JPH09277019A - Exhaust port in internal combustion engine and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust port of an internal conduction engine excellent in durability and to efficiently produce the cylinder head only with ceramic thermal-splay and metal thermal-spray onto a core at a low cost by improving adhesive force of the joining interface between a heat insulation layer provided on the inner surface of an exhaust passage in contact with exhaust gas and an aluminum alloy constituting a cylinder head. SOLUTION: In a producing method of the exhaust port of the internal combustion engine, the ceramic thermal-spray is executed onto the surface of the core 2 for the exhaust port used at the time of producing the cylinder head 1 to provide the ceramic thermal-spray film 7. Successively, the exhaust port is integrally cast with the cylinder head 1 constituted with the aluminum alloy by using this cre 2 and the ceramic thermal-spray film 7 of the core 2 is transferred to the inner surface of the exhaust passage 8 to produce the exhaust port.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust port of an internal combustion engine, and more particularly to an exhaust port of an internal combustion engine in which a ceramic sprayed coating or the like is provided on an inner surface of an exhaust passage which is in contact with exhaust gas for the purpose of heat insulation and heat resistance, and its manufacture. It is about the method.

[0002]

2. Description of the Related Art In a general internal combustion engine, an exhaust port of a cylinder head communicating with a combustion chamber is exposed to high temperature exhaust gas. In order to improve the thermal efficiency of the internal combustion engine, a heat insulating structure that does not transfer combustion heat to the outside is required in the exhaust port, and maintaining a high exhaust gas temperature is necessary to reduce the concentration of unburned components. In addition, the performance of turbocharged vehicles is expected to improve. For this reason, in the conventional internal combustion engine, the exhaust port is made of ceramics having excellent heat insulating properties and heat resistance, or other material having high heat insulating properties to reduce the size and weight of the cooling system and reduce the heat load. We are aiming to improve durability by reducing it.

As a method of manufacturing the exhaust port,
For example, there is one as shown in FIGS. In a cylinder head 51 as shown in FIG. 8, ceramics thermal spraying is applied to the inner surface of the exhaust passage 52 to form an exhaust port 54 having a ceramics thermal spray coating 53. Further, in the cylinder head 51a as shown in FIG. 9, the exhaust line 54a is integrally cast by enclosing the ceramics liner 55 in the aluminum alloy forming the cylinder head 51a. In the figure, 56 is a cooling water passage, 57 is an exhaust valve, 58 is a valve seat, and 59 is a valve guide.

[0004]

However, in the manufacturing method in which the ceramic sprayed coating 53 is applied to the inner surface of the exhaust passage 52, as shown in FIG. 8, ceramic spraying is performed on the inner peripheral surface of the narrow exhaust passage 52. However, the construction work is difficult, and it is difficult to uniformly provide the ceramic sprayed coating 53 on the inner surface of the complicated exhaust passage 52, and further, post-processing such as polishing is required.

Further, in the method of integrally casting the exhaust port 54a, as shown in FIG. 9, when the ceramic liner 55 is cast and wrapped, the ceramic liner 55 may be damaged or a casting defect may occur due to heat shrinkage. , The product was unreliable. Means for solving such a problem include, for example, JP-A-62-254960 and JP-A-6-264.
There are those disclosed in JP-A 1-126956, JP-A-2-197367 and the like.

What can be said to be common to the methods using these ceramic liners is that the ceramics must be preliminarily machined into the inner shape of the exhaust passage with high accuracy, which results in the increase in the number of work steps and the increase in cost. . Moreover, in the technique of Japanese Patent Laid-Open No. 62-254960, when a liner is cast, a cooling medium is circulated in the liner to prevent "sink" between the molten metal and the liner, but in the actual manufacturing process, cooling is performed. Since a control device for controlling the temperature and flow rate of the medium is required, the casting cost is high.

Further, in the technique of Japanese Patent Laid-Open No. 61-126956, an outer surface of a metal liner is coated with a heat insulating layer such as ceramics by thermal spraying, and the liner is cast integrally with a cylinder head. According to this conventional technique, cracking and peeling due to a difference in thermal expansion generated in a liner using ceramics are eliminated, and since a core is not required, productivity is excellent, but a heat insulating effect is insufficient as compared with a ceramic liner. However, the adhesion between the ceramic layer applied to the outer surface and the cast-in metal is weak, which causes damage during operation of the internal combustion engine. Further, in the technique of Japanese Patent Laid-Open No. 2-197367, a metallized layer made of gold braze and titanium is bonded near the opening of the exhaust port liner made of aluminum titanate, and this is firmly bonded to the aluminum alloy without any gap. Problems due to casting defects will be solved. However, this method has a drawback that the number of working steps is increased because the heat treatment is performed to form the metallized layer.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a bonding interface between a heat insulating layer provided on an inner surface of an exhaust passage in contact with exhaust gas and an aluminum alloy forming a cylinder head. Manufacture of an exhaust port of an internal combustion engine that improves adhesion and provides an exhaust port of an internal combustion engine with excellent durability, and that can be efficiently and inexpensively manufactured only by ceramics spraying and metal spraying on a core. To provide a method.

[0009]

In order to solve the problems of the above-mentioned prior art, in the present invention, ceramics thermal spray coating is carried out by performing ceramics thermal spraying on the surface of an exhaust port core used when manufacturing a cylinder head. Then, the core is integrally cast with the cylinder head made of an aluminum alloy, and the ceramic sprayed coating of the core is transferred to the inner surface of the exhaust passage to manufacture the exhaust port.

In another aspect of the present invention, ceramics thermal spraying is performed on the surface of the exhaust port core used when manufacturing the cylinder head to provide a ceramics thermal spray coating, and the surface of the ceramic thermal spray coating is roughened. Further, a metal material having good wettability with aluminum molten metal is sprayed on the surface of the ceramic sprayed coating to provide a metal sprayed coating, and this core is then integrally cast with a cylinder head made of an aluminum alloy, An exhaust port is manufactured by transferring the ceramics sprayed coating and the metal sprayed coating on the core onto the inner surface of the exhaust passage.

Further, in another aspect of the present invention, the surface of the exhaust port core used in manufacturing the cylinder head is sprayed with ceramics to have a thickness of 1.0 to 2.0 mm.
Of the ceramic sprayed coating, the surface of the ceramic sprayed coating is roughened, and the surface of the ceramic sprayed coating is further sprayed with a molten aluminum and a metal material having good wettability to obtain a metal spray having a thickness of 100 to 500 μm. A film is provided, and then this core is used to integrally cast a cylinder head made of an aluminum alloy,
The ceramics sprayed coating and the metal sprayed coating of the core are transferred to the inner surface of the exhaust passage to manufacture the exhaust port.

Another aspect of the present invention is an exhaust port of an internal combustion engine manufactured by the manufacturing method according to any one of claims 1 to 3.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

1 to 3 show an embodiment of a method for manufacturing an exhaust port of an internal combustion engine according to the present invention. In the figure, 1 is a cylinder head which is a casting of an aluminum alloy, and 2 is a core for an exhaust port used when manufacturing the cylinder head 1. An intake port (not shown) opening to the combustion chamber 3 and an exhaust port 4 are formed at left and right positions inside the cylinder head 1, and a plurality of water jackets for cooling the cylinder head 1 are provided in the vicinity of the exhaust port 4. A (cooling water passage) 5 is formed.

Insertion holes 6 that are inclined toward the combustion chamber 3 are provided in the upper portions of the intake port (not shown) and the exhaust port 4, respectively, and the insertion holes 6 are hollow (not shown). A pipe-shaped valve guide can be attached integrally. These valve guides include
An intake valve and an exhaust valve (not shown) for opening and closing the intake port (not shown) and the exhaust port 4 are mounted,
When the internal combustion engine is driven, the high temperature exhaust gas discharged from the combustion chamber 3 is configured to be discharged to the outside through the exhaust port 4.

The exhaust port 4 has a ceramic sprayed coating 7 provided on the surface of the exhaust port core 2 in order to impart heat insulation and heat resistance to the surface in contact with the high temperature exhaust gas.
Is formed on the inner surface of the exhaust passage 8. This ceramic sprayed coating 7 has excellent heat insulation and heat resistance, and the heat escaping effect reduces heat escaping to the cylinder head 1. In FIG. 2, 9 is a core for forming the water jacket 5.

Next, a method of manufacturing the exhaust port 4 of this embodiment will be described.

First, a release agent is applied to the surface of the exhaust port core 2 if necessary. Then, as shown in FIG. 1, zirconia ceramic powder (ZrO ₂ -8% Y ₂ O ₃ ) having excellent heat insulation and heat resistance is sprayed onto the surface of the exhaust port core 2, and the surface of the exhaust port core 2 is sprayed. A ceramic sprayed coating 7 is provided. The ceramic sprayed coating 7 preferably has a thickness of 1.0 to 2.0 mm and a thickness of 1.0 m.
If it is thinner than m, the heat insulation effect will be reduced and the thickness will be 2.0 mm.
If the thickness is thicker, the cost will increase.

Then, using the exhaust port core 2 having the zirconia ceramics sprayed coating 7, as shown in FIG. 2, the core 2 is cast and simultaneously cast integrally with the cylinder head 1 made of an aluminum alloy. At this time, when the ceramic sprayed coating 7 applied to the surface of the exhaust port core 2 comes into contact with the aluminum molten metal, the surface of the ceramic sprayed coating 7 is heated and the aluminum molten metal is fused.

When the exhaust port core 2 is removed after the aluminum melt is solidified, the zirconia layer of the ceramic sprayed coating 7 formed by thermal spraying on the surface of the exhaust port core 2 is transferred to the inner surface of the exhaust passage 8. Then, the exhaust port 4 as shown in FIG. 3 is obtained. At this time, since the outer peripheral shape of the exhaust port core 2 is directly transferred to the surface of the zirconia layer, post-processing is unnecessary. In the present embodiment, zirconia ceramics is used as the ceramic sprayed coating 7 having heat insulation and heat resistance, but alumina (Al ₂ O ₃ ) or silicon nitride (Si ₃ N ₃ ) may be used depending on the operating conditions of the internal combustion engine. It is also possible to use ceramics such as ₄ ).

In the manufacturing method according to the present embodiment, the exhaust port core 2 provided by spraying the ceramic sprayed coating 7 on the surface is used to integrally cast with the cylinder head 1.
Since the ceramic sprayed coating 7 is transferred onto the inner surface of the exhaust passage 8, the exhaust having the layer of the ceramic sprayed coating 7 having excellent heat insulation and heat resistance and keeping good adhesion with the aluminum alloy on the inner surface of the exhaust passage 8. The port 4 can be manufactured efficiently and inexpensively.

4 to 7 show another embodiment of the method for manufacturing an exhaust port of an internal combustion engine according to the present invention. The same members as those of the above-mentioned invention are designated by the same reference numerals and their description is omitted. . In the embodiment of the present invention, when the ceramic sprayed coating 7 provided on the surface of the exhaust port core 2 described above is cast and wrapped, the ceramic sprayed coating is improved in order to improve the adhesion with the aluminum alloy of the cylinder head 1. A metal sprayed coating 10 is provided on the surface of No. 7, and is fused with an aluminum alloy by the heat energy at the time of pouring and the anchor effect.

Next, a method of manufacturing the exhaust port 4a of this embodiment will be described.

First, according to the procedure of the invention described above, the same ceramic sprayed coating 7 as shown in FIG. 1 is provided on the surface of the exhaust port core 2. At this time, in order to improve the adhesion with the metal to be sprayed next time and effectively utilize the anchor effect at the time of pouring, the spraying conditions of the ceramic sprayed coating 7 should be roughened so that the surface thereof becomes appropriately uneven. Adjust. For example, in the present embodiment, the center line average surface roughness of the surface of the ceramic sprayed coating 7 is set to 5 μmRa or more.

Further, as shown in FIG. 4, Zn, Al, and C, which have good general wettability with the molten aluminum on the surface of the ceramic sprayed coating 7 and have versatility as alloying components.
A metal material containing one or more of u and Ni is sprayed. At this time, the lower layer zirconia ceramics sprayed coating 7
Since the surface of the layer is roughened, the metal sprayed layer of the metal sprayed coating 10 is firmly bonded to the zirconia sprayed layer by the anchor effect. The thickness of this metal spray coating 10 is 100
To 500 μm is suitable, and preferably 200 to 300
μm. If the thickness of the metal spray coating 10 is less than 100 μm, the thermal stress due to thermal expansion cannot be relaxed, and if the thickness is more than 500 μm, the cost will increase. Further, the conditions for thermal spraying of the metal have the function of breaking the oxide film when the molten aluminum flows in, and are adjusted so that the surface is appropriately uneven in order to effectively exhibit the anchor effect. For example, in the present embodiment, the metal spray coating 10
The center line average surface roughness of the surface of was set to 15 to 30 μmRa.

Next, the exhaust port core 2 having the zirconia ceramic spray coating 7 and the metal spray coating 10 applied thereto.
As shown in FIG. 5, this is cast-in and simultaneously cast integrally with the cylinder head 1 made of an aluminum alloy. At this time, when the metal spray coating 10 applied to the surface of the exhaust port core 2 comes into contact with the aluminum melt, the surface of the metal spray coating 10 is heated and melted, and the aluminum melt is fused and solidified by the anchor effect. Provides a strong interface. Since the thermal stress applied to the layer of the zirconia ceramics sprayed coating 7 during casting is relieved by the layer of the metal sprayed coating 10, cracking and peeling of the coating are not a problem.

When the exhaust port core 2 is removed after the aluminum molten metal is solidified, the zirconia layer of the ceramic sprayed coating 7 and the metal sprayed layer of the metal sprayed coating 10 which are thermally sprayed on the surface of the exhaust port core 2 are removed. {Ni-Al
The (80% -20%) alloy powder sprayed layer} is transferred to the inner surface of the exhaust passage 8 to obtain the exhaust port 4a as shown in FIG. At this time, the outer peripheral shape of the exhaust port core 2 is transferred to the surface of the zirconia layer as it is, so that post-processing is not required, as in the embodiment of the invention described above.

In the manufacturing method of the present embodiment, the ceramics sprayed coating 7 and the metal sprayed coating 10 are sprayed on the surface of the exhaust port core 2 for integral casting with the cylinder head 1 and the ceramics sprayed. Since the coating 7 is transferred to the inner surface of the exhaust passage 8, the ceramics thermal spray coating 7 and the metal thermal spray coating 10 have excellent heat insulating properties and heat resistances and maintain a better adhesion with the aluminum alloy.
The exhaust port 4a having the above layer on the inner surface of the exhaust passage 8 can be efficiently manufactured at low cost. In the manufactured exhaust port 4a, as shown in the micrograph of FIG. 7, the interface between the metal sprayed layer of the metal sprayed coating 10 and the aluminum alloy of the cylinder head 1 depends on the thermal energy of the molten metal during casting and the anchor effect. You can see that they are firmly attached.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made based on the technical idea of the present invention. is there.

[0030]

As described above, in the method for manufacturing the exhaust port of the internal combustion engine according to the present invention, the surface of the exhaust port core used for manufacturing the cylinder head is sprayed with ceramics to form a ceramic sprayed coating, Next, this core is integrally cast with the cylinder head made of aluminum alloy, and the ceramic sprayed coating of the core is transferred to the inner surface of the exhaust passage to manufacture the exhaust port, so that heat insulation and heat resistance are improved. It is possible to efficiently and inexpensively manufacture an exhaust port having a ceramic sprayed coating, which has excellent properties and is in good contact with an aluminum alloy, on the inner surface of the exhaust passage. Moreover, in the manufacturing method of the present invention, since the outer peripheral shape of the core for the exhaust port is directly transferred to the surface of the ceramic sprayed coating layer, no post-processing is required, and the exhaust port can be manufactured efficiently and at low cost. Becomes

Further, in the method for manufacturing the exhaust port of the internal combustion engine according to the present invention, the surface of the exhaust port core used for manufacturing the cylinder head is sprayed with ceramics to form a ceramics sprayed coating, and the ceramics sprayed. A cylinder made of an aluminum alloy by roughening the surface of the coating, further spraying a molten aluminum and a metal material having good wettability on the surface of the ceramic sprayed coating to form a metal sprayed coating, and then using this core. The head is integrally cast and the ceramic sprayed coating and the metal sprayed coating of the core are transferred onto the inner surface of the exhaust passage to produce the exhaust port, so that the same effect as the above invention can be obtained, while the metal sprayed coating layer is In addition to relieving thermal stress and preventing damage to the coating, it is also possible to eliminate exhaust gas coming in contact with exhaust gas by fusing with aluminum alloy. Bonding interface between the aluminum alloy it is possible to firmly contact constituting the heat insulating layer and a cylinder head provided on the inner surface of the passageway can be produced more exhaust ports more excellent in durability. Moreover, since the manufacturing method of the present invention only performs ceramic spraying and metal spraying on the core, it is far more efficient than the conventional manufacturing method in which the ceramics liner is accurately processed and then cast-in. , Can be manufactured at low cost.

Further, in the method for manufacturing an exhaust port of an internal combustion engine according to the present invention, ceramics is sprayed on the surface of an exhaust port core used when manufacturing a cylinder head,
A ceramic sprayed coating having a thickness of 1.0 to 2.0 mm is provided, the surface of the ceramic sprayed coating is roughened, and aluminum molten metal and a metal material having good wettability are sprayed on the surface of the ceramic sprayed coating. , A metal spray coating having a thickness of 100 to 500 μm is provided, and then the core is integrally cast with a cylinder head made of an aluminum alloy to form the ceramic spray coating and the metal spray coating of the core on the inner surface of the exhaust passage. Since the exhaust port is manufactured by transferring to a metal, the same effects as those of the above invention can be obtained, and on the other hand, a ceramic sprayed coating having a high heat insulating effect can be provided and a metal that relaxes thermal stress due to thermal expansion during casting. The sprayed coating can be surely provided.

Since the exhaust port of the internal combustion engine according to the present invention is manufactured by the manufacturing method of the invention described above,
It is possible to reduce the heat escaping to the cylinder head due to the heat insulation effect of the ceramic sprayed coating layer, which makes it possible to reduce the size and weight of the cooling system and also to reduce the heat load on the cylinder head, thus improving durability. .
Further, in the exhaust port of the present invention, it is possible to improve the turbo efficiency and the catalyst cleaning action by increasing the exhaust gas temperature, and therefore the performance of the vehicle equipped with the turbocharger can be enhanced by using the cylinder head having this. .

[Brief description of drawings]

FIG. 1 is a sectional view conceptually showing a state in which a ceramic sprayed coating is provided on the surface of a core forming an exhaust passage of an exhaust port of an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is a sectional view conceptually showing a state in which an exhaust port is cast using a core provided with the ceramic sprayed coating.

FIG. 3 is a sectional view conceptually showing an exhaust port manufactured by transferring the ceramic sprayed coating to the inner surface of the exhaust passage after removing the core in FIG.

FIG. 4 is a sectional view conceptually showing a state in which a metal spray coating is provided on the surface of the ceramic spray coating of the core in FIG.

FIG. 5 is a sectional view conceptually showing a state in which an exhaust port is cast using a core provided with the above-mentioned two-layer thermal spray coating.

FIG. 6 is a sectional view conceptually showing an exhaust port manufactured by transferring two layers of the sprayed coating to the inner surface of the exhaust passage after removing the core in FIG.

FIG. 7 is a 200 × micrograph showing that the interface between the layer of the metal spray coating and the aluminum alloy is firmly adhered by the heat energy during casting and the anchor effect.

FIG. 8 is a sectional view conceptually showing an exhaust port of an internal combustion engine in which a ceramic sprayed coating is provided on the inner surface of an exhaust passage in a conventional example.

FIG. 9 is a sectional view conceptually showing an exhaust port of an internal combustion engine in which a ceramics liner is cast in another conventional example.

[Explanation of symbols]

 1 Cylinder Head 2 Core for Exhaust Port 4,4a Exhaust Port 7 Ceramic Sprayed Coating 8 Exhaust Passage 10 Metal Sprayed Coating

Claims (4)

[Claims] 1. A cylinder head for exhaust ports, which is used for manufacturing a cylinder head, is sprayed with ceramics to form a ceramic sprayed coating on the surface of the core, and the cylinder head is made of an aluminum alloy. A method for manufacturing an exhaust port of an internal combustion engine, which comprises integrally casting and transferring the ceramic sprayed coating of the core onto an inner surface of an exhaust passage to manufacture an exhaust port. 2. A ceramic sprayed coating is formed by performing ceramics spraying on the surface of an exhaust port core used when manufacturing a cylinder head, and the surface of this ceramic sprayed coating is roughened. A surface of the metal is sprayed onto the surface of the molten aluminum and a metal material having good wettability to form a metal sprayed coating, and then this core is integrally cast with a cylinder head made of an aluminum alloy, and the ceramic sprayed coating of the core and A method for manufacturing an exhaust port of an internal combustion engine, which comprises manufacturing an exhaust port by transferring a metal spray coating to an inner surface of an exhaust passage. 3. A ceramic sprayed coating having a thickness of 1.0 to 2.0 mm is formed on the surface of an exhaust port core used when manufacturing a cylinder head, and a ceramic sprayed coating having a thickness of 1.0 to 2.0 mm is formed. The surface is roughened, and a molten aluminum and a metal material having good wettability are sprayed on the surface of the ceramic sprayed coating to obtain a thickness of 1
A metal sprayed coating having a thickness of 00 to 500 μm is provided, and then this core is integrally cast with a cylinder head made of an aluminum alloy to transfer the ceramic sprayed coating and the metal sprayed coating of the core onto the inner surface of the exhaust passage. A method for manufacturing an exhaust port of an internal combustion engine, which comprises manufacturing an exhaust port. 4. An exhaust port of an internal combustion engine manufactured by the manufacturing method according to claim 1.