KR100205795B1 - Valve lifter and its mamufacturing method of internal combustion engine - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve lifter for use in an internal combustion engine such as an automobile and a method of manufacturing the valve lifter. The object of the present invention is to provide a valve lifter having high abrasion resistance by directly joining a portion contacting a cam with a hard sintered alloy.

In order to achieve the above object, the present invention provides a valve lifter for a valve lifter which is in contact with a cam and performs a valve opening / closing action, the friction portion contacting the cam of the valve lifter is a hard phase of 40 to 80 wt% The present invention relates to a valve leaf for an internal combustion engine and a method for manufacturing such a valve lifter.

Description

Valve lifter for internal combustion engine and manufacturing method thereof

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve lifter for use in an internal combustion engine such as an automobile and a method of manufacturing the valve lifter. More particularly, the valve lifter having a high abrasion resistance is joined to a hard sintered alloy, And a manufacturing method thereof.

A valve lifter for an internal combustion engine such as an automobile is connected to a push rod 3 for opening and closing a valve on its upper side as shown in the first view, It is a dynamic valve system part that moves. The valve lifter 1 is usually made of alloy steel or carbon steel. The bottom of the valve lifter 1 needs to have a predetermined wear resistance in order to prevent damage due to continuous wear.

In order to ensure the abrasion resistance of the bottom surface of the valve lifter, carburizing, quenching, or ion nitriding of a cast iron or steel product or metal spraying has been applied.

However, the valve lifter which has been subjected to the rapid curing treatment or the ion nitriding treatment in the above-mentioned method has a disadvantage in that the durability of the wear resistant layer is insufficient and the manufacturing cost is high due to post-processing which necessarily involves the rapid thermal sprayed product.

On the other hand, the carbide-based hard sintered alloy is generally expensive, and it is difficult to produce a sintered body having a complicated shape. In view of this, there may be a method in which a small sintered body or a part of the base material shape is made into a hard alloy sintered body and bonded to the base material. However, if the carbide-based sintered alloy is heated to a welding temperature, the carbide is decomposed or complex carbide is formed, which deteriorates the mechanical performance.

In this method, as shown in FIG. 2, the valve lifter 10, which is made of a steel material, includes a body portion 12 and a lightweight gold binding material 14, The brazing material 16 is inserted between the brazing material 16, and then the brazing material 16 is brazed. However, it is difficult to obtain a uniform and sound bonding layer throughout the joint by brazing a hard alloy sintered material. It is difficult to obtain sufficient effects at present, and problems such as strength reduction, cracking and peeling are not solved fundamentally have.

As such, the conventional valve lifter has various problems depending on its material and manufacturing method, and the performance of the internal combustion engine has been gradually improved, so that there is a growing demand for a valve lifter having high reliability and high wear resistance.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a valve lifter having excellent wear resistance characteristics and high reliability.

Another object of the present invention is to provide a method of simply manufacturing the valve lifter by liquid-phase sinter bonding of a hard sintered alloy and a base material.

FIG. 1 is a partial schematic view of a valve system waste port in a smoke pipe in a car. FIG.

Fig. 2 is a schematic view of a valve lifter manufactured by a conventional brazing method; Fig.

FIG. 3 is a side view of a hard alloy disk applied to the liquid phase sintering method according to the present invention. FIG.

FIG. 4 is an example of a valve lifter for applying the present invention. FIG.

5 is a schematic view of a valve lifter having a bonding layer formed by the liquid phase sintering method according to the present invention.

In order to achieve the above object, the present invention provides a valve lifter for an internal combustion engine which is in contact with a cam to open and close a valve, wherein the frictional portion abutting the cam is a hard phase of 40-80 wt% To a valve leaf for an internal combustion engine.

The present invention also provides a method of manufacturing a valve lifter for an internal combustion engine, comprising the steps of: B: 1-4%, Si: 2-5%, Fe: 3% -60% of WC: 80-40%, molding the mixture, heating and sintering the formed body in a vacuum sintering temperature range of 1100-1300 ° C, processing the sintered body to a predetermined thickness, To a friction portion of the valve lifter and heat-joining the valve lifter in a vacuum state to a temperature range of 1000 to 1200 占 폚.

Hereinafter, the present invention will be described in detail.

The valve lifter according to the present invention is made of a general steel material (including carbon steel as well as alloy cast iron, etc.), and the friction portion abutting the cam is made of a hard phase and a bonded phase.

In the case of the hard phase, it is preferable to make about 40 to 80% by weight of the entire friction portion. When the hard phase is less than about 40% by weight, the hardness is lowered relative to the cam, and when the hard phase is more than about 80% Rather, the life of the cam is shortened, which is undesirable. The hard phase may consist entirely of WC or may contain 1-3 wt% each of Cr ₃ C ₂ or Mo ₂ C, either alone or in combination. In this case, when Cr ₃ C ₂ or Mo ₂ C is added to the hard phase, the crystal grains of the hard phase are refined and the strength of the friction portion can be improved.

And the combined phase is constituted in balance with the hard phase as a factor increasing the degree of coupling with the base material of the valve lifter. The bonded phase is composed of Ni or Co, where B: 1-4% by weight, Si: 2-5% by weight, Fe: 3% by weight or less, and further contains 16% by weight or less of Cr . When the element such as B or Si is contained in Ni or Co, the melting point of the alloy is lowered by about 300 ° C compared to the melting point of pure Ni and Co by the process reaction, so that the valve lifter can be manufactured at a relatively low temperature.

Hereinafter, a manufacturing method according to the present invention will be described.

The manufacturing method according to the present invention is characterized in that a steel material constituting the body of the light sintered alloy and the lifter is directly liquid phase diffusion bonded to form a uniform and sound diffusion bonding layer throughout the bonding interface, Alloy junction valve lifter.

The manufacturing method according to the present invention will now be described with reference to FIGS. First, as shown in FIG. 3, the hard alloy 21 having the above composition is formed and sintered, and is manufactured through a machining process such as grinding. At this time, sintering is preferably carried out at a temperature of about 1100-1300 캜 in a vacuum state. The machined hard alloy 21 is placed on the friction portion of the overhead valve type valve lifter 20, which is in contact with the cam of FIG. 4, as shown in FIG. 4. When the hard alloy 21 is contacted in the heated state, Since phase B dissolves and B in the bonded phase is an element with a very small particle diameter, the diffusion of B rapidly occurs in the base metal Fe, and B bonds with the Fe in the base metal to form a low-viscosity phase on the base metal surface, To promote mutual diffusion of the respective metal components between the hard alloy and the base metal. Subsequently, diffusion of Ni, Si, etc. from the base metal to the hard alloy and from the hard alloy to the base metal occurs due to the mutual concentration difference between the hard alloy and the base metal. The present invention is to obtain a metallurgically dense and uniform bonding layer (23) over the entire interface by forming an interdiffusion layer between the hard alloy / base material by the liquid phase diffusion bonding method. In this case, for the mutual diffusion reaction, it is preferable to heat in a vacuum state in the range of about 1000-1200 ° C. at which the hard phase of the hard alloy melts.

Hereinafter, the present invention will be described in detail with reference to examples.

[Example]

Powders were formulated to have the composition shown in Table 1 below and wet-kneaded in a solvent. The mixed powder was dried and subjected to liquid phase sintering in a vacuum at a temperature of 1100 to 1300 占 폚 in which a disk shaped compact having a diameter of 40 mm × 2 mm was formed by a dry press. Then, the upper and lower surfaces of the sintered hard alloy disk were ground to a predetermined thickness, and then placed on a separately prepared carbon steel valve lifter and heated at a temperature of 1000-1200 ° C again in vacuum to perform diffusion bonding with the base metal of the valve lifter Respectively.

As shown in Table 1, in Comparative Example (1) in which the hard phase in the bonding layer of the valve lifter is many, the hardness is too high, resulting in shortening of the life of the cam relatively, It was found that the hardness of the friction portion of the valve lifter was too small and the wear resistance was deteriorated.

On the other hand, in the case of Inventive Example (1-3) manufactured according to the present invention, the hardness of the valve lifter is about 700-1000, which indicates that the cam surface hardness is about 700 Hv, Able to know. Further, according to the present invention, the contact lifted valve lifter was cut and its cross-sectional structure was observed under a microscope. As a result, a completely uniform metallurgically bonded layer was formed over the entire interface with a thickness of the diffusion bonding layer of about 20-30 탆.

As described above, according to the present invention, it is possible to form a uniform and sound diffusion bonding layer over the bonding interface of the valve lifter at low cost without requiring a separate intermediate brazing material, and the valve lifter for such internal combustion engine manufactured in this manner has high wear resistance The lifetime of the valve lifter can be prolonged and high reliability can be exhibited.

Claims (8)

A valve lifter for an internal combustion engine in contact with a cam and having a valve opening and closing action, wherein the friction portion abutting the cam is a hard phase of 40-80 wt% and the remainder is a single phase selected from Ni and Co alloys Valve lifter for internal combustion engines. The valve lifter for an internal combustion engine according to claim 1, wherein the hard phase consists entirely of WC. The valve lifter as set forth in claim 1, wherein the hard phase contains at least one kind of Cr ₃ C ₂ and Mo ₂ C each in an amount of 1 to 3 wt%, and the balance WC. 4. The method according to any one of claims 1 to 3, wherein the bonded phase comprises at least one selected from the group consisting of B: 1-4 wt%, Si: 2-5 wt%, Fe: 3 wt% And a valve lifter for lifting the valve lifter. 5. The valve lifter for an internal combustion engine according to claim 4, wherein said bonded phase contains not more than 16% by weight of Cr. 1. A method for manufacturing a valve lifter for an internal combustion engine, comprising the steps of: 1 to 20 parts by weight of a powder selected from the group consisting of B: 1-4%, Si: 2-5%, Fe: 3% -60% of WC: 80-40%, molding the mixture, heating and sintering the formed body in a vacuum sintering temperature range of 1100-1300 ° C, processing the sintered body to a predetermined thickness, Is mounted on a friction portion of the valve leaf, and is heat bonded in a vacuum state to a temperature range of 1000 to 1200 占 폚. 7. The method according to claim 6, wherein the powder is further mixed with not more than 16% by weight of Cr. The valve lifter for an internal combustion engine as claimed in claim 6 or 7, wherein the mixing is performed by adding WC containing at least one selected from among Cr ₃ C ₂ and Mo ₂ C in an amount of 1 to ₃ wt% Gt;