Bicycle chain

Abstract

This bicycle chain (1) comprises a pair of inner plates (21), a roller (22) disposed between the inner plates (21), a pair of outer plates (31) disposed outside the inner plates (21), a pin (32) that connects the outer plates (31) in a state of being inserted through the roller (22), and a bearing part (26) disposed between the pin (32) and the roller (22). The surface of the pin (32) is coated with a coating film including a vanadium carbonitride coating film. The surface of the bearing part (26) is coated with a coating film including any one of a fluorine lubrication plating, a hard chromium plating, and a hard carbon coating film.

Description

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[0001] The present invention relates to a bicycle chain.

[0002] As a type of bicycle chain, the one in Patent Document 1 below is known. The bicycle chain of Patent Document 1 includes a plurality of inner links and a plurality of outer links that are alternately connected. The inner link includes a pair of inner plates, a cylindrical bush that connects both inner plates, and a roller that is externally inserted into the bush. The outer link includes a pair of outer plates that are disposed outside both inner plates, and a pin that connects both outer plates while being inserted through the bush.

[0003] When driving the bicycle chain as described above, sliding occurs between components, for example, between the pin and the bush. In order to protect the components from such sliding, it is common for various coatings such as plating to be applied to each component of the bicycle chain. However, there is still room for improvement in the selection of the coating, such as the case where sufficient wear resistance cannot be obtained depending on the type and combination of the coating.

[0004] Japanese Patent No. 7455378

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a long-life bicycle chain with less wear in the sliding part.

[0006] As a means for solving the above problems, a bicycle chain according to an aspect of the present invention includes a pair of inner plates, a roller disposed between the two inner plates, a pair of outer plates disposed outside the two inner plates, a pin that connects the two outer plates while being inserted through the roller, and a bearing portion disposed between the pin and the roller, wherein the surface of the pin is covered with a coating including a vanadium carbonitride coating, and the surface of the bearing portion is covered with a coating including any one of fluorine lubricant plating, hard chromium plating, and hard carbon coating.

[0007] According to the present invention, it is possible to reduce the wear between the pin and the bearing portion and improve the life of the bicycle chain.

[0008] This is a partially broken plan view showing the structure of a bicycle chain according to one embodiment of the present invention. This is a side view of the bicycle chain. This is a partially exploded perspective view of the bicycle chain. This is a cross-sectional view showing an enlarged portion of Figure 1. This is a table showing the types of coatings applied to the surface of each component of the bicycle chain. This is a figure corresponding to Figure 1 showing a modified example of the above embodiment.

[0009] Preferred embodiments of the bicycle chain of the present invention will be described below with reference to the drawings. The bicycle chain of the present invention is used as a power transmission member that transmits rotational force input from a rider on a bicycle via the pedals to a drive wheel, such as the rear wheel. For example, the bicycle chain is wrapped between a chainring connected to the pedals via a crank and a sprocket fixed to the axle of the drive wheel. As a result, the force with which the rider pedals is converted into rotational force of the chainring, and the rotational force of the chainring is transmitted to the sprocket or drive wheel via the bicycle chain.

[0010] [Structure of Bicycle Chain] Figures 1 to 3 are a partially broken plan view, a side view, and a partially exploded perspective view showing the structure of a bicycle chain 1 according to one embodiment of the present invention. As shown in these figures, the bicycle chain 1 comprises a plurality of inner links 2 and a plurality of outer links 3 that are alternately connected. The bicycle chain 1 is formed in an endless manner when it is used, wrapped between the chainring and the sprocket as described above. In order to make the bicycle chain 1 endless, one end and the other end of the connected body obtained by alternately connecting the inner links 2 and the outer links 3 are connected to each other via a coupling link (not shown). The type of bicycle to which the bicycle chain 1 can be applied is not particularly limited, but in this embodiment, the bicycle chain 1 is applied to a multi-speed bicycle equipped with a gear shifter. In chains used in multi-speed bicycles, the sliding between the pin 32 and the bearing portion 26, which will be described later, is particularly severe when the chain is driven. The bicycle chain 1 of this embodiment can be suitably applied to such a multi-speed bicycle.

[0011] In the following, the direction in which the inner link 2 and outer link 3 are aligned will be defined as the front-to-back direction D1 of the bicycle chain 1. Furthermore, the direction perpendicular to the front-to-back direction D1 in the plan view shown in Figure 1 will be defined as the width direction D2 of the bicycle chain 1. Note that the width direction D2 is synonymous with the left-to-right direction.

[0012] The inner link 2 includes a pair of left and right inner plates 21 and a pair of front and rear rollers 22 positioned between the two inner plates 21. Each of these components 21 and 22 of the inner link 2 is made of a metal material such as carbon steel or alloy steel.

[0013] The outer link 3 includes a pair of left and right outer plates 31 and a pair of front and rear pins 32 that connect the two outer plates 31. Each of these components 31 and 32 of the outer link 3 is made of a metal material such as carbon steel or alloy steel.

[0014] The pair of inner plates 21 are arranged to face each other in the width direction D2. Each inner plate 21 integrally comprises a plate portion 25 and a pair of front and rear bearing portions 26.

[0015] The plate portion 25 has a constant thickness in the width direction D2 and is plate-shaped, extending in the front-rear direction D1. Furthermore, in the side view shown in Figure 2, the plate portion 25 is formed in a gourd shape with a constricted portion 25a in the center in the front-rear direction D1. A pair of through holes h1 (Figures 1 and 3) are formed in front of and behind the constricted portion 25a of the plate portion 25, penetrating the plate portion 25.

[0016] A pair of bearing portions 26 are formed at positions corresponding to the insertion hole h1. The bearing portions 26 are short cylindrical in shape and protrude inward from the plate portion 25 in the width direction D2. In this embodiment, the bearing portion 26 is a burring-processed portion. That is, the bearing portion 26 is a short cylindrical projection formed by burring, which raises the periphery of the insertion hole h1.

[0017] Figure 4 is a cross-sectional view showing an enlarged portion of Figure 1. As shown in Figures 1, 3, and 4, the pair of inner plates 21 are arranged facing each other in the width direction D2 such that their respective bearing portions 26 abut each other. As a result, the bearing portion 26 of one inner plate 21 and the bearing portion 26 of the other inner plate 21 are arranged to be roughly connected coaxially along the width direction D2. The connected bearing portions 26 then form a cylindrical body that extends between the pair of inner plates 21. This cylindrical body, that is, the pair of bearing portions 26 that are roughly connected in the width direction D2, functions as a support shaft for the roller 22.

[0018] The pair of rollers 22 are formed in a cylindrical shape, each surrounding the outer circumference of the front and rear bearing portions 26 of the inner plate 21. That is, the rollers 22 are rotatably held between the pair of inner plates 21 (plate portions 25) with the bearing portions 26 inserted inside. When the bicycle chain 1 is driven, the tooth surfaces of the chainring and sprocket described above come into contact with the outer circumferential surface of the rollers 22.

[0019] The pair of outer plates 31 are positioned on the outside of the pair of inner plates 21 in the width direction D2. In other words, the pair of outer plates 31 are positioned opposite each other in the width direction D2, sandwiching the pair of inner plates 21. The outer plates 31 have a constant thickness in the width direction D2 and are plate-shaped, extending in the front-rear direction D1. In the side view shown in Figure 2, the outer plates 31 are formed in a gourd shape with a constricted portion 31a in the center in the front-rear direction D1. A pair of pin holes h2 (Figure 3) are formed on the front and rear of the constricted portion 31a of the outer plates 31, penetrating the outer plates 31.

[0020] The pair of pins 32 are arranged in the front-to-back direction D1 between the pair of outer plates 31. The pins 32 are formed in a cylindrical shape with their axis extending in the width direction D2. Both ends of the pins 32 are inserted (press-fitted) into the pin holes h2 of the pair of outer plates 31 in a crimp-fit ​​state. That is, the pair of outer plates 31 are connected via the pins 32 by press-fitting both ends of the pins 32 into the front and rear pin holes h2 of the pair of outer plates 31. The pins 32 may also be formed in a hollow cylindrical shape having an inner diameter and an outer diameter.

[0021] The pin 32 is inserted into the through hole h1 of the inner plate 21 in a gap-fit ​​state. That is, the pin 32 is inserted into the bearing portion 26 with a small gap between it and the inner circumferential surface of the bearing portion 26 surrounding the through hole h1. Both ends of the pin 32 extend outward in the width direction D2 beyond the outer surface 21b (Figure 4) of the inner plate 21. In other words, the pin 32 is inserted into the bearing portion 26 with both ends protruding outward from the bearing portion 26. Both ends of the pin 32 that protrude outward from the bearing portion 26 extend to a position approximately corresponding to the outer surface 31b of the outer plate 31 and are press-fitted into the pin hole h2.

[0022] As described above, the roller 22 is positioned on the outside of the bearing portion 26 through which the pin 32 is inserted. In other words, the bearing portion 26 is positioned between the pin 32 and the roller 22. When the bicycle chain 1 is driven, the inner circumferential surface of the bearing portion 26 slides against the pin 32, and the outer circumferential surface of the bearing portion 26 slides against the roller 22.

[0023] [Surface Treatment] Each component of the bicycle chain 1 having the structure described above is subjected to various surface treatments aimed at improving sliding properties or wear resistance. Figure 5 is a table showing the types of coatings applied to the surface of each component by the surface treatment. As shown in this figure, the surface of the inner plate 21, that is, the surface of the plate portion 25 and the bearing portion 26, is covered with one of three types of coatings, A to C.

[0024] Coating A is a double coating combining a chromium carbide coating (CrC) and a fluorine lubricating plating applied on top of it. The chromium carbide coating is formed by a diffusion penetration treatment using, for example, a powder pack method. The fluorine lubricating plating is a plating (Ni-PTFE) in which fine particles of fluororesin (polytetrafluoroethylene: PTFE) are contained in an electroless nickel plating coating. The fluorine lubricating plating has the property of having a very low coefficient of friction and excellent sliding properties (lubricity). Conversely, the fluorine lubricating plating is inferior to the chromium carbide coating in terms of hardness. In other words, the chromium carbide coating applied as an underlayment for the fluorine lubricating plating functions as a backup to protect the substrate of the inner plate 21 even if the fluorine lubricating plating is lost. The total thickness of coating A, which combines the chromium carbide coating and the fluorine lubricating plating, is set to be between 5 μm and 11 μm. The breakdown is as follows: the chromium carbide coating has a thickness of 3 μm to 7 μm, and the fluorine lubricating plating has a thickness of 2 μm to 4 μm.

[0025] Coating B is hard chromium plating. Hard chromium plating is a high-hardness, low-friction plating that contains chromium deposited, for example, by electroplating. The thickness of coating B, which consists of such hard chromium plating, is set to be between 2 μm and 4 μm.

[0026] Coating C is a hard carbon coating known as DLC (diamond-like carbon). A hard carbon coating (DLC) is a coating of an amorphous (non-crystalline) carbon material that combines the bonding structures of both diamond and graphite. Hard carbon coatings are extremely hard, have a low coefficient of friction, and exhibit excellent wear resistance. The film thickness of coating C, which consists of such a hard carbon coating, is set to between 1 μm and 2 μm.

[0027] The surface of the outer plate 31 is covered with one of two types of coatings, D or E.

[0028] Coating D is nickel plating. Nickel plating is a high-hardness plating containing nickel deposited, for example, by electroplating. Nickel plating also has aesthetic appeal, and can be given colors such as gold, silver, or blue. The thickness of coating D, which consists of such nickel plating, is set to be between 1 μm and 4 μm.

[0029] Coating E is a double coating combining the nickel plating described above with a solid lubricating coating applied on top of it. The solid lubricating coating is a dry lubrication coating in which a solid lubricant and organic / inorganic additives are dispersed in a special binder. As the solid lubricant, any of the following can be used: molybdenum disulfide, graphite, and fluororesins such as PTFE. The solid lubricating coating is transparent. This is to avoid obscuring the color tone of the underlying nickel plating. The solid lubricating coating has the property of having a very low coefficient of friction and excellent sliding properties (lubricity). Among them, a solid lubricating coating containing molybdenum disulfide as the solid lubricant is preferred because it has a low coefficient of friction and good compatibility with oil. The thickness of coating E, which consists of such a solid lubricating coating, is set to be between 2 μm and 6 μm. Specifically, the thickness of the nickel plating is between 1 μm and 4 μm, and the thickness of the solid lubricating coating is between 1 μm and 2 μm.

[0030] The surface of pin 32 is coated with a vanadium carbonitride coating. The vanadium carbonitride coating, also known as a VCN coating, is a coating containing vanadium (V), carbon (C), and nitrogen (N). The vanadium carbonitride coating has extremely high hardness, a low coefficient of friction, and excellent wear resistance. The thickness of the vanadium carbonitride coating is set to between 5 μm and 10 μm.

[0031] The surface of the roller 22 is coated with a chromium carbide (CrC) film. The chromium carbide film is the same as the film A described above for the inner plate 21. The thickness of the chromium carbide film is set to 3 μm or more and 7 μm or less.

[0032] [Effects] As described above, in this embodiment, the surface of the pin 32 is coated with a vanadium carbonitride coating. On the other hand, the surface of the inner plate 21 including the bearing portion 26 is coated with one of the following: coating A including fluorine lubrication plating, coating B including hard chromium plating, or coating C including hard carbon (DLC) coating. This configuration has the advantage of reducing wear between the pin 32 and the bearing portion 26, thereby improving the lifespan of the bicycle chain 1.

[0033] In the bicycle chain 1, the sliding between the pin 32 and the bearing portion 26 is particularly intense. In contrast, in this embodiment, where the pin 32 and the bearing portion 26 are coated with the aforementioned coatings, the frictional force generated between the pin 32 and the bearing portion 26 can be reduced, thereby improving wear resistance. Specifically, both the vanadium carbonitride coating that covers the pin 32 and the coatings (coatings A to C) that cover the bearing portion 26, which include fluorine lubricating plating, hard chromium plating, and hard carbon coating, have the property of having a low coefficient of friction. As a result, the sliding properties between the pin 32 and the bearing portion 26 are improved, and the frictional force generated between them is reduced, thereby improving the wear resistance of the pin 32 and the bearing portion 26. This leads to an improvement in the durability of each component 32 and 26, and consequently, the lifespan of the bicycle chain 1.

[0034] Furthermore, in this embodiment, the pin 32, which is the most susceptible to wear, is coated with a very hard vanadium carbonitride film. Combined with the frictional force reduction effect described above, this further improves the wear resistance of the pin 32.

[0035] Furthermore, since the pin 32 and the bearing portion 26 are covered with coatings of different materials, adhesive wear that is likely to occur between the same materials can be suppressed, and in that sense, wear resistance can be improved.

[0036] Furthermore, in this embodiment, when the coating on the inner plate 21 including the bearing portion 26 is coating A, a coating is used that combines a chromium carbide coating and the fluorine lubricating plating applied thereon. With this configuration, it is possible to ensure the wear resistance of the bearing portion 26 over a long period of time while using fluorine lubricating plating, which has a very low coefficient of friction, as the coating on the bearing portion 26.

[0037] Although fluorine lubrication plating has a very low coefficient of friction, its hardness is not very high, so it may be lost due to wear in some cases. Even in that case, in this embodiment, a chromium carbide coating is applied as an undercoat for the fluorine lubrication plating, so the decrease in wear resistance can be suppressed. That is, although the chromium carbide coating has a higher coefficient of friction than fluorine lubrication plating, it has a sufficiently low coefficient of friction compared to the base material of the bearing portion 26. Moreover, the chromium carbide coating has the property of being very hard. Therefore, according to this embodiment in which such a chromium carbide coating is applied as an undercoat for fluorine lubrication plating, wear resistance can be ensured even after the fluorine lubrication plating has been lost, and the durability of the bearing portion 26 can be improved.

[0038] Furthermore, in this embodiment, the surface of the roller 22 is coated with a chromium carbide film. With this configuration, sufficient durability of the roller 22 can be ensured.

[0039] In other words, since the roller 22 comes into contact with the tooth surfaces of the chainring and sprocket, there is a concern about wear of the roller 22 due to such contact. In contrast, in this embodiment, the roller 22 is coated with a highly hard chromium carbide coating, so wear of the roller 22 due to contact with the tooth surfaces can be reduced. Moreover, the chromium carbide coating is not only highly hard but also has relatively high toughness. Therefore, even if an impact is applied to the roller 22 due to contact with the tooth surfaces, it is possible to suppress the occurrence of cracks in the roller 22 due to that impact, and the wear resistance of the roller 22 can be maintained well.

[0040] Furthermore, although the roller 22 also slides against the inner plate 21, the inner plate 21 is covered with one of the low-friction coatings A to C as described above. This reduces the frictional force between the roller 22 and the inner plate 21, improving the wear resistance of both and extending the lifespan of the bicycle chain 1.

[0041] In addition, in the present embodiment, the surface of the outer plate 31 is covered with either a coating D containing nickel plating or a coating E containing a solid lubricant coating. When the coating of the outer plate 31 is the coating D, the most visible outer plate 31 is covered with nickel plating having high design characteristics, so that the appearance of the outer plate 31 and thus the appearance of the bicycle chain 1 can be improved. On the other hand, when the coating of the outer plate 31 is the coating E, the frictional force between the inner plate 21 and the outer plate 31 can be reduced, and the wear resistance of both can be improved.

[0042] More specifically, in the present embodiment, when the coating of the outer plate 31 is the coating E, a coating combining nickel plating and the solid lubricant coating applied thereon is used. Further, as the solid lubricant coating, a transparent coating containing a solid lubricant composed of any one of molybdenum disulfide, graphite, and fluororesin (such as PTFE) is used. According to such a configuration, the coefficient of friction can be reduced while enhancing the design characteristics of the outer plate 31.

[0043] That is, since the solid lubricant coating containing molybdenum disulfide, graphite, and fluororesin has a very low coefficient of friction, by covering the outer plate 31 with such a solid lubricant coating, the frictional force generated between the outer plate 31 and the inner plate 21 can be reduced, and the wear resistance of both can be sufficiently improved. Moreover, since the solid lubricant coating is transparent and nickel plating with high design characteristics is applied as its base, the appearance of the outer plate 31 can be improved.

[0044] [Modification Example] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications are possible without departing from the gist of the present invention. For example, the following modification examples can be considered.

[0045] In the above embodiment, the bearing portion 26, which is positioned between the pin 32 and the roller 22, is formed integrally with the inner plate 21 (plate portion 25). However, the bearing portion may be separate from the inner plate. Figure 6 is a diagram corresponding to Figure 1, showing an example in which the bearing portion is separate from the inner plate. The bicycle chain 100 shown in Figure 6 comprises an inner link 200 and an outer link 300. The outer link 300 has the same structure as the outer link 3 in the above embodiment. That is, the outer link 300 includes an outer plate 331 similar to the outer plate 31 in the above embodiment, and a pin 332 similar to the pin 32 in the above embodiment. The inner link 200 includes an inner plate 221, a roller 222, and a bushing 223 as a bearing portion. Unlike the bearing portion 26 in the above embodiment, the bushing 223 is configured separately from the inner plate 221. Specifically, the bushing 223 is formed in a cylindrical shape with its axis extending in the width direction D2. The inner plate 221 has a bushing hole h3 into which the end of the bushing 223 is press-fitted. The bushing 223 is inserted into the roller 222, and a pin 332 is inserted into the bushing 223. In other words, the bushing 223 is positioned between the pin 332 and the roller 222. In a bicycle chain 1 with this structure, the bushing 223 (bearing portion) is coated with the same coating (Figure 5) as the bearing portion 26 in the above embodiment. That is, the bushing 223 is coated with one of the following: coating A, which is a combination of a chromium carbide coating and a fluorine lubricating plating applied thereon; coating B, which includes hard chromium plating; or coating C, which includes a hard carbon coating (DLC). The coatings applied to parts other than the bushing 223 are the same as in the above embodiment.

[0046] In the above embodiment, an example of applying the bicycle chain of the present invention to a multi-speed bicycle equipped with a gear shifter was described. However, the application of the bicycle chain of the present invention is not limited to this, and it can naturally also be applied to single-speed bicycles that are not equipped with a gear shifter.

[0047] [Summary] The embodiments and their modifications described above include the following inventions.

[0048] The bicycle chain according to one aspect of the present invention includes a pair of inner plates, a roller disposed between the two inner plates, a pair of outer plates disposed outside the two inner plates, a pin that connects the two outer plates in a state of being inserted through the roller, and a bearing portion disposed between the pin and the roller. The surface of the pin is coated with a coating comprising a vanadium carbonitride coating. The surface of the bearing portion is coated with a coating including any one of fluorine lubricating plating, hard chromium plating, and a hard carbon coating.

[0049] According to the present invention, since the surfaces of the pin and the bearing portion are coated with the respective coatings as described above, the frictional force generated between the pin and the bearing portion can be reduced, and the wear resistance can be improved. Thereby, the durability of the pin and the bearing portion, and thus the life of the bicycle chain, can be improved.

[0050] Moreover, in the present invention, since the pin, which is most concerned about wear, is coated with a vanadium carbonitride coating having a very high hardness, the wear resistance of the pin can be further improved in combination with the above-described frictional force reduction effect.

[0051] Furthermore, since the pin and the bearing portion are coated with coatings of different materials, adhesive wear that easily occurs between the same materials can be suppressed, and the wear resistance can be improved in that sense as well.

[0052] Preferably, the surface of the bearing portion is coated with a coating including a chromium carbide coating and the fluorine lubricating plating applied thereon.

[0053] In this aspect, while using fluorine lubricating plating having a very low coefficient of friction as the coating of the bearing portion, the wear resistance of the bearing portion can be ensured over a long period. That is, although the fluorine lubricating plating has a very low coefficient of friction, its hardness is not so high, so it may be lost due to wear in some cases. Even in that case, in this aspect, since a high-hardness chromium carbide coating is applied as the base of the fluorine lubricating plating, the wear resistance can be ensured even after the fluorine lubricating plating is lost, and the durability of the bearing portion can be improved.

[0054] Preferably, the surface of the roller is covered with a coating that includes a chromium carbide film.

[0055] Chromium carbide coatings possess not only high hardness but also relatively high toughness. In this embodiment, where such a chromium carbide coating is applied to the roller, even if the roller is subjected to impacts due to contact with the tooth surfaces of a chainring or sprocket, for example, it is possible to suppress the occurrence of cracks in the roller due to such impacts, and the wear resistance of the roller can be maintained well.

[0056] Preferably, the surface of the outer plate is covered with a coating that includes nickel plating.

[0057] Thus, by covering the most visible outer plate with a highly aesthetic nickel plating, the appearance of the outer plate and, consequently, the bicycle chain can be improved.

[0058] More specifically, the surface of the outer plate is preferably covered with a coating comprising the nickel plating and a solid lubricating coating applied thereon, wherein the solid lubricating coating preferably contains molybdenum disulfide, graphite, or fluororesin as a solid lubricant.

[0059] Solid lubricant coatings containing molybdenum disulfide, graphite, and fluororesin have a very low coefficient of friction. Therefore, in this embodiment, in which the outer plate is coated with such a solid lubricant coating, the frictional force generated between the outer plate and the inner plate can be reduced, and the wear resistance of both can be significantly improved.

[0060] The bearing portion can be, for example, a burring-processed portion integrally formed with the inner plate.

[0061] In this embodiment, the wear resistance of the burring portion (bearing portion) can be improved by applying the above-mentioned coating to the burring portion which is integrated with the inner plate.

[0062] The bearing portion may be a bushing that is press-fitted into a bushing hole formed in the inner plate.

[0063] In this embodiment, the wear resistance of the bush (bearing portion) can be improved by applying the above-described coating to the bush, which is separate from the inner plate.

[0064] 1 Bicycle chain 21 Inner plate 22 Roller 26 Bearing section 31 Outer plate 32 Pin 223 Bushing

Claims

1. A bicycle chain comprising: a pair of inner plates; rollers disposed between the two inner plates; a pair of outer plates disposed outside the two inner plates; pins connecting the two outer plates while inserted through the rollers; and a bearing portion disposed between the pins and the rollers, wherein the surface of the pins is covered with a coating including a vanadium carbonitride coating, and the surface of the bearing portion is covered with a coating including one of fluorine lubricating plating, hard chrome plating, and hard carbon coating.

2. A bicycle chain according to claim 1, wherein the surface of the bearing portion is covered with a coating comprising a chromium carbide coating and the fluorine lubricating plating applied thereon.

3. A bicycle chain according to claim 1, wherein the surface of the roller is covered with a coating containing a chromium carbide coating.

4. A bicycle chain according to claim 1, wherein the surface of the outer plate is covered with a coating including nickel plating.

5. A bicycle chain according to claim 4, wherein the surface of the outer plate is covered with a coating comprising the nickel plating and a solid lubricating coating applied thereon, and the solid lubricating coating comprises molybdenum disulfide, graphite, and fluororesin as a solid lubricant.

6. A bicycle chain according to any one of claims 1 to 5, wherein the bearing portion is a burring portion integrally formed with the inner plate.

7. A bicycle chain according to any one of claims 1 to 5, wherein the bearing portion is a bushing that is press-fitted into a bushing hole formed in the inner plate.

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