JPH10317061A - Re-melting treatment method of cylinder head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a reinforcement part by increasing the re-melting depth without dropping the metal melted by the TIG are into an intake hole, an exhaust hole which are hole parts in a cylinder head, or into a sub combustion chamber. SOLUTION: In the casting stage of a cylinder head 2, narrow parts between hole parts such as an intake hole 4, an exhaust hole 6 and a sub combustion chamber 8 are expanded to the hole part side. The narrow parts including an expansion part 12 is reinforcement-irradiated with the high density energy such as the TIG arc A to increase the re-melting depth. After the cylinder head 2 is cooled, the expansion part 12 is cut by machining an inner circumferential surface of the hole parts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a TIG arc (tu
The present invention relates to a method for strengthening a narrow portion between holes, such as an intake hole, an exhaust hole, and a sub-combustion chamber, which are required to be reinforced by a high-density energy such as ngsten inert gas arc.

[0002]

2. Description of the Related Art As shown in FIG. 2, an intake hole 4 and an exhaust hole 6 are formed in a cylinder head 2, and a sub-combustion chamber 8 is formed by a depression formed on the lower surface of the cylinder head 2 according to the type of engine. Since the area between the holes, such as the intake and exhaust holes 4 and 6, is narrow, the narrow portion 10
Has weaker strength, that is, thermal fatigue characteristics than other parts. For this reason, especially in an aluminum cylinder head, heat treatment such as re-melting the narrow portion 10 with high-density energy typified by a TIG arc (tungsten inert gas arc) is performed to improve thermal fatigue characteristics (for example, special features). See Heihei 8-155628).

[0003]

In recent years, the demands for higher performance of engines have become more severe, and accordingly, measures to enhance the thermal fatigue characteristics of the narrow portion 10 have become even stronger for aluminum cylinder heads. It is being sought.

The narrow portion of the cylinder head 2 is
When re-melting by heating with an arc, the re-melting treatment depth (T
If the IG depth is increased, the reinforced portion becomes deeper and the thermal fatigue characteristics are improved. However, the greater the TIG depth, the greater the possibility that the melted metal will melt into adjacent holes such as the intake and exhaust holes 4 and 6 and the auxiliary combustion chamber 8. For example, as shown in FIG. 3B, when a narrow portion between the exhaust hole 6 and the sub-combustion chamber 8 is re-melted by a TIG arc, if the volume of the re-melted portion becomes large, the molten metal becomes its own weight and the exhaust hole becomes molten. 6 and auxiliary combustion chamber 8
The chances of running down are very high. Therefore TIG
There is an upper limit to the depth D _1, typically about 5mm is a limit in plan section. However, this TIG depth D _{1 of} about 5 mm
Also, since the surface of the cylinder head needs to be cut by about 2 mm by machining after the TIG arc treatment, only a reinforcement layer of about 3 mm remains on the cylinder head 2 as a product.

In FIG. 3B, E is an electrode, and A is a TIG.
The arc, G, indicates the inert gas flow. Inexpensive argon is usually used as the inert gas, but it is known that the TIG depth can be increased to some extent by changing this argon to helium. However, helium is less than 10 times more expensive than argon, and is not a practical solution.

An object of the present invention is to increase the TIG depth and increase the reinforced portion without dropping metal melted by irradiation of high-density energy such as a TIG arc into a hole of a cylinder head.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides high-density energy in a narrow portion between holes such as an intake hole, an exhaust hole and an auxiliary combustion chamber formed in a cylinder head. In the method of irradiating and re-melting, a desired portion of the narrow portion is formed to protrude toward the hole at the stage of casting the cylinder head, and the high-density energy is enhanced in the narrow portion including the protruding portion. Irradiation to increase the remelting depth,
After cooling, the overhang was removed by machining.

Since the surface of the cylinder head and the inner peripheral surface of the hole are portions to be machined after the TIG arc treatment in the prior art, a narrow portion is formed by projecting at the casting stage to form the hole with the TI.
Even if machining is performed after the G arc processing, the number of processes as a whole does not change. Therefore, it is possible to increase the TIG depth at the same cost as that of the conventional TIG arc processing.

In order to increase the amount of heat input to the narrow portion as effectively as possible, when the narrow portion is heated by the reciprocating motion of the TIG arc, the narrow portion is preheated by the TIG arc on the outward path and the heat is returned on the return path. It is preferable to make the moving speed of the TIG arc lower than that of the outward path, and to perform so-called main firing in the narrow portion. Further, the amount of heat input may be increased by bringing the electrode of the TIG arc closer to the narrow portion.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.
It will be described based on. In the method for re-melting a cylinder head according to the present invention, a narrow portion between holes such as an intake hole, an exhaust hole, and a sub-combustion chamber formed in a cylinder head is widened in advance, and the inner circumferential portion of the hole after the TIG arc processing. The surface is cut off by machining and enlarged to a regular shape. Here, the TIG arc processing will be described by taking a narrow portion between the exhaust hole 6 and the sub-combustion chamber 8 as an example as shown in FIGS.

First, in the casting stage of the cylinder head 2, the size of the sub-combustion chamber 8a is made smaller than that of the conventional sub-combustion chamber 8 indicated by a dashed line. That is, the protruding portion 12 is formed toward the sub-combustion chamber 8a when viewed from the narrow portion. The size of the projecting portion 12, when it is desired to further increase the TIG depth D ₂ may be larger than shown.

Next, as shown in FIG. 1 (B), a narrow portion between the exhaust hole 6 and the sub-combustion chamber 8 including the overhanging portion 12 is made TI.
G arc processing is performed. At this time, since the narrow portion is wider than the conventional portion by the overhang portion 12, the molten metal does not drop to the exhaust hole 6 or the sub-combustion chamber 8a side, and the TIG does not fall.
The amount of heat input by the arc can be increased more than before. As a result, the TIG depth D ₂ than the conventional so can be increased. In order to increase the amount of heat input to the narrow portion as effectively as possible, the overhang portion 12
Is heated by the reciprocating motion of the TIG arc, the narrow portion 12 is preheated by the TIG arc on the outward path, and the moving speed of the TIG arc on the return path is set lower than that on the outward path. Further, bringing the electrode E of the TIG arc closer to the narrow portion is also effective for increasing the heat input. After cooling the cylinder head 2, the overhanging portion 12, that is, the inner peripheral surface of the sub-combustion chamber 8 a, is cut down to a dashed line by machining to form a regular sub-combustion chamber 8.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible. For example, in the above embodiment, the exhaust hole 6 and the auxiliary combustion chamber 8a are provided. The present invention is applied to the TIG arc treatment of the narrow portion between the above, but the present invention can be applied to any narrow portion between the intake hole 4, the exhaust hole 6, and the sub-combustion chamber 8. In the above embodiment, the TIG arc is exemplified as the high-density energy irradiating means. However, other high-density energy irradiating means such as a plasma jet torch can be used.

[0014]

As described above, according to the present invention, the re-melting process is performed by the high-density energy-enhancing irradiation in a state where the narrow portion between the holes of the cylinder head is widened by the projecting portion. The depth of remelting can be increased as compared with the related art without dropping the metal melted by remelting into the hole, and the thermal fatigue characteristics of the cylinder head can be improved.

[Brief description of the drawings]

1 (A) and 1 (B) show a TIG strengthening method for a cylinder head according to the present invention, in which (A) is a schematic partial plan view of a lower surface of a cylinder head, and (B) is a view showing (A). B-
FIG. 3 is a cross-sectional view taken along line B.

FIG. 2 is a schematic plan view of a lower surface of a cylinder head.

FIGS. 3A and 3B are TIGs of a conventional cylinder head.
FIG. 4A is a schematic partial plan view of a lower surface of a cylinder head, and FIG. 4B is a cross-sectional view taken along line BB of FIG.

[Explanation of symbols]

2 the cylinder head 4 air inlets 6 exhaust hole 8 auxiliary combustion chamber 10 narrow portion 12 overhanging portion A TIG arc E electrode G inert gas stream D _1, D ₂ remelting depth (TIG depth)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F16J 10/00 F16J 10/00 Z // C22F 1/00 604 C22F 1/00 604 651 651B

Claims (2)

[Claims] 1. A method of irradiating high-density energy to a re-melting process on a narrow portion between holes such as an intake hole, an exhaust hole, and a sub-combustion chamber formed in a cylinder head, the method comprising: A desired portion of the protrusion is formed in the cylinder head at the casting stage so as to protrude toward the hole, and the narrow portion including the protruding portion is irradiated with the high-density energy intensified to increase the remelting depth. A method for re-melting a cylinder head, wherein the overhang portion is removed by machining. 2. When the narrow portion is heated by reciprocation of a TIG arc, the narrow portion is preheated by an outward TIG arc, and the moving speed of the return TIG arc is made lower than that of the outward route. 2. The method according to claim 1, wherein the narrow portion is baked.