JP2006118510A - Common rail and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a common rail capable of increasing an inner pressure fatigue strength at a branch tube connection part by offsetting the occurrence of a tensile stress at the lower end inner peripheral edge part of a branch hole by a compressive residual stress to effectively suppress it. <P>SOLUTION: The branch hole 1-2 having pressure receiving seat face 1-4 communicating with a flow passage 1-1 and opening to the outside is formed in a boss part 1-3 formed at the axial peripheral wall part of a main tube rail 1 having the flow passage 1-1 inside a core, a pressing seat face part 2-3 formed by a connection head part at the end part of the branch tube 2 with a flow passage communicating with the flow passage 1-1 is pressingly engaged with the pressure receiving seat face 1-4, and the common rail is tightened and connected according to the pressing under the neck of the connection head part by threading a boss part 1-3 with a tightening cap nut 3. The compression residual stress is produced around the opening end part of the main tube rail flow passage opening of the branch hole by imparting a pressing force from the outside to the boss part 1-3 in the axial direction by a press system. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates generally to high pressure fuel manifolds or common rails such as block rails in accumulator fuel injection systems for diesel internal combustion engines.

  Conventionally, as this type of common rail, for example, as shown in FIG. 10, a plurality of bosses 11-3 provided at intervals on an axial peripheral wall portion on the main rail 11 side made of a circular pipe are connected to the main pipe. A branch hole 11-2 having a pressure receiving seat surface 11-4 that communicates with the flow passage 11-1 of the rail 11 and opens outwardly is formed, and a pressing seat surface formed by the connecting head 12-2 on the branch pipe 12 side 12-3 is brought into contact with and engaged with the pressure-receiving seat surface 11-4 on the main rail 11 side, and a tightening bag nut 13 previously assembled on the branch pipe side with a washer 14 is attached to the boss portion 11-3. There is known a system in which a connection configuration is formed by screwing together with pressing at the connection head 12-2. In the figure, 12-1 is a flow path of the branch pipe 12.

  However, in the case of a common rail having a structure in which a branch hole 11-2 is provided in a boss 11-3 provided in a main rail 11 made of a circular pipe as shown in FIG. A large stress is generated at the opening end P of the main rail flow passage 11-2, and the opening end P is a starting point, so that cracks are likely to occur, which may lead to leakage.

  The present invention has been made to solve the above-described conventional problems, and provides a common rail capable of improving the internal pressure fatigue strength by reducing the maximum tensile stress value generated at the inner peripheral edge at the lower end of the branch hole. That is.

  In order to achieve the above object, the present invention opens at least one boss portion provided on the axial peripheral wall portion of the main rail having a flow passage in the axial direction thereof, and opens outwardly. A branch hole having a pressure receiving seat surface, and a pressing seat surface portion formed by a connecting head provided at an end portion of a branch pipe having a flow path communicating with the flow passage is brought into contact with and engaged with the pressure receiving seat surface, and the boss portion In the common rail, which is fastened and connected with the pressing at the connecting head by screwing of a fastening cap nut incorporated in advance on the branch pipe side, the main rail flow passage opening end of the branch hole It is characterized by a common rail in which compressive residual stress exists around the part.

  In addition, a branch hole having a pressure receiving seat surface that opens to the outside and opens to the flow passage is provided in at least one boss portion provided in the axial peripheral wall portion of the main rail having the flow passage in the axial direction. The pressing seat surface portion formed by the connection head provided at the end portion of the branch pipe having the flow path leading to the flow passage is brought into contact with and engaged with the pressure receiving seat surface, and is assembled in advance with the boss portion on the branch pipe side. In the method of manufacturing a common rail according to the present invention, wherein the first boss of the present invention is externally connected to the boss from the outside. A compressive residual stress is generated in the vicinity of the main rail flow passage opening end portion of the branch hole by applying a pressing force in the axial direction of the portion, preferably by a pressing method. The embodiment of the present invention is pressed by the external pressure method in the axial direction of the boss from the outside Wherein the punching simultaneously branch hole Granting. Next, in the third embodiment of the present invention, a pressing force is applied to the inner peripheral surface of the main rail in the vicinity of the branch hole by an internal pressure method, and a compression residual is provided around the end of the main rail flow passage opening of the branch hole. The fourth embodiment of the present invention is characterized in that a stress is generated, and the fourth embodiment of the present invention is a tube expansion method in which a pressing force is applied to the inner peripheral surface of the main rail near the branch hole from the inside of the main rail in the radial direction. A pressure is applied to generate a compressive residual stress in the vicinity of the opening end of the main rail flow passage of the branch hole. Further, the fifth embodiment of the present invention relates to the inner peripheral surface of the branch hole. A common rail manufacturing method in which a pressing force is applied by a diameter expansion method that applies a pressing force in a radial direction from the inside of a branch hole, and compressive residual stress is generated around the end of the main rail flow passage opening of the branch hole. It is a feature.

  That is, according to the present invention, the compressive residual stress is present around the opening end of the main rail flow passage of the branch hole, so that the tensile stress generated in the inner peripheral edge P of the lower end of the branch hole due to the high internal pressure of the main rail is compressed. This method cancels the residual stress and lowers the maximum tensile stress value generated at the inner peripheral edge of the lower end of the branch hole. As a method of generating and remaining compressive residual stress around the opening end of the main rail flow passage of the branch hole A method of applying a pressing force from the outside in the axial direction of the boss portion by a pressing method, a method of applying pressure in the flow path of the main rail, or a mechanical pressing in the pipe radial direction from the inside of the main rail. A tube expansion method for applying pressure or a diameter expansion method for mechanically applying a pressing force from the inside of the branch hole in the radial direction of the branch hole is used.

  Here, as a method of applying a pressing force from the outside in the axial direction of the boss portion by a press method or the like, for example, with the rail body fixed to the lower mold, pressurization or pressurization using a punch or rod A method of simultaneously punching the branch holes can be used. Further, as a method of applying pressure in the flow path of the main rail, hydraulic pressure such as hydraulic pressure or water pressure can be used. In addition, as a tube expansion method for mechanically applying a pressing force in the tube radial direction from the inside of the rail, for example, by using a diameter expansion tool such as a sphere or a shell type plug having a diameter slightly larger than the rail inner diameter in the flow path of the main rail. A method of press-fitting by a drawing method or a pressing method, a diameter expanding method by a burnishing tool, or the like can be used. Furthermore, as a diameter expansion method that mechanically applies a pressing force from the inside of the branch hole in the radial direction of the branch hole, the branch hole is made slightly smaller than the predetermined hole diameter, and the inner diameter of the branch hole having the predetermined hole diameter is set. And a method of press-fitting a sphere or plug having substantially the same diameter into the small-diameter branch hole by a pressing method.

  As described above, in the present invention, the compressive residual stress is present around the opening end portion of the main rail flow passage of the branch hole, so that the lower peripheral edge P of the lower end of the branch hole at the time of high pressure fuel pressure in the flow passage at the time of use. It is possible to effectively suppress the occurrence of tensile stress in the above by canceling out by the compressive residual stress, and to improve the internal pressure fatigue strength at the branch pipe connecting portion.

  The common rail of the present invention can effectively suppress the occurrence of tensile stress at the inner peripheral edge of the lower end of the branch hole by compressing residual stress, and can improve the internal pressure fatigue strength at the branch pipe connection portion, so that it is durable. It has an excellent effect that it can reliably perform a stable function by eliminating fluid leakage due to the occurrence of cracks. In addition, according to the common rail manufacturing method of the present invention, it is only necessary to add a pressing force application process to the normal manufacturing process, and it does not require complicated equipment. There is almost no problem such as a decrease in performance, and it has a great effect that a high-quality common rail can be provided at low cost.

  FIG. 1 is a schematic view showing a first embodiment of a method for manufacturing a common rail having a boss portion integral with the main rail of the present invention, FIG. 2 is a schematic view showing a modification of the first embodiment, and FIG. Is an example of a pressing force applying means in the manufacturing method of the above, (A) is a longitudinal sectional view of a boss part partially broken showing a method of pressing using a punch having a pressing surface formed in a reverse concave shape, (B) is a longitudinal cross-sectional view of the boss portion showing a method in which an annular protrusion is provided on the inner bottom portion of the boss portion and pressing is performed using a punch having a flat pressing surface, and (C) is a concave shape formed on the inner bottom portion of the boss portion. A vertical cross-sectional view of the boss portion showing a method of pressing using a punch whose pressing surface is a spherical surface, (D) is a projecting projection of the inner bottom of the boss portion in a chevron shape, and using a punch whose pressing surface is flat A vertical cross-sectional view of the boss showing the pressing method. (E) is the same as the branch hole at the center of the inner bottom of the boss. FIG. 4 is a longitudinal sectional view of a boss portion showing a system in which a bottomed hole having a diameter is provided and a projection having a diameter that can be fitted into the bottomed hole is pressed using a punch provided on the pressing surface. FIG. 5 is a schematic diagram showing an example of a method of punching a branch hole simultaneously with applying a pressing force in the manufacturing method, FIG. 5 is a schematic diagram showing another modification of the first embodiment, and FIG. 6 is a main rail of the present invention. FIG. 7 is a schematic view showing a third embodiment of the method for manufacturing a common rail according to the present invention, and FIG. 8 is also a schematic view showing the third embodiment of the method for manufacturing the common rail according to the present invention. FIG. 9 is a schematic view showing a fourth embodiment of a method for manufacturing a common rail, FIG. 9 is a longitudinal sectional view showing an example of a branch pipe connection structure by a method for manufacturing a common rail having a boss portion integral with the main rail, Pipe rail, 2 is a branch pipe, 3 is a cap nut for tightening, 4 is a sleeve Ssha, 5 lower mold, 6 punch, 7-1 and 7-2 the diameter expanding tool, 8 fixing jig, 9 traction unit, 10 a pressing device.

  The main rail 1 as a common rail is a forged product such as a material S45C having a relatively thick tubular portion having a diameter of 28 mm and a thickness of 9 mm, for example. As a flow passage 1-1, a plurality of bosses 1-3 are provided with an interval in the axial peripheral wall portion.

  The method shown in FIG. 1 includes a boss portion 1-3 integral with the main rail 1 and a branch hole 1-2 having a predetermined diameter communicating with the flow passage 1-1 of the main rail 1, and a large diameter communicating with the branch hole. Are formed on the outer opening end of the branch hole 1-2a, and a pressure receiving seat surface 1-4 that opens to the outside is formed on the outer periphery of the boss 1-3. The male screw 1-5 is processed. The reason why the branch holes are constituted by the small-diameter holes and the large-diameter holes is to allow a pressing force to be applied to the peripheral portion of the branch hole 1-2 having a predetermined diameter with a punch or a rod.

  Next, the vicinity of the boss 1-3 of the main rail 1 is fixed with the lower mold 5. As shown in the figure, the lower die 5 is a mold having a concave cross section having a curved surface 5-1 having substantially the same radius of curvature as the outer peripheral surface of the main rail 1, and the lower die 5 has substantially the lower half circumference of the main rail 1. It is fixed so that it can be restrained. This is to obtain a sufficient press effect.

  When the main rail 1 is fixed to the lower mold 5, the branch hole 1 is inserted into the large-diameter branch hole 1-2 a by a punch 6 that is slightly smaller than the inner diameter of the branch hole and attached to a press device (not shown). A pressing force is applied to the bottom of -2a. The pressing force at this time is not particularly limited, but the extent that the inner peripheral surface of the main rail flow passage 1-1 around the branch hole 1-2 slightly protrudes to form the flat portion 1-6. It's okay. The pressing force by the punch 6 causes the inner peripheral surface of the main rail flow passage 1-1 to slightly protrude and flatten, and when the pressing force is applied, a plastic deformation portion and an elastic deformation portion are generated, and the pressing force is reduced. Compressive residual stress is generated due to deformation caused by the difference in the return amount when removed.

  In the method shown in FIG. 2, first, in the pre-processing step (cutting step), the large-diameter branch hole 1-2a is formed in the boss portion 1-3 of the main rail 1 by, for example, cutting with an end mill. Thereafter, in the pressing step, the vicinity of the boss 1-3 of the main rail 1 is fixed by the lower die 5 and a pressing force is applied to the bottom of the branch hole 1-2a by the same punch 6. The pressing force at this time is also such that the inner peripheral surface of the main rail flow passage 1-1 located just below the bottom of the branch hole 1-2a slightly protrudes to form a flat portion 1-6, as described above. Good. The pressing force by the punch 6 causes the inner peripheral surface of the main rail flow passage 1-1 to slightly protrude and flatten, and when the pressing force is applied, a plastic deformation portion and an elastic deformation portion are generated, and the pressing force is reduced. Compressive residual stress is generated due to deformation caused by the difference in the return amount when removed. Thereafter, a branch hole 1-2 having a predetermined hole diameter is formed at the bottom of the large diameter branch hole 1-2a.

  FIG. 3 exemplifies a pressing force applying means by a pressing method for causing a compressive residual stress to exist around the opening end portion of the main rail flow passage of the branch hole 1-2. In this method, a concave portion 6a having a triangular cross section is formed at the tip (pressing surface), and a pressing force is applied to the inner bottom portion of the large-diameter branch hole 1-2a of the boss portion 1-3 with this punch. In the case of this method, since a large pressing force is applied not only to the central portion of the bottom portion but also to the inner peripheral wall side, the compressive residual stress is effective over a relatively wide range around the branch hole 1-2 provided in the portion. Can remain.

  In (B), an annular protrusion 1-2b is provided on the inner bottom of the branch hole 1-2a of the boss 1-3, and the upper surface of the annular protrusion 1-2b is pressed by a punch 6 having a flat pressing surface. In the same manner as (A), the compression residual stress is left over a relatively wide range around the branch hole 1-2 provided later.

  (C) The inner bottom portion of the branch hole 1-2a of the boss portion 1-3 is formed as a concave portion 1-2c having an inverted triangular cross section, and the bottom surface formed of the concave portion 1-2c has a spherical or elliptical pressing surface. This is a method of pressing with a punch 6. In this method, since the bottom slope is first pressed by the punch 6, the effect of remaining compressive residual stress around the branch hole 1-2 provided later is also great in this case.

  (D) is a method in which a protrusion 1-2d having a mountain-shaped cross section is provided on the inner bottom of the branch hole 1-2a of the boss 1-3, and the bottom formed by the protrusion 1-2d is pressed by a punch 6 having a flat pressing surface. It is. In this method, since the top of the protrusion 1-2d having a mountain-shaped cross section is first pressed by the punch 6, a large pressing force is applied to the center of the bottom. Accordingly, in this case as well, a large compressive residual stress remains in the vicinity of the periphery of the branch hole 1-2 provided later.

  (E) is provided with a bottomed hole 1-2e having the same diameter and appropriate depth as the branch hole 1-2 provided later in the center of the inner bottom of the branch hole 1-2a of the boss part 1-3. This is a method in which a protrusion 6a having a diameter that can be fitted into 1-2e and slightly longer than the depth of the bottomed hole is pressed by a punch 6 provided on the pressing surface. In the case of this method, since the bottomed hole 1-2e is pressed by the protrusion 6a and the periphery thereof is also pressed, a pressing force is concentrated on the portion of the branch hole 1-2 provided later. At the same time, the compressive residual stress inevitably remains around the branch hole 1-2.

  Further, the method of punching the branch hole simultaneously with the application of the pressing force shown in FIG. 4 has a diameter that can be fitted into the bottomed branch hole 1-2a provided in the boss portion 1-3 and has a branch hole 1- 2 and using a punch 6 provided with a projection 6b longer than the remaining thickness of the bottom of the bottomed branch hole 1-2a, while pressing the bottom of the branch hole 1-2a, the branch hole 1-2 This is a method of punching out. In the case of this method, the bottom of the branch hole 1-2a is pressed by the projection 6b, so that a pressing force is concentrated on the part of the branch hole 1-2 punched at the same time, and the branch hole 1 is inevitably produced. -2 also remains compressive residual stress.

As a method of applying a pressing force by the press method according to the present invention and generating a compressive residual stress, the method shown in FIG. 5 can be used as well as the above method.
In FIG. 5, the inner bottom portion of the large-diameter branch hole 1-2a of the boss portion 1-3 is not pressed, but an axial pressing force is applied to the free end portion of the boss portion 1-3 from the outside. The boss portion 1-3 is configured to be pressed in the axial direction. That is, for example, a boss portion of the main rail 1 having a branch hole 1-2 cut to a predetermined hole diameter by cutting with an end mill or the like and provided with a boss portion 1-3 in which a male screw 1-5 is processed on the outer peripheral surface. The vicinity of 1-3 is fixed to the lower mold 5, and then the left and right movable molds 5-2, 5-3 are constrained from both sides by the actuator to the vicinity of the boss part 1-3, and the punch 6 attached to the press device is attached to the punch 6. And applying a pressing force to the free end of the boss. In the case of this embodiment, the entire periphery of the main rail 1 in the vicinity of the boss portion 1-3 is restrained by the lower die 5 when the boss portion 1-3 provided with the branch hole 1-2 is pressed. This is because the vicinity tends to bulge in the outer peripheral direction, and this is suppressed.
Due to the pressing force by such a punch, the inner peripheral surface of the flow passage 1-1 of the main rail 1 slightly protrudes to form a flat portion 1-6, and compressive residual stress is generated. Thereafter, a pressure receiving seat surface 1-4 is formed which is continuous with the branch hole 1-2 and opens outward, whereby the main rail is manufactured. In the above description, the example in which the pressing force is applied to the outer periphery of the boss 1-3 that has been previously processed with the male screw 1-5 and the branch hole 1-2 has been described. 5 and the branch hole 1-2 can also be processed.

  Further, as a method of applying a pressing force by a pressing method such as a punch to generate a compressive residual stress, the branch hole is pressed slightly eccentric from the position where the branch hole is provided, and at least a part of the branch hole, that is, a branch that becomes a starting point of a crack. It is also possible to concentrate and generate compressive residual stress on the inner peripheral edge portion P on the axial direction side of the main rail 1 at the lower end of the hole.

  Next, the method shown in FIG. 6 is used in the flow passage 1-1 of the main rail 1 as means for generating compressive residual stress around the open end of the main rail flow passage 1-1 of the branch hole 1-2. In the case of adopting an internal pressure system in which pressure is applied, at least one of the main rails 1 is sealed and a liquid fluid such as water or oil is sent into the rails, and at least from the inner peripheral surface side of the thickness of the main rail 1 A compressive residual stress is generated around the end of the main rail flow passage opening near the boss portion 1-3 by applying a high pressure that yields 25%, preferably 50 to 75%. Then, in a finishing process, while forming the pressure-receiving seat surface 1-4 which opens circularly outward in the outer end part of the branch hole 1-2, the external thread 1-5 is processed into the outer peripheral surface of the said boss | hub part. . In order to ensure that compressive stress remains, it is preferable to process the branch hole 1-2 before applying the pressing force.

  7 is a means for generating compressive residual stress around the open end of the main rail flow passage 1-1 of the branch hole 1-2. Expanding tool such as a sphere slightly larger than the inner diameter of the rail, a shell-type plug, a roller burnishing tool, etc., in the case where the expanding tube system to be applied is adopted and the main rail 1 is horizontally fixed to the fixing jig 8 The main passage rail 1-1 in the vicinity of the boss 1-3 is expanded by expanding the main passage rail 1-1 by pulling the 7-1 with the pulling device 9 and moving it in the flow passage 1-1 while being pressed. A compressive residual stress is generated around the open end of the path 1-1. Thereafter, in the finishing process, the circumferential surface of each boss 1-3 that opens to the circular outer passage that communicates with the flow passage 1-1 of the main rail 1 and communicates with the flow passage 1-1 is received by the pressure receiving seat surface 1-4. A branch hole 1-2 is formed, and a male screw 1-5 is processed on the outer peripheral surface of the boss portion. Also in this case, in order to ensure that the compressive stress remains, it is preferable to process the branch hole 1-2 before the diameter expansion operation.

  Further, in the method shown in FIG. 8, as a means for generating compressive residual stress in the vicinity of the opening end portion of the main rail flow passage 1-1 of the branch hole 1-2, an expansion that applies a pressing force in the radial direction from the inside of the branch hole. When the diameter method is adopted, a branch hole 1-2 'slightly smaller than the predetermined hole diameter is formed in the boss portion 1-3 in the finishing process, and the diameter is almost the same as the inner diameter of the branch hole 1-2 having the predetermined hole diameter. The diameter of the branch hole 1-2 'is increased by a method in which a diameter expanding tool 7-2 such as a spherical body or a plug is press-fitted into the small diameter branch hole 1-2' by a pressing method. Compressive residual stress is generated around the end of the main rail flow passage opening.

  As described above, in the present invention, the periphery of the opening end of the main rail flow passage opening of the branch hole is achieved by a press method (external pressure method) using a punch or the like, an internal pressure method using water pressure or hydraulic pressure, a tube expansion method using a sphere or a plug, and a diameter expansion method. By generating the compressive residual stress, the tensile stress generated at the inner peripheral edge P of the lower end of the branch hole due to the high internal pressure of the main rail can be greatly reduced by the canceling action with the compressive residual stress. In addition, when a press method such as a punch is adopted as a means for generating compressive residual stress around the opening end of the main rail flow passage, the inner peripheral surface of the main rail flow passage near the branch hole is slightly pressed by pressing. By forming the flat part by projecting, the tensile stress generated in the inner peripheral edge P at the lower end of the branch hole due to the flattening action and the compressive residual stress can be further reduced.

  Note that the common rails in the above-described embodiments have a structure in which the center of the flow path of the main rail and the center of the branch hole of the boss portion coincide with each other, but the present invention is disclosed in Japanese Patent Application No. 9-13141. Needless to say, the present invention can be applied to a common rail in which the center of the branch hole of the boss part is eccentric in the radial direction of the main rail flow passage, and the diameter of the bottomed branch hole 1-2a is the boss part 1-3. As long as the mechanical strength of the connecting head 2-2 is not impaired, it is not always necessary to have a small diameter as shown in the figure, the dimension in the radial direction of the connecting head 2-2 and the size of the sleeve washer 4 at the connecting head 2-2. Depending on the thickness, the diameter can be appropriately increased.

  On the other hand, the branch pipe 2 is composed of a branch branch pipe or a branch metal fitting, and has a flow path 2-1 that communicates with the flow path 1-1 of the main rail 1 inside thereof, and has, for example, a taper at its end. In the case of the branch pipe connection structure shown in FIG. 9, the connection seat 2- on the branch pipe 2 side is provided. 2 is brought into contact with and engaged with the pressure receiving seat surface 1-4 on the main rail 1 side, and the fastening cap nut 3 is previously connected to the boss through the sleeve washer 4 on the branch pipe side. By screwing into the male screw 1-5 of the portion 1-3, the connection head 2-2 is fastened together with the pressing of the sleeve washer 4 at the connection head 2-2 to form a connection.

It is the schematic which shows the 1st Example of the manufacturing method of the common rail which has the boss | hub part integral with the main rail of this invention. It is the schematic which shows the modification of a 1st Example same as the above. (A) is a longitudinal cross-sectional view of a boss part partially broken away showing a method of pressing using a punch having a pressing surface formed in a reverse concave shape. B) is a longitudinal cross-sectional view of the boss portion showing a method in which an annular protrusion is provided on the inner bottom portion of the boss portion and pressing is performed using a punch having a flat pressing surface, and (C) is a concave shape formed on the inner bottom portion of the boss portion. The longitudinal cross-sectional view of the boss | hub part which shows the system pressed using the punch by which the press surface became the spherical surface, (D) is pressing using the punch with which the inner bottom part of the boss | protrusion protrudes in a mountain shape, and the press surface is flat. A vertical cross-sectional view of the boss portion showing the method of performing the above, (E) is provided with a bottomed hole having the same diameter as the branch hole at the center of the inner bottom portion of the boss portion, and a protrusion having a diameter that can be fitted into the bottomed hole is formed on the pressing surface. It is a longitudinal cross-sectional view of the boss | hub part which shows the system pressed using the provided punch. In the manufacturing method of a 1st Example, it is the schematic which shows an example of the system which punches a branch hole simultaneously with pressing force provision. It is the schematic which shows the other modification in a 1st Example same as the above. It is the schematic which shows the 2nd Example of the manufacturing method of the common rail which has the boss | hub part integral with the main rail of this invention. It is the schematic which shows the 3rd Example of the manufacturing method of the common rail of this invention similarly. It is the schematic which shows the 4th Example of the manufacturing method of the common rail of this invention similarly. It is a longitudinal cross-sectional view which shows the example of a branch pipe connection structure by the manufacturing method of the common rail which has a boss | hub part integral with a main pipe rail. It is a longitudinal cross-sectional view which shows the branch pipe connection structure part of the conventional common rail made into the object of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, Main rail 1-1 Flow path 1-2, 1-2 ', 1-2a Branch hole 1-3 Boss part 1-4 Pressure-receiving seat surface 1-5 Male thread 1-6 Flat part 2 Branch pipe 2-1. Flow path 2-2 Connection head 2-3 Press seat 3 Fastening cap nut 4 Sleeve washer 5 Lower mold 5-2, 5-3 Movable 6 Punch 7-1, 7-2 Expander 8 Fixed Jig 9 Pulling device 10 Pressing device

Claims (6)

A branch hole having a pressure-receiving seating surface that communicates with the flow passage and opens outward is provided in at least one boss portion provided in the axial peripheral wall portion of the main rail having the flow passage in the axial direction inside; A pressing seat surface portion formed by a connection head provided at an end portion of a branch pipe having a flow path communicating with the flow passage is brought into contact with and engaged with the pressure receiving seat surface, and the boss portion and a fastening member that is incorporated in the branch pipe side in advance. Compressive residual stress exists in the periphery of the main rail flow passage opening end of the branch hole in the common rail that is fastened and connected with the press under the neck of the connecting head by screwing the attached cap nut A common rail characterized by A branch hole having a pressure-receiving seating surface that communicates with the flow passage and opens outward is provided in at least one boss portion provided in the axial peripheral wall portion of the main rail having the flow passage in the axial direction inside; A pressing seat surface portion formed by a connection head provided at an end portion of a branch pipe having a flow path communicating with the flow passage is brought into contact with and engaged with the pressure receiving seat surface, and the boss portion and a fastening member that is incorporated in the branch pipe side in advance. In the method of manufacturing the common rail that is connected by being tightened and connected with the press under the neck of the connecting head by screwing the attached cap nut, the pressing force is externally applied in the axial direction of the boss portion from the outside. And a compressive residual stress is generated around the opening end portion of the main rail flow passage of the branch hole. 3. The method of manufacturing a common rail according to claim 2, wherein a pressing force is applied from the outside in the axial direction of the boss portion by an external pressure method, and at the same time, the branch hole is punched out. A branch hole having a pressure-receiving seating surface that communicates with the flow passage and opens outward is provided in at least one boss portion provided in the axial peripheral wall portion of the main rail having the flow passage in the axial direction inside; A pressing seat surface portion formed by a connection head provided at an end portion of a branch pipe having a flow path communicating with the flow passage is brought into contact with and engaged with the pressure receiving seat surface, and the boss portion and a fastening member that is incorporated in the branch pipe side in advance. In the method of manufacturing the common rail, which is fastened and connected with the press under the neck of the connecting head by screwing the attached cap nut, an internal pressure method is applied to the inner peripheral surface of the main rail near the branch hole. A method of manufacturing a common rail, wherein a compressive residual stress is generated in the vicinity of an opening end portion of a main rail flow passage of the branch hole by applying a pressing force. A branch hole having a pressure-receiving seating surface that communicates with the flow passage and opens outward is provided in at least one boss portion provided in the axial peripheral wall portion of the main rail having the flow passage in the axial direction inside; A pressing seat surface portion formed by a connection head provided at an end portion of a branch pipe having a flow path communicating with the flow passage is brought into contact with and engaged with the pressure receiving seat surface, and the boss portion and a fastening member that is incorporated in the branch pipe side in advance. In the method of manufacturing the common rail, which is fastened and connected with the press under the neck of the connecting head by screwing the attached cap nut, the inner surface of the main rail is connected to the inner peripheral surface of the main rail near the branch hole. A method of manufacturing a common rail, characterized in that a compressive residual stress is generated in the vicinity of an opening end portion of the main pipe rail flow passage of the branch hole by applying a pressing force by a pipe expansion method that applies a pressing force in the pipe radial direction. . A branch hole having a pressure-receiving seating surface that communicates with the flow passage and opens outward is provided in at least one boss portion provided in the axial peripheral wall portion of the main rail having the flow passage in the axial direction inside; A pressing seat surface portion formed by a connection head provided at an end portion of a branch pipe having a flow path communicating with the flow passage is brought into contact with and engaged with the pressure receiving seat surface, and the boss portion and a fastening member that is incorporated in the branch pipe side in advance. In the method of manufacturing the common rail, which is connected by being fastened together with the press under the neck of the connecting head by screwing the attached cap nut, in the radial direction from the inside of the branch hole to the inner peripheral surface of the branch hole A method of manufacturing a common rail, wherein a compressive residual stress is generated in the vicinity of an opening end portion of a main rail flow passage of the branch hole by applying a pressing force by a diameter expansion method for applying a pressing force.

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