JP2537889B2 - Method of manufacturing engine cylinder head - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing an engine cylinder head.

(Prior Art) In recent high-power engines with a high heat load, cracks due to thermal fatigue easily occur between the intake and exhaust holes in the cylinder head. As shown in Japanese Patent Publication No. 193773, a method of manufacturing a cylinder head has been developed in which a required portion of a cast cylinder head that constitutes a combustion chamber is irradiated with high-density energy heat rays to remelt the irradiated portion of the cylinder head. There is.

According to this manufacturing method, by solidifying the remelted portion, the fine pores and the like that existed before the remelting are extruded to the outside, and the remelted portion is rapidly cooled by the non-remelted portion and the structure is This results in miniaturization, which improves the thermal fatigue strength. This makes it possible to prevent cracking due to thermal fatigue.

(Problems to be Solved by the Invention) However, in the above-mentioned manufacturing method, since only the necessary portion of the combustion chamber is remelted, when the remelted portion solidifies, the solidified portion draws the molten metal around it. As a result, the amount of melting is insufficient and a concave portion is formed in the final portion of the irradiated portion in the combustion chamber. Therefore, if the recess continues to exist, the edge of the recess will locally become hot and abnormal combustion will occur, and in order to prevent abnormal combustion, the recess will be removed by plane cutting. Then, the volume of the combustion chamber changes, the compression ratio decreases, and the chill (quenching) structure decreases, resulting in a decrease in thermal fatigue strength.

On the other hand, as a means for solving such a problem, a method is conceivable in which the irradiation heat amount of the high-density energy heat ray is reduced and the irradiation moving speed of the energy heat ray is increased in the vicinity of the final portion of the irradiated portion. However, even if such a method is taken, assuming that sufficient fatigue strength is ensured, although the depth of the recess can be shallow, it is not possible to prevent the recess from occurring. The above problems cannot be completely solved.

The present invention has been made in view of the above circumstances, and an object thereof is to form a concave portion caused by a high-density energy heat ray,
This is to prevent the occurrence of abnormal combustion, the reduction of the compression ratio, and the reduction of the thermal fatigue strength of the cylinder head.

(Means and Actions for Solving Problems) In order to achieve the above object, according to the present invention, a cast cylinder head that constitutes a combustion chamber is irradiated with high-density energy heat rays to irradiate the cylinder head. In the method of manufacturing a cylinder head of an engine for remelting a portion, the final portion of the irradiated portion is located outside the compartment of the combustion chamber.

With the above-described configuration, the concave portion generated by the high-density energy heat ray is located outside the combustion chamber compartment, and the concave portion does not exist inside the combustion chamber.

(Example) Hereinafter, the Example of this invention is described based on drawing.

1 to 3, reference numeral 1 is a cylinder head made of cast aluminum alloy for four cylinders, and a partition portion 3 which constitutes a part of a combustion chamber 2 is formed in the cylinder head 1 in a longitudinal direction of the cylinder head 1 (see Four compartments are formed in the left-right direction in FIG. 1, and the inner wall surface of each partition portion 3 constitutes a combustion chamber surface 4. Each combustion chamber surface 4 is formed with an intake hole 5, an exhaust hole 6 and an injection port 8 of a sub-combustion chamber 7.
To open.

The cylinder head 1 is irradiated with high-density energy heat rays such as laser, electron beam, plasma arc, and TIG arc in order to improve thermal fatigue strength. In the cylinder head 1 as described above, the irradiation of the high-density energy heat rays is performed for each combustion chamber surface 4 at a portion between the intake hole 5 and the exhaust hole 6 where the thermal fatigue strength needs to be improved and the intake hole. 5 and the injection port 8 of the sub-combustion chamber 7, the irradiation portion is the irradiation portion 9 of the cylinder head 1 in the present embodiment, as shown in FIG. Will be 10.

As for the irradiated portion 9, as shown in FIG. 2, the irradiation of the high-density energy heat ray is started from the point, and the irradiation is sequentially moved to the point. The irradiation of the high-energy heat beam is started from a point, and the irradiation is to be sequentially moved to the point. In each of the irradiated portions 9 and 10, as shown in FIG.
When the high-density energy heat ray is irradiated by, the portion will be re-melted, and the irradiated portion that has been irradiated with the movement of the high-density energy heat ray will be solidified by self-cooling. become. At this time, the remelted portion (hereinafter referred to as the remelted portion) 12 is solidified so as to rise from the base metal side to the surface side, and the micropores existing before remelting are extruded to the outside. Will be done. Also,
In the remelted portion 12, the portion that is not remelted functions as a chill having a large heat capacity with respect to the remelted portion 12, so that the structure is rapidly cooled and becomes finer. Therefore, the fatigue strength of the remelted portion 12 is significantly improved.

The final point, which is the final part of the irradiated parts 9 and 10,
In the vicinity of the points, the recesses 13 are formed respectively. This is based on the fact that when the remelting section 12 is solidified, the molten metal around it is attracted and rises up, and as a result, the melting amount of the final portions of the irradiated portions 9 and 10 is insufficient. This recess 13 is supposed to be formed by irradiation with high-density energy heat rays, which can be confirmed by the experimental results based on various experimental conditions shown in Table 1.

That is, the experiment was carried out by casting a diesel engine cylinder head by a low pressure casting method using JIS AC4B aluminum alloy casting, and irradiating the casting surface of the cylinder head with a TIG arc to perform remelting processing. . The machining is performed by fixing the TIG torch and moving the cylinder head with a moving table.
The irradiation of the TIG arc was performed while moving in the order of →→→ in the irradiated portion 9 shown in FIG. 2 as described above. When irradiating the TIG arc, an AC TIG welding machine was used, an electrode rod made of pure tungsten W having a diameter of 4.8 mm was used as an electrode, and an argon gas was supplied as a shielding gas at a rate of 15 / min. Table 1 shows the specific experimental conditions of each experimental example.

Experimental example 1 is a case where a normal arc current and a normal arc moving speed are used and they are made constant from point to point. In this case, the depth of the recess 13 was the deepest in all the experimental examples. In this case, it is not possible to eliminate the concave portion 13 even when taking into consideration cutting by machining finishing (generally, a cutting allowance of 2 to 3 mm).

In each of Experimental Examples 2 to 4, in each condition, the arc moving speed between the points, which is near the final part of the irradiated portion, is increased more than the arc moving speed between the points, and the arc current between the points is measured between the points. This is the case when the arc current is reduced. In each of these cases, the melting amount was reduced near the final portion of the irradiated portion, and the depth of the recess could be made shallower than in the case of Experimental Example 1. However, in each of Experimental Examples 2 to 4, the concave portion 13 itself could not be eliminated, and the concave portion 13 having the depth h (see FIG. 3) corresponding to the condition of each experimental example was generated. In this case, in Experimental Example 2, it is possible to eliminate the concave portion 13 by performing cutting by ordinary mechanical finishing, but in reality, the concave portion 13 is formed even after the mechanical finishing due to variation in dimensions during casting. There is a risk of leaving. In Experimental Example 3, the recess 13 cannot be eliminated even if the cutting by the normal machining finish is taken into consideration. Further, in Experimental Example 4, the depth of the recess 13 can be made extremely shallow, but cracks occur, and it is not possible to sufficiently improve the fatigue strength, which is a prerequisite.

Thus, as is clear from Table 1, on the assumption that sufficient fatigue strength is ensured, the irradiation of the high-density energy heat ray causes the concave portion 13 to be a problem to reach the final portion of the irradiated portion 9. Will be formed.

However, in the manufacturing method according to the present invention, the final point and the point are to be moved to the outside of the compartment of the combustion chamber 2 (outside the peripheral portion of the combustion chamber 2) as shown in FIG. The recess 13 is to be located at a position corresponding to the gasket mating surface. Therefore, the recess 13 does not exist in the combustion chamber 2 without mechanical cutting, and abnormal combustion occurs due to the recess 13 or the volume of the combustion chamber 2 is increased by the flat cutting for removing the recess 13. Is increased, the compression ratio is decreased, and the chill structure is decreased to prevent the fatigue strength from being decreased. in this case,
From the viewpoint of airtightness, it is preferable that the recess 13 is located outside the grommet portion 15 of the gasket as shown in FIG.

In this way, the cylinder head 1 according to the present invention, in which the recess 13 is located outside the compartment of the combustion chamber 2, and the recess 13 is provided in the combustion chamber 2.
The performance of a cylinder head positioned in the compartment (combustion chamber surface 4) was compared in a diesel engine with a secondary combustion chamber of 2.0.

As a result, the output of the cylinder head having the recess 13 in the compartment of the combustion chamber 2 was lower than that of the cylinder head 1 of the present invention, and the output of the cylinder head 1 of the present invention was not reduced.

In addition, under the conditions of Experimental Example No. 2 in Table 1, heat treatment T is performed by performing TIG remelting treatment between and between points in FIG.
After performing 6, the burner heating was performed in order to compare the thermal fatigue strength of the cylinder head 1 according to the present invention that was machined (cutting thickness of about 2 mm) and the untreated cylinder head that was machined only. (250 ℃) and water jet cooling (30 ℃)
Was repeated.

As a result, the untreated cylinder head cracked after 500 times, and the cylinder head 1 according to the present invention cracked after 1050 times.
The effect of remelting treatment was recognized.

(Effects of the Invention) As described above, the present invention prevents the occurrence of abnormal combustion because the concave portion generated by the high-density energy heat ray is located outside the combustion chamber section and does not exist in the combustion chamber, and the flat surface can be prevented. It is possible to prevent the compression ratio and the thermal fatigue strength of the cylinder head from decreasing due to cutting.

[Brief description of drawings]

FIG. 1 is a plan view showing a cylinder head as seen from the combustion chamber side, FIG. 2 is an enlarged explanatory view showing a manufacturing method of the present invention, and FIG. 3 is an enlarged sectional view of a portion remelted by a TIG arc. . 1: Cylinder head 2: Combustion chamber 9, 10: Irradiated part, :: Final point

Claims (1)

(57) [Claims] 1. A method for manufacturing a cylinder head of an engine, wherein a cast cylinder head constituting a combustion chamber is irradiated with high-density energy heat rays to remelt the irradiated portion of the cylinder head, the final portion of the irradiated portion. Is located outside the compartment of the combustion chamber.