JPS60204843A - Manufacture of wear-resistant and lightweight rocker arm - Google Patents

Abstract

PURPOSE:To obtain a rocker arm which is highly resistant to wear and is light in weight by subjecting the melt of a specifically composed high-silicon Al alloy to fining treatment with P (compd.) at a high temp. then to die casting. CONSTITUTION:The melt of a high-silicon Al alloy contg., by weight, 16-25% Si, 1.5-5.0% Cu, 0.4-1.0% Mg, <=0.5% Mn, <=0.8% Fe, 0.5-1.5% Ni and 0.5- 1.5% Cr is manufactured. Such molten high-silicon Al alloy is subjected to fining treatment by adding 0.3-0.06wt% P or P compd. (e.g.; Cu-8% P-base alloy) at a high temp., more particularly the temp. higher by 70-120 deg.C than the liquidus line temp. The molten high-silicon Al alloy after the fining treatment is then cast by using a known die casting machine using a stationary die and a movable die. The resultant casting has high dimensional accuracy and a smooth casting surface; in addition, the crystal grains of the casting are fine and such fine grains coupled with the above-described characteristics make the casting lend itself to a rocker arm in the as-cast state or simply by polishing lightly the sliding surface at the most.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rocker arm and a method for manufacturing a rocker arm that has high wear resistance and is lightweight.

Rocker arms are used in the valve train of internal combustion engines, but with the recent shift to front-wheel drive vehicles, rocker arms need to be lighter and wear-resistant in order to reduce engine weight and increase rotation speed. .

Conventional rocker arms are made entirely of iron, or the main body is made of aluminum alloy, and the part that slides on the cam, that is, the pad, is made of chill alloy cast iron or iron-based sintered alloy. It is obtained by joining parts.

The latter type is lighter than the former type, but since the material of the cam is generally chilled alloy cast iron or carburized steel, wear, mainly scuffing and pitting, occurs on the sliding surface with the pad section. , These factors occur simultaneously, so the reality is that satisfactory results have not yet been achieved. In addition, in the latter structure where the pad member is made separately and joined, if the pad member is made of ingot material, heat treatment, grinding, and joining processes with the main body are required, whereas if the pad member is made of sintered material This requires steps such as powder compaction, sintering, machining, and adhesion to the main body, and in any case, a large number of man-hours and steps are required, resulting in low productivity and increased costs.

The present invention solves the problems of the conventional rocker arm as described above, and is lightweight and has excellent wear resistance.

Moreover, it aims to provide a new rocker arm manufacturing method that can produce an integrated rocker arm that does not require the production of side materials for the pad section. molten alloy,
After being refined at high temperatures, it is cast using a die-casting method.

That is, the present invention provides SL: 16 to 25 vrt%
.

Cu: 1.5-5. OwtX, Mg: 0.4
~1. OwLX.

Mn: 0.5 wt% or less, Fs: 0.8
wt% or less, N1: 0.5-1゜5 wtX, Cr
: A molten metal with a balance of 0.5 to 1.5 wt% is treated with phosphorus or a phosphorus compound at high temperature to make it fine, and then cast into a predetermined shape by die casting.

The present invention will be specifically explained below.

Figure 1 shows an overhead valve type combustion chamber, where 1°1' is a rocker arm, 2 is a camshaft, 3 is a valve spring, and 4 is an intake pulp.

4' is Nigeshiest pulp, and 5 is a piston. As shown in FIG. 2, the rocker arms 1, 1' have a sliding surface 6 for sliding with the cam, a hole 7 for passing through the rocker shaft, and a valve spring side.

Accordingly, the present invention provides the above rocker arm 1.
1' is composed of an aluminum alloy containing more than a eutectic component of silicon, especially a hypereutectic component containing 16 to 25 wLX silicon.

In general, it is well known that high silicon aluminum alloys have heat resistance, wear resistance, and a small coefficient of thermal expansion. However, high-silicon aluminum alloys have the property that coarse primary crystals s4 crystallize unevenly, and these coarse primary crystals &
has extremely poor rigidity and deteriorates mechanical properties, and since primary crystal Si tends to segregate, it reduces wear resistance.

For this reason, there have been attempts to make cylinder liners and small pistons using sand molds or metal mold casting methods, but in reality, it is difficult to obtain the above characteristics, and the reality is that they have hardly been put to practical use. .

The present invention solves this problem by using a specific alloy component and performing a refinement process in a specific manner, and a practical rocker in which the primary crystals St are refined and uniformly distributed by a die-casting method. This is the one that succeeded in obtaining an arm.

First, in order to obtain a rocker arm, the present invention makes a molten metal of a high silicon aluminum alloy consisting of the following components.

SL: 16-25 wLX, Cu: 1.5-5,
0wt%.

Mg: 0.4-1. OwLX, Mn: 0.5
wt% or less.

Fn: 0.8 wt% or less, Nl: 0.5 to 1.5 w
LX.

Cr: 0.5 to 1.5 wtX, remainder here, S
When L is less than 16 wt%, segregation of primary crystal S4 occurs and eutectic regions are present in some places, resulting in insufficient effect on wear resistance. If S4 exceeds 25%, the primary crystals & cannot be completely refined, so the larger primary crystals st scattered here and there will deteriorate the stiffness. Therefore, the content of 84 is 16 to 2 from the viewpoint of both high temperature strength and wear resistance effects and machinability.
5 wLX.

Cu (!: Mg has age hardening properties and is added to precipitate intermetallic compounds such as Alx Cu, /4tt Cut Fg, Mgkura St, and Ns Cut Mgx during heat treatment to strengthen the matrix. Cu has the effect of improving the fluidity of hot water.However,
Cu is 5. Ovrt%, Mg is 1. Ov++t%
Exceeding each is not preferable because the intermetallic compounds in the metal become coarse and brittle.

Moreover, excessive addition of Mg tends to cause hot cracks.

The lower limit of Cu is 1.5 wt% + the lower limit of Mg is 0.4
The reason for choosing wLX is that the effect of addition is poor below this value.

Since Mn has the property of suppressing the crystallization of primary SL, 1,
Q should be below wt%. Although F's can prevent the formation of a melt layer of hot water and hot cracks in the mold, it has the property of suppressing the crystallization of primary S4, so h was set to 1.5 wLX or less. The reason for adding Ni and Cr is that the former promotes the growth of p-primary crystal &, and the latter prevents the segregation of ° primary crystal S4, resulting in a fast crystallization state. Encouragement limited to, fi'a, SL, etc. and Als
Nl, A! -SL-Cr, Al-fi
This is because precipitating the intermetallic compound of '5-Mn-8L can improve the high-temperature strength and wear resistance.

Although Nl has an effect on the growth of primary crystals &, a region without primary crystals (segregation) is generated on the surface of the cast product.

When Nl and Cr coexist, their segregation is extremely effectively prevented. The reason why this segregation is prevented is not necessarily clear, but if the above segregation is gravitational segregation due to the difference in specific gravity between the primary crystal S4 and the melt, adding Cr will cause the metals of Al-8j and -Cr to Interstitial compounds are formed, which have a good affinity with the primary crystal S4 and adhere to the primary crystal S, acting as a so-called weight, so it appears that the primary crystal S4 settles into the matrix due to an increase in specific gravity. , it is thought that it will be difficult to give too much weight.

When Ni is less than 0.5 wt% and Cr is less than 0.5 wt%, the addition effect is insufficient, and when Ni and Cr are each 1.5 wt%,
t%? Since there is no change in the dispersion uniformity of the refined primary crystals even if the amount is exceeded, the amounts of Ni and Cr added were determined to be the above amounts.

Next, the high-silicon aluminum alloy molten metal obtained as described above is subjected to a refinement treatment. This refinement treatment is carried out by adding phosphorus or a phosphorus compound at a high temperature, particularly at a temperature 0 to 120° C. higher than the liquidus line.

The reason why the lower limit of the refining treatment temperature was set to +70°C above the liquidus line was that below this temperature, the effect of refining primary crystal SL was poor. This is because although it can be achieved, it causes problems such as oxidation.

As the phosphorus or phosphorus compound, copper phosphorus (for example, Cu-8%P master alloy), red phosphorus, a mixture thereof with hexachloroethane, sodium phosphate, calcium phosphate, etc. are used. The appropriate amount of these additions is 0.3 to 0.6 wt%, and it is necessary to achieve a yield of 0.08% or more of phosphorus in the alloy. Sodium fluxes that would make the hypoeutectic or eutectic crystals finer should not be used because they tend to coarsen the primary crystals. It is preferable that the cooling rate after the micronization treatment is high, and the faster the cooling is performed, the more micronization is achieved.

After the primary crystals δ are refined as described above, the temperature of the molten high-silicon aluminum alloy is adjusted or the molten metal is made into a base metal, and then a rocker arm is cast by a die-casting method.

This die-casting is performed using a known die-casting machine that uses a fixed mold and a movable mold, for example, at a mold temperature of 200-280.
°C, molten metal temperature 730 to 780 °C, gate speed 1 to 3 m/1
Iec, injection pressure 500-900 Kq/c! It may be carried out as shown in FIG. 2, and thereby a lightweight integrated rocker arm having a sliding surface 6 in which fine primary crystals SL are uniformly distributed as shown in FIG. 2 can be obtained.

In the case of the present invention, the synergistic effect of promoting the growth and preventing segregation of primary St crystals by adding Nl and Cr, refining treatment with phosphorus or phosphorus compounds at high temperatures, and adopting the die casting method as the casting method is achieved. It has high dimensional accuracy, smooth casting surface, fine crystal grains, high wear resistance, and good rigidity. Therefore, it can be used as a rocker arm as it is cast or by simply polishing the sliding surface, resulting in extremely high productivity.

Next, specific examples of the present invention will be shown.

Example 2 A rocker arm for an automobile engine was manufactured according to the present invention. Table 1 shows the chemical composition, refinement temperature, and mechanical properties of the sample materials.

The test material is bare metal, and the mold temperature is 230 to 270.
℃, molten metal temperature 730-780℃, sprue speed 1.86 m
/sac, injection pressure 081'4/d and p-casting by die casting method.

■ Figures 3 and 4 show the microscopic structure of sample material 3 before and after the refining process. Before the refining process, the primary crystals were as coarse as 150 μm as shown in Figure 3. However, as shown in FIG. 4, the grain size is refined to an average of 25 μm by the grain refinement treatment, and the primary crystals are almost uniformly dispersed without segregation due to the addition of Cr. Figure 5 shows sample material X (St: 17%).
) was subjected to micronization treatment, and Figure 6 shows sample material 5.
(st: 23%) is shown, and in the case of FIG. 6, an average of 1511 fn of refinement has been obtained.

(2) The durability test results of the rocker arm obtained according to the present invention are shown in Table 2 together with comparative examples.

Durability test conditions are engine speed + 300Or, p
, m, durability time: 100J (r, lubricating oil = MS20.
Lubricating oil temperature: 80℃, pulp spring load near 1.2
5Kf, mating cam material: CH Table 2 From Table 2 above, the present invention can achieve a low amount of wear without attaching side pads.

According to the present invention as described above, an excellent effect can be obtained in that an integrated rocker arm that is lightweight, has high wear resistance, and does not require a front pad member as a side member can be mass-produced at a low cost.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing an example of the use of a rocker arm, Fig. 2 is a partially cutaway side view showing an example of a rocker arm according to the present invention, and Fig. 3 is a cross-sectional view showing an example of the rocker arm according to the present invention. A micrograph (100x magnification) showing the structure before micronization treatment, Fig. 4 is a microphotograph (100x magnification) after micronization processing, and Fig. 5 is a microphotograph of 17% SL (100x magnification). FIG. 6 is a micrograph of 23% SL (100x magnification). Patent Applicant Kyoro Gokin Co., Ltd. Figure 1 Figure 2 Drawing 7 (No change in content Figure 3 Figure 4 Figure 5 Figure 6 Procedures Ichisho A) (Method) % formula % 1. Indication of the incident: Patent Application No. 58400 of 1983 2. Name of the invention: Wear-resistant, lightweight rocker arm! 2. Construction method 3. Relationship with the case of the person making the amendment Special gamma 6), Brief explanation of the drawings 7, Contents of amendments as shown in the attached sheet 10 Figures 3 to 6 of the drawings attached to this application are corrected as shown in the attached sheet. 2. In the specification of this application, No. 14 From the 11th line of the page to the same page tube 15
Correct the line as follows.

Claims (1)

[Claims] 1. St: 16 to 25 wt%, Cu: 1.5 to 5
．． Owt%, Mg: 0.4-1. Owt%, Mn
: 0.5 wt% or less, Fa: 0.8 wt%
Below, Ni: 0.5 to 1.5 vt%r Cr:
A method for manufacturing a wear-resistant, lightweight rocker arm, which comprises subjecting a molten metal having a balance of 0.5 to 1.5 wt% to refinement using phosphorus or a phosphorus compound at high temperature, followed by die casting. 2. Claim 1, wherein the temperature of the micronization treatment using phosphorus or a phosphorus compound is approximately 70 to 120°C higher than the liquidus line.
Method for manufacturing the wear-resistant lightweight rocker arm described in Section 1.