JPH06167206A - Valve and valve seat assembly - Google Patents

Abstract

PURPOSE:To provide a combination, which is suitably available for a high performance engine, of a titanium alloy valve and a valve seat. CONSTITUTION:A titanium alloy hardened layer, which is made by solution treatment of oxygen, nitrogen, or oxygen and nitrogen and has Vickers hardness of 600 or more and thickness of 3mum-25mum, is formed on a face part 2 of a titanium alloy valve. The valve face part, the valve, and a valve seat consisting of iron alloy, which consists of carbon of 0.4-1.5%, at least one element, which is selected from a group consisting of copper, cobalt, and nickel, of 0.5-10.0%, and iron of the rest substantially and has Vickers hardness Hv adjusted in the 170-350 range, are combined for using the valve 1 and the valve seat.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve and a valve seat, and more particularly to a combination of a valve and a valve seat made of a titanium (Ti) alloy which is particularly suitable for a high performance engine.

[0002]

2. Description of the Related Art Among the components of an engine, a valve is made of titanium (Ti) alloy instead of a conventional steel valve, especially in a high-performance engine, because weight reduction directly leads to improvement of engine performance. Valves are being used. And as the above titanium alloy,
Ti-6Al-4V is commonly used.

In a conventional high-performance engine having such a valve made of a titanium alloy, Japanese Patent Laid-Open No. 62-2569 is disclosed.
As can be seen from the description of Japanese Patent Publication No. 56, the valve seat has C
Materials made of u-Be-based materials are used.

In an engine constructed by combining a valve made of Ti-6Al-4V and a valve seat made of a Cu-Be-based material as described above, a titanium alloy (Ti-6Al) is used as a valve material. -4V)
As compared with the conventional steel valve, the weight of the valve is about 60% and the weight is reduced. As a result, the output is improved by the high rotation and the fuel consumption is improved by the low friction. Will be planned.

[0005]

However, the valve using Ti-6Al-4V described above does not eliminate the seizure characteristic of titanium (Ti) element, and the above-mentioned Cu-Be. A valve seat made of a system-based material has a drawback that Be oxide is more toxic than an iron (Fe) -based valve seat, so that there is a limitation in manufacturing and processing and a high cost is caused. Therefore, the conventional titanium alloy (Ti-6Al-4V) valve and Cu-B
An engine constructed by combining a valve seat made of an e-based material has a problem of poor mass productivity. Therefore, such a combination of a valve and a valve seat has not yet been applied to a commercial vehicle.

[0006] On the other hand, as conventional knowledge on improvement of wear resistance of titanium alloy products, for example, Titanium Science a
nd Technorogy, Plenum, p185 (1973) .K.Rudinger and AI
It has been reported that the wear resistance is generally improved by forming a solid solution layer of oxygen and nitrogen in a high temperature special salt bath at 800 ° C.

Further, in Japanese Patent Laid-Open No. 62-256956, a valve sheet made of titanium alloy is inexpensive by heat treating a valve made of titanium alloy in a furnace at a temperature of 800 ° C. or lower for several minutes to several hours to form an oxide scale. Although it is said that even iron-based materials will suffice, when using a valve seat that is used together with a normal iron-based valve, compared to the wear amount of the iron-based valve, an oxide scale is produced at a temperature of 800 ° C or less. In the case of the titanium alloy valve having the above-mentioned structure, the result was not sufficient.

The present invention has been made in view of the above circumstances, and an object of the present invention is a valve that can achieve high rotation and low friction due to weight reduction, and is resistant to seizure, and this valve. By providing a valve seat that is resistant to plastic deformation and wear even when used in combination with the above-mentioned valve and can be suitably used in combination with the above valve, it is possible to realize a high-performance engine excellent in long-term durability. To provide a valve seat and valve assembly.

[0009]

In order to achieve the above object, the present invention provides (1) a Vickers hardness Hv ≧ 600 and a thickness of 3 μm or more in which oxygen or nitrogen or oxygen and nitrogen are solid-dissolved, A valve having a valve face portion having a titanium alloy hardened layer of 25 μm or less, and C: 0.4 to 1.5% by weight and at least one element selected from the group consisting of Cu, Co and Ni. A valve and valve seat assembly comprising 5 to 10.0%, the balance being substantially Fe, and a valve seat adjusted to Vickers hardness Hv: 170 to 350. (2) The above (1) ) The valve has a thickness of 1 μm to 25 μm in which oxygen and / or nitrogen is dissolved, and the valve seat further has Pb: 5.0 to 20.0.
%, And (3) the material of the valve face portion in (1) or (2) above is a near α-type titanium alloy.

The valve and valve seat of the present invention will be described in detail below. The present invention, as shown in FIG. 1, has a face portion 2 of a titanium alloy valve 1 having a Vickers hardness (hereinafter referred to as Hv) of 600 or more, oxygen or nitrogen, or a solid solution of oxygen and nitrogen having a thickness of 5 μm or more. 20μ
A valve having a cured layer of m or less is used.

Here, the titanium alloy means that it has a 0.2% proof stress of 50 kg / mm ² or more, and Ti-6Al-4V, T.
An α + β type titanium alloy represented by i-3Al-2.5V and a near α type titanium alloy represented by Ti-8Al-1Mo-1V. The hardened layer is provided on the face portion of the valve. When the hardened layer is not provided, even if the valve sheet of the present invention is used as the mating valve sheet, wear of the face portion of the titanium alloy valve is large, Turned out to be inadequate. However, the wear of the face part of the near α-type titanium alloy is larger than that of the α + β-type titanium alloy,
It was found to be as small as 1/2 to 1/3. It is desirable to use a near α-type titanium alloy as the base under the assumption that the hardened layer is torn at an abnormal time.

In the present invention, the hardness of the face portion of the titanium alloy valve is defined as Hv ≧ 600 even if the solid solution of oxygen, the solid solution of nitrogen, or the solid solution of oxygen and nitrogen is Hv. Based on the findings obtained by the inventor, those having a hardness of less than about 500 have a poor wear preventing effect, and those having a hardness of Hv ≧ 600 exhibit a remarkable wear preventing effect.

Next, the thickness of the titanium alloy hardened layer in which oxygen or nitrogen or oxygen and nitrogen is solid-dissolved is 3 μm or more, 2
The thickness is defined as 5 μm or less because the thickness less than 3 μm is insufficient as the wear preventing thickness of the face portion of the titanium alloy valve, while the thickness over 25 μm may cause the hardened layer to peel off. is there. Oxygen and nitrogen have a significantly higher hardening ability for titanium alloys than other elements, and can be easily solid-dissolved. Further, oxygen has a large diffusion coefficient in the titanium alloy as compared with nitrogen, and is suitable for carrying out the present invention.

Incidentally, referring to the oxide layer and the nitride layer which are inevitably formed during the normal oxidation and nitridation of the titanium alloy, the oxide layer is effective in preventing seizure, but disappears in the initial wear. Although it does occur, there is no problem even if it is left. The nitride layer is also effective in preventing seizure, but when the surface is rough (the roughness is large), the aggressiveness against the mating material is large and the amount of sheet wear increases. The nitride layer with a small surface roughness is, for example, smoothed titanium alloy surface,
It is obtained by forming a nitride layer to a thickness of 3 μm or less in a low temperature range of 850 ° C. or less.

Next, the valve seat of the present invention is formed of an iron alloy containing carbon (C) and, for example, copper (Cu), and the balance being substantially iron (Fe). Here, “substantially the balance” means that a trace component that is unavoidably mixed in the manufacturing process is not excluded.

The above-mentioned carbon component in this iron alloy has a function of maintaining sinterability and strength as a valve seat. The content ratio of the carbon component having such an action is 0.4% to 1.5% as a weight ratio (the content ratio of each component below is a weight ratio (%)), preferably 0.6.
% To 1.3%. If the content ratio is less than 0.4%, the sinterability and the strength as a valve seat may not be maintained. On the other hand, if it exceeds 1.5%, precipitation of cementite occurs and brittleness of the valve seat becomes remarkable.

In addition, the iron alloy forming the valve seat of the present invention contains a copper component, cobalt (C
O) and at least one element selected from the group consisting of nickel (Ni). One or more components selected from the group consisting of a copper component, a cobalt component and a nickel component have the effects of stabilizing the pearlite matrix and strengthening the matrix to improve wear resistance. The content ratio of at least one element selected from the group consisting of copper, cobalt and nickel components in the above iron alloy is 0.5% to 10%, preferably 2.0% to 5.0%. If the content ratio is less than 0.5%, the above-mentioned effects may not be sufficiently exhibited. On the other hand, if it exceeds 10%, it may not be practical in terms of sinterability and strength.

When the valve seat having the above-mentioned components is combined with the above-mentioned titanium alloy valve, sufficient wear resistance is ensured. In addition, solid lubricants are effective in order to prevent rapid wear even when even greater wear resistance is required or when the hardened layer on the valve face is broken during abnormal conditions. As a result of various studies, it was discovered that lead (Pb) is extremely effective for the valve of the present invention. As a result, they have found that the titanium alloy layer formed on the valve face portion of the valve of the present invention may have a thickness of 1 μm or more and 25 μm or less. Here, lead has the function of imparting self-lubricating properties to the iron alloy forming the valve seat and improving the wear resistance of both the valve and the valve seat. The content ratio of such lead is 5.0% to 20%, preferably 10.0% to 15.0%. If the content ratio is less than 5.0%, the above-described effect of imparting self-lubricating property to the valve seat to improve wear resistance may not be sufficiently exhibited. On the other hand, if it exceeds 20%, the skeleton density may be too low, resulting in insufficient strength.

The Hv of an iron alloy containing each of the above components and used as a material for forming a valve seat is 170 to 35.
It is prepared in the range of 0. The Hv is set within the above range in order to prevent wear and plastic deformation when used in combination with the valve described above. This valve seat can be preferably used in combination with the above-mentioned titanium alloy valve.

A valve seat used in combination with an ordinary iron-based valve is, for example, the above-mentioned Fe-C-Cu.
In the system, for example, hard particles of Fe-Mo system are dispersed in the matrix to improve the wear resistance of the sheet, but for the titanium alloy valve having the hardened layer of the present invention, It was found that there is no great difference in the change in the amount of wear on the valve side due to the presence or absence of hard particles. Furthermore, by containing lead, the amount of wear on the valve side can be reduced.

[0021]

【Example】

(Example 1) The face portion of a valve made of Ti-6Al-4V was heated in the atmosphere by propane gas heating at about 950 ° C. for 3 minutes to cure a solid solution of oxygen having a hardness of 600 Hv or more. The layer was formed to 5 μm. The oxide film formed on the surface is harmless, but was removed in order to accurately measure the amount of valve wear. On the other hand, for the valve seat, Fe alloy powder (C: 1.5%, Cu: 2.0%, balance Fe) is compression molded into the shape of the valve seat, and thereafter,
The obtained compression molded product was sintered and then cooled to prepare a valve seat base material. An AX gas furnace was used for the sintering treatment, and the sintering was performed at a temperature of 1160 ° C. for 45 minutes. The cooling rate was 16 ° C / minute. The valve sheet base material thus obtained was impregnated with Pb by the Pb impregnation method to obtain an Fe alloy (C: 1.5%, Cu:
A valve seat composed of 2.0%, Pb: 10%, and the balance Fe) was produced.

Next, Hv was measured for each of the intake valve and the valve seat obtained as described above, and a wear test was conducted to measure the wear amount of the intake valve and the wear amount of the valve seat. The results are shown in Example 1 of Table 1.

The Hv was measured as follows, and the abrasion test was carried out as follows. Measurement of Vickers hardness Hv: Hardness was measured by micro-Vickers for each of the valve face portion and the valve seat of the intake valve. Abrasion test: Using the valve seat abrasion tester shown in FIG. 2, abrasion of the intake valve and valve seat was measured under the following conditions. In addition, in the valve seat wear tester shown in FIG.
Reference numeral 0 is a heat source, and 20 is a valve seat. Test temperature: 220 ℃ (seat surface temperature) Cam rotation speed: 3,000r.pm Valve rotation: 10r.pm Valve lift: 7.5mm Spring load: 24kgf (when seated) Number of contacts: 8 × 10 5 times This test result is As shown in Table 1, the valve seat hardness is 300 Hv, the valve wear amount is 1 μm, and the seat wear amount is
It is 15 μm, and it is understood that the iron-based valve shown in Table 2 is superior to Comparative Examples 1 and 2 which are good combinations.

(Examples 2 to 28) As shown in Table 1, the titanium alloy component of the valve, the hardening method, the thickness of the hardened layer, the alloy component of the valve seat, and the hardness were variously changed to the above-mentioned Example 1
Tests were conducted in the same manner as in (1) to measure the amount of valve wear and the amount of seat wear, and the results are shown in Table 1. Regarding the nitriding valve of Example 4, the nitriding layer on the surface was left. Also,
As shown in Comparative Examples 3 to 6, without the hardening treatment, the valve wear was large. However, considering the case where the hardened layer is broken, as shown in Comparative Examples 4 to 6, Ti-6Al-4V is used.
Compared with, the near α-type titanium alloy shows less valve wear and is superior as a base material. Further, when a sheet containing lead is used, the amount of wear of the valve is reduced regardless of the presence or absence of the valve hardened layer. Here, the oxidation method is the method shown in Example 1, or the titanium alloy valve is heated and oxidized in an atmospheric furnace (for example, at 820 ° C. for 2 hours) or in a reduced pressure atmosphere (for example, 10 ⁻² to 10 ^{−). During 3} Torr,
Any method of 2 hours at 820 ° C. may be used. The nitriding method is performed by heating nitriding (for example, at 850 ° C. for 10 hours) in a pure nitrogen atmosphere. Here, Comparative Examples 1 and 2 are examples of current valves and seats.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

EFFECTS OF THE INVENTION According to the present invention, because of the above-mentioned structure, a valve that is lightweight, does not easily cause seizure, and is excellent in wear resistance; It is possible to provide a valve seat that has excellent properties and does not cause plastic deformation. These valve seats and valves realize a so-called high-performance engine of high rotation and high output type, and because they are also excellent in long-term durability, for example, not only high-performance engines for racing but also general commercial vehicles It can be suitably used for applications.

[Brief description of drawings]

FIG. 1 is a side view schematically showing an example of a valve of the present invention.

FIG. 2 is an explanatory diagram showing an outline of an abrasion tester used in Examples and Comparative Examples.

[Explanation of symbols]

 1 valve 2 valve face 10 heat source 20 valve seat

Claims (3)

[Claims] 1. The Vickers hardness (Hv) is Hv ≧ 600.
And a valve having a valve face portion having a hardness of 3 μm or more and 25 μm or less of a titanium alloy hardened layer in which oxygen or nitrogen or oxygen and nitrogen are solid-dissolved, and C: 0.4 to 1. 5%, Cu, C
and at least one element selected from the group consisting of Ni and 0.5 to 10.0%, the balance being substantially Fe and having a Vickers hardness (Hv) of Hv: 170.
A valve and valve seat assembly comprising a valve seat adjusted to ~ 350. 2. The Vickers hardness (Hv) is Hv ≧ 600.
And a valve having a valve face portion having a hardness of 1 μm or more and 25 μm or less of a titanium alloy hardened layer in which oxygen or nitrogen or oxygen and nitrogen are solid-dissolved, and C: 0.4 to 1. 5%, Pb: 5.0-2
0.0% and 0.5 to 10.0% of at least one element selected from the group consisting of Cu, Co, and Ni, and the balance being substantially Fe and having a Vickers hardness (Hv). Hv: A valve and valve seat assembly comprising a valve seat adjusted to 170 to 350. 3. The valve and valve seat assembly according to claim 1 or 2, wherein the material of the valve face portion is a near α type titanium alloy.