JP6291175B2 - Valve seat and manufacturing method thereof - Google Patents

Description

  The present invention relates to a valve seat for an engine and a method for manufacturing the same, and more particularly to a press-fit high heat transfer valve seat capable of suppressing an increase in valve temperature and a method for manufacturing the same.

  In recent years, so-called downsizing has been promoted to reduce engine displacement by 20 to 50% as a means to achieve both high fuel efficiency and high performance through environmental compatibility of automobile engines, and as a technology to achieve a high compression ratio Combining turbocharging (supercharging) with a direct injection engine is performed. Higher efficiency of these engines inevitably leads to an increase in engine temperature, but the increase in temperature leads to knocking that leads to a decrease in output, so it is necessary to improve the cooling capacity of parts around the valve in particular. .

  As a means for improving the cooling performance, regarding an engine valve, Patent Document 1 discloses a method for manufacturing an engine valve in which a shaft portion of a valve is hollowed and metal sodium (Na) is sealed in the hollow portion. With respect to the valve seat, Patent Document 2 uses a high-density heating energy such as laser light to directly deposit on an aluminum (Al) alloy cylinder head (hereinafter referred to as “laser cladding method”). As a valve seat alloy, Fe-Ni-based nitrides and nitride particles are dispersed in a copper (Cu) matrix, and 1 of Sn and Zn is contained in a Cu-based primary crystal. It teaches a dispersion-strengthened Cu-based alloy for overlaying that dissolves one or both.

  The above metal Na-enclosed engine valve reduces the valve temperature when the engine is driven by about 150 ° C (valve temperature is about 600 ° C) compared to the solid valve, and the Cu-based alloy valve seat by the laser cladding method is The valve temperature of the solid valve has been reduced by about 50 ° C (the valve temperature is about 700 ° C), making it possible to prevent knocking. However, the metal Na-enclosed engine valve is difficult in terms of manufacturing cost and has not yet been widely used except for some vehicles. Cu-based alloy valve seats also have the problem of insufficient wear resistance because the Cu-based alloy is struck and preferentially adheres due to wear. There will also be a problem that a substantial review of the line and capital investment will be required.

  Patent Document 3 aims to provide a highly durable valve seat that can improve the engine performance by efficiently transferring the heat of the valve and combustion gas to the cooling system as a press-fit valve seat. A valve seat is disclosed in which a thin wear-resistant ring made of a highly wear-resistant material is joined to a face portion of a base ring made of a material having high conductivity and rigidity. Specifically, Cu alloy and Al alloy are taught as the material of the base ring, and Fe-based sintered alloy and Fe-based cast alloy are taught as the material of the wear-resistant ring, but the wear-resistant ring is joined to the base ring. No method is taught.

Japanese Patent Laid-Open No. 7-119421 Japanese Patent Laid-Open No. 3-60895 JP 7-279627 A

  In view of the above problems, the present invention provides a press-fit valve seat having high valve cooling ability and wear resistance used in a high-efficiency engine, and more specifically, a valve comparable to a Cu-based alloy valve seat by a laser cladding method. It is an object of the present invention to provide a press-fit valve seat having cooling ability. Furthermore, it aims at providing the manufacturing method of the said press-fit type valve seat.

  As a result of diligent research on the press-fitted valve seat that is press-fitted into an Al alloy cylinder head, the present inventors directly placed a hard alloy sheet layer with high wear resistance on the face portion of the base ring with high thermal conductivity. By selecting a Cu or Cu base alloy for the base ring and a Co base alloy for the seat layer, a complicated intermediate layer can be avoided at the interface between the base ring and the seat layer. It was conceived that a press-fit valve seat with high cooling ability could be obtained.

That is, the valve seat of the present invention is a valve seat that is press-fitted into an Al alloy cylinder head, and the face of a base ring made of Cu or a Cu-based alloy having a thermal conductivity of 100 W / (m · K) or more. A sheet layer made of a Co-based alloy is directly piled on the part, the ratio (h / a) of the valve seat height h to the thickness a is 1.5 to 4, and the thickness t of the sheet layer is 0.05 to 0.2 mm der is, the Co-based alloy, in mass%, Cr: 20.0~35.0%, W : 2.0~15.0%, C: 0.8~2.0%, the balance, wherein Rukoto a Co and unavoidable impurities And The Cu based alloy in wt%, Cr: 0.5 to 1.5%, the balance is not preferable be composed of Cu and unavoidable impurities.

Further, the valve seat manufacturing method of the present invention is a method for manufacturing a valve seat press-fitted into an Al alloy cylinder head, and has a thermal conductivity of 100 W / (m · K) or more from Cu or a Cu-based alloy. characterized in that the sheet layer to the face portion of the composed base ring made of the Co-based alloy for build-up directly by high-speed flame spraying method or a laser metal deposition.

The valve seat of the present invention has a base material by directly overlaying a sheet layer made of a Co-based alloy on the face portion of a base ring made of a Cu-based alloy having a thermal conductivity of 100 W / (m · k) or more. Avoid the formation of a complicated intermediate layer at the interface between the ring and the seat layer, that is, form a seat layer / substrate ring interface with high heat transfer characteristics, and further, the ratio of the height h of the valve seat to the thickness a ( By adjusting the thickness t of the sheet layer composed of h / a) and a hard alloy, a press-fit valve seat with high valve cooling capability can be obtained. Moreover, it can be set as the face part excellent in heat resistance and abrasion resistance by limiting the alloy composition of a sheet | seat layer. These make it possible to obtain a press-fitted valve seat with a valve cooling capacity comparable to that of a Cu-based alloy valve seat by the laser cladding method, without particularly adopting an expensive metal Na-encapsulated valve and reviewing the cylinder head processing line. By reducing abnormal combustion of the engine such as knocking, it is possible to contribute to improving the performance of a high compression ratio and high efficiency engine.

It is sectional drawing of the part which showed the state which the valve seat of this invention press-fitted in the cylinder head and the face surfaces of an engine valve contact. It is the figure which showed typically the temperature distribution from a valve center to a water cooling cylinder head, comparing the valve seat of this invention, and the conventional valve seat. It is sectional drawing to which a part of FIG. 1 was expanded. It is sectional drawing which showed typically the structure of the gun of a high-speed flame spraying. It is sectional drawing which showed typically the nozzle front-end | tip part in the laser metal deposition method. It is the figure which showed the outline | summary of the rig testing machine.

As shown in FIG. 1, the valve seat of the present invention is press-fitted into a water-cooled Al alloy cylinder head 4 and made of Cu or a Cu-based alloy having a thermal conductivity of 100 W / (m · k) or more. and interest directly overlaying the sheet layer 2 made of Co-based alloy on the face of the ring 1. The heat of the valve 3 is transferred to the seat layer 2 of the valve seat, and passes through the seat layer 2, the interface between the seat layer 2 and the base ring 1, the base ring 1, and the base ring 1 and the cylinder head 4 interface. Conducted and transmitted into the water-cooled cylinder head 4. The base material 1 is basically composed of a Cu-based alloy having a high thermal conductivity, and the sheet layer 2 is also preferable as the thermal conductivity is higher. However, since the sheet layer 2 is required to have more heat resistance and wear resistance, Co Consists of a base alloy. In metals, the thermal conductivity is mainly governed by the movement of free electrons in the crystal grains, so the smaller the solid solution element, the higher the thermal conductivity. In that respect, Cu and Co are a preferable combination because even if they are partly dissolved at a high temperature, they hardly dissolve at 400 ° C. or less. When depositing a Co-based alloy on a base ring 1 made of a Cu-based alloy, even if a molten region of the base material is formed, a mixed structure of Cu and Co is formed without forming a complicated intermediate layer. Thus, the thermal conductivity of Cu or Cu-based alloy is not significantly reduced. The thermal conductivity of the base material ring 1 made of a Cu-based alloy is 100 W / (m · k) or more. Of course, it is preferably 150 W / (m · K) or more, more preferably 200 W / (m · K).

The Cu-based alloy of the base material ring 1 is preferably a Cu—Cr alloy having high thermal conductivity and excellent high-temperature hardness. In this case, Cr is preferably 0.5 to 1.5% by mass. Cr also dissolves slightly in Cu at high temperatures, but if cooled, it becomes a mixed structure of Cu and Cr and does not adversely affect the thermal conductivity of Cu. Furthermore, Co-based alloy sheet layers 2, in terms of wear resistance, and Co-Cr-WC alloy, in mass%, Cr: 20.0~35.0%, W : 2.0~15.0%, C: 0.8~2.0 %, and the balance shall such Co and inevitable impurities. These alloys exhibit excellent wear resistance with a hard carbide phase dispersed in a Co matrix in which Cr is dissolved.

  FIG. 2 schematically shows the temperature distribution from the center of the valve to the water-cooled end of the Al alloy cylinder head. The valve seat of the present invention is compared with the valve seat of a conventional iron-based sintered alloy, but here the cooling capacity is the same up to the interface between the valve seat on the cylinder head side and the cylinder head. I consider it. Looking at the temperature gradient of the valve seat, the conventional valve seat has a thermal conductivity of about 20 W / (m ・ K) and the cooling capability is low, so the temperature gradient is large. In the valve seat of the present invention, the thermal conductivity is 100 The temperature gradient is small because of the high cooling capacity above W / (m · K). The difference in valve face temperature due to this difference is the difference in valve center temperature. Since the valve seat of the present invention is composed of the seat layer 2 and the base material ring 1, the temperature gradient is also in two stages.

Naturally, it is desirable that the heat conductivity of the seat layer 2 of the valve seat and the base material ring 1 is high, but for improving the cooling capacity of the valve, as shown in FIG. It is desirable that heat transfer at the interface I _{1 of} the material ring 1 and the interface I ₂ between the base material ring 1 and the cylinder head 4 is efficient (the gap between I ₁ and I ₂ in FIG. 2 is small). The heat transfer at interface I ₁ and interface I ₂ is
Q1 = h ₁ S ₁ ΔT ₁ ……………………………………… (1)
Q2 = h ₂ S ₂ ΔT ₂ ……………………………………… (2)
It can be expressed as _{Here, Q 1 (W), h} 1 (W / (m 2 · K)), S 1 (m 2), ΔT 1 (K) , respectively, the amount of heat that moves the interface I _1, the heat transfer coefficient, Indicates heat transfer area and temperature difference, Q ₂ (W), h ₂ (W / (m ² · K)), S ₂ (m ² ), ΔT ₂ (K) move on interface I ₂ respectively Shows heat quantity, heat transfer coefficient, heat transfer area, and temperature difference. Heat transfer amount Q ₁ at the interface I ₁ of the sheet layer 2 and the substrate ring 1 is larger large extent of the heat transfer coefficient h _1. In this respect, since the heat transfer coefficient h ₁ is significantly reduced when an intermediate layer or a diffusion layer is present, the sheet layer 2 is directly deposited on the base ring 1 and the base ring 1 and the sheet layer 2 are dissolved in each other. In order to prevent the thermal conductivity from being lowered, each of them is composed of a Cu-base alloy and a Co-base alloy. From the viewpoint of the temperature difference ΔT ₁ , it is considered that ΔT ₁ increases as the thermal conductivity of the substrate 1 increases, leading to an increase in the heat transfer amount Q ₁ .

On the other hand, the heat transfer amount Q _{2 at} the interface I ₂ between the base ring 1 and the cylinder head 4 is constant if the heat transfer coefficient h ₂ is constant (in the case of a press-fitted valve seat, as can be seen from equation (2)). The coefficient is influenced by the surface state and stress state of the press-fit surface, but is assumed to be constant here), and is proportional to the heat transfer area S ₂ and the temperature difference ΔT ₂ . Although it is preferable that the heat transfer area S ₂ and the temperature difference ΔT _{2 of the} interface I ₂ are larger, when the volume of the base ring 1 is decreased, the heat transfer area is decreased and the temperature difference ΔT 2 is increased. Since the thickness a of the base material ring 1 cannot be reduced so much in consideration of the face surface, the influence on the heat transfer amount Q ₂ is such that the temperature difference ΔT ₂ increases as the height h of the base material ring 1 decreases, and the heat transfer area S ₂ reduction increased heat transfer amount Q ₂ due to the increase of the temperature difference [Delta] T ₂ increases more than it decreases the heat transfer amount Q ₂ by the. In the valve seat of the present invention, the ratio (h / a) of the height h of the base material ring 1 to the thickness a is 1.25 to 4 . The ratio (h / a) is preferably 1.5 to 4, and more preferably 1.5 to 2.

Further, the sheet layer 2 is required to have heat resistance and wear resistance. However, in consideration of heat conduction, the thickness t of the sheet layer 2 is preferably thin as long as the wear resistance can be maintained. The thickness t of the sheet layer 2 is assumed to be 0.05 to 0.2 mm. The thickness is preferably 0.05 to 0.17 mm, and more preferably 0.05 to 0.14 mm.

  In the valve seat manufacturing method of the present invention, a sheet layer made of a Co-based alloy is applied to a face portion of a base ring made of Cu or a Cu-based alloy having a thermal conductivity of 100 W / (m · K) or higher by high-speed flame spraying. We directly deposit by the method or laser metal deposition method. The base material ring may be preheated when overlaying, and the preheating temperature is preferably 150 to 300 ° C, more preferably 180 to 250 ° C.

  High-speed flame spraying (High-Speed Oxygen Flame (HVOF) spraying) uses a spray gun with a structure as shown in FIG. 4 and applies compressed air flowing between the powder injector 5 and the insert 6 and between the shell 7 and the air cap 8. A high-speed flame is formed by burning a mixed gas of high-pressure propylene gas and oxygen gas flowing between the insert 6 and the shell 7 in a sandwiched manner. The raw material powder blended so as to form a sheet layer having a desired composition is put together with nitrogen gas from the powder injector 5 and sprayed from the tip to form a sprayed sheet layer. Since high-speed flame spraying has a lower flame temperature than plasma spraying, it can be sprayed while maintaining the raw material size substantially, and a thin and fine structure with a thin sheet layer can be formed.

  Further, as shown in FIG. 5, the laser metal deposition is a method in which a raw material powder 10 is supplied from around the laser beam 9 to melt and overlay the sheet layer 2 having a desired composition. Argon gas is allowed to flow as a shielding gas outside the raw material powder flow path. In the laser metal deposition method, since the laser beam can be narrowed down, the thickness can be reduced to about 0.2 to 0.5 mm. Further, since the heat input is small, the influence on the base ring 1 can be suppressed.

Reference example 1
A base ring having an outer diameter of 25 mmφ, an inner diameter of 21 mmφ, and a height of 6 mm having a face surface inclined by 45 ° from the axial direction was prepared from a Cu-based alloy containing 1.2% by mass of Cr. A powder having a composition of 8.5%, Mo: 28.5%, Si: 2.5%, C: 0.05%, the balance being Co-based alloy (hereinafter referred to as “Co-based alloy A”), and having an average particle size of 63 μm, The sheet was deposited directly on the face of the base ring by the laser metal deposition method with a laser output of 1.5 kW to form a sheet layer with a thickness of approximately 0.3 mm. Further, the sheet layer thickness of the face surface was processed to 0.2 mm to obtain a valve seat sample.

[1] Measurement of valve cooling capacity (valve temperature) The valve temperature was measured using the rig testing machine shown in FIG. 6 to evaluate the valve cooling capacity. The valve seat sample is pressed into a valve seat holder 24 of cylinder head equivalent material (Al alloy, AC4A material) and set in a testing machine. This is done by moving the valve 23 up and down in conjunction with the rotation of the cam 22. The valve cooling capacity was measured by making the heat input constant by making the air and gas flow rates and the burner position of the burner 21 constant, and measuring the temperature of the central part of the valve by thermography. The air and gas flow rates (L / min) of the burner 21 were 90 and 5.0, respectively, and the cam rotation speed was 2500 rpm. 15 minutes after the start of operation, the saturated valve temperature was measured.

Comparative Example 1
A valve seat sample having the same shape as in Reference Example 1 was prepared using an Fe-based sintered alloy containing 10% by volume of hard particles made of an Fe—Mo—Si alloy. The thermal conductivity of this Fe-based sintered alloy was about 20 W / (m · K). As in Reference Example 1, the bulb temperature was measured by the rig test, and as a result, the temperature was higher than 800 ° C.

The previously measured valve temperature of Reference Example 1 was 53 ° C. lower than the valve temperature of Comparative Example 1, and showed a valve cooling capacity of −50 ° C. or higher. Since the absolute temperature of the valve temperature varies depending on the heating conditions, etc., in this embodiment, instead of evaluating with the absolute temperature, the valve cooling capacity is controlled by the amount of temperature decrease from the valve temperature of Comparative Example 1 (the decrease is indicated by-). evaluated.

Examples 1 to 3 and Reference Examples 2 to 4
The material and thickness of the sheet layer, and the dimensions of the base ring (height, h / a, but the outer diameter remains at 25 mmφ, and the thickness a is changed by changing the inner diameter) A valve seat sample was prepared in the same manner as in Reference Example 1 except for the changes shown in Table 1, and the valve temperature was measured by a rig test in the same manner as in Reference Example 1. The results are shown in Table 1 including the results of Reference Example 1. It was found that when the height h of the valve seat is reduced, that is, when the ratio (h / a) of the height h of the valve seat to the thickness a is reduced, the valve cooling performance is improved. Further, there was almost no difference in the valve cooling ability depending on the materials A to D of the seat layer.

ここで、「レーザー」はレーザーメタルデポジション法、「材質Ａ」はCr：8.5％、Mo：28.5％、Si：2.5％、C：0.05％、残部がCo、「材質Ｂ」はCr：28％、W：4％、C：1.1％、残部がCo、「材質Ｃ」はCr：30％、W：8％、C：1.6％、残部がCo、「材質Ｄ」はCr：18％、Mo：28％、Si：3.4％、C：0.03％、残部がCoを示す。また、各材質の粉末の平均粒径は60〜70μmの範囲内にあった。

Here, “Laser” is a laser metal deposition method, “Material A” is Cr: 8.5%, Mo: 28.5%, Si: 2.5%, C: 0.05%, the balance is Co, “Material B” is Cr: 28 %, W: 4%, C: 1.1%, balance is Co, “Material C” is Cr: 30%, W: 8%, C: 1.6%, balance is Co, “Material D” is Cr: 18%, Mo: 28%, Si: 3.4%, C: 0.03%, the balance shows Co. Moreover, the average particle diameter of the powder of each material was in the range of 60 to 70 μm.

Example 4 and Reference Examples 5-11
The material of the base ring was changed to 99.9% Cu, and a valve seat sample was prepared in the same manner as in Reference Example 1 with the material and thickness of the seat layer and base ring dimensions shown in Table 2, and Reference Example 1 The valve temperature was measured by the rig test in the same manner as described above. The results are shown in Table 2. By changing the material of the base ring to 99.9% Cu, the thermal conductivity of the base ring was increased to 400 W / (m · K), the thickness of the seat layer, and the dimension (h / a) of the valve seat It was confirmed that the valve cooling capacity was affected.

Example 5
A base ring with an outer diameter of 25 mmφ, an inner diameter of 21 mmφ, and a height of 8 mm having a face surface inclined by 45 ° from the axial direction was prepared from a Cu-based alloy containing 1.2% by mass of Cr, similar to Reference Example 1. The surface roughness (Rzjis) of the face surface was adjusted to about 20 μm by shot blasting. Next, a powder having a composition of a Co-based alloy (material C) composed of Cr: 30%, W: 8%, C: 1.6%, the balance being Co, and having an average particle size of 68 μm, is obtained at a frame rate. A sheet layer having a thickness of about 0.5 mm was formed by directly depositing on the face surface of the base material ring by high-speed flame spraying at 1400 m / sec. Furthermore, the sheet layer thickness of the face surface was processed to 0.1 mm to obtain a valve seat sample. As a result of measuring the valve temperature by the rig test in the same manner as in Reference Example 1, it showed a valve cooling ability of −60 ° C. relative to Comparative Example 1.

Reference Examples 12-14
The material and thickness of the sheet layer, and the material and dimensions (height, h / a) of the base ring were changed as shown in Table 3 (the materials A and B of the sheet layer are the same as those in Reference Example 1 and Example 1 . A valve seat sample was prepared in the same manner as in Example 5 except that the material was the same as the material.) In the same manner as in Reference Example 1, the valve temperature was measured by a rig test. The results are shown in Table 3 including the results of Example 5 .

[2] Engine test
For the valve seat materials of Reference Example 1, Examples 3 and 5, and Comparative Example 1, a 1.2L inline 3-cylinder, direct-injection gasoline engine with a supercharger was subjected to an engine test for 5 hours at 4000 rpm and full load. It was. The valve seat material was pressed into the exhaust port of the Al cylinder head, the face surface was machined, and the thickness of the seat layer was about 0.1 mm. In addition, an iron-based sintered alloy valve seat was used for the intake port portion. During the 5-hour test, when the valve seat of Comparative Example 1 was used, the output decreased due to the knocking phenomenon many times, whereas in the valve seats of Reference Example 1 and Examples 3 and 5 , the output due to knocking, etc. There was no decline.

1 Base material ring
2 sheet layers
3 Valve
4 Cylinder head
5 Powder injector
6 Insert
7 shell
8 Air cap
9 Laser beam
10 Raw material powder flow
11 Shielding gas
21 Burner
22 cam
23 Valve
24 Valve seat holder
25 Thermocouple
26 Thermography

Claims (3)

A valve seat press-fitted into an Al alloy cylinder head, and a sheet layer made of a Co-based alloy on the face portion of a base ring made of Cu or a Cu-based alloy having a thermal conductivity of 100 W / (m · K) or more There is direct padding, the ratio to the thickness a of the height h of the valve seat (h / a) is 1.5 to 4, Ri thickness t 0.05 to 0.2 mm der of the sheet layer, the Co-based alloy, in mass%, Cr: 20.0~35.0%, W : 2.0~15.0%, C: 0.8~2.0%, the valve seat and the balance of Rukoto a Co and inevitable impurities.   2. The valve seat according to claim 1, wherein the Cu-based alloy is, by mass%, Cr: 0.5 to 1.5%, and the balance is made of Cu and inevitable impurities. The valve seat manufacturing method according to claim 1, wherein the Co base alloy is formed on a face portion of a base ring made of Cu or a Cu base alloy having a thermal conductivity of 100 W / (m · K) or more. A method for producing a valve seat, wherein the layer is directly deposited by a high-speed flame spraying method or a laser metal deposition method.

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