Cylinder head blank and method for manufacturing cylinder head

Abstract

A film-forming portion is formed on an annular edge portion along an opening portion (16a) of an air inlet (16) or an opening portion (17a) of an exhaust port (17), wherein a metal film (5) is formed by spraying raw material powder using a cold spray method, and a radial cross-section of the film-forming portion along the air inlet (16) or the exhaust port (17) is formed into a groove shape including a flat bottom surface (G1) and a pair of side surfaces (G2) adjacent to the bottom surface.

Description

Technical Field

[0001] The present invention relates to a cylinder head blank and a method for manufacturing a cylinder head used in an internal combustion engine. Background Art

[0002] A method for manufacturing a sliding member is known in which a raw material powder such as metal is sprayed onto a seating portion of an engine valve by cold spraying to form a valve seat having excellent high-temperature wear resistance (Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2017 / 022505 Pamphlet Summary of the Invention

[0006] Problems to be solved by the invention

[0007] However, engine valve seats have a problem in which the valve seat film formed by cold spraying may crack or peel due to impact caused by hammering input of intake and exhaust valves and wear caused by repeated collisions.

[0008] The problem to be solved by the present invention is to provide a cylinder head blank including a valve seat film having excellent adhesion and high strength, and a method for manufacturing a cylinder head.

[0009] Solutions for solving problems

[0010] The present invention solves the above-mentioned problem by forming a film-forming portion formed by spraying raw material powder by cold spraying into a groove-shaped cross section along the radial direction including a flat bottom surface and a pair of side surfaces adjacent to the bottom surface.

[0011] Effects of the Invention

[0012] According to the present invention, the compressive residual stress of the metal film formed on the film forming portion by cold spraying acts on a pair of side surfaces of the groove shape of the film forming portion, thereby manufacturing a cylinder head including a metal film having excellent adhesion and high strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a cross-sectional view showing the structure of an internal combustion engine including a cylinder head manufactured by the manufacturing method of the present invention using the cylinder head blank of the present invention.

[0014] Figure 2 yes Figure 1 An enlarged cross-sectional view of the valve periphery.

[0015] Figure 3This is a structural diagram of a cold spraying device used in the cylinder head manufacturing method of the present invention.

[0016] Figure 4 It is a process diagram showing the steps of manufacturing the cylinder head of the present invention.

[0017] Figure 5 It is a perspective view showing the structure of the cylinder head blank according to the present invention.

[0018] Figure 6A It indicates the direction of the air inlet. Figure 5 A cross-sectional view taken along line VI-VI.

[0019] Figure 6B It means that in the cutting process Figure 6A A cross-sectional view showing a state in which an intake port forms an annular valve seat portion.

[0020] Figure 6C It means in Figure 6B A cross-sectional view showing a state where the intake port is formed on the valve seat membrane.

[0021] Figure 6D It is a cross-sectional view showing an intake port where a valve seat film is formed.

[0022] Figure 6E Yes Figure 4 Cross-sectional view of the air intake after the finishing process.

[0023] Figure 6F yes Figure 6C Magnified top view of the valve seat membrane.

[0024] Figure 7A It indicates the annular valve seat along Figure 6F An enlarged cross-sectional view of line VII-VII (part 1).

[0025] Figure 7B It indicates the annular valve seat along Figure 6F An enlarged cross-sectional view of line VII-VII (part 2).

[0026] Figure 7C It indicates the annular valve seat along Figure 6F VII-VII line of FIG. 1 is an enlarged cross-sectional view illustrating the dihedral angle (groove angle) of the groove shape of the annular valve seat portion.

[0027] Figure 8 The figure shows the film forming state of the valve seat film of the cylinder head blank of the present invention. Figure 6E An enlarged cross-sectional view of part VIII.

[0028] Figure 9It is an enlarged cross-sectional view showing a film-forming state of a valve seat film of a cylinder head blank according to a comparative example.

[0029] Figure 10 This is a graph showing the relationship between the stress acting on the valve seat film of the cylinder head blank of the present invention and the dihedral angle (groove angle) of the groove shape of the annular valve seat portion.

[0030] Figure 11 This is a cross-sectional view showing the relationship between the film thickness of the valve seat film of the cylinder head blank according to the present invention and the shear force generated by the combustion pressure.

[0031] Figure 12 It is a cross-sectional view showing the relationship between the film thickness of the valve seat film of the cylinder head blank of the comparative example and the shear force generated by the combustion pressure. DETAILED DESCRIPTION

[0032] An embodiment of the present invention will be described below with reference to the drawings. First, an internal combustion engine 1 including a cylinder head manufactured by the manufacturing method of the present embodiment using the cylinder head blank of the present embodiment will be described. Figure 1 It is a cross-sectional view of the internal combustion engine 1, mainly showing the structure around the cylinder head.

[0033] An internal combustion engine 1 includes a cylinder block 11 and a cylinder head 12 assembled to the upper portion of the cylinder block 11. The internal combustion engine 1 is, for example, an inline four-cylinder gasoline engine. The cylinder block 11 has four cylinders 11a arranged in the depth direction of the drawing. Each cylinder 11a houses a piston 13 that reciprocates in the vertical direction of the drawing. Each piston 13 is connected to a crankshaft 14 extending in the depth direction of the drawing via a connecting rod 13a.

[0034] The mounting surface 12a of the cylinder head 12, which is mounted on the cylinder block 11, has four recessed portions 12b formed at positions corresponding to the cylinders 11a. These recessed portions 12b constitute combustion chambers 15 for each cylinder. Combustion chambers 15 are spaces for burning a mixture of fuel and intake air, and are formed by the recessed portions 12b of the cylinder head 12, the top surface 13b of the piston 13, and the inner circumferential surface of the cylinder 11a.

[0035] The cylinder head 12 includes an intake port 16 that connects the combustion chamber 15 to one side surface 12c of the cylinder head 12. The intake port 16 has a curved, generally cylindrical shape and guides intake air from an intake manifold (not shown) connected to the side surface 12c into the combustion chamber 15. Furthermore, the cylinder head 12 includes an exhaust port 17 that connects the combustion chamber 15 to the other side surface 12d of the cylinder head 12. Like the intake port 16, the exhaust port 17 has a curved, generally cylindrical shape and discharges exhaust gas generated in the combustion chamber 15 to an exhaust manifold (not shown) connected to the side surface 12d. Furthermore, the internal combustion engine 1 of this embodiment includes two intake ports 16 and two exhaust ports 17 for each cylinder 11a.

[0036] The cylinder head 12 includes intake valves 18 that open and close the intake port 16 relative to the combustion chamber 15, and exhaust valves 19 that open and close the exhaust port 17 relative to the combustion chamber 15. The intake valves 18 and exhaust valves 19 each include rod-shaped valve stems 18a and 19a, respectively, and disc-shaped valve heads 18b and 19b attached to the tips of the valve stems 18a and 19a. The valve stems 18a and 19a slidably extend through substantially cylindrical valve guides 18c and 19c assembled to the cylinder head 12. This allows the intake valves 18 and exhaust valves 19 to move freely relative to the combustion chamber 15 along the axial direction of the valve stems 18a and 19a, respectively.

[0037] exist Figure 2 The figure shows an enlarged view of the connection between the combustion chamber 15 and the intake port 16 and exhaust port 17. The intake port 16 has a substantially circular opening 16a in the connection with the combustion chamber 15. An annular valve seat film 16b is formed on the annular edge of this opening 16a (the valve seating area) to abut against the valve head 18b of the intake valve 18. When the intake valve 18 moves upward along the axial direction of the valve stem 18a, the upper surface of the valve head 18b abuts against the valve seat film 16b, sealing the intake port 16. Conversely, when the intake valve 18 moves downward along the axial direction of the valve stem 18a, a gap is formed between the upper surface of the valve head 18b and the valve seat film 16b, opening the intake port 16.

[0038] Like the intake port 16, the exhaust port 17 has a generally circular opening 17a in the portion communicating with the combustion chamber 15. An annular valve seat film 17b is formed on the annular edge of this opening 17a (the valve seating portion) to abut against the valve head 19b of the exhaust valve 19. When the exhaust valve 19 moves upward along the axial direction of the valve stem 19a, the upper surface of the valve head 19b abuts against the valve seat film 17b, sealing the exhaust port 17. Conversely, when the exhaust valve 19 moves downward along the axial direction of the valve stem 19a, a gap is formed between the upper surface of the valve head 19b and the valve seat film 17b, opening the exhaust port 17. Furthermore, the diameter of the opening 16a of the intake port 16 is set larger than the diameter of the opening 17a of the exhaust port 17.

[0039] In the four-cycle internal combustion engine 1, only the intake valve 18 opens as the piston 13 descends, thereby introducing the mixed gas from the intake port 16 into the cylinder 11a (intake stroke). Next, with the intake valve 18 and exhaust valve 19 closed, the piston 13 ascends to approximately top dead center, compressing the mixed gas in the cylinder 11a (compression stroke). Then, when the piston 13 reaches approximately top dead center, the spark plug ignites the compressed mixed gas, causing it to explode. Due to this explosion, the piston 13 descends to bottom dead center, where the connected crankshaft 14 converts the explosion into rotational force (combustion / expansion stroke). Finally, when the piston 13 reaches bottom dead center and begins to ascend again, only the exhaust valve 19 opens, discharging the exhaust gas in the cylinder 11a through the exhaust port 17 (exhaust stroke). The internal combustion engine 1 repeats the above cycle to generate output.

[0040] The valve seat films 16b and 17b are formed directly on the annular edges of the openings 16a and 17a of the cylinder head 12, i.e., the valve seating areas, using a cold spraying method. Cold spraying involves injecting a working gas at a temperature lower than the melting or softening point of the raw material powder into a supersonic flow. Raw material powder, transported by a carrier gas, is then injected into the working gas and sprayed from the tip of a nozzle. This solid-phase material collides with the substrate, and the plastic deformation of the powder forms a coating. Compared to spraying methods, which melt the material and adhere it to the substrate, this cold spraying method produces a dense coating that resists atmospheric oxidation and has minimal thermal effects on the material particles. Consequently, it offers the following advantages: thermal degradation is suppressed, film formation is rapid, film thickness can be achieved, and adhesion efficiency is high. In particular, its rapid film formation and ability to form thick films make it suitable for use as a structural material for the valve seat films 16b and 17b of the internal combustion engine 1.

[0041] Figure 3 This figure schematically illustrates a cold spray apparatus 2 used to form the valve seat films 16b and 17b described above. The cold spray apparatus 2 in this example includes a gas supply unit 21 for supplying working gas and transport gas; a raw material powder supply unit 22 for supplying raw material powder for the valve seat films 16b and 17b; a spray gun 23 for spraying the raw material powder using a working gas having a temperature below the melting point of the raw material powder and in a supersonic flow; and a refrigerant circulation circuit 27 for cooling a nozzle 23d.

[0042] The gas supply unit 21 includes a compressed gas cylinder 21a, a working gas line 21b, and a conveying gas line 21c. The working gas line 21b and the conveying gas line 21c each include a pressure regulator 21d, a flow control valve 21e, a flow meter 21f, and a pressure gauge 21g. The pressure regulator 21d, flow control valve 21e, flow meter 21f, and pressure gauge 21g are used to adjust the pressure and flow of the working gas from the compressed gas cylinder 21a and the pressure and flow of the conveying gas.

[0043] A heater 21i, such as a band heater, is installed in the working gas line 21b. This heater 21i receives power from a power source 21h via power supply lines 21j, 21j, thereby heating the working gas line 21b. After being heated by heater 21i to a temperature below the melting point or softening point of the raw material powder, the working gas is introduced into the chamber 23a of the spray gun 23. A pressure gauge 23b and a thermometer 23c are installed in the chamber 23a. These pressure and temperature values are output to a controller (not shown) via respective signal lines 23g and 23h for feedback control.

[0044] Meanwhile, the raw material powder supply unit 22 includes a raw material powder supply device 22a, a meter 22b attached to the raw material powder supply device 22a, and a raw material powder supply line 22c. A carrier gas from a compressed gas cylinder 21a is introduced into the raw material powder supply device 22a via the carrier gas line 21c. A predetermined amount of raw material powder, measured by the meter 22b, is then delivered to the chamber 23a via the raw material powder supply line 22c.

[0045] The spray gun 23 uses a working gas to form a supersonic stream of raw material powder P, which has been transported by a transport gas into the chamber 23a, and sprays it from the tip of the nozzle 23d. This causes the raw material powder P to collide with the substrate 4 in a solid phase or a solid-liquid coexisting state, thereby forming the metal film 5. In this embodiment, the cylinder head 12 is used as the substrate 4, and the raw material powder P is sprayed onto the annular edges of the openings 16a and 17a of the cylinder head 12 by cold spraying, thereby forming the valve seat films 16b and 17b as the metal film 5.

[0046] Nozzle 23d has a flow path (not shown) inside it for a refrigerant such as water to flow. At its tip, nozzle 23d has a refrigerant inlet 23e for introducing refrigerant into the flow path, and at its base, a refrigerant discharge portion 23f for discharging refrigerant from the flow path. Nozzle 23d introduces refrigerant from refrigerant inlet 23e into the flow path, allowing the refrigerant to flow through the flow path, and discharges the refrigerant from refrigerant discharge portion 23f, thereby cooling nozzle 23d.

[0047] The refrigerant circulation circuit 27, which circulates the refrigerant through the flow path of the nozzle 23d, includes a tank 271 storing the refrigerant; an inlet pipe 274 connected to the refrigerant inlet 23e; a pump 272 connected to the inlet pipe 274 to flow the refrigerant between the tank 271 and the nozzle 23d; a cooler 273 to cool the refrigerant; and a discharge pipe 275 connected to the refrigerant discharge port 23f. The cooler 273, which may be a heat exchanger, cools the refrigerant by exchanging heat between the refrigerant, which has risen in temperature by cooling the nozzle 23d, and a refrigerant such as air, water, or gas.

[0048] The refrigerant circulation circuit 27 uses a pump 272 to draw refrigerant stored in the tank 271 and supplies it to the refrigerant inlet 23e via the cooler 273. The refrigerant supplied to the refrigerant inlet 23e flows through the flow path within the nozzle 23d from the tip toward the rear end, exchanging heat with the nozzle 23d during this process, thereby cooling the nozzle 23d. The refrigerant that has flowed to the rear end of the flow path is discharged from the refrigerant discharge portion 23f to the discharge pipe 275, returning to the tank 271. In this way, the refrigerant circulation circuit 27 cools the refrigerant while circulating it, thereby cooling the nozzle 23d. This prevents the raw material powder P from adhering to the injection path of the nozzle 23d.

[0049] The valve seats of the cylinder head 12 are required to have high heat resistance and wear resistance to withstand valve knocking input from the combustion chamber 15, and high thermal conductivity for cooling the combustion chamber 15. To meet these requirements, valve seat films 16b and 17b formed from precipitation-hardening copper alloy powder, for example, can achieve valve seats that are harder than cylinder heads 12 formed from cast aluminum alloys and have superior heat resistance and wear resistance.

[0050] Furthermore, because the valve seat membranes 16b and 17b are formed directly on the cylinder head 12, they achieve higher thermal conductivity than conventional valve seats that press-fit a separate seat ring into the port opening. Furthermore, compared to using a separate seat ring, in addition to achieving closer proximity to the cooling water jacket, secondary benefits such as increased throat diameters for the intake and exhaust ports 16 and 17 and enhanced tumble flow due to optimized port shape are also achieved.

[0051] The raw material powder P used to form the valve seat films 16b and 17b is preferably a metal that is harder than the aluminum alloy used for casting and that provides the heat resistance, wear resistance, and thermal conductivity required for the valve seat. For example, the aforementioned precipitation-hardening copper alloy is preferably used. Furthermore, precipitation-hardening copper alloys such as Corson alloys containing nickel and silicon, chromium-containing copper, and zirconium-containing copper can also be used. Furthermore, for example, precipitation-hardening copper alloys containing nickel, silicon, and chromium, precipitation-hardening copper alloys containing nickel, silicon, and zirconium, precipitation-hardening alloys containing nickel, silicon, chromium, and zirconium, and precipitation-hardening copper alloys containing chromium and zirconium are also applicable.

[0052] Alternatively, the valve seat membranes 16b and 17b may be formed by mixing multiple raw material powders, such as a first raw material powder and a second raw material powder. In this case, the first raw material powder is preferably a metal that is harder than the aluminum alloy used for castings and that exhibits the heat resistance, wear resistance, and thermal conductivity required for the valve seat. For example, the precipitation-hardening copper alloy described above is preferably used. Furthermore, the second raw material powder is preferably a metal that is harder than the first raw material powder. Suitable examples of the second raw material powder include alloys such as iron-based alloys, cobalt-based alloys, chromium-based alloys, nickel-based alloys, and molybdenum-based alloys, as well as ceramics. Furthermore, any one of these metals may be used alone, or two or more may be used in appropriate combinations.

[0053] The valve seat film formed by mixing the first raw material powder and the second raw material powder which is harder than the first raw material powder can obtain heat resistance and wear resistance which are superior to those of the valve seat film formed only by the precipitation hardening type copper alloy. It is believed that the reason for obtaining such an effect is that the oxide film existing on the surface of the cylinder head 12 is removed by the second raw material powder and exposed to form a new interface, thereby improving the adhesion between the cylinder head 12 and the metal film. In addition, it is also believed that the reason is that the adhesion between the cylinder head 12 and the metal film is improved due to the anchoring effect brought about by the embedding of the second raw material powder into the cylinder head 12. Furthermore, it is also believed that the reason is that when the first raw material powder collides with the second raw material powder, part of its kinetic energy is converted into heat energy, or due to the heat generated by a part of the first raw material powder during the plastic deformation process, the precipitation hardening in the part of the precipitation hardening type copper alloy used as the first raw material powder is further promoted.

[0054] In the cold spray apparatus 2 of this embodiment, the cylinder head 12, on which the valve seat films 16b and 17b are to be formed, is fixed to a base 45. The tip of the nozzle 23d of the spray gun 23 is rotated along the annular edges of the openings 16a and 17a of the cylinder head 12 to spray the raw material powder. Since the cylinder head 12 is not rotated, a large footprint is not required. Furthermore, the spray gun 23 has a smaller moment of inertia than the cylinder head 12, resulting in excellent transient characteristics and responsiveness during rotation. However, in the cylinder head blank and cylinder head manufacturing method of the present invention, it is sufficient to relatively move the cylinder head 12, serving as the substrate, and the nozzle 23d. Therefore, the nozzle 23d of the spray gun 23 can be fixed while the cylinder head 12 is rotated and swung, or the cylinder head 12 and the nozzle 23d of the spray gun 23 can be rotated and swung together.

[0055] Next, a method for manufacturing the cylinder head 12 including the valve seat films 16 b and 17 b will be described. Figure 4This is a process diagram illustrating the valve processing steps of the method for manufacturing the cylinder head 12 according to this embodiment. As shown in this diagram, the method for manufacturing the cylinder head 12 according to this embodiment includes a casting step S1, a cutting step S2, a covering step S3, and a finishing step S4. For simplicity of description, processing steps other than those for the valve area are omitted.

[0056] In the casting step S1, an aluminum alloy for casting is poured into a mold containing a sand core, and a cylinder head blank 3 is cast, with the intake port 16, exhaust port 17, and other components formed in the main body. Here, the cylinder head blank 3 is a semi-finished product in the process of being processed into the final cylinder head 12. The intake port 16 and exhaust port 17 are formed by the sand core, and the recess 12b is formed by the mold. Figure 5 This is a perspective view of the cylinder head blank 3, cast in the casting step S1, as viewed from the side of the mounting surface 12a attached to the cylinder block 11. The cylinder head blank 3 has four recesses 12b and two intake ports 16 and two exhaust ports 17 provided in each recess 12b. The two intake ports 16 and two exhaust ports 17 in each recess 12b are integrated into a single channel within the cylinder head blank 3 and communicate with openings provided on both side surfaces of the cylinder head blank 3.

[0057] Figure 6A It is along the cylinder head blank 3 Figure 5 The cross-sectional view taken along line VI-VI of FIG. 1 shows the air intake port 16. The air intake port 16 is provided with a circular opening 16a exposed in the recess 12b of the cylinder head blank 3.

[0058] In the next cutting step S2, the cylinder head blank 3 is subjected to milling processing by an end mill, a ball end mill, etc. Figure 6B As shown, an annular valve seat portion 16 c is formed at the opening portion 16 a of the intake port 16 . Figure 6B It means that in the cutting process Figure 6A 16a. The annular valve seat portion 16c is an annular groove that forms the base shape of the valve seat film 16b and is formed on the outer periphery of the opening 16a. In this embodiment, the annular valve seat portion 16c is used as the film-forming portion.

[0059] In the manufacturing method of the cylinder head 12 of this embodiment, as shown in FIG. Figure 6C and Figure 6F As shown, a coating is formed by spraying raw material powder P along the annular valve seat portion 16c by cold spraying, and the valve seat film 16b is processed based on this coating. Therefore, the annular valve seat portion 16c is formed to be slightly larger than the valve seat film 16b.

[0060] The valve seat formed by the cold spray method has the advantages of excellent heat resistance and wear resistance and can obtain high thermal conductivity. On the other hand, it is required to have a tight fit and high strength to withstand the knock input from the intake and exhaust valves in the combustion chamber 15. Therefore, in the manufacturing method of the cylinder head 12 of this embodiment, Figure 6C As shown, the cross section of the annular valve seat portion 16 c facing the nozzle 23 d of the spray gun 23 of the cold spray device 2 along the radial direction is formed into a groove shape.

[0061] Figures 7A to 7C This is an enlarged cross-sectional view of the radial cross-sectional shape of the annular valve seat portion 16c. The radial direction of the annular valve seat portion refers to a direction perpendicular to the edge of the annular valve seat portion 16c formed along the circumferential direction of the opening portion 16a of the intake port 16. The cross-sectional shape along the radial direction specifically refers to the cross-sectional shape along the radial direction. Figure 6F The cross-sectional shape along line VII-VII is shown.

[0062] like Figure 7A As shown, in this embodiment, the radial cross-section of the annular valve seat portion 16c is machined to form a recess relative to the cylinder head blank 3. More specifically, the portion facing the nozzle 23d of the spray gun 23 of the cold spray device 2 is formed into a groove shape consisting of a flat bottom surface G1 and a pair of adjacent side surfaces G2. As a result, the compressive residual stress of the metal film 5 formed by cold spraying acts on the pair of side surfaces G2 of the groove shape, enabling the manufacture of a cylinder head 12 having a valve seat film 16b with excellent adhesion and high strength.

[0063] For example, in Figure 9 In the comparative example shown in FIG. 2 , where the portion facing the nozzle 23d of the spray gun 23 of the cold spray device 2 is the flat annular valve seat 16c, the compressive residual stress (black arrow) of the metal film 5 acts on the bottom surface of the metal film 5. Meanwhile, the impact load (open arrow) caused by the valve knock input is concentrated on the edge of the valve seat film 16b. As a result, cracks develop near the edge of the valve seat film 16b, or the film peels off as wear progresses.

[0064] In contrast, Figure 8As shown, according to the groove-shaped annular valve seat portion 16c of this embodiment, the compressive residual stress (black arrow) of the metal film 5 embedded in the groove acts on the groove-shaped side surfaces G2, G2, while the impact load (open arrow) from the valve is concentrated on the edge of the valve seat film 16b. The compressive residual stress of the metal film 5 acting on the groove-shaped side surfaces G2, G2 of the annular valve seat portion 16c counteracts the impact load caused by the knock input from the valve, thereby reducing the impact load concentrated on the edge of the valve seat film 16b and suppressing the occurrence of cracks or peeling in the valve seat film 16b.

[0065] Figure 7B This is an enlarged sectional view showing another embodiment of the cross-sectional shape of the annular valve seat portion 16c along the radial direction. In this embodiment, the interface GC between the flat bottom surface G1 and the adjacent side surfaces G2, G2 in the groove shape of the annular valve seat portion 16c is formed into a gentle arc shape. When the interface GC between the flat bottom surface G1 and the side surfaces G2, G2 is a sharp shape, the impact load caused by the knock input from the valve is concentrated on the ridge line between the flat bottom surface G1 and the side surfaces G2, G2. In contrast, when the interface GC between the flat bottom surface G1 and the side surfaces G2, G2 is formed into a gentle arc shape, the impact load caused by the knock input from the valve is dispersed on the curved surface, which alleviates the concentration of stress and thus enables the formation of a valve seat membrane 16b with higher strength.

[0066] Furthermore, the intersection GC between the flat bottom surface G1 and the side surfaces G2, G2 of the groove of the annular valve seat portion 16c is formed into a gentle arc shape, allowing the raw material powder P sprayed by cold spraying to uniformly adhere to the surface of the intersection GC. This improves the adhesion of the valve seat film 16b formed on the annular valve seat portion 16c.

[0067] Figure 7C is a cross-sectional view showing the groove angle Gθ in the groove shape of the annular valve seat portion 16c. Figure 10 Graph showing the relationship between stress acting on the valve seat film 16b and the groove angle Gθ. The groove angle Gθ is the acute side of the dihedral angle formed by the flat bottom surface G1 and one side surface G2 in the groove shape of the annular valve seat portion 16c.

[0068] like Figure 10 As shown, the smaller the groove angle Gθ in the groove shape of the annular valve seat portion 16c is, the smaller the impact load ( Figure 8As the groove angle Gθ increases (shown by the hollow arrow), the impact load concentrated on the edge of the valve seat diaphragm 16b decreases. When the groove angle Gθ is less than 30°, cracks may form in the valve seat diaphragm 16b. Therefore, the groove angle Gθ of the annular valve seat portion 16c is preferably ≥ 30° as the threshold for forming a valve seat that guarantees performance as a finished engine product.

[0069] On the other hand, as the groove angle Gθ in the groove shape of the annular valve seat portion 16c decreases, the compressive residual stress ( Figure 8 The smaller the groove angle Gθ is (black arrow), the larger the groove angle Gθ is, and the greater the compressive residual stress acting on the edge of the valve seat film 16b is. Thus, the larger the groove angle Gθ is, the better the tightness of the valve seat film 16b is. However, after the annular valve seat portion 16c is formed and the raw material powder P is sprayed by cold spraying to form a coating, in the finishing process S4 described later, a ball end mill is inserted into the air intake port 16 to cut the inner peripheral surface of the opening portion 16a side. At this time, if the groove angle Gθ>45°, the following undesirable situation occurs: the ball end mill interferes with the edge of the valve seat film 16b, and mechanical processing cannot be performed. Therefore, as a value of the groove angle of the annular valve seat portion 16c that is not restricted by finishing, the preferred groove angle Gθ≤45°.

[0070] In this manner, by setting the groove angle Gθ in the groove shape of the annular valve seat portion 16c to 30° ≤ groove angle Gθ ≤ 45°, it is possible to avoid restrictions in the manufacturing process after film formation, suppress the occurrence of cracks caused by the concentration of impact loads on the edge portion of the valve seat film 16b, and form a valve seat film 16b with higher strength.

[0071] In addition, the groove angle Gθ in the groove shape needs to be set to 30°≤groove angle Gθ≤45° only on one side of the tool in the radial direction. The opposite side is not restricted during processing and can be outside this range.

[0072] Back to Figure 4 In the covering process S3, the cold spraying device 2 of this embodiment is used to spray the raw material powder P onto the annular valve seat portion 16c of the cylinder head blank 3 to form the valve seat film 16b. More specifically, in the covering process S3, as shown in FIG. Figure 6C As shown, the cylinder head blank 3 is fixed, while the spray gun 23 is rotated so as to keep the annular valve seat portion 16c and the nozzle 23d of the spray gun 23 in the same posture and at a certain distance, while blowing the raw material powder P to the entire circumference of the annular valve seat portion 16c. Figure 6C It means in Figure 6B sectional view showing a state where the intake port 16 is formed with the valve seat film 16b.

[0073] The tip of the nozzle 23d of the spray gun 23 is held by the hand of an industrial robot above the cylinder head 12, which is fixed to the base. The base or the industrial robot positions the cylinder head 12 or the spray gun 23 so that the central axis Z of the air intake port 16, where the valve seat film 16b is to be formed, is perpendicular and coincides with the rotation axis of the spray gun 23. In this position, the spray gun 23 rotates about its rotation axis while spraying raw material powder P from the nozzle 23d toward the annular valve seat portion 16c, thereby forming a film around the entire circumference of the annular valve seat portion 16c.

[0074] During this covering step S3, nozzle 23d introduces refrigerant supplied from refrigerant circulation circuit 27 into the flow path through refrigerant inlet 23e. The refrigerant cools nozzle 23d while flowing from the leading end toward the trailing end of the flow path formed within nozzle 23d. Refrigerant that has reached the trailing end of the flow path is discharged from the flow path through refrigerant discharge portion 23f and recovered.

[0075] After the spray gun 23 completes one rotation around its axis of rotation and the valve seat film 16b is formed, the rotation of the spray gun 23 is temporarily stopped. During this period of rotational inactivity, the industrial robot equipped with the spray gun 23 moves the spray gun 23 so that the center axis Z of the next intake port 16, where the valve seat film 16b is to be formed, aligns with the reference axis of the industrial robot. After the movement of the spray gun 23 by the industrial robot is completed, the rotation of the spray gun 23 is resumed to form the valve seat film 16b on the next intake port 16. This operation is repeated until the valve seat films 16b and 17b are formed on all intake ports 16 and exhaust ports 17 of the cylinder head blank 3.

[0076] Figure 11 This is a cross-sectional view showing the relationship between the film thickness of the valve seat film 16b of the cylinder head 12 of the present invention and the shear force generated by the combustion pressure of the engine. The shear force (slashed arrow) generated by the combustion pressure (open arrow) generated by the combustion chamber 15 acts outwardly on the valve seat film 16b, and the stress is concentrated on the edge. Figure 11 As shown in FIG. 1 , when the annular valve seat portion 16c is formed into a groove shape and the film thickness W of the valve seat film 16b is large, the shear force generated by the combustion pressure acts mainly on the side surfaces G2, G2 of the groove shape of the annular valve seat portion 16c. Figure 12 As shown in the comparative example, when the annular valve seat portion 16c is flat and the film thickness W of the valve seat film 16b is small, the shear force (hatched arrow) generated by the combustion pressure (open arrow) acts on the entire bottom surface of the valve seat film 16b.

[0077] The valve seat film 16b formed by the groove shape of the annular valve seat portion 16c of this embodiment allows the side surfaces G2, G2 of the groove shape to withstand shear forces acting on the valve seat film 16b due to engine combustion pressure. While the thickness W of the valve seat film 16b is not particularly limited, the thickness W of the groove shape of the annular valve seat portion 16c suitable for this embodiment is preferably 300 μm to 1500 μm. This allows the side surfaces G2, G2 of the groove shape to withstand shear forces generated by combustion pressure tending to concentrate on the edges of the valve seat film 16b, thereby enabling the manufacture of a cylinder head equipped with a valve seat film 16b having higher strength.

[0078] Back to Figure 4 In the finishing process S4, the valve seat films 16b, 17b, the intake port 16, and the exhaust port 17 are finished. In the finishing of the valve seat films 16b, 17b, the surfaces of the valve seat films 16b, 17b are cut by milling using a ball end mill, and the valve seat film 16b is adjusted to a predetermined shape. In addition, in the finishing of the intake port 16, the ball end mill is inserted into the intake port 16 from the opening 16a, and the valve seat film 16b is cut along the opening 16a. Figure 6D The processing line PL shown cuts the inner peripheral surface of the air intake port 16 on the side of the opening portion 16 a. Figure 6D This is a cross-sectional view of the intake port having the valve seat film 16b formed therein. The processing line PL indicates the range where the excess film SF, which is deposited by the raw material powder P scattered within the intake port 16, forms a relatively thick layer. More specifically, this is the range where the excess film SF forms to a degree thick enough to affect the intake performance of the intake port 16.

[0079] In this manner, the surface roughness of the air intake port 16 caused by casting can be eliminated in the finishing step S4 , and the excess coating SF formed in the coating step S3 can be removed. Figure 6E Yes Figure 4 A cross-sectional view of the intake port 16 after the finishing process. Similarly to the intake port 16, the exhaust port 17 is formed by forming a small-diameter portion into the exhaust port 17 by casting, forming an annular valve seat portion by cutting, cold spraying the annular valve seat portion, and finishing the process to form a valve seat film 17b. Therefore, a detailed description of the steps for forming the valve seat film 17b relative to the exhaust port 17 will be omitted.

[0080] As described above, according to the cylinder head blank and the cylinder head manufacturing method of this embodiment, the radial cross-sectional shape of the annular valve seat portion 16c is formed into a groove shape consisting of a flat bottom surface G1 and a pair of adjacent side surfaces G2, and the compressive residual stress of the metal film 5 acts on the pair of side surfaces G2 of the groove shape. Therefore, it is possible to manufacture a cylinder head 12 having a valve seat film 16b with excellent sealing properties and high strength.

[0081] Furthermore, according to the cylinder head blank and the cylinder head manufacturing method of the present embodiment, the compressive residual stress of the metal film 5 acting on the groove-shaped side surfaces G2, G2 of the annular valve seat portion 16c counteracts the impact load caused by the knock input from the valve, thereby reducing the impact load concentrated on the edge portion of the valve seat film 16b, and suppressing the occurrence of cracks or peeling in the valve seat film 16b.

[0082] Furthermore, according to the cylinder head blank and the cylinder head manufacturing method of the present embodiment, the interface GC between the flat bottom surface G1 and the side surfaces G2 and G2 in the groove shape of the annular valve seat portion 16c is formed into a gentle arc shape, thereby dispersing the impact load caused by the knock input from the valve on the curved surface and alleviating the concentration of stress, thereby enabling the formation of a valve seat membrane 16b having higher strength.

[0083] Furthermore, according to the cylinder head blank and the cylinder head manufacturing method of the present embodiment, the interface GC between the flat bottom surface G1 and the side surfaces G2 and G2 in the groove shape of the annular valve seat portion 16c is formed into a gentle arc shape, so that the raw material powder P sprayed by the cold spraying method is uniformly adhered to the surface of the interface GC, thereby improving the tightness of the valve seat film 16b formed on the annular valve seat portion 16c.

[0084] Furthermore, according to the cylinder head blank and the cylinder head manufacturing method of the present embodiment, the acute angle side of the dihedral angle formed by the flat bottom surface G1 and the side surface G2 on one side in the groove shape of the annular valve seat portion 16c, i.e., the groove angle Gθ is set to 30°≤groove angle Gθ≤45°. Therefore, it is possible to avoid being restricted in the manufacturing process after film formation, suppress the occurrence of cracks caused by the concentration of impact loads on the edge portion of the valve seat film 16b, and form a valve seat film 16b with higher strength.

[0085] In addition, the groove angle Gθ in the groove shape needs to be set to 30°≤groove angle Gθ≤45° only on one side of the tool in the radial direction. The opposite side is not restricted during processing and can be outside this range.

[0086] Furthermore, according to the cylinder head blank and the cylinder head manufacturing method of the present embodiment, the valve seat film 16b has a film thickness W of 300 μm to 1500 μm, and the groove-shaped side surfaces G2, G2 can be utilized to withstand the shear force generated by the combustion pressure that tends to be concentrated on the edge portion of the valve seat film 16b. Therefore, a cylinder head having a valve seat film 16b having higher strength can be manufactured.

[0087] Description of Reference Numerals

[0088] 1. Internal combustion engine; 11. Cylinder block; 11a. Cylinder; 12. Cylinder head; 12a. Mounting surface; 12b. Recess; 12c, 12d. Side; 13. Piston; 13a. Connecting rod; 13b. Top surface; 14. Crankshaft; 15. Combustion chamber; 16. Intake port; 16a. Opening; 16b. Valve seat diaphragm; 16c. Annular valve seat; 17. Exhaust port; 17a. Opening; 17b. Valve seat membrane; 18, intake valve; 18a, valve stem; 18b, valve head; 18c, valve guide; 19, exhaust valve; 19a, valve stem; 19b, valve head; 19c, valve guide; 2, cold spray device; 21, gas supply unit; 21a, compressed gas cylinder; 21b, working gas pipeline; 21c, delivery gas pipeline; 21d, pressure regulator; 21e, flow control valve; 21f , flow meter; 21g, pressure gauge; 21h, power source; 21i, heater; 22, raw material powder supply part; 22a, 221a, 222a, raw material powder supply device; 22b, metering device; 22c, 221c, 222c, raw material powder supply pipeline; 22d, partition; 23, spray gun; 23a, chamber; 23b, pressure gauge; 23c, thermometer; 23d, nozzle; 23e, refrigerant inlet part; 23f, refrigerant discharge part; 23g, 23h, signal line; 27, refrigerant circulation circuit; 271, tank; 272, pump; 273, cooler; 274, inlet pipe; 275, discharge pipe; 3, cylinder head blank; 4, substrate; 5, metal film; G1, bottom surface; G2, side surface; GC, interface; Gθ, groove angle; P, raw material powder; SF, excess coating.

Claims

1. A cylinder head blank, wherein: The cylinder head blank has the following features in the main body: a port for air intake or exhaust, having an opening; a film-forming portion formed along an annular edge of the opening; as well as a metal film formed on the film-forming portion, The cross section of the film-forming portion along the radial direction of the opening is formed into a groove shape including a flat bottom surface, a pair of side surfaces adjacent to the bottom surface, and an arc-shaped interface connecting the bottom surface and the pair of side surfaces. Compressive residual stress of the metal film acts on the pair of side surfaces.

2. The cylinder head blank according to claim 1, wherein: The groove angle, which is an acute side of a dihedral angle formed by the bottom surface and any one of the pair of side surfaces, is 30 to 45 degrees.

3. The cylinder head blank according to claim 1 or 2, wherein: The metal film formed on the film formation portion has a thickness of 300 μm to 1500 μm.

4. A method for manufacturing a cylinder head, wherein: A cylinder head blank is manufactured, wherein the cylinder head blank has: a port for intake or exhaust having an opening; and a film-forming portion formed on an annular edge along the opening; The cross section of the film-forming portion along the radial direction of the opening is formed into a groove shape including a flat bottom surface, a pair of side surfaces adjacent to the bottom surface, and an arc-shaped interface connecting the bottom surface and the pair of side surfaces; A metal film is formed by spraying a raw material powder onto the film formation portion through a nozzle by a cold spray method, and compressive residual stress of the metal film acts on the pair of side surfaces.

5. The method for manufacturing a cylinder head according to claim 4, wherein: The groove angle, which is an acute side of a dihedral angle formed by the bottom surface and any one of the pair of side surfaces, is formed to be 30 to 45 degrees.

6. The method for manufacturing a cylinder head according to claim 4 or 5, wherein: The metal film is formed on the film formation portion to have a film thickness of 300 μm to 1500 μm.

Images