JPH0215866A - Manufacture of cylinder head - Google Patents

Abstract

PURPOSE:To manufacture a cylinder head, which prevents the lowering of compression ratio and the development of abnormal combustion, etc., by remelting the part of the cast cylinder head raw material to be necessary to excellent thermal fatigue characteristic and executing boring work to the completing part of this remelting. CONSTITUTION:The Al alloy-made cylinder head raw material for gasoline engine is produced with low pressure casting method and laid on X-Y table. Successively, the X-Y table is shifted under irradiating the high energy beam from TIG arc 3 and the irradiation is executed to part between an inlet port 11 and an exhaust port 12 and the part from n point to D point is remelted in succession, to form the remelting part 14. The raw material 1 treated in such way is water-cooled after holding it at about 535 deg.C for about 4hr and again reheated and held to at about 180 deg.C for about 6hr, to execute T6 treatment. Further, after boring a plug hole with machining to the completing point D of the remelting, ASSY is executed, to manufacture the cylinder head.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing a cylinder head for an engine.

(Conventional technology) In recent years, with the increase in the output of engines, the heat load on the engine cylinder head has increased, and cracks due to thermal fatigue occur especially in the areas between the intake and exhaust holes and around the plug hole in the combustion chamber where the heat load is high. This tends to occur, and the mechanical strength of aluminum alloy castings cast using conventional methods is insufficient. Furthermore, the low pressure casting method, which has good productivity among casting methods, has the problem that the mold temperature is generally high, resulting in a coarse cast structure of the cylinder head material and poor thermal fatigue strength.

To solve these problems, there has been a known method of improving the material quality of the cylinder hemlock cable material by placing cooling molds or water-cooled molds in areas where thermal fatigue properties are required to increase the cooling rate. In particular, as a method of strengthening a desired part, it is less restrictive and more effective than the above methods, so a high-energy beam is applied to a desired part of the cylinder head, as shown in Japanese Patent Application Laid-Open No. 193773/1983. A method has been proposed in which a chilled structure is obtained by irradiating, heating and remelting.

(Problem to be Solved by the Invention) However, according to the latter remelting method, as shown in FIG. There is a problem that the amount is insufficient and a crater b is formed in this part. This crater b causes a reduction in compression ratio and occurrence of abnormal combustion, and this problem is particularly serious in cylinder heads for gasoline engines in which the interior of the combustion chamber is not subjected to surface treatment after remelting treatment.

Methods to suppress the occurrence of such problematic craters b include using a slope mechanism that reduces the arc current near the end of remelting when remelting using a high-energy beam, and reducing arc movement. Although methods such as increasing the velocity are known, the occurrence of crater b cannot be avoided even with these methods.

(Purpose of the Invention) In view of the above, the present invention provides that even though the cylinder head material is remelted by a high-energy beam, the resulting cylinder head does not have any craters, thereby reducing the compression ratio and causing abnormalities. It is an object of the present invention to provide a method for manufacturing a cylinder head that can prevent the occurrence of combustion.

(Means for Solving the Problems) In order to achieve the above object, the present invention removes the end portion of remelting by a high-energy beam by hole machining.

Specifically, the solution taken by the present invention is to improve the cylinder head manufacturing method by injecting molten metal into a mold to form a cylinder head material, and then improving the parts of the cylinder head material that require high thermal fatigue properties. In addition to continuously remelting with an energy beam, this remelting is completed at a part corresponding to the hole-machined part for the plug or injection nozzle, and then the hole is machined at the part where the re-melting ends. be.

(Function) With the above configuration, craters generated at the end of remelting when the cylinder head material is remelted with a high energy beam are removed by drilling a hole for a plug or an injection nozzle.

(Example) Hereinafter, one example of the present invention will be described based on FIGS. 1 to 5.

First, a molten aluminum alloy of JIS standard AC4B is poured into a mold, and a cylinder head material 1 for a gasoline engine as shown in FIG. 1 is formed by a low pressure casting method.

Next, the cylinder head material 1 is placed on the X-Y table, and the TIG arc 3, which is a high-energy beam, is
Using an IG welding machine, under the irradiation conditions that the electrode used was pure tungsten with a diameter of 4.8 mg + and the argon gas flow rate was 1597 minutes, the cylinder was moved as shown in Figure 2 while moving on the X-Y table. Irradiation is applied to the portions of the head material 1 where thermal fatigue properties are required. This irradiation is applied to the intake hole 11 in the cylinder head material 1, as shown in FIG.
Starting from point A, which is the opposite end of the plug hole machining section 13 between the intake hole 11 and the exhaust hole 12,
2, which is the end on the hole processing section 13 side, and point 0, which is near the hole processing section 13, to the hole processing section 1.
3 and ends at point D, which is the remelting end point. In this case, the arc current value is 300 A and the processing speed is 0.3 m/min over the melting range of A→B→C→D, and the depth of the crater at point D is 3.0 m/min.
It was 5 mm.

In this way, as shown in FIG. 4, re-melted portions are formed in areas where thermal fatigue characteristics are required, that is, the area between the intake hole 11 and the exhaust hole 12, and the area around the hole-machined part 13 for the plug. After that, this cylinder head material 1 is held at a temperature of 535° C. for 4 hours, and then heated again with water cooling C1 and held at a temperature of 180° C. for 6 hours to perform T6 treatment. Further, a plug hole 15 is formed by machining in the remelted part of the cylinder head material 1, and then assembled, thereby obtaining a cylinder head 2 as shown in FIG. 5.

Note that the high-energy beam is TIG in the above embodiment.
In addition to arc 3, plasma arc, laser, electron beam, etc. can be used, and cylinder head material 1
Depending on the type of remelting, the remelting end portion may be a hole-machined portion for an injection nozzle instead of the above embodiment.

A comparative example will be explained below.

In each of Comparative Examples 1 to 4, a cylinder head material is formed by low-pressure casting of an aluminum alloy of JIs standard AC4B in the same manner as in the above example, and the cylinder head material has the following points: point A → point B → point C in the example above. The same range was irradiated with TIG arc 3 under the same electrode and argon gas flow rate as above, and between points A and B and between points B and C under the following conditions. The following rate was obtained at the 0 point.

Comparative example 1: Between point A → point B: Arc current value 300 A Machining speed 0.3 m/min Between point B → point C: Arc current value 300 A Machining speed 0.3 m/min Crater depth: 3.5 mm Comparative example 2 : Between points A and B: Arc current value 300A Machining speed 0.3m/min Between point B → C: Arc current value 300A → Slope down to OA Machining speed 0.5m/min Crater depth: 1.7mm Comparison Example 3: Between point A and point B: Arc current value 320A Machining speed 0.3m/min Between point B and point C: Arc current value 300A Machining speed 0.5m/min Crater depth: 2.7+am Comparative example 4: Between point A → point B: arc current value 280A Machining speed 0.3m/min Between point B → point C: arc current value 100A → slope down to OA Crater depth 20, 8m+* As is clear from the above results In Comparative Examples 1 and 3, a large crater occurred at the 0 point, and in Comparative Examples 2 and 4, a slope mechanism was used to gradually reduce the TIG current value, so a crater was also generated, although the depth was shallow.

Note that if a slope mechanism is used as in Comparative Examples 2 and 4, the remelting depth in this portion becomes shallow, which reduces the effect of the remelting process, which is not preferable. On the other hand, if the plug hole processing part 13 is made to be the remelting end part as in the above embodiment, no crater remains in the cylinder head 2 after the plug hole 15 is bored, and the crater can be made smaller. Since there is no need to use a slope mechanism for this purpose, the area between the intake and exhaust holes and around the plug hole can be remelted to a predetermined depth.

(Effects of the Invention) As explained above, according to the cylinder head manufacturing method according to the present invention, craters generated at the end of remelting in the cylinder head material are removed by drilling holes for plugs or injection nozzles. Since there are no craters in the resulting cylinder head, it is possible to prevent a reduction in compression ratio and occurrence of abnormal combustion.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a cylinder head material obtained by the cylinder head manufacturing method according to the present invention, Fig. 2 is a perspective view showing the remelting step in the above method, and Fig. 3 shows the order of the above remelting step. 4 is a plan view of the cylinder head material obtained by the above remelting process, FIG. 5 is a plan view of the cylinder head obtained by the above method, and FIG.
The figure is an enlarged sectional view of a cylinder head obtained by a conventional method.

Claims (1)

[Claims] (1) After pouring molten metal into a mold to form a cylinder head material, parts of the cylinder head material that require thermal fatigue properties are continuously remelted using a high-energy beam, and this remelting is removed by plugging. 1. A method for manufacturing a cylinder head, characterized in that the process ends at a part corresponding to a hole-machined part for a fuel or injection nozzle, and then a hole is machined in the part where remelting ends.