JPS60219408A - Rocker arm - Google Patents

Abstract

PURPOSE:To obtain a small rocker arm of light weight in excellent mass-productivity and durability at a low cost, by forming an alloy layer, which contains either carbide or boride of high hardness, in wearing parts of the rocker arm. CONSTITUTION:A steel plate made rocker arm 4 forms in its wearing parts 6, 8 an alloy layer 7, which contains either carbide or boride in high hardness or the both, by applying simple substance powder of a carbide product element and C dust, simple substance powder of a boride product element and B dust, and at least one of these powdery alloys to adhere to the wearing parts 6, 8 and heating the adhering powdery alloy to be melted and welded by a heating source, for instance, electron beam, laser beam, plasma arc, etc. having high density energy.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a valve train rocker arm that follows a cam of an internal combustion engine.

Rocker arms are required to have wear resistance, seizure resistance, pitting resistance, etc. because they slide under high surface pressure against highly hard cam surfaces.

Therefore, conventional rocker arms are made of high-alloy cast iron with a chilled or hardened cam contact surface, or cast iron with hard chrome plating applied to the cam contact surface. etc. are used. However, these rocker arms have the drawback of being heavy, and the performance of the cam contact surface is also insufficient. Furthermore, in recent years, there has been a call for reducing the weight of engine parts in order to save fuel in internal combustion engines, and rocker arms are no exception. Furthermore, in the case of rocker arms, there was a strong desire to reduce their weight in order to reduce inertia and improve cam tracking in order to increase engine speed. Under these circumstances, recently,
Rocker arms made of aluminum alloy with a pad made of hard sintered material encased in them began to be used.

However, in the case of a rocker arm made of aluminum alloy, the pad portion and the main body are not metallurgically connected, so the pad portion is likely to play. Additionally, aluminum alloys generally have lower mechanical strength than steel or cast iron.
Due to the low fatigue ratio (ratio of fatigue strength to tensile strength), the cross-sectional area of the rocker arm body had to be increased.Not only did the weight not reduce as much as expected, but as the rocker arm became larger, This necessitated a larger engine head, which sometimes resulted in an increase in the overall weight of the engine.

The present invention was made against the background of the above-mentioned circumstances, and its purpose is to provide a rocker arm that is inexpensive, mass-producible, has excellent durability, and is small and lightweight. .

In the present invention, at least one of a single powder of a carbide-forming element and a C powder, a single powder of a boride-forming element and a B powder, and an alloy powder thereof is attached to a worn part of a rocker arm made of a steel plate, and high-density energy is generated. The adhering powder is heated and melted using a heat source such as an electron beam, laser beam, plasma arc, etc., and an alloy containing either or both of highly hard carbides and borides is applied to the worn portion of the rocker arm. It is characterized by forming layers.

The carbide and boride forming elements include Cr and Mo.
, W, V, Ti, etc., and the alloy powder includes Fe.
There are Cr5FeB and the like. For materials with high melting points (approximately 1800° C. or higher) such as Cr5W% MO, it is preferable to mix a self-fusing alloy of up to 30% by weight in order to facilitate the formation of an alloy layer. The reason for limiting the content of self-fusing alloy to a maximum of 30% by weight is that self-fusing alloy itself has low hardness and poor wear resistance, and if the content exceeds 30%, formation This is because the hardness and wear resistance of the alloy layer deteriorates.

Note that as the self-fusing alloy, a Ni-based or CO-based self-fusing alloy may be used.

By using heat sources with high energy density such as laser beams, electron beams, and plasma arcs, it is possible to locally harden surfaces that require wear resistance. A fine and uniform structure can be obtained.

When the lubrication condition is relatively good, such as in a rocker arm, the alloy layer obtained by the present invention not only has excellent wear resistance, scarf resistance, and pitting resistance of itself, but also can reduce wear of the mating material.

Examples will be described below.

<Example 1> Test piece shown in Fig. 1 made of 320G low carbon steel ] (
A=16wφ, B=30mφ, C=8mm) After mixing with other powders, the mixture was mixed in a ball mill (or mortar).

The thickness and hardness of the obtained alloy layer are shown in Table 1.

The sample obtained above was subjected to a seizure test using the N testing machine shown in FIG. 2 (test piece 1 is fixed, mating material 2 is rotating, 3 is oil filler).

The test conditions are shown below.

Speed: 2.5 m/sec Lubricating oil: SAE #30 (dropped at 80 cc/min) The powders listed in Table 1 were heat-welded on the surface and subjected to a seizure test.

The compositions (wt%) of FeCr, Fe, B, and self-fusing alloys in Table 1 are as follows.

Cr CSiP S Fe FeCr:63.826.580.180.020.
04 remaining Cr B Si CFeNt ship: 16
．． 23.63.60.43.8 The particle size of the powder used at this time was less than 250 mesos.
A film of 5 m thick was coated on the surface of the test piece 1 by brushing (or dipping may be used), and after drying at 70 to 80°C to remove moisture, a CO laser was used as a heat source and a laser beam was applied in an N2 gas atmosphere. Output 2.5KW, scanning speed 100m/ll1
A high hardness alloy layer was formed on the surface of the test specimen 1 by performing the treatment under conditions of 1.in.

The binder used was water glass (30% or less of the total weight; a small amount of water may be added because of its high viscosity). or,
Particle size of C powder is 325 meso load: 51u from IOkgf
Continuously increase the load at rf/sec to reach the scuff limit load.

Compatible material 2: Mo-Ni-Cr cast iron chilled material C4B The surface roughness of the upper and lower specimens 1 and 2 is 0.6 μRZ.

In addition, the above seizure test was also conducted on test pieces of comparative materials shown below.

A: IIA" (Hv 950) The test results are shown in FIG. 3. According to this, it is clear that the products of the present invention are superior in seizure resistance compared to the conventional product (comparative material).

<Example 2> The results of testing the rocker arm of the present invention using a motoring tester are shown below. The steel plate rocker arm 4 shown in FIGS. 4 and 5 was produced by press working, and the alloy layer 7 was formed by melting and fixing the powder shown in Table 1 on the sliding contact portion 6 of the cam 5 under the same conditions as in Example 1. . After polishing (surface roughness after polishing 1.8, IJRZ), the rocker arm 4 of
A 346CC011C diesel engine was assembled into a modified motoring test machine and tested.

The test conditions are shown below.

Rotation speed: 11000rpm Oil temperature: 60°C Time: 2
00Hr Spring load near 9 to 1r mating cam material: M
o-Ni-Cr cast iron chilled material (components are the same as those shown in Example 1) Surface treated chilled steel H, C52, surface roughness 0.8 μRZ Comparative materials (A, B listed in Example 1, The above test was also conducted on the rocker arm of C1D).

As shown in the test results in FIG. 6, it is clear that the product of the present invention not only has excellent wear resistance but also reduces wear on the mating cam material. The amount of cam wear is calculated by calculating the difference in the dimension p in FIG. 7 before and after the test.

Further, in the above embodiment, an example was given in which the high hardness alloy layer 7 was formed on the cam sliding contact portion 6 of the rocker arm 4, but the present invention is of course not limited to this. Of course, it would be better if the high hardness alloy layer 7 was also formed on the portion 8 (see Fig. 5), and it would be better to form it on either or both of the portion that slides on the cam or bushing rod and the portion that slides on the tappet or valve stem. A high hardness alloy layer is appropriately formed.

[Brief explanation of drawings]

Figure 1 is a vertical cross-sectional view showing the test piece used in the seizure test, Figure 2 is a schematic illustration of the seizure tester, Figure 3 is a diagram showing the results of the seizure test of Example 1, and Figure 4 is a steel plate. FIG. 5 is a front view of the steel plate rocker arm of FIG. 4 in sliding contact with the cam, FIG. 6 is a diagram showing the test results of Example 2, and FIG. 7 is a front view of the cam. It is. 1... Test piece 2... Mating material 3... Oil filler port 4... Rocker arm 5... Cam 6... Cam sliding contact part 7... Alloy layer 8... Tappet sliding contact Ken Okabe, Patent Attorney - Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 7

Claims (5)

[Claims] (1) At least one of a single powder of a carbide-forming element, a single powder of C powder, a single powder of a boride-forming element, a single powder of B, or an alloy powder of these is attached to the worn part of a steel plate rocker arm, and high-density energy is applied. A rocker arm, characterized in that the deposited powder is heated and welded by irradiation with a heat source, thereby forming an alloy layer containing either or both of a highly hard carbide and a boride in a worn portion of the rocker arm. (2) The rocker arm according to claim 1, wherein the worn portion of the rocker arm is a portion that comes into sliding contact with a cam or a bushing rod. (3) The rocker arm according to claim 1, wherein the worn portion of the rocker arm is a portion that comes into sliding contact with a tappet or a valve stem. (4) The rocker arm according to claim 1, wherein the worn parts of the rocker arm are a part in sliding contact with a cam or a bushing rod, and a part in sliding contact with a tappet or a valve stem. (5) The rocker arm according to any one of claims 1 to 4, wherein the powder to be welded to the rocker arm contains at most 30% by weight of a self-fusing alloy.