REDUCED WEAR

CROSS REFERENCE TO RELATED APPLICATION

|Θ0§1] This application claims the benefit of U.S. provisional patent application serial number 62/074340, Sled November 3, 2014, U.S. provisional patent application serial number 62/074892, filed November 4 _S 2014, and U.S. utility patent application serial number 14/7109 8, filed May 13, 2015, the entire contents of which axe incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

|0002] This invention relates generally to a connecting rod for connecting a piston to a crankshaft of internal combustion engine, a wear protection coating applied to the connecting rod, and methods of manufacturing the same.

2. Related Art

fHG03J A connecting rod is used in an internal combustion engine to connect a piston to a crankshaft. The connecting rod converts reciprocating motion from the piston into rotating motion of the crankshaft. The connecting rod generally includes a body formed of metal extending longitudinally between a large end and a small end. The large end of the connecting rod defines a large bore for receiving the crankshaft. The large end also presents a large thrust surface surrounding the large bore. The small end of the connecting defines a small bore for receiving a wrist pin, and the wrist pin extends through pin bosses of the piston. The small end presents a small thrust surface surrounding the small bore.

[D0§4] As the piston reciprocates and the crankshaft rotates during operation of the engine, the thrust surfaces and bores of the connecting rod are subject to wear caused by contact with the piston, bearings, and other components. In order to reduce wear, the material used to form the connecting rod may be subjected to a hardening or shot peensrsg process. The surfaces of the connecting rod can also be coated in order to reduce wear. Examples of wear resistant coatings which have been used include a metal-sprayed coating, such as a molybdenum alloy, or a hard coating, such as chromium nitride. However _} there remains a need for improved wear resistance of the thrust surfaces and bores of the connecting rod.

SUMMARY OF THE INVENTION

[ ΘΘ51 One aspect of the invention provides a connecting rod for connecting a piston to a crankshaft of an internal combustion engine. The connecting rod comprises a body formed of metal extending longitudinally from a first end to a second end. The body includes a first thrust portion adjacent the first end, a second thrust portion adjacent the second end, and a stem connecting the first thrust portion to tire second thrust portion. The first thrust portion includes a pair of first thrust surfaces facing opposite one another and encircling a first bore for receiving the crankshaft The second thrust portion includes a pair of second thrust surfaces feeing opposite one another and encircling a second bore for receiving a wis pin coupled to the piston, A wear resistant coating is applied to at least one of the thrust surfaces. The wear resistant coating includes polymer, solid lubricant, and particles formed of Fe ₂ <¾.

|0006J Another aspect of the invention provides a method of manufacturing the connecting rod for connecting the crankshaft to the piston of the internal combustion engine. The method comprises the steps of providing the body formed of metal, and applying the wear resistant coating to at least one of the thrust surfaces of the body.

ΙΘΘΘ71 The wear resistant coating provides lubrication between the at least one thrust surface of the connecting rod and the components which contact the connecting rod as the piston reciprocates and crank shaft rotates during operation of the interna! combustion engine. Test results show that the wear resistant coating provides exceptional adhesion to the metal thrust surfaces, The test results also suggest that t!ie wear resistant coating can reliably reduce wear, scuff, and seizure along the thrust surfaces of the connecting rod. Thus, the likelihood of engine contamination caused by metal shavings from wear of the connecting rod is reduced, and the life of the connecting rod and engine is increased.

BRIEF DESCRIPTION OF THE DRAWINGS

|00§8| Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

[0009| Figure 1 is a plan view of a connecting rod including a wear resistant coating applied to thrust surfaces according to an example embodiment of the invention,

DESCRIPTION OF THE EXAMPLE EMBODIMENTS

[00101 A connecting rod 20 for connecting a piston to a crankshaft, also referred to as a crank throw or crank pin, of an internal combustion engine according to an example embodiment is generally shown in Figure 1 , A wear resistant coating 22 is applied to at least one thrust surface 24 _s 26 of the connecting rod 20 to provide lubrication and thus reduce wear, scuff, and seizure caused by components contacting the connecting rod 20 as the piston reciprocates and crank shaft rotates during operation of the internal combustion engine.

fOQllj The connecting rod 20 can comprise various different designs and dimensions depending on the intended application of the connecting rod 20. The body of the connecting rod 20 is formed of metal, typically a steel material. The body extends longitudinally from a first end 28, also referred to as a large end, to a second end 30, also referred to as a small end. A first: thrust portion 32 of the body is located adjacent the first end 2§ _s and a second thrust portion 34 is located adjacent the second end 3Θ, A stem 36 connects the first thrust portion 32 to the second thrust portion 34.

f0012J The first thrust portion 32 ©f the connecting rod 20 includes a pair of first thrust surfaces 24 facing opposite one another and encircling a first bore 3S for receiving the crankshaft. The first bore 38 is formed by a first bore surface 4§ which extends between and perpendicular to the first thrust surfaces 24, The first bore surface 40 surrounds a first center axis Al and presents a first diameter J 1 sized to receive the crankshaft. n the example embodiment of Figure 1, the first thrust portion 32 also includes a pair of openings 42 at the first end 2§ on opposite sides of the first bore 3S for receiving fasteners 44, and a bearing cap 46 is located at the first end 2S between the openings 42.

[0013] The second thrust portion 34 includes a pair of second thrust surfaces

26 facing opposite one another and encircling a second bore 48 for receiving a wrist pin which couples the connecting rod 20 to a pin bore of the piston, lite second bore 4§ is formed by a second bore surface 50 extending between and perpendicular to the second thrust surfaces 26, The second bore surface SO surrounds a second center axis A2 parallel to the first center axis Al and presents a second diameter D2. The second diameter D2 is smaller than the first diameter M and is sized to receive the wrist pin,

[§014] The wear resistant coating 22 is applied to at least one of the thrust surfaces 24, 26 of the connecting rod 20. The wear resistant coating 22 can also be applied to at least one of the bore surfaces 4% 50 of the connecting rod 2Θ, in the example embodiment of Figure 1, the wear resistant coating 22 is applied to each of the thrust surfaces 24, 26 and each of the bore surfaces 40, 5Θ. The wear resistant coating 22 can be applied by various different methods, Typically, the wear resistant coating 22 is applied to a thickness of 5 to 50 microns, and preferably 5 to 20 microns. [WSlSj The composition of the wear resistant coating 22 includes polymer, solid lubricant, and particles formed of Fe ₂ 0 ₃ , Example compositions which can be used as the wear resistant coating 22 are disclosed in U.S. Patent Application No, 13/142,887 and U.S. Patent Application No. 13/661,598, which are incorporated herein by reference in their entirety.

[00161 The polymer typically forms a matrix of the wear resistant coating 22.

The wear resistant coating 22 includes the poiyraer in an amount of at least 40.0 volume percent (vol. %), or at least 50 vol, ¾, or at least 60 vol %, or at least 80 vol. %, or at least 85 vol. %, based on the total volume of the wear resistant coating 22, The polymer matrix can be formed ©f a single polymer or a mixture of polymers, resin, plastics, or duroplastics, and either thermoplastic or thermc-set polymers. The polymer matrix can also include synthetic and cross-linked polymers. Preferably, the polymer matrix has a high temperature resistance a d excellent chemical resistance. The polymer matrix typically has a melting point of at least 210° C, preferably at least 220° C, or at least 230° C, or at least 250 ⁸ C. In one embodiment, the polymer matrix includes at least one of polyarylate, polyetheretherkeione (PEEK), polyethersnlfone (PES), polyamide imide (PAI), polyiraide (PI), expoxy resin, polybenzimidazole (PB1), and silicone resin. In another embodiment, the polymer matrix includes a bonding agent, such as an unsaturated polyester resin or silicone, hardened by means of UV radiation. In the example embodiment, the polymer consists of polyamide imide (PAI), and the polyamide imide (PAI) is present in an amount of at least 85,0 vol. %, based on the total volume of the wear resistant coating 22,

|ΘΘ17] The solid lubricant of the wear resistant coating 22 is typically present in an amount of 5.0 to 40,0 vol. %, or 5,0 to 30,0 vol. % ₅ or up to 30.0 vol, %, or up to 9.5 vol, %, based on the total volume of the wear resistant coating 22. The solid lubricant is typically formed of one or more of the following components: MoS ₂ , graphite, ¾ _, hexagonal boron nitride (h-BN), PTFE, and metal sulfides with layered structures,

|00181 The wear resistant coating 22 also includes hard pariicleS _j at least some of which include the FesGsparticles. The hard particles are typically formed of a material having a hardness of at least 600 HV/0.5, more preferably at least 620 HV/0.5, and even more preferably at least 650 HV/0.5, at a temperature of 25° The hard particles also have a particle size sufficient to affect at least one of the ductility, wear resistance, and strength of the coating. In one embodiment, the hard particles have a D50 particle size by volume not greater than 10.0 microns, or not greater than 8.0 microns, or not greater than 6.0 microns, and preferably from 0.1 to 5.0 microns. The D50 particle size by volume is the equivalent spherical diameter of the hard particles, also referred to as a D50 diameter, wherein 50.0 wt % of the hard particles have a larger equivalent spherical diameter and 50,0 wt % of the hard particles have a smaller equivalent spherical diameter. The D50 diameter is determined from a particle size distribution display of the hard particles, before any processing of the hard particles following common testing practice. In one embodiment, the hard particles include a mixture of particle sizes, such as a first group of particles having a smaller particle size than a second group of particles. The first and second groups of the hard particles are typically dispersed evenly throughout the polymer matrix.

[ 19J In addition to the Fe O^particles, the hard particles of the wear resistant coating 22 can also include at least one of metal nitrides, such as such as cubic BN, and Si3N ; metal carbides, such as SiC and B4C; metal oxides, such as Ti{¾ and SiOi; metal silicides, such as M0S12; metal borides; metal phosphides, such as Fe3P; interrnetallic compounds; metal oxymtrides; metal carhonitrides; metal oxycarbides; and metal powders of Ag _s Pb, Au, SnBi and/or Cu. I0020J The wear resistant coating 22 typically includes the hard particles in an amount of 0,1 to 20.0 vol. %, or 3.0 to 8.0 vol, % _» based on the total volume of the wear resistant coaling 22. In the example embodiment _s the wear resistant coating 22 includes the F¾<¾ particles having a D50 particle size of 0.1 to 5,0 microns in an amount of 0.1 to 15,0 vol %, or 0.5 to 8.0 vol %, based on the total volume of the wear resistant coating 22, The additional hard particles, which are different from the FC2O3 particles, are typically present in an amount up to 5.0 vol %, or 3,0 to 5.0 vol. %, based on the total volume of the wear resistant coating 22,

|0021J The wear resistant coating 22 is applied to at least one of the thrust surfaces 24„ 26, and optionally at least one of the bore surfaces 40, 50, as a liquid or a powder. The liquid or powder can be applied by spraying or rolling, but could alternatively by applied by dipping, brushing, atomizing, or printing. The wear resistant coating 22 can be applied directly to the metal surfaces 24, 26, 4§, §§ of the connecting rod 20, or another coating could optionally be disposed between the metal surfaces 24, 26 _s 4 50 and the wear resistant coating 22. For example, a primer could be applied before the wear resistant coating 22. In another example, a layer of the polymer without the Fc2<¾ particles or solid lubricant is applied before or after applying the wear resistant coating 22.

f§022J Typically, one or two layers of the wear resistant coating 22 are applied to the thrust surfaces 24, 26 and bore surfaces 40 _s 50 of the connecting rod 2d such thai the wear resistant coating 22 has a total thickness of 5 to 50 microns. However, additional layers could be applied, and the compositions of the layers could be the same or different from one another. In one example embodiment several layers of the wear resistant coating 22 are applied to the surfaces 24 _} 26, 40 _? 50 as a gradient, with the layer properties continuously changing over the thickness of the wear resistant coating 22. For example, the amount of hard particles could be higher in a base layer than in a top layer, or higher in a top layer than in a base layer.

f§023] A method of manufacturing the connecting rod 20 with the wear resistant coating 22 shown in Figure 1 is also provided. The method generally includes providing the body with the thrust surfaces 24 _s 26 and bores 38, 48, and applying the wear resistant coating 22 to at least one of the metal thrust surfaces 24, 26. The step of providing the body typically includes casting or forging the metal material into the desired shape and dimensions. The method then includes applying the wear resistant coating 22 to at least one of the thrust surfaces 24, 26 _f for example by spraying, rolling, dipping, brushing, atomizing, or printing,

|§024] In the example embodiment, the method first includes ultrasonic cleaning and then drying the surfaces 24„ 26, 4% 5Θ of the metal body to which the wear resistant coating 22 will be applied. The cleaning step is typically conducted for about 30 seconds, followed by air drying for about 5 minutes. The example method next includes sand blasting the surfaces 24, 26, 40, 50 of the metal body to be coated. Typically, two passes of the sand blasting procedure is sufficient. The loose metal material is then blown off with air, and the sand blasted metal body is again subjected to ultrasonic cleaning for an additional 30 seconds.

f uu2§! Once the surfaces 24, 26, 40. 50 of the connecting: tod

the wear resistant coating 22 is applied. In the example embodiment, the step of applying the wear resistant coating 22 includes spraying the wear resistant coating 22 in liquid form onto the thrust surfaces 24 _s 26 and the bore surfaces 4§, 50 using a hand-held air brush spray applicator. Two spray passes using air at 38-40 PS1 are performed, followed by a 15 second hot air polymer drying operation, and then another two spray passes and 15 second hot air polymer drying operation. [0026] After applying the wear resistant coating 22, the method includes cairing the wear resistant coating 22 on the connecting rod 20 in a forced air oven for about 30 minutes at about 200° C, The connecting rod 20 is hung vertically in the oven, with support in the second end 30. After being removed from the oven _f the coated connecting rod 20 is air cooled for about 30 minutes,

[0027] EXPERIMENT

|002§] An experiment was conducted to test the adhesion of the wear resistant coating 22 to the thrust surfaces 24, 26 of the connecting rod 20. The connecting rod 20 tested was formed of steel and included a rod split joint. The wear resistant coating 22 included a polymer matrix formed of PAI, FejOj particles, and solid lubricant. The wear resistant coating 22 was applied to the first tlirust surface 24 and the second thrust surface 26 according to the example method described above. During the sand blasting and coating process _f bearings were installed in the bores 3S, 48 to shield the bore surfaces 40, 5§ from the media of the blasting process.

[01)291 Th ^e condition of the rod split joint was documented before and after the coating process, as well as before and after opening the connecting rod 20 to remove the bearings. The coated thrust surfaces 24„ 26 of the connecting rod 20 were evaluated, and the test results showed that the wear resistant coating 22 did not flake off along the rod cracking interface. An adhesion test _s also referred to as a tape test, was then performed on one of the coated thrust surfaces 24, 26 per a standard polymer bearing adhesion test procedure. According to the procedure, a strip of tape was applied to a portion of the coated tlirust surface and then removed. Only small dots of the wear resistant coaling 22 were removed by the tape _s and none of the wear resistant coating 22 was removed due to scoring. In addition, the connecting rods 2Θ were cracked opened, and the wear resistant coating 22 split nicely along the edge where the rods had been cracked, No peeling of the wear resistant coating 22 f was observed at the crack interface. Thus, the test results indicate thai the wear resistant coating 22 should achieve an acceptable level of adhesion when used in the intended engine application.

[0Θ30] Obviously, many modifications and variations of the present invention are possible in light of the above teachings and may be practiced otherwise than as specifically described while within the scope of the appended claims.

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