A description is given of an antifriction bearing and a process by which its fatigue life may be extended. The method involves a rotating shaft supported by a fluid bearing and a rolling element bearing coupled in series. Each bearing turns at a fraction of the rotational speed of the shaft. The fluid bearing is preferably conical, thereby providing thrust and radial load support in a single bearing structure

Anderson, W. J.

English

NASA Technical Reports Server

REPLY TO
ATTN OF: GP
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WASHINGTON. D.C. 20546
OCT 12 1973
TOt RSI/Scientific & Technical Information Division
Attention: Miss Winnie M. Morgan
PROM: GP/Office of Assistant General Counsel for
Patent Matters
SUBJECT: Announcement of NASA-Owned U.S. Patents in STAR
In accordance with the procedures agreed upon by Code GP
and Code KSI, the attached NASA-owned U.S. Patent is being
forwarded for abstracting and announcement in NASA STAR.
The following information is provided:
U.S. Patent No. :'
Government or
Corporate Employee
Supplementary Corporate
Source (if applicable)
NASA Patent Case No.
gou
NOTE - If this patent covers an invention made by a corporate
employee of a NASA Contractor, the following is applicable:
Yes
 / / No / K/
Pursuant|to Section 305(a) of the National Aeronautics and
Space Act, the name of the Administrator of NASA appears on
the first page of the patent; however, the name of the actual
JLnventor (author) appears at the heading of column No. 1 of
the Specification, following the words "... with respect to
an invention of ...H
Elizabeth A. Carter
Enclosure
Copy of patent cited above
https://ntrs.nasa.gov/search.jsp?R=19730023627 2020-03-17T09:32:05+00:00Z
United States Patent
Anderson
mi- 3,759,588
[45] Sept. 18, 1973
[54] HIGH SPEED HYBRID BEARING
rTlMPDlCIIMr* A PI Ilin RlrABIlMf Str A
ROLLING BEARING CONNECTED .IN
SERIES
1,445,188
1,175,415
2,623,353
3,012,827
3.026,154
2/1923
3/1916
12/1952
12/1961
3/1962
Wadsworth
Eebert
Gerard
Goetz
Marchand
308/160
308/35
308/35
308/35
308/35
[75] Inventor: William J. Anderson, North
Olmsted, Ohio
[73] Assignee: The United States of America as
represented by the Administrator of
the National Aeronautics and Space
Administration, Washington, D.C.
[22] Filed: Nov. 12, 1971
[21] Appl. No.: 198,379
[52] U.S. Cl 308/35, 308/9
[51] Int. Cl F16c 21/00, F16c 39/04
(58] Field of Search 308/35, 9, 160, DIG. 1
[56] References Cited
UNITED STATES PATENTS
3,143,381 8/1964 Vurpillot 308/9
Primary Examiner— Charles J. Myhre
Assistant Examiner—Barry Grossman
Attorney—^. T. Musial et al.
[57] ABSTRACT
A rotating shaft is supported by a fluid bearing and a
rolling element bearing coupled in series. Each bearing
turns at a fraction of the rotational speed of the shaft.
The fluid bearing is preferably conical, thereby provid-
ing thrust and radial load support in a single bearing
structure.
7 Claims, 3 Drawing Figures
(NASA-Case-LEH-11152-1) HIGH SPEED HYBRID
BEARING COHPBISING A FLUID BEARING AND A
ROLLING BEARING CONNECTED IN SERIES
Patent (HASA) 2 p CSCL 131
N73-32359
Unclas
00/15 18001
PATENTED SEP 1819T3 3,759.588
fK.1
FT6.2
a.
cc
30,000
25,000
a 20,000
§ 15,000
cc
£5
I 10,000
5,000
THRUST LOAD,
LB(N)
o 100
A 300 /
SOLID DATA POINTS INDICATE /
_ THEORETICAL LIFTOFF SPEEDS /
OPEN SYMBOLS INDICATE /
EXPERIMENTAL RESULTS /
A /
FIG.3
A /
M- \f/ THRUST UDAD, 300 LB
ANALYSIS
THRUST IDAD, 100 LB
>.
— '- ' - ' - ' - ' - ' INVENTOR
5POO lOpOO BpOO 20JOOO 25JDOO 30pOO
SHAFT SPEED, NS,RPM WILLIAM J. ANDERSON
8. --Anr^  ATTORNEYS
3,759,588
1 2
HIGH SPEED HYBRID BEARING COMPRISING A vantage of hybrid bearings of this design is their large
FLUID BEARING & A ROLLING BEARING power losses compared with conventional ball bearing
CONNECTED IN SERIES which results from the relative inefficiency of the fluid
ORIGIN OF THE INVENTION *' ^  "*" "*"" ^ ^ *"
The invention described herein was made by employ- McNaughton et al. U.S. Pat. No. 2,872,254 discloses
ees of the United States Government and may be man- a device similar in operation to these hybrid bearings.
ufactured and used by or for the Government for gov- However, in contrast to the other prior art devices
ernmental purposes without payment of any royalties which are concerned with high speed bearing applica-
thereon or therefor. 10 tions, McNaughton 's device is useful to achieve opera-
BACKGROUND OF THE INVENTION tion °Ver a wide temperature range. This hybrid in-BACK.URUUNU Uf i Ht IN vbN i ION
 cludes a ^j, Baring element packed with a lubricant
1 . Field of Invention having a high viscosity at room temperature and a slid-
The invention is related to bearings, more specifi- ing element. Heat generated by the sliding element,
cally, to a hybrid bearing in which a rotating shaft is 15 which initially supports the shaft, decreases the viscos-
supported by a fluid film bearing and a rolling element ity of the ball bearing lubricant and causes the sliding
bearing coupled in series in a manner that each turns element to lock, thus transferring the rotation to the
at a fraction of the shaft speed. ball bearings. If the sliding element does not rigidly
2. Description of the Prior Art lock, some speed sharing between the bearings occurs;
Recent developments in gas turbine engines— such as 20 however, it is minimal, uncontrolled and unpredictable.
higher thrust-to-weight ratios, advanced compressor Composite bearings in which the load is shared by the
design, high temperature materials, and increased various bearing elements connected in parallel are also
power output— have necessitated larger shaft diame- known. In this arrangement each of the bearing ele-
ters and higher main shaft bearing speeds for future en- ments turns at the shaft speed. Some increase of bear-
gine designs. For example, bearings in current produc- 25 jng life is attained through load sharing, but at high DN
tion aircraft turbine engines operate in the range from values. This is less than that attained through speed
1.5 to 2 million DN (bearing bore in mm times and sharing. Examples of parallel composites are disclosed
shaft speed in rpm). However, engine designers antici- in U.S. Pat. Nos. 2,875,001; 3,065,036; 3,301,61 1 and
pate that turbine bearing DN values will have to in- 3,305,280.
crease to the range of 2.5 to 3 million in the near future 30 __
and further developments may require bearing DN val- SUMMARY OF INVENTION
ues as high as 4 million after 1980. An object of this invention is therefore to provide a
These higher values create significant wear problems bearing containing a rolling element in which fatigue
since when ball bearings are operated at DN values life is substantially increased while maintaining a level
above 1.5 million, centrifugal forces increase Hertz 35 of power loss no greater than that of an equivalent con-
stresses at the outer-race ball contacts and seriously ventional rolling element bearing.
shorten bearing fatigue life. At typical aircraft thrust A second object of this invention is to reduce the
loads carried by bearings, such as 2,000 and 4,000 stresses on the outer race contacts of a rolling element
pounds, an increase from a DN of 1.8 million to 4.2 bearing caused by centrifugal forces generated at high
million results in a reduction in life of 98 and 96 per- 4^ shaft speeds.
cent, respectively. Another object of this invention is to provide a corn-
Many attempts have been made to reduce the centrif- posite bearing in which each bearing rotates at a frac-
ugal forces and thus increase the life of high speed tion of the shaft speed.
bearings. One method of accomplishing this result is to A further object of this invention is to provide a corn-
decrease the mass of the rolling elements by using hoi- 45 posite bearing composed of a fluid film bearing and a
low or drilled elements. The technique has resulted in rolling element bearing connected in a manner that the
improving fatigue life by a factor of 2.5 at a DN of 3 inner race of the latter bearing rotates at less than the
million and thrust load of 4,000 pounds. shaft speed.
A second technique for diminishing centrifugal A still further object of this invention is to provide a
forces utilizes hybrid bearings to eliminate the use of composite bearing which will support both radial and
rolling bearings at high speeds. These bearings gener- thrust loads.
ally contain a rolling element bearing and a fluid bear- These and other objects are accomplished by provid-
ing. The former is used for starting, stopping and low ing a composite bearing which comprises a fluid film
speed operation when centrifugal forces are minimal. bearing and a rolling element bearing connected in se-
The latter operates only at high speeds. Various devices ries in a manner which reduces the orbital speed of the
are used to achieve this alternate operation. A clutch rolling element by decreasing the speed of the inner
activates a fluid bearing in Banerian U.S. Pat. Nos. race of the rolling element bearing to a fraction of the
2,986,430 and 3,058,786. Centrifugal force disengages shaft rate. This is accomplished by connecting the first
ball bearings in Hiatt et al. U.S. Pat. No. 3,360,3 1 0 and element of the fluid film bearing to a shaft and the sec-
Marchand U.S. Pat. No. 3,026,154. Goetz U.S. Pat. ond element to the inner race of the rolling element
No, 3,012,827 illustrates the use of ball bearings to sup- bearing in a manner that the latter two elements rotate
port a rotating shaft before a gas bearing begins its sup- at the same speed. The outer race of the rolling element
port function. bearing is mounted on a stationary housing. In the con-
The prior art hybrid bearing significantly increases
 65 text of this application the inner race is defined as the
bearing life since the rolling element bearing ceases to one attached to the fluid bearing element; the outer
operate at the higher shaft speeds when the entire rota- race as the one attached to a stationary support. In op-
tional load is supported by the fluid bearing. A disad- eration the first element turns at the full shaft speed
3,759,588
3 4
and the second element and the inner race rotate at a 10 of the roller bearing is mounted in the groove 9 con-
slower rate. tained on the second element of the fluid bearing. The
Since the DN value is a function of bearing bore and outer race 11 is mounted on a stationary housing 13.
shaft speed, it is clear that its value is not decreased by The fluid bearing may be lubricated by any conven-
the hybrid bearing of this invention. However, it is 5 tional means. In the device illustrated in FIG. 1 a jet 15
equally clear that the fatigue life of the bearing will be guides oil into an opening 16 in the shaft 3. The oil
increased because the speed of the rolling element in flows through a canal 17 to a lubricant supply orifice
this bearing is less than the speed of the rolling element 18 and then flows between the bearing elements. Cen-
in a conventional roller bearing at a given DN. The trifugal forces generated by the rotation of the shaft
benefits of the invention are illustrated by comparing 10 pumps the oil to the bearings. Alternatively, the fluid
fatigue life improvement obtained with a hybrid bear- bearing can be lubricated independently of the rotation
ing using a ball bearing, assuming a 30 percent reduc- of the shaft.
tion in roller element speed, with that of hollow ball A rotating shaft which is journaled in the hybrid bear-
bearings. At a 4,000 pound thrust and DN values of 3 ing of the present invention is initially supported only
and 4 million bearing life should theoretically improve 15 by the rolling bearing. That is, the inner race of the roll-
by a factor of 3.2 and 5.7, respectively, over that of ing bearing rotates at the full shaft speed. As shaft
conventional bearings using solid balls. In contrast speed increases, sufficient lubricant pressure is built up
under the same conditions fatigue life using hollow to start the fluid bearing rotating. At this point the
balls was improved only by a factor of 2.5 and 4.2. The inner race speed drops abruptly, indicating that the
theoretical values for the bearings of this invention 20 fluid bearing is now rotating at a portion of the shaft
were obtained by comparing fatigue life values for solid speed. The inner race and the second fluid bearing ele-
ball bearing with those obtained at a DN of 30 percent ment are then rotating at the same rate which is less
less. than the shaft speed.
INSCRIPTION OF THF DRAWINGS F1G 3 graPhicallv '""strates the operation of the sub-DESCRIPTION OF THE DRAWINGS
 25 ject mvention under 100 and 300 pound thrust loads,
FIG. 1 illustrates a cross section of the composite where point A designates the lift off of the fluid bear-
bearing of this invention; ing. In the figure the dashed line illustrates that in a
FIG. 2 is a cross section of the antifriction element of conventional ball bearing the inner race speed is the
the subject invention wherein the rolling element is a same as the shaft speed. It can be seen that at low shaft
combination roller and ball bearing; 30 speeds the hybrid bearing of this invention operates
FIG. 3 graphically illustrates the speed sharing char- similarly to the conventional bearing. (Of course this is
acteristics of the present invention. not true if the fluid bearing is pressurized.) However,
INSCRIPTION OF THF PRFFFRRFH when sufficient shaft sPeed is attained ^ fluid bearingDESCRIPTION F THE PREFERRED ,ifts off an(J ^  jnner face speed drops Note tha, ,he
35
FIG. 1 illustrates the subject invention which com- higher fluid pressures are necessary to float the fluid
prises a fluid film bearing 1 and a rolling element bear- bearing. It is clear from these curves that the inner race
ing 2 connected in series journaled to a rotating shaft speed of the ball bearing of the hybrid bearing is less
3. The fluid bearing is of the conventional type and, than those in conventional ball bearings for the same
comprises first and second elements 4 and 5 containing 40 shaft speed. This decrease results in significant in-
first and second opposed surfaces, 6 and 7, respec- creases in bearing fatigue life.
lively. As in conventional fluid bearings sufficient I claim:
clearance is provided between the surfaces to permit 1. A hybrid bearing comprising
the second surface to float and slide freely on a fluid a fluid film bearing comprising first and second ele-
film maintained between said first and second surfaces. ments
The surfaces may be parallel or perpendicular to the first and second substantially parallel and opposed
axis of the journaled shaft. In the former configuration surfaces on said first and second elements respec-
the bearing will support only radial loads; only thrust lively, and
loads will be supported in the latter case. Alternatively, a rolling element bearing including an inner and an
the bearing may have four surfaces, two aligned paral- outer race, one of said races being mounted on said
lei to the axis and two perpendicular, thus supporting second element whereby said rolling element bear-
axial and thrust loads. This dual support function can ing is connected in series with said fluid bearing so
also be accomplished in the preferred arrangement that said second element rotates at a fraction of the
shown in FIG. 1 wherein the two bearing surfaces are speed of said first element when the driving torque
conical in shape having their apex at the shaft axis. through said fluid film bearing equals the restrain-
The first bearing element has a central hole for jour- ing torque of said rolling element bearing.
naling. The second contains a means for mounting the 2. A hybrid bearing according to claim 1, wherein
inner race of the rolling element bearing. In FIG. 1, this said fluid film bearing surfaces support both radial and
means is shown as a groove 9. „ axial loads.
The rolling element bearing is composed of a first 3. A hybrid bearing according to claim 2, wherein
and second race, 10 and 1 1, respectively, having a plu- said fluid film bearing surfaces are conical in shape.
rality of rolling elements 12 between them. In FIG. 1, 4. A hybrid bearing according to claim 1, wherein
the rolling element is shown as a ball bearing, however, said rolling element bearing is a ball bearing.
any conventional roller or ball and roller combination
 65 5. A hybrid bearing according to claim 1, wherein
bearing can also be used. In FIG. 2, a combination said rolling element bearing is a combination ball and
roller element bearing containing ball and roller ele- roller bearing.
ments 13 and 14, respectively, is shown. The inner race 6. A hybrid bearing comprising
3,759,588
a rotatable first element having a first smooth surface
thereon,
a second element having a second smooth surface
aligned in a substantially parallel and opposed rela-
tionship with said first smooth surface,
means for forming a fluid film between said first and
second surfaces,
an inner race secured to said second element remote
from said second surface,
a fixedly mounted outer race surrounding said inner
race in spaced relationship, and
a plurality of rolling elements interposed between
said inner and outer races so that when the driving
torque through the fluid film equals the restraining
torque of said rolling elements the second element
5 rotates at a constant speed which is less than the
rotational speed of said first element.
7. A hybrid bearing according to claim 6, wherein
said substantially parallel opposed surfaces are conical
in shape having their apices at the axis of rotation of
10 said bearing.
15
20
25
30
35
40
45
50
(I 55
60
65


High speed hybrid bearing comprising a fluid bearing and a rolling bearing convected in series

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server