US 3878822 A
In an internal combustion engine, a plurality of valve cams associated with each intake and each exhaust valve of the engine, a cam follower associated with each valve and movable to engage and follow any one of the associated cams selectively, the cam follower moving mechanism including a mechanical device operable to bias the follower resiliently to a position to engage the desired cam, and a latch operable to secure the cam follower against movement except when the associated valve is fully closed and there is no direct operative connection between the cam and valve.
Claims available in
Description (OCR text may contain errors)
United States Patent 11 1 Real MULTIPLE CAM MECHANISM FOR INTERNAL COMBUSTION ENGINES  Inventor: Robert G. Beal, 3037 Washington Ave, Kansas City. Kans. 66102  Filed: Jan. 7, 1974  Appl. No.2 431,400
 U.S. Cl. l23/90.l6; 74/569; 123/9015  Int. Cl. FOll 1/34  Field of Search 123/9015, 90.16; 74/569  References Cited UNITED STATES PATENTS film [ Apr. 22, 1975 3,273,546 9/1966 Von Arx .f. 123/9015 Primary E.\'aminer-Manuel A. Antonakas Assistant Examiner-Daniel J. OConnor Attorney. Agent, or Firm-John A. Hamilton ABSTRACT In an internal combustion engine, a plurality of valve cams associated with each intake and each exhaust valve of the engine, a cam follower associated with each valve and movable to engage and follow any one of the associated cams selectively, the cam follower moving mechanism including a mechanical device operable to bias the follower resiliently to a position to engage the desired cam, and a latch operable to se cure the cam follower against movement except when the associated valve is fully closed and there is no direct operative connection between the cam and valve.
5 Claims, 6 Drawing Figures MULTIPLE CAM MECHANISM FOR INTERNAL COMBUSTION ENGINES This invention relates to new and useful improvements in internal combustion engines, and has particular reference to a new and novel means for providing cams of variable contours for operating the intake and exhaust valves of each engine cylinder.
In most internal combustion engines within my knowledge. each intake and exhaust valve is operated by a cam on a cam shaft driven at a speed synchronized with that of the engine crankshaft, the cams being angularly distributed around the cam shaft to cause opening and closing of the valves in proper sequence as re quired to permit operation of the engine. Also, each valve is usually provided with only a single operating cam. Many performance characteristics of the engine, at different speeds and loads, are determined by the cam contour, which controls such factors as the speed and degree of lift of the valve, and the precise moment of the engine cycle at which the opening and closing movements of the valve are initiated and terminated. On the other hand, it is well known that different operating conditions, such as in normal driving as compared to race driving in automobiles, better engine performance characteristics and efficiency can be obtained by cams having shapes specially contoured for each condition. In any engine having only a single set of cams, therefore, the cam contours must be selected either to provide the best average performance characteristics and best average efficiency under all operating conditions, such cams being commonly known as *stock cams, or they must be specially designed for particular operating conditions, such as high performance or racing" earns. Different cam contours may also be desired for engines designed for high-load operation, as compared to those designed for low-load operation. The advantages of a single engine having cams designed for a plurality of operating conditions, and being selectively usable whenever those conditions occur, are therefore obvious.
Accordingly, the principal object of the present invention is the provision, in an internal combustion engine, of a plurality of sets of cams each designed for use under a specific set of operating conditions, and control means for selectively rendering any one of said sets of cams operative as desired.
Another object is the provision of a cam mechanism of the character described in which the change or shift from one cam set to another can be made either by some manually actuated means at the will of the operator, or automatically in response to changes of some engine function, such as engine speed.
A further object is the provision of a cam mechanism of the character described which will permit shifting from one cam set to another at any engine speed, despite the fact that the cams associated with each valve can be shifted only when that valve is fully closed and the cam inoperative, and that the valves of the respective cylinders all operate at different points in a complete cycle of the engine.
Other objects are simplicity and economy of construction, and efficiency and dependability of operation.
With these objects in view, as well as other objects which will appear in the course of the specification, reference will be had to the accompanying drawing, wherein:
FIG. I is a fragmentary top plan view, partially broken away and foreshortened, ofan internal combustion engine including a cam mechanism embodying the present invention,
FIG. 2 is an enlarged, fragmentary sectional view taken on line IIII of FIG. 1,
FIG. 3 is a fragmentary sectional view taken on line III-Ill of FIG. 1,
FIG. 4 is a fragmentary sectional view taken on line lV-IV of FIG. 3,
FIG. 5 is an enlarged, fragmentary slightly irregular sectional view taken on line V-V of FIG. I, and
FIG. 6 is a fragmentary sectional view taken on line VI-VI of FIG. 5.
Like reference numerals apply to similar parts throughout the several views. and the numeral 2 applies generally to the head of an internal combustion engine, in the lower surface of which are formed a series of inline combustion chambers 4 (see FIG. 5) to which an air-gas mixture is supplied by an intake passage 6 controlled by an intake valve 8 cooperating with a valve seat 10, and from which the spent combustion gases are later exhausted through an exhaust passage 12 controlled by an exhaust valve 14 cooperating with a valve seat 16. As is well understood in the art, each combustion chamber 4 communicates with a cylinder formed in the engine block, in which a piston is reciprocally slidable by the properly timed sequence of opening and closing of the valves, and ignition of the explosive airgas mixture. In a four-cycle engine, the sequence of piston strokes is a first downward intake stroke in which valve 8 is open, a second upward compression stroke in which both valves are closed, ignition, a third downward power stroke in which both valves remain closed, and a fourth upward exhaust stroke in which valve 14 is open. It will be further understood that the pistons of all of the cylinders are connected to a crankshaft by connecting rods so that said crankshaft is rotated by reciprocation of said pistons. Each of valves 8 and 14 is provided with a rod-like stem 18 which projects upwardly and slidably through a bore 20 provided there for in head 2, and projects above said head, each valve stem being biased upwardly, whereby to close the associated valve, by a coil spring 22 disposed coaxially about the extended end portion thereof, and compressed between an outer surface of the engine head and a retainer 24 mounted on the stem adjacent the upper end thereof.
A cam shaft 26 extends parallel to the line of cylinders, being disposed above the midline of the engine head, and is journalled between bearing seats 28 formed in upright posts 30 formed integrally with the head at intervals along the shaft, and bearing caps 32 secured to each post by screws 34. Each bearing cap is secured by two screws, one at each side of the cam shaft, said screws being fixed at their lower ends in the associated bearing post 30,. extending upwardly through the bearing cap, and having a nut 36 threaded thereon above the cap. The cam shaft is turned by a timing gear 38 (FIG. I) fixed thereon, and driven by suitable connection to the crankshaft, not shown but well understood in the art, so that the cam shaft turns in a fixed ratio to the speed of the crankshaft. In a fourcycle engine, the cam shaft turns one full revolution for each two revolutions of the crankshaft.
A pair of rocker shafts 40 and 42 are disposed above and respectively at opposite sides of the cam shaft, and
mounted in bearing caps 32. Mounted pivotally on the rocker shafts, in association with each intake and exhaust valve, is a rocker arm 44. Shaft 40 carries the rocker arms associated with the intake valves, and shaft 42 carries the rocker arms associated with the exhaust valves. Each intake rocker arm has an inward projection constituting a cam follower 46 which engages and rides against a cam 48 formed integrally with the cam shaft, and each exhaust rocker arm has an inward projection constituting a cam follower 50 which engages and rides slidably against a cam 52 of the cam shaft. Each rocker arm is also provided with an outward extension 54 the outer end portion of which overlies the upper end of the associated valve stem, and in which is threaded a tappet screw 56 adjustably fixed by lock nut 58. FIG. 5 shows one intake and one exhaust valve in their closed positions, that is, with the lobes of earns 48 and 52 turned out of engagement with the cam followers 46 and 50. It will be noted that in this position rocker arm screws 56 do not engage valve stems 18, but that there is a clearance 104 therebetween. This clearance is necessary to avoid any possibility that, due to thermal expansion of the metals, manufacturing tolerances, or the like, the cams and rocker arms could hold the valves partially open at inappropriate phases of the operating cycle, and to permit full valve closure when required. However, as the cam shaft turns, the lobes of its cams will engage and rock the rocker arms to open and close the valves at the appropriate times and in the proper sequence required for operation of the engine.
The structure as thus far described is common and well known in the art, each valve being operable only by a single cam of the cam shaft. However, as already discussed it would often be desirable, from the standpoint of better engine efficiency and performance characteristics, if different sets of cams, designed for different operating conditions, were available. For example, in an automobile, different cam contours will produce better performance and efficiency under normal driving condtions than in racing, or under high load conditions. The provision of such alternatively usable cam sets is the object of the present invention.
.In accordance with the present invention, therefore, shaft 26 is provided with an additional intake cam 48A directly adjacent each cam 48, and an additional exhaust cam 52A directly adjacent each cam 52, and bearing the same positional relation to cam 52 as cam 48A bears to cam 48. However, while only two cams are shownin connection with each valve, it will be readily understood that three or even more could be provided within the spirit of the invention. As shown, cams 48A and 52A differ from cams 48 and 52 principallypnly in that they provide a lesser valve lift, and hence may be termed stock cams, while earns 48 and 52 provide a higher lift, usually required for racing cams. However, it will be understood that the cams may also vary in other aspects of their contours. Each intake rocker arm 44 is movable parallel to its rocker shaft 40, so that its cam follower 46 may engage cam 48 or 48A selectively, and each exhaust rocker arm is movable parallel to its rocker shaft 42 so that its cam follower 50 may engage cams 52 or 52A selectively. Each rocker arm has a hub portion pivotally and slidably mounted on its rocker shaft, but is normally biased to a fixed position longitudinally of said shaft by a pair of centering springs 60 carried on the rocker shaft, said springs bearing at their inner ends against the opposite ends of said hub portion, and at their outer ends respectively against a pair of cross pins 62 fixed in the rocker shaft. The outer extension 54 of each rocker arm is provided with a second tappet screw 56A which will be disposed in operative relationship over the associated valve stem 18 when the cam follower of that arm is positioned to engage the A cam.
The rocker arms 44 are shifted in a direction parallel to the cam shaft, whereby to cause their cam followers 46 to engage earns 48 or 48A, respectively, and followers 50 to engage earns 52 or 52A respectively, by shifting rocker shafts 40 and 42 simultaneously to the left or right, as viewed in FIG. 1, they being shown in their right position as illustrated, so that the cam followers engage earns 48 and 52. For this purpose, the rocker shafts are slidable in bearing caps 32, with bearing cap screws 34 engaged in longitudinally elongated slots 64 of said shafts. At the right end of the engine, also as viewed in FIG. 1, both rocker shafts extend outwardly from the rightmost bearing cap 32, and each is provided in its extended portion with a cross pin 66 fixed therein. Cross pins 66 project upwardly from the shafts respectively into a pair of angled cam slots 68 formed in a slide bar 70 resting on the top of the shafts. Said slide bar is retained vertically between the shafts and a cover plate 72 fixed under the nuts 36 of screws 34 of the endmost bearing cap, and horizontally between said bearing cap and a downturned lip 74 at the outer edge of said cover plate, and further guided in its movement transversely to the rocker shafts by a shouldered screw 76 threaded therein and projecting upwardly through a slot 78 of the cover plate. When the slide is in its downward position, as illustrated in FIG. 1, cam slots 68 have moved pins 66 and the rocker shafts to the right, to engage cam followers 46 and 50 with cams 48 and 52 respectively, and when slide bar 70 is moved upwardly as viewed in FIG. 1, slots 68 cam pins 66 and the rocker shafts to the left to engage cam followers 46 and 50 with cams 48A and 52A respectively. The slide bar is moved selectively to either position by any suitable means, the means shown constituting a double solenoid 80 having two coils 82 and 84 operable when energized to move the slide bar in respectively opposite directions. The solenoid coils may be controlled from suitable switches mounted on the automobile dashboard or elsewhere, not shown, or could be controlled by a suitable speed-responsive device responsive to the speed of engine operation, so that one set of cams is operative above a given engine speed, and another set of cams is operative at lower engine speeds. The slide bar may also be manually controlled if desired.
However, the rocker arm associated with any given valve cannot be allowed to shift from one cam to another while that valve is open, that is, at any time the cam and rocker arm of that valve have imparted a downward movement to the stem 18 of that valve, since to do so could produce interference between the cams and cam followers, and between the tappet screws and valve stems, and cause breakage of parts. In the prevention of this occurrence, centering springs 60 come into play, and also a detent spring 86 associated with each intake-exhaust valve combination. Said detent spring is of the leaf type, with its midportion affixed to head 2 directly beneath cam shaft 26, as by screw 88, and its two arms 90 and 92 extending upwardly at opposite sides of the cam shaft to cooperate respectively with the intake and exhaust rocker arms. Each spring arm is provided intermediatev its ends with an inwardly directed rounded'lobe, 9 4- and'96 respectively, operable to be engaged by at least one intake and one exhaust cam in each 'revolution o'f the cam shaft toldeflect the upper ends of the springarm's outwardly. As "shown in FlG. 6, the detent spring'is of suehwidth that its lobes are engaged and moved by intake cam 48, and exhaust cam SZA. At itsupper end, each of springarrnsSlQand 92 is bifurcated to form two fingers 98 and 100 adapted to engage in a notch l02 forme d'thereof in the hub portion of the associated rocker arm when the spring arm is not deflected by acam, but to bedeflected outwardly from said notch, as shown at the right side of FIG. 5, when the spring arm is engaged and deflected by a cam. Fingers 98 are engaged in notches 102 when the rocker arms are positionedto engage their cam followers with earns 48 and'52, and fingers 100 are engaged in notches 102 when the rocker arms,,are positioned to engage their cam followers with cams 48A and 52A. A careful examination of FIG. 5 will reveal that the spring arm lobes 94 and 96 are disposed in ,angularly offset relation, with regard to the cam shaft, in such degrees relative to the positions of said cam shaft at which the cam followers 46 and 50 are engaged and elevated by the cam lobes, that each rocker arm cannotmove with the longitudinal movement of its rocker shaft whenever the cam follower carried by that rocker arm has been elevated by a cam lobe to open the associated engine valve, but will be restrained against movement with the rocker shaft by the engagement of one or the other of spring fingers 98 or 100 in its notch 102. Only when the cam shaft has turned sufficiently to allow complete closure of each valve, and a clearance 104 opens between the rocker arm tappet screw 56 and 56A then in use, and the upper end of the associated valve stem 18, will a cam lobe 48 or 52A engage lobes 94 or 96 to force spring finger 98 or 100 out of engagement with notch 102 to permit movement of the rocker arm along its rocker shaft 40 or 42.
In operation, assuming first that cam lobes 48 and 52 are in use, the parts have the positions shown in the drawing. Cams 48 and 52 are the high lift or racing cams. To shift to the low lift or stock cams 48A and 52A, slide bar 70 is moved upwardly, as viewed in FIG. 1, either manually, or by energization of coil 84 of double solenoid 80, or by any other suitable means as previously discussed. Movement of slide bar 70 causes its cam slots 68 to act against cross pins 66 to move both of rocker shafts 40 and 42 to the left, the distance of movement being that required to shift all of the rocker arms 44 to position their cam followers 46 and 50 to engage cams 48A and 52A respectively. While this movement of the rocker shafts may be substantially instantaneous, it will be apparent that only those rocker arms associated with valves which are fully closed at that instant, so that tappet clearance 104 exists, can shift with the rocker shafts at this time. Those rocker arms associated with valves which are open to any degree at this instantare locked against movement with the rocker shafts by the described locking action of fingers 98 of detent springs 86. Thus while the rocker arms of open valves cannot shift at this instant, they are nevertheless biased toward the shifted position by compression of the centering springs 60 behind them. Subsequently, as the cam shaft continues to rotate and its cams allow closure of the open valves in the firing sequence of the engine, the operative cam of each newly closed valve will thenc onitactthe spring lobe 94 or 96 of the spring arm +9; associated with the rocker arm of that valve, deflecting ,spring. ,f inger 98 of that arm from notch- 102 of-that'rocker arm, and the rocker arm-.will beshifted to engage its camfollower46 or 50 with cam 48A or 52A respectively, by the recovery of centering springs 60 of that rocker arm from the previously unbalanced loads thereof. Within-a small fraction of asecond, if the engine is operating. shifting of the cams of all, of the'valves' will have been accomplished. Spring fingers 100 of the detent springs then become operative, and function in the same manner as fingers 98 to'delay shifting of the cam followers back to cams 48and 52 whenever such may be desired.
While] have shown and described'aspecific embodiment'of my invention, it is never'theless readily apparent that'many minor changes of structure and operation couldbe made within the spirit of the invention. For example, the concept could be applied to'en gines wherein the valves and valve stems are disposed in an in-line pattern, rather than in the V-pattern shown. Also, while only two sets of cams, selectively usable, have been selected for purposes of illustration,three or even more sets ofjcams could be selectively utilized to provide better performance and efficiency under still other operating conditions, within inherent space limitations. The device as illustrated was built into a stan dard engine normally including only one cam set, with no change of basic engine dimensions. It is considered that these changes, as well as others, fall within the sprit of the present invention. The basic advantages of the concept, in providing for bringing any one of a plurality of cam sets into use, each set being operable to provide the best engine performance and efficiency under a different set of operating conditions, shifting of cam sets being possible at any operating speed of the engine, are believed obvious and clear.
What I claim as new and desire to protect by Letters Patent is:
1. In an internal combustion engine including a series of cylinders each provided with an intake valve and an exhaust valve, and a crankshaft rotated by pistons movable in said cylinders:
a. a cam shaft rotatable by a driving connection thereof to said crankshaft,
b. a plurality of sets of cams, each cam constituting an eccentric formation on said cam shaft, said cams being spaced longitudinally along said cam shaft, said sets each including a series of cams associated respectively with each of said intake and exhaust valves, and the cams of each set being designed for best engine performance and efficiency under a different set of operating conditions,
0. a cam follower associated with each of said intake and exhaust valves, said cam followers being engageable respectively with the individual cams of any one of said sets of cams and each operable to open and close one of said valves in response to movement of its associated cam, each of said cam followers constituting a rocker arm pivoted on a rocker shaft extending parallel to an adjacent said cam shaft, and including a follower portion engaging one of said cams to be rocked thereby to control the associated valve, said rocker shaft being longitudinally movable and said rocker arms being movable therewith, and
d. operating means operable to move said cam followers to engage any one of said sets of cams selectively, said operating means constituting mechanical means operable to move'said rocker shaft longitudinally to move all of the rocker arms carried thereby.
2. The structure as recited in claim 1 wherein each of said rocker arms is carried on said rocker shaft for rocking movement coaxially therewith and for limited sliding movement longitudinally therealong, and with the addition of:
a. resilient means biasing each of said rocker arms yieldably to the central position ofits limited movement longitudinally of said rocker shaft,
b. detent means associated with each of said .rocker arms and operable when engaged to secure said rocker arm against movement with said rocker shaft when the associated valve is open, and
c. release means associated with each of said rocker arms and operable to disengage the associated detent means when the associated valve is closed.
3. The structure as recited in claim 2 wherein said biasing means associated with each of said rocker arms constitutes a pair of compression springs carried on said rocker shaft respectively at opposite sides of said rocker arm. bearing at their proximate ends against 8 said rocker arm and at'their distal ends against stops fixed in said rocker shaft.
4. The structure as recited in claim 2 wherein said detent means comprises a leaf spring fixed at one end in said engine and having at its free end a plurality of fingers each positioned to engage in a notch formed in the associated rocker arm in one position of said rocker arm longitudinally of said cam shaft, when said spring is relaxed. whereby to prevent movement of said rocker arm longitudinally of said rocker shaft. said release means being operable to deflect said detent finger from said notch at a time the associated engine valve is closed.
5. The structure as recited in claim 4 wherein said release means comprises a cam follower lobe formed in each of said leaf spring detents intermediate its ends, and operable to be engaged to deflect said finger from said notch by a cam of said cam shaft associated with the same rocker arm, said spring lobe being so angularly offset, relative to said cam shaft, from the angular position of said cam shaft at which said rocker arm is pivoted by said cam to open the associated engine valve, that said spring lobe is engaged and said detent finger is deflected from said notch, only when said associated engine valve is fully closed.