JP2002097906A - Rocker arm - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rocker arm wherein the coefficient of friction of a sliding region which contacts other members such as the stem ends of a valve is low and the sliding region hardly wears and separates even for long time use and does not wear or tear the mating members. SOLUTION: The sliding and frictional resistance of the rocker arm 1 is reduced by forming a coating film 5 comprising mainly a diamond-like carbon film 53 on the surfaces of the valve receiver 15 contacting at least the valve stem end 3 of the rocker arm 1 or the lash adjuster receiver 14 which contacts a lash adjuster 2 in addition to the valve receiver 15. In addition, wear and abrasion resistance and peeling resistance can be improved with ease by forming a chromium film 51 as an intermediate layer on the surface of the base body B of the rocker arm 1 and making tungsten contained in the diamond-like carbon film 53, and an offensive characteristic against the mating member can be reduced by restraining the surface roughness of the base body B of the rocker arm 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rocker arm which swings by rotation of a cam in a reciprocating engine and presses intake and exhaust valves provided on a cylinder head to open and close them.

[0002]

2. Description of the Related Art In a rocker arm that is interposed between a cam of a reciprocating engine and an intake / exhaust valve and swings by rotation of the cam to open and close the valve by pressing a stem end of the valve, a rocker arm body is generally used. The rocker arm body swings around the swing fulcrum by the rotation of the cam contacting the rotatably supported roller, and the stem end of the valve slidingly contacts the valve receiver provided at the end of the body. Is pressed to open and close the valve.

In this type of rocker arm, there are an end pivot type in which a swing fulcrum is provided at one end of a body and a center pivot type in which a rocking arm is provided at a central portion of the rocker arm body. The lash adjuster receiver provided at one end forms a swing fulcrum by abutting the lash adjuster, and in this case, a roller that abuts on the cam is disposed at the center of the rocker arm body,
A valve receiver is provided at the other end. In the center pivot type, a pivot shaft is usually inserted into a hole formed in the center of the rocker arm body to form a swing fulcrum.
Valve receivers are respectively provided at the other ends.

[0004]

In recent years, in order to improve the fuel efficiency and output of automobiles, it has been required to reduce the friction of a sliding contact portion in an engine valve system.
For such demands, it is particularly effective to reduce the friction coefficient at the sliding contact portion of the rocker arm, that is, the contact portion between the valve receiver and the valve stem end, or the contact portion between the lash adjuster receiver and the lash adjuster. is there. For this reason, conventionally, various surface treatments have been studied for the surfaces of the valve receiver and the lash adjuster receiver in the rocker arm. However, problems such as abrasion and peeling (adhesion) of the film or the stem of the valve as a mating member have been studied. The problem of aggression to end etc. has not been sufficiently solved.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems at once, and has a low coefficient of friction at a sliding portion with respect to other members, and causes abrasion and peeling of the sliding portion even after long-term use. An object of the present invention is to provide a rocker arm that is hard to wear and does not wear or wear the mating member.

[0006]

In order to achieve the above object, a rocker arm of the present invention swings around a fulcrum by rotation of a cam to press a stem end of a valve provided on a cylinder head of an engine. The rocker arm that opens and closes the valve is characterized in that a diamond-like carbon film is formed on at least the surface of a valve receiver that is in sliding contact with the stem end of the valve (claim 1).

Here, in the present invention, in addition to the surface of the above-mentioned valve receiver, a diamond-like carbon film is formed on the surface of the lash adjuster receiver which is in sliding contact with the lash adjuster to form the rocking fulcrum of the rocker arm. (Claim 2) is preferable.

In the present invention, it is preferable to adopt a structure in which a chromium layer is formed between the diamond-like carbon film and the rocker arm substrate surface (claim 3). ,
It is more preferable to contain tungsten (Claim 4), and the surface roughness of the rocker seam base forming the diamond-like carbon film is set to Ry (maximum height μm) 3.2 or less. desirable.

The diamond-like carbon film formed by coating in the present invention has a thickness of 1.0 to 5.0.
μm, and the adhesion to the rocker arm base is preferably 40 N or more (claim 6).

The present invention has various problems such as a coefficient of friction of not more than 1/2 that of a rocker arm base made of an iron-based material, less wear, good adhesion to the base, and aggression to a counterpart member. The surface of the valve contact which comes into contact with the other members of the rocker arm, especially the stem end of the valve (claim 1), and also the surface of the lash adjuster receiver (claim) 2) is intended to achieve the intended purpose.

That is, since the diamond-like carbon film has high lubricity and is hard, it is suitable for covering the sliding contact surface of this kind of rocker arm to reduce frictional resistance, and the invention according to claim 3 As described above, the film is hardly peeled off by forming a film with a chromium layer interposed on the surface of the rocker arm substrate, and tungsten is contained as in the invention according to claim 4, more specifically, diamond. By having a laminated structure of a like carbon film and a tungsten carbide film, internal stress can be relaxed, and the occurrence of cracks caused by internal stress as in the case of a simple diamond-like carbon film can be prevented. In addition, it can withstand a long-term use under severe conditions and maintain a low coefficient of sliding friction.

Further, the surface roughness of the diamond-like carbon film reflects the surface roughness of the film-forming surface. By setting the surface roughness of the rocker arm base in Ry to 3.2 or less,
It is possible to prevent the stem end or the lash adjuster of the valve which is the mating member from being worn or worn away.

In the present invention, the diamond-like carbon film formed on the rocker arm valve receiving surface or the lash adjuster receiving surface has a total film thickness of 1.0 to 5.0 mm. 0μ
By setting m and the adhesion to the rocker arm base to 40 N or more, a film that can be practically used and whose performance can be maintained for a long time can be obtained. If the film thickness is less than 1 μm, peeling occurs early because the stress relaxation ability of the entire film is small. On the other hand, the film thickness is 5 μm
If it exceeds, the coca will be saturated and the cost will increase. A more preferable thickness range is 2.0 to 3.5 μm.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a front view of an embodiment of the present invention, and FIG.
FIG. 3 is a bottom view.

In this embodiment, the present invention is applied to an end pivot type rocker arm.
The rocker arm 1 includes a rocker arm body 11 and a roller 13 rotatably supported by a shaft 12 fixed to the center of the rocker arm body 11 via a needle roller 12a.

A lash adjuster receiver 14 is formed at one end of the rocker arm body 11, and a valve receiver 15 is formed at the other end. When assembled to the engine, the upper surface of the lash adjuster 2 contacts the lower surface of the lash adjuster receiver 14, the stem end 3 of the valve contacts the lower surface of the valve receiver 15, and the camshaft contacts the surface of the roller 13. The cam 4 fixed to 4a comes into contact. Then, by the rotation of the camshaft 4a, the rocker arm 1 swings with the contact portion between the lash adjuster receiver 14 and the lash adjuster 2 as a fulcrum, and the swing causes the valve receiver 15 to swing.
Presses the stem end 3 of the valve to open and close the valve.

The feature of this embodiment is that, as shown in FIG. 2, the surface (lower surface) of the lash adjuster receiver 14 formed at one end of the rocker arm body 11 and in contact with the lash adjuster 2, and the rocker arm body 11 is that a coating film 5 mainly composed of a diamond-like carbon film is formed on the surface (lower surface) of a valve receiver 15 which is formed at the other end of the valve 11 and comes into contact with the stem end 3 of the valve.

Each of the coating films 5 is actually a laminate of a plurality of film bodies, and as shown in a schematic sectional view of FIG.
First, a chromium film 51 is formed as an intermediate layer, and a tungsten carbide film 52 and a diamond-like carbon film 53 are alternately formed on a plurality of layers in this order.

The thickness of the chromium film 51 as an intermediate layer is 0.3
The whole of a stacked body of a plurality of tungsten carbide films 52 and a diamond-like carbon film 53 formed thereon is 1.0 to 5.0 μm.
It has been. A laminated body of the tungsten carbide film 52 and the diamond-like carbon film 53 is formed by PVD or sputtering, and tungsten and carbon are used as a vapor deposition source. As a result, a tungsten carbide film 52 is obtained, and a laminate having the structure shown in FIG. 4 is obtained. The proportion of tungsten in the laminate is in the range of 5 to 25 at%. The surface roughness of the substrate B on which the coating film 5 of the rocker arm body 11 is formed is set to Ry3.2 or less.

The above-mentioned coating film 5 has a sliding friction coefficient of about 0.2 due to the diamond-like carbon film 53, and the rocker arm body 1 made of an iron-based material.
It is 以下 or less of the sliding friction coefficient of one base B. Also,
Due to the presence of the chromium film 51 as the intermediate layer and the tungsten carbide film 52 as the stress relaxation layer, the adhesion to the substrate B is at least 40 N, which is at least twice that of the conventional diamond-like carbon film alone. In addition, no cracks or the like are generated due to internal stress, and a 3/8 "diameter ball made of material SUJ2 is lubricated with oil lubrication to investigate the load resistance. As a result of an experiment of rotating at 1200 rpm while pressing to a pressure of 10 GPa under a pressing force of 3.4 GPa,
^{Even after 8} rotations, no signs of peeling, abrasion, etc. could be found, confirming that they could be put to practical use. Further, since the surface roughness of the rocker arm body 11 on which the coating film 5 is formed is set to Ry 3.2 or less, no large convex portion exists on the surface of the coating film 5, and
Therefore, the aggressiveness of the valve, which is the sliding partner, to the stem end 3 and the lash adjuster 2 is weak, and the partner is not worn.

In the above embodiment, an example is shown in which the present invention is applied to an end pivot type rocker arm. However, it is needless to say that the present invention can be applied to a center pivot type rocker arm. In this case, since there is no lash adjuster, it is sufficient to form a coating film mainly composed of a diamond-like carbon film on the surface of the valve receiver.

However, in the present invention, in addition to the valve receiver and the lash adjuster receiver, for example, the above-mentioned coating film 5 may be formed on the end face of the roller 13. In this case, the contact resistance to the rocker arm body 11 is reduced. be able to.

[0023]

As described above, according to the present invention, since the surface of the valve receiver of the rocker arm body or the surface of the lash adjuster receiver is coated with the diamond-like carbon film as a functional film, the valve stem is provided. The coefficient of sliding friction with the end or the lash adjuster can be reduced to half or less as compared with the case where the rocker arm base is left as it is, which greatly contributes to the improvement of fuel efficiency and output of the automobile.

Further, by interposing a chromium film as an intermediate layer between the rocker arm substrate and the diamond-like carbon film as in the invention according to claim 3, the adhesion of the diamond-like carbon film to the substrate is greatly improved. Further, by incorporating tungsten into the diamond-like carbon film and forming a laminate with the tungsten carbon film as in the invention according to claim 4, the internal stress of the film body is relaxed to prevent the occurrence of cracks and the like. And the surface roughness of the substrate of the rocker arm on which the coating film is to be formed is Ry.
By setting it to 3.2 or less, a convex portion that wears or wears the sliding partner member is not formed on the surface of the film, and the problem of aggression can be solved. Further, as in the invention according to claim 6, the thickness of the coating film using the diamond-like carbon film as the functional film is set to 1.0 to 5.0 μm, and the adhesion to the substrate is set to 40N or more, so that it can be used practically. To obtain a coating film having sufficient strength and longevity.

[Brief description of the drawings]

FIG. 1 is a front view of an embodiment of the present invention.

FIG. 2 is a central longitudinal sectional view of FIG.

FIG. 3 is a bottom view of FIG. 1;

FIG. 4 is a coating film 5 used in the embodiment of the present invention.
FIG. 2 is a schematic sectional view showing the structure of FIG.

[Explanation of symbols]

 Reference Signs List 1 rocker arm 11 rocker arm body 12 shaft 13 roller 14 lash adjuster receiver 15 valve receiver 2 lash adjuster 3 stem end of valve 4 cam 4a camshaft 5 coating film 51 chrome film 52 tungsten carbide film 53 diamond-like carbon film B of rocker arm body 11 Base

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3G016 AA06 AA19 BA49 BB08 BB16 BB17 BB22 BB23 BB24 EA07 EA11 EA24 FA21 GA02 4K029 AA02 BA07 BA34 BA57 BC02 BD04 CA05 EA01

Claims (6)

[Claims] 1. A rocker arm which swings around a fulcrum by rotation of a cam and presses a stem end of a valve provided on a cylinder head of an engine to open and close the valve. A diamond-like carbon film is formed on the surface of a valve receiver that makes sliding contact with the rocker arm. 2. A diamond-like carbon film is formed on a surface of a lash adjuster receiver which forms a rocking fulcrum of the rocker arm by slidingly contacting the lash adjuster in addition to the surface of the valve receiver. The rocker arm according to claim 1, wherein 3. The rocker arm according to claim 1, wherein a chromium layer is formed between the diamond-like carbon film and the substrate surface of the rocker arm. 4. The method according to claim 1, wherein the diamond-like carbon film contains tungsten.
4. The rocker arm according to 2 or 3. 5. The rocker arm substrate at a portion where the diamond-like carbon film is formed has a surface roughness of:
Ry is 3.2 or less,
The rocker arm according to 3, or 4. 6. The diamond-like carbon film,
The thickness is 1.0 to 5.0 [mu] m, and the adhesion to a substrate is 40 N or more.
The rocker arm described in 1.