JPH0551588A - Method of lubricating oil-retaining bearing, oil-retaining bearing, and lubricating oil for oil-retaining bearing - Google Patents

Abstract

PURPOSE:To provide an oil-retaining bearing which reduces friction and prevents abrasion by impregnating a porous bearing member, which supports a metal member in such a manner as to allow the metal member to freely slide, with a lubricating oil contg. a superfine powder having a higher hardness than the metal member. CONSTITUTION:An oil-retaining bearing is produced by impregnating a porous bearing member, which supports a metal member in such a manner as to allow the metal member to freely slide, with a lubricating oil contg. a high-hardness superfine powder having a mean particle diameter of 1mum or smaller and a higher hardness than the metal member (e. g. a diamond powder having a mean particle diameter of 20-100Angstrom ). The bearing, effectively utilizing the effect of the powder on lubrication mechanism, reduces friction and prevents abrasion to such an extent as to be formerly unexpected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for lubricating an oil-impregnated bearing with a special lubricating oil, an oil-impregnated bearing impregnated with the special lubricating oil, and a special lubricating oil for the oil-impregnated bearing. In the present invention, the bearing is in a broad sense, and is not limited to a bearing in a narrow sense that supports the rotating shaft slidably in the circumferential direction of rotation, but a bearing that supports the shaft so as to be slidable in the longitudinal direction, and It is intended to include a so-called surface bearing that slidably supports the surface of the supported member.

[0002]

2. Description of the Related Art Oil-impregnated bearings in which a porous bearing member is impregnated with oils and fats for lubrication are widely used, and are convenient because they do not require the trouble of circulating lubrication oil or lubricating grease. .. The lubricating oil impregnated into the porous bearing member is generally a clean liquid or viscous liquid oil and fat, but solid lubricants such as molybdenum disulfide and graphite are also finely mixed and mixed. Has been. For the sake of convenience of explanation, in the present invention, a finely divided solid of the order of microns is referred to as a fine powder, and a finely divided solid of the angstrom order is referred to as an ultrafine powder.

[0003]

The molybdenum disulfide and graphite mixed with the lubricating oil and grease for oil-impregnated bearings of the conventional example have a function as a solid lubricant by themselves, and therefore fine powder thereof is used as the lubricating oil and fat. Mixing in was done without requiring any particular imagination, but all of these solid lubricants are materials with a hardness lower than that of the supported member (for example, steel rotating shaft). there were. When fine powder having a hardness higher than that of the supported member is mixed in the lubricating oil, this fine powder acts as an abrasive,
The friction surface of the supported member may be abraded early, or in extreme cases, seizure may occur. For this reason, it has been contraindicated that fine powder of high hardness (for example, sand dust floating in the air, abrasion powder of the supported member, etc.) is mixed in the lubricating oil.

The inventors of the present invention have conducted experiments in anticipation that if the average particle size of the above-mentioned high hardness fine powder is further extremely finely pulverized into an ultrafine powder of angstrom order, the mode involved in lubrication-wear will change. It was theoretically discovered and confirmed that high hardness ultrafine powder in lubricating oil can improve the lubrication state depending on the conditions.

Based on the above findings, the present invention is applied to practical use to provide a lubrication method for oil-impregnated bearings, and a lubrication method for oil-impregnated bearings, which can obtain a lubricating function that has not been predicted in the past. Intended to provide oil.

[0006]

In order to apply the above-mentioned improvement of the lubrication condition by the ultra-hard ultrafine powder to the practical use, the lubrication method according to the present invention is a porous bearing member for slidably supporting a metal member. In the lubrication method of impregnating a lubricating oil mixed with solid fine powder, as the solid fine powder, an ultrafine particle having an average particle diameter of 1 micron or less of a substance having a hardness higher than that of the metal member supported by the bearing member is used. It is characterized by using powder.

Further, the oil-impregnated bearing according to the present invention as a concrete constitution for practically applying the above-mentioned improvement of lubrication condition is an oil-impregnated bearing in which a metal member is slidably supported by a porous bearing member impregnated with lubricating oil. In the above lubricating oil,
It is characterized in that ultrafine powder of a substance having a hardness higher than that of the metal member and having an average particle diameter of 1 micron or less is mixed.

[0008]

When the ultrafine powder having a hardness higher than that of the supported member, such as diamond, is mixed in the lubricating oil of the oil-impregnated bearing, the period during which the sliding friction surface becomes familiar is shortened. Further, when the conditions such as the concentration of the ultrafine diamond powder in the lubricating oil and the pressure on the bearing surface are appropriately selected, the friction coefficient is reduced and the progress of wear is suppressed.

[0009]

EXAMPLES Next, three types of examples according to the present invention will be described.
The description will be made in comparison with the comparative example. In the above-mentioned three kinds of examples and comparative examples, a pressure-formed product of copper and tin powder having an average grain size of 100 is sintered to form a porous bearing member, and the supported member is made of carbon steel (S45C). Then, a rolling slip test was performed on the cylindrical end faces of each other using a Suzuki type friction tester.
The main specifications of the work of sintering the porous bearing member are as follows. Composition: Copper 90 Wt%, tin 10 Wt% Sintering step: First step is 400 ° C. × 30 minutes Second step is 790 ° C. for 30 minutes Sintering atmosphere: Argon gas porosity: 13% Hardness: 44 Hv When carrying out, the above composition, porosity, and hardness may be set to the above values with an accuracy of about one digit. That is, almost the same effect is obtained within the range of 85 to 94 Wt% of copper and 6 to 15 Wt% of tin, almost the same effect is obtained at a porosity of 5 to 30%, and almost the same at a hardness of 40 to 45 (Hv). The effect of is obtained.

FIG. 2 shows the appearance of a test piece configured to test the lubrication-friction state of the present example and comparative example by the Suzuki type friction tester, where 1 is a bearing material (porous) and 2 is a coated material. It is carbon steel (S45C) which is a supporting member. The illustrated dimensions are as follows. a = 17
φ, b = 10 mm, c = 15 mm, d = 6 φ, e = 5 φ The above-mentioned four porous bearing members 1 are configured, and four types of lubricating oils A, B, C shown in Table 1 are shown for each of them. Impregnate D.

[0011]

[Table 1]

A is a lubricating oil of a comparative example, ISO22
High purity mineral oil of 0. Particle size 20-in Soviet oil
100 angstroms of diamond ultrafine powder were added.
Lubricating oil B of the example was prepared by using the additive mixed at 5 Wt% and diluting the additive 1000 times with the high-purity mineral oil. Similarly, the lubricating oil C was diluted 100 times and the lubricating oil D was prepared 10 times. The results of conducting tests by making four sets of test pieces by impregnating the four bearing members 1 with each of these four types of lubricating oils A to D will be described below.

Using a bearing member of a comparative example impregnated with lubricating oil A (pure mineral oil), FIG. 3 shows the change over time in the friction coefficient for 2 seconds 4 seconds after the start of sliding. The coefficient of friction is about 0.
It fluctuates in a cycle of 1 second, but its arithmetic average is 0.15.
Is. Calculate the arithmetic mean value for 2 seconds as above,
Similarly, the friction coefficient was measured at intervals of 1 minute, and the progress of 120 minutes is shown in a chart as shown by a curve 4A in FIG. Similarly, lubricating oil B of the example (0.0005 Wt%)
The course of the friction coefficient of the bearing member impregnated with 120 minutes as shown by curve 4B in FIG.
The course of 120 minutes of the bearing member impregnated with (0.05 Wt%) is as shown by curve 4D. Each curve 4A, 4
In both B and 4D, the coefficient of friction decreases with the progress of familiarity and gradually approaches a constant value. In comparison with (curve 4A), the examples (curves 4B and 4D) have a smaller friction coefficient after the fitting is completed. In this way, the result of examining the time required from the start of the test to the completion of familiarization is as shown in FIG. 5A is the familiarization time required for the comparative example (pure mineral oil), and 5B, 5C, 5D are the familiarization times required for impregnating the lubricating oils B, C, D in the examples, respectively. The familiarization time is reduced by mixing the ultrafine diamond powder, and the mixing concentration is 0.
It can be seen that between 0005 and 0.05 Wt%, no difference in familiarization time due to a difference in concentration is observed.

Next, FIG. 5 shows the relationship between the mixing concentration of the ultrafine diamond powder and the friction coefficient after the fitting is completed.
In the mixed concentration range of 0.0005 to 0.05 Wt%, the higher the concentration, the smaller the friction coefficient (after the familiarization is completed). 6B and 6D are lubricating oil B of the embodiment,
The coefficient of friction when D is impregnated is shown. 6C is the coefficient of friction when the lubricating oil of Example C is impregnated, but it is judged that an abnormal value was shown for some reason, so the curve 6 is omitted.

FIG. 6 is a chart showing the relationship between the diamond concentration and the specific wear rate. 6A is the specific wear rate of the bearing member impregnated with pure mineral oil of the comparative example, and 7A is the specific wear rate of the carbon steel tested in combination with it. 6B, 6C, 6D
Are the specific wear rates of the bearing members impregnated with the lubricating oils B, C, and D of the examples, and 7B, 7C, and 7D are the specific wear rates of the carbon steels tested in combination with the bearing members. There is a minimum specific wear rate near the diamond mixture concentration of 0.0005 Wt%, which is 0.0002 to 0.005 Wt.
It is recognized that there is a proper range between%.

FIG. 7 (b) shows a curve 8B depicting the surface roughness of carbon steel tested in combination with the lubricating oil impregnated bearing member of Example B. FIGS. 8C and 8D show curves 8C and 8D that depict the surface roughness of carbon steels in Examples C and D, respectively. The surface roughness becomes rougher as the diamond mixture concentration increases. FIG. 8 is a chart showing the relationship between the mixed concentration and the maximum height roughness. It was also confirmed by microscopic observation of the friction surface with an optical microscope that the roughness of the friction surface increased as the diamond concentration increased.

FIG. 9 is a chart showing the relationship between the hardness of the friction surface and the diamond ultrafine powder mixture concentration after the test. Point 10 indicates the friction surface hardness of the bearing member in the comparative example, and point 11 indicates the friction surface hardness of the carbon steel supported by the bearing member. Curve 12 shows the friction surface hardness of the bearing member in the example, and curve 13 shows the friction surface hardness of carbon steel. The friction surface hardness of carbon steel, which is the supported member, has a maximum value in the vicinity of the diamond ultrafine powder mixture concentration of 0.0005 Wt%. This mixed concentration (0.0005Wt%)
Is the same as the mixed concentration (0.0005 Wt%) corresponding to the minimum wear described with reference to FIG. The reason why the hardness of the friction surface increases and the progress of wear is suppressed is as follows.
It is considered to be (a) work hardening and (b) embedding ultrafine diamond powder on the friction surface. Above (a), (b)
In addition to the hardening of the friction surface due to, it is considered that cutting (abrasive) with ultrafine diamond powder also progresses. Therefore, even if the mixing concentration of the ultrafine diamond powder is excessively large, the specific wear rate is rather increased (as described with reference to FIG. 6). FIG. 10 is a curve 14B showing a change over time in the coefficient of friction when the lubricating oil of Example B was used, when the contact pressure between the bearing member and carbon steel was set relatively high to 67 kg / cm ^2. FIG. 14 is a chart showing a curve 14A when a comparative example (pure mineral oil) is used, and the curve 14B sharply rising after 110 minutes indicates the occurrence of seizure. This shows that in the oil-impregnated bearing of this example, the upper limit value of the contact pressure suitable for use is lower than that of the comparative example (pure mineral oil).

FIG. 11 is a table showing the relationship between the friction coefficient and the contact pressure. The curve 15A drawn by the solid line shows the case of pure mineral oil, and the curve 15B drawn by the broken line shows the lubricating oil of Example B (mixed). The rate is 0.0005 Wt%). The upward arrow in the upper right corner of the curve 15B indicates the occurrence of the image sticking described in FIG. The friction coefficient is the same when the contact pressure is 40 kg / cm ^{2, and at} a contact pressure higher than this, the friction coefficient of the embodiment (curve 15).
B) is larger than the comparative example (pure mineral oil).

FIG. 12 shows the relationship between the specific wear rate of the bearing member and the contact pressure. Curve 16A represents the comparative example (pure mineral oil), and curves 16B and 16C represent the lubricating oils of Examples B and C, respectively. Shows the case when used. FIG. 13 shows the specific wear rate of carbon steel, which is the same as in FIG.
7A is a comparative example (pure mineral oil), and curves 17B and 17C are Examples B and C. When the contact pressure is 30 kg / cm ² or less, the specific wear rate curves 16A and 17A of the comparative example are substantially horizontal (constant value), and gradually increase above 50 kg / cm ² . In contrast to this, the curves 16B and 16 of the embodiment
C, 17B, and 17C are rising steeper than the comparative example. The specific wear rate of the example at 8 kg / cm ² or less is smaller than that of the comparative example (conventional example), and the specific wear rate of the example at 67 kg / cm ² or more is greater than that of the comparative example. When the friction surface of the carbon steel after the test is examined with an optical microscope, many small pits of about several microns which are presumed to have been destroyed by fatigue are observed in the case of the example, and the distribution density of the pits is the contact pressure. The tendency is to increase with the increase of. This is consistent with the fact that the specific wear rate of the example increases as the contact pressure increases, as shown in FIG. The cause of such a phenomenon is that when the concentration of ultrafine diamond powder is high, the surface of carbon steel hardened by embedding ultrafine diamond powder is removed by the impact of ultrafine diamond powder in lubricating oil. It is believed that there is.

Specific wear rate of carbon steel is 1/10 ⁷ mm ³ / mm ・ kg
Table 2 shows the limit PV value of the bearing when the contact pressure is calculated and the contact pressure (calculated value) is assumed to be the limit contact pressure.

[0021]

[Table 2]

As a result, the oil-impregnated bearing of this embodiment exerts a remarkable effect on the reduction of friction and the suppression of wear under the use condition of relatively low contact pressure, but the use condition of relatively high contact pressure (for example, the crank of an internal combustion engine). It is not suitable for bearings, vehicle running shaft bearings, etc.). It is desirable to use the contact pressure of less than 30 kg / cm ² . In the case of carrying out the present invention, it is absolutely necessary that the bearing member is porous, but it is desirable that the bearing metal be a sintered metal made of a copper-tin based non-ferrous metal as shown in the examples. The member supported by the bearing member may be made of metal, but is preferably steel or alloy steel.

Further, the ultrafine powder for carrying out the present invention is required to be a material having a hardness higher than that of the metal member which is a supported member, but is a diamond harder than anything. Most suitable. And the average particle size is required to be 1 micron or less.
It is preferably -100 Angstroms.

Further, in order to easily carry out the lubrication method according to the present invention in practice, it is also effective to supply a lubricating oil mixed with ultrafine diamond powder to the market.

[0025]

As described above, when the present invention is applied to the oil-impregnated bearing, the effect of the high-hardness ultrafine powder on the lubrication mechanism is effectively utilized, and the anti-friction effect and wear control which have not been predicted in the past can be effectively utilized. Play an effect.

[Brief description of drawings]

FIG. 1 is a diagram showing a change with time of a friction coefficient showing a comparison between an example of the present invention and a comparative example.

FIG. 2 is an external view of a test piece for actually measuring the effect of the present invention.

FIG. 3 is a chart showing a change with time of a friction coefficient in a comparative example.

FIG. 4 is a chart showing the relationship between the running-in time of oil-impregnated bearings and ultrafine powder.

FIG. 5 is a chart showing the relationship between the friction coefficient of oil-impregnated bearings and the concentration of ultrafine powder.

FIG. 6 is a chart showing the relationship between the specific wear rate of oil-impregnated bearings and the concentration of ultrafine powder.

[Fig. 7] Surface roughness diagram of wear surface of member supported by oil-impregnated bearing

FIG. 8 is a chart showing the relationship between the maximum height roughness of the member supported by the oil-impregnated bearing and the ultrafine powder concentration.

FIG. 9 is a chart showing the relationship between the hardness of the friction surface of an oil-impregnated bearing and the ultrafine powder concentration.

FIG. 10 is a chart showing changes over time in the friction coefficient of oil-impregnated bearings.

FIG. 11 is a chart showing the relationship between the friction coefficient and contact pressure of oil-impregnated bearings.

FIG. 12 is a chart showing the relationship between the specific wear rate of the bearing member of the oil-impregnated bearing and the contact pressure.

FIG. 13 is a chart showing a relationship between a specific wear rate of a member supported by an oil-impregnated bearing and a contact pressure.

[Explanation of symbols]

 1 ... Bearing material, 2 ... Carbon steel.

Claims (17)

[Claims] 1. A lubrication method in which a porous bearing member that slidably supports a metal member is impregnated with a lubricating oil in which solid fine powder is mixed, and the bearing member supports the solid fine powder as the solid fine powder. A lubrication method for oil-impregnated bearings, which uses ultrafine powder having a hardness higher than that of a metal member and having an average particle diameter of 1 micron or less. 2. The lubrication method for oil-impregnated bearings according to claim 1, wherein ultrafine powder of diamond is used as the ultrafine powder having high hardness. 3. The method for lubricating an oil-impregnated bearing according to claim 1, wherein the ultrafine powder has an average particle size of 20 to 100 angstroms. 4. The method for lubricating an oil-impregnated bearing according to claim 1, wherein the concentration of the ultrafine powder in the lubricating oil is 0.0002 to 0.005 by weight. 5. The bearing of the metal member by the bearing member comprises:
The method for lubricating an oil-impregnated bearing according to claim 1, wherein the bearing is supported at a contact pressure of less than 30 kg / cm ² . 6. The lubrication method for an oil-impregnated bearing according to claim 1, wherein the porous bearing member is an alloy, and the metal member supported by the porous bearing member is steel or alloy steel. 7. The non-ferrous alloy porous bearing member comprises:
The oil-impregnated oil according to claim 1, which is obtained by press-molding 85 to 94 wt% of copper powder having an average particle size of 100 and 6 to 15 wt% of tin powder having an average particle size of 100. Bearing lubrication method. 8. An oil-impregnated bearing in which a metal member is slidably supported by a porous bearing member impregnated with lubricating oil, wherein an average particle diameter of a substance having a hardness higher than that of the metal member is contained in the lubricating oil. An oil-impregnated bearing characterized in that ultrafine powder of 1 micron or less is mixed. 9. The ultrafine powder having a hardness higher than that of the metal member is an ultrafine powder of diamond,
The oil-impregnated bearing according to claim 8. 10. The ultrafine powder has an average particle size of 20 to 100 angstroms.
The oil-impregnated bearing according to claim 8. 11. The oil-impregnated bearing according to claim 8, wherein the concentration of the ultrafine powder in the lubricating oil is 0.0002 to 0.005 by weight. 12. The bearing pressure of the metal member by the bearing member is less than 30 kg / cm ² .
The oil-impregnated bearing according to claim 8. 13. The porous bearing member is an alloy,
9. The oil-impregnated bearing according to claim 8, wherein the metal member supported thereby is steel or alloy steel. 14. The porous bearing member made of an alloy is sintered by press-molding 85 to 94 Wt% of copper powder having an average grain size of 100 and 6 to 15 Wt% of tin powder having an average grain size of 100. The oil-impregnated bearing according to claim 13, characterized in that 15. The oil-impregnated bearing according to claim 13, wherein the porous bearing member made of the alloy has a porosity of 5 to 30% and a hardness of Hv 40 to 50. 16. A lubricating oil for oil-impregnated bearings, characterized in that ultrafine diamond powder having an average particle size of 1 micron or less is mixed in the lubricating oil. 17. The lubricating oil for oil-impregnated bearings according to claim 16, wherein the ultrafine diamond powder has an average particle size of 20 to 100 angstroms.