Lubricants and lubrication methods

Abstract

The objective is to provide a lubricant and a lubrication method that can maintain the lubricating performance of the low-friction powder contained in the lubricant over a long period of time. [Solution] The lubricant consists only of a volatile solvent and a low-friction powder C, and comprises an injection agent A for injecting into the opposing gap between sliding parts 1 and 2, and a water-repellent coating agent B for coating the surfaces of parts 1 and 2. The lubrication method comprises an injection step of injecting the injection agent A into the opposing gap between sliding parts 1 and 2, and a coating step of coating the surfaces of parts 1 and 2 with the coating agent B so as to cover the opposing gap into which the injection agent A has been injected.

Description

Technical Field

[0001] This invention relates to a lubricant for injection into a gap and a lubrication method.

Background Art

[0002] For example, as lubricants for injection into the gaps between sliding parts such as bicycle chains and bearings, oils and waxes are generally used. However, highly viscous oils and waxes are difficult to penetrate into minute gaps, and sufficient lubricating effects may not be obtained. Also, dust or the like may adhere to the portions protruding from the gaps, resulting in a decrease in lubricating performance or solidification. In addition, the solidified wax may scatter from the running bicycle to the surroundings. As a lubricant for solving such problems, a lubricant that does not contain highly viscous oils or waxes has been considered (see Patent Document 1). This lubricant consists only of a volatile solvent and tungsten disulfide powder. Since the volatile solvent has a low viscosity unlike waxes and oils, a liquid in which tungsten disulfide powder is dispersed in the volatile solvent is easily injected into minute gaps. After injection, the solvent evaporates, and the layered tungsten disulfide powder remains in the gaps, exhibiting lubricity between the parts.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As described above, lubricants consisting of low-friction powders such as tungsten disulfide powder and volatile solvents exhibit lubrication performance after the solvent evaporates from the powder after injection between parts. However, when friction occurs in an environment where water or water vapor is present, frictional oxidation, where the surface of the object oxidizes due to friction, is likely to occur. As a result, the low-friction powder oxidizes. Oxidized powder has a higher coefficient of friction. When the coefficient of friction increases due to oxidation, not only does the lubrication performance decrease, but peeling from the part surface may occur, and wear particles may be generated, leading to dust generation. In particular, with bicycles that had lubricant injected between the chain components, riding in the rain would cause the lubricant to oxidize rapidly, sometimes requiring frequent refilling of the lubricant.

[0005] The objective of this invention is to provide a lubricant that can maintain the lubricating performance of low-friction powder over a long period of time. [Means for solving the problem]

[0006] The first invention consists of an injector comprising only a volatile solvent and a low-friction powder for injection into the gap between sliding parts, and a water-repellent coating agent for coating the surface of the parts having the gap into which the injector has been injected.

[0007] The second invention is that the content of the low-friction powder in the injection agent is 25% by weight or less of the volatile solvent.

[0008] The third invention is that the low-friction powder is tungsten disulfide powder.

[0009] The fourth invention is that the coating agent is silicone oil.

[0010] The fifth lubrication method invention comprises an injection step of injecting an injection agent consisting only of a volatile solvent and a low-friction powder into the gap between sliding parts, and a coating step of coating the surface of the parts having the gap into which the injection agent has been injected with a water-repellent coating agent.

[0011] The sixth invention is that the content of the low-friction powder in the injection agent is 25% by weight or less of the volatile solvent.

[0012] The seventh invention is that the low-friction powder is tungsten disulfide powder. [Effects of the Invention]

[0013] According to the first invention, a water-repellent coating agent can be applied to the outside of the gap between opposing sliding parts into which the filler has been injected. This prevents external moisture from entering the gap into which the filler has been injected, thereby preventing frictional oxidation of the low-friction powder. Consequently, the low-friction powder in the gap between the opposing parts maintains its low-friction properties and remains in the gap for a long period of time, eliminating the need for frequent addition of the filler. Furthermore, if the coating agent penetrates into the gaps between parts and mixes with the filler, it can directly cover the surface of the low-friction powder, providing water repellency and suppressing dust generation.

[0014] According to the second invention, the viscosity of the injection agent is made very low by limiting the proportion of low-friction powder in the volatile solvent, so that the injection agent can smoothly penetrate into minute gaps.

[0015] According to the third invention, a powder with high low-friction performance can be obtained at a relatively low cost.

[0016] According to the fourth invention, the water-repellent properties of silicone oil can prevent oxidation of low-friction powders.

[0017] According to the lubrication method of the fifth invention, oxidation of the injection agent injected into the facing gap of the sliding parts can be prevented, and the lubrication performance can be maintained over a long period of time.

[0018] According to the sixth invention, the injection agent can be smoothly injected especially into a minute gap.

[0019] According to the seventh invention, a powder with high low-friction performance can be obtained at a relatively low cost, and sufficient lubricity can be maintained over a long period of time.

Brief Description of the Drawings

[0020] [Figure 1] FIG. 1 is an external view of a container of a lubricant in an embodiment. [Figure 2] FIG. 2 is a schematic diagram showing a cross section of a part treated with the lubricant in the embodiment, in a state where pressure is acting on the opposing parts. [Figure 3] FIG. 3 is a schematic diagram showing a cross section of a part treated with the lubricant in the embodiment, in a state where the pressure acting on the opposing parts is small. [Figure 4] FIG. 4 is an explanatory diagram of a horizontal penetration test method of an injection agent in the embodiment. [Figure 5] FIG. 5 is a schematic diagram showing the horizontal penetration test results of the injection agent in the embodiment, where (a) is the case where the powder content ratio is 30 [% by weight] and (b) is the case where the powder content ratio is 25 [% by weight]. [Figure 6] FIG. 6 is a graph showing the horizontal penetration test results of the injection agent in the embodiment.

Modes for Carrying Out the Invention

[0021] [Embodiment] One embodiment of the present invention will be described below. Here, a method for lubricating a chain by using the lubricant of the present invention for a bicycle chain will be described.

[0022] Figure 1 shows the lubricant L used in this embodiment, which consists of an injection agent A in container 10 and a coating agent B in container 20 as one set.

[0023] The container 10 for the injection agent and the container 20 for the coating agent are similarly configured, with nozzles 12 and 22 attached to the openings 11a and 21a of the flexible tanks 11 and 21. By applying pressure by pinching the tanks 11 and 21 with your fingers, the respective liquids are discharged from the tips of the nozzles 12 and 22.

[0024] Injection agent A is a liquid consisting only of a volatile solvent and a low-friction powder, in which 12.5% ​​by weight of tungsten disulfide powder is dispersed in isopropyl alcohol, which is a volatile solvent. Specifically, isopropyl alcohol with a purity of 99.9% or higher was added to the weighed tungsten disulfide powder, two 4 mm diameter steel balls were added, the mixture was placed in a container, the lid was closed, and it was mixed by shaking.

[0025] On the other hand, coating agent B is a non-volatile, water-repellent liquid. For example, it may be a low-viscosity silicone oil with a viscosity of 50 [cSt] or less.

[0026] [Effects, etc.] The method for lubricating sliding parts using a lubricant L consisting of the above-mentioned injector A and coating agent B is as follows. First, the tank 11 of container 10 is pressed with a finger to drip-inject the filler A into the gap between the sliding parts (injection step). After that, the filler A is allowed to settle in while moving parts such as chains. During this time, the solvent in the filler A evaporates. Note that the method of injecting the filler A is not limited to dripping; a container can also be used in which a sponge member with open bubbles that can be inserted between parts is fixed to the tip of the nozzle 12. In that case, the sponge member is inserted between the outer plates of the chain and the tank 11 is pressed, allowing the filler A that seeps out from the outer circumference of the sponge member to penetrate into the gap between the sliding parts of the chain.

[0027] Furthermore, coating agent B is applied to the surface of the part so as to cover the opposing gap into which the injection agent A has been injected (coating step). The coating agent B may be applied by pressing the tank 21 of the container 20 and dripping it directly onto the surface of the part, or it may be applied by soaking it into a cloth or the like and then coating the surface.

[0028] Figures 2 and 3 are schematic diagrams showing partial cross-sections of parts 1 and 2 described above. Figure 2 shows parts 1 and 2 under pressure, while Figure 3 shows parts 1 and 2 under almost no pressure. Note that parts 1 and 2 shown in Figures 2 and 3 are parts with sliding opposing surfaces and have a gap of several tens of micrometers to 1 mm between them, but the gap is shown larger for illustrative purposes. Furthermore, in Figures 2 and 3, the tungsten disulfide powder, which is a low-friction powder remaining after the solvent in the injection material A evaporates, is indicated by the symbol C.

[0029] In this embodiment, coating agent B is applied over the gap into which injection agent A is injected, so as shown in Figure 2, the opening of the gap between parts 1 and 2 is sealed with the water-repellent coating agent B. Therefore, moisture from the outside is less likely to penetrate the gap between parts 1 and 2 where tungsten disulfide powder C is present. As a result, the tungsten disulfide powder C inside the gap is less susceptible to frictional oxidation, and the lubricating performance of the low-friction powder can be maintained for a long time.

[0030] Furthermore, as shown in Figure 3, when there is little pressure acting on parts 1 and 2, coating agent B penetrates into the gaps between parts 1 and 2 into which injection agent A has been injected. In other words, a layer of coating agent B is formed between the tungsten disulfide powder C and the tungsten disulfide powder C. Additionally, a paste layer D, which is a mixture of both, is formed at the boundary between the tungsten disulfide powder C and coating agent B. Even in this state, the tungsten disulfide powder C is sealed between parts 1 and 2 by the coating agent B, and water repellency is provided to prevent contact with external moisture. As a result, the tungsten disulfide powder C is less susceptible to frictional oxidation.

[0031] Furthermore, in the state shown in Figure 3, when pressure is applied to parts 1 and 2, and parts 1 and 2 move relative to each other, the slippage of the tungsten disulfide powder C, which has the lowest coefficient of friction, can maintain lubrication between parts 1 and 2. In other words, even if coating agent B penetrates between parts 1 and 2, it does not hinder the lubrication performance of tungsten disulfide powder C. Furthermore, if pressure is applied between parts 1 and 2, the coating agent B and paste layer D inside the gap may be pushed out of parts 1 and 2, in which case the situation will be the same as in Figure 2.

[0032] As described above, whether pressure is acting between parts 1 and 2 or not, coating the gap between the sliding parts 1 and 2 with a water-repellent coating agent B prevents the tungsten disulfide powder injected as injection agent A from undergoing frictional oxidation in the presence of moisture and heat. The tungsten disulfide powder has an average particle size of 0.5 μm, a static friction coefficient of 0.07, and a dynamic friction coefficient of 0.03. Because it has such a low friction coefficient, it is expected to function as a solid lubricant after the solvent, isopropyl alcohol, evaporates. Furthermore, its lubricating performance can be maintained over a long period by coating agent B.

[0033] [Durability verification test] As in this embodiment, a durability test was conducted using a bicycle to confirm that the durability of the lubricant L is improved by including a step of coating with coating agent B after the injection step of injector A. In this verification test, the above-mentioned injection agent A was injected between each component of a bicycle chain, the solvent was evaporated, and then coating agent B was applied to the surface of the chain. With a gear ratio of 50:11 and pedaling at 60 rpm, water was continuously poured onto the chain for 60 minutes.

[0034] After 60 minutes, it was confirmed that there was no deterioration in the water repellency of coating agent B, no peeling due to frictional oxidation of the tungsten disulfide powder, and that the low frictional properties of the tungsten disulfide powder were maintained. Furthermore, it was confirmed that there was no dust generation or decrease in low-friction performance even after cycling for more than 1000 km. Furthermore, when only the injection step of injecting agent A into the bicycle chain was performed, and the coating step of coating agent B was omitted, additional injection of injection agent A was required after 100 km of riding. Note that it was not raining during the 100 km ride. In the case of riding in the rain, it is expected that additional injection agent A would be required even more quickly.

[0035] In the above test, lubricant L was applied to a bicycle chain. However, it was confirmed that the lubrication function could be maintained for a long period of time even when applying coating agent B after injecting injector A to parts that move relative to each other, similar to the above method. However, the lubricant L of the present invention is particularly effective when used in parts such as bicycle chains, where the gaps are exposed to the outside air and are susceptible to moisture.

[0036] The injection agent A used in the above test was a mixture of isopropyl alcohol, a volatile solvent, and 12.5% ​​by weight of tungsten disulfide powder, a low-friction powder; however, the powder concentration is not limited to this. The prepared injection material A is liquid, but its viscosity appears to increase as the proportion of tungsten disulfide powder increases. If the viscosity of the injection material is too high, it will have difficulty penetrating into tiny gaps of less than 1 mm, such as those in bicycle parts. Therefore, we investigated the tungsten disulfide powder content and the permeability of the gap pattern.

[0037] [Horizontal penetration test] In this test, as shown in Figure 4, a spacer 5 was placed between a pair of glass plates 3 and 4 to adjust the distance d between the opposing glass plates 3 and 4 to 60 [μm]. The glass plates 3 and 4 are microscope slides for specimen preparation with a length S of 76 [mm] and a width W of 25 [mm], and have a smooth surface. The 60 μm spacing corresponds to the gaps between components in a bicycle chain. While the gaps between components in a bicycle chain may vary depending on the manufacturer and specifications, we believe that they will not deviate significantly from the 60 μm spacing.

[0038] With the width W of the glass plates 3 and 4 positioned horizontally as described above, one drop of the injection agent was injected between the glass plates 3 and 4 from a single injection port p using the nozzle 12 of the container 10. The samples used in this test consisted of seven types, with tungsten disulfide powder content percentages of 30% by weight, 25% by weight, 24% by weight, 23% by weight, 22% by weight, 21% by weight, and 20% by weight.

[0039] The penetration state of each sample was photographed, and the penetration area was calculated using image processing software. In this horizontal penetration test, the injection agent A is pushed into the tiny gap between glass plates 3 and 4 by the pressure of the nozzle 12 and penetrates, but it is less affected by gravity than when dripping from above. This is considered to be closer to the actual conditions of injecting into tiny gaps, such as those in a bicycle chain.

[0040] [Horizontal Penetration Test Results] Figures 5(a) and 5(b) are schematic diagrams of the penetration state when the tungsten disulfide powder content is 30% by weight and 25% by weight. At 30% by weight, as shown in Figure 5(a), a spread occurred along the edges of the glass plates 3 and 4 on both sides of the injection section p, but there was almost no penetration in the injection direction indicated by the arrow. Thus, it was found that when the tungsten disulfide powder content was 30% by weight, the penetration from the injection port p into the microgaps was low, and the tungsten disulfide powder sometimes solidified along the opening. Therefore, additional injection was difficult, and it was difficult to spread the injection agent A into microgaps of about 60 μm.

[0041] In contrast, when the tungsten disulfide powder content was 25% by weight, penetration in the direction of the arrow was confirmed, as shown in Figure 5(b). Note that all samples with a powder content of 25% by weight or less showed penetration in the direction of the arrow. Figure 6 is a graph showing the penetration area calculated using image processing software. The horizontal axis of the graph represents the tungsten disulfide powder content, and the vertical axis represents the penetration area. As shown in Figure 6, the increase in penetration area with respect to changes in the powder content becomes sharply large at 25% by weight or less.

[0042] These results indicate that the less tungsten disulfide powder content in injection agent A, the easier it is to penetrate and the larger the penetration area becomes. In particular, the results in Figure 6 show that when the tungsten disulfide content is 25% by weight, the permeability of injection agent A changes, and the rate of change in the penetration area also changes.

[0043] In other words, it was found that the permeability increased sharply when the content of tungsten disulfide powder was 25% by weight or less. Therefore, for the filler A used to fill minute gaps between sliding surfaces such as the chain and bearings of a bicycle, it is preferable that the content of tungsten disulfide powder be 25% by weight or less.

[0044] However, it is possible to adjust the proportion of tungsten disulfide powder by changing the size of the gap into which it is injected. For example, in a bicycle chain (Shimano DURA-ACE CN-M9100), the concentration of tungsten disulfide powder required to cover the total surface area of ​​the sliding surfaces per link with at least one layer of tungsten disulfide powder using two drops of filler was calculated to be approximately 3.9% by weight. In other words, if the tungsten disulfide powder content is 3.9% by weight, then two drops of filler can supply enough tungsten disulfide powder to coat the entire sliding surface of one link.

[0045] Thus, for lubricating bicycle chains, a tungsten disulfide powder content of 25% by weight in injection agent A is more than sufficient, and it can be assumed that 12.5% ​​by weight in the above embodiment would also be sufficient. Therefore, it is possible to further increase penetration by significantly lowering the tungsten disulfide powder content. If the tungsten disulfide powder content is lowered, the amount of injection agent A should be increased according to the sliding surface area that requires lubrication.

[0046] [Low friction powder] The above describes injection agent A using tungsten disulfide powder as a low-friction powder, but low-friction powders are not limited to tungsten disulfide. For example, molybdenum disulfide, graphene, fullerene (C) 60 Carbon nanotubes and other similar materials are also low-friction powders. These powders can also be mixed with a volatile solvent to form a liquid injection agent A, which then exhibits lubricating properties after the volatile solvent has evaporated.

[0047] Low-friction powders other than tungsten disulfide powder also undergo structural changes due to oxidation, and thus cannot maintain their low-friction properties. However, by applying coating agent B to the part surface after injecting injection agent A, the frictional oxidation of the low-friction powder can be delayed. While various low-friction powders can be used for injection agent A, tungsten disulfide powder is currently the most suitable due to its low coefficient of friction and relatively low cost of acquisition.

[0048] Furthermore, the volatile solvent constituting the injection agent A is not limited to isopropyl alcohol, as long as it is a liquid that evaporates within a suitable time after being injected into the gap. However, if a highly volatile solvent that evaporates instantly is used, it becomes difficult to maintain the liquid state of injection agent A after it has been removed from the container, and handling becomes difficult. Therefore, it is preferable to select a liquid with appropriate volatility for injection agent A.

[0049] Furthermore, lower alcohols such as isopropyl alcohol, ethyl alcohol, and methyl alcohol have the advantage of low viscosity and easily penetrate into minute gaps. In addition, since isopropyl alcohol, ethyl alcohol, and methyl alcohol are readily available as common solvents, the manufacturing cost of injection materials using them can be reduced. In all powders, the viscosity increases and the ability to penetrate gaps decreases as the proportion of the powder relative to the volatile solvent increases. It has been confirmed that if the proportion of the powder relative to the volatile solvent is 25% by weight or less, it can penetrate smoothly into gaps of 1 mm or less.

[0050] Furthermore, although a low-viscosity silicone oil is used as the coating agent in the above embodiment, the coating agent is not particularly limited as long as it is a water-repellent liquid. However, liquids with excessively high viscosity that form clumps on the surface of the parts are unsuitable. In the case of high-viscosity liquids, uniform coating becomes difficult, and they tend to form clumps on the surface of the parts, where dust adheres, which can reduce the lubricating performance of the low-friction powder. Therefore, a low-viscosity oil is preferred as the coating agent. [Industrial applicability]

[0051] The lubricant of the present invention is particularly useful for lubricating bicycle parts and the like, which may be used even in the rain. [Explanation of Symbols]

[0052] L Lubricant A Injectable B Coating agent C (low friction powder) Tungsten disulfide powder 1, 2 parts

Claims

1. It consists only of a volatile solvent and a low-friction powder, and is an injector for injecting into the gap between opposing sliding parts. The above-mentioned injection material is a water-repellent coating agent for coating the surface of the part having the above-mentioned gap into which the injection material has been injected. Lubricant.

2. The proportion of the low-friction powder in the above-mentioned injection agent is 25% by weight or less of the volatile solvent. The lubricant according to claim 1.

3. The low-friction powder mentioned above is tungsten disulfide powder. The lubricant according to claim 1 or 2.

4. The above coating agent is silicone oil. The lubricant according to claim 1.

5. An injection step in which an injection agent consisting only of a volatile solvent and low-friction powder is injected into the gap between opposing sliding parts, A coating step in which the surface of the part having the above-mentioned gap into which the above-mentioned filler has been injected is coated with a water-repellent coating agent. A lubrication method having

6. The content ratio of the low-friction powder in the above-mentioned injection agent is 25% by weight or less of the volatile solvent. The lubrication method according to claim 5.

7. The low-friction powder mentioned above is tungsten disulfide powder. The lubrication method according to claim 5 or 6.

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