Patent Application
20090205873
1. Technical Field
The present invention relates in general to bearing systems for downhole tools and, in particular, to an improved system, method, and apparatus for a downhole tool bearing system containing diamond enhanced materials.
2. Description of the Related Art
Diamond is a unique bearing material with superior wear resistance compared to traditional bearing materials, such as steel. Downhole tools with diamond enhanced bearings have been investigated in an effort to take advantage of diamond's wear resistant properties. Some diamond bearing systems in rolling cone drill bits and mud motor bearings have been proposed with polycrystalline diamond compacts (PDC), chemical vapor deposition (CVD) diamond, and diamond-like carbon (DLC) coatings. Such PDC bearings are mounted in element arrays over the surfaces of the radial and thrust bearings or in frustoconical shapes. For example, U.S. Pat. No. 4,738,322, describes the use of PDC rolling cone bit bearings. U.S. Pat. No. 6,068,070, describes a CVD diamond enhanced bearing for earth boring bits. In addition, U.S. Pat. No. 7,296,641 and U.S. Pat. App. Nos. 2007/0151769, 2007/0186483, 2007/0193782 describe cutting elements that incorporate diamond enhanced materials.
Although each of these designs is workable, a solution that improves the performance of drill bit bearing systems with other types of material would be desirable. A more cost effective solution that provides the necessary performance advantages would be particularly desirable. As will be disclosed herein, diamond enhanced bearing materials provide such an alternative. These materials contain significant amounts of diamond that positively influence their wear performance.
Embodiments of a system, method, and apparatus for downhole tool bearings containing diamond enhanced materials are disclosed. The diamond enhanced materials may comprise diamond grains in a matrix of tungsten carbide, silicon carbide, etc. Alternatively diamond grit may be brazed to a steel bearing surface. Diamond particles coated with a reactive braze also may be used. The braze is activated and a layer of brazed diamond particles forms a wear resistant surface that may be applied to a steel bearing surface. These materials may be used for a variety of bearing systems in downhole tools such as rolling cone drill bits and mud motors.
In some embodiments, bearing rings are formed at least in part with diamond enhanced material, and are installed on at least one of the outer radial bearing surfaces of the journal pin on the rolling cone bit. In other embodiments, the bearing rings are not formed as continuous rings, but as partial or discontinuous rings and attached to the journal pin or cone cavity surfaces. Diamond enhanced material also may be used to form, at least in part, thrust bearings, rollers or balls. In addition, brazed diamond grit may be used to form a diamond enhanced surface on the ball or roller race of the journal pin or cone.
The foregoing and other objects and advantages of the present invention will be apparent to those skilled in the art, in view of the following detailed description of the present invention, taken in conjunction with the appended claims and the accompanying drawings.
So that the manner in which the features and advantages of the present invention are attained and can be understood in more detail, a more particular description of the invention briefly summarized above may be had by reference to the embodiments thereof that are illustrated in the appended drawings. However, the drawings illustrate only some embodiments of the invention and therefore are not to be considered limiting of its scope as the invention may admit to other equally effective embodiments.
Referring to
In another embodiment, a brazed diamond grit may be utilized for bearing applications. The E6 company provides still another type of diamond enhanced surface that is formed by applying diamond particles coated with a reactive braze. The braze is activated and a layer of brazed diamond particles forms a wear resistant surface that may be applied to a steel bearing surface. These materials may be used for a variety of bearing systems in downhole tools such as rolling cone drill bits, mud motors and other downhole tools used in mineral exploration. In addition, these materials may be formed in a bearing system against themselves or against another type of diamond or diamond enhanced wear surface.
Referring to
These diamond enhanced materials may be applied to downhole tool bearing systems to take advantage of their wear resistant properties, thus prolonging tool life. An example of a downhole tool containing a bearing system is a rock drill bit, such as the one shown in
A cone 23 rotatably mounts on bearing pin 17. Cone 23 has a plurality of protruding teeth 25 or compacts (not shown). Cone 23 has a cavity 27 that is slightly larger in diameter than the outer diameter of bearing pin 17. Cone 23 has a back face 29 that is located adjacent, but not touching, last machined surface 19. If the bearing type is a sealed, lubricated bearing, a seal 31 is located in a seal cavity adjacent to the back face 29. Seal 31 may be of a variety of types, and in this embodiment is shown to be an elastomeric o-ring. Seal 31 engages a gland or area of bearing pin 17 adjacent to last machined surface 19. Other types of elastomeric seals may be used such as dual seals, seals with non-circular cross-sectional shapes, etc. Mechanical face seals also may be used.
Cone 23 may be retained in more than one manner. In the embodiment shown, cone 23 is retained on bearing pin 17 by a plurality of balls 33 that engage a mating annular recess formed in cone cavity 27 and on bearing pin 17. Balls 33 lock cone 23 to bearing pin 17 and are inserted through a ball passage 35 during assembly after cone 23 is placed on bearing pin 17. Ball passage 35 extends to the exterior of bit leg 15 and may be plugged as shown after balls 33 are installed.
Portions of cavity 27 slidingly engages journal surfaces 18 and 22. In one embodiment, the outer end of journal surface 18 is considered to be at the junction with the gland area engaged by seal 31, and the inner end of journal surface 18 is considered to be at the junction with the groove or race for balls 33. Journal surfaces 18 and 22 serve as a journal bearing for loads imposed along the axis of bit 11.
In sealed lubricated bearings, a first lubricant port 37 is located on an exterior portion of journal surface 18 of bearing pin 17. In one embodiment, first port 37 is located on the upper or unloaded side of journal surface 18 of bearing pin 17 between balls 33 and seal 31. First port 37 also could be on other areas of journal surface 18. First port 37 is connected to a first passage 39 via ball passage 35. First passage 39 leads to a lubricant reservoir 41 that contains a lubricant.
Lubricant reservoir 41 may be of a variety of types. In one embodiment, an elastomeric diaphragm 43 separates lubricant in lubricant reservoir 41 from a communication port 45 that leads to the exterior of bit body 13. Communication port 45 communicates the hydrostatic pressure on the exterior of bit 11 with pressure compensator 43 to reduce and preferably equalize the pressure differential between the lubricant and the hydrostatic pressure on the exterior.
The precise positioning between bearing pin 17 and cone 23 varies as the drill bit 11 is loaded during service, thereby creating eccentricity. The eccentricity is a result of the differences between the outer diameters of journal surfaces 18 and 22 and the inner diameters of cone cavity surfaces 27 and 28.
Referring again to
In other embodiments, the bearing rings are not formed as continuous rings, but as partial or discontinuous rings, or as ring sections (e.g., half-rings), and attached to the journal pin or cone cavity surfaces. These embodiments may include thrust bearings made of diamond enhanced material, rollers and/or roller race surfaces and balls and/or ball race surfaces made of diamond enhanced material. These bearing surfaces also are formed at least in part with diamond enhanced material and attached to portions of the journal or cone bearing surfaces.
The schematic drawing in
In some embodiments of a downhole tool constructed in accordance with the invention, the tool has a body having a bearing element (e.g., surface, pin, etc.) extending along an axis. The bearing pin has a journal surface and a nose surface with a smaller diameter than that of the journal surface. A rotatable element (e.g., cone) is rotatably mounted to the bearing pin and has a cavity slidingly engaging the journal and nose surfaces. A diamond enhanced bearing system is between the bearing pin and the rotatable element comprising at least one load carrying bearing surface (e.g., ring) formed at least in part with diamond enhanced material.
In other embodiments, the diamond enhanced material may comprise one of: diamond grains in a matrix of tungsten carbide; a high temperature, high pressure sintered silicon bonded polycrystalline diamond; a low pressure, low concentration diamond enhanced polycrystalline material; an aluminum nitride intermetallic bonded diamond and carbide composite; a brazed diamond grit; and diamond particles coated with a reactive braze. The diamond enhanced material may comprise 30% to 70% diamond by volume, with a grain size of 5 to 250 microns. The diamond enhanced material may be unsintered, have an open porosity of about 9%, and a principle binder phase comprising βSiC with some free Si. The diamond may be diamond enhanced WC or diamond film.
In still other embodiments, the bearing ring is installed on at least one of the journal and nose surface of the bearing pin. The bearing ring may comprise a plurality of bearing rings that are formed at least in part with diamond enhanced material. The bearing rings may be installed on both the journal and nose surfaces and on the cavity. The bearing ring may be attached with one of brazing, soldering, adhesives and mechanical locking by shrink fitting, pinning, splinning or keyways. Alternatively, the bearing ring is a partial ring and discontinuous, or may be formed in ring sections, with or without channels as illustrated in the drawings. The bearing ring may comprise a thrust bearing made of diamond enhanced material, a roller, a roller race surface, or a ball and a ball race surface made of diamond enhanced material. Moreover, these various embodiments may be used in many different combinations as well.
While the invention has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention.
This application claims priority to and the benefit of U.S. Provisional Patent Application No. 61/029,719, which was filed on Feb. 19, 2008, and is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61029719 | Feb 2008 | US |
