CYLINDRICAL ROLLER BEARING APPARATUS
FIELD OF THE INVENTION
[0001] Embodiments of the invention relate to wheel drive assemblies of offhighway
vehicles, and, more particularly, to cylindrical roller bearings for use in such
wheel drive assemblies.
BACKGROUND OF THE INVENTION
[0002] Off-highway vehicles ("OHVs"), such as mining vehicles used to haul
heavy payloads excavated from open pit mines, usually employ motorized wheels for
propelling or retarding the vehicle in an energy efficient manner. In particular, OHVs
typically use a large horsepower diesel engine in conjunction with an alternator, a
main traction inverter, and a pair of wheel drive assemblies housed within the rear
tires of the vehicle. The diesel engine is directly associated with the alternator such
that the engine drives the alternator. The alternator, in turn, powers the main traction
inverter, which supplies electrical power having a controlled voltage and frequency to
electric drive motors of the two wheel drive assemblies. Each wheel drive assembly
houses a planetary gear transmission that converts the rotation of the associated drive
motor energy into a high torque low speed rotational energy output which is supplied
to the rear wheels.
[0003] As the weight of an OHV presents challenges for operation and
maintenance of such vehicles, reducing overall vehicle weight is highly desired. As
such, it is generally desirable to provide wheel assembly components, e.g., roller
bearings, that are as light as practicable.
BRIEF DESCRIPTION OF THE INVENTION
[0004] In one embodiment, a cylindrical roller bearing includes an annular
outer race, an annular inner race, a plurality of rollers captured between the inner race
and the outer race and a cage operatively connecting together the plurality of rollers
for rotating and revolving motion of the rollers between the inner and the outer races.
The inner race has an enlarged inner diameter and a reduced thickness relative to the
radial loads to be supported.
[0005] In another embodiment, a wheel assembly for an off-highway vehicle
includes a wheel frame, a torque tube having a ring gear, a wheel hub secured to the
torque tube and supported on the wheel frame and, within the wheel frame, a sun gear
shaft splined to a shaft of an electric motor, the sun gear shaft having a sun gear that is
meshed with a plurality of planet gears carried on a planet gear shaft, the planet gear
shaft having a pinion engaged with the ring gear of the torque tube and being
supported in the wheel frame by a plurality of thrust bearings and at least one
cylindrical roller bearing. The at least one cylindrical roller bearing has an annular
outer race, an annular inner race having a reduced thickness as compared to the outer
race and an enlarged inner diameter so as to permit assembly over the pinion of the
planet gear shaft, a plurality of rollers captured between the outer race and the inner
race and a cage operatively connecting together the plurality of rollers.
[0006] In another embodiment, a cylindrical roller bearing for supporting
radial loads within a wheel drive assembly of an off-highway vehicle includes an
annular outer race, an annular inner race, a plurality of rollers captured between the
inner race and the outer race, and a cage operatively connecting together the plurality
of rollers for rotating and revolving motion of the rollers between the inner and the
outer races. The inner race has an inner diameter of approximately 228 millimeters
and a thickness of approximately 11 millimeters, and the roller bearing has a dynamic
load rating of approximately 217,000 pounds (98,636 kg).
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The present invention will be better understood from reading the
following description of non-limiting embodiments, with reference to the attached
drawings, wherein below:
[0008] FIG. 1 shows a perspective view of an OHV.
[0009] FIG. 2 shows a partial perspective cutaway view showing a wheel
drive assembly of the OHV shown in FIG. 1.
[0010] FIG. 3 shows a perspective view of the wheel drive assembly shown in
FIG. 2, for use with a cylindrical roller bearing in accordance with an embodiment of
the present invention.
[0011] FIG. 4 shows a side sectional view of the wheel drive assembly shown
in FIG. 2, including a cylindrical roller bearing in accordance with an embodiment of
the present invention.
[0012] FIG. 5 shows a detail view from FIG. 4 including the cylindrical roller
bearing.
[0013] FIG. 6 shows a perspective view of the cylindrical roller bearing
shown in FIGS. 4-5, according to an embodiment of the present invention.
[0014] FIG. 7 shows a side sectional detail view of the cylindrical roller
bearing shown in FIGS. 4-6.
[0015] FIG. 8 shows a perspective view of a wheel frame of the wheel drive
assembly shown in FIG. 4.
DETAILED DESCRIPTION OF THE INVENTION
[0016] Reference will be made below in detail to exemplary embodiments of
the invention, examples of which are illustrated in the accompanying drawings.
Wherever possible, the same reference numerals used throughout the drawings refer
to the same or like parts.
[0017] An embodiment of the inventive bearing is configured for use with a
wheel assembly 16 of an OHV 10 as depicted in FIGS. 1 and 2. As shown, the OHV
10 is supported on paired dual rear drive tire assemblies 12 and on single front
steering tire assemblies 14. Each pair of rear drive tire assemblies 12 are mounted on
a wheel assembly 16. Such an OHV may be massive in scale. For example, the OHV
10 may weigh in excess of two hundred sixty (260) tons, empty.
[0018] Referring to FIG. 3, each wheel assembly 16 includes a wheel frame
18, a torque tube 20, and a wheel hub 22 that is fastened to the torque tube and
supported on the wheel frame. In embodiments, the torque tube is bolted to the wheel
hub 22, to which the tire assemblies 12 can be bolted as further discussed herein.
Axially adjacent to the wheel hub 22, a brake assembly 24 also is mounted on the
wheel frame 18 but is not fastened to the wheel hub. Axially opposite the brake
assembly 24, a gear cover 48 is mounted onto the wheel frame 18.
[0019] Each wheel assembly 16 can be bolted to the vehicle 10 by way of a
mounting flange 28 provided on the wheel frame 18. The wheel frame 18 is radially
tapered from the mounting flange 28, through a generally conical or hyperbolic
transition portion 30, to a main cylindrical or substantially cylindrical barrel portion
32 (shown in FIG. 4). The torque tube 20 includes a ring gear 34 adjacent to the
mounting flange 28 of the wheel frame 18, and also includes a tube barrel 36 that
extends from the ring gear 34 along the wheel frame to a wheel hub flange 38.
[0020] Referring to FIG. 4, the ring gear 34 is engaged with planet pinion
gears 40 that are housed in, and protrude through, the wheel frame 18. The wheel hub
flange 38 is an integral part of the wheel hub 22. The torque tube 20 is supported
around the barrel portion 32 of the wheel frame 18 by its attachment to the wheel hub
22 and by its engagement with the planet pinion gears 40.
[0021] As shown in FIG. 4, inboard and outboard tire assemblies 12a, 12b can
be bolted onto the wheel hub 22. Within the wheel hub 22, the barrel portion 32 of
the wheel frame 18 extends from the transition portion 30 to an annular hub end
surface 42, to which the brake assembly 24 is mounted. Adjacent the hub end surface
42, an electric traction motor 44 is housed inside the wheel frame 18. From the
electric motor 44 a shaft 46 protrudes centrally along the wheel frame 18 toward a
first end proximate to the mounting flange 28, and toward a second end within the
brake assembly 24. Within the brake assembly 24, a brake rotor 48 is mounted onto
the second end of the shaft 46. Within the transition portion 30 of the wheel frame
18, a sun gear shaft 50 is splined to the first end of the shaft 46. The end of the sun
gear shaft 50 disposed proximate the gear cover 26 is formed as a sun gear 52. The
sun gear 52 is meshed with a plurality of planet gears 54, each of which is carried on a
common axle 56 with one of the planet pinion gears 40, which mesh with internal
teeth of the torque tube ring gear 34. In embodiments, there are three planet gears 54,
three planet axles 56, and three pinion gears 40. As discussed above, the torque tube
20 is supported between the pinion gears 40 and the wheel hub 22. In embodiments,
the sun, planet gears, planet pinions, and ring gears provide a high gear ratio from the
traction motor 44 to the torque tube 20.
[0022] Turning now to FIGS. 5-7, each of the planet axles 56 is supported in
the wheel frame 18 by paired thrust bearings 58 and by cylindrical roller bearings 60.
Each cylindrical roller bearing 60 is assembled onto one of the planet axles over the
attached planet pinion gear 40. In particular, as shown in FIG. 6, in an embodiment of
the present invention, each roller bearing 60 includes an outer race 62, an inner race
64, a cage ring 66, and a plurality of rollers 68 captured by the cage ring between the
outer race and the inner race. The inner race 64 of each cylindrical roller bearing 60
has an inner diameter sized to pass over the pinion gear 40, while the outer race 62 of
each roller bearing has an outer diameter sized to fit within the wheel frame 18 as
further discussed below. In some embodiments, dimensional constraints on the
cylindrical roller bearing 60 are met by providing an inner race 64 of enlarged inner
diameter and reduced inner race thickness. In selected embodiments, the inner race
64 is through hardened to achieve enhanced fatigue strength for its reduced thickness.
[0023] Referring to FIG. 5 and also to FIG. 8, the wheel frame 18 is formed as
a unitary or jointless structure, e.g., by a casting process. The transition portion 30 of
the wheel frame 18 is formed integrally with the mounting flange 28 and with the
barrel portion 32. The transition portion 30 of the wheel frame 18 defines a plurality
of planet pinion gear openings or apertures 70 that extend from a radially inward
facing surface of the wheel frame 18 to the radially outward facing surface of the
transition portion 30. In embodiments, three pinion gear apertures 70 are provided at
locations suitable for receiving the pinions 40 of the planetary gear set to be housed
within the wheel frame 18. Each pinion gear aperture 70 defines a radial bearing
mount 72 for receiving one of the cylindrical roller bearings 60, and includes a
radially outwardly concave cupped portion 74 that provides structural rigidity for the
radial bearing mount 72 while also providing for engagement of the pinion gear 40
with internal teeth of the ring gear 34 mounted over the wheel frame 18. Adjacent to
each pinion gear aperture 70, in axial opposition to and in alignment with the
corresponding radial bearing mount 72, a thrust bearing mount 76, for receiving thrust
bearings 58, is formed as a significantly thickened portion of the monolithic wheel
frame 18. Thus, the radial bearing mounts 72 and the thrust bearing mounts 76
together absorb loads transferred between the wheel frame 18 and each of the planet
axles 56.
[0024] In embodiments, the thrust bearing mounts 76 is circumferentially
spaced rather than being formed as portions of a continuous thickened ring about the
wheel frame 18. Alternatively or additionally, the pinion gear apertures 70 and the
thrust bearing mounts 76 are symmetrically circumferentially spaced and mutually
axially aligned. Alternatively or additionally, edges of the concave cupped portions
74 are joined by a supporting ring 78 that is disposed substantially coplanar with the
mounting flange 28. Alternatively or additionally, the supporting ring 78 is in turn
joined to the mounting flange 28 by intermediate rings 80 formed by the radial
bearing mounts 72.
[0025] On account of the mutual arrangement of the roller bearing mounts 72,
the concave cupped portions 74, the thrust bearing mounts 76, and the supporting ring
78, loads on the planet axles 56 are transferred such that it is possible for the
cylindrical roller radial bearings 60 to have diminished inner race diameter and
thickness, and thus reduced overall diameter, relative to previously specified roller
bearings for similar designed shaft loadings. Accordingly, it also is possible to
package the three planet axles 56 and the associated gearing 40, 54 within a smaller
and lighter wheel frame transition portion 30, and mounting flange 28, than
previously was possible.
[0026] In connection with the present invention, in order to achieve a
sufficiently high gear ratio, the planet pinion pitch diameter, and thus the pinion
outside diameter, of the pinions 40 within the wheel assembly is increased. In order
to fit the roller bearings 60 over the enlarged pinions 40, however, the inner diameter
of the inner race of the roller bearings 60 would customarily have to be increased,
which, undesirably, translates to increased dimensions of the bearing overall (thus
increasing the size and weight of the wheel assembly). Accordingly, embodiments of
the present invention provide a cylindrical roller bearing for use with the enlarged
pinions 40 wherein all dimensions and load ratings of the roller bearing 60 are
maintained, but wherein the inner diameter or the inner race 64 is enlarged, and the
cross-sectional thickness of the inner race 64 is reduced, to enable the roller bearing
60 to fit over the enlarged pinions 40.
[0027] In an embodiment, the cylindrical roller bearings 60 each have a
dynamic load rating of approximately 217,000 lbs (98,636 kg), a static load rating of
approximately 389,000 lbs (176,818 kg), and a fatigue load limit of approximately
42,900 lbs (19,500 kg). In an embodiment, with these load ratings, the roller bearing
has an inner race 64 having an inner diameter of approximately 228 millimeters and a
thickness of approximately 11 millimeters, and an outer race 62 having an inner
diameter of approximately 299 millimeters and a thickness of approximately 20.5
millimeters. In an embodiment, the ratio of the thickness of the outer race to the
thickness of the inner race is approximately 1.86:1 and the ratio of the inner race
diameter to the inner race thickness is approximately 10:1.
[0028] Accordingly, the present invention provides a cylindrical roller bearing
having an inner race having an enlarged inner diameter and a reduced thickness
relative to the radial loads to be supported. In particular, the enlarged inner diameter
and reduced thickness of the inner race eliminate the need to utilize a standard roller
bearing having an inner race having an increased thickness, and thus increased
dimensions and weight overall, to fit over the enlarged pinion 40 of the wheel
assembly, which would undesirably translate to increased size and weight of the
wheel assembly 16 as a whole.
[0029] In use, embodiments of the invention may include a reduced-weight
cylindrical roller bearing for supporting radial loads within a wheel drive assembly for
use on off-highway vehicles. The cylindrical roller bearing includes an annular outer
race, an annular inner race, a plurality of rollers captured between the inner race and
the outer race, and a cage operatively connecting together the plurality of rollers for
rotating and revolving motion of the rollers between the inner and the outer races.
The inner race is of reduced diameter and thickness relative to the radial loads to be
supported. In particular, the inner race is of a smaller diameter than expected for use
with high-ratio planetary gearing.
[0030] In one embodiment, a cylindrical roller bearing is provided. The
cylindrical roller bearing includes an annular outer race, an annular inner race, a
plurality of rollers captured between the inner race and the outer race and a cage
operatively connecting together the plurality of rollers for rotating and revolving
motion of the rollers between the inner and the outer races. The inner race has an
enlarged inner diameter and a reduced thickness relative to the radial loads to be
supported. The inner diameter of the inner race may be approximately 228
millimeters and the thickness of the inner race may be approximately 11 millimeters.
The thickness of the outer race may be approximately 20.5 millimeters. Accordingly,
the ratio of the thickness of the outer race to the thickness of the inner race may be
approximately 1.86: 1. In connection with these specifications, the roller bearing may
have a dynamic load rating of approximately 217,000 pounds, a static load rating of
approximately 389,000 pounds, and a fatigue load limit of approximately 42,900
pounds (98,636 kg, 176,818 kg, and 19,500 kg, respectively).
[0031] In another embodiment, a wheel assembly for an off-highway vehicle,
includes a wheel frame, a torque tube having a ring gear, a wheel hub secured to the
torque tube and supported on the wheel frame and, within the wheel frame, a sun gear
shaft splined to a shaft of an electric motor, the sun gear shaft having a sun gear that is
meshed with a plurality of planet gears carried on a planet gear shaft, the planet gear
shaft having a pinion engaged with the ring gear of the torque tube and being
supported in the wheel frame by a plurality of thrust bearings and at least one
cylindrical roller bearing. The at least one cylindrical roller bearing has an annular
outer race, an annular inner race having a reduced thickness as compared to the outer
race and an enlarged inner diameter so as to permit assembly over the pinion of the
planet gear shaft, a plurality of rollers captured between the outer race and the inner
race and a cage operatively connecting together the plurality of rollers. The wheel
assembly may also include a brake assembly axially adjacent to the wheel hub and
mounted to the wheel frame. The inner diameter of the inner race may be
approximately 228 millimeters and the thickness of the inner race may be
approximately 11 millimeters. The thickness of the outer race may be approximately
20.5 millimeters. Accordingly, the ratio of the thickness of the outer race to the
thickness of the inner race may be approximately 1.86:1. In connection with these
specifications, the roller bearing may have a dynamic load rating of approximately
217,000 pounds, a static load rating of approximately 389,000 pounds, and a fatigue
load limit of approximately 42,900 pounds (98,636 kg, 176,818 kg, and 19,500 kg,
respectively).
[0032] In another embodiment, a cylindrical roller bearing for supporting
radial loads within a wheel drive assembly of an off-highway vehicle includes an
annular outer race, an annular inner race, a plurality of rollers captured between the
inner race and the outer race, and a cage operatively connecting together the plurality
of rollers for rotating and revolving motion of the rollers between the inner and the
outer races. The inner race has an inner diameter of approximately 228 millimeters
and a thickness of approximately 11 millimeters, and the roller bearing has a dynamic
load rating of approximately 217,000 pounds (98,636 kg). In addition, the roller
bearing may have a static load rating of approximately 389,000 pounds (176,818 kg)
and a fatigue load limit of approximately 42,900 pounds (19,500 kg). The inner race
of the roller bearing may be through hardened. As used herein, the term
"approximately" is defined to mean plus or minus five percent of the given value.
[0033] It is to be understood that the above description is intended to be
illustrative, and not restrictive. For example, the above-described embodiments
(and/or aspects thereof) may be used in combination with each other. In addition,
many modifications may be made to adapt a particular situation or material to the
teachings of the invention without departing from its scope. While the dimensions
and types of materials described herein are intended to define the parameters of the
disclosed subject matter, they are by no means limiting and are exemplary
embodiments. Many other embodiments will be apparent to those of ordinary skill in
the art upon reviewing the above description. The scope of the inventive subject
matter should, therefore, be determined with reference to the appended clauses, along
with the full scope of equivalents to which such clauses are entitled. In the appended
clauses, the terms "including" and "in which" are used as the plain-English
equivalents of the respective terms "comprising" and "wherein." Moreover, in the
following clauses, the terms "first," "second," and "third," etc. are used merely as
labels, and are not intended to impose numerical requirements on their objects.
[0034] This written description uses examples to disclose several
embodiments of the invention, including the best mode, and also to enable any person
of ordinary skill in the art to practice the embodiments of invention, including making
and using any devices or systems and performing any incorporated methods. The
patentable scope of the invention is defined by the clauses, and may include other
examples that occur to those ordinarily skilled in the art. Such other examples are
intended to be within the scope of the clauses if they have structural elements that do
not differ from the literal language of the clauses, or if they include equivalent
structural elements with insubstantial differences from the literal languages of the
clauses.
[0035] The foregoing description of certain embodiments of the present
invention will be better understood when read in conjunction with the appended
drawings. To the extent that the figures illustrate diagrams of the functional blocks of
various embodiments, the functional blocks are not necessarily indicative of the
division between hardware circuitry. Thus, for example, one or more of the
functional blocks (for example, processors or memories) may be implemented in a
single piece of hardware (for example, a general purpose signal processor,
microcontroller, random access memory, hard disk, and the like). Similarly, the
programs may be stand alone programs, may be incorporated as subroutines in an
operating system, may be functions in an installed software package, and the like.
The various embodiments are not limited to the arrangements and instrumentality
shown in the drawings.
[0036] As used herein, an element or step recited in the singular and
proceeded with the word "a" or "an" should be understood as not excluding plural of
said elements or steps, unless such exclusion is explicitly stated. Furthermore,
references to "one embodiment" of the present invention are not intended to be
interpreted as excluding the existence of additional embodiments that also incorporate
the recited features. Moreover, unless explicitly stated to the contrary, embodiments
"comprising," "including," or "having" an element or a plurality of elements having a
particular property may include additional such elements not having that property.
[0037] Since certain changes may be made in the above-described cylindrical
roller bearing apparatus and method, without departing from the spirit and scope of
the invention herein involved, it is intended that all of the subject matter of the above
description or shown in the accompanying drawings shall be interpreted merely as
examples illustrating the inventive concept herein and shall not be construed as
limiting the invention.
What is claimed is:
1. A cylindrical roller bearing comprising:
an annular outer race;
an annular inner race;
a plurality of rollers captured between the inner race and the outer race; and
a cage operatively connecting together the plurality of rollers for rotating and
revolving motion of the rollers between the inner and the outer races;
wherein the inner race has an enlarged inner diameter and a reduced thickness
relative to the radial loads to be supported.
2. The cylindrical roller bearing of claim 1, wherein:
the ratio of the thickness of the outer race to the thickness of the inner race is
approximately 1.86:1.
3. The cylindrical roller bearing of claim 1, wherein:
the ratio of the inner race diameter to the inner race thickness is approximately
10.4:1.
4. The cylindrical roller bearing of claim 1, wherein:
the inner diameter of the inner race is approximately 228 millimeters.
5. The cylindrical roller bearing of claim 1, wherein:
the thickness of the inner race is approximately 11 millimeters.
6. The cylindrical roller bearing of claim 5, wherein:
the thickness of the outer race is approximately 20.5 millimeters.
7. The cylindrical roller bearing of claim 1, wherein:
the roller bearing has a dynamic load rating of approximately 98,636 kg.
8 . The cylindrical roller bearing of claim 1, wherein:
the roller bearing has a static load rating of approximately 176,818 kg.
9. The cylindrical roller bearing of claim 1, wherein:
the roller bearing has a fatigue load limit of approximately 19,500 kg.
10. A wheel assembly for an off-highway vehicle, comprising:
a wheel frame;
a torque tube having a ring gear;
a wheel hub secured to the torque tube and supported on the wheel frame; and
within the wheel frame, a sun gear shaft splined to a shaft of an electric motor,
the sun gear shaft having a sun gear that is meshed with a plurality of planet gears
carried on a planet gear shaft, the planet gear shaft having a pinion engaged with the
ring gear of the torque tube and being supported in the wheel frame by a plurality of
thrust bearings and at least one cylindrical roller bearing;
wherein the at least one cylindrical roller bearing has an annular outer race, an
annular inner race having a reduced thickness as compared to the outer race and an
enlarged inner diameter so as to permit assembly over the pinion of the planet gear
shaft, a plurality of rollers captured between the outer race and the inner race, and a
cage operatively connecting together the plurality of rollers.
11. The wheel assembly of claim 10, wherein:
the ratio of the thickness of the outer race to the thickness of the inner race is
approximately 1.86:1.
12. The wheel assembly of claim 10, wherein:
the inner diameter of the inner race is approximately 228 millimeters.
13. The wheel assembly of claim 12, wherein:
the thickness of the inner race is approximately 11 millimeters.
14. The wheel assembly of claim 10, further comprising:
a brake assembly axially adjacent to the wheel hub and mounted to the wheel
frame.
15. The wheel assembly of claim 10, wherein:
the roller bearing has a dynamic load rating of approximately 98,636 kg.
16. The wheel assembly of claim 10, wherein:
the roller bearing has a static load rating of approximately 176,818 kg.
17. The wheel assembly of claim 10, wherein:
the roller bearing has a fatigue load limit of approximately 19,500 kg.
18. A cylindrical roller bearing for supporting radial loads within a wheel drive
assembly of an off-highway vehicle, the bearing comprising:
an annular outer race;
an annular inner race;
a plurality of rollers captured between the inner race and the outer race; and
a cage operatively connecting together the plurality of rollers for rotating and
revolving motion of the rollers between the inner and the outer races;
wherein the inner race has an inner diameter of approximately 228 millimeters
and a thickness of approximately 11 millimeters; and
wherein the roller bearing has a dynamic load rating of approximately 98,636
kg.
19. The cylindrical roller bearing of claim 18, wherein:
the roller bearing has a static load rating of approximately 176,818 kg.
20. The cylindrical roller bearing of claim 18, wherein:
the roller bearing has a fatigue load limit of approximately 19,500 kg.
21. The cylindrical roller bearing of claim 18, wherein:
the inner race is through hardened.