JP2014224239A - Sliding machine - Google Patents

Abstract

A sliding machine capable of realizing a remarkably low coefficient of friction is provided by a new combination of a sliding member coated with a DLC film and a lubricating oil. A sliding machine of the present invention includes a pair of sliding members having opposed sliding surfaces that can move relative to each other, and a lubricating oil that can be interposed between the opposed sliding surfaces. At least one of the sliding surfaces has a specific element (doping element) composed of at least one of B, Ti, V, or Mo that is 1 to 30% in total when the entire film is 100 atomic%, and 0 It consists of a coated surface covered with an amorphous carbon film composed of ˜25% H and the balance of C and impurities. Further, the lubricating oil contains 25 to 800 ppm of an oil-soluble molybdenum compound having a chemical structure composed of a trinuclear body of Mo in terms of the Mo-containing mass with respect to the entire lubricating oil. [Selection] Figure 5

Description

  The present invention relates to a friction coefficient acting between sliding surfaces by an amorphous carbon film (DLC-M film) containing a specific element (M) and a lubricating oil containing an oil-soluble molybdenum compound having a specific chemical structure. The present invention relates to a sliding machine capable of significantly reducing sliding resistance and the like.

  Many machines are provided with sliding members that move relative to each other while sliding. In a machine having such a sliding member (referred to as “sliding machine” in this specification), performance is improved and operation is reduced by reducing a resistance force (sliding resistance) acting on the sliding portion. The energy required for is reduced. Such reduction in sliding resistance is usually achieved by reducing the coefficient of friction acting between the sliding surfaces.

  The friction coefficient acting between the sliding surfaces varies depending on the surface state of the sliding surface and the lubrication state between the sliding surfaces. Therefore, when reducing the friction coefficient, improvement of the surface modification of the sliding surface and improvement of the lubricant (lubricating oil) supplied between the sliding surfaces are considered. There are various types of surface modification of the sliding surface, but an amorphous carbon film (so-called diamond-like carbon (DLC) film) having low friction and excellent wear resistance is often formed on the sliding surface. . In addition, the lubricant is variously improved according to the type of sliding machine, the usage environment, etc., but is usually dealt with by adding an additive having a friction reducing effect.

  However, the characteristics of the DLC film, which is considered to have a friction reducing effect, also differ between the dry type and the wet type. Moreover, the sliding characteristics of the DLC film under wet conditions may vary depending on the type of lubricating oil interposed. Therefore, it is important to optimally combine a specific DLC film and a specific lubricating oil in order to reduce the friction coefficient. Proposals related to this are made, for example, in the following patent documents.

JP 2001-316686 A WO2005 / 14763 JP 2004-339486 A (European Patent EP 1462508 B1)

  Patent Document 1 proposes a combination of a DLC film containing Mo or Ti and a lubricating oil containing 500 ppm of molybdenum dithiocarbamate (MoDTC). Patent Document 2 proposes to combine a general DLC film not containing a metal element or the like with a lubricating oil containing 9.9% by mass of MoDTC (sulfur-containing molybdenum complex) in a Mo content ratio. MoDTC used in these patent documents is a well-known additive for engine oil, and consists of a binuclear body of Mo.

  Patent Document 3 proposes a combination of a general DLC film not containing a metal element or the like and a lubricating oil in which trinuclear molybdenum dithiocarbamate is added to the base oil in an amount of 550 ppm by Mo amount. However, Patent Document 3 only describes that the friction coefficient is reduced by the combination, and does not clarify any mechanism or the like. Further, the friction coefficient obtained by the combination is about 0.1 at most, and the reduction of the friction coefficient is still insufficient.

  As described above, some proposals have been made regarding a suitable combination of a DLC film and a lubricating oil, but a combination of a DLC film and a lubricating oil that can significantly reduce the friction coefficient has not been proposed yet. Further, the mechanism by which the friction coefficient changes depending on the combination of the DLC film and the lubricating oil has not been clarified.

  The present invention has been made in view of such circumstances, and provides a sliding machine that can reduce the coefficient of friction between sliding surfaces far more than before by a new combination of a DLC film and a lubricating oil. With the goal.

  As a result of intensive studies to solve this problem and repeated trial and error, the present inventor has obtained an amorphous carbon film (DLC-M film) containing a specific element (M) and an oil-soluble molybdenum having a specific chemical structure. It has been discovered that a new combination with a lubricant containing a compound can significantly reduce the coefficient of friction between sliding surfaces. By developing this result, the present invention described below has been completed.

《Sliding machine》
(1) A sliding machine according to the present invention includes a pair of sliding members having opposed sliding surfaces that can move relative to each other and a lubricating oil that can be interposed between the opposed sliding surfaces. Then, at least one of the sliding surfaces has a total of 1 to 30% of boron (B), titanium (Ti), when the entire film is 100 atomic% (simply referred to as “%”), Covered with an amorphous carbon film composed of a specific element composed of at least one of vanadium (V) or molybdenum (Mo), 0 to 25% of hydrogen (H), and the balance of carbon (C) and impurities. The lubricating oil comprises a coated surface, and contains an oil-soluble molybdenum compound having a chemical structure composed of molybdenum (Mo) trinuclear in a mass ratio of 25 to 800 ppm of Mo with respect to the entire lubricating oil.

(2) In the case of the present invention, a sliding surface covered with an amorphous carbon film (referred to simply as “DLC film” as appropriate) containing a specific element consisting of one or more of B, Ti, V or Mo and / or H. In the presence of a lubricating oil containing an oil-soluble molybdenum compound having a specific chemical structure, the coefficient of friction between sliding surfaces is significantly reduced. Specifically, in the case of the present invention, ultra-low friction with a friction coefficient of 0.04 or less, 0.03 or less, or about 0.02 may occur. As a result, the sliding machine according to the present invention can significantly reduce sliding resistance and friction loss, and can achieve remarkable improvements such as motion performance and energy saving. The sliding machine of the present invention that exhibits such a low friction characteristic is suitable for a drive system machine (for example, an engine or a transmission) that operates under severe conditions from boundary lubrication conditions to mixed lubrication conditions.

  The DLC film according to the present invention does not necessarily contain H. As long as the DLC film contains a specific element, the DLC film does not substantially contain H (H content is 0 to 25%, further 0.1 to 24%). Or a low HDLC film having an H content of 0 to 5%, 0.5 to 4%, or even 1 to 3%. Such a DLC film can also exhibit very excellent wear resistance in combination with the low friction characteristics described above. On the contrary, when the DLC film according to the present invention contains an appropriate amount of H, the low friction characteristics can be further improved. In this case, the H content is preferably 5 to 25%.

(3) Although the mechanism by which the combination of the specific DLC film and the lubricating oil according to the present invention exhibits a very excellent friction reducing effect is not necessarily clear, the present inventors have intensively studied, and the present situation is as follows: Conceivable.

  In the case of the DLC film according to the present invention, in a portion where a specific element (one or more of B, Ti, V or Mo) is present, an oil-soluble molybdenum compound composed of a trinuclear body of Mo contained in lubricating oil (simply referred to as “Mo”). Adsorption reaction of “trinuclear compound”) is promoted. As a result, the adsorption reaction on the sliding surface (DLC film) of other additives having a competitive adsorption relationship with the Mo trinuclear compound or its constituent elements is suppressed.

  For example, when there is no Mo trinuclear compound, additives such as overbased Ca sulfonate, which are often added to lubricating oil, are adsorbed on the sliding surface and have a thickness (height) exceeding 10 nm. The compound can be generated unevenly and fine convex portions (projections) can be formed on the sliding surface. Such fine convex portions cause a friction coefficient to increase under boundary lubrication (or mixed lubrication). However, in the sliding machine of the present invention, as described above, the DLC film containing the specific element and the lubricating oil containing the Mo trinuclear compound act synergistically, and as a result, other additives are adsorbed on the sliding surface. This prevents the situation where the surface roughness of the sliding surface increases. In this way, the sliding surface according to the present invention can form fine convex portions by adsorption reaction of other additives, etc. at least after the sliding machine has been trial run and the DLC film and the lubricating oil are in sufficient contact. It can be an extremely smooth surface (for example, the surface roughness (maximum height) is 5 nm or less, further 2 nm or less). And, such a smooth sliding surface moves relative to each other with an oil film made of lubricating oil, so that the fine direct contact between the sliding surfaces is avoided, and the friction coefficient between the sliding surfaces is remarkably reduced. it is conceivable that.

  Furthermore, the DLC film according to the present invention is usually harder than the base material (for example, steel) of the sliding member and has a characteristic that it is difficult to transfer to the sliding surface on the sliding counterpart side. For this reason, the sliding surface according to the present invention is considered to maintain the above-described smooth state stably even during the operation of the sliding machine, to stably achieve low friction and to exhibit high wear resistance. .

The Mo trinuclear compound according to the present invention adsorbs and reacts with the sliding surface, thereby converting the molybdenum sulfide compound having a chemical structure such as Mo ₃ S ₇ , Mo ₃ S ₈ , Mo ₂ S ₆ into the sliding surface. Can be formed on top. Since these molybdenum sulfide compounds have a structure similar to molybdenum disulfide (MoS ₂ ), it is presumed that the low shear characteristics based on the layered structure are exhibited between the sliding surfaces as well as molybdenum disulfide. As a result, direct contact between the sliding surfaces can be avoided, and the boundary friction coefficient can be reduced. Such a point is also considered to contribute to the reduction of the macro coefficient of friction.

(4) The Mo trinuclear body according to the present invention is made of, for example, Mo ₃ S ₇ or Mo ₃ S ₈ , and particularly preferably Mo ₃ S ₇ . As long as the Mo trinuclear compound according to the present invention has a skeleton (molecular structure) composed of such a trinuclear body, there is no limitation on the functional group, molecular weight, or the like bonded to the terminal. For reference, an example of a molybdenum sulfide compound made of Mo ₃ S ₇ is shown in FIG. R in FIG. 19 is a hydrocarbyl group.

<Others>
(1) The “sliding machine” referred to in the present invention is sufficient if it includes a sliding member and lubricating oil, and is not limited to a finished machine as a machine, but may be a combination of machine elements constituting a part thereof. For this reason, the sliding machine of the present invention can be restated as a sliding structure, a sliding system, or the like.

  The coated surface of the DLC film according to the present invention may be formed on at least one sliding surface of the opposed sliding members that move relative to each other. Of course, it is more preferable that both facing sliding surfaces are covered with a DLC film.

(2) Unless otherwise specified, “x to y” in this specification includes a lower limit value x and an upper limit value y. A range such as “a to b” can be newly established with any numerical value included in various numerical values or numerical ranges described in the present specification as a new lower limit value or upper limit value.

It is a schematic diagram which shows the mode of a block on-ring friction test. It is a figure which shows the principal part which detects a frictional force by an engine valve system friction test. It is a bar graph which shows the friction coefficient which concerns on a block on-ring friction test when combining each conventional engine oil and each DLC film. It is a bar graph which shows the friction coefficient which concerns on a block on-ring friction test when combining trial manufacture A type oil which mix | blended various friction modifiers (FM), and 6B-DLC. It is a bar graph which shows the friction coefficient which concerns on a block-on-ring friction test when trial production B type oil which mix | blended Mo type FM and 6B-DLC is combined. It is a graph which shows the friction coefficient which concerns on a block on-ring friction test when combining trial manufacture B type oil and 6B-DLC from which the compounding quantity of Mo trinuclear compound or MoDTC differs. It is a bar graph which shows the friction coefficient which concerns on a block on-ring friction test when combining trial manufacture B type oil which mix | blended Mo trinuclear body compound, and various sliding members. GF-5 development oil C containing Mo trinuclear compound or GF-5 development oil A containing no Mo trinuclear compound and various sliding members It is a bar graph which shows a friction coefficient. It is a bar graph which shows the friction coefficient which concerns on an engine valve system friction test when combining each lubricating oil and each sliding member (shim). It is a three-dimensional view showing the nanoscale surface shape of the initial surface (sliding surface before the test) of 6B-DLC and various sliding surfaces after the block-on-ring friction test observed by SPM. It is a three-dimensional figure which shows the nanoscale surface shape which observed each sliding surface of 6B-DLC after a block-on-ring friction test by SPM in a wider range. It is the SEM image and AES image which observed the sliding surface of 6B-DLC after performing a block-on-ring friction test using the trial B system oil which does not mix | blend Mo trinuclear compound. It is the SEM image and AES image which observed the sliding surface of 6B-DLC after performing a block-on-ring friction test using the trial manufacture B type oil which mix | blended Mo trinuclear compound. It is a spectrum figure which paid its attention to the cations of mass number 40 vicinity of TOF-SIMS regarding the sliding surface after the block on-ring test performed combining various engine oil and DLC film. It is a spectrum figure which paid its attention to the anion of the mass number 300-600 vicinity of TOF-SIMS regarding the sliding surface after the block on-ring test performed combining various engine oil and DLC film. It is a figure which shows the count number (B) of ⁴⁰ Ca ⁺ based on the secondary ion mass spectrum of TOF-SIMS, and a friction coefficient. TOF-SIMS secondary ion mass spectra ⁹⁸ Mo ₃ based on S ₇ ^- is a graph showing count (A) and the relationship between the friction coefficient. ⁴⁰ Ca ⁺ and ⁹⁸ Mo ₃ S ₇ ^- is a graph showing a relationship between the count ratio (A / B) and the coefficient of friction. It is a molecular structure figure showing an example of Mo trinuclear compound concerning the present invention. It is a bar graph which shows the friction coefficient which concerns on a block on-ring friction test when combining GF-5 development oil C which mix | blended Mo trinuclear compound, and various sliding members. It is a bar graph which shows the wear depth which arose in each sliding member by the friction test. It is a figure which shows the sliding surface of each sliding member after the friction test. It is a dispersion | distribution figure which shows the relationship between B content in a DLC film, and a friction coefficient.

  One or two or more components arbitrarily selected from the present specification may be added to the above-described components of the present invention. The contents described in this specification are applicable not only to the entire sliding machine of the present invention, but also to the sliding members and lubricating oil constituting it as appropriate, and even if it is a structural component, it is a configuration related to an object. Can also be an element. Which embodiment is the best depends on the target, required performance, and the like.

"Lubricant"
As long as the lubricating oil according to the present invention contains a Mo trinuclear compound, the type of base oil, the presence or absence of other additives, etc. may be used. Usually, lubricating oils such as engine oils contain various additives including S, P, Zn, Ca, Mg, Na, Ba or Cu. Among such lubricating oils, the Mo trinuclear compound according to the present invention preferentially acts on the sliding surface (coated surface) coated with the DLC film, and the surface roughness of the coated surface by other additive elements. The generation of a compound that degrades is caused by an adsorption reaction or the like. The lubricating oil according to the present invention may contain a Mo-based compound other than the Mo trinuclear compound (for example, MoDTC, molybdenum disulfide, etc.).

  If the amount of the Mo trinuclear compound is too small, the above-described effects are hardly exhibited, but there is no problem if the amount of the Mo trinuclear compound is excessive. However, since Mo is a kind of rare metal, the amount used is preferably as small as possible. Therefore, the Mo trinuclear compound according to the present invention is preferably 5 to 800 ppm, 10 to 500 ppm, 25 to 300 ppm, 40 to 220 ppm, or even 80 to 170 ppm in terms of the mass ratio of Mo to the entire lubricating oil. In addition, when the mass ratio of Mo with respect to the whole lubricating oil is expressed in ppm, it is expressed as ppmMo. Incidentally, when Mo-based compounds other than the Mo trinuclear compound are included in the lubricating oil, the total amount (total mass ratio) of Mo contained in the lubricating oil is naturally different from the above range, but Mo with respect to the entire lubricating oil The upper limit of the total amount is preferably 400 ppmMo, more preferably 350 ppmMo.

<Sliding surface of sliding member>
The sliding member according to the present invention may be of any type, form, sliding form, etc. as long as it has a sliding surface that moves relative to the lubricating oil. In the case of the present invention, if a DLC film containing a specific element is coated on at least one of a pair of opposed sliding surfaces that move relative to each other, the friction coefficient between the sliding surfaces is obtained by the combination with the lubricating oil described above. Can be significantly reduced. In particular, by matching the composition of the DLC film and the lubricating oil, the sliding machine of the present invention has an ultra-low friction characteristic such that the friction coefficient between the sliding surfaces is 0.03 or less, or even near 0.02. Can demonstrate.

  The reason why such a remarkable low friction characteristic is exhibited is that the sliding surface (coated surface) covered with a specific DLC film faces in the presence of lubricating oil containing Mo trinuclear compound. It is mentioned that the surface shape (surface roughness) of the coated surface becomes very smooth by sliding contact with the surface. The degree of smoothness of the coated surface may vary depending on the type of DLC film and lubricant, sliding conditions, etc. For example, a 1 μm × 1 μm square measurement area can be measured against the sliding direction using an atomic force microscope. The surface roughness when measured by scanning in the vertical direction can be 8 nm or less, 5 nm or less, or 2 nm or less as the maximum height (Rmax). Furthermore, even if the measurement area of the coated surface according to the present invention is expanded to 10 μm × 10 μm, Rmax can be within the above range.

The reason why such a noticeable smooth surface is formed is that, as described above, the Mo trinuclear compound contained in the lubricating oil inhibits the generation of a compound that deteriorates the surface roughness on the coated surface. Can be mentioned. As an additive element for generating such a compound, for example, it has been found by research of the present inventor that there is Ca contained in a large amount in an engine oil detergent or the like. Therefore, when the ratio (existence ratio) of Ca ₃ and Mo ₃ S ₇ having a typical chemical structure constituting the Mo trinuclear body on the coated surface was investigated, it was correlated with the friction coefficient between the sliding surfaces. It became clear that there was. Specifically, when the coated surface according to the present invention analyzes the outermost surface using time-of-flight secondary ion mass spectrometry (TOF-SIMS) using Bi ⁺ as a primary ion, a negative ion spectrum is obtained. The count number (A) of the peak attributed to ⁹⁸ Mo ₃ S ₇ ⁻ appearing near the mass number 517.4 measured with respect to ⁴⁰ Ca ⁺ appearing near the mass number 40.0 measured regarding the positive ion spectrum. When the count number ratio (A / B), which is the ratio with the count number (B) of the attributed peak, is 0.006 or more, further 0.01 or more, excellent low friction characteristics can be exhibited. all right. Therefore, on the premise that the sliding surface according to the present invention is coated with a specific DLC film, the lubricating oil according to the present invention has a low Ca content, and the Mo trinuclear compound (especially from Mo ₃ S _7). It can be said that the more the Mo compound), the easier it is to reduce the coefficient of friction between the sliding surfaces. However, since it is sufficient if the ratio between the two is within a certain range, if the content of additive elements that can degrade the surface roughness of the coated surface is small, the Mo trinuclear compound can be reduced accordingly. Is possible.

<< DLC film >>
(1) Composition The DLC film according to the present invention is formed on at least one sliding surface and doped with a predetermined specific element (M). Specifically, the DLC film according to the present invention has at least one or more of B, Ti, V, or Mo, which is 1 to 30% or 5 to 25% in total when the entire film is 100 atomic%. The specific element (M) consisting of When M is too small, the interaction with the Mo trinuclear compound does not function sufficiently, and when M is excessive, it is difficult to form a good DLC film. Note that M may be one or more of B, Ti, V, or Mo, but when M is B or V, particularly excellent low friction characteristics can be exhibited.

  It has also been found that when the DLC film according to the present invention contains H, low friction characteristics are easily exhibited. H is preferably 0 to 25%, 5 to 25%, 10 to 22%, and more preferably 15 to 20% when the entire film is 100 atomic%. An H-free DLC film substantially free of H or a low HDLC film with a low H content exhibits both low friction and wear resistance at a high level. As the amount of H in the DLC film increases, the low friction characteristics are further improved. However, if H is excessive, the DLC film becomes excessively soft and its wear resistance can be reduced.

  In addition to the elements described above, the DLC film according to the present invention may contain a modifying element or an unavoidable impurity that improves its sliding characteristics. Examples of such elements include O, Al, Mn, Si, Cr, W, and Ni. The content of these elements is not limited, but it is preferably less than 8 atomic% or even less than 4 atomic%. Note that the composition of the DLC film may be homogeneous, slightly changed, or even inclined in the thickness direction.

(2) Structure / Characteristic The DLC film according to the present invention has an amorphous structure in the same manner as the conventional DLC film, but it is more preferable that the DLC film is substantially free of carbides and has a non-oriented structure.

  Although the base material (or the base material of the sliding member) on which the DLC film is formed is not limited, it is preferable that the DLC film is harder than the base material and has a smaller elastic modulus than the base material. Thereby, the wear resistance, toughness or impact resistance of the coated surface according to the present invention can be improved. For example, the DLC film according to the present invention preferably has a hardness of 10 to 30 GPa, more preferably 14 to 25 GPa. If the hardness is too low, the wear resistance is lowered, and if the hardness is too high, the DLC film is liable to crack. Further, from the same viewpoint, the elastic modulus of the DLC film is preferably, for example, 100 to 200 GPa, 110 to 190 GPa, 120 to 180 GPa, or 130 to 170 GPa.

(3) Film formation method The film formation method of the DLC film is not limited. For example, a sputtering method, particularly an unbalanced magnetron sputtering (UBMS) method, is preferable because a dense DLC film can be efficiently formed.

Before forming the DLC film, it is preferable to evacuate the chamber to 10 ⁻⁵ Pa or less, or introduce hydrogen gas into the chamber to remove oxygen and moisture remaining in the chamber before film formation. The amount of hydrogen gas introduced may be adjusted according to the amount of H in the DLC film.

As the sputtering gas, for example, one or more of rare gases such as argon (Ar) gas, helium (He) gas, and nitrogen (N ₂ ) gas can be used. As the H-containing gas, one or more hydrocarbon-based gases such as methane (CH ₄ ), acetylene (C ₂ H ₂ ), and benzene (C ₆ H ₆ ) can be used.

The gas flow rate may be, for example, noble gas: 200 to 500 sccm and hydrocarbon gas: 10 to 25 sccm. In addition to these, H ₂ gas: 1 to 25 sccm may be introduced to reduce mixing of O and impurities in the film. The unit: sccm is a flow rate at room temperature of atmospheric pressure (1013 hPa).

  The film forming temperature of the DLC film is preferably 150 to 300 ° C., since it can suppress the formation of carbides. The film formation temperature is the surface temperature of the base material during film formation, and can be measured by a thermocouple or a heat radiation thermometer.

  In addition, it is preferable to perform sputtering with a gas pressure of 0.5 to 1.5 Pa, a power applied to the target of 1 kW to 3 kW, and a magnetic field strength in the vicinity of the base material (sliding surface) of 6 to 10 mT. Further, a negative bias voltage of 100 to 500 V may be applied to the substrate.

  In addition to the sputtering method, a DLC film may be formed by an arc ion plating (AIP) method. The AIP method is a method of forming a DLC film on the surface of a substrate by causing arc discharge in a vacuum and reacting C and B evaporated from each target with a processing gas in a reaction vessel.

<Application>
The sliding machine of the present invention can be widely applied to a wide variety of machines and devices regardless of its specific form and application. In particular, the sliding machine of the present invention expresses an ultra-low friction characteristic in which the friction coefficient between sliding surfaces becomes very small. It is suitable for. For example, the sliding machine of the present invention is suitable for driving system units such as engines and transmissions mounted on automobiles and the like, and sliding bodies constituting a part of them. The sliding body here is a shaft and a bearing, a piston and a liner, meshing gears, a pump, and the like. The sliding members constituting such a sliding body include, for example, a cam, a valve lifter, a follower, a shim, a valve, a valve guide, etc. that constitute a valve system, a piston, a piston ring, a piston pin, a crankshaft, Gears, rotors, rotor housings and the like.

The present invention will be described more specifically with reference to examples.
[Example 1]
《Sliding member》
As test materials to be the sliding members, the following evaluation materials for block-on-ring friction test and evaluation materials for engine valve system friction test were prepared.

<Evaluation material for block-on-ring friction test>
(1) Base Material A block-shaped (6.3 mm × 15.7 mm × 10.1 mm) steel material (JIS SUS440C) subjected to quenching treatment was prepared as a base material. Various DLC films shown in Table 1 were formed on the mirror-finished surface (surface roughness Rzjis 0.1 μm / sliding surface) of the steel as described below. In addition, as a comparative evaluation material not coated with a DLC film, a steel material (JIS SCM420) just carburized was also prepared. The carburized surface (hardness HV800) was also a mirror-finished surface having the same surface roughness. In this way, each block test piece for the block-on-ring friction test was prepared. In addition, the test piece which provided the DLC film | membrane on the sliding surface is represented using the name (refer Table 1) of the DLC film, and the test piece which did not provide the DLC film | membrane on a sliding surface is only represented as "steel material." The same applies to the engine valve friction test described later.

(2) Formation of DLC film The above DLC film was formed using an unbalanced magnetron sputtering apparatus (UBMS504 manufactured by Kobe Steel, Ltd.). Specifically, it is as follows. First, before forming the DLC film, an intermediate layer was formed on the surface of the substrate that had been mirror-finished in advance. The inside of the sputtering apparatus was evacuated to 1 × 10 ⁻⁵ Pa, and a pure chromium target arranged to face the substrate surface was sputtered with Ar gas. Thus, a Cr film was formed on the substrate surface. Subsequently, CH ₄ gas was introduced into the apparatus to form a Cr—C film on the surface of the Cr film. Thus, an intermediate layer having a total thickness of about 0.8 μm was formed. Throughout this example, the distance between the substrate surface and the target surface was adjusted to 100 to 800 mm. In addition, the film thickness was specified by Caltest made by CMS (hereinafter the same).

Next, various dope targets and graphite targets, which are dope element (specific element) sources arranged opposite to the substrate surface, were sputtered with Ar gas. Subsequently, 200 sccm of Ar gas, 10 sccm of CH ₄ gas (hydrocarbon gas) and 1 sccm of H ₂ gas were introduced into the apparatus. At this time, the gas pressure in the apparatus was 0.7 Pa. Thus, evaluation materials in which various DLC films were formed on the intermediate layer were obtained. The thickness of each DLC film was about 1.5 μm. Further, B ₄ C was used as a doping target when the doping element was B. When the doping elements were Ti, V, and Mo, each pure metal was used as a doping target. The DLC film (D7) having no doping element and containing a large amount of H was formed by changing the doping target to C and introducing CH ₄ gas. The H-free DLC film (D6) was formed by the arc ion plating method described in Japanese Patent Application Laid-Open No. 2004-115826.

(3) Film composition The film composition of each DLC film shown in Table 1 was measured as follows. The doping element in the film was quantified by electron probe microanalysis (EPMA), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), or Rutherford backscattering method (RBS). H was quantified by elastic recoil detection method (ERDA). ERDA is a method of measuring the hydrogen concentration by irradiating the surface of a film with a 2 MeV helium ion beam, detecting hydrogen ejected from the film with a semiconductor detector. The composition of each DLC film thus obtained is also shown in Table 1.

(4) Film structure Using a transmission electron microscope (TEM), the electron beam was irradiated to the cross-sectional center part of the thickness direction of each DLC film, and the electron-diffraction image was obtained. From each electron beam diffraction image, a halo pattern was observed, and each DLC film was found to have an amorphous structure.

(5) Surface Hardness and Surface Roughness The surface hardness of each DLC film was determined from the measured values with a nanoindenter testing machine (MTS manufactured by Toyo Corporation). The surface hardness of the DLC film thus obtained is also shown in Table 1. In addition, unless otherwise indicated, such as when using SPM mentioned later, the surface roughness said by this specification was measured with the white interferometry non-contact surface shape measuring machine (NewView5022 by Zygo).

<Evaluation materials for engine valve friction test>
A shim that contacts the cam of an internal combustion engine (gasoline engine) was prepared as an evaluation material for an engine valve system friction test. Each shim is the same as the block test piece for the block-on-ring friction test described above, but the mirror-finished substrate (JIS SUS440C) surface is coated with H-free-DLC and 6B-DLC shown in Table 1. is there. For comparison, a shim (commercially available repair part) made of carburized steel without a DLC film was also prepared.

"Lubricant"
(1) In the block on-ring friction test and the engine valve system friction test, various engine oils shown in Table 2 were prepared as lubricating oils used in combination with the above-described sliding member (test piece). Specifically, it is as follows. First, three types of developed oil corresponding to the ILSAC GF-5 standard with a viscosity grade of 0W-20 were prepared. These are referred to as GF-5 developed oil A, GF-5 developed oil B, and GF-5 developed oil C, respectively.

  Next, based on GF-5 developed oil A, Mo trinuclear compound described as “Trinuclear” in the published material “Molybdenum Additive Technology for Engine Oil Applications” of Infineum (as appropriate, simply as an oil additive) An oil was also prepared in which “Mo trinuclear body” was additionally blended so that the Mo content in the oil was equivalent to 150 ppm Mo. This is called GF-5 development oil A reform.

  GF-5 development oil A and GF-5 development oil B do not contain Mo trinuclear compound, but GF-5 development oil C contains 80 ppm Mo of Mo trinuclear compound. Moreover, none of these oils (lubricating oils L0 and L110 to 130 shown in Table 2) contain molybdenum dithiocarbamate (MoDTC).

(2) As a model engine oil with further simplified components, hydrocracked mineral oil YUBASE8 (dynamic viscosity 8 mm ² / s at 100 ° C.) manufactured by SK Corporation, secondary ZnDTP manufactured by Lubrizol, overbased Ca Prototype A oils containing only three types of sulfonate and alkenyl succinimide were prepared.

  In addition, five types of FM blended oils were prepared in which only one type of each of different types of friction modifiers (hereinafter referred to as “FM”) was added to the prototype A-based oil. Each FM and the amount blended were glycerol monooleate (Reodol Mo-50 manufactured by Kao Corporation, which is referred to as “GMo”): 1.0% by mass, oleylamine (Armin OD manufactured by Lion Corporation, this “amine” 1.0 mass%, fatty acid amide (Fatty Acid Amide O-N manufactured by Kao Corporation, hereinafter referred to as “amide FM”): 1.0 mass%, molybdate amine (stock) Sakuralube 700 manufactured by ADEKA, which is referred to as “Mo amine”): either 0.34 mass% (equivalent to 150 ppm Mo) or Mo trinuclear compound: 0.36 mass% (200 ppm Mo). These FM blended oils will be referred to as “Prototype A oil reform 1 to Prototype A oil reform 5” as appropriate.

Note that the viscosity index improver is not blended in the prototype A-based oil. As described above, the base oil of the prototype A-based oil has a kinematic viscosity at 100 ° C. of 8 mm ² / s because it is the same level as the engine oil of viscosity grade 0-20W.

(3) Further, a prototype B-series oil was prepared by blending 8.0 mass% of the API standard SN grade gasoline engine oil additive package (PV1020 manufactured by Lubrizol) into the mineral oil YUBASE8 serving as the base oil described above.

  Moreover, 0.05 to 0.36 mass% (equivalent to 25 to 200 ppm Mo) of the Mo trinuclear compound described above or 0.10 to 0.61 mass% of the MoDTC manufactured by Infineum Co. Nine types of FM blended oils each containing 50 to 300 ppm Mo) were prepared. These FM blended oils are referred to as Prototype B oil reform 1 to Prototype B oil reform 9 as appropriate. The trial B oil does not contain a viscosity index improver, similar to the trial A oil. In addition, as shown in Table 2, the prototype A oil and the prototype B oil have amounts of S, Zn, P, N, and Ca, which are elemental components of typical engine oil additives, as shown in Table 2. The level was adjusted to approximately the same level as C.

(4) For comparison, a commercially available engine oil (manufactured by Toyota Motor Corporation, Motor Oil SL 5W-30) was also prepared. This is referred to as “GF-3 commercial oil”.

《Block-on-ring friction test》
In the block-on-ring friction test shown in FIG. 1, the friction coefficient (abbreviated as “μ” as appropriate) when each sliding member and each engine oil were combined was measured. In this test, the block test piece side with a sliding surface width of 6.3 mm was used as an evaluation material, and a ring test piece with an outer diameter of φ35 mm and a width of 8.8 mm as a counterpart was made of carburized steel (AISI 4620). A −10 standard test piece (hardness HV800, surface roughness 1.7 to 2.0 μm Rzjis) was used. The test load was 133 N, the sliding speed was 0.3 m / s, the oil temperature was 80 ° C. (constant), a 30-minute friction test was performed, and the μ-average value for 1 minute immediately before the end of the test was used as the friction coefficient in this test. .

<Engine valve friction test>
Cam / sim that partially reproduces the cam and disc-shaped follower (simply called “Shim”) that make up the direct-acting engine valve system of an actual machine (Toyota Motor Corporation in-line 4-cylinder gasoline engine 5A-FE) The friction force during one rotation of the camshaft was measured using an inter-friction tester. The μ average value converted from this frictional force was used as the friction coefficient in this test. Based on this friction coefficient, the friction reduction effect when each sliding member (in this test, a shim having a sliding surface coated with a DLC film) and each engine oil was examined.

  The frictional force was detected by detecting the strain amount of the leaf spring provided between the shim holder that holds the shim and the valve lifter with a strain gauge, as shown in FIG. Details of the testing machine used in this test are described in Tribology Conference Proceedings of the Japanese Society of Tribology, Tokyo 20011-5, P.419-P.420 “Friction Loss Reduction of Direct Stroke Valve System”.

<Evaluation of friction characteristics>
(1) Combination with Conventional Engine Oil FIG. 3 shows a friction coefficient related to a block-on-ring friction test obtained by combining conventional engine oil (lubricating oils L0 to L130) and various DLC films.

  When GF-3 commercial oil is used, 6Ti-DLC and 6B-DLC have low friction characteristics compared to steel. However, when GF-5 developed oil A and GF-5 developed oil B satisfying the current engine oil standard GF-5 are used, the friction coefficient of 6Ti-DLC and 6B-DLC is the same as that of GF-3 commercial oil. It is increasing compared to this. In this case, it can be seen that the DLC film hardly exerts a friction reducing effect on the steel material.

  In other words, in the case of engine oils that do not contain MoDTC, such as GF-5 developed oil A and GF-5 developed oil B, the sliding surface is covered with a DLC film such as 6Ti-DLC or 6B-DLC. However, it can be seen that a reduction in μ cannot be achieved. In addition, with the revision of the engine oil standard, the GF-3 standard oil has been abolished, and it is necessary to ensure low friction characteristics along the current GF-5 standard oil. From this result, it is of great significance to clarify the combination of DLC film and engine oil (lubricating oil) suitable for obtaining the desired low μ characteristics.

(2) Identification of effective engine oil (additive) suitable for 6B-DLC Using a block-on-ring friction test, the friction coefficient when combining a trial oil A with various FM and 6B-DLC This is shown in FIG. As is clear from FIG. 4, it was clarified that by adding the Mo trinuclear compound, the friction coefficient becomes about 0.02, and a very excellent low friction characteristic (ultra-low μ characteristic) can be obtained. . On the other hand, it can be seen that the low friction characteristics cannot be obtained except when the Mo trinuclear compound is blended, which is not much different from the case where the FM is not blended.

  FIG. 5 shows the result of comparing the friction coefficient when combining the trial B-series oil blended with Mo trinuclear compound or MoDTC and 6B-DLC with the same Mo content (150 ppm Mo). Even in the trial production B oil blended with the API standard SN grade additive package, when the Mo trinuclear compound was blended, ultra-low μ characteristics were obtained. On the other hand, when MoDTC was blended, there was almost no reduction in the coefficient of friction with no significant difference from the case of non-blending.

(3) Mixing amount of Mo trinuclear compound suitable for 6B-DLC Using block B-ring friction test with 6B-DLC and prototype B-type oil in which the mixing amount of Mo trinuclear compound or MoDTC is changed The result of measuring the friction coefficient is shown in FIG.

  In the case of the Mo trinuclear compound, the friction coefficient decreases to about 0.03 with a blending amount of only 50 ppm Mo, and it can be seen that the ultra-low μ state is maintained even if the Mo trinuclear compound increases. On the other hand, it can be seen that the coefficient of friction of MoDTC decreases with the blending amount, and about 300 ppm Mo is necessary to reduce the coefficient of friction to about 0.03. Therefore, if the Mo trinuclear compound is used, an ultra-low μ characteristic equivalent to or higher than that of MoDTC can be obtained with a blending amount of about 1/5 to 1/6 of MoDTC. From this result, by using the Mo trinuclear compound, it is possible to reduce the amount of Mo used as a kind of rare metal and to reduce the cost of engine oil.

(4) Identification of DLC film suitable for blended oil of Mo trinuclear compound Using B-system trial oil modified 5 blended with Mo trinuclear compound, sliding member is 6B-DLC, H-free-DLC and steel FIG. 7 shows the coefficient of friction related to the block-on-ring friction test. The friction coefficient of H-free-DLC is about 0.06, which is slightly smaller than the friction coefficient of steel (about 0.08), but still much larger than that of 6B-DLC (about 0.02). . Therefore, even when the Mo trinuclear compound is added, not all DLC films can obtain ultra-low μ characteristics, and at least from FIG. 7, DLC films not containing H cannot obtain ultra-low μ characteristics. I understand.

  The μ characteristics related to the block-on-ring friction test when the GF-5 developed oil C containing the Mo trinuclear compound and the sliding member coated with various DLC films are combined are shown in FIG. For comparison, μ characteristics when GF-5 developed oil A not containing a Mo trinuclear compound and each sliding member are combined are also shown.

  When GF-5 development oil C containing Mo trinuclear compound is used, excellent low μ characteristics by combining with sliding member covered with DLC film containing B, V, Ti or Mo It can be seen that In particular, the friction coefficient when combined with a DLC film doped with B or V is low. On the other hand, like the H-free-DLC shown in FIG. 7, when combined with 26H-DLC, the friction coefficient decreased slightly.

  In addition, when GF-5 developed oil A not containing Mo trinuclear compound is used, no reduction in the friction coefficient is observed when combined with any DLC film, and particularly when combined with 6B-DLC, friction is not observed. The coefficient hardly decreased.

  Therefore, by combining the lubricating oil blended with the Mo trinuclear compound and the sliding member coated with the DLC film containing one or more of B, V, Ti, or Mo, extremely excellent low friction characteristics are obtained. It was revealed that it was selectively expressed.

(5) Friction reduction effect by engine valve system friction test Based on the above results, GF-5 developed oil A, GF-5 developed oil A modified or GF-5 developed oil C, 6B-DLC, H free The friction coefficient concerning the engine valve system friction test when combining DLC and steel is shown in FIG.

  The friction coefficient related to the engine valve system friction test showed the same tendency as the friction coefficient related to the block on-ring test described above. In other words, by combining an engine oil containing a Mo trinuclear compound and a sliding member coated with a specific DLC film (6B-DLC in this test), excellent low friction characteristics can be obtained selectively. It was also confirmed in this test close to the actual machine.

《Analysis of low friction characteristics》
(1) Surface shape of sliding surface The following analysis was performed in order to analyze the mechanism in which the low μ characteristic is expressed by the combination of 6B-DLC and the engine oil blended with the Mo trinuclear compound. The nanoscale surface shape of the sliding surface (after degreasing) of the block test piece subjected to the block-on-ring friction test was measured with a scanning probe microscope (manufactured by Shimadzu Corporation, SPM-9500J3, hereinafter simply referred to as “SPM”). And measured in an atomic force microscope (AFM) mode. As the SPM probe, a Si probe (PP-CONTR manufactured by Nanosensors) having a tip radius of curvature of 10 nm or less was used.

  The sliding surface after the block-on-ring friction test that can be obtained by combining a trial B oil not containing FM or a trial B oil containing a Mo trinuclear compound with 6B-DLC or H-free-DLC is 1 μm. FIG. 10 shows the result of measurement in a region of × 1 μm. Moreover, the result of having similarly measured the sliding surface (initial surface) before the test of 6B-DLC is also shown in FIG.

  First, the initial surface of 6B-DLC has fine irregularities having a height of about 50 nm. Next, when trial B-type oil not containing Mo trinuclear compound is used, the sliding surface after the 6B-DLC test has a maximum surface roughness of 10 nm or less. Compared to smoothing. Furthermore, it was found that when a prototype B-based oil containing a Mo trinuclear compound was used, the surface roughness of the sliding surface after the 6B-DLC test was an ultra-smooth surface with a maximum height of 2 nm or less. . Even when a trial B-series oil containing a Mo trinuclear compound is used, the sliding surface after the H-free DLC test is smoothed, but the surface roughness is about 20 nm at the maximum height. It was.

  The sliding surface after the block-on-ring friction test that can be obtained by combining the prototype B-based oil not blended with FM or the prototype B-series oil blended with the Mo trinuclear compound and 6B-DLC, is more extensive 10 μm × 10 μm The results of measurement in the region are shown in FIG. The micro convex part formed in the sliding surface of 6B-DLC after each test is clearly grasped by this FIG.

  The ultra-smooth surface of the sliding surface after the test that can be obtained by combining the trial B-series oil blended with the Mo trinuclear compound and 6B-DLC is at the same level as the Si wafer used for semiconductor components, and is a normal machine. It is difficult to obtain by polishing or the like. Such an ultra-smooth surface is formed by sliding combining a lubricating oil blended with a Mo trinuclear compound and a specific DLC film. When such an ultra-smooth surface is formed on the sliding surface, the oil film tends to exist stably on the sliding surface, and direct contact between the opposing sliding surfaces is suppressed. As a result, it is considered that the ultra-low μ characteristic as described above was developed as a macro phenomenon.

(2) Formation mechanism of ultra-smooth surface In order to analyze the mechanism by which the above-described ultra-smooth surface is formed, a prototype B system oil that does not contain Mo trinuclear compound or a trial B system that contains Mo trinuclear compound The sliding surface after the block-on-ring friction test when oil and 6B-DLC were combined was observed or analyzed using a scanning electron microscope (SEM) and Auger electron spectroscopy (AES). The results obtained when the Mo trinuclear compound is not blended are shown in FIG. 12, and the results obtained when the Mo trinuclear compound is distributed are shown in FIG.

  From the SEM image shown in FIG. 12, it was observed that when the engine oil containing no Mo trinuclear compound was used, many spots having a diameter of submicron or less were present on the sliding surface after the test. . This almost coincides with the distribution of the site where a large amount of Ca appears in the AES image. Ca is considered to be an adsorbate or reaction product derived from an overbased Ca sulfonate compounded as a metal detergent in engine oil.

  On the other hand, from the SEM image and the AES image shown in FIG. 13, when engine oil containing Mo trinuclear compound was used, the above-mentioned spots and Ca unevenly distributed portions were hardly observed on the sliding surface after the test. I couldn't. When the results shown in FIG. 11 and the results shown in FIG. 12 and FIG. 13 are comprehensively taken into account, when engine oil not containing a Mo trinuclear compound is used, the maximum formed on the sliding surface after the test The convex portion having a height of about 20 nm is considered to be caused by a Ca-based compound generated by an adsorption reaction on the sliding surface. On the contrary, when engine oil containing Mo trinuclear compound is used, the sliding surface after the test becomes an ultra-smooth surface because it is difficult to form such a Ca compound on the sliding surface. It is done. The reason for this is that the Mo trinuclear compound, which is in a competitive adsorption relationship with the overbased Ca sulfonate, is selectively adsorbed on a specific part (part where the doping element is present) on the DLC film covering the sliding surface, This is presumably because the overbased Ca sulfonate inhibited the adsorption reaction on the sliding surface. Here, 6B-DLC has been described. However, since a very low μ characteristic is generated in a DLC film in which the doping element is Ti, V, or Mo other than B, what kind of phenomenon occurs in the case of 6B-DLC. It is thought that it has occurred.

(3) Products on the sliding surface After analyzing the block-on-ring test in which various engine oils and DLC membranes were combined in order to analyze the factors that cause the low-μ characteristics to occur, focusing on the products on the sliding surface. The sliding surface (as appropriate, simply referred to as “friction surface”) was measured by time-of-flight secondary ion mass spectrometry (TOF-SIMS). Using a TOF-SIMS5 device manufactured by Ion-Tof, high resolution spectrum measurement was performed on a 100 μm × 100 μm measurement region on the sliding surface using a 30 keV Bi + beam as a primary ion.

  FIG. 14 and FIG. 15 show typical secondary ion mass spectra in which characteristics are recognized in the relationship between the μ characteristic and the product on the sliding surface by this measurement. In each figure, μ values obtained by the block-on-ring friction test are also shown.

FIG. 14 is a secondary ion mass spectrum of a sliding surface focusing on ⁴⁰ Ca ⁺ . When the engine oil blended with the Mo trinuclear compound and 6B-DLC are combined, it is recognized that the spectrum intensity of ⁴⁰ Ca ⁺ is small and the production of Ca-based compounds is small. In such a case, an ultra-low μ characteristic with a friction coefficient of about 0.02 was developed. On the other hand, in other cases, it is recognized that the spectrum intensity of ⁴⁰ Ca ⁺ is large and the production of Ca-based compounds is large. In this case, the friction coefficient also increased to about 0.06 to 0.08.

FIG. 15 is a secondary ion mass spectrum of a sliding surface focusing on negative ions having a mass number of 300 to 600. In the engine oil blended with the Mo trinuclear compound, generation of molybdenum sulfide compounds such as Mo ₂ S ₆ ⁻ , Mo ₃ S ₇ ⁻ , and Mo ₃ S ₈ ^— is recognized. Among these, on the sliding surface showing the ultra-low μ characteristic where the friction coefficient is about 0.02, a spectrum related to Mo ₃ S ₇ ⁻ was relatively strongly recognized. This Mo ₃ S ₇ ⁻ coincides with the chemical structure constituting the skeleton of the Mo trinuclear compound (Triumclear), as can be seen by referring to the published material “Molybdenum AddiTive TecHnology for Engine Oil ApplicaTions” by Infineum (see FIG. 19).

Based on the amount and secondary ion mass spectrum obtained by the relationship above TOF-SIMS of μ ^compounds, 40 Ca ⁺ and _{^{Mo 3 S 7 - - (4}} ) Ca compound and _Mo 3 _{S 7} of the ionic strength Paying attention, the relationship between the amount of Ca-based compound and Mo ₃ S ₇ compound produced and μ is arranged in FIGS. 16 to 18.

As shown in FIG. 16, it is difficult to recognize a clear quantitative relationship between the count of ⁴⁰ Ca ⁺ and μ. Moreover, as shown in FIG. 17, it is difficult to recognize a clear quantitative relationship between the count of Mo ₃ S ₇ ⁻ and μ. However, paying attention to the count number ratio (Mo ₃ S ₇ ⁻ / ⁴⁰ Ca ⁺ ) of both, it can be seen that a quantitative relationship clearly exists between μ as shown in FIG. That is, it is recognized that the friction coefficient is about 0.02 in a region where the count number ratio is 0.006 or more, further 0.01 or more. In other words, in the presence of lubricating oil containing the Mo trinuclear compound, a DLC film with a small amount of adsorption of the Ca-based compound and a large amount of adsorption of the Mo trinuclear compound is formed on the sliding surface. It was found that the coefficient can be made much lower than before.

[Example 2]
(1) Film formation As in the case of Example 1, after forming an intermediate layer made of a Cr-C-based film on the surface of a block-shaped steel material (JIS SUS440C), H containing B is contained on the intermediate layer. A substantially free DLC film (hereinafter simply referred to as “H-free B-DLC”) was formed. The H-free B-DLC was formed by sputtering using B ₄ C and graphite as targets. This sputtering was basically performed using an unbalanced magnetron sputtering apparatus in the same manner as in Example 1, but in the apparatus such as CH ₄ gas (also serving as C source) or H ₂ gas serving as an H source. Was not introduced.

  Thus, the film composition (atomic%) is C-11.8% B-1.6% H (appropriately expressed as “B: 12%”) and C-19.8% B-1.0% H ( 2 types of block test pieces having each H-free B-DLC on the sliding surface were prepared. The film composition and film structure were determined in the same manner as in Example 1. The reason why these H-free B-DLCs contain a slight amount of H is that residual moisture and oxygen exist in the film forming furnace.

(2) Friction test Using these block test pieces (sliding members) and the lubricating oil L130 (GF-5 developed oil C containing 80 ppm Mo of Mo trinuclear compound) shown in Table 2 of Example 1 A block-on-ring friction test was performed as in the case, and the friction coefficient of each block specimen was obtained. Further, each sliding surface after the test was measured with the above-described non-contact surface shape measuring instrument, and the wear depth and the three-dimensional shape of each sliding surface were obtained. The wear depth was defined as the distance from the non-sliding surface to the deepest portion of the sliding surface, measured based on the three-dimensional shape obtained with a non-contact surface shape measuring machine. The friction coefficient of each test piece thus obtained is shown in FIG. 20, each wear depth is shown in FIG. 21, and the three-dimensional shape of each sliding surface is shown in FIG.

  For comparison, a test piece made of the steel material (SCM420) used in Example 1, a test piece coated with 6B-DLC (D1 in Table 1), and H-free-DLC (D6 in Table 1) were used. Three kinds of comparative test pieces similar to the test pieces prepared were prepared. These test pieces were also subjected to the above-described block-on-ring friction test. The respective friction coefficients, wear depths, and sliding surface shapes thus obtained are also shown in FIGS.

(3) Evaluation As can be seen from FIG. 20, the friction coefficient of H-free B-DLC is around 0.035, which is about half of the friction coefficient (0.07) of H-free DLC not containing B. Became clear. In addition, the friction coefficient of H-free B-DLC does not change much even when its B content changes, and it has also been clarified that H-free B-DLC exhibits low friction characteristics stably.

  As can be seen from FIGS. 21 and 22, the friction coefficient of H-free B-DLC is 0.2 to 0.3 μm, which is approximately 1 / 0.1 with respect to the wear depth (0.6 μm) of H-containing B-DLCB. It became clear that it became 3-1 / 2. The wear depth of H-free B-DLC does not change much even when the B content changes, and it has also been clarified that H-free B-DLC stably exhibits high wear resistance. This is considered to be obtained by increasing the film hardness due to the H-free.

From the above, it was found that H-free B-DLC can achieve both low friction and wear resistance at a high level when used in combination with a lubricating oil containing a Mo trinuclear compound. The reason why H-free B-DLC also exhibits high wear resistance in addition to low friction characteristics is not necessarily clear, but at present, it is considered as follows. A DLC film usually has a film structure in which a C sp ² hybrid orbital component (simply referred to as “sp ² component”) and a C sp ³ hybrid orbital component (simply referred to as “sp ³ component”) are mixed. Although depending on the production method of the DLC film, in general, as the sp ³ component increases, the DLC film becomes harder and its wear resistance can be improved. Since the H-free B-DLC according to the present invention contains B and the amount of H is reduced, the sp ³ component is increased while maintaining an appropriate sp ² component, and high wear resistance is combined with low friction characteristics. It is thought that was expressed.

[Example 3]
(1) Film Formation, Friction Test and Measurement A block test piece on which a new B-DLC having a composition different from that of the B-DLC shown in Example 1 and Example 2 was further prepared and subjected to a friction test. The film forming conditions and the friction test conditions are the same as in Example 2. The friction coefficient concerning the new block test piece obtained in this way is shown in Table 3 together with the friction coefficient concerning the block test piece manufactured in Example 1 and Example 2. Further, based on Table 3, the relationship between the B content in the DLC film and the friction coefficient is shown in FIG.

  Table 4 shows the hardness and elastic modulus measured for each B-DLC film. In addition, the elasticity modulus was measured with the nano indenter test machine mentioned above similarly to hardness.

(2) Evaluation First, as is apparent from Table 3 and FIG. 23, the friction coefficient when B or the like is not contained in the DLC film is large. It was found that the coefficient decreased rapidly. And it became clear that even if the B content in the DLC film changes, a stable low friction characteristic is exhibited. In each DLC film shown in Table 3 and FIG. 23, in order to evaluate the influence of the B content, the H content in the DLC film was about 20 atomic%.

  Next, from Table 4, it was found that the hardness and elastic modulus of the DLC film increased as the H content in the DLC film increased and were not significantly affected by the B content in the DLC film. This is because, for example, Sample 31 and Sample 32 with a small change in H content and a large change in B content, or Sample 32 and Sample 33 with a large change in H content and a small change in B content, It is clear if each is compared.

Claims (6)

A pair of sliding members having opposing sliding surfaces that are capable of relative movement;
Lubricating oil that may be interposed between the opposing sliding surfaces;
A sliding machine comprising:
At least one of the sliding surfaces has a total of 1 to 30% of boron (B), titanium (Ti), vanadium (V) when the entire film is 100 atomic% (simply referred to as “%”). Or a coated surface coated with an amorphous carbon film composed of at least one specific element of molybdenum (Mo), 0 to 25% hydrogen (H), and the balance carbon (C) and impurities. ,
A sliding machine characterized in that the lubricating oil contains an oil-soluble molybdenum compound having a chemical structure composed of a trinuclear body of molybdenum (Mo) in a mass ratio of 25 to 800 ppm of Mo with respect to the entire lubricating oil.   The sliding machine according to claim 1, wherein H contained in the amorphous carbon film is 0 to 5%. A pair of sliding members having opposing sliding surfaces that are capable of relative movement;
Lubricating oil that may be interposed between the opposing sliding surfaces;
A sliding machine comprising:
At least one of the sliding surfaces has a total element of at least one of B, Ti, V, or Mo that is 5 to 30% when the entire film is 100%, and 5 to 25% of H. And the balance consists of a coated surface covered with an amorphous carbon film composed of C and impurities,
The lubricating oil contains an oil-soluble molybdenum compound having a chemical structure composed of a trinuclear body of Mo in an amount of 25 to 300 ppm in terms of the mass ratio of Mo to the entire lubricating oil. The sliding machine according to claim 1, wherein the trinuclear body is made of Mo ₃ S ₇ or Mo ₃ S ₈ .   The coated surface has a surface roughness of 8 nm at the maximum height (Rmax) measured by scanning a rectangular measuring region of 1 μm × 1 μm in a direction perpendicular to the sliding direction using an atomic force microscope. It is the following, The sliding machine in any one of Claims 1-4. The coated surface has a mass number 517.4 measured with respect to the negative ion spectrum when the outermost surface is analyzed using time-of-flight secondary ion mass spectrometry (TOF-SIMS) using Bi ⁺ as primary ions. The count number of peaks attributed to ⁹⁸ Mo ₃ S ₇ ⁻ appearing in the vicinity (A) and the count number of peaks attributed to ⁴⁰ Ca ⁺ appearing in the vicinity of the mass number 40.0 measured for the positive ion spectrum (B The sliding machine according to any one of claims 1 to 5, wherein a count number ratio (A / B), which is a ratio to (1)), is 0.006 or more.