US2063567A - Internal combustion engine - Google Patents

Description

Dec. 8, 1936.

M. TIBBETTS 2,063,567

INTERNAL COMBUSTION ENGINE Filed March '21,. 1932 i 3 Z .24 III/III 6 2:1" 35 I j :rtafi 1-9 Z1 fJE E Patented Dec. 8, 1936 I I UNITED STATES PATENT OFFICE INTERNAL COMBUSTION ENGINE- Milton Tibbctts, Detroit, Mich., assignor to Packard Motor Car Company, Detroit, Mich., a corporation of Michigan Application March 21, 1932, Serial No. 600,095

7 Claims. (01. 123-90) This invention relates to internal combustion Other objects of the invention will appear from engines and particularly to the valve mechanism the following description taken in connection clearance adjustment. with the drawing, which forms a part of this spe- It has previously been proposed to use a valve cification, and in which:

mechanism adjuster in which the rocker arms Fig. 1 is a vertical transverse section through of the valve mechanism are regulated hydraulian engine which includes an embodiment of the cally to compensate for expansion and contracinvention, and

tion due to temperature variations. The prior art Fig. 2 is an enlarged View of a portion of Fig. 1.

shows such a mechanism adapted both to over- Referring to the drawing, I0 illustrates an en head valves and to valves for L-head engines. In gine comprising a cylinder block I I, a crank case 10 each case the take-up device includes a hydraulil2, integrally attached to the cylinder block, and cally controlled piston and a valve located in the IS illustrates the cam shaft carried on suitable piston to permit the venting of air from the oil bearings in the engine. A valve I4 which may and to permit replacement of such oil which be either an intake or an exhaust valve, mounted may have leaked past the piston during operation in the cylinder block, is normally urged to closed 15 of the device. position by a spring I6. The drawing also shows The construction shown in the prior art dea tappet member I! below the valve for transpends for its operation on the incompressibility mitting thereto the opening force from the cam of the oil, and consequently it is extremely imshaft I3. Between the cam shaft and the tappet portant that the air be removed therefrom, and is located a rocker arm I8 pivoted on a cylindrical 20 that the parts be manufactured so accurately surface I9 the nature of which is to be further that the amount of oil that leaks past the piston described. Thus as the cam shaft I3 rotates, it will be reduced to a minimum. Since all oil has transmits an opening force through the rocker 1 some air entrapped therein, and since a leakarm roller 2i, rocker arm I8, and the tappet H to proof piston is not inexpensive to manufacture, the valve I4, opening the valve and compressing 25 this construction is not altogether desirable in the spring I6. As soon as the cam on the cam some types of engines, particularly those in which shaft has rotated past the roller 2|, the spring low cost is an important item. I6 is then effective to close the valve and cause It is one of the objects of this invention to dethe rocker arm roller 2I to tend to follow the convise a valve take-up mechanism which will not tour of the cam. 30 be subject to the above mentioned objections to Due to manufacturing variations, the length a hydraulically controlled mechanism. of the several valve stems in a multi-cylinder en- Another object is to reduce the number of parts gine will not be the same, and due to temperature required to maintain a valve mechanism in revariations and wear, the length of each stem will duced clearance relationship under all conditions not be a constant. Normally, there is a certain 35 of temperature and wear. clearance between the parts of the valve mecha- Another object of the invention is to provide a nism just described. An inspection of the drawvalve take-up mechanism which depends entirely ing will indicate that if the cylindrical surface I9, upon inertia to maintain a minimum clearance about which the rocker arm pivots, is moved upin the parts of the valve operating system. wardly, it will tend to tilt the rocker arm and in- 40 Still another object of the invention is to procrease this clearance and if it is moved downvide a valve take-up mechanism in which a rewardly, such movement will tend to reduce the silient means tends to reduce the clearance beclearance. It is the purpose of this invention to tween the parts of the valve mechanism, and the provide a novel mechanism for accomplishing inertia of a mass tends to maintain the clearance, this movement and for controlling it. 45 both the resilient means and the inertia of the Referring particularly to Fig. 2, it is seen that mass permitting an expansion of the parts of the the cylindrical surface I9 forms the outer surface valve mechanism, due to heat, for example, withof an eccentric member 22 which is journaled on out causing riding of the valve upon its opening a shaft 23 the center of which is removed from mechanism. the center of the cylindrical surface I9. Thus, 50

A further object of the invention is to provide rotation of the eccentric member 22 about the a valve take-up mechanism in which a mass will shaft 23 will raise or lower the center 24 of the assist in reducing the clearance and resist any surface I9 and tilt the rocker arm to increase or tendency undesirably to increase the clearance in decrease the clearance. Projecting from the ec l the valve mechanism. centric at one side of the rocker arm I8 is an x r O arm member 26 against which bears the end 21 of a lever 28. This lever is mounted on a pivot 29 which in turn is suppomd by a rocker arm box 3| bolted to the side of the crankcase in operative adjacency to the camshaft and valve tappet or stem. The box 3| serves also to support the shaft 23 in suitable bearings, not shown, and has projecting inwardly therefrom an arm 32, the purpose of which will later be evident. The construction shown permits the removal from the engine, as a unit, of the entire rocker arm and the mechanism for automatically maintaining the desired clearance in the valve mechanism.

Between the arm 32 and the lever 28 is located a resilient member, such as a spring 33, which normally tends to oscillate the lever 28 in a counter-clockwise direction about the pivot 29. This rotation of the lever causes the arm' 2'! thereof to bear upwardly against the nose 26 projecting from the eccentric and tends to cause a clockwise rotation of the eccentric about the shaft 23. This latter rotation in turn tends to move the center 24 of the cylindrical surface l9 downwardly and tends to cause the rocker arm 18 to move to a position in which there is a minimum clearance between the cam shaft, the rocker arm, and the tappet, or valve stem, in case the tappet is-omitted. Thus, we have a resilient yieldable member 33 continually urging the parts of the valve operating mechanism into a reduced clearance relationship.

When the cam shaft [3 tries to open the valve,

the rocker arm l8 is urged against the end of the valve tappet or valve stem and, because of the resistance due to the valve spring it, there is a tendency for the right-hand end of. the rocker arm to push the cylindrical surface l9 upwardly,

rotating the eccentric 22 about its center on the shaft 23. Such upward movement of the surface I9 is, of course, undesirable because it brings a reduction in the valve opening movement. Such upward movement of the surface must be resisted and to provide such a resistance I use a mass 34, the inertia of which is sufficient to resist such movement. In order that a small mass may have sufiicient inertia effect, I mount a mass 34 at a considerable distance from the pivot 29 of the lever 28 and I make the arm 21 of the lever as short as is possible. Thus, when the cam shaft l3 tends to rotate the eccentric 22 in a counterclockwise direction about the center of the rocker arm shaft 23, the nose 26 of the eccentric tends to rotate the lever 28 in a clockwise direction about the pivot point 29. This movement is resisted by the inertia of the weight 34.

It is evident that the only essential element of the arrangement of the parts is that the spring 33 be so located with respect to the nose 26 on the eccentric as to tend to reduce the clearance in the valve mechanism and that the movement of the mass 34, which opening of the valve tends to cause, be resisted by inertia of the mass.

Thus, there is no necessity for having the mass 34 located in such a way that gravity will tend to reduce the clearance in the valve mechanism. I have, however, shown the parts arranged in such a way that the gravitational attraction for the mass 34 will assist the spring 33 in reducing the clearance in the valve mechanism when the valve mechanism is at rest, that is to say, after the valve has been opened.

Under certain circumstances, it is conceivable that the spring 33 could be dispensed with if the weight 34 were so located with respect to the pivot point 29 that gravity would be able to effect a decreased valve clearance. However, in high speed engines, it is preferable to rely primarily on the spring 33 to reduce the clearance in the valve opening mechanism and to rely on the inertia of the mass 34 to maintain this reduced clearance during opening operation of the mechanism.

The above described construction operates, during the closing movement of the valve and during idle operation of the valve mechanism, to decrease the clearance, by means of the lever 28 and the eccentric 22, which latter also may be considered as a lever, both levers being urged by the spring 33 to move the rocker arm I8 into a minimum clearance position. If the engine, and consequently the valve stem I4, is cold, the spring 33 will be able to take up considerable clearance, but as the valve stem I4 warms up and expands axially, it will have a tendency to compress the spring 33 through the several levers. The spring 33 is designed and installed in such a way that its strength is insufiicient to overcome the valve closing tendency of the valve spring I6. Thus the eccentric is rotated counter-clockwise upon warming up of the engine and. no riding of. the valve will occur.

While I have herein described in some detail a specific embodiment of my invention, which I deem to be new and advantageous and may specifically claim, I do not desire it to be understood that my invention is limited to the exact details of the construction, as it will be apparent that changes may be made therein without departing from the spirit or scope of my invention.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. In an intermittent valve opening mechanism, a valve, a cam actuated means associated therewith to open said valve, means including a plurality of levers to position said opening means in unvarying close relation to said valve after opening thereof, and a mass of sufficient inertia associated with said levers to maintain said parts in said close relation during subsequent opening movement of said mechanism.

2. In a valve gear mechanism, a valve tappet actuating rock lever, and fulcrum means for the rock lever comprising a rotatably mounted eccentric bushing and a weighted control member acting solely as an inertia device disposed in relation with the bushing to retain it in a. position whereby the rock lever is maintained in continuous contact with the tappet.

3. In an engine, valve gear mechanism comprising a earn, a tappet spring pressed toward the cam, a rocl: lever having a free end intermediate the cam and the tappet, a pair of shafts fixed to the engine, a bushing having a projecting arm rotatably mounted eccentrically on one shaft, said rock lever being journaled on the bushing, a lever fulcrumed on the other shaft, said lever having one end engaging the bushing arm, a weight fixed to the other end of the lever, the inertia of said weighted lever co-acting with the arm to retain the bushing in a position to maintain the rock lever in constant contact with the tappet, and a spring carried by the engine and exerting pressure against the lever to apply a force thereto in a direction to have the same effect on the bushing as that resulting from the inertia of the weight.

4. In a valve gear, a cam, a tappet spring pressed toward the cam, a rock lever intermediate the cam and the tappet, a fixed lever supporting shaft, a bushing rotatably mounted eecentrically on the shaft, said lever being mounted '75 on the bushing, an arm extending from the bushing, a lever having one end engaging said arm, and a mass on the other end of the arm, said weighted lever exerting continuous pressure against the arm in a direction to hold the hearing in a position on its shaft maintaining the rock lever in constant contact with the tappet.

5. In a valve mechanism, the combination of a spring-closed valve, means for opening the valve, reversible take-up means between the valve opening means and the valve, and means including an inertia element tending to resist, solely by its inertia action, the displacement of said take-up mechanism during the opening movement of the valve.

6. In an internal combustion engine, the combination with the engine valve, the cam shaft for operating the valve, and an intermediate device between the cam shaft and the valve, of a clearance take-up mechanism operating in conjunction with said intermediate device and comprising a lever arm, a weight thereon, resilient means associated with the lever arm tending to decrease the valve clearance, and connections between the lever arm and said intermediate device whereby the weight by reason of its inertia forms the principal element maintaining the valve clearance substantially constant.

7. A clearance take-up device for a valve mechanism including a cam shaft and a valve, said device comprising a lever connected to said mechanism, resilient means connected to said lever tencling to reduce the clearance in the mechanism, and a mass of sufficient inertia operating in connection with said lever to resist any tendency undesirably to increase said clearance during operation of the mechanism.

MILTON TIBBE'I'IS.

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