JPS608295B2 - How to combine valve stem and valve guide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of combining a valve stem and a valve guide.

Since the valve stem and valve guide are provided in direct or indirect contact with the combustion chamber, they are constantly exposed to high temperatures during engine operation, and moreover, they slide violently relative to each other.

Therefore, it is important that both have wear resistance and scuffing resistance at the same time. By the way, in the conventional combination of a valve stem and a valve guide, the outer surface of the valve stem is subjected to surface treatment such as hard chromium plating or nitriding to improve wear resistance. However, surface treatment of the outer circumferential surface of the valve stem requires a great deal of labor and time, and in the case of hard chrome plating, it has difficulty in retaining oil and is insufficient in scuffing resistance.

The present invention has been made in view of the above, and it is an object of the present invention to provide a method of combining a valve stem and a valve guide that simultaneously has excellent wear resistance and scuffing resistance. That is, in the present invention, the material is HV200-5.
The valve stem is selected from heat-resistant steel in the range of 0.00 and has no surface treatment on the outer surface, and the area ratio is 1 to 1.
20% graphite and 0.5-22% Fe, Cr, Mo, W
This is a combination method characterized by combining a valve guide made of an iron-based sintered alloy in which one or more types of carbides are simultaneously precipitated and distributed.

The combination method of the present invention will be explained below. First, the valve stem is made of heat-resistant steel with a hardness in the range of HV200-500 (
The valve stem is made of heat-resistant steel (as specified in JIS G4311), and the outer surface of the valve stem is not subjected to any surface treatment. In this case, if the hardness of the valve stem is less than HV200, scuffing is likely to occur on the outer surface of the valve stem, and the strength is weakened.
If it is 500 or more, wear on the inner circumferential surface of the valve guide tends to increase significantly.

Therefore, the material for the valve stem should have a hardness of HV200 to 5.
It is necessary to select and set from heat-resistant steel in the range of 00. Next, the other valve guide's area ratio is 1~
20% graphite and 0.5-22% Fe, Cr, Mo
, W is made of an iron-based sintered alloy in which one or more carbides of W are distributed.

If the graphite precipitation distribution is less than 1% in terms of area ratio, desired scuffing resistance and wear resistance cannot be obtained;
% or more, the strength tends to decrease.

Next, regarding the cough distribution of carbide, the area ratio is 0.5%.
If it is less than 22%, the wear resistance decreases, and if it exceeds 22%, the strength tends to decrease significantly and the workability tends to decrease.

The carbide of the valve guide used in the present invention is Fe,
One or more of Cr, Mo, W, etc. may be used.

In the method of combining the valve stem and valve guide of the present invention, the valve guide used in the present invention has extremely high scuffing resistance because it has precipitated graphite that has excellent self-lubricity and oil lubricity. Moreover, since high-hardness carbides are also precipitated and distributed at the same time, it is possible to exhibit excellent wear resistance at the same time.

In addition, since the valve guide used in the present invention is constructed in this way, when it is combined with a valve stem made of heat-resistant steel of a specific hardness, the valve stem and valve can be combined without any surface treatment on the outer surface. Both guides exhibit excellent wear resistance and scuffing resistance, and perform stable and good operation. Furthermore, in the combination method of the present invention, there is no need for any surface treatment on the outer surface of the valve stem, making it possible to significantly reduce manufacturing costs. Next, in order to prove the superiority of the combination method of the present invention, the following tests were conducted.

1 Wear Resistance Test Samples of the combinations shown in Table 1 were prepared as valve stem materials and valve guide materials.

Table 1 The samples thus formed were tested using a rotary abrasion tester, using a valve guide sample (15 mm x 2 mm x 7 mm) used in the present invention and conventional combination as a fixed piece, and rotating the fixed piece. A pressure bale is placed on the upper surface of a valve stem sample (disc-shaped) used in the present invention and the conventional combination as a piece, and the disc-shaped sample is rotated while constantly supplying lubricating oil to the compressed surface. The amount of wear after operation was measured.

Test conditions Lubricating oil temperature: 8000 Lubricating oil amount: 0.6 zo/hr Lubricating oil: Daphne oil #65 (50%) kerosene (5
0%) Load: 20k9/Ground wear rate: Chest/sec Travel distance: 300 The above test results are as shown in Figure 1.

2 Scuffing resistance test Using the same testing machine as used for the wear resistance test, run for one hour, and when no scuffing occurs, gradually increase the pressure welding load and find the limit load at which scuffing occurs.

Test condition Load: starting 20kg/ Running time: pitch 5k9/average Each pitch every 1 hour Conditions other than the above are the same as the wear resistance test.

The above test results are as follows.

As is clear from the above test results, it has been found that the relative combination of the present invention is excellent in both wear resistance and scuffing resistance.

[Brief explanation of drawings]

FIG. 1 shows a graph showing the results of the wear resistance test. illustration ship

Claims (1)

[Claims] 1. A valve stem whose material is selected from heat-resistant steel with a hardness in the range of HV 2.00 to HV 500 and whose outer surface is not subjected to any surface treatment, and which is made of 1 to 20% graphite and 0.5% graphite on an area basis.
A valve stem and a valve characterized in that they are combined with a valve guide made of an iron-based sintered alloy in which 5 to 22% of one or more carbides of Fe, Cr, Mo, and W are simultaneously precipitated and distributed. How to combine with guide.