JP4010786B2 - Connection structure between common rail and injection pipe assembly and method for forming the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a connection structure between a common rail and an injection pipe assembly in a common rail fuel injection device for a diesel engine, and a method for forming the connection structure.
[0002]
[Prior art]
In a common rail fuel injection device for a diesel engine, a pipe for connecting an injector (hereinafter referred to as an injection pipe) is connected to the common rail.
[0003]
5 to 7 show a first conventional example of the above connection structure. As shown in FIG. 5, a common rail hole 52 extending in the rail length direction is formed at the center of the common rail 51, and a branch hole 53 (orifice hole) extending in a direction perpendicular to the rail length by crossing the common rail hole 52 and the seal It is shown that the surface 54 is formed. A small cylindrical collar 62 is press-fitted and fixed to the end of the injection pipe 61, and a convex spherical seal surface 64 is formed at the tip of the collar 62. A large cylindrical union 71 is passed around the injection pipe 61. The injection pipe 61, the collar 62, and the union 71 are assembled as an injection pipe assembly 60 in advance.
[0004]
FIG. 6 shows a cross-sectional view of the state where the injection pipe assembly 60 shown in FIG. 5 is screwed to the common rail 51. The fuel pressurized by the fuel pump and sent to the common rail 51 is introduced into the branch hole 53 from the common rail hole 52, and sent from the injection pipe 61 to the injector through the through hole in the collar 62. At that time, the inside of the common rail hole 52 becomes an ultra-high pressure (20 ← → about 200 MPa) accompanied by a pressure fluctuation generated by the pressurized fuel sent from the fuel pump. Therefore, as shown in FIG. 7 which is a detailed view of the periphery of the branch hole 53, tensile strain accompanied by fluctuations is repeatedly generated at the intersection opening edge 57 of the branch hole 53 with respect to the common rail hole 52. Then, a crack 58 due to metal fatigue is likely to occur at the cross opening edge 57, and the quality becomes unstable. In order to prevent this crack, the strength of the common rail 51 is increased by hardening, such as carburizing and quenching, curving of the cross opening edge 57 by electrolytic deburring, and material change. Then, the cost will be significantly increased and the weight will be increased.
[0005]
8 to 10 show a second conventional example of the above connection structure (Japanese Patent Laid-Open No. 11-287166). In the second conventional example, a branch hole 83 having an inner diameter of 2 mm or more is formed instead of the branch hole 53 described in the first conventional example. Further, by forming the collar tip at the tip of the seal surface 94 at the tip of the injection pipe 91, the outer diameter is reduced to be smaller than the inner diameter of the branch hole 83, and the inner diameter of the internal through hole is reduced. The narrowed first tubular narrowing portion is also formed. The protruding portion 95 made of the first throttle portion is loosely inserted into the branch hole 83. The through hole 96 formed inside the protruding portion 95 has an inner diameter of 0.7 to 1.0 mm and is an orifice hole. In this structure, as in the first conventional example, instead of a narrow tubular branch hole that directly serves as an orifice hole in the common rail 51, a branch hole 83 having an inner diameter of 2 mm or more is opened, so that processing is facilitated.
[0006]
[Problems to be solved by the invention]
Due to the performance requirement of further reducing pressure fluctuations in the common rail, it is necessary to further reduce the inner diameter of the orifice hole to about 0.4 to 0.7 mm.
[0007]
However, it is formed by a method of using the branch hole 53 of the common rail 51 of the first conventional example as an orifice hole or a method of narrowing the tip of the collar at the tip of the seal surface 94 of the tip of the injection pipe 91 of the second conventional example. Thus, the outer diameter is reduced to be smaller than the inner diameter of the branch hole 83, the inner diameter of the internal through hole is also reduced to form an orifice hole, and the projecting portion 95 of the narrow tubular first restricting portion is formed. In order to reduce the inner diameter to about 0.4 to 0.7 mm, advanced technology is necessary and difficult.
[0008]
An object of the present invention is to solve the above-mentioned problems, to prevent the occurrence of cracks and to stabilize quality, and to facilitate processing and reduce costs. Furthermore, it is providing the connection structure of the common rail and injection pipe assembly which can reduce the pressure fluctuation in a common rail, and its formation method.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the connection structure between the common rail and the injection pipe assembly of the present invention has a branch hole with an inner diameter of 2 mm or more formed in the common rail,
At the tip of the collar of the injection pipe assembly consisting of an injection pipe, collar and union, the outer diameter is reduced smaller than the inner diameter of the branch hole, and the inner diameter of the internal through hole is also reduced to 0.7 to 1.0 mm. since, first throttle portion capillary-like is squeezed formed,
A fine tubular second constriction portion having an outer diameter further reduced at the distal end portion of the first constriction portion and an inner diameter of the internal through hole further reduced to an orifice hole of 0.4 to 0.7 mm. Is drawn,
The protruding portion including the first throttle portion and the second throttle portion is loosely inserted into the branch hole.
[0010]
Here, the first diaphragm portion and the first diaphragm portion of the second diaphragm portion are only provided for convenience of explanation, and are not limited to two stages, and are not limited to the first diaphragm portion and the second diaphragm portion. In the meantime, this also includes the case where an intermediate diaphragm portion is formed.
[0011]
Taking the case of narrowing down to two stages as an example, for each inner diameter, a through hole in the collar (inner diameter 2.0 mm), a first restrictor (inner diameter 0.7 to 1.0 mm), and a second restrictor (orifice) It is preferable to reduce the diameter within a range of (hole) (inner diameter 0.4 to 0.7 mm).
[0012]
The reason why the inner diameter of the branch hole is set to 2 mm or more is not particularly limited, but is to make the branch hole easy and to prevent the protruding portion to be loosely inserted from being too thin. More preferably. The upper limit of the inner diameter of the branch hole is not particularly limited in terms of numerical values, but is practically up to the inner diameter of the common rail hole. Further, the inner diameter of the through hole is not particularly limited as long as the inner diameter is continuously reduced, but it may be a curved surface or a flat surface, and more preferably, the diameter is reduced to a conical shape. It is in a state.
[0013]
Here, the positional relationship between the front end surface of the protruding portion and the intersection opening of the branch hole with respect to the common rail hole is not particularly limited, but is preferably substantially flush.
[0014]
The method for forming the common rail and the injection pipe assembly of the present invention is to form a branch hole having an inner diameter of 2 mm or more in the common rail,
By compressing the tip of the injection pipe assembly collar consisting of the injection pipe, collar and union, the outer diameter is reduced to be smaller than the inner diameter of the branch hole by plastic deformation so that compressive residual strain remains. The inner diameter of the tube is reduced to 0.7 to 1.0 mm to form a first narrow tubular narrowed portion,
By further deforming the tip of the first throttle part so as to leave a compressive residual strain, the outer diameter is further reduced, and the inner diameter of the inner through hole is further reduced to an inner diameter of 0.4 to Forming a second narrowed portion of a fine tube, which is a 0.7 mm orifice hole,
The protruding portion including the first throttle portion and the second throttle portion is loosely inserted into the branch hole.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below with reference to FIGS. FIG. 4 shows an outline of a common rail type fuel injection device for a diesel engine. A pipe 3 for connecting a fuel pump 2 and an injection pipe assembly 20 for connecting an injector 4 are connected to the side of the common rail 1. A relief valve 6 and a pressure sensor 7 are connected to the end of the common rail 1. The fuel pump 2 and the injector 4 are controlled by an electronic control device 8. 1 to 3 show a joint structure between the common rail 1 and the injection pipe assembly 20 according to the present embodiment.
[0016]
As shown in FIG. 1, a common rail hole 12 extending in the rail length direction is formed at the center of the metal common rail 1 and has an inner diameter of 6 to 11 mm (for example, 11 mm). In the cylindrical wall portion of the common rail 1, a branch hole 13 extending in a direction perpendicular to the rail length and extending in a direction perpendicular to the rail length, a tapered seal surface 14, and a female screw 16 on the inner periphery are cut in order from the inside to the outside. A mounting hole 15 is formed. The inner diameter of the branch hole 13 is 3.5 mm, and if it is about this size, it can be formed by cutting, so the branch hole 13 of this embodiment is drilled.
[0017]
A large cylindrical union 31 as a mounting member is passed around the injection pipe 5, a male screw 32 is cut on the outer periphery of the union 31, and a hexagonal portion 33 is formed. A step portion 34 is formed on the inner periphery of the union 31. Is formed. The injection pipe 5, the collar 22, and the union 31 are assembled in advance as the injection pipe assembly 20.
[0018]
FIG. 2 shows an aspect in which the injection pipe assembly 20 is connected to the common rail 1. That is, the male thread 32 of the union 31 is screwed into the female thread 16 of the mounting hole 15, the step part 34 of the union 31 is engaged with the flange part 23 of the collar 22, and the seal surface 24 of the collar 22 is connected to the common rail 1. The sticking portion 25 may be brought into close contact with the sealing surface 14, and the protruding portion 25 may be loosely inserted into the branch hole 13 concentrically so that the front end surface of the protruding portion 25 is substantially flush with the intersection opening of the branch hole 13 with respect to the common rail hole 12. . By this loose insertion, a circumferential gap 27 of 0.25 mm or more is generated between the protruding portion 25 (within 3 mm) and the branch hole 13 (3.5 mm).
[0019]
The fuel pressurized by the fuel pump 2 and sent to the common rail 1 is directly introduced from the common rail hole 12 into the through hole 26 of the protruding portion 25 of the collar 22 and sent from the injection pipe 5 to the injector 4. That is, in the present embodiment, the through hole 26 of the protruding portion 25 functions as a hole for introducing fuel, like the branch hole 53 of the conventional example.
[0020]
2 and a detailed view of the main part show a method of forming the protruding portion 25 shown in FIG. 3 and a through-hole inside thereof. The injection pipe 5 has an outer diameter of 6.35 mm and an inner diameter of 3 mm. A small cylindrical collar 22 made of metal is press-fitted and fixed to the end of the injection pipe 5. The main part has an outer diameter of 8 mm and an inner diameter of 2 mm. A convex spherical seal surface 24 is formed in the middle of the collar 22, and a protruding portion 25 including a first diaphragm portion 25 a and a second diaphragm portion 25 b is formed at the tip of the collar 22. First, the protruding portion 25 is plastically deformed so as to retain compressive residual strain by a method of squeezing the tip portion of the collar 22, so that the outer diameter is reduced to be smaller than the inner diameter of the branch hole, and the inner diameter ( 26a) is also reduced in diameter to form a narrow first throttle portion 25a. Next, the outer diameter is further reduced and the inner diameter of the internal through hole is further reduced by plastically deforming so that the compression residual strain remains by the method of further reducing the tip of the first throttle portion 25a. A fine tubular second constriction portion 25b, which is the hole 26b, is formed. Finally, the entire length of the protruding portion 25 is made substantially the same as the length of the branch hole 13. Further, the outer diameter of the protruding portion 25 is set to be within 3 mm smaller than the inner diameter of the branch hole 13, and the protruding portion 25 is loosely inserted into the branch hole 13.
[0021]
When the sealing surface 14 and the protruding portion 25 are formed from the tip end portion of the collar 22 in two stages, the through hole 26 continuing from the injection pipe 5 into the collar 22 and into the protruding portion 25 is formed in two stages. The inner diameter of the second throttle portion 25b at the tip of the through hole is the orifice hole 26b. The inner diameter of the through hole 26 is the through hole in the collar 22 (inner diameter 2.0 mm), then the first restrictor internal hole 26a (inner diameter 0.7 to 1.0 mm), and finally the second restrictor internal passage through the tip. The diameter of the hole (orifice hole) 26b (inner diameter 0.4 to 0.7 mm) is continuously reduced in two stages toward the tip.
[0022]
According to the common rail 1 of the present embodiment, the following functions and effects (1), (2), and (3) are obtained.
(1) Since the inner diameter of the branch hole 13 of the common rail 1 is increased to about 3 mm as described above, the branch hole 13 can be easily formed by cutting or other methods, thereby reducing facility investment and reducing costs. Can be achieved. On the other hand, the structure of the injection pipe assembly 20 is complicated as much as the protruding portion 25 is formed on the collar 22, but since the processing is easy, the total including the common rail 1 is shown in FIGS. 1 Manufacturing is easier than the conventional example, and the cost merit is great.
[0023]
(2) As shown in FIG. 3, the ultra high pressure due to the pressurized fuel in the common rail hole 12 is applied to the protruding portion 25 of the collar 22. However, since there is a gap 27 between the protruding portion 25 and the branch hole 13, the protruding portion 25 receives the same pressure on the inner peripheral surface (through hole 26) and the outer peripheral surface, the generated stress is suppressed, and the fluctuation is reduced. The accompanying tensile strain does not occur and the occurrence of cracks can be prevented. As a result, the quality is stabilized. Accordingly, it is not necessary to increase the strength by hardening treatment such as carburizing and quenching as in the first conventional example shown in FIGS. No. The ultra high pressure is applied to the intersection opening edge 17 of the branch hole 13 with respect to the common rail hole 12, but since the inner diameter thereof is large, local stress concentration can be achieved by curving the surface by a simpler method (eg, fluid polishing). Since it can be relaxed, performance can be ensured.
[0024]
(3) Further, as shown in FIG. 2, the through hole 26 is changed from the through hole (inner diameter: 2.0 mm) in the collar 22 to the first throttle portion inner hole 26 a (inner diameter: 0.7 to 1.0 mm). Furthermore, when the diameter of the throttle is reduced in two stages with the second throttle part through hole 26b (orifice hole, inner diameter 0.4 to 0.7 mm), the diameter can be reduced to 0.4 to 0.7 mm. Due to the reduced diameter of the through hole by the two-stage restriction, the orifice hole can have a smaller inner diameter than the second conventional example shown in FIGS. As a result, propagation of pressure waves generated by fuel injection can be reduced, and pressure fluctuations in the common rail can be reduced. Furthermore, by taking the shape of such a two-stage throttle, attenuation of the pressure wave in the through hole on the injection side is also observed.
[0025]
In addition, this invention is not limited to the said embodiment, For example, it can also be suitably changed and embodied as follows, for example in the range which does not deviate from the meaning of invention.
(1) The configuration of the injection pipe assembly is changed, for example, a protruding portion is directly formed at the tip of the injection pipe 5 and the collar is fixed to the outer periphery of the injection pipe 5.
(2) The dimensions such as the inner diameter of the through hole, the outer diameter of the protruding portion or the diameter of the branch hole should be changed as appropriate.
[0026]
【The invention's effect】
As described above in detail, according to the connection structure of the common rail and the injection pipe assembly and the method of forming the same according to the present invention, it is possible to prevent the occurrence of cracks and stabilize the quality, and to facilitate the processing and cost. You can go down. Furthermore, the pressure fluctuation in the common rail generated by the fuel injection is reduced, and an excellent effect is obtained that the pressure wave in the injection-side through hole is also attenuated .
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a connection structure between a common rail and an injection pipe assembly according to an embodiment of the present invention before connection.
FIG. 2 is a cross-sectional view after connection of the connection structure.
3 is an enlarged cross-sectional view of a main part of FIG.
FIG. 4 is a schematic view of a common rail fuel injection device for a diesel engine.
FIG. 5 is a cross-sectional view before connection of a connection structure between a common rail and an injection pipe assembly according to a first conventional example.
FIG. 6 is a cross-sectional view after connection of the connection structure.
7 is an enlarged cross-sectional view of a main part of FIG.
FIG. 8 is a cross-sectional view before connection of a connection structure between a common rail and an injection pipe assembly according to a second conventional example.
FIG. 9 is a cross-sectional view after connection of the connection structure.
10 is an enlarged cross-sectional view of a main part of FIG. 9;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Common rail 5 Injection pipe 12 Common rail hole 13 Branch hole 20 Injection pipe assembly 22 Collar 25 Projection part 26 Through hole 27 Clearance 31 Union

Claims (2)

A branch hole with an inner diameter of 2 mm or more is formed in the common rail,
The outer diameter of the injection pipe assembly collar consisting of an injection pipe, collar, and union is reduced to an outer diameter smaller than the inner diameter of the branch hole, and the inner diameter of the inner through hole is also reduced to 0.7 to 1.0 mm. became the first throttle portion capillary-like is squeezed formed,
A fine tubular second throttle having an outer diameter further reduced at the tip of the first throttle part, and an inner diameter of an internal through hole further reduced to an orifice hole of 0.4 to 0.7 mm. Part is drawn,
A connection structure between a common rail and an injection pipe assembly, wherein a projecting portion including the first throttle portion and the second throttle portion is loosely inserted into the branch hole. A branch hole with an inner diameter of 2 mm or more is formed in the common rail,
The outer diameter of the injection pipe assembly consisting of an injection pipe, a collar and a union is reduced by a method of squeezing the tip of the collar of the injection pipe assembly so that residual compressive strain remains. The inner diameter of the hole is also reduced to 0.7 to 1.0 mm, forming a first narrowed throttle portion,
By further plastically deforming so that compression residual strain remains by the method of further reducing the tip of the first throttle part, the outer diameter is further reduced, and the inner diameter of the inner through hole is further reduced to 0.4 to Forming a second narrowed portion of a fine tube, which is a 0.7 mm orifice hole,
A method for forming a connection structure between a common rail and an injection pipe assembly, wherein a protruding portion including the first throttle portion and the second throttle portion is loosely inserted into the branch hole.

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