CA1083211A - Sleeve bearing - Google Patents

Abstract

Abstract of the Disclosure A sleeve bearing of the halfshell type wherein an oil film is disposed between the bearing and journaled member during operation and which bearing improves bearing fatigue resistance. The thickness of one of the half-shells is increased to thereby reduce the radius of curva-ture thereof and the thickness of the other halfshell is reduced by an equal amount to thereby increase the radius of curvature thereof. The halfshells are disposed so as to closely surround a journaled member in a manner such that the higher loads generated during bearing cycling are carried by the halfshell having the greater thickness.
This structure acts to reduce destructive oil film pressures developed between the bearing and journaled member during that period of bearing cycling when elevated loads are experienced. In heavy duty sleeve bearing constructions of the trimetal type, the differences in thickness and radius of curvature are achieved through differences in the so called intermediate layers.

Description

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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 ~.

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.

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- ~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 .

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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-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 .

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 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 _ . . . . . .

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, .. . . _ _ .. .. . . _ 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 ~,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 , .

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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.
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Claims (18)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. In a bearing of the type having a substantially cylindrical bearing area with inner and outer surfaces which surrounds a substantially cylindrical journaled member in a close spaced relationship therewith in a manner defining a clearance area between the inner surface of said bearing area and the outer peripheral surface of said journaled member adapted to receive a load supporting oil film, said bearing area being defined by a bearing material having a substantially constant radial thickness t throughout and wherein said bearing area has a substantially constant radius of curvature r at said inner surface with said journaled member having a substantially constant radius of curvature rr at the outer peripheral surface thereof slightly less than radius r and wherein said bearing is subjected to differential loading during cycling, the improve-ment comprising:
a first circumferential portion of said bearing area having a thickness slightly greater than t so as to reduce the radius of curvature of said inner surface to less than r but greater than rr; and, a second circumferential portion of said bearing area opposed from said first portion having a thickness slightly less than t so as to increase the radius of curvature of said inner surface to greater than r.

2. The improvement as defined in claim 1 wherein said first portion comprises one-half of the circumference of said generally cylindrical bearing area and said second portion com-prises the other half of the circumference of said bearing area.

3. The improvement as defined in claim 2 wherein said bearing area is defined by a pair of opposed semi-cylindrical halfshells, one of said halfshells comprising said first portion and the other of said halfshells comprising said second portion.

4, The improvement as defined in claim 1 wherein said bearing area is defined by a bearing sleeve, said first portion being operably disposed relative to said journaled member to receive the highest forces incurred during said differential loading with said second portion being operably disposed relative to said journaled member to receive the lower forces incurred during said differential loading.

5. The improvement as defined in claim 4 wherein said sleeve is comprised of two opposed semi-cylindrical bearing halfshells, one of said halfshells comprising said first portion and the other of said halfshells comprising said second portion.

6. The improvement as defined in claim 1 wherein the increase in thickness and resultant decrease in the radius of curvature of said first portion are substantially equal to and opposite from the decrease in thickness and resultant in-crease in the radius of curvature of said second portion.

7. A cylindrical sleeve bearing having inner and outer surfaces adapted to be operably associated in a close spaced surrounding relationship with a cylindrical journaled member in a manner defining a clearance area between the inner sur-face of said bearing and the outer surface of said journaled member adapted to receive a load supporting oil film with said journaled member having a radius rr at the outer peripheral surface thereof, said bearing comprising:
a first portion having a radius of curvature x to said inner surface which is greater than the radius of curvature rr;
and, a second portion having a radius of curvature z to said inner surface which is greater than said radius of curvature x.

8. The bearing as defined in claim 7 wherein said first portion comprises one-half of the circumference of said generally cylindrical sleeve bearing and said second portion comprises the other half of said sleeve bearing.

9. The bearing as defined in claim 8 wherein said sleeve bearing is comprised of a pair of opposed semi-cylindrical bearing halfshells, one of said halfshells comprising said first portion and the other of said halfshells comprising said second portion.

10. The bearing as defined in claim 7 wherein said first portion is adapted to be operably disposed relative to said journaled member to receive the higher forces in-curred during differential loading of said bearing and said second portion is adapted to be operably disposed relative to said journaled member to receive the lower forces in-curred during said differential loading.

11. The bearing as defined in claim 10 wherein said sleeve is comprised of two opposed semi-cylindrical bearing halfshells, one of said halfshells comprising said first portion and the other of said halfshells comprising said second portion.

12. The bearing as defined in claim 7 wherein said first portion has a radial thickness w and said second portion has a radial thickness y, said thickness w being greater than said thickness y.

13. The bearing as defined in claim 12 wherein said thickness w and radius of curvature x of said first portion and said thickness y and radius of curvature z of said second portion vary substantially equal to and opposite from each other relative to a mean bearing thickness and radius of curvature.

14. In a bearing of the type having a substantially cylindrical bearing area with inner and outer surfaces which surrounds a substantially cylindrical journaled member in a close spaced relationship therewith in a manner defin-ing a clearance area between the inner surface of said bearing area and the outer peripheral surface of said journaled member adapted to receive a load supporting oil film, said bearing area being defined by a bearing material having a substantially constant radial thickness t throughout and wherein said bearing area has a substantially constant radius of curvature r at said inner surface with said journaled member having a substantially constant radius of curvature rr at the outer peripheral surface thereof slightly less than radius r and wherein said bearing is subjected to a differential loading during cycling, the improvement comprising:
a first circumferential portion comprising one-half of said bearing area and having a thickness slightly greater than t so as to reduce the radius of curvature of said inner surface to less than r but greater than rr; a second circum-ferential portion comprising the other half of said bearing area opposed from said first portion having a thickness slight-ly less than t so as to increase the radius of curvature of said inner surface to greater than r; and, said first and second portions of said generally cylindrical bearing area each being comprised of distinct layers including a backup layer, an intermediate layer and an innermost overlay layer having said inner surface wherein at least the intermediate layer of said first portion has a thickness greater than the thickness of the intermediate layer of said second portion for achieving the difference in thickness between said portions.

15. The improvement as defined in claim 14 wherein said bearing area is defined by a pair of opposed semi-cylindrical halfshells comprised of said backup, intermediate and innermost overlay layers with one of said halfshells com-prising said first portion and the other of said halfshell comprising said second portion, said semi-cylindrical half-shells having opposed and substantially mating end faces with said halfshells having substantially the same thickness at least at the mating end faces thereof.

16. The improvement as defined in claim 14 wherein the difference in thicknesses in said first and second portions is in the intermediate and overlay layers thereof with the overlay layer of said second portion having a greater thickness than the overlay layer of said first portion.

17. The improvement as defined in claim 14 wherein said bearing area is defined by a bearing sleeve comprised of said backup, intermediate and innermost overlay layers, said first portion being operably disposed relative to said journaled member to receive the highest forces incurred during said differential loading with said second portion being operably disposed relative to said journaled member to receive the lower forces incurred during said differential loading.

18. The improvement as defined in claim 14 wherein the increase in thickness and resultant decrease in the radius of curvature of said first portion as effected through any of the individual of said layers thereof are substantially equal to and opposite from the decrease in thickness and resultant increase in the radius of curvature of said second portion as effected through the corresponding of the individual of said layers thereof.