BACKGROUND OF THE INVENTION
[0001] The subject matter disclosed herein relates to bearings. More specifically, the
subject disclosure relates to clutch bearings for transport refrigeration systems.
[0002] In a transportation refrigeration unit in, for example, a trailer or rail car, a
clutch, such as an electromagnetic clutch, serves as the interface between a power supply
such as an engine and an evaporator blower of the refrigeration unit. When the clutch is
engaged, rotational energy is transferred from the power supply to the blower. When the
evaporator unit is not running, and the clutch is disengaged, the bearings are not rotating, but
are still subject to vibratory forces. Vibratory forces cause wear such as false brinelling or
fretting corrosion in the bearings resulting in damage to and/or failure of the bearings which
requires premature replacement of the bearings.
BRIEF DESCRIPTION OF THE INVENTION
[0003] According to one aspect of the invention, a clutch bearing for a transportation
refrigeration unit includes one or more rolling elements supportive of one or more
components of an electromagnetic clutch for a transportation refrigeration unit, and bearing
races configured to retain the one or more rolling elements. The bearing races include a
coating of thin dense chromium to reduce corrosion and/or damage of the clutch bearing.
[0004] According to another aspect of the invention, an electromagnetic clutch for a
transportation refrigeration unit includes a rotor located at a central axis and an armature
located at the central axis and having an axial air gap to the rotor when the clutch is in a
disengaged position. A clutch bearing is positioned at the central axis and is supportive of the
rotor. The clutch bearing includes one or more rolling elements supportive of one or more
components of the electromagnetic clutch and bearing races configured to retain the one or
more rolling elements. The bearing races include a coating of thin dense chromium to reduce
corrosion and/or damage of the clutch bearing.
[0005] According to yet another aspect of the invention, a transportation refrigeration
unit includes a power source and a blower of the transportation refrigeration unit. An
electromagnetic clutch is operably connected to the power source and the blower and is
located between the power source and the blower such that engagement of the
electromagnetic clutch allows for transfer of rotational energy from the power source to the
blower. The electromagnetic clutch includes a rotor positioned at a central axis and an
armature positioned at the central axis and having an axial air gap to the rotor when the clutch
is in a disengaged position. A clutch bearing is located at the central axis and is supportive of
the rotor. The clutch bearing includes one or more rolling elements supportive of one or more
components of the rotor and bearing races configured to retain the one or more rolling
elements and including a coating of thin dense chromium to reduce corrosion and/or damage
of the clutch bearing.
[0006] These and other advantages and features will become more apparent from the
following description taken in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The subject matter, which is regarded as the invention, is particularly pointed
out and distinctly claimed in the claims at the conclusion of the specification. The foregoing
and other features, and advantages of the invention are apparent from the following detailed
description taken in conjunction with the accompanying drawings in which:
[0008] FIG. 1 is a partial schematic view of an embodiment of a transportation
refrigeration unit; and
[0009] FIG. 2 is a cross-sectional view of an embodiment of a clutch bearing for a
transportation refrigeration unit.
[0010] The detailed description explains embodiments of the invention, together with
advantages and features, by way of example with reference to the drawings.
DETAILED DESCRIPTION OF THE INVENTION
[0011] Shown in FIG. 1 is a partial view of an embodiment of a transportation
refrigeration unit 10, more particularly an interface between the transport refrigeration unit 10
and a power supply 12, for example an engine of a railway or other vehicle. The interface in
FIG. 1 is an electromagnetic clutch 14. The electromagnetic clutch 14 includes a rotor 16 and
an armature 18 located about a center axis 20. When the electromagnetic clutch 14 is in a
disengaged position, there is an axial gap 22 between the rotor 16 and the armature 18. The
rotor 16 is connected to the power supply 12, for example, a vehicle engine. In the
embodiment of FIG. 1, the rotor 16 is configured substantially as a pulley, and is driven by a
belt 24, located at an outer diameter 26 of the rotor 16, which is connected to the power
supply 12. The electromagnetic clutch 14 includes a field coil 28 that, when energized,
creates a magnetic field that draws the armature 18 into contact with a face 30 of the rotor 16.
The frictional contact caused by the strength of the magnetic field results in a transfer of
rotational energy from the rotor 16 to the armature 18. Rotation of the armature 18 drives a
blower 32 of the refrigeration unit 10 to which it is connected.
[0012] The rotor 16 is supported at an inner diameter by a bearing 34. The bearing 34,
as shown in FIG. 1, is a deep-groove ball bearing, but it is to be appreciated that other types
of rolling element bearings 34 may be utilized and are contemplated within the scope of the
present disclosure. These include angular contact bearings, taper bearings, spherical bearings,
cylindrical bearings, needle bearings, or the like.
[0013] Referring to FIG. 2, a bearing race 36 supports rolling elements 38 of the
bearing 34. An inner surface of the bearing race 36, which contacts the rolling elements 38, is
coated with a thin dense chromium coating such as available from a variety of sources, for
example, Armoloy® of Illinois, Inc. The thin dense chromium coating from Armoloy® is a
specific type of thin dense chromium, nodular thin dense chromium. In some embodiments,
the coating can be as thin as 0.000040". The coating prevents false brinelling and/or fretting
corrosion which can occur between a steel rolling element 38 and a steel bearing race 36. In
some embodiments, to further prevent false brinelling and fretting corrosion, the rolling
elements 38 are formed from a ceramic material, thus eliminating some of the steel from the
bearing 34. .
[0014] While the invention has been described in detail in connection with only a
limited number of embodiments, it should be readily understood that the invention is not
limited to such disclosed embodiments. Rather, the invention can be modified to incorporate
any number of variations, alterations, substitutions or equivalent arrangements not heretofore
described, but which are commensurate with the spirit and scope of the invention.
Additionally, while various embodiments of the invention have been described, it is to be
understood that aspects of the invention may include only some of the described
embodiments. Accordingly, the invention is not to be seen as limited by the foregoing
description, but is only limited by the scope of the appended claims.

CLAIMS:
1. A clutch bearing for a transportation refrigeration unit comprising:
one or more rolling elements supportive of one or more components of an
electromagnetic clutch for a transportation refrigeration unit; and
a plurality of bearing races configured to retain the one or more rolling
elements, the plurality of bearing races including a coating of thin dense chromium to
reduce corrosion and/or damage of the clutch bearing.
2. The clutch bearing of Claim 1, wherein the coating is at least 0.000040" thick.
3. The clutch bearing of Claim 1, wherein the bearing is one of a roller bearing,
angular contact bearing, taper bearing, spherical bearing, cylindrical bearing or needle
bearing.
4. The clutch bearing of Claim 1, wherein the rolling elements are formed from a
ceramic material.
5. An electromagnetic clutch for a transportation refrigeration unit comprising:
a rotor disposed at a central axis;
an armature disposed at the central axis and having an axial air gap to the rotor
when the clutch is in a disengaged position; and
a clutch bearing disposed at the central axis and supportive of the rotor, the
clutch bearing including:
one or more rolling elements supportive of the rotor; and
a plurality of bearing races configured to retain the one or more rolling
elements, the bearing race including a coating of thin dense chromium to
reduce corrosion and/or damage of the clutch bearing.
6. The electromagnetic clutch of Claim 5, wherein the coating is at least 0.000040"
thick.
7. The electromagnetic clutch of Claim 5, wherein the bearing is one of a roller
bearing, angular contact bearing, taper bearing, spherical bearing, cylindrical bearing or
needle bearing.
8. The electromagnetic clutch of Claim 5, wherein the rolling elements are formed
from a ceramic material.
9. A transportation refrigeration unit comprising:
a power source;
a blower of the transportation refrigeration unit; and
an electromagnetic clutch operably connected to the power source and the
blower and disposed between the power source and the blower such that engagement
of the electromagnetic clutch allows for transfer of rotational energy from the power
source to the blower, the electromagnetic clutch including:
a rotor disposed at a central axis;
an armature disposed at the central axis and having an axial air gap to
the rotor when the clutch is in a disengaged position; and
a clutch bearing disposed at the central axis and supportive of the rotor,
the clutch bearing including:
one or more rolling elements supportive of the rotor; and
a plurality of bearing races configured to retain the one or more
rolling elements, the bearing race including a coating of thin dense
chromium to reduce corrosion and/or damage of the clutch bearing.
10. The transportation refrigeration unit of Claim 9, wherein the coating is at least
0.000040" thick.
11. The transportation refrigeration unit of Claim 9, wherein the rolling element
bearing is one of a roller bearing, angular contact bearing, taper bearing, spherical bearing,
cylindrical bearing or needle bearing.
12. The transportation refrigeration unit of Claim 9, wherein the rolling elements are
formed from a ceramic material.
13. The transportation refrigeration unit of Claim 9, wherein the rotor is belt-driven.