JP3385415B2 - High pressure fuel pipe connection structure - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-pressure fuel pipe connection structure suitable for high-pressure fuel equipment such as a common rail type unit injector. More specifically, a connection structure of a high-pressure fuel pipe for connecting a high-pressure fuel pipe by surface-contacting a tapered end of the pipe with a high pressure in a diverging concave portion formed at an edge of a fuel inlet / outlet of a high-pressure fuel device. It is about.

[0002]

2. Description of the Related Art In recent years, in order to prevent environmental pollution, exhaust gas regulations for automobile engines have become more stringent, and reduction of NOx and particulates in exhaust gas has become an urgent task. It is known that in a diesel engine, when the fuel injection pressure is increased to make the fuel finer, the particulates are reduced. As such an engine, one having a unit injector that can always inject high-pressure fuel is known. In an engine having this unit injector, a unit injector is provided for each cylinder of the engine. A common rail is connected to these injectors, a supply pump is connected to the common rail,
The fuel pumped from the supply pump is stored in the common rail. The high-pressure fuel accumulated in the common rail is injected from the unit injector into the cylinder of the engine, so that the injection pressure of the fuel is increased and the fuel is made finer to reduce the particulates.

Conventionally, a fuel injector is used to connect the unit injector, which is such a high-pressure fuel equipment, and the common rail, or the common rail and the supply pump. As shown in FIG. 4, the ends of the fuel pipes 2 are tapered, and the ends of the pipes 2 are inserted into the diverging recesses 4 formed at the edges of the fuel inlet / outlet 3 of each high-pressure fuel equipment. As shown in FIG. 3, the tip of the pipe 2 is plastically deformed by being brought into contact with it at a high pressure so as to fit into the recess 4, and the end of the pipe 2 is brought into surface contact with the recess 4 for connection. By thus bringing the end portion of the pipe 2 into surface contact with the recess 4, it is possible to prevent the high-pressure fuel flowing inside the pipe 2 from leaking at the connection portion of the pipe 2.

[0004]

However, in recent years, as the demand for purification of exhaust gas has increased, the need for making the fuel into finer particles has increased. It is possible to deal with the atomization of the fuel by increasing the injection pressure of the fuel, but the strength of the high pressure fuel pipe 2 itself and the high pressure fuel pipe 2
There is a need to prevent fuel leaks at the connections.
The strength of the high-pressure fuel pipe 2 itself may increase the wall thickness of the pipe 2 or manufacture the pipe 2 from a high-strength material typified by stainless steel. Further, in order to prevent fuel leakage at the connection portion of the high-pressure fuel pipe 2, it is conceivable to increase the contact surface pressure between the end portion of the pipe 2 and the recess 4.

However, increasing the wall thickness of the pipe 2 causes a decrease in the cross-sectional area through which the fuel flows or an increase in the outer diameter of the pipe 2, which increases the fuel flow resistance or enlarges the engine itself. is there. On the other hand, manufacturing the pipe 2 from a high-strength material has a problem in that the pressure at the time of making surface contact with the recess 4 of the fuel inlet / outlet 3 of the high-pressure fuel equipment has to be increased due to its high strength. If the amount is insufficient, the plastic deformation of the tip of the pipe 2 is not sufficient, and the tip of the pipe 2 may not fit in the recess 4, which may cause fuel leakage at the connection portion of the high-pressure fuel pipe 2.

Further, increasing the contact surface pressure between the end of the pipe 2 and the recess 4 may cause plastic deformation of the tip of the pipe 2 to exceed the recess 4, as shown in the enlarged view of the figure. A flat surface portion 2a orthogonal to the force for pressing the pipe 2 is formed at a position deviated from the above, and there is a problem that a reaction force R that opposes the force for pressing the pipe 2 is generated on this flat surface portion 2a.
Therefore, when the flat surface portion 2a is formed, the pressure at the contact portion of the high-pressure fuel pipe 2 decreases, fuel leakage occurs at the connection portion, and the pipe 2 having the flat surface portion 2a cannot be reused. There is. An object of the present invention is to provide a connection structure for a high-pressure fuel pipe, which can increase the strength of the fuel pipe itself without increasing the wall thickness of the pipe. Another object of the present invention is to provide a high-pressure fuel pipe connection structure capable of reliably preventing fuel leakage at the connection portion of the high-pressure fuel pipe by ensuring the contact area between the end of the pipe and the recess.

[0007]

The invention according to claim 1 is
As shown in FIG. 1, high-pressure fuel is obtained by making high-pressure surface contact with the end of the tapered pipe 12 in a diverging concave portion 22 formed at the rim of the fuel inlet / outlet 21 of the high-pressure fuel equipment 11, 13, 14. This is an improvement in the structure that connects the pipes. Its distinctive feature is the composite steel pipe fuel pipe 12 are integrated and an outer tube 12b made of an inner tube 12a and stainless steel from soft steel made of stainless steel, concave
The inner pipe 12a so that only the outer pipe 12b comes into surface contact with the portion 22.
Is the end of the taper taper .

Since the fuel pipe 12 is a composite steel pipe having an inner pipe 12a made of stainless steel, the pipe 1
The strength of the fuel pipe 12 itself can be increased without increasing the wall thickness of 2. By forming the end portion of the inner pipe 12a into a tapered shape and bringing the recess 22 into surface contact with only the outer pipe 12b made of a steel material softer than stainless steel, compatibility with the recess 22 is improved. Examples of steel materials softer than stainless steel include STS340.

[0009]

The invention according to claim 2 is a high-pressure fuel equipment 1,
This is an improvement in the structure for connecting the high-pressure fuel pipes by making high-pressure surface contact with the ends of the tapered pipe 12 in the diverging recesses 22 formed at the edges of the fuel inlet / outlet ports 13 and 14. The characteristic structure is that the fuel pipe 12
Is a composite steel pipe in which an inner pipe 12a made of stainless steel and an outer pipe 12b made of a steel material softer than stainless steel are integrated, and an end portion of the inner pipe 12a so that only the outer pipe 12b comes into surface contact with the recess 22. Is formed in a tapered shape, a shoulder portion 24 having a divergence angle that is larger than the divergence inclination angle of the recess portion 22 is formed on the peripheral edge of the recess portion 22, and the end portion of the pipe 12 that has been plastically deformed beyond the recess portion 22 becomes the shoulder portion 24. It is where it is configured to contact. In the present specification, the "fuel inlet / outlet" refers to an outlet or an inlet for the high-pressure fuel, or an outlet for both the outlet and the inlet.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described in detail with reference to the drawings. As shown in FIG. 3, in this example, the diesel engine 10 has six cylinders, and the unit injector 11 is arranged for each of these cylinders. A common rail 13 is connected to these injectors 11 via a high-pressure fuel pipe 12. A supply pump 14 is connected to the common rail 13 via a high-pressure fuel pipe 12, and the fuel pumped from the pump 14 is supplied to the common rail 13.
Is stored in. Although not shown, this supply pump 14 is provided with a cam, and when the cam rotates, the piston moves up and down to supply the fuel drawn up from the fuel tank by the feed pump to the common rail 13.

The unit injector 11, which is a high-pressure fuel device, the common rail 13, and the high-pressure fuel pipe 12, which connect the supply pump 14, respectively, have the same structure. The connection structure between the fuel pipe and the high-pressure fuel device will be described below. As shown in FIG. 1, a diverging concave portion 22 is formed at the edge of the fuel inlet / outlet 21 of the high-pressure fuel equipment. The end of the pipe 12 is formed in a tapered shape, and the high pressure fuel pipe 12 is connected by bringing the end of the pipe 12 into surface contact at high pressure. The fuel inlet / outlet 21 is formed at the center of a cylindrical body 23 formed so as to project from the high-pressure fuel equipment, and an external thread 23a is formed on the outer peripheral surface of the cylindrical body 23. Further, a shoulder portion 24 having a divergence angle that is greater than the divergence inclination angle of the recess 22 is provided on the periphery of the recess 22 of the fuel inlet / outlet 21.
Is formed.

On the other hand, the fuel pipe 12 is a composite steel pipe in which an inner pipe 12a and an outer pipe 12b are integrated, the inner pipe 12a is made of high strength stainless steel, and the outer pipe 12b is softer than stainless steel. It is composed of STS340 which is a steel material. The end portion of the inner pipe 12a is tapered, and the outer pipe 1
2b covers the tapered portion, and a bulged portion 12c having an increased outer diameter is formed on the outer peripheral surface thereof. Pipe 1
When the end of 2 is brought into contact with the recess 22 at high pressure, the outer tube 1
2b is plastically deformed to fit in the concave portion 22, and only the outer tube 12b comes into surface contact with the concave portion 22.

The connection of the fuel pipe 12 to the high-pressure fuel equipment in the high-pressure fuel pipe connection structure thus configured will be described. First, the fuel pipe 12 has a step 26a.
The female screw 26 having the is inserted. Next, the stepped portion 26 a of the female screw 26 and the bulging portion 12 c of the fuel pipe 12 are engaged with each other via the spacer 27, and the female screw 26 is screwed onto the male screw 23 a of the cylindrical body 23. The internal thread 26 is screwed onto the external thread 23a to move as shown by the arrow in the figure, and the step 26
a is the bulging portion 12 of the fuel pipe 12 through the spacer 27.
c is brought close to the cylindrical body 23. The bulging portion 12c is the cylindrical body 23.
And the end of the pipe 12 is recessed into the recess 2
2, the fuel pipe 1 is pressed at high pressure, as shown in FIG.
The outer pipe 12b of No. 2 is plastically deformed and fits in the recess 22, and the end of the fuel pipe 12 comes into surface contact with the recess 22 and the fuel pipe 1
2 is connected to the high-pressure fuel equipment 11, 13, 14. When the plastic deformation of the outer pipe 12b exceeds the recess 22, the outer pipe 12b of the fuel pipe 12 is plastically deformed at the shoulder 24 as shown in the enlarged view of FIG. Prevents fuel leakage without reducing pressure at the contact area.

[0015]

As described above, according to the present invention, the composite steel pipe in which the inner pipe made of stainless steel and the outer pipe made of a steel material softer than stainless steel are integrated is used for the fuel pipe. By improving the strength of the pipe itself, the strength of the fuel pipe itself can be increased without increasing the wall thickness of the pipe. Further, since the end of the inner pipe is tapered so that only the outer pipe comes into surface contact with the recess of the fuel inlet / outlet, the familiarity when the end of the fuel pipe is brought into contact with the recess is not impaired. . Further, by forming a shoulder portion having a divergence angle that is larger than the divergence inclination angle of the concave portion on the periphery of the concave portion, even if the outer pipe is plastically deformed beyond the concave portion, the pressure at the contact portion of the concave portion is not reduced. . As a result, the contact pressure between the end portion of the pipe and the recess can be ensured, and fuel leakage at the connection portion of the high-pressure fuel pipe can be prevented. Further, forming the shoulder portion on the peripheral edge of the concave portion also has an effect of preventing the formation of a flat surface portion at a pipe tip portion outside the concave portion that is orthogonal to the force pressing the pipe, thereby enabling reuse of the pipe. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a connection structure of the present invention.

FIG. 2 is a view corresponding to FIG. 1 showing a state where an end portion of the fuel pipe is plastically deformed.

FIG. 3 is a side view of a diesel engine having the connection structure.

FIG. 4 is a diagram corresponding to FIG. 1 showing a conventional example.

[Explanation of symbols]

11 unit injector 12 High-pressure fuel pipe 12a inner tube 12b outer tube 13 common rail 14 Supply pump 21 Fuel entrance / exit 22 recess 24 Shoulder

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Claims (2)

(57) [Claims] 1. The fuel inlet / outlet (2) of the high-pressure fuel equipment (11, 13, 14)
In the structure for connecting a high-pressure fuel pipe by surface-contacting the end of the pipe (12) taperingly formed in the diverging concave portion (22) formed in the rim of 1) with high pressure, the fuel pipe (12) Inner tube made of stainless steel (12a)
And an outer tube made of a steel material softer than the stainless steel (12b)
A composite steel pipe in which the end of the inner pipe (12a) is tapered so that only the outer pipe (12b) comes into surface contact with the recess (22). High pressure fuel pipe connection structure. 2. The fuel inlet / outlet (2) of the high-pressure fuel equipment (11, 13, 14)
In the structure for connecting a high-pressure fuel pipe by surface-contacting the end of the pipe (12) taperingly formed in the diverging concave portion (22) formed in the rim of 1) with high pressure, the fuel pipe (12) Inner tube made of stainless steel (12a)
And an outer tube made of a steel material softer than the stainless steel (12b)
In the composite steel pipe integrated with, the end of the inner pipe (12a) is tapered so that only the outer pipe (12b) is in surface contact with the recess (22), the recess (22) A shoulder portion (24) having a divergence angle larger than the divergence inclination angle of the recessed portion (22) is formed on the periphery of the recessed portion (22), and the end of the pipe (12) plastically deformed beyond the recessed portion (22) is the A high-pressure fuel pipe connection structure, characterized in that it is configured to contact the shoulder portion (24).