valve stem.

While each of the above-mentioned expedients is highly useful per se so that it would be desirable to incorporate both in the design of an internal combustion engine, it is apparent that this would be attended by an objectionable increase in the number of components of the valve gear, especially in the case of multi-cylinder engines.

Itis hence an object of this invention to provide a novel valve gear design for internal combustion engines, which will simultaneously incorporate an automatic hydraulic clearance-compensation feature, and a substantially frictionless connection between rocker arm and valve stem, while reducing the total number of valve gear components as compared to the number that such combination would entail using conventional valve gear designs.

Another object is to provide valve gear including automatic valve clearance compensating means that are more conveniently located in respect to accessibility for servicing, than heretofore.

A broad object is to provide novel valve gear for internal combustion engines which will be highly efficient yet compact and relatively simple.

In accordance with a chief aspect of the invention, in internal combustion valve gear including a poppet Valve having a projecting stem, a rocker arm, and cam means for reciprocating the rocker arm, the invention provides a two-part hydraulic link having its ends respectively connected to the rocker arm and the valve stem for transmitting reciprocating motion from the rocker arm to the valve, and hydraulic means connected to act between the parts of the link in a direction to take up clearance present in the valve gear.

It will be evident that with such an arrangement there is simultaneously provided automatic hydraulic compensation for valve actuating clearance, and a substantially frictionless transmission link between rocker and valve stem, with a saving of one component per valve as compared to the conventional design, since the hydraulic actuator itself constitutes the transmission link. Further, the positioning of the hydraulic clearance-compensator near the top of the valve gear just below the rocker arm` and above the valve stem greatly facilitates dismantling and replacement operations.

The above and other objects and features of the invention will be clearly understood from the ensuing description relating to an exemplary embodiment selected by way of illustration but not of limitation and shown in the accompanying drawings wherein:

FIG. l is a sectional view of part of a valve actuating mechanism for an `internal combustion engine incorporating the invention; and i FIG. 2 is a sectional view of a detail of FIG.A 1, speciiically the piston element of the hydraulic compensator therein, in a modied form.

The valve gear mechanism partly shown in FIG. l, includes a conventional pushrod 1 adapted to be reciprocated up and down by way of a tappet at its lower end, not shown, from a conventional cam. The upper end' of pushrod 1 actuates one end of a rocker 2 of generally conventional shape, mounted for rocking movement about a fixed pivot 3 supported from the casing of the internal combustion engine, part of the cylinder head of which is shown at 4. By way of an expansible two-part hydraulic.

link genrally designated 5 and described in detail hereinafter, the free end of the rocker 2 actuates the upper end of the stem 6 of a poppet valve 7, the head of which cooperates with a valve seat 8 secured in the cylinder head 4.

The valve 7 is urged in an upward, i.e. sealing, direction by a valve spring 11 which is a coil spring surrounding the upper projecting end of valve stem 6 and seated at its lower end on a spring seat 12 fixed to the cylinder head and at its upper end against a spring seat 13 secured t0 the upper end of valve stem 6 through any suitable means.

The pushrod 1 at its upper end is formed with a partspherical convex surface cooperating with a complementary concave seat formed in an insert 15 threadedly secured in a tapped opening formed in the related end of the rocker arm and locked in position with a lock-nut 16.`

ance compensator and for this purpose is made up of two parts, a cylinder part Z1 and a piston part 22 sliding therein. The upper end of cylinder 21 is formed with a partspherical convex surface 21a cooperating with a concave seating surface 24a formed on an annular insert 24 pressfitted into a socket formed in the related end of the rocker 2. The piston 22 is cup-shaped and from its lower end extends a shank 26 which projects freely into an axial bore 27 formed in the upper part of valve stem 6. At its lower end the piston rod or shank 26 is formed with an enlargement 28 preferably formed with a part-spherical convex under surface which cooperates with a complementary seating surface formed in the bottom of bore 27.

A coil spring 31 positioned Within the piston 22 has its lower end seated against the bottom of the piston recess and its upper end seated against a shoulder defined by a centering insert 32 force-fitted into a socket provided at the top of cylinder 21. The insert 32 has a recess formed in its upper surface to define a valve chamber with the upper surface of cylinder 21, and a valve-ball 34 is freely movable in said valve chamber, so as to cooperate with the lower end of a duct 35 formed through the top of the cylinder 21 and opening into the valve chamber. The

Patented Alpi'. 20, 1965.

latter further communicates with the interior of cylinder 21 by way of one or more passages 36 formed through the insert 32.

The previously mentioned rocker pivot 3 is provided with` an axial bore externally connected with a source of pressure fluid, e.g. engine lubricating oil, and said axial passage is connected by way of a radial passage 38 formed through the rocker with a longitudinal passage 39 extending through the rocker and opening at one end into a chamber 41 formed in the related end of the rocker, which chamber communicates with the upper end of the aforementioned cylinder passage 35. It will be noted that a short tube extending upwardly from the top of cylinder 21 around the upper opening of passage 35 extends freely through a relatively large-diameter hole formed in the spherical seating insert 24 to project into the oil pressur chamber 41 regardless of the angular position of the rocker around its pivot.

The longitudinal passage 39 is extended in the opposite direction to connect with an annular groove 42 formed in the periphery of the insert 155. The annular groove 42 is connected by way of one or more radial holes 43 with anV axial passage 44 in the insert 15 for lubricating the spherical swivel joint which connects the rocker arm with the upper end of the pushrod 1. The valve gear described operates as follows:

In the normal seated condition of the poppet valve 7 against its seat 8, as produced by the action of the valve spring 11, the two parts 21 and 22 of link 5 are pushed away from each other by the combined actions of the relatively weak spring 31 and the oil pressure acting in the upper part of the cylinder member 21, the oil under pressure being admitted into the cylinder from the pressure passage 3 through passages 38 land 39, chamber 41, duct 35 and past the check-valve 34 which prevents outflow of the oil from the cylinder. The relative dimensioning of the parts is such that the resultant force of the oil pressure and spring 31 is substantially less than the force of valve spring 11. Thus the expansible hydraulic link acts at all times to take up any clearance that might otherwise be present in the valve actuating linkage due to Wear, differential thermal expansion and the like, without impairing the normal operation of the valve. At the same time, due tothe spherical swivel connections provided between the opposite ends of the hydraulic link 5 and the rocker arm 2 and valve stem 6 respectively, said link serves to convert:r the arcuate motion of the rocker into the desired linear motion of the valve stem in a smoother manner than would be the case if the rocker arm were in direct engagement with the stem. It will be noted that the hydraulic link 5 is very easily accessible for dismantling or replacement from the top of the engine case.

As shown in FIG. 2, the shank 26a of the piston member 22a there shown may desirably be formed with an axial through passage 46 so as to conduct a small amount of pressure oil into the end of the bore 27 in the valve stem, creating a slight back-pressure of oil therein for eiective lubrication of the lower spherical seat 28 of the link 5. It will be noted that the upper swivel seat of the link 5 at 21a-24a is similarly lubricated with oil directly from pressure chamber 41.

It will be understood that various changes and modiications may be introduced into the single embodiment illustrated and described without exceeding the scope of the invention, v

What is claimed is:

l. In an internal combustion engine the combination comprising a poppet Valve having a stem, a rocker arm reciprocable from said engine, a two-part expansible hydraulic link having its ends respectively swivellingly connected to the rocker arm and the valve stern for transmitting reciprocation from the rocker arm to the Valve, and hydraulic pressure means connected to act between the two parts of the link in a direction to expand the link.

2. In an internal combustion engine the combination comprising a poppet valve having a head and stern, a valve seat cooperating wit-h said valve head, a valve spring associated with said valve to urge the Valve head into sealing engagement with said seat, a rocker arm reciprocable from the engine, a two-part expansible hydraulic link, part-spherical swivel surfaces for respectively pivotally connecting the ends lof the link with said rocker arm and said valve stem whereby the reciprocation of the rocker arm will reciprocate the valve to cyclically lift the valve head off its seat in opposition to the spring, and hydraulic pressure means connected to act between the two parts of the link in a direction to expand the link.

3. The combination claimed in claim 2, wherein said link comprises a cylinder part and a piston part slidable therein, part-spherical swivel surfaces on an outer surface of the cylinder part and on the rocker arm providing the pivotal connection of said link with the rocker arm, a shank extending from the piston part, a bore formed axially in an end portion of the valve stem and receiving said shank freely therein over a major portion of the extent thereof, and part-spherical swivel surfaces at the end of said shank and in the end wall of said bore providing the pivotal connection of said link with said valve stem..

4. In an internal combustion engine the combination comprising a poppet valve having a stem, a rocker arm reci-procable from said engine, a two-part expansible hydraulic link including a cylinder part and a piston part slidable therein, means pivotally connecting said cylinder part with said rocker arm, a source of pressure iluid, flow means including passage means through the rocker arm for connecting the interior of said cylinder with said `source for expanding said link, including check-valve means opposing outflow of the fluid from the cylinder, said piston part having a shank projecting therefrom, said valve stem having an outer end portion provided with an axial bore, said shank having a diameter substantially smaller than that of said axial bore over a major portion of its length, and part-spherical mating surfaces at the end of said shank and in said end wall of said bore for swivellingly connecting said piston part with said valve stem.

5. The combination claimed in claim 4, including means defining a small-diameter duct extending axially through said shank for delivering said uid into the end of the bore for lubricating said swivel surfaces.

References Cited by the Examiner UNlTED STATES PATENTS 1,617,986 2/27 Blank 123-90 1,798,938 3/31 Hallett 123,-90 2,036,936 4/ 36 Halford 123-90 2,380,051 7/45 Kettering 123-90 2,878,796 3/59 Mannerstedt 123-90 FRED E. ENGELTHALER, Primary Examiner.

Claims (1)

1. 2. IN AN INTERNAL COMBUSTION ENGINE THE COMBINATION COMPRISING A POPPET VALVE HAVING A HEAD AND STEM, A VALVE SEAT COOPERATING WITH SAID VALVE HEAD, A VALVE SPRING ASSOCIATED WITH SAID VALVE TO URGE THE ALVE HEAD INTO SEALING ENGAGEMENT WITH SAID SEAT, A ROCKER ARM RECIPROCABLE FROM THE ENGINE, A TWO-PART EXPANSIBLE HYDRAULIC LINK, PART-SPHERICAL SWIVEL SURFACES FOR RESPECTIVELY PIVOTALLY CONNECTING THE ENDS OF THE LINK WITH SAID ROCKER ARM AND

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