Engine finger follower type rocker arm assembly

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.

FIELD OF THE INVENTION 
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 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 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 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 cost of 
manufacture. Furthermore, in most instances, the rollers are located above 
the cam and are not self-lubricating, i.e., the recesses in which they are 
located will not retain oil or other lubricant when the engine is shut 
down. 
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 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 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 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 construction 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 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.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 illustrates schematically a portion 10 of an automotive type engine. 
In this case, it includes a valve train of the overhead camshaft type in 
which a camshaft (not shown) rotates a cam 12 fixed thereon. The engine 
contains a cylinder head 14 in which is mounted for reciprocation a valve 
stem 16 attached at its lower end to a valve (not shown). The stem is 
surrounded by the usual return spring 18 and a valve keeper 20, and slides 
in a sleeve 22 for a reciprocating motion for opening and closing the 
valve in a known manner. The cylinder head also contains a tappet 24 
movable in a pocket 26 in the head, and acting as a fulcrum for the 
pivotal movement of a finger follower lever type rocker arm 28. 
More specifically, the lever or rocker arm 28 has an elongated body 30 with 
a cup-shaped fulcrum end 32. The latter receives the spherical end 34 of 
the tappet body. The other end of lever 28 is formed as shown with a valve 
actuating portion 36 engagable with the upper end of the stem 16 for 
reciprocating the same. The central portion of lever 28 is stamped with a 
recess or hollow pocket (FIGS. 2 and 3) 38 that need not be precision 
machined or polished. The pocket or recess is essentially of a bathtub 
shaped configuration opening upwardly and receives therein a one-piece 
precision molded plastic bearing cup 40 that has a precision molded or 
polished surface 42. On the surface is slidably supported a hollow 
axleless roller follower 44. The outside diameter of the roller slides on 
the smooth bearing surface of the insert and in turn is rolled by 
engagement above with the cam 12 during pivotal movement of the lever. The 
bathtub shape also retains the roller follower against lateral movement. 
It will be seen in this case that with the camshaft located above the 
finger follower lever, and the roller being contained in the insert in the 
pocket of the lever, that during operation of the engine, when engine oil 
or lubricant is sprayed thoroughly and continuously in the area around the 
valve train, lubricant will collect in the pocket and be retained therein 
so that during a restart after engine shutdown the parts will be 
lubricated. Furthermore, the benefits of using the insert is that it 
provides a wide range of material selection to ensure bearing 
compatibility and long roller life. Some of these materials would be, for 
example, high molecular weight plastics that are especially engineered for 
dry or lubricated operation. These materials would not gall when run 
against metal and would burnish the high spots during break-in without 
damaging the roller. The use of powdered metal bearing cups would be 
another material choice, and bearing materials such as bronze could be 
used with graphite, lead or other materials known to those skilled in the 
art and suggested by this disclosure. 
The bearing insert cup 40 in this case being of a molded composite or 
powdered metal could easily be configured to prevent rotation about the 
tappet axis merely by molding a tab or tabs that extend beyond the tappet 
outside diameter. 
The use of a plastic insert also has the added advantage of reducing valve 
train inertia. This can be a trade-off for better performance and/or fuel 
economy, reduced NVH and reduced component stress and wear. The use of 
ceramic rollers also has the ability to further reduce valve train weight 
for even greater improvement, since they could be as much as 40% lighter 
than the use of metal rollers. Plastic is a lubricating type material. 
Therefore, the use of a plastic insert can be self-lubricating. The 
plastic, per se, is a slick material and lubricating material can be 
embedded in it, or together alloyed. Once the engine began operation and 
oil slung in the area, then it can provide self-lubrication. Those skilled 
in the art will appreciate in view of this disclosure that insert 40 could 
be modified to include retention means, for example in the form of tabs 
molded integrally with the insert, to prevent the roller from becoming 
separated from the follower assembly prior to installation in an engine. 
From the above, it will be seen that the invention provides a low weight 
and reduced friction type valve train by the use of a precision molded 
insert operable in a pocket provided in a finger follower lever type 
rocker arm, the insert having a bearing surface that is extremely smooth 
for a sliding engagement with a roller follower of light weight movable by 
a cam of an overhead camshaft type engine construction. Such a 
construction provides an easy assembly of the parts, and with continuous 
lubrication because of the bathtub-shaped reservoir assuring that the 
bearing surfaces always contain lubricant or oil, even after a lengthy 
shutdown. Furthermore, the construction assures the pivotal movement of 
the finger follower lever with a minimum of friction by the use of low 
weight elements. 
While the invention has been shown and described in its preferred 
embodiment, it will be clear to those skilled in the arts to which it 
pertains, that many changes and modifications may be made thereto without 
departing from the scope of the invention.