JPH10148107A - Valve lifter for internal combustion engine and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide with a superior abrasion resistance, and high reliability by forming a frictional part which is brought into contact with a cam as a hard phase with a specified composition, and forming the rest thereof as a binder phase made of Co alloy. SOLUTION: A valve lifter 20 is made of a general steel material, its frictional part abutting on a cam consists of a hard phase and a binder phase. A hard phase of the frictional part is about 40 to 80weight% preferably. In the case where the hard phase is about 40weight% and less, the degree of hardness is reduced relatively comparing with that of the cam. On the other hand, in the case where it exceeds about weight%, the binder phase is reduced, and bonding power between the frictional part of the valve lifter 20 and a hard sintered body 21 is not sufficient. The hard phases may be made of WC, or Cr3 C2 or Mo2 C of each 1 to 3 weight% may be contained therein. When Cr3 C2 or Mo2 O is added therein, crystal grain of the hard composition is formed into a fine size, and the strength of the hard phase is improved. The binder phase is formed in order to increase a bonding degree between the valve lifter and the hard sintered body 21, its main composition is Ni or Co.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve lifter for use in an internal combustion engine of an automobile or the like and a method for manufacturing the same, and more particularly, to a cam (c).
The present invention relates to a valve lifter having high wear resistance and a method for manufacturing the valve lifter, the portion of which is in direct contact with a hard sintered alloy.

[0002]

2. Description of the Related Art Valve lifters 1 for internal combustion engines of automobiles and the like
As shown in FIG. 1, a push rod 3 for opening and closing a valve is abuttedly connected to the upper part thereof, and the relative cam 2 and the frictional friction are repeatedly applied to the floor under a high pressure. A moving dynamic valve system component. The structure of the valve lifter has various structures as shown in FIG. 2, FIG. 4, and FIG. The valve lifter 1 is made of a common alloy cast iron or carbon steel, and its floor is damaged by constant wear. To prevent such damage, a predetermined wear resistance is required. Need to be secured.

In order to ensure the wear resistance of such a valve lifter floor, the floor of the valve lifter made of cast iron or steel is carburized and quenched, and quenched and hardened.
Alternatively, ion nitriding or metal spraying has been applied. However, valve lifters that have undergone quenching hardening or ion nitriding during the above method have the disadvantage that the durability of the wear-resistant layer is insufficient, and metal sprayed products require high post-processing due to the inevitable post-processing. There is.

On the other hand, carbide-based hard sintered alloys are generally expensive and it is difficult to produce a sintered body having a more complicated shape. In consideration of such points, there is a method in which a small-sized sintered body or a part of the shape of a base material is usually made of a hard alloy sintered body and is used by being joined to the base material. However, if the ordinary carbide-based sintered alloy is heated to a temperature at which welding can be performed, carbides are decomposed or composite carbides are formed, thereby deteriorating the mechanical performance.

[0005] Therefore, a brazing method has recently been developed which is different from such a welding method. In this method, as shown in FIG. 2, a brazing material 16 is inserted between a body portion 12 of a valve lifter 10 made of steel and a hard alloy sintered material 14, and then brazed. However, it is difficult to obtain a uniform and sound bonding layer over the entire surface of the joint, and it is difficult to obtain a sufficient effect at present. Problems such as the peeling phenomenon have not been fundamentally solved.

As described above, the conventional valve lifter has various problems due to its material and manufacturing method. Further, as the performance of an internal combustion engine has been gradually improved recently, a highly reliable and highly wear-resistant valve has been developed. The fact is that demand for lifters is increasing.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a valve lifter having excellent wear resistance and high reliability. Another object of the present invention is to provide a method for easily manufacturing the valve lifter by liquid sintering bonding between a hard sintered alloy and a base material.

[0008]

In order to achieve the above object,
The present invention provides a valve lifter for an internal combustion engine that performs a valve opening / closing action by contacting with a cam, wherein a friction portion that contacts the cam is a hard phase of 40 to 80% by weight,
An object of the present invention is to provide a valve lifter for an internal combustion engine comprising a binder phase whose balance is a Ni or Co alloy.

Further, the present invention relates to a method for manufacturing a valve lifter for an internal combustion engine which performs a valve opening / closing action by contacting a cam, wherein B: 1 to 4% by weight, Si: 2 to 5% by weight, F:
e: 3% by weight or less, and 20 to 60% by weight of a binder phase powder consisting of Ni or Co, and WC powder: 80 to 60% by weight.
After mixing 40% by weight and molding it, this molded body is heated in a vacuum sintering state in a temperature range of 1100 to 1300 ° C and sintered, and this sintered body is processed into a certain thickness,
The processed sintered body is placed on the friction portion of the valve lifter that comes into contact with the cam, and is placed in a vacuum state at 1000 to 1200
The present invention relates to a method for manufacturing a valve lifter for an internal combustion engine that is heated and joined in a temperature range of ° C.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The valve lifter according to the present invention is a general steel material (
Examples include carbon steel as well as alloy cast iron. ), And the friction portion in contact with the cam comprises a hard phase and a binder phase. It is desirable that the hard phase of the friction portion is about 40 to 80% by weight. This is because when the hard phase is less than about 40% by weight, the hardness is relatively reduced as compared with the cam, and the hardness is reduced to about 80% by weight.
If the ratio exceeds, the binder phase is reduced and the bonding force between the friction portion of the valve lifter and the hard sintered body is not sufficient, which is not desirable. The hard phase may be entirely WC, and each may contain 1-3% by weight of Cr ₃ C ₂ or M
o ₂ C may be contained alone or in combination. At this time, if Cr ₃ C ₂ or Mo ₂ C is added to the hard phase, there is an advantage that the crystal grains of the hard phase are refined and the strength of the hard phase can be improved.

[0011] The binder phase increases the degree of binding between the valve lifter and the hard sintered body, and is formed in balance with the hard phase. The binder phase is mainly composed of N
i or Co to which B: 1 to 4% by weight, S
i: 2 to 5% by weight and Fe: 3% by weight or less may be contained, and further, 16% by weight or less of Cr by weight of the binder phase may be contained. B or Si to Ni or Co
When such an element is contained, the melting point of the alloy is lowered by about 300 ° C. as compared with the melting points of pure Ni and Co due to the process reaction, so that a valve lifter can be manufactured at a relatively low temperature.

Hereinafter, a method of manufacturing a valve lifter according to the present invention will be described. The production method according to the present invention comprises:
No need to intervene ordinary brazing intermediate material, the hard sintered alloy and the steel material that forms the body of the lifter are directly liquid diffusion bonded, forming a uniform and sound interdiffusion bonding layer over the entire bonding interface, high reliability It is characterized in that a hard alloy-joined valve lifter is obtained.

The manufacturing method according to the present invention will be described with reference to FIGS. First, B: 1 to 4% by weight, Si: 2 to 5%
% By weight, Fe: 3% by weight or less, and a binder phase powder composed of Ni or Co: 20 to 60% by weight, and WC powder: 80 to 40% by weight. Then, as shown in FIG. 3, the sintered body is manufactured into a desired shape and size through grinding and other processing steps. The binder phase powder preferably has a particle size of 53 μm or less. The reason for this is that if the particle size is too large, the deviation of the hardness of the sintered body increases because the binder phase and the like are non-uniformly present during sintering. On the other hand, if the particle size of the WC powder is too small, WC separates into W and C, and C reacts with Ni to generate pores, and the hardness also decreases. If the size is large, the deviation of the hardness of the sintered body becomes large, so that the particle size of the WC powder is 1 to 5 μm.
Is desirable. The sintering is performed in a vacuum state for about 1100 to 13
It is desirable to carry out within a temperature range of 00 ° C. The sintered body sintered as described above has a bonding phase of Ni-B-Si
It has a structure in which the eutectic alloy and the hard phase WC are dispersed.

Next, the sintered body processed as described above is placed as shown in FIG. 5 on a friction portion 22 which comes into contact with a cam of an OHV (Over Head Valve) type valve lifter 20 in FIG.
A valve lifter for an internal combustion engine having excellent abrasion resistance is manufactured by heating to a certain temperature range and mutually diffusing and bonding the sintered body to the friction portion 22 of the valve lifter 20. In FIG. 5, reference numeral 21a denotes an interdiffusion region.
The heating step for the interdiffusion is desirably controlled so that the binder phase of the sintered body is primarily dissolved at a portion where the frictional part of the sintered body and the valve lifter are in contact with each other. If the binder phase of the sintered body is dissolved at the portion where the sintered body and the friction part of the valve lifter are in contact with each other as described above, B is an element having a very small particle diameter. The diffusion of B occurs quickly, and the B diffused to the friction part is combined with Fe of the friction part to form a low-melting phase on the friction part surface, that is, an Fe-B shape, and the sintered body and the valve lifter It promotes mutual diffusion of each metal component between the friction parts. At the time of the interdiffusion, the diffusion of Fe occurs from the friction part to the sintered body due to the mutual concentration difference between the sintered body and the friction part, and the diffusion of Ni, Si, etc. from the sintered body to the friction part occurs. become.

In the above-mentioned interdiffusion step, a portion corresponding to the surface of the valve lifter that comes into contact with the friction portion, that is, a region of a predetermined thickness of the surface portion of the sintered body that comes into contact with the relative cam ensures sufficient wear resistance. Therefore, it is desirable that diffusion is hardly caused. In the above interdiffusion step, if the diffusion temperature is too low or the diffusion time is too short, sufficient diffusion does not occur over the entire interface between the sintered body and the valve lifter, so that a dense and uniform bonding layer can be formed. However, since the bonding strength between the sintered body and the valve lifter is deteriorated, the diffusion temperature is desirably 1100 ° C. or more, and the diffusion time is desirably 5 minutes or more.

On the other hand, if the diffusion temperature is too high or the diffusion time is too long, the diffusion region of the sintered body becomes large, the hardness of the sintered body surface decreases, and the abrasion resistance decreases. Preferably, the diffusion time is limited to 240 minutes or less. The diffusion temperature and the time are inversely proportional to each other. When the diffusion speed is high, the target diffusion effect can be obtained even when the diffusion is performed in a shorter time than when the diffusion speed is low.

[0017]

The present invention will be specifically described below with reference to examples. (Experimental Example 1) Powders were blended so as to have the composition shown in Table 1 below, and were wet-mixed in a solvent. The mixed powder was dried, and a disc-shaped (disc) molded body having a diameter of 40 mm × 2 mm formed by a dry press was heated at 1300 ° C. in vacuum.
The liquid sintering was performed at a temperature of 2 hours for 2 hours. Next, after grinding the upper and lower surfaces of the sintered hard alloy disk to a predetermined thickness, the disk was placed on a friction portion of a valve lifter made of a separately prepared carbon steel material, and further heated at 1200 ° C. in vacuum.
, And diffusion bonding was performed between the valve lifter and the sintered hard alloy disk.

[0018]

[Table 1]

As shown in Table 1 above, in the case of Comparative Example 1 in which the bonding phase of the valve lifter has many hard phases, fine pores are formed at the boundary of the diffusion bonding layer, but the bonding strength is high. In the case of Comparative Example 2 in which the ratio of the hard phase was low, the hardness of the valve lifter was considerably low, so that the abrasion resistance was low.

On the other hand, Examples (1 to 1) manufactured according to the present invention
In the case of 3), the hardness of the valve lifter is about 700-100.
0, which is usually about 700H
Considering that the value is about v, it can be seen that the material shows appropriate hardness and has excellent wear resistance. Further, the cross section structure of the valve lifter, which has been joined according to the present invention, is cut and observed with a microscope. As a result, the thickness of the diffusion joining layer is about 20 to 30 μm, and the metallurgy is completely uniform over the entire interface. A suitable bonding layer was formed.

(Experimental Example 2) A powder having the same composition as that of Example 1 in Table 1 was blended and wet-mixed in a solvent. This mixed powder was dried, and a disk-shaped (disc) compact formed by a dry press into a shape having a diameter of 40 mm × 2 mm was subjected to liquid sintering in a vacuum at a temperature of 1050 to 1350 ° C. for 30 to 300 minutes. Next, the upper and lower surfaces of the sintered hard alloy disk are ground to a certain thickness and placed on a friction portion of a valve lifter made of a separately prepared carbon steel material. After heating for one minute, diffusion bonding between the valve lifter and the sintered hard alloy disk was performed.

[0022]

[Table 2]

As shown in Table 2 above, in the temperature range of 1350 ° C. or more, many pores are observed, which is not preferable as a structure. This is not preferred because it does not occur.
On the other hand, when sintering is performed according to the present invention (Examples 4 to 9)
In addition to the high hardness, the WC particles and the like are uniformly distributed in the liquid of the Ni alloy as the binder phase, and the sintered body has uniform hardness as a whole.

(Experimental Example 3) A powder having the same composition as that of Example 1 in Table 1 was blended and wet-mixed in a solvent. The mixed powder was dried, and a disk-shaped formed body having a diameter of 40 mm × 2 mm formed by a dry press was subjected to liquid sintering at 1300 ° C. for 2 hours in a vacuum.
Then, after grinding the upper and lower surfaces of the sintered hard alloy disk to a fixed thickness, the disk is placed on a separately prepared valve lifter made of carbon steel material, and further subjected to 900 to
In a temperature range of 1300 ° C., heating was performed for 10 to 300 minutes to perform diffusion bonding between the valve lifter and the sintered hard alloy disk.

[0025]

[Table 3]

As shown in Table 3 above, when joining the sintered body and the base material, the base material at the bonding portion is deformed at a temperature of 1300 ° C. or more, and necessary for diffusion bonding at a temperature of 900 ° C. or less. Bonding was not performed satisfactorily due to insufficient energy. On the other hand, in the case of diffusion bonding according to the present invention (Examples 10 to 12), it can be seen that the bonding state is good.

[0027]

As described above, according to the present invention, it is possible to form a uniform and sound diffusion bonding layer over the entire bonding interface of the valve lifter at a low cost without the need for a separate brazing intermediate material. The valve lifter for an internal combustion engine manufactured in this way has high reliability, such as exhibiting high wear resistance and extending the life of the valve lifter.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a part of a valve opening / closing mechanism in an automobile internal combustion engine.

FIG. 2 is a configuration diagram illustrating a valve lifter manufactured by a conventional brazing method.

FIG. 3 is a side view showing a hard alloy disk manufactured by the liquid sintering method of the present invention.

FIG. 4 is a configuration diagram showing an example of a valve lifter of the present invention.

FIG. 5 is a structural view showing a valve lifter on which an interdiffusion bonding layer is formed by the manufacturing method of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Valve lifter, 2 ... Relative cam, 3 ... Push rod, 10 ... Valve lifter, 12 ... Body part, 1
4 ... hard alloy sintered material, 16 ... brazing material,
20: Valve lifter, 21: Hard alloy disk, 21a: Interdiffusion area, 22
..Friction part.

──────────────────────────────────────────────────の Continuation of front page (51) Int.Cl. ⁶ Identification symbol FI C22C 32/00 C22C 32/00 NP // C22C 1/05 1/05 H (71) Applicant 597158610 300-18, Sungsu- 2-Ga, Songdong-ku, Seoul, Korea (72) Inventor Kang Yun-sik South Korea, Kungkid, Sangnam-shi, Bandang-ku, Keumkok-dong, Chungsol apartment, No. 902-1008 (72 Inventor Jin Jung Geun South Korea, Kungkid, Kungposh, Sandong-dong, Sejongg apartment, No. 649-703

Claims (8)

[Claims] 1. A valve lifter for an internal combustion engine which contacts a cam to perform a valve opening / closing operation, wherein a friction portion in contact with the cam is a hard phase of 40 to 80% by weight, and the rest is a Ni or Co type. A valve lifter for an internal combustion engine, comprising a bonded phase of an alloy. 2. The valve lifter for an internal combustion engine according to claim 1, wherein the hard phase is entirely made of WC. 3. The hard phase comprises 1 to 3% by weight of Cr
₃ C ₂ or Mo ₂ C is contained alone or in combination,
2. The valve lifter for an internal combustion engine according to claim 1, wherein the remainder is made of WC. 4. The binder phase comprises: B: 1 to 4% by weight;
The valve lifter for an internal combustion engine according to any one of claims 1 to 3, wherein i: 2 to 5% by weight, Fe: 3% by weight or less, and the balance is made of Ni or Co. 5. The valve lifter for an internal combustion engine according to claim 4, wherein the binder phase contains 16% by weight or less of Cr. 6. A method of manufacturing a valve lifter for an internal combustion engine which performs a valve opening / closing operation by contacting with a cam, wherein B: 1 to 4
% By weight, Si: 2 to 5% by weight, Fe: 3% by weight or less, and the balance is 20 to 20% by weight of a binder phase powder composed of Ni or Co.
After mixing WC: 80 to 40% by weight to 60% by weight and molding the same, the molded body is vacuum-sintered to 1100%.
Sintering in a temperature range of １1300 ° C., processing the sintered body to a constant thickness, placing the processed sintered body on the friction portion of the valve lifter,
A method for manufacturing a valve lifter for an internal combustion engine, comprising: performing heat bonding in a temperature range of 200 ° C. 7. The method for manufacturing a valve lifter for an internal combustion engine according to claim 6, wherein the powder of the binder phase is additionally mixed with 16 wt% or less of Cr. 8. Each of the WC powders has a content of 1 to 3% by weight.
8. The method for manufacturing a valve lifter for an internal combustion engine according to claim 6, wherein Cr ₃ C ₂ or Mo ₂ C is contained alone or in combination.