Note: Descriptions are shown in the official language in which they were submitted.
~ j]-A
lOB3;211
Background of the Invention
This invention pertains to the art of
bearings and more particularly to bearings of the
type having an oil film or layer disposed between
the bearing surface and a journaled member.
The invention is particularly applicable
to half-shell bearings used in internal combustion
engines in cooperation with crankshafts and con-
necting rods and will be described with particular
reference thereto. However, it will be appreciated
by those skilled in the art that the invention has
broader applications and may be used in many other
environments of this general type.
As is known, internal combustion engine
main and connecting rod bearings are sub~ected to
repetitive loads which can ultimately fatigue the
bearing alloy if it does not have sufficient strength
for the particular applications involved. Metal-
lurgical advances through the years have produced
progressively stronger alloys, however, those metal-
lurgical alterations and advances which have thus far
been made appear to have reached the limit inso~ar as
improving or increasing fatigue resistance. The pri-
mary reason for this is that in order to make an alloy
stronger, it must be made harder or alloyed with higher
percentages of elements which are not, themselves, good
bearing materials. Bearings constructed from bearing
materials which are made stronger by either of the
two above noted means will, while theoretically having
a higher fatigue strength, have a much greater tendency
.
1083Zll
to seize during operation and will invariably fail
from such seizure.
Typical internal combustion engine main and
connecting rod bearings are comprised Or halfshells or semi-
circular arrangements constructed from conventional bearingmaterials and are installed within the engines in a manner
well known in the art. Because these particular er.gine
components are recei~-ed in what amounts to continuously
circulated oil bath, there is a clearance area provided
between the outer peripheral surface of the journaled member
or crankshaft and the inner peripheral surface of the
bearing. This arrangement not only facilitates relative
rotation between the parts in the proper manner during nor-
mal engine operation but more importantly, facilitates the
creation of an oil film therebetween which acts as a load
supporting medium during engine operation. The hydrodynamic
wedge effect which causes the shaft or journaled member to
float on an oil film is a result of there being a difference
between shaft and bearing radii at the associated areas
thereof.
For some period of time, it was believed in the
industry that fatigue of a bearing alloy could be expressed
in terms of maximum unit load (peak load divided by pro-
jected bearing area, i.e., length x shaft diameter). How-
ever, this belief or concept did not satisfactorily explainwhy bearings with the same area, but different lengths
and diameters, exhibited different fatigue lives under
identical loading. Modern analytical methods, specifically
the journal orbit analysis, have now explained this phenomenon.
Basically, geometric factors such as bearing length, diameter
~.
1083211
an~ clearance a~fect the pcak pressure devcloped in the
loacl supporting oil film. Those bearings exposed to higher
pressures fatigue sooner or to a greater e~tent in the same
amount of time as bearings exposed to lower pressures.
Through the use of bearing orbit analysis tech-
niques, it can be slown that the peak oil film pressure
developed in a bearing increases in an essentially linear
fashion with increased bearing clearance. Thus, a seemingly
ready answer for improving fatigue strength for these bear-
ings is to reduce the oil film pressures by simply reducing
the bearing clearance. I~owever, a simple reduction in such
clearance is not generally preferred since it would reduce
the "slop" between the bearings and journaled member and
thus be more sensitive to misalignments. Moreover, such a
reduction in clearance would also cause the bearing to run
hotter than one of normal clearance and it could, therefore,
burn up during normal use.
The subject invention contemplates a new structural
arrangement which overcomes all of the above referred to prob-
lems and others and provides a new bearing structure which
is simple in design, provides improved fatigue resistance over
conventional bearing structures and which is readily adapt-
able to use in a number of environments.
Brief Descri tion of the Invention
P
In accordance with the present invention, there is
provided a new and improved cylindrical sleeve bearing adapted
to be operably associated in a close spaced surrounding re-
lationship with a journaled member having a substantially
constant radius of curvative rr over the circumference thereof.
, . . . . .
D-j7~1-A
- ~OB3Z~l
The ncw an~l improved bearing includes ~ firs~ portion having
a thickness w and a radius of curvature x which is greater
than the radius of curvature rr of Lhe journaled member.
The bearing structure also includes a second portion having
a thickness ~ which is less than thickness w and a radius
of curvature z which is greater than the radius of curvature
x of the first portion. By means of this structurel the first
portion of the bearing will "see" a journaled member radius
more nearly equal its own radius during the high load portion
of the bearing cycle so that a lower oil film pressure will
develop The second portion of the bearin~ is disposed
in a manner so that it will receive oil film pressure during
the low load portion of the bearing cycle.
In accordance with another aspect of the present
invention, the first portion of the bearing comprises one-half
of the circumference of the generally cylindrical bearing
area and the second portion comprises the other half of the
bearing area.
In accordance with another aspect of thç present
invention, the bearing area is defined by a pair of bearing
halfshells with one of the halves comprising the first por-
tion and the other of the halves comprising the second portion.
In accordance with yet another aspect of the present
invention, the thickness w and radius of curvature x of the
first portion and the thickness ~ and radius of curvature
z of the second portion vary from each other substantially :~
equal to and opposite from a mean bearing thickness and
radius of curvature.
In accordance with a more specific aspect of the
present invention when utilizing the concepts thereof with
.
D~
1083211
a trimetal type of sleeve bearing, the ~ifferences in thick-
nesses w, ~ and radii of curvature x, z are obtained through
differcnces in thickness of the intermediate layers.
The principal object of the present invention is a
provision of a new and improved sleeve bearing which increases
fatigue resistance.
Another object of the present invention is the
provision of a new and improved sleeve bearing which is simple
in design.
Another object of the present invention is the pro-
vision of a new and improved sleeve bearing which utilizes
conventional bearing components and materials.
A further object of the present invention is the
provision of a new and improved sleeve bearing which is readily
adapted to use in any number of environments of the type where-
in an oil film is provided between the cooperating bearing
and the journaled member surfaces.
Brief Description of the Drawin~s
The invention may take physical form in certain
parts and arrangements of parts, a preferred embodiment of
which. will be described in detail in this specification and
illustrated in the accompanying drawings which form a part
hereof and wherein:
FIGURE 1 is a perspective view of a halfshell bearing
arrangement to which the subject invention is particularly
adapted for use;
FIGURE 2 is a front elevational view in partial
cross-section showing a conventional prior art halfshell
bearing arrangement. as installed in a typical internal com-
--6--
5 1 ~
~083211
busl,i.on engine environment;
~ IGUR~ 3 is a view similar to FIGURE 2 showing
the concepts of the subjec~ invention as incorporated into a
connecting rod bearing for an internal combustion engine;
and,
~IGURE 4 is an enlarged partial view of an arrange-
ment similar to that of FIGURE 3 and showing the concepts of
the subject invention as incorporated into a trimetal type
of sleeve bearing.
Description of the Preferred ~mbodiment
- Referring now to the drawings wherein the showings
are for purposes of illustrating the preferred embodiment of
the invention only and not for purposes of limiting the same,
the FIGUR~S show a pair of halfshell bearings A and B of the
type normally employed on, for example, internal combustion
engine main and connecting rod bearings.
Halfshell bearing A is comprised of a band-like semi- :
circular body lO and halfshell B is comprised of a band-like
semi-circular body 12. Body 10 has end faces 14,16 and body
12 has end faces 18,20. Bodies 10,12 are dimensioned and
cor,figured so that end faces 14,1& and 16,20 will substan-
tially mate with each other. Bodies 10,12 also include inner
bearing surfaces or areas 22,24 and outer surfaces 26,28
respectively. These halfshell bearings may, of course, be
constructed from conventional bearing materials in any con-
ventional manner. For internal combustion engine usage
such as that to which the subject invention is particularly
directed, materials such as, but not limited to, lead base
babbitt, aluminum alloys and copper-lead alloys are employed
.
~083211
for the inner bearing surfaces or areas 22,24 of bodies
10,1,2.
Wi~h reference to FIGURE 2, description wi.ll
hereinafter be made to a prior art connecting rod bearing
employing the bearing halfshells shown in l~IGUr~E 1. Here,
the crankshaft or journaled member is shown in cross-section
and generally designated by numeral 30. The shaft is sub-
stantially circular in cross section and is shown as having
. a radius rr at the outer peripheral surface thereof.
The connecting rod bearing is comprised of half-
shell bearings A and B disposed in a closely spaced relation-
ship with crankshaft or journaled member 30. To provide the
desired bearing installation, an upper rod bearing housing
32 which includes connecting rod 34 as an integral part
thereof is provided along with a cooperating lower rod bearing
housing 36. Each housing has a generally semi-circular open-
ing adapted to closely receive bodies 10,12. Specifically,
housing 32 includes a semi-circular receiving or mounting
surface 38 adapted to closely receive outer bearing surface
26 of body 10 and lower'rod bearing housing 36 includes a
se.-mi-circular receiving or mounting surface 40 adapted to
'closely receive outer surface 28 of body 12.
Moreover, housing 32 includes a pair of outwardly
e~.tending flanges 42 and housing,36 includes a pair of similar
connecting flanges 44 with flanges 42,44 dimensioned and
located so as to mate with each other. The housings are
rigidly connected together by means of, threaded fasteners
46 in a conventional manner. Bodies 10,12 are received in
housings 32,36 in the manner shown in FIGU~E 2 with substan-
tially mating ends 14,18 and 16,20 in an abutting relationship
D-575l-A
1083~11
with each o~her. Housings 32,36 ancl bo~ies 10,12 are di~en-
sioned so tha~ this abutting area is in substantial alignment
with ~he parting line or line of separation be~ween the
housings themselves at flanges 42,44. Bodies 10,12 are
retained in the housings by the dimensioned relationship
between the components when the housings are tightly con-
nected together by means of fasteners 46 and the bodies
typically and advantageously~ include small tabs or lips as
shown in ~IGURE 1 for purposes of assuring proper align-
ment between them. The structure described with reference
to FIGURE 2 is deemed conventional and is well kno~m in the ~ .
art so that further elaboration on the specifics thereof
noted above is deemed unnecessary.
As shown in FIGURE 2 in an exaggerated form, an
annular clearance area a is provided between. the outer peri-
pheral surface or crankshaft or journaled member 30 and inner
bearing surfaces 22,24 of halfshell bearing bodies 10.,12.
In practical application, this clearance is fairly small
and may only comprise a few thousandths of an inch. The
size of the clearance will vary depending upon the specific
application of the bearing within an internal combustion
engine as well as the characteristics of the engine design
itself. Also in the prior art, both halfshell bearing bodies
10,12 have had a substantially identical thickness desig-
nated t in FIGURE 2 and this thickness may vary from a few
hundredths of an inch to a tenth of an inch or so. With this
substantially constant thickness, a radius of curvature _
is defined from the center of the bearing outwardly to bearing
surfaces 22,24. Because of clearance area a, radius _ will be
greater tllan radius rr. In order to facilitate ease of under-
_g _
_ . . _ .. .. ..
~- 5 ~ 5 1 - ~
101~3211
standing ~he spacial rela~ionships be~wecn ~lle coml)onell~s radii
_ and rr are shown as being coaxial. In actual practice,
however, and due to machining charac~eristics and t~lerances
encountered during component manufacture, the centers for the
bearing and crankshaft radii may be slightly oEfset relative
to each other involving some eccentric relationship between
the components. This relationship does not, however, have
any effect on the concepts of the subject invention as de-
scribed herein.
During operation of an engine which incorporates
the prior art connecting rod arrangement sllown in FIGURE 2,
oil is received in annular clearance area a forming an oil
film. This film has a hydrodynamic wedge effect which causes
shaft 30 to float on the oil film during engine operation
and bearing cycling. During such cycling, the oil film pres-
sure which has a destructive effect on halfshell bearing
bodies 10,12 at bearing surfaces 22,24 is particularly trouble-
some during the upstroke of the connecting rod and through
the cylinder bore. It is during this portion of the cycle,
i.e., when crankshaft or journaled member 30 is acting against
lhe oil film disposed between that member and inner bearing
s~lrface 22 of halfshell body 10 that the peak or maximum oil
f lm pressures are developed. While there are oil film pres-
sures developed between the crankshaft and inner bearing sur-
face 24 of halfshell body 12 during the downstroke, such pres-
sures are not nearly as great or destructive as those incurred
on the upstroke.
Thus, and in a typical internal combustion engine
environment, the crankshaft bearings are different~ially loaded
during each cycle and such loading is dependent upon the position
-10-
.
10832~1
of the bearing cluring the cycle. When th~ rod bearings are
subjected to repetitive loads such as tllose described above,
it can ultimately ~atigue the bearing alloy i.f the alloy does
not have sufficient strength for the application involved.
Accordingly, it has been desired to improve this fatigue
strength in order to yield better overall engine operation.
It has been thought that simple metallurgical im-
- provements to bearing materials would solve this problem.
However, in order to make a bearing alloy stronger, it must
necessarily be hardened or be alloyed with higher percentages
of elements which are not themselves good bearing materials.
~hen these solutions are employed, the bearings, while
theoretically having a higher fatigue strength, also have a
much greater tendency to seize during operation.
Knowing that a decrease in clearance area _ would
act to reduce peak oil film pressures developed during bearing
cycling, another apparent solution to the problems would be to
simply reduce the clearance area itself. Such a reduction
in clearance is not generally preferred or desirable since
the elimination of some "slop" within the bearing arrangement
will render it far more sensitive to misalignment. Moreover,
such a bearing arrangement would run hotter than one of normal
clearance and could burn up during normal use.
The subject invention focuses on a solution to the
above noted problems as shown in FIGUR~ 3. The structural
solution is shown as it has been incorporated into a conven-
tional rod bearing arrangement identical to the arrangement
shown in FIGURE 2. For this reason and for ease in appre-
ciating the scope of the invention, like c~mponents are
identified by like numerals with the inclusion of a primed
.
D-5751-~ 1083211
(') suffix while new components are identified by new
numerals or letter designations,
Basically, the concepts of the present invention
are directed toward increasing bearing fatigue resistance
S and still maintaining the same overall diametral bearing clear-
ance as has been conventionally employed in order to prevent
seizures or excessive operating temperatures. The desired
results are achieved by specific modiÇications made to half-
shell bearing bodies 10,12. ~lore particularly al~d in accord-
ance with the present invention, the desired results are
obtained by increasing the bearing wall thickness in the
heavily loaded of the halfshells by a given amount and by
decreasing the bearing wall thickness of the lightly loaded
of the halfshells by an equal amount. In this manner, the
bearing will "see" or be associated with a crankshaft or
journaled member radius more nearly equal to its own radius
during the high load portion of the cycle. This arrangement
results in a lower peak film pressure being developed there
than with conventional bearing structures such as that shown
and described with reference to FIGURE 2.
With reference to FIGURE 3, bearing body 10' has
a thickness w and bearing body 12' has a thickness ~. Thick-
ness w is greater than the thickness t of the conventional
arrangement shown in FlGURE 2 and thickness ~ is less than
the thickness t. In order to prevent seizures or excessive
, temperatures when utilizing the concepts of the subject inven-
tion, the increase in thickness w over thickness t is compen- ;
sated for by a corresponding identical decrease in thicknes,s
under thickness t. Thus, it is possible to' maintain the
same overall diametral clearance as is used in the present
-12-
U~
lV83211
convell~ional bearings while still ac~lievin~ better overall
operational results insofar as increasing fatigue resistance.
By increasing the thickness of halfshell bearing
body 10' to thickness w, the effective radius of curvature
x of body 10' is decreased slightly from radius r shown in
FIGURE 2, although radius x is still greater than radius
rr' of crankshaft or journaled member 30'. In FIGURE 3,
the clearance area between inner bearing surface 22' and the
outer peripheral surface of crankshaft 30' is designated b
10 and is smàller than clearance area a of FIGURE 2. Moreover,
and due to the decrease of thickness ~ in FIGURE 3, radius
of curvature z of halfshell bearing body 12' is increased.
so that it is greater than the radius of curvature x and the
radius of curvature r. Accordingly, a clearance area c is
15 defined between inner bearing surface 24' and the outer peri-
pheral surface of crankshaft 30' and which clearance area is
larger than clearance area a in FIGURE 2 as well as clearance
area b in FIGURE 3.
With the structural arrangement disclosed above
20 with reference to FIGURE 3, during the upstroke of the piston
when the greatest peak oil film pressures are developed, the
destructive forces normally attendant thereto o~rer long
periods of time or operation under heavy loads are decreased
due to the decrease in the clearance area b. Again, as
25 bearing clearance increases, the peak oil film pressures
developed increase in an essentially linear manner so that
conversely, a decrease in bearing clearance causes a decrease
in peak oil film pressures. Furthermore, since lower oil film
pressures are developed in the downstroke portion of the
30 cycle, the corresponding increase in clearance area c will
1083Zll
noL be signiLicant insofar as any destruc~ion of lower half-
shel.l bearing 12' during cycling.
Because of the differences in ~hlckness between
hali.-sllell bearing bodies 10',12', undesired oil wiper areas
would be created at the parting lines be~ween the two bo~ies
at the substantially mating end faces 14',18' and 16',20'
thereof. To eliminate these wiper areas, shallow reliefs 50,
52,54 and 56 are provided across the widths of bodies 10',12'
at the end face areas. The radial depths o~ these reliefs
are calculated so that the halfshell bearing bodies will have
the same thickness at the parting lines to thereby eliminate
the discontinuities resulting in undesired oil wipers.
The various dimensions and clearances shown in
FIG~RE 3 have been exaggerated for purposes of appreciating
the scope and intent of the present invention. In actuality
and with some typical internal combustion engines, the in-
crease in thickness w of body 10' may only be on the order
and magnitude of .001" with a corresponding identical reduc-
tion in thickness ~ of body 12'. While these changes may seem
minimal from a structural point of view, the arrangement
shown in FIGURE 3 does provide increased bearing fatigue
resistance over the conventional prior art arrangement shown
in FIGURE 2. By way of example an~ based upon the results
of a series of calculations based upon a diesel engine rod
bearing, an increase in the upper halfshell bearing wall
thickness of .001" with a corresponding reduction in the lower
halfshell bearing wall thickness resulted in a reduction in
peak oil film pressures of approximately 35%.
While the subject invention has been described with
specific reference to adaptation and use on a connecting rod
-14-
_ . . . . . .
1083211
bearin~, it should also be appreciated tllat the invenLion has
been equally adapted for use on the engine main bearings.
When adap~e~ for use on main bearings, however, the thicker
walled halfshells are employed on the lower main bearing posi-
tions with the thinner halfshells being employed in the
upper main bearing positions. The subject inven~ion is also
adaptablé to use in other environments and installations where
bearing fatigue resistance is a problcm and where an oil film
is disposed between the bearing and the journaled member to
provide a hydrodynamic wedge effect thus developing peak oil
film pressures during cycling which could have a destructive
effect on the bearings themselves.
~or example and with reference to FIGURE 4, the
invention is readily adaptable to use in heavy duty sleeve
bearings more conventionally known as the trimetal type.
For ease of illustration and appreciation of this modifica- .
tion, like components are identified by like numerals including
a double primed ('') suffix and new components are identified
by new n~nerals. The various dimensions and clearances
shown in FIGURE 4 have been conveniently exaggerated for pur-
poses of appreciating the scope and intent of the invention.
In FIGURE 4 semi-circular bodies 10" ,12" are each
comprised of three distinct laminations or layers 60,62,64
and 70,72,74, respectively. Layers 60,70 comprise steel
backings. Intermediate layers 62,72 comprise a bearing alloy
capable of withstanding high loads. These layers are typically
comprised o an alloy of copper-lead-tin or alwninwm although
other alloys could also be advantageously employed. Layers
64,74 comprise thin electroplated or cast layers of a soft
ma~erial. Typically, these layers are comprised of lead-tin,
-15-
.. . . _ _ .. .. . . _
D-57jl-~
lU83Zll
lead-tin-copper, tin base babbit or lead-indi~ materials
although other materials could also be u~il.ized.
Layers 64,74 comprise what are conventionally
termed overlay layers and provide the bearing structure with
the ability to embed dirt particles circulating in the oil
therein. They also ~urnish "slippery" surfaces to prevent
shaft-to-bearing seizure a~ start-up and shut down and are
further such that they may "adjust" to minor irregularities
in geometry an~/or alignment. For many years the thiclcness
of layers 64,74 were the same and have been in the nominal
range of 0.001" for typical diesel truck engines. ~s engine
loads were increased, however, this thickness had to be re-
duced to around nominally 0.0006" for preventing premature
loss of overlay layers 64,74 due to fatigue.
~ince the fatigue resistance of a bearing alloy
decreases as its thickness increases, the above change
solved the premature fatigue problem but simultaneously
introduced new problems. First, the overlay layers wore
out sooner simply because there was less overlay to,wear.
Second, the overlay could not absorb as much circulating
dirt. Once the overlay layers bccome worn, the harder in-
termediate layers 62,72 were exposed to the shaft. The
resultant shaft-bearing assembly was then much more prone
to seizure and susceptible to damage caused by circulating
dirt.
In applying the concepts of the subject invention ~ .
to a trimetal type sleeve bearing in the same manner described
above in substantial detail, the total thickness of layers
62,64 has been made,sli~htl~y thicker than the nominal thick-
ness and the total thickness of layers 72,74 is then made
-16-
~,oB3,~
~hinner by a correspondillg amount. S~c~l ~acking layers
60,70 each have the same thickness. Similar to the FIGURE 3
arrangement, halfshell or body 10'' which includes layers
62,64 is positioned to receive the hcavier loading during
use or cycling. Halfshell or body 12'' which includes
layers 72,74 is positioned to receive the lighter loading
~uring use or cycling. The increased total thickness of
layers 62,64 provides a smaller radial clearance b'' between
the surface thereof and the surface of crankshaft or journaled
member 30''. The reduced total thickness of layers 72,74
provides a larger radial clearance c'' between the surface
thereof and the surface of the crankshaft or journaled
member .
Insofar as the relative difference in total thick-
ness between layers 62,64 and 72,74 is concerned, the thick-
nesses of layers 64,74 are generally equal to each other
with the thickness of layer 62 being greater than the thickness
of layer 72. This is primarily for the reason that it is
easier and less costly for practical production reasons to
let overlay layers 64,74 be of the same magnitude.
~owever, it is possible and sometimes desirable
to also vary the thickness of overlay layers 64,74. In
that instance, overlay layer 74 of the thinner halfshell
bearing body, i.e., body 12" , is made thicker than overlay
layer 64 of the thicker halfshell bearing body, i.e., body
10''. This modificztion may be desirable in order to pro-
vide better cmbcddability and is possible because the
thinner ~ody 12'l is only subjected to light loads so that,
thereEore, the additional thickness of overlay layer 74
will not suL`fer fatigue. Here again, however, necessary
-17-
, .
~ l-A
1083Z~l
alterations ~o the layered halfshell bearin~ bodics to accom-
modate the alternative thicknesses for layers 64,74 will be
compensated for in the intermediate layers.
Overall operation of the modified arrangement of
FIGURE 4 is substantially identical to that hereinabove de-
scribed witll reference to FIGU~E 3. l~owever and specifically
as to heavy-duty trimetal type sleeve bearings, utilization
of the subject inventive concepts acilitates use of thicker
more wear resistan~ and dirt tolerant overlays. Accordingly,
layers 64,74 may be dimensioned in a manner to thereby extend
overlay layer wear life an~ dirt ingesting capabilities with-
out simultaneously sacrificing fatigue resistance.
The invention has been described with reference to
the preferred embodiment. Obviously, modifications and
alterations will occur to others upon the reading and under-
standing of this specification. It is my intention to include
all such modifications and alterations insofar as they come
within the scope of the appended claims or the equivalents
thereof.
~' .
' ` ~.
