KR19980028998A - Valve lifter for internal combustion engine and its manufacturing method - Google Patents

Abstract

The present invention relates to a valve lifter used in an internal combustion engine such as an automobile, and a manufacturing method thereof; The purpose is to provide a valve lifter having high wear resistance by directly joining the cam contact portion with a hard small alloy.

The present invention for achieving the above object is a friction part of the valve lifter for the internal combustion engine which is in contact with the cam and the valve lifter (40) to 80% by weight of the hard phase, the rest is a Ni or Co-based coupling The technical subject matter of the valve lifter for internal combustion engines which consists of phases, and the manufacturing method of such a valve lifter is made.

Description

Valve lifter for internal combustion engine and its manufacturing method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve lifter used in an internal combustion engine such as an automobile, and a manufacturing method thereof. More specifically, a valve lifter having high wear resistance is formed by directly joining a portion of the cam contact with a hard sintered alloy. And to a method for producing the same.

Valve lifters for internal combustion engines, such as automobiles, are connected to push rods 3 for valve opening and closing on the upper side thereof, as shown in FIG. 1, and repeated friction with the counterpart cam 2 under high pressure on the bottom surface thereof. It is a dynamic valve system part that moves. The valve lifter 1 is usually made of cast iron or carbon steel, the bottom portion of it is necessary to secure a certain wear resistance in order to prevent damage caused by endless wear.

In order to secure wear resistance of the bottom surface of the valve lifter, cast iron or steel products have been subjected to carburizing, quench hardening, ion nitriding, or metal spray treatment.

However, the valve lifter subjected to the quench hardening treatment or the ion nitriding treatment of the above method has a disadvantage in that the manufacturing cost is high due to the lack of durability of the wear-resistant layer and the inevitable post-processing of the metal-spray treated product.

On the other hand, carbide-based hard nitrogen binder alloys are generally expensive, and moreover, it is difficult to produce a sintered body of a complicated shape. Considering this point, there may be a method of making a small sintered body or a portion of the base material into a hard alloy sintered body and joining the base material. However, heating the carbide base alloy to the weldable temperature usually decomposes carbides or produces complex carbides, which degrades mechanical performance.

By the way, in recent years, such a welding method has been developed by the method of brazing bonding, this method is as shown in Figure 2, the valve lifter 10 made of steel body 12 and hard alloy sintered material (14) After inserting the brazing material 16 between the), it is a method of brazing it. However, the brazing of hard alloy sintered materials is difficult to achieve sufficient effects at present, such as hard to obtain a uniform and sound bonding layer on the entire surface of the joint, and problems such as strength degradation, cracking and peeling are not fundamentally solved. have.

As such, the conventional valve lifters have respective problems according to their materials and manufacturing methods, and moreover, as the performance of internal combustion engines is gradually improved, demand for high reliability and high wear resistance valve lifters is increasing.

Accordingly, an object of the present invention is to provide a valve lifter having excellent wear resistance and high reliability by solving the above problems.

Another object of the present invention is to provide a method for producing the valve lifter simply by liquid phase sintering of the hard nitrogen alloy and the base material.

1 is a partial configuration diagram of a valve opening and closing mechanism in an automobile internal combustion engine

2 is a configuration of a valve lifter manufactured by a conventional brazing method

Figure 3 is a side view of a hard alloy disc applied to the liquid sintering method according to the present invention

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

5 is a configuration diagram of a valve lifter in which a bonding layer is formed by the liquid phase sintering method according to the present invention;

The present invention for achieving the above object is a valve lifter for an internal combustion engine that is in contact with the cam to open and close the valve, the friction portion in contact with the cam is a hard phase of 40-80% by weight, the rest is Ni or Co-based alloy A valve lifter for an internal combustion engine comprising a phosphorus bonded phase.

In addition, the present invention is a method for producing a valve lifter for an internal combustion engine, in the weight%, B: 1-4%, Si: 2-5%, Fe: 3% or less, and the rest of the powder consisting of Ni or Co: 20 -60% of WC: 80-40% was mixed and molded, and then the molded body was heated and sintered at a temperature range of 1100-1300 ° C. under vacuum sintering, and then the sintered body was processed to a predetermined thickness, and the processed sintered body The present invention relates to a method for manufacturing a valve lifter for an internal combustion engine which is placed in a friction part of the valve lifter and heat-bonded in a temperature range of 1000 to 1200 ° C in a vacuum state.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated 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 part contacting the cam is made of a hard phase and a combined phase.

In the case of the hard phase, it is desirable to form about 40-80% by weight of the total friction portion. When the hard phase becomes less than about 40% by weight, the hardness is relatively lower than that of the cam, and when it exceeds about 80% by weight, the hardness is too high. It becomes larger and shortens the life of the cam, which is not preferable. The hard phase may consist entirely of WC or contain 1-3 wt% Cr ₃ C ₂ or M _{O 2} C, alone or in combination, respectively. At this time, when Cr ₃ C ₂ or M _{O 2} C is added to the hard phase, the hard phase crystal grains may be refined to improve the strength of the friction part.

And the coupling phase is configured in balance with the hard phase as an element to increase the degree of coupling with the base material of the valve lifter. The bonding phase is composed of Ni or Co as a main component of B: 1-4% by weight, Si: 2-5% by weight, Fe: 3% by weight or less, or 16% by weight or less of Cr. Can be. When Ni or Co contains elements such as B and Si, the melting point of the alloy is lowered by about 300 ° C. compared with 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 forms a uniform and sound diffusion bonding layer directly over the bonding interface by directly liquid-diffusion bonding the hard sintered alloy and the steel constituting the body of the lifter without the need for intervening with a conventional brazing intermediate material to form a high reliability and rigidity. It is characteristic to obtain an alloy junction valve lifter.

The manufacturing method according to the present invention will be described with reference to FIGS. 3 to 5 as follows. First, as shown in FIG. 3, the hard alloy 21 having the above-mentioned composition is molded and sintered and manufactured through a process such as grinding. At this time, the sintering is preferably carried out at a temperature of about 1100-1300 ℃ in a vacuum state. The processed hard alloy 21 is then placed on the frictional portion that is in contact with the cam of the OHV (over head valve) valve lifter 20 of FIG. 4 as shown in FIG. Since B is dissolved in the bond and B is an element having a very small particle diameter, B is rapidly diffused into the base metal Fe, and B is combined with Fe of the base metal to form a low melting point phase, that is, Fe-B. Forming a phase promotes the mutual diffusion of each metal component between the hard alloy and the base metal. Subsequently, due to the mutual concentration difference between the hard alloy and the base metal element, Fe, from the base metal to the hard alloy, and the diffusion of Ni and Si from the hard alloy to the base metal occur. The present invention produces an interdiffusion layer between the hard alloy / base metal by the liquid phase diffusion bonding method to obtain a metallically dense and uniform bonding layer 23 over the entire interface. At this time, it is preferable to heat in a vacuum state in the range of about 1000-1200 ° C., which is a temperature at which the hard phase of the hard alloy melts for such a mutual diffusion reaction.

Hereinafter, the present invention will be described in detail through examples.

EXAMPLE

Powders were blended to have a composition as shown in Table 1 and wet mixed in a solvent. The mixed powder was dried, and a disk shaped compact formed by dry press into a shape having a diameter of 40 mm × 2 mm was subjected to liquid phase sintering at a temperature of 1100-1300 ° C. in a vacuum. Then, the upper and lower surfaces of the sintered hard alloy disc are ground to a predetermined thickness, and then placed on a separately prepared carbon steel valve lifter and heated again at a temperature of 1000-1200 ° C. in vacuum to carry out diffusion bonding with the base material of the valve lifter. It was.

TABLE 1

As shown in Table 1, in Comparative Example (1) having many hard phases in the bonding layer of the valve lifter, the hardness thereof was too high, resulting in relatively shortening of the cam life, and the ratio of hard phases of Comparative Example (2) was small. In this case, it was found that the wear resistance of the valve lifter was so small that 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. In addition, according to the present invention, after the completion of the bonding, the valve lifter was cut and the cross-sectional structure was observed under a microscope. The thickness of the diffusion bonding layer was about 20-30 μm, thereby forming a metallurgically uniform bonding layer throughout the interface.

As described above, according to the present invention, a uniform and sound diffusion bonding layer can be formed throughout the bonding interface of the valve lifter at low cost without the need for intervening a separate brazing intermediate material, and the valve lifter for the internal combustion engine thus manufactured has high wear resistance. It is effective to exhibit high reliability, such as extending the life of the valve lifter.

Claims (8)

In a valve lifter for an internal combustion engine in contact with the cam to open and close the valve, the friction part contacting the cam is made of a hard phase of 40-80 wt%, and the rest is made of a bonded phase of Ni or Co-based alloy. Valve lifters for internal combustion engines The valve lifter for an internal combustion engine according to claim 1, wherein the hard phase is entirely made of WC. The valve lifter for an internal combustion engine according to claim 2, wherein the hard phase contains 1-3 wt% of Cr ₃ C ₂ or M _{O 2} C alone or in combination, and the rest is composed of WC. The method according to any one of claims 1 to 3, wherein the bonding phase is B: 1-4% by weight, Si: 2-5% by weight, Fe: 3% by weight or less, and the rest is made of Ni or Co. Valve lifters for internal combustion engines The valve lifter for an internal combustion engine according to claim 4, wherein the bonding phase contains 16 wt% or less of Cr. In the method for producing a valve lifter for an internal combustion engine, the powder is composed of B: 1-4%, Si: 2-5%, Fe: 3% or less, and Ni or Co: 20-60% by weight in WC. : 80-40% is mixed and molded, and then the molded body is heated in a vacuum sintered state to a temperature range of 1100-1300 ° C. and sintered, and then the sintered body is processed to a predetermined thickness, and the processed sintered body of the valve lifter The method of manufacturing a valve lifter for an internal combustion engine, characterized in that it is placed in a friction part and heated and bonded in a vacuum at a temperature in the range of 1000-1200 ° C. 7. The method of claim 6, wherein the powder is further mixed with 16 wt% or less of Cr. The method of claim 6 or 7, wherein the mixing is the production of a valve lifter for an internal combustion engine, characterized in that the addition of WC containing 1-3 wt% Cr ₃ C ₂ or M _{O 2} C alone or in combination, respectively. Way