JP2015102194A - High-pressure metal piping having connecting head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide high-pressure metal piping having a connecting head comprising a connecting washer which can secure a more favorable flow of a material at the molding of the connecting head of a heavy-thickness steel pipe.SOLUTION: High-pressure metal piping comprises a connecting head 2 which is molded into a truncated conical shape at a connecting end part of a heavy-thickness steel pipe 1, and whose outside peripheral face becomes a seat face 2a, and a connecting washer 4 which covers an external peripheral face of a neck lower part of the connecting head 2 while being externally fit thereto at the molding of the connecting head 2 in advance. A diameter-expanded part 4a which covers the external peripheral face of the neck lower part of the connecting head 2 is formed at the connecting washer 4. The diameter-expanded part 4a is composed of only a single curved line whose cross section is indicated by one mathematical expression, for example, by an equation of a circle. By forming the diameter-expanded part 4a in such a way, a smooth flow of a material at the molding of the connecting head 4 can be secured. As a result, an annular recess 5 inside the connecting head 2 which is formed in association with the molding of the connecting head 2 can be formed shallow while having a mild curved line.

Description

  The present invention relates to a high-pressure metal pipe having a connection head made of a thick steel pipe having a relatively small diameter.

  Examples of the high-pressure metal pipe having a connection head include a high-pressure fuel pipe having a pipe diameter of 4 mm to 20 mm and a wall thickness of about 1 mm to 8 mm, which is disposed as a fuel supply path in a diesel internal combustion engine. In this high-pressure fuel pipe, for example, as shown in FIG. 4, the outer peripheral surface is formed into a sheet surface by buckling by pressing in the axial direction by the punch member from the outside at the connection end of the thick steel pipe 11. A conical connecting head 12 having a truncated conical shape 12a is formed. Further, a nipple 14 as a connection washer is fitted to the lower part of the neck of the connection head 12 formed in this way.

  Here, such a high-pressure fuel pipe formed with the connecting head 12 has a large annular sharp wrinkle or pocket deep on the inner peripheral surface of the head due to the outward expansion of the peripheral wall due to buckling by pressing. That is, it may be used in a state where the annular recess 15 is generated. When a high-pressure fuel pipe is provided for use in a diesel internal combustion engine, the annular recess 15 may become a starting point for fatigue failure due to supply or vibration of the high-pressure fuel.

  Therefore, for example, in the high-pressure metal pipe having a connection head shown in Patent Document 1 and the method of forming the head thereof, a stepped diameter-expanding portion is provided on the connection washer that covers the outer peripheral surface of the neck lower portion of the connection head. It has become. When the stepped enlarged diameter portion is provided in the connection washer as described above, a space is formed between the stepped enlarged diameter portion of the connection washer and the thick steel pipe, and the tip of the thick steel pipe is pivoted by the punch member. When pressed in the direction of the core, the portion of the head machining allowance enters the space by plastic flow. As a result, the stepped enlarged diameter portion of the connection washer restrains the expansion of the connection head (i.e., the outer diameter of the molded portion) and suppresses the expansion of the peripheral wall to the outside due to the buckling by pressing of the punch member. The wrinkles or pockets formed on the inner peripheral surface of the portion, that is, the annular concave portion can be made shallow and gentle.

Japanese Patent No. 4636515

  In the above-described conventional high-pressure metal pipe having a connection head and a method for forming the head thereof, a washer (connection washer) having a stepped enlarged diameter portion formed on the inner periphery on the connection head side is used. The stepped enlarged diameter portion of the washer connects the large diameter mouth portion formed on approximately 1/20 to 1/2 of the washer axial direction on the connecting head side, and the large diameter mouth portion and the washer inner diameter portion. It is formed from a tapered surface or a curved surface. In this case, when the connection head is formed on the thick-walled steel pipe, the head is formed in the space formed between the inner peripheral surface of the large-diameter mouth portion of the stepped enlarged diameter portion and the outer peripheral surface of the thick-walled steel pipe. The portion of the machining allowance enters through plastic flow, but smooth plastic flow (material flow) may be hindered by the tapered surface or curved surface forming the stepped enlarged diameter portion.

  The present invention has been made to address the above-described problems, and one of its purposes is to provide a connection washer capable of ensuring a better material flow when forming the connection head of a thick-walled steel pipe. An object of the present invention is to provide a high-pressure metal pipe having a connecting head provided.

  In order to achieve the above object, the feature of the present invention is that it is formed into a truncated cone shape or a truncated cone shape having a spherical tip at the connection end of a thick steel pipe having a relatively small diameter. A connecting head whose outer peripheral surface serves as a seat surface to the mating seat, and an outer periphery of the neck of the connecting head is covered after the connecting head is formed by fitting outside the connecting head. In a high-pressure metal pipe provided with a connection washer, and an annular recess inside the connection head generated along with the formation of the connection head is a shallow and gentle curve curve, an outer peripheral surface of a neck lower portion of the connection head is A single curve in which a cross-sectional shape of the enlarged-diameter portion in a plane including the axis of the connection washer is represented by one mathematical formula, which is covered by the enlarged-diameter portion formed on the inner peripheral surface of the connection washer. It consists only of.

In this case, the single curved line has a direction that coincides with the axis of the connection washer as an X axis, a direction perpendicular to the axis as a Y axis, It may be represented by a single XY function that is established in a coordinate system having the intersection with the axis as the origin. In this case, more specifically, the XY function can be expressed by, for example, an equation X ² + Y ² = R ² of the following circle having a radius R as an inner peripheral maximum radius of the expanded diameter portion.

  Furthermore, in these cases, after the connection head is formed, the maximum diameter portion of the connection head may cover the end surface on the diameter expansion portion side of the connection washer.

  According to these, it is possible to provide the connection washer with a diameter-enlarged portion having a cross-sectional shape consisting only of a single curve represented by one mathematical expression (XY function), and this diameter-expanded portion is connected to the connection head. The outer peripheral surface of the lower part of the neck can be covered. As a result, for example, the expansion of the outer diameter of the connection head formed by plastic deformation is effectively restrained, and the material is extremely smooth inside the space formed between the enlarged diameter portion and the thick steel pipe. Can be made to flow. As a result, the material can be satisfactorily projected on the inner diameter side of the connection head, and the stress acting in the direction of forming the annular recess on the inner peripheral surface of the connection head can be reduced with molding. The depth of the annular recess can be reduced and the cross-sectional shape thereof can be a gentle curve. Therefore, in the high-pressure metal pipe having the connection head portion to which the connection washer is fitted, it is possible to effectively prevent the annular recess from being the starting point of fatigue failure due to stress concentration inside the connection head portion.

  In addition, after the connection head is formed, the maximum diameter portion of the connection head covers the end surface on the enlarged diameter portion side of the connection washer. As a result, the axial force generated by an excessive tightening torque during pipe connection acts on the contact surface perpendicular to the axis between the maximum diameter portion of the connection head and the enlarged portion side end surface of the connection washer. The force also acts only in the axial direction, and no component force is generated in the thickness direction of the connecting washer. Thereby, the expansion of the connection washer in the radially outward direction can be suppressed, and for example, the occurrence of a nut fixing phenomenon due to excessive tightening torque can be reliably prevented.

It is sectional drawing which shows the high-pressure fuel piping as a high-pressure metal pipe which has a connection head concerning embodiment of this invention. It is sectional drawing for demonstrating the manufacturing process of the high pressure fuel piping of FIG. It is sectional drawing for demonstrating the cross-sectional shape (single curve) of the enlarged diameter part formed in the nipple of FIG. It is sectional drawing which shows an example of the conventional high voltage | pressure metal piping.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing a high-pressure metal pipe having a connection head according to an embodiment of the present invention. Here, the high-pressure metal pipe is, for example, a high-pressure fuel pipe that is disposed in a diesel internal combustion engine and supplies high-pressure fuel.

  The high-pressure fuel pipe is made of a thick steel pipe 1. The thick-walled steel pipe 1 is, for example, a carbon steel material for high-pressure piping that has been cut to a predetermined size in advance, and is composed of a relatively small-diameter thick-walled pipe having a pipe diameter of 4 mm to 20 mm and a wall thickness of about 1 mm to 8 mm.

When the connection head 2 is formed at the connection end of the thick steel pipe 1, as shown in FIG. 2, a substantially cylindrical nut 3 covering the connection head 2 near the forming portion of the connection head 2. And the nipple 4 as a connecting washer is pre-fitted in advance with a head machining allowance of the thick-walled steel pipe 1. The nipple 4 has a diameter-enlarged portion 4a on the inner periphery of the head-forming side of the thick-walled steel pipe 1 that is fitted externally. The enlarged diameter portion 4a has only a single curve represented by one mathematical expression (function) without having a straight line portion in its cross-sectional shape. Specifically, for example, as shown in FIG. 3, the single curve has a direction that coincides with the axis of the nipple 4 as the X axis and a direction perpendicular to the axis of the nipple 4 (that is, the radial direction of the mouth of the nipple 4). In the coordinate system having the origin O as the intersection of the plane of the nipple 4 and the plane including the end face 4d as the end face on the enlarged diameter side of the nipple 4 and the axis of the nipple 4. It is represented by the following formula (circle equation which is an XY function) 1 indicating a circle.
X ² + Y ² = R ² ... Formula 1

  However, the radius R in Formula 1 represents the inner peripheral maximum radius of the enlarged diameter portion 4 a of the nipple 4. Further, in the above coordinate system, the range of the Y value in Equation 1 is as shown in FIG. 3, where the radius of the inner peripheral general portion 4b (portion excluding the enlarged diameter portion 4a) of the nipple 4 is R0. R0 ≦ Y ≦ R and −R ≦ Y ≦ −R0. In this case, in the coordinate system, the range of the value of X is 0 ≦ X.

  As described above, the nipple 4 having the enlarged diameter portion 4a having only a single curve represented by the formula (XY function), that is, the formula 1 in the cross-sectional shape is externally fitted to the thick-walled steel pipe 1. Is done. Thereby, as shown in FIG. 2, an annular space portion 4 c is formed between the inner peripheral surface of the enlarged diameter portion 4 a of the nipple 4 and the outer peripheral surface of the thick steel pipe 1.

  Subsequently, as shown in FIG. 2, with the nipple 4 and the thick steel pipe 1 held by the chuck C, the tip of the thick steel pipe 1 is provided with a head mold corresponding to the frustoconical sheet surface. The punch P is pressed in the axial direction. As a result, the thick-walled steel pipe 1 is plastically deformed to form a frustoconical sheet surface 2a, and the head portion of the thick-walled steel pipe 1 is inserted into the space 4c of the nipple 4 that has been fitted over the thick-walled steel pipe 1 in advance. The part of the machining allowance enters through plastic flow. That is, the outer peripheral surface of the lower part of the neck of the connection head 2 is covered with the enlarged diameter portion 4 a of the nipple 4. Further, when the connection head 2 is formed by plastic deformation of the thick steel pipe 1, the maximum diameter portion of the connection head 2 covers the end face 4 d of the nipple 4 as shown in FIGS. 1 and 2. Thereby, the connection head 2 having the frustoconical sheet surface 2a to the mating seat is formed at the tip of the thick-walled steel pipe 1, and the nipple 4 is fitted.

  Here, at the time of forming the connection head 2, the diameter-enlarged portion 4 a of the nipple 4 having a cross-sectional shape consisting only of a single curve represented by the formula 1 restrains the expansion of the outer diameter of the connection head 2. By doing so, the expansion to the outer side of the surrounding wall accompanying the buckling process by the press of the punch P is suppressed. Further, since the enlarged diameter portion 4a of the nipple 4 has a cross-sectional shape consisting of only a single curve, the material that has entered the space portion 4c by plastic flow flows very smoothly along the inner peripheral surface of the enlarged diameter portion 4a. Let

  As can be understood from the above description, according to the above embodiment, for the nipple 4 as a connection washer that covers the outer peripheral surface of the neck lower part of the connection head 2, a single curve represented by the above equation 1 The enlarged-diameter portion 4a having a cross-sectional shape made only of can be provided. Thereby, expansion of the outer diameter of the connection head 2 formed by plastic deformation can be restricted and the material can flow extremely smoothly inside the space 4c. As a result, the material can be satisfactorily projected on the inner diameter side of the connection head 2, and the stress acting in the direction in which the annular recess 5 is formed on the inner peripheral surface of the connection head 2 is reduced. As a result, the depth of the annular recess 5 can be reduced and the cross-sectional shape thereof can be made gentle. Therefore, in the high-pressure fuel pipe (high-pressure metal pipe) having the connection head 2 to which the nipple 4 is fitted, for example, when the high-pressure fuel is supplied or when vibration occurs due to running of the vehicle, the inner peripheral side of the connection head 2 Even when stress concentration occurs in the annular recess 5, the annular recess 5 can be effectively prevented from becoming a starting point of fatigue failure.

  Further, when the connection head 2 is formed by plastic deformation of the thick steel pipe 1, the maximum diameter portion of the connection head 2 covers the end surface 4 d of the nipple 4. Thereby, when the nut 3 is excessively tightened without torque control at the time of piping connection, the axial force generated by the excessive tightening torque is the contact surface between the maximum diameter portion of the connection head 2 and the end surface 4d of the nipple 4. Act on. Here, since the contact surface is formed perpendicular to the axis, the reaction force (component force) against the axial force generated by the tightening torque also acts only in the axial direction, and in the radial direction (thickness direction) of the nipple 4. There is no component force. Thereby, the expansion of the nipple 4 in the radially outward direction can be suppressed. For example, the expanded diameter portion 4a side of the nipple 4 is deformed and bites into the inner peripheral surface of the nut 3, and the nut 3 is fixed. This can also be reliably prevented.

  In carrying out the present invention, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the object of the present invention.

  For example, in the above-described embodiment, as the diameter-expanded portion 4a of the nipple 4, the equation 1 (XY) having the radius R (specifically, the maximum inner radius of the diameter-expanded portion 4a) centered on the origin O, that is, the origin O. It was carried out so as to have a cross-sectional shape consisting only of a single curve represented by In this case, as one mathematical expression (XY function) representing a single curve, for example, an elliptical equation can be adopted instead of the circular equation.

Specifically, when the ellipse equation is adopted, in the XY coordinate system shown in FIG. 3, when the length of the major axis of the ellipse is 2A and the length of the minor axis of the ellipse is 2B, The curve can be expressed by the following formula 2 obtained by modifying the formula 1.
^{X 2 / A 2 + Y 2} / B 2 = 1 ... Equation 2
However, even in this case, the range of the Y value in the formula 2 is R0 ≦ Y ≦ R and −R ≦ Y ≦ −R0, and the range of the X value is the same as in the above embodiment. Similarly, 0 ≦ X.

  And even if it is a case where a single curve is expressed using the equation of the ellipse of said Formula 2, the cross-sectional shape of the enlarged diameter part 4a of the nipple 4 does not have a linear part. Therefore, the same effect as the above embodiment can be obtained.

Moreover, in the said embodiment and the said modification, it implemented by making the origin O into the center of a circle or an ellipse. In this case, in the XY coordinate system shown in FIG. 3, the center can be translated in the negative direction in the X-axis direction. Specifically, when a single curve is represented by Equation 1 (circle equation) in the same manner as in the above embodiment, in the XY coordinate system shown in FIG. When translated in the negative direction by C, a single curve is represented by the following formula 3 which is a modification of the formula 1.
(X + C) ² + Y ² = R ² Equation 3
However, in this case, the length (depth) in the X-axis direction of the diameter-enlarged portion 4a of the nipple 4 is shorter (shallow) by the amount of parallel movement C than in the case of the above-described embodiment. An effect equivalent to that of the embodiment can be expected. Even in this case, the range of the Y value in the equation 3 is R0 ≦ Y ≦ R and −R ≦ Y ≦ −R0, and the range of the X value in the equation 3 is 0 ≦ X.

  Furthermore, in the said embodiment, it implemented by employ | adopting the connection head 2 shape | molded by the truncated cone shape where a front-end | tip part becomes planar shape. In this case, it is also possible to implement the connecting head 2 by forming it into a truncated cone shape whose tip is spherical. Even in this case, since the outer peripheral surface of the connection head 2 functions as the seat surface 2a with respect to the mating seat portion, the same effect as that of the above embodiment can be obtained.

DESCRIPTION OF SYMBOLS 1 ... Thick-walled steel pipe, 2 ... Connection head, 2a ... Seat surface, 3 ... Nut, 4 ... Nipple (connection washer), 4a ... Diameter expansion part, 4b ... General inner peripheral part, 4c ... Space part, 4d ... End Part (expansion part side end) 5 ... annular recess, C ... chuck, P ... punch

Claims (4)

At the connecting end of a thick steel pipe with a relatively small diameter, it is formed into a truncated cone shape or a truncated cone shape with the tip end being spherical, and its outer peripheral surface becomes the seat surface to the mating seat. A connecting head, and a connecting washer that is externally fitted when the connecting head is molded and covers an outer peripheral surface of a neck lower portion of the connecting head after the connecting head is formed, and with the molding of the connecting head In the high-pressure metal piping in which the annular recess inside the connecting head that is generated is a shallow and gentle curve curve,
The outer peripheral surface of the neck lower part of the connection head is covered with an enlarged diameter portion formed on the inner peripheral surface of the connection washer,
A high-pressure metal pipe consisting of only a single curve in which the cross-sectional shape of the enlarged-diameter portion in a plane including the axis of the connection washer is represented by one mathematical expression. The high-pressure metal pipe according to claim 1,
The single curve is
A coordinate system in which the direction that coincides with the axis of the connection washer is the X axis, the direction perpendicular to the axis is the Y axis, and the origin is the intersection of the plane including the end face on the enlarged diameter side of the connection washer and the axis A high-pressure metal pipe represented by one XY function established in FIG. The high-pressure metal pipe according to claim 2,
The XY function is
The following circle equation X ² + Y ² = R ² with the radius R as the maximum inner radius of the expanded portion
High-pressure metal piping represented by In the high-pressure metal pipe according to any one of claims 1 to 3,
High-pressure metal piping in which the maximum diameter portion of the connection head covers the end surface of the connection washer after the molding of the connection head.

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