JP2012172125A - Low friction sliding mechanism - Google Patents

Abstract

The present invention provides a low friction sliding mechanism that can further reduce the friction coefficient of sliding members that slide with each other in the presence of a lubricant as compared with a conventional sliding member.
In a sliding mechanism including a sliding member that slides with each other in the presence of a lubricant containing one or both of an oxygen-containing organic compound and an aliphatic amine compound, at least a sliding surface of the sliding member is provided. In part, a layer containing fluorinated diamond particles having a fluorine content of desirably 5 to 20% is formed.
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Description

  The present invention relates to a sliding mechanism applied to sliding parts in various mechanical devices such as automobiles, and is capable of greatly reducing the friction coefficient between sliding members in the presence of a lubricant. The present invention relates to a sliding mechanism.

  For example, in an internal combustion engine for automobiles, higher rotation, higher compression ratio, lighter weight, and improved fuel efficiency are more strongly demanded than ever before, resulting in lower friction and wear / seizure resistance of sliding parts. Realization such as improvement is desired.

  As one measure for this, one of the inventors of the present invention is composed of a sliding member that slides on each other and a lubricant interposed therebetween, and at least a part of the sliding surface of the sliding member is hydrophilic. Proposed a low-friction sliding mechanism comprising a friction modifier made of a resin material containing conductive fine particles and the lubricant comprising an organic oxygen-containing compound or an aliphatic amine compound. Specifically, a resin material such as a polyamide resin or a polysulfone resin containing hydrophilic fine particles such as diamond particles and silica particles is provided on the sliding surface (see Patent Document 1).

JP 2008-101189 A

  However, the market needs for a low friction technology that leads to an improvement in fuel consumption are increasing year by year, and further development of a friction reduction technology at a sliding part is required.

  The present invention has been made in view of the above-described problem relating to the low friction technology. The object of the present invention is to further reduce the friction coefficient of the sliding member based on the technology described in Patent Document 1. It is an object of the present invention to provide a low friction sliding mechanism that can be used.

  In order to achieve the above object, the present inventors have further studied the material constituting the sliding surface and the lubricant composition, and as a result, have slid the layer containing diamond (fluorinated diamond) particles having fluorine atoms. The present inventors have found that the above problems can be solved by forming on the moving surface, and have completed the present invention.

  That is, the present invention is based on the above knowledge, and the low friction sliding mechanism of the present invention is a sliding mechanism including sliding members that slide with each other under the presence of a lubricant. The lubricant includes a layer containing fluorinated diamond particles on a part or the whole of at least one sliding surface, and the lubricant contains an oxygen-containing organic compound and / or an aliphatic amine compound. To do.

  According to the present invention, sliding members having a layer containing fluorinated diamond particles on a sliding surface slide relative to each other under the intervention of a lubricant containing an oxygen-containing organic compound or an aliphatic amine compound. Therefore, the friction coefficient of the sliding member can be greatly reduced.

It is explanatory drawing which shows the point of the cylinder-on-disk single-piece | unit reciprocating friction test used for evaluation of a friction characteristic in the Example of this invention.

  Hereinafter, the low friction sliding mechanism of the present invention will be described in more detail. In the present specification and claims, “%” for concentration, content, added amount, etc. means mass percentage unless otherwise specified.

In the low friction sliding mechanism of the present invention, as described above, the sliding member in which the layer containing the fluorinated diamond particles is formed on the sliding surface contains one or both of the oxygen-containing organic compound and the aliphatic amine compound. They slide with each other under the presence of lubricant.
Here, the fluorinated diamond particle-containing layer described above may be provided on at least one of the sliding surfaces sliding on each other, and can be formed on the entire sliding surface or partially formed. It is.

On the other hand, the oxygen-containing organic compound and the aliphatic amine compound contained in the lubricant function as friction modifiers. By combining these friction modifiers and fluorinated diamond particles, the fluorinated diamond particles become frictional. By adsorbing the adjusting agent, it is possible to obtain excellent lubrication characteristics particularly in the boundary lubrication region.
In addition, since the fluorine on the surface of the fluorinated diamond repels, it is difficult to form agglomerates of particles that deteriorate the friction. In addition, the apparent surface area of the particles is increased, so that a good friction reduction effect is obtained. Can do.

  The fluorinated diamond particles used in the present invention may use either natural diamond or artificial diamond as a starting material, but it is desirable to use artificial diamond that can obtain fine particles having a stable particle size and is inexpensive.

For the synthesis of artificial diamond, a high-temperature and high-pressure method in which graphite is phase-transformed into a diamond structure at a high static pressure of 13 to 16 GPa in a sealed high-pressure vessel and at a high temperature of 3000 to 4000 ° C., methane gas or the like is used near atmospheric pressure. Chemical vapor deposition method (CVD method) that grows diamond crystals on the substrate as a raw material, explosion that explodes oxygen-deficient explosives in an inert medium and applies a dynamic impact, and phase transition of graphite to diamond structure Laws are known.
Among these, diamond by explosion method is also called cluster diamond because it is a structure in which nano-order particles are aggregated, and stable fine particles can be obtained and manufacturing cost is low, so fluorination used in the present invention It is particularly suitable as a starting material for diamond.

In obtaining the fluorinated diamond used in the present invention, there is no particular limitation on the particle diameter of the diamond as a starting material, but diamond having a primary particle diameter of 3 to 20 nm (generally called “nanodiamond”). It is particularly preferable to use as a raw material.
The explosive diamond described above is particularly preferable as a raw material because the primary particle size matches the value of the nanodiamond. In addition, the particle diameter of the cluster diamond (aggregate) which the primary particle of such an explosion method diamond aggregated is about 50-7500 nm.

The fluorinated diamond is produced by direct reaction between the diamond particles (natural diamond or artificial diamond) and fluorine gas, or fluorination by fluorine plasma.
Generally, the fluorination reaction of diamond occurs only on the outermost surface of the primary diamond particles, and fluorinated diamond whose surface is covered with fluorine atoms is generated. In addition, the particle diameter of diamond after fluorination reaction, that is, fluorinated diamond is substantially dependent on the primary particle diameter of the starting diamond.

  At this time, the fluorine content (maximum fluorine content) when fluorine is added to the entire surface varies depending on the particle size of the primary particles. For example, assuming that the primary particles are all 4 nm in diameter and the crystal structure of the diamond is an octahedral single crystal, the maximum fluorine content is about 30% of the total mass of the diamond particles, When the diameter is 5 nm, it is calculated as 25%.

However, when trying to obtain a fluorinated diamond with a high fluorine content, there is a tendency for a large amount of unreacted fluorine gas to be adsorbed between the surfaces of the diamond particles and between the particles, so the fluorine content of the fluorinated diamond is 20% or less. Fluorination is preferably performed under the following conditions.
On the other hand, in order to ensure the dispersion effect by fluorination, it is desirable that at least 20% of the number of surface elements of the diamond particles is fluorinated, and the fluorine content of the fluorinated diamond particles Is preferably 5% or more.

  The fluorine content of the fluorinated diamond can be controlled mainly by the reaction temperature during the fluorination reaction. For example, in the case of direct reaction with fluorine gas, diamond reacts with fluorine from room temperature, and the fluorine content increases as the reaction temperature increases.

Therefore, in order to obtain a fluorinated diamond having a fluorine content of 5% to 20% as described above, it is preferable to fluorinate in a reaction temperature range of 100 to 500 ° C. Further, in order to obtain uniform fluorinated diamond, it is necessary to set the reaction time sufficiently long.
The required reaction time varies depending on the purity of the raw material, the type of reactor, the fluorine gas flow rate, etc., so the optimum reaction time can be determined by, for example, actually measuring the fluorine content of the produced fluorinated diamond. It is desirable to determine.

  In the present invention, a layer containing fluorinated diamond particles is formed on the sliding surface of the sliding member, but the matrix material of this layer is not particularly limited. For example, metal, ceramic, resin, rubber, or the like can be used, and fluorinated nanodiamond can be dispersed therein. Among these, use of a resin coating material is particularly preferable in terms of convenience.

  As the resin coating material, any thermoplastic resin or thermosetting resin can be used. Specifically, polyamide resin, polysulfone resin, polyetherimide resin, polyethersulfone resin, polyamideimide resin, polyimide resin can be used. Polyether ether ketone resin, epoxy resin, and the like can be preferably used. These resins are excellent in heat resistance and can be applied under severe sliding environments such as automobile engine parts.

In addition, from the viewpoint of having a glass transition temperature of 250 ° C. or higher and high heat resistance, and having a cross-linked structure in the molecular chain, the film is strong and has excellent adhesion to the substrate. It is desirable to contain it as a base material resin.
When a polyamideimide resin is applied as a base resin, the number average molecular weight of the polyamideimide resin material is preferably 1000 to 10000 before being dried or fired to form a film, and is 2000 to 8000. Is more preferable, and it is more preferable that it is 4000-8000.

  Here, when the number average molecular weight is less than 1000, since the molecular chain is less entangled, the wear resistance of the resin composition may be lowered. On the other hand, when the number average molecular weight exceeds 10,000, the friction coefficient of the polyamideimide resin as a base resin increases, and as a result, the friction coefficient of the resin composition may increase. Moreover, the adhesiveness with the base material of a resin composition may fall, and it may become easy to generate | occur | produce peeling.

The resin material may be a kneaded resin material melted by biaxial extrusion, or may be dispersed in a coating material and coated with a metal or resin material as a film.
At this time, in addition to fluorinated diamond particles, PTFE, MoS ₂ , and graphite are added as appropriate, which is more effective for friction and wear resistance, and the mixing ratio is selected according to the surface pressure, speed, and lubrication used. Good.

In addition, as content of the fluorinated diamond particle in the said layer, it is desirable to set it as 0.1 to 10% of range by mass ratio. That is, when it is less than 0.1%, the effect of containing particles is not sufficiently obtained, and when it exceeds 10%, the coating film tends to become brittle and tends to be peeled off.
Further, as described above, the fluorinated diamond particle-containing layer does not necessarily have to be formed on the entire sliding surface, but at least 50% or more of the sliding area is required to ensure the effect of reducing the friction coefficient. It is desirable to form.

  As the base material of the sliding member in the present invention, that is, the substrate material for forming the fluorinated diamond particle-containing layer, for example, iron-based materials such as carburized steel and hardened steel, copper-based materials, and zinc-based materials. Non-ferrous metal materials such as aluminum-based materials can be used.

As the lubricant interposed on the sliding surface of the sliding member, a lubricant containing at least one of an oxygen-containing organic compound and an aliphatic amine compound is used.
Examples of the oxygen-containing organic compound include a compound having a hydroxyl group, a carboxyl group, a carbonyl group, etc., an ester bond, a compound having an ether bond, etc. (these may have two or more groups or bonds). Can be mentioned. At this time, it is preferable to have one or more groups or bonds selected from a hydroxyl group, a carboxyl group, a carbonyl group, and an ester bond, and one or more groups or bonds selected from a hydroxyl group, a carboxyl group, and an ester bond or More preferably, it is an oxygen-containing organic compound having two or more.

Among these, it is preferable to have a hydroxyl group because it is more excellent in reducing friction. Of the hydroxyl groups, an alcoholic hydroxyl group is more preferable than a hydroxyl group directly bonded to a carbonyl group such as a carboxyl group because the friction reducing effect is more excellent.
Further, the number of such hydroxyl groups in the compound is not particularly limited, but it is preferable to have more hydroxyl groups because of more excellent friction reduction effect. However, when used together with a medium such as a lubricating base oil to be described later, the number of hydroxyl groups may be limited from the viewpoint of solubility.

  Specific examples of the oxygen-containing organic compound include ethanol, propanol, oleic alcohol, glycerin, diethyl ether, oleic acid, stearic acid, methyl stearate, and glycerin monooleate.

Examples of the aliphatic amine compound include those having a linear or branched aliphatic hydrocarbon group having 6 to 30 carbon atoms, preferably 8 to 24 carbon atoms, and particularly preferably 10 to 20 carbon atoms. Can do.
Here, when the number of carbon atoms is outside the range of 6 to 30, the friction reduction effect may not be sufficiently obtained. In addition, as long as it has the linear or branched aliphatic hydrocarbon group of the said range, it is natural that you may have another hydrocarbon group.

  Specific examples of the aliphatic amine compound that can be suitably used include laurylamine, oleylamine, stearylamine, dioctylamine, dimethyllaurylamine, and polyoxyethylene laurylamine.

The oxygen-containing organic compound and the aliphatic amine compound are used as a low friction agent composition alone (that is, as an oxygen-containing organic compound or an aliphatic amine compound 100 on the sliding surface having a layer containing fluorinated diamond particles. %) Or a mixture of the two, it exhibits extremely low friction characteristics.
However, as the lubricant used in the present invention, an oxygen-containing organic compound and / or an aliphatic amine compound mixed with other components can be used and supplied to the sliding surface for lubrication. is there. Examples of other components include a medium such as a lubricating base oil, various additives, and the like.

In this case, the content of the oxygen-containing organic compound and the aliphatic amine compound is not particularly limited, but the total amount thereof is preferably 0.01 to 5.0%. Moreover, the range of 0.05 to 2.5% is more preferable, and the range of 0.5 to 2.5% is particularly preferable.
While increasing the amount of these friction modifiers is effective in improving fuel economy, the effect of adding less than 5.0% is realistic when the blending amount exceeds 5.0%. . Moreover, since an effect is not expectable if it is less than 0.01%, it is preferable to set it as 0.01% or more.

Specifically, as the above-mentioned medium, for example, mineral oil, synthetic oil, natural fats and oils, diluent oil, grease, wax, hydrocarbons having 3 to 40 carbon atoms, hydrocarbon solvents, organic solvents other than hydrocarbons, Water, etc., and mixtures thereof, particularly those which are liquid, grease-like or wax-like at the sliding conditions and at normal temperature.
Further, as the medium, it is particularly preferable to use a lubricating base oil. Further, such a lubricating base oil is not particularly limited, and can be used regardless of whether it is a mineral base oil or a synthetic base oil, as long as it is normally used as a base oil of a lubricating oil composition. it can.

  Examples of the additives include metal detergents, antioxidants, viscosity index improvers, ashless dispersants, antiwear agents, as well as ashless friction modifiers other than the oxygen-containing organic compounds and aliphatic amine compounds. , Extreme pressure agent, rust preventive agent, nonionic surfactant, demulsifier, metal deactivator, defoaming agent, etc. Performance can be increased.

  Hereinafter, the present invention will be described in more detail based on examples and comparative examples. Needless to say, the present invention is not limited to these examples.

(Production of cylindrical specimen)
In a cylinder-on-disk single-piece reciprocating friction test described later, a cylinder-shaped test piece serving as a mating sliding member of a disk-shaped test piece having a fluorinated diamond particle-containing layer was produced using high carbon chromium bearing steel.
That is, using a SUJ2 steel defined in JIS G4805 as a raw material, it was machined into a cylindrical shape having a diameter of 24 mm and a length of 7.9 mm, and then the surface roughness Ra was finished to 0.04 μm to obtain a cylindrical test piece 1.

(Adjustment of lubricant)
Based on gasoline engine oil Nissan SM Strong Save X (5w-30), one of each of glycerol monooleate as an oxygen-containing organic compound and oleylamide as an aliphatic amine-based compound is added to each 1%, As shown in Table 1, three types of lubricating oil were prepared for convenience.

(Evaluation test method)
The cylinder-shaped test piece 1 manufactured as described above and the disk-shaped test piece 2 manufactured in the manner described later are combined as shown in FIG. 1, and the cylinder-on-disk single-unit reciprocating friction is performed with the lubricant shown in Table 1 being dropped. The test was conducted. The friction test conditions are as follows. Moreover, about the friction coefficient, it was set as the average value during test time 20-30 minutes.
Test equipment: Cylinder-on-disk unit reciprocating friction tester Sliding side test piece: φ15 × 22mm cylindrical test piece Counterpart test piece: φ24 × 7.9mm disc-shaped test piece Load: 50N )
Amplitude: 3.0 mm
Frequency: 5Hz
Test temperature: 80 ° C
Measurement time: 30 minutes

Example 1
[1] Preparation of fluorinated diamond particles 20 g of explosive diamond particles with a primary particle size of 4 to 5 nm (manufactured by Gansu Ryunouchi Material Co., Ltd., nanodiamond purified powder) are heated and dried at 400 ° C. for 24 hours, and then made of nickel. The fluorinated nanodiamond was produced under the following conditions by direct reaction with fluorine gas.
Gas flow rate: (fluorine) 40 ml / min, (argon) 360 ml / min
Reaction temperature: 450 ° C
Reaction time: 96 hours The fluorine content of the obtained fluorinated diamond was 13% based on the total mass of diamond particles as measured by elemental analysis by a combustion method.

[2] Preparation of resin composition precursor To the N-methyl-2-pyrrolidone (NMP), the above fluorinated diamond particles (average primary particle size: 4 to 5 nm) are added and stirred for 30 minutes in a bead mill. The polyamideimide resin material synthesized in (1) was added, and the polyamideimide resin was adjusted so that the fluorinated diamond particles became 1%, and this was used as a resin composition precursor.

[3] Preparation of disc-shaped test piece (sliding member) A T6-treated aluminum alloy A6061 disc (φ24 × 7.9 mm, surface roughness Ra 0.1 μm) was used as a base material, and after degreasing with alcohol, The resin composition precursor was spray-coated so that the dry film thickness was 20 ± 5 μm. And it heated at 180 degreeC for 60 minutes, the layer of the resin composition containing a fluorinated diamond particle was formed, and the disk-shaped test piece used for this example was obtained.

  Then, in combination with the lubricant 1 shown in Table 1 (containing 1% glycerin monooleate), a cylinder-on-disk single-piece reciprocating friction test was performed in the manner shown in FIG. The results are shown in Table 2.

(Example 2)
A cylinder-on-disk single-piece reciprocating friction test was performed on the same disk-shaped test piece as in Example 1 in combination with the lubricant 2 shown in Table 1 (containing 1% oleylamide). The results are also shown in Table 2.

(Example 3)
A cylinder-on-disk single-piece reciprocating friction test was performed on the same disk-shaped test piece as in Example 1 above in combination with the lubricant 3 shown in Table 1 (containing 1% glycerin monooleate and 1% oleylamide). The results are also shown in Table 2.

Example 4
The lubricant shown in Table 1 was prepared using a disk-shaped test piece prepared by repeating the same operation as in the above example except that a polyimide resin was used instead of the polyamideimide resin in preparing the resin composition precursor. In combination with 1, a cylinder-on-disk single-piece reciprocating friction test was performed. The results are also shown in Table 2.

(Example 5)
In adjusting the fluorinated diamond particles, the fluorine content was adjusted to 4% by repeating the same operation as in the above example except that the reaction temperature of fluorination was reduced to 50 ° C. and the reaction time was 50 hours. Fluorinated diamond was synthesized.
Then, except that the fluorinated diamond particles obtained as described above were used, a disk-like test piece produced by the same operation as in Example 1 was used, and the same cylinder on was combined with the lubricant 1 shown in Table 1. A single disk reciprocating friction test was performed. The results are also shown in Table 2.

(Comparative Example 1)
In preparing the resin composition precursor, the same operation as in the above example was performed except that diamond particles obtained by an explosion method (average primary particle size 4 to 5 nm) were used as they were instead of fluorinated diamond particles. By repeating, the disk-shaped test piece used for the said comparative example was produced. Then, in combination with the lubricant 1 shown in Table 1, a cylinder-on-disk single-unit reciprocating friction test was performed. The results are also shown in Table 2.

  Based on the above results, a sliding member having a sliding surface with a resin layer in which fluorinated diamond particles containing a predetermined amount of fluorine are dispersed is slid in the presence of a lubricant containing a predetermined friction modifier. Thus, it was confirmed that the low friction characteristic superior to the combination of the conventional sliding member and the lubricant can be obtained.

Claims (4)

A sliding mechanism comprising sliding members that slide relative to each other under the presence of a lubricant,
A layer containing fluorinated diamond particles on a part or the whole of at least one sliding surface of the sliding member,
The low-friction sliding mechanism characterized in that the lubricant contains an oxygen-containing organic compound and / or an aliphatic amine compound.   The low friction sliding mechanism according to claim 1, wherein the fluorine content of the fluorinated diamond particles is 5 to 20%.   The low friction sliding mechanism according to claim 1 or 2, wherein the layer containing fluorinated diamond particles is a resin layer containing the fluorinated diamond particles.   The organic oxygen-containing compound is at least one compound selected from the group consisting of a compound having a hydroxyl group and / or a carboxyl group, a compound having an ester bond or an ether bond, and a compound having an oleyl group. The low friction sliding mechanism according to any one of claims 1 to 3.

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