JPS637350A - Valve gear mechanism member for internal combustion engine - Google Patents

Abstract

PURPOSE:To obtain the titled valve gear mechanism member excellent in wear resistance and reducing cam wear, by forming at least the working face of a member to be in sliding contact with a cam by the use of a ferrous sintered alloy consisting of C, Cr, Mo, Ni, Sn, W, V, P, B, and Fe. CONSTITUTION:In the valve gear mechanism for internal combustion engine, at least the working face of the member to be in sliding contact with a cam is formed of a ferrous sintered alloy having a composition consisting of, by weight, 1-4% C, 1-5% Mo, 5.5-10% Ni, 0.2-5% Sn, 0.1-4% W and/or V, 0.05-5% P and/or B, and the balance Fe with inevitable impurities. In this way, wear resistance of the above valve gear mechanism member is improved and wear of a cam as opposite material is reduced. As a result, overall wear of valve gear mechanism is reduced and the prolongation of service life can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a valve mechanism of an internal combustion engine, which includes:
This invention relates to an iron-based sintered alloy that is particularly suitable for rocker arms, valve lifters, etc., which are members that come into sliding contact with cams and require a high degree of wear resistance.

[Conventional technology and its problems] As demands for internal combustion engines become higher and higher, higher speeds and higher outputs are becoming more and more important. Requirements for the durability of sliding contact surfaces are becoming extremely strict.
There is a strong desire to develop an alloy that can withstand this. It is particularly important that the members that come into sliding contact with these cams not only have high wear resistance themselves, but also that they do not wear out the cams of the mating members.

Conventionally, these parts were generally made of steel, alloyed cast iron, etc., and in order to increase wear resistance, the surface that contacts the cam was surface hardened by heat treatment, chill hardened, hard chrome plating, or self-fusing alloy sprayed. However, carburized and quenched materials have poor scuffing resistance, chill-hardened materials have poor durability, and hard chrome plating may cause peeling due to local contact or abrasion peeling. In the case of self-fusing alloy thermal spraying, there were problems such as cost disadvantages due to increased production man-hours and the use of expensive materials, and quality instability during the thermal spraying process.

In recent years, wear-resistant members of various compositions made of sintered alloys have been proposed for such conventional materials.
The present invention provides valve train members for internal combustion engines as shown in Japanese Patent Publication No. 34628 and Japanese Patent Publication No. 60-35983. Compared to conventional materials, these members can significantly reduce the wear of the cam and the mating material that makes sliding contact with it, as well as the overall wear, and can contribute to extending the life of the valve mechanism. However, as a result of research aimed at further improving performance, the present invention was achieved.

[Means for Solving the Problems] In the valve train member of the present invention for solving the above-mentioned problems, the entire member or at least the surface in contact with the cam has C... 1 to 4%, Cr-5~30%, MO...
1-5%, Ni...5.5-10%, Sn.0.
2 to 5%, at least one of W and V...o, i to 4%, at least one of P and B...0.05 to 5%, Fe and unavoidable impurities...the remainder It is formed from a sintered alloy of the same composition.

The composition of the member of the present invention was determined based on the following findings.

(a) In a Fe-based sintered alloy containing C, Cr, Mo, ■, w% p, when Ni is added to this alloy composition,
The wear resistance of the material itself is improved and the wear of the mating material is reduced, which is best when the content is about 5% Ni, and (b) the Fe-based sintering described in item (a) above When Sn is added to the alloy, the wear resistance is further improved, and is best when Ni is about 7 to 9% and Sn is about 2%.

That is, by adding both Ni and Sn, it is possible to significantly improve the wear resistance.

Regarding the above, various Fe-based sintered alloys including the alloy of the present invention were applied to rocker arms, and wear tests were conducted. The results are shown in FIGS. 1 to 3.

The present invention will be explained in more detail below based on the results shown in the figure. In addition, when testing the member, the rocker arm body other than the contact surface with the cam was made of low alloy steel, and a pad made of Fa-based sintered alloy was bonded to the contact surface portion to prepare a test sample.

First, preparation of a test sample and bench test conditions will be explained.

Graphite powder, nickel powder, tin powder, iron-phosphorus alloy powder, and various iron alloy powders were prepared and blended to have the compositions shown in Tables 1 and 2. In addition, in sample A and sample 2 in Table 1, the Ni amount was in the range of no addition and 2 to 12%,
In addition, mixed powders were prepared with various compositions in which the amount of Sn was not added and in the range of 0.2 to 7%.

Next, these mixed powders were molded into a predetermined pad shape at 6 t/cm 2 , and sintered and heat treated under the following conditions to prepare a sample.

Sintering = Surrounding atmosphere: Vacuum (I It was attached to an arm and incorporated into a water-cooled inline 4-cylinder 1800cc engine, and the wear status of the pads and cams was examined through a bench test.

The mating cam used was one made of low-alloy cast iron with a chilled cam top. The test conditions were to keep the engine oil of 5AEIOW30 at 45±5℃, operate continuously at 650 rpm, disassemble after 250 hours, measure the amount of wear on each component, and calculate the total amount of wear by calculating the sum of each amount of wear. And so.

Table 1, Table 2, and FIG. 1 show the measurement results for sample A and show the effect of adding Ni and Sn. When the amount of Ni added is increased without adding Sn, the amount of wear reaches a minimum when the amount of Ni is about 5%, and when more than 9% Ni is added, the amount of wear increases.

Snf! for this sample! : When added, the minimum value of the wear amount decreases and shifts to the side with a large amount of Ni. Addition of Sn exhibits an effect at 0.2%, and shows the best results when it is 2%, but it becomes worse when it exceeds 5%. In addition, as shown by the dotted line in Figure 1, the amount of Ni that results in a wear amount of 40 μm or less, which is about 20% lower than the minimum value of the total wear amount of Snt# and additives, is 0.2% Sn. .

The minimum value is about 5.5% Ni, and when it is 5% Sn, the maximum value is about 10% Ni. In addition. For 2% Sn, satisfactory results can be obtained in the range of 2.5 to 11% Ni.

FIG. 2 shows the measurement results for sample B with a Ct content of 20%. The trend is the same as that shown in FIG. 1, except that the total wear amount is generally lower than that shown in FIG. 1 due to the difference in the alloy composition of sample B itself.

Figure 3 shows the measurement results for sample C shown in Table 2, and shows the effect of C. From this figure, it can be seen that Crj
It can be seen that l is preferably in the range of 5 to 30%.

[Function] Next, the function of each component of the valve mechanism member of the present invention will be explained. The member according to the present invention has improved wear resistance of the member itself by dispersing hard particles made of metal carbide in a matrix of martensite. Appropriate selection of the material also contributes to reducing wear on the cam, which is the mating material.

Cr: Strengthens the matrix and reacts with C to form hard carbide, improving wear resistance. However, as shown in Figure 3, if the amount of Cr added is less than 5%, the desired effect cannot be expected, and if it is added in excess of 30%, the mating cam is likely to wear out, resulting in a large total amount of wear. In addition, there are disadvantages such as a marked decrease in sinterability.

Mo: Like Cr, Mo strengthens the matrix and reacts with C to form hard carbide, improving wear resistance. However, if the amount added is less than 1%, the material becomes brittle in some places.

W and V: Both react with C to form MC type hard carbide, contributing to improvement of wear resistance.

The desired effect cannot be obtained unless the amount of at least one of the two components added is 0.1% or more;
If it exceeds %, the rigidity will decrease and the mating material will be likely to wear out.

Sn: Diffuses into a solid solution in the matrix and has the effect of suppressing austenitization caused by Ni. Addition amount is 0.2
If it is less than 5%, no effect will be observed, and if it is added more than 5%, the carbide particles will become coarser, reducing mechanical strength and worsening wear resistance.

Ni: Diffuses into the iron matrix to strengthen the matrix and prevent carbides from falling off. In addition, sinterability is improved,
It has the effect of improving compatibility with the mating cam. If added in an amount exceeding 5% without Sn, an austenite phase will be formed in the matrix and the wear resistance will be reduced.
When the amount is within the above-mentioned range, good wear resistance is exhibited when the amount of Ni added is 5.5 to 10%.

C: In addition to strengthening the matrix, as mentioned above (reacts with Cr and other additive components to precipitate a hard phase and improve wear resistance. However, if it is less than 1%, the desired effect cannot be obtained; If it exceeds 4%, the toughness will decrease.

P and B: Elements that have the effect of promoting sintering and increase the density of the sintered member, and either one of them may be used, or both may be added. If the amount added is less than 0.05%, the desired effect will not be obtained; on the other hand, if it is added more than 5%,
This is not preferable because it produces an excessive liquid phase and increases the rate of dimensional change during sintering.

[Example] Next, preferred examples of the present invention will be explained in comparison with comparative examples.

The preparation procedure for each test sample is as follows, but the bench test conditions and measurements are the same as the test conditions in FIGS. 1 to 3.

Example-1 Iron powder, graphite powder, iron-phosphorus alloy powder, alloy steel powder, etc.
・9,9C...2,5 Mo...3,1W...0.5V -
0,4Mn...0,3N i---1,0Sn---2,0P...
・0.25 Fe...The remainder (weight%) was blended and molded into a predetermined pad shape at a molding pressure of 6 t/cm2, which was then sintered and heat treated under the following conditions. A sample was prepared.

Sintering atmosphere: Vacuum (1x 10-3 mmt (g) Sintering temperature: 1130℃ Sintering time = 60 minutes Quenching conditions: 900℃, Oil quenching and tempering conditions:
The sample obtained at 180°C had a structure in which fine hardened materials were distributed in a martensitic matrix, and the sintered density and hardness were as follows.

Sintered density (g/am3): 7.7 hardness
(lIRc): 57-62 Example-2 The wood is the same sample as sample C5 in Table 2.

Cr... iron powder, graphite powder, iron-phosphorus alloy powder, alloy steel powder, etc.
・20,3C-2,5 MO...2-8W...0. 8V ---1,1Mn-=0.3Ni ・
・・7,05n-2, 0P = 0.25 Fe・=Remaining part (weight%)
The composition was blended to give a molding pressure of 6 C/C [I+
2 into a predetermined pad shape, and sintered and heat-treated the pad under the following conditions to prepare a sample.

Sintering atmosphere: Vacuum (I x 10-30] mHg)
Sintering temperature: 1190℃ Sintering time: 60 minutes Quenching conditions: 900℃, oil quenching and tempering conditions:
The sample obtained at 180°C had a structure in which fine hardened materials were distributed in a martensitic matrix, and the sintered density and hardness were as follows.

Sintered density (g/cm3): 7.7 Hardness
(HRC): 55-60 In addition, samples prepared under the following conditions were used as comparative materials.

Comparative Example 1 The sample was an alloy cast iron rocker arm whose contact surface was plated with hard chrome.

Comparative Example-2 Iron powder, graphite powder, iron-phosphorus alloy powder, alloy steel powder, etc.
-6,3C---1,7P...0,4W...1.0Fe---Remainder (wt%) The molding pressure was 6shi/C1l+
2 into a predetermined pad shape, and sintered and heat-treated the pad under the following conditions to prepare a sample.

Sintering atmosphere: Decomposed ammonia gas Sintering temperature: 1180°C Quenching conditions: 1180°C Oil quenching and tempering conditions: 550°C The obtained sample exhibits a structure in which the hardened material is distributed in a network in a martensitic matrix, and the sintered density is low. The hardness was as follows.

Sintered density (g/cm3): 7.6 Hardness
(H, C): 50-60 Comparative Example-3 Iron powder, graphite powder, iron-phosphorus alloy powder, alloy copper powder, etc.
-6,5V ---0,8P...0,4Mo
...0.3C...2,OFe...The balance (weight %) is blended and the molding pressure is 6 j/c.
A sample was prepared by molding the pad into a predetermined pad shape using 2 m2 and subjecting it to sintering and heat treatment under the following conditions.

Sintering atmosphere: Vacuum (I x 10-'mmHg) Sintering temperature: 1180°C Quenching conditions: TTSO°C, oil quenching and tempering conditions = 550°C The obtained sample has a structure in which the hardened material is distributed in a network in a martensitic matrix. The sintered density and hardness were as follows.

Sintered density (g/am3): 6.7 Hardness
(HRC): 50 to 65 Comparative Example-4 Iron powder, graphite powder, iron-phosphorus alloy powder, alloy steel powder, etc. to Cr-4
,3W ・=5.0 C...1.7 Mo=4.0 V -0,3P...0.4 Fe---Remainder (wt%) 6j/cm2
A sample was prepared by molding into a predetermined pad shape and subjecting it to sintering and heat treatment under the following conditions.

Sintering atmosphere: Vacuum (I x 10-'mmHg) Sintering temperature: 1200°C Quenching conditions: 1200°C, oil quenching and tempering conditions = 550°C The obtained sample has a structure in which the hardened material is distributed in a network in the martensitic matrix. The sintered density and hardness were as follows.

Sintered density (g/cm3): 7.4 Hardness
(H, C): 50-65 Figure 4 shows the test results for the above sample, where the white part of the bar graph shows the amount of wear on the cam top, and the spotted or shaded part shows the amount of wear on the rocker arm contact surface. Represents the amount of wear. Note that the dots represent members of the present invention, and the diagonal lines represent conventional materials.

As is clear from this figure, when a sample of the material of the present invention is used for a pad, the pad itself is less abraded and the cam of the mating member is less likely to be abraded. The total amount of wear on the cam and pad was only about 15% of that in Comparative Example 1 for the conventional member. In addition, Comparative Examples 2 to 4 of sintered alloys
It can be seen that it has decreased by 30 to 40% compared to .

In addition, by subjecting the sintered valve train member of the present invention to surface treatments such as soft nitriding and sulfur-nitriding, initial wear can be reduced.
Furthermore, wear resistance can be improved.

[Effects of the Invention] As is clear from the above test results, the present invention significantly reduces the individual wear and total wear of the cam and the mating member that comes into sliding contact with the cam, thereby extending the life of the valve mechanism. This is extremely useful in achieving this goal.

[Brief explanation of drawings]

Each figure is a graph showing the wear state of valve train members in an engine bench test, and Figures 1 and 2 show the relationship between the amount of Ni added and the amount of Sn added and the amount of wear at a predetermined Cr addition amount, respectively. 3 is a graph showing the relationship between the amount of Cr added and the amount of wear, and FIG. 4 is a graph showing the results of a wear comparison test between the member according to the present invention and a conventional member.

Claims (1)

[Claims] (1) A valve train member for an internal combustion engine, characterized in that at least the contact surface of the member that makes sliding contact with the cam is formed of an iron-based sintered alloy having the following composition (% by weight): C ...1-4%, Cr...5-30%, Mo...
1-5%, Ni...5.5-10%, Sn...0.
2 to 5%, at least one of W and V...0.1 to 4%, at least one of P and B...0.05 to 5%, Fe and unavoidable impurities...remainder.