JPH06330713A - Valve seat of internal combustion engine - Google Patents

Abstract

PURPOSE:To improve initial matching property between a valve seat and a valve so as to reduce initial abrasion amount of a seat surface, so as to improve durability of the valve seat by forming a chrome film on the seat surface while manufacturing the valve seat with alloy, in the valve seats facing the intake/ exhaust valves of an internal combustion engine. CONSTITUTION:In an internal combustion engine, an intake/exhaust passage 2 communicated with a combustion chamber 1 is opened and closed by a valve 3. A valve seat 4 is arranged in the position of a part which is closed by the valve 3 in the intake/exhaust passage 2. A seat surface 4a is arranged in the position where the valve seat 4 and the valve 3 are slide and fit with each other. In this case, a chrome film is formed on the seat surface 4a while manufacturing the valve seat 4 with alloy. The chrome film of the seat surface 4a is beaten by the valve 3 and deformed plastically so as to generate surface contact condition. The chrome film is exposed to a high temperature, the surface thereof becomes chromium oxide so as to generate self lubricating action. It is thus possible to improve durability of the valve seat since initial matching property between the valve seat 4 and the valve 3 is improved and the initial abrasion amount of the seat surface 4a is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve seat of an internal combustion engine such as an automobile engine.

[0002]

2. Description of the Related Art FIG. 1 schematically shows a structure of a main part of an internal combustion engine, and shows a structure in which an intake or exhaust passage 2 leading to a combustion chamber 1 is opened and closed by a valve 3. In this structure, a ring-shaped valve seat 4 is fitted in a portion of the combustion chamber 1 that closes the passage 2 corresponding to the valve 3 to prevent wear, and the valve seat 4 is slidably or closely attached to the valve seat 4. The portion 4a is generally called a seat surface.

The valve seat 4 for such an internal combustion engine
Is exposed to the combustion chamber 1, exposed to high temperatures, and opens and closes at high speed, so it is a part that requires particularly high heat resistance and wear resistance. Therefore, various improved sintered alloys are used. There is. An example of this sintered alloy is, for example, Japanese Patent Laid-Open No.
1-1110119, JP-A-56-152947, JP-A-62-10244, JP-A-64-6.
Examples include sintered alloys described in Japanese Patent No. 8447.

These alloys are composed of Cr (chromium) and Mo.
(Molybdenum), Ni (nickel), Co (cobalt)
A hard alloy such as Cr, Mo, W (tungsten), V (vanadium) or a sintered alloy in which an intermetallic compound is not dispersed in an iron alloy matrix in which the base is strengthened by containing Pb (lead) in the pores of the sintered alloy
Is a material impregnated with.

[0005]

The wear of the valve seat made of such a sintered alloy increases with the operating time according to the wear resistance of the alloy, but the form of the wear is that the initial wear is large. , And then tend to be gradual. It is considered that the initial wear is large because the seat surface of the valve seat and the valve surface are initially in line contact with each other due to processing accuracy and assembly accuracy, and local wear occurs. Therefore, along with the selection of the valve seat material having such wear resistance, how to reduce the initial wear was a future task.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a valve seat of an internal combustion engine which is less worn and has excellent durability.

[0007]

In order to achieve the above object, the present invention is directed to a valve seat of an internal combustion engine provided for an intake / exhaust valve, wherein the valve seat is made of an alloy, and the seat surface is A chrome coating is formed.

Here, the chromium film of the present invention can be formed by plating or the like. In this case, as a pretreatment for plating, it is desirable that the pores of the sintered alloy be impregnated with lead or resin to seal the pores. The film thickness is 5 to 20 μm.
Is desirable. This is because if the thickness is thin, the effect is small, and if it is too thick, the coating peels off and wears on the contrary, increasing the wear.

[0009]

According to the above construction, the chromium on the surface of the seat portion is hit by the mating valve and plastically deforms to easily form surface contact. In addition, when exposed to a high temperature of about 300 to 400 ° C. together with plastic deformation, the surface becomes chromium oxide, which causes a self-lubricating action.

[0010]

EXAMPLES The present invention will be described below with reference to examples. The valve seat of the present invention is arbitrary in shape, and the typical example is the first
It has a ring shape similar to that in the figure. The molding conditions are such that the composition is 6.5% Co-1.5% Ni-1.5% Mo.
A mixed powder obtained by adding 1% of graphite powder and 0.5% of a molding lubricant to the iron powder of No. 3 was compacted into a ring shape and sintered in a reducing gas at a temperature of 1240 ° C.

Next, a sintered body was prepared by impregnating Pb into the pores and sealing it, and by impregnating it with a thermosetting resin and sealing it. A sample was prepared by chrome plating. Plating film thickness is 10-1
2 μm. Further, as a comparative sample, a sintered body impregnated with lead was prepared.

Each sample was mounted on a simple valve seat wear tester and operated for a total of 100 hours, respectively, after 50 hours and 100 hours.
The amount of wear of the seat surface of the valve seat after the lapse of time was measured.

The simple valve seat wear tester can be equipped with a jig made of aluminum alloy in which the valve seat is press-fitted, and a valve made of heat-resistant steel having a composition of 21% Cr-4% Ni on the seat surface of the valve seat. To open and close at 6000 times per minute, and propane combustion gas is injected near the valve seat to increase the temperature of the valve seat to 300 to 40.
It has a structure that can be maintained at 0 ° C.

Using this tester, the temperature of each sample shown in Table 1 was set to 300 ° C., and the amount of wear was measured after 50 hours of continuous operation and after 100 hours of continuous operation. Similarly, the results shown in Table 1 were obtained.

[0015]

[Table 1]

In the invention product, the effect of the chromium coating is recognized in the wear amount up to 50 hours as compared with the conventional product. This is because the chromium film plated on the surface at the initial stage is hit by the valve and plastically deforms to easily form a surface contact with the valve, and is exposed to a high temperature of 300 to 400 ° C together with the plastic deformation. It is thought that the surface becomes chromium oxide and exhibits a self-lubricating effect. The amount of wear during the subsequent 50 to 100 hours was almost the same for all samples, and almost no wear was observed on the valve side.

The same effect was observed when the thickness of the chrome coating was in the range of 5 to 20 μm. If the thickness is thinner than this, the effect is small. On the contrary, if the thickness is too large, the coating peels off and the wear increases. It has been found.

[0018]

As described above, in the valve seat of the internal combustion engine according to the present invention, by providing the chrome coating on the seat surface of the valve seat, the initial conformability with the valve is good and the seat surface portion Since the initial wear amount of is reduced, the total wear amount after long-time use can be reduced.

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing a main structure of an internal combustion engine.

[Explanation of symbols]

 3 valve 4 valve seat 4a seat surface.

Claims (1)

[Claims] 1. A valve seat of an internal combustion engine provided corresponding to intake and exhaust valves, wherein the valve seat is made of an alloy and a chrome coating is formed on a seat surface of the internal combustion engine. Valve seat.