FUEL INJECTION TUBE FOR DIESEL ENGINE

Abstract

 Problem to be solved
Provided is a diesel engine fuel injection pipe configured such that an orifice member is fixed inside of one end or the vicinity of the end of the injection pipe, wherein the orifice member is provided by a fixing means capable of withstanding extra-high fluid pressure.
Solving Means
A diesel engine fuel injection pipe comprising an orifice member having an outside diameter smaller than or substantially equal to the diameter of a pipe conduit in the diesel engine fuel injection pipe, inside of at least one end or the vicinity of the end of the injection pipe, the end having a connection head with a conical or spherical seat surface, and a fastening nut; wherein the orifice member is fixedly wedged by a reduced diameter portion of the pipe conduit in the injection pipe.

Description

Technical Field

[0001] The present invention relates to a high-pressure fuel injection pipe for use in connection with a common rail system or a P-L-D (pump line delivery) injection system, and the like for a diesel internal combustion engine.

Background Art

[0002] A conventional diesel engine fuel injection pipes has, for example, a truncated conical connection head 12 which is provided at an end of a thick-walled steel pipe 11 and has its outer circumferential surface serving as a seat surface 13 as illustrated in FIG. 11, or a connection head 22 which is provided at an end of a thick-walled steel pipe 21 and has its outer circumferential surface serving as a spherical seat surface 23 as illustrated in FIG. 12, either of which is configured to be molded by a buckling process that involves the use of external pressure toward the axial center by a punching member and in association therewith, outward broadening of the peripheral wall according to the buckling process that involves the use of pressure causes an annular pocket 15-1 (FIG. 11) or an annular notch 15-2 (FIG. 12) to be formed in an inner side of the connection head, and is made available for use in such a state under the present set of circumstances. It should be noted that the reference numeral 14 refers a sleeve washer fitted at the back of the connection head, and the reference numeral 16 a fastening nut.

[0003] In a fuel injection system which employs such a diesel engine fuel injection pipe, the fuel injection pipe is made short so as to make it possible to inject a sufficient amount of fuel into a combustion chamber without causing a loss in pressure inside of the pipe, and to take convenience of piping into consideration. However, even with such a short injection pipe, there occur fluctuations in pressure inside of the injection pipe at the time of closing of a valve after fuel injection. Such fluctuations in pressure turn into pulsations, which are introduced from inside of the pipe into the common rail or the like, and also which affect an injection pipe in the next cylinder, this leads to a problem of making stable fuel injection impossible.

[0004] Such a problem can be dealt with by reducing fluctuations in pressure due to, for example, increasing the inside diameter or length of the injection pipe or the common rail so as to increase the volume of the pipe. However, such measures undesirably cause quick transmission of pulsations. In order to dampen such pulsations and to delay and reduce transmission, methods for providing a common rail with an orifice have been developed.
Known examples of such methods include, for example, a method for providing the functionality of an orifice by reducing the diameter of a branch hole provided in a common rail, and a method for putting an orifice-equipped metal ring member (piece) in a branch hole of a common rail. Each of these methods can dampen pulsations and delay transmission.

[0005] However, the former method has a drawback that it is not easy to make an orifice because, in preparation for high repeated pressure that is applied to the branch hole, even the smallest portion of the wall thickness is 7 mm or greater and furthermore processing must be made in a place far from an end face of the common rail. Meanwhile, the latter method has a disadvantage of being poor in sealing stability because two places between the common rail and the metal ring member and between the injection pipe and the metal ring member must be sealed by the axial force of a single fastening nut incorporated at the side of the injection pipe.

[0006] In order to deal with such problems, Patent Literatures 1 to 3 have proposed the following fuel injection pipes.
The common rail fuel injection pipe disclosed in Patent Literature 1 is configured so as to prevent a metal ring member (piece) having an orifice from affecting sealing properties, and to cause the axial force of a fastening nut incorporated at the side of the injection pipe to act as the force to fix the metal ring member. This common rail fuel injection pipe has a connection head in which a metal ring member having an orifice is embedded, whereby the metal ring member serves solely as an orifice without affecting the sealing properties, and further whereby the axial force in fastening and connecting along with pressure applied a part below a neck of the connection head by screwing the fastening nut acts as the force to fasten the metal ring member.

[0007] The diesel engine fuel injection pipe disclosed in Patent Literature 2 is configured such that an orifice tube is provided at an end of the injection pipe so as to dampen pulsations and to delay and reduce transmission, thereby making stable fuel injection possible. The orifice tube having an outside diameter smaller than or equal to the diameter of a pipe conduit in the injection pipe is provided either at an opening at the distal end of the connection head of the fuel injection pipe or at an inner part of the opening at the distal end, and is fixed in the pipe conduit due to external diameter-reducing force.

[0008] The diesel engine fuel injection pipe disclosed in Patent Literature 3 is configured such that an orifice ring is provided at an end of the injection pipe so as to dampen pulsations and to delay and reduce transmission, thereby making stable fuel injection possible. At least one orifice ring having a smaller inside diameter than the diameter of a pipe conduit in the injection pipe is provided either at an opening at the distal end of the connection head of the fuel injection pipe or at an inner part of the opening at the distal end.

Prior Art Literature

Patent Literature

[0009] 

Patent Literature 1: JPA-2000-27731

Patent Literature 2: JPA-2001-227431

Patent Literature 3: JPA-2002-174155

Summary of Invention

Problem to be solved by the Invention

[0010] Among the conventional diesel engine fuel injection pipes as above, the diesel engine fuel injection pipe disclosed in Patent Literature 2, in particular, has excellent effects that the action of the orifice tube fixedly fitted in the vicinity of the opening at the distal end of the connection head achieves high sealing stability, dampens pulsations, and further delays and reduces transmission, thereby making stable fuel injection possible. However, the configuration for fixation of the orifice tube in the diesel engine fuel injection pipe disclosed in Patent Literature 2 raises the concern that extra-high fluid pressure may cause slippage or disengagement of the orifice tube. Therefore, it is becoming difficult to sufficiently address increased pressure during use of the pipe or extra-high pressure during use of autofrettage, as has been required in recent years.

[0011] The present invention has been made in order to solve the problems posed by the diesel engine fuel injection pipe disclosed in Patent Literature 2, and it is an object of the present invention to provide a diesel engine fuel injection pipe configured such that an orifice tube having an outside diameter smaller than or substantially equal to the diameter of a pipe conduit in the injection pipe is fixed at the inside of at least one end or of the vicinity of the end of the diesel engine fuel injection pipe, wherein the orifice tube is provided by a fixing means capable of withstanding extra-high fluid pressure.

Means for solving the Problem

[0012] A diesel engine fuel injection pipe according to the present invention comprises an orifice member having an outside diameter smaller than or substantially equal to the diameter of a pipe conduit in the injection pipe at the inside of at least one end or of the vicinity of the end of the diesel engine fuel injection pipe, the end having a connection head with a conical or spherical seat surface, and a fastening nut; wherein the vicinity of an outer circumferential part of a posterior end of the orifice member is fixedly wedged by a reduced diameter portion of the pipe conduit in the injection pipe.
According to a preferred aspect of the present invention, in addition to the vicinity of an outer circumferential part of the posterior end of the orifice member, the vicinity of an outer circumferential part of an end of the orifice member on the side of the distal end is also fixedly wedged by a reduced diameter portion of the pipe conduit in the injection pipe.
Further, according to the present invention, the reduced diameter portion of the pipe conduit is composed of an evaginated portion formed by pressure buckling processing of the connection head.
Moreover, the present invention may be configured such that a part of the end of the orifice member on the side of the distal end projects further outward than an end face of the connection head.
Still further, according to another preferred aspect of the present invention, the orifice member is in such a position that the length h from the end face of the connection head to the posterior end face of the orifice member along the axial direction of the injection pipe is not more than 1.3 times as long as the length H from the end face of the connection head to a part below a neck of the connection head along the axial direction of the injection pipe.

Effects of the Invention

[0013] A diesel engine fuel injection pipe according to the present invention employs, as a method for fixing an orifice member provided inside of a connection head, a method for fixedly wedging the orifice member by a reduced diameter portion formed on an inner wall of the connection head. Thereby, excellent effects of the orifice member to achieve high sealing stability, to dampen pulsations, and to delay and reduce transmission, which make stable fuel injection possible, can be obtained. In addition to these effects, since the orifice member is more firmly fixed due to the action of fixedly wedging the orifice member by the reduced diameter portion, the orifice member is restrained from slipping or moving due to fluid pressure, making it possible to sufficiently address the securing stabilities of sealing of jigs and tools under increased pressure during use of the injection pipe or under extra-high fluid pressure during use of autofrettage, as has been required in recent years.

Brief Description of the Drawings

[0014] 

FIG. 1 is a longitudinal cross-sectional view illustrating a diesel engine fuel injection pipe according to a first embodiment of the present invention;

FIG. 2 is a longitudinal cross-sectional view illustrating a diesel engine fuel injection pipe according to a second embodiment of the present invention;

FIG. 3 is a longitudinal cross-sectional view illustrating a diesel engine fuel injection pipe according to a third embodiment of the present invention;

FIG. 4 is a longitudinal cross-sectional view illustrating a diesel engine fuel injection pipe according to a fourth embodiment of the present invention;

FIG. 5 is a longitudinal cross-sectional view illustrating a diesel engine fuel injection pipe according to a fifth embodiment of the present invention;

FIG. 6 is a longitudinal cross-sectional view illustrating a diesel engine fuel injection pipe according to a sixth embodiment of the present invention;

FIG. 7 is a longitudinal cross-sectional view illustrating a diesel engine fuel injection pipe according to a seventh embodiment of the present invention;

FIG. 8 is a longitudinal cross-sectional view illustrating a diesel engine fuel injection pipe according to an eighth embodiment of the present invention;

FIG. 9 is a longitudinal cross-sectional view illustrating a diesel engine fuel injection pipe according to a ninth embodiment of the present invention;

FIG. 10 is a longitudinal cross-sectional view illustrating a diesel engine fuel injection pipe according to a tenth embodiment of the present invention;

FIG. 11 is a longitudinal cross-sectional view illustrating an example of a conventional diesel engine fuel injection pipe; and

FIG. 12 is a longitudinal cross-sectional view illustrating another example of a conventional diesel engine fuel injection pipe.

Best Mode for carrying out the Invention

[0015] FIG. 1 is a longitudinal cross-sectional view illustrating a diesel engine fuel injection pipe according to a first embodiment of the present invention; FIG. 2 is a longitudinal cross-sectional view illustrating a diesel engine fuel injection pipe according to a second embodiment of the present invention; FIG. 3 is a longitudinal cross-sectional view illustrating a diesel engine fuel injection pipe according to a third embodiment of the present invention; FIG. 4 is a longitudinal cross-sectional view illustrating a diesel engine fuel injection pipe according to a fourth embodiment of the present invention; FIG. 5 is a longitudinal cross-sectional view illustrating a diesel engine fuel injection pipe according to a fifth embodiment of the present invention; FIG. 6 is a longitudinal cross-sectional view illustrating a diesel engine fuel injection pipe according to a sixth embodiment of the present invention; FIG. 7 is a longitudinal cross-sectional view illustrating a diesel engine fuel injection pipe according to a seventh embodiment of the present invention; FIG. 8 is a longitudinal cross-sectional view illustrating a diesel engine fuel injection pipe according to an eighth embodiment of the present invention; FIG. 9 is a longitudinal cross-sectional view illustrating a diesel engine fuel injection pipe according to a ninth embodiment of the present invention; FIG. 10 is a longitudinal cross-sectional view illustrating a diesel engine fuel injection pipe according to a tenth embodiment of the present invention. In each of the drawings, the reference numeral 1 refers to a thick-walled and small-diameter steel pipe, the reference numeral 2 a connection head, the reference numeral 3 a pipe conduit, the reference numerals 4 and 5 reduced diameter portions, the reference numerals 6a and 6b orifice members, the reference numeral 7 a spherical seat surface (pressure bearing surface), the reference numeral 8 an annular flange, the reference numeral 9 a mating part, the reference numeral 10 a fastening nut, and the reference numeral 11 a washer (sleeve washer).

[0016] The thick-walled and small-diameter steel pipe 1 is a thick-walled steel pipe having a comparatively small diameter, which is made of steel material cut in advance to a standard size, such as stainless steel, TRIP steel, carbon steel for high-pressure piping or alloy steel, and which has a pipe diameter of approximately 6 to 10 mm and a wall thickness of approximately 1.25 to 3.5 mm.

[0017] The diesel engine fuel injection pipe according to the first embodiment illustrated in FIG. 1 is an example of a washerless type which is configured such that a short orifice member 6a having an outside diameter substantially equal to the inside diameter of a pipe conduit 3 is fixedly fitted inside of a connection head 2 which has a seat surface (pressure bearing surface) 7 provided at an end of the thick-walled and small-diameter steel pipe 1 and whose outer circumferential surface takes on a truncated conical shape and whose contact portion with a mating seat takes on a spherical shape, and an annular flange 8 provided at a distance from the seat surface 7 along an axial direction of the injection pipe. The present invention employs a method, as a means for fixing the orifice member 6a, in which the orifice member 6a has been fitted in advance into the end of the thick-walled and small-diameter steel pipe 1 or into a punch, and then fixedly wedging in the vicinity of an outer circumferential part of the posterior end of the orifice member 6a by a reduced diameter portion 4 composed of an evaginated portion formed due to plastic flow caused in the inner circumferential surface of the pipe conduit 3 by pressure buckling processing of the connection head 2.
That is, this diesel engine fuel injection pipe is embodied by carrying out a pressure buckling processing with the orifice member 6a having been fitted in advance into a part to be processed in the connection head, and thereby shaping the connection head 2 and, at the same time, by fixedly wedging the orifice member 6a by the reduced diameter portion 4 composed of the evaginated portion formed due to the plastic flow in the inner circumferential surface of the pipe conduit 3. This diesel engine fuel injection pipe has a fastening nut 10 fitted in advance onto the thick-walled and small-diameter steel pipe 1.
It should be noted that the reduced diameter portion composed of the evaginated portion formed on the inner circumferential surface of the pipe conduit 3 by pressure buckling processing of the connection head 2 is not only formed in the vicinity of the outer circumferential part of the posterior end of the orifice member, but also simultaneously formed in the vicinity of an outer circumferential part of the end of the orifice member 6a on the side of the distal end, as illustrated in FIG. 1, depending on the size of the orifice member 6a and the cross-sectional shape of the connection head, so that the orifice member 6a may be fixedly wedged in both the vicinity of the outer circumferential part of the posterior end of the orifice member 6a and the vicinity of the outer circumferential part of the end of the orifice member 6a on the side of the distal end.

[0018] Here, the orifice member 6a is provided in such a position that the length h from an end face of the connection head to the posterior end face of the orifice member 6a along the axial direction of the injection pipe is not more than 1.3 times as long as the length H from the end face of the connection head to the part below a neck of the connection head along the axial direction of the injection pipe. The reason for this is that, if the length h to the posterior end face of the orifice member 6a is more than 1.3 times as long as the length H from the end face of the connection head to the part below a neck of the connection head along the axial direction of the injection pipe, it will be difficult to form the reduced diameter portion 4 of the pipe conduit 3 to pin the vicinity of the outer circumferential part of the posterior end of the orifice member 6a while securing a sufficient strength to fixedly wedge the orifice member 6a at the time of pressure buckling processing of the connection head 2. It should be noted that the present embodiment is an example where the length h is approximately 0.72 time as long as the length H.

[0019] In the diesel engine fuel injection pipe thus configured, the orifice member 6a is fixedly wedged by the reduced diameter portion 4 formed on the inner wall of the connection head 2 and preferably further by the reduced diameter portion 5. Thereby, excellent effects of the orifice member 6a to achieve high sealing stability, to dampen pulsations, and to delay and reduce transmission, which make stable fuel injection possible, can be obtained. In addition to these effects, since the orifice member 6a is more firmly fixed due to the action of fixedly wedging the orifice member 6a by the reduced diameter portions 4 and 5, the orifice member 6a is restrained from slipping or moving due to fluid pressure.

[0020] The diesel engine fuel injection pipe according to the second embodiment illustrated in FIG. 2 is an example of a general washer type which is configured to be substantially identical in structure to the washerless type illustrated in FIG. 1, except that a tightening nut 10 has been fitted in advance onto a thick-walled and small-diameter steel pipe 1 via a washer (sleeve washer) 11. That is, this diesel engine fuel injection pipe is configured such that a short orifice member 6a having an outside diameter substantially equal to the inside diameter of a pipe conduit 3 is fixedly fitted inside of a connection head 2which has a seat surface (pressure bearing surface) 7 provided at an end of the thick-walled and small-diameter steel pipe 1 and whose outer circumferential surface takes on a truncated conical shape and whose contact portion with a mating seat takes on a spherical shape, and an annular flange 8 provided at a distance from the seat surface 7 along an axial direction of the injection pipe so that the orifice member 6a is in such a position that the length h from an end face of the connection head to the posterior end face of the orifice member along the axial direction of the injection pipe is not more than 1.3 times as long as the length H from the end face of the connection head to the part below a neck of the connection head along the axial direction of the injection pipe. It should be noted that the present embodiment is an example where the length h is approximately 0.93 time as long as the length H.
In this embodiment, as in the case of the washerless type described above, this diesel engine fuel injection pipe is embodied by, as a means for fixing the orifice member 6a, carrying out a pressure buckling processing with the orifice member 6a having been fitted in advance into a part to be processed in the connection head or into a punch, and thereby shaping the connection head 2 and, at the same time, by fixedly wedging the orifice member 6a by a reduced diameter portion 4 composed of an evaginated portion formed due to plastic flow caused in an inner circumferential surface of the pipe conduit 3. Further, in this embodiment, as in the case of the washerless type illustrated in FIG. 1, the reduced diameter portion composed of the evaginated portion formed due to the plastic flow caused in the inner circumferential surface of the pipe conduit 3 by pressure buckling processing of the connection head 2 may be fixedly wedged not only in the vicinity of the outer circumferential part of the posterior end of the orifice member, but in both the vicinity of the outer circumferential part of the posterior end of the orifice member 6a and the vicinity of the outer circumferential part of the end of the orifice member 6a on the side of the distal end, as illustrated in FIG. 2.

[0021] It should be noted that the washer (sleeve washer) 11 is tightly or freely fitted onto a part below a neck of the annular flange 8 by means of caulking or other means. The contact surface of the washer (sleeve washer) 11 with the fastening nut 10 is not limited to be a flat surface, but may be a conical surface or a spherical surface. Further, the contact surface of the annular flange 8 with the washer may be a flat surface perpendicular to the axis of the injection pipe, or a conical or spherical surface that becomes smaller in diameter toward backward along the axis of the diesel engine injection pipe.

[0022] In the diesel engine fuel injection pipe thus configured, as in the case of the injection pipe illustrated in FIG. 1, the orifice member 6a is fixedly wedged by the reduced diameter portion 4 formed on the inner wall of the connection head 2 and preferably further by the reduced diameter portion 5. Thereby, excellent effects of the orifice member 6a to achieve high sealing stability, to dampen pulsations, and to delay and reduce transmission, which make stable fuel injection possible, can be obtained. In addition to these effects, since the orifice member 6a is more firmly fixed due to the action of fixedly wedging the orifice member 6a by the reduced diameter portions 4 and 5, the orifice member 6a is restrained from slipping or moving due to fluid pressure.

[0023] The diesel engine fuel injection pipes according to the third to sixth embodiments illustrated in Figs. 3 to 6, are examples that employ a long orifice member 6b which is different in length from the short orifice member 6a illustrated in Figs. 1 and 2 on a washerless type. The diesel engine fuel injection pipe according to the third embodiment illustrated in FIG. 3 is similar in structure to that illustrated in FIG. 1, and configured such that a long orifice member 6b having an outside diameter substantially equal to the inside diameter of a pipe conduit 3 is fixedly fitted inside of a connection head 2 which has a seat surface (pressure bearing surface) 7 provided at an end of the thick-walled and small-diameter steel pipe 1 and whose outer circumferential surface takes on a truncated conical shape and whose contact portion with a mating seat takes on a spherical shape, and an annular flange 8 provided at a distance from the seat surface 7 along an axial direction of the injection pipe, so that the orifice member 6b is in such a position that the length h from an end face of the connection head to the posterior end face of the orifice member 6b along the axial direction of the injection pipe is not more than 1.3 times (0.65 times in this embodiment) as long as the length H from the end face of the connection head to the part below a neck of the connection head along the axial direction of the injection pipe, and furthermore so that the end of the orifice member on the side of the distal end projects further outward than the distal end face of the connection head 2. Also in the case of this orifice member 6b, as in the case of those described above, the diesel engine fuel injection pipe is embodied by carrying out a pressure buckling processing with the orifice member 6b having been fitted in advance into a part to be processed in the connection head or into a punch, and thereby shaping the connection head 2 and, at the same time, by fixedly wedging the orifice member 6b by a reduced diameter portion 4 composed of an evaginated portion formed due to plastic flow caused in an inner circumferential surface of the pipe conduit 3.
It should be noted that, also in this embodiment, the reduced diameter portion 4 composed of the evaginated portion formed due to the plastic flow caused in the inner circumferential surface of the pipe conduit 3 by pressure buckling processing of the connection head 2 may be not only formed in the vicinity of the outer circumferential part of the posterior end of the orifice member, but also simultaneously formed in the vicinity of an outer circumferential part of the end of the orifice member 6b on the side of the distal end as a reduced diameter portion 5.

[0024] The diesel engine fuel injection pipe according to the fourth embodiment illustrated in FIG. 4 is similar in structure to that illustrated in FIG. 3, configured such that a long orifice member 6b having an outside diameter substantially equal to the inside diameter of a pipe conduit 3 is fixedly fitted inside of a connection head 2 which has a seat surface (pressure bearing surface) 7 provided at an end of the thick-walled and small-diameter steel pipe 1 and whose outer circumferential surface takes on a truncated conical shape and whose contact portion with a mating seat takes on a spherical shape, and an annular flange 8 provided at a distance from the seat surface 7 along an axial direction of the injection pipe, so that the orifice member 6b is in such a position that the length h from an end face of the connection head to the posterior end face of the orifice member along the axial direction of the injection pipe is not more than 1.3 times (0.71 times in this embodiment) as long as the length H from the end face of the connection head to the part below a neck of the connection head along the axial direction of the injection pipe, and furthermore so that the end of the orifice member on the side of the distal end is substantially flush with the distal end face of the connection head 2. Also in the case of this orifice member 6b, as in the case of those described above, the diesel engine fuel injection pipe is embodied by carrying out a pressure buckling processing with the orifice member 6b having been fitted in advance into a part to be processed in the connection head or into a punch, and thereby shaping the connection head 2 and, at the same time, by fixedly wedging the orifice member 6b by a reduced diameter portion 4 composed of an evaginated portion formed due to plastic flow caused in an inner circumferential surface of the pipe conduit 3.
It should be noted that, also in this embodiment, the reduced diameter portion 4 composed of the evaginated portion formed in the inner circumferential surface of the pipe conduit 3 by pressure buckling processing of the connection head 2 may be not only formed in the vicinity of the outer circumferential part of the posterior end of the orifice member, but also simultaneously formed in the vicinity of an outer circumferential part of the end of the orifice member 6b on the side of the distal end as a reduced diameter portion 5.

[0025] The diesel engine fuel injection pipes according to the fifth and sixth embodiments illustrated in Figs. 5 and 6 are respectively configured to be similar in structure to those illustrated in Figs. 3 and 4 except that the long orifice member 6b is fixedly fitted in an inner part of the connection head 2 than the opening end thereof. The diesel engine fuel injection pipe according to the fifth embodiment illustrated in FIG. 5 is configured such that a long orifice member 6b having an outside diameter substantially equal to the inside diameter of a pipe conduit 3 is fixedly fitted in an inner part than the opening end in a connection head 2 which has a seat surface (pressure bearing surface) 7 provided at an end of the thick-walled and small-diameter steel pipe 1 and whose outer circumferential surface takes on a truncated conical shape and whose contact portion with a mating seat takes on a spherical shape, and an annular flange 8 provided at a distance from the seat surface 7 along an axial direction of the injection pipe, so that the orifice member 6b is in such a position that the length h from an end face of the connection head to the posterior end face of the orifice member 6b along the axial direction of the injection pipe is not more than 1.3 times (0.85 times in this embodiment) as long as the length H from the end face of the connection head to the part below of neck of the connection head along the axial direction of the injection pipe. Also in the case of this orifice member 6b, as in the case of those described above, the diesel engine fuel injection pipe is embodied by carrying out a pressure buckling processing with the orifice member 6b having been fitted in advance into a part to be processed in the connection head or into a punch, and thereby shaping the connection head 2 and, at the same time, by fixedly wedging the orifice member 6b by a reduced diameter portion 4 composed of an evaginated portion formed due to plastic flow caused in an inner circumferential surface of the pipe conduit 3.
Further, the diesel engine fuel injection pipe according to the sixth embodiment illustrated in FIG. 6 is configured such that a long orifice member 6b having an outside diameter substantially equal to the inside diameter of a pipe conduit 3 is fixedly fitted in an further inner part of a connection head 2 than the opening end thereof as compared to the orifice member 6b in FIG. 5, the connection head 2 which has a seat surface (pressure bearing surface) 7 provided at an end of the thick-walled and small-diameter steel pipe 1 and whose outer circumferential surface takes on a truncated conical shape and whose contact portion with a mating seat takes on a spherical shape, and an annular flange 8 provided at a distance from the seat surface 7 along an axial direction of the injection pipe, so that the orifice member 6b is in such a position that the length h from an end face of the connection head to the posterior end face of the orifice member 6b along the axial direction of the injection pipe is not more than 1.3 times (0.95 times in this embodiment) as long as the length H from the end face of the connection head to the part below a neck of the connection head along the axial direction of the injection pipe. Also in the case of this orifice member 6b, as in the case of those described above, the diesel engine fuel injection pipe is embodied by carrying out a pressure buckling processing with the orifice member 6b having been fitted in advance into a part to be processed in the connection head or into a punch, and thereby shaping the connection head 2 and, at the same time, by fixedly wedging the orifice member 6b by a reduced diameter portion 4 composed of an evaginated portion formed due to plastic flow caused in an inner circumferential surface of the pipe conduit 3.
It should be noted that, also these embodiments illustrated in Figs. 5 and 6, the reduced diameter portion 4 composed of the evaginated portion formed in the inner circumferential surface of the pipe conduit 3 by pressure buckling processing of the connection head 2 may be not only formed in the vicinity of the outer circumferential part of the posterior end of the orifice member, but also simultaneously formed in the vicinity of an outer circumferential part of the end of the orifice member 6b on the side of the distal end as a reduced diameter portion 5.

[0026] The diesel engine fuel injection pipes according to the seventh to tenth embodiments illustrated in Figs. 7 to 10, are examples employ such a long orifice member 6b as those described above on a washer type. The diesel engine fuel injection pipe according to the seventh embodiment illustrated in FIG. 7 is similar in structure to that illustrated in FIG. 2 and configured such that a long orifice member 6b having an outside diameter substantially equal to the inside diameter of a pipe conduit 3 is fixedly fitted inside of a connection head 2 which has a seat surface (pressure bearing surface) 7 provided at an end of the thick-walled and small-diameter steel pipe 1 and whose outer circumferential surface takes on a truncated conical shape and whose contact portion with a mating seat takes on a spherical shape, and the washer type of an annular flange 8 provided at a distance from the seat surface 7 along an axial direction of the injection pipe, so that the orifice member 6b is in such a position that the length h from an end face of the connection head to the posterior end face of the orifice member 6b along the axial direction of the injection pipe is not more than 1.3 times (0.94 times in this embodiment) as long as the length H from the end face of the connection head to the part below a neck of the connection head along the axial direction of the injection pipe, and furthermore so that the end of the orifice member on the side of the distal end projects further outward than the distal end face of the connection head 2. Also in the case of this orifice member 6b, as in the case of those described above, the diesel engine fuel injection pipe is embodied by carrying out a pressure buckling processing with the orifice member 6b having been fitted in advance into a part to be processed in the connection head or into a punch, and thereby shaping the connection head 2 and, at the same time, by fixedly wedging the orifice member 6b by a reduced diameter portion 4 composed of an evaginated portion formed due to plastic flow caused in an inner circumferential surface of the pipe conduit 3.
It should be noted that, also in this embodiment, the reduced diameter portion 4 composed of the evaginated portion formed in the inner circumferential surface of the pipe conduit 3 by pressure buckling processing of the connection head 2 may be not only formed in the vicinity of the outer circumferential part of the posterior end of the orifice member 6b, but also simultaneously formed in the vicinity of an outer circumferential part of the end of the orifice member 6b on the side of the distal end as a reduced diameter portion 5.

[0027] The diesel engine fuel injection pipe according to the eighth embodiment illustrated in FIG. 8 is similar in structure to that illustrated in FIG. 7 and configured such that a long orifice member 6b having an outside diameter substantially equal to the inside diameter of a pipe conduit 3 is fixedly fitted inside of a connection head 2which has a seat surface (pressure bearing surface) 7 provided at an end of the thick-walled and small-diameter steel pipe 1 and whose outer circumferential surface takes on a truncated conical shape and whose contact portion with a mating seat takes on a spherical shape, and the washer type of an annular flange 8 provided at a distance from the seat surface 7 along an axial direction of the injection pipe, so that the orifice member 6b is in such a position that the length h from an end face of the connection head to the posterior end face of the orifice member 6b along the axial direction of the injection pipe is not more than 1.3 times (0.87 times in this embodiment) as long as the length H from the end face of the connection head to the part below a neck of the connection head along the axial direction of the injection pipe, and furthermore so that the end of the orifice member on the side of the distal end is substantially flush with the distal end face of the connection head 2. Also in the case of this orifice member 6b, as in the case of those described above, the diesel engine fuel injection pipe is embodied by carrying out a pressure buckling processing with the orifice member 6b having been fitted in advance into either that part to be processed in the connection head or into a punch, and thereby shaping the connection head 2 and, at the same time, by fixedly wedging the orifice member 6b by a reduced diameter portion 4 composed of an evaginated portion formed due to plastic flow caused in an inner circumferential surface of the pipe conduit 3. It should be noted that, also in this embodiment, the reduced diameter portion 4 composed of the evaginated portion formed in the inner circumferential surface of the pipe conduit 3 by pressure buckling processing of the connection head 2 may be not only formed in the vicinity of the outer circumferential part of the posterior end of the orifice member 6b, but also simultaneously formed in the vicinity of an outer circumferential part of the end of the orifice member 6b on the side of the distal end as a reduced diameter portion 5.

[0028] The diesel engine fuel injection pipes according to the ninth and tenth embodiments illustrated in Figs. 9 and 10 are respectively configured to be similar in structure to those illustrated in Figs. 7 and 8, except that the long orifice member 6b is fixedly fitted in an inner part of the connection head 2 than the opening end thereof. The diesel engine fuel injection pipe according to the ninth embodiment illustrated in FIG. 9 is configured such that a long orifice member 6b having an outside diameter substantially equal to the inside diameter of a pipe conduit 3 is fixedly fitted in an inner part than the opening end in a connection head 2 which has a seat surface (pressure bearing surface) 7 provided at an end of the thick-walled and small-diameter steel pipe 1 and whose outer circumferential surface takes on a truncated conical shape and whose contact portion with a mating seat takes on a spherical shape, and the washer type of an annular flange 8 provided at a distance from the seat surface 7 along an axial direction of the injection pipe, so that the orifice member 6b is in such a position that the length h from an end face of the connection head to the posterior end face of the orifice member 6b along the axial direction of the injection pipe is not more than 1.3 times (1.09 times in this embodiment) as long as the length H from the end face of the connection head to the part below a neck of the connection head along the axial direction of the injection pipe. Also in the case of this orifice member 6b, as in the case of those described above, the diesel engine fuel injection pipe is embodied by carrying out a pressure buckling processing with the orifice member 6b having been fitted in advance into a part to be processed in the connection head or into a punch, and thereby shaping the connection head 2 and, at the same time, by fixedly wedging the orifice member 6b by a reduced diameter portion 4 composed of an evaginated portion formed due to plastic flow caused in an inner circumferential surface of the pipe conduit 3.
Further, the diesel engine fuel injection pipe according to the tenth embodiment illustrated in FIG. 10 is configured such that a long orifice member 6b having an outside diameter substantially equal to the inside diameter of a pipe conduit 3 is fixedly fitted in an further inner part of a connection head 2 than the opening end thereof as compared to the orifice member 6b in FIG. 9, the connection head 2 which has a seat surface (pressure bearing surface) 7 provided at an end of the thick-walled and small-diameter steel pipe 1 and whose outer circumferential surface takes on a truncated conical shape and whose contact portion with a mating seat takes on a spherical shape, and the washer type of an annular flange 8 provided at a distance from the seat surface 7 along an axial direction of the injection pipe, so that the orifice member 6b is in such a position that the length h from an end face of the connection head to the posterior end face of the orifice member 6b along the axial direction of the injection pipe is not more than 1.3 times (1.3 times in this embodiment) as long as the length H from the end face of the connection head to the part below a neck of the connection head along the axial direction of the injection pipe. Also in the case of this orifice member 6b, as in the case of those described above, the diesel engine fuel injection pipe is embodied by carrying out a pressure buckling processing with the orifice member 6b having been fitted in advance into a part to be processed in the connection head or into a punch, and thereby shaping the connection head 2 and, at the same time, by fixedly wedging the orifice member 6b by a reduced diameter portion 4 composed of an evaginated portion formed due to plastic flow caused in an inner circumferential surface of the pipe conduit 3.
It should be noted that, also in these embodiments illustrated in Figs. 9 and 10, the reduced diameter portion 4 composed of the evaginated portion formed in the inner circumferential surface of the pipe conduit 3 by pressure buckling processing of the connection head 2 may be not only formed in the vicinity of the outer circumferential part of the posterior end of the orifice member 6b, but also simultaneously formed in the vicinity of an outer circumferential part of the end of the orifice member 6b on the side of the distal end as a reduced diameter portion 5.

[0029] In the diesel engine fuel injection pipes configured as illustrated in Figs. 3 to 10, as in the case of the injection pipes illustrated in Figs. 1 and 2, the orifice member 6b is fixedly wedged by the reduced diameter portion 4 formed on the inner wall of the connection head 2 and preferably further by the reduced diameter portion 5. Thereby, excellent effects of the orifice member 6b to achieve high sealing stability, to dampen pulsations, and to delay and reduce transmission, which make stable fuel injection possible, can be obtained. In addition to these effects, since the orifice member 6b is more firmly fixed due to the action of fixedly wedging the orifice member 6b by the reduced diameter portions 4 and 5, the orifice member 6b is restrained from slipping or moving due to fluid pressure.
It should be noted that an orifice member in the present invention is not limited to a tubular one as illustrated above or cylindrical one, but, needless to say, may be also for example one formed in a washer or doughnut shape whose axial length is shorter than the diameter of the pipe conduit 3. Although the tubular or cylindrical orifice member (orifice tube) is illustrated as if it had smooth concave and convex portions formed on its outer circumferential surface, the orifice member (orifice tube) originally has its outer circumferential surface of a substantially cylindrical shape, and does not necessarily have concave and convex portions formed in advance on its outer circumferential surface to be fixed (fitted) to the injection pipe.

Industrial Applicability

[0030] A diesel engine fuel injection pipe according to the present invention employs, as a method for fixing an orifice member provided inside of a connection head, a method for fixedly wedging the orifice member by a reduced diameter portion formed on an inner wall of the connection head. This allows the orifice member to bring about its beneficial effects of exhibiting high sealing stability, dampening pulsations, and delaying and reducing transmission so that fuel can be stably injected. In addition to these effects, since the orifice member is more firmly fixed due to the action of fixedly wedging the orifice member by the reduced diameter portion, the orifice member is restrained from slipping or moving due to fluid pressure, making it possible to sufficiently address the securing stabilities of sealing of jigs and tools under increased pressure during use of the injection pipe or under extra-high fluid pressure during use of autofrettage, as has been required in recent years.

Discription of Reference Numerals

[0031] 

1:

Thick-walled and small-diameter steel pipe

2:

Connection head

3:

Pipe conduit

4, 5:

Reduced diameter portion

6a, 6b:

Orifice member

7:

Spherical seat surface (pressure bearing surface)

8:

Annular flange

9:

Mating part

10:

Fastening nut

11:

Washer (sleeve washer)

Claims

1. A diesel engine fuel injection pipe comprising an orifice member having an outside diameter smaller than or substantially equal to the diameter of a pipe conduit in the injection pipe, inside of at least one end or the vicinity of the end of the diesel engine fuel injection pipe, the end having a connection head with a conical or spherical seat surface, and a fastening nut;
wherein the vicinity of an outer circumferential part of a posterior end of the orifice member is fixedly wedged by a reduced diameter portion of the pipe conduit in the injection pipe.

2. The diesel engine fuel injection pipe according to claim 1, wherein the vicinity of an outer circumferential part of an end of the orifice member on the side of the distal end is fixedly wedged by a reduced diameter portion of the pipe conduit in the injection pipe.

3. The diesel engine fuel injection pipe according to claim 1, whereby the reduced diameter portion of the pipe conduit is composed of an evaginated portion formed by pressure buckling processing of the connection head.

4. The diesel engine fuel injection pipe according to any one of claims 1 to 3, wherein a part of the end face of the orifice member on the side of the distal end projects further outward than an end face of the connection head.

5. The diesel engine fuel injection pipe according to any one of claims 1 to 4, wherein the orifice member is in such a position that the length h from the end face of the connection head to the posterior end face of the orifice member along the axial direction of the injection pipe is not more than 1.3 times as long as the length H from the end face of the connection head to a part below a neck of the connection head along the axial direction of the injection pipe.

Drawing