Lubricants used for pumping

Abstract

The invention proposes a pump lubricant capable of penetrating microscopic gaps to produce low friction without protruding and without allowing foreign matter to adhere to the surrounding environment. The lubricant consists only of tungsten disulfide powder and a volatile solvent. The tungsten disulfide powder content is 25% by mass or less.

Description

Injectable Lubricant

[0001] The present invention relates to an injectable lubricant for use in small gaps, such as between sliding surfaces of a bicycle.

[0002] Oil and wax are known as lubricants to be injected into sliding parts, but as a more powerful lubricant, a mixture of oil or wax with a solid lubricant component that has a low coefficient of friction is also known.

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

[0004] While the above-mentioned oil- and wax-based lubricants have excellent adhesion to required areas, they have the problem of being difficult to penetrate into tiny gaps, such as those in bicycle chains and bearings. Because the oil or wax is forced into the gap from the outside, excess wax adheres not only to the sliding parts but also to the outer periphery. Furthermore, foreign matter such as sand and dust adheres to the oil or wax, forming clumps. Furthermore, with bicycle chains and other devices, solidified wax can fly off the chain and into the surrounding area while riding.

[0005] An object of the present invention is to provide an injectable lubricant that smoothly penetrates into minute gaps, does not spill out to the outside, and does not cause foreign matter to adhere, thereby achieving low friction.

[0006] The first invention is an injectable lubricant to be injected into minute gaps between sliding surfaces, which is composed only of tungsten disulfide powder and a volatile solvent, and the content of the tungsten disulfide powder is less than 25% by weight.

[0007] In a second aspect of the present invention, the volatile solvent is a lower alcohol.

[0008] According to the first aspect of the present invention, a low-viscosity liquid lubricant can be easily injected into minute gaps. The injected lubricant spreads over the sliding surface, and after the volatile solvent evaporates, only tungsten disulfide remains on the sliding surface, achieving low friction. Furthermore, because the lubricant does not contain adhesive substances such as oil or wax, dust and other particles do not adhere to the lubricant, forming clumps, or are not dispersed.

[0009] Furthermore, because the tungsten disulfide does not protrude beyond the required areas, no tungsten disulfide is wasted. Furthermore, when used on bicycles, the low-viscosity liquid lubricant can be injected into minute gaps while the chain is still attached to the bicycle. For example, when waxing a chain, the chain must be removed from the bicycle and immersed in heated, liquid wax to allow the wax to penetrate. However, using the lubricant of this invention eliminates the need to melt the wax, remove the chain from the bicycle, and then reinstall the chain.

[0010] According to the second aspect of the present invention, the viscosity of the lubricant is low, making it easy to inject into minute gaps. In addition, since the volatile solvent is water-based, there is no need to wipe off any liquid that spills out of the gap.

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

[0012] One embodiment of the present invention is described below. The injection lubricant of this embodiment is a liquid consisting of only isopropyl alcohol and tungsten disulfide, with tungsten disulfide powder mixed 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 with the lid closed, and shaken to mix. At this time, the content of tungsten disulfide powder was changed to prepare lubricants of various concentrations.

[0013] The prepared lubricant is liquid, and the viscosity appears to increase slightly as the content 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 the minute gap that will become the 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 described above, tungsten disulfide powder has a very low friction coefficient, so it can be expected to function as a solid lubricant after the isopropyl alcohol evaporates.

[0014] [Vertical Penetration Test] A test for confirming the permeability of the lubricant of the embodiment into a small gap will be described below. FIG. 1 shows a test jig used in a vertical penetration experiment. In this test, as shown in FIG. 1, spacers 3 and 4 were provided between a pair of glass plates 1 and 2, and the opposing distance d between the glass plates 1 and 2 was adjusted to 60 μm. The glass plates 1 and 2 were slide glasses for preparations, each having a length S of 76 mm and a width W of 25 mm, and each having a smooth surface.

[0015] With the glass plates 1 and 2 as described above in an upright position with their widths W aligned vertically, lubricant was dripped between the glass plates 1 and 2 from above using a dropper 5 attached to the tip of a bottle (not shown). The penetration distance of the lubricant from the upper edge of the glass plates 1 and 2 between the glass plates 1 and 2 was then measured. The lubricant samples dripped were four types: Sample A, which contained 60 wt% tungsten disulfide powder; Sample B, which contained 50 wt% tungsten disulfide powder; Sample C, which contained 45 wt% tungsten disulfide powder; and Sample D, which contained 40 wt% tungsten disulfide powder. The 60 μm gap corresponds to the gaps g1, g2, g3, and g4 between the components of the bicycle chain shown in FIG. 9 . While the gaps g1, g2, g3, and g4 between the components of the bicycle chain are likely to vary depending on the bicycle chain manufacturer and specifications, it is believed that the gaps will not deviate significantly from the 60 μm gap, regardless of the bicycle chain manufacturer and specifications.

[0016] [Vertical Penetration Test Results] Figure 2 shows the results of a penetration test in which lubricants containing varying amounts of tungsten disulfide powder were penetrated between the glass plates 1 and 2. The photographs are taken from the front side of the glass plate 1. The tungsten disulfide powder content is shown in Figure 2 for samples A, B, C, and D, in order from left to right. The black area extending between the glass plates 1 and 2 in this photograph is the tungsten disulfide powder in the lubricant. As shown in Figure 2, the penetration distance of the tungsten disulfide powder from the upper end 1a of the 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] The test results showed that when the tungsten disulfide powder content was 50 wt % or more, the entire amount of the dripped lubricant did not penetrate between the glass plates 1 and 2, and the tungsten disulfide powder remained piled up on the upper edges of the glass plates 1 and 2, with a penetration distance of less than 4 mm. In contrast, when the tungsten disulfide powder content was 45 wt % or less, which corresponds to sample C, the entire amount of the dripped lubricant penetrated between the glass plates 1 and 2, with a penetration distance of 5 mm or more. Furthermore, no tungsten disulfide powder remained on the upper edges of the glass plates 1 and 2. This result is thought to be due to the fact that the viscosity of the lubricant increases as the tungsten disulfide powder content increases.

[0018] On the other hand, it is believed that the lower the content 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 wt%, it was confirmed that the lubricant dropped from above the glass plates 1 and 2 reached a distance of 25 mm, which is the lower end of the glass plates 1 and 2. From these results, it was found that when the tungsten disulfide content was 45 wt% or more, the entire amount of the dropped lubricant could not penetrate into the minute gap of 60 μm.

[0019] [Horizontal Penetration Test] Next, a horizontal penetration test shown in Fig. 3 was conducted. In this horizontal penetration test, the same glass plates 1 and 2 as those used in the vertical penetration test shown in Fig. 1 were placed horizontally, and one drop of lubricant was injected between the glass plates 1 and 2 using a dropper 5 from a single injection portion p. The samples used in this test were seven types, each containing tungsten disulfide powder at a percentage of 30 wt%, Sample F at 25 wt%, Sample H at 24 wt%, Sample I at 23 wt%, Sample J at 22 wt%, Sample K at 21 wt%, and Sample L at 20 wt%.

[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 forced into the small gap between the glass plates 1 and 2 by the pressure of the dropper 5, but is less susceptible to the influence of gravity as in the vertical penetration test. This is thought to be closer to the actual situation of injecting the lubricant from the gap g1 of a bicycle chain toward the pin 11 (see Figure 9).

[0021] [Horizontal Penetration Test Results] Figures 4(a) and (b) are schematic diagrams of the penetration state for sample F (30 wt%) and sample G (25 wt%), which have a tungsten disulfide content. As shown in Figure 4(a), sample F spread along the edges of glass plates 1 and 2 on both sides of injection site p, but there was almost no penetration in the injection direction indicated by the arrow. In contrast, sample G was confirmed to have penetrated in the direction of the arrow, as shown in Figure 4(b). All samples F to L, which had a powder content of 25 wt% or less, 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 of Figure 5. As shown in Figures 5 and 6, the increase in penetration area with respect to the change in powder content becomes rapidly large at 25 wt % or less.

[0023] From these results, it can be seen that in the horizontal penetration test, as in the vertical penetration test, the lower the content of tungsten disulfide powder, the easier the penetration and the larger the penetration area. In particular, from the results of Figures 5 and 6, it was found that when the content of tungsten disulfide powder is 25 [wt%], the permeability of the lubricant changes and the rate of change in the penetration area also changes. In other words, it was found that the permeability suddenly increases when the content of tungsten disulfide powder is 25 [wt%] or less.

[0024] On the other hand, when the tungsten disulfide powder content is 30% by weight, the penetration from the injection part p into the minute gap is low, and the tungsten disulfide powder solidifies along the opening. Therefore, additional injection is difficult, and it is difficult to ensure that the lubricant reaches the minute gap. Therefore, it is considered preferable that the tungsten disulfide powder content be 25% by weight or less for an injection lubricant to be injected into the minute gaps between sliding surfaces such as bicycle chains and bearings.

[0025] [Diffusion Test] Next, a diffusion test was conducted to confirm the extent to which the tungsten disulfide powder in the lubricant spread by changing the content of the tungsten disulfide powder. The test samples were three types: Sample A with a tungsten disulfide powder content of 60 [wt%], Sample E with a tungsten disulfide powder content of 12.5 [wt%], and Sample M with a tungsten disulfide powder content of 1.0 [wt%]. One drop of each of Samples A, E, and M was dropped onto a horizontally placed piece of paper using a dropper, and the area of ​​diffusion was measured. This measurement was performed 10 times for each of Samples 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 taken as the diffusion area. The results are shown in Figure 8.

[0027] For each sample, the average value of 10 points was 168.1 mm for sample M, which contains 1 wt% tungsten disulfide powder. ２ ], and sample E with 12.5 [wt %] was 69.0 [mm ２], and 60 [wt %] sample A was 5.4 [mm ２ ]. In Sample A, the tungsten disulfide powder solidified and rose to the surface of the paper. This is thought to be because Sample A contains a high proportion of powder, causing the isopropyl alcohol to evaporate before the liquid had time to fully diffuse. On the other hand, Sample F has a very large diffusion area, which is why the color appears very light in the photograph.

[0028] From the above test results, it was found that the lower the content of tungsten disulfide powder, the greater the spread of the liquid lubricant, but even in sample M, which had a content as low as 1.0 wt %, the tungsten disulfide powder spread sufficiently along with the liquid.

[0029] [Running Test] Next, to confirm the effectiveness of the lubricant of the above embodiment, a running test was conducted on a bicycle injected with the lubricant. The chain 6 shown in Figure 9 is the structure of the bicycle chain used in the running test. The chain 6 is composed of outer plates 7, 7, inner plates 8, 8, rollers 9, bushings 10, and pins 11. The gap g1 between the outer plates 7 and the inner plates 8, the gap g2 between the inner plates 8 and the end faces of the rollers 9, the gap g3 between the inner circumferential surfaces of the rollers 9 and the outer circumferential surfaces of the bushings 10, and the gap g4 between the inner circumferential surface of the bushings 10 and the outer circumferential surfaces of the pins 11 were each approximately 60 μm.

[0030] The test method is as follows. The lubricant of the embodiment and bicycle chain oil were injected into the gaps g1, g2, and g3, as well as into the hub bearing and freewheel ratchet, and the running time for 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, which uses isopropyl alcohol as a solvent and contains 12.5% ​​by weight of tungsten disulfide powder. The bicycle chain oil of the comparative example is Roadrace SP / BIc-004 from AZ Co., Ltd. One drop of each was injected near the gaps g1 and 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 distance of 21.01 km was traveled multiple times on the same section of National Route 134. The equipment, parts, bicycle, tire pressure, and bicycle rider were all the same, and the travel distance and time were measured using an app (Strava) that uses GPS information.

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

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

[0034] In addition, the lubricant of the embodiment is a liquid using isopropyl alcohol as a solvent, and the tungsten disulfide powder content is less than 25% by weight, so it has high permeability and diffusibility into minute gaps, easily reaching gaps g1, g2, g3, g4, etc. Furthermore, because isopropyl alcohol is a volatile solvent, the liquid lubricant evaporates relatively quickly after being injected. Therefore, only the tungsten disulfide powder remains in the minute gaps, fully demonstrating its effectiveness as a solid lubricant.

[0035] Furthermore, the lubricant of the embodiment does not contain adhesive substances such as oil or wax. Therefore, the adhesive substances do not adhere to sand or dust, forming clumps, or scattering these clumps. As described above, after the solvent evaporates, the lubricant of the embodiment exhibits its lubricating function, leaving only the tungsten disulfide powder remaining on the sliding surface, thereby ensuring stable low-friction effects. Furthermore, the lubricant of this embodiment is in a liquid form with low viscosity that can be injected into minute gaps. Therefore, unlike when using lubricants containing wax, there is no need to dissolve the wax or remove and reattach 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 reasonable time after being poured 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 is poured out of the container, and handling becomes difficult. Therefore, it is preferable to select a liquid with a suitable volatility.

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

[0038] The content of tungsten disulfide powder in the lubricant is preferably less than 25% by weight, and is selected appropriately depending on the injection location. Furthermore, if the solvent evaporates over time and the powder concentration becomes too high, it can be diluted with the same solvent before use.

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

[0040] The lubricant used in the running test (12.5 wt %; sample E) contains three times as much tungsten disulfide powder as the 3.9 wt % mentioned above. Therefore, it is believed that in the running test, injection of two drops per link was sufficient to supply tungsten disulfide powder to cover the entire sliding surface. Here, the volume of one drop is set to 0.013 cm. ３ ], and the tungsten disulfide powder was calculated as a sphere with a diameter of 0.5 [μm].

[0041] The injection lubricant of the present invention can be used in the same manner as described above when lubricating sliding surfaces with small gaps other than bicycle chains. If the tungsten disulfide powder content is less than 25% by weight, penetration into small gaps is sufficient, but if the content is reduced to increase penetration, the injection amount can be increased according to the sliding area requiring lubrication.

[0042] Suitable for lubricating various small gaps.

Claims

1. An injectable lubricant to be injected into minute gaps between sliding surfaces, which is composed only of tungsten disulfide powder and a volatile solvent, and 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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