FLUID DEVICE OUTPUT SHAFT WITH COATING
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is being filed on August 22, 2014, as a PCT International Patent
application and claims priority to U.S. Patent Application Serial No. 61/869,348 filed on
August 23, 2014, the disclosure of which is incorporated herein by reference in its
entirety.
BACKGROUND
Hydraulic motors have many different shaft configurations and are used in many
different applications. Some shaft configurations include tapered roller bearings, ball
bearings, needle bearings and journal bearings. These bearings are used to support the
output shaft in the hydraulic motor.
Many applications apply radial loads on the output shaft of the hydraulic motor.
As a result, the type of hydraulic motor chosen for an application may depend on the
magnitude of the radial load being applied to the output shaft.
Hydraulic motors having journal bearings typically have lower side load
capability than hydraulic motors having other types of bearings. While hydraulic motors
using journal bearings are typically less expensive than other hydraulic motors using
other types of bearings, the use of the other hydraulic motors may be necessitated solely
as a result of side load capability. Therefore, it is desired to provide a hydraulic motor
having journal bearings with improved side load capability.
SUMMARY
An aspect of the present disclosure relates to a fluid device. The fluid device
includes a housing defining a central bore, a plurality of commutator holes that extend
radially outward from the central bore and a plurality of axial passages in fluid
communication with the commutator holes. A fluid displacement assembly is in fluid
communication with the housing. The fluid displacement assembly includes a plurality of
volume chambers in fluid communication with the axial passages of the housing. An
output shaft includes a valving portion disposed in the central bore of the housing. The
valving portion includes a first land, a second land and a valving land disposed between
the first and second lands. The first land cooperates with the central bore to define a first
journal bearing and the second land cooperates with the central bore of the housing to
define a second journal bearing. A coating is applied to the first and second lands of the
output shaft. The coating includes a polyamide 11 material.
Another aspect of the present disclosure relates to a fluid device. The fluid device
includes a housing defining a central bore, a plurality of commutator holes that extend
radially outward from the central bore and a plurality of axial passages in fluid
communication with the commutator holes. A fluid displacement assembly is in fluid
communication with the housing. The fluid displacement assembly includes a plurality of
volume chambers in fluid communication with the axial passages of the housing. An
output shaft includes a valving portion disposed in the central bore of the housing. The
valving portion includes a first land and an oppositely disposed second land. The first
land cooperates with the central bore to define a first journal bearing and the second land
cooperates with the central bore of the housing to define a second journal bearing. A
coating is applied to the first and second lands of the output shaft. The coating includes a
material selected from the group consisting of polyamide, polytetrafluoroethylene and
combinations thereof.
Another aspect of the present disclosure relates to a fluid device. The fluid device
includes a housing defining a central bore, a plurality of commutator holes that extend
radially outward from the central bore and a plurality of axial passages in fluid
communication with the commutator holes. A fluid displacement assembly is in fluid
communication with the housing. The fluid displacement assembly includes a plurality of
volume chambers in fluid communication with the axial passages of the housing. An
output shaft includes a valving portion disposed in the central bore of the housing. The
valving portion includes a first land, a second land and a valving land disposed between
the first and second lands. The first land cooperates with the central bore to define a first
journal bearing and the second land cooperates with the central bore of the housing to
define a second journal bearing. The valving portion of the output shaft defines a first
groove disposed between the first land and the valving land and a second groove disposed
between the second land and the valving land. The first and second journal bearings are
lubricated by fluid from the first and second grooves, respectively, during operation of the
fluid device. A coating is applied to the first and second lands and the valving land of the
output shaft. The coating includes a material selected from the group consisting of
polyamide, polytetrafluoroethylene and combinations thereof.
Another aspect of the present disclosure relates to a method for manufacturing an
output shaft for a fluid device. The method includes machining a first land and a second
land of a valving portion of an output shaft of a fluid device. The output shaft is heat
treated. A first grinding operation is performed on the output shaft. A coating is applied
the first land and second land of the output shaft. The coating includes a material selected
from the group consisting of polyamide, polytetrafluoroethylene and combinations
thereof. A second grinding operation is performed on the first land and the second land
of the output shaft.
Another aspect of the present disclosure relates to a method for manufacturing an
output shaft for a fluid device. The method includes machining an interface portion, a
sealing portion and a valving portion of an output shaft, the sealing portion being
disposed between the interface portion and the valving portion, wherein the valving
portion includes a first land, a second land and a valving land disposed between the first
and second lands. The output shaft is heat treated. A first grinding operation is
performed on the output shaft. A coating is applied the first land and second land of the
output shaft. The coating includes a polyamide material. A second grinding operation is
performed on the first land and the second land of the output shaft following the
application of the coating.
DRAWINGS
FIG. 1 is a cross-sectional view of a fluid device having exemplary features of
aspects in accordance with the principles of the present disclosure.
FIG. 2 is side view of an output shaft of the fluid device of FIG. 1.
FIG. 3 is a side view of the output shaft of FIG. 2 with an applied coating.
FIG. 4 is a graph of side load capacity versus rotational speed of the output shaft.
FIG. 5 is a representation of a method of manufacturing an output shaft.
DETAILED DESCRIPTION
Reference will now be made in detail to the exemplary aspects of the present
disclosure that are illustrated in the accompanying drawings. Wherever possible, the
same reference numbers will be used throughout the drawings to refer to the same or like
structure.
Referring now to FIG. 1, a fluid device 10 is shown. In the subject embodiment,
the fluid device 10 is a fluid motor. In another embodiment, the fluid device 10 is a fluid
pump.
The fluid device 10 includes a body 12. In the depicted embodiment, the body 12
includes a plurality of sections. In the depicted embodiment, the body 12 includes a
flange 14, a housing 16, a spacer plate 18, a fluid displacement assembly 20, and an end
cap 22. The sections of the body 12 are held together in tight sealing engagement by a
plurality of bolts 24.
The housing 16 is made of a metallic material. In the depicted embodiment, the
housing 16 is made of a ferrous metal (e.g., grey iron, ductile iron, etc.). The housing 16
includes a first axial end 26 and an oppositely disposed second axial end 28. In the
depicted embodiment, the flange 14 abuts the first axial end 26 of the housing 16 while a
first face 30 of the spacer plate 18 abuts the second axial end 28. The fluid displacement
assembly 20 abuts a second face 32 of the spacer plate 18. In the depicted embodiment,
the fluid displacement assembly 20 is a geroler® assembly. The fluid displacement
assembly 20 includes a ring 34, a star 36 and a plurality of rollers 38. The star 36 is
disposed in a central opening of the ring 34 and is adapted to obit and rotate about a
central axis of the ring 34. The ring 34, star 36 and rollers 38 cooperatively define a
plurality of fluid volume chambers 40 that expand and contract as the star 36 orbits and
rotates about the central axis of the ring 34.
In the depicted embodiment, the housing 16 defines a fluid inlet port (not shown)
and a fluid outlet port 42. The housing 16 defines a central bore 44 that extends through
the first and second axial ends 26, 28. The fluid inlet port is in fluid communication with
the central bore 44 through a first fluid passage (not shown). The fluid outlet port 42 is in
fluid communication with the central bore 44 through a second fluid passage 46.
The housing 16 defines a plurality of commutator holes 48. The commutator
holes 48 extend radially outward from the central bore 44. The housing 16 further defines
a plurality of axial passages 50 in fluid communication with the plurality of commutator
holes 48. The axial passages 50 are in fluid communication with the fluid volume
chambers 40 of the fluid displacement assembly 20.
The fluid device 10 further includes an output shaft assembly 52. In the depicted
embodiment, the output shaft assembly 52 includes a bearing assembly 54 and an output
shaft 56. In the depicted embodiment, the bearing assembly 54 includes a bearing race 58
and a thrust bearing 60.
Referring now to FIGS 1 and 2, the output shaft 56 is shown. The output shaft 56
is adapted to rotate about a central axis 62. The output shaft 56 is made from a metallic
material. In the depicted embodiment, the output shaft 56 is made from a ferrous metal
(e.g., steel, etc.).
The output shaft 56 includes an interface portion 64, a sealing portion 66 and a
valving portion 68. In the depicted embodiment, the sealing portion 66 is disposed
between the interface portion 64 and the valving portion 68.
The interface portion 64 of the output shaft 56 is adapted for coupling to a
customer application (e.g., a coupler, a wheel hub, a winch, etc.). The interface portion
64 extends outwardly from the flange 14 of the fluid device 10. In the depicted
embodiment, the interface portion 64 defines a keyway 70 that is adapted to receive a
shaft key 72.
The sealing portion 66 of the output shaft 56 is operably associated with a shaft
seal 74 (shown in FIG. 1). The shaft seal 74 is disposed in the flange 14 of the motor 14
and is adapted to prevent fluid in the interior of the fluid device 10 from leaking to the
exterior of the fluid device 10 at the shaft-flange interface. An outer diameter of the
sealing portion 66 of the output shaft 56 is greater than an outer diameter of the interface
portion 64.
The valving portion 68 of the output shaft 56 is disposed in the central bore 44 of
the housing 16. The valving portion 68 includes a first end 76 and an oppositely disposed
second end 78. The first end 76 of the valving portion 68 is disposed immediately
adjacent to the sealing portion 66.
The valving portion 68 further includes a first land 80, a second land 82 and a
valving land 84. The first land 80 is disposed adjacent to the first end 76 while the
second land 82 is disposed adjacent to the second end 78. The valving land 84 is
disposed between the first and second lands 80, 82.
The valving portion 68 defines a first groove 86 that is disposed between the first
land 80 and the valving land 84. The first groove 86 extends circumferentially about the
central axis 62 of the output shaft 56. In the depicted embodiment, the first groove 86 is
in fluid communication with the first fluid port of the housing 16 when the valving
portion 68 of the output shaft 56 is disposed in the central bore 44 of the housing 16.
The valving portion 68 defines a second groove 88 that is disposed between the
second land 82 and the valving land 84. The second groove 88 extends circumferentially
about the central axis 62 of the output shaft 56. In the depicted embodiment, the second
groove 88 is in fluid communication with the second fluid port 52 of the housing 16 when
the valving portion 68 of the output shaft 56 is disposed in the central bore 44 of the
housing 16.
The valving land 84 of the valving portion 68 defines a first plurality of slots 90
that is in fluid communication with the first groove 86 and a second plurality of slots 92
that is in fluid communication with the second groove 88. The first and second pluralities
of slots 90, 92 extend in an axial direction. In the depicted embodiment, the first and
second pluralities of slots 90, 92 are alternately disposed about the valving land 84 of the
valving portion 68 of the output shaft 56.
As the output shaft 56 rotates in the central bore 44 of the housing 16, the first and
second pluralities of slots 90, 92 are in commutating fluid communication with
commutator holes 48 in the housing 16. This commutating fluid communication provides
selective fluid communication between the first and second fluid ports of the housing 16
and the volume chambers 40 of the fluid displacement assembly 20.
The first land 80 of the output shaft 56 and the central bore 44 of the housing 16
cooperatively define a first journal bearing 94 (shown in FIG. 1). The second land 82 of
the output shaft 56 and the central bore 44 of the housing 16 cooperatively define a
second journal bearing 96 (shown in FIG. 1).
The first and second journal bearings 94, 96 allow the fluid device 10 to function
when a radial force F (shown in FIG. 1) is applied to the output shaft 56. The first and
second journal bearings 94, 96 are lubricated by fluid in the first and second grooves 86,
88, respectively, of the output shaft 56. Fluid in the first and second grooves 86, 88
passes over the first and second lands 80, 82 of the output shaft 56, respectively. This
fluid creates a hydrodynamic film across the first and second journal bearings 94, 96.
This film allows the output shaft 56 to rotate when the radial force F is applied to the
output shaft 56.
Referring now to FIG. 3, a coating 100 is applied to a surface of the rotating
component of the first and second journal bearings 94, 96 (shown in FIG. 1). In the
subject embodiment, the coating 100 is applied to the first land 80 and the second land 82
of the output shaft 56. In the depicted embodiment, the coating 100 is also applied to the
valving land 84 of the output shaft 56.
In the depicted embodiment, the coating 100 includes a polyamide (PA) material.
In one embodiment, the coating 100 includes a polyamide 11 (PA11) material. In one
embodiment, the polyamide material is at least about 50% by weight of the coating 100.
In another embodiment, the coating 100 includes a polytetrafluoroethylene
(PTFE) material. In one embodiment, the polytetrafluoroethylene material is at least
about 50% by weight of the coating 100.
In the subject embodiment, a thickness of the coating 100 at the first and second
lands 80, 82 of the output shaft 56 is greater than or equal to about 0.1 mm. In another
embodiment, the thickness of the coating 100 at the first and second lands 80, 82 of the
output shaft 56 is less than or equal to about 0.2 mm. In another embodiment, the
thickness of the coating 100 at the first and second lands 80, 82 of the output shaft 56 is in
a range of about 0.1mm to about 0.2 mm.
Referring now to FIG. 4, a graph of side load capability of a fluid device having a
standard output shaft without the coating 100 and the fluid device 10 having the output
shaft 56 with the coating 100 is shown. The dashed line in FIG. 4 represents the side load
capability of a standard output shaft that has a phosphate coating that is adapted to reduce
galling between the lands of the output shaft and the central bore of the housing. The
solid line in FIG. 4 represents the side load capacity of the output shaft 56 with the
coating 100 that includes polyamide 11.
As shown in FIG. 4, applying the coating 100 to the output shaft 56 provides a
significant increase in shaft side load capacity. In the depicted embodiment, the side load
capacity of the output shaft of the fluid device 10 with the coating 100 is about 150% of
the side load capacity of the output shaft without the coating 100. In order to achieve
these side load capacities in the standard output shaft (shown in dashed lines in FIG. 4),
the radial clearance between the lands of the output shaft and the central bore of the
housing would need to be increased significantly to allow for more fluid from the first
and second grooves to pass across the lands. However, such an increase in radial
clearance would have a negative effect on the volumetric efficiency of the fluid device.
The coating 100 applied to the output shaft 56 of the fluid device 10 allows for the
radial clearance between the first and second lands 80, 82 to be minimized while
providing significantly improved side load capability. This minimization of radial
clearance allows the fluid device 10 to perform at volumetric efficiencies greater than or
equal to the standard fluid device at rated side load capabilities. Thus, the coating 100
provides increased side load capability without sacrificing volumetric efficiency.
Referring now to FIGS. 2, 3 and 5, a method 200 for manufacturing the output
shaft 56 of the fluid device 10 is shown. In step 202, the output shaft 56 is machined
from an output shaft blank. In one embodiment of step 202, the interface portion 64, the
sealing portion 66 and the valving portion 68 are machined (e.g., turned, milled, etc.). In
one embodiment, the first land 80, the second land 82 and the valving land 84 of the
valving portion 68 are machined in step 202.
In step 204, the output shaft 56 is heat treated to a desired hardness. In step 206, a
first grinding operation is performed on the heat treated output shaft 56. In one
embodiment, the grinding operation 206 is performed on the outer diameter of the
interface portion 64, the sealing portion 66 and the valving portion 68 of the output shaft
56.
After the grinding operation 206, the interface portion 64 and the sealing portion
66 of the output shaft 56 are masked (e.g., concealed or covered) by a covering in step
208. In step 210, the output shaft 56 is coated with the coating 100. In step 210, the
coating 100 is applied to the output shaft 56. In the subject embodiment, a portion of the
output shaft 56 is masked. Therefore, the coating 100 is only applied to the unmasked
portion of the output shaft 56. In the depicted embodiment, the coating 100 is applied to
the valving portion 68 of the output shaft 100. In the depicted embodiment, the coating
100 is applied to the first land 80, the second land 82, and the valving land 84 of the
output shaft 56. In one embodiment, the coating 100 is sprayed onto the output shaft 56.
In another embodiment, the output shaft 56 is dipped into the coating 100.
After the coating 100 has been applied to the output shaft 56, the masking is
removed from the output shaft 56 in step 212. In step 214, a second grinding operation is
performed on the portion of the output shaft 56 having the coating 100. In the depicted
embodiment, the second grinding operation is performed on the first land 80, the second
land 82 and the valving land 84. The second grinding operation is adapted to remove
excess amounts of the coating 100 from the output shaft 56. In the depicted embodiment,
the second grinding operation is adapted to provide a thickness of the coating 100 that is
greater than or equal to about 0.1 mm. In another embodiment, the second grinding
operation is adapted to provide a thickness of the coating 100 that is less than or equal to
about 0.2 mm. In another embodiment, the second grinding operation is adapted to
provide a thickness of the coating 100 that is in a range of about 0.1 mm to about 0.2 mm.
Various modifications and alterations of this disclosure will become apparent to
those skilled in the art without departing from the scope and spirit of this disclosure, and
it should be understood that the scope of this disclosure is not to be unduly limited to the
illustrative embodiments set forth herein.

What is claimed is:
1. A fluid device comprising:
a housing defining a central bore, a plurality of commutator holes that extend
radially outward from the central bore and a plurality of axial passages in fluid
communication with the commutator holes;
a fluid displacement assembly in fluid communication with the housing, the fluid
displacement assembly including a plurality of volume chambers in fluid communication
with the axial passages of the housing;
an output shaft having a valving portion disposed in the central bore of the
housing, the valving portion having a first land, a second land and a valving land disposed
between the first and second lands, wherein the first land cooperates with the central bore
of the housing to define a first journal bearing and the second land cooperates with the
central bore of the housing to define a second journal bearing; and
a coating applied to the first and second lands and the valving land of the output
shaft, the coating including a polyamide 11 material.
2. The fluid device of claim 1, wherein the polyamide 11 material is at least 50% by
weight of the coating.
3. The fluid device of claim 1, wherein a thickness of the coating is greater than or
equal to about 0.1 mm.
4. The fluid device of claim 3, wherein the thickness of the coating is less than or
equal to about 0.2 mm.
5. The fluid device of claim 1, wherein the coating is applied to the valving portion
of the output shaft.
6. The fluid device of claim 1, wherein the valving portion of the output shaft
includes a first groove disposed between the first land and the valving land and a second
groove disposed between the second land and the valving land.
7. The fluid device of claim 6, wherein the first and second journal bearings are
lubricated by fluid from the first and second grooves, respectively, during operation of the
fluid device.
8. The fluid device of claim 1, wherein the housing defines a fluid inlet port and a
fluid outlet port.
9. A fluid device comprising:
a housing defining a central bore, a plurality of commutator holes that extend
radially outward from the central bore and a plurality of axial passages in fluid
communication with the commutator holes;
a fluid displacement assembly in fluid communication with the housing, the fluid
displacement assembly including a plurality of volume chambers in fluid communication
with the axial passages of the housing;
an output shaft having a valving portion disposed in the central bore of the
housing, the valving portion having a first land and an oppositely disposed second land,
wherein the first land cooperates with the central bore of the housing to define a first
journal bearing and the second land cooperates with the central bore of the housing to
define a second journal bearing; and
a coating applied to the first and second lands of the output shaft, the coating
including a material selected from the group consisting of polyamide,
polytetrafluoroethylene and combinations thereof.
10. The fluid device of claim 9, wherein the material is at least 50% by weight of the
coating.
11. The fluid device of claim 9, wherein a thickness of the coating is greater than or
equal to about 0.1 mm.
12. The fluid device of claim 11, wherein the thickness of the coating is less than or
equal to about 0.2 mm.
13. The fluid device of claim 9, wherein the output shaft includes a valving land
disposed between the first and second lands, the valving land defining a first plurality of
slots that extend axially outward from a first groove disposed between the first land and
the valving land and a second plurality of slots extends outwardly from a second groove
disposed between the valving land and the second groove.
14. The fluid device of claim 13, wherein the first and second journal bearings are
lubricated by fluid from the first and second grooves, respectively, during operation of the
fluid device.
15. The fluid device of claim 14, wherein the coating is applied to the valving land.
16. The fluid device of claim 9, wherein the coating is applied to the valving portion
of the output shaft.
17. A fluid device comprising:
a housing defining a central bore, a plurality of commutator holes that extend
radially outward from the central bore and a plurality of axial passages in fluid
communication with the commutator holes;
a fluid displacement assembly in fluid communication with the housing, the fluid
displacement assembly including a plurality of volume chambers in fluid communication
with the axial passages of the housing;
an output shaft having a valving portion disposed in the central bore of the
housing, the valving portion having a first land, a second land and a valving land disposed
between the first and second lands, the first land cooperating with the central bore of the
housing to define a first journal bearing and the second land cooperating with the central
bore of the housing to define a second journal bearing, the valving portion of the output
shaft defining a first groove disposed between the first land and the valving land and a
second groove disposed between the second land and the valving land, wherein the first
and second journal bearings are lubricated by fluid from the first and second grooves,
respectively, during operation of the fluid device; and
a coating applied to the first and second lands and the valving land of the output
shaft, the coating including a material selected from the group consisting of polyamide,
polytetrafluoroethylene and combinations thereof.
18. The fluid device of claim 17, wherein the material is at least 50% by weight of the
coating.
19. The fluid device of claim 17, wherein a thickness of the coating is greater than or
equal to about 0.1 mm.
20. The fluid device of claim 17, wherein a thickness of the coating is less than or
equal to about 0.2 mm.
21. A method for manufacturing an output shaft for a fluid device comprising:
machining a first land and second land of a valving portion of an output shaft of a
fluid device;
heat treating the output shaft;
performing a first grinding operation on the output shaft;
applying a coating to the first land and second land of the output shaft, the coating
including a material selected from the group consisting of polyamide,
polytetrafluoroethylene and combinations thereof; and
performing a second grinding operation on the first land and second land of the
output shaft.
22. The method of claim 21, wherein the thickness of the coating on the first land and
second land of the output shaft after the second grinding operation is in a range of about
0.1 mm to about 0.2 mm.
23. The method of claim 21, wherein the material includes polyamide 11.
24. The method of claim 23, wherein the material is at least 50% by weight of the
coating.
25. The method of claim 21, wherein a valving land that is disposed between the first
land and the second land of the valving portion of the output shaft is coated with the
coating.
26. A method for manufacturing an output shaft for a fluid device comprising:
machining an interface portion, a sealing portion and a valving portion of an
output shaft, the sealing portion being disposed between the interface portion and the
valving portion, wherein the valving portion includes a first land, a second land and a
valving land, the valving land being disposed between the first and second lands;
heat treating the output shaft;
performing a first grinding operation on the output shaft;
applying a coating to the first land and the second land of the output shaft, the
coating including a polyamide material; and
performing a second grinding operation on the first land and second land of the
output shaft following the application of the coating.
27. The method of claim 26, wherein the polyamide material includes polyamide 11.
28. The method of claim 26, wherein the valving land of the valving portion of the
output shaft is coated with the coating.
29. The method of claim 26, wherein the thickness of the coating on the output shaft
after the second grinding operation is in a range of about 0.1mm to about 0.2 mm.