JPH021583Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an improvement in the mounting structure of a fuel injection pipe that supplies high-pressure fuel to a fuel injection valve of a diesel engine.

(Prior art) In the conventional fuel injection pipe mounting structure, as shown in FIG. A substantially conical nipple portion 8 is formed at the end of the tube 2 by press working, and the sleeve 6 is
into the upper end surface of the nipple part 8, and then tighten the cap nut 4.
into the joint part 10 and connect the fuel injection pipe 2 to the joint part 1.
It is installed at 0.

Incidentally, various measures have been taken to meet the recent demands for higher output and lower fuel consumption of diesel engines, and for fuel injection systems, it is said that shortening the injection period is effective. As a countermeasure to this, it is unavoidable to increase the internal pressure of the fuel injection pipe, and currently, pressures up to 1200 kg/cm ² have been put into practical use. It is expected that higher pressures will continue to increase in the future, and it is desirable to achieve around 1500Kg/cm ² . On the other hand, in low-quality oil-fired engines, as a countermeasure to the difficulty of combustion due to the properties of the fuel (low cetane number) and high viscosity,
In order to improve combustion, the internal pressure of fuel injection pipes is increasing.

However, in such a conventional example, the pressure limit of the injection pipe 2 is about 1000 kg/cm ² , and it cannot cope with the recent high-pressure injection of low-quality oil. In other words, in the conventional structure,
When manufacturing the fuel injection pipe 2, a material larger than the outside diameter of the product is stretched and finished. At this time, the fuel passage is formed by inserting and removing a core bar or plug, which tends to create vertical wrinkles. It is difficult to remove it externally. For this reason, when internal pressure is applied, vertical wrinkles often become starting points that lead to cracks. Furthermore, since the large-diameter nipple portion 8 is formed by upset processing (forging), creases occur in the circumferential direction on the inner surface of the nipple portion 8 that constitutes the fuel passage, and when the nipple portion 8 is assembled with the cap nut 4, the nipple portion 8 is Axial force is generated on the contact surface with the sleeve 6,
As a result, stress concentration occurs at the stepped portion of the nipple portion 8 and the wrinkles, and cracks occur. Moreover, since the manufacturing method is as described above, a high tensile strength material cannot be used for the fuel injection pipe 2. Therefore, the fuel injection pipe 2
The durability is not sufficient, and the pressure limit is almost 1000
Limited to around Kg/ ^cm2 . In addition, the nipple portion 8 must be machined with the cap nut 4 and sleeve 6 passed through the injection pipe 2 in advance, which is troublesome. In addition, since the nipple portion 8 is formed by upset processing, the straight pipe portion of the fuel injection pipe 2 is required to be long as a length of chuck at the time of upset, and the cap nut 4 after the upset processing is required when bending the fuel injection pipe 2. It is necessary to perform this operation with the sleeve 6 and sleeve 6 integrated, and for this reason as well, the straight pipe portion of the fuel injection pipe 2 is required to be long, and as a result, the length of the fuel injection pipe 2 becomes long. fuel injection pipe 2
The same mounting structure is usually adopted for both ends of the cap nut 4, but since the nipple part 8 is formed after the cap nut 4 and sleeve 6 are installed, the cap nut 4 at one end
Alternatively, even if only the sleeve 6 is damaged, it is not possible to replace these parts individually and the whole must be replaced.

(Purpose of the invention) The present invention improves the pressure limit of the fuel injection pipe to enable high-pressure injection, and also makes it possible to easily process the ends of the fuel injection pipe, shorten the fuel injection pipe, and further improve the parts of the fuel injection pipe. The purpose of the present invention is to provide a mounting structure for fuel injection pipes that can be replaced individually.

(Structure of the invention) In order to achieve the above object, the fuel injection pipe mounting structure of the present invention connects the fuel injection pipe and the joint using a cap nut whose tip is screwed into the joint. In the mounting structure, the fuel injection pipe is
A fuel passage is formed by cutting, and the pipe end is straight with a uniform outer diameter, and the pipe end is formed into a tapered surface that closely contacts the mating surface of the joint part, and this fuel injection On the outer peripheral surface of the pipe end,
An annular groove is formed over the entire length in the circumferential direction, and a plurality of vertically split pieces in the circumferential direction that fit into the annular groove are arranged on the outer periphery of the pipe end of the fuel injection pipe, and the outer periphery of the vertically split pieces A surface is formed into a tapered surface that closely contacts the proximal end of the cap nut directly or through a sleeve and becomes smaller in diameter as it moves away from the pipe end of the fuel injection pipe, and is fitted onto the outer periphery of the vertically split cotter. An annular holding member is provided to hold each divided piece of the vertically split kotta.

(Example) In FIG. 1 showing a mounting structure for a fuel injection pipe of a diesel engine according to the present invention, 20 is a fuel injection pipe. This fuel injection pipe 20 is, for example, S50C
Fuel passage 2 is made by gun drilling on a round bar of carbon steel such as
2 is formed, and the inner surface of the passage 22 is finished smooth by sizing processing to prevent stress concentration. An annular groove 24 is formed on the outer circumferential surface of the end of the injection pipe 20, and the annular groove 24 is formed by pressing, machining, etc. so that the cross section has a half-moon shape. Further, the end surface 26 of the injection pipe 20 is formed into a truncated conical shape forming an angle of 58 degrees, for example, and the end surface 26 is finished smoothly so as to be in close contact with the mating surface 30 of the joint portion 28 of the fuel injection valve. . Furthermore, the injection tube 20 is subjected to a heat treatment such as hardening to harden it to a hardness of about H _S 26 to 35.

In the annular groove 24, a two-part vertically divided cotter 32 is arranged. The inner peripheral surface of the cotter 32 has an annular groove 24
It is formed in a curved shape that fits closely to the kotta 32
A tapered surface 34 whose diameter becomes larger toward the bottom is formed on the outer peripheral surface of. Also Kotta 32
An annular groove 36 is formed in the lower part of the outer circumferential surface of.

A retaining ring 38 (holding member) is fitted into the annular groove 36, and the retaining ring 38, which is made of rubber, for example, holds the vertically split cotter 32, which is divided into two, together, and also allows the cotter 32 to fit into the annular groove 24. They are positioned so that they fit together.

A cap nut 40 is provided on the outer periphery of the bolt 32. On the inner surface of the proximal end of the cap nut 40, there is a dent 3.
A tapered surface 42 that taper-fits into the tapered surface 34 of No. 2.
A threaded portion 46 is formed on the inner surface of the tip end of the cap nut 40 to be screwed into the threaded portion 44 of the joint portion 28.
is formed.

Next, the effect will be explained. First, the injection pipe 20, the bolt 32, the cap nut 40, etc. are individually processed. Then, perform the installation work as follows. That is, after passing the cap nut 40 through the injection pipe 20, the bolt 32 is placed in the annular groove 24 of the injection pipe 20, and the bolt 32 is held together with the retaining ring 38 for positioning.In this state, the taper of the cap nut 40 is While taperingly fitting the surface 42 to the tapered surface 34 of the bolt 32, tighten the cap nut 4.
Screw the threaded part 46 of 0 into the threaded part 44 of the joint part 28, and connect the mating surface 30, the end surface 26, and the tapered surface 3.
4 and 42 are brought into close contact with each other, and the injection pipe 20 is attached to the joint portion 28.

(Effect of the invention) As explained above, according to the invention, the fuel passage 22 of the fuel injection pipe 20 is formed by cutting with a gun drill or the like, so that the occurrence of vertical wrinkles on the wall surface of the fuel passage 22 can be effectively prevented. This prevents cracks from occurring due to vertical wrinkles. In addition, an annular groove is formed on the outer circumferential surface of the end of the fuel injection pipe over the entire length in the circumferential direction, and a plurality of longitudinally divided cotters in the circumferential direction are formed on the outer periphery of the end of the fuel injection pipe to fit into the annular groove. , and the outer circumferential surface of the vertically split kotta is formed into a tapered surface that closely contacts the proximal end of the cap nut either directly or via a sleeve, and that becomes smaller in diameter as it moves away from the end of the fuel injection pipe. There is no need to process the nipple portion 8 with a large diameter, wrinkles along the circumferential direction on the inner circumference of the nipple portion 8 due to upset processing are not generated, and axial force is not applied to the contact surface of the nipple portion 8 with the sleeve 6. Therefore, naturally, there is no possibility that stress concentration would occur between the stepped portion of the nipple portion 8 and the wrinkles, resulting in cracks. Further, the fuel passage 22 is formed by cutting, and includes a tip end surface 26 and an annular groove 24.
The fuel injection pipe 2 can also be formed by cutting.
A high tensile strength material can be used as the material. From the above, the durability of the fuel injection pipe 20 can be greatly improved, and the pressure resistance limit can be increased to about 1500 kg/cm ² . Furthermore, the fuel injection pipe 20 does not have a large-diameter nipple portion 8, and the vertically split nipple 3
2 is configured into multiple parts in the circumferential direction, so each part can be assembled after being processed individually, eliminating the trouble of forming the nipple part 8 by upset processing after attaching the sleeve 6 and the cap nut 4 as in the conventional case. This eliminates the need for additional machining, making the overall machining extremely easy. Furthermore, since there is no large-diameter nipple portion 8, the straight pipe portion of the fuel injection pipe 20 is not required to have a long chuck length at the time of upset, unlike in the past.
Furthermore, when bending the fuel injection pipe 20, it is not necessary to bend the cap nut 4 and the sleeve 6 after upset processing in a state that they are integrated, so that the length of the fuel injection pipe 20 can be shortened. Further, although the same mounting structure is normally adopted for both ends of the fuel injection pipe 20, since there is no large-diameter nipple part 8, a vertically split stopper 32 or a retaining member (retaining ring 38 or sleeve 50) at one end is used. If the parts are damaged, they can be replaced individually, making repairs easy and economical. In addition, the vertically split cotter 32, which is divided into multiple parts in the circumferential direction, is attached to a holding member (retaining ring 38, sleeve 5
0), it is possible to effectively prevent each divided piece of the vertically split cotter 32 from falling off, which is a small part that tends to fall off when installing and removing the fuel injection pipe 20. The work can be done easily, and there is no fear of losing the divided pieces of the vertically split cotter 32.

(Another embodiment) (1) The holding member is not limited to the retaining ring 38, for example, the second
As shown in the figure, a cap nut 40 may be provided on the outer periphery of the sleeve 50 as a sleeve 50 that taper-fits onto the tapered surface 34 of the clasp 32.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing a fuel injection pipe mounting structure according to the present invention, FIG. 2 is a longitudinal sectional view showing another embodiment, and FIG. 3 is a longitudinal sectional view showing a conventional example. 20... Fuel injection pipe, 24... Annular groove, 32...
...Vertically split kotta, 38... Retaining ring (retaining member),
40... Fukuro Natsuto.

Claims (1)

[Scope of utility model registration request] In the fuel injection pipe mounting structure in which the fuel injection pipe and the joint are connected using a cap nut whose tip end is screwed into the joint, the fuel injection pipe has a fuel passage formed by cutting and a pipe end. The pipe portion has a straight pipe shape with a uniform outer diameter, and the pipe end is formed into a tapered surface that comes into close contact with the mating surface of the joint portion,
An annular groove is formed on the outer circumferential surface of the end of the fuel injection pipe over the entire length in the circumferential direction, and a plurality of longitudinal sections in the circumferential direction are formed on the outer circumference of the end of the fuel injection pipe to fit into the annular groove. A split piece is arranged, and the outer circumferential surface of the vertically split piece is formed into a tapered surface that closely contacts the proximal end of the cap nut either directly or via a sleeve and becomes smaller in diameter as it moves away from the end of the fuel injection pipe. . A mounting structure for a fuel injection pipe, characterized in that an annular holding member is provided that fits around the outer periphery of the vertically split kotta to hold each divided piece of the vertically split kotta.