Patent Publication Number: US-2023151852-A1

Title: Self-lubricating bearing

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a non-provisional application of, and claims priority to U.S. Provisional Patent Application No. 63/280,189, entitled “Self-Lubrication Bearing,” filed on Nov. 17, 2021, the entire contents of which are incorporated herein by reference in their entirety. 
    
    
     FIELD OF THE TECHNOLOGY 
     The present technology is directed to a self-lubricating bearing and more particularly to a self-lubricating bearing having a metallic outer ring, a self-lubricating liner, and a metallic inner member with a physical vapor deposition coating thereon. The self-lubricating liner is bonded to the outer ring. Optionally, a lubricant is disposed between the self-lubricating liner and the physical vapor deposition coating. 
     BACKGROUND 
     Various types of bearings are used in aircraft applications where vibrations are known to occur due to bearing wear. When vibration of the aircraft airframe occurs, it can be detected by the persons inside the aircraft. Depending on the root cause of the vibration, it may be experienced either as physical movement, noise, or both movement and noise. These occurrences can cause passenger distress and malaise. Furthermore, any vibration can cause increased wear of components. As the airframe vibration increases, it causes premature failure of the bearings. Options for replacement of the failed bearing is limited because of space constraints. Thus, there is a need for a bearing that is resistant to wear. 
     In addition, there are environmental standards that limit the use of certain materials in components such as bearings. For example, REACH (i.e., Registration, Evaluation, Authorization and Restriction of Chemicals) is a regulation of the European Union adopted to improve the protection of human health and the environment from the risks that can be posed by chemicals while enhancing the competitiveness of the EU chemicals industry. Thus, certain materials must be avoided in the design of bearings. 
     SUMMARY 
     There is disclosed herein a self-lubricating bearing that includes an outer ring having a concave inside surface defining an interior area of the outer ring. The self-lubricating bearing has an inner member having a convex exterior surface. The inner member is disposed at least partially in the interior area. The convex exterior surface has a physical vapor deposition coating thereon. The self-lubricating bearing has a self-lubricating liner bonded to the concave inside surface. The outer ring comprises a first metallic alloy, and the inner member comprises a second metallic alloy. 
     In some embodiments, a chemical composition of the first metallic alloy and a chemical composition of the second metallic alloy are the same. 
     In some embodiments, the chemical composition includes a precipitation hardened stainless steel. 
     In some embodiments, the precipitation hardened stainless steel includes an AMS 5643 17-4PH stainless steel or an AMS 5629 13-8 PH stainless steel. 
     In some embodiments, the precipitation hardened stainless steel includes an AMS 5643 17-4PH stainless steel heat treated per 17-4PH H1150. 
     In some embodiments, the chemical composition includes a martensitic stainless steel. 
     In some embodiments, the martensitic stainless steel includes a 440C stainless steel or an AMS 5630, AMS 5880 or AMS 5618 stainless steel. 
     In some embodiments, the martensitic stainless steel is heat treated to HRc 55 to 62. 
     In some embodiments, a chemical composition of the first metallic alloy includes a precipitation hardened stainless steel, and a chemical composition of the second metallic alloy includes a martensitic stainless steel. 
     In some embodiments, the precipitation hardened stainless steel includes an AMS 5643 17-4PH stainless steel or an AMS 5629 13-8 PH stainless steel, and the martensitic stainless steel comprises a 440C stainless steel or an AMS 5630, AMS 5880 or AMS 5618 stainless steel. 
     In some embodiments, the precipitation hardened stainless steel includes an AMS 5643 17-4PH stainless steel heat treated per 17-4PH H1150. 
     In some embodiments, the martensitic stainless steel is heat treated to HRc 55 to 62. 
     In some embodiments, the self-lubricating bearing further includes a lubricant disposed between the self-lubricating liner and the physical vapor deposition coating. 
     In some embodiments, the lubricant includes a silicone grease with a plurality of first self-lubricating particles dispersed therein. 
     In some embodiments, the physical vapor deposition coating includes chromium nitride, titanium nitride, tungsten carbide or zirconium nitride. 
     In some embodiments, the physical vapor deposition coating is coated on the convex exterior surface via at least one of cathode arc evaporation, magnetron sputter, electron beam evaporation, ion beam sputter, and laser ablation. 
     In some embodiments, the plurality of first self-lubricating particles includes polytetrafluoroethylene. 
     In some embodiments, the polytetrafluoroethylene includes at least one of a powder, a floc and fibers. 
     In some embodiments, the self-lubricating liner includes a woven material with a thermosetting resin embedded therein and a plurality of second self-lubricating particles dispersed in the resin. 
     In some embodiments, the woven material includes a fabric comprising at least one of fiberglass, polyethylene terephthalate, polyester, nylon, cotton, meta-aramid material, polytetrafluoroethylene and aromatic polyamide fibers. 
     In some embodiments, the self-lubricating liner includes a thermally-consolidated, machinable, moldable non-woven material. 
     In some embodiments, the non-woven material includes a plurality of second self-lubricating particles integral to the non-woven material or as an additive to a resin. 
     In some embodiments, the resin includes polyester, epoxy, phenolic, urethane, polyimide, thermoplastic polymers or a thermoset polymer. 
     In some embodiments, the self-lubricating bearing is a spherical bearing or a journal bearing. 
     In some embodiments, the outer ring has at least one axial split therein. 
     In some embodiments, the inner member has at least one axial split therein. 
     In some embodiments, the self-lubricating bearing has a diametral clearance between the inner member and the physical vapor deposition coating of less than 0.1 mm after 30,000,000 cycles of operation. 
     In some embodiments, the inner member has a cylindrical bore extending axially therethrough, the bore is defined by a concave interior surface having another self-lubricating liner adhered thereto, the self-lubricating bearing further includes a shaft extending through the bore and another physical vapor deposition coating on a cylindrical exterior surface of the shaft, and the shaft is in sliding relation to the inner member. 
     In some embodiments, the self-lubricating bearing further includes a lubricant disposed between the other self-lubricating liner and the other physical vapor deposition coating. 
     In some embodiments, the other physical vapor deposition coating includes chromium nitride, titanium nitride, tungsten carbide or zirconium nitride. 
     In some embodiments, the other physical vapor deposition coating is coated on the cylindrical exterior surface via at least one of cathode arc evaporation, magnetron sputter, electron beam evaporation, ion beam sputter, and laser ablation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  is a cross-sectional view of a self-lubricating spherical bearing according to an embodiment of the present invention; 
         FIG.  1 B  is an enlarged view of Detail 1B of  FIG.  1 A ; 
         FIG.  1 C  is a cross-sectional view of a self-lubricating spherical bearing according to another embodiment of the present invention; 
         FIG.  2    is a cross-sectional view of a self-lubricating journal bearing according to another embodiment of the present invention; 
         FIG.  3 A  is a schematic view of the self-lubricating liner of the bearing; 
         FIG.  3 B  is a schematic view of the silicone grease employed in some embodiments of the present invention; 
         FIG.  4    is a graph with plots of endurance test results for the self-lubricating bearing according to an embodiment of the present invention and a prior art bearing; 
         FIG.  5 A  is a cross-sectional view of the self-lubricating spherical bearing of  FIG.  1 A  taken across Section 5-5 and showing diametral clearance; and 
         FIG.  5 B  is a cross-sectional view of the self-lubricating spherical bearing according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     As shown in  FIGS.  1 A,  1 B, and  5 A , a self-lubricating bearing is generally designated by the numeral  10 . For example, the self-lubricating bearing  10  illustrated in  FIG.  1 A  is a spherical bearing. The self-lubricating bearing  10  has utility in aerospace applications, for example, in flight control surfaces including primary flight control surfaces (e.g., ailerons, elevator, rudder), and secondary (i.e., auxiliary) flight control surfaces (e.g., flaps, spoilers, leading edge devices, high lift systems). The self-lubricating bearing  10  also has utility in applications where there are vibration and dithering motions, such as but not limited to railway applications, anti-roll bars and damper bearings. The self-lubricating bearing  10  also has utility in applications in drones/helicopters which contain pitch link bearings and tail rotor link bearings. The self-lubricating bearing  10  also has utility in applications in motorsports which contain linkages and suspension bearings. 
     The self-lubricating bearing  10  includes an outer ring  12  having an interior area  14  defined by a concave inside surface  16  of the outer ring  12 . The outer ring  12  is manufactured from a stainless steel (e.g., martensitic steel, ferritic steel, precipitation hardened steel, austenitic steel, austenitic-ferritic steel), corrosion-resistant superalloy (e.g., nickel based, cobalt based, iron based), or titanium-based alloys. In some embodiments, the stainless steel is a precipitation hardened stainless steel and is an AMS 5643 17-4PH stainless steel or an AMS 5629 13-8 PH stainless steel. In some embodiments, the AMS 5643 17-4PH stainless steel is heat treated per 17-4PH H1150. 
     The self-lubricating bearing  10  includes an inner member  20  having a convex exterior surface  22 . The inner member  20  is disposed at least partially in the interior area  14 . The inner member  20  is manufactured from a stainless steel (e.g., martensitic steel, ferritic steel, precipitation hardened steel, austenitic steel, austenitic-ferritic steel), corrosion-resistant superalloy (e.g., nickel based, cobalt based, iron based), or titanium-based alloys. In some embodiments, the stainless steel is a precipitation hardened stainless steel such as AMS 5629 13-8 PH stainless steel or a martensitic steel per AMS5630, AMS5880, or AMS5618. In some embodiments, the martensitic steel per AMS5630, AMS5880 or AMS5618 is heat treated to HRc 55 to 62. The convex exterior surface  22  has a physical vapor deposition coating  24  thereon (see  FIG.  1 B ). 
     In some embodiments, the outer ring  12  is made from a first metallic alloy and the inner member  20  is made from a second metallic alloy. In some embodiments, the chemical composition of the first metallic alloy and the chemical composition of the second metallic alloy are the same. In some embodiments, the chemical composition of the first metallic alloy and the second metallic alloy consist of a precipitation hardened stainless steel. The precipitation hardened stainless steel is, for example, an AMS 5643 17-4PH stainless steel or an AMS 5629 13-8 PH stainless steel. In some embodiments, the precipitation hardened stainless steel is, for example, an AMS 5643 17-4PH stainless steel heat treated per 17-4PH H1150. In some embodiments, the chemical composition of the first metallic alloy and of the second metallic alloy is a martensitic stainless steel such as 440C stainless steel (e.g., having a composition of 78-83.1% iron, 16-18% chromium 1-1.2% carbon 1% (max) silicon, 1% (max) manganese, 0.8% molybdenum, 0.04% phosphorus and 0.02% sulfur). 
     In some embodiments, where the chemical composition of the first metallic alloy and the second metallic alloy are the same, the chemical composition of the first metallic alloy and the second metallic alloy is, for example, a martensitic stainless steel. The martensitic stainless steel is a 440C stainless steel or an AMS 5630, AMS 5880 or AMS 5618 stainless steel. In some embodiments, the martensitic stainless steel is heat treated to HRc 55 to 62. 
     In some embodiments, the chemical composition of the first metallic alloy and the chemical composition of the second metallic alloy are different. For example, the chemical composition of the first metallic alloy is a precipitation hardened stainless steel and the chemical composition of the second metallic alloy is a martensitic stainless steel. In some embodiments, the precipitation hardened stainless steel is an AMS 5643 17-4PH stainless steel or an AMS 5629 13-8 PH stainless steel and the martensitic stainless steel is an AMS 5630, AMS 5880 or AMS 5618 stainless steel. In some embodiments, the precipitation hardened stainless steel is 440C stainless steel or an AMS 5643 17-4PH stainless steel heat treated per 17-4PH H1150. In some embodiments, the martensitic stainless steel is heat treated to HRc 55 to 62. 
     A self-lubricating liner  30  is bonded to the concave inside surface  16 . In some embodiments, the physical vapor deposition coating  24  is a chromium nitride material. In some embodiments, the physical vapor deposition coating  24  is a titanium nitride material. In some embodiments, the physical vapor deposition coating  24  is a tungsten carbide material. In some embodiments, the physical vapor deposition coating  24  is a zirconium nitride material. The physical vapor deposition coating  24  is performed via cathode arc evaporation, magnetron sputter, electron beam evaporation, ion beam sputter or laser ablation. 
     In some embodiments, a lubricant  40  (e.g., silicone grease) with a plurality of first self-lubricating particles  44  (see  FIG.  3 B ) dispersed therein is disposed between the self-lubricating liner  30  and the physical vapor deposition coating  24 . In some embodiments, the plurality of first self-lubricating particles  44  are made of polytetrafluoroethylene (PTFE) material such as but not limited to a powder, a floc and fibers. The physical vapor deposition coating  24 , self-lubricating liner  30 , and lubricant  40  facilitate relative rotational or translational movement between the inner member  20  and the outer ring  12 . 
     In some embodiments, the inner member  20  has a cylindrical bore  28  extending axially therethrough and concentric with a longitudinal axis B of the self-lubricating bearing  10 . The bore  28  is defined by a concave interior surface  29  of the inner member  20 . In some embodiments, a shaft  50  extends through the bore  28  and a cylindrical exterior surface  52  of the shaft  50  engages the concave interior surface  29  of the inner member  20 . In some embodiments, the shaft  50  is press fit into the bore  28 . However, in some embodiments, the cylindrical exterior surface  52  of the shaft  50  axially and/or rotationally slidingly engages the concave interior surface  29 . 
     As shown in  FIG.  1 C , the inner member  20  has a cylindrical bore  28  extending axially therethrough and concentric with a longitudinal axis B of the self-lubricating bearing  10 . The bore  28  is defined by a concave interior surface  29 . A self-lubricating liner  30  is bonded to the concave interior surface  29  of the inner member  20  (similar to that described herein with reference to the self-lubricating bearing  10  illustrated in  FIGS.  1 A and  1 B ). In some embodiments, the cylindrical exterior surface  52  of the shaft  50  axially and/or rotationally slidingly engages the self-lubricating liner  30  that is bonded to the concave interior surface  29 . In some embodiments, the cylindrical exterior surface  52  of the shaft  50  also has a physical vapor deposition coating  24  (similar to that described herein with reference to the self-lubricating bearing  10  illustrated in  FIGS.  1 A and  1 B ). In some embodiments, a lubricant  40  is disposed between the physical vapor deposition coating  24  and the self-lubricating liner  30 . 
     As best shown in  FIG.  3 A , in some embodiments, the self-lubricating liner  30  is a woven structure  80  embedded with a resin  90  and a plurality of second self-lubricating particles  84 . The woven structure  80  includes a fabric that has a plurality of fibers  80 A,  80 B,  80 C, and  80 D interwoven with one another and the second self-lubricating particles  84  (e.g., polytetrafluoroethylene (PTFE) fibers, powder or floc) interwoven or dispersed therewith. The plurality of second self-lubricating particles  84  are integral to the fabric or as an additive to the resin  90 . The fibers  80 A,  80 B,  80 C, and  80 D include those made of a polyester material, a glass material fiberglass, polyethylene terephthalate, nylon, polyester, cotton, a meta-aramid material, polytetrafluoroethylene (PTFE), aromatic polyamide (aramid), a para-aramid synthetic material or combinations thereof. In some embodiments, the resin  90  is a polyester, epoxy, phenolic, urethane, polyimide and/or polyamide material, or other thermoplastic or thermoset polymers. 
     While the self-lubricating liner  30  is shown and described as having a woven structure  80 , the present invention is not limited in this regard as in some embodiments, the self-lubricating liner  30  is a thermally-consolidated, machinable, moldable or non-woven material that has a reinforced polymer matrix composite with the plurality of second self-lubricating particles  84  integral to the non-woven material and/or as an additive to the matrix. 
     While  FIG.  1 A  illustrates the self-lubricating bearing  10  as being a spherical bearing, the present invention is not limited in this regard, as other types of bearing such as but not limited to journal bearings may be employed. A journal bearing  100  according to an embodiment is shown in  FIG.  2   . The journal bearing  100  includes a bushing  112  that has a tubular body portion  112 T and a flange  112 F extending radially outward from an axial end  112 A of the tubular body  112 T. The tubular body  112 T has an exterior surface  112 E and a cylindrical inside surface  116  which defines a bore  114  extending axially therethrough and concentric with a longitudinal axis A of the journal bearing  100 . The cylindrical inside surface  116  has a self-lubricating liner  30  (similar to that described herein with reference to the self-lubricating bearing  10  illustrated in  FIGS.  1 A,  1 B and  3 A ) bonded thereto. The bushing  112  is manufactured from a stainless steel (martensitic steel, ferritic steel, precipitation hardened steel, austenitic steel, austenitic-ferritic steel), corrosion-resistant superalloy (e.g., nickel based, cobalt based, iron based), or titanium-based alloy. In some embodiments, the stainless steel is a precipitation hardened stainless steel and is an AMS 5643 17-4PH stainless steel or an AMS 5629 13-8 PH stainless steel. 
     The bushing  112  is press fit into a cylindrical inside surface  68  of a housing  66 . A shaft  120  extends through the bore  114 . The shaft  120  has a cylindrical exterior surface  122 . In some embodiments, the shaft  120  is manufactured from a stainless steel (e.g., martensitic steel, ferritic steel, precipitation hardened steel, austenitic steel, austenitic-ferritic steel), corrosion-resistant superalloy (e.g., nickel based, cobalt based, iron based), or titanium-based alloy. In some embodiments, the stainless steel is a precipitation hardened stainless steel and is an AMS 5643 17-4PH stainless steel or an AMS 5629 13-8 PH stainless steel. The cylindrical exterior surface  122  has a physical vapor deposition coating  24  thereon (similar to that described herein with reference to the self-lubricating bearing  10  illustrated in  FIGS.  1 A and  1 B ). 
     As shown in  FIG.  2   , a lubricant  40  (e.g., silicone grease) with a plurality of first self-lubricating particles  44  (see  FIG.  3 B ) dispersed therein is disposed between the self-lubricating liner  30  and the physical vapor deposition coating  24 . In some embodiments, the plurality of first self-lubricating particles  44  are made of polytetrafluoroethylene (PTFE) material such as but not limited to a powder, a floc and fibers. 
     As shown in  FIG.  4   , a graph  200  of endurance test data has diametral clearance DC (also known by those skilled in the relevant art as radial play) in millimeters on the Y-axis and cycles of operation of the bearing  10  on the X-axis. The diametral clearance DC plotted on the graph  200  for plot  202  is equal to two times the clearance D between the self-lubricating liner  30  and the physical vapor deposition coating  24  as shown in  FIG.  5 A . The diametral clearance DC plotted on the graph  200  for plot  201  for the prior art bearing is equal to two times the clearance D between the inner member and the outer ring thereof. The prior art bearing employed in the endurance test had no physical vapor deposition coating on the inner member. The cycles of operation in the endurance test continuously tested the bearing in a dithering phase (which simulates an airplane in cruise mode) which included a unidirectional load (i.e., 10 MPa) and ±2° movement. The prior art bearing and the spherical self-lubricating bearing  10  according to an embodiment of the present invention were tested under the same conditions. 
     The plot  201  is of diametral clearance DC versus cycles for a prior art baseline bearing. The plot  201  illustrates that the prior art bearing has a diametral clearance DC of about 0.5 mm after about 2,000,000 cycles, which exceeds operational wear limits. 
     Plots  202  is the test data for the spherical self-lubricating bearing  10  according to an embodiment of the present invention with a chromium nitride physical vapor deposition coating  24  on the inner member  20  and with the silicone grease lubricant  40 , with the plurality of first self-lubricating particles  44  dispersed therein, disposed between the self-lubricating liner  30  and the physical vapor deposition coating  24 . As shown in plot  202 , the self-lubricating bearing  10  has a diametral clearance between the self-lubricating liner  30  and the physical vapor deposition coating  24  of less than 0.1 mm after 30,000,000 cycles of operation. While the endurance tests were performed for the spherical self-lubricating bearing  10  of the present invention, the test results are also applicable to the journal type self-lubricating bearing  100  illustrated in  FIG.  2   . 
     In some embodiments, the inner member  20  has a split configuration in which the inner member  20  has one or more axial splits therein. For example, in the embodiment shown in  FIG.  5 B , the inner member  20  has a two-piece split configuration with two axial splits  21 A and  21 B creating a first inner member segment  20 A and a second inner member segment  20 B that are abutted against one another at the axial splits  21 A and  21 B. The two-piece split configuration with the two axial splits  21 A and  21 B creating the first inner member segment  20 A and the second inner member segment  20 B allows the inner member  20  to be assembled in the outer ring  12 . While the inner member  20  is shown and described as having the two inner member segments  20 A and  20 B with the two axial splits  21 A and  21 B, the present invention is not limited in this regard as the inner member  20  may have one segment and one axial split or more than two segments and more than two axial splits. 
     In some embodiments, the outer ring  12  has a split configuration in which the outer ring  12  has one or more axial splits therein. For example, in the embodiment shown in  FIG.  5 B , the outer ring  12  has a two-piece split configuration with two axial splits  13 A and  13 B creating a first outer ring segment  12 A and a second outer ring segment  12 B that are abutted against one another at the axial splits  13 A and  13 B. The two-piece split configuration with the two axial splits  13 A and  13 B creating the first outer ring segment  12 A and the second outer ring segment  12 B allows the outer ring  12  to be assembled on the inner member  20 . While the outer ring  12  is shown and described as having the two outer ring segments  12 A and  12 B with the two axial splits  13 A and  13 B, the present invention is not limited in this regard as the outer ring  12  may have one segment and one axial split or more than two segments and more than two axial splits. 
     Although this invention has been shown and described with respect to the detailed embodiments thereof, it will be understood by those of skill in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed in the above detailed description, but that the invention will include all embodiments falling within the scope of the appended claims.