JP5455303B2 - High pressure fuel injection pipe with connecting head - Google Patents

Description

The present invention, for example, relates to the high-pressure fuel injection pipe having a connecting head distribution設多for the the tube diameter 4mm to 20 mm, by thick-walled thin-diameter steel tube having a thickness of approximately 1mm to 8mm as a supply passage of fuel in a diesel internal combustion engine It is.

  Conventionally, as a high-pressure fuel injection pipe having this type of connection head, as illustrated in FIG. 15, a spherical sheet surface 113 and a sheet surface 113 are connected to a connection end of a thick thin steel pipe 111. It has a connecting head portion 112 formed of an annular flange portion 115 provided at an interval in the axial direction, and a conical surface 114 that continues to the seat surface 113 and tapers toward the tip to the annular flange portion 115. One is known (see FIG. 1 of Patent Document 1). This type of connecting head 112 is formed by the buckling process by pressing in the axial direction by the punch member from the outside, and spreads to the outside of the peripheral wall due to the buckling process by the pressing. Thus, a pocket (annular recess) 116 having an increased inner surface tensile stress due to an increase in inner diameter and stress concentration is formed on the inner peripheral surface of the head, and it has been used in such a state. Cavitation erosion occurs near the pocket due to the high-pressure fluid during installation, radial cracks due to fatigue failure occur radially from the pocket at the connection head, or fatigue failure around the pocket There was concern about the occurrence of circumferential cracks.

As a countermeasure, the present applicant externally fits a connection washer having a stepped portion near the connection end of a thick thin steel pipe, and presses the punch member to make the outer peripheral surface a frustoconical shape to the mating seat. Alternatively, a method of forming a connecting head having an annular groove having a shallow and gentle inner depth by performing head processing to be a truncated arc-shaped sheet surface (see FIG. 1 of Patent Document 1), A spherical sheet surface by pressing with a punch member at the connection end of the thin-walled steel pipe, an annular flange portion provided at an interval in the axial direction from the sheet surface, and the annular flange connected to the sheet surface In a method of manufacturing a high-pressure fuel injection pipe for forming a connection head formed from a conical surface that is tapered toward the tip to the tip, an annular curved concave groove having a shallow depth is provided in a part of the conical surface. With the formation of the connecting head For example, a punch member with a cored bar may be used to prevent the inner pocket of the connecting head from being shallow and smooth (see FIG. 1 of Patent Document 2) or to prevent the inner peripheral wall surface of the connecting head from becoming concave. A method of forming a connection head by the same method as described above (see FIGS. 8 to 15 of Patent Document 3) was previously proposed.
JP 2002-54770 A JP 2003-336560 A Japanese Patent Publication No.55-35220

The present invention relates to the generation of cracks in the valleys of the pockets due to the formation of the pockets during head molding, and the occurrence of cracks due to cavitation erosion that occurs in the vicinity of the pockets due to the flow of high-pressure fluid during use. As a means for preventing the occurrence of an increase in the tensile stress of the inner surface due to the occurrence of an increase in the inner diameter and stress concentration accompanying the formation of the pockets during the formation of the head, It is an object of the present invention to propose a high-pressure fuel injection pipe having a connection head that can achieve the above effects.

In order to achieve the above-mentioned object, the present invention provides a spherical sheet surface at a connection end of a thick thin steel pipe, an annular flange formed at a distance from the sheet surface in the axial direction, and the sheet A conical surface that is continuous with the surface and tapers toward the tip to the annular flange portion, and further has a connecting head in which a circular curved concave groove having a shallow depth is formed in a part of the conical surface. A high-pressure fuel injection pipe having an inner wall surface in which a contour of a cross section in a tube axial direction of the steel pipe is a continuous and smooth tapered surface extending toward the opening in the flow path of the connection head In the pipe, an annular curved groove provided in a part of the conical surface is provided on the seat surface side from the annular flange portion of the connection head, and the annular flange of the curved groove is formed in a cross-sectional shape of the connection head. Part side edge is A1 point, same flange Opposite edge is A2 point, length from spherical sheet surface edge to A1 point is L, length parallel to the tube axis between A1 point and A2 point (width of curved groove) is W, outside tube When the diameter is d and the outer diameter of the A2 point is DA, DA / d = 0.95 to 1.3, the outer diameter of the curved groove portion between the points A1 and A2 ≧ DA, W / L = 0.3 And a connecting washer provided with a stepped diameter-increased portion at the neck lower portion of the connection head and provided with a stepped diameter-increased portion corresponding to the stepped diameter-increased portion on the inner peripheral portion. The gist of the invention is to have a structure that covers the lower neck of the connection head .

Moreover, as a core metal of the said punch member, it is set as a preferable aspect to use what satisfies the conditions described below.
(1) Satisfy the condition of do / Do = 1.11 to 1.23, where do is the core core maximum diameter do and the steel pipe inner diameter is Do.
(2) The condition of h / H = 0.78 to 0.87, where h is the axial direction length of the tapered surface of the cored bar and H is the axial direction length of the inner wall of the punch member. To be satisfied.
(3) a taper-shaped surface of the core metal root portion and a taper-shaped surface that is continuous with the taper-shaped surface of the core portion and gradually narrows toward the tip end, and The taper angle θ1 formed and the taper angles θ2 formed by the opposing ridge lines of the tapered surface connected to the taper-shaped surface of the base portion are 7 to 10 degrees and 2.5 to 3 degrees, respectively.
(4) The taper-shaped surface of the core metal root part, the intermediate-part taper-shaped surface that is continuous with the base-part taper-shaped surface and gradually narrows toward the tip side, and the intermediate-part taper-shaped surface that is gradually constricted toward the front-end side. A length in the axial direction of the taper-shaped surface of the core metal root portion is h1, and a length in the axial direction from the base of the metal core to the intermediate taper-shaped surface is h2, When the axial direction length of the inner wall of the punch member is H, the conditions of h1 / H = 0.49 to 1.0 and h2 / H = 1.23 to 1.35 are satisfied.
(5) The taper angle θ1 formed by the opposing ridgeline of the taper-shaped surface of the core metal root portion, the taper angle θ2 formed by the opposing ridgeline of the intermediate-portion tapered surface connected to the root-portion tapered surface, and the intermediate-portion tapered shape The taper angles θ3 formed by the opposing ridgelines of the tip tapered surface that is continuous with the surface and gradually narrows toward the tip side are 7 to 10 degrees, 5 to 6.25 degrees, and 2.5 to 3 degrees, respectively.

The high-pressure fuel injection pipe of the present invention has an inner wall surface that is a continuous and smoothly tapered surface in which the contour of the cross section in the tube axis direction of the steel pipe extends toward the opening in the flow path of the connection head. In addition, since there are almost no pockets or molded wrinkles on the inner wall surface, there is no fear of cavitation erosion due to fluid pressure in the head, and the possibility of starting fatigue failure due to stress concentration is extremely small. It has the effect of exhibiting high internal pressure fatigue strength and excellent durability reliability .

  In the high-pressure fuel injection pipe of the present invention, the inner wall surface of the flow path of the connection head is a continuous smooth taper-shaped surface in which the contour of the cross section in the tube axis direction of the steel pipe spreads toward the opening. This is in order to obtain a connection head having a flow path in which almost no pockets or molding flaws are present on the inner wall surface.

  In the present invention, DA / d is limited to 0.95 to 1.3, as described in Patent Document 2 (Japanese Patent Application Laid-Open No. 2003-336560). On the other hand, if the point is too close to the tip of the connecting head, it is difficult to secure a contact seal surface with the mating metal. On the other hand, if it exceeds 1.3, the point A2 is too close to the point A1 and the annular curved recess ( This is because the effect of reducing the inner surface recess depth of the pocket portion is reduced.

  Furthermore, the reason why the outer diameter of the curved groove portion is set to DA or more is to eliminate the undercut portion when the head is formed by the punch. That is, if the outer diameter of the curved groove is provided at a position smaller than DA (the position of point A2), an undercut portion is formed, so that the connecting head cannot be punched.

Further, in the method of manufacturing the high pressure fuel injection pipe of the present invention, the tube axial direction cross-sectional shape of the core metal of the punch member is a continuous and smoothly tapered surface whose base is thick and gradually narrows toward the tip side. This is because the material is made to plastically flow so that the tube material is pushed into the portion where pockets are likely to be generated in the conventional method in such a manner as to be sandwiched from opposite sides in the tube axis direction.

As the metal core before Symbol punch member, a core metal base maximum diameter do, when the steel pipe inner diameter and Do, preferably define a do / Do and from 1.11 to 1.23. The reason is that if the volume is less than 1.11, the amount of pipe protrusion increases as the volume at the tip of the pipe head increases, so that pockets are likely to occur. This is because the rigidity is reduced and the deformation is easily caused by the decrease, and the seal axial force is reduced when the injection pipe is assembled to the counterpart part.

Furthermore, as the core metal of the punch member, h the axial direction length of the tapered face of the core metal root portion, when the axial direction length of the inner wall of the punch member was H, the h / H It is preferable to define it as 0.78 to 0.87 . The reason is that the pocket portion sandwiches the tubing from the site would result that deviates the tube tip end, reducing the cormorants effect has Eliminating the occurrence of pockets in the conventional method is less than 0.78, on the other hand, in the conventional method exceeds 0.87 by site sandwiching the tubing from the site would pocket occurs is shifted to the tube flange side is for reducing the cormorants effect has eliminating the occurrence of the pocket.

Furthermore, as the core metal of the punch member employed in the above method, two-stage taper having a gradually narrowed tapered surface toward the distal end side continuous to the tapered surface and該根source unit tapered face of the core metal root portion The taper angle θ1 formed by the opposing ridgeline of the tapered surface of the cored bar of the cored bar with the shape surface, and the taper angle θ2 formed by the opposing ridgeline of the tapered surface connected to the tapered surface of the base part, respectively. It is preferably limited to 7 to 10 degrees and 2.5 to 3 degrees . This is due to the reason described below.
That is, the taper angle θ1 is limited to 7 to 10 degrees. When the taper angle θ1 is less than 7 degrees, the pressing force of the punch member against the pipe material becomes weak at the time of molding, so that the pipe material does not sufficiently plastic flow, and pockets are generated in the conventional method. effect is reduced which would leave to plastic flow of material to herd the tubing at the site it would, on the other hand, during molding exceeds 10 degrees, the tubing is smooth plastic flow at the pressing force becomes too strong with respect to the tubing of the punch member without, in the conventional method because the effect that would leave to plastic flow of material to herd the tubing at a site would pocket occurs is reduced. Further, the taper angle θ2 is limited to 2.5 to 3 degrees because if the pressure is less than 2.5 degrees, the pressing force of the punch member against the pipe material becomes weak at the time of molding. in reducing the effect that would leave to the material to herd the tubing at a site would pocket occurs plastic flow, while during molding exceed 3 degrees, tubing by pressing force becomes too strong with respect to the tubing of the punch member not smoothly plastic flow, in the conventional method because the effect that would leave to plastic flow of material to herd the tubing at a site would pocket occurs is reduced.

Furthermore, as the core metal of the punch member, tapered surfaces of the core metal root portion gradually narrowed intermediate portion tapered face toward the distal end side continuous to該根source portion tapered surface and intermediate The inter tapered face The length of the taper-shaped surface of the cored bar base portion of the three-step tapered surfaced core having a tip tapered surface that is continuous with and gradually narrows toward the tip side is h1, and the base of the cored bar When the axial direction length from the intermediate tapered surface to h2 is h2, and the axial direction length of the inner wall of the punch member is H, h1 / H is 0.49 to 1.0, and h2 / H is Preferably, it is defined as 1.23 to 1.35 . The reason is that the conventional method is less than h1 / H 0.49 By site sandwiching the tubing from the site would pocket occurs is shifted to the tube distal end side, and the cormorants effect has Eliminating the occurrence of pockets reduced, while in the conventional method exceeds 1.0 by site sandwiching the tubing from the site would pocket occurs is shifted to the tube flange portion side, in order to reduce the cormorants effect has eliminating the occurrence of pockets is there. Moreover, h2 / H In the conventional method is less than 1.23 that the site sandwiching the tubing from the site would pocket occurs is shifted to the tube distal end portion side, reduced the cormorants effect has Eliminating the occurrence of the pocket, on the other hand, in the conventional method exceeds 1.35 by site sandwiching the tubing from the site would pocket occurs is shifted to the tube flange side is for reducing the cormorants effect has eliminating the occurrence of the pocket.

Further, in the above three-step tapered surfaces with metal core, metal core root of tapered face of the opposing ridges of forming taper angle .theta.1, opposite of the intermediate portion tapered surface leading to該根source portion tapered face The taper angle θ2 formed by the ridge line and the taper angle θ3 formed by the shaft core of the tip tapered surface that is continuous with the intermediate tapered surface and gradually narrows toward the tip side are 7 to 10 degrees and 5 to 6.25, respectively. It is preferable that the angle is specified as 2.5 to 3 degrees . This is due to the reason described below.
That is, when the taper angle θ1 is less than 7 degrees, the material that pushes the pipe material into the portion where the tube material may not be sufficiently plasticized due to weak pressing force of the punch member against the pipe material at the time of molding, and pockets may occur in the conventional method. in the reduced is effect that will leave to plastic flow, while during molding exceeds 10 degrees, without tubing is smooth plastic flow by a pressing force is too strong for the tubing of the punch member, the pocket occurs in the conventional method the material to herd the tubing at a site will allo is to reduce the effect that will leave to plastic flow. In addition, when the taper angle θ2 is less than 5 degrees, a material that pushes the pipe material into a portion where a pocket is likely to be generated in the conventional method because the pressing force of the punch member against the pipe material becomes weak at the time of molding and the pipe material does not flow sufficiently plastically. the reduced is effect that will leave to plastic flow, while during molding exceed 6.25, without plastic flow tube is smoothly by the pressing force becomes too strong with respect to the tubing of the punch member, the pocket occurs in the conventional method the material to herd the tubing at the site will be to reduce the effect that will leave to plastic flow. Further, when the taper angle θ3 is less than 2.5 degrees, the pressing force of the punch member against the pipe material becomes weak at the time of molding, so that the pipe material does not sufficiently plastically flow, and the pipe material is driven into a portion where pockets may be generated in the conventional method. Yo material reduces the effect that would leave to plastic flow, and the other, during molding exceed 3 degrees, without plastic flow tube is smoothly by the pressing force becomes too strong with respect to the tubing of the punch member, in the conventional method pocket effect that will leave to the material to herd the tubing at a site would result plastic flow is because the reduced.

  FIG. 1 is a longitudinal side view showing a first embodiment of the connection head of the high-pressure fuel injection pipe according to the present invention, FIG. 2 is a longitudinal side view showing the second embodiment of the connection head, and FIG. 4 is a longitudinal side view showing the fourth embodiment of the connection head, and FIG. 5 is a longitudinal side view showing the fifth embodiment of the connection head. FIG. Is a longitudinal side view showing the sixth embodiment of the connection head, FIG. 7 is a longitudinal side view showing the seventh embodiment of the connection head, and FIG. 8 is a longitudinal side view showing the eighth embodiment of the connection head. FIGS. 9 and 9 are longitudinal side views showing a first embodiment of a punch member with a cored bar used for forming a connecting head of a high-pressure fuel injection pipe according to the present invention, and FIG. FIG. 11 is a longitudinal side view showing a third embodiment of the punch member with the cored bar, and FIG. 12 is the same. FIG. 13 is a longitudinal sectional view showing a fourth embodiment of a punch member with a cored bar, FIG. 13 is an explanatory view by a longitudinal section showing a first embodiment of a processing step according to a method for forming a connection head of a high pressure fuel injection pipe of the present invention, FIG. 14 is an explanatory view of a second embodiment of the machining step according to the method of forming the connection head, wherein 1 is a thick thin steel pipe, 2A to 2H are connection heads, and 3A to 3H are spherical surfaces. Sheet surface, 4A to 4H are conical surfaces, 5A to 5H are annular flange portions, 6A to 6H are tapered surfaces, 7A to 7E are washers (sleeve washers), 8A to 8D are punch members, 8A-1 to 8D -1 is a cored bar, 8A-1a, 8A-1b, 8B-1a, 8B-1b, 8B-1c are tapered surfaces, and 9 is a chuck.

  The thick thin steel pipe 1 has a pipe diameter d of 4 mm to 20 mm and a wall thickness t of about 1 mm to 8 mm made of a steel material such as stainless steel, trip steel, carbon steel for high pressure piping, alloy steel, etc. cut to a predetermined size in advance. Made of steel pipe.

  The high-pressure fuel injection pipe shown in FIG. 1 has a spherical seat surface 3A with an outer peripheral surface facing the mating seat at the connection end of the thick-walled thin steel pipe 1, and an interval in the axial direction from the seat surface 3A. 5A, and the conical surface 4A that is continuous with the seat surface 3A and tapers toward the tip to the annular flange portion 5A. It has a connecting head portion 2A having an inner wall surface that is a continuous and smoothly tapered surface 6A in which the contour of the cross section in the tube axis direction of the steel pipe extends toward the opening, and there are almost no pockets on the inner circumferential surface. .

The high-pressure fuel injection pipe shown in FIG. 2 has a spherical seat surface 3B with the outer peripheral surface facing the mating seat at the connecting end of the thick-walled thin steel pipe 1, and an interval in the axial direction from the seat surface 3B. An annular flange portion 5B provided in the above, a conical surface 4B which is continuous to the seat surface 3B and tapers toward the tip to the annular flange portion 5B, and a circular curve having a shallow depth in a part of the conical surface 4B. The inner surface of the thick thin steel pipe 1 is a continuous and smoothly tapered surface 6B in which the outline of the cross section in the tube axis direction of the steel pipe extends toward the opening. It has the connection head 2B which has a wall surface and has few pockets on the inner peripheral surface.
Here, the annular curved groove 4B-1 provided in a part of the conical surface 4B is provided closer to the seat surface 3B than the annular flange portion 5B of the connection head 2B. In the cross-sectional shape of the connecting head, the curved groove 4B-1 has an A1 point on the annular flange 5B side edge of the curved groove 4B-1, an A2 point on the opposite edge of the flange, The diameter is d, the A2 point outer diameter is DA, the length parallel to the tube axis between the points A1 and A2 (the width of the curved groove) is W, and the length from the spherical sheet surface edge to the point A1 is L. In this case, the length parallel to the tube axis between the points A1 and A2 (width of the curved groove) W / L = 0.3 to 0.7 , DA / d = 0.95 to 1.3, It is assumed that the outer diameter of the curved groove portion ≥ DA.

  The high pressure fuel injection pipe shown in FIGS. 3 to 8 is an example in which a washer is fitted to the lower part of the neck of the connection head. The high pressure fuel injection pipe shown in FIG. 3 is the same as the high pressure injection pipe shown in FIG. A high pressure fuel injection pipe shown in FIG. 4 having a short washer 7A fitted to the lower part of the neck of a connecting head 2C having the same seat surface 3C, conical surface 4C, annular flange portion 5C, and tapered surface 6C. Is a high pressure in which a short stepped washer 7B is fitted to the lower part of the neck of a connecting head 2D having a seat surface 3D, a conical surface 4D, an annular flange portion 5D, and a tapered surface 6D similar to the high pressure injection pipe shown in FIG. The fuel injection pipe, the high pressure fuel injection pipe shown in FIG. 5, has the same seat surface 3E, conical surface 4E, curved concave groove 4E-1, annular flange portion 5E, and tapered surface 6E as the high pressure injection pipe shown in FIG. A short washer under the neck of the connecting head 2E The high pressure fuel injection pipe fitted with -7A, the high pressure fuel injection pipe shown in FIG. 6, has the same seat surface 3F, conical surface 4F, curved concave groove 4F-1, and annular flange portion 5F as the high pressure injection pipe shown in FIG. The high-pressure fuel injection pipe in which a washer 7C having a tapered back surface is fitted to the lower part of the neck of the connection head 2F having the tapered surface 6F, and the high-pressure fuel injection pipe shown in FIG. 7 is the high-pressure injection pipe shown in FIG. A washer 7D whose front and back surfaces are tapered is fitted to the lower portion of the neck of the connecting head 2G having the same seat surface 3G, conical surface 4G, curved groove 4G-1, annular flange portion 5G, and tapered surface 6G. The attached high-pressure fuel injection pipe, shown in FIG. 8, has the same seat surface 3H, conical surface 4H, curved concave groove 4H-1, annular flange portion 5H, and tapered surface as the high-pressure injection pipe shown in FIG. At the lower neck of the connecting head 2H having 6H A high-pressure fuel injection pipe having fitted the sleeve washer 7E.

  In the present invention, the curved grooves 4B-1, 4E-1, 4F-1, 4G-1, and 4H-1 take the curved grooves 4B-1 as an example, and the bottom of the curved grooves is A1. Needless to say, it may be formed (undercut) so as to be located between the points A2 and A2.

Next, a cored punch member used for forming a connection head of a high pressure fuel injection pipe according to the present invention will be described with reference to FIGS.
A punch member 8A with a cored bar shown in FIG. 9 has a cored bar 8A-1 protruding from the center, and curved concave grooves 4B-1, 4E-1 etc. on the conical surface shown in FIGS. Spherical surfaces 8A-2, conical surfaces 8A-3, and flat portions 8A-4 corresponding to the seat surfaces 3A, 4C, conical surfaces 4A, 4C, and annular flange portions 5A, 5C of the connection heads 2A, 2C not formed, respectively, were formed. Is.
Here, the cored bar 8A-1 is formed as continuous smooth tapered surfaces 8A-1a and 8A-1b whose cross-sectional shape in the tube axis direction is thick at the base and gradually narrows toward the tip side. The core metal has a maximum root diameter do, a thick thin steel pipe inner diameter Do, an axial length of the tapered surface of the root portion h, and an axial length of the inner wall of the punch member H The taper angle formed by the opposite ridge line of the taper-shaped surface 8A-1a of the core metal root portion is θ1, and the taper angle formed by the opposite ridge line of the taper-shaped surface 8A-1b connected to the root portion taper-shaped surface 8A-1a. When θ2, do / Do is 1.11 to 1.23, h / H is 0.78 to 0.87, θ1 is 7 to 10 degrees, and θ2 is 2.5 to 3 degrees.

  A punch member 8B with a cored bar shown in FIG. 10 has a cored bar 8B-1 protruding from the center, and curved concave grooves 4B-1, 4E-1 etc. on the conical surface shown in FIGS. Spherical surfaces 8B-2, conical surfaces 8B-3, and flat portions 8B-4 corresponding to the seat surfaces 3A, 3C, conical surfaces 4A, 4C, and annular flange portions 5A, 5C of the connection heads 2A, 2C not formed, respectively, were formed. The cored bar 8B-1 includes a taper-shaped surface 8B-1a at the base of the cored bar, and a taper-shaped surface of the intermediate part that continues to the taper-shaped surface 8B-1a and gradually narrows toward the tip side. 8B-1b and a taper-shaped length of the taper-shaped surface of the core metal base portion having a tip-shaped taper-shaped surface 8B-1c that is continuous with the intermediate taper-shaped surface 8B-1b and gradually narrows toward the tip side. H1, the taper-shaped surface of the intermediate portion from the base of the cored bar The length in the axial direction at h2 is H2, the axial length in the axial direction of the inner wall of the punch member is H, the taper angle θ1 formed by the opposing ridge line of the tapered surface of the core metal root portion, When the taper angle θ2 formed by the opposite ridge lines of the intermediate tapered surface and the taper angle θ3 formed by the axial center of the distal tapered surface that is continuous with the intermediate tapered surface and gradually narrows toward the distal end side H1 / H is 0.49 to 1.0, h2 / H is 1.23 to 1.35, θ1 is 7 to 10 degrees, θ2 is 5 to 6.25 degrees, and θ3 is 2.5 to 3 degrees. It has become.

  The cored punch members 8C and 8D shown in FIG. 11 and FIG. 12 are annular curved grooves 4B-1, 4E-1, 4F-1, 4G- on the conical surfaces shown in FIGS. 1. Corresponding to connecting heads having 1 and 4H-1, cored bars 8C-1 and 8D-1 projecting from the center of each connecting head, and the cones shown in FIGS. Connecting heads 2B, 2E, 2F, 2G, 2H having the curved curved grooves 4B-1, 4E-1, 4F-1, 4G-1, 4H-1 on the surface 4B, 4E, 4F, 4G 4H, spherical grooves 8C-2, 8D- corresponding to the curved grooves 4B-1, 4E-1, 4F-1, 4G-1, 4H-1 and the annular flange portions 5B, 5E, 5F, 5G, 5H, respectively. 2. Conical surfaces 8C-3 and 8D-3, flat portions 8C-4 and 8D-4, and convex curved portions 8C-5 and 8D-5 are formed. Otherwise, each of the 9, metal core with a punch member 8A shown in FIG. 10 is similar to 8B.

Next, a method for forming the head of the high-pressure fuel injection pipe of the present invention FIG. 13 will be described with reference to FIG. 14. Here, a method of forming a connecting head without a washer and a connecting head with a washer by using the punch member 8A shown in FIG. 9 as a punch member will be described.

Referring to a method of forming a head of a high-pressure fuel injection pipe shown in FIG. 13, when the molding of the connecting head, a distal end portion of the steel pipe 1 while holding the thick-walled thin-diameter steel tube 1 by the chuck 9 the punch When pressed in the axial direction by the member 8A, the head machining allowance portion of the thick thin steel pipe 1 is plastically flowed, and the outer peripheral surface is spherical to the opposite seat at the tip of the thick thin steel pipe 1 Sheet surface 3A, an annular flange portion 5A spaced from the seat surface 3A in the axial direction, and a conical surface 4A that continues to the sheet surface 3A and tapers toward the tip to the annular flange portion 5A. 2A, and a connecting head 2A having no pockets or wrinkles in the thick thin steel pipe 1 is obtained. According to this head molding method, the tube axis direction cross-sectional shape is thick at the base and the core bar 8A having a continuous smooth taper surface gradually narrowing toward the tip side is used to produce the Narrowing of the inner diameter is suppressed by the presence of the tapered surface 8A-1b portion of the core metal 8A, and at the same time, a material is formed around the boundary between the tapered surfaces 8A-1a and 8A-1b of the core metal 8A. By plastic flow and press-contacting with the outer peripheral surface of the cored bar 8A, a flow path having almost no pockets or molding ridges on the inner wall surface of the connecting head 2A is obtained.

A method of forming a head of a high-pressure fuel injection pipe shown in FIG. 14, the thick-walled thin-diameter steel tube 1 of Washa 7A near the connecting head is fitted in advance with a head machining margin. Subsequently, when the tip of the steel pipe 1 is pressed in the axial direction by the punch member 8A while the thick thin steel pipe 1 is held by the chuck 9 as described above, the head processing of the thick thin steel pipe 1 is performed. At the same time, the connecting head 2A is molded, and at the same time, the washer 7A covers the outer peripheral surface of the neck lower portion of the connecting head 2A, and the outer peripheral surface is formed on the tip of the thick thin steel pipe 1. A spherical seat surface 3A to the mating seat, an annular flange portion 5A spaced from the seat surface 3A in the axial direction, and the annular flange portion 5A connected to the seat surface 3A toward the tip. A connecting head 2A is obtained which is composed of a conical surface 4A which is tapered and which has almost no pockets or wrinkles inside the thick-walled thin steel pipe 1. Also in the molding process of the washers with connecting head, the same, the action of the metal core 8A the tube axis direction cross-sectional shape without a smooth tapered surface gradually narrowed continuously toward the thick distal end side base portion As a result, a flow path having almost no pockets or molding flaws on the inner wall surface of the connection head 2A is obtained.

  In addition, although the head shaping | molding method by 8 A of punch members was demonstrated here, it cannot be overemphasized that the same effect is acquired also when it shape | molds using punch members 8B, 8C, and 8D.

The high-pressure fuel injection pipe of the present invention has an inner wall surface that is a continuous and smoothly tapered surface in which the contour of the cross section in the tube axis direction of the steel pipe extends toward the opening in the flow path of the connection head. In addition, since there are almost no pockets or molding flaws on the inner wall surface, there is no concern about cavitation erosion due to fluid pressure in the head, and the possibility of becoming a starting point of fatigue failure due to stress concentration is extremely small. It has the effect. Moreover, against the flow path of the connection head, the contour of the tube axis direction cross-section of the steel pipe has a inner wall surface was no smooth tapered surface which continuously extends toward the opening, and the inner wall Since it is possible to mold a connection head that has almost no pockets or molding flaws, there is no concern about cavitation erosion due to fluid pressure in the connection head, and there is a very high possibility of starting fatigue failure due to stress concentration. There is an excellent effect that a small high-pressure fuel injection pipe can be easily manufactured with existing equipment.
Therefore, the present invention is not limited to high-pressure fuel injection pipes that are frequently used as fuel supply passages in diesel internal combustion engines, but can also be applied to various high-pressure metal pipes having connection heads made of thick-walled thin-diameter steel pipes. The industrial utility value is extremely high.

It is a vertical side view which shows 1st Example of the connection head of the high pressure fuel injection pipe which concerns on this invention. It is a vertical side view which similarly shows 2nd Example of a connection head. It is a vertical side view which similarly shows 3rd Example of a connection head. It is a vertical side view which similarly shows 4th Example of a connection head. It is a vertical side view which similarly shows 5th Example of a connection head. It is a vertical side view which similarly shows 6th Example of a connection head. It is a vertical side view which similarly shows 7th Example of a connection head. It is a vertical side view which similarly shows 8th Example of a connection head. It is a vertical side view which shows 1st Example of the punch member with a metal core used for the shaping | molding process of the connection head of the high-pressure fuel injection pipe which concerns on this invention. It is a vertical side view which similarly shows 2nd Example of the punch member with a metal core. It is a vertical side view which similarly shows 3rd Example of the punch member with a metal core. It is a vertical side view which similarly shows 4th Example of the punch member with a metal core. It is explanatory drawing by the longitudinal cross-section which shows 1st Example of the manufacturing process which concerns on the shaping | molding method of the connection head of the high pressure fuel injection pipe of this invention. It is explanatory drawing by the longitudinal cross-section which shows the 2nd Example of the manufacturing process which similarly concerns on the formation method of a connection head. It is a vertical side view which shows an example of the connection head of the conventional high pressure fuel injection pipe made into the object of this invention.

DESCRIPTION OF SYMBOLS 1 Thick-walled thin steel pipe 2A-2H Connection head 3A-3H Spherical sheet surface 4A-4H Conical surface 5A-5H Annular flange part 6A-6H Tapered surface 7A-7E Washer (sleeve washer)
8A to 8D Punch member 8A-1 to 8D-1 Core 8A-1a, 8A-1b, 8B-1a, 8B-1b, 8B-1c Tapered surface 9 Chuck

Claims (1)

At the connection end of the thick thin steel pipe, there is a spherical sheet surface, an annular flange formed at a distance from the sheet surface in the axial direction, and the tip to the annular flange connected to the sheet surface. A high-pressure fuel injection pipe having a connection head formed with a conical surface tapered toward the surface and further having a circular curved concave groove having a shallow depth formed in a part of the conical surface. A high-pressure fuel injection pipe having an inner wall surface in which the contour of the cross section in the tube axis direction of the steel pipe extends toward the opening in a continuous smooth tapered surface, An annular curved groove to be provided is provided on the seat surface side from the annular flange portion of the connection head, and in the cross-sectional shape of the connection head, the edge of the curved groove on the side of the annular flange is A1. the part opposite edge point A2, spherical Sea A length parallel to a length of the surface edge and the point A1 to the tube axis between L, the point A1 -A2 points (width of the curved grooves) W, the the tube outer diameter d, A2 Tengai径DA when, have a connection head you satisfy the following conditions, said stepped increased diameter portion provided on the neck lower portion of the connecting head, stepped expansion corresponding to the stepped diameter portion on the inner peripheral portion high-pressure fuel injection pipes which have a connecting head, characterized in that the connecting washer provided with a diameter and a structure in which covered the neck lower portion of the connection head.
Record
DA / d = 0.95-1.3
Outer diameter of curved groove between A1 point and A2 point ≧ DA
W / L = 0.3-0.7