JPH01303376A - Transmission - Google Patents

Abstract

PURPOSE:To extremely improve the durability in the title transmission by forming a surface layer of metal carbonate or metal nitride on at least one of sliding surfaces of a cam and a follower member. CONSTITUTION:On the sliding surface of the cam of a locker arm 3 to a cam nose part 2a, there is formed a surface layer 4 of metal carbonate or metal nitride. Thus, with the excellent wear resistance of the surface layer 4, wear is reduced in a severe condition, thereby extremely improving the durability.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a transmission device, and for example, to a transmission device consisting of a combination of a cam and a rocker arm or tappet used in a valve mechanism of an internal combustion engine.

Conventionally, camshafts have been made of cast iron with a chilled cam nose surface, and the rocker arm or tappet, which is a follower member that swings or reciprocates in sliding contact with the cam, has a sliding surface. Chilled cast iron or high chromium cast iron are used.

As internal combustion engines have become smaller and faster in recent years, the number of cams on camshafts used in valve train mechanisms has decreased, or the number of revolutions has increased, and the sliding conditions between the cams and rocker arms or tappets have become more difficult. It's getting harsher. In other words, the sliding speed between the two becomes high, and not only does the pressure with which the upper jaw arm or tappet presses against the cam become high, but also the rocker arm or tappet is struck by the cam nose of the cam that rotates at high speed. It has come to be used under extremely harsh conditions where sliding and impact are combined.

As a result, wear progresses rapidly, causing problems in the durability of these members.

FIG. 5 is a perspective view of the main parts showing an example of the relationship between the main parts of the internal combustion engine. As the camshaft 1 rotates, the rocker arm 3 in sliding contact with the cam 2 swings, and the coffin 11 reciprocates to perform intake and exhaust. The valve 21 is biased toward the closed state by the coil spring 22, and the tip of the rocker arm 3 is pressed against the cam 2. Valve 21
The tip of the cylinder is located in a cylinder head (not shown).

The valve 21 reciprocates (opens and closes) to cause intake explosion and exhaust, and the piston 23 reciprocates in a cylinder (not shown).
This reciprocating motion rotates the crankshaft 25, which is connected to the piston 23 via the connecting rod 24, and generates power. The timing of the opening and closing of the valve 21 and the reciprocating movement of the piston 23 is determined by a chain (or timing belt) 26 that is passed between the camshaft 1 and the crankshaft 25. From such a mechanism,
It will be understood that as the rotational speed of the camshaft 1 increases or as the pressing force of the rocker arm 3 on the cam 2 increases, the cam 2 and the rocker arm 3 will slide under extremely severe conditions.

In order to solve the above-mentioned wear problem, attempts have been made to use a sintered alloy with excellent wear resistance for the sliding contact portion of the nose portion of the cam, the rocker arm, or the tappet.

However, as internal combustion engines have become faster and faster in recent years, wear-resistant sintered alloy parts have little wear on themselves, but they have a marked tendency to wear out the surfaces of other parts, such as chilled cast iron. There is also a tendency for scuffing to occur.

Purpose of the Invention The present invention has been made in view of the above circumstances, and includes:
The objective is to provide a transmission device that has excellent durability even when used under harsh conditions.

21. Constitution of the Invention The present invention provides a transmission device including a cam as a reverse part and a follower member that comes into sliding contact with the cam, wherein the sliding contact surface that the follower member of the cam comes into sliding contact with, and the At least one of the sliding contact surfaces of the follower member that comes into sliding contact with the cam has a thickness of 1 to 2
00 (tm) A transmission device characterized in that a surface layer of metal nitride or metal carbide is formed.

E, Example The present invention will be explained in detail below.

Cast iron or steel made by casting or forging can be used as the material for the camshaft and the rocker arm or tappet as a follower member having a surface layer of metal nitride or metal carbide. The rocker arm, tappet, or camshaft that comes into sliding contact with the surface layer of the metal nitride or metal carbide may have a sliding portion made of chilled cast iron or wear-resistant sintered alloy.

The metal nitride or metal carbide surface layer is formed by reactive ion blasting. In particular, the sliding surface layer of the rocker arm or tappet formed by reactive ion brating, and the cast iron camshaft with chilled cam nose surface or the sliding portion of wear-resistant sintered alloy on the cam nose surface. A combination with a camshaft is preferred. Forming a surface layer of metal nitride or metal carbide only on the cam portion of the camshaft by reactive ion blasting makes the device complicated and large, and the operation becomes complicated. However, a large number of cam pieces (individual cam members) are manufactured separately, a surface layer of metal nitride or metal carbide is formed on the cam nose part of these cam pieces, and these cam pieces are fixed to the shaft. By doing so, the surface layer of the metal nitride or metal carbide described above can be easily provided on the camshaft side. In this case, it is preferable to attach the cam piece to a moving jig using, for example, a cam mechanism so that the distance between the surface of the cam nose portion and the metal evaporation source described later is constant. In addition, the above surface layer is a cam,
It may be provided on both sides of the follower member so that the surface layers are in sliding contact with each other.

A typical type of surface layer formed by reactive ion blasting is chromium nitride. Crz N5CrN as chromium nitride
CrN has higher hardness and better wear resistance than Cr2N, but the film tends to be less flexible and has relatively poor adhesion, but there is no problem in practical use (Patent Application No. 62-3)
No. 15751, No. 62-316965). A method of further forming adhesion under severe conditions can be used to obtain a film with good adhesion and excellent abrasion resistance.

Alternatively, an ultrafine mixed structure of metallic chromium, CrzN, and CrH may be used (Japanese Patent Application Nos. 61-27772 and 59-207986).

The reason why the component constituting the surface layer is a layered structure of chromium and its nitride is that the chromium phase formed on the surface of the raw metal by reactive ion blasting has good adhesion to the raw metal, and The coefficient of thermal expansion is close to the coefficient of thermal expansion of the material metal (therefore, the surface layer can be prevented from peeling off from the metal material during use. Also, the reason why chromium is adopted as a component of the surface layer is This is because the deposition rate of metallic chromium by ion plating is higher than that of other metals, and is extremely advantageous in terms of productivity.

In addition, we have developed a composite coating consisting of chromium nitride and titanium nitride (Japanese Patent Application No. 61-27773), a base layer consisting of metallic chromium and chromium nitride, and a composite coating consisting of a wear-resistant layer of titanium nitride on the base layer (Patent Application No. 61-27773). (Sho 61-124669), a surface layer made of a solid solution of titanium carbide and titanium nitride (Japanese Patent Application No. Sho 60-1)
No. 20563) etc. can be considered. Although titanium nitride has higher hardness and better wear resistance than chromium nitride, it is less flexible and peels more easily than chromium nitride, but titanium nitride alone poses no practical problem.

The reason why the thickness of the surface layer was limited to 1 to 200 μm is that 1 μm
If it is less than 200 μm, the surface layer will wear out due to initial break-in and wear resistance will be lost. If it exceeds 200 μm, problems such as chipping or cracking will occur in the surface layer, and the cost will increase.

Ion brating device heater 1 used for surface layer formation
3, the material 11 is heated to a predetermined temperature.

Below the material 11, a water-cooled copper crucible 15 containing metal chromium 14A and metal titanium 14B, which are evaporation sources, is rotatably installed so that the positions of metal chromium 14A and metal titanium 14 can be exchanged. It is. A nitrogen gas supply port 17 and an HCD (h
A (low cathode discharge) type electron gun 18 is attached, and the electron gun 18 is provided with an introduction pipe 19 for plasma argon gas.

The electron beam emitted from the electron gun 18 is sent to the converging coil 2
Metal chromium 1 as an evaporation source in a water-cooled crucible 15 converged at 0
Irradiate with 4A. The pressure inside the vacuum container 16 is reduced by a vacuum pump (not shown).

Argon gas is introduced into the vacuum container 16, and 1×1O−2
Depressurize to about torr and bombard with electron beam (b
ombard) to clean the surface of the material 11. Next, after reducing the pressure to about 3x10-', nitrogen gas is gradually introduced. Next, the metal chromium 14A serving as the evaporation source is heated and evaporated by the HCD type electron gun 18. The evaporated metallic chromium reacts with nitrogen in the container to form a surface layer of chromium nitride on the material 11.

When forming the surface layer of titanium nitride, the crucible 15 is
The titanium metal 14B is evaporated in the same manner as above.

When forming a carbide film, use Cz instead of nitrogen gas.
Hz gas is introduced, and when forming a surface layer of chromium carbide, metal chromium 14A is evaporated, and when forming a titanium carbide film, metal titanium 14A is evaporated in the same manner as described above.

Using 345C carbon steel for mechanical structures as the material, it was formed into a rocker arm shape by cold forging, and then formed to a thickness of 20 μm by a mechanical ion blating method. Also,
Similarly, a surface layer of titanium nitride with a thickness of 5 μm was formed,
One type of specimen was used.

Material temperature: 400°C Beam output crab 3QV-300A convergence current:
150A Nitrogen gas partial pressure: 0~3X10-' Evaporation source 2 Metal chromium or titanium treatment time: 6
After puff finishing each specimen for 0 minutes, it was subjected to a motoring test.

The following two types of camshafts were used in combination with these rocker arms. One of them is 3.3% by weight (hereinafter, "weight%" is simply expressed as "%") C12,3%S.
i, 0.76%Mn, 0.36%Cr, 0.24%
Mo.

It is made of cast iron with 0.39%Nt, 0.05%P, 0.02%S1 and the balance being Fe, and has a chilled cam nose surface. The other one is 1.9%C10, 95%Si on the cam nose surface of the cast iron camshaft with the above composition.
.

0.11% Mn, 0.1% Ni, 17.3% Cr,
A thin piece of sintered alloy having a composition of 0.66% P, 0% old S, and the balance Fe is integrally provided.

The combinations of the rocker arm and camshaft are shown in the table below.

Table 1 is a schematic front view schematically showing the sliding contact between the camshaft and the rocker arm, and the sliding surface 5 of the surface layer 4 of the rocker arm 30 is in contact with the cam nose portion 2a of the cam 2 of the camshaft 1. The rotation of the camshaft 1 (arrow a) causes the rocker arm 3 to swing as shown by the arrow A.

The motoring test was conducted using a gasoline engine with a displacement of 1800 cc under the following conditions.

Test conditions Engine rotation speed: 200 Orpm (cam rotation: 11000
rp 200 hours) Oil temperature: 60°C Oil used: 1OW30 After engine operation, measure the depth of the tappet and camshaft, and determine the amount of wear on the camshaft by measuring the depth of wear at the top of the cam nose, and find the most worn part. It is expressed as the wear depth with respect to the original curved surface. The measurement results are shown in FIG.

Figure 3 shows 3.55%C, 1.62%C for comparison.
Si, 0.52%Mn50.48%Ni, 17.
A combination of a rocker arm made of high chromium cast iron with a chill structure of 5% Cr, 0.09% P\0.02% S, and the balance Fe, and a camshaft with the same manufacturing loft used in Example 1.2. (Comparative Example 1) and 2.9% C10, 2% S
i, a rocker arm made of a high chromium iron-based sintered alloy having a composition of 12.0% Cr, 2.2% Mo, 0.66% P, and the balance Fe, and which is liquid-phase sintered; Combination with a camshaft from the same manufacturing lot used (Comparative Example 2)
The results of a similar test are also listed.

From Figure 3, compared to Comparative Examples 1 and 2, both the rocker arm wear and the cam nose wear of the Examples are significantly reduced, and the wear resistance is greatly improved, and therefore the durability is greatly improved. I understand that

The above example is an example in which a rocker arm is used as the follower member, but a similar test using a tappet as the follower member also yielded substantially the same results as in FIG. 3.

FIG. 2 is a schematic cross-sectional view illustrating the sliding contact between the camshaft and the tappet, in which the sliding surface 10 of the surface layer 9 of the tappet 80 is in contact with the cam nose portion 7a of the cam 7 of the camshaft 6. By rotating the camshaft 6 (arrow C), the tappet 8 can be modified in various ways based on the technical idea of the present invention, in addition to the above embodiment. For example, the metal nitride or metal carbide constituting the surface layer may be a nitride or carbide of chromium or titanium, or other hard metal nitrides or metal carbides. Further, the shape of the cam may be oval as shown in FIGS. 1 and 2, or any other suitable shape. Further, as the follower member, in addition to a rocker arm and a tappet, a follower member having a roller at the tip and other follower members can be used.

1. Effects of the Invention In the transmission device according to the present invention, a surface layer of metal nitride or metal carbide is formed on at least one of the sliding surface of the cam and the sliding surface of the follower member that slides on the cam. Therefore, due to the excellent wear resistance of the metal nitride or metal carbide that constitutes this surface layer, there is little wear even under severe usage conditions, and durability is greatly improved.

[Brief explanation of the drawing]

1 to 4 show embodiments of the present invention. FIG. 1 is a schematic front view showing the state of sliding contact between the camshaft and the rocker arm, and FIG. 2 is a schematic front view showing the state of sliding contact between the camshaft and the tappet. FIG. 3 is a graph showing the results of a motoring test. FIG. 4 is a schematic front view of the interior of the on-blating device. FIG. 5 is a perspective view of the main parts showing an example of the relationship between the main parts of the internal combustion engine. In addition, in the symbols shown in the drawings, 1.6... camshaft 2.7...
...Cam 2a, 7a...Cam nose part 3...
...Rocker arm 4.9 ...Surface layer 5.10 ... Sliding surface of surface layer 13 ...
...... Heater 14A, 14E3 ...... Evaporation source metal 15.
......Water-cooled copper crucible 17...Reaction gas inlet 18...
...Electron gun 19...Argon gas inlet 20...
・・・・・・It is a convergence coil. Agent Patent Attorney Mail Order HiroshiFigure 1Figure 2Figure 3

Claims (1)

[Claims] 1. In a transmission device that uses a cam as the master unit and includes the cam and a follower member that comes into sliding contact with the cam, there is a sliding contact surface on which the follower member of the cam comes into sliding contact with the cam of the follower member. A thickness of 1 to 200μ on at least one side of the sliding contact surface.
A transmission device characterized in that a surface layer of metal nitride or metal carbide of m is formed.