JP2539794B2 - Valve for internal combustion engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement of a valve used in an internal combustion engine.

[Prior Art] In an internal combustion engine, conventionally, a heat-resistant steel or a Ni alloy or a Co alloy is used for a face portion in contact with a valve seat, and an alloy steel is used for a valve straight portion sliding in a guide.

[Problems to be Solved by the Invention] A valve of an internal combustion engine repeatedly moves up and down to open and close fuel intake and exhaust in a cycle according to the engine speed. Since it is composed of an iron-based alloy that uses a part of Co alloy, there is a problem that the weight is large, the inertial weight during operation is large, and there is a restriction on the drastic improvement in high-speed followability.

In view of the above, the present invention has been developed to solve such a problem. The present invention will be described in detail below.

[Means for Solving Problems] That is, in the valve for an internal combustion engine of the present invention, the face portion in contact with the valve seat is excellent in wear resistance and heat resistance, and has a Young's modulus of 80% or less.
Made of aluminum alloy manufactured by powder metallurgy with 00Kgf / mm ² or more, the straight part sliding in the valve guide has excellent wear resistance, and manufactured by powder metallurgy with Young's modulus of 8000Kgf / mm ² or more. It is characterized in that it is made of an aluminum alloy and is constructed by joining both.

[Operation] Change to conventional iron-based material to reduce inertial weight of valve
It is made of Al alloy. However, the conventional casting aluminum alloy has a problem that it does not satisfy the required characteristics in terms of heat resistance and wear resistance when used as a valve.

In order to solve this problem, the present invention manufactures an aluminum alloy by powder metallurgy. That is, the aluminum alloy powder as a raw material is produced by a rapid solidification method having a cooling rate of 10 ³ ° C / sec or more, or by a mechanical alloying method. Not only can this result in an alloy composition that was difficult to achieve with conventional casting methods,
It becomes possible to make crystals finer and finely disperse the precipitates finely, and to obtain heat resistance and wear resistance that cannot be obtained by conventional aluminum casting alloys. FIG. 1 shows a valve configuration diagram of the present invention. The face portion (1) of the valve receives the heat of the combustion gas in the cylinder and is hit by the valve seat. Therefore, the aluminum alloy used for the face portion is required to have heat resistance, wear resistance and high rigidity.

As a guide for heat resistance, it is desirable to have a tensile strength of 15 Kgf / mm ² or more at 300 ° C. If it is lower than this, there is a problem that the valve is damaged during long-time operation.

Regarding the wear resistance, as a means for improving the wear resistance, it is considered to add a wear resistance improving element as a material. These elements include Si or C, and hard elements such as W, WC, TiC, Al ₂ O ₃ and SiC.

When Si is added, it is desirable to alloy the powder at the stage of the molten metal when the powder is manufactured by the rapid solidification method. This enables alloy powder in which Si is homogeneously dispersed. The amount of Si added at this time must be in the range of 10 to 35% by weight. If Si is less than 10%, the wear resistance becomes insufficient, while if it exceeds 35%, plastic working such as extrusion casting in the subsequent step becomes difficult.

In addition, when adding a hard element such as C or W, WC, SiC, Al ₂ O ₃ or the like, there is a method of mixing with the above-mentioned rapidly solidified powder later or a method of producing an alloy powder by using a mechanical alloying method. However, the mechanical alloying method is preferable in that the hard elements are uniformly dispersed and alloyed to increase the heat resistance. The addition amount is preferably in the range of 2 to 10% by weight. If it is less than 2%, the effect of addition is small and wear resistance and heat resistance are insufficient. If it exceeds 10%, post-processing such as extrusion and casting becomes difficult.

With regard to rigidity, it is desirable that the Young's modulus is 8000 Kgf / mm ² or more. If it is less than 8000 Kgf / mm ² , the valve seat is hit by the valve seat and the face of the face portion comes into contact with the tire.

Further, depending on the specifications of the internal combustion engine, the above materials may not have sufficient wear resistance or heat resistance. In such a case, the valve face is subjected to a surface treatment in order to improve wear resistance or protect from high temperature combustion gas. The surface treatment includes plating of Ni alloy or Cr alloy, chemical treatment such as hard alumite treatment, or thermal spraying of ceramics.

Next, the valve straight portion will be described. This portion is not required to have heat resistance as much as the face portion, but it is required to have wear resistance because it slides in the valve guide, and rigidity is required to receive compressive force from the cam or rocker arm.

The aluminum alloy used for the straight portion in order to improve wear resistance preferably contains Si in a range of 10 to 35% by weight. If it is less than 10%, the abrasion resistance is insufficient, and if it exceeds 35%, its effect is small.

Regarding the rigidity, it is desirable that the Young's modulus is 8000 Kgf / mm ² or more. If it is lower than 8000 Kgf / mm ² , the material will sag or bend, and normal reciprocating motion will not be possible.

Although each of the alloys used for the face portion and the straight portion has been described above, needless to say, the same material may be used if both satisfy the above required characteristics.

[Examples] Examples of the present invention will be described below.

Example 1 An alloy powder having a composition containing Si20%, Fe3%, Ni2%, Cu3% and Mg1% in a weight ratio and the balance being Al and inevitable impurities was prepared by a rapid solidification method by air atomization. The powder cooling rate during air atomization was 10 ³ ° C / sec. 2% by weight of Al ₂ O ₃ powder (average particle size 3.0 μm) was mixed with this powder to obtain a composite powder. This composite powder is φ150mm by CIP method
After making a molded body of and degassing this at 400 ℃, 350 ~ 45
Extrusion processing was carried out at a temperature of 0 ° C. to prepare a φ9 mm round bar. This was cut into a predetermined size and used as a material for the straight portion.

Next, an alloy powder having a composition containing Si 10%, Fe 5%, and Ni 2% by weight and the balance being Al and inevitable impurities was prepared by the air atomization method as in the above.

W powder (average particle size 5.2 μm), WC powder (average particle size 3.1 μm), Al ₂ O ₃ powder (average particle size 3.0 μm), SiC
Four types of composite powders were prepared by mixing and adding powders (average particle size 2.5 μm). The composition of each composite powder was as follows.

A compact having a diameter of 150 mm was prepared from this mixed powder by the CIP method, degassed at 400 ° C., and then extruded at a temperature of 350 to 450 ° C. into a round rod having a diameter of 30 mm. From this round bar, by cutting,
It was processed into the shape of the face part. The material for the face portion and the material for the straight portion were joined by friction welding. The joined valve materials were subjected to final finishing by cutting and polishing to make a valve having a predetermined size and shape.

The Young's modulus of the straight part alloy at this time is 9800 Kgf /
It was mm ² . The Young's modulus and tensile strength at 300 ° C. of the face alloys 1 to 4 were as follows.

Example 2 An alloy powder was prepared by the same air atomization method as in Example 1 with a weight ratio of 10% of Si and 2% of Fe and the balance of Al and inevitable impurities.

To the powder, 2% by weight of C was added, and mechanical alloying treatment was performed with an attritor to prepare an Al-Si-C based alloy powder.

A φ150 mm molded body was formed from this by the CIP method, degassed at 450 ° C., and then extruded at a temperature of 350 to 500 ° C. to form a φ30 mm round bar.

After cutting this round bar to a predetermined size, it was cast at a temperature of 400 ° C to 500 ° C to prepare a face material.

The same material as in Example 1 was used as the material for the straight portion, and the material for the face portion was joined by friction welding.

This valve material was finished by cutting and polishing to prepare a valve having a predetermined size.

At this time, the Young's modulus of the face part alloy is 9200 Kgf / mm ² , 3
The tensile strength at 00 ° C was 27 Kgf / mm ² .

Example 3 The valves of Examples 1 and 2 were hard anodized only at the face portion.

[Effect of the Invention] According to the present invention, for example, in the above-described embodiment, it is possible to achieve a weight reduction of about 60% as compared with the conventional valve. Due to this significant weight reduction, the inertial weight can be greatly reduced, and the internal combustion engine can be rotated at high speed and efficiency can be improved.

[Brief description of drawings]

FIG. 1 illustrates a valve configuration diagram of the present invention. (1) …… Face part, (2) …… Straight part,
(3) …… Joint part.

Claims (1)

(57) [Claims] 1. In a valve for an internal combustion engine, a valve head portion in contact with a valve seat and a valve shaft portion sliding in a valve guide are made of aluminum 71 to 86% by weight, C,
2 to 10% by weight of one or more of W, WC, SiC, and Al ₂ O ₃ and the balance being an integral body of an aluminum alloy manufactured by powder metallurgy consisting of Si, Fe and Ni A valve for an internal combustion engine characterized by: