JP2002357262A - Cam provided with dlc and cam shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a sliding wear between a cam used for a power transmission base controlling the opening/closing for a fuel valve of an engine and the follower or tappet. SOLUTION: In a metallic cam used for a transmission base for transmitting a driving power by the rotary motion of the cam to a reciprocating motion member, a diamond-like carbon membrane, an intermediate layer composed of (a) a silicide or silicious carbide chiefly made of at least one kind selected from the fifth A group metal (V, Nb, Ta), the six A group metal (Cr, Mo, W), Ti, and Zr, (b) a metallic film chiefly made of at least one kind selected from the fifth A group metal (V, Nb, Ta), and of a Si film formed thereon, or a metallic film chiefly made of Si, or (c) at least a kind of metallic film selected from the fifth A group metal (V, Nb, Ta), the six A group metal (Cr, Mo, W), Ti, or Zr, and silicon carbide film formed thereon, and the diamond-like carbon membrane are formed in this order.

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 in an internal combustion engine of an automobile or the like. In particular, the present invention relates to a cam and a camshaft provided with a wear-resistant coating film.

[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 transmitting a driving force due to a rotational motion of a cam to a fuel valve or the like via a reciprocating member such as a tappet is used. Since the cam is brought into contact with a contact object such as a tappet surface or a shim surface fixed thereto so as to transmit the driving force to the tappet or the like and slides while receiving a high surface pressure, the cam surface is also a tappet or shim surface. Even wear damage becomes severe. In particular, in the case of an OHC (overhead camshaft) type engine, it is important to adjust the interval between the cam and the tappet (or shim). If these adjustments are insufficient, a problem such as a source of noise may occur. Or
Even if the adjustment is made, if the wear of these parts is severe, the parts may deviate from a desired interval, causing a decrease in engine horsepower due to friction loss, which may lead to a decrease in fuel efficiency. In addition, there is a possibility that it may become unusable due to galling with the partner material.

FIG. 1 shows a power transmission system for opening and closing a fuel valve. FIG.
The cam 3 fixed to the shaft 1 driven by a crankshaft that transmits the engine output rotates while sliding on the lower surface of the tappet 7. This allows the tappet 7 to reciprocate.
Transmits power to one end of the rocker arm 13 supported on the rocker arm shaft 15 via the push rod 9 to swing it. The other end of the rocker arm 13 is
The fuel valve 23 is opened and closed by pressing the valve shaft 21 supported by the spring 17 held at the timing of the cam 3,
Supply fuel to the piston / cylinder of the engine. The distance between the camshaft 1 and the shim 5 is adjusted by an adjusting screw 11. FIG. 2 shows an example of a transmission system using a double overhead cam (DOHC) system, which is a type of OHC system. A cam 3 fixed to camshafts 1 and 1 'driven by a crankshaft for transmitting engine output is provided. , Rotating while sliding on the upper surfaces of the tappets 7, 7 '. As a result, the reciprocating tappets 7, 7 'press the valve shafts 21, 21' supported by the springs 17, 17 'held therein by retainers 19, 19' at the timing of the cam 3 to release the exhaust valve 23. , And the fuel valve 23 is opened and closed to supply and exhaust fuel to the piston / cylinder of the engine.

The contact surface between the cam and the tappet is subjected to a greater frictional action depending on the distance between them and the force of the spring 8, so that there is sufficient low friction between the cam surface and the contact surface of the mating member. And it is necessary to impart abrasion resistance. In order to solve this problem, Japanese Patent Application Laid-Open No. H11-280419 discloses FIG.
As described in (1), it is described that a shim 5 made of a diamond-like carbon film (DLC) having high wear resistance is provided on an end face of a tappet 7 which comes into contact with the cam 3. However, the document describes that a shim made of a diamond-like carbon film alone cannot provide sufficient wear resistance, and that the cam surface must be precisely polished to an Ra of 0.08 μm or less. As another countermeasure, Japanese Unexamined Patent Publication No. 11-280419 discloses a method in which a material having a higher hardness than the cam sliding surface, for example, a diamond-like thin film is coated on a metal alloy base material, and the surface has a ten-point average surface roughness Rz of 0. A combination of a shim finished to 0.07 to 0.2 μm and a cam having open pores for holding a large number of lubricating oils such as sintered metal is described.

[0005]

SUMMARY OF THE INVENTION Japanese Patent Application Laid-Open No. H11-2804
In the technique described in No. 19, there is a problem that the cam surface must be mirror-polished to 0.08 μm or less in Ra with respect to a shim made of a diamond-like carbon film having high wear resistance. The step of polishing the cam surface is a time-consuming and time-consuming step, and is inefficient and costly. on the other hand,
In the technique described in Japanese Patent Application Laid-Open No. 11-280419, the finished surface of the shim may be relatively rough. There is. SUMMARY OF THE INVENTION It is an object of the present invention to provide a cam or a camshaft which does not require precise polishing of a cam surface or a shim surface and has improved wear resistance. A camshaft refers to a shaft with a cam, including a cam alone or integrally secured to such a shaft.

[0006]

(1) The present invention relates to a cam made of a metal material used for a transmission system for transmitting a driving force due to a rotational motion of a cam to a reciprocating member. A cam characterized in that a diamond-like carbon film is formed on the surface of a cam that dynamically engages. (2) Preferably, 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 the diamond-like carbon film is silicon. 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 Carbon film. (3) Preferably, the diamond-like carbon film is formed of the CHxSiyOzNvFw (subscripts are as defined above).
Or at least two layers of the diamond-like carbon film represented by CHn and the CHn (subscript is as defined above), or one of these compositions is replaced by the other And a layer in which a continuously changed layer is formed. In these cases, it is more preferable to provide a layer containing H and Si as the first layer. (4) According to another aspect of the present invention, in a cam made of a metal material used for a transmission system for transmitting a driving force due to a rotational motion of a cam to a reciprocating member, a sliding engagement with the reciprocating member is provided. (A) a Group 5A metal (V, N
b, Ta), Group 6A metals (Cr, Mo, W), Ti,
Or a silicide containing at least one selected from Zr and Zr, and (b) a Group 5A metal (V, N
b, Ta) and a metal film mainly composed of at least one selected from the group consisting of Si and a metal film mainly composed of Si, or (c) a Group 5A metal (V, N
b, Ta), Group 6A metals (Cr, Mo, W), Ti,
And at least one metal film selected from Zr and Zr, an intermediate layer formed of a silicon carbide film formed thereon, and at least one layer of a diamond-like carbon film. You. (5) In the above (4), preferably, the diamond-like carbon film is composed of carbon and hydrogen and has a composition of CHn.
When represented by a molar ratio, 0.05 ≦ n ≦ 0.7 or the diamond-like carbon film may contain silicon, and may contain oxygen, nitrogen, and fluorine.
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 Carbon film. (6) In the above (2), preferably, the diamond-like carbon film is formed of the CHxSiyOzNvFw.
Forming at least two layers of a diamond-like carbon film represented by (subscripts are defined above) and a diamond-like carbon film represented by CHn (subscripts are defined above), or A layer continuously changed from one composition to the other composition.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have found that a diamond-like thin film (DLC film) formed on a cam (particularly a cam of a camshaft) according to the prior art is a shim (or mating material) having a relatively large surface roughness. As a result of exploring the reason why large abrasion is caused when used in combination with the above, it has been found that there is a problem in the adhesion between the metal substrate of the shim and the diamond-like thin film, which makes long-term use impossible. The present inventors are not using tappets or shims as in the past,
Improve the adhesion by coating the cam with a diamond-like thin film, and especially by properly selecting the material of the diamond-like carbon film and / or using an appropriate intermediate layer,
The wear resistance was significantly improved. Since the cam has a complicated shape, there has been no appropriate film forming method, and no attempt has been made in the past. When the cam having the configuration of the present invention is employed, it is not necessary to precisely grind the surface roughness of the shim to 0.08 μm or less, and sufficient wear resistance is provided even with a surface roughness greater than 0.1 μm. In addition, when a similar structure is employed on the surface of the shim base metal or alloy, the wear resistance is further improved.

In particular, the present invention provides (a) a Group 5A metal (V, Nb, Ta) and a Group 6A metal (Cr, Mo, Cr) between at least a sliding surface of a cam and a diamond-like carbon film.
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,
An intermediate layer comprising at least one metal film selected from W), Ti, and Zr and a silicon carbide film formed thereon is provided. In another embodiment, the present invention provides a wear-resistant coating made of a diamond-like carbon film containing at least H and Si on at least the sliding surface of the cam. When such an intermediate layer is formed, the diamond-like carbon film is not particularly limited. H-containing diamond-like carbon film, H and S
A diamond-like carbon film containing i, or a combination thereof, can be used.

According to the present invention, if a diamond-like carbon film, especially a diamond-like carbon film containing H and Si, is formed on at least the surface of the cam without using an intermediate layer, the wear resistance is greatly improved. It is possible to improve. In this case, it is also possible to further form a diamond-like carbon film containing H on the diamond-like carbon film containing H and Si. This configuration has particularly good adhesion to the substrate, and further improvement in wear resistance can be expected. Hereinafter, the diamond-like carbon film may be abbreviated as DLC for simplicity.

As the material that can be used as the base material of the cam in the present invention, any material conventionally used in the art can be used. These materials include, for example, various types of carbon steel and cast iron (gray cast iron, spheroidal graphite cast iron, malleable cast iron, alloy cast iron, etc.), cast steel and the like, and ultra-tough steel (SNCM420, SC
M440, SCM420, SCR420, H11 etc.), high speed tool steel (high speed steel: JIS standard SKH)
System), alloy tool steel (die steel: SKD6 etc.), maraging steel (KMS180-20 etc.), ausform steel, stainless steel (SUS304, SUS430, 17)
-4PH), bearing steel (such as SUJ2), Al alloy (such as AC4C), and Ti alloy.

[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.

[0012]Middle class  Next, the intermediate layer used in the present invention comprises: (a) a Group 5A metal
(V, Nb, Ta), Group 6A metals (Cr, Mo,
At least one selected from W), Ti, and Zr
Or silicide containing as a main component, (b) Group 5A
At least one selected from metals (V, Nb, Ta)
And a Si film formed thereon and
Is a metal film containing Si as a main component, or (c) Group 5A gold
Genus (V, Nb, Ta), Group 6A metal (Cr, Mo,
At least one selected from W), Ti, and Zr
Metal film and a silicon carbide film formed thereon
These are described in Japanese Patent Application Laid-Open No. 2000-2000 by the present inventors.
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 intermediate layer preferably has a thickness of 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, and the frequency is 1 for high frequency sputtering.
~ 50MHz, 50kHz ~ 1MHz at low frequency, 0.5 ~ 30
About W / cm ² is preferable. The deposition rate is 1 to 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 / min.
The degree is preferred.

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.

[0021]Diamond-like carbon film  Diamond-like carbon (DLC) film is made of diamond-like carbon
It may also be called an elementary film, an i-carbon film, or the like. Diamond
The mond-like carbon film is disclosed in, for example,
No. 5646, No. 62-145647, New Di
amond Forum, Vol. 4, No. 4, October 25, 1988
Line).

The DLC film is described in the above document (New Diamond Foru).
as described in m), Raman spectroscopy, broad to 1550cm ^-1 (1520~1560cm
^-1) has a peak of the Raman absorption, and diamond having a sharp peak at 1333 cm ^-1, and graphite having a sharp peak at 1581 cm ^-1, it is a substance having a distinctly different structure. The DLC film is an amorphous thin film represented by CHn (0.05 ≦ n ≦ 0.7) containing carbon and hydrogen as main components, and is formed by sp3 bonds between carbon atoms present at random. ing. D
The absorption peak in the Raman spectroscopic analysis of the LC film was broad at 1550 cm ^-1 (1520 to 1560 cm
^-1 ), but may fluctuate by about ± 100 cm ^-1 due to the inclusion of the above elements other than carbon and hydrogen.

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

The DLC film is made of Si in addition to carbon and hydrogen.
And one or more of O, N, and F may be contained. When the intermediate layer is not used, at least the first layer is made of Si in addition to hydrogen in order to improve the adhesion to the substrate.
Should be contained. In this case, the DLC film is CHxS
When expressed as iyOzNvFw, x, y, z, v and w are respectively 0.05 ≦ x ≦ 0.7, 0.01 ≦ y ≦ 3.0,
It is preferable that 0 ≦ z ≦ 1.0, 0 ≦ v ≦ 1.0, and 0 ≦ w ≦ 0.2. 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
As a source, H ₂ or the like, H + O source, H ₂ O, etc., N source, N ₂ N + H source, NH ₃ or the like, 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. The composition and film quality can be changed by adjusting Vd, Va and the magnetic field of the coil. 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. High frequency sputtering power is usually 50W ~ 2kW
It is about. Generally, the operating pressure is preferably from 10 ^{-3 to} 0.1 Pa.

[0033]

Next, an embodiment of the present invention will be described. Table 1
The intermediate layer and the DLC film were formed on the surfaces of the cam and the shim in the combinations shown in the following. SNCM420 was used for all cams and shims. The surface roughness of the cam and shim base materials of the examples was all Ra = 0.1 μm.
Place the cam or shim in place in the vacuum chamber,
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)
90 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]

<Deposition of DLC> The DLC film is self-biased.
A film was formed by the RF plasma CVD method under the following conditions.DLC1  Raw material gas: C_TwoH_Four(0.017 Pa · m^Three・ S^-1Power 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 μmDLC2  Source gas: Si (OCH_Three)_Four (0.085 Pa · m^Three
・ S^-1Power supply: RF Operating pressure: 66.5 Pa Input power: 500 W Film formation rate: 100 nm / min Film composition: CH_0.2Si_0.1O_0.17  Film thickness: 2 μmDLC3  Source gas: Si (CH_Three)_Four (0.085 Pa · m^Three・
s^-1Power supply: RF Operating pressure: 66.5 Pa Input power: 500 W Film formation rate: 100 nm / min Film composition: CH_0.24Si_0.22  Film thickness: 2 μm

<Evaluation Method> A cam without DLC coating (Comparative Example) and a cam or shim coated with DLC (Example) were subjected to a durability test under the following conditions. Thereafter, the abrasion states of the cams were compared. The test is DO
In an automobile engine using HC, a shim is fixed to a surface of a tappet, and a cam is abutted and rotated. It should be noted that this condition is an acceleration test corresponding to a much harsher F1 level as compared with the rotational speed (2000 to 4000 rpm) in a general running of a commercial vehicle. The results were as shown in Table 2. However, the test time was terminated at a maximum of 20 hours.

[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 embodiment of the present invention, it is possible to provide a cam or a camshaft which is extremely durable compared to Comparative Example 1 as well as Comparative Example 2 corresponding to a known example using DLC. I understand. As can be seen from Examples 1 to 21, in the present invention, excellent durability was obtained despite the fact that the shim surface was not subjected to precision polishing as in Comparative Example 2, so that the process was shortened and the cost was reduced. According to the present invention, which can be reduced, at least by appropriately selecting the material of the diamond-like thin film coated on the cam and / or by using an appropriate intermediate layer, the adhesion is improved, and the wear resistance is markedly improved. Could be improved.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view illustrating another structure of a power transmission system including a cam and a tappet to which the present invention can be applied.

FIG. 3 is a diagram showing a relationship between a cam and a shim according to a conventional example.

[Explanation of symbols]

 1, 1 'camshaft 3, 3' cam 5 shim 7, 7 'tappet 9 thrust rod 11 adjusting screw 13 rocker arm 15 rocker arm shaft 17, 17' spring 19, 19 'retainer 21, 21' valve shaft 23 fuel valve 23 'exhaust valve

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F01L 1/04 F01L 1/04 J (72) Inventor Ryoko Yoshino 1-13-1 Nihonbashi, Chuo-ku, Tokyo Within TDK Corporation (72) Inventor Yasushi Hashimoto 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK Corporation (72) Inventor Yasuhiro Matsuba 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK Corporation In-house (72) Inventor Izumi Miyauchi 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDC F-term (reference) 3G016 AA04 AA19 BA34 FA21 GA02 3J030 EA01 EB07 EC04 EC07 4K029 AA02 BA02 BA07 BA11 BA16 BA17 BA34 BA35 BA41 BA52 BA56 BB02 BD04 CA01 CA03 CA05 4K030 AA09 AA10 AA13 BA24 BA28 BA29 BB13 FA01 LA23 4K044 AA02 AB10 BA18 BB01 BB1 7 BC06 CA13 CA14 CA34

Claims (6)

[Claims] In a cam made of a metal material used for a transmission system for transmitting a driving force due to a rotational motion of a cam to a reciprocating member, a diamond-like carbon is formed on a surface of the cam slidingly engaged with the reciprocating member. A cam formed with a film. 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 2. The cam 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.
diamond-like carbon represented by 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 2. The cam according to claim 1, wherein a layer is formed. 4. A cam made of a metal material used for a transmission system for transmitting a driving force due to a rotational motion of a cam to a reciprocating member, wherein a surface of the cam slidingly engaged with the reciprocating member is (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; A) 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) 5A Intermediate layer consisting of at least one metal film selected from Group 6 metals (V, Nb, Ta), Group 6A metals (Cr, Mo, W), Ti, and Zr and a silicon carbide film formed thereon And at least one layer of the diamond-like carbon film A cam formed in this order. 5. 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 5. The cam according to claim 4, wherein the cam is a carbon film. 6. The diamond-like carbon film according to claim 6, wherein
diamond-like carbon represented by xSiyOzNvFw (provided that 0.05 ≦ x ≦ 0.7 0.01 ≦ y ≦ 3.0 0 ≦ z ≦ 1.00 0 ≦ 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 5. The cam of claim 4 including a layer formed.