Abstract:
A diamond bearing assembly comprises a support ring having at least one diamond bearing segment attached thereto. A plurality of bearing pads are disposed on the diamond bearing segment. The plurality of bearing pads have a plurality of flow micro-channels between the bearing pads. A flow channel is disposed in the support ring proximate the bearing segment, wherein the flow channel has a fluid flowing therethrough for cooling the bearing segment. In another aspect, a method of cooling a diamond bearing comprises disposing a plurality of bearing pads on a diamond bearing segment. The diamond bearing segment are attached to a support ring. A fluid flows through a substantially radial channel in the support ring to cool the diamond bearing segment.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is a Continuation of U.S. patent application Ser. No. 10/397,482 filed on Mar. 26, 2003, now abandoned which is incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to thrust bearings and more particularly to diamond bearing segments with cooling and lubrication channels. 
   2. Description of the Related Art 
   Diamond bearings have found application in oil drilling and other environments demanding high load carrying ability under extreme wear conditions. As used herein, the term diamond includes synthetic diamond such as polycrystalline diamond. When used as a thrust bearing, a pair of load carrying structures containing diamond pads, also called inserts, are arranged in opposition to bear against one another. One such common arrangement for a thrust bearing is shown in  FIG. 1 , where a load ring  1  has a number of individual diamond bearing inserts  2  disposed concentrically therein. The thrust load is carried by the bearing surface  3  of each insert. 
   The load carrying capacity of such a bearing is limited by the frictional heat build up in the diamond bearing inserts. The heat buildup is related to the unit area loading of the bearing insert and to the availability of cooling mechanisms to remove the heat generated. A thermal limit is eventually reached beyond which the inserts begin to degrade and ultimately may disintegrate. Replacement of any bearing in a downhole environment is undesirable due to the expense and downtime involved in pulling and repairing such equipment. 
   The methods and apparatus of the present invention overcome the foregoing disadvantages of the prior art by providing a novel bearing having an increased surface area for lowering the unit loading and integral flow channels for cooling the bearing. 
   SUMMARY OF THE INVENTION 
   The present invention contemplates a novel diamond bearing having an increased surface area for lowering the unit loading and integral flow channels for cooling the bearing. In one aspect of the invention, a diamond bearing assembly comprises a support ring having at least one diamond bearing segment attached thereto. A plurality of bearing pads are disposed on the diamond bearing segment. The plurality of bearing pads have a plurality of flow micro-channels between the bearing pads. A flow channel is disposed in the support ring proximate the bearing segment, wherein the flow channel has a fluid flowing therethrough for cooling the bearing segment. 
   In another aspect, a method of cooling a diamond bearing comprises disposing a plurality of bearing pads on a diamond bearing segment. The diamond bearing segment are attached to a support ring. A fluid flows through a substantially radial channel in the support ring to cool the diamond bearing segment. 
   Examples of the more important features of the invention thus have been summarized rather broadly in order that the detailed description thereof that follows may be better understood, and in order that the contributions to the art may be appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject of the claims appended hereto. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For detailed understanding of the present invention, references should be made to the following detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, in which like elements have been given like numerals, wherein: 
       FIG. 1  is a schematic drawing showing a prior art diamond bearing; 
       FIG. 2A  is a schematic drawing of a diamond bearing assembly according to one preferred embodiment of the present invention; 
       FIG. 2B  is a cross section of a portion of a bearing assembly as depicted in  FIG. 2A ; 
       FIG. 2C  is a schematic drawing of an interface between moving bearing surfaces according to one embodiment of the present invention; 
       FIG. 3  is a schematic drawing of a diamond bearing segment according to one embodiment of the present invention; 
       FIG. 4  is a schematic drawing of a diamond bearing according to one embodiment of the present invention; 
       FIG. 5  is a schematic drawing of a diamond bearing segment having a hexagonal pattern of bearing pads according to one embodiment of the present invention; 
       FIG. 6  is a schematic drawing of a diamond bearing segment having a rhomboidal pattern of bearing pads according to one embodiment of the present invention; 
       FIG. 7  is a schematic drawing of a diamond bearing segment having a hexagonal pattern of bearing pads and a macro-channel according to one embodiment of the present invention; 
       FIG. 8  is a schematic drawing of a diamond bearing segment having a triangular pattern of bearing pads according to one embodiment of the present invention; 
       FIG. 9  is a schematic drawing of a diamond bearing segment having a circular or button pattern of bearing pads according to one embodiment of the present invention; 
       FIG. 10  is a schematic drawing of a diamond bearing segment having a rhomboidal pattern of bearing pads where each pad has a cavity according to one embodiment of the present invention; 
       FIG. 11  is a schematic drawing of a diamond bearing segment having a diamond bearing surface with a pattern of fluid holding cavities in the surface according to one embodiment of the present invention; 
       FIG. 12  is a schematic drawing of a diamond bearing segment having a diamond bearing surface with a pattern of annular fluid holding cavities in the surface according to one embodiment of the present invention; and 
       FIG. 13  is a schematic drawing of a diamond bearing assembly having cooling channels located beneath at least one diamond bearing segment according to one embodiment of the present invention. 
   

   DESCRIPTION OF PREFERRED EMBODIMENTS 
   In one preferred embodiment, a diamond bearing assembly  4 ,  FIG. 2A , has multiple bearing segments  5  attached to a bearing support ring  15 , see  FIG. 2B . A pattern of bearing pads  8  are disposed in the front surface  12  of the bearing segment  5  and each bearing pad  8  has an associated load surface  9 . The bearing pads  8  are triangularly shaped such that the total area of all the load surfaces  9  of bearing assembly  4  is substantially greater than the corresponding load surface area of the prior art bearing of  FIG. 1 . The bearing pads  8  are spaced such that flow micro-channels  11  are created between the bearing pads  8 . The micro-channels  11  provide a path for a fluid to flow for cooling and lubricating the bearing pads  8 . As will be appreciated by one skilled in the art, the outer housings (not shown) surrounding and supporting such a bearing may force the cooling/lubricating fluid to flow from an outer diameter  18  of the bearing support ring  15  to an inner diameter  19  as shown in  FIG. 2A . Alternatively, the fluid may be forced to flow from the inner diameter to the outer diameter. 
   The multiple bearing segments  5  are arranged on support ring  15  such that macro-channels  21  are formed between the bearing segments  5  to provide a larger volume of coolant flow through the bearing assembly  4 . The macro-channels may be sized, using techniques known in the art, to provide a predetermined pressure differential across the bearing assembly thereby ensuring a fluid flow through the bearing micro-channels sufficient to cool and lubricate the bearing pads  8 . 
     FIG. 2B  shows a section through a bearing section A-A of  FIG. 2A  in which the bearing pads  8  are integral with the bearing segment  5 . The bearing surface  9  extends a predetermined distance from the surface  12 . In this preferred embodiment, as shown in  FIG. 2B , the entire bearing segment  5  is made of a diamond material, such as for example, polycrystalline diamond. The bearing pads  8  may be press formed during the manufacture of bearing segment  5 . Alternatively, the bearing pads may be formed by removing material from a formed diamond surface using techniques known in the art. Such techniques include, but are not limited to, electric discharge machining (EDM) and laser ablation techniques. The removal of such material results in the raised pads and the interrelated micro-channels. 
   The multiple bearing segments  5  are bonded to the bearing ring  15  using any of a number of techniques known in the art. Such bonding techniques include, but are not limited to, brazing, sintering, and diffusion bonding. The bearing ring is commonly a tungsten carbide material. Alternatively, a steel ring may be used. 
   In one preferred embodiment, the back side of the bearing segment  5  is formed to have a pattern of locking pads  16  extending from back surface  14 , see  FIG. 2B . The locking pads act to improve the bonding of the bearing segments  5  to the bearing ring  15 . The pattern of locking pads  16  may be similar to the pattern of bearing pads  8 . Alternatively, the pattern of locking pads  16  may be determined using available numerical modeling techniques such that the pattern of locking pads  16  acts to reduce stress concentrations induced in bearing segment  5  by the compressional loading on bearing pads  8  and the thermal stresses induced by the frictional heating of the bearing pads  8 . Such numerical modeling techniques, such as finite element analysis, are known to one skilled in the art and commercial packages are available for performing such an analysis. Such an analysis is application dependent on the size, shape, and loading characteristics of such a bearing system and a locking pad pattern shape may be determined without undue experimentation by one skilled in the art. 
   The bottom corners  20  of micro-channels  11 , see  FIG. 2B , may be formed to reduce stress concentration at the corners. Such corners  20  are commonly formed with a predetermined radius to reduce such stress concentrations. The actual shape may be determined using the analytical modeling techniques described previously. In one preferred embodiment, the corner  20  has a radius substantially equal to half of the width of micro-channel  11 . 
   In another preferred embodiment, an upper edge  21 ( see    FIGS. 2B ,  2 C) of bearing pad  8  is formed to provide an entrance ramp such that fluid  22  is forced into the interface  23  by the relative motion of mating bearing  30 . This action acts to lubricate the bearing and to draw heat away from the bearing surfaces  9 . The form of the upper edge  21  may be a chamfer, a radius, or any other suitable shape that provides a wedging action to the fluid  22 . 
   The bearing segments previously discussed with respect to  FIGS. 2A , B, C and  3 , have bearing pads  8  as an integral part of bearing segment  5 . Alternatively, the bearing pads  8  may be individual shaped diamond inserts that are bonded or captured in a metallic matrix bearing ring using techniques known in the art. Commonly, such a metallic matrix is a tungsten carbide material. 
   In one preferred embodiment, see  FIG. 4 , a diamond bearing  45  is shown with a plurality of hexagonal bearing pads  41  arranged in a concentric pattern on bearing ring  40 . Micro-channels  42  are formed between the bearing pads  41 . The bearing pads  41  are integral to the bearing ring  40  and are formed using any of the techniques described above. 
     FIGS. 5-9  show other examples of patterns and shapes of diamond bearing segments similar to that shown in  FIG. 2 .  FIG. 5  shows a bearing segment  50  having a hexagonal pattern of bearing pads  51  and flow micro-channels  52 .  FIG. 6  shows a bearing segment  60  having rhomboidal pattern of bearing pads  61  and flow micro-channels  62 .  FIG. 7  shows a bearing segment  70  having a hexagonal pattern similar to that of  FIG. 5  but with a macro-channel  73  extending across the bearing segment  70  to provide additional fluid flow to the bearing pads  51 .  FIG. 8  shows a bearing segment  80  having a triangular pattern that is a variation of that shown in  FIG. 2 .  FIG. 9  shows a bearing segment  90  having a spaced pattern of circular, or button, shaped bearing pads  91  and flow micro-channels  92 . 
     FIG. 10  shows a bearing segment  100  having bearing pads  101  and flow micro-channels  102 . A cavity  103  is formed in bearing surface  104  of each bearing pad  101 . The cavity  103  acts as a fluid reservoir and acts to help provide fluid into the bearing interface  23  (see  FIG. 2C ) to lubricate and cool the bearing pads  101 . 
   The exemplary bearings described above have bearing pads integrally formed with the bearing segment. Alternatively, the bearing pads may be individual shaped diamond inserts that are bonded or captured in a metallic matrix bearing ring using techniques known in the art. Commonly, such a metallic matrix is a tungsten carbide material. 
     FIG. 11  shows a diamond segment  110  having a continuous diamond surface  112  and a pattern of fluid cavities  111  disposed in the surface  112 . The cavities  111  act as fluid reservoirs to lubricate and cool the bearing surface  112 .  FIG. 12  shows a diamond segment  120  having a continuous diamond surface  122  and a pattern of annular fluid cavities  121  disposed in the surface  122 . The cavities  121  act as fluid reservoirs to lubricate and cool the bearing surface  122 . 
   In another preferred embodiment,  FIG. 13  shows a portion of a bearing assembly  139  having bearing segment  130 , similar to those described previously Bearing segment  130  has bearing pads  131  and flow micro-channels  132 . Bearing segment  130  is bonded to bearing ring  135  that has macro flow channels  133 , formed therein, for flowing fluid  134  through the channels  134  and cooling the back side of bearing segment  130 . The number and shape of such flow channels  133  may be determined, without undue experimentation, from analytical methods previously described to provide adequate cooling to the bearing pads  131  to prevent degradation. 
   It will be appreciated by one skilled in the art that all of the exemplary bearing surfaces described herein, have substantially greater bearing surface area than that of prior art bearings. 
   The foregoing description is directed to particular embodiments of the present invention for the purpose of illustration and explanation. It will be apparent, however, to one skilled in the art that many modifications and changes to the embodiment set forth above are possible. It is intended that the following claims be interpreted to embrace all such modifications and changes.