Lubricant for injection

Abstract

[Problem] To provide a lubricant for injection that penetrates into tiny gaps and achieves low friction without bleeding to the outside or causing foreign matter to adhere to the surrounding area. [Solution] A lubricant comprising only tungsten disulfide powder and a volatile solvent, the content ratio of tungsten disulfide powder being 25 wt% or less.

Description

Lubricant for injection

[0001] This invention relates to a lubricant for injection for minute gaps, which is used, for example, between sliding surfaces of a bicycle.

[0002] As lubricants to be injected into sliding parts, oil and wax are known. Further, as a more high-performance lubricant, a lubricant in which a solid lubricant component having a small coefficient of friction is mixed with oil or wax is known.

[0003] Japanese Patent Application Laid-Open No. 2020-33491

[0004] Lubricants using oil or wax as a medium as described above are excellent in adhesion to necessary parts, but have a problem that they are difficult to penetrate into minute gaps such as a bicycle chain or bearing. In order to force oil, wax, etc. to be pushed in from the outside of the gap, not only the sliding part but also an excessive amount of wax or the like adheres to the outer peripheral surface. Then, foreign matters such as sand and dust adhere to the oil or wax and form lumps. Also, in the case of a bicycle chain or the like, solidified wax or the like may scatter from the chain or the like to the surroundings during running.

[0005] An object of this invention is to provide a lubricant for injection that smoothly penetrates into minute gaps and realizes low friction without protruding to the outside or adhering foreign matters.

[0006] The first invention is a lubricant for injection to be injected into minute gaps between sliding surfaces, which consists only of tungsten disulfide powder and a volatile solvent, and the content ratio of the tungsten disulfide powder is less than 25 [wt%].

[0007] The second invention is that the volatile solvent is a lower alcohol.

[0008] According to the first invention, it is easy to inject a liquid lubricant having a low viscosity into minute gaps. The injected lubricant spreads on the sliding surface, and after the volatile solvent evaporates, only tungsten disulfide remains on the sliding surface to realize low friction. Further, since the lubricant does not contain sticky substances such as oil and wax, dust or the like does not adhere to the lubricant and form lumps or scatter.

[0009] Furthermore, since tungsten disulfide does not spill out from where it is needed, no tungsten disulfide is wasted. In addition, when used on a bicycle, the low-viscosity liquid lubricant can be injected into minute gaps while the chain remains attached to the bicycle. For example, when applying wax to a chain, it is necessary to heat the wax to make it liquid and then immerse the chain, which has been removed from the bicycle, in the wax to allow it to penetrate. However, using the lubricant of this invention eliminates the need for dissolving the wax, removing the chain from the bicycle, and reinstalling the chain.

[0010] According to the second invention, the lubricant has low viscosity and is easy to inject into minute gaps. Also, since the volatile solvent is water-based, there is no need to wipe away any liquid that spills out of the gap.

[0011] Figure 1 is an explanatory diagram of a vertical penetration test method to confirm the penetration of lubricant into minute gaps. Figure 2 is a photograph showing the results of the vertical penetration test. Figure 3 is an explanatory diagram of a horizontal penetration test method according to an embodiment. Figure 4 is a schematic diagram showing the results of the horizontal penetration test, where (a) is sample F (30 [weight %]) and (b) is sample G (25 [weight %]). Figure 5 is a table showing the results of the horizontal penetration test. Figure 6 is a graph showing the results of the horizontal penetration test. Figure 7 is a photograph showing the diffusion state of the lubricant according to an embodiment. Figure 8 is a table showing the diffusion test results. Figure 9 is a partial cross-sectional view of a bicycle chain. Figure 10 is a table showing the results of a running test.

[0012] One embodiment of this invention is described below. The injection lubricant of this embodiment is a liquid consisting only of isopropyl alcohol and tungsten disulfide, obtained by mixing tungsten disulfide powder with isopropyl alcohol as a volatile solvent. Specifically, isopropyl alcohol with a purity of 99.9% or higher was added to weighed tungsten disulfide powder, placed in a container, the lid was closed, and it was shaken to mix. At this time, several concentrations of lubricant were prepared by changing the content of tungsten disulfide powder.

[0013] The prepared lubricant is liquid, and its viscosity appears to increase slightly as the proportion of tungsten disulfide powder increases. 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. When the lubricant of the embodiment is injected into a minute gap that forms a sliding surface, the isopropyl alcohol evaporates in the minute gap in a short time, leaving only the tungsten disulfide powder on the sliding surface. As mentioned above, tungsten disulfide powder is a substance with a very low friction coefficient, so it can be expected to function as a solid lubricant after the isopropyl alcohol has evaporated.

[0014] [Vertical Penetration Test] The following describes a test to confirm the penetration of the lubricant of the embodiment into minute gaps. Figure 1 shows the test fixture used for the vertical penetration experiment. In this test, as shown in Figure 1, spacers 3 and 4 were placed between a pair of glass plates 1 and 2, and the distance d between the opposing glass plates 1 and 2 was adjusted to 60 [μm]. The glass plates 1 and 2 are microscope slides with a length S of 76 [mm] and a width W of 25 [mm], and have a smooth surface.

[0015] With the glass plates 1 and 2 positioned vertically with their width W in the vertical direction, lubricant was dripped from above between the glass plates 1 and 2 using a dropper 5 (not shown) at the tip of a bottle. The penetration distance of the lubricant between the glass plates 1 and 2 from the upper edges of the glass plates 1 and 2 was then measured. The dripped lubricant samples consisted of four types: Sample A with a tungsten disulfide powder content of 60% by weight, Sample B with 50% by weight, Sample C with 45% by weight, and Sample D with 40% by weight. Note that a 60 μm gap corresponds to the gaps g1, g2, g3, and g4 between components in a bicycle chain shown in Figure 9. While the gaps g1, g2, g3, and g4 between components in a bicycle chain are thought to vary depending on the manufacturer and specifications of the bicycle chain, it is believed that these gaps will not deviate significantly from a 60 μm gap.

[0016] [Vertical Penetration Test Results] Figure 2 shows the results of a penetration test in which lubricants with varying tungsten disulfide powder content were penetrated between the glass plates 1 and 2 described above. The photograph was taken from the surface side of glass plate 1. The tungsten disulfide powder content is shown in the photographs of samples A, B, C, and D from left to right in Figure 2. The black area spread between glass plates 1 and 2 in these photographs is the tungsten disulfide powder in the lubricant. As shown in Figure 2, the distance reached by the tungsten disulfide powder from the upper edge 1a of glass plate 1 was 2.60 [mm] for sample A, 3.25 [mm] for sample B, 5.15 [mm] for sample C, and 5.70 [mm] for sample D.

[0017] These test results showed that when the tungsten disulfide powder content was 50% by weight or more, the entire amount of dropped lubricant did not penetrate between glass plates 1 and 2, and the tungsten disulfide powder remained piled up on the upper edges of glass plates 1 and 2, with a penetration distance of less than 4 mm. In contrast, when the tungsten disulfide powder content was 45% by weight or less, corresponding to sample C, the entire amount of dropped lubricant penetrated between glass plates 1 and 2, and the penetration distance was 5 mm or more. Furthermore, no tungsten disulfide powder remained on the upper edges of glass plates 1 and 2. These results are thought to be due to the increased viscosity of the lubricant as the tungsten disulfide powder content increases.

[0018] On the other hand, it is thought that the lower the proportion of tungsten disulfide powder, the lower the viscosity of the lubricant and the better its penetration. For example, in sample E (not shown), which has a tungsten disulfide powder content of 12.5% ​​by weight, it was confirmed that the lubricant dropped from above the glass plates 1 and 2 reached the bottom edge of the glass plates 1 and 2 at 25 mm. From these results, it was found that when the tungsten disulfide content is 45% by weight or more, the entire amount of dropped lubricant cannot penetrate into the minute gap of 60 μm.

[0019] [Horizontal Penetration Test] Next, a horizontal penetration test was conducted as shown in Figure 3. In this horizontal penetration test, the same glass plates 1 and 2 used in the vertical penetration test shown in Figure 1 were placed horizontally, and one drop of lubricant was injected between the glass plates 1 and 2 from one injection point p using a dropper 5. The samples used in this test were seven types: Sample F with a tungsten disulfide powder content of 30 [weight], Sample G with 25 [weight], Sample H with 24 [weight], Sample I with 23 [weight], Sample J with 22 [weight], Sample K with 21 [weight], and Sample L with 20 [weight].

[0020] The penetration state of each sample was photographed, and the penetration area was calculated using image processing software. In this horizontal penetration test, the lubricant is pushed into the minute gap between glass plates 1 and 2 by the pressure of the dropper 5, and penetrates, but it is less affected by gravity than in the vertical penetration test. This is considered to be closer to the actual situation of injecting lubricant from the gap g1 in a bicycle chain toward the pin 11 (see Figure 9).

[0021] [Horizontal Penetration Test Results] Figures 4(a) and 4(b) are schematic diagrams of the penetration state of sample F (30 [wt%]) and sample G (25 [wt%]) with tungsten disulfide content. In sample F, as shown in Figure 4(a), a spread occurred along the edges of glass plates 1 and 2 on both sides of the injection section p, but there was almost no penetration in the injection direction indicated by the arrow. In contrast, it was confirmed that sample G penetrated in the direction of the arrow, as shown in Figure 4(b). Samples F to L, with a powder content of 25 [wt%] or less, all penetrated in the direction of the arrow.

[0022] Figure 5 is a table showing the penetration area calculated using image processing software, and Figure 6 is a graph of the results from Figure 5. As shown in Figures 5 and 6, the increase in penetration area with respect to changes in the powder content becomes sharply large when it is 25% by weight or less.

[0023] These results show that, similar to the vertical penetration test, the lower the tungsten disulfide powder content, the easier the penetration and the larger the penetration area. In particular, the results in Figures 5 and 6 show that when the tungsten disulfide content reaches 25% by weight, the penetration of the lubricant changes, and the rate of change in the penetration area also changes. That is, it was found that the penetration increases sharply when the tungsten disulfide powder content is 25% by weight or less.

[0024] On the other hand, when the tungsten disulfide powder content was 30% by weight, it was found that the penetration from the injection port p into the minute gap was low, and the tungsten disulfide powder solidified along the opening. Therefore, additional injection was difficult, and it was difficult to spread the lubricant throughout the minute gap. Accordingly, for an injection lubricant used to fill minute gaps between sliding surfaces such as chains and bearings in bicycles, it is preferable that the tungsten disulfide powder content be 25% by weight or less.

[0025] [Diffusion Test] Next, a diffusion test was conducted to check how far the tungsten disulfide powder spread in the lubricant by changing the content ratio of tungsten disulfide powder. There were three test samples: Sample A with a tungsten disulfide powder content of 60 [weight], Sample E with 12.5 [weight], and Sample M with 1.0 [weight]. One drop of each sample A, E, and M was dropped onto a horizontally placed piece of paper using a dropper, and the area over which it diffused was measured. This measurement was performed 10 times for each sample A, E, and M.

[0026] [Diffusion Test Results] Figure 7 is a photograph showing the diffusion state of the dropped lubricant. For each sample, the spread on the paper was measured. Specifically, the major and minor axes of the area where the lubricant spread were measured, and the area of ​​the circle with the average diameter was defined as the diffusion area. The results are shown in Figure 8.

[0027] For each sample, the average of 10 points was 168.1 mm for sample M, which contained 1% by weight of tungsten disulfide powder. ２ In sample E, which was 12.5 [weight %], the result was 69.0 [mm ２In sample A, which was 60 [weight %], the result was 5.4 [mm ２ ] was the result. In addition, in sample A, the tungsten disulfide powder solidified on the paper. This is thought to be because, due to the high proportion of powder in sample A, the isopropyl alcohol evaporated before the liquid could diffuse sufficiently. On the other hand, in sample F, the diffusion area was very large, so the color in the photograph is very light.

[0028] From the above test results, it was found that the lower the tungsten disulfide powder content, the greater the spread of the liquid lubricant. However, even with a low content of 1.0 [weight%] in sample M, the tungsten disulfide powder spread sufficiently together with the liquid.

[0029] [Driving Test] Next, in order to confirm the effect of the lubricant of the above embodiment, a driving test was conducted on a bicycle to which the lubricant had been injected. The chain 6 shown in Figure 9 is the structure of the bicycle chain used in the driving test. The chain 6 consists of outer plates 7, 7, inner plates 8, 8, rollers 9, bushings 10, and pins 11. The gap g1 between the outer plate 7 and the inner plate 8, the gap g2 between the inner plate 8 and the end face of the roller 9, the gap g3 between the inner circumferential surface of the roller 9 and the outer circumferential surface of the bushing 10, and the gap g4 between the inner circumferential surface of the bushing 10 and the outer circumferential surface of the pin 11 are each approximately 60 [μm].

[0030] The test method is as follows: In addition to the gaps g1, g2, and g3 mentioned above, the lubricant of the embodiment and bicycle chain oil were injected into the hub bearing and freewheel ratchet, and the travel time over a certain distance was compared. It is assumed that the lubricant penetrates into gap g4 through gap g1. The lubricant of the embodiment is sample E, in which the solvent is isopropyl alcohol and the content of tungsten disulfide powder is 12.5 [weight], and the bicycle chain oil used in the comparative example is Road Race SP / BIc-004 from AZ Corporation. One drop of each was injected into the gaps g1 and near g1 on both ends of the pin 11. The bicycle chain used was a Shimano DURA-ACE CN-M9100.

[0031] Each lubricant was injected, and the same section of National Route 134, covering a distance of 21.01 km, was ridden multiple times. The equipment, parts, bicycle, tire pressure, and cyclist were all identical. Distance and time were measured using a GPS-based application (Strava).

[0032] [Driving Test Results] The results of the driving test are shown in Figure 10. As shown in Figure 10, the driving time was 47 minutes and 50 seconds when the lubricant of the embodiment of the present invention (Sample E), which contains 12.5% ​​by weight of tungsten disulfide powder, was injected, and 48 minutes and 40 seconds when general bicycle chain oil was injected. As described above, when the lubricant of the embodiment was used, the driving time was on average 50 seconds, or about 1.71%, faster than when oil was used.

[0033] The test results when using the lubricant of the above embodiment are the average of 23 measurements, and the test results when using oil are the average of 22 measurements. Both are averages of 20 or more measurements, and a statistically significant difference is observed. From this, it was confirmed that the lubricant of the embodiment containing tungsten disulfide powder in isopropyl alcohol achieves lower frictional resistance and less power loss than bicycle chain oil.

[0034] Furthermore, the lubricant of this embodiment is a liquid with isopropyl alcohol as the solvent, and since the content of tungsten disulfide powder is less than 25% by weight, it has high penetration and diffusion properties into minute gaps, and can easily spread to gaps g1, g2, g3, g4, etc. Also, since isopropyl alcohol is a volatile solvent, it evaporates relatively quickly after the liquid lubricant is injected. As a result, only the tungsten disulfide powder remains in the minute gaps, fully exhibiting its effect as a solid lubricant.

[0035] Furthermore, the lubricant of this embodiment does not contain any sticky substances such as oil or wax. Therefore, sticky substances do not adhere to sand or dust and form clumps, nor do they scatter. As described above, after the solvent evaporates, only the tungsten disulfide powder remains on the sliding surface and exerts its lubricating function, thus providing a stable low-friction effect. Moreover, since the lubricant of this embodiment is a liquid with low viscosity that can be injected into minute gaps, unlike when using a lubricant containing wax, there is no need for the hassle of dissolving wax or removing and reinstalling the chain from the bicycle.

[0036] In the above embodiment, isopropyl alcohol is used as the volatile solvent, but the solvent is not limited to isopropyl alcohol as long as it is a liquid that evaporates within a suitable amount of time after being injected into the gap. However, if a solvent that is too volatile and evaporates instantly is used, it becomes difficult to maintain the liquid state of the lubricant after it has been removed from the container, and handling becomes difficult, so it is preferable to select a liquid with appropriate volatility.

[0037] Furthermore, lower alcohols such as isopropyl alcohol, ethyl alcohol, and methyl alcohol have low viscosity and easily penetrate into minute gaps, and because they are water-based, there is no need to wipe away any liquid that spills out of the gaps. In addition, since isopropyl alcohol, ethyl alcohol, and methyl alcohol are readily available as common solvents, the manufacturing costs of lubricants using them can be kept down.

[0038] Furthermore, the content of tungsten disulfide powder in the above lubricant is preferably less than 25% by weight, and should be appropriately selected depending on the injection site. In addition, if the powder concentration becomes too high due to the evaporation of the solvent over time, it is possible to dilute it with the same solvent before use.

[0039] For example, in a bicycle chain (Shimano DURA-ACE CN-M9100) as shown in Figure 9, the total area per link of the opposing surfaces of the gaps g1, g2, g3, g4, which are the sliding surfaces, and the outer surface of the roller 9 is approximately 215 mm². ２The result was calculated to be approximately 3.9% by weight, which is the concentration of tungsten disulfide powder in two drops of lubricant that can cover this area with at least one layer of tungsten disulfide powder. In other words, if the tungsten disulfide powder content is 3.9% by weight, then two drops of lubricant can supply enough tungsten disulfide powder to coat the entire sliding surface of one link.

[0040] Furthermore, the 12.5% ​​by weight (Sample E) lubricant used in the above running test contains more than three times the amount of tungsten disulfide powder compared to the 3.9% by weight mentioned above. Therefore, it is considered that in the running test, injecting two drops per link was sufficient to supply enough tungsten disulfide powder to cover the entire sliding surface. Here, the volume of one drop is assumed to be 0.013 cm³. ３ The calculation was performed assuming that the tungsten disulfide powder was in the form of a sphere with a diameter of 0.5 [μm].

[0041] The injection lubrication method of the present invention is the same as described above when lubricating sliding surfaces with minute gaps other than bicycle chains. If the content of tungsten disulfide powder is less than 25% by weight, the penetration into minute gaps is sufficient. However, if the content is reduced further to increase penetration, the injection amount should be increased according to the sliding surface area that needs lubrication.

[0042] It is suitable for lubricating various minute gaps.

Claims

1. An injection lubricant for injecting into minute gaps between sliding surfaces, comprising only tungsten disulfide powder and a volatile solvent, wherein the content of the tungsten disulfide powder is 25% by weight or less.

2. The injection lubricant according to claim 1, wherein the volatile solvent is a lower alcohol.

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