US 3090368 A
Description (OCR text may contain errors)
y 1, 1963 R. M. BUCHWALD 3,090,368
VALVE ACTUATION MEANS Filed June 6, 1961 4 Sheets-Sheet 1 Z INVENTOR. fifiar/ Wide/4 4% ATTORNEY y 1963 R. M. BUCHWALD 3,090,368
VALVE ACTUATION MEANS Filed June 6, 1961 4 Sheets-Sheet 2 INVENTOR.
May 21, 1963 R. M. BUCHWALD 3,090,368
VALVE ACTUATION MEANS ram A TTORNEY y 1, 1963 R. M. BUCHWALD 3,090,368
VALVE ACTUATION MEANS Filed June 6, 1961 4 Sheets-Sheet 4 JNVENTOR.
United States Patent 3,090,368 VALVE ACTUATION MEANS Robert M. Buchwald, Berkley, Mich, assignor to General Motors Corporation, Detroit, Micln, a corporation of Delaware Filed June 6, 1961, Ser. No. 115,120 3 Claims. (Cl. 123-?0) This invention relates to valve actuation means for internal combustion engines, and more particularly to positive actuation means for the usual intake and exhaust Valves of an internal combustion engine.
Internal combustion engines are generally provided with a plurality of cylinders, each cylinder having a pair of valves opening thereinto. One of the valves conducts the gas mixture to the cylinder for explosion and the other valve permits the exhaust from the explosion to be conveyed away from the engine. It is the general practice to operate such valves by means of rocker arms, valve lifters and push rods, actuated in some manner by a camshaft, whereby the valves are opened or closed by means of hydraulic or spring principles in the valve lifter devices. It may be advantageous to provide positive opening and closing of the valves in the cylinders. In other words, valve actuation is by direct mechanical connection with the camshaft. This type of valve actuation is commonly known as desmodromic.
Desmodromic valve actuating mechanisms that have been used in the past have had many disadvantages. The major problem is that these devices are usually cumbersome, complicated and expensive mechanical linkages extending between the camshaft and the valve stem, which present numerous problems from the standpoint of efficiency, repair and assembly.
The device in which this invention is embodied comprises, generally, valve actuation means of the desmodromic type utilizing a groove or track formed about the camshaft for actuating a rocker arm which is suit ably connected to the valve stem. A pair of camshafts may be provided, and a positive drive from the vehicle engine crankshaft to the camshafts permits the proper relative rotation between the various shafts for proper driving of the valves. The device is relatively uncomplicated and simple in construction and assembly and does not require more than normal disassembly for repair or reconstruction purposes. Thus, the device represents an inexpensive and eflicient means for positive valve actuation.
These and other advantages will become more apparent from the following description and drawings, in which:
FIGURE 1 is an elevational view of .a portion of an internal combustion engine with parts broken away and in section to illustrate the camshaft drive mechanism;
FIGURE 2 is a cross-sectional view of the engine illustrated in FIGURE 1 taken substantially along the line 22 of FIGURE 1 and looking in the direction of the arrows to illustrate the purpose of the various parts of the engine;
FIGURE 3 is an end view of the engine illustrated in FIGURE 1 with parts broken away and in section and taken substantially along the line 33 of FIGURE 1 and looking in the direction of the arrows to show the drive mechanism for the camshafts;
FIGURE 4 is an elevational view of a portion of the engine illustrated in FIGURES 1-3 showing the camshaft construction and the parts associated therewith;
FIGURE 5 is a View of a portion of the engine illustrated in FIGURES 13 illustrating the valve-to-rockerarm connection; and
FIGURE 6 is a view of a portion of the engine illus trated in FIGURES 1-3 taken substantially along the 3 ,090,368 Patented May 21, 1963 line 66 of FIGURE 3 and looking in the direction of the arrows.
FIGURES 1-3 of the drawings illustrate an inline internal combustion engine utilizing the positive valve actuation means embodying this invention. An inline engine is shown only for illustration purposes and it is to be understood that the construction-s to be described are equally applicable to V-type or other type internal combustion engines.
Referring more particularly to the drawings, an engine block, illustrated generally by the numeral 10, contains a plurality of cylinders 12. A piston 14 is creciprocably received in each of the cylinders 12 and contains the usual piston rings 16. Engine block 10* has skirt portions 18 which extend downwardly and outwardly to define a crankcase 20 which may be closed by a sheet metal cover 22 in any suitable manner. Gasket means 24 may be provided between the cover 22 and the beads 26 formed on the skirts 18.
A conventional crankshaft, illustrated generally by the numeral 28, extends lengthwise of the engine block 10 and within the crankcase 20. Crankshaft 28 includes crank throws 30 and counterweights 32 in the usual manner. Crankshaft 28 is secured in the engine block 10 by means of support portions 34 and bearing cap members 36. Suitable fastening means, such as nuts and bolts, may be used to secure the caps 36 to the portions 34. Suitable bearings 38 are provided between the crankshaft 2'8 and the mounting members.
In order to drive crankshaft 28 a connecting rod 40 is secured to each of the pistons 14. This may be done in the conventional manner, as by wrist pins 42 extending through the pistons 14 and through a suitable eye,
not shown, in the upper part of connecting rods 40. Connecting rods 40 engage crank throws 30 in the usual manner and are retained thereon by bearing caps 44 secured to the upper portions of connecting rod-s 40 in any suitable manner, as by nut and bolt assemblies 46. Suitable bearings 48 are provided between the crank throws 30 and the connecting rods and bearing caps 40 and 44, respectively.
In order to drive the usual engine accessories, such as the pump 4-9, a gear and sleeve assembly '50 may be secured to the crankshaft 28 by means of a suitable key 52 received ina slot 54 in the crankshaft 28 and a groove 56 in the sleeve assembly 50. Thus, the gear and sleeve assembly 50 is rotatable with the crankshaft 28.
Closing the top of the engine block 10 is a cylinder head, illustrated generally by the numeral 58. Cylinder head 58 includes combustion chambers 60 above each of the cylinders 12 and into which extend spark plugs 62 and valve members 64 and 66. As shown in FIGURE 2, cylinder head '58 includes an intake passage '68 for conveying the gas and air mixture to the combustion chamber 60' and an exhaust passage 69 leading from combustion chamber 60 for conveying the products of combustion therefrom. Valves 64 and 66 open and close these passages as necessary, acting against valve seat inserts 6S and 67 if the material so requires.
In order to drive the valves 64 and 66 a pair of camshafts, illustrated generally by the numeral 76" and both substantially alike, may be located above the combustion chambers 69' in the cylinder head 58, and above the valves 64 and 66. Cylinder head 58 includes a pair of bosses 72 which serve as front supports for the camshaft 7ti, and a similar construction, not shown, may be provided to support the rear of the camshafts 70'.
To protect the camshaft areas, sheet metal camshaft gallery covers 74 may be provided, engaging cylinder head 58 with suitable gasket members 76 disposed therebetween. Further, to enclose the front of the engine a cover assembly 78 may be secured to the engine block 10 and the cylinder head 58 in any suitable manner, as by bolts 80. Front cover 78 may also support the accessory members, such as pump 49, and may also serve as a front support for crankshaft 28, as indicated at 82.
The drive means for camshafts 70 is best shown in FIGURES l and 3. Located about crankshaft 28 and rotatable therewith by means of key 52 is a drive gear 84. Drive gear 84 engages and causes to rotate a larger driven gear 86 which is supported on a shaft 88. Shaft 88 is journaled, as at 96, in a rear support 92 which may form a portion of the engine block The front of shaft 88 is supported by a front support member 94 which is provided with bosses 96 to space the front support plate 94 from the engine block 10 and cylinder head 58. Suitable bolts 98 may be provided to secure the front support plate 94 to the front of the engine. Shaft 88 is journaled, as at 180, in the front support plate 94 and secured therein by means of a nut 182 received on threaded portion 104 at the end of shaft 88.
Also received on shaft 88 are a pair of eccentric members 106 and 108 which are rotatable along with gear 86 in any suitable manner. Eccentric members 106 and 108 receive camshaft drive links 110 and 112 which extend upwardly to engage similar eccentrics 114 and 116 secured on the ends of the camshafts 70. Links 110 and 112 may be noted in FIGURE 3 as being triangular, and each link engages one of the eccentrics on each of the shafts 70 and shaft 88. It may also be noted in FIGURE 3 that the links and eccentrics are phased 90 away from each other in order to eliminate a dead center condition which would prevent rotation of the camshafts 70 by the crankshaft 28.
This may be illustrated by reference to FIGURE 3 wherein points A represent the centers of the respective shafts on which the eccentrics are mounted. Point-s B represent the centers of one set of eccentrics, and points C represent the centers of the other of the sets of eccen trics. It is noted that points B and C are 90 displaced with respect to points A.
The particular manner in which the eccentrics are mounted or secured to camshafts 70 is best illustrated in FIGURE -6. Eccentrics 114 and 116 are received about a portion 118 of the camshaft 70 of reduced diameter and a pin 120 passes through the eccentrics 114 and 116 into the body of camshaft 70. Retainer members 122 and 124 secure the links to the eccentrics and are secured in place by means of bolts 123, as seen in FIGURE 1. Securing nut 126 engaging portion 118 holds the eccentrics and links on the camshaft 70. The manner in which the other two sets of eccentrics are secured to their respective shafts and gear may be substantially the same as illustrated in FIGURE 6.
In order to actuate valves 64 and 66 in the combustion chambers 60, rocker arms 128 are provided in the camshaft galley. Each rocker arm is pivotally secured to the cylinder head 58, as by a pivot 130, and extends transversely of the camshaft 70 toward the valve. Rocker arm 128 is provided with a pocket 132 which is closed at the bottom by a web 134 having an aperture 136 formed therethrough. Valve stern 138 extends through the aperture 136 in Web 134 and is provided with grooves 140 and 142. Spring retainers 14-4 and 146 are secured to the valve stem 138 by means of tapered split rings 148, and springs 150 and 152 extend between the spring seats 144 and 146 and the web 134 of rocker arm 128. In this manner, excessive forces exerted on the valve and transmitted to the connection are taken up by the springs 150 and 152. However, the spring rates for normal operation of the valves are such that the rocker arm will impart positive movement to the valve stem 138 and the springs will not be compressed in either direction unless abnormal forces of resistance are applied.
, Referring to FIGURE 4, the construction of the camshaft and drive means is best illustrated. Camshaft 70 is supported in the cylinder head 58 by means of suitable pedestals 154 at spaced points in the camshaft gallery. Beneath each rocker arm 128 are a pair of integrally formed cams 156 having cam surfaces 158 inclined towards each other. Between camshaft 7t) and each of the pedestals 154 is a cam ring, illustrated generally by the numeral 168, which is spline connected, as at 162, or otherwise positively connected, to the camshaft 70 for rotation therewith. Cam rings 160 have cam surfaces 164 extending about the integrally formed cams 156 to define an annular channel or groove 166 eccentric about the axis of the camshaft 70. The cam surfaces 164 are inclined in a direction opposite to the direction of inclination of cam surfaces 158, such that the cross-sectional configuration of the grooves 166 is substantially trapezoidal.
It is to be noted that grooves 166 could be formed out of an integral flange extending from camshaft 70. However, it is the preferred construction to provide integral cams 156 surrounded by cam rings 160, for purposes to become hereinafter apparent.
In order to secure cam rings 160 and the camshaft 70 to the cylinder head 58, bearing caps 168 are received over cylindrical portion of cam rings 160 and may be connected to the pedestals 154 in any suitable manner, as by bolts. Suitable bearings 170 are provided between the pedestal and cap assemblies and the cam rings 1'60.
Rocker arms 128 are caused to oscillate, and valves 64 and 66 to operate, upon rotation of camshafts 70 by cam followers 172 rotatably secured to the rocker arms 128, as by shaft 174. Cam followers 172 may be frustoconical and are received in the grooves 166 formed by the internal and external cam surfaces 158 and 164. Since the followers 172 are received in the grooves 166 they are positively moved upwardly and downwardly by the eccentric motion of the groove about the axis of camshaft 70.
Manufacturing tolerances, clearances, and any wear that might occur between cam followers 172 and the cam surfaces, are taken up by springs 176 engaging the outer cam ring 160 in "any suitable manner and biasing the cam ring 160 in the direction of the cam follower 172. This causes constant engagement of the cam followers 172 with both the cam surface 164 on the outer cam ring 160 and the cam surface 158 on the inner cam 156. Springs 176 may be so placed as to bias two adjacent cam rings 160 in opposite directions, except at the ends of the camshaft 70 where a suitable spring seat '17 8 maybe provided. Spring seat 178 may be secured to camshaft 70 in any suitable manner.
In the operation of the above-described construction,
' valves 64 and 66 are positively actuated in either direction by the driving of rocker arms 128. The rotation of camshafts 70 causes positive motion of rocker \arms 128, since the cam followers 172 are restricted to the eccentric grooves 166 formed by the cam surfaces. The drive from the crankshaft 28 to the camshafts 70 is positive, being through gears 84 and 86, and the eccentrics actuated by the links and 112.
The drawings illustrate an inline engine having exhaust valves on one side and operated by one camshaft and intake valves located on the opposite side and actuated by another camshaft. This is not absolutely necessary, as only modifications to the phasing of the cam surfaces would be necessary to change an exhaust valve to an intake valve for purposes of timing. Furthermore, it is conceivable that a single, lengthy camshaft could be utilized for the purposes above described.
Thus, a positive valve actuating means, or desmodromic valve actuating means, is provided which is relatively simple in construction and which is efficient'and inexpensive to use. The rocker-arm-to-valve-stem connection serves as a safety feature to protect the assembly from abnormal resistance forces without detracting from the posiand means for rotating said camshaft to oscillate said rocker arm through said cam followers and said eccentric grooves for actuating said valve in said cylinder.
3. In an internal combustion engine having a row of cylinders therein and valves in said cylinders, means for actuating said valves comprising:
a camshaft mounted in said engine and having a pair of integral cams formed therefrom for each of said valves, said cams being axially spaced on said camti-ve actuation features desired. The device is relatively inexpensive and simple to manufacture and assemble.
What is claimed is:
1. Desmodromic valve actuating means for an internal combustion engine having a cylinder and valves opening therein and a piston and a crankshaft driven by said piston, said actuating means comprising:
camshaft mounted in said engine and parallel with said crankshaft and spaced therefrom and having a plurality of cams formed thereon; 10 link means operatively connected to said crankshaft shaft and having the cam surfaces thereof inclined and to said camshaft to rotate said camshaft upon toward each other; rotation of said crankshaft; a cam ring surrounding each of said integral cams cam rings mounted on said camshaft and about each mounted on said camshaft and rotatable therewith of said cams defining with said cams a plurality of and having a cam surface inclined in a direction eccentric grooves around said camshaft, said cam opposite the inclination of said cam surface of said rings being resiliently biased axially of said camintegral cam associated therewith, said cam ring and shaft; said integral cam defining an eccentric groove havrocker arm means pivotally secured to said engine g a g n r lly rapezoi al Cross-Sectional configuraand extending transversely of said camshaft and beti ing positively secured to said valves; a rocker arm for each of said valves pivotally mounted a plurality of follower means secured to said rocker 011 Said engine at One end of said rocker arm and arm means and received in said eccentric grooves and held in positive engagement with said cams by engaging said valve at the other end of said rocker arm and extending transversely of said camshaft;
said cam rings for positive movement of said rocker pair of frusto-conical cam followers rotatably sear m an and id valv upon r tati n f id cured in each of said rocker arms and on opposite camshaft by said crankshaft. sides thereof and received in said eccentric grooves; 2. In an internal combustion engine having a cylinder spring means engaging said cam rings and biasing said and a valve opening into said cylinder, means for actuatcam rings intc engagement i said am followers in s id v 1v comprising; to take up wear and manufacturing tolerances and a am haft mounted in id engine nd having a i to insure positive contact between said cams and of integral cams formed thereon, said cams being Said 0am followers at all times; axially spaced and having cam surfaces in lined to and means for rotating said camshaft to cause said wards each othe rocker arms to oscillate and actuate said valves. a pair of cam rings secured to said camshaft and rotatable therewith and surrounding said integral cams, References Cited in the file of this Patent said cam rings and said integral cams forming ec- UNITED STATES PATENTS centric grooves about said camshaft; a rocker arm pivotally mounted at one end to said '610682 f et Sept 1898 engine and secured at the other end to said valve; 40 1,239,933 M11161 et a1 P 1917 cam followers secured to said rocker arm and received 1,309,339 Reynolds y 8, 1919 in said eccentric grooves; 1,454,499 l'e May 8, 1923 spring means biasing said cam rings into engagement 1,671,973 AIIdBISOH June 5, 1928 with said cam followers to insure positive engage- Murray July 5, 1938 ment between said cams and said followers; 2,779,321 Roder J an. 29, 1957