JP5748326B2 - Common rail - Google Patents

Description

  The present invention relates to a common rail such as a high pressure fuel manifold and a high pressure fuel block in an accumulator fuel injection system for an internal combustion engine such as a diesel engine or a direct injection gasoline engine, and more specifically, internal pressure fatigue strength while maintaining a high injection pressure. It is related to a common rail for diesel engines that excels in performance.

  Conventionally, a direct injection internal combustion engine that supplies high-pressure fuel directly from an injector to a combustion chamber has been developed with a diesel internal combustion engine as the mainstream, but a branched body for connecting an injection pipe or the like that injects high-pressure fuel into the combustion chamber. As the connection structure, for example, as shown in FIG. 9, a pressure receiving seat that opens outwardly in a conical shape at a space in the axial peripheral wall portion of the main rail 21 having a flow passage 21-1 inside the shaft center. A plurality of through-holes 21-2 formed with a surface 21-3 are provided, and the peripheral portions of the pressure-receiving seat surface 21-3 of each through-hole 21-2 are surrounded, and a female screw 23-1 is formed on the inner peripheral surface. The formed cylindrical sleeve nipple 23 is fixed, a small diameter channel 22-1 is provided at the shaft center, and a tapered cone-shaped pressing seat surface 22-3 is formed at the tip of the connecting head 22. -2 with the branch connection body 22 in contact, The screw 23-1 provided in the pull 23 and the male nut 24 incorporated in the branch connection body 22 are screwed together to be fastened by pressing the branch connection body 22 under the neck of the connection head 22-2. A connection structure is known (see, for example, Patent Document 1). However, in such a conventional connection structure, when an internal pressure is applied to the main rail 21, it is connected to a small-diameter channel 22-1 provided at the axis of the branch connection body 22 including a fuel injection pipe and the like. Therefore, maximum stress is generated in the opening inner peripheral edge portion P of the through hole 21-2 formed in the peripheral wall of the flow passage 21-1 of the main rail 21, and the internal pressure fatigue strength of the portion is reduced, and the opening is reduced. It was feared that the inner peripheral edge P would be the starting point and that cracks would easily occur, resulting in fuel leakage. In addition, in such a conventional main rail, since the length of the engine itself is limited due to the layout, it is impossible to increase the pressure accumulation volume by extending the rail length. There was also a problem that there was not enough means to prevent an instantaneous pressure drop during injection.

  As an example of the connection structure of the branch connection body in the common rail in order to eliminate the inconvenience of the conventional connection structure, a long tube body is used for the main rail 11-1 as shown in FIG. By bending the U-shape from the substantially central part of the body, tubular U-shaped main rails 11-1 parallel to each other are formed, or provided at both ends of the connecting pipe 12-3 as shown in FIG. By connecting straight pipes to the branch pipes 12-6 via joints 12-4, straight main pipe rails 12-1 parallel to each other are formed, and the former substantially parallel metal pipe portions 11-1a or the latter of the straight main rail 12-1 is formed with a plurality of branch holes at intervals, and the injection pipes 11-2 and 12-2 are connected to the branch holes. Obtained by Shaped common rail 11 or the connection structure of the branching connection body consisting of parallel 設型 common rail 12 has been disclosed (for example, see Patent Document 2).

Japanese Patent Laid-Open No. 10-213044 JP 2005-264921 A

  According to the U-shaped common rail 11 and the side-by-side common rail 12 proposed in Patent Document 2, the main rail is lengthened in spite of a compact structure, which is shown in Patent Document 1. A large pressure accumulation volume that could not be obtained in such a conventional connection structure is secured, and an excellent effect that the injection pressure of each fuel injection pipe as a branch connection body is maintained at a high level has been confirmed. However, even in the connection structure using the U-shaped or side-by-side common rail disclosed in Patent Document 2, the inner peripheral surface has a plurality of branch holes formed at intervals in the peripheral wall portion of the main rail. Alternatively, the cylindrical sleeve nipple provided with a screw surface on any of the outer peripheral surfaces, or means for connecting the branch connection body through the joint fitting is substantially the same as the connection structure shown in Patent Document 1, When a high internal pressure is applied to the main rail, maximum stress is generated at the inner peripheral edge P of the branch hole (or through hole) formed in the peripheral wall of the flow path of the main rail, and In order to eliminate such anxiety, the internal pressure fatigue strength is reduced and cracks are generated from the inner peripheral edge P of the opening. Axis of A measure is taken to further reduce the diameter of the formed flow passage and increase the thickness of the portion to ensure strength. However, by reducing the diameter of the flow passage, the pressure accumulation volume is reduced and fuel injection is performed. The conflicting unsolved problem that the high injection pressure of time cannot be maintained was left.

  The present invention has an initial object of solving the problems remaining in the prior art, and is preferably a polyhedral thick branch member between pressure accumulating containers composed of straight tubes arranged coaxially. As a result of various investigations on the connection structure of the thick branch member, the tubular pressure accumulating container, and the tubular branch connection body, In spite of its relatively compact structure, we have created a connection structure for a branch connection consisting of a common rail for a diesel engine that can secure a sufficient pressure accumulation volume and is excellent in internal pressure fatigue strength. Is.

  A common rail for a diesel engine according to the present invention for solving the above-mentioned problems is a thick-walled branching member fixed by screwing between two tubular pressure accumulating containers arranged substantially coaxially. The outer wall of the branch member, preferably a polyhedron, is provided with a small-diameter branch hole communicating with the inside of the shaft center, and a conical opening for connecting a tubular branch connector to the outer peripheral surface of the branch hole. And a cylindrical screw boss is attached in advance integrally or by fixing so as to surround the pressure receiving seat surface, and a tapered conical connection head between the pressure receiving seat surface and the branch connection body The screw boss and the nut that is pre-assembled on the branch connector side are screwed together to press the branch connector under the connection head neck. Due to the accompanying fastening, the thick pipe member In the common rail to which the branch connection body is integrally connected, each joint end surface of the tubular pressure accumulating vessel and the thick branch member has a substantially flat surface that communicates with a branch hole formed in the outer wall of the thick branch member. Or a substantially curved bottom having a large curvature radius and a substantially spherical bottom having a large radius of curvature, and having a thin diameter communicating with the flow passages of the tubular pressure accumulating vessels on both sides of the thick branch member between the bottoms. It is a characteristic constituent feature that the flow path is formed.

In the common rail according to the present invention, the outer wall of the thick branch member, preferably a polyhedron, is substantially trapezoidally inclined from the flat top formed outside the thick branch member to the left and right in the axial direction. A plurality of the small-diameter branch holes provided in communication with the inside of the shaft center from the outer wall, and intersecting each other in an X shape on a plane projection without communicating with each other. the bottom of the substantially flat or substantially song surface shape provided on the connecting end container, in which each and which are located in communication with each other.

  Further, in the common rail according to the present invention, at least one of the tubular branch connection bodies connected to the outer wall of the thick branch member, preferably a polyhedron, via a screw boss is a fuel supply pipe. The plurality of branch connectors are fuel injection pipes.

  The common rail according to the present invention is also provided with a female for engaging with a male screw formed on an outer peripheral surface of a connection end portion of the tubular pressure accumulating container on each of vertical wall surfaces facing the left and right of the thick branch member. Each of the tubular pressure accumulating containers formed with screws and connected so as to sandwich the thick branching member from the left and right is connected to the branch connection body from the flow passage provided in the axial center via the side wall of the accumulating container. A branch hole for communication is not formed.

  In the common rail according to the present invention, a female screw is formed on the inner peripheral surface of one connection end of the tubular pressure accumulating container, and the pressure sensor pipe or the fuel return pipe is arbitrarily connected to the female screw. It is characterized by being connected.

  In the common rail according to the present invention, the screw boss made of a cylindrical member that is integrally provided in advance or integrally by fixing to the outer wall of the thick branch member, preferably a polyhedron, and the female screw on the inner peripheral surface thereof. It is either formed or a male screw is formed on the outer peripheral surface thereof.

  According to the connection structure of the branch connection body in the common rail according to the present invention, a thick branch member having an outer wall is disposed between two tubular pressure accumulating containers arranged substantially coaxially, and the thick branch member is A branch hole communicating from the outer wall to the inside of the shaft center is formed, and a pressure receiving seat surface for connecting the tubular branch connector is provided on the outer peripheral surface portion of the branch hole, and the peripheral edge portion of the pressure receiving seat surface is surrounded. In this way, a cylindrical screw boss is integrally provided, and the pressure receiving seat surface and the pressing seat surface of the connecting head of the branch connection body are brought into contact engagement with each other, so that the screw boss and the nut assembled in advance in the branch connection body are provided. In the common rail in which the thick branch member and the branch connection body are integrally connected by fastening with pressing under the connection head neck of the branch connection body, the tubular pressure accumulating container and the thickness are The thick branch is formed on each joint end face with the meat branch member. A substantially planar or substantially spherical bottom portion communicating with the branch hole drilled in the outer wall of the material is provided, and the flow path of the tubular pressure accumulating vessels on both sides is provided at the substantial axis of the thick branch member between the bottom portions. A plurality of branch holes that are drilled to communicate with the inside of the shaft center from the outer wall are projected on a plane. The top communicates with each of the substantially planar or substantially spherical bottoms of the thick branching member facing the joint end of the tubular pressure accumulating vessel without crossing each other in an X shape. A common rail branch connection structure is constructed.

  According to the common rail of the present invention having such a structure, all of the plurality of tubular branch connections are connected to the thick pipe member disposed so as to be sandwiched between the tubular pressure accumulating containers, and are arranged on both sides of the thick pipe member. The peripheral wall of the tubular pressure accumulating container to be arranged is not provided with a branch hole for connecting the branch connector, and in addition, even when an internal pressure is applied at the time of pressurization, it is in a portion that is difficult to deform. The stress concentration at the opening end is effectively suppressed, and it is lightweight and has excellent flexibility in layout, so there is enough room to increase the pressure accumulation volume, and the instantaneous pressure drop during injection is sufficiently prevented. The effect that it is possible can also be produced. In addition, the thick-walled branch member, which is the main axis of the connection structure, is a strong structure despite its compactness. Therefore, factors such as reduced vibration fatigue strength are eliminated, and durability as a connection structure is achieved. And the excellent reliability is guaranteed over a long period of time.

It is a whole perspective view which shows the connection structure of the branch connection body in the common rail by 1st Example which concerns on this invention. FIG. 4 is a four-side view of a single thick-walled branch member in the same embodiment, where (a) is a view from the arrow A (front view) in FIG. 1, (b) is a view from the arrow B (plan view) in FIG. ) Is a C arrow view (left side view) of (b), and (d) is a D arrow view (right side view) of (b). It is principal part sectional drawing which shows each connection structure of the thick branch member in the same Example, a tubular accumulator, and a tubular branch connection body. It is a typical figure for demonstrating the internal structure of the thick branch member in the Example, and is EE sectional drawing of (d). It is a whole perspective view which shows the connection structure of the branch connection body in the common rail by 2nd Example which concerns on this invention. It is a 4th view of the thick branch member simple substance in the Example, (a) is an A arrow view of FIG. 5 (front view, (b) is a B arrow view of (a) (plan view), (c) (B) is a C arrow view (left side view), (d) is a D arrow view (right side view) of (b). It is principal part sectional drawing which shows each connection structure of the thick branch member in the same Example, a tubular accumulator, and a tubular branch connection body. It is a typical figure for demonstrating the internal structure of the thick branch member in the Example, and is EE sectional drawing of FIG.6 (d). It is a principal part expanded sectional view for demonstrating the connection structure of the branch connection body in the common rail of a prior art example. It is the schematic for demonstrating the connection structure of the branch connection body in the common rail of another prior art example. Similarly, it is the schematic for demonstrating the connection structure of the branch connection body in the common rail of a prior art example.

  Hereinafter, the embodiments of the present invention will be described more specifically with reference to the accompanying drawings and examples. However, the present invention is not restricted thereby, and the design can be freely changed within the scope of the gist of the present invention. Is possible.

  As shown in FIG. 1, the common rail 1 according to the first embodiment of the present invention has a thick branch member 2 between two tubular pressure accumulating containers 1-1 arranged substantially coaxially by male and female screwing. The thick branch member 2 is made of a carbon steel material, alloy steel or stainless steel material of the same type as the pressure piping carbon steel used as the tubular pressure accumulating vessel 1-1 as a material, and is forged and pressed. A thick steel member formed by molding, mechanical cutting, or a combination thereof. Specifically, as shown in FIGS. Two vertical walls 2-3 facing each other, and a flat top 2-2 at the center on both sides and above the vertical wall 2-3, and preferably at substantially the same angle from the top 2-2 to the left and right. A six-sided outer wall 2-1 inclined substantially trapezoidally at an angle of 45 degrees is provided. 2-9 is formed of a plane portion having a substantially turtle shell pattern, forming a thick member having a substantially pentagonal cross section when viewed from the front, and each of the two vertical walls 2-3 facing the left and right sides of the thick member. As shown in FIG. 2 (a), there is a connection hole 2-10 in which a female screw 2-6 is formed on the inner periphery for connecting the connection end 1-5 of the tubular pressure accumulating container 1-1. A substantially spherical bottom portion 2-4 having a substantially planar shape or a curved surface, preferably having a large curvature radius, is provided on the back wall portion connected to the connection hole 2-10, and a substantial axis between the bottom portions 2-4. A flow path 2-5 that communicates with each other is provided at the center portion, and five small-diameter branch holes 2-8 that communicate with the outer wall 2-1 are projected on a plane in this embodiment. Each of the portions that intersect but do not interfere with each other and touch the outer wall 2-1 of the branch hole 2-8 is directed outward. The pressure receiving seat surface 2-7 that opens in a substantially conical shape is formed, and five screw bosses 3-1 are formed on the inner peripheral surface so as to surround the peripheral edge of the pressure receiving seat surface 2-7. -3-5 are fixedly provided as an integral or separate member, and the thick branch member 2 according to this embodiment based on the present invention is formed.

  In addition, a narrow branch hole 2-8 communicating from the outer wall 2-1 of the thick-walled branch member 2 to the bottom portion 2-4 having a substantially flat shape or a substantially curved shape with a large curvature radius formed inside the shaft center is provided as follows. In the outer wall 2-1, which is inclined at an angle of approximately 45 degrees to the left and right across the flat top portion 2-2, each of the outer walls 2-1 is drilled at a different phase, so that in the EE cross-sectional view of FIG. As shown in FIG. 4, the projections onto the plane intersect with each other in an X-shape, but without communicating with each other, as shown in FIGS. The openings 3-4a, 3-5a and 3-1a, 3-2a, 3-3a are formed respectively. Screw bosses 3-1 to 3-5 are respectively provided integrally with the thick branch member 2 at the peripheral edge of the pressure receiving seat surface 2-7 formed in the branch hole 2-8. As shown in FIGS. 2A to 2D, -1 to 3-5 are provided with different phases in accordance with the branch holes 2-8, as shown in FIGS. Further, the connection between each branch hole 2-8 and the tubular branch connector 4 is a tapered cone formed in the connection head 4-A of the tubular branch connector 4-1 to 4-4 as shown in FIG. The pressure seating surface 4-B having the shape is brought into contact with and engaged with the pressure receiving seating surface 2-7 that opens outward at the peripheral edge of the outer wall portion 2-1 of the branch hole 2-8. -1 to 4-4, and the male nuts 5-1 to 5-5 and the screw bosses 3-1 to 3-5 are screwed together to connect the branch connectors 4-1 to 4-4. The thick branching member 2 and the tubular branch connecting members 4-1 to 4-4 are firmly bonded to each other while maintaining high airtightness due to fastening accompanying pressing under the connecting head neck. In this embodiment, as shown in FIG. 1 and FIGS. 2A to 2D, a screw boss 3-1 provided independently on the trapezoidal outer wall 2-1 has a high pressure pump (not shown). ) Is connected to a tubular branch connector 4-1 that serves as a fuel supply pipe, and tubular branch connectors 4-2 to 4-5 that serve as fuel injection pipes are respectively connected to the other screw bosses 3-2 to 3-5. Connected and piped to an injector (not shown).

  As shown in FIGS. 1 and 3, each of the connection holes 2-10 provided in the vertical walls 2-3 opposite to the left and right of the thick branching member 2 according to the present embodiment formed as described above. A tubular pressure accumulating vessel 1-1 serving as a main rail is screwed. The tubular pressure accumulating vessel 1-1 is a tube made of thick steel pipe having an inner diameter of 8 mm and an outer diameter of 16 mm made of pressure pipe carbon steel or stainless steel. A connection end portion 1-5 having an outer diameter of 20 mm, in which a male screw 1-4 is formed at one end to be engaged with a female screw 2-6 formed in the connection hole 2-10 of the thick branch member 2. However, the other end is provided with a connecting end 1-6 having an outer diameter of 20 mm and formed with a female screw 1-7 for connection to either the fuel return pipe or the pressure sensor pipe, respectively. The male screw 1-4 formed on 1-5 is connected to the vertical wall 2 of the thick-walled branching member 2 described above. By screwing the female screw 2-6 is formed connection hole 2-10 3 was obtained according to the present embodiment based on the present invention the common rail 1 direct-injection four-cylinder type. The axial center portion of the tubular accumulator 1-1 in the obtained common rail becomes the flow passage 1-2 with an inner diameter of 8 mm as it is, and a branch hole that penetrates from the inner wall to the outer wall of the flow passage 1-2 is provided in the present invention. Therefore, the stress concentration at the peripheral edge of the branch hole in the peripheral wall of the flow passage in the tubular pressure accumulating vessel 1-1 (main rail) was avoided, and the possibility of cracks due to this was also eliminated.

  In addition, with respect to the common rail 1 obtained by the present embodiment, as a result of FEM analysis when the internal pressure is 100 MPa, the openings 3-1a to 3-3a of the branch holes 2-8 in the thick branch member 2 have a maximum of 173 MPa. The maximum tensile stress at the inner peripheral edge (P portion) of the branch hole of the conventional common rail having an outer diameter of 30 mm, a wall thickness of 10 mm, an inner diameter of 10 mm, a boss outer diameter of 14 mm and a branch hole diameter of 3 mm is 463 MPa. Has a stress reduction effect of 60% or more. Further, the common rail 1 according to the present invention has an extremely compact structure and has a function with excellent layout characteristics, and is recognized for its excellent durability as a common rail for supplying high-pressure fuel to a diesel internal combustion engine or the like. It was also confirmed that a highly reliable common rail that can sufficiently withstand repeated contact and vibration and shock during operation can be manufactured at a relatively low cost.

As shown in FIG. 6A, the common rail 1a according to the second embodiment of the present invention forms a thick member having a substantially hexagonal cross section when viewed from the front, and is provided on the opposing vertical wall 2a-3. A substantially planar or substantially spherical bottom 2a-4 having a large curvature radius is formed on a wall surface perpendicular to the axial center of the connection hole 2a-10, and an approximately trapezoidal eight outer wall 2a- formed on the outer peripheral surface. 1, seven screw bosses 3a-1 to 3a-7 are fixed, and as shown in FIG. 5, a tubular branch connector 4a-7 for supplying fuel is attached to the screw boss 3a-7, and the other screw bosses 3a. Direct injection having the same basic configuration as that of the first embodiment except that the tubular branch connecting bodies 4a-1 to 4a-6 serving as fuel injection pipes are integrally coupled to each other by screwing to -1 to 3a-6. A common rail for a 6-cylinder diesel internal combustion engine.
That is, as shown in FIG. 5, the thick branch member 2a is integrally fixed and disposed between two tubular pressure accumulating vessels 1a-1 arranged substantially coaxially as shown in FIG. The thick branch member 2a is made of a carbon steel material, an alloy steel or a stainless steel material, which is almost the same as the pressure pipe carbon steel used as the tubular pressure accumulating vessel 1a-1, as in the first embodiment. , A thick steel member formed by press forming, mechanical cutting, or a combination thereof, and specifically symmetrical as shown in FIGS. 6 (a) to 6 (d) Two vertical walls 2a-3 facing each other parallel to each other, and a flat top 2a-2 at the center on both sides and above the vertical wall 2a-3, and from the top 2a-2 to the left and right at substantially the same angle. Preferably outside of 8 faces inclined in a substantially trapezoidal form at an angle of 45 degrees 2a-1 is provided, and a thick member having a substantially octagonal cross section when viewed from the front is formed. Each of the two vertical walls 2a-3 facing the left and right sides of the thick member has a structure shown in FIG. ), A connection hole 2a-10 in which a female screw 2a-6 is formed on the inner peripheral portion for connecting the connection end 1a-5 of the tubular pressure accumulating container 1a-1 is provided, and the connection hole 2a The bottom wall 2a-4 having a substantially flat shape or a substantially curved surface with a large curvature radius is provided in the back wall portion continuous to -10, and a substantially axial center portion between the bottom portions 2a-4 is connected to the flow path 2a-5. In the present embodiment, seven small-diameter branch holes 2a-8 communicating with the outer wall 2a-1 intersect with each other on the projection on the plane, but are formed without interfering with each other. Each portion of the branch hole 2a-8 that is in contact with the outer wall 2a-1 has a substantially conical shape outward. A pressure receiving seat surface 2a-7 is formed, and seven screw bosses 3a-1 to 3a-7 each having a female screw formed on the inner peripheral surface so as to surround the peripheral portion of the pressure receiving seat surface 2a-7 are provided. The thick branch member 2a is formed by being fixedly provided as an integral or separate member.

  In the above embodiment, the screw boss provided on the outer wall of the thick branch member may be provided integrally with the thick branch member by forging, press molding, mechanical cutting, or the like. It is also possible to form a female screw and screw it in, or to fix it integrally by welding or brazing. In the above embodiment, the screw boss and the tubular branch connection body are coupled to each other by fastening a female screw formed on the inner peripheral surface of the screw boss and a male nut incorporated in advance in the tubular branch connection body. However, it is also possible to form a male screw on the outer peripheral surface of the screw boss and incorporate a cap nut in advance in the tubular branch connection body to fasten the male and female in reverse. Further, the tube diameter and the inner diameter of the tubular pressure accumulating container can be freely changed in design as long as the accumulating volume required in the present invention and the internal pressure fatigue strength are ensured and the excellent performance is ensured.

  In the present embodiment, the small-diameter branch hole 2a communicating with the bottom 2a-4 having a substantially flat shape or a substantially curved shape with a large curvature radius formed inside the shaft center from the outer wall 2a-1 of the thick-walled branch member 2a. -8 is an outer wall 2a-1 that is inclined at an angle of approximately 45 degrees to the left and right across the flat top 2a-2. As shown in FIG. 8 which is a cross-sectional view taken along the line E-E, the projections onto the plane intersect with each other in an X-shape, and are connected to the bottom 2a-4 on the opposite side without interfering or communicating with each other. 3a-1a to 3a-7a are formed. Similarly to the first embodiment, screw bosses 3a-1 to 3a-7 are integrally provided on the peripheral edge of the pressure receiving seat surface 2a-7 formed in each branch hole 2a-8. The screw bosses 3a-1 to 3a-7 are provided on the outer walls 2a-1 in different phases according to the branch holes 2a-8 as shown in FIGS. 6 (a) to 6 (d). Each branch hole 2a-8 is connected to the tubular branch connector 4a-1 to 4a-7 in a tapered conical shape formed in the connection head 4a-A of the tubular branch connector 4a as shown in FIG. The pressure seat surface 4a-B is brought into contact with and engaged with the pressure receiving seat surface 2a-7 that opens outward at the peripheral edge of the outer wall 2a-1 of the branch hole 2a-8, and the tubular branch connector 4a-1 is preliminarily engaged. Thread between the male nuts 5a-1 to 5a-7 incorporated in -4a-7 and the screw bosses 3a-1 to 3a-7 Therefore, the thick branch member 2a and the tubular branch connection body 4a are firmly maintained in a state in which high airtightness is maintained by fastening with the press of the branch connection bodies 4a-1 to 4a-7 under the connection head neck. Combined. In this embodiment, as shown in FIGS. 5 and 6 (a) to 6 (d), a screw boss 3a-7 fixed independently to the trapezoidal outer wall 2a-1 has a tubular shape serving as a fuel supply pipe. Branch connection body 4a-7 is connected, and tubular branch connection bodies 4a-1 to 4a-6 that are fuel injection pipes are connected to the other screw bosses 3a-1 to 3a-6, respectively.

  The obtained common rail 1a according to the present embodiment is also the same as in the first embodiment. As a result of FEM analysis when the internal pressure is 100 MPa, the opening 3a-1a of each branch hole 2a-8 in the thick branch member 2a is obtained. In 3a-7a, a large stress reduction effect is obtained as in the first embodiment, and the structure of the common rail for the direct injection 6-cylinder is extremely compact, and has a function with excellent layout characteristics. In terms of performance, excellent results were confirmed as in Example 1. Further, the common rail 1a according to the present invention, as in the first embodiment, is extremely compact in structure and has a function with excellent layout characteristics, and in particular as a common rail for high pressure fuel supply such as a diesel internal combustion engine. A highly reliable common rail that can withstand repeated contact with high-pressure fuel and vibration and shock during operation, with excellent durability, can be manufactured at a relatively low cost. Was also confirmed. Moreover, although the example which comprised the thick branch member by the polyhedron was shown here, a thick branch member is not limited to a polyhedron, and if it is in the technical idea of this invention, an ellipsoid, an ellipsoid or Needless to say, it may have a curved outer wall, such as a sphere, or a part provided with a flat surface.

  As is clear from each of the above embodiments, according to the common rail of the present invention, the plurality of tubular branch connectors are all connected to the thick pipe member disposed so as to be sandwiched between the tubular pressure accumulating containers, In the peripheral wall of the tubular pressure accumulating vessel arranged on both sides of the thick pipe member, no branch hole for connecting the branch connector is drilled, and even when internal pressure is applied during pressurization, Since the stress concentration at the opening end in a flat or curved surface with a large radius of curvature is difficult to be deformed, it is also lightweight and has excellent layout flexibility. It is possible to obtain an effect that a margin for increasing the pressure accumulation volume is ensured only by lengthening the path, and a pressure drop during injection can be sufficiently prevented. In addition, the thick branch member that is the base of the connection structure is a compact structure that is strong despite being compact and extremely lightweight. The durability is remarkably improved and its excellent reliability is ensured for a long time. As described above, the present invention provides the above-described effects as a common rail connection structure, and also has excellent effects such as an improvement in productivity due to simplification of the assembly process as a structure and a reduction in cost. A wide range of applications are expected as a connection structure of a branch connection body that pipes from a main pipe rail to an injector, such as an accumulator fuel injection system in a diesel internal combustion engine. In addition, although demonstrated here for diesel engines with a high fuel pressure, it cannot be overemphasized that it is applicable also for the direct-injection gasoline engine in which high pressure progresses.

DESCRIPTION OF SYMBOLS 1, 1a Common rail 1-1, 1a-1 Accumulation container 1-2, 1a-2 Flow path 1-3, 1a-3 Open end 1-4, 1a-4 Male screw 1-5, 1a-5, 1 -6, 1a-6 Connection end 1-7, 1a-7 Female screw 2, 2a Thick branch member 2-1, 2a-1 Outer wall 2-2, 2a-2 Top 2-3, 2a-3 Vertical wall 2-4, 2a-4 Bottom 2-5, 2a-5 Flow path 2-6, 2a-6 Female screw 2-7, 2a-7 Pressure-receiving seat surface 2-8, 2a-8 Branch hole 2-9 Bottom 2 -10, 2a-10 Connection hole 3-1, 3-2, 3-3, 3-4, 3-5, 3a-1, 3a-2, 3a-3, 3-1a, 3-2a, 3- 3a, 3-4a, 3-5a, 3a-1a, 3a-2a, 3a-3a, 3a-4a, 3a-5a, 3a-6a, 3a-7a Opening 3a-1, 3a-2, 3a-3 , a-4, 3a-5, 3a-6, 3a-7 screw boss 4-1, 4-2, 4-3, 4-4, 4-5, 4a-1, 4a-2, 4a-3, 4a -1, 4a-2, 4a-3, 4a-4, 4a-5, 4a-6, 4a-7 Tubular branch connector 4-A, 4a-A Connection head 4-B, 4a-B Press seat surface 5-1, 5-2, 5-3, 5-4, 5-5, 5a-1, 5a-2, 5a-3, 5a-1, 5a-2, 5a-3, 5a-4, 5a- 5, 5a-6, 5a-7 Nut 6 Fuel return piping 7 Pressure sensor piping

Claims (6)

  A thick branch member fixed by screwing between two tubular pressure accumulating containers arranged substantially coaxially, and a thin branch hole communicating with the inside of the shaft center on the outer wall of the thick branch member And a pressure receiving seat surface that opens in a conical shape for connecting the tubular branch connecting body is provided on the outer peripheral surface portion of the branch hole, and a cylindrical screw boss is provided in advance so as to surround the pressure receiving seat surface. The pressure receiving seat surface and the pressing seat surface provided on the tapered conical connecting head of the branch connection body are brought into contact with and engaged with each other, and the screw boss and the above-mentioned A common rail in which the thick branch member and the branch connection body are integrally connected by being screwed with a nut assembled on the branch connection body side and tightening in accordance with pressing of the branch connection body under the connection head neck. Each of the tubular pressure accumulating container and the thick-walled branch member. The joint end face is provided with a substantially planar or substantially curved bottom that communicates with a branch hole formed in the outer wall of the thick branch member, and the thick shaft branch between the bottoms has a substantially axial center. The common rail is characterized in that a small-diameter channel is formed in communication with the flow passages of the tubular pressure accumulating containers on both sides. A plurality of outer walls of the thick-walled branch member are provided in a substantially trapezoidal shape inclined from the flat top formed on the outer side of the thick-walled branch member to the left and right in the axial direction, and communicate with the inside of the shaft center from the outer wall. The small-diameter branch holes drilled in this manner are substantially flat or substantially provided at the connection end of the tubular pressure accumulating vessel without intersecting each other while intersecting each other in an X shape when projected onto a plane. The common rail according to claim 1, wherein the common rail is provided in communication with each of the curved bottom portions .   At least one of the tubular branch connectors connected to the outer wall of the thick branch member via a screw boss is a fuel supply pipe, and the other plurality of branch connectors are fuel injection pipes. The common rail according to claim 1 or 2.   Each of the vertical wall surfaces opposed to the left and right of the thick-walled branch member is formed with a female screw for screwing into a male screw formed on the outer peripheral surface of the connection end of the tubular pressure accumulating container. Each of the tubular pressure accumulators connected so as to sandwich the branch member from the left and right has a branch hole for communicating with the branch connector through the side wall of the pressure accumulator vessel from the flow passage provided in the shaft center. The common rail according to any one of claims 1 to 3, wherein the common rail is not drilled.   A female screw is formed on the inner peripheral surface of one connection end of the tubular accumulator, and either the pressure sensor pipe or the fuel return pipe is arbitrarily connected by being screwed to the female screw. The common rail according to any one of claims 1 to 4.   On the outer wall of the thick-walled branch member, the screw boss made of a cylindrical member provided integrally in advance or integrally by fixing is formed with a female screw on its inner peripheral surface or a male screw on its outer peripheral surface. The common rail according to claim 1, wherein the common rail is any one of the above.

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