Lubricant distribution system for bearings and bushings

A shaft bearing or bushing includes a hydrodynamic wedge film lubricant pumping surface along one edge region and an essentially continuous cylindrical land surface along the other opposed edge region. Lubricant moves circumferentially along the pumping surface and axially along the continuous land surface. The bearing provides extensive surface area oil film support for the rotating shaft and may be optimized for supporting a specific shaft load distribution.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a plain bearing or bushing having both a 
ramped and a cylindrical surface profile for distributing lubricating 
fluid to load-bearing surfaces under both hydrodynamic wedge film 
lubrication and conventional cylindrical film lubrication. 
2. Description of Prior Developments 
Rotational motion of a shaft is commonly used to maintain a load supporting 
lubricant film between annular support surfaces provided on the inner 
surfaces of bearings and bushings, (hereinafter collectively referred to 
as bushings) and the outer surface of the shaft. Rotation of the 
cylindrical shaft draws lubricant into one or more small clearance spaces 
between the shaft and the load bearing surfaces of the bushing. 
The internal support surfaces of the bushing may include a fluid entrance 
surface spaced radially from the shaft side surface, a land surface having 
a minimal clearance with respect to the shaft surface and a concave ramp 
surface joining the fluid entrance surface and the land surface. 
Lubricating oil is drawn in a circumferential direction from the fluid 
entrance surface along the ramp surface and onto the land surface. 
The oil is wedged into a small radial clearance between the land surface 
and the shaft side surface to form a pressurized load supporting film. The 
pressurized wedge-shaped oil film is not readily displaced out of the 
small clearance space, and is thus able to absorb or sustain relatively 
large radial shaft loads. This type of bearing lubrication is sometimes 
referred to as hydrodynamic wedge film lubrication. 
Although hydrodynamic wedge film lubrication provides satisfactory results 
when used in many conventional bearing and bushing applications, the 
presence of ramped bearing surfaces over the full axial extent of the 
bearing or bushing decreases the stability provided to a rotating shaft as 
compared to a nonramped or nominally cylindrical bearing support surface. 
Moreover, such a ramped design produces a larger leak path for lubricant 
to escape from between the bearing and shaft. 
U.S. Pat. No. 1,236,511 shows a bearing construction that utilizes wedge 
film lubrication of the above-mentioned type wherein oil is introduced to 
the bearing through four axially extending grooves in the bearing inner 
surface. As the shaft rotates, the oil clinging to the shaft surface is 
drawn circumferentially into small clearance spaces located midway between 
the grooves. The oil film established in the small clearance spaces 
provides a low friction support for the shaft, thereby protecting the 
shaft and bearing against contact and wear. 
The circumferentially moving oil film is confined to circumferential motion 
by rims or lands that form shoulders along edge areas of the wedge film 
surfaces. A disadvantage of such rims is that if they are fully effective 
they can be in direct contact with the shaft surface, thereby producing 
frictional wear. Also, by confining the oil to a circumferential motion, 
any circulation of oil through the bearing is prevented because there is 
no convenient oil path out of the bearing. The oil will endlessly 
circulate in a circumferential direction around the bearing, thereby 
eventually heating the oil and generating carbon particulates. 
Other patents showing wedge film lubrication achieved by circumferential 
oil motion are U.S. Pat. Nos. 2,631,905 and 3,680,932. In these patented 
arrangements, the edge areas of the wedge film surfaces are bounded by 
endless circular rim or land surfaces designed to prevent axial leakage of 
the circumferentially moving oil film away from the wedge film surfaces. 
SUMMARY OF THE INVENTION 
The present invention is directed to a radial bearing using wedge film 
lubrication together with a controlled axial flow of the wedge film oil 
through a cylindrical gap so that the oil circulates through the bearing 
in an expeditious manner. 
The invention is primarily embodied in a sleeve bearing wherein 
approximately one-quarter to one-half the axial length of the bearing is 
internally ramped and contoured to form one or more wedge film pump 
surfaces designed to promote a circumferential flow of lubricant around 
the internal surface of the bearing. The remaining portion of the axial 
length of the bearing includes a cylindrical surface having a 
substantially uniform radial clearance relative to the shaft surface. 
The lubricant moves circumferentially around the bearing while in contact 
with the wedge film surfaces and axially and/or helically while in contact 
with the cylindrical bearing surface. The cylindrical bearing surface 
establishes an essentially continuous load-supporting film around the 
shaft surface, thereby providing an essentially continuous uniform support 
action around the entire shaft circumference so as to stabilize the shaft. 
With the described arrangement, the unit loadings on the bearing are 
lessened as compared to a purely wedge-film bearing because the entire 
circumference of the bearing provides support to the shaft over a 
significant axial extent of the bearing. 
The clearance between the cylindrical shaft surface and cylindrical bearing 
surface can be closely controlled by conventional machining or forming 
procedures so that the quantity of oil circulated through the bearing can 
be limited to a reasonable value consistent with the aim of controlling 
the thermodynamic effect. 
By providing a hydrodynamic wedge effect over only a portion of the axial 
extent of the bushing or bearing, the bushing or bearing may be optimized 
to match its load handling capabilities with a particular shaft loading 
distribution while reducing lubricant leakage and improving shaft 
stability. That is, hydrodynamic ramps may be limited to that axial 
portion of the bearing which receives the greatest radial loads while the 
remaining axial extent of the bearing surface is of conventional circular 
or cylindrical shape for improving shaft stability and controlling or 
reducing axial lubricant flow and leakage. 
Moreover, by providing a portion of the bearing with a full round 
cylindrical support surface, shaft support is increased so as to reduce 
stress concentrations and the breakdown of the lubricant film in the 
hydrodynamic wedge region, This in turn prevents metal-to-metal contact 
since the lubricant wedge is maintained. 
Additional features and advantages of the invention will be further 
apparent from the attached drawings and drawing descriptions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIGS. 1 and 2, there is shown a shaft and bearing assembly 
constructed accordance with the present invention. A cylindrical or 
circular shaft 10 has a cylindrical surface 12 and a flat end surface 14. 
As shown in FIG. 1., the shaft is supported in the radial direction by a 
sleeve-type bearing or bushing 16 which is press fit in housing 17. End 
wall 19 of the housing is facially engaged with end surface 14 of the 
shaft to form an annular lubricant chamber 27 surrounding the shaft near 
its right end portion. The shaft is designed to rotate around the shaft 
axis 23. 
Bushing 16 includes an outer annular steel backing layer or strip 18 
laminated to an annular layer or inner strip 20 of a bearing alloy having 
anti-friction properties, e.g., an aluminum-tin, an aluminum-lead or other 
suitable bearing alloy. A flat bimetal strip is typically curled into a 
circular configuration to form an annular bushing. 
A conventional annular radial lip seal 25 is press fit in housing 17 to 
form an annular lubricant chamber 21 bordering the left end edge portion 
of bushing 16. As indicated by the directional arrows, lubricating oil 26 
is pumped into chamber 27 thereby pressurizing chamber 27. The pressurized 
lubricant has a circumferential and axial motion as it passes leftwardly 
through the clearance space between bushing 16 into the annular chamber 
21. The oil 26 passes out of chamber 21 through an exit opening 29. 
The left axial half portion of bushing 16 designated by numeral 31 is 
internally contoured to form a wedge film pump surface designated 
generally by numeral 33 in FIG. 2. This left portion of the bushing 
experiences the greatest deflection and loading. The right half portion of 
bushing 16 designated by numeral 35 in FIG. 1 has a cylindrical internal 
surface 36 having a uniform radial clearance relative to the shaft side 
surface 12. This right portion of the bushing experiences a lower load 
distribution than the left portion. 
In FIG. 1, the uniform radial clearance is designated by numeral 37. 
Typically, clearance 37 is about 0.001 inch, whereby a relatively thin 
load supporting oil film is maintained in the clearance space while the 
oil is moving in a right-to-left direction as shown in FIG. 1. 
Wedge film pump surface 33 includes two axial grooves 39 for supplying 
lubricating fluid to two fluid entrance surfaces 41 spaced radially 
outwardly from the cylindrical shaft surface 12. Pump surface 33 further 
includes two cylindrical portion land surfaces 43 that are coextensive or 
coplanar with cylindrical surface 36 constituting the right half of the 
bushing. 
Land surfaces 43 promote shaft stability while maintaining the lubricant in 
a highly pressurized condition. An arcuate ramp surface 45 joins fluid 
entrance surface 41 to land surface 43. Although land surfaces 43 can be 
quite narrow and essentially define a line contact with the shaft, it is 
preferred to extend land surfaces 43 circumferentially over at least 
several degrees of arc, i.e. 2 to 5 degrees, so as to provide a portion of 
a cylindrical support surface which reduces shaft whip and promotes shaft 
stability. 
As shaft 10 rotates in a clockwise direction as shown in FIG. 2, the 
circumferentially moving shaft surface draws oil along the ramp surface 45 
to form a wedge type oil film on land surface 43. Simultaneously, the 
pressurized condition of lubricant chamber 27 tends to move the oil 
axially in a right-to-left direction across the cylindrical bushing 
surface 36 and onto the ramped region 31. 
The oil is introduced onto the ramped region 36 primarily at or near the 
groove 39 and is distributed through the ramp of bushing surface 41 by the 
movement of cylindrical shaft surface 12. The oil is distributed uniformly 
on land surface 43 thereby increasing its load carrying capability. The 
oil on surfaces 36 and 43 provides the desired lubricant support for shaft 
10. The system is designed to provide a continuous circulation of the oil 
through the bearing or bushing while the shaft is rotating. 
By aligning and mounting the ramped portion 31 of the bushing adjacent that 
section of the shaft which produces the greatest unit loading, such as by 
shaft whip or other deflection, the bushing may be optimized for maximum 
loading performance. Since the ramped portion 31 can withstand greater 
dynamic loading than cylindrical portion 35, overall bearing performance 
may be increased. In addition, the cylindrical portion 35 provides greater 
stability than that normally possible with only the hydrodynamic portion 
31, and thereby reduces the peak loading applied over portion 35. 
The bushing performance can be even further optimized by circumferentially 
aligning the land surfaces 43 with that circumferential portion or 
portions of the shaft surface which experiences the greatest loading. For 
example, if it is known that the greatest radial loading on a particular 
shaft occurs at the 6 o'clock and 12 o'clock positions, the bushing would 
be aligned as shown in FIG. 2 such that land surfaces 43 are located 
adjacent the corresponding 6 o'clock and 12 o'clock circumferential 
locations. 
FIGS. 3 through 5 illustrate a second shaft bearing arrangement that is 
generally similar in a functional sense to the system depicted in FIGS. 1 
and 2. However, in the FIG. 3 system, the pressurized lubricant is 
introduced to the wedge film pump surface through a hole 49. The oil has a 
right-to-left motion through the bushing in addition to the desired 
circumferential motion. 
In FIG. 3, the right portion of the bushing designated by numeral 31 is 
internally contoured to form the wedge film pump surface. The left portion 
of the bushing designated by numeral 35 has a cylindrical internal surface 
36 having a uniform radial clearance relative to the shaft side surface. 
Oil discharged from the clearance 37 flows into an annular chamber 51 
defined by the left end edge of the bushing and an annular lip seal 25. 
Seal 25 and end wall 19 form fluid barriers or confinement mechanisms for 
the oil circulated through the bushing. 
As shown in FIGS. 4 and 5, the wedge film fluid pump surface portion 31 
includes a fluid entrance surface 53 in the form of a groove or channel 
adapted to be spaced or recessed from the shaft surface, a ramp surface 55 
extending from surface 53 and a land surface 57 axially and radially 
coextensive or coplanar with the bushing surface 36 defining the left 
portion of the bushing axial dimension. In the FIG. 3 arrangement, the 
wedge film pump surface is located within or forms an annular lubricant 
inlet chamber surrounding the shaft 10. Lubricant is introduced to the 
pump surface through hole 49. 
As the shaft rotates around the shaft axis, oil is drawn circumferentially 
along the ramp surface 55 onto land surface 57. The pressurized condition 
of the rightmost chamber defined by the wedge film pump surface causes the 
oil to have a leftward motion across the bushing cylindrical surface 36. 
The shaft loading is supported on the oil film established on surfaces 36 
and 57. The bearing system of FIG. 3 operates in approximately the same 
fashion as the system depicted in FIG. 1. 
FIGS. 6 through 8 show a shaft bearing system according to the invention 
designed to use a self-contained supply of lubricant, i.e. a bearing 
wherein there is no external lubricant source. In FIG. 6, the lubricant 
has two-directional flow through the bushing as determined by the relative 
pressures in two annular chambers 61 and 63 bordering the left and right 
edge portions of the bushing. Chambers 61 and 63 are defined by two 
fluid-confinement lip seals 65 and 67. 
FIGS. 7 and 8 show the bushing unfolded to a flat condition. In the actual 
bushing, as depicted in FIG. 6, the axial edges 69 and 71 of the bushing 
wall are abutted and secured together to form an endless tubular bushing 
sleeve. The bushing has wedge film pump surfaces that define fluid 
entrance surfaces 73 which are spaced or recessed from the shaft surface 
12 as shown in FIG. 6, land surfaces 75 extending axially and radially 
coplanar or coextensive with the inner bushing load support surface 36 and 
arcuate sloping ramp surfaces 77 joining surfaces 73 to land surfaces 75. 
FIG. 7 includes arrows denoting the flow of lubricant 26 along surfaces 73, 
77 and 75 during rotational motion of the shaft. The shaft circumferential 
motion draws the lubricant along ramp surfaces 77 onto land surfaces 75. 
The flow of oil along surface is 73 and 77 transfers oil from chamber 61 
to chamber 63, thereby pressurizing chamber 63 while depressurizing 
chamber 61. A pressure differential is thus established tending to cause 
oil on bearing surface 36 to move in a right-to-left direction as shown in 
FIG. 6. An internal oil circuit is established across the bushing. 
The bearing system of FIG. 7 operates in essentially the same fashion as 
the systems of FIGS. 1 and 3, except that the lubricant supply is 
self-contained, i.e. not remote from the shaft support. 
Bearing systems of the present invention can be used at one or both ends of 
a rotary shaft, as shown in FIGS. 1 and 3. Also, such bearings can be used 
at intermediate points along a shaft, as shown in FIG. 6. When the bearing 
is supported at an end of the rotary shaft, the bearing advantageously 
adopts to orbital shaft motions of the shaft produced by transverse 
loadings at intermediate points along the shaft. In this case, the 
cylindrical bearing surface 36 is located closest to the end surface 14 of 
the shaft. 
The continuous circumferential shaft support provided by the oil films on 
the cylindrical bearing surfaces 36 absorbs the multi-directional load 
forces sometime is associated with orbital shaft motions, i.e. minor 
cyclic motions of the shaft surface toward or away from the shaft axis. 
Surfaces 35 and 36 may be of differing axial length to suit a particular 
shaft load distribution. 
The drawings show specific forms of the invention. However, it will be 
understood that the invention can be practiced in various forms.