WO2012081198A1

WO2012081198A1 - Drive cam and valve operating device for engine

Info

Publication number: WO2012081198A1
Application number: PCT/JP2011/006823
Authority: WO
Inventors: 亜紀小鯛; 聡顕市; 耕三砂野
Original assignee: 川崎重工業株式会社
Priority date: 2010-12-13
Filing date: 2011-12-06
Publication date: 2012-06-21
Also published as: JP5898092B2; EP2653671A1; EP2653671B1; CN103189604A; JPWO2012081198A1; EP2653671A4; US20130291813A1

Abstract

Provided are a drive cam in which the wear resistance of a sliding surface is improved to achieve higher durability, and a valve operating device for an engine comprising the same. This drive cam (13a) is made of a nitrided steel, and has a cured layer formed by nitrocarburizing on the sliding surface, wherein the cured layer is present on the face of the sliding surface. A follower mechanism (33) used in combination with the drive cam preferably comprises, on a sliding surface for contacting the drive cam, a chromium plating layer and a diamond-like carbon membrane provided on the chromium plating layer.

Description

Driving cam and engine valve operating device

The present invention relates to a drive cam used in an engine valve operating apparatus, and an engine valve operating apparatus including the drive cam.

Drive cams configured to interlock with the rotation of the crankshaft in the valve gear of the engine have a high degree of wear resistance so that the sliding surface with the driven mechanism (for example, rocker arm or tappet) that slides on the cam is not worn. Sex is required. Therefore, it is known that the drive cam is made of chill cast iron having high wear resistance, and various surface hardening treatments are performed on the chill cast iron in order to further improve wear resistance. For example, Patent Document 1 discloses a technique for improving wear resistance by forming a sliding part such as a cam with chill cast iron and performing a PVD treatment on the surface thereof to form a hardened film. In addition, as one of such surface hardening treatments, the driving cam is formed of chill cast iron and then subjected to soft nitriding treatment, so that nitrogen is diffused and penetrated into the surface, and the compound layer and the hardening layer (diffusion layer) are formed. By forming it, the wear resistance is improved.

In Patent Document 2, the wear resistance of the rocker arm is improved by performing chrome plating on the sliding surface of the rocker arm that slides with the drive cam in the valve gear of the engine, and then performing a two-step polishing process. Techniques for making them disclosed are disclosed.

On the other hand, in Patent Document 3, for example, the rotational motion of the drive cam is converted into the reciprocating motion of the valve by the swing cam mechanism, and the swing angle range of the swing cam mechanism is changed, so that the rotation speed of the drive cam is changed. There has been disclosed a variable valve timing type valve operating apparatus in which a control device for realizing valve timing control is introduced.

JP 2004-204762 A JP 2010-156247 A JP 2009-103083 A

With the recent increase in engine output, the air-fuel mixture flow rate increases and the lift amount of the valve increases, and accordingly, the pressure acting on the sliding surface tends to increase. In particular, in a variable valve timing type valve gear, the pressing force by the drive cam is increased in order to reciprocate the valve. For this reason, there is a problem that the sliding frictional force generated on the sliding surface of the driving cam is increased, and the sliding surface of the driving cam is very easily worn.

When the pressure acting on the sliding surface of the drive cam is increased, it is required to further improve the wear resistance achieved by the conventional surface treatment method. In particular, in a drive cam in which a compound layer and a hardened layer are formed by soft nitriding the chill cast iron surface, the compound layer on the cam surface is hard and brittle. The compound layer on the moving surface becomes easy to peel off. When the compound layer is slightly peeled off, peeling of the entire surface easily proceeds. When the peeling of the compound layer proceeds, the hardened layer is exposed. However, the hardened layer of chilled cast iron has a low wear resistance, so that there is a problem that the wear resistance of the drive cam is greatly reduced.

Therefore, an object of the present invention is to provide a drive cam with improved wear resistance of a sliding surface and improved durability, and an engine valve gear including the drive cam.

The present invention has been made in view of the above circumstances, and the drive cam of the present invention is a drive cam having a sliding surface that is interlocked with the rotation of a crankshaft in an engine valve gear, and is nitrided. It is made of steel, and has a hardened layer formed by soft nitriding on the sliding surface, and the hardened layer exists on the surface of the sliding surface.

According to the above configuration, since the sliding surface of the drive cam is made of the hardened layer and does not have the compound layer formed by soft nitriding, the problem that the compound layer is peeled off by sliding of the drive cam is avoided. can do. The hardened layer formed by soft nitriding is exposed on the surface of the sliding surface of the drive cam of the present invention. The hardened layer is softer than nitrided steel instead of conventional chill cast iron. Since it is a hardened layer formed by nitriding, it has sufficient hardness and thickness, and extremely high wear resistance. As a result, the drive cam of the present invention having the above-described configuration has greatly improved wear resistance as compared with a conventional drive cam that has been subjected to soft nitriding treatment on chill cast iron and has a compound layer on the surface.

The drive cam of the present invention is preferably manufactured by removing the compound layer after forming the hardened layer and the compound layer by performing the soft nitriding treatment on the sliding surface. According to this method, the drive cam of the present invention can be easily produced.

The hardened layer is preferably a layer having a Vickers hardness of 550HV100 gf or more and a thickness of 100 to 300 μm. Thereby, since the hardened layer exposed on the surface of the sliding surface of the drive cam has sufficient hardness and thickness, the drive cam of the present invention can achieve more excellent wear resistance.

It is preferable that the nitrided steel has a bainite structure. When such a nitrided steel is subjected to soft nitriding treatment, a hardened layer having sufficient hardness and thickness can be formed, so that the drive cam of the present invention can achieve more excellent wear resistance.

The present invention also includes an engine valve operating system including the drive cam and a driven mechanism that is driven by sliding with the drive cam and has a sliding surface that contacts the sliding surface of the drive cam. Also related. Since the valve drive apparatus uses the drive cam of the present invention, the sliding surface of the drive cam is excellent in wear resistance. Therefore, even when the operating conditions of the engine are severe and the sliding friction force against the drive cam is large. Good durability can be exhibited.

It is preferable that a chrome plating layer and a diamond-like carbon film are formed on the chrome plating layer on the sliding surface of the driven mechanism in the valve operating device. Abrasion resistance can be improved by providing a chromium plating layer on the sliding surface of the driven mechanism. Furthermore, by providing a diamond-like carbon layer on the surface of the chromium plating layer, it is possible to improve the seizure resistance that can be a problem under severe operating conditions, and at the same time, further improve the wear resistance.

The chromium plating layer is preferably polished so that the surface roughness Rz is 0.5 μm or less and the period of the irregularities of 0.1 μm or more is 50 μm or more. Thereby, since the friction between a driven mechanism and a drive cam is reduced, it becomes possible to suppress wear of both sliding surfaces.

The diamond-like carbon film is preferably a metal-containing diamond-like carbon film. Thereby, improvement of seizure resistance and improvement of wear resistance can be reliably achieved.

In the first embodiment of the present invention, the driven mechanism has a sliding surface that contacts the sliding surface of the drive cam and a sliding surface that contacts the tappet. In the valve gear of this embodiment, the drive cam and the driven mechanism (for example, rocker arm) have sliding surfaces with respect to each other, and the driven mechanism and the tappet have sliding surfaces with respect to each other. In this form, it is possible to achieve the effects of the present invention.

In the first embodiment, it is preferable that the valve gear is of a variable valve timing type. Here, the variable valve timing type valve operating device includes a drive cam interlocking with the rotation of the crankshaft of the engine, a driven member that contacts the drive cam, and a movement of the driven member attached to the driven member. A swinging member that transmits to the tappet and a relative position changing mechanism that changes the relative position between the driven member and the swinging member are provided. In such a variable valve timing type valve operating device, the surface pressure with respect to the sliding surface of the drive cam fluctuates greatly, and the sliding surface of the driving cam is likely to be worn. The valve device is also preferable because the sliding surface of the drive cam hardly wears.

In the second embodiment of the present invention, the driven mechanism includes a tappet having a sliding surface that directly contacts the sliding surface of the drive cam. In the valve gear of this embodiment, the tappet is in direct contact with the sliding surface of the drive cam, and the tappet corresponds to the driven mechanism. Even in this form, it is possible to achieve the effects of the present invention.

According to the present invention, the wear resistance of the sliding surface of the drive cam can be improved and the durability can be improved in the valve gear of the engine. In particular, even in variable valve timing type valve gears in which the operating conditions are severe and the sliding surface of the conventional drive cam is easily worn, the wear resistance can be improved and the durability can be improved.

Sectional drawing which showed the variable valve timing type valve operating apparatus in 1st embodiment, and its periphery Cross-sectional enlarged view conceptually showing the vicinity of the surface of nitrided steel subjected to soft nitriding The cross-sectional enlarged view which conceptually showed the surface vicinity of the sliding surface of the drive cam which concerns on this invention Sectional drawing which extracted and showed the principal part of the valve operating apparatus of the engine in 2nd embodiment

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a cross-sectional view showing engine valve gears 11A and 11B and their surroundings in the first embodiment. As shown in FIG. 1, the engine is a double overhead camshaft type (DOHC type) engine. The cylinder head 12 of the engine is provided with an intake port 12A and an exhaust port 12B connected to the combustion chamber 14. An intake side drive camshaft 13 and an exhaust side drive camshaft 15 are disposed above the cylinder head 12, and a cylinder head cover 16 is placed thereon. The drive camshafts 13 and 15 are connected to a crankshaft (not shown) of the engine via a rotation transmission mechanism (not shown) such as a chain, and rotate in conjunction with the crankshaft (not shown). To do. The cylinder head 12 is provided with an intake valve mechanism 17A for opening / closing the combustion chamber 14 with respect to the intake port 12A and an exhaust valve mechanism 17B for opening / closing the combustion chamber 14 with respect to the exhaust port 12B. . The intake valve mechanism 17A is opened and closed by the intake side valve operating device 11A, and the exhaust valve mechanism 17B is opened and closed by the exhaust side valve operating device 11B. The valve gears 11A and 11B are variable valve timing types. Since the

valve mechanisms

17A and 17B and the valve gears 11A and 11B have substantially the same structure on the intake side and the exhaust side, the following description will be made on the intake side as a representative.

The intake valve mechanism 17A includes a valve body 20 having a flange portion 20a for opening and closing the intake port 12A and a stem portion 20b extending upward from the flange portion 20a. A groove is formed at the upper end of the stem portion 20 b, a cotter 21 is sandwiched in the groove, and a spring retainer 23 is attached to the cotter 21. A spring seat 24 is attached to the upper surface of the cylinder head 12, and a valve spring 22 is interposed between the spring seat 24 and the spring retainer 23. Therefore, the valve body 20 is biased upward by the valve spring 22 and the intake port 12A is closed. A tappet 31 is attached to the upper surface of the cotter 21.

The valve gear 11A includes a drive cam shaft 13 that is interlocked with the rotation of the crankshaft of the engine, a drive cam 13a that is fixed to the drive cam shaft 13, and a movement of the drive cam 13a in contact with the drive cam 13a. A swing cam mechanism 32 that transmits to the tappet 31 of the mechanism 17A is provided. The swing cam mechanism 32 includes a driven member 33 that contacts the drive cam 13a, a swing member 34 that is attached to the driven member 33 and presses the tappet 31 of the intake valve mechanism 17A, and the driven member 33 and the swing member 34. And a relative position changing mechanism for changing the relative position between the two. The relative position changing mechanism includes a control shaft 35 that swingably supports the swing member 34, a connecting pin 36 that connects the driven member 33 to the swing member 34 so as to be angularly displaceable, and a part of the control shaft 35. A roller 37 that is rotatably provided to support the driven member 33 against the force from the drive cam 13a, and a driven spring (not shown) that biases the driven member 33 toward the drive cam 13a. Have. By angularly displacing the control shaft 35 with a motor (not shown), the relative positional relationship between the swing member 34 and the driven member 33 in the circumferential direction around the control shaft 35 changes, and the valve opening time of the valve body 20 and The lift amount can be changed.

The drive cam 13 a is in contact with the driven member 33 in the swing cam mechanism 32. In the present invention, the drive cam 13a is obtained by forming nitrided steel into a predetermined shape. Nitride steel is conventionally known, and for the purpose of nitriding, aluminum (Al) or chromium (Cr) is alloyed so that a hard surface layer portion can be easily obtained, and further, manganese (Mn), molybdenum ( It is a special steel to which Mo), vanadium (V) and the like are appropriately added. In the present invention, various types of nitrided steel can be used. Among them, nitrided steel having a bainite structure is preferable because soft nitriding is performed quickly and a deep hardened layer is easily obtained.

The nitrided steel constituting the drive cam 13a is subjected to soft nitriding at least on the sliding surface with the driven member 33. As soft nitriding, gas soft nitriding, plasma soft nitriding, ion soft nitriding, tuftride, sulfur nitriding, etc. are known, and the implementation conditions are not particularly limited, but cam distortion caused by heat treatment at high temperature is not limited. In order to suppress, it is preferable to process at 520 degrees C or less. In this embodiment, gas soft nitriding treatment is used.

By soft nitriding, nitrogen diffuses and permeates into the surface of the nitrided steel, increasing the amount of nitrogen near the surface, forming a compound layer made of nitride on the outermost layer, and nitrogen below the compound layer. A hardened layer formed by diffusion is formed. This layer structure is shown in FIG. In FIG. 2, a hardened layer 52 in which nitrogen is diffused and permeated is formed on the non-nitrided layer 53 in which nitrogen is not diffused and permeated, and a compound layer 51 made of nitride is formed on the hardened layer 52. ing. The compound layer 51 constitutes the outermost layer.

The compound layer 51 is a layer of about several μm to several tens of μm formed on the outermost layer of nitrided steel subjected to soft nitriding. In terms of composition, it is a layer made of a composite nitride such as iron or chromium. On the other hand, the hardened layer 52 is also called a diffusion layer, and is a layer formed immediately below the compound layer 51. No iron nitride is formed and the layer is simply a solid solution of nitrogen, or the nitride of an additive element such as aluminum or chromium is dispersed in the parent phase of solid solution of nitrogen. It is a composite layer.

The compound layer formed by the soft nitriding treatment is hard and brittle and is easily broken. Therefore, when the driving cam is formed using the nitrided steel having the compound layer on the outermost surface, the compound layer easily peels off due to the surface pressure during operation, which causes a problem in durability.

Therefore, in the present invention, after the compound layer and the hardened layer are formed by soft nitriding the surface of the nitrided steel constituting the drive cam 13a, only the compound layer is removed and the hardened layer is exposed on the outermost surface. Configured. A hardened layer formed by subjecting nitrided steel to soft nitriding has sufficient hardness and thickness, and has extremely high wear resistance. The presence of such a hardened layer on the outermost surface of the sliding surface of the driving cam greatly improves the wear resistance of the driving cam. FIG. 3 shows the layer structure in the vicinity of the surface of the sliding surface of the drive cam according to the present invention. In FIG. 3, a hardened layer 52 in which nitrogen is diffused and permeated is formed on an unnitrided layer 53 in which nitrogen is not diffused and permeated. Unlike FIG. 2, the hardened layer 52 is exposed on the outermost surface. The compound layer 51 is not formed on the hardened layer 52.

It is preferable that the hardened layer formed on the outermost surface of the sliding surface of the drive cam according to the present invention is a layer having a Vickers hardness of 550HV100 gf or more. The thickness of the cured layer exhibiting such hardness is preferably 100 to 300 μm. When the hardened layer has such hardness and thickness, it is possible to exhibit more excellent wear resistance. In the non-nitrided layer, the Vickers hardness is significantly lower than 550, for example, about 300, and the hardness is poor.

The drive cam of the present invention can be manufactured by sequentially performing the following steps.
(1) A step of forming a drive cam made of nitrided steel.
(2) A step of forming a hardened layer and a compound layer by performing a soft nitriding treatment on at least the sliding surface of the surface of the formed drive cam.
(3) A step of removing the compound layer from the sliding surface and exposing the hardened layer to the outermost surface of the sliding surface.

In step (3), the method of removing the compound layer from the sliding surface is not particularly limited, and a method of removing by a normal mechanical polishing treatment or the like can be used. In order to confirm that the compound layer has been removed by the removal treatment, a method of measuring the hardness distribution in the cross section of the sliding surface or a method of observing the cross sectional structure of the sliding surface with an electron microscope is applied. Can do.

The inventors have a drive cam having a sliding surface on which a hardened layer and a compound layer are formed by performing a soft nitriding treatment, and the hardened layer is exposed on the outermost surface by removing the compound layer after the soft nitriding treatment. Four types of drive cams each having a sliding surface were prepared, subjected to a rotational sliding test under specific conditions, and the amount of wear was measured at five specific locations on the surface of the driving cam. As a result, in any drive cam, the amount of wear was significantly reduced by the drive cam from which the compound layer was removed at any measurement location on the sliding surface. On average, the result was that the amount of wear decreased to less than half by removing the compound layer. From the above, it has been experimentally confirmed that the wear resistance of the sliding surface of the driving cam is remarkably improved by removing the compound layer on the sliding surface.

It was also confirmed that when the compound layer was not removed, the wear resistance was poor regardless of the thickness of the compound layer. That is, when a driving cam having a sliding surface with a thickness of the outermost compound layer of 3 μm and a driving cam having a sliding surface with a thickness of 16 μm were prepared, the amount of wear was measured as described above. A considerable amount of wear occurred in any of the drive cams. From this result, it was confirmed that the wear resistance could not be improved even if the thickness of the compound layer was reduced. As described above, in order to improve the wear resistance of the sliding surface of the drive cam, it is necessary to remove the compound layer and expose the hardened layer.

Next, the driven member 33 that is in contact with the drive cam 13a will be described. As this driven member, a member formed by subjecting the surface of the formed body made of steel to a chrome plating process to the surface of the sliding surface (sliding surface with the drive cam) can be used. This chrome plating is intended to improve wear resistance.

However, the present inventors use a variable valve timing type in which the fluctuation of the surface pressure is severe using the driven member subjected to the chromium plating treatment and the driving cam in which the compound layer is removed and the hardened layer is exposed as described above. It has been found that when the valve operating apparatus is operated, seizure is likely to occur and seizure resistance (adhesion resistance) decreases. Specifically, the material of the surface of the drive cam is peeled off, and the problem arises that the material adheres to the surface of the driven member. This is presumed to be due to the intermetallic bond that occurs between the hardened layer on the surface of the drive cam and the surface of the driven member. In the conventional driving cam having the compound layer on the outermost surface, since the compound layer is a kind of ceramic, it plays the role of a protective film for preventing the intermetallic bond, and it is considered that the seizure resistance has not been a problem. In the present invention, since the compound layer on the surface of the drive cam is removed, the protective film is eliminated, and the drive cam material adheres to the surface of the driven member under severe operating conditions in the variable valve timing type valve gear. It is thought that it came to do.

In order to avoid the problem of seizure resistance, the present inventor has considered performing various surface treatments on the sliding surface (sliding surface with the drive cam) of the driven member that has been subjected to chrome plating. did. However, when tin plating, Kanigen plating (electroless nickel plating), or Kaniflon plating is applied as the surface treatment, the plating layer itself peels off and wear occurs on the sliding surface of the driven member. There was no improvement in adherence.

However, when the sliding surface of the driven member subjected to the chrome plating is further covered with a diamond-like carbon film, the seizure resistance is remarkable as compared with the case where the driven member subjected only to the chrome plating is used. It was confirmed that it improved.

Here, the evaluation of seizure resistance was performed based on the load when seizure occurred (hereinafter referred to as “seizure load”). In the five samples, which are driven members having only a chrome plating layer, the seizure load was dispersed in the range of 10 to 70 kgf, and was uneven and unstable. The seizure resistance was insufficient with the following. On the other hand, in the three samples in which the diamond-like carbon film is formed on the chrome plating layer, the seizure load is in the range of 40 to 50 kgf, showing excellent seizure resistance and seizure resistance. It was stable at a high level. Thus, a remarkable improvement in seizure resistance due to the formation of the diamond-like carbon film was confirmed.

In addition to the improvement in seizure resistance described above, it was confirmed that the wear resistance of the drive cam surface was further improved. That is, when a driven member covered with a diamond-like carbon film is further coated on the chromium plating layer, the hardened layer is exposed on the outermost surface as compared with the case where a driven member having only the chromium plating layer is used. The amount of wear on the drive cam surface was reduced to about half.

From the above, on the sliding surface of the driven member (sliding surface in contact with the drive cam), the diamond-like carbon film is formed on the chrome plating layer, and the seizure resistance (adhesion resistance) and the anti-seizure resistance. This is preferable from the viewpoint of wear. Therefore, in this embodiment, a driven member having such a configuration is used as the driven member 33.

The diamond-like carbon film in the driven member is not particularly limited as long as it is a thin film composed of diamond-like carbon. Diamond-like carbon is an amorphous hard film mainly composed of carbon, and various conventionally known ones can be used in the present invention. However, metal-containing diamond-like carbon is preferable from the viewpoints of toughness, adhesion to the chromium plating layer, and seizure resistance. In this embodiment, tungsten-containing diamond-like carbon is used.

The thickness of the diamond-like carbon film may be about 1 to 4 μm.

The chromium plating layer formed under the diamond-like carbon film has an effect of improving the adhesion of the diamond-like carbon film and making it difficult to peel the film from the driven member. Furthermore, in the unlikely event that the diamond-like carbon film peels off under severe operating conditions, it is also expected to exhibit a certain degree of seizure resistance.

The chrome plating layer is preferably subjected to a polishing process similar to that disclosed in Patent Document 2 (Japanese Patent Laid-Open No. 2010-156247) in advance on the sliding surface with the drive cam. By such polishing treatment, the surface of the chrome plating layer is adjusted so that the surface roughness Rz is 0.5 μm or less and the period of unevenness of 0.1 μm or more is 50 μm or more. As a result, the friction between the driven member and the drive cam is reduced, so that wear on the sliding surface of the drive cam can be suppressed. Since the surface hardness of the diamond-like carbon film is extremely high, the surface roughness of the chromium plating layer surface before forming the diamond-like carbon film is adjusted in advance to avoid wear of the driving cam sliding surface by the diamond-like carbon film. It is preferable.

After the chromium plating layer is polished as described above, a diamond-like carbon film is formed. The diamond-like carbon film can be formed by a conventional method.

(Second embodiment)
FIG. 4 is a cross-sectional view showing a main part of a valve operating apparatus for an engine in the second embodiment. In this embodiment, the swing cam mechanism 32 is excluded from the first embodiment, and the drive cam 13 a is in direct contact with the tappet 31.

The tappet 31 has a chromium plating layer on the sliding surface (sliding surface with the drive cam) surface of a molded body made of steel, and further has a diamond-like carbon film thereon. As a result, like the driven member 33 in the first embodiment, the seizure resistance is improved, and the wear resistance of the drive cam can be further improved. Details of the chromium plating layer and the diamond-like carbon film are the same as those in the first embodiment.

The second embodiment is the same as the first embodiment except that the swing cam mechanism 32 is not provided, and the surface of the sliding product of the tappet 31 has a chromium plating layer and a diamond-like carbon film. The description of the same points as the embodiment is omitted.

As described above, the drive cam and the engine valve gear according to the present invention can suppress deterioration due to wear on the sliding surface of the drive cam, and can be widely applied to a vehicle engine such as a motorcycle. Is possible.

11A, 11B Variable valve timing type valve gear 12 Cylinder head 13 Intake side drive camshaft 14 Combustion chamber 15 Exhaust side drive camshaft 17A Intake valve mechanism 17B Exhaust valve mechanism 20 Valve body 31 Tappet 32 Oscillating cam mechanism 33 Followed Member 34 Swing member 35 Control shaft 36 Connecting pin 37 Roller 51 Compound layer 52 Hardened layer 53 Non-nitrided layer

Claims

A drive cam having a sliding surface that interlocks with rotation of a crankshaft in a valve gear of an engine,
Made of nitrided steel,
A drive cam having a hardened layer formed by soft nitriding on the sliding surface, wherein the hardened layer is present on the surface of the sliding surface.
The drive cam according to claim 1, wherein the hardened layer and the compound layer are formed by performing the soft nitriding treatment on the sliding surface, and then the compound layer is removed.
2. The drive cam according to claim 1, wherein the hardened layer is a layer having a Vickers hardness of 550HV100 gf or more and a thickness of 100 to 300 μm.
The drive cam according to claim 1, wherein the nitrided steel is formed with a bainite structure.
The drive cam according to any one of claims 1 to 4,
A driven mechanism having a sliding surface that is driven by sliding with the driving cam and that contacts the sliding surface of the driving cam;
A valve operating system for an engine, including:
6. The valve gear according to claim 5, wherein a chrome plating layer and a diamond-like carbon film are formed on the chrome plating layer on the sliding surface of the driven mechanism.
7. The valve operating valve according to claim 6, wherein the chromium plating layer is polished so that the surface roughness Rz is 0.5 μm or less and the period of irregularities of 0.1 μm or more is 50 μm or more. apparatus.
7. The valve gear according to claim 6, wherein the diamond-like carbon film is a metal-containing diamond-like carbon film.
6. The valve gear according to claim 5, wherein the driven mechanism is a mechanism having a sliding surface that contacts the sliding surface of the drive cam and a sliding surface that contacts the tappet.
In addition to the drive cam, the valve operating device includes a driven member that contacts the drive cam, a swinging member that is attached to the driven member and transmits the movement of the driven member to a tappet, the driven member, and the The valve operating apparatus according to claim 9, further comprising a relative position changing mechanism that changes a relative position between the swing member and the swing member.