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United States Patent  [ii] Patent Number: 5,010,856
Ojala  Date of Patent: Apr. 30, 1991
 ENGINE FINGER FOLLOWER TYPE ROCKER ARM ASSEMBLY
 Inventor: William K. Ojala, Birmingham, Mich.
 Assignee: Ford Motor Company, Dearborn, Mich.
 Appl. No.: 597,460
 Filed: Oct. 15,1990
 Int. CI.' F01M 9/10; FOIL 1/18
 U.S. CI 123/90.36; 123/90.44;
123/90.41; 74/519; 74/559
 Field of Search 123/90.33, 90.36, 90.27,
123/90.39, 90.41, 90.42, 90.44, 90.45, 90.47;
 References Cited
U.S. PATENT DOCUMENTS
1,210,871 1/1917 Suffa 123/90.35
1,363,398 12/1920 Davids 123/90.52
1,409,878 3/1922 Mainland 384/28
2,081,390 5/1937 Trapp 74/569
2,151,832 3/1939 Bugatti 74/569
2,322,173 6/1943 Spencer 123/90.36
2,385,309 9/1945 Spencer 74/519
2,572,968 10/1951 Bachle 123/90.33
2,733,619 2/1956 Smith 74/569
3,108,580 10/1963 Crane, Jr 123/90.5
3,137,283 6/1964 Sampietro 123/90.43
3,977,370 8/1976 Humphreys 123/90.5
4,204,814 3/1978 Matzen 74/569
4,406,257 9/1983 Keske et al 123/90.48
4,614,171 9/1986 Malhotra 123/90.44
4,796,483 1/1989 Patel et al 123/90.44
4,825,717 5/1989 Mills 123/90.44
4,909,197 3/1990 Perr 123/90.39
FOREIGN PATENT DOCUMENTS
172409 10/1983 Japan 123/90.33
Primary Examiner—David A. Okonsky
Assistant Examiner—Weilun Lo
Attorney, Agent, or Firm—Jerome R. Drouillard;
Clifford L. Sadler
A valve train for an overhead camshaft type engine includes a finger follower lever type rocker arm assembly. The lever is of lightweight stamped construction containing a pocket or recess in which is received a precision molded plastic bearing cup. The cup has a smoothly polished bearing surface for slidably receiving an axleless roller that is contained laterally within the insert and is rotated by the engine driven cam located above the roller for pivotally moving the lever to actuate the engine valves. The inclusion of the pocket in the lever assures lubrication of the parts at all times since it will collect and retain lubricant or engine oil during engine operation so that even during a lengthy shutdown, upon restart, the elements will be fully lubricated.
9 Claims, 1 Drawing Sheet
ENGINE FINGER FOLLOWER TYPE ROCKER
FIELD OF THE INVENTION 5
This invention relates in general to an automotive type engine valve train. More particularly, it relates to a valve train of the overhead cam, finger follower lever rocker arm type for reducing weight and friction, the rocker arm assembly including a roller nested within a low friction bearing insert in the lever.
BACKGROUND OF THE INVENTION
To improve automotive engine fuel economy, a current objective in the design of valve trains is weight and friction reduction. This has been accomplished in the past, for example, by the use of stamped steel rocker arms instead of heavier forged or cast arms, and the use of roller bearings between the engine cam and rocker 2Q arm surface for reducing friction. A switch to finger follower lever type rocker arms also has reduced weight and complexity and friction; but, in general, these latter type constructions generally employ only a cylindrical surface or an axle type roller rotatable on 25 needle bearings or bronze bushings.
For example, U.S. Pat. No. 2,081,390 to Trapp, U.S. Pat. No. 3,977,370 to Humphreys, U.S. Pat. No. 3,137,283 to Sampietro, and U.S. Pat. No. 3,108,580 to Crane, Jr., all show the use of rollers in cam followers 30 for reducing friction and weight between the parts. However, it will be noted then in each of the instances, the rollers all have axles, generally with roller bearings or other suitable low friction parts. This not only complicates the construction but increases the weight and 35 cost of manufacture. Furthermore, in most instances, the rollers are located above the cam and are not selflubricating, i.e., the recesses in which they are located will not retain oil or other lubricant when the engine is shut down. 40
U.S. Pat. No. 1,363,398 to Davids, U.S. Pat. No. 1,210,871 to Suffa, and U.S. Pat. No. 1,409,878 to Mainland, are other examples of push rod type valve lifters in which a ball or roller is received in a cage but is movable only in a vertical direction and is retained in a 45 housing that is difficult to machine and generally without consideration of weight reduction.
U.S. Pat. No. 2,151,832 to Bugatti shows a finger follower type rocker arm assembly in which a ball is used between the cam and tappet. However, in this 50 case, a number of balls/rollers are required for rolling against their bearing surfaces, and a retainer is additionally required to maintain the intermediate roller in place. The size and weight of this construction would be excessive, and the roller does not slide in the lever 55 bearing surface but rolls against the other rollers. Also, the cam being located below the lever prevents retention of lubricant for the rolling bearing surfaces upon engine shutdown.
U.S. Pat. No. 4,204,814 to Matzen also shows a con- 60 struction in which the roller performs a dual function of being an axle and a camshaft follower. It is contained within a two-piece roller shaft 18 which, from a construction standpoint, provides alignment problems for the split bearing surface. Furthermore, while a gap 14 is 65 provided for the introduction of lubricant or oil to the roller, upon engine shutdown, the lubricant will drain out and provide a dry start for the next cycle.
U.S. Pat. No. 4,406,257 to Keske et al. shows a roller follower in which a roller 30 has in effect a pair of laterally extending axles 34, 36 supported upon bearing surfaces 26, 28, each part of a two-piece support, the central portion of the roller being interdigited with the support. The cam follower surface, therefore, is separate from the rolling surface. The construction as disclosed is difficult to machine and assemble the bearing surfaces 26, 28 with precision in order to avoid edge riding of the bearing. Neither friction nor weight appears to be minimized with such construction.
SUMMARY OF THE INVENTION
The present invention relates to a finger follower lever type assembly in which the lever includes a recess in which is received a precision molded bearing insert. The insert has a configuration mating with the outer surface of a roller that is received within the bearing insert and in turn is engaged by the cam of an overhead camshaft type valve train. The use of the insert enables the use of a stamped type finger follower with ordinary machining. This allows weight reduction and eliminates or minimizes the use of precision machining and polishing equipment for the manufacture of the follower lever itself. The insert in this case could be molded from a plastic with a high precision surface permitting sliding of the roller with a minimum of friction as it is rotated by the engine driven cam. The use of plastic or similar material also provides increased weight reduction as compared to conventional constructions. Furthermore, the ability of the roller in this case to run on the polished surface of the insert eliminates the need for an axle or roller with needle bearings, such as was described above in connection with the prior art references. The roller can be hollowed out, made of various lightweight materials, and of various configurations for weight reduction. Also, the bathtub-shaped pocket receiving the roller and insert collects and retains lubricant or oil during engine operation, when the latter is sprayed on various parts of the valve train, so that when the engine is shut down, lubricant will still be available upon engine start-up.
It is, therefore, a primary object of the invention to provide a valve train of the finger follower lever type with an assembly in which an axleless roller is received within the lever for sliding movement against a polished bearing surface for both weight reduction and minimization of friction between the parts.
It is a further object of the invention to provide the lever with a precision molded bearing insert having a surface mating with the outer annular surface of the roller with which it is engaged and which also engages the cam of an overhead camshaft type engine valve train.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, features and advantages of the invention will become more apparent upon reference to the succeeding, detailed description thereof, and to the drawings illustrating the preferred embodiment thereof; wherein,
FIG. 1 schematically illustrates a cross-sectional view of a portion of an engine valve train embodying the invention, and
FIGS. 2 and 3 are cross-sectional views taken on planes indicated by and viewed in the direction of the arrows 2—2 and 3—3 of FIG. 1.
T _ tv_i^x_ material. Therefore, the use of a plastic insert can be
locccnPc^ cxi^^ix^vT-r self-lubricating. The plastic, per se, is a slick material
PREFERRED EMBODIMENT and lubricating material can be embedded in it, or to
FIG. 1 illustrates schematically a portion 10 of an gether alloyed. Once the engine began operation and oil
automotive type engine. In this case, it includes a valve 5 slung in the area, then it can provide self-lubrication,
train of the overhead camshaft type in which a camshaft Those skilled in the art will appreciate in view of this
(not shown) rotates a cam 12 fixed thereon. The engine disclosure that insert 40 could be modified to include
contains a cylinder head 14 in which is mounted for retention means, for example in the form of tabs molded
reciprocation a valve stem 16 attached at its lower end integrally with the insert, to prevent the roller from
to a valve (not shown). The stem is surrounded by the 10 becoming separated from the follower assembly prior to
usual return spring 18 and a valve keeper 20, and slides installation in an engine.
in a sleeve 22 for a reciprocating motion for opening From the above, it will be seen that the invention and closing the valve in a known manner. The cylinder provides a low weight and reduced friction type valve head also contains a tappet 24 movable in a pocket 26 in train by the use of a precision molded insert operable in the head, and acting as a fulcrum for the pivotal move- 15 a pocket provided in a finger follower lever type rocker ment of a finger follower lever type rocker arm 28. arm, the insert having a bearing surface that is exMore specifically, the lever or rocker arm 28 has an tremely smooth for a sliding engagement with a roller elongated body 30 with a cup-shaped fulcrum end 32. follower of light weight movable by a cam of an overThe latter receives the spherical end 34 of the tappet head camshaft type engine construction. Such a conbody. The other end of lever 28 is formed as shown 20 struction provides an easy assembly of the parts, and with a valve actuating portion 36 engagable with the with continuous lubrication because of the bathtubupper end of the stem 16 for reciprocating the same. shaped reservoir assuring that the bearing surfaces alThe central portion of lever 28 is stamped with a recess ways contain lubricant or oil, even after a lengthy shutor hollow pocket (FIGS. 2 and 3) 38 that need not be down. Furthermore, the construction assures the pivprecision machined or polished. The pocket or recess is 25 otal movement of the finger follower lever with a miniessentially of a bathtub shaped configuration opening mum of friction by the use of low weight elements, upwardly and receives therein a one-piece precision While the invention has been shown and described in molded plastic bearing cup 40 that has a precision its preferred embodiment, it will be clear to those skilled molded or polished surface 42. On the surface is slidably in the arts to which it pertains, that many changes and supported a hollow axleless roller follower 44. The 30 modifications may be made thereto without departing outside diameter of the roller slides on the smooth bear- from the scope of the invention, ing surface of the insert and in turn is rolled by engage- I claim:
ment above with the cam 12 during pivotal movement 1. A reduced friction finger follower type rocker arm of the lever. The bathtub shape also retains the roller assembly for an overhead camshaft type engine includfollower against lateral movement. 35 ing a one-piece pivotally movable finger follower type It will be seen in this case that with the camshaft lever having a fulcrum at one end and engaging an located above the finger follower lever, and the roller engine valve stem at its opposite end for reciprocation being contained in the insert in the pocket of the lever, thereof, the lever having a recess therein opening upthat during operation of the engine, when engine oil or wardly and containing an axleless roller bearing therein lubricant is sprayed thoroughly and continuously in the 40 against lateral movement and an engine rotated cam area around the valve train, lubricant will collect in the located above the roller and contiguous thereto for pocket and be retained therein so that during a restart rotating the roller in the lever, the recess including a after engine shutdown the parts will be lubricated. Fur- smoothly formed one-piece bearing insert in the lever thermore, the benefits of using the insert is that it pro- upon which the roller slides during rotation by the cam vides a wide range of material selection to ensure bear- 45 for reducing friction between the parts, the recess reing compatibility and long roller life. Some of these taining engine lubricant admitted thereto during operamaterials would be, for example, high molecular weight tion of the engine for further reducing friction between plastics that are especially engineered for dry or lubri- the parts and for a lubricated restart after engine shutcated operation. These materials would not gall when down.
run against metal and would burnish the high spots 50 2. An assembly as in claim 1, wherein the recess has during break-in without damaging the roller. The use of an essentially bathtub pocket configuration which repowdered metal bearing cups would be another mate- ceives said insert with a precision molded low friction rial choice, and bearing materials such as bronze could bearing surface against which the roller is supported in be used with graphite, lead or other materials known to a low friction sliding manner.
those skilled in the art and suggested by this disclosure. 55 3. An assembly as in claim 1, wherein the recess is
The bearing insert cup 40 in this case being of a pocket-shaped to conform to the shape of the roller, and
molded composite or powdered metal could easily be receives therein said one-piece bearing insert of preci
configured to prevent rotation about the tappet axis sion molded configuration to mate with the surface of
merely by molding a tab or tabs that extend beyond the the roller for reducing friction.
tappet outside diameter. 60 4. An assembly as in claim 1, wherein the recess in the
The use of a plastic insert also has the added advan- lever is defined by a pocket, the pocket containing said
tage of reducing valve train inertia. This can be a trade- one-piece bearing insert of a configuration precision
off for better performance and/or fuel economy, re- molded to mate with the surface pocket of the roller to
duced NVH and reduced component stress and wear. thereby eliminate the necessity of a precision molded
The use of ceramic rollers also has the ability to further 65 surface in the lever.
reduce valve train weight for even greater improve- 5. A rocker arm assembly for an overhead camshaft
ment, since they could be as much as 40% lighter than engine including a pivotally movable finger follower
the use of metal rollers. Plastic is a lubricating type type rocker arm lever engaging a fulcrum at one end