JP2002371809A - Rocker arm coated with dlc - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability of an engine by improving wear resistance of a cam rocker arm. SOLUTION: In a transmission system provided with a cam and the rocker arm, an intermediate layer made of (a) silicide or silica carbide made mainly of at least one selected from among 5A group metal (V, Nb, Ta), 6A group metal (Cr, Mo, W), Ti and Zr, (b) a metal film made mainly of at least one selected from among the 5A group metal (V, Nb, Ta) and a metal film made mainly of a Si film or Si formed on the metal film or (c) at least one metal film selected from among the 5A group metal (V, Nb, Ta), the 6A group metal (Cr, Mo, W), Ti and Zr and a silicon carbide film formed on the metal film and at least one layer of a diamondlike carbon films are formed in this order, or the diamondlike carbon films containing H, Si and O are formed, on one surface of sliding engaged surfaces of the cam and the rocker arm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cam lobe (hereinafter simply referred to as a cam) made of a metal material used in a power transmission system for converting a driving force due to a rotational motion of a cam into a reciprocating motion of a rocker arm in an internal combustion engine such as an automobile. And a rocker arm provided with a wear-resistant coating film that slides and engages with the rocker arm.

[0002]

2. Description of the Related Art In an internal combustion engine such as an automobile engine,
2. Description of the Related Art A power transmission system for converting a driving force due to a rotational motion of a cam into a reciprocating motion of a rocker arm and transmitting the reciprocating motion to a fuel valve or the like is used. Since the cam is brought into contact with the contact object, for example, the surface of the rocker arm to transmit the driving force to the rocker arm and slides while receiving a high surface pressure, the cam surface and the contact surface of the rocker arm are significantly worn and damaged. Become. In particular, in the case of an OHC (overhead camshaft) type engine, it is important to adjust the distance between the cam and the rocker arm. If these adjustments are insufficient, problems such as a noise source may occur or the adjustment may be made. However, if these parts are severely worn, the parts may deviate from the desired intervals, causing a decrease in engine horsepower due to friction loss, which may lead to a reduction in fuel efficiency. In addition, there is a possibility that it may become unusable due to galling with the partner material.

[0003] A typical example of a power transmission system for opening and closing a fuel valve is a rocker arm type transmission system shown in FIG. 1, which is mounted on a shaft (camshaft) driven from a crankshaft for transmitting engine output. Fixed cam 3,
3 'rotates while slidingly contacting the lower surfaces of the cam followers 12, 12'. As a result, the cam becomes the rocker arm shaft 1
Power is transmitted to one ends of the rocker arms 13, 13 'supported by 5, 15' to swing them. The other end of the rocker arms 13, 13 'transmits power to the valve rods 21, 21' via retainers 19, 19 'biased by springs 17, 17', thereby allowing the fuel valve 2
3 and the exhaust valve 23 'are opened and closed at the timing of the cams 3 and 3' to supply or exhaust fuel to the piston / cylinder of the engine.

Since the contact surfaces of the cams 3, 3 'and the followers 12, 12' receive a large frictional action depending on their distance, there is a sufficiently low gap between the cam surface and the contact surface of the rocker arm. It is necessary to provide friction and wear resistance.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an excellent wear-resistant protective film which does not cause such problems. Another object of the present invention is to provide a rocker arm or a combination thereof which has good adhesion to a substrate and has a long life.

[0006]

According to the present invention, there is provided a rocker arm having the following configuration. (1) In a transmission system including a cam and a rocker arm that receives a driving force due to its rotational movement, a rocker arm is provided with a diamond-like carbon film on a surface of the rocker arm that slidably engages with the cam. arm. (2) In the above, the diamond-like carbon film is composed of carbon and hydrogen, and when its composition is represented by a molar ratio of CHn, 0.05 ≦ n ≦ 0.7 or silicon is added to the diamond-like carbon film. And may contain oxygen, nitrogen and fluorine, and the composition is CHxSi
When represented by yOzNvFw, a diamond represented by the following formula: 0.05 ≦ x ≦ 0.7 0.01 ≦ y ≦ 3.0 0 ≦ z ≦ 1.00 0 ≦ v ≦ 1.00 ≦ w ≦ 0.2 A rocker arm comprising at least one layer of a carbon-like film. (3) In the above (1), the diamond-like carbon film is made of CHxSiyOzNvFw (provided that 0.05 ≦ x ≦ 0.7 0.01 ≦ y ≦ 3.0 0 ≦ z ≦ 1.00 ≦ v ≦ 1. At least two layers of a diamond-like carbon film represented by 0 0 ≦ w ≦ 0.2) and a diamond-like carbon film represented by CHn (where 0.05 ≦ n ≦ 0.7), or A rocker arm comprising a layer that continuously changes from one of these compositions to the other. (4) In any one of the above (1) to (3), (a) a Group 5A metal (V, Nb, Ta) or a Group 6A metal between the rocker arm surface and the diamond-like carbon film. (Cr, Mo, W), a silicide or a silicide containing at least one selected from Ti and Zr as a main component,
(B) a metal film mainly composed of at least one selected from Group 5A metals (V, Nb, Ta) and a Si film or a metal film mainly composed of Si formed thereon, or (c) At least one metal film selected from Group 5A metals (V, Nb, Ta), Group 6A metals (Cr, Mo, W), Ti, and Zr, and a silicon carbide film formed thereon Rocker arm with an intermediate layer. (5) A combination of a rocker arm and a cam, wherein a diamond-like carbon film is formed on a surface of the cam that slides and engages with the rocker arm according to any one of the above (1) to (4). (6) In the above (5), the diamond-like carbon film formed on the surface of the cam is composed of carbon and hydrogen, and when its composition is represented by a molar ratio of CHn, 0.05 ≦ n ≦ 0.7 Embedded image or the diamond-like carbon film may contain silicon, and may contain oxygen, nitrogen and fluorine. When the composition is represented by CHxSiyOzNvFw, 0.05 ≦ x ≦ 0.7 Combination of rocker arm and cam composed of at least one layer of a diamond-like carbon film represented by 0.01 ≦ y ≦ 3.0 0 ≦ z ≦ 1.00 0 ≦ v ≦ 1.00 ≦ w ≦ 0.2 . (7) In the above (5), the diamond-like carbon film formed on the surface of the cam is CHxSiyOzNvFw (provided that 0.05 ≦ x ≦ 0.7 0.01 ≦ y ≦ 3.0 0 ≦ z ≦ 1.0 At least two layers of a diamond-like carbon film represented by 0 ≦ v ≦ 1.00 ≦ w ≦ 0.2) and a diamond-like carbon film represented by CHn (where 0.05 ≦ n ≦ 0.7) Or a combination of a rocker arm and a cam that forms a layer that continuously changes from one of these compositions to the other. (8) In the above (5) to (7), (a) a Group 5A metal (V, Nb, Ta) or a Group 6A metal (Cr, Mo,
W) a silicide or silicide mainly composed of at least one selected from Ti and Zr; (b) a metal mainly composed of at least one selected from Group 5A metals (V, Nb, Ta) A film and a Si film formed thereon or a metal film containing Si as a main component, or (c) a Group 5A metal (V, Nb, Ta) or a Group 6A metal (Cr, Mo,
W) a combination of a rocker arm and a cam having an intermediate layer formed of at least one metal film selected from Ti, Zr and a silicon carbide film formed thereon.

[0007]

DETAILED DESCRIPTION OF THE INVENTION The present inventors have developed a diamond-like thin film (DLC) formed on a rocker arm according to the prior art.
When the film) is used in combination with a cam having a relatively large surface roughness, the reason why large wear is caused, as a result, there is a problem in the adhesion between the rocker arm or the metal substrate of the cam and the diamond-like thin film, It has been found that long-term use becomes impossible. The present inventors have conducted intensive studies and found that the formation of a diamond-like thin film on the rocker arm (or its cam) or the use of an appropriate intermediate layer improved the adhesion and significantly improved the wear resistance. I was able to do it. Preferably, the diamond-like carbon film has at least H and S on the sliding surface of the rocker arm with the cam.
When the rocker arm or the cam and the rocker arm having the structure of the present invention in which a wear-resistant coating made of a diamond-like carbon film containing i is adopted, the surface roughness of the base material of the contact surface is precisely polished to, for example, 0.08 μm or less. No need to do
Sufficient wear resistance is provided even with a surface roughness greater than μm.

That is, according to the present invention, a diamond-like carbon film is formed on a sliding surface of a follower of a rocker arm, or
(A) a silicide or silicide containing at least one selected from Group 5A metals (V, Nb, Ta), Group 6A metals (Cr, Mo, W), Ti, and Zr;
(B) a metal film mainly composed of at least one selected from Group 5A metals (V, Nb, Ta) and a Si film or a metal film mainly composed of Si formed thereon, or (c) At least one metal film selected from Group 5A metals (V, Nb, Ta), Group 6A metals (Cr, Mo, W), Ti, and Zr, and a silicon carbide film formed thereon An intermediate layer is provided. When such an intermediate layer is formed, the diamond-like carbon film is not particularly limited, and a diamond-like carbon film containing H and a diamond-like carbon film containing H and Si can be used.

According to the present invention, it is sufficient to provide a diamond-like carbon film containing H on at least the sliding surface of the rocker arm without using an intermediate layer. If a diamond-like carbon film containing Si is formed, the adhesion is increased, and the wear resistance can be greatly improved. It is possible to further form a diamond-like carbon film containing H on the diamond-like carbon film containing H and Si, and further improvement in wear resistance can be expected. Hereinafter, the diamond-like carbon film may be abbreviated as DLC for simplicity.

The material that can be used as the base material of the rocker arm (or the shim formed on the surface of the follower of the rocker arm) (and the base material of the cam) in the present invention is any material conventionally used in the art. it can. Examples of these materials include various types of carbon steel and cast iron (grey cast iron, spheroidal graphite cast iron, malleable cast iron, alloy cast iron, etc.), cast steel, and the like.
Super tough steel (SNCM420, SCM440, SCM42
0, SCR420, H11, etc.), high speed tool steel (HSS steel: JIS standard SKH), alloy tool steel (die steel: SKD6, etc.), maraging steel (KMS180-2)
0, etc.), ausform steel, stainless steel (SUS3
04, SUS430, 17-4PH etc.), bearing steel (S
UJ2, etc.), Al alloy (AC4C, etc.), Ti alloy and the like.

[0011] The metal used as the base material may be quenched under appropriate conditions to improve the hardness of the material. For quenching, for example, induction hardening, flame quenching, carburizing quenching and the like can be used. Further, a surface hardening treatment may be performed on these substrates or on the quenched substrate, and a diamond-like carbon film or a diamond-like carbon film may be coated thereon with an intermediate layer interposed therebetween. Examples of the surface hardening include nitriding, carburizing, and boring.

Intermediate Layer Next, the intermediate layer used in the present invention comprises (a) a Group 5A metal (V, Nb, Ta) and a Group 6A metal (Cr, Mo,
W) a silicide or silicide containing at least one selected from Ti and Zr as a main component; and (b) a metal containing at least one selected from Group 5A metals (V, Nb, Ta) as a main component. A film and a Si film formed thereon or a metal film containing Si as a main component, or (c) a Group 5A metal (V, Nb, Ta) or a Group 6A metal (Cr, Mo,
W), at least one metal film selected from Ti and Zr, and a silicon carbide film formed thereon.
178736, 2000-178737, 2000
177,046, 2000-178,738, 200
0-90842 and the like.

In the case of the intermediate layer (a), the composition is M
SiaCb (where M is V, Nb, Ta, Cr, Mo,
W is at least one of W, Ti and Zr), and 0.3 ≦ a ≦ 10, preferably 1 ≦ a ≦ 6, 0
≦ b ≦ 5, preferably 0 ≦ b ≦ 3, 0.3 ≦ a + b ≦ 1
0, preferably 1 ≦ a + b ≦ 6. If a is larger than this and the amount of silicon increases, the adhesion to the base material deteriorates.
If a is smaller than this and silicon is small, the adhesion to the DLC film will be poor. When b is larger than this and the amount of carbon is large, the adhesion to the base material is deteriorated. When b is smaller than this and carbon is reduced, the adhesion to the DLC film is deteriorated. Also, if a + b is larger than this, the adhesion to the base material will be poor, and if a + b is smaller than this, the adhesion to the DLC film will be poor.

The thickness of the intermediate layer is preferably 2 nm to 5 μm, more preferably 5 nm to 1 μm. With such a thickness, the adhesion is improved. On the other hand, if the intermediate layer is too thin, the effect of improving the adhesion will not be sufficient, and if it is too thick, the impact resistance will deteriorate.

The intermediate layer of the present invention can be formed by a PVD method such as a vacuum evaporation method, a sputtering method, an ion plating method, or a thermal CVD method.
It can be formed by a CVD method such as a plasma CVD method, a photo CVD method, or the like. Wet plating, thermal spraying,
It may be formed by clad bonding or the like. Specifically, a known method is used. In particular, the intermediate layer of the present invention is preferably formed by a sputtering method. In this case, using a target according to the target composition, high-frequency power, AC power,
The target is sputtered by applying any one of DC power, and the target is sputter-deposited on a base material (substrate) to form an intermediate layer.

Usually, the target may have the same composition as that of the intermediate layer. However, it may be a multi-source sputtering using a metal such as Ta as a target and Si, or a case where C or Si is introduced by reactive sputtering. The target which does not contain the component can be used.

As the sputtering gas, an inert gas used in a usual sputtering apparatus can be used. Above all, Ar, K
r or Xe, or at least one of these
It is preferable to use a mixed gas containing at least one kind of gas.
Further, reactive sputtering may be performed. When carbon is introduced as the reactive gas, CH ₄ , C ₂ H ₂ , C _{2
When 2} H ₄ , CO or the like is used to introduce silicon, a silane gas or the like is used. When hydrogen is introduced, H
_{Use 2} etc. Even if these reactive gases are used alone,
You may mix and use 2 or more types. The operating pressure during sputtering is preferably in the range of 0.2 to 70 Pa. Further, by changing the pressure of the sputtering gas within the above range during the film formation, an intermediate layer having a concentration gradient can be easily obtained.

As the sputtering method, a high frequency sputtering method using an RF power source or a DC sputtering method may be used. The power of the sputtering apparatus is about 0.5 to 30 W / cm ^{2 for} DC sputtering, 1 to 50 MHz for high frequency sputtering, and 50 kHz to 1 MHz for low frequency.
It is preferably about 0.5 to 30 W / cm ² . The deposition rate is 1
The range of -300 nm / min is preferable. Further, the substrate temperature is preferably 10 to 150 ° C.

Further, the intermediate layer of the present invention may be formed by a vapor deposition method. The evaporation method may be a resistance heating method or an electron beam heating method. The evaporation source is Ta
Or a single vapor deposition using the same composition as the intermediate layer. 1
Even in the original deposition, a film composition substantially the same as the composition of the deposition source can be obtained stably with time. The conditions for vacuum deposition are not particularly limited, but the degree of vacuum is preferably 10 ⁻³ Pa or less, particularly preferably 10 ⁻⁴ Pa or less. The deposition rate is usually 1 to 300 nm / m
In degree is preferable.

The intermediate layer can also be formed by a plasma CVD method or an ionization vapor deposition method.
The film may be formed with reference to the LC film.

Diamond-like carbon film A diamond-like carbon (DLC) film is sometimes called a diamond-like carbon film, an i-carbon film or the like. The diamond-like carbon film is disclosed in, for example, JP-A-62-14.
Nos. 5646 and 62-145647, New
Diamond Forum, Vol. 4 No. 4 (Showa 6
Issued October 25, 2013).

The DLC film is described in the above-mentioned reference (New Diam).
as described in Raman
1550 cm for spectroscopic analysis^-1(15
20-1560cm^-11) having a peak of Raman absorption;
333cm^-1Diamonds with sharp peaks at
581cm^-1Graphite with a sharp peak at
It is a substance with a distinctly different structure. DLC film
The absorption peak in Raman spectroscopy is 1 as described above.
550cm ^-1Broad to (1520 ~ 1560cm^-1)
But has the above-mentioned elements other than carbon and hydrogen.
By having, from now on ± 100cm^-1Fluctuate
In some cases. The DLC film mainly contains carbon and hydrogen.
A thin film in an amorphous state, wherein the carbon-to-carbon sp3
Formed by the random presence of bonds
You. When the composition of the DLC film is represented by the molar ratio of CHn,
0.05 ≦ n ≦ 0.7.

In the present invention, the thickness of the DLC film is usually 1 to 10000 nm, preferably 10 nm to 3 μm.
It is.

The DLC film is made of Si in addition to carbon and hydrogen.
And may further contain one or more of O, N, and F. When the intermediate layer is not used, at least the first layer preferably contains Si in addition to hydrogen. In this case, the DLC film has a basic composition of CHxSiyOzNvF
When expressed as w, x, y, z, v, and w representing the molar ratio are respectively 0.05 ≦ x ≦ 0.7, 0.01 ≦ y ≦ 3.
0, 0 ≦ z ≦ 1.0, 0 ≦ v ≦ 1.0, 0 ≦ w ≦ 0.2
It is preferable that Also, a plurality of layers may be formed, but instead, the composition may be continuously variable in the thickness direction from a portion containing Si to a portion not containing Si.

The DLC film can be formed by a plasma CVD method, an ionization evaporation method, a sputtering method, or the like. DL
When the C film is formed by a plasma CVD method, the C film can be formed by a method described in, for example, JP-A-4-41672. Plasma in the plasma CVD method may be either direct current or alternating current, but it is preferable to use alternating current. The alternating current can be used from a few hertz to a microwave. In addition, E described in diamond thin film technology (published by Comprehensive Technology Center), etc.
CR plasma can also be used. Further, a bias voltage may be applied.

When the DLC film is formed by the plasma CVD method, it is preferable to use the following compound as a source gas. Methane, as a compound containing C and H,
Hydrocarbons such as ethane, propane, butane, pentane, hexane, ethylene, propylene and the like can be mentioned. Compounds containing C, H and Si include methylsilane, dimethylsilane, trimethylsilane, tetramethylsilane, diethylsilane, tetraethylsilane, tetrabutylsilane, dimethyldiethylsilane, tetraphenylsilane,
Examples include methyltriphenylsilane, dimethyldiphenylsilane, trimethylphenylsilane, trimethylsilyl-trimethylsilane, and trimethylsilylmethyl-trimethylsilane. These may be used in combination, or a silane compound and a hydrocarbon may be used. Compounds containing C + H + O include CH ₃ OH, C ₂ H ₅ OH, HCHO, CH ₃
COCH _{3 and the} like. Examples of the compound containing C + H + N include ammonium cyanide, hydrogen cyanide, monomethylamine, dimethylamine, allylamine, aniline, diethylamine, acetonitrile, azoisobutane, diallylamine, ethylazide, MMH, DMH, triallylamine, trimethylamine, triethylamine, triphenylamine and the like. is there. In addition, Si + C + H, Si
A compound containing + C + H + O or Si + C + H + N may be combined with an O source or an ON source, an N source, an H source, or the like.

O source, O ₂ , O ₃ etc., C + O source, CO, CO ₂ etc., Si + H source, SiH ₄ etc., H
H ₂ or the like as source, H ₂ O or the like as H + O source, N ₂ as the N source, NH ₃ as the N + H source, N ₃ as the N + O source, N
Compounds of N and O, such as O, NO ₂ , and N ₂ O, which can be represented by NOx, such as (CN) ₂ as an N + C source, NH ₄ F as an N + H + F source, and OF ₂ , O ₂ F ₂ as an O + F source. , O
₃ F ₂ or the like may be used.

The flow rate of the raw material gas may be appropriately determined according to the type of the raw material gas. The operating pressure is typically between 1 and 70
Pa and the input power are usually preferably about 10 W to 5 kW.

The DLC film may be formed by an ionization vapor deposition method. The ionization deposition method is described in, for example, Japanese Patent Application Laid-Open No. 58-17 / 1983.
No. 4507, JP-A-59-174508 and the like. However, the present invention is not limited to the methods and apparatuses disclosed therein, and another type of ion vapor deposition technology may be used as long as the ionized gas for the raw material can be accelerated. As a preferable example of the device in this case, for example, an ion straight type or an ion deflection type described in Japanese Utility Model Laid-Open No. 59-174507 can be used.

In the ionization vapor deposition method, the inside of the vacuum vessel is set to a high vacuum of about 10 ⁻⁴ Pa. A filament that is heated by an AC power supply and generates thermoelectrons is provided in the vacuum vessel. A counter electrode is arranged around the filament, and a voltage Vd is applied between the filament and the filament. In addition, an electromagnetic coil that surrounds the filament and the counter electrode and generates a magnetic field for trapping ionized gas is arranged. The source gas collides with the thermoelectrons from the filament to generate positive thermal decomposition ions and electrons, and the positive ions are accelerated by the negative potential Va applied to the grid. By adjusting Vd, Va and the magnetic field of the coil, the composition and film quality can be changed. Further, a bias voltage may be applied.

When the DLC film is formed by the ionization deposition method, the same material gas as in the plasma CVD method may be used. The flow rate of the source gas may be appropriately determined according to the type. The operating pressure is usually 1 to 70 Pa
The degree is preferred.

The DLC film can be formed by a sputtering method. In this case, a gas such as O ₂ , N ₂ , NH ₃ , CH ₄ , H ₂ or the like is introduced as a reactive gas in addition to a sputtering gas for sputtering such as Ar or Kr, and C, Si,
Targeting SiO ₂ , Si ₃ N ₄ , SiC, etc.
A target may be a mixed composition of C, Si, SiO ₂ , Si ₃ N ₄ , and SiC, and in some cases, C, Si, N, O
May be used. Further, a polymer can be used as a target. A DLC film is formed by applying any one of high-frequency power, AC power, and DC power using such a target, sputtering the target, and sputter depositing the target on a substrate. The high frequency sputtering power is usually 50 W to 2 k
It is about W. The operating pressure is usually 10 ^{−3 to} 0.1 Pa
Is preferred.

[0033]

Next, embodiments of the present invention will be described. In the combinations shown in Table 1, an intermediate layer and a DLC film were formed on the surfaces of the cam and the follower of the rocker arm. SNCM420 was used for all cam and follower materials. The surface roughness of the base material of the cams and followers of the examples was all Ra = 0.1 μm. A cam or a follower was placed at a predetermined position in a vacuum chamber, and after evacuation, a film was formed under the following conditions.

<Deposition of Intermediate Layer> The intermediate layer 1 shown in Table 1 was produced by sputtering under the following conditions. Working gas: Ar (5.1 × 10 ^-2 Pa · m ³ · s ^-1 ) =
30 sccm Sputtering pressure: 40 Pa Input power: 500 W Target: Ta, Si Film thickness: Ta (first layer) 10 nm, Si (second layer) 9
0 nm

The intermediate layer shown in Table 1 was formed under the same film forming conditions while changing the target. When a single intermediate layer was used, the film thickness was all 100 nm.

[0036]

[Table 1]

<DLC Film Formation> A DLC film was formed by the self-bias RF plasma CVD method under the following conditions. DLC1 source gas: C ₂ H ₄ (0.017 Pa · m ³ · s ⁻¹ ) Power supply: RF Operating pressure: 66.5 Pa Input power: 500 W Film formation rate: 100 nm / min Film composition: CH _0.21 Film thickness: 2 μm DLC2 Source gas: Si (OCH ₃ ) ₄ (0.085 Pa · m ³ ·
s ^-1 ) Power supply: RF Operating pressure: 66.5 Pa Input power: 500 W Deposition rate: 100 nm / min Film composition: CH _0.2 Si _0.1 O _0.17 Film thickness: 2 μm DLC3 source gas: Si (CH ₃ ) ₄ (0. 085 Pa ・ m ³・ s
^-1 ) Power supply: RF Operating pressure: 66.5 Pa Input power: 500 W Film formation rate: 100 nm / min Film composition: CH _0.24 Si _0.22 Film thickness: 2 μm

<Evaluation Method> A durability test was performed by applying the following conditions to the rocker arm not coated with DLC (Comparative Example), the rocker arm coated with DLC (Example), and optionally the cam. Subsequent wear conditions were compared. In the test, in an automobile engine using an OHC (but a single rocker arm type), a shim is fixed to the follower surface of the rocker arm, and the cam is brought into contact with the rocker arm and rotated. This condition is based on the number of revolutions (2
000-4000 rpm)
It should be noted that this is an accelerated test corresponding to the level. The results were as shown in Table 2. However, the test time was terminated at a maximum of 20 hours. The durability is the durability of the shim surface of the rocker arm.

[0039]

[Table 2]

[0040]

In Table 1, the endurance time indicates that the operation of the engine is stopped if the endurance time is exceeded. According to the example of the present invention, it can be seen that a cam / rocker arm having extremely high durability was provided in comparison with Comparative Example 1. According to the present invention, the material of the diamond-like thin film to be coated on at least the rocker arm is properly selected and / or
Alternatively, by using an appropriate intermediate layer, the adhesion was improved, and the abrasion resistance was significantly improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structure of a power transmission system including a cam and a follower to which the present invention can be applied.

[Explanation of symbols]

 3, 3 'cam 12, 12' follower 13, 13 'rocker arm 15, 15' rocker arm shaft 17, 17 'spring 19, 19' retainer 21, 21 'valve rod 23 fuel valve 23' exhaust valve

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuhiro Matsuba 1-13-1 Nihonbashi, Chuo-ku, Tokyo Inside TDK Corporation (72) Inventor Ryoko Yoshino 1-13-1 Nihonbashi, Chuo-ku, Tokyo Inside DK Co., Ltd. (72) Inventor Yasushi Hashimoto 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK Corporation (72) Inventor Izumi Miyauchi 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK F term (reference) 3G016 AA06 AA19 BA34 BB09 BB21 BB29 EA07 EA11 EA24 FA18 FA21 GA02 4G046 CA02 CB03 CC06 4K030 AA06 AA09 AA10 AA14 BA18 BA22 BA24 BA28 BA29 BA35 BA48 BA56 BA57 BB12 BB13 CA02 FA01 LA23

Claims (8)

[Claims] 1. A transmission system comprising a cam and a rocker arm receiving a driving force due to its rotational movement, wherein a surface of the rocker arm slidingly engaged with the cam is provided with a diamond-like carbon film. Rocker arm. 2. The diamond-like carbon film is composed of carbon and hydrogen, and when its composition is represented by a molar ratio of CHn, 0.05 ≦ n ≦ 0.7 or silicon is added to the diamond-like carbon film. Oxygen, nitrogen, fluorine may be contained, and the composition is CHxSi
When represented by yOzNvFw, a diamond represented by the following formula: 0.05 ≦ x ≦ 0.7 0.01 ≦ y ≦ 3.0 0 ≦ z ≦ 1.00 0 ≦ v ≦ 1.00 ≦ w ≦ 0.2 The rocker arm according to claim 1, comprising at least one layer of a carbon-like film. 3. The method according to claim 2, wherein the diamond-like carbon film is made of CHxS.
iyOzNvFw (provided that 0.05 ≦ x ≦ 0.7 0.01 ≦ y ≦ 3.0 0 ≦ z ≦ 1.00 ≦ v ≦ 1.00 ≦ w ≦ 0.2) Forming at least two layers of a film and a diamond-like carbon film represented by CHn (where 0.05 ≦ n ≦ 0.7), or continuously changing from one of these compositions to the other The rocker arm of claim 1, comprising a layer formed. 4. A method comprising: (a) a Group 5A metal (V, Nb,
Ta), a silicide or silicide containing at least one selected from Group 6A metals (Cr, Mo, W), Ti and Zr; (b) a Group 5A metal (V, Nb,
Ta) a metal film mainly composed of at least one selected from Ta) and a Si film or a metal film mainly composed of Si formed thereon, or (c) a Group 5A metal (V, Nb, T
a) an intermediate layer comprising at least one metal film selected from Group 6A metals (Cr, Mo, W), Ti, and Zr and a silicon carbide film formed thereon; 4. A rocker arm according to claim 1, 2 or 3, wherein: 5. A combination of a rocker arm and a cam, wherein a diamond-like carbon film is formed on a surface of the cam which is slidably engaged with the rocker arm according to claim 1. 6. The diamond-like carbon film formed on the surface of the cam is composed of carbon and hydrogen, and the composition thereof is represented by the following formula when the molar ratio of CHn is 0.05 ≦ n ≦ 0.7. The diamond-like carbon film or the diamond-like carbon film may contain silicon, and may contain oxygen, nitrogen, and fluorine. When the composition is represented by CHxSiyOzNvFw, 0.05 ≦ x ≦ 0.7 0.01 ≦ 6. The combination of a rocker arm and a cam according to claim 5, comprising at least one layer of a diamond-like carbon film represented by y ≦ 3.0 0 ≦ z ≦ 1.00 0 ≦ v ≦ 1.00 ≦ w ≦ 0.2. . 7. The diamond-like carbon film formed on the surface of the cam is CHxSiyOzNvFw (0.05 ≦ x ≦ 0.7 0.01 ≦ y ≦ 3.00 ≦ z ≦ 1.00 ≦ v ≦ 1.00 ≦ w ≦ 0.2) and at least two layers of a diamond-like carbon film represented by CHn (where 0.05 ≦ n ≦ 0.7) 6. The combination of a rocker arm and a cam according to claim 5, wherein a layer in which one of these compositions is continuously changed from the other composition to the other composition is formed. 8. Between the surface of the cam and the diamond-like carbon film, (a) a Group 5A metal (V, Nb, Ta);
A silicide or silicide containing at least one selected from Group 6A metals (Cr, Mo, W), Ti, and Zr; and (b) a Group 5A metal (V, Nb, Ta). Or a Si film or a Si-based metal film formed thereon, or (c) a Group 5A metal (V, Nb, Ta) or a Group 6A metal ( 8. An intermediate layer comprising at least one metal film selected from the group consisting of Cr, Mo, W), Ti, and Zr and a silicon carbide film formed thereon. Combination of Kano rocker arm and cam.