JPS61178506A - Cylinder head - Google Patents

Abstract

PURPOSE:To reduce heat distorsion and enhance a bonding strength of a wear- resistant covering material, by forming a valve seat part of a cylinder head by a fiber-reinforced metal material whose property is changed continuously or stepwise. CONSTITUTION:A cylinder head 1' is formed of aluminium or magnesium alloy. A valve seat part is formed of a fiber-reinforced metal material, and is provided with a wear-resistant covering layer 4. A property of the fiber-reinforced metal material such as kind, size, volumetric percentage, and orientation of fibers is changed continuously or stepwise according to temperature or stress distribution in using. Thus, heat distorsion at the periphery of the valve seat may be reduced, and a bonding strength of the wear-resistant covering layer may be improved to thereby prevent separation of the covering layer and increase a degree of freedom of material selection.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cylinder head for an internal combustion engine, and more particularly to a light alloy cylinder head without a valve seat ring.

[Conventional technology]

Conventionally, in light alloy cylinder heads, in order to ensure sealing performance with the valve and wear resistance, firstly, a valve seat ring f made of iron, which has good wear resistance, is press-fitted into the contact portion with the valve. This method of installing valve seat rings not only requires a large amount of cost and time to prepare the cylinder head for the seat ring, process the seat ring, and press fit the ring, but also has poor thermal conductivity. Due to poor quality, the cooling effect of the valve is low and the temperature becomes high, so expensive heat-resistant and wear-resistant materials,
Since it is necessary to use 1, which results in high costs, it has also been an obstacle to achieving high performance l purification for internal combustion engines.

Therefore, it may be possible to eliminate the valve seat ring as seen in cast iron cylinder heads, but since even the intake valve seat on the low temperature side locally reaches a temperature close to that of the exhaust gas, the normal A/alloy or Mg Alloys have problems such as insufficient heat-resistant strength and high-temperature wear resistance, are susceptible to entrapment of precipitates such as combustion products, and lack corrosion resistance.

Therefore, it is being considered to directly coat the valve contact surface of the A/alloy or Mg alloy cylinder head with a material that has excellent heat resistance, φ wear resistance, etc., by thermal spraying, cladding, alloying, etc.

[Problem that the invention seeks to solve]

However, even if the material is coated with a heat-resistant and wear-resistant material as described above, it is susceptible to thermal distortion due to thermal cycles during operation due to differences in thermal expansion with the base material, differences in elastic modulus, and lack of rigidity of the base material. υ
There was a problem in that the coating material was likely to peel off.

The present invention is intended to solve the above-mentioned problems in the prior art, and its purpose is to provide a cylinder head in which the portion corresponding to the valve seat has excellent heat resistance and wear resistance, and in which peeling does not occur in this portion. It's about doing.

[Means for solving problems]

In other words, in the cylinder head of the present invention, a portion corresponding to the valve seat of a cylinder head made of A/alloy or Mg alloy of an internal combustion engine is modified by reinforcing fiber type, size, and volume depending on the temperature or stress distribution during use of the corresponding portion. The present invention is characterized in that it is a fiber-reinforced metal body whose properties such as ratio and orientation are changed stepwise or continuously, and a wear-resistant coating layer is formed on the valve contact surface of the fiber-reinforced metal body.

The reinforcing fibers that can be used in the present invention are not particularly limited as long as they can withstand high temperatures during casting and have sufficient mechanical properties, such as metal fibers, ceramic fibers, and glass fibers. For example, as a metal fiber, 5Cr20.8
Iron-based fibers such as steel or cast iron such as 0M40.5US410, Ni-based, Co-based, 'f'i-based, Cu
Examples of the ceramic fiber include alloy fibers such as 8i0z.

Examples include fibers made of Al203, 8iC, etc.

These fibers can be used in the form of long fibers or short fibers. Further, various diameters and lengths of fibers can be used, but long fibers are preferably 5-s and oop in diameter, and short fibers are preferably 5-20μ in diameter and 10-500μ in length.

Characteristics vary depending on the type of fiber. For example, metal fibers have better wettability with base metals than non-metal fibers such as ceramic fibers, and are also cheaper. Opposite: Ceramic fibers are superior in terms of strength and other properties. Furthermore, the temperature and stress during use of the valve seat portion are not uniform depending on the location.

Therefore, the portion corresponding to the valve seat is replaced with a fiber-reinforced metal body (F
RM), it is preferable to arrange the fibers optimally by changing their properties such as type, size, volume fraction, orientation, etc. stepwise or continuously.

For example, by using ceramic fibers on the side closer to the contact surface with the valve, where the temperature is higher, and using metal fibers on the opposite side, or by increasing the volume fraction of each of the above fibers on the side closer to the contact surface with the valve. By using long fibers on the side near the contact surface with the valve and short fibers on the side far from the valve, the Ap gold alloy of the base material has a thermal expansion coefficient of that of the Mg alloy and the material of the covering layer. Thermal strain caused by the difference in temperature can be gradually corrected by reinforcing fibers.

Furthermore, by optimizing the arrangement, the rigidity of the portion corresponding to the valve seat is improved, so peeling and cracking of the coating layer can be prevented.

As light alloys that can be used for the FRM base material in the present invention, those that have been conventionally used for this purpose can be used. Examples include AC4C aluminum alloy and AZ91 magnesium alloy. If desired, an alloy with better heat resistance and wear resistance, such as ADT4
etc. may also be used.

As a method for forming the F RM section, for example, a molded product made of long fiber reinforcing fibers wound concentrically, or a molded product oriented in a mesh pattern is placed in a portion corresponding to the valve seat of a cylinder head mold (shell mold). It is preferable that the molded body is impregnated with a light alloy and then cast integrally with the cylinder head body.

Another method is to mold reinforcing fibers in the form of short fibers into a predetermined shape using an appropriate binder. For example, for A/gold alloy, Mg
One method is to manufacture an annular FRM member by die-casting using an alloy, and then cast it into the cylinder body in the same manner as above.6 Materials used for the wear-resistant coating layer formed on the valve contact surface include, for example, For the low-temperature intake valve seat portion, a wear-resistant material based on the A/gold alloy or Mg alloy may be used.

Although its heat resistance is inferior to ordinary Fe-based alloys, it has good thermal conductivity, and the base material A/gold alloy is Mg-gold alloy RM.
It is characterized by good bondability with. Fe, Ni, Co
It is preferable to form a coating layer made of one of the following: and Cu-based wear-resistant alloys. The thickness of the coating layer is preferably determined by taking into consideration the type of alloy and usage conditions.

〔Example〕

The invention will be explained in further detail in the following examples. Note that the present invention is not limited to the following examples.

Example 1: FIG. 1 shows an embodiment of a cylinder head 1 of the present invention.

In the figure, 2 is an alumina-silica long fiber reinforced metal body, 5 is a stainless steel long fiber reinforced metal body, 4 is a wear-resistant coating layer,
5 is a valve contact surface portion. The manufacturing method will be described below.

First, alumina-silica (A1) with an average diameter of 20 pm was used.
203-5m1%5iOz) Long fibers and average diameter 50
pm (7) Stainless steel (SU8) Long fibers are concentrically bundled and formed into annular bodies 6 and 7, respectively, and stacked in two stages to form an at fiber molded body 8 shown in Fig. 2, and then molded into a mold for a cylinder head. The alumina-silica long fibers 6 are placed in the intake and exhaust valve seat parts of the valve seat so as to face the valve seat side, and the valve seats are made of alumina-silica fibers by suction casting using molten M alloy (AC4C). 6 long fibers and 7 tons of stainless steel long fibers - each with a volume ratio of 1
The FRM containing 5% and 20% was then subjected to heat treatment and machining to obtain a cylinder head rough material 9 shown in FIG.

Next, as a wear-resistant coating material on the intake-side valve contact surface of the alumina-silica-based long fiber reinforced metal 2 of the cylinder head rough material 9, Al-17% 5i-4,5%Cu by weight was added.
(Hereinafter, CH is weight%) is used as a base material, and intermetallic compound powder Co-301Mo-8 of Co base material is used as a base material.
After applying a predetermined amount of a paste made by adding and mixing two parts of ToCr-2%Si, it is locally heated with a laser beam to perform liquid phase sintering in a semi-molten state, and then quenched with an air blower to form the first
A wear-resistant coating layer 4 shown in the figure was formed.

In addition, Co-10%Cr is applied to the exhaust side valve contact surface.
A wear-resistant coating layer 4t was formed in the same manner using a powder paste t consisting of -5%W-1%Mo-(L5%Vt,ssc).Then, a wear-resistant coating layer 4t was formed by machining. A cylinder head 1 of the present invention was obtained by forming a valve contact surface portion 5 on the top.

Example 2: Using the alumina-silica long fibers 6 used in Example 1, three types of annular bodies of 10° and 11.12 tons with different volume ratios were formed and stacked in three stages to form fibers as shown in FIG. 4. Obtained body 8. The volume percentage of the fiber molded body 8 is 15%, 11 inches, and 7 inches on the intake side, and 420% and 151%, 10% on the exhaust side, respectively, from the side closer to the valve contact surface. Missing
The cylinder head 1 shown in FIG. 5 was obtained in the same manner as in Example 1. FIG. 5 shows the intake side, and in the figure, numeral 13 is an alumina-krica long fiber reinforced metal body having a volume ratio of 15%, 14 a volume ratio of 11 cm, and 15 a volume ratio of 7 cm.

〔Effect of the invention〕

As described above, in the cylinder head of the present invention, the portion corresponding to the valve 7 is formed of a fiber-reinforced metal body, and the shape of the fibers is changed stepwise or continuously, and the valve contact surface portion is made of a fiber-reinforced metal body. Forming an abrasion-resistant coating layer increases the high-temperature strength and rigidity of the contact surface base material, suppresses thermal expansion, reduces thermal strain around the valve seat, and increases the bonding strength of the wear-resistant coating material on the contact surface. It is possible to prevent peeling of the coating material and increase the degree of freedom in selecting the coating material.

In addition, since the thermal conductivity of the valve seat part is improved, the temperature of the valve seat is lowered, and the high temperature strength of the valve seat part is improved.
Since there is a margin in hardness, wear resistance, corrosion resistance, etc., and the valve diameter can be designed larger, it can withstand higher loads and easily improve performance. Alternatively, a low cost hammer can be used for the wear resistant coating. In addition, the heat of the other valve is well cooled through the valve seat, which lowers the valve temperature and increases the valve's high-temperature strength, hardness, wear resistance, corrosion resistance, etc.
As with valve seats, it is easy to reduce costs or improve performance.

Furthermore, the wall thickness around the valve seat of the cylinder head can be reduced, leading to weight reduction, and the cooling effect of cooling water is increased, making it easier to improve performance. This leads to a reduction in warm-up time.

Furthermore, the present invention can reduce the number of parts for the valve seat ring, and since there is no need to press fit the valve seat ring, there is no need for the ninth cylinder head prepared hole and high precision machining of the seat ring alone. .

Furthermore, since the properties of the reinforcing fibers are changed stepwise or continuously, various deformations are possible, and there are various effects such as being able to quickly respond to changes in required characteristics.

[Brief explanation of drawings]

FIG. 1 shows part #? of an embodiment of the cylinder head of the present invention.
42 is a perspective view of the fiber molded body used to prepare the cylinder head in Figure 1, and Figure 5 is a partial cross section showing the cylinder head in Figure 1 before the wear-resistant coating layer is formed. 4 is a perspective view showing another example of a fiber molded body, and FIG. 5 is a partial sectional view of another embodiment of the cylinder head of the present invention. In the figure, 1.1... Cylinder head 2... Alumina-silica long fiber reinforced metal body 3... Stainless steel long fiber reinforced metal body 4... Wear-resistant coating layer 5... Valve Contact surface part 6.7.10.11.12... Annular body 8... Fiber molded body 9... Cylinder head rough material 'Is, 14.15, , each volume ratio 15
%, 11%, 7% alumina-7 re-strength long fiber reinforced gold 4
Body (1 other person)ゝ-

Claims (5)

[Claims] (1) Properties such as type, size, volume fraction, orientation, etc. of reinforcing fibers are determined in the valve seat portion of an Al alloy or Mg alloy cylinder head of an internal combustion engine, depending on the temperature or stress distribution during use of the corresponding portion. 1. A cylinder head comprising: a fiber-reinforced metal body in which the texture of the fiber-reinforced metal body changes stepwise or continuously, and a wear-resistant coating layer is formed on a valve contacting surface of the fiber-reinforced metal body. (2) Claim 1, wherein the fiber-reinforced metal body is formed by placing a molded body of reinforcing fibers in a portion corresponding to the valve seat, pouring hot water into the body, and casting the body integrally with the cylinder head.
Cylinder head described in section. (3) A patent claim characterized in that the fiber-reinforced metal body is formed by placing a separately manufactured fiber-reinforced metal member in a portion corresponding to the valve seat, pouring hot water into the cylinder head, and integrally casting the fiber-reinforced metal member into the cylinder head. The cylinder head according to the range 1 above. (4) The cylinder head according to claim 1, wherein the wear-resistant coating layer is made of an Al alloy or a Mg alloy as a base material. (5) The cylinder head according to claim 1, wherein the wear-resistant coating layer is made of any one of Fe, Ni, Co, and Cu base alloys.