Valve seat for engine and manufacturing method therefor

Abstract

An embodiment of the present invention provides a valve seat for an engine, which is in contact with a valve within a combustion chamber of the engine to perform a sealing function, wherein a stacked portion in which 40 to 100 wt% of a Co-based alloy and the remaining Fe-based alloy are mixed and stacked is provided on a contact surface of the valve seat that is in contact with the valve.

Description

Valve seat for engine and method of manufacturing the same

[0001] The present invention relates to an engine valve seat and a method for manufacturing the same, and more specifically, to an engine valve seat and a method for manufacturing the same in which high-temperature wear resistance can be improved by mixing and laminating 40 to 100 weight percent of a Co-based alloy and the remainder of an Fe-based alloy on the contact surface of the valve seat that contacts the valve.

[0002] An engine refers to a mechanism that converts thermal energy into mechanical work; generally, it refers to a reciprocating type of engine that moves a piston by igniting and exploding a mixture of fuel and air within a cylinder.

[0003] Generally, an engine comprises a cylinder block and a cylinder head coupled to one side of the cylinder block, and a combustion chamber is formed by the cylinder block and the cylinder head. Specifically, the cylinder head is coupled to one side of the cylinder block and seals one side of the combustion chamber formed inside the cylinder block. A piston is inserted into the other side of the combustion chamber and installed to enable linear reciprocating motion, and the other side of the combustion chamber is sealed by the piston. Thus, as a mixture of fuel and air flows into the combustion chamber and explodes, the piston moves linearly back and forth.

[0004] An exhaust port is formed in the cylinder head for exhausting combustion gases generated during the combustion of the gas mixture, and the exhaust port is opened and closed by an exhaust valve. Specifically, the exhaust valve includes a head portion located in the combustion chamber that moves up and down to open and close the exhaust port, and a spindle that extends from the head portion to the outside of the cylinder head.

[0005] At this time, the cylinder head is equipped with a valve seat made of a metal ring that acts as a sealing surface during the opening and closing of the valve between the engine's combustion chamber and the port. Conventionally, cast materials were used as valve seats, but recently, powder-sintered materials are used to improve wear resistance.

[0006] However, since the combustion chamber is subject to high temperature and pressure and the valve seat comes into contact with the valve under high load due to the explosion inside the chamber, excessive wear may occur where the valve seat wears down beyond an appropriate level. If excessive wear occurs, it affects the valve clearance or reduces sealing performance, posing a problem as it becomes a major cause of engine performance degradation.

[0007] Therefore, high-temperature wear resistance of the valve seat is required to enable longer use of the valve seat at high temperatures.

[0008] The present invention aims to provide an engine valve seat capable of improving high-temperature wear resistance by mixing and laminating 40 to 100 weight percent of a Co-based alloy and the remainder of an Fe-based alloy on the contact surface of the valve seat that contacts the valve, and a method for manufacturing the same.

[0009] The technical problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art to which the present invention belongs from the description below.

[0010] One embodiment of the present invention for solving the above problem provides an engine valve seat that contacts a valve in the combustion chamber of an engine and performs a sealing function, wherein the contact surface of the valve seat that contacts the valve is provided with a laminated portion in which 40 to 100 weight percent of a Co-based alloy and the remainder of an Fe-based alloy are mixed and laminated.

[0011] According to an example, the Co-based alloy may be composed of 20 to 30 weight% Mo, 8 to 20 weight% Cr, 0 to 20 weight% Ni, and the remainder Co.

[0012] According to an embodiment, the Fe-based alloy may be composed of 1 to 2 weight% C, 4 to 6 weight% Cr, 0 to 1 weight% Mo, 0 to 1 weight% V, and the remainder Fe.

[0013] According to an example, the hardness of the laminated portion may be in the range of 350 HV to 500 HV at room temperature and in the range of 100 HV to 300 HV at 600°C, depending on the weight percentage of the Co-based alloy.

[0014] According to an embodiment, when the Fe-based alloy is included in the laminated portion in an amount of 30 to 60 weight%, the hardness of the laminated portion can be increased to a range of 500 HV to 600 HV at room temperature when the laminated portion is heat-treated.

[0015] According to an embodiment, the thickness of the laminated portion may be 300 μm or more.

[0016] According to an embodiment, the width of the laminated portion may be within the range of 1 mm to 4 mm.

[0017] According to an embodiment, the laminated portion may be laminated by a Direct Energy Deposition (DED) method or a laser cladding method.

[0018] According to an embodiment, when the laminated portion is laminated by the DED method or the laser cladding method, the base material component may be mixed within 30% in the laminated portion.

[0019] An embodiment of the present invention for solving the above problem provides an engine comprising: a cylinder head that seals one side of a combustion chamber of an engine; a valve that opens or closes an intake port or an exhaust port of the cylinder head; and a valve seat according to any one of claims 1 to 7 that is provided in the cylinder head and contacts the valve, wherein the valve seat is configured separately from the cylinder head and coupled to the cylinder head or is configured integrally with the cylinder head.

[0020] One embodiment of the present invention for solving the above problem provides a method for manufacturing an engine valve seat that contacts a valve in the combustion chamber of an engine and performs a sealing function, comprising: a lamination step of mixing and laminating 40 to 100 weight percent of Co-based alloy powder and the remainder of Fe-based alloy powder on the contact surface of the valve seat that contacts the valve.

[0021] According to an embodiment, the lamination step may be performed by a Direct Energy Deposition (DED) method or a laser cladding method.

[0022] According to an embodiment, when a laminated portion is laminated by the DED method or the laser cladding method in the lamination step, the base material component may be mixed within 30% in the laminated portion.

[0023] According to an example, the Co-based alloy powder and the Fe-based alloy powder may be spherical powders having a size of 45 μm to 150 μm.

[0024] According to an embodiment, when the Fe-based alloy is included in an amount of 30 to 60 weight%, a heat treatment step for heat-treating the laminated portion laminated in the lamination step may be further included.

[0025] According to the present invention, a laminated portion is provided in which 40 to 100 weight percent of a Co-based alloy and the remainder of an Fe-based alloy are mixed and laminated to increase the surface hardness of the contact surface of a valve seat that contacts a valve, so that the amount of wear is reduced even when the valve seat is exposed to a high-temperature combustion chamber.

[0026] In particular, high hardness can be secured at high temperatures by including more than 40 wt% of a Co-based alloy containing Co, Mo, Cr, and Ni, while high hardness can also be secured at room temperature through an Fe-based alloy containing Fe, C, Cr, Mo, and V.

[0027] In addition, since the lamination is performed by the Direct Energy Deposition (DED) method or the laser cladding method, a separate molding process is not required, so the problem of moldability that may occur when the Co-based alloy is included in the conventional powder sintering method (40% or more) does not occur, and high-temperature wear resistance can be improved by including more than 40% of the Co-based alloy.

[0028] The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the configuration of the invention described in the detailed description of the invention or the claims.

[0029] FIG. 1 is a cross-sectional view illustrating a part of an engine according to one embodiment of the present invention.

[0030] Figure 2 is a cross-sectional view showing an enlarged view of the valve seat portion of Figure 1.

[0031] FIG. 3 is a cross-sectional view illustrating another embodiment of FIG. 2.

[0032] Figure 4 is a graph showing the hardness (HV) at different temperatures according to the mixing ratio of Co-based alloys and Fe-based alloys and the manufacturing method.

[0033] Figure 5 is a graph showing the amount of wear (μm) at different temperatures according to the mixing ratio of Co-based alloys and Fe-based alloys and the manufacturing method.

[0034] Hereinafter, preferred embodiments of the engine valve seat and the method for manufacturing the same according to the present invention will be described with reference to the attached drawings.

[0035] Furthermore, the terms described below are defined considering their functions in the present invention, and these may vary depending on the intention or practice of the user or operator; additionally, the following embodiments are not intended to limit the scope of the present invention but are merely exemplary details of the components presented in the claims of the present invention.

[0036] To clearly explain the present invention, parts unrelated to the description have been omitted, and the same reference numerals are used for identical or similar components throughout the specification. Throughout the specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may additionally include other components.

[0037] In addition, components referred to as '~parts' throughout the specification may consist of two or more components combined into a single component, or a single component may be divided into two or more components based on more detailed functions. Furthermore, each component described below may additionally perform some or all of the functions performed by other components in addition to its primary function, and it goes without saying that some of the primary functions performed by each component may be exclusively performed by other components.

[0038]

[0039] First, let us look at an engine according to one embodiment of the present invention with reference to FIGS. 1 and 2.

[0040] The engine includes a cylinder head (100) that seals one side of the combustion chamber (C) of the engine, a valve (200) that opens or closes the intake or exhaust port of the cylinder head (100), and a valve seat (300) provided in the cylinder head (100) and in contact with the valve (200).

[0041] The valve seat (300) is formed in a ring shape and is positioned toward the combustion chamber (C) to be exposed to high temperature and high pressure gas. In this embodiment, the valve seat (300) is configured separately from the cylinder head (100) and is coupled to the cylinder head (100).

[0042] The valve seat (300) must come into contact with the valve (200) when the valve (200) closes the intake port or exhaust port and perform a sealing function, and must have high high-temperature wear resistance to maintain the sealing function without wearing out even at high temperatures.

[0043] To this end, in the present invention, a laminated portion (320) is provided on the contact surface of a valve seat (300) that contacts a valve (200), wherein 40 to 100 weight percent of a Co-based alloy and the remainder of an Fe-based alloy are mixed and laminated. FIG. 2 illustrates a state in which the laminated portion (320) is provided on the contact surface of a valve seat (300).

[0044] In order to ensure high-temperature wear resistance, hard particles with excellent high-temperature wear resistance must be included. In the present invention, the Co-based alloy, which is a hard particle, is composed of 20 to 30 weight% Mo, 8 to 20 weight% Cr, 0 to 20 weight% Ni, and the remainder Co. By including 40 weight% or more of the Co-based alloy containing Co, Mo, Cr, and Ni in this manner, high hardness can be secured at high temperatures. That is, since the Co-based alloy improves surface hardness at high temperatures, it can contribute to reducing wear of the valve seat (300) under high-temperature conditions.

[0045] In addition, the Fe-based alloy consists of 1 to 2 weight% C, 4 to 6 weight% Cr, 0 to 1 weight% Mo, 0 to 1 weight% V, and the remainder Fe. Through the Fe-based alloy containing Fe, C, Cr, Mo, and V in this way, high hardness can be secured even at room temperature.

[0046] Depending on the needs, the mixing ratio of Co-based alloys and Fe-based alloys can be adjusted from 40:60 to 100:0. In particular, by increasing the proportion of Co-based alloys from 40% to a maximum of 100%, hardness specifications at high temperatures that could not be secured with conventional technology can be achieved.

[0047] As can be seen in Table 1 below, the hardness of the laminated portion (320) is within the range of 350 HV to 500 HV at room temperature and within the range of 100 HV to 300 HV at 600°C, depending on the weight percentage of the Co-based alloy. Table 1 is the result of comparing the hardness (HV) by temperature according to the mixing ratio of the Co-based alloy and the Fe-based alloy and the manufacturing method. In addition, FIG. 4 shows a graph of the hardness (HV) by temperature according to the mixing ratio of the Co-based alloy and the Fe-based alloy and the manufacturing method.

[0048] #Manufacturing Method Mixing Ratio 25℃ Hardness (HV) 300℃ Hardness (HV) 600℃ Hardness (HV) Co-based Alloy Fe-based Alloy 1 Mixed Powder Laser Additive Manufacturing 40% 60% 4 2 7 2 5 0 1 3 6 2 7 0% 30% 4 3 2 7 0 2 0 3 3 1 0 0% 0% 3 8 4 3 2 8 2 7 6 4 Conventional Sintering 40% 60% 4 8 0 2 9 0 1 1 5

[0049]

[0050] In addition, Table 2 below shows the results of comparing the amount of wear (μm) at different temperatures according to the mixing ratio of Co-based alloys and Fe-based alloys and the manufacturing method. Figure 5 shows a graph of the amount of wear (μm) at different temperatures according to the mixing ratio of Co-based alloys and Fe-based alloys and the manufacturing method.

[0051] #Manufacturing Method Mixing Ratio 100℃ Wear Amount (㎛) 350℃ Wear Amount (㎛) Co-based Alloy Fe-based Alloy 1 Mixed Powder Laser Additive Manufacturing 40% 60% 58 30 270% 30% 60 25 3100% 0% 63 16 4 Conventional Sintering 40% 60% 25 36

[0052]

[0053] The valve and valve seat rig testers for Tables 1 and 2 were designed to simulate the movement of actual valves and used a dry chamber method heated via heating coils to simulate the effect of engine combustion temperature. High temperature conditions were used to compare the amount of wear at high temperatures, and, for example, the seating velocity could be 0.9 m / s.

[0054] Referring to Tables 1 and 2, it can be seen that as the proportion of Co-based alloy increases, the hardness (HV) at high temperatures increases and the amount of wear decreases.

[0055] In some cases, the hardness of the laminated portion (320) can be improved through heat treatment. Specifically, when the laminated portion (320) contains 30 to 60 weight percent of an Fe-based alloy, if the laminated portion (320) is heat-treated, the hardness of the laminated portion (320) can be increased to within the range of 500 HV to 600 HV at room temperature. That is, the room temperature hardness of the laminated portion (320) can be increased by approximately 10% to 40% through separate heat treatment. Specific conditions for heat treatment will be examined in the heat treatment steps below.

[0056] It is preferable that the thickness (t) of the laminated portion (320) be 300㎛ or more. The actual valve seat (300) typically experiences wear of 100㎛ to 200㎛ on average, and in severe cases, excessive wear of 300㎛ or more may occur. Therefore, considering this, it is preferable to laminate the laminated portion (320) to a thickness of 300㎛ or more to ensure a laminated thickness greater than the average wear depth. If the laminated thickness of the laminated portion (320) is less than 300㎛, the laminated portion (320) may wear out completely during use and fail to perform its function. Additionally, considering the structural stability of the product, it is preferable that the thickness (t) of the laminated portion (320) be less than 50% of the total valve seat (300) thickness.

[0057] Additionally, it is preferable that the width of the laminated portion (320) be within the range of 1 mm to 4 mm. Since the valve seat (300) is formed in a ring shape, the laminated portion (320) will also be formed in a ring shape along the circumferential direction of the valve seat (300), and the width of the laminated portion (320) will correspond to the value obtained by subtracting the inner diameter from the outer diameter.

[0058] The width of wear on the valve seat (300) is 1 mm to 4 mm depending on the type and size of the engine. If the width of the laminated portion (320) is less than 1 mm, a surface pressure greater than the designed surface pressure may occur, and the sealing function may not be performed properly. On the other hand, if the width of the laminated portion (320) is greater than 4 mm, there may be non-functional aspects, resulting in inefficiency in process and cost.

[0059] In the present invention, the laminated portion (320) can be laminated by a Direct Energy Deposition (DED) method or a Laser Cladding method. This will be examined in more detail in the manufacturing method below.

[0060] In FIG. 2, the valve seat (300) is described as being configured separately from the cylinder head (100), but this is not limited thereto. In some cases, as shown in FIG. 3, the valve seat (1320) may be configured integrally with the cylinder head (100). In this case, the laminated portion (1320) may be provided directly on the cylinder head (100), more specifically on the contact surface of the portion that acts as the valve seat (1320). In this case, a separate valve seat component is omitted, and the process for attaching it to the cylinder head is also omitted, so the effect of maintaining the seal of the engine's combustion chamber can be secured in a more simplified manner.

[0061]

[0062] Next, we will look at the method for manufacturing the engine valve seat of the present invention.

[0063] The method for manufacturing an engine valve seat of the present invention includes a lamination step of mixing and laminating 40 to 100 weight percent of Co-based alloy powder and the remainder of Fe-based alloy powder on the contact surface of a valve seat (300, 1300) that contacts a valve (200).

[0064] Here, the additive manufacturing step can be carried out by the Direct Energy Deposition (DED) method, which uses a high-power laser beam, or by the laser cladding method. The DED method is a metal 3D printing method in which metal powder or wire is sprayed directly onto the surface of an object, and the material is melted and bonded using energy such as a high-power laser, electron beam, or plasma arc to form layers. Additionally, the laser cladding method is a surface modification method in which powder or wire is melted using a high-power laser and then continuously deposited.

[0065] In the above lamination step, when the laminated portion (320) is laminated by the DED method or the laser cladding method, the base material component may be mixed within 30% in the laminated portion (320). Specifically, during the DED or laser cladding process, the coating material is melted by the laser and coated onto the base material of the valve seat (300), and at the same time, the base material is also partially melted by the heat input from the laser. As a result, the molten base material is mixed with the coating material, and as a result, the base material component is included within 30% in the laminated portion (320).

[0066] In this way, when Co-based alloy powder and Fe-based alloy powder are simultaneously supplied to the contact surface of the valve seat (300, 1300) in a desired ratio, they can be melted by a high-power laser and bonded to the contact surface of the valve seat (300, 1300) and laminated. At this time, in order to laminate smoothly using the above method, it is preferable that the supplied Co-based alloy powder and Fe-based alloy powder be spherical powders having a size of 45㎛ to 150㎛.

[0067] As such, in the present invention, since lamination is achieved by the DED method or laser cladding method, a separate molding process is not required, so the problem of moldability that may occur when including more than 40% of Co-based alloy in the conventional powder sintering method does not occur. That is, when using the conventional sintering method, it is difficult to include more than 40% of hard particles due to moldability issues, and this may result in limitations on the high-temperature wear resistance that can be improved; however, in the present invention, since molding is not required, it is possible to freely include more than 40% of Co-based alloy to improve high-temperature wear resistance.

[0068] Furthermore, looking at Table 1 above, the hardness of the valve seat having a laminated section laminated by laser lamination has a higher value at high temperatures compared to the hardness of the valve seat manufactured by the conventional sintering method.

[0069] In some cases, the method for manufacturing an engine valve seat of the present invention may further include a heat treatment step for heat treating a laminated portion (320) laminated in the lamination step when the Fe-based alloy is included in an amount of 30 to 60 weight%. Specific heat treatment conditions are shown in Table 3 below, and the heat treatment may be performed in the order listed in Table 3.

[0070] Heat Treatment Sequence 1 2 3 Heat Treatment Annealing Quenching Tempering Temperature 860°C 1040°C 570°C Holding Time 1 hour 1 hour 1 hour Cooling Time Furnace Cooling Air Cooling Air Cooling

[0071]

[0072] Consequently, the hardness of the laminated portion (320) can be increased through heat treatment. Specifically, as seen above, when the laminated portion (320) is heat-treated, the hardness of the laminated portion (320) can be increased to within the range of 500 HV to 600 HV at room temperature.

[0073] The present invention is not limited to the specific embodiments and descriptions described above, and various modifications can be made by anyone with ordinary knowledge in the technical field to which the present invention pertains without departing from the essence of the invention as claimed in the claims, and such modifications fall within the scope of protection of the present invention.

[0074] The present invention relates to an engine valve seat and a method for manufacturing the same, and more specifically, to an engine valve seat and a method for manufacturing the same in which high-temperature wear resistance can be improved by mixing and laminating 40 to 100 weight percent of a Co-based alloy and the remainder of an Fe-based alloy on the contact surface of the valve seat that contacts the valve.

Claims

1. An engine valve seat that contacts a valve within the combustion chamber of an engine and performs a sealing function, An engine valve seat characterized by having a laminated portion formed by mixing and laminating 40 to 100 weight percent of a Co-based alloy and the remainder of an Fe-based alloy on the contact surface of the valve seat that contacts the valve.

2. In Paragraph 1, An engine valve seat characterized in that the above Co-based alloy is composed of 20 to 30 weight% Mo, 8 to 20 weight% Cr, 0 to 20 weight% Ni, and the remainder Co.

3. In Paragraph 1, An engine valve seat characterized in that the above Fe-based alloy is composed of 1 to 2 weight% C, 4 to 6 weight% Cr, 0 to 1 weight% Mo, 0 to 1 weight% V, and the remainder Fe.

4. In Paragraph 1, An engine valve seat characterized in that the hardness of the laminated portion is within the range of 350HV to 500HV at room temperature and within the range of 100HV to 300HV at 600℃, depending on the weight% of the Co-based alloy.

5. In Paragraph 4, An engine valve seat characterized in that, when the above laminated portion contains 30 to 60 weight percent of the Fe-based alloy, the hardness of the above laminated portion increases to within the range of 500 HV to 600 HV at room temperature when the above laminated portion is heat-treated.

6. In Paragraph 1, An engine valve seat characterized by the thickness of the laminated portion being 300㎛ or more.

7. In Paragraph 1, An engine valve seat characterized in that the width of the laminated portion is within the range of 1 mm to 4 mm.

8. In Paragraph 1, An engine valve seat characterized in that the above-mentioned laminated portion is laminated by a Direct Energy Deposition (DED) method or a laser cladding method.

9. In Paragraph 8, An engine valve seat characterized in that, when the laminated portion is laminated by the above DED method or the above laser cladding method, the base material component is mixed in the laminated portion to within 30%.

10. A cylinder head that seals one side of the combustion chamber of an engine; A valve for opening or closing the intake or exhaust port of the cylinder head; A valve seat according to any one of claims 1 to 9, provided in the cylinder head and in contact with the valve; comprising An engine characterized in that the valve seat is configured separately from the cylinder head and coupled to the cylinder head or formed integrally with the cylinder head.

11. A method for manufacturing an engine valve seat that contacts a valve within the combustion chamber of an engine and performs a sealing function, A method for manufacturing an engine valve seat, characterized by including a lamination step of mixing and laminating 40 to 100 weight percent of Co-based alloy powder and the remainder of Fe-based alloy powder on the contact surface of the valve seat that contacts the valve.

12. In Paragraph 11, A method for manufacturing an engine valve seat, characterized in that the above lamination step is performed by a Direct Energy Deposition (DED) method or a laser cladding method.

13. In Paragraph 12, A method for manufacturing an engine valve seat, characterized in that when a laminated portion is laminated by the DED method or the laser cladding method in the above lamination step, the laminated portion contains a base material component mixed within 30%.

14. In Paragraph 12, A method for manufacturing an engine valve seat, characterized in that the above Co-based alloy powder and the above Fe-based alloy powder are spherical powders having a size of 45 μm to 150 μm.

15. In Paragraph 11, A method for manufacturing an engine valve seat, characterized by further including a heat treatment step of heat-treating a laminated portion laminated in the lamination step when the above Fe-based alloy is included in an amount of 30 to 60 weight%.

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