Chain

Abstract

This chain comprises: multiple outer links each having a pair of outer plates and a pin connecting both ends of the pair of outer plates; and multiple inner links each having a pair of inner plates, a bush connecting both ends of the pair of inner plates, and a roller rotatably fitted to the bush, wherein the inner links and the outer links are alternatively connected. A coating (20) of a-C:H type diamond-like carbon is formed on outer peripheral surfaces of the bush and the roller. The thickness of the coating (20) is 1.5-4.0 μm, and the thickness of the bush outer peripheral surface is equal to larger than the thickness of the roller outer peripheral surface.

Description

chain

[0001] The present invention relates to a chain.

[0002] Previously, a motorcycle drive system has been proposed in which a chain, the outer surfaces of the bushings and rollers of which are coated with a pure ta-C coating, is wound around a drive pinion and a sprocket (see Patent Document 1). The ta-C coating is extremely hard and highly aggressive to mating components, but in the drive system of Patent Document 1, the surface of the ta-C coating has a roughness Ra of 0.03 μm to 0.2 μm and / or a roughness Rz of 0.3 μm to 2 μm, thereby reducing wear.

[0003] Special Publication No. 2021-501291

[0004] Thus, efforts have been made to reduce wear in the past, but as mentioned above, the ta-C coating has a very high hardness and tends to be highly aggressive towards the mating surface.

[0005] The present invention provides a chain with reduced wear.

[0006] One aspect of the present invention is a chain comprising: a plurality of outer links each having a pair of outer plates and a pin connecting both ends of the pair of outer plates; a pair of inner plates, bushings connecting both ends of the pair of inner plates; and rollers rotatably fitted onto the bushings; a plurality of inner links connected alternately with the outer links; and a coating of a-C:H type diamond-like carbon formed on the outer surfaces of the bushings and rollers, wherein the coating has a thickness of 1.5 to 4.0 μm, and the film thickness on the outer surface of the bushings is greater than or equal to the film thickness on the outer surface of the rollers.

[0007] It is possible to provide a chain with reduced wear.

[0008] Other features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings, in which the same or similar elements are designated by the same reference numerals.

[0009] The present invention relates to a chain transmission device, a chain drive system, a chain drive mechanism ...

[0010] (General Configuration of Chain Transmission Device) Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The chain transmission device 1 shown in Figure 1 is a chain transmission device for driving a two-wheeled vehicle driven by a drive source such as an engine or a motor, and includes a drive sprocket 2 and a driven sprocket 3 driven by the drive source, and a chain 5 wound around the drive sprocket 2 and the driven sprocket 3.

[0011] The chain 5 is a roller chain, as shown in FIGS. 2A to 2C . The chain includes inner links 13, each of which has a pair of inner plates 10 connected at their ends by bushings 11 and a roller 12 rotatably fitted around the bushings 11, and outer links 17, each of which has a pair of outer plates 15 connected at their ends by pins 16. The pins 16 are inserted into the bushings 11 to connect the inner links 13 and the outer links 17 in an endless fashion. The inner links 13 are fixed by press-fitting the ends of the bushings 11 into bushing holes formed in the inner plates 10, and the outer links 17 are fixed by caulking, with the ends of the pins 16 fitted into pin holes in the outer plates 15. A seal ring is disposed between the inner plates 10 and the outer plates 15 to retain grease sealed between the pins 16 and the bushings 11. To reduce friction, the seal ring (gasket) 18 is preferably coated on the outside or contains a chemical agent inside.

[0012] For example, as an external coating to reduce friction, it is desirable to apply a coating such as PTFE (polytetrafluoroethylene) to the outside of the seal ring 18. Furthermore, for example, rubber or resin can be used as a chemical to be compounded in the seal ring 18 to reduce friction.

[0013] Furthermore, in consideration of oil resistance, the material used for the seal ring 18 may be acrylic rubber (ACM / AEM), hydrogenated nitrile rubber (H-NBR), nitrile rubber (NBR), or a fluorine-based rubber polymer, or the seal ring 18 may be made of the above-mentioned PTFE.

[0014] The acrylic rubber is a copolymer containing an acrylic ester, such as an acrylic ester copolymer (ACM) or an acrylic ester-ethylene copolymer (AEM), and these can be used alone or in combination as polymer components of the rubber composition that constitutes the seal ring 18.

[0015] Furthermore, there are no limitations on the hydrogenated nitrile rubber used in the seal ring 18, and rubbers with various nitrile contents, hydrogenation rates, and Mooney viscosities can be used. Examples of hydrogenated nitrile rubbers that can be used include, but are not limited to, Zetpol 0020, Zetpol 1010, Zetpol 1020, and Zetpol 2020 manufactured by Zeon Corporation, THERBAN 1706, THERBAN 1707, THERBAN 1907, and THERBAN 2207 manufactured by Bayer, and CHEMISAT manufactured by Goodyear. A blend of multiple hydrogenated nitrile rubbers may also be used. The hydrogenated nitrile rubber preferably has a hydrogenation rate of 90% or higher, and more preferably a hydrogenation rate of 95% or higher.

[0016] Furthermore, as the nitrile rubber, an acrylonitrile-butadiene rubber having a bound acrylonitrile content of 15 to 48%, preferably 22 to 35%, and a Mooney viscosity ML1+4 (100°C) of 25 to 85, preferably 30 to 60, can be used, and in practice, a commercially available product may be used. For example, N240S, N241, etc. manufactured by JSR Corporation can be used.

[0017] Furthermore, any fluorine-based rubber containing fluorine atoms may be used as the material for the seal ring 18. For example, vinylidene fluoride-based fluorine-based rubber (FKM), whose main component is vinylidene fluoride, can be used. Examples of usable binary fluorine-based rubbers include vinylidene fluoride-hexafluoropropylene, vinylidene fluoride-chlorotrifluoroethylene, tetrafluoroethylene-perfluoro, and tetrafluoroethylene-propylene. Examples of usable ternary fluorine-based rubbers include vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, vinylidene fluoride-perfluoroalkyl vinyl ether-tetrafluoroethylene, and tetrafluoroethylene-propylene-vinylidene fluoride. Ternary fluorine-based rubbers have excellent cold resistance. In addition to using a single type of fluorine-based rubber, multiple types can also be used in combination. The degree of polymerization of the fluororubber can be determined to obtain appropriate sealing and sliding properties depending on the application of the sealing member (DLC coating).

[0018] Next, we will explain the DLC (Diamond Like Carbon) coating of the chain 5. The bushings 11 and rollers 12 of the chain 5 described above are coated with an aC:H type DLC film.

[0019] Specifically, as shown in FIG. 3, the DLC coating 20 applied to the outer peripheral surfaces of the bushing 11 and the roller 12 includes an intermediate layer 22 formed on a base material 21 of the bushing 11 and the roller 12, and a DLC layer 23.

[0020] The base material 21 is made of a steel material such as high-carbon chromium bearing steel or chromium-molybdenum steel, and its surface is polished by barrel polishing or the like. The intermediate layer 22 formed on the surface of the base material is a metal carbide layer containing, for example, chromium (Cr), silicon (Si), tungsten (W), etc., and is softer (having a lower hardness) than the DLC layer 23. The presence of such a relatively soft intermediate layer 22 between the base material 21 and the DLC layer 23 makes the DLC layer 23 less likely to peel off. The intermediate layer 22 may be formed as a single layer or multiple layers. Furthermore, polishing the intermediate layer 22 would easily allow foreign matter to enter between the intermediate layer 22 and the DLC layer 23, reducing adhesion, so the intermediate layer 22 is not polished.

[0021] The DLC layer 23 is made of a-C:H type DLC. The a-C:H type DLC contains, for example, 5 to 50 at % hydrogen within the film, and has a structure in which carbon atoms with sp2 hybrid orbitals like graphite are mixed in greater numbers than carbon atoms with sp3 hybrid orbitals like diamond. Furthermore, the a-C:H type DLC contains hydrogen, which makes the film softer than the ta-C type DLC and has a lower coefficient of friction.

[0022] The DLC layer 23 formed from the a-C:H type DLC is formed, for example, by sputtering a hydrocarbon gas as a hydrogen-containing raw material, and its surface has a roughness Ra of 0.025 μm to 0.4 μm. More preferably, the DLC layer 23 has a surface roughness Ra of 0.025 μm to 0.25 μm, and even more preferably, 0.1 μm to 0.25 μm. Furthermore, the surface roughness of the DLC layer 23, expressed in terms of Rz, is preferably in the range of Rz 0.025 μm to 2.5 μm. In addition to sputtering, the DLC layer 23 may also be formed by a physical vapor deposition (PVD) method such as ion plating, a thermal CVD method using hydrocarbon gas or organic solvent vapor as a raw material, a plasma CVD method, or the like.

[0023] The thickness of the DLC layer 23 is 1.5 to 4.0 μm, and in this embodiment, the thickness T1 of the DLC layer on the outer peripheral surface of the bushing is equal to or greater than the thickness T2 of the DLC layer on the outer peripheral surface of the roller (T1≧T2).

[0024] The hardness of the DLC layer 23 is set to 10 GPa to 25 GPa. If it exceeds 25 GPa, it becomes highly aggressive toward the mating member. If it is less than 10 GPa, durability cannot be ensured and the desired wear resistance may not be achieved. Since the film thickness is set to 1.5 μm to 4.0 μm and the hardness is set to 10 GPa to 25 GPa, the adhesion of the DLC layer 23 is HF1 to HF4, which is good. As long as the film thickness and hardness are within the above ranges, the film thickness T1 of the DLC layer 32 on the outer circumferential surface of the bushing and the film thickness T2 of the DLC layer 32 on the outer circumferential surface of the roller may be set to be approximately the same. The adhesion was evaluated by an indentation test using a Rockwell hardness tester in accordance with the German VDI 3198 standard.

[0025] As described above, in this embodiment, the a-C:H type diamond-like carbon coating 20 is formed on the outer circumferential surfaces of the rollers 12 of the chain 5 that slide against the sprockets 2 and 3 and on the outer circumferential surfaces of the bushings 11 that slide against the rollers 12. By forming the high-hardness, high-durability a-C:H type diamond-like carbon coating 20 on the parts of the chain 5 that are subject to heavy wear, even if an oil film break occurs between the bushing and roller or between the roller and the sprocket tooth surface, wear on the parts that are subject to heavy wear, such as the bushings 11 and rollers 12, can be suppressed, thereby extending the life of the chain. Furthermore, the improved wear resistance allows the user to reduce the frequency with which lubricant is applied to the chain 5, reducing the user's maintenance burden. This, combined with the reduction in lubricant used, also reduces the environmental impact.

[0026] Furthermore, while aC:H type DLC has high durability, it is less hard and less aggressive to mating members than ta-C type DLC, which prevents excessive wear on the sprockets 2 and 3 (the mating members of the roller 12) and the inner circumferential surface of the roller 12, thereby extending the life of the entire chain transmission device.

[0027] In addition, the low friction resistance and excellent sliding characteristics at the sliding portions of the chain described above improve fuel economy of a drive device such as a motorcycle equipped with the chain transmission device 1. While the DLC coating 20 is applied only to the outer peripheral surfaces of the bushings 11 and rollers 12 in the above-described embodiment, the DLC coating 20 may be applied to the entire outer peripheral surfaces of the bushings 11 and rollers 12. Furthermore, the DLC coating 20 may be applied not only to the bushings 11 and rollers 12 but also to sliding components such as the sprockets 2 and 3 and the pins 16. Furthermore, while the above-described embodiment describes an example in which the present invention is applied to a sealed chain, the present invention may also be applied to, for example, a sealless chain. Furthermore, the present invention may also be applied to bush chains that do not have rollers 12. Furthermore, the present invention may be applied not only to transmission chains for motorcycles but also to, for example, timing chains for automobile engines.

[0028] The present invention can be widely implemented in the field of chains.

[0029] The present invention is not limited to the above-described embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to apprise the public of the scope of the present invention.

[0030] 5: Chain, 10: Inner plate, 11: Bush, 12: Roller, 13: Inner link, 15: Outer plate, 16: Pin, 17: Outer link, 20: Coating (DLC coating)

Claims

1. an outer link having a pair of outer plates and a pin connecting the pair of outer plates; an inner link including a pair of inner plates, a bushing connecting the pair of inner plates, and a roller rotatably fitted to the bushing; a coating of a-C:H type diamond-like carbon formed on an outer peripheral surface of the bushing; a coating of a-C:H type diamond-like carbon formed on the outer peripheral surface of the roller; the coating formed on the outer peripheral surface of the bushing has a film thickness of 1.5 to 4.0 μm, a surface roughness of Ra 0.025 μm to 0.4 μm, a hardness of 10 GPa to 25 GPa, and an adhesion of HF1 to HF2; the coating formed on the outer peripheral surface of the roller has a film thickness of 1.5 to 4.0 μm, a surface roughness Ra of 0.025 μm to 0.4 μm, a hardness of 10 GPa to 25 GPa, and an adhesion of HF1 to HF2; a thickness of the coating formed on the outer peripheral surface of the bushing is equal to or greater than a thickness of the coating formed on the outer peripheral surface of the roller; chain.

2. 2. The chain according to claim 1, wherein a thickness of the coating formed on the outer peripheral surface of said bushing is the same as a thickness of the coating formed on the outer peripheral surface of said roller.

3. The surface roughness of the coating formed on the outer peripheral surface of the bushing is Ra 0.25 μm or less, The surface roughness of the coating formed on the outer peripheral surface of the roller is Ra 0.25 μm or less. A chain according to claim 1 or 2.

4. The surface roughness of the coating formed on the outer peripheral surface of the bushing is Ra 0.1 μm to 0.25 μm, 3. The chain according to claim 1, wherein the coating formed on the outer peripheral surface of the roller has a surface roughness of Ra 0.1 μm to 0.25 μm.

5. a seal ring disposed between the outer plate and the inner plate and configured to hold grease between the pin and the bushing; 2. The chain according to claim 1, wherein a surface of said seal ring is coated with PTFE.

6. a seal ring disposed between the outer plate and the inner plate and configured to hold grease between the pin and the bushing; 2. The chain according to claim 1, wherein the material of said seal ring is selected from the group consisting of acrylic rubber, hydrogenated nitrile rubber, nitrile rubber, fluorine-based rubber and PTFE.