JP2000240529A - Relief valve for fuel distribution pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure a pressure governing function and simplify the structure of a relief valve, while using a ball valve body by reducing pressure difference between the inside and the outside of a fuel distribution pipe. SOLUTION: This relief valve 3 is prepared by assembling, in a valve body 10 fixed to a fuel distribution pipe 1 of a direct injection type engine, a valve element 22, a valve seat 24 having a seat surface 24a opened and closed by the valve element 22, and a valve spring 20 energizing the valve element 22 in the closing direction. The valve element 22 is a ball valve element. A restriction hole 15 having an aperture smaller than a passage area of the valve seat 24 is formed on a fuel passage in the downstream of the ball valve element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel distribution pipe provided in a fuel distribution pipe in an in-cylinder injection type engine (also referred to as an internal combustion engine) for directly injecting high-pressure fuel into an engine cylinder. The present invention relates to a relief valve for a pipe.

[0002]

2. Description of the Related Art There is known a fuel injection device for a direct injection type engine in which high-pressure fuel stored in a high-pressure fuel distribution pipe is directly injected from a plurality of injectors into an engine cylinder. Further, the fuel distribution pipe distributes and supplies high-pressure fuel to a plurality of injectors provided corresponding to a plurality of cylinders of the multi-cylinder engine. As a fuel distribution pipe in such a direct injection type engine, there is a fuel injection pipe in which a relief valve for preventing an abnormal rise in fuel pressure is fixed by screwing (see, for example, JP-A-9-303233).

A conventional example of a relief valve for a fuel distribution pipe in a direct injection type engine (hereinafter, simply referred to as a relief valve) will be described with reference to a sectional view of FIG. The relief valve 103 has a valve body 121, a valve seat 124 having a seat surface 124 a opened and closed by the valve body 121, and a valve body 121 closed on a valve body 110 fixed to the fuel distribution pipe 101 by screwing. A valve spring 120 for biasing in the valve direction is incorporated.

The valve body 110 is connected to the fuel distribution pipe 1.
High pressure side upper body 110A inserted inside
And a male screw portion 116 connected to the upper body 110A by welding and screwed to the fuel distribution pipe 101.
And the lower part 110B on the low pressure side having the following two parts. The upper body 110A is made of a SUS-based metal material, and has a substantially stepped cylindrical shape with a small diameter in the first half and a large diameter in the second half. Upper body 1
A strainer 126 made of a SUS-based metal material is inserted into the front of 10A.

[0005] The lower body 110B is made of a SUS-based metal material, and is formed in a substantially stepped cylindrical shape having a large diameter in the first half and a small diameter in the second half. The upper body 1
The valve seat 124 is sandwiched between 10A and the lower body 110B. The valve seat 124 is
An O-ring 132 made of a SUS-based metal material, and made of a rubber material that maintains airtightness with the lower body 110B is fitted to the rear end outer peripheral surface. The external thread 116 of the lower body 110B is connected to the valve seat 124.
And at a position overlapping radially.

The valve body 121 is formed of a needle valve body made of a SUS-based metal material (the same reference numeral as that of the valve body 121), and is provided inside the valve body 110 so as to be axially movable. Needle valve body 121
Opens and closes the seating surface 124a of the valve seat 124 by its axial movement. At the rear end of the needle valve body 121, a valve holder 123 made of a SUS-based metal material slidable inside the lower body 110B is welded.

[0007] The valve spring 120 is a coil spring made of a SUS-based metal material, and is inserted into the lower body 110B. A pipe-like stopper pin 125 made of a metal material is inserted in the lower body 110B after the valve spring 120 is inserted.
Are fixed by caulking. Thus, the valve spring 120 always biases the needle valve body 121 forward, that is, in the valve closing direction. Also,
From the front end opening of upper body 110A, lower body 110
A series of fuel passages 128 are formed in the internal space up to the rear end opening of B.

At the axially open end of the fuel distribution pipe 101 to which the relief valve 103 is attached, a stepped hole (not shown) having a female thread 101c is formed. The relief valve 103 has a lower body 110 </ b> B having a male threaded portion 116 on the fuel distribution pipe 101.
It is fixed by screwing to c. A gasket 130 made of a copper-based metal material is provided between mutually facing surfaces of the upper body 110A and the fuel distribution pipe 101.
Is pinched.

Next, the operation of the relief valve 103 configured as described above will be described. The high-pressure fuel pressurized by the high-pressure pump is supplied to the inside of the fuel distribution pipe 101 and accumulated at a predetermined pressure, for example, 12 MPa. Fuel distribution pipe 1
The high-pressure fuel stored at a predetermined pressure inside 01 is supplied from a branch pipe of a fuel distribution pipe 101 to injectors provided for each cylinder of a direct injection engine, though not shown. The fuel pressure inside the fuel distribution pipe 101 is reduced by the relief valve 103.
Is adjusted by

In the relief valve 103, the fuel supplied into the fuel distribution pipe 101 is supplied to the upper body 11.
The water is filtered by the strainer 126 in the inside of the valve seat 0A and reaches near the seating surface 124a of the valve seat 124. However, when the fuel pressure inside the fuel distribution pipe 101 is equal to or lower than a predetermined pressure, the needle valve body 121 is moved by the elasticity of the valve spring 120 so that the seat surface 124 a
The fuel is not discharged out of the fuel distribution pipe 101 because the valve is closed.

When the fuel pressure inside the fuel distribution pipe 101 exceeds a predetermined pressure, the valve spring 12
When the needle valve body 121 is retracted against the elasticity of 0, the valve is opened, and the fuel inside the fuel distribution pipe 101 is discharged outside the pipe. Thereby, destruction of the high-pressure pump and other components is prevented.

[0012]

According to the above-described conventional relief valve 103 for a fuel distribution pipe, the valve body 1
10 are integrated by welding two parts, an upper body 110A and a lower body 110B.
The valve seat 124 is incorporated between them. Therefore, the two-part structure of the valve body 110, the upper body 1
O-ring 132 required by sandwiching valve seat 124 between 10A and lower body 110B, valve holder 123 required due to adoption of needle valve body 121
For example, the number of constituent parts increases, and the valve body 121 which is difficult to mold such as the needle valve body 121 is employed. Therefore, the cost remains high and the relief valve 103 is enlarged.

By the way, instead of the needle valve body 121, it is simply conceivable to employ a ball valve body which has excellent moldability and is advantageous for reducing the size and weight of the relief valve 103. However, since the fuel pressure inside the fuel distribution pipe 101 is high, the differential pressure between the inside and the outside of the fuel distribution pipe 101 is considerably large. For this reason, when a ball valve body is employed, the ball valve body is likely to dance when the valve is opened, and it is difficult to close even when the pressure reaches a predetermined pressure. There is a problem that the performance is deteriorated.

For the reasons described above, a needle valve body 121 that can easily maintain the pressure regulation performance even when the pressure difference between the inside and outside of the fuel distribution pipe 101 is large is conventionally used. In addition, the use of the needle valve body 121 requires the valve seat 124 to be firmly fixed to the valve body 110, so that the valve body 110 is connected to the upper body 1
A configuration having a large number of components, such as two parts, 10A and a lower body 110B, and incorporating a valve seat 124 between the valve bodies 110 has to be adopted.

The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to reduce the differential pressure between the inside and outside of a fuel distribution pipe by reducing the pressure difference.
It is an object of the present invention to provide a relief valve for a fuel distribution pipe, which can secure pressure regulation performance while using a ball valve body and can simplify the structure by using the ball valve body.

[0016]

According to a first aspect of the present invention, there is provided a valve body fixed to a fuel distribution pipe in a direct injection type engine for directly injecting high pressure fuel into an engine cylinder. A relief valve for a fuel distribution pipe incorporating a body, a valve seat having a seat surface opened and closed by the valve body, and a valve spring for urging the valve body in a valve closing direction, wherein the valve body is a ball valve A relief valve for a fuel distribution pipe, wherein a throttle hole having an opening area smaller than a passage area of the valve seat is provided in a fuel passage downstream of the ball valve body. With this configuration, the differential pressure between the inside and outside of the fuel distribution pipe can be reduced by providing a throttle hole having an opening area smaller than the passage area of the valve seat in the fuel passage downstream of the ball valve body. Thereby, the pressure regulation performance can be ensured while using the ball valve body. Also, by using the ball valve body, it is not necessary to fix the valve seat between the two parts of the body, and the valve body can be integrally formed with one part, thereby simplifying the structure. Can be. Further, with the simplification of the structure, the number of components can be reduced, and the cost and size and weight can be reduced.

According to a second aspect of the present invention, there is provided a relief valve for a fuel distribution pipe according to the first aspect, wherein a male thread portion of the valve body fixed to the fuel distribution pipe by screwing is provided at a position which does not radially overlap the valve seat. . With this configuration, it is possible to prevent the deformation of the valve seat due to the distortion of the male screw portion due to the screwing force of the valve body, and it is possible to avoid a decrease in the oil-tight performance of the ball valve body. That is, since the pressure of the fuel stored in the fuel distribution pipe is high, the force for screwing the valve body into the fuel distribution pipe becomes large. In this case, as in the conventional example (see FIG. 10),
When the external thread of the valve body is located at a position radially overlapping with the valve seat, the external thread is distorted due to the effect of the screwing force of the valve body, and as a result, the valve seat is deformed. There is a possibility that the sealing performance of the body, that is, the oil-tight performance may be reduced. However, by providing the external thread of the valve body at a position that does not radially overlap with the valve seat, it is possible to prevent deformation of the valve seat due to distortion of the external thread due to the screwing force of the valve body as described above. Therefore, it is possible to avoid a decrease in the oil-tight performance of the ball valve body.

According to a third aspect of the present invention, there is provided the fuel according to the first or second aspect, wherein the seating surface of the valve seat is formed in a tapered hole shape, and the ball seat is pressed against the ball valve body with a predetermined pressing force. It is a relief valve for distribution piping. With this configuration, the seating surface of the valve seat is formed in a tapered shape, so that the seating property of the ball valve body can be improved. In addition, by performing the hitting process with the ball valve body on the seat surface, the dimensional accuracy of the seat surface is improved, and the oil-tight performance of the ball valve body can be improved.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the drawings. As shown in a side view in FIG. 1, the returnless type fuel distribution pipe 1 has a plurality of branch pipes 1a to which a plurality of injectors 2 provided corresponding to a plurality of cylinders in a direct injection type engine are connected. ing. At one axial end of the fuel distribution pipe 1 (left side in FIG. 1),
A relief valve 3 as a fuel pressure adjusting member is fixed by screwing. As is well known, the fuel distribution pipe 1 is attached to an engine cylinder head (not shown) by bolts (see a two-dot chain line 1B in FIG. 1).

A fuel inlet (not shown) is formed at one axial end of the fuel distribution pipe 1 to which a fuel supply pipe 6 passing through a fuel tank 4 and a high-pressure pump 5 is connected. I have. A pressure sensor 8 is attached to the other axial end of the fuel distribution pipe 1. The pressure sensor 8 detects the pressure of the fuel stored in the fuel distribution pipe 1 and controls the engine control device (also referred to as ECU) 9.
As a pressure signal.

The high-pressure fuel pressurized by the high-pressure pump 5 is supplied to the inside of the fuel distribution pipe 1 through the supply pipe 6 and is stored at a predetermined pressure, for example, 12 MPa. Fuel distribution pipe 1
The high-pressure fuel stored inside is supplied from a branch pipe 1a to injectors 2 arranged in each cylinder of a direct injection type engine. The fuel pressure inside the fuel distribution pipe 1 is adjusted by the relief valve 3, and when the fuel pressure inside the fuel distribution pipe 1 exceeds the predetermined pressure, the relief valve 3
Excess fuel from the fuel tank 4 through the return pipe 7
Etc. are returned.

Next, the structure of the relief valve 3 will be described in detail. FIG. 3 is a side view of the relief valve 3, and FIG.
5 shows a front view, and FIG. 5 shows a cross-sectional view. In the figure, the valve body 10 of the relief valve 3 is integrally formed as one part. The valve body 10 includes a brass-based metal material that is more advantageous in reducing costs than a SUS-based metal material,
For example, C3604 material is used, and the metal material is formed into a substantially cylindrical shape by cutting or cold forging and then cutting.

More specifically, as shown in FIG. 5, the inner peripheral surface of the valve body 10 is provided with a strainer press-in hole 11 and a strainer press-in hole 11 in that order from the front end (the left end in FIG. 5). A valve seat press-fitting hole 12 having a diameter smaller than the inner diameter, a valve spring fixing hole 13 having a diameter smaller than the inner diameter of the valve seat press-fitting hole 12, and a spring seat surface 1 forming the bottom surface of the valve spring fixing hole 13.
4 and the valve body 1 through the spring seat surface 14 thereof.
0 and the valve spring fixing hole 1
A throttle hole 15 having a diameter smaller than the inner diameter of No. 3 is formed (see the explanatory diagram of FIG. 8).

On the outer peripheral surface of the valve body 10, in order from the front end thereof, a male screw portion 16 which is located substantially around the outer periphery of the strainer press-fitting hole 11, and an outer peripheral portion of the front half of the valve seat press-fitting hole 12. And a six-sided width portion 17 which is located substantially at
A pipe connection portion 18 which is located substantially around the rear half of the valve seat press-fitting hole 12 and has a cylindrical shape having a diameter smaller than the inner diameter of the male thread portion 16; the valve spring fixing hole 13 and the throttle hole; A bulging portion 19 having a substantially mountain-shaped cross section, which is located substantially on the outer periphery of the bulge 15 and bulges from the pipe connecting portion 18 is formed. The piping connection 18
The return pipe 7 (see FIG. 1) communicating with the fuel tank 4 and the like is connected to the bulging portion 19 by fitting.
The distal end of the external thread 16 is a threadless portion 16a having no thread.

A valve spring 20 is inserted into the valve body 10 through the opening of the strainer press-fitting hole 11. The valve spring 20 is made of a SUS-based metal material such as SU for the purpose of preventing breakage due to corrosion.
S304-A coil spring made of a WPB material is employed. Further, the insertion side end of the valve spring 20 is fitted into the valve spring fixing hole 13 of the valve body 10 so that the spring seating surface 14 is formed.
It is positioned in contact with The insertion-side end of the valve spring 20 may be fixed in a state of being in contact with the spring seating surface 14 by being pressed into the valve spring fixing hole 13 using elasticity.

Inside the valve body 10, the valve spring 2 is inserted through the opening of the strainer press-in hole 11.
After 0, a ball valve body 22 as a valve body is inserted. The ball valve body 22 is made of a SUS-based metal material, for example, SUS440C material for the purpose of preventing abrasion.

The ball valve body 22 is inserted into the valve body 10 through the opening of the strainer press-fitting hole 11.
Subsequently, a substantially cylindrical valve seat 24 is inserted and fixed to the valve seat press-fitting hole 12 by press-fitting. The valve seat 24 is made of a SUS-based metal material, for example, a SUS440C material for the purpose of preventing abrasion. Further, the valve seat 24 is press-fitted to a position that does not radially overlap with the external thread portion 16 of the valve body 10. Note that the outer peripheral surface 24b of the insertion side end of the valve seat 24 is formed to have a gently tapered shape (FIG. 7).
).

A seating surface 24a having a tapered hole shape is formed on the insertion-side end surface of the valve seat 24 (see FIG. 7). The ball valve body 22 always comes into contact with the seat surface 24a with the urging force of the valve spring 20. The seating surface 24a is hit by a ball valve body 22 prior to assembling the valve seat 24 to the valve body 10. This seat 24a
A ball valve body for hitting (to be described later) formed in the same shape as the ball valve body 22 is employed as the ball valve body 22 for hitting.

The passage diameter φD of the valve seat 24 and the opening diameter φd of the throttle hole 15 of the valve body 10 are set to satisfy the relation of φD> φd. Thus, the opening area of the throttle hole 15 is smaller than the passage area of the valve seat 24.

A strainer 26 is inserted into the valve body 10 from the opening surface of the strainer press-fitting hole 11, following the valve seat 24 and the strainer 2
6 is opposite to the strainer press-fitting hole 11
Is fixed by press fitting. The strainer 26 is made of a synthetic resin material, for example, a PA66 material. In the present embodiment, the cost is reduced by diverting the opening part used for the injector 2. Also,
A series of fuel passages 2 is provided in the internal space from the front end opening of the valve body 10 to the rear end opening of the throttle hole 15 of the valve body 10.
8 are formed.

As shown in the sectional view of FIG. 2, a stepped hole 1b having a female thread 1c is formed at the axially open end of the fuel distribution pipe 1 to which the relief valve 3 is attached. The relief valve 3 is provided with a male thread 16 of the valve body 10 in the fuel distribution pipe 1 and a female thread 1c.
It is fixed by screwing it. At this time, a tool (not shown) such as a wrench is engaged with the hexagonal width portion 17 of the valve body 10, and the valve body 10 is fastened to the fuel distribution pipe 1 using the tool. Thus, between the mutually facing end faces of the valve body 10 and the fuel distribution pipe 1,
An O-ring 30 is clamped. The O-ring 30 is made of a synthetic resin material, for example, a fluorine (FKM) material, and in the present embodiment, like the strainer 26,
Cost reduction is achieved by diverting the mouthpiece parts to the injector 2.

Next, the operation of the relief valve 3 configured as described above will be described. In FIG. 2, fuel distribution pipe 1
The fuel supplied to the inside of the valve body is filtered by a strainer 26 in the valve body 10 and the seat surface 2 of the valve seat 24 is
It has reached almost 4a. However, fuel distribution pipe 1
When the fuel pressure inside the fuel cell is equal to or lower than a predetermined pressure, for example, 12 MPa, the ball valve body 22 is held in a closed state in which the seating surface 24a of the valve seat 24 is closed by the elasticity of the valve spring 20. Not released outside the tube.

When the fuel pressure inside the fuel distribution pipe 1 exceeds a predetermined pressure, the ball valve body 22 is retracted against the resilience of the valve spring 20 to open the valve. The fuel inside 1 is discharged outside the tube. This prevents the high-pressure pump 5 (see FIG. 1) and other components from being broken.

Next, the manufacturing process of the relief valve 3 will be described. First, in the valve seat contacting step P1 shown in FIG. 6, as shown in FIG.
The hitting ball valve body 22x is pressed against the seating surface 24a with a predetermined pressing force, for example, a pressing force F of about 3 KN to perform the hitting process. Thereby, the seat surface 2
4a is improved in dimensional accuracy, and thus the ball valve body 2
2 is improved in oil-tight performance.

Next, in the valve opening pressure adjusting step P2 shown in FIG. 6, the valve spring 20 and the ball valve body 22 are inserted into the valve body 10 as shown in FIG.
The valve opening pressure of the ball valve body 22 is set to a predetermined value by press-fitting the valve seat 24 into the valve seat press-fitting hole 12 and adjusting the press-fit amount.

Next, a strainer press-fitting step P3 shown in FIG.
In FIG. 9, the strainer 26 is press-fitted into the valve body 10 as shown in FIG. Thereafter, as shown in FIG. 6, in a high-pressure oil-tightness measuring step P4, if the oil tightness of the relief valve 3 is measured and passed, a manufacturing lot is placed at a predetermined position of the valve body 10 in a next manufacturing lot marking step P5. Engrave. Further, after the relief valve 3 is finally cleaned in the cleaning step P6, and after the appearance of the relief valve 3 is inspected in the appearance inspection / packing step P7, the relief valve 3 is packed in a box.

According to the above-described relief valve 3, the throttle hole 15 having an opening area smaller than the passage area of the valve seat 24 is provided in the fuel passage 28 downstream of the ball valve body 22. The differential pressure can be reduced. Thereby, the pressure regulation performance can be ensured while using the ball valve body 22. Also,
By using the ball valve body 22, it is not necessary to fix the valve seat 24 between the two parts of the body, and the valve body 10 can be integrally formed with one part, thereby simplifying the structure. be able to.
Further, with the simplification of the structure, the number of components can be reduced, and the cost and size and weight can be reduced.

Further, since the external thread 16 of the valve body 10 fixed to the fuel distribution pipe 1 by screwing is provided at a position which does not overlap the valve seat 24 in the radial direction, the external thread due to the screwing force of the valve body 10 is provided. The deformation of the valve seat 24 due to the distortion of the portion 16 can be prevented, and a decrease in the oil-tight performance of the ball valve body 22 can be avoided. That is, since the pressure of the fuel stored in the fuel distribution pipe 1 is high, the force for screwing the valve body 10 into the fuel distribution pipe 1 is also large. In this case, the conventional example (FIG. 10)
If the external thread 16 of the valve body 10 is radially overlapped with the valve seat 24 as shown in FIG.
When the ball valve body 24 is deformed, and the valve seat 24 is deformed, the sealing performance of the ball valve body 22, that is, the oil-tight performance may be deteriorated. However, the male thread 16 of the valve body 10 is
4, the valve seat 24 can be prevented from being deformed due to the distortion of the male screw portion 16 due to the screwing force of the valve body 10 as described above. Can be prevented from deteriorating in oil-tight performance.

Further, the seat surface 24a of the valve seat 24 is formed in a tapered hole shape, so that the ball valve body 2
2 can improve sitting comfort. Also, the seat surface 24a
Since the ball valve body 22 is subjected to hitting processing, the sealing performance of the ball valve body 22 with respect to the seat surface 24a can be improved, and the oil-tight performance of the ball valve body 22 can be improved.

The strainer 26, the valve seat 24 and the valve spring 2 are formed in the valve body 10 by forming the strainer press-fitting hole 11, the valve seat press-fitting hole 12, and the valve spring fixing hole 13 in a three-stage hole shape.
It is easy to assemble such as positioning and fixing of 0, and the assembling workability is improved.

The present invention is not limited to the above embodiment, but can be modified without departing from the scope of the present invention. Although the above-described fuel distribution pipe 1 is of a returnless type, the relief valve 3 of the present invention can also be applied to a return-type fuel distribution pipe 1 provided with a return pipe. Further, the portion including the spring seat surface 14 and the throttle hole 15 of the valve body 10 is
May be formed separately from this, and this separate member may be attached to the valve body 10 by press fitting or the like.

[0042]

According to the relief valve for a fuel distribution pipe of the present invention, by reducing the differential pressure between the inside and the outside of the fuel distribution pipe, the pressure regulation performance can be ensured while using a ball valve body. The structure can be simplified by using a ball valve body.

[Brief description of the drawings]

FIG. 1 is a side view of a fuel distribution pipe.

FIG. 2 is a partial cross-sectional view showing the vicinity of a mounting portion of a relief valve.

FIG. 3 is a side view of the relief valve.

FIG. 4 is a front view of a relief valve.

FIG. 5 is a sectional view of a relief valve.

FIG. 6 is a manufacturing process diagram of the relief valve.

FIG. 7 is an explanatory diagram of a sheet contacting step.

FIG. 8 is an explanatory diagram of a valve opening pressure adjusting step.

FIG. 9 is an explanatory view of a strainer press-fitting step.

FIG. 10 is a sectional view of a relief valve showing a conventional example.

[Explanation of symbols]

 Reference Signs List 1 fuel distribution pipe 3 relief valve 10 valve body 15 throttle hole 16 male screw part 20 valve spring 22 ball valve body (valve body) 24 valve seat 24a seat surface 28 fuel passage

Continuing from the front page (72) Inventor Yasutaka Yamada 1-1, Kyowa-cho, Obu-shi, Aichi Prefecture 1 Ai San Kogyo Co., Ltd. (72) Inventor Yoshinobu Kato 1-1-1, Kyowa-cho, Obu City, Aichi Prefecture Ai San 3G066 AA02 AB02 AD12 BA12 BA36 BA49 BA56 BA61 BA67 CB01 CB03 CB07T CB09 CB11 CB12 CB15 CB17 CD04 CD14 CD15 CD17 CD29 CE13 CE34 DC18

Claims (3)

[Claims] A valve seat fixed to a fuel distribution pipe of a direct injection type engine for directly injecting high-pressure fuel into an engine cylinder has a valve body and a seat surface opened and closed by the valve body. And a relief valve for a fuel distribution pipe incorporating a valve spring for urging the valve body in a valve closing direction, wherein the valve body is a ball valve body and a fuel passage downstream of the ball valve body is provided. A relief valve for a fuel distribution pipe provided with a throttle hole having an opening area smaller than a passage area of the valve seat. 2. The relief valve for a fuel distribution pipe according to claim 1, wherein a male thread portion of the valve body fixed to the fuel distribution pipe by screwing is provided at a position that does not radially overlap the valve seat. 3. The relief valve for a fuel distribution pipe according to claim 1, wherein the seating surface of the valve seat is formed in a tapered hole shape, and is subjected to a hitting process for pressing the ball valve body with a predetermined pressing force.