SINGLE CRYSTAL ENGINE VALVE

Abstract

Motor valve (100) for use in an internal combustion engine (200), wherein the motor valve (100) comprises: a shaft (104) with a first end and a second end; a tip (102) positioned at the first end of the shaft (104); as well as a plate section (116) with a throat (108) and a combustion surface (114), wherein the plate section (116) is friction-welded to the second end of the shaft (104), wherein the plate section (116) is cast from a single-crystal metal (306), has no grain boundary (406) and is resistant to temperatures above 850 °C wherein the shaft (104) is made of polycrystalline forged steel and wherein the single-crystal metal (306) is a nickel-based superalloy.

Description

Technical field

[0001] The disclosure relates to a heat-resistant engine valve, and in particular a heat-resistant engine valve for a reciprocating engine, which is manufactured by a single-crystal metal casting process. background

[0002] Engine intake valves are positioned in an intake port, which is located between the intake and a combustion chamber. During an intake stroke, a cam or rocker arm opens the intake valve, allowing a fuel-air mixture to enter the combustion chamber. Exhaust valves are positioned in an exhaust port, which is located between the combustion chamber and an exhaust or exhaust flow channel. During an exhaust stroke, the cam or rocker arm opens the exhaust valve, and combustion gases are expelled from the combustion chamber.

[0003] However, as engine power density increases and new combustion strategies are explored, the demands on the operating temperatures of engine exhaust valves also rise. These increasing temperatures are driven by both emissions regulations and industry-wide trends toward greater fuel efficiency and power density. The conventional limit was an operating temperature of approximately 725 °C under continuous load, with possible spikes up to around 800 °C for short periods. Standard valves are manufactured from forged, iron-based austenitic stainless steel alloys, such as 23-8N (with a theoretical composition of 23% Cr, 8% Ni, 2.5% Mn, 0.53% C, 0.43% N, balance Fe) or 21-4N (with a theoretical composition of 21% Cr, 4% Ni, 9% Mn, 0.75% Si, 0.33% C, 0.30% N, balance Fe). However, these standard valves generally cannot be operated above 750 °C for extended periods.

[0004] The published PCT patent application WO 2004 / 079237A2 discloses a valve for an internal combustion engine, the method for its manufacture, and the heat-resistant titanium alloy comprising the following proportions of components in mass percent: aluminum 7.5–12.5, molybdenum 1.6–2.6, zirconium 1.4–2.4, silicon 0.1–0.2, yttrium 0.05–0.1, titanium balance. The claimed alloy has a content of the α+α2+β phase, wherein the α2 phase is based on the compound Ti3Al, which is dispersively distributed in the α phase. The claimed method consists of manufacturing the valve from a cylindrical cavity by deformation treatment with prior heating and subsequent heat treatment. The shaft is preheated to a temperature 5–20 °C below the alloy's complete polymorphic transformation (Tpc) temperature. The shaft is then deformed by transverse rolling.The valve disc is deformed by forging with prior heating to a temperature 5–50 °C higher than the alloy's Tpc (temperature at the start of the forging process). The forging process ends at a temperature below Tpc, resulting in the disc-shaped valve disc and a smooth transition between the stem and disc. The technical benefit of the invention is to obtain the valve and enable its operation within a range of operating temperatures. However, valves produced by this method are not capable of operating at temperatures above 850 °C for extended periods.

[0005] If the valve is operated above its rated temperature, surface instability can occur, and oxidation layers can form on the surface, eventually flaking off and entering the combustion chamber. Additionally, the high temperature can cause valve fatigue or alterations in the microstructure or properties of the alloy, leading to valve failure during operation.

[0006] Therefore, there is a need for an improved method that provides a motor valve capable of operating at high temperatures for extended periods. A one-piece motor valve made of a nickel-based superalloy is known from DE 32 40 461 A1. A multi-piece motor valve made of titanium-based materials is known from DE 10 2009 020 227 A1. Summary

[0007] According to one aspect, a valve for use in an internal combustion engine is disclosed. The valve may comprise: a stem with a first end and a second end, a tip positioned at the first end of the stem; and a disc section with a throat and a combustion surface, wherein the disc section is friction-welded to the second end of the stem, the disc section being cast from a single-crystal metal, having no grain boundary, and being resistant to temperatures exceeding 850 °C. The stem is made of polycrystalline forged steel, and the single-crystal metal is a nickel-based superalloy.

[0008] According to a further aspect, an internal combustion engine is disclosed. The engine comprises a combustion chamber, at least one air inlet leading into the combustion chamber and defining a port configured to receive a valve, the valve comprising: a stem with a first end and a second end, a tip positioned at the first end of the stem; and a disc section with a throat and a combustion surface, the disc section being friction-welded to the second end of the stem, the disc section being cast from a single-crystal metal, having no grain boundary, and being resistant to temperatures exceeding 850 °C. Brief description of the drawings Fig. Figure 1 illustrates a valve that can serve as an inlet valve or an outlet valve according to one aspect of the disclosure. Fig. Figure 2 illustrates the valve of Fig. 1, which is positioned inside an engine of the vehicle, according to one aspect of the revelation. Fig. Figure 3 illustrates an exemplary casting system according to one aspect of the revelation. Fig. Figure 4 illustrates a single grain growing with a grain boundary, according to one aspect of the Revelation. Detailed description

[0009] Fig. Figure 1 illustrates a valve 100 that can serve as an inlet valve or an exhaust valve according to one aspect of the disclosure. The valve 100 comprises a stem 104 friction-welded to a disc section 116. The stem 104 may include a tip 102 at one end and finally connects at a second end to a groove 108. The groove 108 serves to connect the stem 104 to a seat 110. The seat 110 may be arranged between the groove 108 and a rim 112, which is located between the seat 110 and a combustion surface 114. The disc section 116 may comprise the groove 108, the seat 110, the rim 112, and the combustion surface 114. During engine operation, a large temperature gradient occurs in the valve 100 between the combustion surface 114 and the tip 102.For example, during engine operation, the combustion surface 114 may experience a temperature of 850 °C or more due to the combustion event, while the tip 102 may experience a temperature of approximately 100 °C. Therefore, the plate section 116, including the combustion surface 114, can be made of a metallic material that can withstand high temperatures at or above 850 °C.

[0010] The shaft may be made of polycrystalline forged steel, such as carbon steel (1540 and 1541) and martensitic stainless steel (Silchrome 1). Since the shaft is subjected to impact by a rocker arm during use, it should be made of a material that is wear-resistant even at low temperatures. The tip 102 may include a hardened steel knob, attached by resistance welding or projection welding, to protect the shaft from damage by the rocker arm during operation. The tip may also include a fusion-welded pad of hardened material. The plate section 116 may be made of any material, including a single grain of metal with few or no grain boundaries, and is further explained below.

[0011] Fig. Figure 2 illustrates valve 100 from Fig. 1, which is positioned within an engine 200 of the vehicle, according to one aspect of the disclosure. The valve 100 can be an inlet valve, which can be installed in a cylinder head 202, which can define an air inlet 204 that terminates at an inlet port 206. The inlet port 206 can lead to a combustion chamber 208, which contains a piston 210 (only partially in Fig. (2 shown) can be slidably accommodated therein. The valve 100 can be moved into the space provided by a spring or other preload element 212. Fig. The closed position shown in Figure 2 can be pre-tensioned. The shaft 104 can extend upwards through the pre-tensioning element 212 to be connected to an actuating element in the form of a rocker arm or cam (in Figure 2). Fig. 2 (not shown) to intervene. As in Fig. As shown in Figure 2, the seat surface 110 in the closed position can engage with a valve seat insert 214 to seal the combustion chamber 208. The valve seat insert 214 is generally designed as part of the engine to make this part of the engine wear-resistant. Also in Fig. Figure 2 shows another valve 100' or exhaust valve, which is installed in the cylinder head 202, which also defines an exhaust passage 216 and an exhaust port 218. Another valve seat insert 214 is provided for the seat surface 110', so that the seat surface 110' seals the combustion chamber 208 in the closed position.

[0012] According to one aspect of the disclosure, in order to withstand high temperatures at or above 850 °C, the plate section 116 can be made from various materials, including single-crystal metal such as nickel-based superalloys.Nickel-based superalloys can include: CMSX-4 (with weight percentages of approximately 6.5% Cr, 9.0% Co, 0.6% Mo, 6.0% W, 6.5% Ta, 3% Re, 5.6% Al, 1.0% Ti, 0.10% Hf and the remainder nickel or other materials), CMSX 3 (with weight percentages of approximately 8.0% Cr, 5.0% Co, 0.6% Mo, 8.0% W, 6.0% Ta, 5.6% Al, 1.0% Ti, 0.10% Hf and the remainder nickel or other materials) from Cannon Muskegon Corporation, or Rene N5 (with weight percentages of approximately 7.0% Cr, 7.5% Co, 1.5% Mo, 5.0% W, 6.5% Ta, 3% Re, 6.2% Al, 0.15% Hf and The remaining nickel or other materials), or Rene N6 (with weight percentities of approximately 4.2% Cr, 12.5% ​​Co, 1.4% Mo, 6.0% W, 7.2% Ta, 5.4% Re, 5.8% Al, 0.15% Hf and the remainder being nickel or other materials) from GE Aircraft Motors. CMSX-4 is a rhenium-containing, nickel-based single-crystal alloy capable of enabling operation at higher peak temperatures / loads of at least 2125 °F (1163 °C).However, according to one aspect of the disclosure, any single-crystal metal capable of withstanding high temperatures of approximately 850°C or more in an engine without fatigue or degradation, or that is resistant to corrosive or oxidizing environments, may be used. Furthermore, the selected single-crystal metal should be capable of being cast as a single crystal. Generally, under high temperatures for extended periods, a grain structure tends to creep along the grain boundaries, leading to component failure. Thus, a single-crystal metal formed with no or minimal grain boundaries creates a product that is highly resistant to creep deformation. In addition, the process used to cast the valve head as a single crystal requires precisely controlled melting and solidification processes.These processes result in a reduced probability of defects, such as pores or inclusions, being present in the finished casting, even compared to equiaxial investment casting. Defects like pores and inclusions are known to be starting points for cracks, especially fatigue cracks at high cycle counts. Therefore, a cast valve that is essentially free of pores and inclusions will have a longer service life in a reciprocating engine application.

[0013] Many different methods can be used to cast the plate section 116, such as the Bridgman method using a Bridgman furnace or the Czochralski method. Fig. Figure 3 illustrates a casting system 300 according to one aspect of the disclosure. The Bridgman process is based on directed solidification by transferring a melt with the temperature gradient that arises in the casting system 300. A crucible 302 provides a single-crystal metal 306. The single-crystal metal 306 may be in ingot form before being melted in a crucible 302 by induction coils 304. The induction coils 304 are configured within the inner wall of the crucible 302 and generate heat at a temperature at or above the melting point of the ingot. The single-crystal metal 306 may be poured into a mold 308 having the shape of the plate section 116. The mold may be made of ceramic materials such as silicate, alumina, or zirconium.The mold 308 can be formed slowly by building up the ceramic layer on a wax model, which is eventually melted using a thermal cycle. The mold 308 is typically used once to produce the plate section 116. The casting system 300 may also include induction coils 310 embedded in a wall of a furnace 316. Insulation 312 may also be provided in the furnace 316 to maintain the temperature within it. The extension 328 formed during the casting process is suspended from a starting point 320 located on a cooling plate 324. According to one aspect of the disclosure, the cooling plate may be water-cooled or cooled by another coolant. The cooling plate 324 is attached to or positioned on a lifting device 322, which is moved in the direction of arrow 326.

[0014] In general, the furnace provides a temperature range that is maintained above the melting point of the single-crystal metal 306 by using the induction coils 310. The numerous induction coils 310, which are in Fig. Figure 3 helps to establish a temperature gradient (highest) from the top of furnace 316 to the point where extension 328 (lowest) begins to form. The single-crystal metal 306, in the form of an ingot, is placed in a crucible 302, which is heated by induction coils 304 to a temperature above the melting point of the single-crystal metal 306. The molten single-crystal metal 306 is poured into mold 308, which is heated by induction coils 310 to a temperature above the melting point of the single-crystal metal 306. As noted above, the lower section of furnace 316 has a lower temperature (below the melting point of the single-crystal metal 306) than the upper section of the furnace, and thus solidification begins in the lower section of the furnace. The cooling plate 324 also provides the lower temperature, so that solidification begins at a starting point of 320.As the cooling plate 324 is slowly moved by the lifting device 322 in the direction of arrow 326 (or lower), and the temperature gradient is controlled by the induction coils 310, the single-crystal metal 306 is forced to grow vertically. The extension can filter out the grain growth until only a single grain grows through the remaining part of the mold 308. Once cast, the plate section 116 can be subjected to heat treatment cycles and machining to obtain the desired final product.

[0015] Fig. Figure 4 illustrates a single grain 402 growing with a grain boundary 406, according to one aspect of Revelation. While the single grain 402, according to the one in Fig.As described in the 3 process, a grain boundary propagates forward as the individual grain grows. However, the finished casting of the plate section 116 contains no grain boundary, or only a minimal number of grain boundaries. With few or no grain boundaries, defects that can occur in other types of castings, such as a large number of grain boundaries, can be minimized. This allows the plate section 116, and in particular the combustion surface 114, to withstand an operating temperature in the combustion chamber 208 of more than 850 °C.

[0016] As noted above, the stem 104 can be made of polycrystalline forged steel, and the tip 102 can include a protective weld or a resistance weld. The stem 104 can be friction-welded to the disc section 116, produced by the method described herein, to form the valve 100. According to one aspect of the invention, the stem 104 can also be formed using the method described herein so that the stem 104 can withstand the high temperatures during combustion. Thus, the entire valve 100 can be cast in one piece using the single-crystal metal 306. Commercial applicability

[0017] Improved valves for internal combustion engines are provided. Intake and exhaust valves exposed to temperatures exceeding 850°C in an engine's combustion chamber can fail due to fatigue or cracking, causing engine downtime for valve replacement and adjustment. The improved valves are manufactured, at least in part (the head section), from a single-crystal 306 metal using a casting process that produces no or a minimal number of grain boundaries. The single-crystal 306 metal can be a nickel-based superalloy, including CMSX-4 or CMSX-3 from Cannon Muskegon Corporation, or Rene N5 and Rene N6 from GE Aircraft Motors. The low or absence of grain boundaries minimizes defects that can occur in other types of castings, such as a large number of grain boundaries.This allows the plate section 116 and in particular the combustion surface 114 to withstand an operating temperature in the combustion chamber 208 of more than 850 °C.

Claims

[1] Engine valve (100) for use in an internal combustion engine (200), the engine valve (100) comprising: a shaft (104) with a first end and a second end; a tip (102) positioned at the first end of the shaft (104); as well as a plate section (116) with a throat (108) and a combustion surface (114), wherein the plate section (116) is friction-welded to the second end of the shaft (104), wherein the plate section (116) is cast from a single-crystal metal (306), has no grain boundary (406) and is resistant to temperatures above 850 °C wherein the shaft (104) is made of polycrystalline forged steel and wherein the single-crystal metal (306) is a nickel-based superalloy. [2] Valve (100) according to claim 1, wherein the tip (102) comprises a wear-resistant material. [3] Valve (100) according to claim 2, wherein the wear-resistant material is formed by hardened steel. [4] Valve (100) according to claim 2, wherein the wear-resistant material is formed by resistance welding. [5] Valve (100) according to claim 1, wherein the single crystal metal (306) is a CMSX-3 or CMSX-4 or Rene N5 or Rene N6. [6] Valve (100) according to claim 1, wherein the single crystal metal (306) has weight percent fractions of about 6.5% Cr, 9.0% Co, 0.6% Mo, 6.0% W, 6.5% Ta, 3% Re, 5.6% Al, 1.0% Ti, 0.10% Hf and the remainder is nickel or other materials. [7] Valve (100) according to claim 1, wherein the single crystal metal (306) has weight percent fractions of about 8.0% Cr, 5.0% Co, 0.6% Mo, 8.0% W, 6.0% Ta, 5.6% Re, 1.0% Al, 0.10% Ti, 0.10% Hf and the remainder is nickel or other materials. [8] Valve (100) according to claim 1, wherein the single-crystal metal (306) has weight percent fractions of about 7.0% Cr, 7.5% Co, 1.5% Mo, 5.0% W, 6.5% Ta, 3% Re, 6.2% Al, 0.15% Hf and the remainder is nickel or other materials.

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