JP2006199836A - Low friction sliding mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low friction sliding mechanism that can largely decrease the friction coefficient of the sliding member having a hard carbon thin film applied thereto in the presence of lubricating oil. <P>SOLUTION: The low friction sliding mechanism is constituted with sliding members as they mutually slide on and lubricating oil that fills spaces between the sliding members. The sliding members are coated with a hard carbon thin film with a hydrogen content of less than 20 atom% and the lubricating oil comprises a base oil having a sliding velocity of 4.4 m/s, a Hertz pressure of 0.53 GPa, and an oil film thickness of less than 95 nm at 100°C oil temperature. To the lubricating oil, are added a calcium salicylate cleaning agent and an ash-free friction-controlling agent. A compound bearing oleyl group is used as an ash-free friction controlling agent. A compound bearing ester group is also used. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a low-friction sliding mechanism, and more particularly to a low-friction sliding mechanism that can reduce the frictional resistance of a sliding portion of an internal combustion engine such as an automobile and improve fuel efficiency.

  In recent years, environmental problems on a global scale have become serious, and global warming has been highlighted. In particular, carbon dioxide emissions, which are said to have a significant impact on global warming, are increasing year by year. At the Global Warming Prevention Conference held in Kyoto in 1997, CO2 emissions reduction targets Is stipulated.

On the other hand, the amount of carbon dioxide emitted by the Japanese transportation sector accounts for 20% of the total amount of carbon dioxide emissions. By 2010, the transportation sector is obliged to improve fuel efficiency by about 20% compared to 1995 levels. Efforts to reduce emissions are being made.
Against this background, further improvement in the efficiency of automobile internal combustion engines aimed at improving fuel efficiency and reducing carbon dioxide emissions is one of the most important issues.

  As means for solving this problem, there is a technique for reducing the frictional resistance of each sliding portion of the internal combustion engine. Recently, a hard carbon thin film has been applied to the sliding portion. Among them, diamond-like carbon (hereinafter referred to as “DLC”) is a metal nitride such as titanium nitride (TiN) or chromium nitride (CrN). Compared to materials, it has a high friction reducing effect and is excellent in wear resistance, and therefore is highly expected as a low friction material.

In addition, the lubricating oil that lubricates the internal combustion engine plays a major role in improving the fuel efficiency of the internal combustion engine.
For example, by adding an organomolybdenum compound to lubricating oil, research on reducing the frictional resistance of each sliding part of an internal combustion engine has been actively conducted, and it is highly effective for sliding parts made of conventional steel materials. (See, for example, Patent Documents 1 to 6).
JP 2001-348591 A Japanese Patent Laid-Open No. 2002-12884 JP 2002-371292 A JP 2001-181664 A JP-A-8-302378 Japanese Patent Laid-Open No. 9-3463

However, it has been reported that a general DLC material having excellent low friction characteristics in air has a small friction reducing effect in the presence of lubricating oil (see, for example, Non-Patent Document 1).
Further, it has been found that even if a lubricating oil containing an organomolybdenum compound is applied to the sliding material, the friction reducing effect is not sufficiently exhibited (for example, see Non-Patent Document 2).
Kano et al., Proceedings of Japan Society of Tribology, Tokyo 1999,5, p11-12 Kano et. al. World Tribology Congress 2001.9, Vienna, Proceeding, p342

  The present invention has been made in view of such problems of the prior art, and its object is to greatly reduce the friction coefficient of a sliding member to which a hard carbon thin film is applied under the presence of lubricating oil. An object of the present invention is to provide a low friction sliding mechanism that can be used.

  In order to solve the above-mentioned problems, the present inventors have conducted various studies on various sliding members used in internal combustion engines and combinations of these materials and lubricating oils. Or the hard carbon thin film which prescribed | regulated hydrogen content was formed in both, and it discovered that the said subject could be solved by including the base oil of a specific property in the lubricating oil to be used, and came to complete this invention.

  That is, the low friction sliding mechanism of the present invention comprises a sliding member that slides on each other and a lubricating oil interposed therebetween, and the sliding member has a hard carbon thin film on at least a part of the sliding surface. The hard carbon thin film has a hydrogen content of 20 atomic% or less, and the lubricating oil was measured under the conditions of a sliding speed of 4.4 m / s, a Hertz pressure of 0.53 GPa, and an oil temperature of 100 ° C. A base oil having an oil film thickness of 95 nm or less is included.

  Further, the preferred form of the low friction sliding mechanism of the present invention is such that the hydrogen content of the hard carbon thin film is 10 atomic% or less, more preferably 0.5 atomic% or less, and particularly preferably the hard carbon thin film. The carbon thin film is substantially free of hydrogen.

  Furthermore, another preferred embodiment of the low friction sliding mechanism of the present invention is characterized in that the lubricating oil contains a calsim salicylate detergent and an ashless friction modifier.

  Furthermore, in another preferred embodiment of the low friction sliding mechanism of the present invention, the addition amount of the calcium salicylate detergent is 0.5 to 10.0%, and the addition amount of the ashless friction modifier. Is 0.01 to 5.0%.

  According to the present invention, the friction coefficient of a sliding member to which a hard carbon thin film is applied can be greatly reduced under the presence of lubricating oil.

  Hereinafter, the low friction sliding mechanism of the present invention will be described in detail. In this specification, “%” indicates mass percentage unless otherwise specified.

The low-friction sliding mechanism of the present invention includes a sliding member that slides on each other and a lubricating oil that is interposed therebetween.
Then, by forming a hard carbon thin film with a specified hydrogen content on the sliding surface of the sliding member and including a base oil with specific properties in the lubricating oil, the friction coefficient during sliding is greatly reduced. The Typically, the amount of carbon dioxide emitted can be greatly reduced, and an automobile with excellent fuel economy can be provided.

Here, the hard carbon thin film is amorphous mainly composed of carbon elements, and the bonding form between carbons consists of both a diamond structure (SP ³ bond) and a graphite bond (SP ² bond).
Specifically, aC (amorphous carbon) consisting only of carbon elements, aC: H (hydrogen amorphous carbon) containing hydrogen, and some metal elements such as titanium (Ti) and molybdenum (Mo). MeC included in

The hard carbon thin film of the sliding member has a hydrogen content of 20 atomic% or less. This is because the coefficient of friction increases as the hydrogen content increases.
Further, in order to sufficiently reduce the coefficient of friction during sliding in the lubricating oil and to secure more stable sliding characteristics, the hydrogen content is preferably 10 atomic% or less, and more preferably 0. More preferably, it is 5 atomic% or less.
In particular, the low friction sliding mechanism of the present invention is preferably made of an aC-based material that does not substantially contain hydrogen from the viewpoint of exerting a significant friction reducing effect on the hard carbon thin film. Note that “substantially” as used herein indicates that the amount of hydrogen atoms contained in such a material is measured by secondary ion mass spectrometry (SIMS), and as a result, is below the measurement limit.

Such a hard carbon thin film having a low hydrogen content or not containing hydrogen is obtained by forming a film by a PVD method that substantially does not use hydrogen or a hydrogen-containing compound, such as a sputtering method or an ion plating method.
In this case, not only a gas not containing hydrogen is used during the film formation, but in some cases, the film may be formed after the reaction vessel and the base material holder are sufficiently baked and the surface of the base material is sufficiently cleaned. Desirable to reduce the amount of hydrogen in it.

The sliding member is coated with a hard carbon thin film on at least a part of the sliding surface. In other words, the hard carbon thin film can be coated on one or both of the sliding members constituting the sliding surface and part or all of the sliding surface.
Therefore, in the low-friction sliding mechanism of the present invention, the sliding surface is constituted by the sliding members provided with the hard carbon thin film, and the sliding member provided with the hard carbon thin film and the slide not provided with the hard carbon thin film. A sliding surface may be comprised with a moving member.
In a sliding mechanism in which sliding members each having a hard carbon thin film constitute a sliding surface, both sliding materials are preferably formed by coating a hard carbon thin film on a metal material. In this case, it is more preferable that both hard carbon thin films are a-C type DLC containing no hydrogen.

  Here, regarding the sliding member used in the low friction sliding mechanism of the present invention, “sliding member (A)” having a hard carbon thin film and “sliding member (B)” not having a hard carbon thin film This will be explained separately.

  For the base material of the sliding member (A) (before coating with the hard carbon thin film), for example, non-ferrous metals such as carburized steel, hardened steel, and aluminum can be used.

Further, the surface roughness of the sliding member (A) before coating with the hard carbon thin film is that the film thickness of the hard carbon thin film is considerably thin and greatly affects the roughness of the film surface even after film formation. The thickness Ra (centerline average roughness) is preferably 0.1 μm or less.
When the surface roughness Ra is more than 0.1 μm, the protrusion due to the roughness of the film surface may increase the local contact surface pressure with the counterpart material, and may induce film cracking. Becomes higher.

Furthermore, the surface hardness of the base material (before coating of the hard carbon thin film) of the sliding member (A) is preferably Rockwell hardness, C scale, and HRC 45-60. This case is effective because the durability of the hard carbon thin film can be maintained even under sliding conditions under a high surface pressure of about 700 MPa as in the cam follower member.
If the surface hardness is out of the above range, if it is less than HRC45, it may be easily buckled and peeled off under high surface pressure.

Furthermore, the sliding member (A) has a surface hardness after coating the hard carbon thin film of Hv 1000-3500 in terms of micro Vickers hardness (10 g load), and the thickness of the hard carbon thin film is 0.3-2. It is desirable to be 0 μm.
When the surface hardness and thickness are out of the above ranges, they are likely to wear out when the Hv is less than 1000 and the thickness is less than 0.3 μm. On the other hand, when the thickness exceeds Hv3500 and a thickness of 2.0 μm, the film is easily peeled off.

On the other hand, the constituent material of the sliding member (B) is not particularly limited (may be the same as the constituent material of the sliding member (A)). Specifically, for example, an iron-based material, an aluminum-based material, Metal materials such as magnesium-based materials and titanium-based materials can be used. In particular, iron-based materials, aluminum-based materials, and magnesium-based materials are effective in that they can be easily applied to sliding parts of existing machines and devices, and can contribute widely to energy-saving measures in various fields.
Moreover, nonmetallic materials, such as resin, a plastic, and carbon, can also be used as a constituent material of a sliding member (B).

  There is no restriction | limiting in particular as said iron-type material, Not only high purity iron but various iron-type alloys (Nickel, copper, zinc, chromium, cobalt, molybdenum, lead, silicon, or titanium, and these are arbitrarily combined) Etc.) can be used. Specific examples include carburized steel SCM420 and SCr420 (JIS).

  Moreover, when using an iron-type material, the surface hardness is Rockwell hardness and it is desirable that it is HRC45-60 in C scale. This case is effective because the durability of the film can be maintained even under sliding conditions under a high surface pressure of about 700 MPa as in a cam follower member.

  There is no restriction | limiting in particular as said aluminum-type material, Not only high purity aluminum but various aluminum-type alloys can be used. Specifically, for example, it is desirable to use a hypoeutectic aluminum alloy or a hypereutectic aluminum alloy containing 4 to 20% of silicon (Si) and 1.0 to 5.0% of copper (Cu). Preferable examples of the aluminum alloy include AC2A, AC8A, ADC12, ADC14 (JIS) and the like.

  Moreover, when using an aluminum-type material, it is desirable that the surface hardness is Brinell hardness HB80-130. If the surface hardness of the aluminum-based material is out of the above range, the aluminum-based material may be easily worn if it is less than HB80.

Various thin film coatings can be applied to the metal material and non-metal material which are constituent materials of the sliding member (B).
Specifically, for example, the surface of the iron-based material, the aluminum-based material, the magnesium-based material, or the titanium-based material is coated with a thin film such as titanium nitride (TiN) or chromium nitride (CrN). Can do.

  In this case, the surface hardness of the coating surface is preferably microvickers hardness (10 g load) of Hv 1000 to 3500, and the film thickness is preferably 0.3 to 2.0 μm. When the surface hardness and thickness are out of the above ranges, it tends to wear out when the Hv is less than 1000 and the thickness is less than 0.3 μm. On the other hand, when the thickness exceeds Hv3500 and a thickness of 2.0 μm, it may be easily peeled off.

  The surface roughness Ra of the sliding member (A) (after coating with the hard carbon thin film) and the sliding member (B) described above is 0.1 μm or less, preferably 0.08 μm or less from the viewpoint of sliding stability. It is good to be. When it exceeds 0.1 μm, scuffing is locally formed, and the friction coefficient may be greatly improved.

Next, the lubricating oil used in the low friction sliding mechanism of the present invention will be described.
The lubricating oil includes a base oil having an oil film thickness of 95 nm or less measured under conditions of a sliding speed of 4.4 m / s, a Hertz pressure of 0.53 GPa, and an oil temperature of 100 ° C.
By interposing such lubricating oil on the sliding surface of the above-described sliding member, the friction coefficient and sliding resistance are reduced, and for example, an extremely excellent effect that the fuel efficiency performance of the engine can be improved is brought about.

In the method for measuring the oil film thickness under the above conditions, when a base oil having an oil film thickness exceeding 95 nm is used, it is difficult to exhibit sufficient low friction characteristics.
In addition, as the said oil film thickness measuring method, the method described in FIG. 1 of literature SAE TECHNICICAL PAPER 961142 is employable.

  The base oil contained in the lubricating oil is not particularly limited as long as the oil film thickness measured in the above measurement is satisfied. Mineral oil-based lubricating oil, synthetic oil-based lubricating oil, or two or more kinds selected from these What mixed lubricating oil in arbitrary ratios etc. can be used. For example, mineral oil-based lubricating oil, mixed oil of mineral oil-based lubricating oil and non-aromatic synthetic oil-based lubricating oil, mixing of aromatic-containing synthetic oil and non-aromatic-containing synthetic oil-based lubricating oil Oil etc. are mentioned. Typically, mineral oil-based lubricants include solvent refined oils, solvent dewaxed oils, hydrocracked oils, etc., and synthetic oil-based lubricants include poly-α-olefins and alkylnaphthalenes, Diesters such as alkylbenzene, ditridecyl glutarate, dioctyl adipate, diisodecyl adipate, ditridecyl adipate, and dioctyl sebacate, and trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, and penta Examples thereof include polyol esters such as erythritol pelargonate.

Further, from the viewpoint of further improving the low friction characteristics, the lubricating oil can contain a salicylate detergent and an ashless friction modifier together with the base oil. This is effective because a sliding mechanism with excellent fuel efficiency can be obtained.
For example, in a valve train of an internal combustion engine, such a lubricating oil includes a disk-shaped shim or lifter crown coated with DLC on a base of steel material, low alloy chilled cast iron, carburized steel, tempered carbon steel, and these It is preferable to interpose on a sliding surface with a cam lobe using a material related to an arbitrary combination.

As the salicylate detergent, it is preferable to use calcium salt or magnesium salt. A total alkali number is preferably 50 to 400 mgKOH / g.
This is because, in the case of alkyl salicylate beryllium salt and barium salt, a water-soluble salt may be generated by the reaction of moisture caused by combustion of the internal combustion engine and weak acid formed by oxidative degradation of the lubricating oil. This is because it is not environmentally preferable in terms of biotoxicity. In the case of beryllium salt, the crystal hardness of beryllium carbonate produced by the reaction with carbon dioxide gas is high, so there is a concern that the wear resistance is deteriorated. For other metals, the cost of the metal is high and it is difficult to put it to practical use.

Further, as the salicylate detergent, it is particularly preferable to use calcium alkylbenzene salicylate.
This calcium alkylbenzene salicylate is an oil-soluble basic salt of an aromatic carboxylic acid and a metal of Group II of the periodic table between atomic numbers 12 to 56, and has a total alkali number of 12 mg KOH / g or more. (For example, refer to Japanese Patent Nos. 12712215 and 1031507.)

Furthermore, it is preferable that the addition amount of the salicylate detergent is 0.5 to 10.0%. More preferably, it is 1.0 to 8.0%, particularly preferably 2.0 to 5.0%.
An increase in the amount of the salicylate-based detergent is effective for improving the cleanliness and oxidation stability, but if it exceeds 10.0%, the effect of addition may be reduced with an increase in cost. Further, since a large amount of addition leads to an increase in ash content in the lubricating oil and causes an increase in the amount of piston deposit produced, it is realistic that it is 10.0% or less. Moreover, since an effect cannot be anticipated if it is less than 0.5%, it is good to set it as 0.5% or more.

On the other hand, as the ashless friction modifier, a compound having an oleyl group is preferably used.
Ashless friction modifiers such as alkyl carboxylic acids, alkyl carboxylic acid esters, alkyl amines, alkyl amides, and alkyl ethers have a greater friction reduction effect as the alkyl group length increases, but lubrication as the alkyl chain length increases. Solubility in oil will decrease. On the other hand, the ashless friction modifier having an oleyl group has a sufficient length for the alkyl group to exert a friction reducing action, and further contains an unsaturated bond in the molecule. Solubility is higher than other ashless friction modifiers. Therefore, it is more advantageous than other ashless friction modifiers in terms of friction reduction effect.

Moreover, it is preferable that the said ashless type | system | group friction modifier contains the compound which has an ester group from the surface of the friction reduction effect.
Examples of such compounds include glycerol monooleate, glycerol diolate, sorbitan monooleate, and sorbitan diolate.

Furthermore, the addition amount of the ashless friction modifier is preferably 0.01 to 5.0%. Further, it is more preferably 0.05 to 2.5%, particularly preferably 0.5 to 2.5%.
Increasing the amount of ashless friction modifier is effective for improving fuel economy, but if it exceeds 5.0%, the additive effect decreases with increasing cost, so 5.0% or less is realistic. is there. Moreover, since an effect cannot be expected if it is less than 0.01%, 0.01% or more is preferable.

  In addition to the base oil, the detergent, and the friction modifier, the lubricating oil described above includes an anti-wear agent, an ashless dispersant, an antioxidant, a viscosity index improver, a fluid, as well as a general lubricating oil. It is effective to appropriately add various additives such as a point depressant, a rust inhibitor, and an antifoaming agent.

  As the antiwear agent, in addition to zinc dithiophosphate (ZnDTP) generally blended, in the present invention, in particular, the alkyl group having 3 to 12 carbon atoms and the alcohol residue thereof is secondary (Sec-ZnDTP). ) Or primary (Pri-ZnDTP) or a mixture thereof is desirable. The added amount is desirably 0.03 to 0.1% in terms of the amount of phosphorus element, and more preferably 0.03 to 0.08% in terms of the amount of phosphorus element.

  As said ashless type | system | group dispersing agent, it mix | blends in the ratio of 5 to 10% normally, As a kind, polyalkenyl succinimide, polyalkenyl succinic acid ester etc. are mentioned, for example. Moreover, it is also possible to mix | blend the boronation derivative | guide_body of these compounds (for example, refer Japan patent 1336796, 1667140, 1302811, 1743435).

  Examples of the antioxidant include 2-t-butylphenol, 2-t-butyl-4-methylphenol, 2-t-butyl-5-methylphenol, 2,4-di-t-butylphenol, and 2,4. -Dimethyl-6-t-butylphenol, 2-t-butyl-4-methoxyphenol, 3-t-butyl-4-methoxyphenol, 2,6-di-t-butylphenol, 2,6-di-t-butyl -4-methylphenol, 2,6-di-t-butyl-4-ethylphenol, 2,6-di-t-butyl-4-methoxyphenol, 2,6-di-t-butyl-4-ethoxyphenol 3,5-di-tert-butyl-4-hydroxybenzylmercapto-octyl acetate, n-dodecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propiyl 2'-ethylhexyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 2,6-di-t-butyl-α-dimethylamino-p-cresol, 4,4 ' -Methylenebis (2,6-di-t-butylphenol), 4,4'-bis (2,6-di-t-butylphenol), 2,2-bis (3,5-di-t-butyl-4-) Hydroxyphenyl) propane, 4,4'-cyclohexylidenebis (2,6-tert-butylphenol), hexamethylene glycol bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] ( Ciba Specialty Chemicals: Irganox L109), 2,2'-thio- [diethyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) pro ONATE] (manufactured by Ciba Specialty Chemicals: Irganox L115), tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane (manufactured by Ciba Specialty Chemicals) : Irganox L101), 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene (manufactured by Shell Japan: Ionox330), bis- [ 3,3′-bis- (4′-hydroxy-3′-t-butylphenyl) butyric acid] glycol ester, 2- (3 ′, 5′-di-t-butyl-4-hydroxyphenyl) methyl- 4- (2 ″, 4 ″ -di-tert-butyl-3 ″ -hydroxyphenyl) methyl-6-tert-butylphenol, 2, Phenolic antioxidants such as bis (2'-hydroxy-3'-t-butyl-5'-methyl-benzyl) -4-methylphenol, p, p'-dioctyl-diphenylamine, p, p'-di -Α-methylbenzyl-diphenylamine, Np-butylphenyl-Np'-octylphenylamine, mono-t-butyldiphenylamine, monooctyldiphenylamine, di (2,4-diethylphenyl) amine, di (2- Ethyl-4-nonylphenyl) amine, octylphenyl-1-naphthylamine, Nt-dodecylphenyl-1-naphthylamine, 1-naphthylamine, phenyl-1-naphthylamine, phenyl-2-naphthylamine, N-hexylphenyl-2- Naphthylamine, N-octylphenyl-2-naphthylamine, N, Examples include amine antioxidants such as N'-diisopropyl-p-phenylenediamine and N, N'-diphenyl-p-phenylenediamine, and organic molybdenum compounds such as molybdenum dithiocarbamate and molybdenum alkylamine salts. Can be used alone or in combination. Further, the addition amount is preferably 0.01 to 5%, particularly preferably 0.1 to 3%.

As the viscosity index improver, for example, styrene-butadiene copolymer, styrene-isoprene star copolymer, polymethacrylate, ethylene-propylene copolymer and the like can be used (for example, Japanese Patent No. 954077, No. 1031507, No. 1468752, No. 1764494, No. 1751082). In addition, a dispersion type viscosity index improver obtained by copolymerizing a polar monomer containing a nitrogen atom or an oxygen atom in the molecule can also be used. These can be added at a ratio of 1 to 20%.
Moreover, as said pour point depressant, a polymethacrylate type | system | group etc. can be used, for example (for example, refer Japan patent 1195542, 1264056).
Furthermore, as said rust preventive agent, alkenyl succinic acid or its partial ester, a benzotriazole type compound, a thiadiazole type compound etc. can be used, for example.
Furthermore, as said antifoamer, dimethyl polycyclohexane, polyacrylate, etc. can be used, for example.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in full detail, this invention is not limited to these Examples.

1. Base oils Base oils 1 to 5 shown in Table 1 were prepared.

For these base oils, the oil film thickness was measured by the method described in FIG. 1 of the document SAE TECHNIC PAPER 961142, under the conditions of a sliding speed of 4.4 m / s, a Hertz pressure of 0.53 GPa, and an oil temperature of 100 ° C. .
Further, the high-temperature high shear viscosity at 100 ° C. was measured by a test method defined in ASTM D5481.
Furthermore, the kinematic viscosities at 100 ° C. and 40 ° C. were measured by the test method specified in JIS K2283.
These measurement results are shown in Table 1.

2. Lubricating oil As shown in Table 2, base oils 1 to 5 were mixed with various additives to prepare lubricating oils used in Examples 1 and 2 and Comparative Examples 1 to 5.

3. Fabrication of sliding mechanism As shown in Table 2, after a hard carbon thin film was formed on the crown surface of chromium molybdenum steel or gas soft nitriding, the sliding surface was formed by this lifter crown surface and cast iron cam. The sliding oils of Examples 1 and 2 and Comparative Examples 1 to 5 were obtained by interposing the lubricating oil on the sliding surface.
The hard carbon thin film was formed on the lifter-crown surface by the PVD arc ion plating method, the hydrogen atoms were 0.5 atomic% or less, the Knoop hardness Hk = 2170 kg / mm2, and Ry = 0.03 μm. A DLC film having a thickness of 0.5 μm was obtained.

<Fuel saving evaluation test>
Using the friction torque measuring device shown in FIG. 1, the fuel efficiency of the engine provided with the sliding mechanism obtained in the example and the comparative example was evaluated.
A 3.0-liter gasoline engine with a direct-acting mechanical tappet mechanism as a valve drive system is used as the test engine 1, and the engine speed is controlled from an idle speed to 2400 rpm by an electric motor 3 as a power source. By measuring the friction torque at 0 ° C. with the friction torque detector 2, the fuel efficiency of the engine equipped with the sliding mechanism was evaluated.

  As a result of the fuel efficiency evaluation test, the friction torque reduction rate at each engine speed based on Comparative Example 1 is shown in FIGS.

  As shown in FIGS. 2 and 3, in the sliding mechanisms of Examples 1 and 2, which are preferred embodiments of the present invention, the friction torque is reduced at each rotational speed, and the low friction characteristic of the sliding surface is remarkably high. It can be seen that it has improved.

It is the schematic which shows the friction torque measuring apparatus used by the fuel-saving evaluation test. 5 is a graph showing a friction torque reduction rate based on Comparative Example 1. 5 is a graph showing a friction torque reduction rate based on Comparative Example 1.

Explanation of symbols

1 Test Engine 2 Friction Torque Detector 3 Electric Motor

Claims (10)

A low-friction sliding mechanism composed of sliding members that slide relative to each other and a lubricating oil interposed therebetween,
The sliding member is coated with a hard carbon thin film on at least a part of the sliding surface, and the hydrogen content of the hard carbon thin film is 20 atomic% or less,
The lubricating oil includes a base oil having an oil film thickness of 95 nm or less measured under conditions of a sliding speed of 4.4 m / s, a Hertz pressure of 0.53 GPa, and an oil temperature of 100 ° C. Moving mechanism.   The low-friction sliding mechanism according to claim 1, wherein the hydrogen content of the hard carbon thin film is 10 atomic% or less.   2. The low friction sliding mechanism according to claim 1, wherein the hydrogen content of the hard carbon thin film is 0.5 atomic% or less.   The low-friction sliding mechanism according to claim 1, wherein the hard carbon thin film does not substantially contain hydrogen.   The sliding member according to any one of claims 1 to 4, wherein the surface roughness of the sliding member before coating the hard carbon thin film is 0.1 μm or less in terms of Ra. The low friction sliding mechanism as described.   The above base oil having an oil film thickness of 95 nm or less measured under conditions of a sliding speed of 4.4 m / s, a Hertz pressure of 0.53 GPa, and an oil temperature of 100 ° C. occupies 5% or more of the total base oil. The low friction sliding mechanism according to any one of claims 1 to 5.   The low-friction sliding mechanism according to any one of claims 1 to 6, wherein the lubricating oil contains a calcium salicylate detergent and an ashless friction modifier.   The addition amount of the calcium salicylate detergent is 0.5 to 10.0%, and the addition amount of the ashless friction modifier is 0.01 to 5.0%. A low friction sliding mechanism as described in 1.   The low friction sliding mechanism according to claim 7 or 8, wherein the ashless friction modifier is a compound having an oleyl group.   The low friction sliding mechanism according to any one of claims 7 to 9, wherein the ashless friction modifier includes a compound having an ester group.

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