US2288831A - Engine rocker arm - Google Patents

Description

C. T. OHARROW V'ENGINE RocKER ARM Filed oma `1o, 1940 ww, E1 WM July 7, 1942. Y

Patented July 7, 1942 UNITEDA STATES PATENT OFFICE signor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis.,` a corporation of Deiaware Application October 10, 1940, Serial N0. 360,619

(Cl. 184-6i 8 Claims.

This invention relates generally to engine rocker arms and more particularly to the rocker arms employed in the overhead valve type of internal combustion engine.

In engines of this type, lubrication of the rocker arm and push rod assembly and of the valve stems actuated thereby is generally eiiected by employing av hollow rockerv arm shaft having axially spaced transversely extending bores arranged for communication with a bore extending transversely through the hub portion of each of the rocker arms mounted on said shaft and lby delivering lubricant under pressure into the interior of the hollow shaft whereby lubricant flows therethrough and out along the top surface of the rocker arm and then down onto the upper -end portionsof the associated push rod and valve stem. The lubricant which is thus transmitted to the valve stems flows downward on the stems and when the valve stem is moved downward to open the valve thereon, some of the lubricant will flowalong the stem and into the engine cylinder where it is burned or otherwise wasted thereby unnecessarily increasing oil consumption.4 This action is particularly noticeable with respect to the intake valves since when an intakevalve is'` opened the piston in the associated cylinder is moving downward which produces a high degree of suction which in turn accelerates the flow of lubricant into the cylinder.

'I'he quantity of lubricant flowing through said bores and out onto the top surface ofthe rocker arm is determined -by the pressure of the lubricant and by the size and arrangement of the said bores and attempts have -been made to cor-` relate the pressure of the lubricant, the size and arrangement of the saidbores including the degree of communication effected by the movement .of the rocker arm in order to control the quantity of lubricant flowing along the top surface of that .portion of the rocker arm which engages the valve stem and thereby prevent an excessive consumption of lubricant. However, the .control l of the quantity of lubricant flowing to the valve stems by means of the aforementioned correlation has not been entirely satisfactory as it re quires the use of relatively small bores which frequently become clossed and the'result is insumcient lubrication and stuck push rods and valve stems. Attempts to overcome this defect by increasing the pressure of lthe lubricant has not solved the problem since a pressure sumcient to 'keep thelboresclearatalltiznesresultsintoo `much lubricant being forced out through the .lubricant flow control edge or surface over which the lubricant must flow in passing from the hubv bores whichin turn resultsinanexceasive con-.55

sumption of lubricant as previously pointed out. Moreover, the use of a high pressure lubricating system is highly undesirable as it is conducive to leakage at numerous points throughout the system and in addition materially increases the initial cost of the engine.

The primary object of this invention is to provide an improved engine rocker arm construction which will entirely eliminate the aforementioned defects.

Another object of this invention is to provide an improved engine rocker arm construction which will positively control the quantity of lubricant that reaches the outer end of the valve stem actuating portion of the rocker arm from the hub portion thereof irrespective of the size and arrangement of the communicating bores inV the rocker arm shaft and the rocker arm hubl which lubricant flows in passing. fromv the hubv portion to the valve' stem actuating end thereof is provided with means operative to prevent lu- |bricant in excess of that required for Asatisfactory lubrication of the associated valve stein` from reaching the valve stem actuating end of the rocker arm.

A further object of this invention is to provide an improved engine rocker arm construction in that the top surface of the rocker arm along which lubricant-flows in passing from the hub portion to the valve stem actuating end thereof is provided with a relatively long and narrow portion to the valve actuating end thereof.

'I'he invention accordinly consists of the various features of construction, combinations vof element and arrangements of partsv as mor e fully pointed out in the appended claims and in the detailed description, in which:

Fig.' i is a paz-ual transverse section through an emine embodying the invention;

Fig. 2 is a partial longitudinal section of the engine shown in Fig. l;

Fig. 3 is a plan view of an engine rocker arm embOdyiDs the invention;

rig. 4 is a side elevation o: .me rocker am showninFlg. 3;

l"ls.5iss.transversesectionthroushtherx-izerl amitakenonline V--Vof Fis. 4;

rias:nummertransversesectionofthemen f Fig. 7 is a side elevation of a rocker arm similar to that shown in Fig. 4; and p Figs. 8 and 9 are graphs shownglubricant ow curves obtained in accordance with this invention.

Referring to the drawing and particularlyk to Figs. 1 and 2, it is seen that the valve operating mechanism comprises a rocker arm I mounted for angular movement on a hollow rocker arm shaft 2 and a push rod 3. The upward movement of the push rod 3, which is preferably actuated iny the usual manner by a cam means (not shown),

effects an angular movement of the rocker arm I about the.V shaft 2 suflicient to effect a downward -movement of the engaged valve stem 4 which in turn opens a valve (not shown). Upward movement of the valve stem 4 and closure of the associated valve (not shown) is effected by the compression spring 6 which was further compressed by the downward movement-of the valve stem 4 and which acts to cause the push rod 3 to follow its actuating cam (not shown). This method of valve operation is well known in the art and a more detailed description in this connection is unnecessary for a complete understanding of the invention.

The hollow rocker shaft 2 is supported by suitable axially spaced supports I only one of which is shown'and lubricant under pressure from a suitable source (not shown) is delivered to the in- 1 teriorof the shaft 'l by means of the pipe 8, the passage 9 in the cylinder head block I0 which communicates with the lower portion of. the threaded stud bore II', and the rocker arm support stud I2 which is provided with an axially extending groove I3, placing the lower portionof the threaded stud bore II in communication with the interior of the rocker shaft 2. The open end of the rocker shaft 2 is Isealed against the escape of lubricant by a suitable plug means I4.

'I'he rocker shaft support 'I includes a shaft engaging sleeve `5 the opposite sides of which are engaged by the sides of the hub portions of the rocker arms I. The rocker arm on the outer end of the shaft 2 is held with its hub portion abutting the sleeve 5 of the support 'I by .means of the washer I6 and cotter pin I`I. The cotter pin I'I also functions to retain the sealing I4 in the position shown. The rocker arm abutting the inner side surface of the sleeve 5 is held in this position by means of the usual compression spring I5, The valve actuating mechanism is enclosed by means of the cylinder 'headl cover` I8 which is removably secured to the cylinderhead I0 by any suitable means such as the studs I9.

Therocker arms I, which are preferablyl of l stamped and brazed construction, asbest seen` in Figs. 13 and 4, each comprises a hollow hub portion 2I having oppositely extending push rod and valve stem engaging arms 22 and 23, respectively. The outerend of the push rod engaging arm 22 is 'enlarged and provided with a tapped bore 24 adapted to receive an adjusting screw 26 having a bulb-shaped end 2I"which engages a socket in the upper end of the vpush rod 3 as shown in Fig. 1.. The outer end of the valve `stern engaging arm -23 is provided with a cam means 28 which engages the upper end of the valve stem 4 as shown in Figs. land 2. The hub portion 2| is provided with a bore 29 which registers with a transversely extendingbore 3|v in the hollow rocker shaft 2 so that the lubricant 'A delivered under pressure to the interior of shaft 2 will flow out through said registering bores and onto the outside topsurface of that portion of the of the arm 23 along which the lubricant for the' associated valve stem normally flows in passing from the hub portion to the valve stem engaging portion thereof is provided with or shaped to provide alubricant flow control operative to limit the quantity of lubricant which `reaches the associated valve stem. The flow-control means employed may vary considerably within the scope of this invention, but a preferred construction operative to produce this result consists, as best shown in Figs. 3, 4, 6 and 7, in providing the upper edge of the arm 23 with a relatively long and narrow lubricant flow control edge or surface 33 over which the lubricant must flow in passing from the hub portion to the valve stem engaging portion of the rocker arm. The rocker -arm shown in Fig. '7 is similar to that shown inFigs. 3 and 4 vand since the only differencevis in the length of the lubricant flow control edge or surface employed, like numerals are used to designate the corresponding parts of this structure. The description of Figs. 3 and 4 is applicable in all respect to the structure shown in Fig. 7 and therefore a further description in this connection is believed unnecessary for a complete understanding of the invention. l

When an engine is relatively new no appreciable quantity of the lubricant flowing down the valve stem enters the engine cylinder as there is only a.slight tolerance between the valve stem and the wall of the bore in which the valve stem is guided to permit the reciprocating valve opening and closing movements thereof. However, when the valve stem and the guide therefor have worn sufliciently to produce a clearance therebetween of as little as ve'one-thousandths of an inch, a large portion of the llubricant owing down the valve stem then enters the engine cylinder whereupon it is consumed or otherwise wasted which results in an excessive consumption of lubricant. Experiments in this connection havedetermined (l) that the quantity of lubricant which should be delivered to a single valve stem in order to insure satisfactory lubrication under all operating conditions is approximately 0.04gram per hour of engine operation, (2) that when only 0.01 gram of lubricant per hour of engine operation is delivered to a valve stem, the

result is marginal ylubrication which invariably produces'stuck valves, and (3) that when more than 0.10 of agram of lubricant is delivered to a valve stem the result is excessive lubricant consumption. Consequently, it is necessary inforder to insure proper and trouble free lubrication of l Figs. 8 and 9graphically illustrate the vfe'asibility of accomplishing the desired result by the use of a relatively long and narrow flowcontrol or metering edge or surface over which the lubricant must ow in passing from the. hub

portion tothe valve stem engaging portion of the rocker arm. Fig. 8 shows three curves A, B and C each representing the quantity of lubricant flowing over a relatively long and narrow flow control or metering edge or surface of fixed length, L, when the width, W, of such edge or `surface is varied.

These three curves were plotted from actual test data using the `ordinates to represent the quantity of lubricant flowing ting curve A was obtained by using a metering edge of an inch long and by varying the width W from 0.018-of an inch to 0.675 inch. The data for plotting curves B and C was obtained by using metering edges 1/4 and H inch in length, respectively, and by varying the width of the edge as specified with respect to 'curve A. The shaded area on the graph represents the preferred range throughout which the quantity of lubricant can be varied without producing undesirable results. of lubricant producing excessive oil consumption and line E represents the quantity of lubricant producing marginal or insuicient lubrication. Fig. 9 shows three curves F, G and H each representing the flow of lubricant obtained by using a metering edge or surface of fixed width, W, and varying the length, L, thereof. These curves were Line D represents the quantity.

plotted by selecting a width, W, on the graph shown in Fig. 8 and obtaining the corresponding abscissa to represent the length, L, of the metering edge or surface. The shaded area and lines D and E represent the same conditions as specified with respect to Fig. 8. Curve F was obtained using an edge width of 0.07 of an inch and curves end ofthe rocker arm. Generally speaking. the `greater the length of the metering edge or surface employed the greater the cost of producing such an edge since more excess metal must be removed and since a greater degree of accuracy is required to maintain the width, W, within the necessary limits. lEntirely satisfactory results have been obtained in producing and using metering edges having a length of approximately of an inch and a width varying between 0.025 and 0.035 of an inch.

I t should be understood that although the inventio'n has been shown as applied to the type of rocker arm generally employed on an overhead valve type of engine, the invention is not limited to this type ofrocker arm as the invention is obviously applicable to any type of rocker arm having a valve actuating portion overrwhich lubricant must flow in passing from the hub portion of the rocker arm to the valve stem engaging portion thereof. Moreover, the valve stem engaging portion of rocker arm may be provided with or shaped to provides. lubricant flow control or metering means other than the relatively long and narrow edge .or surface herein shown and described and it should therefore be obvious that it is not intended to limit the invention to the exact details of construction and arrangements of parts herein shown and described as various modifications withinthe scope of the appended claims may occur to persons skilled in the art.

It is claimed and desired to secure by Letters Patent:

1. In an engine having a rocker. arm, means for delivering lubricant to said rocker arm, and

means for conducting a predetermined quantity GV and H were obtained using edge widths of 0.05 and 0.03 of an inch, respectively.

From a consideration of the curves A, B and C of Fig. 8 and curves F, G and H of Fig. 9 it is readily seen (l) that when the length of the flow control or metering edge or surface is much less than 1% of an inch even a knife edge will permit the passage of entirely too much lubricant and in this connection, actual tests have demonstrated `this to be true when the length of the metering edge is as much as 1/5 of an inch, (2) that when the width of the metering edge or surface is even as much as 0.067 of an inch the length of the metering'edge or surface must be in excess of H of an inch in order to prevent en excessive consumption of lubricant, and (3) that the best results are obtained using a metering edge or surface having a length width ratio, i. e., the length divided by the width, equal to or greater than four. The metering edge or surface 33 as shownV in Figs. 3, 4, 6 and 7 is devoid of means operative to confine lubricant thereon, i. e. the edge or surface 33 has no appreciable impediment to the flow of lubricant from said surface in a direction transverse with respect to the direction the lubricant flows thereover in passing from the hub portion of the rocker arm to the valve stem engaging end thereof. Consequently, the lubricantpassing thereover is free to flow laterally therefrom and as a result only that portion of the lubricant which is retained on said edge or surface primarily b y surface tension and its adhesion thereto passes over the said edge or surface and to the valve stem engaging of said lubricant to a part on said rocker arm which engages mechanism operatively associated therewith comprising a relatively narrow surface portion of said rocker arm over which lubricant flows in passing to said part and on which the lubricant flowing thereover is substantially solely retained by its surface tension and adhesion to said surface portion, said surface portion having an effective length width ratio such that said predetermined quantity. of lubricant adheres thereto and flows thereover to the said part.

2. In an engine having a rocker arm, means for delivering lubricant to said rocker arm, and means for conducting a predetermined quantity of said lubricant to a part on said rocker arm which engages mechanism operativelyassociated therewith comprising a surface portion of said rocker arm over which lubricant flows' in passing to said part and on which the lubricant flowing thereover is preponderantly retained by its surface tension and adhesion to said surface, said surface portion having an effective length-width ratio such that said predetermined quantity of lubricant adheres thereto and ows thereover to the said part.

3. In an engine, a rocker arm, mechanism operatively connected with a part of said rocker arm, means for flowing lubricant onto a portion offsaid rocker arm which is spaced from said part, and means for conducting a predetermined quantity of said lubricant from said portion toy eratively connected with a part of said rocker arm, means for flowing' lubricant onto a portion of said rocker arm which is spaced from said part, and means for conducting a predetermined quantity of said lubricant from'said portionto said part comprising an intermediate surface portion of said rocker arm having no appreciable impediment to the ow -of lubricant from said surface in a direction which is transverse with respect to the direction the lubricant flows thereover in passing from said portion to said part,

.said surface having a length greater than oneeighth of an inch' and an effective length-width ratio such that, primarily because of the surface tension of said lubricant-and its adhesion to said surface, said predetermined 'quantity of lubricant flows over said surface and onto said part.

5. In anv engine, a rocker arm, mechanism oplera'tively connected with a part of said rocker arm, means for iiowing lubricant onto a portion part, and means for conducting a predetermined quantity of said lubricant from said portionvto said part comprising an'intermediate portion of said rocker arm presenting a relatively narrow and upwardly facing surface having no appreciable impediment to the flow of lubricant from a,ass,ss1

termined quantity of said lubricant from said portion to said part comprising an intermediate portionV of said rockerarm presenting a substaniially flat and relatively narrow top surface over which lubricant flows in passing from said portion tosaid part, said surface having an effective. length-width ratio such that, primarily be cause of the surface tension.` of said lubricant and its adhesion to said surface, said predetermined quantity of lubricant flows over said surface and onto said part.

7. In an engine, a rocker arm, mechanism operatively connected with a part of said, rocker arm, means for owing lubricant onto a'portion 4of said rocker arm. which is spaced from said part, and means-forconducting a predetermined quantity of said lubricant from said portion to said partcomprising an intermediate portion of said rocker arm presenting a substantially flat and relatively narrow top vover which lubricant A flows in passing from said portion to said part,

. of said rocker arm which is spaced from sus said surfacehaving a length greater than oneeighth of an linch and an effective length-width ratio such that, primarily because of the surface tension of said lubricant audits adhesion tc said surface. said predetermined quantity of 8; An engine rocker arm'comprising a hollow hub portion having a bore therein arranged to f conduct lubricant from the interior of said hub portion to the outside surface thereof, and means said surface in a direction which is transverse with respect to the direction 4the lubricant flows,l thereover in passing from said portion tosaid' part. said surface having an' effective lengthwidth ratio Vsuch that. primarily because of the surface tension of said lubricant and its adhesion to said surface, said predetermined quantity of lubricant flowsl over said .surface and onto said part.

6. l,In an engine. a rocker arm, mechanism opi Veratively connected with a part of said rocker arm. means for'flowing lubricant onto a portion of said rocker arm which is spacedv from said part', and means for conducting a predefor conducting a predeterminedquantity of saidV lubricant from said outside surface to one end of said arm comprising an intermediate surface portion of said arm having no appreciable impediment to the flow of lubricant from said surface in a direction which is transverse with respect-.tothe direction the lubricant flows thereover in passing from said hub portion to said 'one' end. said surface having an effective lengthwidth ratio ,such that, primarily because' of the surface tension of said lubricant and its to said surface, said predetermined quantity of lubricant iiows over said surface and on the said CHARLES 'raum on'anaow.V

one end.

lubricant hows overI said surface and onto said

Images