Hollow engine valve and method of manufacturing the same

Abstract

A hollow engine valve 100 having a shaft portion 111 and a petal portion 113 which is expanded in diameter in an umbrella shape at a base end of the shaft portion 111, into which a cooling material is enclosed in a hollow portion 115 provided at least in the inside of the shaft portion 111, wherein the shaft portion 111 has a first shaft portion 111a on a tip end side, a second shaft portion 111b on a base end side which is larger in outer diameter than the first shaft portion 111a, and a step portion 111c which is formed by the difference in outer diameter between the first shaft portion 111a and the second shaft portion 111b, and the wall thickness t2 of the step portion 111c is thicker than the wall thickness t1 of the second shaft portion 111b.

Description

Technical Field

[0001] This invention relates to hollow engine valves and their manufacturing methods. Background Technology

[0002] Previously, in engine valves used to allow intake gas to flow into the combustion chamber of engines for motor vehicles, ships, etc., and to allow exhaust gas to be discharged, there were hollow engine valves (hereinafter also referred to as engine valves) with hollow interiors designed to seal in cooling materials such as metallic sodium to suppress temperature rise (see Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-190759 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, with the stricter restrictions on CO2 exhaust gas and the resulting increase in combustion temperature, the valve neck temperature in such a hollow engine will also rise, raising concerns about insufficient strength.

[0008] The present invention was made in view of the above-mentioned problems, and its object is to provide a hollow engine valve with improved shaft strength and a method for manufacturing the same.

[0009] means for solving problems

[0010] (1) A first aspect of the present invention is a hollow engine valve having a shaft portion and an umbrella portion that expands in the shape of an umbrella at the base end of the shaft portion, wherein cooling material is sealed in a hollow portion provided at least inside the shaft portion, wherein the shaft portion has: a first shaft portion on the front end side; a second shaft portion on the base end side, the outer diameter of which is larger than the outer diameter of the first shaft portion; and a stepped portion formed by the difference in the outer diameters of the first shaft portion and the second shaft portion, wherein the wall thickness of the stepped portion is greater than the wall thickness of the second shaft portion.

[0011] According to the structure described in (1) above, it is possible to increase the strength relative to the bending stress on the step portion.

[0012] (2) A second aspect of the present invention is a hollow engine valve having a shaft portion and an umbrella portion that expands in the shape of an umbrella at the base end of the shaft portion, wherein cooling material is sealed in a hollow portion provided at least inside the shaft portion, wherein the shaft portion has: a main shaft portion at a front end side; and a neck portion that is continuous with the umbrella portion and has an outer diameter larger than the outer diameter of the main shaft portion, the neck portion having a wall thickness greater than the wall thickness of the main shaft portion, and the hollow portion being provided with a constant inner diameter at least throughout the main shaft portion and the neck portion.

[0013] Based on the structure described in (2) above, the strength of the neck can be improved, and the movement of the cooling material inside the hollow part can be made smoother.

[0014] (3) A third aspect of the present invention is a method for manufacturing a hollow engine valve, the hollow engine valve comprising: a shaft portion having a first shaft portion and a second shaft portion, the second shaft portion being continuous with the first shaft portion and having an outer diameter larger than the outer diameter of the first shaft portion; an umbrella portion having an umbrella-shaped expansion at one end of the second shaft portion; and a hollow portion being hollow inside at least the shaft portion, wherein the manufacturing method comprises: a first step, in which a cylindrical portion having the same outer diameter as the second shaft portion and being cylindrical in shape is formed by forging and drilling a raw material made of special steel, and an umbrella portion having the same shape as the umbrella portion being formed at one end of the cylindrical portion. The process involves forming a semi-finished umbrella-shaped part, and a second step in which the cylindrical part in the semi-finished part is reduced in diameter by means of deep drawing, thereby forming the shaft portion. In the second step, the cylindrical part is reduced in diameter up to a predetermined specific position in the axial direction of the cylindrical part, thereby making the reduced-diameter portion the first shaft portion, the unreduced-diameter portion the second shaft portion, and the portion formed by reducing the diameter together with the first shaft portion and by the difference in the outer diameters of the first shaft portion and the second shaft portion a stepped portion. The wall thickness of the reduced-diameter first shaft portion and the wall thickness of the stepped portion are greater than the wall thickness of the second shaft portion.

[0015] Based on the structure described in (3) above, it is possible to manufacture hollow engine valves with a shaft portion that has increased strength.

[0016] (4) A fourth aspect of the present invention is a method for manufacturing a hollow engine valve, the hollow engine valve comprising: a shaft portion; a canopy portion having an umbrella-shaped expansion at the base end of the shaft portion; a neck portion being continuous with the canopy portion at the base end of the shaft portion, and having an outer diameter larger than the outer diameter of the shaft portion; and a hollow portion being at least disposed inside the shaft portion and having a predetermined specific diameter, wherein the manufacturing method comprises: a first step, in which a semi-finished part having a cylindrical portion having an opening at the front end and an umbrella-shaped expansion at the base end of the cylindrical portion is formed by forging and drilling a raw material made of special steel; and a second step, in which a semi-finished part having ... third step, in which a semi-finished part having an opening at the front end and an umbrella-shaped expansion at the base end of the cylindrical portion is formed by forging and drilling a raw material made of special steel; and a fourth step, in which a semi-finished part having an opening at the front end and an umbrella-shaped expansion at the base end of the cylindrical portion is formed by forging and drilling a raw material made of special steel; and a fifth step, in which a semi-finished part having an opening at the front end and an umbrella-shaped expansion at the base end of the cylindrical portion is formed by forging and drilling a raw material made of special steel; and a sixth step, in which a semi-finished part having an opening at the front end and an umbrella-shaped expansion at the base end of the cylindrical portion is formed by forging and drilling a semi-finished part. The cylindrical portion is reduced in diameter by deep drawing, thereby forming the shaft portion and the neck. In the first step, a neck tapered portion, which is thicker than the wall thickness of the cylindrical portion and decreases in diameter exponentially towards the front end, is formed at the base end side of the cylindrical portion. The second step includes: a first forming, in which the outer diameter of the cylindrical portion including the neck tapered portion is reduced to the point where the inner diameter of the neck tapered portion becomes the specific diameter, thereby forming the neck of the semi-finished product; and a second forming, in which the outer diameter of the cylindrical portion near the front end side of the neck of the semi-finished product is reduced to the point where the inner diameter of the cylindrical portion becomes the specific diameter, thereby making the reduced diameter portion the shaft portion and the unreduced diameter portion the neck portion.

[0017] Based on the structure described in (4) above, it is possible to manufacture a hollow engine valve that improves the strength of the neck and allows for smooth movement of the cooling material within the hollow section.

[0018] Invention Effects

[0019] According to the present invention, it is possible to manufacture hollow engine valves with improved shaft strength. Attached Figure Description

[0020] Figure 1 This is a longitudinal sectional view of the hollow engine valve in the first embodiment.

[0021] Figure 2 This is a schematic diagram illustrating the manufacturing process of hollow engine valves in the same way.

[0022] Figure 3 This is a schematic diagram illustrating the manufacturing process of hollow engine valves in the same way.

[0023] Figure 4 This is a longitudinal sectional view of the hollow engine valve in the second embodiment.

[0024] Figure 5 This is a schematic diagram illustrating the manufacturing process of hollow engine valves in the same way.

[0025] Figure 6 This is a schematic diagram illustrating the manufacturing process of hollow engine valves in the same way. Detailed Implementation

[0026] The following is for reference Figures 1-6 The present invention will be described in detail through one embodiment of the invention, but the following embodiments are examples and are not intended to limit the invention involved in the technical solutions.

[0027] (First Implementation)

[0028] Reference Figures 1-3 The first embodiment will be described below. Furthermore, regarding the direction of the hollow engine valve 100 in this embodiment, ... Figure 1 The direction of the engine valve 100 (valve umbrella 110) (for example, with the front end side (shaft end member 120 side) of the shaft 111 as the top and the base end side (umbrella 113 side) of the shaft 111 as the bottom) as the bottom will be described with reference to the direction of the engine valve 100 (valve umbrella 110).

[0029] (Hollow engine valve 100)

[0030] Hollow engine valves (hereinafter referred to as engine valves) 100 are valve cores disposed inside the intake port and exhaust port of an engine (not shown) in a motor vehicle or the like, which are located in the cylinder head and communicate with the combustion chamber. During engine operation, they move vertically to open and close the intake port and exhaust port. By opening the intake port, the engine valves 100 supply intake gas into the combustion chamber, and by opening the exhaust port, they discharge exhaust gas from the combustion chamber to the outside of the combustion chamber.

[0031] like Figure 1 As shown, the engine valve 100 includes a valve umbrella portion 110 as the main body and a shaft end member 120 as the cover portion.

[0032] The valve umbrella portion 110 includes a cylindrical shaft portion 111 and an umbrella portion 113 that is continuous with the lower end of the shaft portion 111, concentrically facing downwards, and has an umbrella-shaped expanded diameter.

[0033] The shaft portion 111 has an upper first shaft portion 111a and a lower second shaft portion 111b with an outer diameter larger than that of the first shaft portion 111a. Between the first shaft portion 111a and the second shaft portion 111b, there is a tapered stepped portion 111c that gradually narrows upward in order to connect the two shaft portions 111a and 111b with different outer diameters.

[0034] Inside the shaft portion 111 of the valve umbrella portion 110, there is a bottomed hollow portion 115 with an opening at the top. The hollow portion 115, that is, the inner shape of the valve umbrella portion 110, is roughly similar to the outer shape of the first shaft portion 111a and the second shaft portion 111b. Specifically, the inner diameter Φd' of the first shaft portion 111a is set to be smaller than the inner diameter Φd of the second shaft portion 111b, and the hollow portion 115 in the stepped portion 111c (the inner shape of the stepped portion 111c) becomes a cone shape that gradually narrows upwards.

[0035] like Figure 1 As shown, the thickness t3 (e.g., 1.6 mm) of the first shaft portion 111a and the thickness t2 (e.g., 1.6 mm) of the step portion 111c are thicker than the thickness t1 (e.g., 1.0 mm) of the second shaft portion 111b (t3 = t2 > t1).

[0036] Therefore, in the shaft portion 111, when the engine is running, by setting the engine valve, the strength of the step portion 111c generated by the maximum bending stress can be improved, and the deterioration and damage of the engine valve 100 can be suppressed.

[0037] After introducing getter material such as titanium (not shown) and cooling material such as metallic sodium into the hollow portion 115, the opening of the shaft portion 111 is sealed by engaging (e.g., friction pressing) and fixing the shaft end member 120 to the upper end of the shaft portion 111. Thus, the hollow portion 115 is closed, and the cooling material is sealed inside. As a result, the shaft end member 120 is formed integrally with the shaft portion 111 (and cannot be separated), the shaft portion 111 is formed, and the engine valve 100, sealed with the cooling material, is completed.

[0038] In addition, as needed, heat-insulating coatings can be applied to all or part of the engine valve 100 (part or all of the umbrella portion 113, all or part of the shaft portion 111), for example by a metal with low thermal conductivity such as ceramic, or surface treatments such as nitriding or grinding can be applied.

[0039] (Manufacturing method of valve umbrella 110 in engine valve 100)

[0040] Roughly speaking, the forming process of the valve umbrella 110 consists of the first process of forming a semi-finished part 300 from a solid round bar 10 (see reference). Figure 2 ), and the second process of forming the valve umbrella part 110 from the semi-finished part 300 (refer to Figure 3 )composition.

[0041] like Figure 2As shown in (4), the semi-finished part 300 has a cylindrical part 301 before machining of the shaft part 111 in the valve umbrella part 110, a cylindrical hole 305 before machining of the hollow part 115 in the valve umbrella part 110, and an umbrella-shaped part 303 before machining of the umbrella part 113 in the valve umbrella part 110.

[0042] Regarding the cylindrical portion 301, the outer diameter is ΦD (e.g., φ7mm), the inner diameter (aperture) is Φd (e.g., φ5mm), and the thickness is t1 (e.g., 1.0mm), forming a straight cylindrical shape. Furthermore, the umbrella-shaped portion 303 has the same shape as the umbrella portion 113.

[0043] (First process)

[0044] In this embodiment, in the first step, by... Figure 2 The extrusion process shown in (1) is, for example, the extrusion of a solid round bar 10 made of special steel in the form of a cylindrical shape, such as... Figure 2 As shown in (2), the extruded solid bar 20 is formed by providing a semi-finished shaft portion 21 that is partially reduced in diameter to correspond to the shaft portion 111 of the engine valve 100, and a head 23 whose outer diameter is larger than that of the semi-finished shaft portion 21. Furthermore, by forging the extruded solid bar 20, a structure is formed that... Figure 2 The umbrella-shaped portion 33 is formed by expanding the diameter of the head 23 of the extruded solid rod 20 shown in (3), and by shortening the axial dimension of the semi-finished shaft portion 21 and providing the expanded diameter solid shaft 31, thus forming the umbrella-shaped solid rod 30. Furthermore, in the extrusion and forging processes of the first step, the workpiece is loaded into the die K provided with the downwardly concave forming portion S, and the workpiece is formed by pressing it from a position above the stamping device (not shown) provided with the punch P. Further, by... Figure 2 The hole-making process performed on the solid shaft 31 after the umbrella-shaped solid rod 30 is flipped up and down as shown in (3), such as Figure 2 As shown in (4), for example, a cylindrical portion 301 is provided by drilling a bottomed cylindrical hole 305 along the axial direction by drilling M, thereby forming a semi-finished part 300. In addition, the shape of the umbrella-shaped portion 303 of the semi-finished part 300 is the same as that of the umbrella-shaped portion 33 of the solid rod 30 with an umbrella, and the outer diameter of the cylindrical portion 301 is the same as that of the solid shaft 31.

[0045] Furthermore, regarding the first step of this embodiment, the extrusion process can be omitted. Additionally, a cylindrical hole 305 can be provided before the umbrella-shaped portion 33 is formed. The forming of this cylindrical hole 305 can be done without drilling or other hole-making processes. For example, one end of the solid round rod 10 can be formed into a wine glass shape by forging, and then the outer wall can be straightened by deep drawing, thus proceeding in stages.

[0046] (Second process)

[0047] like Figure 3 As shown, in the second process, the cylindrical portion 301 is reduced in diameter in stages by using multiple dies 51, 52, and 53 (hereinafter collectively referred to as dies 51 to 53) for cold forging to form the valve umbrella portion 110. Furthermore, the number (type) of dies can be appropriately increased or decreased depending on the number of processes, etc.

[0048] Dies 51-53 have a through forming hole 50. The forming hole 50 has: a reduced diameter portion 50a with a constant inner diameter; and a tapered portion 50b that expands downward from the lower end of the reduced diameter portion 50a. The reduced diameter portion 50a can reduce the diameter of the cylindrical portion 301 of the semi-finished part 300 to form the first shaft portion 111a of the valve umbrella portion 110, and the tapered portion 50b can form the stepped portion 111c of the valve umbrella portion 110.

[0049] Dies 51 to 53 are configured in the second process according to the progress of the process, and the relationship between the inner diameters of each forming hole 50 (reduced diameter portion 50a and tapered portion 50b) is: die 51 > die 52 > die 53.

[0050] In the second process, by making Figure 3 As shown in (1), the die 51 reciprocates from above the semi-finished part 300, with the middle position (specific position) C of the semi-finished part 300 as the turning point, thereby causing... Figure 3 The semi-finished part 320 shown in (2) is formed, and further, through the reciprocating motion of the die 52, the semi-finished part 320 is formed. Figure 3 The semi-finished part 330 shown in (3) is formed, and finally, through the reciprocating motion of the die 53, the semi-finished part 330 is formed. Figure 3 The valve umbrella portion 110 shown in (4) is formed. In addition, the intermediate position C can be appropriately changed according to the specifications of the engine valve.

[0051] Specifically, Figure 3 The semi-finished part 320 shown in (2) is made by causing the semi-finished part 320 to be in Figure 3 The inner and outer diameters of the semi-finished part 300 shown in (1) are reduced, and the wall thickness is increased (hereinafter referred to as thickening), and it is extended in the axial direction to form the semi-finished first shaft part 321a, the semi-finished stepped part 321c and the semi-finished hollow part 325 with steps.

[0052] in addition, Figure 3The semi-finished part 330 shown in (3) is obtained by further reducing the inner and outer diameters of the semi-finished first shaft portion 321a and the semi-finished stepped portion 321c of the semi-finished part 320 in the previous process, thickening the walls, and extending them in the axial direction, so as to form the semi-finished first shaft portion 331a, the semi-finished stepped portion 331c and the stepped hollow portion 335.

[0053] in addition, Figure 3 The valve umbrella portion 110 shown in (4) is obtained by further reducing the inner diameter and thickening the outer diameter of the semi-finished first shaft portion 331a and the semi-finished stepped portion 331c of the semi-finished part 330 in the previous process, and extending them in the axial direction, so that the first shaft portion 111a, the stepped portion 111c and the hollow portion 115 with steps are formed.

[0054] As a result, the thickness t3 of the first shaft portion 111a and the thickness t2 of the step portion 111c can be made thicker than the thickness t1 of the second shaft portion 111b of the valve umbrella portion 110.

[0055] Therefore, the strength of the step portion 111c generated by the maximum bending stress can be improved, and the deterioration and damage of the engine valve 100 can be suppressed.

[0056] On the other hand, in the second process... Figure 3 (2) Figure 3 In (3) shown, the semi-finished second shaft portions 321b and 331b, as well as the umbrella-shaped portions 323 and 333 in the semi-finished parts 320 and 330 are not formed objects, so the shape of each part is maintained. Therefore, the outer diameter ΦD and inner diameter Φd of the cylindrical portion 301, the semi-finished second shaft portions 321b and 331b, and the second shaft portion 111b, and the umbrella-shaped portions 303, 323, 333, and the umbrella portion 113 have the same shape.

[0057] (Second Implementation)

[0058] Reference Figures 4-6 The engine valve 200 of the second embodiment will be described.

[0059] Furthermore, the shape and processing method of the valve umbrella portion 210 of the engine valve 200 in this embodiment differ from those of the engine valve 100 in the first embodiment, but other structures (shaft end member 120, cooling material, etc., heat insulation coating) are common, therefore, descriptions of these common structures are omitted. Additionally, regarding the orientation of the hollow engine valve 200 in this embodiment, ... Figure 4 The direction of the engine valve 200 (valve umbrella 210) is described with reference to (for example, with the front end side (shaft end member 120 side) of the shaft 211 as the top and the base end side (umbrella 213 side) of the shaft 211 as the bottom).

[0060] like Figure 4 As shown, the valve umbrella part 210 includes a cylindrical shaft part (main shaft part) 211 and an umbrella part 213 which is continuous with the lower end of the shaft part 211, concentrically facing downwards, and formed by umbrella-shaped expansion.

[0061] A flat umbrella front surface 213a is provided on the lower end face of the umbrella portion 213, and an umbrella-shaped umbrella back surface 213b is provided on the upper surface. When the engine valve 200 is disposed in the port of the engine cylinder head, the engine valve 200 is configured such that the umbrella front surface 213a faces the combustion chamber side of the engine, and the umbrella back surface 213b faces the port side.

[0062] like Figure 4 As shown, a neck 214 is formed at the lower part of the shaft portion 211, which is continuous with the upper part of the umbrella back 213b and has an outer diameter larger than that of the shaft portion 211. Between the neck 214 and the shaft portion 211 where the neck 214 is not provided, a tapered step portion 214a is provided, which is tapered upward in order to connect the two structures 211, 214 with different outer diameters.

[0063] The thickness t5 of the neck 214 (e.g., 1.8 mm) is greater than the thickness t4 of the shaft portion 211 (e.g., 1.6 mm) (t4 < t5).

[0064] By providing a thick-walled neck 214 in the engine valve 200, the strength of the neck, where the temperature rises the most, can be increased, thus suppressing the deterioration and damage of the engine valve 200.

[0065] Inside the valve umbrella portion 210, there is an opening at the top and a hollow portion 215 is provided over the entire range from the shaft portion 211 to the umbrella portion 213. The hollow portion 215 has a bottom, and the hollow portion 215 of the shaft portion 211 (including the neck 214) has a constant inner diameter Φd2 (a specific diameter, for example, φ3mm). The hollow portion 215 of the umbrella portion 213 expands in diameter downward (towards the bottom), and the inner diameter Φd (for example, φ10mm) of the bottom 215a becomes the maximum diameter within the hollow portion 215.

[0066] Therefore, since the volume of the hollow portion 215 of the umbrella portion 213 can be ensured, a certain amount of getter material (such as titanium powder) and cooling material (such as metallic sodium) can be sealed inside the hollow portion 215. In addition, since there are no steps or the like in the hollow portion 215 of the shaft portion 211, the movement of the cooling material inside the hollow portion 215 can be made smooth, and the cooling efficiency based on the rocking effect of the engine valve 200 can be improved.

[0067] (Manufacturing method of valve umbrella 210 in engine valve 200)

[0068] The forming process of the valve umbrella 210 in this embodiment consists of the first process of forming a semi-finished part 400 from a solid round bar 10 (see reference). Figure 5 ), and the second process of forming the valve umbrella part 210 from the semi-finished part 400 (refer to Figure 6 )composition.

[0069] Figure 5 The first process shown is performed using the same steps as the first process in the first embodiment, therefore detailed description is omitted. Furthermore, regarding... Figure 5 The solid round rod 10 shown in (1) and Figure 5 The extruded solid rod 20 shown in (2) is the same as the components and method in the first embodiment, so the description is omitted.

[0070] Figure 5 The solid rod 40 with an umbrella shown in (3) is subjected to... Figure 5 In (2) shown, the extruded solid rod 20 is forged to form an umbrella-shaped portion 43 with an enlarged head 23, and a solid shaft 41 is formed by shortening and enlarging the semi-finished shaft portion 21 along the axial direction. Furthermore, on the umbrella-shaped portion 43 (base end) side of the solid shaft 41, a neck-tapered portion 44 is provided that gradually narrows from the umbrella-shaped portion 43 towards the solid shaft 41 (front end). At this time, relative to the total length R (e.g., 48 mm) of the umbrella-shaped solid rod 40, the neck-tapered portion 44 extends a distance L (e.g., 17 mm, approximately 1 / 3 of the total length R) from the umbrella-shaped portion 43's umbrella-face 43a, forming an exponentially inclined surface with a taper angle α° (e.g., 3°). Thus, the wall thickness of the neck-tapered portion 44 gradually increases towards the base end.

[0071] Furthermore, Figure 5 The semi-finished part 400 shown in (4) is processed by making Figure 5 The solid shaft 41 of the umbrella-shaped solid rod 40 shown in (3) is drilled after being flipped up and down, thereby forming a cylindrical part 401 with an inner diameter Φd. In addition, the semi-finished part 400 has the same shape as the umbrella-shaped solid rod 40, so a neck tapered part 404 with the same shape as the neck tapered part 44 is provided.

[0072] (Second process)

[0073] like Figure 6 As shown, in the second process, the cylindrical portion 401 is reduced in diameter in stages by using multiple dies 61, 62, and 63 (hereinafter collectively referred to as dies 61 to 63) for cold forging to form the valve umbrella portion 210. Furthermore, the number (type) of dies can be appropriately increased or decreased depending on the number of processes, etc.

[0074] Dies 61-63 have a through-hole 60. The through-hole 60 has: a reduced-diameter portion 60a with a constant inner diameter; and a tapered portion 60b that expands downwards from the lower end of the reduced-diameter portion 60a. Depending on the type of die, the reduced-diameter portion 60a can reduce the diameter of the cylindrical portion 401 and the tapered neck portion 404 of the semi-finished part 400 to form the shaft portion 211 and the neck portion 214 of the valve umbrella portion 210, and the tapered portion 60b can form the portion described later... Figure 6 Part of the semi-finished neck 414 of the semi-finished part 410 shown in (2), and Figure 6 The stepped portion 214a of the valve umbrella portion 210 shown in (3) is formed.

[0075] Dies 61 to 63 are configured in the second process according to the progress of the process, and the relationship between the inner diameters of each forming hole 60 (reduced diameter portion 60a and tapered portion 60b) is: die 61 > die 62 > die 63.

[0076] In the second process, by making Figure 6 The die 61 (which becomes die 62 after forging) shown in (1) moves reciprocally from above the semi-finished part 400 with the first position C1 of the semi-finished part 400 (semi-finished part 410) as the turning point, thereby causing Figure 6 The semi-finished part 410 shown in (2) is formed (hereinafter referred to as the first forming). Further, by causing the die 63 to perform a reciprocating motion with a second position C2 above the first position C1 of the semi-finished part 410 as the turning point, thereby making Figure 6 The valve umbrella portion 210 shown in (3) is formed (hereinafter referred to as the second forming). Furthermore, the second position C2 can be appropriately changed according to the specifications of the engine valve.

[0077] Specifically, the first forming is achieved through die 61 and die 62, so that... Figure 6 In the semi-finished part 400 shown in (1), the portion corresponding to the shaft portion 211 of the valve umbrella portion 210 and the portion corresponding to the neck portion 214 of the valve umbrella portion 210 (inner diameter and outer diameter) are reduced in diameter in stages, and the wall is thickened and extended in the axial direction, so that the semi-finished shaft portion 411 with an inner diameter of Φd1 and the semi-finished neck portion 414 with an inner diameter of Φd2 are formed, thereby forming the semi-finished part 410.

[0078] Through this forming stage, the neck 414 of the semi-finished product is thicker than the shaft portion 411 of the semi-finished product due to the thickness of the neck tapered portion 404 of the semi-finished product 400. In addition, the outer diameters of the shaft portion 411 and the neck 414 of the semi-finished product are formed by the die 62 to be the same as the area near the first position C1 (the range of movement of the diameter reduction portion 60a in the die 62), but the inner diameter Φd2 of the neck 414 is formed to be smaller than the inner diameter Φd1 of the shaft portion 411 by the waisted portion 415a formed by the inward waisting.

[0079] In the first forming process, the cylindrical part 401 is cold forged until the inner diameter of the neck 414 of the semi-finished product is Φd2.

[0080] Next, the second forming is achieved through die 63. Figure 6 The semi-finished part 410 shown in (2) has a further reduced diameter and thickened wall of the semi-finished shaft portion 411 (inner diameter, outer diameter) above the semi-finished neck 414, and extends in the axial direction, so that the shaft portion 211 with an inner diameter of Φd2, as well as the neck 214 and the step portion 214a are formed.

[0081] In the second forming process, the semi-finished shaft portion 411 is cold-forged until the inner diameter of the shaft portion 211 as a whole is Φd2. Furthermore, in the second process, the outer shape of the umbrella-shaped portion 403 of the semi-finished part 400 and the inner diameter Φd of the cylindrical hole 405 are respectively maintained as the outer shape of the umbrella portion 213 of the valve umbrella portion 210 and the inner diameter of the bottom 215a of the hollow portion 215.

[0082] As a result, by making the wall thickness of the neck 214 thicker than that of the shaft 211, the strength of the neck, where the temperature rises the most, can be improved in the valve umbrella portion 210 of this embodiment, thereby suppressing the deterioration and damage of the engine valve 200.

[0083] Furthermore, by gradually expanding the diameter of the hollow portion 215, which is formed over the entire range from the neck 214 to the umbrella portion 213, toward the bottom 215a, which maintains the inner diameter Φd, a certain amount of getter material (e.g., titanium powder) and cooling material (e.g., metallic sodium) can be sealed in by ensuring the capacity of the hollow portion 215.

[0084] Furthermore, by forming a constant inner diameter Φd2 in the hollow portion 215, which is formed over the entire range from the shaft portion 211 to the neck portion 214, the cooling material inside the hollow portion 215 can move smoothly during engine operation, thereby improving the cooling efficiency based on the rocking effect of the engine valve 200.

[0085] Explanation of reference numerals in the attached figures

[0086] K: Die; P: Punch;

[0087] S: Forming part;

[0088] 10: Solid round bar; 20: Extruded solid bar;

[0089] 21: Semi-finished shaft section; 23: Head;

[0090] 30: A solid rod with an umbrella; 31: A solid shaft;

[0091] 33: Semi-finished umbrella part;

[0092] 40: A solid rod with an umbrella; 41: A solid shaft;

[0093] 43: Umbrella-shaped part; 44: Neck-shaped conical part;

[0094] 50: Forming hole; 50a: Reduction section;

[0095] 50b: tapered section; 51, 52, 53: punching die;

[0096] 60: Forming hole; 60a: Reduced diameter part

[0097] 60b: tapered section; 61, 62, 63: punching die;

[0098] 100: Hollow engine valve; 110: Valve umbrella section;

[0099] 111: Shaft portion; 111a: First shaft portion;

[0100] 111b: Second shaft section; 111c: Stepped section;

[0101] 113: Umbrella section; 115: Hollow section;

[0102] 120: Shaft end component;

[0103] 210: Valve umbrella part; 211: Shaft part;

[0104] 213: Umbrella part; 214: Neck;

[0105] 215: Hollow part;

[0106] 300: Semi-finished part; 301: Cylindrical part;

[0107] 303: Umbrella-shaped part; 305: Cylindrical hole;

[0108] 320: Semi-finished part; 321a: First shaft part of semi-finished product;

[0109] 321b: Second shaft section of semi-finished product; 321c: Step section of semi-finished product;

[0110] 323: Semi-finished umbrella part; 325: Semi-finished hollow part;

[0111] 330: Semi-finished part; 331a: First shaft part of semi-finished product;

[0112] 331b: Second shaft section of semi-finished product; 331c: Step section of semi-finished product;

[0113] 333: Semi-finished umbrella part; 335: Semi-finished hollow part;

[0114] 400: Semi-finished part; 401: Cylindrical part;

[0115] 403: Umbrella-shaped part; 404: Neck-shaped conical part;

[0116] 405: Cylindrical hole; 410: Semi-finished part;

[0117] 411: Semi-finished shaft section.

Claims

1. A hollow engine valve having a shaft portion and an umbrella-shaped, expanded portion at the base end of the shaft portion, wherein cooling material is sealed within a hollow portion disposed at least inside the shaft portion, characterized in that, The shaft portion has: a first shaft portion on the front end side; a second shaft portion on the base end side, the outer diameter of which is larger than the outer diameter of the first shaft portion; and a stepped portion formed by the difference in the outer diameters of the first shaft portion and the second shaft portion. The wall thickness of the first shaft portion and the stepped portion is greater than the wall thickness of the second shaft portion.

2. A method for manufacturing a hollow engine valve, the hollow engine valve comprising: a shaft portion having a first shaft portion and a second shaft portion, the second shaft portion being continuous with the first shaft portion and having an outer diameter larger than the outer diameter of the first shaft portion; an umbrella portion having an umbrella-shaped expansion at one end of the second shaft portion; and a hollow portion being hollow inside at least the shaft portion, characterized in that, The manufacturing method includes: a first step, in which a cylindrical portion having the same outer diameter as the second shaft portion and being cylindrical in shape, and an umbrella-shaped portion having the same shape as the umbrella portion at one end of the cylindrical portion, are formed by forging and drilling a raw material made of special steel; and a second step, in which the diameter of the cylindrical portion in the semi-finished part is reduced by deep drawing, thereby forming the shaft portion. In the second step, the cylindrical portion is reduced in diameter up to a predetermined specific position along its axial direction. This reduces the diameter of the cylindrical portion to become the first shaft portion, and the unreduced portion becomes the second shaft portion. The portion formed by the reduction in diameter along with the first shaft portion, and the difference in outer diameter between the first and second shaft portions, becomes a stepped portion. The wall thickness of the first shaft portion after the diameter reduction and the wall thickness of the stepped portion are greater than the wall thickness of the second shaft portion.

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