JPH01177440A - Cylinder head of aluminum alloy make - Google Patents

Abstract

PURPOSE:To prevent an early occurrence of a crack and a separation and enhance durability by forming paddings at a position corresponding to a valve seat in an aluminum alloy cylinder head and an inter-valve part, and making both paddings continuous to each other. CONSTITUTION:In the manufacture of an aluminum alloy cylinder head, a cylinder head raw material is cast from an aluminum alloy, and subjected to a pertinent process, in accordance with a normal practice. Then, paddings are so applied to valve seat parts 13A and 13B, and an inter-valve part 15A as to be continuous to each other. Thereafter, a finishing process applies whenever necessary. In this case, it is allowed to use a metal or an alloy having heat and abrasion resistance better than the aluminum alloy of a cylinder head base material, and good heat conduction as an alloy used for padding. For example, an alloy of Cu-Ni-Fe and the like are used. And the padding is applied, using a high density energy source such as a laser, a TIG or plasma arc and an electron beam as a heating source.

Description

[Detailed Description of the Invention] Industrial Application Field This invention is used in internal combustion engines such as automobiles! Regarding the alloy cylinder head, a build-up alloy layer is formed in the area corresponding to the valve seat to eliminate the need for a press-fit valve seat, and the area between the valves is also strengthened by the build-up alloy layer.
It is installed between the cylinder head made of l1 alloy.

Conventional technology Al alloys are often used in recent cylinder heads, but since the aluminum alloy itself does not have sufficient heat resistance (high temperature strength) or wear resistance, it is particularly difficult for the pulp face to repeatedly collide and be severely damaged. Conventionally, it has been widely practiced to press-fit a valve seat material made of an iron-based sintered material into a valve seat portion that is exposed to severe temperature conditions. However, in the case of a press-fit valve seat, there is a problem that the cooling efficiency of the valve seat deteriorates due to the gap between it and the Al1 alloy cylinder head body, resulting in the valve seat becoming hot and reducing its properties such as wear resistance. When a press-fit valve seat is used, the cylinder head body and the valve seat material must be processed with high precision, resulting in high processing costs. Therefore, recently, as shown in Japanese Patent Application Laid-Open No. 62-150014, an alloy with excellent heat resistance and wear resistance, such as a copper alloy, has been overlaid on the valve seat part of the cylinder head body made of Heβ alloy. By,
It has been proposed to eliminate the need for a press-fit valve seat, thereby improving heat conductivity from the valve seat to the cylinder head body, thereby preventing a temperature rise in the valve seat, and reducing processing costs. .

On the other hand, among the parts of the cylinder head on the combustion chamber side,
In particular, the areas between the intake valves and exhaust valves, that is, the areas between the valves, are susceptible to embrittlement due to large heat loads, and require excellent heat resistance. The intervalve part is T
A method of strengthening by IG re-melting treatment is disclosed in JP-A-61-1.
93773, and the same method of applying an alloying treatment to the valve gap of an Al alloy cylinder head was proposed in Japanese Patent Laid-Open No. 62-38786.

Problems to be solved by Hikama In order to eliminate the need for press-fit valve seats in aluminum alloy cylinder heads and at the same time strengthen the valve gap,
It is conceivable to build up a copper alloy or the like with good heat resistance and wear resistance on the valve seat portion, and to strengthen the valve seat portion by TIG remelting treatment or alloying. As an extension of this idea, a method can be considered in which the valve seat portion is overlaid with a copper alloy or the like, and the valve gap portion is also overlaid with the same copper alloy or the like to strengthen it.

However, it has been found that when both the valve seat portion and the valve gap portion of a cylinder head made of He1 alloy are cladded with copper alloy or the like as described above, the following problem occurs.

That is, as shown in FIG. 5, for example, the valve seat part 2 of the exhaust boat 1 and the valve seat part 4 of the intake boat 3 in the Al alloy cylinder head are overlaid with copper alloy or the like to form a valve seat overlay layer 5. .6
In addition, if the valve gap area 7 between the exhaust boat 1 and the intake boat 3 is similarly overlaid with copper alloy or the like to form the valve area build-up layer 8, the exhaust boat 1 and the intake boat 3 On the surface of the narrow area between them, from the side of the exhaust boat 1 to the side of the intake boat 3, the valve seat inner lining 115, the Ai' alloy base material portion 9A, the valve gap area cladding layer 8, and the Al alloy base material. The portion 9B and the valve seat overlay IW6 are arranged in that order. However, the overlay layer 5.6 made of copper alloy, etc.
There is often a difference in thermal expansion coefficient between 8 and A2 alloy base material parts 9A and 9B, and in that case, thermal stress occurs due to the difference in thermal expansion due to large temperature fluctuations during engine use, but as mentioned above, Thermal stress acts intensively on the part where the overlay layer 5.6.8 and the Al alloy base material part 9Al9B are alternately located in a narrow area, and cracks are likely to occur near the boundary part. . Not only that, but the build-up layer 5.6.
The Al alloy base material portions 9A and 9B sandwiched between the aluminum alloys 8 and 8 are often embrittled by the heat generated during overlaying, and as a result, cracks are likely to occur, and cracks that have already formed are likely to grow. Furthermore, copper alloy is often used as the overlay material, but in this case, brittle CLI-A & gold intermetallic compounds are generated near the interface between the overlay copper alloy layer and the Al alloy base material, causing cracks. This condition is likely to occur.

When copper alloy, etc. is overlaid on both the valve seat and the valve gap, the narrow area between the valves creates unfavorable conditions for crack generation and growth, resulting in repeated heating-cooling cycles. During this process, cracks 10 or peeling often occur in those areas, as shown in FIG.

If such cracking or peeling occurs, engine output will decrease due to compression down, leading to engine destruction. Therefore, even if the overlay is applied as described above, there is a problem that the durability cannot be improved.

Specifically, when the present inventors conducted an actual machine durability test at a full load of 6600 rp Ilx on an Al alloy cylinder head in which copper alloy was individually overlaid on the valve seat portion and the valve gap portion, the continuous operation was only 30 hours. It has been found that cracks occur over time, which actually reduces durability.

This invention was made against the background of the above circumstances, and in order to eliminate the need for a press-fit valve seat and strengthen the valve gap, both the valve seat part and the valve gap in a cylinder head made of a beta alloy are simultaneously thickened. It is an object of the present invention to provide a cylinder head that has a high profile and significantly improved durability.

Means for Solving the Problems In the Al alloy cylinder head of the present invention, a build-up layer is formed at a portion of the cylinder head made of an Al alloy that corresponds to the valve seat, and a build-up layer is also formed between the valves. It is characterized in that the built-up layer of the valve seat portion and the built-up layer of the inter-valve portion are continuous.

Function: In the Al alloy cylinder head of this invention, β
In the alloy cylinder head, a build-up layer is formed on the valve seat part and at the same time, a build-up layer is also formed in the valve gap area. Therefore, as a build-up alloy, it has better heat resistance (high temperature strength) than the Al alloy base material. By using a copper alloy etc. that has excellent wear resistance and good thermal conductivity, the heat resistance and wear resistance of the valve seat part are improved, eliminating the need for a press-fit valve seat, and when using a press-fit valve seat. The cooling effect of the valve seat part becomes better than that of the valve seat part, and the part between the valves is strengthened, and the cooling effect of that part becomes better. The improvement of the cooling effect of the valve gap and valve seat is as follows:
Improves engine ignition timing and fuel efficiency,
Contributes to improving engine performance.

In particular, in this invention, since the built-up layer of the valve seat part and the built-up layer of the valve gap part are formed continuously,
This means that there is no boundary between the two overlay layers.

In other words, there is no part where the Al alloy base material is exposed to the surface because it is sandwiched between the discontinuous build-up layer of the valve seat part and the build-up layer of the gap area, and therefore the gap between the valves is narrow. Thermal stress due to the difference in thermal expansion between the base material A2 alloy and the overlay alloy does not concentrate on the part, making it difficult for cracks to occur. Furthermore, although the Al alloy base material sandwiched between the overlay layers is likely to become brittle due to the heat during overlay, the absence of such a portion also contributes to a reduction in the occurrence of cracks.

Detailed Description for Carrying Out the Invention In manufacturing the Al alloy cylinder head of the present invention, a cylinder head rough shape is cast from β alloy according to a conventional method, and after being appropriately processed, a valve seat is formed. It is sufficient to apply overlay continuously to the part and the part between the valves, and then perform finishing processing as necessary.

Here, the overlay alloy to be overlaid may be any metal or alloy that has better heat resistance (high temperature strength) and wear resistance than the A2 alloy of the cylinder head base material, and also has good thermal conductivity. Copper alloys such as Cu-Ni-Fe alloys are typical.

The overlay is preferably performed using a high-density energy source such as a laser, TIG arc, plasma arc, or electron beam as a heating source. In other words, the valve seat portion or valve gap area to be overlaid is coated with powder or a thin plate of overlay material, and high-density energy such as a laser is applied thereon, or the area to be overlaid is overlaid. While supplying the material, high-density energy such as a laser beam is applied to melt the overlay material and weld it to the base material portion. In order to make the build-up layer on the valve seat part and the build-up layer in the valve gap area continuous, the application position of high-density energy such as a laser is moved continuously from the valve seat area to the valve gap area, and It is only necessary to continuously move it from the intermediate part to another valve seat part.

Here, many general internal combustion engines are of the four-valve type, that is, equipped with two intake boats and two exhaust boats, and in this case, the valve seats exist in four locations, and the is between two intake boats, between two exhaust boats, between an intake boat and an exhaust boat (2 locations),
It exists in a total of four locations. However, in the present invention, it is not necessarily necessary to form the build-up layer on all valve seat parts and all valve spaces, and the necessary parts may be selected as appropriate depending on the required level of improvement.

FIG. 1 shows a cylinder head of a four-valve engine, that is, an Al alloy cylinder head equipped with a pair of intake boats 11A, 1186 and a pair of exhaust ports 12Al12B, each intake boat 11A,
11B Pulp Sea.

An example is shown in which a built-up layer 16 is formed continuously on the top portions 13A, 13B and the valve gap portion 15A between them. Note that the built-up layer 16 is a hatched portion in the figure.

FIG. 2 also shows a built-up layer on the valve seat part 13A of the intake boat 11A, the valve seat part 14A of the exhaust boat 12A, and the intervalve part 15B between them in the Al alloy cylinder head of a four-valve engine. 16A is formed continuously, and intake boat 1
Valve seat portion 13B of Exhaust Boat 1B and valve seat portion 14B of Exhaust Boat 1B, and the intervalve portion 1 between them.
An example in which the built-up layer 16B is continuously formed on 5C is shown.

Furthermore, Figure 3 shows the same 4-valve engine Ai! In the alloy cylinder head, each exhaust boat 12
An example is shown in which the built-up layer 16 is continuously formed on the valve seat portions 14A and 14B of A and 12B and the intervalve portion 15D between them.

FIG. 4 shows all the valve seat parts 13Al13B and 14A of the intake boat 11Al11B and the exhaust boats 12A and 12B.

14B and the entire valve area between the adjacent valve seat parts 15
A, 158115G and 15D show a state in which the overlay layer 16 is continuously formed.

In either case, for example, as shown by the arrows in FIGS. 1 and 2, the valve seat and valve can be bonded by continuously applying overlay in the shape of glasses or cursive letter Q. A continuous build-up layer can be formed between the parts.

EXAMPLE A specific example in which a build-up layer was formed continuously on the valve seat part and the valve gap part of an Aββ alloy cylindrical render head of a four-valve engine by laser build-up method will be described below.

The specific processing conditions and materials are as follows, and are common to all Examples.

Laser processing conditions: Output 3.8~4.0 Machining speed 800 darkness/1II11 Focus range 30~35 darkness Beam oscillation amplitude 7fR#I Beam oscillation frequency 200Hz Base material to be overlaid (cylinder head): JIS A02G alloy Overlay material: Cu-Ni-1”e alloy (Ni 20wt%, 1”e
8 wt%, B 1.5 wt%, Si 3.0 wt%, balance Cu) [Example 1] As shown in FIG.
Overlay W116 was formed continuously on 5A.

[Example 21 As shown in FIG. 2, a built-up layer 16A is formed continuously on the intervalve portion 13Al14A of the intake boat IIA and the exhaust boat 12A and the intervalve portion 15B between them,
Also, the valve spaces 13B and 14B of the intake boat 11B and the exhaust boat 12B and the valve space 1 between them.
5G, a build-up layer 16B was formed.

[Example 31 Exhaust boat 12Al12B as shown in FIG.
A built-up layer 16 was formed so as to communicate with the intervalve parts 14A and 14B and the intervalve part 15D between them.

A cylinder head with a layer of flesh formed according to each of the above examples and an untreated cylinder head as a comparative example, 1600cc4. It was installed in a 1rlD 01-I G engine, and a continuous high-speed durability test was conducted using an actual vehicle at a rotational speed of 6,600 rpm and full load. The results are shown in Table 1. In Table 1, durability performance indicates the time required for the engine to malfunction or stop due to cracks in the cylinder head.

Table 1 As is clear from Table 1, when the cylinder heads of Examples 1 to 3 of the present invention are used, the engine performance is improved compared to when an untreated cylinder head (comparative example) is used. As well as improving durability.

As mentioned above, if the build-up layers are formed separately on the valve seat part and the valve gap area (that is, if the build-up layers are discontinuous), cracks will occur in about 30 hours under a full load x eeo6 rpl. Therefore, in the embodiment of the present invention, by making the built-up layer of the valve seat part and the built-up layer of the valve gap part continuous, excellent durability can be achieved without causing the problems that would occur in the case of discontinuity. It is clear that he was able to obtain sex.

Effects of the Invention According to the Al alloy cylinder head of the present invention, a build-up layer is formed on both the valve seat portion and the valve space, and in particular, the build-up layer on the valve seat portion and the build-up layer on the valve space are formed. By making these continuous, it is possible to achieve a remarkable effect of not only increasing durability compared to the conventional method but also improving engine performance without causing early cracking or peeling.

[Brief explanation of the drawing]

FIG. 1 to FIG. 4 are schematic plan views of the main parts of the A2 alloy cylinder head of the embodiment as viewed from the combustion chamber side. FIG. 5 is a schematic plan view of a main part of an Al alloy cylinder head according to the prior art, viewed from the combustion chamber side. 11A, 11B...Intake boat, 12Al1
2B...Exhaust boat, 13A, 13B; 1
4A, 14B...Valve seat part, 15A to 15D
... Between the valves, 16.16Al16B... Overlay layer. Applicant Toyota Motor Corporation Agent Patent Attorney Yutaka 1) Hisashi Take (and 1 other person) Figure 1 Figure 2 Figure 15C Figure 3 Figure 4

Claims (1)

[Claims] A build-up layer is formed in a portion corresponding to the valve seat in a cylinder head made of an Al alloy, and a build-up layer is also formed in the area between the valves, and the build-up layer on the valve seat portion and the build-up layer between the valves Al characterized in that the layers are continuous.
Alloy cylinder head.