Method for manufacturing a valve seat member for a fuel injection valve

Abstract

This method for manufacturing a valve seat member of a fuel injection valve makes it possible to shorten the manufacturing time and achieve more precise manufacturing of a valve seat member. This manufacturing method comprises a main step (S2) in which a billet material (17) that is to serve as a valve seat member (1) is molded into the shape of the valve seat member (1). In the main step (S2): a punch (18) is used that is shaped such that the cross-section reduction rate when side walls of the valve seat member (1) are formed will be less than 35% and the apex angle of a valve seat surface (5) will be an obtuse angle of at least 100°; and the punch is driven one time so that the thickness t of a bottom portion at a center position of a sack surface (4) is less than 2mm and at least 1mm.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a valve seat member for a fuel injection valve having a cylindrical, bottomed shape. [Background technology]

[0002] Conventionally, a valve seat member of a fuel injection valve having a cylindrical shape with a bottom has, at its bottom, a conical valve seat surface that abuts against and moves away from a spherical valve body as the valve body reciprocates in the axial direction, a spherical crown-shaped sac surface that continues to the downstream side of the valve seat surface, and a fuel nozzle hole provided in the center of the sac surface (see, for example, Patent Document 1).

[0003] Conventionally, a known method for manufacturing such a valve seat member involves cutting a bar material to form a bottomed cylinder, heat treating it, polishing and finishing the guide surface for the valve body on the inner wall of the bottomed cylinder, the portion that becomes the fuel passage, and the valve seat surface at the bottom, and then providing a fuel injection hole and the like and lapping the valve seat surface and the like.

[0004] Another known method for manufacturing the valve seat member involves forming a bottomed cylindrical body and then molding the valve seat surface and the like in a press process (see, for example, Patent Document 1).

[0005] In the method of Patent Document 1, a nozzle with a valve seat (valve seat member) is manufactured as follows: First, a bottomed cylinder that will become the nozzle material is formed from a metal material. Next, a first press process is used to form a surface in the center of the top bottom surface of this bottomed cylinder, which has a conical surface that has a contact area with the valve disc and a spherical concave surface that has a smaller radius of curvature than the valve disc adjacent to the conical surface.

[0006] Next, a blind hole that will become the fuel injection hole is formed in the center of the tip of the spherical concave surface created in the first press process in a second press process. Next, a corner between the spherical concave surface and the blind hole is rounded in a third press process. Next, the blind hole is punched out by cutting the plastic flow portion that was pushed out toward the underside of the bottom of the bottomed cylinder in the first to third press processes, and then hardening and other processes are performed to complete the production of a nozzle with a valve seat. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 2568323 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the above-described method of manufacturing a valve seat member by cutting a bar material, the parts of the valve seat member that overlap with the fuel passage, such as the inner wall of the valve seat member, and the valve seat surface are all formed by cutting, and then these parts are finished by polishing after the heat treatment, so manufacturing takes a considerable amount of time.

[0009] Furthermore, the polishing process of the valve seat surface requires high precision in the roundness and surface roughness of the valve seat surface, which increases the manufacturing cost.

[0010] Furthermore, according to the method of Patent Document 1, multiple pressing processes are performed to maintain the surface roughness and roundness of the valve seat surface, so it is necessary to change the press mold for each pressing process and adjust the coaxiality of these press molds. Moreover, this coaxiality adjustment error accumulates each time the press mold is changed, resulting in greater variation in the precision of the formed valve seat surface, etc. Furthermore, since multiple pressing processes are performed, the manufacturing time is considerably longer.

[0011] In view of the above problems of the prior art, an object of the present invention is to provide a method for manufacturing a valve seat member for a fuel injection valve that shortens the manufacturing time and enables the manufacture of a valve seat member with higher accuracy. [Means for solving the problem]

[0012] A method for manufacturing a valve seat member of a fuel injection valve according to the present invention includes the steps of: 1. A method for manufacturing a valve seat member for a fuel injection valve, the valve seat member having a cylindrical shape with a bottom having a side wall and a bottom, the inside of the bottom being provided with a spherical crown-shaped sack surface that opens rearward from a tip center, a truncated conical valve seat surface continuing to the rear of the sack surface, and a conical connecting surface continuing from a rear end edge of the valve seat surface to an inner wall surface of the side wall, the inner wall surface forming a guide surface that guides a spherical valve element as it reciprocates to contact and separate from the valve seat surface, a pre-process of annealing and bonding a cylindrical forging material to be used as the valve seat member; After the previous process, a main process of forming the inner wall surface and the inner surfaces of the bottom portion on the inside of the forging material; After the main process, a post-process is performed on the forging material to perform appearance finishing and heat treatment, The present step a plastic flow processing step in which a punch is pressed from above along a central axis against the forging material placed inside a die having a cylindrical inner surface whose bottom surface is closed by a backing plate, thereby performing backward extrusion forging to form the side wall; a surface forming step of pressing and forming the guide surfaces of the side walls and the inner surfaces of the bottom portion with an outer surface of the punch when performing the plastic flow processing step, The method is characterized in that the cross-sectional area reduction rate when the side wall is formed is less than 35%, the punch forms a conical connecting surface, and the apex angle of the truncated cone shape of the valve seat surface is an obtuse angle of 100° or more, and the punch is driven in one operation so that the thickness from the center position of the sack surface to the bottom surface of the forging material is less than 2 mm and 1 mm or more.

[0013] In the present invention, by setting the reduction of area when the side wall is formed to less than 35%, multiple forging processes are unnecessary, and the valve seat member can be formed by a single punching operation, eliminating the need for multiple dies. Furthermore, by forming the truncated cone shape of the seat surface with an obtuse apex angle of 100° or more, a valve seat surface with high circularity can be formed, eliminating the need for finish processing such as polishing the valve seat surface. This shortens the cycle time of the entire manufacturing process for the valve seat member, allowing high-precision valve seat members to be manufactured at low cost.

[0014] Furthermore, this process uses a punch of the above shape and is carried out so that the thickness from the sack surface to the bottom surface of the forging material is less than 2 mm and at least 1 mm, which suppresses the amount of plastic flow of the forging material from the bottom surface to the side wall and forms grain flows that are uniformly compressed in the circumferential direction, resulting in a conical valve seat surface with high roundness and high surface roughness, which also eliminates the need for finish polishing of the valve seat surface.

[0015] Therefore, according to the present invention, the cycle time for manufacturing the valve seat member can be shortened, and a highly accurate valve seat member can be manufactured at low cost.

[0016] In the present invention, the punch may have an outer surface that forms a polygonal cylindrical shape, with a plurality of flat portions that form the guide surface and a plurality of inner corner portions that form the fuel passages being alternately arranged in the circumferential direction.

[0017] This makes it possible to prevent defects from occurring in the flat surface that serves as the guide surface. That is, normally, when backward extrusion forging is completed and the punch is withdrawn from the forging material, the periphery of the inner corner is subjected to tension and compression of the material surface, so it is possible to prevent defects (covering, buckling, cracking) from occurring in the flat surface that serves as the guide surface.

[0018] In the present invention, the punch may have all of the surfaces corresponding to the plurality of flat surfaces, the sack surface, the connecting surface, and the valve seat surface connected by curved surfaces, which makes it possible to accurately control the plastic flow in this step.

[0019] In the present invention, the punch may have a shape in which a conical portion of the connecting surface that is continuous with the valve seat surface has an apex angle of 150° or more.

[0020] This more reliably prevents deterioration of the roundness of the valve seat surface when the punch presses each surface of the bottom. If the angle is less than 150°, the forging material will tend to flow toward the side wall, but if the angle is 150° or more, the forging material will be prevented from flowing toward the outer periphery, making it easier to maintain the roundness of the valve seat surface with high precision.

[0021] In the present invention, the exterior finishing process in the subsequent step may include a step of forming an assembly portion for assembling the valve seat member to the fuel injection valve by cutting the outer periphery of the forging blank, which makes it possible to form the forging blank into a shape appropriate for assembling the valve seat member to the fuel injection valve. [Brief explanation of the drawings]

[0022] [Figure 1A] 1 is a cross-sectional view showing a longitudinal section of a valve seat member of a direct injection fuel injection valve manufactured by a manufacturing method of a valve seat member of a fuel injection valve according to an embodiment of the present invention. [Figure 1B] 1B is a diagram showing the valve seat member of FIG. 1A as viewed from the tip end side. FIG. [Figure 2] 1 is a cross-sectional view showing a longitudinal section of a valve seat member of a port fuel injection valve manufactured by a manufacturing method of a valve seat member of a fuel injection valve according to an embodiment of the present invention. [Figure 3A] 1B is a cross-sectional view of a workpiece (work in progress) in a state where appearance finishing processing for manufacturing the valve seat member of FIG. 1A has been completed. FIG. [Figure 3B] 3B is a plan view showing the workpiece of FIG. 3A as viewed from above. FIG. [Figure 4A] FIG. 3 is a view showing a workpiece in which an uneven portion is provided on the outer periphery in the appearance finishing process after the main step for the port fuel injection valve of FIG. 2, and in which a valve hole and a fuel collecting chamber are provided. [Figure 4B] 4B is a plan view showing the workpiece of FIG. 4A as viewed from above. FIG. [Figure 5A] 1C is a side view of the tip of a punch used to manufacture the valve seat member of FIGS. 1A and 1B. FIG. [Figure 5B] 5B is a front view showing the punch of FIG. 5A as viewed from the tip side. FIG. [Figure 6A] 3 is a side view of the tip of a punch used to manufacture the valve seat member of FIG. 2. FIG. [Figure 6B] 6B is a front view showing the punch of FIG. 6A as viewed from the tip side. FIG. [Figure 7] 3 is a flowchart showing a method for manufacturing a valve seat member of a fuel injection valve according to one embodiment of the present invention. [Figure 8] 8 is a cross-sectional view showing how the forging material is shaped by plastic flow processing using backward extrusion forging in this step of the manufacturing method shown in FIG. 7. FIG. [Figure 9] 9 is a cross-sectional view of a billet material formed in a main step of the manufacturing method shown in FIG. 8, for illustrating the cross-sectional area reduction rate in the main step. [Figure 10] 9 is a diagram showing the influence of the cross-sectional area reduction rate when the main step of the manufacturing method of FIG. 8 is performed. [Figure 11A] 9 is a diagram showing the influence of the shape of the valve seat surface and the like on the billet material when performing the main step of the manufacturing method of FIG. 8. FIG. [Figure 11B] 9 is a diagram showing the influence that the shape of the connection surface and the like has on the billet material when performing the main step of the manufacturing method of FIG. 8. FIG. [Figure 12] 9 is a diagram showing the influence of the value of the bottom thickness t, which corresponds to the punch pressing amount, on the molding of each surface of the inside of the bottom when performing the main step of the manufacturing method of FIG. 8. FIG. [Figure 13] 9 is a diagram showing a seat angle α of the valve seat surface and an upstream angle β of the connecting surface formed in this step of the manufacturing method of FIG. 8. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1A is a cross-sectional view showing a cross section along the axial direction of a valve seat member of a fuel injection valve manufactured by a manufacturing method according to an embodiment of the present invention, and Fig. 1B shows the valve seat member as viewed from the tip side.

[0024] 1A and 1B, this valve seat member 1 has a cylindrical shape with a bottom, a side wall 2, and a bottom 3, and the inside of the bottom 3 is provided with a spherical crown-shaped sack surface 4 that opens rearward from the tip, a truncated conical valve seat surface 5 (seat surface) that continues to the rear of the bottom 3, and a connecting surface 7 that continues from the rear edge to an inner wall surface 6 of the side wall 2. In addition, the outer periphery of the side wall 2 is provided with an assembly portion 19 for assembling the valve seat member 1 to a fuel injection valve 9.

[0025] The center of the sack surface 4 is located on the central axis of the valve seat member 1. The inner wall surface 6 constitutes a guide surface that guides the spherical valve element 8 as it reciprocates to abut against and separate from the valve seat surface 5.

[0026] The valve seat member 1 is provided at the tip of the fuel injection valve 9. The reciprocating motion of the valve body 8 is performed by a drive unit of the fuel injection valve 9 via a rod 10. The bottom portion 3 is provided near the center of the sack surface 4 with a plurality of fuel nozzle holes 11 for injecting the supplied fuel from inside the sack surface 4.

[0027] 1B, the valve seat member 1 has a hexagonal cylindrical shape in which six flat portions 12 and six inner corners 13 are alternately arranged in the circumferential direction. A fuel passage 14 leading to the sack surface 4 is formed between the inner corners 13 and the valve body 8.

[0028] Fig. 2 shows a longitudinal cross section of a valve seat member manufactured by a manufacturing method for a valve seat member for a port fuel injection valve according to one embodiment of the present invention. As shown in Fig. 2, in this valve seat member 1b, instead of the sack surface 4 in the above-described valve seat member 1, a valve hole 21 that is opened and closed when a valve element 8b abuts against and separates from a valve seat surface 5b is configured as a fuel collecting chamber 22 that temporarily collects fuel before fuel injection, and fuel is injected from this fuel collecting chamber 22 through an injector plate 23 having a plurality of fuel nozzle holes 11b.

[0029] In addition, an assembly portion 19 for assembling the valve seat member 1 to a fuel injection valve is provided on the outer periphery of the side wall 2. In addition, the valve seat member 1b has an inner wall surface 6b and a connection surface 7b, similar to the valve seat member 1 described above.

[0030] Fig. 3A shows a workpiece W1 in the middle of manufacturing the valve seat member 1, in which the billet material 17 has been subjected to the exterior finishing process S31 described below. Fig. 3B shows the workpiece W1 as viewed from above. The sack surface 4, the valve seat surface 5, the connecting surface 7, and the flat surface 12 have already been formed in the workpiece W1.

[0031] Fig. 4A shows a workpiece W2 in the middle of manufacturing the valve seat member 1b, after the appearance finishing process S31 of the billet material 17b has been completed. Fig. 4B shows the workpiece W2 as viewed from above.

[0032] In the workpiece W2, the valve hole 21 and the fuel collecting chamber 22 are also formed by the external finishing process S31, which will be described later. However, when the main process S2, which will be described later, is completed, the billet material 17b is in a state where it has been formed up to the spherical crown-shaped portion SC by the punch, and the subsequent external finishing process S31 removes the spherical crown-shaped portion SC, and the valve hole 21 and the fuel collecting chamber 22 are formed.

[0033] 5A shows a side view of the tip of a punch 18 used in step S2, which will be described later, when manufacturing the valve seat member 1 shown in FIGS. 1A and 1B. FIG. 5B shows the punch 18 as viewed from the tip side. As shown in FIGS. 5A and 5B, the punch 18 has shapes corresponding to the multiple flat portions 12, inner corners 13, and connecting surface 7 shown in FIGS. 1A and 1B. These corners are smoothly connected via a curved surface SF.

[0034] Fig. 6A shows a side view of the tip of punch 18b used in step S2, which will be described later, when manufacturing the valve seat member 1b of Fig. 2. Fig. 6B shows punch 18b as viewed from the tip side. As shown in Figs. 6A and 6B, punch 18b has shapes corresponding to the multiple flat portions 12b, inner corners 13b, and connecting surface 7b in Fig. 2. These corners are smoothly connected via curved surface SF.

[0035] Fig. 7 is a flowchart showing a method for manufacturing a valve seat member for a fuel injection valve according to one embodiment of the present invention. As shown in Fig. 7, this manufacturing method includes a pre-process S1 in which a cylindrical forging material that will become the valve seat member 1 is annealed S11 and bonded S12, a main process S2 in which an inner wall surface 6 and the inner surfaces of the bottom portion 3 are formed on the inside of the forging material, and a post-process 3S in which an exterior finishing process S31 and a heat treatment S32 are performed on the forging material.

[0036] The forging material to be subjected to the annealing process S11 is a billet material having a diameter and height suitable for forming the valve seat member 1. In the annealing process S11, the billet material is annealed by heating it for a predetermined period of time. In the bonding process S12, a bonding coating is formed on the billet material.

[0037] Fig. 8 is a cross-sectional view showing how the billet material is shaped by plastic flow processing using backward extrusion forging in step S2. In step S2, as shown in Fig. 8, a plastic flow processing step S21 is performed in which a punch 18 is pressed from above along the central axis against billet material 17 placed inside a die 16 having a cylindrical inner surface with an inner diameter substantially the same as the outer diameter of the valve seat member 1, the bottom of which is closed by a flat receiving plate 15, to form the side wall 2.

[0038] At this time, the billet material 17 is pushed backward as shown by the arrow due to the pressing force of the punch 18. At the same time, a surface forming step S22 is carried out in parallel, in which the punch 18 forms the inner wall surface 6 of the side wall 2 and the inner surfaces of the bottom portion 3. This forming is carried out by transferring the outer shape of the punch 18 to the billet material 17 by the pressing force of the punch 18.

[0039] That is, as described above with reference to Figures 5A and 5B, the side surface of the punch 18 has the shape of the inner wall surface 6 of the valve seat member 1, and the tip surface has the shapes of the sack surface 4, the valve seat surface 5, and the connecting surface 7 of the valve seat member 1, and these shapes are transferred to the billet material 17 in the surface forming process S22.

[0040] The forming of the billet material 17 in this main step S2 is carried out under the following first to third conditions: First, as the first condition, this step S2 is carried out so that the cross-sectional area reduction rate when the billet material 17 is plastically deformed to form the side wall 2 is less than 35% for the following reason.

[0041] 9 is a cross-sectional view of the billet material 17 formed in the main step S2 to explain the area reduction rate. As shown in FIG. 9, if the cross-sectional area before processing, which is calculated from the diameter φ of the billet material 17, is taken as the raw material cross-sectional area A, and the cross-sectional area of ​​the side wall 2 (the outer portion of the regular hexagonal inner wall surface 6) after the billet material 17 is formed in the main step S2 is taken as the processed cross-sectional area B, the area reduction rate R is given by R = {(AB) / A} × 100 This becomes:

[0042] Fig. 10 shows the effect of the area reduction rate R when step S2 is performed. Fig. 10 shows the "strain distribution" in the billet material 17 when step S2 is performed at each "area reduction rate R," along with the corresponding "flow net" and "roundness profile" for the valve seat surface 5. Note that Fig. 10 shows the results when each area reduction rate R is obtained by changing the diameter of the billet material 17 while keeping the indentation amount of the punch 18 constant and the shape of each surface of the bottom portion 3 constant.

[0043] As can be seen from Figure 10, when the area reduction rate R is 44% or 38%, as shown in the "Strain distribution" and "Flow net" columns, material flows into the side wall 2, so the strain on the bottom side of the billet material 17 is small and the strain on the side wall 2 is large.

[0044] Therefore, since the inner wall surface 6 of the side wall 2 has a cylindrical cross section with a regular hexagonal shape, the material is pulled toward the inner wall surface 6 and is affected by its shape, which impairs the roundness of the valve seat surface 5, as shown in the "Circularity Profile" column.

[0045] On the other hand, in comparison, when the area reduction rate R is 34% or 30%, there is no flow of material into the side wall 2, so the strain on the bottom surface 20 side of the billet material 17 is large and the strain on the side wall 2 is small. Therefore, the material is not pulled toward the inner wall surface 6 of the side wall 2 and is not affected by the shape of the inner wall surface 6, so the roundness of the valve seat surface 5 is not impaired.

[0046] Therefore, this step S2 is performed so that the cross-sectional area reduction rate R is less than 35% so as not to impair the roundness of the valve seat surface 5. That is, the pushing amount of the punch 18, the diameter of the billet material 17, etc. are set so as to satisfy this, and this step S2 is performed.

[0047] Next, as a second condition, the forming of the billet material 17 in this process S2 is performed so that the seat angle α of the valve seat surface 5 is an obtuse angle of 100° or more for the following reason. As shown in Fig. 13, the seat angle α is the apex angle of the truncated cone shape of the valve seat surface 5.

[0048] 11A shows the influence of the shape of the valve seat surface 5 and the like on the billet material 17. FIG. 11A shows the strain distribution in the billet material 17 when this step S2 is performed at each "seat angle α." The "seat angle α" is the apex angle of the truncated cone-shaped valve seat surface (seat surface) 5.

[0049] 11A, when the seat angle α is 90°, the material flows more easily onto the side wall 2 than when the seat angle α is 106° or 120°, making it difficult to maintain the shape of the valve seat surface 5. On the other hand, when the seat angle α is 106° or 120°, the material does not flow easily onto the side wall 2, making it possible to maintain the shape of the valve seat surface 5 well.

[0050] For this reason, the forming of the billet material 17 in this step S2 is performed so that the seat angle α of the truncated cone shape of the valve seat surface 5 is an obtuse angle of 100° or more. That is, this step S2 is performed using a punch 18 in which the apex angle of the truncated cone part at the tip thereof corresponding to the valve seat surface 5 is an obtuse angle of 100° or more.

[0051] 11B, step S2 may be performed so that the upstream angle β of the connecting surface 7 is 150° or more. The upstream angle β is the apex angle of the conical portion of the connecting surface 7 that continues to the valve seat surface 5 with respect to the central axis of the billet material 17, as shown in FIG. 13. If the upstream angle β is less than 150°, for example 120°, the material will more easily flow to the side wall 2 than if the upstream angle β were 150° or more, making it difficult to maintain the shape of the valve seat surface 5.

[0052] Furthermore, as a third condition, the billet material 17 is formed in this process S2 so that the pressing amount of the punch 18 is such that the thickness t (bottom thickness t; see Figure 8) from the center position of the sack surface 4 to the bottom surface of the billet material 17 is less than 2 mm and 1 mm or more, for the following reasons.

[0053] Fig. 12 shows the effect of the bottom thickness t, which corresponds to the pressing amount of the punch 18, on the forming of each surface inside the bottom portion 3. Fig. 12 shows the "strain distribution" in the billet material 17 when this step S2 is performed with each bottom thickness t, together with the "roundness profile" for the corresponding valve seat surface 5.

[0054] As shown in Figure 12, when the bottom thickness t is 2.8 mm, it can be seen that only the distortion near the surface of the punch 18 is large, and the material flows toward the side wall 2. When the bottom thickness t is 0.9 mm, the thickness to the bottom surface of the billet material 17 is thin, and the material flows toward the side wall 2 more, making it difficult for the shape of the front end of the punch 18 to be transferred to the billet material 17 and making it difficult to maintain the transferred shape. In these cases, the roundness of the valve seat surface 5 deteriorates.

[0055] On the other hand, when the bottom thickness t is 2.0 mm, 1.8 mm, 1.6 mm, 1.4 mm, or 1.2 mm, the strain reaches the bottom surface of the billet material 17, expanding the range of the strain and suppressing strain penetration into the side wall 2. In this case, the circularity of the valve seat surface 5 is well maintained. Therefore, as described above, the formation of the valve seat member 1 in this step S2 is performed with the pushing amount of the punch 18 such that the bottom thickness t is less than 2 mm and not less than 1 mm.

[0056] In the external finishing process S31 in the subsequent process S3 after the completion of the main process S2, the external appearance of the billet material 17 formed in the main process S2 is finished so as to have the external appearance shown in Fig. 1A. In the next heat treatment S32, quenching and tempering are performed.

[0057] After the completion of the post-process S3, the inner wall surface 6 and the valve seat surface 5 are lapped, and further, the fuel nozzle holes 11 are provided, and the valve seat member 1 is completed.

[0058] When manufacturing the valve seat member 1b of FIG. 2, the pre-step S1, main step S2, and post-step S3 of FIG. 7 are performed in the same manner as when manufacturing the valve seat member 1, except that a billet material 17b having a diameter and height suitable for manufacturing the valve seat member 1b is used as the billet material, and the punch 18b shown in FIGS. 6A and 6B is used as the punch.

[0059] However, when this step S2 is completed, as described above with reference to FIG. 4A, the billet material 17b has been formed with the punch up to the spherical crown-shaped portion SC, so in the subsequent exterior finishing process S31, the spherical crown-shaped portion SC is removed and the valve hole 21 is formed.

[0060] As described above, according to this embodiment, the internal shape of the valve seat member 1 is formed by one punching (one driving), which eliminates the need for multiple forging processes using multiple dies, reduces manufacturing costs, and prevents cumulative deterioration of accuracy caused by positioning errors when changing dies. Furthermore, the relief shape required when forming the valve seat surface 5 by polishing is no longer necessary, which reduces the corresponding dead volume and avoids the adverse effect of the relief shape on fuel injection.

[0061] Furthermore, this step S2 is performed under the conditions that the area reduction rate R is less than 35%, the apex angle α of the valve seat surface 5 is an obtuse angle of 100° or more, and the thickness t of the billet material 17 from the center position of the sack surface 4 to the bottom surface is less than 2 mm and at least 1 mm, thereby suppressing the amount of plastic flow of the material from the bottom portion 3 to the side wall 2 and forming grain flows that are compressed uniformly in the circumferential direction, thereby obtaining a valve seat surface 5 with high circularity. This also makes it unnecessary to perform finish processing such as polishing the valve seat surface 5.

[0062] Therefore, according to this embodiment, the cycle time for manufacturing the valve seat member 1 can be shortened, and a highly accurate valve seat member 1 can be manufactured at low cost.

[0063] In addition, the exterior finishing process S31 includes a step of cutting the outer periphery of the billet material 17 to form an assembly portion 19 for assembling the valve seat member 1 to the fuel injection valve, so that the billet material 17 can be formed into a shape suitable for assembling to the fuel injection valve.

[0064] Furthermore, when manufacturing the valve seat member 1b, the exterior finishing process S31 in the subsequent process S3 includes a step of providing the valve hole 21, so that the method can also be used to manufacture the valve seat member 1b of a port fuel injection valve.

[0065] Furthermore, the inner wall surface 6 of the side wall 2 is shaped like a hexagonal tube with multiple flat portions 12 and inner corner portions 13 arranged alternately in the circumferential direction, and the fuel passage 14 is formed between the inner corner portions 13 and the valve body 8, so that strain and stress are allowed to flow through the inner corner portions 13, and flow defects in the flat portions 12 that serve as guide surfaces can be avoided.

[0066] Furthermore, if this process S2 is performed so that the apex angle β of the truncated cone at the connection surface 7 that connects to the valve seat surface 5 is 150° or more, the movement of the material toward the side wall 2 can be further suppressed, and the forming accuracy of each surface of the bottom portion 3 by the punch 18 can be improved.

[0067] Furthermore, the punch 18 has shapes corresponding to the multiple flat portions 12, the inner corner portions 13, and the connecting surfaces 7, and these shapes are smoothly connected by curved surfaces. Therefore, by using this punch to perform this step S2, the plastic flow processing step S21 of this step S2 can be carried out smoothly.

[0068] The above-described effects obtained when manufacturing the valve seat member 1 are also obtained when manufacturing the valve seat member 1b.

[0069] Although the embodiments of the present invention have been described above, the present invention is not limited to this. For example, instead of providing a plurality of fuel nozzle holes 11 in the sack surface 4, a valve hole may be provided in the sack surface 4, and an injector plate having a plurality of fuel nozzle holes 11 communicating with the valve hole may be fixed to the outside of the valve hole. Furthermore, the inner wall surface 6 of the side wall 2 is not limited to a regular hexagon and may be another polygon. [Explanation of symbols]

[0070] 1, 1b... valve seat member, 2, 2b... side wall, 3... bottom, 4... sack surface, 5, 5b... valve seat surface, 6, 6b... inner wall surface, 7, 7b... connection surface, 8, 8b... valve body, 9... fuel injection valve, 10... rod, 11, 11b... fuel nozzle hole, 12, 12b... flat portion, 13, 13b... inner angle portion, 14... fuel passage, 15... receiving plate, 16... die, 17, 17b... billet material, 18... punch, 19, 19b... assembly portion, 20... bottom surface, 21... valve hole, 22... fuel collection chamber, SC... spherical crown portion, SF... curved surface, W1, W2... workpiece

Claims

1. 1. A method for manufacturing a valve seat member for a fuel injection valve, the valve seat member having a cylindrical shape with a bottom having a side wall and a bottom, the inside of the bottom being provided with a spherical crown-shaped sack surface that opens rearward from a tip center, a truncated conical valve seat surface continuing to the rear of the sack surface, and a conical connecting surface continuing from a rear end edge of the valve seat surface to an inner wall surface of the side wall, the inner wall surface forming a guide surface that guides a spherical valve element as it reciprocates to contact and separate from the valve seat surface, a pre-process of annealing and bonding a cylindrical forging material to be used as the valve seat member; After the previous process, a main process of forming the inner wall surface and the inner surfaces of the bottom portion on the inside of the forging material; After the main process, a post-process is performed on the forging material to perform appearance finishing and heat treatment, The present step a plastic flow processing step in which a punch is pressed from above along a central axis against the forging material placed inside a die having a cylindrical inner surface whose bottom surface is closed by a backing plate, thereby performing backward extrusion forging to form the side wall; a surface forming step of pressing and forming the guide surfaces of the side walls and the inner surfaces of the bottom portion with an outer surface of the punch when performing the plastic flow processing step, a punch having a shape in which the cross-sectional area reduction rate when the side wall is formed is less than 35%, the punch has a conical connecting surface, and the frustum-shaped valve seat surface has an obtuse apex angle of 100° or more, and the punch is driven in one operation so that the thickness from the center position of the sack surface to the bottom surface of the forging material is less than 2 mm but 1 mm or more.

2. 2. The method for manufacturing a valve seat member for a fuel injection valve according to claim 1, wherein the punch has an outer surface that forms a polygonal cylindrical shape in which a plurality of flat portions that form the guide surface and a plurality of inner corners that form the fuel passage are alternately arranged in the circumferential direction.

3. 3. The method for manufacturing a valve seat member for a fuel injection valve according to claim 2, wherein the punch has all of the surfaces corresponding to the plurality of flat portions, the sack surface, the connecting surface and the valve seat surface connected by curved surfaces.

4. 3. The method for manufacturing a valve seat member for a fuel injection valve according to claim 2, wherein the punch has a shape such that a portion of the connecting surface that is continuous with the valve seat surface has an apex angle of 150° or more.

5. 2. The method for manufacturing a valve seat member for a fuel injection valve according to claim 1, wherein the external finishing process includes a step of forming an assembly portion for assembling the valve seat member to the fuel injection valve by cutting an outer periphery of the forging material.

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