JP2002130076A - High-pressure fuel injection pipe having connection head part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-pressure fuel injection pipe capable of increasing the strength of a buckling forming part by preventing an annular acute-angle wrinkle or the cracking produced inside of a head part in accompany with the machining of the head part, and to prevent the possibility of the fatigue failure inside of the head part. SOLUTION: The connecting head part having an outer peripheral face to be used as a truncated conical or circular arc seat face to a counterpart seat part, is formed on a connecting end part of a comparatively small thick steel pipe, an outer peripheral face of a neck lower part of the connection head part is covered, a connection washer having a chamfering elevation θ at a connection head part side of 20-40 degrees, a chamfering depth 1 of 0.1-0.6 d (d: pipe diameter), and an axial length L of 0.5-1.5 d, is mounted, and the connection washer and the injection pipe are closely abutted on each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pipe diameter of 4 m / m to 20 m / m, a wall thickness of 1 m / m to 8 m, which is frequently used as a fuel supply path in a diesel internal combustion engine, for example.
The present invention relates to a high-pressure fuel injection pipe having a connection head made of a thick steel pipe having a relatively small diameter of about / m.

[0002]

2. Description of the Related Art Conventionally, as a high-pressure fuel injection pipe having a connection head of this kind, as shown in FIGS. 7 and 8, an outer peripheral surface provided at an end of a thick steel pipe 11 has a sheet surface. In connection with the frusto-conical connection head 12 being formed by buckling processing by pressing from the outside in the axial direction by the punch member, the peripheral wall accompanying the buckling processing by the pressing is formed. Due to the outward expansion, a deep and large annular acute wrinkle 15 or pocket is formed on the inner peripheral surface of the head.
A washer (connection washer) having a length of 5 mm or less as a part necessary for applying an effective axial force to attach the second member 2 to the mating seal surface, or as a reinforcement when vibration is applied.
4, or a sleeve (connection washer) 15 having a flange 15-1 having a length of 5 mm or less was fitted. The hardness of the conventional washer 14 and sleeve 15 was less than 400 Hv.

[0003]

However, such a conventional high-pressure fuel injection pipe having a connection head is disposed and used by a deep and large annular acute wrinkle 15 or pocket formed inside the head. There is a problem that the wrinkles or pockets become the starting point of fatigue failure due to the high pressure fluid at the time. In addition, in the case of such a high-pressure fuel injection pipe, the axial force required for sealing is large, and the tightening torque for applying this axial force applies a large torsional force to the buckled molded portion of the head. When used in this state, the torsional force is used as the initial stress, and as a fluctuating stress due to repeated internal pressure (furthermore, the stress that generates vibration is added), the buckled molded part may be damaged from wrinkles or cracks. Was. As a countermeasure, a method of reducing stress by reducing wrinkles or cracks generated inside the head forming portion by buckling molding can be considered, but the washer 14 or the sleeve 15 is plastically deformed by tightening the nut at the time of pipe connection. Thus, there is a problem that the axial force does not increase even when the nut is tightened. Further, in this method, there is a problem that the head forming portion is deformed and the sealing axial force is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has been developed in order to reduce the sharp wrinkles or cracks formed in the inside of the head due to the processing of the head. It is an object of the present invention to provide a high-pressure fuel injection pipe which can eliminate the fear of fatigue fracture inside the head by increasing the surface pressure of the seal portion.

[0005]

According to the present invention, in order to achieve the above object, a connecting end of a thick steel pipe having a relatively small diameter is provided.
A connecting head having an outer peripheral surface as a frusto-conical or truncated arc seat surface to the mating seat is provided, and the outer peripheral surface is mated to the mating end of a thick-walled steel pipe having a relatively small diameter. A connecting head having a frusto-conical or truncated arc-shaped sheet surface is provided on the connecting portion, the outer peripheral surface of the lower part of the neck of the connecting head is covered, and the chamfering elevation angle θ is 20 to 40 degrees on the connecting head side, Chamfer depth 1 is 0.1d
Not less than 0.6d (d: pipe diameter) and the axial length L is 0.5
A high-pressure fuel injection pipe having a connection washer of d to 1.5d, and the connection washer and the injection pipe being in close contact with each other. The hardness of the connection washer is 400 Hv or more, and the head diameter of the connection head is the pipe diameter. d is 125% or more and 200% or less. Here, the connection washer is a washer or a sleeve washer.

That is, according to the present invention, a chamfered portion is provided on a contact type washer that covers the outer peripheral surface of the lower portion of the neck of the connection head, so that the chamfered portion restrains the outer diameter of the formed portion and stretches the material on the inner diameter side. It is possible to reduce sharp wrinkles or cracks formed in the annular concave groove portion (pocket portion) on the inner side of the head caused by buckling molding by causing it to come out,
It is possible to reduce the possibility of starting fatigue fracture due to stress concentration inside the head. In addition, since the connection washer has a high hardness, deformation when an axial force acts on the high-hardness connection washer is reduced, and the maximum diameter portion of the connection head is covered on the chamfered portion side end surface of the connection washer. With this structure, the axial force generated by excessive tightening torque can be absorbed between the maximum diameter portion of the connection head and the end face on the chamfered portion side of the connection washer, so that the expansion of the connection washer can be suppressed. It is possible to prevent the connection washer from being deformed due to excessively large size.

In the present invention, the angle of elevation of the chamfer of the connection washer θ
Is limited to 20 to 40 degrees because if it is less than 20 degrees, sharp wrinkles or cracks cannot be reduced, and if it exceeds 40 degrees, the washer or the sleeve is crushed and spread. Further, the chamfering depth 1 is set to 0.1d or more and 0.6d or more.
(D: pipe diameter) The reason for limiting the diameter to less than 0.1d is that wrinkles and cracks cannot be reduced below 0.1d. In addition, it is because the spread of the connection washer cannot be suppressed. Further, the axial length L of the connection washer is set to 0.5d to 1.5d.
The reason for limiting to d is that if it is less than 0.5 d, the volume of absorbing the torsional energy generated by the torque at the time of tightening the nut by the connection washer and the injection pipe in close contact with the connection washer is small, the absorbed energy is reduced, and the pocket portion has The shear energy acting on the shear plane increases, while 1.5
Even if d is exceeded, there is no difference in the torsional energy absorbing effect of the connection washer and the injection pipe closely contacting the washer, and the connection washer and the nut become large and heavy, and the cost increases. In addition, the hardness of the connection washer is 400 Hv.
The reason why the above is limited is to suppress the spread of the connection washer. Further, the diameter of the buckled forming head of the connection head is changed to the pipe diameter d.
125% or more and 200% or less of
If it is less than 25%, the head is plastically deformed and no axial force can be obtained, while if it exceeds 200% of the pipe diameter d, sharp wrinkles or cracks occur.

[0008]

FIG. 1 is a longitudinal sectional view showing one embodiment of a connecting head of a high-pressure fuel injection pipe according to the present invention, FIG. 2 is a longitudinal sectional view showing another embodiment of the present invention, and FIG. Is an enlarged longitudinal sectional view of the sleeve washer shown in FIGS. 1 and 2, and FIGS. 4, 5, and 6 are longitudinal sectional views showing washers having chamfers and different sectional shapes, and 1 is a thick wall. Steel pipe, 2-
1, 2-2 are connection heads, 3a, 3b are sleeve washers, 3c, 3d, 3e are washers, 4a, 4b are annular concave grooves.

The thick steel pipe 1 has a pipe diameter of 4 m / m to 20 m, which is made of a carbon steel material for a high-pressure fuel injection pipe which has been cut to a predetermined size.
m / m, a relatively thin thick pipe having a wall thickness of about 1 m / m to 8 m / m.

The high-pressure fuel injection pipe shown in FIG.
A connection head 2-1 having an outer peripheral surface as a frusto-conical seat surface 2-1a to the mating seat portion is provided at a connection end of the connection head, and an open end covering an outer peripheral surface of a lower portion of a neck of the connection head. And a contact-type sleeve washer 3a provided with a chamfered portion 3a-1 on the end face of the sleeve washer 3a on the chamfered portion 3a-1 side.
This is a structure in which the maximum diameter portion of -1 is covered. 4a
Is an annular groove having a shallow depth inside and a gentle cross section.

The high-pressure fuel injection pipe also shown in FIG. 2 has a connection head 2-2 at the connection end of the thick steel pipe 1, with the outer peripheral surface having a truncated arc-shaped seat surface 2-2 a to the mating seat. 2 and a chamfered portion 3b at the opening end covering the outer peripheral surface of the neck lower portion of the connection head
-1 is provided as a close contact type sleeve washer 3b in which the maximum diameter portion of the connection head 2-2 is covered on the end face on the chamfered portion 3b-1 side of the sleeve washer 3b. Reference numeral 4b denotes an annular groove having a contour shape with a shallow inside and a gentle cross section, as described above.

The sleeve washer 3a shown in FIGS.
3b, as shown in an enlarged manner in FIG. 3, the chamfered elevation angles θ of the chamfered portions 3a-1 and 3b-1 at the opening ends are 20 degrees to 40 degrees.
Degree, chamfering depth l is 0.1d or more and 0.6d (d: pipe diameter)
Hereinafter, the axial length L is set to 0.5d to 1.5d. The hardness of the sleeve washers 3a, 3b is 400 Hv or more. On the other hand, the buckling formed head diameter of the connection heads 2-1 and 2-2 of the thick steel pipe 1 is set to 125% to 200% of the pipe diameter d.

4, 5 and 6, the contact type washer 3c, 3d, 3c has an overall axial length L shorter than that of the sleeve washer 3a, 3b shown in FIGS. However, the overall axial length L, the chamfered elevation angles θ of the chamfers 3c-1, 3d-1, and 3e-1 at the opening ends, the chamfering depth l, and the hardness of the washers 3c, 3d, and 3e are as follows. , The sleeve washers 3a and 3b shown in FIGS.
It is formed so as to satisfy the same conditions as described above. Here, FIG.
The washer 3c shown in FIG. 5 has a shorter overall axial length L than the washers 3a and 3b shown in FIG. 3, and the washer 3d shown in FIG.
6 has a longer overall axial length L than the washer 3c shown in FIG. 4, is shorter than the washers 3a and 3b shown in FIG. 3, and the chamfer 3d-1 is larger than the chamfer 3c-1, and the washer 3e shown in FIG. The overall length L in the axial direction and the length of the chamfer 3e-1 are the same as those of the washer shown in FIG.
The inner periphery is formed with a taper whose diameter is increased toward the chamfered portion 3e-1. The inclination angle of the taper of the washer 3e shown in FIG. 6 is not particularly limited, but is suitably 5 degrees or less.

Next, a method of forming a head of a high-pressure fuel injection pipe according to the present invention is characterized in that a substantially cylindrical tubular portion which covers the connection head near the connection head of a thick steel pipe and an inner periphery on the head formation side. The sleeve washer 3a, 3b or the washer 3c, 3d, 3e having a chamfered portion is externally fitted in advance with a head machining allowance,
In this state, when the tip of the steel pipe 1 is pressed in the axial direction by the punch member 7 while holding the washer and the thick steel pipe on the chuck, the chamfered part of the washer previously fitted to the thick steel pipe is formed. The portion of the head machining allowance of the thick-walled steel pipe plastically flows, and at the same time the connection head is formed, the thick-walled steel pipe closely adheres to the inner periphery of the washer, and the largest diameter portion of the connection head covers the end face of the washer. A washer covers the outer peripheral surface of the lower part of the neck of the connection head, and a frusto-conical or truncated arc-shaped seat surface 2-1a, 2- to the mating seat (not shown) is provided at the tip of the thick steel pipe. A connection head having 2a is obtained.

In this head forming method, when forming the head, the chamfered portion of the washer restrains the outer diameter of the formed portion, so that the head expands outwardly due to buckling due to the pressing of the punch member. Annular groove 4 formed on the inner peripheral surface
Reference numerals a and 4b each have a contour shape of a shallow depth and a gentle cross section. In addition, the maximum diameter portion of the connection head is in a state of covering the end face of the washer.

As described above, in the case of the high-pressure fuel injection pipe according to the present invention, the annular groove 4a or 4b formed on the inner peripheral surface of the connection head 2-1 or 2-2 has a shallow and gentle cross section. Therefore, there is almost no possibility of becoming a starting point of fatigue failure due to stress concentration inside the head.

When the nut is tightened at the time of pipe connection, sleeve washers 3a, 3b and washers 3c, 3d, 3e
In addition to the axial force acting on the connection fittings, a torque corresponding to the friction coefficient between the nut and the contact surface is transmitted, and the transmitted fittings are twisted by the transmitted torque. Since the torsion energy is absorbed by both the connection fitting and the injection pipe that is in close contact with the inner peripheral surface of the connection fitting,
If excessive tightening is performed without performing torque control, the axial force generated by the excessive tightening torque will be applied to the connection head 2-1 or 2
-2 can be absorbed between the maximum diameter portion and the end face of the washer or the sleeve on the chamfered side, and because the washer hardness or the sleeve hardness is high, the expansion of the washer or the sleeve can be suppressed. It does not collapse and deform. Therefore, since the axial force increases in proportion to the tightening torque, the range of the axial force at the same tightening torque is widened. Further, by increasing the outer diameter of the head, the head plastically deformed by the axial force is not plastically deformed into the inner periphery of the washer or the sleeve, and a part of the head does not enter.

[0018]

As described above, in the high-pressure fuel injection pipe according to the present invention, the chamfered portion is provided on the close contact type washer which covers the outer peripheral surface of the lower portion of the neck of the connection head. By restricting the diameter and projecting the material to the inner diameter side, sharp wrinkles or cracks can be reduced, and the possibility of becoming a starting point of fatigue fracture due to stress concentration inside the head can be reduced. it can. In addition, since the connection washer has a high hardness, deformation when an axial force acts on the high hardness connection washer is reduced. Furthermore, by increasing the length of the connection fitting in the axial direction, the length of the injection pipe that is in close contact with the connection fitting is also increased, and the volume thereof is also increased. As the volume increases, the energy absorbed by the connection fitting and the injection pipe that is in close contact with it Increases, and it is possible to reduce the shear stress in the shear plane from the maximum diameter portion of the connection head pocket to the maximum diameter portion of the connection head that receives torsional energy transmitted to the back of the connection head,
This can prevent breakage due to shearing in the shear plane from the pocket, and improve reliability. Furthermore, by adopting a structure in which the connection head maximum diameter portion is placed on the chamfered portion side end surface of the connection washer, the axial force generated by excessive tightening torque can be applied to the connection head maximum diameter portion and the connection washer chamfered portion side end surface. Since it is possible to suppress the spread of the connection washer by being able to absorb between the above and the above, there is an excellent effect that a higher axial force can be given.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of a connection head of a high-pressure fuel injection pipe according to the present invention.

FIG. 2 is a longitudinal sectional view showing another embodiment of the present invention.

FIG. 3 is an enlarged longitudinal sectional view showing the sleeve washer shown in FIGS. 1 and 2;

FIG. 4 is a longitudinal sectional view showing an example of a washer according to the present invention.

FIG. 5 is a longitudinal sectional view showing another example of the washer according to the present invention.

FIG. 6 is a longitudinal sectional view showing another example of the washer according to the present invention.

FIG. 7 is a longitudinal sectional view showing an example of a connection head of a conventional high-pressure fuel injection pipe.

FIG. 8 is a longitudinal sectional view showing another example of the connection head of the conventional high-pressure fuel injection pipe.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Thick steel pipe 2-1 and 2-2 Connection head 3a, 3b Sleeve washer 3c, 3d, 3e Washer 4a, 4b Annular groove

Claims (3)

[Claims] 1. A connecting head of a thick steel pipe having a relatively small diameter having a frusto-conical or truncated arcuate seat surface on the outer peripheral surface to a mating seat portion is provided at a connecting end of a thick steel pipe having a relatively small diameter. The outer peripheral surface of the lower part of the neck of the connection head is covered, the elevation angle θ of the chamfer is 20 degrees to 40 degrees, and the chamfer depth 1 is 0.1d or more and 0.6d (d:
A high-pressure fuel injection pipe having a connection head, wherein a connection washer having an axial length L of 0.5d to 1.5d is provided, and the connection washer is brought into close contact with the injection pipe. 2. The high pressure fuel injection pipe having a connection head according to claim 1, wherein the hardness of the connection washer is 400 Hv or more. 3. A high-pressure fuel injection pipe having a connection head according to claim 1, wherein a diameter of the connection head is 125% to 200% of a pipe diameter d.