JPS6025499B2 - Rocker arm for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a rocker arm for an internal combustion engine, in which at least a pad surface portion is made of Fe-based neighboring alloy, which exhibits excellent wear resistance and does not damage a cam, which is a mating member. It is related to.

In recent years, various demands have been placed on internal combustion engines, such as higher speeds, higher outputs, improved fuel efficiency, and measures against exhaust emissions.As a result, valve train wear in internal combustion engines has become a problem. In particular, the demands on the durability of rocker arm pad surfaces in valve train systems are becoming extremely strict, and there is a strong desire to develop an alloy that can withstand these demands.

On the other hand, the follower and rocker arms are made of chilled cast iron,
Rocker arms made of chilled cast iron have problems in terms of pitting damage and wear resistance, and although there are rocker arms that have been subjected to surface treatments such as Cr plating or thermal sprayed overlay of hot-melt alloy on the butt surface of the rocker arm body, The plated Rotsuka arm has
Both rocker arms satisfy the above requirements, as there are problems such as scuffing and peeling of the Cr plating layer, and rough thermal spray overlay rocker arms have problems such as scuffing and significant wear of the cam of the mating member. It does not have any characteristics. Therefore, from the above-mentioned viewpoint, the inventors of the present invention have developed a material that has excellent wear resistance, pitching resistance, and scuffing resistance, and also does not damage the cam, which is the mating member, which is required for the pad surface of the rocker arm. As a result of conducting research to obtain materials with all of the characteristics by powder metallurgy, we found Fe-Cd powder and Fe-Mo powder, each having a hardness in the range of 600 to 1300 on the Pickers scale, as reduced raw material powders. , Fe-W
one of powder, Fe-Nb powder, and Fe-V powder
seeds or two or more types of hard particles, iron oxide powder, carbon powder, Cr oxide powder, Mo oxide powder, and any one or two of W oxide powder and V oxide powder. After blending these reduced raw material powders to have a predetermined final component composition, pulverizing and mixing, the alloy powder is produced by a so-called co-reduction method, which is heated and reduced in a vacuum or in a reducing atmosphere. Manufactured by normal powder metallurgy method from this alloy powder, in weight% (hereinafter % indicates weight%),
Fe-Cr, Fe-Mo, Fe-W, Fe-Nb, having a Vickers hardness in the range of 600 to 1300,
and hard particles consisting of one or more of Fe-V: 10 to 50%, C: 1 to 6%, Cr: 5 to 30%, Mo: 0.5 to 10%, Furthermore, it contains one or two of the following: W: 4 to 8%, V: 0.5 to 5%, and the remainder is Fe and unavoidable impurities, and in the martensitic or baenite matrix. , Cr, Mo, W, and V having a structure in which double carbides and the above-mentioned hard particles are uniformly dispersed.
When at least the pad surface portion (or the entire rocker arm) of a rocker arm for an internal combustion engine is made of a base sintered alloy, the resulting rocker arm has excellent wear resistance and pitting resistance due to the double carbide in the Fe-based sintered alloy. Furthermore, they discovered that the undissolved hard particles also provide excellent scuffing resistance, as well as the ability to prevent damage to the mating member, the cam.

This invention has been made based on the above findings, and the reason why the composition of the overlying e-based sintered alloy is limited as described above will be explained below.

(a) If the hardness of the hard particles itself is less than 60 degrees Vickers hardness, the desired excellent wear resistance cannot be obtained; on the other hand, if the hardness exceeds 1300 degrees, damage to the mating member will be significant. Therefore, the hardness of the hard particles is 60 on the Bitkers hardness scale.
It was set as 0 to 1300.

In addition, if the content is less than 10%, the desired effect of improving scuffing resistance and reducing damage to the opposing part cannot be ensured, while even if the content exceeds 50%,
Not only does it not have the effect of further improving wear resistance, but it also reduces balling properties and causes pitting.
Its content was set at 10-50%.

Note that the content is preferably 20 to 40%. (b
The I C C component combines with Cr, Mo, W, and V to form carbides and has the effect of improving the wear resistance of the alloy, but if its content is less than 1%, the carbides of the metals are The amount of precipitation was too small to ensure the desired wear resistance.
On the other hand, if the content exceeds 6%, the amount of carbide precipitated will be too large, resulting in high hardness, but the wear of the cam of the opposing part will be significant, and the toughness will also decrease. , its content was determined to be 1 to 6%.

{c} Cr, Mo, W, and V These components combine with C to form a double carbide of Cr having high hardness, Mo, and W and/or V,
It has the effect of improving the wear resistance of the alloy and also improves the heat resistance and impact resistance of the alloy by being partially dissolved in the base material, but Cr: less than 5% and Mo: less than 0.5%, respectively. , W: 4%, and V: less than 0.5%, the desired effect cannot be obtained, while Cr: 30%, M
If the content exceeds O: 10%, W: 8%, and V: 5%, the damage to the opposing part will become significant and the strength will decrease, so Cr: 5 to 3%, respectively.
0%, Mo: 0.5-10%, W: 4-8%, V: 0.
It was set at 5-5%.

Next, the rocker arm for an internal combustion engine according to the present invention will be explained using examples.

As reduced raw material powders, Fe-Cr powder (containing 65% Cr) having a Vickers hardness of 1050, Fe-Mo powder (containing 63% Mo) having a Vickers hardness of 1100, and 110 Vickers hardness were used.
Fe-W powder (W: 81% content) with 0, same 100
Fe-Nb powder (Nb: 65% content) with 0, same 1
Fe-V powder with 150 (V: 52% content), Cr
, Mo, W, and V oxide powder, carbon powder, and iron oxide powder are prepared, and these reduced raw material powders are blended to have a predetermined final component composition, and after being pulverized and mixed in a ball mill, they are placed in a hydrogen atmosphere. Alloy powder is produced by heat reduction treatment maintained at a temperature of 1000 qo for 3 hours, and then a green compact is formed from these alloy powders at a pressure of 5 tons/ground. :1160~1200
By holding at o0 for 1 hour, the present invention Fe-based composite alloy rocker arm pad face parts 1 to 15 (hereinafter referred to as the present invention pad face member) having the component compositions shown in Table 1 and the comparative Fe-based Rocker arm pad face members 1 to 10 made of Akatsuki Kinkin (hereinafter referred to as comparative pad face members) were manufactured, respectively.

Note that the comparative pad surface members 1 to 10 are F
Any component (first
Those marked with * in the table have compositions outside the scope of this invention.

Next, the pad surface member 1 of the present invention obtained in this manner
~15 and comparative padding surface members 1 to 10 are respectively fixed to the padding surface of the rocker arm, and this rocker arm is fixed to the padding surface of the rocker arm.
When installed in a cylinder OHC engine, engine speed: 95. p. m. A wear test was conducted under the following conditions: oil: 20W-3M, operating time: 300 hours, and the maximum wear depth on the pad surface of the rocker arm and the maximum wear depth on the cam, which is the mating member, was measured. The occurrence of scuffing and pitching on the putting surface was observed.

The occurrence of scuffing and pitching was evaluated as follows: A: No occurrence at all, B: Slight occurrence, C: Much occurrence, and D: Significant occurrence. These results are also shown in Table 1. For comparison purposes, Table 1 also includes the results of wear tests conducted under the same conditions on a rocker arm made of chilled casting (hereinafter referred to as conventional member 1) and a rocker arm with Cr plating (hereinafter referred to as conventional member 2). Also shown.

Furthermore, Table 1 also shows the measurement results of the Vickers hardness of the padding surfaces of these members. Table 1-1 Table 1-2 [Effects of the invention] As is clear from the results shown in Table 1,
, 2 have a very high amount of wear on the rocker arm and cam, and the occurrence of scuffing and pitching is also extremely bad, whereas the pad surface members 1 to 15 of the present invention all have excellent wear resistance. In addition to this, it hardly damages the cam of the mating member, and furthermore, it has extremely excellent scuffing resistance and pitting resistance.

On the other hand, as seen in Comparative Pad Surface Members 1 to 10, if any of the constituents of the Fe-based neighboring alloy constituting the pad surface members falls outside the scope of the present invention, the wear resistance and the resistance against the cam, which is the counterpart component, may deteriorate. It is clear that at least one of the characteristics of aggressiveness (resistance to opponent's attack), scuffing resistance, and pinching resistance becomes inferior, and it does not have all the characteristics required of a rotsuka arm. be.

As mentioned above, the rocker arm for an internal combustion engine of the present invention has the following features:
At least the pad surface portion includes hard particles, Cr, Mo, W,
Fe having a structure in which double carbides of V and V are uniformly dispersed.
Since it is composed of a basic 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 made of Fe-Cr, Fe-Mo, Fe-W, Fe-Nb, and Fe-V having a hardness in the range of 600 to 1300 on the Vickers hardness 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%, and further W: 4 to 8%, V: 0.5 to 5%, a composition containing one or two of the following, with the remainder consisting of Fe and unavoidable impurities (more than % by weight), and a matrix of martensite or bainite. , Cr, Mo, W, and V double carbides and the above-mentioned hard particles are uniformly dispersed in a Fe-based sintered alloy for an internal combustion engine.