Fluid cooled bearing method

BACKGROUND

The present invention relates generally to the field of bearings and the temperature control of such bearings. More particularly, the invention relates to a novel arrangement for simply and economically cooling a bearing or the lubricant of a bearing by enhancing the heat dissipation from the bearing liner.

A wide variety of bearings is available and such bearings are currently in use throughout a range of industrial applications. Bearings are generally used for facilitation of rotational movement in a mechanical application. In general, a typical bearing includes a plurality of bearing elements situated in a housing. Depending upon the application and the anticipated loading, the bearing elements may be sleeve bearings, needle bearings, roller bearings, ball bearings, and so forth.

A sleeve bearing, or journal bearing, is formed from a plain cylindrical or profiled sleeve that carries a rotating shaft. Such bearings are sometimes referred to as fluid film bearings because of the presence of a small film of lubricant formed between the cylindrical sleeve and the rotating shaft. The coefficient of friction experienced by the rotating shaft is dependent on whether a fluid film is fully developed. In essence, a fully developed fluid film creates a hydrodynamic pressure sufficient to float the shaft and its respective load relative to the sleeve or journal. The result of a fully developed fluid film is that there is no physical contact between the rotating shaft and the sleeve during operation. Proper development of a fluid film is dependent upon adequate lubrication of the bearing journal. As will be appreciated, sleeve bearings may be disposed in conventional housings of various styles, including pillow block styles, two- and four-bolt flange styles, and so forth.

Another bearing type, antifriction bearings, relies on bearing elements disposed between inner and outer rings or races. In these bearings, too, lubrication is important to reduce the coefficient of friction between the component parts. The lubricant also aids in cooling the bearing elements and carrying away contaminants or small debris which may find their way into the bearing or which may be released from the component parts over time.

Adequate lubrication has other related and consequential benefits in addition to proper fluid film development. For example, it is commonplace to equip a bearing with a means for lubricating the bearing elements during operation to prolong the useful life of the bearings. This is typically accomplished by providing a synthetic or mineral grease or oil to coat the surfaces of the bearing elements. The application of grease or oil serves to preclude the ingress of contaminants, such as dirt, debris, moisture, and so forth into the bearing. In some bearings, the application of oil is accomplished by use of an oil ring. An oil ring hangs loosely over a shaft and rotates as the shaft rotates due to contact of the ring with the shaft. Lubricant is carried from an oil sump to the shaft, then to the bearing surface or liner. Another method is to use a circulating oil system wherein a pressurized lubricant is supplied directly to the bearing surface or liner. In other applications, a pressurized oil mist may be circulated through a bearing cavity to provide continuous lubrication of the bearing. Each lubrication method operates to prevent the ingress of contaminants, while flushing the bearing cavity of contaminants and moisture.

Oil rings of the type described above are also sometimes used in certain fluid film bearings, an oil ring hangs loosely from the shaft into a lubricant bath. The bath is formed in a lower region of the bearing housing often referred to as the oil sump. The rotation of the shaft induces a rotation in the oil ring. The oil ring thus travels through the oil sump causing some of the lubricant to adhere. The lubricant then disperses onto the surface of the shaft and eventually drains back down into the oil sump below. Heat, generated between the shaft and the bearing or conducted by the shaft or bearing, is transferred to the lubricant, which drains to the oil sump and transfers the heat to the bath. Heat is typically removed from the bath in one of two ways. The heat may be transferred from the oil bath to the interior of the bearing housing by convection, through the bearing housing by conduction, and then from the exterior of the bearing housing to the atmosphere by convection. This method of dissipating heat by convection may be limited by the design of the housing as well as the ambient temperature of the atmosphere relative to the temperature of the bearing housing. The alternative to convection is to use a circulating oil system. Such systems can, however, add significantly to the cost of the installation and to the maintenance required for its upkeep.

A circulating oil system is an effective means of removing heat from a bearing. A circulating oil system takes the lubricant from the oil sump and passes it through a heat exchanger. The lubricant in the oil sump is thus repetitively or continuously removed and replenished with cooled lubricant. Circulating oil systems also may employ other features such as filtration. Filtration keeps the lubricant in a useable condition for a longer period of time. Filtration also helps to keep contaminants from being introduced, or re-introduced, to the bearing elements. However, as previously noted, oil circulation systems are often expensive and can require additional maintenance.

As noted above, another advantage provided by proper lubrication is the cooling of the bearing during operation. A number of advantages are offered by effective control of the temperature of bearings. The principle advantage is that the shaft or bearing elements may become damaged by operation at elevated temperatures. Likewise, lubrication is adversely affected by elevated temperatures. Lubricants are chosen according to certain criteria, one of them being an anticipated or calculated operating temperature range. If the lubricant is exposed to temperatures outside of the specified range, the effectiveness of the lubricant may be greatly diminished. If, for example, a lubricant exceeds the recommended upper temperature limit, the viscosity of the lubricant may be reduced, the lubricant itself may be degraded, and the bearing elements and shaft may experience a greater amount of friction, and ultimately even more heat will be generated. Thus, operating temperature is an important factor in the proper operation of a bearing.

There is a need, therefore, for an improved technique for efficiently and effectively removing heat from a bearing.

BRIEF DESCRIPTION

In accordance with certain embodiments, the present technique provides an exemplary method for manufacturing a bearing device having an embedded cooling coil for dissipating heat in the device. The exemplary method includes disposing a cooling coil in a casting mold for a bearing component. The method also includes casting the bearing component in the mold having the cooling coil. In certain embodiments, a coolant is circulated through the cooling coil during at least a portion of the casting process. This results in a bearing component having the cooling coil embedded within the component, facilitating active cooling of the bearing during operation.

In accordance with further embodiments, an alternative method for manufacturing a bearing having a cooling network is provided. This exemplary method includes providing a bearing component and machining a coolant passageway therein. In certain embodiments, cooling tubes may be inserted into the passageway and brazed together to form a cooling conduit. The passageway may be machined in a number of manners, including drilling one or more holes in the bearing component, such that the holes define a conduit through the bearing component.

Additionally, a third method of manufacturing a bearing having a cooling network is provided in accordance with the present techniques. In this exemplary method, first and second portions of a bearing component are provided. Each of these portions includes one or more channels formed in a surface of the respective portion. The method also includes assembling the two portions such that the channels of each portion cooperate with one another to define an internal cooling conduit in the bearing component to enable additional heat extraction during bearing operation.

DRAWINGS

These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

FIG. 1 is a front elevational view of a bearing assembly according to one embodiment of the invention;

FIG. 2 is a partial sectional view of the embodiment shown in FIG. 1;

FIG. 3 is a cross-sectional view of the lower bearing liner of FIG. 2, taken along the line 3-3;

FIG. 4 is a plan view illustrating an alternative bearing liner having a single cooling conduit in accordance with one embodiment of the present techniques;

FIG. 5 is a plan view of a second alternative bearing liner having two cooling conduits therein in accordance with a further embodiment of the present techniques;

FIG. 6 is a front perspective view of still another alternative bearing liner having a machined cooling conduit in accordance with another embodiment of the present technique;

FIG. 7 is a top plan view of the bearing liner depicted in FIG. 6;

FIG. 8 is a front perspective view of a two-piece bearing liner in accordance with yet another embodiment of the present techniques;

FIG. 9 is a flowchart indicative of an exemplary method of manufacturing a bearing component in accordance with one embodiment of the present techniques;

FIG. 10 is a flowchart illustrating an alternative method of manufacturing a bearing component in accordance with another embodiment of the present techniques; and

FIG. 11 is a flowchart illustrating another exemplary method of manufacturing a bearing component in accordance with an embodiment of the present techniques.

DETAILED DESCRIPTION

Turning now to the drawings and referring to FIGS. 1 and 2, a bearing assembly 10 is shown. The bearing assembly 10 includes a bearing housing 12 which is formed from a base 14 and a cap 16. The cap 16 is coupled to the base 14 to house various internal components. In the illustrated embodiment, the housing 12 also includes a spherical seat support 18 (see FIG. 2) adapted for receiving a bearing element 20. In a present embodiment, the bearing element is formed of a lower bearing liner 22 and an upper bearing liner 24 which are mating and cooperating components. The inner surface of the bearing liners 22 and 24 may be coated with a babbitt lining 26 in a manner well known to those skilled in the art. The bearing element 20 is fixed relative to the housing 12 with an anti-rotation pin 28.

The bearing assembly 10 is depicted as a fluid film bearing, but is contemplated as being a bearing of any type for facilitating motion of a rotating shaft or other machine element. Also, while a particular style of housing is depicted, numerous bearing housings are within the scope of this disclosure. For example, typical housings may conform to ISO standards 11687-1, 11687-2, or 11687-3. These and any other suitable housings may be incorporated in alternative embodiments.

A shaft 30 is received by the bearing element 20 and traverses the bearing housing 12. In the illustrated embodiment the shaft 30 is defined as having an inboard side 32, an outboard side 34 and center portion known as the journal 36. Flanking the bearing journal 36 are a pair of thrust collars defined as the inboard thrust collar 38 and the outboard thrust collar 40. Each collar abuts a babbitt lined thrust shoulder 42 located on the bearing element. The thrust collars 38 and 40 work in conjunction with the thrust shoulder 42 to restrict the transverse or lateral movement of the shaft 30 within the bearing. It should be noted that not all bearings are capable of resisting thrust and that non-thrust bearings are contemplated as being suitable for use in alternative embodiments.

An oil ring 44 loosely surrounds the journal 36 and is shown to be hanging from the top side of the shaft 30 adjacent a small void 46 in the inner surface of the upper bearing liner 24. The oil ring 44 also encircles the lower bearing liner 22 and the lower portion of the oil ring is exposed to an oil sump 48 located beneath the shaft 30 and bearing element 20. The oil ring 44 maintains loose contact with the shaft 30 and rotational motion of the shaft induces motion of the oil ring 44. As the oil ring 44 rotates, it travels through the oil sump 48 which contains a bath of oil or other lubricant. A small portion of the lubricant from the oil sump 48 adheres to the oil ring 44 and travels with the oil ring until it contacts the top portion of the shaft 30. The lubricant then spreads on the bearing journal 36 and works its way between the bearing journal 36 and the babbitt lining 26. The lubricant forms a thin film between the bearing journal 36 and the babbitt lining 26. With a properly formed fluid film, the shaft 30 rotates without actually contacting the babbitt lining 26 on the bearing element 20. A set of seal assemblies 50 and 52 are mounted to the bearing housing 12 to contain the lubricant within the housing as well as to keep various contaminants from entering into the housing. The seal assemblies 50 and 52 are shown to be similar in construction to one another; however, they may differ from each other in design and construction depending on the operating environment of the bearing as well as with other operating parameters.

Besides providing proper lubrication, the oil ring 44 and oil sump 48 of the lubrication system also serve to transfer heat away from the shaft 30 and bearing element 20. The lubricant acts as a heat transfer agent to absorb heat from the bearing element 20 and shaft 30, and to transfer it to the oil sump 48. Heat is subsequently transferred from the oil sump 48 to the bearing housing 12, and finally from the bearing housing 12 to the surrounding atmosphere. Cooling fins 54, integrated into the bearing housing 12, can be employed to aid in the transfer of heat from the bearing housing 12 to the atmosphere. Cooling fins 54 offer increased surface area for convective heat transfer to the atmosphere, thus allowing heat to be transferred more effectively. The bearing will also typically include a temperature sensor (not shown) disposed within the bearing housing 12. A port 56 is shown as a possible location for the temperature sensor in the area of the oil sump 48. Another desired location is in the bearing element 20 adjacent the babbitt lining 26. The temperature sensor is utilized for determining the operating temperature of the bearing and to indicate when cooling of the bearing is desirable.

Heat is also removed from the bearing assembly 10 by routing a coolant through a cooling network in the assembly. Particularly, a coolant is introduced into and removed from assembly 10 via coolant ports 58. Within assembly 10, the coolant, which may include any suitable fluid or gas, is routed through conduits 60 and 62 of the lower and upper bearing liners 22 and 24 respectively. While passing through conduits 60 and 62, the coolant absorbs heat from the bearing liners 22 and 24 and such heat is removed with the coolant exiting the assembly 10.

While multiple conduits are illustrated in each of bearing liners 22 and 24, it should be noted that the present techniques are not limited to such an arrangement. As will be appreciated by one skilled in the art, other embodiments may include one or more bearing liners having a different number of conduits, such as single-conduit bearing liners, or bearing liners having three or more conduits. Further, it should be noted that while certain embodiments are illustrated herein for explanatory purposes, use of conduits of varying dimensions, shapes, materials, and form are envisaged and may be employed in full accordance with the present techniques. By way of example, although conduits 60 and 62 have generally circular cross sections, other embodiments may employ conduits having other shapes, including elliptical or rectangular cross sections. Moreover, cross sections in certain embodiments could include extensions or indentations in the general shape of the cross section, such as grooves formed in the side of the conduit to enhance the surface area of the conduit, thereby increasing heat-dissipation efficiency.

To more clearly illustrate the present cooling arrangements, a cross-sectional view of lower bearing liner 22 is provided in FIG. 3. A cooling coil 68 extends through lower bearing liner 22 and generally defines fluid conduit 60. Cooling coil 68 may be formed from any of a number of various materials known in the art and selected for their structural and thermal properties, such as copper, aluminum, steel, other alloys, thermoconductive ceramics, to name but a few examples. A coolant may be introduced into cooling coil 68 via an inlet port 70 and exit cooling coil 68 through an outlet port 72. As noted above, the coolant is routed through fluid conduit 60 to absorb heat from lower bearing liner 22. It will be appreciated that, as the coolant is circulated, the heated coolant exits lower bearing liner 22 through outlet port 72, while unheated coolant enters through inlet port 70. It should be noted that, although cooling coil 68 generally lies in a two-dimensional plan, this arrangement is merely for illustrative purposes. Other embodiments may include cooling coils or pipes in a variety of other configurations, including those which vary in three dimensions, i.e. both vertically and horizontally.

Along these lines, alternative bearing liners are illustrated in FIGS. 4 and 5. Particularly, bearing liner 78 of FIG. 4 includes an internal cooling coil 80 defining a labyrinthine conduit 82. As above, any suitable coolant may be circulated through bearing liner 78 via inlet and outlet ports 84 and 86 respectively. In another embodiment, bearing liner 92 of FIG. 5 includes cooling coils 94 and 96, which generally define conduits 98 and 100, respectively. A suitable coolant may be introduced into bearing liner 92 via inlet ports 102. The coolant is routed through cooling coils 94 and 96 to remove heat from bearing liner 92 before exiting outlet ports 104.

Other embodiments of the present techniques need not include a cooling coil, such as exemplary bearing liner 110 of FIG. 6. Bearing liner 110 has a curved inner surface 112 that is configured to receive a portion of a shaft. As will be appreciated, surface 112 could be babbitt lined if desirable for a particular application. Notably, the presently illustrated embodiment has a plurality of holes 114 forming a cooling network in the body of bearing liner 110. In certain embodiments, cooling tubes 116 are inserted into holes 114 and brazed together to generally define a cooling conduit 118 that extends through bearing liner 110. As may be appreciated, cooling tubes 116 may be formed from any suitable material, such as copper, aluminum, or the like. However, in alternative embodiments, a cooling conduit may be defined by the inner surfaces of holes drilled into a bearing liner without inserting cooling tubes.

A top plan view of bearing liner 110 is provided in FIG. 7. As presently illustrated, a pair of holes 114 is formed in the body of bearing liner 110 such that the holes intersect to form a passageway for insertion of cooling tubes 116. As may be appreciated, a different number of holes may be formed in alternative embodiments. For instance, in one alternative embodiment, a single hole may be formed through a bearing liner to define a linear passageway for the insertion of a cooling tube or the transmission of coolant without a cooling tube. Likewise, three or more holes may be formed in the body of a bearing liner to define a cooling network therethrough. As will be appreciated, holes 114 or the holes of alternative embodiments can be formed in numerous ways, including various machining techniques such as drilling.

Yet another exemplary bearing liner 122 is depicted in FIG. 8. Notably, bearing liner 122 is a two-piece design having an inner portion 124 and an outer portion 126. Inner portion 124 includes a curved surface 128 configured to receive a shaft. Particularly, the portions are configured such that, when assembled, an outer surface 130 of portion 124 abuts an inner surface 132 of portion 126. As may be appreciated, assembly of bearing liner 122 may include securing portions 124 and 126 to one another in some manner, such as through use of one or more fastening devices, through brazing the portions together, or the like. The assembled bearing liner 122 includes a cooling conduit 134. Coolant may be routed through cooling conduit 134 via inlet port 136 and outlet port 138. As will be appreciated, such circulation advantageously dissipates heat from bearing liner 122. Cooling conduit 134 is defined by the cooperation of one or more channels 140, formed in surface 130 of portion 124, with one or more channels 142, which are formed in surface 132 of outer portion 126. Once portions 124 and 126 are assembled, the channels 140 and 142 interface with one another to form cooling conduit 134.

One exemplary method of manufacturing a bearing is provided in the flowchart of FIG. 9. Method 148 includes disposing a cooling coil within a mold for a bearing component, such as a sleeve bearing liner, as indicated block 150. As noted above with respect to FIG. 3, the disposed cooling coil may be formed from a number of materials having desirable thermal properties, including copper or aluminum. A coolant is then circulated through the cooling coil, as indicated in block 152, during some or all of the casting of the bearing component, as indicated in block 154.

As may be appreciated, the temperature of any material cast in the mold might be similar to or exceed the melting point of the material forming the cooling coil. However, in such an instance, the circulation of a coolant through the coil dissipates heat from the cooling coil, and may prevent structural failure of the cooling coil, during the casting of the bearing component. Again, a number of different coolants may be used in accordance with the present techniques, such as water, another fluid, or a gas. Further, the casting material of step 154 may be any number of suitable casting materials, including iron or steel. Once cooled, the bearing component will have an embedded cooling coil to facilitate heat dissipation in the manufactured bearing.

An alternative method of manufacturing a bearing, such as sleeve bearing, is provided in FIG. 10. The exemplary method 160 includes providing a bearing component, such as a liner, as indicated in block 162, and machining a passageway in the bearing component, as provided in block 164. As discussed above, machining such a passageway may be accomplished by drilling one or more holes into the bearing component, or in some other fashion. Cooling tubes may be inserted into the machined passageway, as indicated in block 166, and brazed to one another, as provided in block 168, to define a cooling network. As discussed above, any suitable material may be used for the cooling tubes, including copper. Alternatively, the machined holes may themselves define the coolant passageway without use of the cooling tubes.

A third exemplary method for manufacturing a bearing having a cooling network is provided in FIG. 11. Particularly, method 174 includes providing two or more portions of a bearing component, as indicated in block 176, that cooperate with one another to form a cooling conduit upon assembly, as indicated in block 178. As discussed above with respect to the bearing liner illustrated in FIG. 8, each of two portions of the bearing liner could have one or more channels formed in a surface of the respective portion. The channels can be formed in a number of manners, including casting, inscription, machining, or the like. In various embodiments, assembly of the bearing component includes securing the portions together via one or more fastening devices, such as a bolt or screw; a brazing process; or some other technique. When using a mechanical fastener such as a bolt or screw, a polymeric washer or contoured seal may be advantageously employed to prevent coolant from leaking out of the cooling conduit at the interface between two components. Through cooperation between the channels formed in the various bearing component portions, the assembled bearing component includes a cooling conduit that enables heat removal from the component and bearing.

While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

Fluid cooled bearing method

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CPC

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