US2997991A

US2997991A - Variable valve timing mechanism for internal combustion engines

Info

Publication number: US2997991A
Application number: US7367A
Authority: US
Inventors: Henry A Roan
Original assignee: Individual
Current assignee: Individual
Priority date: 1960-02-08
Filing date: 1960-02-08
Publication date: 1961-08-29
Anticipated expiration: 1978-08-29

Description

H. A. ROAN Aug. 29, 1961 VARIABLE VALVE TIMING MECHANISM FOR INTERNAL COMBUSTION ENGINES 3 Sheets-Sheet 1 Filed Feb. 8, 1960 INVENTOR. figs/way A.R0A- z WWW I02; wzmao NN PR ON BN mm mm ATTORNEYS Aug. 29,

H. A. ROAN VARIABLE VALVE TIMING MECHANISM FOR INTERNAL COMBUSTION ENGINES Filed 3 Sheets-Sheet 2 llli I l I 40 2 1|. I I 22 I /j I I i I 23 32 \I \l l J. I, l

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I 'ii' I /8 4 /r i N I Z2 i I 9, 32 x I 115ml m l ll VENTOR. HENRY ROAN A T TOPNEYS Aug. 29, 1961 ROAN 2,997,991

VARIABLE VALVE TIMING MECHANISM FOR INTERNAL COMBUSTION ENGINES Filed Feb. 8, 1.960 5 Sheets-Sheet 3 FIG. 6

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HENRY A. RaAN ATTORNEYS 2,997,991 VARIABLE VALVE TIMING MECHANISM FOR INTERNAL COMBUSTION ENGINES Henry A. Roan, 1308 Harmon Place, Minneapolis, Minn. Filed Feb. 8, 1960, Ser. No. 7,367 8 Claims. (Cl. 123--90) My invention relates generally to improvements in variable valve timing mechanisms for internal combustion engines, and more specifically to such mechanisms for engines of the overhead valve variety.

More particularly, my present invention is in the nature of an improvement on the mechanism disclosed and claimed in my prior United States Letters Patent 2,880,- 711.

An important object of my invention is the provision of highly simplified means for varying the valve timing of an internal combustion engine, whereby to attain a maximum of operating efiiciency of the engine over the entire range of operating speeds of the engine.

Another object of my invention is the provision of variable valve timing mechanism for engines having a rocker arm operatively associated with the valve, a push rod operatively associated with said rocker arm, and an engine driven cam for imparting longitudinal reciprocatory movements to said push rod, said mechanism including an oscillatory cam interposed between said push rod and rocker arm, and of novel means for shifting the field of oscillatory movement of said cam relative to said rocker arm.

Another object of my invention is the provision of mechanism as set forth, wherein said oscillatory cam engages a working face of the rocker arm, said working face being normally disposed at an oblique angle to the direction of reciprocatory movement of said push rod, shifting movement of said oscillatory cam being in a direction generally parallel to said working face of the rocker arm and simultaneously circumferentially on the axis of said oscillatory movement.

Another object of my invention is the provision of novel mounting means for said oscillatory cam, whereby the same is guided in said shifting movement generally parallel to the rocker arm working face.

Still another object of my invention is the provision of variable valve timing mechanism as set forth, which may be mounted on overhead valve equipped engines without substantially modifying the engine structure.

Another object of my invention is the provision of variable valve timing mechanism which is relatively inexpensive to produce an install, which is highly efiicient in operation, and which is rugged in construction and durable in use.

The above, and still further highly important objects and advantages of my invention will become apparent from the following detailed specification, appended claims and attached drawings.

Referring to the drawings, which illustrate the invention, and in which like reference characters indicate like parts throughout the several views:

FIG. 1 is a fragmentary view in transverse section of a portion of a conventional internal combustion engine of the overhead valve type, showing my invention in connection with the valve train of one of the valves thereof;

FIG. 2 is an enlarged fragmentary view in top plan, as seen from the line 22 of FIG. 1;

FIG. 3 is a fragmentary transverse section taken on the line 3-3 of FIG. 2;

FIG. 4 is a fragmentary detailed end section, taken on the line 44 of FIG. 2;

FIG. 5 is a fragmentary transverse section taken substantially on the line 55 of FIG. 2;

FIG, 6 is a fragmentary transverse section taken on Patented Aug. 29, 1961 the line 6-6 of FIG. 2, some parts being broken away;

FIG. 7 is a view corresponding substantially to FIG. 6, but showing a different position of some of the parts;

FIGS. 8 and '9 are views corresponding to FIGS. 6 and 7 respectively, but showing a modified form of rocker arm construction, on a reduced scale; and

FIGS. 10 11 and 12 are diagrams showing the valve timing obtained by my invention at high, medium and low engine speeds respectively.

In the prefered embodiment of my invention illustrated in FIGS. 1-7 an internal combustion engine, shown fragmentarily in FIG. 1 is indicated in its entirety by the numeral 1, and comprises a cylinder block 2 defining a cylinder 3, and a crankcase, indicated generally at 4. A piston 5 is slidably mounted for reciprocatory movement in the cylinder 3, and is provided with the usual wrist pin or piston pin 6, to which is mounted a connecting rod 7 which may be assumed to be journalled at its lower end to the engine crankshaft not shown.

The engine further includes a cylinder head 8 which is bolted or otherwise rigidly secured to the top of the block 2, the head 8 being sealed to the top of the cylinder block by the usual gasket 9. The cylinder head 8- cooperates with the cylinder 3 to define a combustion chamber 10 which is adapted to communicate with a gas passage 11 by means of a poppet valve 12 that is provided with an elongated valve stem 13 slidably mounted in a guide bushing or the like 14 carried by the head 8. Although one valve 12 is shown, it will be appreciated that each cylin: der 3 is provided with a pair of such valves, one thereof being an intake valve, and the other thereof being the exhaust valve.

The valve stem 13 extends upwardly of the cylinder head 8, and at its upper end is provided with the usual washer 15, between which and the upper end of the valve guide bushing is interposed a coil compression spring 16 which yieldingly urges the valve 12 toward its closed position in engagement with its respective valve seat 17 formed in the cylinder head 8.

For the purpose of the instant example, the poppet valve 12 may be assumed to be the intake valve for the combustion chamber 10, the same being adapted to be opened against yielding bias of the valve spring 16, by a rocker arni 18. The rocker arm 18 is journalled, intermediate its ends, on a tubular bearing shaft 19 that extends generally longitudina-lrly of the engine 1, and which is supported in overlying spaced relation to the cylinder head 8 by a plurality of brackets 20', one of which is shown, the brackets being bolted or otherwise rigidly secured to the cylinder head, as indicated at 21. In FIG- URE 2, a second rocker arm 22 is also shown as being journalled on the tubular bearing 19, and it may be assumed that the rocker arm 22 is operatively associated with the exhaust valve, not shown, to the combustion chamber 10, or with a valve affording communication to one of the other combustion chambers of the engine. As shown, one end of each of the

rocker arms

18 and 22 are provided with lock nut-equipped headed screws 23 that engage the upper ends of their respective valve stems. Further, with reference to FIG. 1, it will be seen that the rocker arms, together with parts associated therewith, are enclosed by a cover element 24 releasably secured to the top of the cylinder head 8', in the usual manner.

In FIG. 1, the engine 1 is shown as being provided with the usual cam shaft 25 which is driven from the engine crankshaft in the usual manner, and on which is mounted a rotary cam 26 that engages a tappet 27 slidably mounted in the engine block 2. A conventional push rod 28 extends upwardly from the upper end of the tappet 27, terminating at its upper end within the con fines of the cover element 24 and in downwardly spaced relation to the adjacent end 29 of the rocker arm 18. The upper end of the push rod 28 is provided with the usual rounded head which heretofore made engagement with the adjacent end of the rocker arm, to move the same in a direction of rocking movement to open the valve associated therewith.

. With reference to FIGS. 1, 3, 6 and 7, it will be seen that the end portion 29 of the rocker arm 18 is formed at its bottom side to provide a flat downwardly directed cam-engaging working face 31 which normally slopes longitudinally inwardly and downwardly of the rocker arm 18, and which is normally disposed at an oblique angle to the extended axis of the push rod 28.

Interposed between the upper end of the push rod 28 and the working face 31 of the rocker arm 18 is an oscil latory cam 32 that is journalled on a mountingbar or shaft 33carried by the several brackets 20 in spaced parallel relation to the rocker arm bearing shaft 19. At its lower portion, the oscillatory cam 32 is provided with a hemispherical recess 34 which receives the rounded head 31) of the push rod 28, the upper portion of the cam 32 having a lobe surface 35 that engages the working face 31 of the rocker arm 18. Yielding means, such as a coil spring 36 is suitably connected at one end to the oscillatory cam 32 and at it-s'other end to the mounting bracket 20, to yieldingly urge the cam 32 in one direction of its oscillatory movement about the axis of the shaft 33, preferably in a direction to move the lobe surface 35 away from the Working face 31 of the rocker arm 18. 1t willbe noted, particularly with reference to FIGS 1, 3, 6 and 7, that the recess 34 is disposed laterally outwardly with respect to a vertical center line of the bearing shaft 33, so that the push rod 28 engages the oscil latory cam 32 at the outer side of dead center relationship between the axis of oscillatory movement of the cam 32 and the opposite or lower end of the push rod 28. Hence, upward movement of the push rod 28, responsive to rotation'of the cam 26, will impart'oscillatory move ment to the oscillatory cam 32 against bias of the spring 36 to move the rocker arm 18 in a direction to open the valve 12, against yielding bias of its spring 16.

For the purpose of shifting the field of oscillatory movement of the cam 32 about its axis of oscillatory movement, the mounting bar or shaft 33 is movable with respect to the mounting brackets 20, selectively in Opposite directions generally parallel to the downwardly slop ing Working face 31 of the rocker arm 18. Each mounting bracket 20 is formed to provide a slot or guideway 37 that extends transversely of the axis of the shaft 33 and which supports said shaft. 'A guide shoe or the like 38 is slidably mounted in the slot 37, and is rigidly secured to the shaft 33 by a machine screw or the like 39, see particularly FIG. 5. The guide shoe 38 supports the shaft '33 in the slot 37 and holds the shaft 33 against rotation. It will be appreciated that, although but one guide shoe is shown, each of the several brackets 20 will be slotted as indicated at 3'7, and each thereof will be provided with a guide shoe identical to the guide shoe 38. It will be further appreciated that each of the several rocker arms, such as

therocker arms

18 and 22, will be operated by a different cam 32, each cam 32 being independently oscillated by its respective push rod 28.

Move ment of theshaft 33 in either direction longitudinally'of the slots 37 is achieved through suitable control mechanism including a control shaft 40; a plurality of eccentric elements 41, one of which is shown, rigidly secured to the control shaft in axially spaced relationship,

, and a plurality of crank arms 42, one of which is shown.

Each crank arm 42 is journalled at one end on the bar or shaft 33, and at its other end on one of the eccentric elements '41, whereby rotation of the control shaft 40 will cause the mounting shaft 33 to be bodily moved toward or away from the inner end of the slots 31 in "the mounting brackets 20. As shown, the control'shaft 40 is 'journalled in the brackets 29cm an axis parallel to the 7 axes of the shaft 33 and rocker arm bearingshaft 19.

The control shaft 40 may be rotated selectively in either direction by any suitable and well-known means, not shown, governed by the speed of the engine, or manually if desired.

As is customary with engines using overhead valves, the bearing shaft 19, being tubular, is utilized to supply lubricantto the

rocker arms

18 and 22. The proper lubricant, such as engine oil, is pumped to the interior of the bearing shaft 19 from whence it flows outwardly through radial openings 43 to lubricate the rocker arm. For the purpose of lubricating the oscillatory cams 32 and the upper end 30 of the push rod 28, the rocker arms are provided with oil passages 44 which are adapted to reg-- ister with the passages 43' and conduct lubricant to the working faces 31 of the several rocker arms. The oscillatory cams'32 are provided with internal channels 45 and radial passages 46 and 47', the former of which communicate with their respecdve channels 45 and'the lobe surfaces 35, and the latter of which communicate with the channels 45 and their respective recesses 34. With reference to FIG. 5, it will be seen that the tubular hearing shaft 19 is provided with other radial passages 48 which register with passages 49 in the brackets 20, which passages 49 extend to the slots 37, whereby to lubricate the cam mounting bar or shaft 33 and the several guide shoes 38. If desired, and as shown, in FIG. 2, set screw equipped spacing washers or collars 50 may be mounted on the shaft 33 to properly locate the several cams 32 and crank arms 42 in the desired axially spaced relationship to the mounting brackets 20. In FIGS. l-6, the various parts are positioned, with the valve 12 in a closed position, to provide optimum valve timing for low speed engine operation. With the parts thus positioned, and with reference particularly to FIGS. 3 and 6-, it will be seen that the angular relationship between the working face 31 and the lobe surface 35 is such that the cam 32 must rotate a substantial number of degrees in a clockwise direction before the lobe surface 35 imparts lifting movement to the end portion 29 of the rocker arm 18. With the cam 32 thus initially positioned, the valve timing for the engine will be as indicated in FIG. 12, the intake valve 12 opening at substantially 10 degrees after top dead center and closing at substantially '30 degrees past bottom dead center. The diagram of FIG. 12 also indicates at what pointsthe exhaust valve opens and closes relative to theopening and closing of the intake valve 12.

When the control shaft isrotated from its position shown in FIG. 3, the several crank arms 42 move the cam mounting shaft 33 to its position of FIG. 7. This inward movement of the shaft 33, combined with the angular relationship between the direction of bodily movement of the shaft 33 with respect to the axis of the push rod 28, causes the oscillatory cam 32 to rotate to its position of FIG. 7 against bias of the spring'36, whereby to diminish the angle between the working face 31 and the cam lobe surface 35'; With the cam 32 thus positioned, the cam 32 operatively engages the end portion 29 of the rocker arm' 18 to impart rocking movement thereto in a valve opening direction immediately upon upward movement of the push rod 28; Thus, the 180 rotation of the control shaft 40 causes the field of oscillatory movement of the cam 32 to be shifted and the resultant valve timing is substantially that indicated in FIG. 10, wherein it is seen that the intake valve 12 opens substantially 30 degrees earlier than its point of opening at low speed, closing of the intake valve occurring at 60 degrees past bottom dead center or 30 degrees later than at low engine speed. A 790 degree rotation'of the control shaft 40 will result in valve timing substantially as shown in FIG. 11, which indicates the'relative positions of valve openingand closing at medium engine speeds. a s

The above-described structure is such that the shaft 33 moves approximately one-fourth inch between :its low engine speed position and its high engine speed position,

this movement results in a rotation of the oscillatory cam 32 of 15 of circular arc. At the low speed setting of the cam 32, said cam is rotated 15 of its oscillatory movement by the push rod 28 toward the rocker arm working face 39, before movement of the rocker arm 18 in a valve opening direction occurs. As above indicated, when the oscillatory cam 32 is adjustably moved 15 by movement of the mounting shaft 33 to its inward position of FIG. 7, the cam 32 immediately begins to move the rocker arm toward a valve open position upon upward movement of the push rod 28. Inasmuch as the crank shaft, not shown, of the usual internal combustion engine, makes two revolutions for each single revolution of the cam shaft such as the cam shaft 25, it will be obvious that rotation of the oscillatory cam 32 to the extent of 15 of circular arc will result in a difference of 30 of rotary movement of the crank shaft between opening of the valve 12 at low and high engine speeds. Further, in view of the fact that the cam 32 oscillates to move the rocker arm 18, the time of valve closing, relative to rotation of the crank shaft, is likewise effected.

It will be noted that, due to the oblique angle between the direction of bodily movement of the shaft 33 and the axis of the push rod 28, such movement of the shaft 33 results substantially solely in rotation of the cam 32, with a minimum of lateral movement being imparted to the upper end of the push rod 28. This is made possible by the oblique angle between the direction of shaft movement and the axis of the push rod 28. Obviously, if the direction of movement of the shaft 33 were at a right angle to the push rod 28, little if any rota-tion would be imparted to the cam 32, and the push rod 28 would merely swing laterally in accordance with such shifting movement. Obviously by reducing the angle between the direction of bodily movement of the shaft 33 and the axis of the push rod 28, a given amount of movement of the shaft 33 would result in a greater angular displacement of the oscillatory cam 32.

FIGS. 8 and 9 show the oscillatory cam 32 as being utilized with a modified form of rocker arm. In this arrangement, the mounting bracket, cam supporting shaft, guide shoe, and control shaft, are identical to those of FIGS. l-7, and carry like reference numerals. In FIGS. 8 and 9 a rocker arm 51 is shown as being journalled on the tubular bearing shaft 19, the arm 51 having a valve stem engaging end 52, the opposite end of the arm 51 having a generally vertically disposed adjustment screw 53 screw threaded therein and being provided with a lock nut 54. The adjustment screw 53 is provided at its lower end with a reduced stem 55 that is received in an upwardly opening socket 56 of a cam-engaging plate 57 which defines a downwardly directed cam-engaging working face 58 equivalent to the working face 31 of the structure shown in FIGS. 1-7. As shown, the inner end of the cam-engaging plate 57 slidably engages the adjacent side of a lug 59 on the rocker arm 51 to permit vertical adjustment movement of the plate 57 and to prevent rotation thereof on the axis of the adjustment screw 53. The operation of the structure of FIGS. 8 and 9 is identical to that of the structure of FIGS. 17.

My invention has been thoroughly tested on a plurality of internal combustion engines, and has enabled these engines to operate with a high degree of eificiency not heretofore obtained by fixed valve timing at low as well as at high engine speeds. While I have shown and described a preferred embodiment of my novel variable valve timing mechanism, and a single modified form thereof, it will be understood that the same is capable of further modification without departure from the spirit and scope of the invention, as defined in the claims.

What I claim is:

1. In an engine, a valve, a valve actuating cam, and valve actuating connections between said cam and valve, said valve actuating connections including a rocker arm mounted on said engine for rocking movements and having one portion operatively associated with said valve and having a cam engaging working face directed toward and operatively associated with said cam, said cam being pivotally mounted for oscillatory movements toward and away from the working face of the rocker arm, means including a longitudinally reciprocating push rod pivotally engaging said cam for imparting said oscillatory movements to the cam, and means for independently adjustably moving said cam in opposite directions generally parallel to said working face of the rocker arm and at an oblique angle to the longitudinal dimension of said push rod, whereby said cam partakes of pivotal movement during the adjustable movement thereof to shift the field of oscillatory movement of the cam with respect to the working face of the rocker arm, said last mentioned means including an elastic element yieldingly urging said cam in one direction of the adjustable movement thereof, and a crank and cooperating connecting rod for moving said cam in the opposite direction against the bias of said elastic element.

2. In an engine, a valve, a valve actuating cam, and valve actuating connections between said cam and valve, said valve actuating connections including a rocker arm mounted on said engine for rocking movements and having one portion operatively engaging said valve and having a cam-engaging working face directed toward said cam, means mounting said cam for oscillatory movements on an axis parallel to the axis of rocking movement of the rocker arm, a push rod mounted for longitudinal reciprocatory movements toward and away from the working face of the rocker arm and disposed at an oblique angle to the plane of the working face, engine driven means for imparting said reciprocatory movements to the push rod, one end of the push rod pivotally engaging the cam radially outwardly of the axis of oscillatory movement of the cam and at one side of dead center relationship therebetween, the cam mounting means being movable in opposite directions generally parallel to the working face of the rocker arm, means for imparting adjusting movements to the cam mounting means in said opposite directions, the angular relationship between said push rod and the direction of movement of the cam mounting means being so arranged that the cam will notate on its axis of oscillatory movement responsive to said movement of the cam mounting means in one direction whereby to shift the field of said oscillatory movement of the cam angularly with respect to the working face of the rocker arm.

3. The structure defined in claim 2 in which said means for imparting adjusting movements to the cam mounting means comprises a rockshaft, an eccentric on said rockshaft, and a connecting rod journalled on said eccentric and connected to said cam mounting means.

4. The structure defined in claim 2 in which said cam mounting means comprises a shaft having its axis extending generally parallel to the axis of rocking movement of the rocker arm, said cam being journalled on said shaft for said oscillatory movements.

5. The structure defined in claim 2 in further combination with spring means yieldingly urging said cam in one direction of said oscillatory movement, said push rod imparting oscillatory movements to the cam in the opposite direction against yielding bias of said spring means.

6. In an engine, a valve, a valve actuating cam, and valve actuating connections between said cam and valve, said valve actuating connections including a rocker arm, bracket means mounting said rocker arm intermediate its ends for rocking movements, said rocker arm having one end portion operatively associated with said valve and a cam engaging working face at its other end portion direction toward said cam, means carried by said bracket and journalling said 0am for oscillatory movements on an axis parallel to the axis of rocking movement of the rocker arm, a push rod mounted for longitudinal reciprocatory movements toward and away from said working face of the rocker arm and disposed at an oblique angle to the plane of said working face, engine driven means for imparting said reciprocatory movements to the push-rod, one end of the push rod pivotally engaging the cam radially outwardly of the axis of oscillatory movement of the cam and at one side of dead center relationship therebetween, the cam journalling means being movable in opposite directions generally parallel to the working face of the rocker arm, rotary means carried by said bracket means for imparting adjusting movements to the cam journalling means in said opposite directions, the angular relationship between said push rod and the direction of movement of the cam journalling means being so arranged that the cam will rotate on its axis of oscillatory movement responsive to said movement of the cam'joun nailing means in one direction whereby to shift the field of said oscillatory movement of the cam angularly with respect to the working face of the rocker arm, said means for imparting adjusting movement to the cam journalling means including a rotary'control shaft journalled in said bracket means, an eccentric on said control shaft, and a connecting rod journalled at one end on said eccentric and at its other end on the cam journalling means.

7. In an engine including, a cylinder head, a cylinder block and a crankcase; a valve in said cylinder head, a valve actuating earn, a rocker arm mounted on said cyl-. inder head for rocking movements and having one portion operatively associated with said valve and having a cam-engaging working face directed toward and operatively associated with said cam, said cam being pivotally mounted on said cylinder head for oscillatory movements toward and away from the working face of the rocker arm, a longitudinally reciprocating push rod extending from said crank case to said cylinder head and having one end pivotally engaging said cam radially outwardly of the axis of oscillatory movement of the cam and at one side of dead center relationship therebetween, engine driven means in said crankcase imparting reciprocatory movements to said push rod to oscillate said cam, and means for independently adjustably moving said cam in directions'to shift the field of oscillatory movement thereof with respect to said working face of the rocker arm.

8. In an engine including, a cylinder head, a cylinder block and a crankcase; a valve in said cylinder head, an oscillatory valve actuating cam, 'a rocker arm mounted on said cylinder head for rocking movements and having one portion operatively associated with said valve and having a cam engaging working face directed toward and operatively associated with said cam, a longitudinally reciprocating push rod extending from said crankcase to said cylinder head and having one end pivotally engaging said cam radially outwardly of the axis of oscillatory movement of the cam and at one side of dead center relationship therebetween, engine driven means in said crankcase imparting reciprocatory movements to said push rod, means on said cylinder head mounting said cam for oscillatory movements toward and away from said working face of the rocker arm and for bodily movements generally parallel to said working face, and means for adjustably moving said cam in opposite directions of said bodily movement thereof, whereby to shift t he field of oscillatory movement of said cam.

References Cited in the file of this patent UNITED STATES PATENTS 2,260,983 Walker Oct. 28, i941 FOREIGN PATENTS 264,407 Great Britain Ian. 20, 1927