JPS6035983B2 - Internal combustion engine valve train components - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides the following features among the materials constituting the valve mechanism of an internal combustion engine:
The present invention relates to an iron-based sintered alloy that is particularly suitable for rocker arms, valve lifters, etc., which require a high degree of wear resistance due to swamp heat with cams.

To explain the general structure of a valve mechanism, first
The figure shows an example of the OHC type, in which as the cam 2 rotates, the rocker arm 1 performs a seesaw motion with its axis as a fulcrum, opening and closing the valve 5. In this type of type, the wear resistance of the contact surface of the cam 2 of the rocker arm 1 is a problem. Next, FIG. 2 shows an example of a push rod type, in which a valve lifter 3 and a push rod 4 are interposed between the cam 2 and the rocker arm 1, and the movement of the cam 2 is transmitted to the valve 5 through these. It has become a mechanism. In this type of model, the valve lifter
The wear resistance of the contact surface with the cam 2 of No. 3 becomes a problem. In addition,
In either type, it is particularly important not only to have the wear resistance of the member itself but also to prevent the mating member cam 2 from being worn out. In the past, these parts were generally made of steel, alloyed cast iron, etc., and in order to improve wear resistance, the contact surface with the cam 2 was surface hardened by heat treatment, chill hardened, hard chromium plating, or self-fusing alloy sprayed. It is used in a variety of ways.

However, carburized and quenched materials have poor scuffing resistance, chill-hardened materials have poor durability, and in the case of hard chrome plating, there are quality problems such as peeling due to local contact or peeling due to wear. However, in the case of self-fusing alloy thermal spraying, there are disadvantages in terms of cost due to increased production man-hours and the use of expensive materials, and there are concerns about quality assurance in the thermal spraying process.

As described above, there are problems with each of the materials used in conventional construction materials, and there has been a desire to develop better materials.

The present invention has been made in view of the above-mentioned circumstances, and the present invention has been made in the above-mentioned valve mechanism member, in which the entire member or at least the contact surface with the cam 2 is made of Cr. ,2~7% Mbi”0
,1~1.5%C...0.5~3%V...0.1~
3% At least one of P and B...0.1 to 2% F
The gist is that it is formed of a leech alloy having a composition consisting of e and unavoidable impurities...the remainder.

Hereinafter, an example in which the present invention is applied to a rocker arm will be described in detail.

In addition, during the tests carried out by the present invention department, the rocker arm body 1a, excluding the contact surface with the cam, was made of low-alloy steel, and a pad made of the present invention alloy was placed on the contact surface, as shown in Figure 3.
b was joined and discussed. Example: Iron powder, graphite powder, iron-phosphorus alloy powder, alloy steel powder, etc. were mixed to have the following composition and formed into the desired pad shape using a molding pressure turbulence/mechanism, which was then sintered and heat treated under the following conditions. A sample was prepared by applying

Sintering atmosphere: Vacuum (1×10-3 pig Hg) Sintering temperature:
1180q○ Heat treatment conditions: 1180qo oil quenching in argon gas,
The sample tempered to 550 qo exhibited a structure in which the hardened material was distributed in a network pattern on a martensitic base, and the compaction density and hardness were as follows.

Sintered density (g/): 6.7 Hardness (HRC): 50-65 Next, this pad lb was joined to a rocker arm la and installed in a water-cooled inline 4-cylinder 1800cc engine, and a bench test was performed to determine the pad lb. The wear status of cam 2 was compared with that of conventional members.

The test conditions were SAEIOW30 engine oil at 45±5℃.
It was maintained at 200 pm and operated continuously, and after 250 hours it was disassembled and the wear amount of each member was measured. Figure 4 shows the results.The white part of the graph shows the amount of wear on the cam top of cam 2, and the spotted or shaded part shows the amount of wear on the contact surface of the rocker arm. and
The dots represent members of the present invention, and the diagonal lines represent conventional members.

In each example in the figure, the cam is made of low-alloy cast iron in both the comparative example and the example, and the cam top part is chill-hardened, and the rocker arm is plated with hard chrome on its contact surface in the comparative example. I am using the one that has been prepared. As is clear from this figure, when the sample according to the present invention is used as a pad, the wear of the pad itself is reduced to 1% of that of the conventional member, and the total wear including the cam is reduced to about 41%. .

(This means an improvement in wear resistance of about 2.3 tones.) As the above test results clearly show, the present invention reduces the wear of the cam and the mating part that makes sliding contact with the cam, as well as the joint wear. This is extremely useful for extending the life of the valve mechanism.

Finally, the composition of the material, which is a feature of the present invention, will be described as follows.

The member according to the present invention basically improves the wear resistance of the member itself by dispersing a hard phase made of metal carbide in a martensitic base, but at the same time,
Appropriate selection of the type, amount and mutual combination of metal carbides contributes to the wear resistance of the cam. Cr: In addition to strengthening the base, it reacts with C to form hard carbide,
Improves wear resistance.

However, if the addition amount is less than 2%, the desired effect cannot be obtained, while if it is added in excess of 7%, disadvantages such as stiffening of the material and reduction in machinability will occur. Mo: Like Cr, along with strengthening the base,
Reacts with C to form hard carbides and improves wear resistance.

However, if the amount added is less than 0.1%, the desired effect cannot be obtained.
On the other hand, if more than 1.5% is added, the cam of the mating member is likely to be damaged. V: Reacts with C to form carbide and contributes to improving wear resistance.

However, if the addition amount is less than 0.1%, the desired effect cannot be obtained, while if it is added in excess of 3%, the machinability decreases and the other party is likely to be damaged. C: In addition to strengthening the matrix, as mentioned above, it reacts with Cr and other additive components to precipitate a hard phase to improve wear resistance.

However, the desired effect cannot be obtained with 0.5% concentration; on the other hand,
If it exceeds 3%, toughness decreases. P and B: Both are elements that cause liquid phase brazing to increase the density of the sintered member, and their effects are almost the same, but the required effect is not achieved when the addition amount is 0.1%. On the other hand, if it is added in an amount exceeding 2%, an excessive liquid phase will be generated and the dimensional change flow at the time of freezing will become large, which is not preferable.

[Brief explanation of drawings]

Figures 1 and 2 are drawings illustrating the configuration of the valve operating mechanism of an internal combustion engine, Figure 3 is an enlarged view of the rocker arm, and Figure 4 shows the wear status of valve mechanism members in an engine bench test. It is a graph. 1...rocker arm, lb...pad, 2...cam,
3... Valve lifter, 4... Push rod, 5...
Valve, 6...Valve guide. Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. In a valve operating mechanism of an internal combustion engine in which a rocker arm 1 is driven directly by a cam 2 or via a valve lifter 3 and a push rod 4, a rocker arm 1 or a valve lifter 3 that is in sliding contact with a cam 2 is provided. A valve train member for an internal combustion engine, characterized in that a contact surface is formed of an iron-based sintered alloy having the following composition. Cr...2~7% Mo...0.1~1.5%C...0.5~
3% V...0.1-3% At least one of P and B...0.1-2% Fe and unavoidable impurities...the remainder