WO2020004286A1 - Method for manufacturing hollow engine valve - Google Patents

Abstract

Provided is a method for manufacturing a hollow engine valve, whereby the surface state of an inside surface for forming a hollow hole is satisfactory, and the volume of the hollow hole can be increased. This manufacturing method is provided with a forging step (S3) for obtaining an intermediate component (7) provided with a cylindrical part (8B) and a half-umbrella-shaped part (9B) continuous with a shaft-end side of the cylindrical part by a forging process, a heat treatment step (S4) for heat treating the intermediate component for a heating retention time (t2) determined in accordance with the wall thickness (t) of the cylindrical part (8B) to soften the intermediate components, a spinning step (S5) for elongating the cylindrical part of the heat-treated intermediate component in the axial direction by a spinning process, and a necking step (S6) for forming a shaft part (2) and an umbrella-shaped part (3) by reducing the diameter of the axially elongated cylindrical part by a drawing process.

Description

Manufacturing method of hollow engine valve

The present invention relates to a method for manufacturing a hollow engine valve, and more particularly, to a hollow engine valve including a shaft portion and an umbrella-shaped portion connected to the shaft end side of the shaft portion, wherein a hollow hole is formed over the shaft portion and the umbrella-shaped portion. And a method for producing the same.

As a conventional method for manufacturing a hollow engine valve, an intermediate component having a cylindrical portion and a semi-umbrella-shaped portion connected to the shaft end side of the cylindrical portion is manufactured by forging, and the cylindrical portion of the intermediate component is spinned. A method of manufacturing a hollow engine valve by drawing and reducing the diameter after the drawing is described (see claim 5 of Patent Document 1 and paragraph [0023] of the specification).

International Publication No. 2011/104903

However, in the above-described conventional method for manufacturing a hollow engine valve, the intermediate part obtained by forging is heat-treated for a heating and holding time determined based on literature, materials, and the experience of the operator, and the heat-treated intermediate part is heated. Since the cylindrical portion is subjected to spinning, the cylindrical portion of the intermediate part may not be easily stretched during spinning. In that case, the surface condition is different between the processing surface (that is, the outer peripheral surface of the cylindrical portion) of the cylindrical portion of the intermediate part and the inner peripheral surface where the processing tool does not contact. Specifically, the inner peripheral surface of the cylindrical portion of the intermediate part, and eventually the inner surface of the hollow engine valve forming the hollow hole, is roughened and the surface condition is deteriorated. Therefore, the strength of the hollow engine valve is reduced. Further, in some cases, metallic sodium for cooling is put into the hollow hole of the hollow engine valve, but in that case, the fluidity of metallic sodium in the hollow hole is low and the cooling function is reduced.
In addition, the above-described problem is particularly conspicuous when a difficult-to-work material such as an austenitic heat-resistant material (eg, a nickel-based superalloy, an austenitic stainless steel, etc.) is processed.

Here, in the case of a hollow engine valve, it is required to increase the volume of the hollow hole in order to reduce the weight. However, in the conventional method of manufacturing a hollow engine valve, as described above, the intermediate part obtained by forging is heat-treated for a heating and holding time determined based on literature, materials, and the experience of an operator. Since the cylindrical part of the intermediate part is spin-finished, the cylindrical part of the intermediate part does not easily stretch during drawing in addition to spinning. For this reason, it is necessary to draw with a metal mold deeply to the bottom end side of the cylindrical portion of the intermediate part so that the pressing force is increased. As a result, the outer peripheral side of the hollow hole of the umbrella-shaped portion of the hollow engine valve is easily crushed, and the volume of the hollow hole of the umbrella-shaped portion cannot be increased.

The present invention has been made in view of the above situation, and provides a method of manufacturing a hollow engine valve which has a good surface condition on an inner surface forming a hollow hole and can increase the volume of the hollow hole. The purpose is to:

The present invention is as follows.
1. A method for manufacturing a hollow engine valve, comprising: a shaft portion and an umbrella-shaped portion connected to the shaft end side of the shaft portion, wherein a hollow hole is formed over the shaft portion and the umbrella-shaped portion. And a forging step of obtaining an intermediate part having a semi-umbrella-shaped part connected to the shaft end side of the cylindrical part, and a heat treatment for heating and holding time determined according to the thickness of the cylindrical part to soften the intermediate part. Heat treatment step, and a spinning step of extending the heat-treated intermediate part in the axial direction by spinning the cylindrical part, and reducing the diameter of the axially-extended cylindrical part by drawing. A necking step of forming a shaft portion and the umbrella-shaped portion.
2. The intermediate part is formed of an austenitic heat-resistant material, and in the heat treatment step, the intermediate part is heated and held at 1000 to 1100 ° C. and then water-cooled. A method for manufacturing the hollow engine valve according to the above.
3. In the heat treatment step, the heated intermediate component is held for a heating holding time of 3 to 8 minutes per 1 mm of the thickness of the cylindrical portion. A method for manufacturing the hollow engine valve according to the above.
4. In the heat treatment step, the intermediate component is placed in cooling water stirred in a container or cooling water circulated in the container, and water-cooled. Or 3. 5. The method for manufacturing a hollow engine valve according to item 1.
5. 3. The temperature of the cooling water is 15 to 35 ° C. A method for manufacturing the hollow engine valve according to the above.
6. The spinning step includes moving the processing roller in the axial direction with respect to the cylindrical portion while pressing an outer circular arc surface of the processing roller against the outer peripheral surface of the cylindrical portion by a predetermined cut amount. In the axial direction, the radius of curvature of the outer circumferential arc surface of the processing roller is 3 to 5 times the thickness of the cylindrical portion before spinning, and at the time of the spinning, In a cross section along the axial direction, a straight line connecting one end and the other end of the arc where the outer circumferential surface of the processing roller contacts the outer circumferential surface of the cylindrical portion is 5 to 7 degrees with respect to the axial direction of the cylindrical portion. The above-mentioned 1. which is inclined at an inclination angle of 1. To 5. The method for manufacturing a hollow engine valve according to any one of claims 1 to 3.
7. In the hollow engine valve, the inner surface forming the hollow hole has a surface roughness Ra of 4.0 to 22.0. To 6. The method for manufacturing a hollow engine valve according to any one of claims 1 to 3.
8. The forging step forms an arc surface on the bottom end side of the inner peripheral surface of the cylindrical part of the intermediate part, and the necking step sets the cylindrical part to the upper side and the semi-umbrella part to the lower side. Then, a portion above the arc surface in the axial direction of the cylindrical portion is drawn. To 7. The method for manufacturing a hollow engine valve according to any one of claims 1 to 3.
9. The spinning step spins the cylindrical portion of the intermediate component using a processing roller, and the processing roller includes front and rear bearings that are arranged along the axial direction of the processing roller with the processing roller interposed therebetween. 1 above, which is rotatably supported by the support member via To 8. The method for manufacturing a hollow engine valve according to any one of claims 1 to 3.

According to the method for manufacturing a hollow engine valve of the present invention, a forging process for obtaining an intermediate part having a cylindrical part and a semi-umbrella-shaped part connected to the shaft end side of the cylindrical part, and for softening the intermediate part A heat treatment step of performing a heat treatment for a heating and holding time determined according to the thickness of the cylindrical part, a spinning step of extending the cylindrical part of the heat-treated intermediate part in the axial direction by spinning, A necking step of forming a shaft portion and an umbrella-shaped portion by reducing the diameter of the cylindrical portion by drawing. As described above, by heat-treating and softening the intermediate part obtained by forging, the cylindrical part of the intermediate part is easily elongated at the time of spinning and drawing, and is excellent in workability of spinning and drawing. . As a result, the occurrence of surface roughening on the inner surface of the hollow engine valve forming the hollow hole is suppressed, and the surface condition is improved. Therefore, a decrease in the strength of the hollow engine valve is suppressed. Further, when metal sodium for cooling is put in the hollow hole of the hollow engine valve, the metal sodium flows smoothly in the hollow hole and effectively exerts a cooling function. Further, since the drawing processability is excellent, the height position of the mold at the time of the drawing die clamping can be easily adjusted so that the outer peripheral side of the hollow hole of the umbrella-shaped portion is suppressed. As a result, the volume of the hollow hole of the hollow engine valve can be increased.
In the case where the intermediate component is formed of an austenitic heat-resistant material and the heat treatment step is performed by heating and holding the intermediate component at 1000 to 1100 ° C. and then cooling with water, the intermediate component is effectively subjected to a solution heat treatment. Can be softened.
In the case where the heat treatment step holds the heated intermediate part for a heating holding time of 3 to 8 minutes per 1 mm of the thickness of the cylindrical portion, the heating holding time of the intermediate part is compared. It is possible to reduce the length of the oxide film on the surface of the intermediate component after the heat treatment.
Further, in the case where the heat treatment step is performed in which the intermediate component is put into cooling water stirred in a container or cooling water circulated in the container and water-cooled, the temperature rise of the cooling water is suppressed. The intermediate parts can be quenched effectively in the process.
When the temperature of the cooling water is 15 to 35 ° C., the intermediate part can be cooled rapidly in the heat treatment step.
Further, the spinning step includes moving the processing roller in the axial direction with respect to the cylindrical portion while pressing an outer circular arc surface of the processing roller against the outer peripheral surface of the cylindrical portion by a predetermined cutting amount. The radius of curvature of the outer peripheral arc surface of the processing roller is 3 to 5 times the thickness of the cylindrical part before spinning, and the cylindrical part is stretched during the spinning. In a cross section along the axial direction of the portion, a straight line connecting one end and the other end of an arc in which the outer peripheral arc surface of the processing roller contacts the outer peripheral surface of the cylindrical portion is 5 to 5 with respect to the axial direction of the cylindrical portion. In the case of inclination at an inclination angle of 7 degrees, the radius of curvature of the outer peripheral arc surface of the processing roller is set in consideration of the maximum value and the minimum value of the cutting amount. The shape can be effectively stretched.
Further, when the hollow engine valve has a surface roughness Ra of 4.0 to 22.0 on the inner surface forming the hollow hole, the surface condition of the inner surface forming the hollow hole of the hollow engine valve is extremely good. is there.
Further, the forging step forms an arc surface on the bottom end side of the inner peripheral surface of the cylindrical part of the intermediate part, and the necking step sets the cylindrical part upward and the semi-umbrella downward. When the upper part of the hollow portion of the hollow engine valve is obtained by forging, when the portion above the arc surface is drawn in the axial direction of the cylindrical portion, the cylindrical shape of the intermediate part is obtained. It can be made substantially the same as the inner diameter of the opening of the part. As a result, the volume of the hollow hole of the hollow engine valve can be further increased.
Furthermore, the spinning step spins the cylindrical portion of the intermediate component using a processing roller, and before and after the processing roller is disposed along the axial direction of the processing roller across the processing roller. When the support member is rotatably supported by a support member via a bearing, the falling of the processing roller is suppressed, so that the cylindrical portion of the intermediate component is effectively spinned.

The invention will be further described in the following detailed description, given by way of non-limiting example of an exemplary embodiment according to the invention and with reference to the figures referred to, wherein like reference numerals being used in the figures. Similar parts are shown throughout the several figures.
FIG. 5 is an explanatory diagram for explaining the method for manufacturing the hollow engine valve according to the embodiment. It is explanatory drawing for demonstrating the manufacturing method of the hollow engine valve which concerns on a present Example, (a) shows the longitudinal section of a raw material, (b) shows the longitudinal section of the intermediate part obtained by a 1st forging process. (C) shows a longitudinal section of the intermediate part after the ironing step. It is explanatory drawing for demonstrating the manufacturing method of the said hollow engine valve, (a) shows the longitudinal section of the intermediate part which passed through the 2nd forging process, (b) shows the longitudinal cross section of the intermediate part which passed through the spinning process. (C) shows a longitudinal section of the hollow engine valve obtained in the necking step. FIG. 3 is an explanatory diagram for explaining a heat treatment step according to the embodiment. It is explanatory drawing for demonstrating the said heat processing process. It is an explanatory view for explaining the above-mentioned spinning process. It is explanatory drawing for demonstrating the said necking process, the left side of a center line shows the longitudinal section of the intermediate part immediately before a drawing process, and the right side of a center line shows the longitudinal section of the hollow engine valve at the time of completion of a drawing process. . It is explanatory drawing for demonstrating the necking process of another form. It is explanatory drawing for demonstrating the surface state of the hollow engine valve which concerns on a present Example, (a) is a longitudinal section image processing figure of the principal part of the intermediate part which passed through the spinning process, (b) is a hollow engine valve. 3 shows a vertical cross-sectional image processing diagram of a main part of FIG. It is explanatory drawing for demonstrating the surface state of the hollow engine valve which concerns on a comparative example, (a) shows the longitudinal section image processing figure of the principal part of the intermediate part which passed through the spinning process, (b) shows the hollow engine valve. The longitudinal section image processing figure of the principal part is shown. 9 is a table showing experimental results of a method for manufacturing a hollow engine valve according to Experimental Examples 1 to 7. 14 is a table showing experimental results of a method for manufacturing a hollow engine valve according to Experimental Examples 8 to 13. 20 is a table showing experimental results of a method for manufacturing a hollow engine valve according to Experimental Examples 14 to 19 and Comparative Example. It is explanatory drawing for demonstrating the spinning process of another form. It is a principal part enlarged view of FIG. It is a table | surface which shows the experimental result of the spinning process which concerns on an experimental example, (a) shows the experimental result of Experimental Examples 20-24, (b) shows the experimental result of Experimental Examples 25-27.

The matters shown here are for the purpose of exemplifying the exemplary embodiments and the embodiments of the present invention, and should be described so that the principles and conceptual features of the present invention can be most effectively and easily understood. It is intended to provide what is considered. In this regard, it is not intended to show the structural details of the invention beyond that which is necessary for a fundamental understanding of the invention, and that some forms of the invention will be It will be clear to those skilled in the art how it is actually embodied.

The method for manufacturing a hollow engine valve according to the present embodiment includes a shaft portion (2) and an umbrella-shaped portion (3) connected to the shaft end side of the shaft portion, and extends over the shaft portion (2) and the umbrella-shaped portion (3). A method for manufacturing a hollow engine valve (1) in which a hollow hole (4) is formed, comprising a cylindrical portion (8B) and a semi-umbrella-shaped portion (9B) connected to the shaft end side of the cylindrical portion by forging. In a forging step (S3) for obtaining an intermediate part (7C) having the following, and a heating holding time (t2) determined according to the thickness (t) of the cylindrical part (8B) to soften the intermediate part (7C). A heat treatment step (S4) for heat treatment, a spinning step (S5, S5 ') for extending the cylindrical part (8B) of the heat-treated intermediate part (7C) in the axial direction by spinning, and a cylinder elongated in the axial direction. The shaft portion (2) is formed by reducing the diameter of the shape portion (8B) by drawing. A necking step of forming a fine cone-shaped part (3) (S6), provided with a (for example, see FIGS. 1-3).

In the method for manufacturing the hollow engine valve according to the present embodiment, for example, the intermediate part (7C) is formed of an austenitic heat-resistant material, and the heat treatment step (S4) is performed by using the intermediate part (7C) of 1000 to 1100. A mode of heating and holding at a temperature of 10 ° C. (preferably 1030 to 1070 ° C., particularly 1040 to 1060 ° C.) and then cooling with water (for example, see FIGS. 11 to 13). Examples of the austenitic heat-resistant material include a nickel-based superalloy such as NCF751 (Inconel 751 (registered trademark)), a stainless steel such as SUS304, and a heat-resistant steel such as SUH35 and SUH38.

In the case of the above-described embodiment, for example, in the heat treatment step (S4), the heated intermediate part (7C) is heated for 3 to 8 minutes (preferably, per mm) of the thickness (t) of the cylindrical portion (8B). (4 to 6 minutes) (see, for example, FIGS. 11 to 13). In this case, for example, the wall thickness (t) of the cylindrical portion (8B) of the intermediate part (7C) is 1 to 3 mm, and the heat treatment step (S4) is performed by heating the heated intermediate part (7C) to 3 to 24 mm. Minutes (preferably 4 to 18 minutes, especially 5 to 15 minutes).

In the case of the above-described embodiment, for example, in the heat treatment step (S4), the intermediate component (7C) is put into cooling water (23) stirred in the container (22) or into cooling water circulated through the container. And water-cooled (see, for example, FIG. 5). In this case, for example, the water temperature of the cooling water can be 15 to 35 ° C. (preferably 20 to 30 ° C.) (see, for example, FIGS. 11 to 13).

As a method for manufacturing the hollow engine valve according to the present embodiment, for example, as shown in FIGS. 14 and 15, the spinning step (S5 ′) includes the step of forming the processing roller (132) on the outer peripheral surface of the cylindrical portion (8B). The processing roller (132) is axially moved (moved relatively) with respect to the cylindrical portion (8B) while pressing the outer circular arc surface (132a) at a predetermined cutting amount (d), and the cylindrical portion ( 8B) can be stretched in the axial direction. In this case, for example, the radius of curvature (R) of the outer circular arc surface (132a) of the processing roller (132) is 3 to 5 times the thickness (t) of the cylindrical portion (8B) before spinning. At the time of spinning, in the cross section along the axial direction of the cylindrical portion (8B), one end (p1) of the circular arc where the outer peripheral arc surface (132a) of the processing roller (132) is in contact with the outer peripheral surface of the cylindrical portion (8B). The straight line (L1) connecting to the other end (p2) can be inclined at an inclination angle (θ1) of 5 to 7 degrees with respect to the axial direction of the cylindrical portion (8B).

As a method for manufacturing the hollow engine valve according to the present embodiment, for example, the hollow engine valve (1) has a surface roughness Ra of 4.0 to 22.0 (preferably the inner surface forming the hollow hole (4)). 4.0 to 12.0, particularly 4.0 to 8.0, and more preferably 4.0 to 6.0) (for example, see FIG. 9 and the like). In addition, arithmetic mean roughness (Ra) was adopted as the surface roughness. The surface roughness Ra indicates the surface roughness after the necking step.

As a method of manufacturing the hollow engine valve according to the present embodiment, for example, the forging step (S3) includes the step of forming an arc surface (17) on the bottom end side of the inner peripheral surface of the cylindrical portion (8B) of the intermediate part (7C). Is formed, and the necking step (S6) includes, when the cylindrical portion (8B) is on the upper side and the semi-umbrella-shaped portion (9B) is on the lower side, an arc surface (17) in the axial direction of the cylindrical portion (8B). ) Is drawn (for example, see FIG. 8 and the like). In this case, for example, in the hollow engine valve (1), the opening of the cylindrical portion (8B) of the intermediate part (7C) in which the maximum outer diameter (D1 ′) of the hollow hole (4) is obtained in the forging step (S3). Can be the same as the inner diameter (D2).
The same is intended to be substantially the same, and includes a difference of about ± 5%.

As a method for manufacturing the hollow engine valve according to the present embodiment, for example, in the spinning step (S5, S5 ′), the cylindrical part (8B) of the intermediate part (7C) is formed using the processing rollers (32, 132). The spinning processing rollers (32, 132) support the support members (35, 132) via front and rear bearings (34, 134) disposed along the axial direction of the processing rollers across the processing rollers (32, 132). 135) (for example, see FIGS. 6 and 14).

As a method of manufacturing the hollow engine valve according to the present embodiment, for example, a solid cylindrical material (6) is forged to reduce the diameter of the cup-shaped enlarged portion (8A) and the cup-shaped enlarged portion. A first forging step (S1) for obtaining an intermediate part (7A) having a cylindrical part (9A) connected to the shaft end side, and ironing the cup-shaped enlarged part (8A) into a cylindrical part (8B) by ironing. Step (S2), wherein the forging step is a second forging step (S3) in which the columnar portion (9A) is forged into a semi-umbrella-shaped portion (9B) (for example, FIG. 1 to FIG. 1). 3 etc.).

In addition, reference numerals in parentheses of each configuration described in the above embodiment indicate a correspondence relationship with a specific configuration described in an example described later.

Hereinafter, the present invention will be described in detail with reference to the drawings using examples.

(1) Configuration of Hollow Engine Valve The hollow engine valve 1 according to the present embodiment includes a shaft portion 2 and an umbrella-shaped portion 3 connected to the shaft end of the shaft portion 2 as shown in FIG. I have. A hollow hole 4 is formed over the shaft portion 2 and the umbrella-shaped portion 3. The maximum outer diameter D1 of the hollow hole 4 is a value slightly smaller than the inner diameter D2 (see FIG. 3A) of the opening of the cylindrical portion 8B of the intermediate part 7C obtained in the forging step S3 described below. Further, the hollow engine valve 1 has an inner surface forming the hollow hole 4 with a surface roughness Ra of about 4.0 (see FIG. 9).

(2) Manufacturing Method of Hollow Engine Valve As shown in FIG. 1, the manufacturing method of the hollow engine valve according to the present embodiment includes a first forging step S1, an ironing step S2, a second forging step S3, a heat treatment step S4, and spinning. Step S5 and necking step S6 are provided.

2) The first forging step S1 is a step of hot-forging a solid cylindrical material 6 made of a nickel-based superalloy to obtain an intermediate part 7A, as shown in FIGS. 2 (a) and 2 (b). The intermediate part 7A includes a cup-shaped enlarged-diameter portion 8A and a columnar portion 9A connected to the shaft end side of the cup-shaped enlarged-diameter portion 8A whose diameter is reduced. Further, in the first forging step S1, a mold 11 having a convex portion 11a for forming the inner wall of the cup-shaped enlarged-diameter portion 8A and the outer wall of the cup-shaped enlarged-diameter portion 8A while holding the raw material 6 are formed. And a mold 12 having a concave portion 12a.

The ironing step S2 is, as shown in FIGS. 2B and 2C, mainly a step of obtaining the intermediate part 7B as the cylindrical part 8B by cold ironing the cup-shaped enlarged diameter part 8A of the intermediate part 7A. is there. The outer diameter of the cylindrical portion 8B is substantially the same as the outer diameter of the columnar portion 9A. Further, in the ironing step S2, a mold 14 having a through hole 14a for ironing the cup-shaped enlarged diameter portion 8A and a mold 15 having a protrusion 15a for pressing the columnar portion 9A are used. Can be

In the second forging step S3, as shown in FIGS. 2C and 3A, the semi-finished product of the umbrella-shaped part 3 is mainly formed by hot forging the cylindrical part 9A of the intermediate part 7B. This is the step of obtaining the intermediate part 7C as the semi-umbrella-shaped part 9B. That is, the intermediate component 7C obtained in the second forging step S3 includes a cylindrical portion 8B and a semi-umbrella-shaped portion 9B connected to the shaft end of the cylindrical portion 8B. An arc surface 17 is formed on the bottom end side of the inner peripheral surface of the cylindrical portion 8B. Further, in the second forging step S3, the mold 18 having the convex portion 18a for pressing the bottom surface of the columnar portion 9A and the through hole 19a holding the outer peripheral side of the columnar portion 9A and the cylindrical portion 8B are formed. The formed mold 19 and a pin 20 inserted into the through hole 19a and abutting on the bottom end side of the cylindrical portion 8B are used.
The thickness t of the cylindrical portion 8B of the intermediate part 7C obtained in the second forging step S3 is about 2 mm.

熱処理 The heat treatment step S4 is a step of performing a solution heat treatment for a heating holding time t2 determined according to the wall thickness t of the cylindrical portion 8B in order to soften the intermediate part 7C. In the heat treatment step S4, as shown in FIG. 4, the intermediate component 7C is heated and held at a predetermined heating temperature T1 (for example, 1050 ° C.) and then water-cooled. Specifically, the intermediate component 7C at the normal temperature T2 (for example, 20 ° C.) is heated up to the heating temperature T1 in a predetermined heating time t1 (for example, 5 minutes), and is heated to the heating temperature T1 for a predetermined heating holding time t2. (Eg, 10 minutes). Thereafter, the intermediate component 7C is rapidly cooled to the normal temperature T2 for a predetermined cooling time t3 (for example, 10 seconds). The heating holding time t2 is set to a value that is about 5 minutes per 1 mm of the thickness t of the cylindrical portion 8B of the intermediate part 7C.

水 In the water cooling, as shown in FIG. 5, cooling water 23 (for example, tap water) stored in a container 22 is used. A nozzle 25 connected to a pump 24 and capable of jetting water is arranged in the container 22. The nozzle 25 is arranged so as to stir the cooling water 23 by spraying water. Therefore, even if a large number (for example, 20 to 30) of the intermediate components 7C are put into the container 22, the temperature of the cooling water 23 is maintained at 20 to 30 ° C.

In the spinning step S5, as shown in FIGS. 3A and 3B, the cylindrical part 8B of the heat-treated intermediate part 7C is axially stretched by cold spinning to make the intermediate part 7D thin. It is a process. In the spinning step S5, as shown in FIG. 6, a chuck mechanism 31 for gripping the semi-umbrella-shaped portion 9B and rotating the intermediate part 7C around the axis, and pressing the outer peripheral surface against the outer peripheral surface of the cylindrical portion 8B. Processing roller 32 to be used. A support shaft 33 extending in the axial direction of the processing roller 32 is rotatably supported by a support member 35 via bearings 34 on both surface sides of the processing roller 32. In other words, the processing roller 32 is rotatably supported by the support member 35 via the front and rear bearings 34 disposed along the axial direction of the processing roller 32 with the processing roller 32 interposed therebetween. The support member 35 can be moved in the radial direction and the axial direction of the cylindrical portion 8B by a moving mechanism (not shown). Note that one or a plurality of the processing rollers 32 may be used.

In the spinning step S5, the holding pin 37 is inserted inside the cylindrical portion 8B of the intermediate component 7C. However, the holding pin 37 has its tip only in contact with the bottom end side of the cylindrical portion 8B. It does not contact the inner peripheral surface of the cylindrical portion 8B. That is, in the spinning process S5, no tool is in contact with the inner peripheral surface of the cylindrical portion 8B of the intermediate component 7C.

Here, the thickness of the cylindrical portion 8B of the intermediate part 7C obtained in the second forging step S3 may be uneven, but even in such a case, the thickness of the cylindrical portion 8B after the spinning process is reduced. The irregularities are eliminated. On the other hand, when swaging is employed instead of spinning, it is difficult to eliminate irregularities in the thickness of the cylindrical portion 8B.

In the necking step S6, as shown in FIGS. 3 (b) and 3 (c), the cylindrical portion 8B extended in the axial direction is gradually reduced in diameter by a plurality of stages (for example, nine stages) of cold drawing. This is the step of forming the shaft portion 2 and the umbrella-shaped portion 3 (that is, the step of obtaining the hollow engine valve 1). Specifically, the shaft portion 2 is formed at a reduced diameter portion other than the bottom end side of the cylindrical portion 8B, and the reduced diameter portion at the bottom end side of the cylindrical portion 8B and the semi-umbrella-shaped portion 9B Thus, an umbrella-shaped portion 3 is formed. In the necking step S6, a mold 38 for holding the semi-umbrella-shaped portion 9B of the intermediate part 7D and a mold 39 having a forming hole 39a for drawing the cylindrical portion 8B are used. As the mold 39, a plurality of types having different hole diameters of the forming holes 39a according to a plurality of stages of drawing are used.

In the necking step S6, as shown in FIG. 7, a portion including the arc surface 17 in the axial direction of the cylindrical portion 8B of the intermediate part 7D is drawn. Specifically, at the time of the final stage (for example, the ninth stage) of the die clamping in the drawing, the lower end surface of the mold 39 is at the upper end of the circular arc surface 17 of the cylindrical portion 8B of the intermediate part 7D before the drawing (FIG. 7 is indicated by an alternate long and short dash line.).

(3) Effects of Embodiment According to the method of manufacturing the hollow engine valve of the embodiment, the intermediate component 7C including the cylindrical portion 8B and the semi-umbrella-shaped portion 9B connected to the shaft end side of the cylindrical portion 8B by forging. , A heat treatment step S4 of performing a heat treatment for a heating holding time t2 determined according to the thickness t of the cylindrical portion 8B to soften the intermediate component 7C, and a cylindrical portion of the heat treated intermediate component 7C. A spinning step S5 for axially extending 8B by spinning, and a necking step S6 for forming the axial part 2 and the umbrella-shaped part 3 by reducing the diameter of the cylindrical part 8B extended in the axial direction by drawing. , Is provided. In this way, by heat-treating and softening the intermediate part 7C obtained by forging, the cylindrical part 8B of the intermediate part 7C is easily elongated at the time of spinning and drawing. Excellent in nature. As a result, the occurrence of surface roughening on the inner surface forming the hollow hole 4 of the hollow engine valve 1 is suppressed, and the surface condition is improved. Therefore, a decrease in the strength of the hollow engine valve 1 is suppressed. Further, when metal sodium for cooling is put in the hollow hole 4 of the hollow engine valve 1, the metal sodium flows smoothly in the hollow hole 4 and effectively exerts a cooling function. Furthermore, since the drawing processability is excellent, the height position of the mold 39 at the time of the drawing die clamping can be easily adjusted so that the outer peripheral side of the hollow hole 4 of the umbrella-shaped portion 3 is suppressed. . As a result, the volume of the hollow hole 4 of the hollow engine valve 1 can be increased.

Also, in the present embodiment, the intermediate component 7C is formed of a nickel-based superalloy, and in the heat treatment step S4, the intermediate component 7C is heated and held at 1050 ° C. and then water-cooled. Thereby, the intermediate part 7C can be effectively softened by solution heat treatment.

Further, in the present embodiment, the heat treatment step S4 is a heating holding time t2 (specifically, 5 minutes per 1 mm of the thickness t (specifically, 2 mm) of the cylindrical portion 8B). (10 minutes). Thereby, the heating holding time t2 of the intermediate component 7C can be relatively shortened, and the generation of an oxide film on the surface of the intermediate component 7C after the heat treatment can be reduced.

In the present embodiment, in the heat treatment step S4, the intermediate component 7C is put into cooling water 23 stirred in the container 22 and water-cooled. Thereby, the temperature rise of the cooling water 23 is suppressed, so that the intermediate component 7C can be rapidly cooled in the heat treatment step S4 effectively. In particular, in the present embodiment, since the water temperature of the cooling water 23 is 20 to 30 ° C., the intermediate component 7C can be rapidly cooled effectively in the heat treatment step S4.

In addition, in this embodiment, the hollow engine valve 1 has an inner surface forming the hollow hole 4 with a surface roughness Ra of 4.0. Thereby, the surface condition of the inner surface forming the hollow hole 4 of the hollow engine valve 1 is extremely good.

Further, in the present embodiment, in the spinning step S5, the cylindrical portion 8B of the intermediate part 7C is subjected to spinning using the processing roller 32, and the processing roller 32 is disposed along the axial direction of the processing roller 32 with the processing roller 32 interposed therebetween. It is rotatably supported by a support member 35 via front and rear bearings 34 which are arranged in front. Thereby, the falling of the processing roller 32 is suppressed, so that the cylindrical portion 8B of the intermediate part 7C is effectively spinned.

Further, in this embodiment, a solid cylindrical material 6 is forged, and an intermediate portion having a cup-shaped enlarged portion 8A and a columnar portion 9A connected to a shaft end side of the cup-shaped enlarged portion 8A whose diameter is reduced. A first forging step S1 for obtaining the part 7A, an ironing step S2 for ironing the cup-shaped enlarged-diameter portion 8A to form a cylindrical portion 8B, and a forging process for the columnar portion 9A to form a semi-umbrella portion 9B. 2 forging step S3. This makes it possible to easily form the relatively thin cylindrical portion 8B with a relatively small pressing force.

(4) Experimental Examples 1 to 19 and Comparative Example Next, test results of the method of manufacturing the hollow engine valve according to Experimental Examples 1 to 19 and the comparative example will be described with reference to FIGS. In these experimental examples 1 to 19, the first forging step S1, the ironing step S2, the second forging step S3, the heat treatment step S4, the spinning step S5, and the necking step were performed in the same manner as in the method of manufacturing the hollow engine valve of the above-described embodiment. Through S6, a hollow engine valve was manufactured. On the other hand, in the comparative example, a hollow engine valve was manufactured by omitting the heat treatment step S4 among the above steps S1 to S6. Then, the surface condition of the hollow engine bal obtained by each of the production methods of Experimental Examples 1 to 19 and Comparative Example was confirmed, and the workability of spinning was confirmed, and a comprehensive evaluation was made.

Here, in Experimental Examples 1 to 7, a nickel-based superalloy material having a nickel content of about 50% was used, and in Experimental Examples 8 to 13, a nickel-based superalloy material having a nickel content of about 80% was used. In Experimental Examples 14 to 19 and Comparative Example, a material made of a nickel-based superalloy having a nickel content of about 30% was used. In the heat treatment steps of Experimental Examples 1 to 19, the heating temperature, the heating holding time, the cooling method, the processing amount, and the like were changed. In particular, in Experimental Examples 1 to 17, the intermediate components were put into the unstirred cooling water and water-cooled, and in Experimental Examples 18 and 19, the intermediate components were put into the stirring cooling water and water-cooled. Further, in Experimental Examples 1 to 16, one intermediate component was put in cooling water and cooled with water, and in Experimental Examples 17 to 19, 10 to 20 intermediate components were charged in cooling water and cooled with water.

As a result, in the hollow engine valve obtained by the manufacturing method of the comparative example, remarkable roughening occurred on the inner surface forming the hollow hole, and the surface roughness Ra was about 22.0 (see FIG. 10). Furthermore, the elongation of the material during spinning was poor and the workability was extremely low.

On the other hand, in the hollow engine valve obtained by the manufacturing method of Experimental Examples 1, 2, 6, 9 and 11, a slight roughening occurs on the inner surface where the hollow hole is formed. It was good. In addition, the hollow engine valves obtained by the production methods of Experimental Examples 3-5, 7, 8, 10, and 12-19 did not have rough surfaces on the inner surface where the hollow holes were formed, and the surface condition was extremely good. In particular, in the hollow engine valve obtained by the production method of Experimental Example 19, the generation of an oxide film on the inner surface forming the hollow hole was small.

In the production methods of Experimental Examples 1-15 and 17, the elongation of the material during spinning was slightly poor, but the workability was higher than that of the comparative example. In the production methods of Experimental Examples 16, 18, and 19, the material elongation during spinning was good, and the workability was extremely high.

Here, in the production methods of Experimental Examples 18 and 19, even if a large number of intermediate parts were treated at one time, water was effectively cooled. This is because the temperature rise of the cooling water is suppressed by cooling with the cooling water accompanied by stirring. Furthermore, in the manufacturing method of Experimental Example 19, the generation of an oxide film on the inner surface forming the hollow hole of the hollow engine valve was small. This is because the heating holding time t2 is as short as 10 minutes. From this point, by holding the intermediate part 7C obtained in the forging step S3 for a heating holding time t2 of about 5 minutes per 1 mm of the wall thickness t of the cylindrical part 8B, the component structure necessary for spinning is performed. Can be said to be obtained.

<Another form of spinning process>
Next, a description will be given of a spinning step S5 'of another embodiment. Parts having substantially the same configuration as those of the above-described spinning step S5 are denoted by the same reference numerals, and detailed description thereof will be omitted.

(1) Spinning Step In the spinning step S5 ′, as shown in FIGS. 3A and 3B, the cylindrical part 8B of the heat-treated intermediate part 7C is stretched in the axial direction by cold spinning to obtain a thin wall. This is the step of obtaining the intermediate part 7D by the conversion. In the spinning step S5 ′, as shown in FIG. 14, a chuck mechanism 131 that grips the semi-umbrella-shaped portion 9B and rotates the intermediate component 7C around the axis, and the outer peripheral arc surface 132a of which is formed on the outer peripheral surface of the cylindrical portion 8B And a processing roller 132 pressed against the roller. The processing roller 132 has front and rear bearings 134 (specifically, front and rear) disposed along the axial direction of the processing roller 132 with the processing roller 132 interposed therebetween with respect to a support shaft 133 (that is, a support member 135) extending in the axial direction. And is rotatably supported via a thrust bearing 134). The support member 135 is movable in a radial direction and an axial direction of the cylindrical portion 8B by a moving mechanism (not shown).

Note that one or a plurality of the processing rollers 132 may be used. In the cylindrical portion 8B in FIG. 14, the portion above the center line indicates the thickness before spinning (for example, 1.65 mm), and the portion below the center line after spinning (for example, 1.65 mm). For example, 1.0 mm).

In the spinning process S5 ′, as shown in FIG. 15, the processing roller 132 is pressed against the outer peripheral surface of the cylindrical portion 8B while pressing the outer circular arc surface 132a of the processing roller 132 at a predetermined cutting amount d. By moving in the processing direction P along the axial direction and repeating this, the cylindrical portion 8B is stretched in the axial direction. The cut amount d and the number of movements in the stretching direction P in the spinning process S5 'are not particularly limited. In the spinning process S5 ', an amount smaller than the cut amount d usually occurs during the spinning process.

Here, the radius of curvature R of the outer circular arc surface 132a of the processing roller 132 is 3 to 5 times the thickness t of the cylindrical portion 8B before spinning. Then, at the time of spinning, in a cross section along the axial direction of the cylindrical portion 8B, a straight line L1 connecting one end p1 and the other end p2 of the arc where the outer circumferential arc surface 132a of the processing roller 132 contacts the outer circumferential surface of the cylindrical portion 8B is formed. Is inclined at an inclination angle θ1 of 5 to 7 degrees with respect to the axial direction of the cylindrical portion 8B. As a result, the radius of curvature R of the outer circular arc surface 132a of the processing roller 132 is set by assuming the maximum value and the minimum value of the cutting amount d, so that the cylindrical portion 8B of the intermediate part 7C is effectively used during spinning. Stretching is possible.

Note that the one end p1 usually passes through the center of the radius of curvature R of the outer circular arc surface 132a of the processing roller 132 in the cross section along the axial direction of the cylindrical portion 8B during spinning, and is in contact with the axis of the cylindrical portion 8B. This is a point where the orthogonal straight line L2 intersects the outer peripheral surface of the cylindrical portion 8B. The same conditions as the radius of curvature R and the inclination angle θ1 of the processing roller 132 in the spinning step S5 ′ are employed as the radius of curvature R and the inclination angle θ1 of the processing roller 32 in the spinning step S5.

(2) Experimental Examples 20 to 27 Next, test results of the spinning step according to Experimental Examples 20 to 27 will be described with reference to FIG. In these Experimental Examples 20 to 27, the thickness of the cylindrical portion 8B was increased with respect to the intermediate part 7C that had undergone the first forging step S1, the ironing step S2, the second forging step S3, and the heat treatment step S4 (Experimental Example 19). A plurality of spinning processes were performed until t became 1.65 mm to 1 mm. In each of Experimental Examples 20 to 24, the cut amount d of the processing roller 132 with respect to the cylindrical portion 8B was set to 0.15 mm. Further, in each of Experimental Examples 25 to 27, the cut amount d of the processing roller 132 into the cylindrical portion 8B was set to 0.1 mm. Then, the surface state of the intermediate component 7D after the spinning was confirmed, and an evaluation was made based on the surface state and the number of times of spinning.

In the experimental examples 20 to 27, the rotation speed of the intermediate part 7C was set to 1200 rpm and the feed speed of the processing roller 132 was set to 0.13 mm / s using a general-purpose NC lathe.

In Experimental Examples 21 to 23, 25 and 26, the radius of curvature R of the outer circular arc surface 132a is 3 to 5 times the thickness t of the cylindrical portion 8B before spinning, and the straight line L1 is the cylindrical portion 8B. The working roller 132 is inclined at an inclination angle θ1 of 5 to 7 degrees with respect to the axial direction. As a result, the surface condition of the intermediate part 7D obtained in Experimental Examples 21 to 23 is smooth and good, the number of spinning is 10 times, and the workability is excellent. Further, the surface condition of the intermediate part 7D obtained in Experimental Examples 25 and 26 is smooth and good, the number of spinning is 13 times, and the workability is excellent.

On the other hand, in Experimental Example 20, the radius of curvature R of the outer circular arc surface 132a is about 1.8 times the thickness t of the cylindrical portion 8B before spinning, and the straight line L1 is in the axial direction of the cylindrical portion 8B. A processing roller 132 inclined at an inclination angle θ1 of 9 degrees is used. As a result, the surface condition of the intermediate part 7D obtained in Experimental Example 20 showed a slightly rough skin, but the number of spinning was 10 times, and the workability was excellent.

In Experimental Example 24, the radius of curvature R of the outer circular arc surface 132a is a value approximately six times the thickness t of the cylindrical portion 8B before spinning, and the straight line L1 is aligned with the axial direction of the cylindrical portion 8B. The processing roller 132 is inclined at an inclination angle θ1 of 4.5 degrees. As a result, the surface state of the intermediate part 7D obtained in Experimental Example 24 was smooth and good, but the number of times of spinning was 16 times.

Further, in Experimental Example 27, the radius of curvature R of the outer circumferential arc surface 132a is a value five times the thickness t of the cylindrical portion 8B before spinning, and the straight line L1 is defined with respect to the axial direction of the cylindrical portion 8B. A processing roller 132 inclined at an inclination angle θ1 of 4.5 degrees was employed. As a result, although the surface state of the intermediate part 7D obtained in Experimental Example 27 was smooth and good, the number of times of spinning was 20 times.

The present invention is not limited to the above embodiments, but may be variously modified within the scope of the present invention according to purposes and applications. That is, in the above-described embodiment, hot forging, cold ironing, cold spinning, cold drawing, and the like are exemplified, but the invention is not limited thereto. And cold working. Further, each of these processes may be a single process or a plurality of processes.

In the above-described embodiment, the intermediate part 7C formed of an austenitic heat-resistant material (specifically, a nickel-based superalloy) is exemplified. However, the present invention is not limited thereto. The intermediate part 7C made of a material may be used. In this case, in the heat treatment step S4, heat treatment suitable for the material of the intermediate part 7C is performed.

In the above embodiment, the intermediate component 7A having the cup-shaped enlarged portion 8A is formed by forging, and the intermediate component 7B having the cylindrical portion 8B as the cylindrical portion 8B by ironing the cup-shaped enlarged portion 8A. However, the present invention is not limited to this. For example, the intermediate component 7B including the cylindrical portion 8B may be obtained by forging without forming the cup-shaped enlarged portion 8A.

Further, in the above embodiment, the cooling water 23 is stirred in the container 22 by spraying the water from the nozzle 25. However, the present invention is not limited to this. For example, the cooling water 23 is cooled in the container 22 by rotating a stirring blade or a stirring screw. The water 23 may be stirred. Further, for example, a circulation path may be connected to the container 22 so that the cooling water 23 is circulated through the container 22. Even in this case, since the temperature rise of the cooling water 23 is suppressed, the intermediate part 7C can be rapidly cooled in the heat treatment step S4.

Further, in the above-described embodiment, in the spinning processes S5 and S5 ′, the processing roller 132 in which the radius of curvature R of the outer circular arc surface 132a is 3 to 5 times the thickness t of the cylindrical portion 8B before the spinning is performed. Although the form of use is illustrated, the present invention is not limited to this. For example, the radius of curvature R of the outer peripheral arc surface 132a is a value less than three times or more than five times the thickness t of the cylindrical portion 8B before spinning. May be used.

Further, in the above-described embodiment, in the spinning processes S5 and S5 ′, the form in which the processing roller 132 in which the straight line L1 is inclined at an inclination angle θ1 of 5 to 7 degrees with respect to the axial direction of the cylindrical portion is used is exemplified. For example, a processing roller 132 may be used in which the straight line L1 is inclined at an inclination angle θ1 of less than 5 degrees or more than 7 degrees with respect to the axial direction of the cylindrical portion 8B.

Further, in the above-described embodiment, the necking step S6 in which the portion including the arc surface 17 is drawn in the axial direction of the cylindrical portion 8B of the intermediate part 7D is illustrated. However, the present invention is not limited to this. For example, as shown in FIG. Next, when the cylindrical portion 8B of the intermediate part 7D is set to the upper side and the semi-umbrella-shaped portion 9B is set to the lower side, the necking process S6 for drawing the portion above the arc surface 17 in the axial direction of the cylindrical portion 8B. It may be. In this case, the lower end surface of the mold 39 is closed at the upper end of the circular arc surface 17 of the cylindrical portion 8B of the intermediate part 7D before drawing (the height indicated by a dashed line in FIG. 8). It is located above. Thereby, the maximum outer diameter D1 'of the hollow hole 4 of the hollow engine valve 1 can be made the same as the inner diameter D2 of the opening of the cylindrical portion 8B of the intermediate part 7D obtained in the forging step S3 (see FIG. 3A). As a result, the volume of the hollow hole 4 of the hollow engine valve 1 can be further increased.

Further, in the above-described embodiment, the processing roller 32 supported at both ends by the front and rear bearings 34 is exemplified. However, the present invention is not limited to this. For example, the processing roller 32 may be supported at one end. Furthermore, for example, instead of or in addition to the processing roller 32, a spinning step S5 using a processing spatula may be performed.

The present invention is suitably used as a technique for manufacturing a hollow engine valve that is lightweight and has excellent heat resistance.

DESCRIPTION OF SYMBOLS 1; Hollow engine valve, 2; Shaft part, 3; Umbrella part, 4; Hollow hole, 7C: Intermediate part, 8B; Cylindrical part, 9B; Semi-umbrella part, 17; Cooling water, 32, 132; processing roller, 33; support shaft, 34, 134; bearing, 35, 135; support member, 39, 139; mold, S3; second forging step, S4; S5 ': spinning step, S6: necking step, T1: heating temperature, t2: heating holding time.

Claims (9)

A method for manufacturing a hollow engine valve, comprising: a shaft portion and an umbrella-shaped portion connected to a shaft end side of the shaft portion, wherein a hollow hole is formed over the shaft portion and the umbrella-shaped portion,
By forging, a forging step of obtaining an intermediate part having a cylindrical portion and a semi-umbrella-shaped portion connected to the shaft end side of the cylindrical portion,
A heat treatment step of performing a heat treatment for a heating holding time determined according to the thickness of the cylindrical portion to soften the intermediate part,
A spinning step of extending the heat-treated intermediate part in the axial direction by spinning the cylindrical part,
A necking step of forming the shaft portion and the umbrella-shaped portion by reducing the diameter of the cylindrical portion stretched in the axial direction by drawing. A method for manufacturing a hollow engine valve. The intermediate component is formed of an austenitic heat-resistant material,
The method for manufacturing a hollow engine valve according to claim 1, wherein, in the heat treatment step, the intermediate component is heated and held at 1000 to 1100 ° C and then water-cooled. The method according to claim 2, wherein in the heat treatment step, the heated intermediate component is held for a heating holding time of 3 to 8 minutes per 1 mm of the thickness of the cylindrical portion. 4. The method for manufacturing a hollow engine valve according to claim 2, wherein, in the heat treatment step, the intermediate component is put into cooling water stirred in a container or cooling water circulated in the container and water-cooled. 方法 The method for manufacturing a hollow engine valve according to claim 4, wherein a temperature of the cooling water is 15 to 35 ° C. The spinning step includes moving the processing roller in the axial direction with respect to the cylindrical portion while pressing an outer circular arc surface of the processing roller against the outer peripheral surface of the cylindrical portion by a predetermined cut amount. Is stretched in the axial direction,
The radius of curvature of the outer circumferential arc surface of the processing roller is 3 to 5 times the thickness of the cylindrical portion before spinning,
At the time of the spinning process, in a cross section along the axial direction of the cylindrical portion, a straight line connecting one end and the other end of an arc in which the outer circumferential surface of the processing roller is in contact with the outer circumferential surface of the cylindrical portion is the cylindrical portion. The method of manufacturing a hollow engine valve according to any one of claims 1 to 5, wherein the hollow engine valve is inclined at an inclination angle of 5 to 7 degrees with respect to the axial direction. The method for manufacturing a hollow engine valve according to any one of claims 1 to 6, wherein the hollow engine valve has an inner surface forming the hollow hole having a surface roughness Ra of 4.0 to 22.0. The forging step forms an arc surface on the bottom end side of the inner peripheral surface of the cylindrical portion of the intermediate part,
The said necking process draws the part above the said circular-arc surface in the axial direction of the said cylindrical part, when the said cylindrical part is an upper side and the said semi-umbrella-shaped part is a lower side. A method for manufacturing a hollow engine valve according to any one of claims 7 to 13. The spinning step, spinning the cylindrical portion of the intermediate component using a processing roller,
9. The processing roller according to claim 1, wherein the processing roller is rotatably supported by a support member via front and rear bearings disposed along the axial direction of the processing roller with the processing roller interposed therebetween. 10. A method for manufacturing the hollow engine valve according to the above.

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