JPS62220B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention provides a rocker arm for an internal combustion engine, in which at least the part surface portion is made of an Fe-based sintered alloy that exhibits excellent wear resistance and does not damage a cam, which is a mating member. It is related to. [Prior art] In general, rocker arms for internal combustion engines are made of chilled cast iron, or have surface treatments such as Cr plating or thermal spray overlay of self-fluxing alloy on the part surface of the rocker arm body. It has been known. [Problems to be solved by the invention] On the other hand, in recent years, various demands have been made on internal combustion engines, such as higher speed, higher output, improved fuel efficiency, and measures against exhaust emissions. Accordingly, wear of the valve train of an internal combustion engine is becoming a problem, and in particular, demands on the durability of the rocker arm parts of the valve train are becoming extremely strict. However, the chilled cast iron Rotsuka arm has
There are problems with pitting damage and wear resistance, and Cr-plated rocker arms have problems such as scuffing and peeling of the Cr-plated layer.Furthermore, thermal spray cladding rocker arms have problems such as scuffing and peeling of the cam of the mating member. None of the rocker arms have the characteristics that satisfy the above requirements, such as problems such as wear. [Means for Solving the Problems] Therefore, from the above-mentioned viewpoints, the present inventors have developed a technology that has excellent wear resistance, pitting resistance, and scuffing resistance, and that does not damage the cam, which is a mating member. In other words, as a result of conducting research to obtain a material with all the characteristics required for the part surface of the Rocker arm using powder metallurgy, we found that each material has a Vickers hardness of 600 as a reduced raw material powder.
Fe-Cr powder, Fe with hardness in the range of ~1300
-Using one or more hard particles of W powder, Fe-Nb powder, and Fe-V powder, iron oxide powder, carbon powder, Cr oxide powder, and Mo oxide powder After blending these reduced raw material powders to have a predetermined final component composition, pulverizing them, mixing them, and then heating and reducing them in a vacuum or in a reducing atmosphere, an alloy powder is produced by the so-called co-reduction method. Fe-Cr, Fe- produced from this alloy powder by normal powder metallurgy method and having a hardness in the range of 600 to 1300 on the Bitkers hardness scale in terms of weight% (hereinafter % indicates weight%). W, Fe—Nb, and Fe—
Hard particles consisting of one or more of V: 10 to 50%, C: 1 to 6%, Cr: 5 to 30%, Mo: 0.5 to 10%, and the rest is Fe and unavoidable An Fe-based sintered alloy having a composition consisting of impurities and a structure in which double carbides of Cr and Mo and the above-mentioned hard particles are uniformly dispersed in a matrix of martensite or bainite, and is used at least on the part surface of a rocker arm for an internal combustion engine. (the entire Rocker arm may be used), the resulting Rocker arm has excellent wear resistance and pitting resistance due to the double carbide in the Fe-based sintered alloy, and also has excellent wear resistance and pitting resistance due to the double carbide in the Fe-based sintered alloy. As a result, they found that the material has excellent scuffing resistance and also has the property of not damaging the mating member, the cam. This invention has been made based on the above findings, and the reason why the composition of the Fe-based sintered alloy is limited as described above will be explained below. (a) Hard particles The hardness of the hard particles themselves is 600 on the Bitkers hardness scale.
If the hardness is less than 1300, it will not be possible to obtain the desired excellent wear resistance, while if the hardness exceeds 1300, the damage to the mating member will be significant. Ta. In addition, if the content is less than 10%, the desired effect of improving scuffing resistance and reducing damage to the mating member cannot be secured;
Even if the content exceeds 10%, not only will there be no effect of further improving wear resistance, but also the toughness will decrease and pitting will occur, so the content was set at 10% to 50%. Note that preferably
A content of 20 to 40% is desirable. (b) C The C component combines with Cr and Mo to form carbides and has the effect of improving the wear resistance of the alloy, but if its content is less than 1%, the amount of carbide precipitation of the metal increases. If the content is too low, it will not be possible to secure the desired wear resistance, while if the content exceeds 6%, the amount of carbide precipitated will be too large, resulting in high hardness, but it will not be possible to secure the desired wear resistance. The content was determined to be 1 to 6% because the wear becomes significant and the toughness also decreases. (c) Cr and Mo These components combine with C to form double carbides of Cr and Mo that have high hardness, improving the wear resistance of the alloy, and some of them are dissolved in the matrix. However, if the content is less than 5% Cr and less than 0.5% Mo, the desired effect cannot be obtained; :Ten
If the content exceeds 5% to 30%, the damage to the mating member will become significant and the strength will decrease.
Mo: set at 0.5 to 10%. [Example] Next, the rocker arm for an internal combustion engine according to the present invention will be described with reference to an example. Fe-Cr powder (contains 65% Cr) with a Bitkers hardness of 1050 is used as the reduced raw material powder,
Fe-W powder (W: 81% content) with 1100
Fe-Nb powder (Nb: 65% content) with 1000
1150 Fe-V powder (V: 52% content), Cr and Mo oxide powder, carbon powder, and iron oxide powder were prepared, and these reduced raw material powders were blended to have a predetermined final component composition. , After pulverization and mixing in a ball mill, in a hydrogen atmosphere, temperature: 1000℃
An alloy powder is manufactured by subjecting it to a time-retained heating reduction treatment, and then a green compact is formed from the alloy powder at a pressure of 5 tons/cm ² , and then this green compact is heated in a vacuum at a temperature of 1160 to 1200°C. The rocker arm part surface members 1 to 20 made of the Fe-based sintered alloy of the present invention (hereinafter referred to as the present invention pad surface member) having the component compositions shown in Table 1 and the comparative Fe Rocker arm part face members 1 to 8 made of a base sintered alloy (hereinafter referred to as comparative part face members) were manufactured, respectively. In addition, for comparative part surface members 1 to 8, one of the constituent components of the Fe-based sintered alloy (those marked with * in Table 1) was outside the scope of the present invention. It has a composition. In addition, the pad surface members 1 to 20 of the present invention and comparative pad surface members 1 to 8 were left in the as-sintered state;
The patch surface members 18 and 19 of the present invention have a temperature of 1000
After quenching from ℃, temperature: 550℃

【table】

〔Effect of the invention〕

As is clear from the results shown in Table 1, conventional members 1 and 2 had extremely high amounts of wear on the rocker arm and cam, and were also extremely prone to scuffing and pitting, whereas the present Inventive pad face members 1 to 20 not only exhibit excellent wear resistance, but also hardly damage the cam of the mating member.
Furthermore, it has excellent scuffing and pitting resistance. In addition, the pad surface members 18 to 20 of the present invention have increased hardness through heat treatment, and exhibit even better wear resistance. On the other hand, as seen in Comparative Part Surface Members 1 to 8, if any of the constituents of the Fe-based sintered alloy constituting the parts falls outside the scope of the present invention, the wear resistance and attack resistance against the cam, which is the mating member, may deteriorate. It is clear that at least one of the following properties (resistance to opponent attack), scuffing resistance, and pitching resistance becomes inferior, and it does not have all of the properties required of a locking arm. . As described above, the rocker arm for an internal combustion engine of the present invention has at least its part surface portion made of Fe-based material having a structure in which hard particles and double carbides of Cr and Mo are uniformly dispersed in a matrix of martensite or bainite. Since it is made of a sintered alloy, it has excellent wear resistance, attack resistance, scuffing resistance, and pitting resistance, and exhibits excellent performance over an extremely long period of time.

Claims (1)

[Claims] 1. At least the pad surface portion of the rocker arm is
Fe-Cr, Fe-W, Fe-Nb, and Fe-V with hardness in the range of 600 to 1300 on the Bitkers scale
Hard particles consisting of one or more of the following:
10 to 50%, C: 1 to 6%, Cr: 5 to 30%, Mo: 0.5 to 10%, with the remainder consisting of Fe and unavoidable impurities (wt%), and martensite or bainite. It has a structure in which double carbides of Cr and Mo and the above hard particles are uniformly dispersed in the matrix.
A rock arm for internal combustion engines characterized by being made of Fe-based sintered alloy.