Patent Application
20060137423
This application is based on Japanese Patent Application No. 2004-374696 filed on Dec. 24, 2004, the contents of which are incorporated herein by reference in its entirety.
The present invention relates to a method for manufacturing a high-pressure piping part and a high-pressure piping part manufactured by the method and, in particular, is suitably applied to a high-pressure piping part for an internal combustion engine.
For example, a high-pressure piping part having therein a passage for passing high-pressure fuel to be supplied to an internal combustion engine is a constituent part for forming a body of an injector for a diesel engine.
Generally, in a case of manufacturing this piping part, because of convenience in terms of equipment, a billet 101 shaped like a circular column shown in
The fuel flowing through the passage of this injector body has a very high pressure (for example, pressure of 180 MPa) and hence a large degree of allowance is provided to the resistance to pressure of the injector body.
In recent years, in order to respond to a trend toward larger power and cleaner exhaust gas of a diesel engine, the pressure of fuel to be supplied has been desired to be further increased. However, it is difficult to further improve the resistance to pressure of the injector body of a high-pressure piping part manufactured by the above-mentioned manufacturing method in the related art. Hence, there is presented a problem that it is difficult to secure the same degree of allowance of the resistance to pressure as ever.
The present inventors earnestly studied measures to improve the degree of allowance of the resistance to pressure of a body structure. As a result, the present inventors found that the fracture of the body structure in a high internal pressure test for checking the degree of allowance of resistance to pressure easily developed when the direction in which stress was applied to the body structure by the internal pressure agreed with the direction of fiber flow of the body structure. That is, the present inventors found that by controlling the fiber flow, the degree of allowance of the resistance to pressure of an injector body of a high-pressure piping part could be improved.
In view of the above-described problems, it is an object of the present invention to provide a method for manufacturing a piping part for a high-pressure fluid, in which a degree of allowance of resistance to pressure is improved.
It is another object of the present invention to provide a piping part for a high-pressure fluid, which can effectively improve a degree of allowance of resistance to pressure.
According to the present invention, a method for manufacturing a piping part for a high-pressure fluid, includes a step of arranging a billet made of a raw material in a closed space within a die, and a step of forming a body structure before a passage for the high-pressure fluid is formed by pressing a punch to the billet after the arranging step to plastically deform the billet. Further, in the forming step, the billet is plastically deformed in such a way that fiber flows along the passage are formed in the body structure.
Because the fiber flows of the body structure forged in the closed space is along the passage for the high-pressure fluid, the direction in which stress is applied to the passage by an internal pressure is approximately perpendicular to the directions of the fiber flows. In this manner, the degree of allowance of the resistance to pressure of the body structure can be effectively improved in the piping part.
For example, the closed space within the die includes a forward extrusion portion in which the billet is arranged in the arranging step and which extends to plastically deform the billet in a pressing direction of the punch in the forming step, and a side extrusion portion branching from the forward extrusion portion in such a way as to plastically deform the billet in a direction different from the pressing direction of the punch in the forming step. In this case, in the forming step, the body structure is formed to include a main portion that is plastically deformed in correspondence with the forward extrusion portion and has therein the fiber flow along the passage, and a side arm portion that is plastically deformed in correspondence with the side extrusion portion and has therein the fiber flow along the passage. Therefore, the body structure having the main portion and the side arm portion branching from the main portion can improve the degree of allowance of the resistance to pressure of the high-pressure piping part.
The side extrusion portion can be formed to extend in a direction approximately perpendicular to an extending direction in which the forward extrusion portion extends. In this case, during the forming step, the billet in the forward extrusion portion can be easily plastically deformed from the forward extrusion portion to the side extrusion portions. Therefore, the fiber flow along the passage can be stably formed in the side arm portion formed in the side extrusion portion.
For example, the side extrusion portion includes a plurality of extrusion parts. In this case, in the forming step, the billet can be plastically deformed in balance in a circumferential direction of an axis of the forward extrusion portion from the forward extrusion portion to the plurality of extrusion parts. According to this, the plastically deformed portions of the billet entering from the forward extrusion portion into the plurality of side extrusion portions are in balance in the circumferential direction of the axis of the forward extrusion portion and hence the fiber flow of the main portion formed in the forward extrusion portion is not disturbed. Therefore, the fiber flow along the passage can be stably formed in the main portion of the body structure. Alternatively, the plurality of extrusion parts can be arranged at equal intervals in the circumferential direction of the axis of the forward extrusion portion. In this case, the fiber flow along the passage can be stably formed in the main portion of the body structure having the side arm portions.
Furthermore, the billet arranged in the forward extrusion portion in the arranging step is provided with a fiber flow in the pressing direction of the punch. In this case, it is extremely easy to stably form the fiber flow along the passage in the main portion of the body structure.
According to another aspect of the present invention, a piping part for a high-pressure fluid includes a body structure forged in a closed space, and the body structure includes a passage through which the high-pressure fluid flows and a plurality of fiber flows provided along the passage. Therefore, it is possible to improve the degree of allowance of the resistance to pressure of the high-pressure piping part. The body structure can include a main portion extending in an extending direction, and a side arm portion branching from the main portion and extending in a directions different from the extending direction of the main portion. In this case, the fiber flows along the passage can be provided in the main portion and the side arm portion.
In the present invention, the high-pressure fluid can be suitably used as fuel for an internal combustion engine.
The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments made with reference to the accompanying drawings, in which:
Preferred embodiments of the present invention will be described with reference to the drawings.
A high-pressure piping part in an embodiment is a body of an injector for injecting high-pressure fuel (for example, light oil of a pressure of 200 MPa) into a diesel engine of an internal combustion engine.
As shown in
The body structure 10 is formed of steel (SCM 415 in this embodiment) and is formed in the shape shown in
Next, a method for forging the body structure 10 using a die 20 will be described.
As shown in
The die space 24 is formed by a forward extrusion portion 25 extending in the up and down directions in the drawing and by a pair of side extrusion portions 26, 27 branching from the forward extrusion portion 25 and extending in the left and right directions (i.e., directions perpendicular to a direction in which the forward extrusion portion 25 extends) in the drawing.
The pair of side extrusion portions 26, 27 are formed at symmetric positions across the forward extrusion portion 25 (positions symmetric with respect to the axis of the forward extrusion portion 25). That is, the two extrusion portions 26, 27 are arranged equally in the circumferential direction of the axis of the forward extrusion portions 25.
When the body structure 10 is manufactured by the use of the die 20 constructed in the above-described manner, as shown in
This billet 1 is a circular column-shaped member made of the above-mentioned steel (SCM 415 in this embodiment) and is prepared by cutting a round bar in a specified length by a billet shear or the like.
Moreover, this billet 1 has an outside diameter that is a little smaller than the inside diameter of the forward extrusion portion 25 (specifically, inside diameter of a middle portion in the up and down directions in the drawing) and hence can be easily inserted into an elongated hole forming the forward extrusion portion 25. Then, after the billet 1 is inserted into the elongated hole, the axis of the billet 1 can be easily consistent with the axis of the forward extrusion portion 25.
When the billet 1 is arranged in the die space 24 of the die 20, as shown in
When the punch 23 is further pressed into the billet 1, as shown in
When the forging is completed as shown in
This body structure 10 is constructed with the main body portion 11 plastically deformed in correspondence with the forward extrusion portion 25 of the die space 24 and side arm portions 12, 13 plastically deformed in correspondence with the side extrusion portions 26, 27. That is, the body structure 10 is constructed of the main body portion 11 extending in one direction (in the up and down directions in
The step shown in
Here, the billet 1 arranged in the die space 24 in the arranging step shown in
When the temperature of the billet 1 is lower than 600° C., ductility is little and hence forging is difficult. When the temperature of the billet 1 is higher than 950° C., forging accuracy becomes lower. From the viewpoint of the ease of forging and forging accuracy, the temperature of the billet 1 is preferably in a range between 600° C. and 950° C., and more preferably in a range between 750° C. and 800° C.
Both the side arm portions 12, 13 of the body structure 10 formed in this manner are bent upward in
The body structure 10 shown in
Here, the formation of a fiber flow in the forging step shown in
In
When the billet 1 is being plastically deformed in the manner shown in
Meanwhile, because the material to be processed is plastically deformed in the left and right directions in the drawing in the side extrusion portions 26, 27, a fiber flow extending in the left and right directions in the drawing is formed.
Because both side extrusion portions 26, 27 extend nearly in directions perpendicular to the axial direction (i.e., extending direction) of the forward extrusion portion 25, the material to be processed is plastically deformed with stability from the forward extrusion portion 25 to both the side extrusion portions 26, 27. Hence, as compared with a case where the directions in which the side extrusion portions 26, 27 extend is inclined to the axial direction of the forward extrusion portion 25, a stable fiber flow is formed in the directions in which the side extrusion portions 26, 27 extend.
Moreover, both the side extrusion portions 26, 27 branch from the forward extrusion portion 25 at symmetric positions (positions at equal distances in the circumferential direction of the axis) on the same height positions in the axial direction of the forward extrusion portion 25. Therefore, when the material to be processed is plastically deformed in the side extrusion portions 26, 27, the material to be processed enters from the forward extrusion portion 25 into both the side extrusion portions 26, 27 in good balance and hence does not disturb the fiber flow of the material to be processed at the points where the side extrusion portions 26, 27 branch from the forward extrusion portion 25.
Hence, as shown in
As shown in
That is, the fiber flow 111 along the passage 14a is formed in the main body portion 11, and the fiber flow 121 along the passage 14b is formed in the side arm portion 12.
According to the above-mentioned structure and manufacturing method, in the main body portion 11 and the side arm portion 12 of the body structure 10, the fiber flows 111, 121 are along the passage 14 (i.e., passage 14a and passage 14b) formed in the main body portion 11 and the side arm portion 12 of the body structure 10. Hence, the direction in which stress is applied to the passage 14 by an internal pressure due to the high-pressure fuel is approximately perpendicular to the directions of the fiber flows 111, 121.
When the fiber flows are formed, nonmetallic inclusions such as sulfur and the like causing fatigue fracture in the billet (material to be processed) 1 are stretched along the fiber flows (i.e., flow of the material to be processed). Therefore, fracture strength becomes comparatively larger in a case where the direction in which stress is applied to the passage 14 by the internal pressure does not agree with the direction of the fiber flow.
According to the present embodiment, the direction in which stress is applied to the passage 14 by the internal pressure is nearly perpendicular to the directions of the fiber flows 111, 121 and hence the degree of allowance of the resistance to pressure of the body 10A for the injector can be increased.
When a body structure 110 is formed by a half-closed forging method shown in
The present inventors conducted the test of applying internal pressure repetitively on the body structure 10 manufactured by the present embodiment and on the body structure 110 manufactured by the forging method shown in
In recent years, the request of increasing the pressure of fuel supplied to an internal combustion engine has increased and hence the effect of increasing the degree of allowance of the resistance to pressure of the body 10A for the injector is extremely large.
It is possible to form the main portion and the side arm portion from separate parts and to combine them into one part by a fastening structure by screwing to form a body for an injector in which a fiber flow is along the passage. However, in this case, when the fuel pressure increases, it is difficult to secure the reliability of the resistance to pressure of portions fastened to each other by screwing. The body 10A for an injector according to the present embodiment in which the main body portion 11 and the side arm portion 12 are integrally formed has an advantage in the reliability of resistance to pressure.
Moreover, according to the structure and the manufacturing method of the present embodiment, the flash 103 formed in the method shown in
Furthermore, a raw material can be set by inserting the billet 1 into the forward extrusion portion 25 and hence such a gripping portion 104 for setting the raw material that is required in the conventional method as shown in
Still furthermore, in contrast to the case of applying the conventional method, the body structure 10 can be formed with higher accuracy. In particular, a portion lower than the side arm portions 12, 13 of the main body portion 11 of the body structure 10 is formed in one depressed space of the lower die 22 and hence can be formed with extremely high accuracy. Therefore, this can eliminate the need for cutting its outer peripheral surface and hence can reduce load in post-working by a large amount.
Still furthermore, when the passage 14 is formed in the body structure 10 by drilling, a drill is moved along the fiber flows 111, 121 and hence can be accurately moved in a straight line. Therefore, the passage 14 can be also formed with high accuracy.
Although the present invention has been described in connection with the preferred embodiment thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art.
For example, in the above-mentioned embodiment, the side extrusion portions 26, 27 in the die space 24 are formed at the symmetric positions across the forward extrusion portion 25. That is, the side extrusion portions 26, 27 in the die space 24 are formed at symmetric positions with respect to the axis of the forward extrusion portion 25. Furthermore, the body structure 10, constructed of the main body portion 11 extending in the up and down directions and the pair of side arm portions 12, 13 branching from the main body portion 11 and arranged at symmetric positions with respect to the main body portion 11, is forged. However, the side extrusion portions of the die space, that is, the side arm portions of the structure to be forged are not limited to two portions but may be three or more portions.
For example, as shown by the top plan view in
Moreover, when the material to be processed enters in good balance from the forward extrusion portion into a plurality of side extrusion portions, for example, even if the side arm portions 312 branch from the main body portion 11 as shown by the top plan view in
Furthermore, in the above-mentioned embodiment, the die 20 is divided into the upper and lower dies 21, 22 and the punch 23 is provided on the side of the upper die 21. However, it is not intended to limit the structure of the die to this but any structure may be employed if a material to be processed can be forged in a closed space. For example, the structure of the die may be of the type in which the die is divided into left and right dies or of the type in which the die is divided into three parts. In addition, the die may be provided with a plurality of punches.
Still furthermore, in the above-mentioned embodiment, the forward extrusion of forming the main body portion 11 and the side extrusion of forming the side arm portions 12, 13 are performed at the same time, but they may be performed separately. It is also recommended that after the forward extrusion is performed, the side extrusion can be performed.
Still furthermore, in the above-mentioned embodiment, the material to be processed of the billet 1 is SCM415 but may be other material. For example, the material to be processed may be steel such as S45C or SCM435.
Still furthermore, in the above-mentioned embodiment, the high-pressure piping part forged in the closed space is the injector body structure for the internal combustion engine (diesel engine) but the present invention can be effectively applied to the other high-pressure piping parts.
For example, the present invention may be applied to a common rail for distributing and supplying fuel to an injector and may be applied to piping parts for passing other high-pressure fluid. In addition, the shape of the high-pressure piping part is not limited to the structure constructed of the main portion and the side arm portion.
While the invention has been described with reference to preferred embodiments thereof, it is to be understood that the invention is not limited to the preferred embodiments and constructions. The invention is intended to cover various modification and equivalent arrangements. In addition, while the various elements of the preferred embodiments are shown in various combinations and configurations, which are preferred, other combinations and configuration, including more, less or only a single element, are also within the spirit and scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-374696 | Dec 2004 | JP | national |
